Cathode Materials, Samples, Pristine, Layered, Doping, Discharge Capacity
LiCoO2 has been commonly used in Li-ion batteries (Li-ion batteries) designed for portable electronics as one of the earliest-emerged cathode materials. The inherent shortcomings with toxicity, low capacity of LiCoO2, and high cost, severely deter its widespread application in lithium-ion batteries (Li-ion batteries).
LiCoO2 has been commonly used in Li-ion batteries (Li-ion batteries) designed for portable electronics [57, 58] as one of the earliest-emerged cathode materials . The inherent shortcomings with toxicity, low capacity of LiCoO2, and high cost, severely deter its widespread application in lithium-ion batteries (Li-ion batteries) . It remains a considerable challenge to simultaneously avoid the formation of undesired metal ion impurities in the commodities and synthesize materials with homogeneous cation distribution even though a wide range of progresses have been obtained in the fabrication process . At molecular level, molten-salt routes  can attain homogeneous, which mixes of raw materials, though certain quantities of metal ion impurities are formed in the commodities, which might worsen the electrochemical performances  among the traditional preparation techniques . Li+ can not be coprecipitated together with other transition metal ions even though many scholars can fabricate material without impurities formed in the final commodities by employing special precipitant to substitute Na2CO3  or NaOH . It is highly advantageous to examine a new path; this path can simultaneously precipitate Li+ with transition metal ions . Synthesis of LNMO cathode material is summarized by the investigation through a modified oxalate coprecipitation technique, which is combined with high-temperature solid-state reaction . The insoluble property of lithium oxalate, nickel oxalate in ethanol solution, and manganese oxalate, assures the coprecipitation of all metal ions . Lithium ions are coprecipitated with transition metal ions, forming a precursor with homogeneous cation distribution at molecular level during the process . Due to the homogeneous cation distribution inside the material, the LNMO cathode, which the modified oxalate coprecipitation technique prepared, displays high capacity, superior rate capability, and excellent cycle performance .
High-voltage LiNi0.5Mn1.5O4 (LNMO), as a derivative of the spinel LiMn2O4, has been regarded as one of the hottest cathode candidates, because of the theoretical capacity of 146.7 mAh g−1, cubic spinel structure, satisfactory electrochemical performance, environment-friendly properties [56, 62, 63, 64, 65], and low cost of raw material . Carbonate coprecipitation is viewed as one of the most efficient ways to prepare excellent electrochemical performance of materials  and multiple morphologies . In recent decades [55, 66, 67, 68], hollow structures with well-defined morphology, interior, and composition, have aroused intense attention among the multiple structured electrode materials . Hollowing the electrode materials with well-defined nano-architectures might lead to the enhanced electrochemical performance . The hollow structure, which is made of nanoparticles, frequently has a lowered efficient diffusion distance for Li+ and a bigger surface area, leading to enhanced rate capability . Throughout the lithium insertion/extraction cycling, the void space in the hollow sphere might buffer against the local volume change, fostering the systemic stability of the electrode material and enhancing the cycleability [2, 55, 67, 68, 69, 70]. Given the particular advantages of hollow structures, LNMO hollow structures might be a quite appealing cathode material for Li-ion batteries . A cheap and straightforward technique for synthesis of LNMO hollow structures is required . A facile coprecipitation approach to fabricate hollow LNMO microspheres for LIB applications is summarized by the investigation . The (Ni0.25Mn0.75)CO3 precursors directly blend with a stoichiometric quantity of Li2CO3, and calcine in air to derive the final commodities; these commodities indicate satisfactory electrochemical performances including rate capability, specific capacity, and cycling stability .
LiMn2O4 has been reasonably well indicated [71, 72]. Various cation-substituted and it has been noted that co-doping of metal ions has a synergetic effect on the amelioration of the cycle life . Our earlier results  revealed that dual doping of Zn and La into the LiMn2O4 cathode material substantially enhanced the electrochemical performance including charge capacity and cycling stability at high current . Spinel LiMn2O4 material doped with single metal ions provides a high initial capacity though with restricted cyclability upon prolonged charge/discharge cycling . Through an impurity LixNi1–xO stage because of oxygen deficiency, synthesis of heavily Ni-doped spinel LiMn2O4 is normally accompanied and partial Ni ions seem to occupy the Li (8a) sites in the spinel matrix which results in inferior stability and lower capacity during charge/discharge cycling [3, 74]. Especially in the handful initial cycles , an attempt has been made in the past to co-dope vanadium ions (V5+) along with Cr3+; a serious capacity fading had been noticed around 4.0 V . Between 0.1 and 0.5, two things which are common to both reports are (i) employing high-content dopants (Ni and/or Cr) x to substitute Mn and (ii) charge/discharge researches at low current rates it is of paramount importance to examine the affects of variability in dopant quantities particularly at low content on the electrochemical performance of the material including the cycling performance at greater rates, i.e. 0.15 C. Therefore, and the identical is the aim of this quite report . Given the indicated scientific literature, many strong synergetic effect of Cr and Ni co-doping is supposed to manifest substantially the enhanced electrochemical performance of spinel LiMn2O4 .
Since it can provide a high operating voltage of ~4.7 V (vs. Li/Li+), which emerges from fast 3D lithium-ion diffusion channels and Ni2+/Ni4+ redox couple, within the cubic lattice [76, 77, 78], LiNi0.5Mn1.5O4 spinel has received significant interest among the cathode materials . For example, solid-state technique, the Mn3+ content could be enforced by synthesis conditions (such as the kinds and quantities of raw materials, calcining temperature and time, etc.), which have critical relevance on the crystalline structure, then on the electrochemical performance if the synthesis technique is fixed . There have been various conclusions about the effect of lithium excess quantities on electrochemical properties and the crystalline to the optimal of our knowledge . Porous MnCO3 microsphere had been utilized by Chen and others  as precursor, and the lithium excess quantity had been selected at 0, 2, 5, and 8%, respectively . That the LixNi1–xO impurity stage is progressively increasing with lithium excess quantity increased had been founded by Chen and others [4, 79]. Octahedral LiNi0.5Mn1.5O4 cathode materials were synthesizeded by Deng and others  via a single-step nonaqueous coprecipitation technique, and the lithium excess quantity had been selected at 0, 1, 3, and 5% . The subsample with 5% lithium excess quantity has the smallest lattice parameter and Mn3+ content, which is just contrary to the results of Ref. . Through a facile solid-state technique, LiNi0.5Mn1.5O4 cathode material had been synthesized, and the impacts of various lithium excess quantities (0, 2, 6, and 10%) on electrochemical properties including the physicochemical properties were systematically examined .
Throughout the first charging process, the huge initial ICL and fast capacity fading primarily emerge from the activation reaction of Li2MnO3 element . Some methodologies have been taken to enhance the electrochemical performance of LMNC materials, such as surface modification [81, 82], mild acidic treatment [83, 84], cation doping [85, 86, 87], and structure and morphology controlling [5, 88, 89]. Some metal cations (e.g., Mg , Zn , Al , and Cr ) have been efficiently doped into the structure of Li-rich cathode materials . That the Li(Li0.19Mn0.54Ni0.13Co0.12Ru0.01)O2 cathode indicates a high discharge capacity of 182 mAh g−1 at 5 C with a capacity fade of 0.06% per cycle in 700 cycles because the suitable Ru-doping can foster the stage transition from layered Li(Li1/3Mn2/3)O2 to certain spinel-like stages  and enhance the Li+ diffusion in LMNC had been indicated by B. Song and others . Via a sol-gel technique, X. Jin and others efficiently synthesized Mg-doped LMNC, and the Mg-doping can expand the inter-slap distance of lattices to enhance the Li+ insertion/extraction and enhance rate performance (160.5 mAh g−1 at 1000 mA g−1 and remains 127.5 mAh g−1 after 50 cycles) of cathode materials  and the cycle stability . That Zr dopant can enhance the Li+ diffusion, which efficiently improves the cycle stability and rate performance of LMNC  and sustain the crystal structure of Li-rich cathode had been founded by X. Jin and others . Through improving the systemic stability , the Sn4+ dopant can distinctively enhance the electrochemical performance of cathodes . There has no report on the amelioration in the electrochemical performance of Li-rich Li1.2Mn0.54Ni0.13Co0.13O2 cathode materials by the doping of Sn ions . Sn4+ ions were introduced into the crystal structure of LMNC materials to partially substitute Mn4+ through a sol-gel technique .
The comparatively low electrical conductivity of LiNi0.5Mn1.5O4 results in meager high-rate performance and inevitably limits its practical applications [6, 98]. A surface coating treatment and a solid-state process are usually utilized to synthesize and sustain LiNi0.5Mn1.5O4 with high electrochemical performance [99, 100] as a common technique . The coating modification not just prevents the direct contact of the electrolyte with the inner elements though also enhances the reversible capacity, rate capability of LiNi0.5Mn1.5O4, and cycle performance . The disproportionation reaction of Mn3+ and the oxidation decomposition of the electrolyte could be lowered, and subsequently, the systemic stability of LiNi0.5Mn1.5O4 will be increasing . In surface modification due to its high electronic electrical conductivity, excellent systemic stability , and huge surface area, Graphene has attracted much attention . Designing a LiNi0.5Mn1.5O4-graphene composite structure has been shown as an effective way to enhance electrochemical performance by offering a highly conductive matrix [6, 102]. The distinctive nanostructure, enhanced electrocatalytic activity of the CNF, and graphitic structure, extend their potential application in the electronic, electrochemical, and electrocatalytic, energy-storage fields . We synthesized LiNi0.5Mn1.5O4 cathode materials with nano-micro structures by a process, which spray-drys coprecipitation and calcining, and efficiently introduced the CNF into the LiNi0.5Mn1.5O4 spheres during the coprecipitation spray-drying period . CNF not just increases the bulk electrical conductivity of LiNi0.5Mn1.5O4 powders though also protects the surface of sub-particles .
It is required to break the bottleneck of high capacity density, long cycle life, excellent rate capability for lithium-ion batteries [103, 104, 105], and satisfactory security, with the increased development of the portable electronic tools, hybrid electrical vehicles (HEVs) and electric vehicles (EVs) . Li(NixM1–x)O2 cathode materials were layered by Nickel-rich with high discharge specific capacity, comparatively low cost and considerable rate capability are becoming one of the most fruitful cathode materials for lithium-ion battery . LiNi0.8Co0.15Al0.05O2 with a high tap density, cycling stability and an excellent rate capability is regarded to be the next generation cathode materials for green lithium-ion battery  as the isomorphous solid solution of LiAlO2, and LiNiO2, LiCoO2 . Cathode materials have been devised in the direction of high tap density with the increased requirements of high volume capacity density had been layered by Nickel-rich . An suitable quantity of Ti, which dopes in Nickel-rich, layered materials can improve thermostability and systemic integrity because the Ti4+ ions deter impurity Ni2+ migration into the lithium sites [107, 108, 109] among the doping elements . The LiNi0.8Co0.15Ti0.05O2 cathode materials with a high tap density and a satisfactory spherical morphology have been prepared efficiently by employing the spherical Ni0.8Co0.15(OH)1.9 as precursor; this precursor had been synthesized through a co-oxidation-controlled crystallization technique .
Two crucial improvements could be made to increase the electrochemical performance of Li2FeSiO4, such as coating it with carbon materials [110, 111] and declining the Li2FeSiO4 particle size to circumvent these hurdles . Through tedious calcinations, employing a solid-state reaction technique, micro-sized Li2FeSiO4 particles were prepared at high temperature although the huge particle size had a negative effect on electrochemical performance [8, 112]. Based on iron, soluble lithium, and silicon sources and hydrothermal-assisted or microwave-solvothermal sol-gel techniques, Li2FeSiO4/C commodities can attain satisfactory rate performance [8, 113, 114]. Both the carbon-coating method and carbon source wide range can affect the electrochemical performance of Li2FeSiO4/C . One efficient strategy to enhance the electrochemical performance of Li2FeSiO4/C is cation doping . Hitherto, zinc-, copper-, nickel-, chromium-, vanadium-, magnesium-doped Li2FeSiO4/C cathodes, and cobalt-, have been prepared by the sol-gel technique [8, 115, 116, 117, 118, 119, 120]. Our group indicated that the capacity retention had been substantially enhanced by 10 proportion points after magnesium doping, and doping with magnesium cation had been beneficial for enhancing the cycle performance of Li2FeSiO4/C . It might be supposed that strontium cation doping can improve the electrochemical performance of Li2FeSiO4/C compared with magnesium cation doping . Through the sol-gel technique, we efficiently synthesized strontium-doped Li2FeSiO4/C for the first time . It had been proven that rate performance and the special discharge capacity were enhanced after strontium cation doping because of the Li+ diffusion capability, which is enhanced substantially, via examining electrochemical impedance spectra of the undoped and strontium-doped Li2FeSiO4/C cathodes for the cells .
LiCoO2 had been the cathode material since lithium-ion batteries (Li-ion batteries) had been marketed by Sony in 1991 , which is utilized most extensively . Ni2+ is the just electrochemically active element to lead the high capacity whilst Mn4+ plays as the stable octahedral ion to assure the stability of the layered structure during the intercalation/de-intercalation of Li ions in this material . That material suffers from inherent low electronic electrical conductivity and meager lithium-ion diffusivity that drastically lessen this material’s discharge capacity at high current density even though the LiNi0.5Mn0.5O2 cathode material has many advantages . Kiziltas-Yavuz and others  synthesized LiNi0.4Ru0.05Mn1.5O4 material employing the citric acid-assisted sol-gel technique which delivered the enhanced electrochemical performances . The Ru-doped LiNi0.5Mn1.5O4 cathodes, which summarized high-rate capability, which is enhanced pronouncedly, because of the enhanced ionic and electronic electrical conductivity were indicated by Wang and others [9, 123]. Through doping the Ru element, Wang and others  indicated the amelioration of the electrochemical properties of LiFePO4 cathode materials . We prepared LiNi0.5Mn0.45Ru0.05O2 employing a moist chemical technique, and the structure and electrochemical property of the as-synthesized material were examined for the first time .
The cathode material is a crucial material in lithium-ion batteries, and research and development into high-potential cathode materials is one of the principal ways to enhance the energy density of lithium-ion batteries . At roughly 4.7 V, Spinel LiNi0.5Mn1.5O4 has the advantage of discharge voltage plateaus: low cost, heat stability, and excellent systemic stability, and is regarded one of the most fruitful cathode materials for lithium-ion batteries . The cycling stability of LiNi0.5Mn1.5O4 is meager, and cycling of this material results in the Jahn-Teller effect and Mn break-up [10, 125, 126, 127, 128]. Modification of the material by coating and doping has been utilized to restrain the Jahn-Teller effect and to lessen Mn deterioration in order to enhance the electrochemical properties of the material . Through employing a small quantity of and doping, surface coating and, doping can enhance the rate capability and cycling performance of the material [129, 130, 131], the volume change in the material during the insertion/extraction process of Li ions could be efficiently repressed .
Since an mean 4.0 V (~0.6 V greater than LiFePO4) extraction/reinsertion voltage could be obtained between 3.0 and 4.8 V and the greater theoretical capacity of 197 mAh g−1 for full removal of three lithium ions, NASICON conceptual framework monoclinic Li3V2(PO4)3 (LVP) had been regarded as a prospective candidate for employing as the cathode in lithium-ion battery . LVP undergoes serious capacity, which fades whilst charging up to 4.8 V for the extraction of more than two lithium ions [11, 132]. One efficient strategy is aliovalent or isovalent doping at the transition metal sites, for example, in Li3V2(PO4)3, V3+ has been partly replaced with W5+ , Ti4+ , Zr4+ , Fe3+ , Al3+ [137, 138, 139, 140], Cr3+ , Sc3+ , Y3+ , Mn2+ , Mg2+ [145, 146], and Co2+  to enhance the electrochemical performance by stabilizing the structure during high voltage charging [11, 137]. That Li3V2–xWx(PO4)3/C (x = 0.10) showed better cycle stability than the pure one and greater discharge capacity had been indicated by Xia and others . The initial discharge capacity had been 160.3 mAh g−1 and 95.5% capacity retention had been detected after 50 cycles at 0.5 C rate  for the optimum composition of Li3V1.93W0.07(PO4)3/C . It is required to research metal or LVP/C ions doping LVP/C as cathode material for Li-ion batteries . LVP displays greater capacity and better cycle stability than that of undoped LVP had been carbon-coateded by the Y-doped and .
The high specific energy and power readily available from lithium-ion batteries and the possibility to charge and discharge them hundreds of times are the reason for their crucial relevance in electronic portable tools and future development of hybrid vehicles [12, 148]. Once a battery is operative, the redox reactions affect the electrode materials molecular/crystalline structure, influencing their stability, and consequently necessitate frequent replacement after numerous cycles . In the electrodes that eventually give rise to performance degradation , the high rate exchange of lithium ions requiring produces and more power faster charging strains and significant emphasizes . The issues rise from the effort to increase the cycle life and stability of the cathode materials in standard commercial LIB’s [12, 150]. That work on AuPt alloy transition metal alloy-surface modified spinel LiMn2O4 cathode materials can offer a network for electron diffusion because of a shortened transportation path, i.e., highly crystalline nanostructures , enhanced stage transition kinetics of Li-ion intercalation/deintercalation and high rate discharge capacities , which connects better .
Traditional cathode materials including LiFePO4, LiCoO2 suffer from high cost, inferior cycle stability [153, 154], and huge capacity deterioration . Traditional cathode materials including LiFePO4, LiCoO2’s derivatives and Layered LiNiO2 are fruitful cathode materials for lithium-ion batteries due to low cost  and Traditional cathode materials including LiFePO4, LiCoO2’s high theoretical capacity . LiNiO2 is difficult to synthesize, and its structure is unstable during cycling due to the cation mixing, which results from the comparable ion radius of Li+ (0.76 Å) and Ni2+ (0.69 Å) ions . Ni relates to increase the specific capacity, though the increase content of Ni results in irreversible initial capacities and more cation mixing [13, 156, 157]. Ni-rich layered oxides LiNi1–y–zMnyCozO2 has been extensively researched because of low cost and co’s high discharge capacity in recent decades , including LiNi0.8Co0.15Al0.05O2  and LiNi0.5Co0.2Mn0.3O2 [13, 160]. To circumvent the shortcomings of Ni-rich oxides LiNi1–y–zMnyCozO2 materials by doping with cations [161, 162] and coating with an suitable material [163, 164] are primary techniques till date, doping cations such as Cr3+ , Al3+ , Mg2+ , and so on . We designed a novel composite material with the nominal compositions of 0 in order to build alternatives of traditional cathode materials and LiNiO2 . The novel composite materials were among the medium-high nickel class with low content of cobalt (0.1 ≤ × ≤ 0.19); this class had a comprehensive advantage in the facets of cost control, capacity, and sintering technology compared with Ni-poor or Ni-rich materials . Four various compositions of cathode materials Li(Ni0.56Co0.19Mn0.24Al0.01)1–yAlyO2 (y = 0, 0.02, 0.04, 0.06) were undertaken the researches on electrochemical behaviour . The results were compared with that of the traditional LiNi0.8Co0.15Al0.05O2 and LiNixCoyMn1–x–yO2 materials .
Due to its low cost, relative abundance, eco-friendliness, stability [168, 169, 170], and high columbic efficiency, LiMn2O4 with a 3-D tunnel structure for the migration of lithium ions appears to be one of the most fruitful cathode materials for Li-ion batteries among the multiple cathode materials . LiMn2O4 has satisfactory cycle performance and high capacity, while lithium ions’ rate performance needs to be enhanced compared with the other cathode materials . Another of the tactics to enhance the lithium-ion intercalation capacity and rate capability of electrodes is to prepare and use materials with nano-size [14, 171, 172, 173]. The preparation of nano materials normally entails some various mechanisms, such as sol-gel technique , hydrothermal techniques [175, 176, 177], and coprecipitation , though these techniques are normally expensive, complex, and time-consuming . We have synthesized nano-sized LiMn2O4 materials employing a comparatively straightforward single-step solid-state reaction technique . Is utilized as a functional material to lose volatile gases during the process of calcining in order to change the particle size of materials [179, 180, 181] and control the morphology had been acided by Oxalic . The suitable crystallinity needs to be reasonably well controlled for obtaining the surface area of the particles including satisfactory electrochemical performance at high C-rates . Through adjusting the content of oxalic acid, the crystallite structure, capacity, powder properties, and power capability of obtained LiMn2O4 with various morphologies and particle sizes have been assessed and compared .
High capacity cathode materials with long-lasting cycle life is one of the hottest topics in lithium-ion battery research in recent decades . The marketed cathode materials for lithium-ion batteries including LiCoO2, LiMn2O4, LiNi1/3Co1/3Mn1/3O2 and LiFePO4 indicate discharge capacities of below 200 mAh g−1 with the operating voltage variety of 2.8–4.4 V [15, 182]. More and more scholars have concentrated on the series of Li-rich layered composite xLi2MnO3·(1−x)LiMO2 (M = Ni, Co, Mn, Ni1/2Mn1/2, Ni1/3Co1/3Mn1/3…) as cathode materials for their high reversible capacities (200–300 mAh g−1) [15, 138, 183, 184, 185, 186, 187, 188]. Li2MnO3 is the crucial element because it can offer further high capacity when electrochemically activated above 4.4 V [189, 190, 191, 192] and sustain the crystal structure for the composite in this material . The diffusion of lithium ions from octahedral sites in the Li2MnO3 element to tetrahedral sites in the lithium-depleted layer, considerably stabilizing the composite structure during the cycling process [15, 193]. Complete extraction of Li2O from the inactive Li2MnO3 element yields electrochemically active layered MnO2 stage, improving the discharge capacity of the material [15, 194, 195]. In the preparation of the Li-rich layered composites, by which the starting materials could be mixed on molecular level, coprecipitation technique is commonly used . Throughout the washing process, employing coprecipitation technique, many of the transition metal ions in the raw materials will be lost . Materials have been synthesized by hydrothermal technique [196, 197, 198] had been layered by Li-rich . There are handful reports about Li-rich layered material preparation by a combined technique of hydrothermal process and template . We first report the use of carbon nanotubes (CNTs) as template actor during hydrothermal process to synthesize nanosized Li-rich layered material 0 .
Lithium-ion batteries with LiNi0.5Mn1.5O4 as the cathode material are regarded to be the most fruitful rechargeable energy storage systems due to the advantageous properties of LiNi0.5Mn1.5O4, including its low production cost, long cycle life, environmental compatibility, in particular, and satisfactory thermal stability, high energy density of 630 Wh kg−1 [199, 200, 201] and its high discharge voltage of 4.7 V . The electrochemical performance of cathode materials is dependent upon both academia and industry’s composition not just though also on both academia and industry’s morphology and particle size [16, 202, 203]. Some scholars have sought synthesizing LiNi0.5Mn1.5O4 with nanoparticles because small size and its huge specific surface area favour fast electrode kinetics, shortening pathways for Li+ and, nanoparticles aggregate readily electronic transportation, which can improve the rate capability of the cathode material [56, 204, 205]; and have a small tap density, which are disadvantageous to the other electrochemical properties of the material . Spherical secondary microparticles, formed via aggregation of nanosized primary particles, are complementary to the insufficiency of the nanoparticles and enhance the electrochemical performance of the cathode materials . Some spherical secondary LiNi0.5Mn1.5O4 particles have been synthesized [16, 206, 207, 208, 209, 210]. The principal techniques of preparing these spherical secondary particles are the spray, which drys granulation [206, 207], and template techniques [16, 208, 209, 210]. Materials that are synthesized by this reaction display inferior electrochemical and physical properties due to huge particle sizes , and their block-like, irregular morphology . Micrometer-sized, spherical secondary LiNi0.5Mn1.5O4 particles, comprised of nano-and/or sub-micrometer-sized particles, were efficiently prepared employing this technique . We synthesized two LiNi0.5Mn1.5O4 samples employing the enhanced and conventional (LNMO-A) solid-state techniques (LNMO-B) to examine the electrochemical properties .
Lithium-ion batteries (Li-ion batteries) have been extensively employed as the storage of renewables and power vehicles, in view of their several virtues associate with high-energy-density, environmental benignity, and long cycle life . That fosters the development of high-power cathode and high-energy materials (Goodenough and Kim ; Tarascon and Armand ), . Such lithium-rich high-capacity materials suffer from meager cycle stability and inferior rate property; this stability hinder their successful commercialization in high-energy-density lithium-ion batteries (Boulineau and others ; Thackeray and others ; Xu and others ), . Under consequence in inferior cycling performance (Guo and others ) and high operating potentials, these nanoscaled materials with high surface activity might arouse undesired electrode-electrolyte reactions . It is reasonably well recognized that the morphology of the cathode materials has a significant effect on the electrochemical performance . Nano-sized hierarchical hollow structures and Micro have been indicated as optimal architectures for cathode materials to attain long cycling stability and high rate capability because they present the advantages of both nano-sized building blocks and microsized assemblies (Li and others [216, 217]; Wu and others ; Lin and others ; He and others ), . Throughout electrochemical process, which ows to the short diffusion pathways of electrons and an suitable contact area between electrode and electrolyte, lithium ions, and stable structure, these hollow structure electrode materials might exhibit excellent electrochemical performances . An efficient technique to prepare hollow sphere materials in microsize (Abdelaal and Harbrecht ) is employing cetyltrimethylammonium bromide (CTAB) and Sucrose as a combined template . We employ sucrose and CTAB as a soft template, which is combined with hydrothermal assisted homogenous precipitation technique to fabricate hollow sphere cathode material, to improve the electrochemical performance of the Li1.2Mn0.54Ni0.13Co0.13O2 material . That technique indicates a route to synthesize the hollow microspheres assembled by nano-sized primary particles and provides a strategic strategy to enhance electrochemical performances for lithium-ion batteries .
The layered structure series material LiNi1–x–yCoxMnyO2 (NCM) has received increased attention [18, 222]. LiNi1/3Co1/3Mn1/3O2 compound, which Makimura  and Ohzuku devised, has been regarded as a fruitful candidate of next-generation cathode materials to substitute LiCoO2 for rechargeable Li-ion batteries . Since the combination of nickel, cobalt, and manganese, can offer advantages including greater theoretical capacity, milder thermal stability, and lower material cost, this material has aroused significant interest . LiNi1/3Co1/3Mn 1/3 – O2 suffers from two shortcomings of the toxicity and high cost of cobalt; in addition, thermal stability, the actual capacity, and rate capacity of LiNi1/3Co1/3Mn1/3O2 needs to be enhanced [18, 224]. The development of alternative cheap cathode materials with satisfactory thermal stability and high-specific capacity becomes the unavoidable trend [18, 225]. That Co3+ is just oxidized to Co4+ at rather high voltage in this material  had been revealed by principles computation , Some scholars have attempted to cost decrease and enhanced the capacity and thermal stability by employing other element to substitute of Co . It has been shown that Al or Ti substitute of Coon LiNi1/3Co1/3Mn1/3O2 compound enhanced the thermal stability [18, 227]. Fe3+ has variable valence; this valence means ferrum additive on Li[Ni1/3Co1/3Mn1/3]O2 will have greater discharge capacity in theory . Preliminary discharge specific capacity of Li[Ni1/3Co0.67/3Mn1/3Fe0.33/3]O2 had been 122.24 mAh/g with a charge and discharge rate of 36 mAh/g in 3.0–4.5 V, which had been similar to the specific capacity of the state-of-art LiCoO2 cathode material of LIB [18, 228]. Li[Ni1/3Co1/6Mn1/3Fe1/6]O2 compound has been revealed that Fe substitution gives rise to a lower potential at the end of charge synthesized .
The spinel-type LiNi0.5Mn1.5O4 with a high operating-voltage (∼5 V) retains the readily available 3-D channels for the fast diffusion of Li+ ions, providing a high energy density of 640 Wh kg−1 and a theoretical specific capacity of 147 mAh g−1 [229, 230, 231, 232] with the previously marketed positive electrode materials including LiCoO2, LiFePO4, etc. . That material LiNi0.5Mn1.5O4 still suffers from numerous difficulties that should be circumvented, including comparatively low first-cycle columbic efficiency (75–85%) because of the electrolyte decomposition at high operating voltage, dissatisfied rate performance [230, 233] and meager cycling performance at high temperatures (50–60 °C) . Some tactics including surface coating, lattice doping, and high-voltage-tolerant electrolytes, are devised to additional enhance its electrochemical properties to fulfil the commercial demands . Some articles have indicated various coating materials for LiNi0.5Mn1.5O4, including Li4Ti5O12 , Li3PO4 , Al2O3 , carbon [237, 238, 239], ZnO , and so on, which can safeguard the particle surface against the electrolyte erosion at a high temperature or at a high voltage . Zhong and others have prepared lattice-doped LiNi0.5Mn1.5O4 materials employing trivalent Fe, Cr, Co, and Al to substitute Mn or Ni in LiNi0.5Mn1.5O4 [19, 241, 242]. They have barely accomplished considerably amelioration on their electrochemical properties compared with the trivalent metal-doped LiNi0.5Mn1.5O4 and the pristine . It is reasonable to say that the lattice, which dops with high valence (>+2) metal ions, has been quite mature, though the effect of divalent doping for the LiNi0.5Mn1.5O4 is not good . Especially at a high temperature (55 °C), the LiNi0.45Cu0.05Mn1.5O4 subsample indicates satisfactory cycling stability .
Hereinto, the tavorite-like LiMPO4F (M = V, Mn, Fe, Co, Ni.) cathode materials are composed of 1D chains of metal octahedral interlinked by phosphate tetrahedral; this tetrahedral enable electron transport [20, 243]. It has been examined as cathode materials for Li-ion batteries since LiFePO4F indicated by Barker and others without electrochemical performance [20, 244]. LiFePO4F has been synthesized efficiently through multiple techniques, including solid-state [245, 246, 247, 248], sol-gel , ionothermal  technique, solvothermal [251, 252], and others Recham and others highlight the efficacy of ionothermal synthesis in the preparation of irregular morphology LiFePO4F with the particle size of 2–5 μm, and the as-prepared LiFePO4F displays ~130 mAh g−1 at C/15 after ten cycles [20, 250]. A cheap and environmental friendly solvothermal process to prepare matchstick-like LiFePO4F with lengths up to 1 μm, which exhibits a discharge capacity of ~123 mAh g−1 at C/50  is indicated by Ellis and others . Through Choudhury and others utilizing a low melting flux route, Plate-like LiFePO4F with numerous hundred nanometers is prepared, and the synthesized subsample retains the discharge capacity of 146 mAh g−1 (97% of theoretical capacity) at C/50 [20, 253]. There are seldom indicated about almost monodisperse LiFePO4F nanospheres . It is highly advantageous to build an approach to synthesize homogeneous LiFePO4F nanospheres . We build an approach to synthesize almost monodisperse LiFePO4F nanospheres through solid-state route, which is correlated with precipitation technique . The FePO4 had been subsequently mixed with LiF, and had been sintered to derive almost monodisperse LiFePO4F nanospheres . The structure and electrochemical performance of almost monodisperse LiFePO4F nanospheres are examined .
Oxides xLi2MnO3·(1−x)LiMO2 (M frequently relates to Ni, Co, Cr, and Mn) are regarded to be alternative cathode materials because of greater capacity (>250 mAh g−1), winder voltage variety (2.0–4.8 V), better security [254, 255, 256, 257, 258, 259], and lower cost, were layered by the lithium-rich . Some efforts have been indicated to enhance the electrochemical performance by many techniques including surface modification, doping [260, 261, 262], and nanoparticle, in order to satisfy requirement commercialization . Cations doping has been demonstrated as an efficient technique to enhance the systemic stability of cycle stability  and cathode materials . Partial substitutions of the transition metal in xLi2MnO3·(1−x)LiMO2 with Cr , Zr , V , Mg , Al , or Na , have been indicated for improving the longer-term cycle performance by enhancing the systemic stability . As one of the most efficient doping elements, Cr has been intensively utilized by scholars to improve the electrochemical performance of lithium-rich layered oxides over the past numerous years [21, 264, 269, 270, 271, 272]. Some of the advantages of Cr doping can be outlined as (i) Cr doping can improve the activation of Li2MnO3 below room temperature  and (ii) the following: (i) Cr3+/Cr6+ redox is electrochemically active in contributing capacity in Li-rich layered cathodes [21, 269]. The samples Li1.2Ni0.16Mn0.56Cr0.08O2 and Li1.2Ni0.2Mn0.6O2 were selected as a representative material of the Mn-based layered oxides to highlight the Cr-doping processes by the application of electron and lithium-ion diffusion X-ray and coefficient diffraction (XRD) and XPS (before and after cycling) .
Previous studies were concentrated on understanding and tailoring either the chemical composition or physical structure of the material (Ding and others ; Pampal and others ) for additional improving the comprehensive performances of Li(Ni0.5Co0.2Mn0.3)O2 . The physical structures, including particle size, particle morphology and its distribution, stage purity, and crystallinity in addition to Li+/Ni2+ cation mixing (Ding and others ; Kuriyama and others ; Yuan and others ), which substantially impacted the electrochemical properties of the cathodes, were optimized, as reasonably well . The crystallite size is as crucial as crystalline stage, the elemental composition, and morphology because of its feature systemic elements in between the isolated atoms and the bulk macroscopic material (Waje and others ) in a nanometer-sized crystalline material . Several relationship between crystallite sizes for multiple materials and the properties have been examined (Pukazhselvan ; Mguni and others ; Iqbal and others ; Upadhyay and others ; Zhao and others ; Tlili and others ), . It could be observed that the natures of the material could be substantially dependent upon crystallite size (Burton and others ; Uvarov and Popov [285, 286]; Yashpal and others ; Sikora and others ), . XRD is a method for crystallite size determination of nanocrystalline materials, which is utilized potent and frequently, in the present time . The impacts of the calcining temperatures on the morphology, electrochemical performances of Li(Ni0.5Co0.2Mn0.3)O2, and structure, have been deeply examined (Kong and others [289, 290]) . Calcination temperature had been observed to specify the microstructure (particularly the crystallite size) of the material in the process of preparing Li(Ni0.5Co0.2Mn0.3)O2 by a high-temperature solid-state technique . In the thermal and electrochemical stability performances of the material, the crystallite size plays a distinctive role . No or handful researches have been carried out systematically on insights into the correlation between crystallite size and the performance of the Li(Ni0.5Co0.2Mn0.3)O2 active material up to now .
LiCoO2, LiNiO2, LiFePO4, LiMn2O4 and LiNixCoyMn1–x–yO2 are the most frequent cathode materials utilized in Li-ion batteries [23, 291, 292, 293]. Spinel LiMn2O4 has been intensively studied as cathode material for nontoxicity [294, 295] and its low cost among the several transition metal oxides . The development of hybrid electric vehicles (HEVs) and plugin hybrid electric vehicles (PHEVs) demands for lithium-ion batteries with high power and safety stability, though the conventional LiMn2O4 material can not satisfy the technical requirements . Some studies have concentrated on the substitution of Mn with other transition metal elements to form novel spinel cathode material [296, 297] to enhance the cycle performance of LiMn2O4 . LiNi0.5Mn1.5O4 cathode material has been observed as one of the most prospective lithium-ion battery materials because of high discharge platform [298, 299] and its high theoretical capacity (147 mAh g−1) among multiple doped materials . Carbonate and oxalate are utilized as precipitants for preparing LiNi0.5Mn1.5O4 cathode material by coprecipitation technique . Through hydroxide coprecipitation technique [300, 301], compared with oxalate precipitation technique or carbonate, some spherical cathode materials (LiCoO2, LiNiO2, LiCo1/3Ni1/3Mn1/3O2) with high tap density, better thermal stability and homogeneous particle size can be synthesized . The high content of OH− and Mn2+ is easy to form fine hydroxide precipitant nucleation , and the pure LiNi0.5Mn1.5O4 cathode material with regular spherical morphology is hard to be prepared by hydroxide coprecipitation technique . Spherical LiNi0.5Mn1.5O4 cathode material had been efficiently synthesized through coprecipitation technique with the help of sodium hydroxide as ammonia as complexing actor and precipitant . Excellent electrochemical properties were shown by the prepared pure LiNi0.5Mn1.5O4 cathode material with spherical morphology .
LiFePO4 has low electrical conductivity (∼10−11 S cm−1) and low lithium ion diffusion dynamics (∼1.8 × 10−14 cm2 s−1) at room temperature (RT) [24, 303]. Two properties-small-sized cathode and homogeneous conductive coating-are thought to substantially improve the ionic and electric kinetics of LiFePO4 under low temperature and foster −20 °C’s low-temperature performance among multiple techniques to solve this issue . The nano-scale size of LiFePO4 and homogeneous carbon coating of 6.7 wt% by oleylamine medium and post-heat treatment for 4 h; this composite material, which is delivered excellent low-temperature performance, had been accomplished by Fan [24, 304]. Wu  devised a polyol route to fabricate two layers of carbon-coated nano-LiFePO4 cathodes with mean primary particle size of ca 90 nm, which a later calcining process for 8 h to attain satisfactory low-temperature performances followed . Uniform carbon coating and these nanosized commodities are responsible for the excellent low-temperature performance . The production expenses of these mechanisms are fairly high because not just are the raw materials including Fe (Cl)2 costly and Fe (Ac)2, though also these soluble raw materials might give rise to low crystallinity of the commodities after liquid-phase decrease . Such fine-sized particles below 100 nm might decline the tap density and give rise to inferior processing performance, which is utilized when commercially as cathodes for lithium batteries . We have observed that LiFePO4/C prepared by a polyol route retains a high capacity retention after 300 cycles  and an excellent room temperature performance with a high rate capability . The low-temperature performance (0, −10, and −20 °C) of as-prepared LiFePO4/C will be examined .
Since organic electronic tools are based upon thin films, flexibility, light weight, large-area application [307, 308, 309, 310] including semitransparency, such materials showed their low processing and cost advantages . CNTs have been intensively studied for their distinctive properties including 1D tubular structure, high thermal and electrical conductivities, exceedingly huge surface area and mechanical, optical properties since discovery in 1991 [25, 311]. The development of novel electrodes having a huge surface area, high electric/thermal conductions and a short diffusion is required to circumvent the drawbacks of traditional materials . Shao et al.  has indicated the synthesis of SnO2-based composite coaxial nanocables with multi-walled CNTs and polypyrrole (PPy), SnO2@CNTs@SnO2@PPy; these nanocables display a reversible capacity as high as 600 mAh g−1 and a columbic efficiency close to 100%, which is potential for practical application in lithium-ion batteries . Zhao et al.  indicated the synthesis of a new CNTs@SnO2@PPy coaxial nanocable as superior anode material with SnO2 particle size of 2–3 nm, furthermore this composite showed a high capacity of 823 mAh g−1 after 100 cycles . The combination of P3HT and CNTs might be interest materials for potential cathode materials in Li-ion batteries . The approach to increase the dispersion of P3HT-g-CNTs in solution to form the nannocomposite, which additional utilized to combine with doped spinel LiNi0.5Mn1.5O4 (LNMO) for fabrication of cathode materials as LNMO/P3HT-g-CNTs nano-composites in Li-ion batteries had been summarized by us . Through electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), the efficiency of the electrode materials employing LNMO/P3HT-g-CNTs nano-composites had been assessed .
Lithium-sulphur accumulators are one of the fruitful potential ways of commercial accumulators’ development . Practical use of lithium-sulphur accumulators is quite tempting due to the quite high theoretical capacity of sulfur-1675 mAh/g; this mAh/g, in combination with the potential around 2.1 V against lithium, means that its gravimetric energy density reaches about 3000 Wh/kg [26, 314, 315]. The theoretical capacity of sulfur is considerably greater than the capacity of currently readily available cathode materials as LiMn2O4 (148 mAh/g) , LiNi1/3Mn1/3Co1/3O2 (280 mAh/g) [151, 316, 317] or LiFePO4 (170 mAh/g) [26, 318]. The fact that there is no intercalation process of lithium ions during conversion of materials though cycling happens during cycling is one of the largest difficulties of this accumulator kind . A compound of sulfur and lithium-Li2S (lithium sulfide) is the consequence of this conversion . The resulting polysulphides, Li2S8 to Li2S4, are soluble in the electrolyte and they deposit on the anode surface of metal lithium during cycling which gives rise to a quite steep drop of the capacity during cycling [26, 319]. Its low electrical conductivity (5 · 10−30 S/cm), which results from the fact that sulfur is an insulator [320, 321], is an further drawback of the material . Another possibility is to encapsulate sulfur with carbon; this carbon prevents the release of polysulphides into the electrolyte and increases electrical conductivity of the sulfur particles [26, 322, 323]. Such polymers are conductive and deter the break-up of polysulphides into the electrolyte and these materials have their own capacity [26, 324]. The creation of a special 3D cathode structure into which sulfur is enclosed, which prevents thereby the deposition of polysulphides at the anode side [325, 326, 327], is another possibility .
The olivine LiFePO4 (LFP) has aroused more substantial attentions because of its stable performance, high capacity retention, excellent thermal stability, environment-friendly, and cheap since the first introduction to science community in 1997 . Some synthesis procedures (e.g., ball-mill combination with solvothermal/hydrothermal) were indicated to give the practical capacity closely to theoretical value as 170 mAh/g  among various methodologies for improving the electrochemical performance of LPF material; these methodologies were previously indicated . A detailed review of advancements of issues of LiFePO4 and lithium-ion batteries as one fruitful cathode material had been carried out by Li and others [27, 329]. That significant progress was made in enhancing the electrochemical performance of LiFePO4 cathode material by coating, doping supervalent cation, and minimization of particle size, had been concluded by previous reports . The exact mechanism for increasing electronic electrical conductivity to comprehend the kinetic behaviour of LiFePO4 synthesis is required [27, 330, 331]. Based on carbon coating appears to be efficient strategy to improve electrochemical performance of LiFePO4, particularly at high charge-discharge rate . The results were because of the wrapping of highly conductive thin rGO sheets; these sheets increasing the electronic electrical conductivity of the LiFePO4 . Several researches which examined the electrochemical performance of LiFePO4 composite by use of graphene are observed in [27, 332, 333, 334, 335]. The transport properties should be greater, which depends additional on the mixing/coating of substances on molecular level  in order to derive the satisfactory electrochemical performance of cathode materials . The principal issue is to synthesize the homogenous mixture of LiFePO4 and C, and consequently, in situ techniques are required which motivated authors to examine its electrochemical performance and build a novel cathode material (nanocomposite) of LiFePO4/C .
Lithium-ion batteries (Li-ion batteries) continue to power consumer electronics and are increasingly utilized in defense, aerospace, and automotive, applications due to their high energy density (Larcher and Tarascon ; Thackeray and others ) as a state-of-art energy storage system . It is hard for sodium-ion batteries (SIBs) to compete with Li-ion batteries in compact applications because of lowered energy density, SIBs are considered as the most fruitful complements to Li-ion batteries for large-scale electrical storage applications (Palomares and others ), . Mn-based cathodes for Li-ion batteries and a critical criterion for the development of future Fe-is to attain similar or even greater energy densities . Through discharge potential and its Li storage capacity, the energy density of cathode material is dictated collectively . Taking advantage of plentiful Na sources, SIBs hold the promise to support large-scale energy storage applications, which is critical in harnessing intermittent renewable energies including wind and solar power . The research advancements on Fe- and Mn-based cathode materials for Li-ion batteries and SIBs, respectively, which are grouped into polyanion compounds, oxides, and hexacyanometalates (for SIBs) are presented by this review . We additional put forth many insight into the opportunity of Fe- and Mn-based cathode materials and explore the impendent issues and prospects in this field with a grasp of the inherent properties and up-to-date accomplishments of these candidates, particularly highly stable SIB cathodes and high-energy LIB cathode candidates . That this review can inform Mn-based cathode materials and readers of the rationality and priority of Fe-as candidates for future Li-ion batteries and SIBs, and call for additional efforts to satisfy this aim is hoped by us .
LiNi0.5Mn1.5O4 has been acknowledged as one of the most tremendous high-voltage cathode materials for Li-ion batteries [29, 339, 340]. The electrolyte becomes instable and easy to be broken down at high voltage (4.7 V), leading to the formation of a deleterious solid electrolyte interface (SEI) film that inhibits the Li+ ion migration and induces the capacity fading [341, 342] the practical application of the LiNi0.5Mn1.5O4 material is restricted because LiNi0.5Mn1.5O4 suffers from serious drawbacks: (1) and (2) the break-up of Mn ion degrades the quality of LiNi0.5Mn1.5O4 cathode during cycling, resulting in the irreversible capacity deterioration [343, 344, 29]. A series of tactics have been undertaken to circumvent these shortcomings, such as surface modification and cation substitution in order to improve electrochemical properties of the LiNi0.5Mn1.5O4 material . Surface coating materials can deter the immediate contact between electrolyte and the spinel LiNi0.5Mn1.5O4 material so as to safeguard the active material from HF corrosion . Some compounds, including metal oxides (e.g., ZnO [240, 345], Bi2O3 , Al2O3 ), metal phosphates (e.g., FePO4 , LiFePO4 ), and metal fluorides (e.g., AlF3 , MgF2 , BiOF ), have been utilized as a coating film of LiNi0.5Mn1.5O4, leading to the amelioration in cyclic stability of the LiNi0.5Mn1.5O4 materials and the rate performance . An optimal electrode material for Li-ion batteries because of its high reversible capacity, huge theoretical Li-storage capacity of 770 mAh g−1 (9 mol Li could be stored in 1 mol BiFeO3) [351, 352], and excellent capacity retention, is BiFeO3 . Given the semiconductor character of BiFeO3 and the excellent electrochemical properties, it could be reasonably anticipated that the surface coating of BiFeO3 might enhance the electrochemical properties of LiNi0.5Mn1.5O4 cathode material . Through a BiFeO3 coating on the spinel LiNi0.5Mn1.5O4 through moist chemical technique and a combined coprecipitation, the cathode materials were obtained . It had been demonstrated that the coating of BiFeO3 can improve the electrochemical performance of coated materials .
The layered lithium transition metal oxides have been intensively examined as the cathode materials in the next generation of the rechargeable lithium-ion battery (LIB) [30, 223, 353]. In contrast with the commonly used layered ternary or LiCoO2 cathode materials with α-NaFeO2 structure, layered Li-rich Mn-based ones constituted as yLi2MnO3·(1–y)LiMO2 (M = Co, Ni, Mn, etc.) or Li[Li(1/3–2x/3)MxMn(2/3–x/3)]O2 have many advantages including lower cost, safer on overcharge [194, 354, 355], and less toxic . They have high capacities about 250 mAh g−1 at high voltage, which can play a key role in stabilizing the electrode structure [189, 194] and supply the excess lithium to the layered structure . Such coatings are usually unfavourable for both lithium ion conduction and interfacial charge transfer of the electrode, because above insulative coatings can increase the Li+ diffusion length, which results in the deterioration of electrochemical performance [30, 356, 357]. Nano-sized monoclinic Li2TiO3 has a high AC electrical conductivity of 10−3 S cm−1 , considerably greater than that (10−6 S cm−1) of the layered Li-excess Mn-based oxides [30, 359]. 2.5 × 10−7 S cm−1 , considerably greater than that (10−16–10−12 S cm−1) of the layered Li-rich Mn-based ones [361, 362] because of the meager lattice and electrical conductivity disorder of Li2MnO3 domain is the Li+ ion electrical conductivity of Li2TiO3 . Li2TiO3 has a 3-D diffusion path for lithium ion diffusion, where the Li+ migration can occur along c-direction [357, 363] as a layered material . The impact of the Li2TiO3 loading on the rate capability and cyclability of the Li-rich layered oxide had been especially tackled .
Nickel-rich layered Li(Ni1–x–yMnxCoy)O2, whereby the composition of Ni is hegemonic over Mn and Co, is a fruitful material due to its lower cost, lesser toxicity, enhanced thermal stability, safety [364, 365, 366, 367], and sound cycling stability . High capacity is provided by Ni, Mn establishes an excellent cycling stability, because of co’s sound chemical and electrochemical stabilities when electrolyte contact happens, and Co offers an increasing electrical conductivity that affects rate performance, in these materials . The electrochemical performance of Ni-rich materials still needs to be additional enhanced . The serious capacity fading of Ni-rich materials during cycling, particularly those materials with high cut-off voltage, is because of the comparatively meager low diffusion and electronic electrical conductivity rate of Li+ within the structure [31, 368]. A handful studies on Na-doped layered Li-rich materials have been carried out . Ni-rich cathode materials have not yet been examined whilst both of these groups indicated that Na doping had been efficient for improving the rate capability, systemic properties of Na-doped, layered and the impacts of Na+ on the cycling performances . We examined the impacts of Na doping on the structure, electrochemical performances of the Ni-rich cathode material, and morphology, and explore the details .
Layered LiMO2 (M = Mn, Co, Ni), LiNi0.3Mn0.3Co0.3O2, olivine-type LiFePO4, spinel-type LiMn2O4, lithium-rich material xLi2MnO3·(1−x)LiMO2 (M = Co, Fe, Ni1/2Mn1/2), etc. are the principal cathode materials for rechargeable lithium-ion batteries . Throughout the cycling process [369, 370, 371, 372, 373], coating the cathode material with multiple particles or films such as SiO2, ZnO, CeO2, LaF3, FePO4, etc. can efficiently minimize the direct contact area between electrolyte and additional hinder the Mn break-up and the LiMn2O4 electrode . ZnO had been viewed as an advantageous surface-coating material because of thermal stability and its excellent chemical . Some researches of ZnO-coated LiFePO4, LiMn1.5Ni0.50O4, LiMn2O4, and LiNi0.5Co0.2Mn0.3O2, have been indicated by employing various coating methods to enhance their electrochemical performance [32, 374, 375, 376, 377, 378]. Via the melting impregnation technique, ZnO had been coated by Tu and others  on LiMn2O4 particles . ZnO-coated LiMn2O4 had been indicated by Liu and others  by the sol-gel technique . An mean capacity deterioration of 0.19% per cycle in 50 cycles under a current rate of 0.5 Zhao, C. More recently and others  utilized the ALD technique to deposit highly conformal and ultra-thin ZnO coatings onto LiMn2O4 cathodes had been delivered by the 2 wt% ZnO-coated LiMn2O4 . There are no reports on ZnO-coated LiMn2O4 cathode materials prepared by a combustion technique till date to the optimal of our knowledge . ZnO had been sampled for coating over the surface of LiMn2O4 cathodes to additional enhance cycling performance and their capacity . The impacts of coating on the structure, electrochemical performance of cathode materials, and morphology, are examined in detail .
Layered LiNi1/3Co1/3Mn1/3O2 as cathode material has been paid extensive attention because of its high reversible capacity, low cost, and excellent systemic, thermal stability, as reasonably well [33, 223, 381]. Serious problems concerning the capacity must be circumvented for their additional application, which would consequence from the decomposition of electrolyte at the high operating voltage, hydrofluoric acid (HF) attack in LiPF6-based electrolyte, and stage transition, particularly at temperature [382, 383], which is elevated, even though tremendous progress has been made in layered LiNi1/3Co1/3Mn1/3O2 as much inferior rate performances and fading . Tremendous efforts have been dedicated to the amelioration of the cyclic stability and thermal stability for layered LiNi1/3Co1/3Mn1/3O2 by coating with carbon or conducting materials, doping with metal ions, and reducing the particle size . Liu and others  have confirmed that the surface modification of LiNi1/3Co1/3Mn1/3O2 with FePO4 indicates high discharge capacity of 143 mAh g−1 with a retention of 87.7% at a current density of 150 mAh g−1 after 100 cycles . The inherent semiconducting behaviour of metal oxide might consequence in the meager rate performances and increase the electrical resistance among LiNi1/3Co1/3Mn1/3O2 particles . High electronic electrical conductivity of coating layer must be highly advantageous for high rate lithium batteries besides the protection from HF attack in electrolyte . Owing to its injecting photocurrent behaviours by irradiates, Eu2O3 is regarded as a fruitful coating layer for examining the link between coating layer electrical conductivity and the enhanced performances, and even for potential application in novel notion batteries . Eu2O3 material has excellent thermal stability, refractory properties, and chemical stability . LiNi1/3Co1/3Mn1/3O2@Eu2O3 present enhanced thermal stability and considerably better electrochemical performances .
Significant attention has been paid to lithium-rich manganese-based layered structure electrode materials [usually designated as xLi2MnO3·(1−x)LiMO2 (M = Ni, Co, Mn, etc.)] and has been one of the most fruitful energy storage tools for large-scale applications because of their high power density, long calendar life (Yuan and others ; Zhou and others ; Jin and others ) and huge theoretical specific capacity (~250 mAh g−1), . That lithium-rich layered materials are comprised of Li2MnO3 element and LiMO2 element to form a homogeneous solid solution structure (Lee and Manthiram ; Tabuchi and others ) is usually thought by scholars . Upon the activation of the Li2MnO3 element which refers to an irreversible potential platform for the extraction of Li and oxygen (as Li2O) by initially charging to 4.5 V (Nayak and others ; Li and others ), the lithium-rich layered materials display a high discharge specific capacity . In the subsequent discharge/charge process, the transition metal ions occupy oxygen vacancies formed during the activation process and seem to migrate to the octahedral vacancies in the lithium layers via the adjoining tetrahedral sites, resulting in the reconstruction of the surface layer structure (Zheng and others ; Chen and others ; Zheng and others ), . Rate performance of lithium-rich layered materials and the unsatisfactory cycle performance need to be additional enhanced . The surface coating of lithium-rich layered cathodes can offer a physical protective layer to change their surface chemistry, improving the electrochemical properties of these cathode materials (Chen and others ; Zhao and others ; Li and others ), . It is indicated that FePO4-coated cathode material Li1.2Mn0.54Co0.13Ni0.13O2 (Wang and others ) for delivering a discharge specific capacity of 202.6 mAh g−1 between 2.0 and 4.8 V at 0.05 C with a high coulomb efficiency of 85.1% after 100 cycles . That excellent electrochemical performance had been attributable to the coating layer to electrochemical performances of Al2O3 coated Li1.2Mn0.54Co0.13Ni0.13O2 materials and additional research the structure .
The capacity deterioration upon cycling at elevated temperatures (55 °C) of LiMn2O4 is still an obstacle for its practical application, which results from the synergetic effect of following possible processes [169, 399, 400, 401, 402]: (1) Mn2+ break-up into the electrolyte through the disproportionation reaction of 2Mn3+ → Mn2+ + Mn4+, (2) irreversible systemic reconfiguration which is caused by Jahn-Teller distortion, and (3) the thermal decomposition of electrolyte at high voltages . Doping with transition metal (Al [403, 404], Mg [405, 406], Ni , Co [408, 409], Cr ) is utilized to enhance its performance at temperature, which is elevated, and sustain the structure of LiMn2O4 . One common strategy is coating with metal oxides including Al2O3 , Fe2O3 , TiO2 , Y2O3 , and V2O5  to lessen the electrochemically active surface area and deter undesired side reactions between cathode material and electrolyte . The intercalation/de-intercalation of lithium ion will be hampered by those metal oxides, so it is required to seek for an optimal coating layer to improve the interfacial stability of LiMn2O4 electrode without influencing the Li ions’ transfer between electrolyte and electrode . Electrode material like LiNi0.5Mn0.5O2 , LiNi1/3Co1/3Mn1/3O2 , LiNi0.5Mn1.5O4  as surface coating layer for LiMn2O4, and LiNixMn2–xO4 , has drawn the attention of persons . That Li2MnO3 can act as a stabilized coating layer on the surface of other cathode materials to safeguard those materials from directly exposing to the electrolyte without impeding the intercalation/de-intercalation of lithium ion had been anticipated by us . We report a facile technique to synthesize LiMn2O4@ Li2MnO3 composites with multiple coating content, then the Li2MnO3 stage had been coated on the surface of the spinel, which a sol-gel route LiMn2O4, and in which the pristine LiMn2O4 powder had been fabricated through a characteristic high-temperature solid-state reaction .
The most fruitful candidate among the 5 V cathode materials for Li-ion batteries because of its flat plateau at 4.7 V , a two-electron process Ni2+/Ni4+, and huge specific capacity (146.6 mAh g−1), where the Mn4+ ions remain electrochemically inactive [339, 420] is the high-voltage LiNi0.5Mn1.5O4 (LNMO) cathode . LNMO had been systematically studied and extensively examined as a sort of HVLIB cathode material . The advancements in the doping of LNMO cathode material for 5 V Li-ion batteries, in which the rate capability, cyclic life of multiple doped LNMO materials, and rate performance, were explained were indicated by Yi and others [36, 421]. The progress in high-voltage cathode materials and corresponding matched electrolytes, in which they introduced LNMO as high-voltage cathode materials had been presented by Hu and others [36, 291]. Zhu and others  emphasised the advances in the development of advanced electrolytes for enhancing the cycling stability and rate capacity of LNMO-based batteries . The advantages of LNMO as the HVLIBs cathode, electrolytes, etc. or the modification techniques of doping were just outlined by these reviews . It is required to compare various modification techniques based upon cyclic degradation processes of LNMO and the architectural elements and observe an efficient technique to enhance the cycle performance of LNMO . Focus is given to the methodologies to enhance the cycling stability of LNMO, which is based upon the synthesis of highly purified LNMO, systemic reversibility of and cycling degradation mechanism of undesirable reactions between electrolyte and LNMO .
LiCoO2 has been the primary cathode material in commercial lithium-ion batteries since 1992 . A doping technique, which employs Mg2+, Al3+, Ti3+, Cr3+ or other ions, is clear-cut considerably more and helpful to enhance the properties of lithium-ion batteries [423, 424, 425, 426, 427], which is because the doping technique can lower the extent of Li/Ni cation mixing and ameliorate voltage degradation . That Ti-ion and Al-ion were utilized to prepare LiNi0.5Mn0.45Ti0.05O2 and LiNi0.475Al0.05Mn0.475O2, and in turn, the discharge capacity had been enhanced the extent of Li/Ni cation maxing of the LiNi0.5Mn0.5O2 is 9.8% which lowers to 4.8 and 5.1% by Al-doping and Ti-doping, respectively; and the cycle stability had been enhanced  is indicated by Myung and others . That Mg-ion had been replaced for Ni-ion in LiNi0.5Mn0.5O2, which can keep the structure stable because of the greater bond of dissociation energy of Mg–O (394 kJ mol−1) than that of Ni–O (391.6 kJ mol−1), enhancing the cycle stability  is devised by Xiao and others . Ca2+ is replaced for Ni2+ to produce a series of LiNi0.5–xCaxMn0.5O2 (0 ≤ x ≤ 0.2) cathode materials employing a combination of coprecipitation and O a solid-state technique because of the greater bond of dissociation energy of Ca-and the effect on declining the extent of Li/Ni cation maxing in the present study . The amelioration of the electrochemical properties from Ca-doping is attributable to the increasing stability of the structure, lower Li/Ni cation, which mixes, lowered polarization, which is declined enhanced the migration rate of the Li-ion and migration resistance .
Scholars have been attempting to synthesize materials which can operate at a potential of Zhang, greater than 4.3 V. More recently and others indicated a core-shell-structured LiNi0.5Co0.2Mn0.3O2 comprised of a shell of (Ni1/3Co1/3Mn1/3)3/14(Ni0.4Co0.2Mn0.4)1/2](OH)2  and a core of (Ni0.8Co0.1Mn0.1)2/7 to improve the energy density of batteries . At a current density of 18.5 mA g−1, this material delivered a comparatively low capacity of 200 mAh g−1 and preserved 95% of its capacity when cycled for 40 cycles to an upper cutoff voltage of 4.5 V. Arguably, the spinel shell of Li1+x[CoNixMn2–x]2O4 enhanced its stability; even when the material had been charged to high potential of 4.5 V, it delivered just 200 mAh g−1 at 18 mA g−1 . That they indicated Thackeray and others Li2MnO3 plays a main role in supporting the structure stability during the discharge/charge process, and preparing lithium-rich layered oxide materials (LLOs) xLi2MnO3–(1−x)LiMO2 can consequence in high electrochemical capacity ∼250 mAh g−1 if charged to high potentials >4.6 V, had been indicated by Thackeray and others . We have indicated that manganese oxide shell can substantially enhance the cyclic stability of LiMO2  nickel-rich layered materials, and replacing a small quantity of lithium with sodium can increase the discharge capacity of the material [38, 431, 432]. Since it is a lithium-rich material, this core-shell material delivers quite high discharge capacity, and this material is thermally stable, Li2MnO3 is electrochemically active at a potential greater than 4.5 V. Furthermore and could be safely cycled at a high potential of 4.7 V and delivers a considerably greater mean potential and a greater energy density than that of traditional Ni-rich materials .
Through the cathode materials, rechargeable lithium-ion batteries (LIB)’s performances, including voltage and capacity, are predominately dictated as one of the most fruitful energy storage tools . The xLi2MnO3·(1−x)LiNi1/3Co1/3Mn1/3O2 series compounds of the cathode materials in lithium-ion batteries have brought about a considerable explosion in researches because of the high capacities, low cost, and lowered toxicity . The xLi2MnO3·(1−x)LiNi1/3Co1/3Mn1/3O2 series compounds of the cathode materials in lithium-ion batteries are regarded as viable alternatives compared with traditional LiCoO2 cathode materials [433, 434], as reasonably well . Surface coating, including AlPO4, CaF2 , CeF3 , and graphene  coating on the surface of the cathode materials, can restrain the undesirable reactions between cathode materials with electrolyte . Metal element doping, including Al, Zr , Y, Mo, and Mg  replaced for the transitional metal elements in the oxide materials, can weaken the adverse change of crystal structure . Cycling performance and systemic stability of cathode materials, which are revealed by some inquiries [262, 434] could be enhanced by these techniques . We attempt to substitute traces of Al element for various transitional metal elements of Li1.2Mn0.54Ni0.13Co0.13O2, in order to enhance the electrochemical performance of the Li-rich materials . The structure, electrochemical performance of the pristine, and morphology, and Al-doped materials have been typified .
High stable reversible capacity of >250 mAh g−1 when it is cycled in the voltage window of 2.5–4.8 V [194, 438, 439, 440, 441, 442, 443] is delivered by LMR-NMC . Throughout cycling need to be tackled before it is regarded as a potential candidate for next generation cathode material for lithium-ion batteries [194, 437, 438, 439, 440, 441, 442, 443], the energy deterioration because of suppression of voltage profiles during cycling which is linked with the stage reconfiguration from a layered structure to spinel structure, capacity, and high irreversible capacity, fade . That the substitution of 6 mol% of Al3+ ions with Ni [Li1.15(Ni0.275–x/2Mn0.575–x/2Alx)O2] and Mn can avoid the systemic deterioration of electrode material, which enables higher discharge capacities of 210 mAh g−1 at a cut off voltage of 2.5–4.6 V, whilst the undoped cathode delivers 150 mAh g−1  had been confirmed by Park and others . Through partial substituting 4% of Mg with [Li(Li0.2–2xMgxCo0.13Ni0.13Mn0.54)O2] lithium in transitional metal layer and delivers an initial capacity of 272 mAh g−1 (between 2.0 and 4.8 V) and preserves 93% of capacity after 300 discharge/charge cycles , Wang and others stabilized the crystal structure . Improvement in electrochemical performance, thermal stability, rate capability, and tap density of NMC by substituting partially oxygen with fluorine which results stabilization of the crystal lattice structure [446, 447, 448, 449, 450, 451, 452, 453] because of smaller c-axis variability and fluorine coatings had been indicated by Kim and others . Kim and others explained both magnesium and fluorine substitution in NMC [Li(Ni1/3Co1/3Mn1/3–xMgx)O2–yFy] and asserted decrease in cation, which mixes during amelioration in crystallinity, cycling, and tap density this density in turn impact the amelioration in thermal stability [446, 451] and capacity retention; this density in turn impact the amelioration in thermal stability [446, 451] and capacity retention .
LiCoO2 one of the layered structure cathode material has been commonly used as cathode materials in commercial applications [41, 454]. Nevertheless; the requirements for high energy applications could be not fulfilled by this cathode material since, even though its theoretical capacity is 274 mAh/g, the practical capacity in applications roughly 150 mAh/g by charging up to 4.2 V [41, 454, 455]. Of all cathode materials NMC’s (LiNi1–x–yMnxCoyO2) are mainly researched materials because of their high discharge capacity, satisfactory systemic stability  and high rate capability . Another of these constraints is that NMC cathode materials indicate undesireable irreversible capacity deterioration during first charge-discharge [41, 457]. That due to an overlap of the metal: 3d band with the top of the oxygen: 2p band, layered oxide cathode materials seem to loose oxygen from the lattice at consequence in a tremendous capacity deterioration  and deep charge had been asserted by Choi and others . One restriction is that when LiPF6 which is the crucial element of electrolyte decomposes in the existence of moisture, one of the product is HF; this HF gives rise to transition metal break-up in electrolytes resulting surface corrosion of cathode material [41, 459]. The reactions between electrolytes and cathode materials decreases capacity and cyclic performance of the battery [41, 455]. Surface modification can deter the reactions between cathode materials and electrolytes and can lessen the oxygen activity of the cathode at high voltages [41, 455, 460]. It is indicated that Al2O3 coating lowers capacity difference between discharge and cathode surface corrosion  and first charge . The goal of the investigation is examining the effect of sonication power on alumina distribution on the LiNi0.5Mn0.3Co0.2O2 cathode materials and examining cathode performance .
More than 270 mAh g−1, though just half of this capacity could be delivered because of the inherent systemic turbulence of the LCO material in a high delithiated state and interfacial turbulence between the electrode and electrolyte [462, 463] is the theoretical specific capacity of LCO . It has been observed that surface coating had been an efficient approach to enhance electrochemical performance of cathode materials [42, 464, 465]. The surface coating indicates considerable advantages on suppressing the break-up of Co into the electrolyte and the decomposition of the electrolyte and altering the LCO surface chemistry to sustain the structure at high cut-off voltage . Numerous coating materials primarily include (1) metal oxides, including ZrO2 [466, 467, 468, 469], and Al2O3, ZnO, can act as the HF scavenger and which are electrochemically inactive; (2) phosphates and silicates [357, 470], which are beneficial to enhance thermal stability of bulk materials and the overcharge safety; and (3) fluorides and other materials, including AlF3, MgF2, and AlWxFy [471, 472, 473], which is useful for enhancing the systemic stability of LCO materials at high cut-off voltage . That the AZO-coated LCO electrodes delivered a greater reversible capacity of 112 mAh g−1 at 12 C (1680 mA g−1) between 3.0 and 4.5 V versus Li+/Li than ZnO-coated electrodes had been demonstrated by the results . It means that the coating layer with electron transport or enhanced lithium-ion might be efficient to enhance the electrochemical performance of LiCoO2 at high cut-off voltage . Based on 0.5–4, the LiCoO2 cathode materials coated with multiple quantities of NaAlO2 wt .
High power lithium-ion rechargeable batteries and enhanced high capacity is needed by these applications . A wide range of cathode materials have been devised to satisfy the expanding requirement for high power lithium-ion batteries and high capacity, though just handful of them have cycle stability and high specific capacity . Due to electrochemical properties and a better cycling stability, Co and Al co-substituted material (LiNi0.8Co0.15Al0.05O2) is regarded as one of the most fruitful candidates as positive electrode materials for high-power lithium-ion batteries . LiNi0.8Co0.15Al0.05O2 as a cathode material for automotive applications has been a commercial success ever since the inception of Tesla . LiNi0.8Co0.15Al0.05O2 with compositionally homogenous mixing at the atomic level and micron-sized spherical particle with narrow size distribution is readily obtained by coprecipitation, and this technique has been utilized for the commercial synthesis of LiNi0.8Co0.15Al0.05O2 cathode material . It is of paramount importance to build a straightforward, effective, and rapid, synthesis approach to allow large-scale synthesis of LiNi0.8Co0.15Al0.05O2 cathode material, without compromising its electrochemical performance . Solid-state technique is useful for large-scale production of cathode materials for lithium-ion batteries because it is cost-efficient and straightforward . That the electrochemical properties of Ni-rich cathode material, which traditional solid-state technique prepared, are not good, which is primarily attributed to the inhomogeneous distribution of transition metal ions, despite repeated mechanical ball milling before calcining is confirmed by these results . The Ni–Co–Al oxide precursor based on the decomposition of oxalates displays small particle size, which is beneficial to the mixing with lithium source and a porous and loose structure . Through traditional solid-state technique, the LiNi0.8Co0.15Al0.05O2 cathode material is synthesized, as reasonably well .
That they indicated Thackeray and others Li2MnO3 plays a main role in systemic stability during the charge-discharge process, and preparing lithium-rich layered oxide materials (LLOs) xLi2MnO3–(1−x)LiMO2 can produce high electrochemical capacities of ∼250 mAh, which is charged g−1 when to high potentials of >4.6 V, had been indicated by Thackeray and others . Kim and others’ results revealed that the pristine material delivered a discharge capacity of ∼200 mAh g−1 at 0.5 C and preserved 85% of its capacity after 30 cycles in the potential variety 2–4.6 V, whilst the material, which is surface-modified and fluorine-doped, preserved 92% of its capacity when cycled under the identical conditions [44, 474]. The aims of the present study were (1) to enhance the thermal stability of this material by making it a core-shell structured material with a core of LiMO2 and a shell of Li2MnO3, and (2) to increase the discharge capacity of NCM 111 by preparing NCM 111 with the formula xLi2MnO3–(1−x)LiMO2, i.e., a lithium-rich material with a high capacity [44, 194]. Li2MnO3 has two advantages: this material can increase the systemic and thermal stability of the material during the charge-discharge process [474, 475, 476], and this material can partake in the electrochemical reactions at potentials >4.5 V, resulting in greater capacities, in this structure . Since potentials greater than this can give rise to a rapid decline in systemic disintegration  and capacity, whilst the core-shell material can be cycled to an upper cut-off potential of 4.7 V with high stability, the pristine subsample had been charged by us to an upper cut-off potential of 4.5 V .
Lithium intercalation compounds based upon manganese oxides are safer cheaper, and, provide an especially appealing replacement for the latter compound as a cathode material in Li-ion batteries [478, 479, 480, 481] and less toxic than the layered compound, which is based upon cobalt or nickel oxides . Of the lithium manganese oxides cathode materials researched, layered oxides (LiMnO2), spinel oxides (LiMn2O4), and Li-rich Mn-based layered compounds [Li2MnO3·LiMO2 (M = Mn, Ni, Co)] cathodes have been devised and extensively examined [45, 97, 482, 483, 484, 485, 486, 487]. Due to their high theoretical capacity (285 mAh g−1), layered LiMnO2 compounds have come to be of interest as cathode material, though layered LiMnO2 is not thermodynamically stable, which is readily converted to a spinel-like structure during electrochemical extraction/insertion of Li ions [45, 488]. Li-rich Mn-based layered compounds have been regarded as one of the most fruitful cathode material for future Li-ion batteries due to their advantage of high reversible capacity (>200 mAh g−1), which is charged when above 4.5 V [45, 476, 489, 490, 491]. Throughout the first charge, a common characteristic of Li-rich Mn-based layered compound cathode is an irreversible high voltage plateau at around 4.5 V versus Li/Li+ , Preliminary discharge capacity values of this materials are usually high after activation of Li2MnO3 stage, though inherently inferior rate capability and cycling turbulence are detected in all reports [45, 479, 492, 493]. It might be beneficial to reinvestigate the properties of Li2MnO3 material to help additional understanding of the properties of Li-rich Mn-based layered compounds .
Owing to high-performance rechargeable batteries’ high voltage, high specific capacity, excellent and other advantages, lithium-ion batteries (Li-ion batteries) are viewed as the most likely power sources for electric vehicles . Great efforts have been made to maximize the cathode materials with high energy densities [182, 494, 495] because the performances of lithium-ion batteries are largely dictated by the cathode materials . The primary strategy to enhance the energy density of batteries is to build cathode materials with greater operating voltages [496, 497] and high capacity . A competitive candidate of the active cathode material due to its low cost, high specific capacity [498, 499], and low toxicity, is layered nickel-rich oxide LiNi0.5Co0.2Mn0.3O2 (NCM523) . An efficient approach to enhance the electrochemical performance of LiNixCoyMn1–x–yO2 is coating the powder particles with many metal oxides including CeO2 , and Al2O3 , ZrO2 [46, 502]. Lithium-containing oxides, including LiTiO2 , Li3VO4 , Li2SiO3 , and Li2ZrO3 , have been extensively examined as the coating materials because offer 3-D paths for the migration of lithium ions during the charge and discharge process  though they not just provide a protective layer against side reactions on the surface .
The cathode material had been an essential part of lithium-ion battery . Ni-rich layered oxide LiNi0.8Co0.1Mn0.1O2 is regarded as one of the most fruitful cathode materials, because LiNi0.8Co0.1Mn0.1O2 has lower cost and bigger reversible specific capacity (~200 mAh g−1) and is more environment-friendly [507, 508, 509, 510, 511, 512] among multiple types of the cathode materials [96, 493, 513, 514, 47]. The nickel-rich material has a highly water absorption issue, resulting in an impurity stages (LiOH/Li2O) on the particle surface; this surface triggers an irregular thickness on Al foil, which coates cathode material . That the coating should be thick sufficiently had been founded by scholars and can not respond with the raw material . The LiAlO2 as the coating material has been utilized for some cathodes, including LiNi0.4Co0.2Mn0.2O2, and the LiAlO2-coated material displays better electrochemical performance, and Li[Li0.2Mn0.54Co0.13Ni0.13]O2, LiNi1/3Co1/3Mn1/3O2 . An excellent coating material comparable to the layered structure of LiNi0.8Co0.1Mn0.1O2 materials [515, 516] is the α-LiAlO2 . LiAlO2 retains satisfactory lithium-ion electrical conductivity due to the material, which is inhabited partly, internal lithium ion sites [47, 517]. Thermal stability and the cycling stability at a high temperature of LiAlO2-coated LiNi0.8Co0.1Mn0.1O2, which hydrolysis obtained, -hydrothermal were investigated in detail . A hydrolysis-hydrothermal strategy for the successful preparation of LiAlO2-coated LiNi0.8Co0.1Mn0.1O2 cathode material is indicated by us . The impurity stages (LiOH/Li2O) on the surface of LiNi0.8Co0.1Mn0.1O2 are discarded as raw materials to synthesize a novel LiAlO2 coating layer . In contrast with conventional coating materials, the LiAlO2 coating layer not just inherited the advantages of Al3+ doping though also discarded the impurity stage on the raw materials .
Research in the field of Li-ion batteries is revolved around the development of systems with increased energy and longer life and power density; with the goal of employing Li-ion batteries as a power source for pure electric (EV)  or hybrid vehicles (HEV) . In recent decades, a significant number of research groups worldwide have invested considerable effort to enhance the electrochemical properties of materials previously utilized and build novel materials for electrolytes (ionic liquids, polymeric electrolyte, inorganic solids) and separators positive electrodes (oxides, phosphates), negative (various kinds of carbon, alloys, etc.); these electrodes have better performance in terms of energy, power, cost, validity, time of life, and safety . A series of fluorophosphates materials including LiVPO4F , Na3V2(PO4)2F3 , NaVPO4F , and Li2MPO4F (M = Fe and Co) , have demonstrated tremendous promise as possible replacements for the current generation of materials . Through solid-state carbothermal decrease (CTR), which employs two-stage reaction process involving VPO4, the electrochemical properties of NASICON-type Na3V2(PO4)2F3 were investigated by Gover and others , it had been prepared as intermediate and followed by reaction with NaF . More than 90% of the specific capacity had been preserved by the material, so it might be of interest to enhance the detected electrochemical properties of this stage . Another way to improve the electrochemical properties is to investigation the aliovalent doping , positive impacts detected, such as enhanced electric conductivity and structure stability attributed and for instance, the impacts of the vanadium substitution with other elements (Mg2+, Co2+, Al3+) in various materials including Li3V2(PO4)3 have been examined [48, 522]. The effect of Al substitution on the electrochemical and systemic properties of cathode materials have been examined .
Owing to its high capacity, low toxicity [523, 524], and excellent thermal stability, cheap, the LiNixCoyMn1–x–yO2 might be supposed to substitute the conventional LiCoO2 cathode material in the next generation of lithium-ion battery . The hydroxide precursor NixCoyMn1–x–y(OH)2 for the LiNixCoyMn1–x–yO2 cathode materials are primarily synthesized through coprecipitation, which employs NH3·H2O, as chelating actor [49, 525]. He and others  have indicated that the hydroxide precursor Mn(OH)2 had been synthesized employing citric acid and oxalic acid as the chelating actor to control the activity of Mn2+ in the solution, and then the spherical spinel LiMn2O4 cathode materials with tap density as high as 1.9 g cm−3 and the initial discharge capacity, which reachs 116 mAh g−1 were obtained . Zhang and others  and Zhao and others  have indicated that the sol-gel synthesis of LiNi1/3Mn1/3Co1/3O2 and Li[Li0.2Co0.13Ni0.13Mn0.54]O2 had been carried out employing tartaric acid (TA), oxalic acid, and then suggested that the tartaric acid-derived cathode materials owns excellent columbic efficiency, and succinic acid (SA) as chelating actors . Zhou’s group [290, 529, 530] indicated that the spherical cathode materials with excellent electrochemical properties were synthesized employing oxalic acid as chelating actor . The quasi-spherical hydroxide precursor (Ni0.5Co0.2Mn0.3)(OH)2 has been synthesized employing sodium lactate as chelating actor through coprecipitation technique , and the corresponding cathode materials display stable cycleability and satisfactory rate capability . The impact of lactic acid concentration on the structure and electrochemical performance of LiNi0.5Co0.2Mn0.3O2 cathode material has not yet been investigated till now . Lactic acid had been utilized to synthesize the spherical LiNi0.5Co0.2Mn0.3O2 cathode materials in here .
Due to operating voltage and low capacity, LiCoO2 cathode material in commercial lithium-ion batteries, which is utilized frequently, have confined energy density . Overcharging frequently triggers significant systemic distortions (reconfiguration from hexagonal to monoclinic structures), which yield extensive defects between and within the particles, and induces potential surface reactions including Co break-up at voltages above 4.4 V [50, 223, 532]. LiMn1.5Ni0.5O4 sometimes includes the LixNi1–xO impurity stage and it triggers huge lattice stress during cycling, which results in degradation of the electrochemical performance [50, 533, 534, 535]. Surface modification by coating with metal oxides including ZnO, Bi2O3, AlPO4, and Al2O3, has been demonstrated to improve the cycleability and lessen the corrosion reaction between the cathode and the electrolyte [50, 98, 346]. The nitridation process in battery and the photocatalyst has been investigated to increase the efficiency, electrochemical property, and electric conductivity, because it can aid the formation of the nitride film on the surface [536, 537] and change the oxygen stoichiometry . Above the valence band edge, the replaced N 2p states in the O-sites are situated, inducing a decline in the bandgap as a consequence in the case of nitridation of a surface, which is coated with a metal oxide . That process has been utilized for surface modification of electrode materials, as reasonably well . Some groups have indicated that surface nitridation of an active material can enhance electrochemical performance and the electric conductivity . The as-synthesized subsample had been assessed for its suitability as a cathode electrode material for lithium-ion batteries; it revealed satisfactory cycling performance and greater rate capability when compared to pristine LiMn1.5Ni0.5O4 .
Water-based binders having high resistances to electrochemical oxidation during charging process must be devised to use these fruitful high-capacity and high-voltage cathodes in the next-generation lithium batteries prepared in ecologically compatible electrode fabrication mechanisms with a water-based binder . An aqueous hybrid polymer (TRD202A, JSR) had been comprised of fluoropolymer and acrylic polymer and had been sampled as a binder for the Li-rich solid-solution layered cathode material Li[Ni0.18Li0.20Co0.03Mn0.58]O2 . A cathode, which is prepared with Li[Ni0.18Li0.20Co0.03Mn0.58]O2 particles, conductive carbon additive, and TRD202A binder, CMC, had been evaluated and examined for charge/discharge capacity, cycle stability, rate performance, resistance of electrochemical oxidation, mechanical resistance, and transformations of the surface composition and structure after water-treatment utilized for preparing water-based slurry . Wu and coworkers have not investigated the water-based binders for charge/discharge capacities, long cycle stability, rate performance, resistance of electrochemical oxidation, mechanical resistance, or transformations of the surface composition and structure after water-treatment, which is utilized for preparing the water-based slurry . Li-rich solid-solution layered cathode materials’ stable charge/discharge performances are accurate for the performance tests of the water-based TRD202A binder with a high-voltage Li-rich solid-solution layered cathode material; the TRD202A binder had been blamed for the performance degradation of the cathode, which is prepared with that binder . The relative merits of the PVdF and TRD202A binders are outlined relating to the charge/discharge capacities, long cycling stability, rate performance, resistance of electrochemical oxidation, mechanical resistance, and transformations of the surface composition and structure after water-treatment for the preparation of a water-based slurry .
The main element within the Li-ion batteries, which offers significant influence on electrochemical performance and capacity is Cathode . Lithium manganese phosphate (LiMnPO4) is primarily centred as a useful candidates in the olivine group among LiFePO, LiNiPO and LiCoPO for cathode application [52, 538, 539]. 701 Wh kg with low electronic/ionic electrical conductivity, which affect the electrochemical property [540, 541] and meager lithium diffusion is the theoretical energy density of LiMnPO . Haemoglobin-like LiMnPO microspheres were prepared for better electrochemical activity because of presence of 3-D (3D) hierarchical structures [52, 542]. That irregular flaky influenced LiMnPO4 is accomplished by a hollow-sphere Li3PO4 precursor, which is utilized to control the particle growth of LiMnPO had been indicated by Cui et al. [52, 543]. That dry ball milling showed satisfactory electrochemical properties at high temperature and high charge/discharge rate of 2 C and the carbon-coated nanostructured LiMnPO through combination of spray pyrolysis had been indicated by Nam et al. [52, 544]. Cation, which dopes in LiMnPO, is observed to be an alternative technique to upgrade ionic electrical conductivity [52, 545]. Previous work suggested that cesium (Ce)-doped LiMnPO contributed to easy diffusion of Li-ion in bulk materials [52, 546]. Given this fact, this work is an effort to enhance LiMnPO by partial natrium substitution on lithium sites . Numerous attempts have been done to enhance electrochemical performance of cathode materials by partial natrium doping . That Na substitution for Li minimizes, which mixes cation, enhances reversibility and constrains charge transfer impedance during cycling had been indicated by Chen et al. [52, 547]. Partial Na substitution for Li site has not been centred for LiMnPO-based energy storage application .
That novel trend in the car market suggests that requirement for Li-ion batteries will be continually expanding . An increase in Li-ion batteries entails that there will be more battery waste in the near future . One fact is that Li-ion battery waste includes useful metal elements including Li, Ni, Co, Cu, and Mn . There have been some efforts to recycle Li-ion batteries [53, 548, 549, 550, 551]. Lithium ion battery recyclers centred solely on cobalt as LiCoO2 had been the principal cathode material in the market; the high price of cobalt motivated recycling efforts [53, 552, 553, 554]. The waste stream comprises Li-ion batteries with various cathode chemistries . An effective Li-ion battery recovery process must not target a single cathode chemistry . A “mixed cathode” recycling process had been first devised and devised [555, 556], by which certain quantities of Li-ion batteries with heterogeneous cathode materials could be recovered together without battery sorting . Through plasma optical emission spectrometry (ICP-OES), which is coupled inductively, the concentrations of these useful metal elements could be dictated and adjusted by adding MSO4 (M = Ni, Mn, Co) salts, cathodes with various Ni and so metal hydroxide precursors: Mn: Co molar ratios could be synthesized directly . The leaching solution from the recovery stream had been employed to synthesize heterogeneous LiNixMnyCozO2 cathodes . The molarities of transition metal elements were adjusted to 5:3:2 and 6:2:2 to derive LiNi0.5Mn0.3Co0.2O2 and LiNi0.6Mn0.2Co0.2O2 .
2.2 Cathode Materials, Samples, Spinel, Calcination, Discharge Capacity
2.2.1 Synthesis of Spinel LiNi0.5Mn1.5O4 as Advanced Cathode via a Modified Oxalate Co-precipitation Method 
Spinel-type LiNi0.5Mn1.5O4 (LNMO) cathode materials for Li-ion batteries have been synthesized through a modified oxalate coprecipitation technique . Following one-pot reaction, the target materials could be obtained without subsequent mixing with lithium salts by virtue of the coprecipitation of Li+ with transition metal ions . The results confirm that the as-prepared material owns a cubic spinel structure with a space group of Fd-3 m, high crystallinity, excellent electrochemical performances, and homogeneous particle size . Superior rate performance and a greater initial capacity are delivered compared with that of material by traditional coprecipitation technique .
2.2.2 LiNi0.5Mn1.5O4 Hollow Nano-micro Hierarchical Microspheres as Advanced Cathode for Lithium-Ion Batteries 
Hollow LNMO microspheres have been synthesized through coprecipitation technique, which is accompanied with high-temperature calcinations . The results confirm that the microspheres combine hollow structures inward and own high crystallinity, a cubic spinel structure with space group of Fd-3m, and excellent electrochemical performances . The hierarchical LNMO microspheres display 138.2 and 108.5 mAh g−1 at 0.5 and 10 C, respectively with the short Li+ diffusion length and hollow structure .
2.2.3 Low Content Ni and Cr Co-doped LiMn2O4 with Enhanced Capacity Retention 
Nanoparticles of the pure and Ni–Cr codoped lithium manganese oxides Li[NixCryMn2–x–y]O4 (x = y = 0.01–0.05) have been synthesized by sol-gel technique, which employs citric acid as a chelating actor . That low-content Ni-Cr substitution considerably enhances the systemic stability and high rate cycling performance of LiMn2O4 had been established by impedance and electrochemical measurements . 82% of the initial discharge capacity at 0.1 C is preserved at a considerably high current rate of 5 C . A discharge capacity of 104 mAh g−1 is resumed upon reducing the current rate to 0.1 C which is 91% of the specific capacity in the first cycle after deep cycling at high rates . It could be observed that the stoichiometry of all the samples is close to the nominal compositions . It could be observed that the cycling performance of the Ni–Cr-substituted samples is substantially enhanced .
2.2.4 Effects of Lithium Excess Amount on the Microstructure and Electrochemical Properties of LiNi0.5Mn1.5O4 Cathode Material 
The effect of lithium excess quantity on the microstructure, electrochemical properties of LiNi0.5Mn1.5O4 materials, and morphology, had been systematically examined . With the increase of lithium excess quantity, the cation disordering extent (Mn3+ content) and stage purity first increase and then decline, whilst the cation mixing extent has the opposite trend . The LiNi0.5Mn1.5O4 material with 6% lithium excess quantity displays greater disordering lower impurity content and extent and cation mixing extent, leading to the optimal electrochemical properties, with discharge capacities of 125.0, 126.1, 124.2, and 118.9 mAh/g at 0.2-, 1-, 5-, and 10-C rates and capacity retention rate of 96.49% after 100 cycles at 1-C rate . Recent reports [558, 559] indicate that the spinel LiMn2O4 with the I 311/I 400 intensity ratios between 0.96 and 1.1 normally indicates better electrochemical performances than those outside this region .
2.2.5 Sn-Doped Li1.2Mn0.54Ni0.13Co0.13O2 Cathode Materials for Lithium-Ion Batteries with Enhanced Electrochemical Performance 
Sn-doped Li-rich layered oxides of Li1.2Mn0.54–xNi0.13Co0.13SnxO2 have been synthesized through a sol-gel technique, and electrochemical performance and their microstructure have been researched . The electrochemical performance of Li1.2Mn0.54–xNi0.13Co0.13SnxO2 cathode materials is substantially enhanced after doped with an suitable quantity of Sn4+ . The superior rate capability with discharge capacities of 239.8, 198.6, 164.4, 133.4, and 88.8 mAh g−1 at 0.2, 0.5, 1, 2, and 5 C, respectively, which are considerably greater than those of Li1.2Mn0.54Ni0.13Co0.13O2 (196.2, 153.5, 117.5, 92.7, and 43.8 mAh g−1 at 0.2, 0.5, 1, 2, and 5 C, respectively) is shown by the Li1.2Mn0.53Ni0.13Co0.13Sn0.01O2 electrode . The substitution of Sn4+ for Mn4+ widens the Li+ diffusion channels because of its bigger ionic radius compared to Mn4+ and improves the systemic stability of Li-rich oxides, leading to the enhanced electrochemical performance in the Sn-doped Li1.2Mn0.54Ni0.13Co0.13O2 cathode materials .
2.2.6 Co-precipitation Spray-Drying Synthesis and Electrochemical Performance of Stabilized LiNi0.5Mn1.5O4 Cathode Materials 
Through a process, which spray-drys coprecipitation and calcining, the LiNi0.5Mn1.5O4 cathode materials of lithium-ion batteries are synthesized . Through a calcining treatment at the optimized temperature of 750 °C, the use of a spray-drying process to form particles, followed to generate spherical LiNi0.5Mn1.5O4 particles with a cubic crystal structure, a specific capacity of 132.9 mAh g−1 at 0.1 C. and a specific surface area of 60.1 m2 g−1, a tap density of 1.15 g mL−1 . The carbon nanofragment (CNF) additives, introduced into the spheres during the coprecipitation spray-drying period, substantially improve the rate performance and cycling stability of LiNi0.5Mn1.5O4 .
2.2.7 Synthesis and Electrochemical Performance of Spherical LiNi0.8Co0.15Ti0.05O2 Cathode Materials with High Tap Density 
Through X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively, the crystal structure and particles morphology of the as-prepared powders were typified . “All samples correspond to the layered α-NaFeO2 structure with R-3m space group” . The LiNi0.8Co0.15Ti0.05O2 prepared at 800 °C introduces better spherical particles and a better hexagonal ordering structure and retains a high tap density of 3.22 g cm−3 .
2.2.8 A Strontium-Doped Li2FeSiO4/C Cathode with Enhanced Performance for the Lithium-Ion Battery 
That a strontium cation occupies the Fe site in the lattice and that strontium-doped Li2FeSiO4 has a monoclinic P21/n structure is revealed by rietveld refinement . The grain size of strontium-doped Li2FeSiO4 is roughly 20 nm, and the nanoparticles are interlinked tightly with amorphous carbon layers . Strontium-doped Li2FeSiO4/C delivers a high discharge capacity of 181 mAh g−1 at a rate of 0.5 as the cathode material of a lithium-ion battery C . It could be concluded that strontium cation doping enables to increase the Li+ diffusion capability and weakens side reactions between the electrode and electrolyte by examining the electrochemical impedance spectra . Throughout charging and discharging after strontium cation doping, the amelioration of the electrochemical performance could be attributable to the undermined crystal structure stability . The evident capacity degradation can not be detected and all the capacity retentions stayed above 90% for the three cathodes, as the rate ranged from 2 to 5 C .
2.2.9 Enhanced Electrochemical Performances of Layered LiNi0.5Mn0.5O2 as Cathode Materials by Ru Doping for Lithium-Ion Batteries 
Through a moist chemical technique, which a high-temperature calcining process followed, Ru-doped LiNi0.5Mn0.5O2 cathode materials and the pristine are synthesized . The galvanostatic charge/discharge measurements highlight that the electrochemical properties of the LiNi0.5Mn0.5O2 subsample are enhanced by Ru doping . Ru doping is regarded an efficient way to improve the electrochemical performances of LiNi0.5Mn0.5O2 cathode materials . Two apparent splittings of (006)/(102) and (108)/(110) doublet peaks could be detected, which indicate a well-ordered layered structure [9, 560]. It could be observed that the lattice parameters (a and c) of LiNi0.5Mn0.45Ru0.05O2 are greater than those of LiNi0.5Mn0.5O2 . The SEM images indicate that the as-prepared samples have a polyhedral or spherical morphology in the primary particle . The SAED patterns of LiNi0.5Mn0.45Ru0.05O2 show a characteristic hexagonal ɑ-NaFeO2 structure (3m) diffraction in the  zone, and corroborate that the primary particles are single crystalline .
2.2.10 Synthesis and Electrochemical Properties of LiNi0.5Mn1.5O4 Cathode Materials with Cr3+ and F− Composite Doping for Lithium-Ion Batteries 
Through the solid-state technique, F− and a F−5 composite-doped LiNi0.5Mn1.5O4 cathode material had been synthesized, and the impact of the doping quantity on the electrochemical and physical properties of the material had been examined . The results of the charge/discharge tests, electrochemical impedance spectroscopy (EIS) test results, and cyclic voltammetry (CV), indicated that LiCr0.05Ni0.475Mn1.475O3.95F0.05 in which the F− and F−5 doping quantities were both 0.05, had the optimum electrochemical properties, with discharge rates of 0.1, 0.5, 2, 5, and 10 C and specific capacities of 134.18, 128.70, 123.62, 119.63, and 97.68 mAh g−1, respectively . LiCr0.05Ni0.475Mn1.475O3.95F0.05 revealed exceedingly satisfactory cycling performance, with a capacity retention rate of 97.9% and a discharge specific capacity of 121.02 mAh g−1 after 50 cycles at a rate of 2 C .
2.2.11 Y-Doped Li3V2(PO4)3/C as Cathode Material for Lithium-Ion Batteries 
On the structure and electrochemical performance of Li3V2(PO4)3, the Y-doping quantity plays a crucial role . The capacity retention had been observed to be 93.9% after 50 cycles and the capacity of Li3Y0.03V2(PO4)3/C stayed around 100 mAh g−1 at a current density of 100 mA g−1. the Li3V2(PO4)3/C samples (LVP) doped with various quantities of Y were synthesized . That the Y-doping quantity plays a crucial role on the structure and electrochemical performance of Li3V2(PO4)3/C is demonstrated by the results . The cycle performance of the samples is quite satisfactory and the reversible capacity of the as-prepared Li3Y0.03V2(PO4)3/C is greater than the theoretical capacity (148.99 mAh g−1 after 50 cycles) . That the aggregation of the sub-micrometer size particulates in both Li3YxV2(PO4)3/C and Li3V2(PO4)3/C powders, since the materials were prepared by a rheological stage reaction at high temperature with a comparatively long duration is clearly demonstrated by the SEM pictures . It could be observed that porous carbon layers enmeshed the networks of aggregated particles or coated on the surface of the particles . AC impedance curves of the LVP samples indicate that Li3YxV2(PO4)3/C with 3% Y-doping is the optimal material to examine the modification of Li3V2 (PO4)3/C .
2.2.12 Nano Transition Metal Alloy Functionalized Lithium Manganese Oxide Cathodes-System for Enhanced Lithium-Ion Battery Power Densities 
Manganese oxide cathode material of rechargeable lithium-ion batteries provides a distinctive blend of lower cost and toxicity, which is compared to the usually utilized cobalt, and has been shown to be safer on overcharge . Alloy nanoparticles were synthesized and utilized as coating material with the aim to enhance the catalytic and microstructure activities of pristine LiMn2O4 . The pristine modified and LiMn2O4 materials were investigated employing a combination of microscopic and spectroscopic methods along with in detail galvanostatic charge-discharge tests . Microscopic results showed that the new composite cathode materials had high stage purity, congruent morphological structures with narrow size distributions and well-crystallized particles . The systemic changes, which take place during Li+ ion insertion with exchange current density i 0 (A cm−2) of 1.83 × 10−4 and 3.18 × 10−4 for LiMn2O4. greater electrode columbic efficiency of the LiPtAuxMn2–xO4 and the enhancement of the capacity retention were significant, particularly at high C rate were efficiently accommodated by the LiPtAuxMn2–xO4 cathode .
2.2.13 Synthesis and Electrochemical Properties of Li(Ni0.56Co0.19Mn0.24Al0.01)1−yAlyO2 as Cathode Material for Lithium-Ion Batteries 
The LiNi0.5376Co0.1824Mn0.2304Al0.0496O2 (y = 0.04) cathode material had the optimal electrochemical performance . At 0.1 C, the reversible capacity of 174.9–115.9 mAh g−1 at 1 C between 2.75 and 4.4 V. had been offered by the material  Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were carried out to additional investigation the novel composite cathode materials, as reasonably well .
2.2.14 One-Step Solid-State Synthesis of Nanosized LiMn2O4 Cathode Material with Power Properties 
That optimum LiMn2O4 particles (S0.5) is synthesized when the molar ratios of total Mn source and oxalic acid are 0.5:1 is revealed by the electrochemical test results . The obtained subsample S0.5 with middle size displays a high initial discharge capacity of 125.8 mAh g−1 at 0.2 C and 91.4% capacity retention over 100 cycles at 0.5 C, superior to any one of other samples . In this work, the optimum S0.5 can still attain a discharge capacity of 80.8 mAh g−1 when cycling at the high rate of 10 C . That observation could be tackled to the fact that the middle size particles balance the conflicting of diffusion length in solid stage and particle agglomeration; this stage gives rise to perfect contacts with the optimum performance of S0.5, and the conductive additive, substantial evident lithium ion diffusion rate . It could be observed that among all the samples, S0.5 acquires a minimum value of I222/I400 ratio, suggesting that the crystal orientation in S0.5 along the (400) direction is more influential than that in other samples .
2.2.15 Nanosized 0.3Li2MnO3·0.7LiNi1/3Mn1/3Co1/3O2 Synthesized by CNTs-Assisted Hydrothermal Method as Cathode Material for Lithium-Ion Battery 
Through a hydrothermal process with carbon nanotubes as template, 3Li2MnO3·0.7LiNi1/3Mn1/3Co1/3O2 as new cathode material had been synthesized . 3Li2MnO3·0.7LiNi1/3Mn1/3Co1/3O2 material revealed excellent electrochemical performance, and the LR-1.0 subsample had rate capability and the optimal cycling stability . Once the LR-1.0 subsample had been evaluated as a cathode at 0.1 and 2.0 C the LR-1.0 sample’s its initial discharge capacities can attain up to 267.0 and 146.6 mAh g−1, respectively . 3Li2MnO3·0.7LiNi1/3Mn1/3Co1/3O2 prepared by this technique had been a novel fruitful cathode material for Li-ion batteries . To additional show the electrochemical behaviour of the 0 .
2.2.16 Improvement of the Electrochemical Properties of a LiNi0.5Mn1.5O4 Cathode Material Formed by a New Solid-State Synthesis Method 
To avoid the drawbacks of huge particle size and meager homogeneity of material, which the conventional solid-state technique synthesized, straightforward amelioration of calcining process is employed (i.e., calcining-milling-recalcination) based upon the conventional solid-state synthesis to efficiently prepare a huge number of well-distributed, micrometer-sized, spherical secondary LiNi0.5Mn1.5O4 particles . Findings of the electrochemical performance tests indicate that the material displays a striking cycle performance and rate capability, which is compared with that derived from conventional synthesis technique; the spherical LiNi0.5Mn1.5O4 particles can deliver a huge capacity of 135.8 mAh g−1 at a 1 C discharge rate with a high retention of 77% after 741 cycles and a satisfactory capacity of 105.9 mAh g−1 at 10 C. Cyclic voltammetry measurements corroborate that the substantially enhanced electrochemical properties are because of enhanced electronic electrical conductivity and lithium-ion diffusion coefficient, which results from the optimized morphology and particle size .
2.2.17 Hierarchical Li1.2Mn0.54Ni0.13Co0.13O2 Hollow Spherical as Cathode Material for Li-Ion Battery 
High reversible capacity, excellent rate property, and satisfactory cycling stability, is shown by the as-prepared material . The as-prepared material delivers a high initial discharge capacity of 305.9 mAh g−1 at 28 mA g−1 with columbic efficiency of 80% . The subsample indicates a stable discharge capacity of 215 mAh g−1 even at high current density of 560 mA g−1 . The enhanced electrochemical properties are attributable to the stable hierarchical hollow sphere structure and the suitable contact area between electrode and electrolyte, efficiently enhance the lithium-ion intercalation and deintercalation kinetics . That the hollow structure is capable of enabling the layered lithium-rich cathode with an outstanding rate performance could be thought by us . Apart from, it could be detected that the subsample HS exhibits a pair of reversible redox peaks at 3.25 V in the second cycle, in congruent with the decrease and oxidation reaction of Mn3+/Mn4+ (Sathiya and others ), .
2.2.18 The Properties Research of Ferrum Additive on Li[Ni1/3Co1/3Mn1/3]O2 Cathode Material for Lithium-Ion Batteries 
Through means of cyclic voltammetry (CV), galvanostatic charge/discharge test, and electrochemical impedance spectroscopy (EIS), the electrochemical properties of Li[Ni1/3Co(1–x)/3Mn1/3Fex/3]O2 were compared . Electrochemical test results suggest that Li[Ni1/3Co0.9/3Mn1/3Fe0.1/3]O2 decline charge transfer resistance and improve Li+ ion diffusion velocity and . The initial discharge specific capacity of Li[Ni1/3Co0.9/3Mn1/3Fe0.1/3]O2 had been 178.5 mAh/g and capacity retention had been 87.11% after 30 cycles at 0.1 C, with the battery, which indicates satisfactory cycle performance . The initial columbic efficiencies and the initial discharge capacity reaches the highest value when x = 0.1 .
2.2.19 Comparative Study of the Electrochemical Properties of LiNi0.5Mn1.5O4 Doped by Bivalent Ions (Cu2+, Mg2+, and Zn2+) 
Scanning X-ray diffraction and electron microscopy analyses suggest that these doped LiNi0.45M0.05Mn1.5O4 samples remain the 5 V-positive electrode materials LiNi0.45M0.05Mn1.5O4 (M = Cu, Mg and Zn)’s spinel structure with an octahedral morphology . The LiNi0.45Mg0.05Mn1.5O4 and LiNi0.45Cu0.05Mn1.5O4 samples display excellent rate performance with specific capacities of 98.3 and 92.4 mAh g−1, respectively, at the charge-discharge rate of 10 C, whilst the LiNi0.5Mn1.5O4 subsample delivers just 78.9 mAh g−1 at 10 C. Apart from, the LiNi0.45Cu0.05Mn1.5O4and LiNi0.45Mg0.05Mn1.5O4 samples indicate satisfactory capacity retention at high temperature (55 °C) with the capacities of 117.6 and 119.5 mAh g−1, respectively, after 100 cycles at 1 C .
2.2.20 Nearly Monodispersed LiFePO4F Nanospheres as Cathode Material for Lithium-Ion Batteries 
Through a solid-state route, which is correlated with chemically caused precipitation technique for the first time, almost monodisperse LiFePO4F nanospheres with high purity are efficiently synthesized . Approximately monodisperse nanospheres particles are summarized by the synthesized LiFePO4F with mean particle size of ~500 nm . That the initial discharge capacity is 110.2 mAh g−1 at 0.5 C, after 200 cycles is still preserved 104.0 mAh g−1 with the retention rate of 94.4% is demonstrated by the results . The excellent cycle performance is primarily attributable to the homogeneous nanospheres-like morphology; this homogeneous is not just beneficial to shorten the transport distance of electrons and ions, though also enhance the interface area between electrode and electrolyte, and . The excellent cycle performance could be attributable to the homogeneous nanospheres-like morphology; this homogeneous is beneficial to enhance the interface area between electrolyte and electrode, shorten the transport distance of electrons and ions and improve the power and energy densities of batteries, and enhance the kinetics of Li ions .
2.2.21 Investigation of the Structural and Electrochemical Performance of Li1.2Ni0.2Mn0.6O2 with Cr-doping 
Cr-doped layered oxides Li[Li0.2Ni0.2–xMn0.6–xCr2x]O2 (x = 0, 0.02, 0.04, 0.06) were synthesized by high-temperature solid-state reaction and coprecipitation . HRTEM results and XRD patterns suggest that Cr-doped Li1.2Ni0.2Mn0.6O2 and the pristine indicate the layered stage . The first discharge specific capacity of Li1.2Ni0.16Mn0.56Cr0.08O2 is 249.6 mAh g−1 at 0.1 C, whilst that of Li1.2Ni0.2Mn0.6O2 is 230.4 mAh g−1 . The discharge capacity of Li1.2Ni0.16Mn0.56Cr0.08O2 is 126.2 mAh g−1 at 5.0 C, whilst that of the pristine Li1.2Ni0.2Mn0.6O2 is about 94.5 mAh g−1 . XPS results indicate that the content of Mn3+ in the Li1.2Ni0.2Mn0.6O2 could be restrained after Cr doping during the cycling, which results in restraining formation of better mid-point voltages and spinel-like structure .
2.2.22 An Insight into the Influence of Crystallite Size on the Performances of Microsized Spherical Li(Ni0.5Co0.2Mn0.3)O2 Cathode Material Composed of Aggregated Nanosized Particles 
Relationships between the performance and the crystallite size of the microsized spherical Li(Ni0.5Co0.2Mn0.3)O2 cathode material, which is comprised of aggregated nano-sized primary particles, have been comprehensively researched . The electrochemical attributes of Li(Ni0.5Co0.2Mn0.3)O2, including discharge capacity, thermal stability, and rate performance, are closely linked to the crystallite size . Through that of crystallite size, the retention of discharge capacity is dictated in Li(Ni0.5Co0.2Mn0.3)O2 after 100 cycles .
2.2.23 Synthesis and Electrochemical Performances of High-Voltage LiNi0.5Mn1.5O4 Cathode Materials Prepared by Hydroxide Co-precipitation Method 
X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical measurements were undertaken to LiNi0.5Mn1.5O4 cathode material, which is prepared describe . Electrochemical tests at 25 °C indicate that the LiNi0.5Mn1.5O4 cathode material, which is prepared after annealing at 600 °C, has the optimal electrochemical performances . The initial discharge capacity of prepared cathode material delivers 113.5 mAh g−1 at 1 C rate in the variety of 3.50–4.95 V, and the subsample possesses 96.2% (1.0 C) of the initial capacity after 50 cycles . The discharge capacities of obtained cathode material could be maintained at about (0.1 C) 145.0, (0.5 C) 113.5, (1.0 C) 126.8 and 112.4 (2.0 C) mAh g−1, the corresponding initial coulomb efficiencies maintain above 95.2 (0.1 C)%, 95.0 (0.5 C)%, 92.5 (1.0 C)% and 94.8 (2.0 C)%, respectively under various rates with a cut-off voltage variety of 3.50–4.95 V at 25 °C .
2.2.24 Highly Enhanced Low-Temperature Performances of LiFePO4/C Cathode Materials Prepared by Polyol Route for Lithium-Ion Batteries 
Based on 25 to −20 °C, the electrochemical performance of the LiFePO4/C, which polyol route prepared, had been examined at a temperature variety . In contrast to commercial ones, as-prepared LiFePO4/C indicates a considerably better low-temperature performance with a reversible capacity of 30 mAh g−1 even at 5 C under −20 °C and a capacity retention of 91.1% after 100 cycles at 0.1 C under 0 °C .
2.2.25 Synthesis and Characterization of Nanocomposites Based on Poly(3-Hexylthiophene)-Graft-Carbon Nanotubes with LiNi0.5Mn1.5O4 and Its Application as Potential Cathode Materials for Lithium-Ion Batteries 
The nanocomposite, which is premised doped spinel LiNi0.5Mn1.5O4 (LNMO) and on P3HT-g-CNTs, have been fabricated through mixing process . The structure and morphologies of LNMO/P3HT-g-CNTs nano-composites have been carried out by SEM, TEM and XRD, as reasonably well . The structure and morphology of the electrode were typified employing XRD, TEM and SEM . Through electrochemical impedance spectroscopy and cyclic voltammetry, the electrochemical performance of LNMO/P3HT-g-CNTs nano-composites as cathode materials of lithium-ion batteries were examined and showed the high diffusion of lithium ions in the charge-discharge process . That the electrochemical reaction of LNMO/P3HT-g-CNTs nano-composites is better than that of LNMO/VC materials as a consequence of high diffusion of lithium ions in the charge-discharge process is revealed by these results .
2.2.26 Lithium-Sulphur Batteries Based on Biological 3D Structures 
Enough space is offered by this 3D electrode for sulfur . The electrode structure enables high sulfur loading . The resultant novel cathode configuration enables reaching quite high sulfur area loading of 4.9 mg/cm2 which is nearly four times more than in the case of a standard coated electrode . Throughout cycling in comparison with a standard electrode, the electrode establishes high stability and the electrode structure reaches considerably greater square capacity, exceeded 3.0 mAh/cm2 despite the high sulfur loading . The results indicate that the 3D structured electrode establishes a stable plateau at 2.4 V including its stability .
2.2.27 Carbon-Coated LiFePO4–Carbon Nanotube Electrodes for High-Rate Li-Ion Battery 
A fruitful cathode material for high-rated lithium-ion batteries is Olivine LiFePO4 (LFP) . A serious drawback of low electrical conductivity and sluggish transportation of Li+ ions, which slows down hence the retention capacity of battery and the chemical reactions had been confronted by Olivine . A mixing of carbon nanotubes (CNTs) on the composite electrode had been examined to improve the electrochemical performance of nanocomposite LiFePO4/C . An increase of DLi had been detected with the increase of CNT quantity in electrode composite . Upon 200 cycles, an excellent performance in rate capability and cycling test had been shown by the composite electrode LFP/C/10% CNTs; a retention capacity of 98% had been detected .
2.2.28 Recent Advances on Fe- and Mn-Based Cathode Materials for Lithium and Sodium Ion Batteries 
The ever-increasing market of electrochemical energy storage impels the advancements on environment-friendly and cost-efficient battery chemistries . The development of cathode materials, which is based upon Earth’s plentiful elements (Fe and Mn), largely determines the prospects of the batteries . The development of a high-performance and cheap battery necessitates the advance of the anode part . Prospects and issues are outlined to direct the possible development of high-performance and cost-efficient cathode materials for future rechargeable batteries . Mn-based cathodes for Li-ion batteries and a critical criterion for the development of future Fe-is to attain similar or even greater energy densities . That this review can inform Mn-based cathode materials and readers of the rationality and priority of Fe-as candidates for future Li-ion batteries and SIBs, and call for additional efforts to satisfy this aim is hoped by us . Considering the cost’s elemental relative abundance, Fe-based and Mn-cathode materials are hence preferable decisions, and the cost’s sodium analogues are attracting considerably attention, as they would allow the future of Li-free SIBs, which might be optimal decisions for large-scale applications . We assume better development of Fe and understanding-and Mn-based cathode materials will help to make rechargeable Na-ion and lithium batteries cheaper, better, and greener .
2.3 Pristine, Layered, Cathode Materials, Samples, Coating Layer
2.3.1 BiFeO3-Coated Spinel LiNi0.5Mn1.5O4 with Improved Electrochemical Performance as Cathode Materials for Lithium-Ion Batteries 
BiFeO3-coated LiNi0.5Mn1.5O4 materials were prepared through the structure, morphology and a moist chemical technique, and electrochemical performance of the materials were researched . Cubic spinel structure with space group of Fd3m is shown by all BiFeO3-coated LiNi0.5Mn1.5O4 materials . The coating of 1.0 wt% BiFeO3 on the surface of LiNi0.5Mn1.5O4 displays a substantial enhancement in specific capacity, rate performance, and cyclic stability . The coating of BiFeO3 has no apparent impact on the crystal structure of LiNi0.5Mn1.5O4 . 1.0 wt% BiFeO3-coated LiNi0.5Mn1.5O4 electrode indicates excellent rate performance with discharge capacities of 117.5, 110.2, 85.8, and 74.8 mAh g−1 at 1, 2, 5, and 10 C, respectively, which is greater than that of LiNi0.5Mn1.5O4 (97.3, 90, 77.5, and 60.9 mAh g−1, respectively) . The surface coating of BiFeO3 efficiently decreases charge transfer resistance and impedes side reactions between electrolyte and active materials and induces the enhanced electrochemical performance of LiNi0.5Mn1.5O4 materials . That the rate performance of the LNMO electrode is substantially enhanced after being coated with 1.0 wt% BiFeO3 is revealed by these results .
2.3.2 Li-Ion-Conductive Li2TiO3-Coated Li[Li0.2Mn0.51Ni0.19Co0.1]O2 for High-Performance Cathode Material in Lithium-Ion Battery 
Li2TiO3 is utilized as a new coating material to alter Li(Li0.2Mn0.51Ni0.19Co0.1)O2 electrode to improve the electrochemical performance of the host material . The subsample coated with optimal cyclability (discharge capacity of 207.1 mAh g−1 at 0.5 C after 100 cycles), 3 wt% Li2TiO3 displays the highest rate capability (169.9 mAh g−1 at 2 C rate and 149.1 mAh g−1 at 5 C rate), and enhanced initial columbic efficiency (69.5%) in the voltage variety of 2.0–4.8 V . The electrochemical impedance spectroscopy (EIS) tests confirm that the suitable Li2TiO3 coating layer can efficiently restrain the increased impedance of the host electrode . That the efficient Li+-conductive Li2TiO3 coating layer can sustain the host structure, restrain the undesirable surface side reactions on the electrode surface, which the EIS tests demonstrated, and safeguard the electrode surface from HF attack, is-confirmed by the charge discharge curves .
2.3.3 Na-Doped Layered LiNi0.8Co0.1Mn0.1O2 with Improved Rate Capability and Cycling Stability 
That Na-doped LNMCOs deliver a rate capability and cycling stability at high cut-off voltages of 4.3 and 4.5 V that are more efficient than those of undoped LNMCO is shown by electrochemical measurements . Electrochemical impedance spectroscopy (EIS) measurement reveals that Na doping reduces both the impedance of the charge transfer and the solid electrolyte interface layer . The superior electrochemical performances of Na-doped LNMCOs are attributable by us to a pillared structure; this structure simultaneously favours the amelioration of cycling stability and Li+ mobility .
2.3.4 ZnO-Coated LiMn2O4 Cathode Material for Lithium-Ion Batteries Synthesized by a Combustion Method 
Through a combustion technique, which employs glucose as fuel, ZnO-coated LiMn2O4 cathode materials were prepared . Through X-ray diffraction (XRD), the stage structures, size of particles, electrochemical performance of pristine, and morphology, and ZnO-coated LiMn2O4 powders are researched in detail, scanning electron microscopy (SEM), transmission electron microscopy (TEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), galvanostatic discharge/charge test, and X-ray photoelectron spectroscopy (XPS) . Rate performance and galvanostatic charge/discharge test revealed that the ZnO coating can enhance the capacity and cycling performance of LiMn2O4 . Upon 500 cycles at 0.5 C. Apart from, a satisfactory rate capability at various current densities from 0.5 to 5.0 C could be acquired, the 2 wt% ZnO-coated LiMn2O4 subsample showed an initial discharge capacity of 112.8 mAh g−1 with a capacity retention of 84.1% .
2.3.5 Enhanced Electrochemical Properties and Thermal Stability of LiNi1/3Co1/3Mn1/3O2 by Surface Modification with Eu2O3 
The Eu2O3-coated subsample reveals better electrochemical performances and thermal stability than that of the pristine one . The Eu2O3-coated LiNi1/3Co1/3Mn1/3O2 cathode reveals stable cycleability with capacity retention of 92.9%, which is greater than that (75.5%) of the pristine one in voltage variety 3.0–4.6 V. Analysis from the electrochemical measurements demonstrates that the remarkably enhanced performances of the surface-modified composites are primarily attributed to the presence of Eu2O3-coating layer, which can effectively restrain increased impedance and the undesired side reaction, and improve the systemic stability of active material after 100 cycles at 1 C . In Ar-filled glove box, the both cells were disassembled and the electrodes were immersed into DEC solution respectively after 100 cycles . The obtained results show that the presence of Eu2O3 on LiNi1/3Co1/3Mn1/3O2 surface plays important roles in declining the interfacial impedance, fostering kinetic behaviours of Li ions, suppressing reactivity between electrolyte and electrode and enhancing systemic stability .
2.3.6 Surface Modification of Cathode Material 0.5Li2MnO3·0.5LiMn1/3Ni1/3Co1/3O2 by Alumina for Lithium-Ion Batteries 
Preliminary discharge specific capacity of 211.7 mAh g−1 between 2.0 and 4.8 is delivered by the 2-wt% coated subsample at a rate of 1 C V with an initial columbic efficiency of 73.2% as a cathode material for lithium-ion batteries . The results displays the highest discharge specific capacity of 206.2 mAh g−1 with 97.4% capacity retention after 100 cycles considerably elevated rate capability and at compared to uncoated material . More superior rate property and the excellent cycling stability could be attributed to alumina coating layer, which has a surface stabilization effect on these cathode materials, lessening the break-up of metal ions . Cyclic voltammetry researches and the electrochemical impedance suggest that coated by alumina enhanced the kinetic performance for lithium-rich layered materials, demonstrating a prospect for practical lithium battery application . That lithium-rich layered materials are comprised of Li2MnO3 element and LiMO2 element to form a homogeneous solid solution structure (Lee and Manthiram ; Tabuchi and others ) is usually thought by scholars . Through hydrothermal technique, 5Li2MnO3·0.5LiMn1/3Ni1/3Co1/3O2 cathode material had been prepared and a thin layer of alumina had been efficiently coated on the surface of material, which is prepared, under the hydrolysis of aluminium isopropoxide which could be detected by TEM images .
2.3.7 Enhanced High Power and Long Life Performance of Spinel LiMn2O4 with Li2MnO3 Coating for Lithium-Ion Batteries 
In contrast with the pristine subsample, 3 wt% Li2MnO3-coated subsample reveals an excellent cycle performance with a capacity retention of 94.17% after 500 cycles at 25 °C and 89.75% after 200 cycles at 55 °C . An excellent rate performance with a capacity of 97.6 mAh g−1 at 12 C, which could be primarily attributable to the stable stage interface between host LiMn2O4 material and Li2MnO3 coating layer is shown by the composite material . An efficient way to improve the electrochemical performance of LiMn2O4 is the functionalized Li2MnO3 coating . There is no further peak corresponding to Li2MnO3 that could be detected; this peak which could be attributable to its tiny amount . The electrochemical results indicate that the 3 wt% Li2MnO3-coated subsample introduces excellent electrochemical performances compared with the pristine one, delivering a discharge capacity of 97.6 mAh g−1 at 12 C, with a capacity retention of 94.17% after 500 cycles at 25 °C and 89.75% after 200 cycles at 55 °C .
2.3.8 Research Progress in Improving the Cycling Stability of High-Voltage LiNi0.5Mn1.5O4 Cathode in Lithium-Ion Battery 
High-voltage lithium-ion batteries (HVLIBs) are regarded as fruitful tools of energy storage for hybrid electric vehicle, electric vehicle, and other high-power equipment . High-voltage lithium-ion batteries (HVLIBs) with moderate theoretical discharge capacity, stable high discharge platform, and high thermodynamic stability, provide novel possibilities for next batteries with high energy density [36, 513, 561, 562]. Lithium nickel manganese spinel LiNi0.5Mn1.5O4 (LNMO) cathode is the most fruitful candidate among the 5 V cathode materials for HVLIBs because of its flat plateau at 4.7 V. Nevertheless, the degradation of cyclic performance is quite serious when LNMO cathode operates over 4.2 V . We summarize many techniques for improving the cycling stability of LNMO cathodes in lithium-ion batteries, which comprises doping, electrolyte altering, cathode surface coating, and other techniques .
2.3.9 Improvement in the Electrochemical Performance of a LiNi0.5Mn0.5O2 Cathode Material at High Voltage 
The results of XRD, Rietveld refinement, SEM and XPS measurements confirmed that Ca-doping can lower the quantity of Li/Ni cation mixing and increase the stability of the structure . The results of electrochemical measurements indicate that a 3 mol% Ca-doping displays the optimal electrochemical performance, which comprises the optimal cycle stability and rate performance and the highest capacity . Ca-doping had been not detected to affect the morphology or oxidation states of the LiNi0.5Mn0.5O2 . The electrochemical measurements revealed that the pristine LiNi0.5Mn0.5O2 material has the lowest discharge capacity of 88.6 mAh g−1 between 4.5 V and 3 at a constant density of 0.2 C; this C had been enhanced 38% by doping with 3 mol% of Ca . The capacity retention of the 3 mol% Ca-doping is 20% greater than that of the pristine LiNi0.5Mn0.5O2 material in the voltage variety of 3.0–4.5 V. Furthermore, we examined the source of the enhancement of the electrochemical properties from Ca-doping .
2.3.10 High Energy Density and Lofty Thermal Stability Nickel-Rich Materials for Positive Electrode of Lithium-Ion Batteries 
We have prepared a core-shell material, which is comprised of a monoclinic (C2/m) Li2MnO3 shell and a core of NCM811 (R-3m), to circumvent this barrier . That core-shell is quite various from the traditional core-shell materials . The traditional core-shell materials are layered R-3 m structures which are instable at state (>4.5 V) because of the high repulsion between the two oxygen atoms facing every other across the empty Li site, which is delithiated highly, whilst our synthesized material could be safely cycled at high upper cutoff potential of 4.7 V with high capacity retention . Based on 4.3–4.7 V. Differential scanning calorimetry (DSC) results indicate that the exothermic peak of the core-shell structured material seems at 360 °C with a heat evolution of 575.1 J g−1, whilst that of the pristine material seems at 250 °C with a heat evolution of 239.1 J g−1, the upper cutoff potential is elevated .
2.3.11 Effects of Doping Al on the Structure and Electrochemical Performances of Li[Li0.2Mn0.54Ni0.13Co0.13]O2 Cathode Materials 
That all the materials revealed surface morphology and comparable XRD patterns had been confirmed by the results . Nonetheless kept a discharge capacity of 135.6 mAh g−1at 5.0 C. and the discharge capacity had been 265.2 mAh g−1 at 0.1 C . The capacity retention can still be 58.2 and 66.8% after 50 cycles at 1.0 and 2.0 C, respectively . Electrochemical impedance spectra results demonstrated that cycling performance and the rate capability, which is enhanced remarkably, can be attributed to enhanced reaction kinetics and the low charge transfer resistance .
2.3.12 Synergistic Effect of Magnesium and Fluorine Doping on the Electrochemical Performance of Lithium-Manganese Rich (LMR)-Based Ni–Mn–Co–Oxide (NMC) Cathodes for Lithium-Ion Batteries 
Through combustion technique, which is followed by fluorine doping by solid-state synthesis, Mg-doped-LMR-NMC (Li1.2Ni0.15–xMgxMn0.55Co0.1O2) is synthesized . Mg–F-doped LMR-NMC (Mg 0.02 mol) composite cathodes indicates excellent discharge capacity of ~300 mAh g−1 at C/20 rate while pristine LMR-NMC indicates the initial capacity around 250 mAh g−1 in the voltage variety between 2.5 and 4.7 V. Mg–F-doped LMR-NMC indicates lesser Ohmic and charge transfer resistance, cycles reasonably well, and delivers a stable high capacity of ~280 mAh g−1 at C/10 rate . In Mg–F-doped LMR-NMC, the voltage decay which is the main problem of LMR-NMC is mitigated compared to pristine LMR-NMC . That a handful nanometer-thick Lipon film is an efficient way to enhance the interfacial stability against high voltage cycling, which gives rise to better high C-rate performance, greater usable capacity , and cycle life, is demonstrated by researches .
2.3.13 Effect of Sonication Power on Al2O3 Coated LiNi0.5Mn0.3Co0.2O2 Cathode Material for LIB 
In battery performance, these difficulties mainly linked with cathode materials, an amelioration in cathode materials might cause significant transformations . To circumvent cycle life issue, which coates Al2O3 on LiNi0.5Mn0.3Co0.2O2 cathode material, which sol generated, gel technique . At 600 °C, last heat treatment for Al2O3 crystallization had been done for 4 h. X-ray (XRD) diffraction measurements revealed that the material had a layered structure, which is ordered reasonably well-ordered layered structure and Al had been not in the LiNi0.5Mn0.3Co0.2O2 after the second gel is obtained . Improved cycling performance is demonstrated by Al2O3 coated materials compared to the pristine material . It is thought that, this amelioration is induced by the fact that Al2O3 layer prevents direct contact between electrolyte and reducing decomposition reactions and active material .
2.3.14 Improved Electrochemical Performance of NaAlO2-Coated LiCoO2 for Lithium-Ion Batteries 
The NaAlO2 layer is coated on the LiCoO2 particles efficiently . The enhanced cycling stability and rate capability at a high cut-off voltage of 4.5 V versus Li+/Li is shown by NaAlO2-coated LiCoO2 materials . NaAlO2-coating layer acts as a physical barrier; this barrier separates the LCO electrode and electrolyte, which will restrain the oxidation of solvents, the evolution of oxygen at high cut-off voltage, and break-up of cobalt ions . Two-dimensional ion diffusion channel for lithium ions, which results in amelioration of electrochemical performance for LiCoO2, could be offered by the NaAlO2 layer . It could be observed that all samples display the comparable diffraction peaks, matching reasonably well with R-3m space group (JCPDS No. 50-0653) and α-NaFeO2-layered structure, and no diffraction peaks from possible impurities (e.g., NaAlO2, Al2O3) in all samples were observed . It could be observed that the NA-coated LCO samples indicate a slight lower capacity than the pristine one; particularly, the capacity of LCO@NA-4% is 10% smaller than that of pristine LCO .
2.3.15 A Ternary Oxide Precursor with Trigonal Structure for Synthesis of LiNi0.80Co0.15Al0.05O2 Cathode Material 
Through calcining Ni–Co–Al composite oxalates formed by employing a facile chemical strategy, a Ni–Co–Al ternary oxide precursor with a trigonal structure, which could be utilized to synthesize LiNi0.8Co0.15Al0.05O2 cathode material, had been prepared . The LiNi0.8Co0.15Al0.05O2 cathode material, which is calcined at a temperature as low as 650 °C, had satisfactory electrochemical performance with an initial discharge capacity of 183.9 mAh g−1 . Through traditional solid-state technique, the LiNi0.8Co0.15Al0.05O2 cathode material is synthesized, as reasonably well . That investigation offers a facile way to synthesize layered cathode material with satisfactory electrochemical performance at a lower calcining temperature . That the electrochemical properties of Ni-rich cathode material, which traditional solid-state technique prepared, are not good, which is primarily attributed to the inhomogeneous distribution of transition metal ions, despite repeated mechanical ball milling before calcining is confirmed by these results .
2.3.16 LiMO2@Li2MnO3 Positive-Electrode Material for High Energy Density Lithium-Ion Batteries 
Li[Ni1/3Co1/3Mn1/3]O2 (NCM 111)’s capacity of 155 mAh g−1 is fairly low, and cycling at potentials above 4.5 V gives rise to rapid capacity deterioration . A successful synthesis of lithium-rich layered oxides (LLOs) with a shell of Li2MnO3 (C2/m) (the molar ratio of Ni, Co to Mn is the identical as that in NCM 111) and a core of LiMO2 (R-3m, M = Ni, Co) is indicated by us . The core-shell material Li1.15Na0.5(Ni1/3Co1/3)core(Mn1/3)shellO2 could be cycled to a high upper cut-off potential of 4.7 V, delivers a high discharge capacity of 218 mAh g−1 at 20 mA g−1, and possesses 90% of its discharge capacity at 100 mA g−1 after 90 cycles; the use of this material in Li-ion batteries can considerably increase their energy density .
2.3.17 Enhanced Electrochemical Performances of Li2MnO3 Cathode Materials by Al Doping 
The Al-LMO subsample displays a considerable amelioration on the rate capability and cycling stability, which is compared to the LMO subsample . The differential capacity versus voltage (dQ/dV) results show that Al doping might be to downturn the rate of reconfiguration upon cycling and deter the first charge stage reconfiguration from a layered stage to a cubic spinel-like stage . Electrochemical impedance spectroscopy (EIS) results corroborate that Al doping decreases the charge-transfer resistance and enhances the electrochemical reaction kinetics . Li-rich Mn-based layered compounds have been regarded as one of the most fruitful cathode material for future Li-ion batteries due to their advantage of high reversible capacity (>200 mAh g−1), which is charged when above 4.5 V [45, 476, 489, 490, 491].
2.3.18 Improving the Electrochemical Performance of LiNi0.5Co0.2Mn0.3O2 by Double-Layer Coating with Li2TiO3 for Lithium-Ion Batteries 
The dual-layer Li2TiO3 coating of LiNi0.5Co0.2Mn0.3O2 (NCM523) compound has been efficiently synthesized by a facile technique for the first time . The enhanced electrochemical performance is attributable to the stable dual-layer Li2TiO3; this dual-layer serves as a protective layer that prevents side reactions between electrode and electrolyte and a 3D-diffusion pathway for Li+ ions . A fruitful technique to enhance rate capability and cycle performance of NCM523 is the double-layer coating by Li2TiO3 . The surface of the double-layer coated subsample N5@ (0.5 + 0.5)% LT is smoother than those of the single-layer and more homogeneous coated samples as could be observed from the SEM images .
2.3.19 Modification Research of LiAlO2-Coated LiNi0.8Co0.1Mn0.1O2 as a Cathode Material for Lithium-Ion Battery 
Through hydrolysis-hydrothermal technique, the LiNi0.8Co0.1Mn0.1O2 with LiAlO2 coating had been obtained . That the LiAlO2 layer had been nearly totally covered on the surface of particle had been demonstrated by the results, and the thickness of coating had been about 8–12 nm . At 40 °C, side reaction between electrolyte and composite had been repressed by the LiAlO2 coating; the electrochemical performance of the LiAlO2-coated LiNi0.8Co0.1Mn0.1O2 had been enhanced . Upon 100 cycles at room temperature and 87.4% capacity retention after 100 cycles at 40 °C, the LiAlO2-coated subsample delivered a high discharge capacity of 181.2 mAh g−1 (1 C) with 93.5% capacity retention .
2.3.20 Aluminum Doped Na3V2(PO4)2F3 via Sol-Gel Pechini Method as a Cathode Material for Lithium-Ion Batteries 
The solid solution series Na3V2–xAlx(PO4)2F3 (where x = 0, 0.02, 0.05, and 0.1) powders have been prepared employing the Pechini technique to investigation the effect of aluminium doping on the electrochemical properties of these cathode materials for Li-ion batteries . Through X-ray diffraction, differential and thermo-gravimetric analysis, specific surface area, the structure, morphology, and composition, of the compounds were examined, and pore size analysis, which employs Brunauer-Emmett-Teller-Barret-Joyner-Halenda techniques, scanning electron microscopy, elemental chemical analysis with caused coupled plasma-optical emission spectrometry, and charge/discharge galvanostatic experiments . The stage with 0.05 mol of aluminium gave the optimal consequence electrochemical charge/discharge capacities of 123–101 mAh/g with a capacity retention of 82% and cell voltage of 4.4 V versus Li, compared to undoped material which gave 128–63 mAh/g, and 49% capacity retention . Improved electrochemical performance maybe attributed to enhanced structure stability had been demonstrated by Al-doped samples compared to the undoped material .
2.3.21 Co-precipitation Synthesis of Precursor with Lactic Acid Acting as Chelating Agent and the Electrochemical Properties of LiNi0.5Co0.2Mn0.3O2 Cathode Materials for Lithium-Ion Battery 
Through coprecipitation, which employs lactic acid as the environmentally friendly chelating actor, hydroxide precursor Ni0.5Co0.2Mn0.3(OH)2 had been efficiently prepared . Through sintering the mixture of Li2CO3 and as-prepared Ni0.5Co0.2Mn0.3(OH)2 precursor, the LiNi0.5Co0.2Mn0.3O2 cathode materials were obtained . Through employing X-ray diffraction (XRD), land battery tester, and field-emission scanning electron microscopy (FE-SEM), electrochemical performances of LiNi0.5Co0.2Mn0.3O2 cathode materials, and Morphological, were examined . The results revealed that the quasi-spherical LiNi0.5Co0.2Mn0.3O2 with the size of about 5 μm showed the excellent electrochemical performance when its Ni0.5Co0.2Mn0.3(OH)2 precursor had been synthesized at the molar ratio of 1:1 between transition metal ion and lactate ion .
2.3.22 Effect of Nitridation on LiMn1.5Ni0.5O4 and Its Application as Cathode Material in Lithium-Ion Batteries 
Through a solid-state reaction, which nitridation followed, Nitridated LiMn1.5Ni0.5O4 had been prepared to examine the effect of nitrogen on the electrochemical and systemic performance of LiMn1.5Ni0.5O4 cathode material for lithium-ion batteries . Electrochemical researches on the nitridated LiMn1.5Ni0.5O4 had been carried out employing the galvanostatic charge-electrochemical impedance spectroscopy and discharge process . Rate capability and enhanced cycleability had been shown by the nitridated LiMn1.5Ni0.5O4 compared with LiMn1.5Ni0.5O4, which originated from the enhanced electric conductivity, which the increasing number of Mn3+ hopping carriers including increasing proximity between active Ni redox centres triggered .
2.3.23 The Application of a Water-Based Hybrid Polymer Binder to a High-Voltage and High-Capacity Li-Rich Solid-Solution Cathode and Its Performance in Li-Ion Batteries 
Uniform cathode films were prepared with a Li-rich solid-solution (Li[Li0.2Ni0.18Co0.03Mn0.58]O2) cathode material and a water-based hybrid polymer binder (TRD202A, JSR, Japan), which is comprised of acrylic polymer and carboxymethylcellulose, fluoropolymer, and conducting carbon additive . A cathode film, which is prepared with the water-based hybrid polymer binder, revealed long-term validity including greater electrochemical resistance when compared with a cathode film, which employs the traditional polyvinylidene difluoride binder, after 80 cycles in the chemical environment of lithium ion cells .
2.3.24 Na-Doped LiMnPO4 as an Electrode Material for Enhanced Lithium-Ion Batteries 
Via a straightforward sol-gel technique, Li1–xNaxMnPO4 with various mole ratios (0.00 ≤ x ≤ 0.05) of sodium is synthesized . The discharge capacity of Li1–xNaxMnPO4 differs relating to mole ratios of sodium incorporated . In Li0.97Na0.03MnPO4, which is greater than that of pristine LiMnPO4 and other Na-incorporated LiMnPO4, the maximal discharge capacity of 92.45 mAh g−1 is detected .
2.3.25 Synthesis of Diverse LiNixMnyCozO2 Cathode Materials from Lithium-Ion Battery Recovery Stream 
In some nations, a huge quantity of spent Li-ion batteries is being landfilled every year; in order to recover and re-use critical materials, an a high-efficiency Li-ion and cheap battery recovery process had been devised at Worcester Polytechnic Institute . It had been revealed that high performance Ni1/3Mn1/3Co1/3(OH)2, Ni0.5Mn0.3Co0.2(OH)2, LiNi1/3Mn1/3Co1/3O2 and Ni0.6Mn0.2Co0.2(OH)2 precursors, LiNi0.5Mn0.3Co0.2O2, LiNi0.6Mn0.2Co0.2O2 cathode materials could be synthesized from the leaching solutions of a Li-ion battery recovery stream . Electrochemical tests results shown that all cathode materials synthesized from spent Li-ion battery recovery streams carried out at a discharge capacity greater than 155 mAh/g at first cycle of 0.1 C, and after 100 cycles at 0.5 C, with over 80% of the capacity preserved . An increase in Li-ion batteries signifies that there will be more battery waste in the near future . That LiNi1/3Mn1/3Co1/3O2, LiNi0.6Mn0.2Co0.2O2, and LiNi0.5Mn0.3Co0.2O2, have excellent specific rate capacities is demonstrated by the electrochemical test results .
Without an further mixing process of lithium salts and retains homogeneous cation distribution, the material could be obtained with the coprecipitation of Li+ with transition metal ions . The material delivers enhanced electrochemical performances such as cycle stability and rate capability, as shown by a high reversible capacity of 104.0 mAh g−1 at 10 C, and more than 98.5% capacity retention after 100 cycles at 1 C. On the basis of this work, LNMO materials prepared by the present synthetic route can be a fruitful candidate cathode for high-power Li-ion batteries .
Hierarchical hollow LiNi0.5Mn1.5O4 microspheres as a 5-V cathode material for Li-ion batteries has been synthesized by a coprecipitation strategy accompanied with high-temperature calcinations . The obtained commodities deliver enhanced electrochemical performances with satisfactory rate capability and cycle stability; this stability makes it a fruitful cathode candidate for high-energy density Li-ion batteries .
Electrochemical measurements have demonstrated that Ni-Cr codoped samples display more stable cycling performance than the pure LiMn2O4 . The cycling performance had been considerably better at high current rates even though the initial discharge specific capacity of the LiNi0.01Cr0.01Mn1.98O4 cell had been observed lower than the pure LiMn2O4 . A discharge capacity of 91% of the initial has been regained upon reducing the current rate to 0.1 C. In contrast with the pure LiMn2O4, the enhanced capacity retention of LiNi0.01Cr0.01Mn1.98O4 had been attributable to the inhibition of the Jahn-Teller distortion effect, considerably easier Li+ ion diffusion because of shortening of the diffusion length and formation of homogeneous smaller particle size after cycling at 5 C .
Spinel LiNi0.5Mn1.5O4 cathode materials were synthesized through a facile solid-state technique and the impacts of various lithium excess quantities on the crystalline structure, particle morphology, and electrochemical performance were systematically examined . The slightly inferior electrochemical performance of LNMO-10% subsample could be attributed to the greater cation, which mixes more LixNi1–xO impurity stage and extent . It could be concluded that in solid-state technique, the lithium excess quantity has little impact on size and particle morphology, and the electrochemical performance is primarily dependent upon the crystalline structure, more specifically, Mn3+ content (disordering extent), extent, which mixes cation, and LixNi1–xO impurity quantity (stage purity) .
The Sn4+-doped LMNC cathode materials with the enhanced electrochemical performance were synthesized employing the sol-gel technique . The electrochemical performance of Sn4+-doped LMNC cathode has been substantially enhanced, particularly when the doping quantity of Sn4+ is 0.01 . A faster Li+ diffusion process and better systemic stability, which are favourable for the electrochemical performance of the LMNC cathode material is demonstrated by these .
The usage of CNF and the synthetic technique offer an alternative for the synthesis of LiNi0.5Mn1.5O4 cathode materials with greater performance and suggest their promise in practical applications .
The LiNi0.8Co0.15Ti0.05O2 subsample prepared at 800 °C displays a greater extent of the least cation mixing and ordering hexagonal structure and demonstrates excellent electrochemical performance with the capacity retention of 86.7% after 30 cycles at 0.2 C. and the discharge capacity of 174.2 mAh g−1 .
The integrity of the Li2FeSiO4 crystal structure can be enhanced by strontium cation doping because of lowered Li/Fe anti-site disorder in the lattice . The 1% strontium cation-doped Li2FeSiO4/C delivered a high discharge capacity of 181 mAh g−1 at 0.5 C rate as a cathode material of a lithium-ion battery . Li2FeSiO4/C cathode showed high specific capacity, satisfactory rate performance had been cation-doped by the 1% strontium, and stable cycle performance, which is attributed to the enhanced Li+ diffusion capability, undermined crystal structure stability, and restrained side reactions between the electrode and electrolyte .
Through XRD, SEM, TEM, XPS, galvanostatic discharge/charge test, CV, and EIS, the structure and electrochemical properties of the materials are examined . That LiNi0.5Mn0.45Ru0.05O2 can deliver a preferable electrochemical performance is revealed by the electrochemical measurement . The EIS and CV results corroborate that LiNi0.5Mn0.45Ru0.05O2 has a satisfactory reversibility, an enhanced diffusion coefficient to assure excellent electrochemical performance, and a low charge-transfer resistance .
“The specific discharge capacities of LiCr0.05Ni0.475Mn1.475O3.95F0.05 at 0.1, 0.5, 2, 5, and 10 C were 134.18, 128.70, 123.62, 119.63, and 97.68 mAh g−1, respectively” . The specific discharge capacity had been 121.02 mAh g−1 after 50 cycles at 2 C, which is of 97.9% the initial discharge capacity . The capacity retention rate of LiCr0.05Ni0.475Mn1.475O3.95F0.05 had been the largest among the samples . Cr3+, F− codoped of the materials substantially enhanced the specific discharge capacity at greater rate, enhanced the cycling stability, lowered the impedance value, and enhanced the reversibility of lithium ions .
Li3YxV2(PO4)3/C composites with various quantities of Y-doping were efficiently prepared by a rheological stage reaction process . Y-doping and the carbon coating have considerably impact on the electrochemical properties of Li3V2(PO4)3 . The optimal electrochemical performance with the initial discharge capacity of 158.75 mAh g−1 and the capacity of 148.99 mAh g−1 after 50 cycles at a current density of 0.1 C. Hence, carbon coating and metal ions doping are efficient ways to attain materials of greater capacity and better cycling stability is shown by Li3Y0.03V2(PO4)3/C among all materials .
LiMn2O4 had been coated by new transition metal alloy (Mx = PtAu) with enhanced high rate performances have been efficiently designed and synthesized . The smaller potential variations of alloy functionalized-LiMxMn2–xO4 cathodes indicate smaller polarization because of faster insertion/extraction of Li+ ions in the spinel structure . The amelioration in diffusivity of Li+ ions might be attributable to three reasons . The vacancies at the octahedral sites created by Mx coating offer further diffusion pathways for lithium ions . The increase in lattice parameter after Mx coating helped faster lithium diffusion . Such improvements are because of enhanced lithium and electronic electrical conductivity diffusivity, which results from transition metal alloy coating . That the PtAu0.02 coating particles act as a protective layer can be a novel viable strategy for generating advanced Li-ion battery cathodes with enhanced electrochemical properties and that prevents the oxygen from outgoing which contributed to main improvements is demonstrated by the results .
In the compound, increased the relative content of aluminium can enhance structure stability and decline the extent of cation mixing . Changing the relative content of aluminium properly is an efficient and straightforward technique to enhance the electrochemical performance of LiNi0.56Co0.19Mn0.24Al0.01O2 cathode composite materials for lithium-ion batteries . Structure and rate capacities of the novel material need to be additional enhanced in later investigation .
The resulting S0.5 material displays an excellent cycling performance that 91.4% of its discharge capacity can be preserved after 100 cycles . S0.5 with excellent rate performance that the discharge capacities of S0.5 subsample are 125.7, 118.1, 111.7, and 96.6 mAh g−1 at 0.2, 0.5, 2, and 5 C . The discharge capacities of the S0.5 subsample are 80.8 mAh g−1 even at greater rate (i.e., 10 C) . The middle particle size of S0.5 subsample balances the conflicting of diffusion length in solid stage and particle agglomeration; this stage gives rise to perfect contacts with the conductive additive, substantial evident lithium ion diffusion rate, and the optimum performance .
The highest discharge capacity, the most excellent rate capability and the optimal cycling performance is shown by the LR-1.0 among all the samples . The discharge capacity retention of 93.3% after 50 cycles and the discharge capacity of 266.6 mAh g−1 is shown by the LR-1.0 at 0.1 C . 266.6 mAh g−1’s discharge capacity can retain at 146.6 mAh g−1 at 2.0 C . That investigation offers a novel applicable route to synthesize advanced Li-rich layered cathode materials .
Through utilizing an enhanced (i.e., calcining-milling-recalcination) calcining technique, which had been based upon a conventional solid-state synthesis, micrometer-sized, spherical LiNi0.5Mn1.5O4 had been prepared . The spherical particles composed a huge number of nano-and/or sub-micrometer-sized primary particles and showed striking rate capability and cycling performance than the reference material, which is formed through the conventional synthesis route . A convenient and effective strategy for the solid-state synthesis of LiNi0.5Mn1.5O4 cathode material is amelioration of the calcining process .
A hierarchical hollow spherical lithium-rich, which employs Li1.2Mn0.54Ni0.13Co0.13O2 cathode material CTAB and sucrose as a soft template, which is combined with hydrothermal assisted homogenous precipitation technique, had been efficiently synthesized by us . That this hollow spherical cathode composite displays high electrochemical performance in terms of reversible capacity and cycle stability life including rate capacity is shown, in comparison with the solid sphere subsample, by the results . Especially cycled at 560 mA g−1, the hollow spherical subsample indicates high discharge capacity of 215 mAh g−1 and can attain 143.3 mAh g−1 after 100 cycles . That work offers an strategy to enhancing cycling ability of the layered lithium-rich cathode and the rate capacity .
Li[Ni1/3Co(1–x)/3Mn1/3Fex/3]O2 (x = 0.0, 0.1, 0.3, 0.5, 0.7, 0.9) cathode materials have been synthesized through hydroxide coprecipitation technique . A small quantity of Fe3+ replaced for Co3+ when preparing cathode materials will give excellent electrochemical performance .
Both have a well-defined cubic structure, which includes the P4332 space group, with Mg2+ and Cu2+ ions replacing Ni2+ occupying the 4b sites is randomly selected by analyses, LCNM and the LMNM . Especially at a high temperature (55 °C), LMNM and the LCNM samples both display cycling stability and excellent rate performance .
Through a solid-state route, which is correlated with chemically caused precipitation technique for the first time, the tavorite-structured LiFePO4F nanospheres are efficiently synthesized . Exhibits homogeneous almost monodisperse nanospheres-like particles with the mean particle size of 500 nm had been based on FePO4 nanospheres by the LiFePO4F . The Li-ion diffusion coefficient (D) of LiFePO4F is 1.0 × 10−11 cm2 s−1 computed on account of EIS data . The excellent cycle performance could be attributable to the homogeneous nanospheres-like morphology; this homogeneous is beneficial to enhance the interface area between electrolyte and electrode, shorten the transport distance of electrons and ions and improve the power and energy densities of batteries, and enhance the kinetics of Li ions .
In contrast with pristine Li1.2Ni0.2Mn0.6O2 cathode material, better cycling and rate performance and a greater coulomb efficiency is demonstrated by the Cr-doped Li1.2Ni0.16Mn0.56Cr0.08O2 material . The XRD and XPS results after cycling indicate that the spinel stage could be restrained after Cr doping in the layered Li1.2Ni0.2–xMn0.6–xCr2xO2 materials . Electronic electrical conductivity in the Cr-doped Li1.2Ni0.16Mn0.56Cr0.08O2 material and lower transfer resistance, and greater structure stability, lithium ion, might be responsible for the better electrochemical performance of Li1.2Ni0.16Mn0.56Cr0.08O2 .
The calcining temperature had a considerable impact on the crystallite (XS) size though had little effect on the microstructures including lattice (a, c and V) parameters, the extent of the cation mixing, and refined density, during the process of preparing Li(Ni0.5Co0.2Mn0.3)O2 cathode employing a microsized spherical (Ni0.5Co0.2Mn0.3)(OH)2 precursor, which a high-temperature solid-state technique in the variety of 750 to 820 °C comprised of aggregated nano-sized particles . The electrochemical properties of the Li(Ni0.5Co0.2Mn0.3)O2 cathode heavily rely upon its crystallite size . The variability trend of the retention for the electrochemical capacity is nearly the identical as that of the retention for the crystallite size .
Through hydroxide coprecipitation technique, the high-voltage spherical LiNi0.5Mn1.5O4 cathode material for lithium-ion batteries had been efficiently synthesized . The discharge capacity is 109.2 mAh g−1 at 1.0 C with a cut-off voltage variety of 3.50–4.95 V at 25 °C and the capacity retention is 96.2% after 50 cycles . Under various rates with a cut-off voltage variety of 3.50–4.95 V at 25 °C, when the obtained LiNi0.5Mn1.5O4 cathode material discharges, the discharge capacities are maintained at about (0.1 C) 145.0, (0.5 C) 113.5, (1.0 C) 126.8 and 112.4 (2.0 C) mAh g−1 and the initial coulomb efficiencies maintain above 95.2 (0.1 C)%, 95.0 (0.5 C)%, 94.8 (2.0 C)%, respectively and 92.5 (1.0 C)% . The results might lead to performance amelioration and industrial production of LiNi0.5Mn1.5O4 cathode materials for 5 V lithium batteries .
The low-temperature properties of LiFePO4/C prepared by polyol route were completely examined . The as-prepared LiFePO4/C summarized an excellent low-temperature electrochemical properties, delivering 146.7, 128.7, and 109.2 mAh g−1 at 0.1 C under 0, −10, and −20 °C, respectively . That prepared LiFePO4/C can maintain a specific discharge capacity of 133.7 mAh, which is recycled g−1 when at 0.1 C under 0 °C, after charge/discharge measurements at lower targeted temperatures and greater rates .
We have efficiently prepared the cathode materials based upon LNMO/P3HT-g-CNTs through mixing process . The LNMO/P3HT-g-CNTs nano-composites has been typified and demonstrated a remarkably greater efficiency of and Ni2+/Ni4+ redox couples in comparison to conventional cathodes based upon LNMO/vulcan carbon . LNMO/P3HT-g-CNTs nano-composites can act as fruitful cathode materials for the development of potential power lithium rechargeable batteries with this proof of notion .
It had been clearly shown that an easily accessible, environment-friendly and cheap material of the sea sponge Spongia officinalis could be utilized as a conductive matrix for electrodes of lithium-sulphur accumulators . The biological material of the sea sponge had been, employing a quite straightforward technique, converted to a conductive carbon network with high concentration of nanopores on the surface . In the 3D structured electrode, which is based upon the sea sponge, we attained exceedingly high loading of sulfur-nearly 5 mg/cm2 even though the most basic possible electrode slurry, which comprises of the Super P carbon and the basic binder PVDF, had been utilized . That is presumably because of the presence of nitrogen inside the 3D carbon matrix; this matrix enhances the polysulphide retention inside the electrode .
The current study emphasised the research issue (low electrical conductivity and sluggish transportation of Li+ ions) on employing olivine LiFePO4 (LFP) as a cathode material for high-rate lithium-ion batteries . The electrochemical results revealed that electrode composite LFP/C/10% CNTs delivered a specific capacity of 190 mAh/g at C/10 rate after 200 cycles . An excellent performance at rate capability had been detected with a capacity near to 200 mAh/g . The generalization of this protocol on the bigger scale can improve the manufacturing of batteries with greater scored capacity; this capacity is highly desired for automotive industry applications including electric vehicles .
Cathode materials entail removable Li ions as charge carriers, and transition metal ions serving as redox centres, which account for most of the cost as the costliest sector of a LIB . Considering the cost’s elemental relative abundance, Fe-based and Mn-cathode materials are hence preferable decisions, and the cost’s sodium analogues are attracting considerably attention, as they would allow the future of Li-free SIBs, which might be optimal decisions for large-scale applications . That review entails the discussion of most of the Mn-based and Fe-cathode materials for SIBs and Li-ion batteries, such as polyanion compounds, oxides, and hexacyanometalates (for SIBs) . It is easy to comprehend the various development stages and objectives of cathode materials for SIBs and Li-ion batteries from the clear-cut comparison . In (1) the intensively examined tactics of tailoring particle size and constructing conductive composites readily cause further materials and processing expenses including inadequate volumetric and gravimetric energy densities, significant issues in this field remain: to satisfy the requirement of practical applications . Some electrode materials have been indicated for cycling performance and outstanding rate capability (over 50 °C) by tailoring particle shape and size and forming conductive composites in the case of cathodes for Li-ion batteries . Regarding SIB cathodes, which are experiencing even quicker advancements with a variety of candidatures being devised, instead of merely mimicking the host structures of Li+ during synthesis, many novel complex structures have been introduced to cope with the issues because of the distinct ionic size and electron configuration of Na+ .
The cubic spinel structure with space group of Fd3 m is shown by all LiNi0.5Mn1.5O4-based materials . The 1.0 wt% BiFeO3 LiNi0.5Mn1.5O4 electrode displays the excellent cyclic stability with the capacity retention of 89.11% after 100 cycles that is greater than that of the LNMO (77.6%) . The rate capability of 1.0 wt% BiFeO3 LiNi0.5Mn1.5O4 has been evidently enhanced, displaying discharge capacities of 85.8 and 74.8 mAh g−1 at 5 and 10 C, respectively . Good cyclic stability of BiFeO3-coated LiNi0.5Mn1.5O4 electrode and the enhanced rate capability must be attributable to the surface modification of BiFeO3; this modification impedes side reactions at electrolyte and reduces the charge transfer resistance and the cathode .
At room temperature, the significant improvements in the initial columbic efficiency, cyclic performance, and rate capability, are accomplished with proper quantity of Li2TiO3 coating layer . The subsample coated with 3 wt% Li2TiO3 displays the highest rate capability, enhanced initial columbic efficiency, and optimal cyclability .
We utilized Na doping to Ni-rich, cycling stability of Li-ion batteries and layered LNMCO (LiNi0.8Mn0.1Co0.1O2) to enhance the rate capability . The electrochemical properties of Na-LNMCOs were examined by us, and the results indicate the excellent rate capability (142 mAh g−1 at 7 C) and cycling stability (94.9% of capacity-retention rate after 100 cycles) of 0.2Na-LNMCO . For the LNMCO along with Na doping we can derive rate capability and cycling stability that are both sound .
The enhanced performance of the surface-coated subsample is because the ZnO coating on the surface of LiMn2O4 can efficiently minimize electrochemical charge and polarization transfer resistance during discharge/charge cycling . In the electrode material, the XRD results of the 2 wt% ZnO-coated LiMn2O4 material after 500 cycles confirmed that ZnO coating enhances the stability of the spinel structure, making lithium ions efficiently diffuse . ZnO coating enhances the electrochemical performances of LiMn2O4 comparing with the pristine subsample in terms of rate capability and cycling .
In contrast to the bare LiNi1/3Co1/3Mn1/3O2, stability and better electrochemical performances are showed by LiNi1/3Co1/3Mn1/3O2@Eu2O3 . Thermal safety, which is enhanced Notably, is shown by LiNi1/3Co1/3Mn1/3O2@Eu2O3 because of the stabilized interface .
Through hydrothermal technique, 5Li2MnO3·0.5LiMn1/3Ni1/3Co1/3O2 cathode material had been prepared and a thin layer of alumina had been efficiently coated on the surface of material, which is prepared, under the hydrolysis of aluminium isopropoxide which could be detected by TEM images . Good electrochemical performance, which comprises the lowered first irreversible capacity deterioration and the cycling stability, were accomplished for A-LMNCO materials and the reversibility of 2 wt% of A-LMNCO subsample had been the optimal . The 2 wt% of A-LMNCO subsample still had a discharge specific capacity of 206.2 mAh g−1 after 100 cycles at 1 C rate with a high capacity retention of 97.4%, and the discharge specific capacity rebuilt to the original 95% or more assessed at low rates after cycling at high rates . The alumina coating layer, which acts as a fast electron-conducting path, efficiently alleviates the side reaction between the electrolyte and the cathode material, with a low charge-transfer resistance and repress the change of surface structure .
An efficient approach has been introduced to improve cycle ability and rate capacity of the LiMn2O4 cathode . The structures and electrochemical performances of the LiMn2O4 cathodes with various quantities of Li2MnO3 coating were examined . The results of XPS, and SEM, TEM, highlight that Li2MnO3 has been efficiently coated onto the surface of LiMn2O4 cathode by the sol-gel route . An efficient way to enhance the performance of LiMn2O4 cathode materials for Li-ion batteries is surface modification by Li2MnO3 .
The cycling degradation of LNMO at high voltage becomes the largest restrict in application . Several types of tactics were utilized to lessen cycling degradation; this degradation can be presented as doping, electrolyte altering, cathode surface coating, and other efficient techniques . Doping enhanced the cycle performance of LNMO primarily through metal ion changing structures, the crystal compositions, and parameters, including fostering the formation of structure . Through employing the coating layer on the surface of LNMO, cathode surface coating can efficiently deter the undesirable side reactions, though the coated technology is complex under normal conditions . Electrolyte altering is an optimal approach compared with doping and cathode surface coating; it not just prevents the undesirable side reactions between electrolyte and cathode though retains easy technology . They are not able to stop the undesirable side reactions even though other techniques can enhance the cycle stable of LNMO in HVLIBs . Electrolyte altering, and Doping, cathode surface coating, are able to attain the desired cycling stability in HVLIBs . We outlined these methodologies to enhance the cycling stability of LNMO cathodes based upon cyclic degradation processes and its architectural elements . The inquiries for high-voltage LNMO cathodes goal to ascertain the ways to enhance service and cycle performances of LNMO for the life . The cycle performance of LNMO, which is based upon the synthesis of highly purified LNMO, cycling degradation mechanism of undesirable reactions between LNMO and electrolyte, and systemic reversibility of, must be enhanced by us . Electrolyte additives and organic coating might be satisfactory ways to enhance the cycle performance of LNMO in multiple modification techniques .
The results of systemic analysis revealed that all of the materials have satisfactory crystallinity, comparable morphology and comparable size distribution . The results of electrochemical measurements indicate that a 3 mol% Ca-doping displays the optimal electrochemical performance, which comprises the optimal cycle stability and rate performance and the highest capacity . The charge transfer resistance of the 3 mol% Ca-doped cathode material is substantially smaller than that of the un-doped material; this material means that it has a faster lithium-ion migration rate . 3 mol% Ca-doping can lower Li/Ni cation mixing, increase the systemic stability, decline the migration resistance, lessen polarization and enhance the migration rate of the Li-ion, which, in turn, improves the electrochemical properties of LiNi0.5Mn0.5O2 .
We have revealed that the materials are core-shell structured, and the core is a layered LiMO2 stage (R-3 m), whilst the shell is a monoclinic Li2MnO3 stage (C2/m) by employing the XPS, and XRD, TEM, methods . That the core-shell structures make Li+/Ni+2 cation disorder less than the pristine material does, and XPS indicates that the quantity of Ni2+ increases along with the increase of Mn content is demonstrated by the Rietveld refinements . It is thought make the composite functionally sounder and its thermal stability greater and that many Mn+4 in the shell and Ni+2 in the core interdiffuse into the counter parts . The core-shell-structured materials could be safely cycled to greater upper cutoff potential of 4.7 V, in contrast to that of the pristine material, just 4.3 V; this material suggests that the Li2MnO3 shell has considerably enhanced the electrochemical performance of NCM811 in terms of energy density and discharge capacity . The thermal analyses of the highly delithiated materials, which are prepared by charging a surface-modified material to 4.3 and 4.7 V respectively and the cells of the pristine and maintaining potential for 2 h, corroborate the greater stability of the core-shell structured materials . At 360 °C, the exothermic peak of the surface-modified material seems with a heat evolution of 239.144 J g−1, whilst those of the pristine material seem at 250 °C with a heat evolution 575.136 J g−1 .
FESEM and XRD results of Al-doped materials indicate surface morphology and the comparable XRD patterns to those of Li[Li0.2Mn0.54Ni0.13Co0.13]O2 . Electrochemical discharge and charge measurements suggest that LNCMAl1 displays better rate capability, greater discharge capacity, and better cycling performance than the other materials . A high reversible capacity of 213.7 and 193.8 mAh g−1 at 1.0 and 2.0 C, respectively is displayed by LNCMAl1 . The corresponding capacity retention ratio can still be 58.2 and 66.8% after 50 cycles at 1.0 and 2.0 C. EIS results indicate that substituting traces of Al element for Co element of Li[Li0.2Mn0.54Ni0.13Co0.13]O2 can decline charge-transfer impedance and improve the reaction kinetics; these kinetics is thought to be the main reason for satisfactory rate capability of LNCMAl1 .
F and Mg doping does not change the crystal system of LMR-NMC which is apparent from XRD plot where no impure stage peaks are detected . At C/20 rate, 10, F-doped LMR-NMC indicate excellent electrochemical performance and (1:50 wt%-LiF: LMR-NMC) doped subsample particularly 0.02 mol% of Mg, delivers capacity ~300 mAh g−1 −15% excess capacity than pristine LMR-NMC . Doped subsample indicates enhanced capacity retention, mitigated voltage decay, and high C rate performances compared to pristine LMR-NMC . The enhanced electrochemical performance is attributable because of minimize stabilization of crystal structure and cation mixing during cycling .
LiNi0.5Mn0.3Co0.2O2 cathode material had been generated by sol-gel technique . Al2O3 had been coated on LiNi0.5Mn0.3Co0.2O2 cathode material by employing ultrasonic stirrer and selected as a surface modifier . The first discharge capacities of the samples are 99.01 178.28, 130.22 and 141.34, respectively and columbic efficiencies are observed to be 91.95 and 99.56% for pristine, NMC-45 and NMC-100 samples . The first discharge capacities and charge variations of the samples are computed as 54.62, 30.94 and 31.99 for pristine, NMC-100 and NMC-45 respectively .
Through heating method and means of hydrolyzing, the LiCoO2 cathode materials coated with multiple quantities of NaAlO2 were synthesized . The NaAlO2 layer had been coated onto the LiCoO2 particles efficiently without influencing the crystal structure of LiCoO2 . An effective strategy to enhance the electrochemical performance of LiCoO2 at high cut-off voltage of 4.5 V versus Li+/Li, which could be referred for other cathode material including Li-and Mn-rich and the nickel-manganese-cobalt materials layered oxide materials is the NaAlO2 coating .
A facile approach has been devised to synthesis LiNi0.8Co0.15Al0.05O2 cathode material by chemically pretreating raw reactants to derive a ternary oxide precursor with a trigonal structure . In LiNi0.8Co0.15Al0.05O2 cathode material, which traditional solid-state reaction at low-temperature prepared, a small quantity of impurity stage LiCoO2 had been detected . That the ternary oxide precursor with a trigonal structure is beneficial to the formation of pure stage high performance of the materials and LiNi0.8Co0.15Al0.05O2 is regarded by us .
The core-shell material is comprised of a core of a layered LiMO2 stage (R-3 m), whilst the shell is a monoclinic Li2MnO3 stage (C2/m) . That the core-shell structured material has less Li+/Ni2+ cation disorder than the pristine material is demonstrated by rietveld refinements . That stronger M \* -O (M * = Mn, Co, Ni) ties are present in the core-shell material, which gives rise to high systemic stability during the charge-discharge process is confirmed by rietveld . At a greater upper cut-off potential of 4.7 V than that of the pristine material (4.5 V), the core-shell material could be cycled . The core-shell material exhibits a greater mean voltage, better cycling stability than those of the pristine material, and a greater energy density .
The electrochemical behaviour of cycled Al-LMO and LMO samples suggests the stage reconfiguration from a layered to a spinel . The Al-LMO subsample showed a considerable amelioration on rate performances and cycle compared to the LMO subsample . The dQ/dV results indicate that Al doping might downturn the rate of spinel stage reconfiguration of stage, which is layered, in the following cycles and deter the stage reconfiguration in the first charge process . EIS results corroborate that Al doping decreases the charge-transfer resistance and enhances the electrochemical reaction kinetics .
It is demonstrated that both single-layer coating and double-layer coating can enhance the cycling stability and rate capability of this high-energy cathode material . The double-layer Li2TiO3-coated subsample N5@ (0.5 + 0.5)% LT indicates the optimum properties due to its homogeneous and full coating layer, even increases the specific capacity at all current densities, which is compared with the bare non-coated powder .
LiAlO2-coated LiNi0.8Co0.1Mn0.1O2 material has been efficiently prepared by hydrolysis-hydrothermal technique . The results indicate that the LiAlO2-coated layer of 8–12 nm enhances the thermal stability of the material at 40 °C via a series of electrochemical tests, morphology, and characterization of the structure . A rate capability, thermal stability compared with the pristine material, and cyclic performance, which is enhanced markedly, had been shown by LiAlO2-coated material .
The Al-doped Na3V2(PO4)2F3 with various Al concentration (x = 0, 0.02, 0.05, and 0.1) have been synthesized by Pechini technique . Since ionic radius of Al3+ is smaller than V3+, the cell parameters of the vanadium fluorophosphates lattice could be declined by aluminium doping . The Na3V2(PO4)2F3 with just 5% (x = 0.05 mol) of Al doping displays greater discharge capacity, capacity retention and better charge/discharge stability than the pristine Na3V2(PO4)2F3 . Al-doping Na3V2(PO4)2F3 provides many favourable properties to be look at as a fruitful cathode material for Li-ion batteries . The results of this first strategy to the investigation and preparation of this material highlight that Al-doping is a novel approach for improving the electrochemical performance of the Na3V2(PO4)2F3 .
Through coprecipitation technique, which employs lactate ion as the chelating actor, Ni0.5Co0.2Mn0.3(OH)2 precursors were efficiently synthesized . At the molar ratio of 1:1 between transition metal ion and lactate ion, when the Ni0.5Co0.2Mn0.3(OH)2 precursor had been synthesized, its LiNi0.5Co0.2Mn0.3O2 cathode revealed retention rate (93.3%) and the highest discharge capacity (194.2 mAh g−1) after 100 cycles .
Through a solid-state reaction, which post-process nitridation and characterization by XRD, XPS, and electrochemical analysis followed, Nitridated LiMn1.5Ni0.5O4 had been synthesized . In terms of its bulk crystallographic structure, grain size, and morphology, the nitridated LiMn1.5Ni0.5O4 had been not basically altered . Excellent cycleability and high rate capability, which is attributable to the increasing number of Mn3+ hopping carriers including the enhanced electric conductivity, which active Ni redox centres triggered, had been shown by the nitridated LiMn1.5Ni0.5O4 .
Throughout the preparation of a water-based slurry, the charge/discharge capacities, cycle stability, rate performance, mechanical resistance, resistance of electrochemical oxidation, structure and transformations of the surface composition were researched after water-treatment . The TRD202A binder had been identified as a fruitful water-based binder that satisfies some required attributes for the development of environment-friendly cathodes and high-performance . Some Li-rich solid-solution cathode materials having various compositions of Li, Mn, Co ions, and Ni, showed gradual decreases in the discharge capacity . Especially after water-treatment of the cathode particles, the stability of the charge/discharge performance could be enhanced by the protective layers . To recognize stable charge/discharge performances at all compositions, a water-stable surface layer, including Al2O3 or carbon, must be formed on the cathode particles . We will try to pinpoint protective surface layers for a wide range of Li-rich solid-solution cathode materials, which haves various compositions of Li, Mn, Co ions, and Ni, in our next work .
That work shown the effect of Na doping in LiMnPO . In the LiMnPO system through the sol-gel technique, na of various concentrations had been replaced . Through natrium addition (LiNaMnPO, irreversible capacity deterioration had been lowered compared with pristine LiMnPO . That superior electrochemical performance could be achieved via optimizing adequate Na doping in LiMnPO towards Li-ion battery application had been demonstrated by these experimental results .
The following heterogeneous cathode commodities synthesized from the leaching solution were investigated: LiNi1/3Mn1/3Co1/3O2, LiNi0.6Mn0.2Co0.2O2, and LiNi0.5Mn0.3Co0.2O2 . The recycling process becomes a “closed loop” process raising the possibility of scaling the recovery process up and having a viable commercial battery recovery and re-use process by synthesizing novel cathode materials that could be implemented into novel batteries . The electrochemical properties of the LiNixMnyCozO2 synthesized via re-use (recycling) and recovery are satisfactory compared to those synthesized from pure commercial product .
2.5 Related Work
Thackeray MM, Kang SH, Johnson CS, Vaughey JT, Benedek R, Hackney SA (2007) Li2MnO3-stabilized LiMO2 (M = Mn, Ni, Co) electrodes for lithium-ion batteries. J Mater Chem 17:3112–3125 [ https://doi.org/10.1039/b702425h]
Complete extraction of Li2O from the inactive Li2MnO3 element yields electrochemically active layered MnO2 phase, improving the discharge capacity of the material [15, 194, 195]. Such lithium-rich high-capacity materials suffer from meager cycle stability and inferior rate property; this stability hinder their successful commercialization in high-energy-density lithium-ion batteries (Boulineau and others ; Thackeray and others ; Xu and others ), . In contrast with the commonly used layered ternary or LiCoO2 cathode materials with α-NaFeO2 structure, layered Li-rich Mn-based ones constituted as yLi2MnO3·(1–y)LiMO2 (M = Co, Ni, Mn, etc.) or Li[Li(1/3–2x/3)MxMn(2/3–x/3)]O2 have many advantages including lower cost, safer on overcharge [194, 354, 355], and less toxic . They have high capacities about 250 mAh g−1 at high voltage, which can play a key role in stabilizing the electrode structure [189, 194] and supply the excess lithium to the layered structure . Metal element doping, including Al, Zr , Y, Mo, and Mg  replaced for the transitional metal elements in the oxide materials, can weaken the adverse change of crystal structure . High stable reversible capacity of >250 mAh g−1 when it is cycled in the voltage window of 2.5–4.8 V [194, 438, 439, 440, 441, 442, 443] is delivered by LMR-NMC . Throughout cycling need to be tackled before it is regarded as a potential candidate for next generation cathode material for lithium-ion batteries [197, 437, 438, 439, 440, 441, 442, 443], the energy deterioration because of suppression of voltage profiles during cycling which is linked with the stage reconfiguration from a layered structure to spinel structure, capacity, and high irreversible capacity, fade . The aims of the present study were (1) to enhance the thermal stability of this material by making it a core-shell structured material with a core of LiMO2 and a shell of Li2MnO3, and (2) to increase the discharge capacity of NCM 111 by preparing NCM 111 with the formula xLi2MnO3–(1−x)LiMO2, i.e., a lithium-rich material with a high capacity [44, 194].
Ohzuku T, Makimura Y (2001) Chem Lett 7:642–643 [ https://doi.org/10.1246/cl.2001.642 ]
LiNi1/3Co1/3Mn1/3O2 compound, which Makimura  and Ohzuku developed, has been regarded as a fruitful candidate of next-generation cathode materials to substitute LiCoO2 for rechargeable Li-ion batteries . The layered lithium transition metal oxides have been intensively examined as the cathode materials in the next generation of the rechargeable lithium-ion battery (LIB) [30, 223, 353]. Layered LiNi1/3Co1/3Mn1/3O2 as cathode material has been paid extensive attention because of its high reversible capacity, low cost, and excellent structural, thermal stability, as reasonably well [33, 223, 381]. Overcharging frequently triggers significant systemic distortions (transformation from hexagonal to monoclinic structures), which generate extensive defects between and within the particles, and induces potential surface reactions including Co break-up at voltages above 4.4 V [50, 223, 532].
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