Pure LiFePO4 and LiNi x Fe1−x PO4/C (x = 0.00–0.20) nanocomposite cathode materials have been synthesized by cheap and convenient sol–gel-assisted carbothermal reduction method. X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy, and inductively coupled plasma have been used to study the phase, morphology, and chemical composition of un-doped and Ni-doped materials. XRD patterns display the slight shrinkage in crystal lattice of LiFePO4 after Ni2+ doping. The SEM images have revealed that Ni-doped particles are not agglomerated and the particle sizes are practically homogeneously distributed. The particle size is found between 50 and 100 nm for LiNi0.20Fe0.80PO4/C sample. The discharge capacity at 0.2 C rate has increased up to 155 mAh g−1 for the LiNi0.05Fe0.95PO4/C sample and good capacity retention of 99.1 % over 100 cycles, while that of the unsubstituted LiFePO4/C and pure LiFePO4 has showed only 122 and 89 mAh g−1, respectively. Doping with Ni has a noticeable effect on improving its electrical conductivity. However, serious electrochemical declension will occur when its doping density is beyond 0.05 mol LiNi0.20Fe0.80PO4/C electrode shows only 118 mAh g−1, which is less than un-doped LiFePO4/C sample at 0.2 C. The cycling voltammogram demonstrates that Ni-doped LiNi0.05Fe0.95PO4/C electrode has more stable lattice structure, enhanced conductivity, and diffusion coefficient of Li+ ions, in which Ni2+ is regarded to act as a column in crystal lattice structure to prevent the collapse during cycling process.
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This study was supported by the Scientific Research Projects Commission of Sakarya University (project number: 2010-02-04-028 and 2012-50-02-015).
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Örnek, A., Bulut, E., Can, M. et al. Characteristics of nanosized LiNi x Fe1−x PO4/C (x = 0.00–0.20) composite material prepared via sol–gel-assisted carbothermal reduction method. J Solid State Electrochem 17, 3101–3107 (2013). https://doi.org/10.1007/s10008-013-2201-5
- Lithium-ion batteries
- Nickel substitution
- Carbon coating