Investigation of the synergetic effects of LiBF4 and LiODFB as wide-temperature electrolyte salts in lithium-ion batteries
Herein, we present the use of lithium tetrafluoroborate (LiBF4) as an electrolyte salt for wide-temperature electrolytes in lithium-ion batteries. The research focused on the application of blend salts to exhibit their synergistic effect especially in a wide temperature range. In the study, LiCoO2 was employed as the cathode material; LiBF4 and lithium difluoro(oxalate)borate (LiODFB) were added to an electrolyte consisting of ethylene carbonate (EC), propylene carbonate (PC), and ethyl methyl carbonate (EMC). The electrochemical performance of the resulting electrolyte was evaluated through various analytical techniques. Analysis of the electrical conductivity showed the relationship among solution conductivity, the electrolyte composition, and temperature. Cyclic voltammetry (CV), charge-discharge cycling, and AC impedance measurements were used to investigate the capacity and cycling stability of the LiCoO2 cathode in different electrolyte systems and at different temperatures. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were applied to analyze the surface properties of the LiCoO2 cathode after cycling. The results indicated that the addition of a small amount of LiODFB into the LiBF4-based electrolyte system (LiBF4/LiODFB of 8:2) may enhance the electrochemical performance of the LiCoO2 cell over a relatively wide temperature range and improve the cyclability of the LiCoO2 cell at 60 °C.
KeywordsLithium-ion batteries Lithium tetrafluoroborate Lithium difluoro(oxalate)borate Wide temperature Blend salts
This work is supported by the Joint Funds of the National Natural Science Foundation of China (Nos. U1407105 and U1407106), the Applied Basic Research Program of Qinghai Province (No.2015-ZJ-740), and Qinghai Provincial Thousand Talents Program for High-level Innovative Professionals.
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