The cathodic solid electrolyte interphase(CEI)film will affect the high-temperature performance of Li-ion battery.Commercial electrolytes have poor thermal stability at high temperature and the formed CEI film is not stable enough,which can easily lead to battery failure.Lithium difluorosulfonate(LiTFSI)and lithium difluorooxalate borate(LiODFB),which have good thermal stability and film-forming performance,are used as lithium salts,EC+EMC(volume ratio is 3∶7)are used as the solvent,to construct an electrolyte system.The cycle performance of the prepared LiCoO2/Li half cell is investigated.At 70 ℃,the initial specific discharge capacity of LiCoO2/Li half cell in a 0.5 mol/L LiTFSI+0.5 mol/L LiODFB based electrolyte system is 131.2 mAh/g,the capacity retention rate is 90.8％after 100 cycles at 1.0 C in 2.7-4.2 V.This is due to the uniform and dense CEI film formed on the electrode surface by the electrolyte system,it also has good ionic conductivity.
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