The effects of lithium bisoxalatoborate (LiBOB) and lithium difluorooxalatoborate (LiDFOB) as electrolyte additives on the high voltage cycling performance of lithium-ion cells are investigated. With traces of 0.2 wt. % LiBOB or 0.5 wt. % LiDFOB added, the cycling performance of Li/LiNi 1/3 Co 1/3 Mn 1/3 O 2 cells charged to 4.6 V is improved. The electrochemical impedance spectroscopy (EIS) suggests that the additives can decrease impedance. The results of scanning electron microscopy (SEM) of the LiNi 1/3 Co 1/3 Mn 1/3 O 2 cathode indicated the existence of this film. X-ray photoelectron spectroscopy (XPS) indicates the additives are justified to modify cathode surface films and suppress electrolyte oxidation reactions on the cathode surface. In addition, differential scanning calorimetric (DSC) studies show that thermal stability of fully charged Li 1-x Ni 1/3 Co 1/3 Mn 1/3 O 2 cathode is improved in the presence of additives.
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