Enhancement of high voltage cycling performance and thermal stability of LiNi1/3Co1/3Mn1/3O2 cathode by use of boron-based additives

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/LiNi1/3Co1/3Mn1/3O2 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 LiNi1/3Co1/3Mn1/3O2 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 Li1-xNi1/3Co1/3Mn1/3O2 cathode is improved in the presence of additives.