Inorganic additives for passivation of high voltage cathode materials

The incorporation of additives designed to sacrificially react on the surface of cathode materials of lithium ion batteries has been investigated. Addition of low concentrations of inorganic additives including lithium bisoxalatoborate (LiBOB), lithium difluorooxalatoborate (LiBF2(C2O4)), and tetramethoxy titanium (TMTi) to 1 M LiPF6 in 1:1:1 EC/DEC/DMC improves the capacity retention of Li/Li1.17Mn0.58Ni0.25O2 cells cycled to 4.9 V vs. Li. Surface analysis of the cathode materials (XPS and IR) suggests that structure of the cathode surface film is modified by the presence of the additives resulting in a decrease in detrimental electrolyte oxidation reactions on the cathode surface.