Tris(trimethylsilyl)phosphite as electrolyte additive for high voltage layered lithium nickel cobalt manganese oxide cathode of lithium ion battery

• Cyclic stability of LiNi1/3Co1/3Mn1/3O2 is improved significantly by using TMSPi as additive.
• Protective SEI film is formed on LiNi1/3Co1/3Mn1/3O2 due to the preferential oxidation of TMSPi.
• SEI film suppresses electrolyte decomposition and LiNi1/3Co1/3Mn1/3O2 destruction.

Tris(trimethylsilyl) phosphite (TMSPi) is reported as an effective electrolyte additive for high voltage layered lithium nickel cobalt manganese oxide cathode of lithium ion battery. Charge/discharge tests demonstrate that the cyclic stability and rate capability of LiNi1/3Co1/3Mn1/3O2 can be improved significantly by adding 0.5wt% TMSPi into a standard electrolyte, 1.0 M LiPF6 in ethylene carbonate/dimethyl carbonate (1/2, in volume). The capacity retention of LiNi1/3Co1/3Mn1/3O2 is improved from 75.2% to 91.2% after 100 cycles at 0.5 C rate (1C = 160 mA g−1), while its discharge capacity at 5 C is enhanced from 122.4 mAh g−1 to 134.4 mAh g−1. This improvement can be ascribed to the suppression of electrolyte decomposition and transition metal ion dissolution by TMSPi, due to the preferential oxidation of TMSPi to electrolyte and the formation of a protective solid electrolyte interphase on LiNi1/3Co1/3Mn1/3O2, which are confirmed by electrochemical measurements and surface characterizations.