Tris(2,2,2-trifluoroethyl) phosphite as an electrolyte additive for high-voltage lithium-ion batteries using lithium-rich layered oxide cathode

Abstract In this paper, we report positive effect of Tris(2,2,2-trifluoroethyl) phosphite (TTFP) as additive during initial activation and cycling of Li-rich-NMC x Li 2 MnO 3 –(1 −  x )LiMO 2 ( x  >> 1; M = Ni, Co, Mn) cathode in EC/DMC + 1 M LiPF 6 electrolyte. Firstly conductivity and viscosity of electrolyte with x wt.% TTFP; 0 wt.% x vs . Li + /Li (up to 301 mAh g −1 in charge). The beneficial effect of TTFP improves the long-term cycling stability of the cathode with more than 95% of initial capacity in Gr//Li-Rich -NMC full cell is maintained after 50 cycles at C rate. Finally, XPS analysis of Li-rich -NMC electrodes show presence of TTFP on the surface during cycling and confirm the presence of Mn 3+ at the end of discharge. The convergence of all characterizations indicates that TTFP should act as a catalyst to several surface reactions which are beneficial to long cycling cell performances.