An electrolyte for SiOx/LiNi0.5Mn1.5O4 batteries

Abstract The Li-ion batteries composed of high-capacity SiOx anode and high-potential LiNi0.5Mn1.5O4 cathode is the most realistic options to meet the increasing demands for higher-energy-density storage systems. However, the absence of electrolytes covering the multifaceted issues from highly reducing and oxidizing conditions at the SiOx anode and LiNi0.5Mn1.5O4 cathode, respectively, has limited its applications. Herein, we present an electrolyte that can solve these issues simultaneously. A concentrated LiN(SO2F)2/methyl (2,2,2-trifluoroethyl) carbonate electrolyte upshifts the reaction potentials of the SiOx anode and enables an earlier formation of a robust anion-derived passivation film upon charge to diminish the reductive degradation of the electrolyte. The weak solvating ability of the electrolyte provides a high oxidation tolerance against Al corrosion and transition metal dissolution from the cathode material. Excellent long-term cycling of 5 V-class SiOx|LiNi0.5Mn1.5O4 full cells (96% capacity retention after 500 cycles at a low constant current of 0.5 C-rate) was achieved.