Chemically-induced cathode electrolyte interphase created by lithium salt coating on Nickel-rich layered oxides cathode

Abstract

Nickel-rich layered transition metal oxides have been highlighted as advanced cathode materials; however, their poor cycling performance at elevated temperatures is a critical hurdle that limits the expansion of their applications. We propose a novel approach for the development of a chemically induced cathode electrolyte inter phase on cathodes using a lithium tetra(trimethylsilyl) borate as a functional precursor. This precursor contains a silyl-borate functional group that forms the cathode electrolyte interphase layer via chemical reactions, which mitigates electrolyte decomposition and scavenges fluoride species. The precursor is prepared by a convenient one-step synthesis and it readily forms a nanoscale artificial cathode electrolyte interphase layer through chemical reactions with cathode material during the mixing process used for the preparation of cathode slurries. Our first-principles calculations reveal a thermodynamically favorable reaction between lithium tetra(trimethylsilyl) borate and the fluoride species. We demonstrate that the artificial cathode electrolyte interphase layer effectively mitigates electrolyte decomposition and the dissolution of transition metal components, thereby improving the interfacial stability of cathodes. As a result, a cell cycled with lithium tetra(trimethylsilyl) borate modified cathode material shows comparable cycling retention at room temperature and much improved cycling performance at a high temperature after 100 cycles.