Interfacial Architectures Derived by Lithium Difluoro(bisoxalato) Phosphate for Lithium-Rich Cathodes with Superior Cycling Stability and Rate Capability

Abstract

Lithium difluoro(bisoxalato)phosphate (LiDFBP) is introduced as a novel lithium-salt-type electrolyte additive for lithium-rich cathodes in lithium-ion batteries. The investigation reveals that LiDFBP is oxidized to form a uniform and electrochemically stable solid electrolyte interphase (SEI) on the lithium-rich cathode. The LiDFBP-derived SEI layer effectively suppresses severe electrolyte decomposition at high voltages and mitigates the voltage decay of the lithium-rich cathodes caused by undesirable phase transformation to spinel-like phases during cycling. Furthermore, the cell with electrolyte containing LiDFBP achieves substantially improved cycling performance and delivers a high discharge capacity of 116mAhg(-1) at a high C rate (20C). The unique function of the LiDFBP additive on the surface chemistry of lithium-rich cathodes is confirmed through X-ray photoelectron spectroscopy, SEM, and TEM analyses.