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

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 116 mA h g−1 at a high C rate (20 C). 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. Surface alterations: The lithium difluoro(bisoxalato)phosphate (LiDFBP)‐derived solid electrolyte interphase (SEI) layer effectively suppresses unwanted electrolyte decomposition at high voltages and mitigates the voltage decay of lithium‐rich cathodes caused by phase transformation to spinel‐like phases during cycling (see figure). Lithium‐rich cathodes with the LiDFBP additive exhibit substantially improved cycling performance and rate capability.