Improving Compatibility between Trimethyl Phosphate and Graphite Anodes by Preconstructing a Stable Solid Electrolyte Interphase Film

Abstract

The electrolyte additive of trimethyl phosphate (TMP) shows a good flame-retardant property for lithium-ion batteries (LIBs) comprising nonaqueous carbonate solvents. However, TMP is not conducive to cycle performance because of its poor compatibility with graphite anodes. Herein, a stable solid electrolyte interphase (SEI) film on the graphite surface is preconstructed by cycling the Li||graphite half-cell with the 1.5 M lithium difluoro(oxalato)borate (LiDFOB)-ethylene carbonate (EC)/dimethyl carbonate (DMC) electrolyte for five cycles. The as-generated stable SEI film is relatively rich in LiF and lithium oxalate, which helps to restrain the cointercalation of Li+-TMP and improves the compatibility between TMP and the graphite anode. As a result, the modified Li||graphite cell enables a good flame-retardant property and excellent electrochemical performance, even if the 0.7 M LiDFOB-EC/DMC/TMP(40%) electrolyte is used in the subsequent cycles. This study emphasizes the importance of constructing a stable SEI film and provides a reference method for designing safe and practical electrolytes for LIBs.