Nonflammable Dual-Salt Electrolytes for Graphite/LiNi0.8Co0.1Mn0.1O2 Lithium-Ion Batteries: Li+ Solvation Structure and Electrode/Eelectrolyte Interphase

Abstract

Trimethyl phosphate (TMP) is the most promising safe solvent for lithium-ion battery (LIB) electrolyte because of the nonflammability, oxidation stability, and low cost, but its application is hindered by incompatibility with the graphite anode. Herein, nonflammable electrolytes with ordinary concentration (1 mol L–1) are designed for graphite/LiNi0.8Co0.1Mn0.1O2 (Gr/NCM811) LIBs with TMP/2,2,2-trifluoroethyl methyl carbonate (FEMC) binary solvents. Stable cycling of the Li/Gr half cells with high capacity is achieved via modulation of the Li+ solvation structure. A dual-salt strategy of lithium hexafluorophosphate/lithium difluoro(oxalato)borate is further used to realize the high performance of the Gr/NCM811 full cells. More significantly, the functions and relationship of Li+ solvation structure and electrode/electrolyte interphase are elucidated. Li+ solvation structure and interphase are respectively the thermodynamic and kinetic factors for the side reactions of the electrolyte occurring at the electrode/electrolyte interphase, which should be considered comprehensively in the design of electrolytes for high-energy density LIBs.