Low-Concentration Flame-Retardant PC-Based Electrolytes for Wide-Temperature and High-Voltage Lithium-Ion Batteries

Propylene carbonate (PC) is regarded as a promising solvent for replacing ethylene carbonate due to its high dielectric constant and wide working temperature range. However, the co-intercalation behavior between PC and Li⁺ on graphite poses limitations to its further application. In this study, a weakly solvating solvent of methyl trifluoromethyl carbonate (FEMC) and lithium bis(oxalato)difluorophosphate (LiDODFP) synergistically enable reversible cycling of low-concentration PC-based electrolytes on graphite. Nuclear magnetic resonance spectroscopy and theoretical calculations indicate that FEMC partially substitutes PC in the solvation structure and interacts with PC through intermolecular forces, facilitating desolvation of Li⁺. Moreover, the utilization of LiDODFP enhances the solvation structure of Li⁺, effectively resolving the compatibility issue between graphite and PC. This electrolyte exhibits exceptional oxidative stability and nonflammability properties. At a cut-off voltage of 4.5 V, the NCM811/graphite full cell exhibits 88.86% capacity retention after 300 cycles at 25 °C, and retains 76.23% capacity after 100 cycles at 60 °C; even at -40 °C, it still delivers a capacity of 67 mAh g^-1. This work presents a novel strategy for developing low-concentration, wide-temperature-applicable, high-safety, and high-voltage PC-based electrolytes.