Monofluorinated Phosphate with Unique P−F Bond for Nonflammable and Long‐Life Lithium‐Ion Batteries

Abstract

AbstractLithium‐ion batteries (LIBs) with conventional carbonate‐based electrolytes suffer from safety concerns in large‐scale applications. Phosphates feature high flame retardancy but are incompatible with graphite anode due to their inability to form a passivated solid electrolyte interphase (SEI). Herein, we report a monofluorinated co‐solvent, diethyl fluoridophosphate (DEFP), featuring a unique P−F bond that allows a trade‐off between safety and electrochemical performance in LIBs. The P−F bond in DEFP weakens ion‐dipole interactions with Li+ ions, lowering the desolvation barrier, and simultaneously reduces the lowest unoccupied molecular orbital (LUMO) of DEFP, promoting the formation of a robust and inorganic‐rich SEI. Additionally, DEFP exhibits improved thermal stability due to both robust SEI and the inherent flame‐retardant properties of the P−F bond. Consequently, the optimized DEFP‐based electrolyte exhibits improved cyclability and rate capacity in LiNi0.8Co0.1Mn0.1O2||graphite full cells compared with triethyl phosphate‐based electrolytes and commercial carbonate electrolytes. Even at a low E/C ratio of 3.45 g Ah−1, the 1.16 Ah NCM811||Gr pouch cells achieve a high capacity retention of 94.2 % after 200 cycles. This work provides a promising approach to decouple phosphate safety and graphite compatibility, paving the way for safer and high‐performance lithium‐ion batteries.