Solvent‐Fluorine‐Free, Anion‐Enriched, and Non‐Flammable Electrolyte Enables Safe Sodium‐Ion Battery from −40 to 50 °C

Abstract High‐safety sodium energy storage across a broad‐temperature range is essential for large‐scale energy storage systems. Effective ion transport in the electrolyte and stable interface phase on the electrode are essential prerequisites for the secure operation of sodium ion batteries under challenging environmental conditions. Herein, a non‐flammable electrolyte with high ionic conductivity is designed by incorporating low‐melting‐point, weak solvation methyl propionate (MP) and a flame‐retardant triethyl phosphate (TEP). The dipole‐dipole interaction between MP and TEP weakens the coordination of TEP, thereby increasing the proportion of anions involved in the solvation structure. This electrolyte configuration promotes the formation of a resilient inorganic‐enriched interface and enhances the electrode compatibility of the TEP‐based electrolyte, enabling the sodium vanadyl phosphate (NVP)||Na half cell and NVP||hard carbon (HC) full cell to deliver excellent electrochemical performance from −40 to 50 °C. Undoubtedly, this work proposes a new electrolyte design strategy based on synergistic dipole–dipole interaction, paving the way for high‐safety sodium‐ion batteries operating in extreme environments.