Implanting a Fire‐Extinguishing Alkyl in Sodium Metal Battery Electrolytes via a Functional Molecule

Abstract Room‐temperature sodium metal batteries (SMBs) have gained tremendous interest owing to the cost‐efficiency and wide geographical availability of sodium, whereas severe safety issues have long handicapped their practical applications. Here a fire‐extinguishant‐implanted electrolyte (FEIE) is demonstrated where a nonpolar fluoroether simultaneously bonds the fluorinated carbonate‐based electrolyte and a sodium‐compatible extinguishant via its amphiphilicity. The as‐designed FEIE enables intrinsic safety and eliminates fire hazards. Furthermore, the FEIE‐induced inorganic‐enriched solid electrolyte interphase (SEI) dramatically improves the Na deposition, Coulombic efficiency (CE), and further offers the cycling stability for 1100 h at 10 mAh cm⁻² in symmetric cells and 1000 cycles with a high average CE (99.8%) in full cells. Usage of the functional molecules possessing amphiphilicity extends the scope for applying immiscible agents in battery electrolytes.