Inherently flame-retardant solid polymer electrolyte for safety-enhanced lithium metal battery

The solid polymer electrolyte (SPE) has been regarded as a promising candidate for the next-generation rechargeable Li metal battery with high-energy density. However, the current SPEs are still challenged by insufficient security owing to their flammability. Here, we reported a novel inherently flame-retardant SPE (IFR-SPE), which was fabricated via the one-step in situ crosslinking of two novel synthetic P-containing monomers with porous polyimide film as a supporting host. Compared with liquid and conventional solid polyethylene oxide electrolytes, the unique IFR-SPE exhibits outstanding flame-retardant ability. Furthermore, it demonstrates a high Li-ion conductivity (0.28 mS cm−1 at 25 °C), a stable electrochemical window up to 4.12 V, and effective Li dendrite suppression via a LiF/Li3PO4-rich solid electrolyte interphase formed on the Li anode. Consequently, the Li/IFR-SPE/LiFePO4 cell shows acceptable electrochemical performances. We believe that this work offers a novel and effective strategy for establishing a promising Li metal battery system with high safety.