LAUSR

In situ polymerized solid‐state electrolytes have attracted much attention due to high Li‐ion conductivity, conformal interface contact, and low interface resistance, but are plagued by lithium dendrite, interface degradation, and inferior thermal stability, which thereby leads to limited lifespan and severe safety hazards for high‐energy lithium metal batteries (LMBs). Herein, an in situ polymerized electrolyte is proposed by copolymerization of 1,3‐dioxolane with 1,3,5‐tri glycidyl isocyanurate (TGIC) as a cross‐linking agent, which realizes a synergy of battery thermal safety and interface compatibility with Li anode. Functional TGIC enhances the electrolyte polymeric level. The unique carbon‐formation mechanism facilitates flame retardancy and eliminates the battery fire risk. In the meantime, TGIC‐derived inorganic‐rich interphase inhibits interface side reactions and promotes uniform Li plating. Intrinsically safe LMBs with nonflammability and outstanding electrochemical performances under extreme temperatures (130 °C) are achieved. This functional polymer design shows a promising prospect for the development of safe LMBs.