Self‐Thermoregulating Polymer Electrolytes Enabling Intrinsic Safety in High‐Energy Lithium Metal Batteries

Abstract The pursuit of safe lithium metal batteries (LMBs) with ultrahigh energy density is fundamentally challenged by thermal runaway risks. This study proposes a thermal management strategy through the rational design of a multifunctional gel polymer electrolyte (PPW@GPE). By engineering phase change materials (paraffin wax) within flame‐retardant PPBES copolymer matrices via coaxial electrospinning, a self‐regulating separator with a dual‐phase thermal response is constructed. Subsequent in situ polymerization immobilizes liquid electrolytes into a 3D crosslinked network, achieving simultaneous temperature modulation and ionic conduction optimization. The electrolyte can achieve a uniform hotspot, improve the electrochemical performance and safety of the battery, restrain hotspots, and mitigate temperature rise. In addition, PPW@GPE has excellent flame retardant properties and effectively forms the stabilized carbon layer at high temperatures, effectively protecting battery safety. This Li/PPW@GPE/LFP cell has excellent cycling performance, maintaining 500 stable cycles at 0.2C with only 0.0596% degradation per cycle. In addition, the fluorine‐containing monomer helps to form a stable SEI layer and inhibits the growth of lithium dendrites. Through intelligent detection and Comsol simulation, the safety effectiveness of the battery under localized hot spots and external penetration nailing conditions is verified, which provides a new idea for the battery thermal management system.