Ceramic Nanofiber Network Reinforced Polyurethane Composite Solid Electrolyte with Robust Stability and Flame Retardancy

Conventional liquid electrolytes cause lithium dendrite growth, which penetrates separators and leads to internal short circuits, posing serious fire and explosion risks. To address these safety issues, we developed a flame-retardant composite solid electrolyte (HP-LLZO) by embedding Li 7 La 3 Zr 2 O 12 (LLZO) nanoparticles into an polyurethane (PU)-based poly(ethylene oxide) (PEO) hybrid polymer (HP) matrix. The Li||Li symmetric cell achieves over 2500 h of stable operation without short-circuit failure. The Li||LiFePO 4 full cell retains 86.2% capacity after 300 cycles at 0.2 C. The enhanced safety arises from the synergistic effect of uniform LLZO dispersion and the PU hydrogen-bonding network, which suppress dendrites, ensure homogeneous Li + flux, and provide intrinsic flame retardancy.