A caddisfly larva case–mimicked gel polymer electrolyte with high toughness and enhanced ion transport for safe lithium metal batteries

Lithium (Li) metal batteries (LMBs) promise higher energy density than Li-ion cells but face a trade-off between ionic conductivity and mechanical strength in gel polymer electrolytes (GPEs). Inspired by caddisfly larvae cases, which assemble silk with particles for toughness and permeability, we develop a caddisfly larva case–mimicked gel polymer electrolyte (CLC GPE) with high toughness and enhanced ion transport. It integrates an electrospun polyvinylidene fluoride-hexafluoropropylene scaffold with shear thickening fluid. CLC GPE achieves a high ionic conductivity (2.80 × 10 −3 siemens per centimeter), a Li + transference number of 0.89, superior toughness (7.29 megajoules per cubic meter), and a puncture energy of 49.69 millijoules, which can resist thermal abuse (150°C), flame, and bullet impact (225 kilometers per hour). Symmetric Li||Li cells exhibit stable cycling over 800 hours, while Li||LFP (LiFePO 4 ) full cells maintain 97.6% capacity after 700 cycles at 0.5C. This design couples mechanical robustness with fast ion transport, offering a scalable route to safer, high-performance LMBs.