All-Material Crosslinked Solid Polymer Electrolytes for High-Performance and Flexible Lithium Metal Battery

Solid polymer electrolytes (SPE) offer advantages including compatibility with conventional electrolyte systems and mechanical flexibility; however, low ionic conductivity and high interfacial resistance present significant challenges. Here, systems are proposed that randomly crosslink all-materials constituting SPE based on diazide and develop novel flexible SPEs by covalently networking fluorinated polymers and succinonitrile. This all-material crosslinking reduces crystallinity of the constituents, thus simultaneously boosting ionic conductivity, mechanical elasticity, and adhesion strength. Solvent-assisted conformal coating ensures complete contact with the lithium surface and completely wets the porous cathode. The SPE exhibits high ionic conductivities of 4.7 mS·cm⁻¹, lithium-ion transference numbers of 0.64, and oxidation stability up to 5.29 V. It demonstrates stable lithium plating/stripping with ∼5 mV of overpotential over 1400 h in Li//Li tests and outstanding performance in Li//LFP flexible full cells, achieving discharge capacities of 136.5 mAh g⁻¹ at 3 C and maintained even after bending at 5 mm or cutting in half.