Designing Thermomechanical Stable Gel‐Polymer Electrolytes Mediated by Block‐Copolymer Nanofibers for Quasi‐Solid‐State Lithium Batteries

Gel‐polymer electrolytes (GPEs) are expected to play an important role in the next‐generation quasi‐solid‐state lithium batteries (SSLBs), but they suffer from severe thermal and mechanical instability. Herein, a viscoelastic nanofibrous GPE film with high thermomechanical stability for constructing stable quasi‐SSLBs is reported. The GPE is fabricated by in situ polymerization of methyl acrylate in a blockcopolymer (PVDF‐ b ‐PTFE) nanofiber film followed by being immersed into the commercial liquid electrolytes and then dried. The tough blockcopolymer film shows high polarity that not only enhances the thermomechanical stability, but also promotes the dissociation of Li salts to release more free ions, thereby improving the ionic conductivity of GPE. As a result, the GPE shows high heat resistant to 150 °C, a wide electrochemical window of 5.1 V, and a high Li + ‐ion transference number of 0.56. When matching high loading cathodes of LiFePO 4 (13.36 mg cm −2 ) or NCM523 (12.25 mg cm −2 ), both kinds of batteries present high cycling stability and rate capability at 25 °C. More practically, the GPE can be used to construct soft pack batteries with high capacities, showing appealing application prospects.