Photoexcitation‐Enhanced High‐Ionic Conductivity in Polymer Electrolytes for Flexible, All‐Solid‐State Lithium‐Metal Batteries Operating at Room Temperature

Designing solid polymer electrolytes (SPEs) with high ionic conductivity for room‐temperature operation is essential for advancing flexible all‐solid‐state energy storage devices. Innovative strategies are urgently required to develop SPEs that are safe, stable, and high‐performing. In this work, we introduce photoexcitation‐modulated heterojunctions as catalytically active fillers within SPEs, guided by photocatalytic design principles, and employ natural bacterial cellulose to enhance the mechanical properties of the inorganic‐filled SPEs. In‐situ photothermal experiments and theoretical calculations reveal that the strong photogenerated electric field produced by trace heterojunctions within poly(ethylene oxide) electrolytes under photoexcitation significantly enhances lithium salt dissociation, increasing the concentration of mobile Li+. This results in a substantial increase in ionic conductivity, reaching 0.135 mS cm−1 at 25 °C, with a Li+ transference number as high as 0.46. The flexible all‐solid‐state lithium‐metal pouch cells exhibit an impressive discharge capacity of 178.8 mAh g−1 even after repeated bending and folding, and demonstrate exceptional long‐term cycling stability, retaining 86.7% of their initial capacity after 250 cycles at 1 C (25 °C). This research offers a novel approach to developing high‐performance flexible lithium‐metal batteries.