Toward High‐Performance, Flexible, Photo‐Assisted All‐Solid‐State Sodium‐Metal Batteries: Screening of Solid‐Polymer‐Based Electrolytes Coupled with Photoelectrochemical Storage Cathodes

The advancement of photo-assisted rechargeable sodium-metal batteries with high energy efficiency, lightweight structure, and simplified design is crucial for the growing demand in portable electronics. However, addressing the intrinsic safety concerns of liquid electrolytes and the sluggish reaction kinetics in existing photoelectrochemical storage cathodes (PSCs) remains a significant challenge. In this work, functionalized light-driven composite solid electrolyte (CSE) fillers are systematically screened, and optimized PSC materials are employed to construct advanced photo-assisted solid-state sodium-metal battery (PSSMB). To further enhance the mechanical properties and poly(ethylene oxide) compatibility of the CSE, natural lignocellulose is incorporated, enabling the fabrication of flexible PSSMBs. In situ tests and density functional theory calculations reveal that the light-driven electric field facilitated sodium salt dissociation, reduced interfacial resistance, and improved ionic conductivity (0.1 mS cm^-1). Meanwhile, energy-level matching of the PSC maximized the utilization of photogenerated carriers, accelerating reaction kinetics and enhancing interface compatibility between the electrolyte and cathode. The resulting flexible pouch-type PSSMB demonstrates a remarkable discharge capacity of 117 mAh g^-1 and outstanding long-term cycling stability, retaining 89.1% of its capacity and achieving an energy storage efficiency of 96.8% after 300 cycles at 1 C. This study highlights a versatile strategy for advancing safe, high-performance solid-state batteries.