Flexible and Compact PVDF/PMMA-Based Gel Polymer Electrolytes for High-Performance Sodium Metal Batteries

Sodium is gaining recognition as a promising alternative to lithium for battery applications, particularly in sodium metal batteries (SMBs), where the performance is critically influenced by the choice of electrolyte. Although conventional organic liquid electrolytes are widely used, they pose significant issues. Gel membrane (GM)-based electrolytes have demonstrated enhanced reliability and stability. Nevertheless, there remains a pressing need to improve their electrochemical and mechanical properties to fulfill the demands of next-generation batteries, which require extended lifespan, rapid charging capabilities, and excellent flexibility. To address these challenges, a compact and flexible GM is developed by gelating a cast Polyvinylidene fluoride (PVDF)/Polymethyl methacrylate (PMMA) blend film. The resulting GM possesses a suitable sodium ionic conductivity of 0.507 mS cm^-1 and an impressive ion transference number of 0.47, enabling dendrite-free reversible sodium plating and stripping for up to 300 h at a current density of 0.8 mA cm^-2. Furthermore, the effectiveness of sodium dendrite suppression is demonstrated in Na/GM/Na₃V₂(PO₄)₃ cells, which exhibit a high discharge capacity and excellent cycling stability. The flexible SMB retains stable voltage output and continues to function even when bent or twisted. This study introduces a novel strategy for creating gel electrolytes for high-performance flexible SMBs.