Progress and Perspectives of In Situ Polymerized Solid‐State Electrolytes for Sodium Batteries

ABSTRACT Sodium batteries have attracted considerable attention for large‐scale energy storage because of the abundance and low cost of sodium resources. Conventional liquid electrolytes still face substantial safety concerns. In contrast, solid polymer electrolytes can reduce reliance on volatile liquids but often exhibit limited room temperature ion transport and poor contact with porous electrodes. In situ polymerization offers a route to address these issues due to its compatibility with existing sodium‐ion battery manufacturing processes and its potential for scalable production. This review summarizes the advantages and limitations of in situ polymerization for sodium batteries, polymerization initiation conditions and mechanisms, fabrication strategies, and recent advances in sodium‐based in situ polymerized solid‐state electrolytes (SSEs). The key scientific and technological challenges at the current stage are further identified. Finally, future directions for sodium‐based in situ polymerized SSEs are discussed from the materials to the cell level, along with perspectives on structural design for solid‐state sodium‐ion batteries.