In-Situ Polymerized Solid-State Polymer Electrolytes for High-Safety Sodium Metal Batteries: Progress and Perspectives

The practical usage of sodium metal batteries is mainly hampered by their potential safety risks caused by conventional liquid-state electrolytes. Hence, solid-state sodium metal batteries, which employ inorganic solid electrolytes and/or solid-state polymer electrolytes, are considered an emerging technology for addressing the safety hazards. Unfortunately, these traditional inorganic/polymer solid electrolytes, most of which are prepared via ex-situ methods, frequently suffer from inadequate ionic conductivity and sluggish interfacial transportation. In light of this, in-situ polymerized solid-state polymer electrolytes are proposed to simplify their preparation process and simultaneously address these aforementioned challenges. In this review, the up-to-date research progress of the design, synthesis, and applications of this kind of polymer electrolytes for sodium batteries of high safety via several in-situ polymerization methods (including photoinduced in-situ polymerization, thermally induced in-situ free radical polymerization, in-situ cationic polymerization, and cross-linking reaction) are summarized. In addition, some perspectives, opportunities, challenges, and potential research directions regarding the further development of in-situ fabricated solid-state polymer electrolytes are also provided. We expect that this review will shed some light on designing high-performance solid-state polymer electrolytes for building next-generation sodium batteries with high safety and high energy.