In Situ Polymerization Enhances Anion Solvation Structure for Stable High‐Temperature Cycling in Quasi‐Solid‐State Sodium Metal Batteries

ABSTRACT While sodium metal batteries (SMBs) possess remarkable superiority for next‐generation energy storage systems, interfacial reactions, and dendrite growth due to the dissolution of solid electrolyte interphase (SEI) have seriously hindered the large‐scale application of SMBs, especially at high temperatures. Here, a vinyl ethylene carbonate‐based quasi‐solid electrolyte (PVEC‐QSPE) capable of enhancing the high‐temperature stability of Na anodes is successfully synthesized by in situ curing of oligomeric poly(vinyl ethylene carbonate) (PVEC). The increased steric hindrance of PVEC reduces the coordination ability of C═O toward Na + , which promotes the cooperative migration of Na + with anions and the decomposition of anions to form the SEI. Furthermore, PVEC‐QSPE significantly reduces the dissolution of SEI, which contains more organic components and fewer inorganic components, thereby minimizing the release of gases including CO 2 and inhibiting the growth of sodium dendrites. The stable interface between PVEC‐QSPE and Na helps Na|PVEC‐QSPE|Na 3 V 2 (PO 4 ) 3 (NVP) batteries to operate stably at high temperatures, whose capacity retention rate reaches 80% at 80°C and 93.3% at 60°C after 3000 cycles employing high rate of 10 C. This work provides an efficient strategy to solve the problems of unstable SEI and dendrite growth, thereby promoting the development of safe and practical SMBs.