A Molecularly Engineered Crosslinked Polyether Electrolyte with Anion‐Trapping Nano‐Networks for Fast‐Charging and Safe Sodium Metal Batteries

ABSTRACT In‐situ polymerized polyether electrolytes are highly promising for solid‐state sodium metal batteries (SMBs) owing to their high ionic conductivity and favorable interfacial contact. However, their practical application is limited by poor thermal stability, low Na + transference number, and unstable Na/electrolyte interface, leading to rapid degradation and safety risks. Herein, we demonstrate a molecularly engineered, anion‐anchoring crosslinked polyether electrolyte (AICPE) fabricated by in‐situ polymerization of 1,3‐dioxolane with epoxy‐functionalized halloysite nanotubes (e‐HNTs). The e‐HNTs function as a dual‐surface ion‐regulator: the inner‐surface Al–OH groups act as Lewis acid sites for anion‐trapping, while the outer siloxane surface weakens Na + ‐polymer interactions through competitive coordination. This synergy between the crosslinked network and bidirectional ion‐regulation endows the AICPE with a high ionic conductivity of 2.17 mS cm − 1 , an elevated Na + transference number of 0.72, significantly improved thermal stability, and superior interfacial compatibility. Consequently, Na/Na symmetric cells achieve ultra‐stable cycling over 3600 h at 0.1 mA cm − 2 without dendrite penetration. Importantly, the solid‐state SMBs exhibit remarkable rate capability and outstanding long‐term durability, with 87.5% capacity retention after 1200 cycles at an ultra‐high rate of 10 C. Practical pouch cells further confirm exceptional thermal safety, highlighting the practical potential of this design for high‐performance, safe, and fast‐charging SMBs.