Thermoplastic Polyurethane Elastomer‐Based Gel Polymer Electrolytes for Sodium‐Metal Cells with Enhanced Cycling Performance

Abstract Sodium batteries have been recognized as a promising alternative to lithium‐ion batteries. However, the liquid electrolyte used in these batteries has inherent safety problems. Polymer electrolytes have been considered as safer and more reliable electrolyte systems for rechargeable batteries. Herein, a thermoplastic polyurethane elastomer‐based gel polymer electrolyte with high ionic conductivity and high elasticity was reported. It had an ambient‐temperature ionic conductivity of 1.5 mS cm−1 and high stretchability, capable of withstanding 610 % strain. Coordination between Na+ ions and polymer chains increased the degree of salt dissociation in the gel polymer electrolyte compared with the liquid electrolyte. An Na/Na3V2(PO4)3 cell assembled with gel polymer electrolyte exhibited good cycling performance in terms of discharge capacity, cycling stability, and rate capability, which was owing to the effective trapping ability of organic solvents in the polymer matrix and uniform flux of sodium ions through the gel polymer electrolyte.