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 electrolyte has been considered as a safer and more reliable electrolyte system for rechargeable batteries. Herein, we report a thermoplastic polyurethane elastomer-based gel polymer electrolyte with high ionic conductivity and high elasticity. It has an ambient temperature ionic conductivity of 1.5 mS cm-1 and high stretchability, capable of withstanding 610% strain. The coordination between Na+ ions and polymer chains increases the degree of salt dissociation in the gel polymer electrolyte compared to the liquid electrolyte. The Na/Na3V2(PO4)3 cell assembled with gel polymer electrolyte exhibits good cycling performance in terms of discharge capacity, cycling stability and rate capability, which is due to the good trapping ability of organic solvents in the polymer matrix and uniform flux of sodium ions through the gel polymer electrolyte.