A Composite Gel–Polymer/Glass–Fiber Electrolyte for Sodium‐Ion Batteries

An integrated preparation of a low‐cost composite gel–polymer/glass–fiber electrolyte with poly(vinylidene fluoride‐ co ‐hexafluoropropylene) (PVDF‐HFP) reinforced by a glass–fiber paper and modified by a polydopamine coating to tune the mechanical and surface properties of PVDF‐HFP is shown to be applicable to a sodium‐ion battery. The composite polymer matrix exhibits excellent mechanical strength and thermal stability up to 200 °C. After saturating with a liquid electrolyte, a wide electrochemical window and high ionic conductivity is obtained for the composite gel–polymer/glass–fiber electrolyte. When tested in a sodium‐ion battery with Na 2 MnFe(CN) 6 as cathode, the rate capability, cycling performance, and coulombic efficiency are significantly improved. The results suggest that the composite polymer electrolyte is a very attractive separator for a large‐scale battery system where safety and cost are the main concerns.