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 degrees 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 Na2MnFe(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.