High durable SPEEK/TiO₂ nanopaper composite membrane for vanadium redox flow battery

Sulfonated poly (ether ether ketone) (SPEEK) ion exchange membranes for VRFB are promising alternatives to Nafion, but require improved mechanical and chemical stability for long-term operation. Here, we have fabricated composite membranes using SPEEK as proton conductive medium and TiO₂ nanopapers as reinforcing framework to improve the mechanical and chemical stabilities of SPEEK membranes. The SPEEK/TiO₂ nanopaper composite membranes exhibited almost twice the tensile strength and only one-third the vanadium ion permeability compared to pristine SPEEK (DS=60 %). Due to the excellent cell performance such as high EE, slow capacity degradation and long-term lifetime, these high durable composite membranes could be found their potential use as ion exchange membranes for commercial VRFBs.