Polymer electrolyte membranes prepared by pre-irradiation induced graft copolymerization on ETFE for vanadium redox flow battery applications

The application of grafted membranes based on modified poly(ethylene-alt-tetrafluoroethylene) (ETFE) in redox flow-batteries is reported. In analogy to commercial Nafion® 117 based membranes ETFE backbone material provides chemical, thermal, and mechanical stability. Side chains composed of 2-hydroxyethyl methacrylate (HEMA) and glycidyl methacrylate (GMA) grafted to ETFE were sulfonated to achieve the required proton exchange capacity. Application in a vanadium based redox flow-battery demonstrates the applicability of this kind of membranes for energy storage systems. The degree of grafting was identified as the key parameter to tune the membrane properties.