Sulfonation of poly(phenylene oxide) anion exchange membrane for all vanadium flow redox battery

Abstract

To develop a low cost non-fluorinated membrane for vanadium redox flow battery (VRFB), several commercial ion exchange membranes (IEM) were compared in terms of primary properties such as ion exchange capacity (IEC), vanadium ion permeability (P) and water transfer (WT) and chemical stability, and an anion exchange membrane (AEM) DF-a (based on Poly(phenylene oxide) polymers) was sulfonated into amphoteric ion exchange membranes (DF-a1 and DF-a2) to restrain WT. Effects of sulfonation on morphologies, selective proton conductivity (σ), WT and chemical stability of membranes were investigated. The results showed that sulfonation can improve IEC, σ, Selectivity and chemical stability of the AEM (DF-a). Due to Donnan effect, DF-a2 had a more dramatic reduction in WT and self discharge in VRFB than DF-a. Cell test showed that the membrane DF-a2 had higher coulombic efficiency (CE) and energy efficiency (EE) than DF-a and DF-a1, possessing a better potential application in VRFB.