SPES/PVDF Binary Membrane as an Alternative Proton Exchange Membrane in Vanadium Redox Flow Battery Application

Abstract

SPES/PVDF blends were employed to prepare the ion exchange membranes for vanadium redox flow battery (VRB) application for the first time. The addition of the highly crystalline and hydrophobic PVDF effectively limited the swelling behavior of SPES. The vanadium ion permeability of SPES/PVDF membranes was one order of magnitude lower than that of Nafion117 membrane and pristine SPES membrane. Single cells with SPES/PVDF composite membranes showed significantly lower capacity loss, higher coulombic efficiency and higher energy efficiency than that with Nafion117 and pristine SPES membranes. The blend membrane with 40wt% of PVDF (denoted as S0.6P0.4) showed energy efficiency of 83.2% at 30 mA∙cm-2, which was superior to that of the Nafion117 and SPES membranes. In the self-discharge test, S0.6P0.4 membrane showed twice longer duration in open circuit decay than that with Nafion117 membrane. With all the good properties and low cost, the SPES/PVDF membranes are expected to have excellent commercial prospects as ion exchange membranes for VRB system.