Proton exchange membranes with ultra-low vanadium ions permeability improved by sulfated zirconia for all vanadium redox flow battery

Suppressing vanadium ions crossover is a top priority in the development of membranes for vanadium redox flow battery (VRFB). One method is to dope inorganic fillers into polymer matrix, which usually decreases membrane's ion conductivity. In this work, sulfated zirconia (S-ZrO2) is synthesized as a novel additive doped in sulfated poly (ether sulfone) (SPES) to simultaneously enhance the proton conduction and inhibit vanadium migration of the membranes. Membrane characterizations including battery test are carried out to reveal the effects of S-ZrO2 on the membrane performance. The SPES/S-ZrO2 composite membranes show vanadium permeability one order of magnitude lower than that of Nafion 212 and enhanced proton conductivity, which lead to superior cell performance. The columbic efficiency and energy efficiency of the VRFB reach 98.89% and 86.78%, respectively, at 100 mA cm(-2). Cycling test is carried out to evaluate the chemical and electrochemical stability of the membrane. Energy efficiency above 86% is maintained after70 charge-discharge cycles at 100 mA cm(-2). (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.