Ion-selective soft glass membrane for vanadium redox flow battery

Abstract

In vanadium redox flow battery (VRFB), membranes requiring both high ion-selectivity and proton conductivity are the key factors to increase overall efficiencies and reduce cost. However, due to intrinsic trade-off relation between ion-selectivity and proton conductivity within the membrane, it has been difficult to dramatically increase overall efficiencies and effectively prevent capacity decay caused by multivalent vanadium electrolytes crossover. In this work, we developed silane-based soft glass thin membrane with 100 nm thickness which effectively blocks the crossover of multivalent vanadium electrolytes while allowing for proton transport. Ascribing to the soft glass membrane’s superior capability to exclude vanadium ions and thin thickness, the soft glass composite membrane achieves a coulombic efficiency of 98% at 40 mA cm-2 and a capacity retention of 97% during 5 cycles. It demonstrates that high ion-selectivity and low membrane area resistance of soft glass composite membrane could offer a practical application for VRFB as it overcomes the capacity decay.