Degradation Analysis and Design Strategies for Ion-Exchange Membrane-Based Aqueous Flow Batteries to Enhance Cyclability in Large-Scale Energy Storage Systems

Abstract

Aqueous flow batteries generate or store energy by the directional flow of ions through an ion exchange membrane (IEM). In particular, due to the less safety concern and low rare-metal dependence, bipolar membrane acid-base flow battery (B-ABFB) has great potential for the next-generation energy storage system. B-ABFB constructs with a cation exchange membrane (CEM), anion exchange membrane (AEM), and bipolar membrane (BPM) which is fabricated by attaching the CEM and AEM. In the BPM, discharge and charge reactions can be conducted by neutralization of acid/base (H+ + OH− → H2O, discharge) and dissociation of water (H2O → H+ + OH− , charge), respectively. Despite these advantages, previously reported B-ABFBs have poor energy efficiency and cycle durability. The reason for poor performance is undesirable ion leakage, which inevitably occurs because the ion selectivity of IEMs is not ideal. In this study, I will investigate the degradation mechanism of B-ABFB caused by ion leakage and propose strategies to address the problems. In detail, based on the degradation mechanism, strategies to decrease the leakage of co-ions and the permeation of counter-ions will be suggested by designing the electrochemical system which includes the arrangement of ion exchange membranes.