Transport phenomena in flow battery ion-conducting membranes

Selectively tuning ion transport through redox flow battery separators is a promising approach toward increasing cell capacity, power density, and, ultimately, economic feasibility. However, this process is complex with numerous forces and coupled molecular interactions driving and impacting transport under different operating regimes. A fundamental description of ion transport in flow-battery separators can guide the development of new separators by identifying the nature of ion selectivity under given conditions. In this paper, we highlight different contributing factors of transport phenomena, explore how these factors influence cell performance, and the performance tradeoffs inherent in membrane design.