Selective Ion Transport through Hydrated Micropores in Polyelectrolyte Membranes

With increasing reliance on renewable but intermittent energy sources like solar and wind, electrochemical technologies are essential for on-site energy storage and integrating low-carbon power into the grid. Aqueous organic redox flow batteries (RFBs) offer great potential for grid-scale, long-duration energy storage, but their development is limited by the need for ion-selective polymer membranes. Here, I will discuss our recent efforts in the development of microporous membranes designed for precise ion transport in RFB applications. Through modular synthesis of microporous polymers, we introduce ion-coordinating functionalities to enhance rapid ion transport, while optimizing pore geometry and channel topology in hydrated membranes for efficient size-sieving selectivity. These membranes demonstrate faster ion conduction and orders-of-magnitude higher ion selectivity than commercial alternatives, resolving the trade-off challenges typical of conventional membranes. When paired with energy-dense organic redox couples, these membranes enable higher energy efficiency and significantly lower capacity decay in RFB systems.

References: Wang, A., Breakwell, C., Foglia, F. et al. Selective ion transport through hydrated micropores in polymer membranes. Nature 635, 353–358 (2024). https://doi.org/10.1038/s41586-024-08140-2