Suppressing vanadium crossover using sulfonated aromatic ion exchange membranes for high performance flow batteries

Liquid flow batteries have potential to achieve high energy efficiency as a large-scale energy storage system. However, the ion exchange membranes (IEMs) currently used in flow batteries do not have high ion selectivity and conductance at the same time, owing to the trade-off between ionic membrane resistance and ion selectivity. Here, we report a rationally designed sulfonated aromatic polymer membrane which can greatly mitigate the trade-off limitation and achieve high performance vanadium RFB. Small-angle X-ray scattering studies and density functional theory calculations indicated that the narrowly distributed aqueous ionic domain of just the right width (