Nafion‐Based Proton Exchange Membranes for Vanadium Redox Flow Batteries

The sustainable development of future societies depends on advanced energy storage technologies. Vanadium redox flow batteries (VRFBs) are a preferred solution for large‐scale, long‐duration energy storage due to their high capacity, long lifespan, rapid response, and safety. The proton exchange membrane (PEM) is a pivotal component of VRFBs, playing a crucial role for conducting protons and preventing vanadium ion crossover. Currently, perfluorinated sulfonic acid membranes, represented by Nafion, are the most commonly used PEMs in VRFBs. However, the size discrepancy between vanadium ions (~0.6 nm) and the ionic domains in Nafion membranes (3‐5 nm) leads to significant vanadium permeability, resulting in reduced battery performance. Therefore, rationally regulating the structure of Nafion membranes to enhance their conductive selectivity is an urgent issue. This review focuses on recent advancements in Nafion modification, offering valuable insights for inspiring the fundamental innovation of high‐selective Nafion membranes for VRFB technology.