Recent Advances in Polybenzimidazole-Based Membrane for Flow Batteries

Abstract Polybenzimidazole (PBI)-based membranes are promising for flow batteries (FB) due to their excellent ion selectivity, thermal stability, and tunable ion conductivity. This review systematically summarizes recent advances in PBI-based membranes for various flow battery systems, categorized by fabrication method and membrane type. First, the effects of solvent evaporation-induced phase inversion (EIPS), water-induced phase inversion (NIPS), vapor-induced phase inversion (VIPS), and mixed-phase inversion on membrane structure and performance are summarized. Second, based on membrane type, the ion conduction mechanisms and performance differences of dense membranes, porous membranes, and blend membranes are discussed separately.Third, applications and challenges of PBI-based membranes in vanadium redox flow batteries (VRFB), zinc-based flow batteries (ZRFB) and iron-based flow batteries (IRFB) are discussed. Finally, structure-property relationships are summarized, and design strategies for high-performance PBI membranes are proposed. Nevertheless, PBI based membranes still face critical bottlenecks for real world RFB applications. Their ionic conductivity strongly relies on acid base doping, and irreversible dopant loss during continuous electrolyte circulation would induce progressive performance decay over cycling. This review provides a systematic reference for the rational design and application of PBI-based membranes in flow batteries.