Ionic crosslinking‐induced nanochannels with fast proton‐selective conduction in flow battery membrane

Abstract Charge‐governed ion transport is a critical mechanism in various industries, particularly in energy conversion and storage applications. Drawing inspiration from this, a novel ion‐conductive membrane (ICM) was developed through ionic crosslinking of sulfonated poly(arylene ether ketone) (SPEEK) and polybenzimidazole (PBI) to fully harness ionic‐charge effects for enhanced performance in vanadium redox flow batteries. The ionic crosslinking induces nanophase separation, leading to the aggregation of ion pathways with ionic‐charge effects, which significantly enhances proton/vanadium ion selectivity and facilitates efficient proton transport (36.5 mS·cm −1 ) via the Grotthuss mechanism. The optimized ICM demonstrates simultaneous improvements in battery performance with enhanced energy efficiency (EE: 91.1%–82.8% at 40–200 mA·cm −2 ), while exhibiting excellent long‐term stability for 1000 cycles over 500 h (EE: 78.9% at 120 mA·cm −2 ). This study highlights the potential of ionic crosslinking‐induced angstrom‐scale channels with tailored functionalities, thereby advancing the applications of ICMs in rapid energy conversion, energy storage devices, and beyond.