Ion‐Regulating Membranes with Surface‐Enriched Charge Networks Enabling Stable Zinc‐Manganese Flow Batteries

Abstract Zinc‐based flow batteries are promising for sustainable energy storage owing to their high energy density and eco‐friendliness. When coupling with Mn ²⁺ /MnO ₂ posolyte, the zinc‐manganese flow batteries promise an ultra‐low electrolyte cost (0.0039 $ Ah ⁻¹ ). However, their practical application is limited by low areal capacity (<20 mAh cm ⁻² ) and poor lifespan (<100 cycles with accumulated capacity < 2000 mAh cm ⁻² ), associated with proton crossover and zinc dendrite formation. To address the two bottlenecks, an ion‐regulating membrane with surface‐enriched positive charges of Zn ²⁺ crosslinked networks is proposed. The enriched‐charged networks amplify H⁺ retention (60% elevated proton transport barrier to 0.104 eV) via imposing charge‐enhanced dehydration barriers and nitrogen‐groups synergism, leveraging the higher ionic potential of protons to discriminate the conduction ions (K ⁺ ). Simultaneously, the surface charges electrostatically guide the uniform distribution of near‐electrode zinc ions for zinc‐oriented growth without dendrites. The synergistic strategy achieves a near‐neutral zinc‐manganese flow system with a record accumulated capacity of 6510 mAh cm ⁻² (>200 cycles) at 30 mA cm ⁻² , high areal capacity of 100 mAh cm ⁻² (130.1 mWh cm ⁻² ) at 20 mA cm ⁻² , representing one of the most stable zinc‐manganese flow batteries reported. This study provides an effective membrane design strategy for low‐cost and high‐energy‐density zinc‐based flow batteries.