Zn Anode Surviving Extremely Corrosive Polybromide Environment with Alginate‐Graphene Oxide Hydrogel Coating

Abstract Zinc–bromine (Zn‐Br) redox provides a high energy density and low‐cost option for next‐generation energy storage systems, and polybromide diffusion remains a major issue leading to Zn anode corrosion, dendrite growth, battery self‐discharge and limited electrochemical performance. A dual‐functional Alginate‐Graphene Oxide (AGO) hydrogel coating is proposed to prevent polybromide corrosion and suppress dendrite growth in Zn–Br batteries through negatively charged carboxyl groups and enhanced mechanical properties. The battery with anode of plain zinc coated with AGO (Zn ] AGO) survives a severely corrosive environment with higher polybromide concentration than usual without a membrane, and achieves 80 cycles with 100% Coulombic and 80.65% energy efficiencies, four times compared to plain Zn anode. The promising performance is comparable to typical Zn–Br batteries using physical membranes, and the AGO coating concept can be well adapted to various Zn–Br systems to promote their applications.