Dynamic Amorphous Zn_0.17MnO_2−n·0.52H₂O Electrochemical Crystal Transition for Highly Reversible Zinc‐Ion Batteries with Ultrahigh Capacity and Long Lifespan

Abstract Mn‐based oxides promise high energy density and low toxicity cathodes for aqueous zinc‐ion batteries (ZIBs) but suffer from complex irreversible phase transitions, accompanied by continuous disproportionation reactions and manganese dissolution. Tailor‐made reversible and robust crystal structure in Mn‐based material is crucial and challenging. Here a controllable electrochemical oxidation induced crystal transition strategy is developed for the transformation of cubic α‐Mn₂O₃ into amorphous Zn_0.17MnO_2−n·0.52H₂O, which serves as the host of Zn²⁺, empowering more highly accessible built‐in zincophilic sites whilst alleviating the lattice repulsion of Zn²⁺ (de)intercalation. As confirmed by crystal structure evolution characterizations and theoretical simulations, the amorphous Zn_0.17MnO_2−n·0.52H₂O with excellent electronic properties and low zinc‐ion migration barrier can be reversibly converted into ZnMn₃O₇·3H₂O. This stabilized dynamic electrochemical crystal transition equilibrium contributes ultrahigh capacity (558 mAh g⁻¹), high‐energy density (696 Wh kg⁻¹@6 kW kg⁻¹), and superior stability (5000 cycles). The approach can also extend to Mn₃O₄ and α‐MnO₂, opening new insights into electrochemical oxidation induced crystal conversion to build highly reversible and durable ZIBs.