Dynamic Amorphous Zn0.17MnO2−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 ‐Mn 2 O 3 into amorphous Zn 0.17 MnO 2−n ·0.52H 2 O, which serves as the host of Zn 2+ , empowering more highly accessible built‐in zincophilic sites whilst alleviating the lattice repulsion of Zn 2+ (de)intercalation. As confirmed by crystal structure evolution characterizations and theoretical simulations, the amorphous Zn 0.17 MnO 2−n ·0.52H 2 O with excellent electronic properties and low zinc‐ion migration barrier can be reversibly converted into ZnMn 3 O 7 ·3H 2 O. 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 Mn 3 O 4 and α ‐MnO 2 , opening new insights into electrochemical oxidation induced crystal conversion to build highly reversible and durable ZIBs.