Joint Charge Storage for High‐Rate Aqueous Zinc–Manganese Dioxide Batteries

Abstract Aqueous rechargeable zinc–manganese dioxide batteries show great promise for large‐scale energy storage due to their use of environmentally friendly, abundant, and rechargeable Zn metal anodes and MnO 2 cathodes. In the literature various intercalation and conversion reaction mechanisms in MnO 2 have been reported, but it is not clear how these mechanisms can be simultaneously manipulated to improve the charge storage and transport properties. A systematical study to understand the charge storage mechanisms in a layered δ‐MnO 2 cathode is reported. An electrolyte‐dependent reaction mechanism in δ‐MnO 2 is identified. Nondiffusion controlled Zn 2+ intercalation in bulky δ‐MnO 2 and control of H + conversion reaction pathways over a wide C‐rate charge–discharge range facilitate high rate performance of the δ‐MnO 2 cathode without sacrificing the energy density in optimal electrolytes. The Zn‐δ‐MnO 2 system delivers a discharge capacity of 136.9 mAh g −1 at 20 C and capacity retention of 93% over 4000 cycles with this joint charge storage mechanism. This study opens a new gateway for the design of high‐rate electrode materials by manipulating the effective redox reactions in electrode materials for rechargeable batteries.