Co^2+/3+/4+‐Regulated Electron State of Mn‐O for Superb Aqueous Zinc‐Manganese Oxide Batteries

Abstract Aqueous rechargeable Zn – MnO x batteries are very attractive due to their low‐cost and high energy density. However, Mn(III) disproportionation and Jahn–Teller distortion can induce Mn(II) dissolution and irreversible phase changes, greatly deteriorating the cycling life. Herein, a multi‐valence cobalt‐doped Mn 3 O 4 (Co‐Mn 3 O 4 ) with high capacity and reversibility, which lies in the multiple roles of the various states of doped cobalt, is reported. The Co 2+ doping between the phase change product δ‐MnO 2 layer acts as a “structural pillar,” and the Co 4+ in the layer can increase the conductivity of Mn 4+ and hold the high specific capacity. More importantly, Co ion (Co 2+ , Co 3+ ) doping can effectively inhibit the Jahn–Teller effect in discharge products and promote ion diffusion. Using X‐ray absorption spectra results and density functional theory modelling, the multiple roles of doped cobalt are verified. Specifically, the Co‐Mn 3 O 4 cathode shows high specific capacity of 362 mAh g –1 and energy density of 463.1 Wh kg –1 at 100 mA g –1 . After 1100 cycles at 2.0 A g –1 , the capacity retention rate reaches 80%. This work brings a new idea and approach to the design of highly reversible Mn‐based oxides cathode materials for Zn‐ion batteries.