Co~(2+/3+/4+)-Regulated Electron State of Mn-O for Superb Aqueous Zinc-Manganese Oxide Batteries

摘要

Aqueous rechargeable Zn-MnOx 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 Mn3O4 (Co-Mn3O4) with high capacity and reversibility, which lies in the multiple roles of the various states of doped cobalt, is reported. The Co2+ doping between the phase change product delta-MnO2 layer acts as a "structural pillar," and the Co4+ in the layer can increase the conductivity of Mn4+ and hold the high specific capacity. More importantly, Co ion (Co2+, Co3+) 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-Mn3O4 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.