Surface Adsorption and Proton Chemistry of Ultra‐Stabilized Aqueous Zinc‐Manganese Dioxide Batteries

Abstract

Aqueous rechargeable Zn batteries incorporating MnO₂ cathodes possess favourable sustainability properties and are being considered for low‐cost, high‐safety energy storage. However, unstable electrode structures and unclear charge storage mechanisms limit their development. Here, we utilize advanced transmission electron microscopy, electrochemical analysis, and theoretical calculations to study the working mechanisms of a Zn/MnO₂ battery with a Co²⁺‐stabilized, tunnel‐structured α‐MnO₂ cathode (Co_xMnO₂). We show that Co²⁺ can be pre‐intercalated into α‐MnO₂ and occupy the [2 × 2] tunnel structure, which improves the structural stability of MnO₂, facilitate the proton diffusion and Zn²⁺ adsorption on the MnO₂ surface upon battery cycling. We further reveal that for the MnO₂ cathode, the charge storage reaction proceeds mainly by proton intercalation with the formation of α‐H_yCo_xMnO₂, and that the anode design (with or without Zn metal) affects the surface adsorption of by‐product Zn₄SO₄(OH)₆·nH₂O on MnO₂ surface. Our work advances the fundamental understanding of rechargeable Zn batteries and also sheds light on efficient electrode modifications toward performance enhancement.

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