Unveiling the Intricate Intercalation Mechanism in Manganese Sesquioxide as Positive Electrode in Aqueous Zn‐Metal Battery

Abstract

Abstract In the family of Zn/manganese oxide batteries with mild aqueous electrolytes, cubic α‐Mn 2 O 3 with bixbyite structure is rarely considered, because of the lack of the tunnel and/or layered structure that are usually believed to be indispensable for the incorporation of Zn ions. In this work, the charge storage mechanism of α‐Mn 2 O 3 is systematically and comprehensively investigated. It is demonstrated that the electrochemically induced irreversible phase transition from α‐Mn 2 O 3 to layered‐typed L‐Zn x MnO 2 , coupled with the dissolution of Mn 2+ and OH − into the electrolyte, allows for the subsequent reversible de‐/intercalation of Zn 2+ . Moreover, it is proven that α‐Mn 2 O 3 is not a host for H + . Instead, the MnO 2 formed from L‐Zn x MnO 2 and the Mn 2+ in the electrolyte upon the initial charge is the host for H + . Based on this electrode mechanism, combined with fabricating hierarchically structured mesoporous α‐Mn 2 O 3 microrod array material, an unprecedented rate capability with 103 mAh g −1 at 5.0 A g −1 as well as an appealing stability of 2000 cycles (at 2.0 A g −1 ) with a capacity decay of only ≈0.009% per‐cycle are obtained.