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

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$^{2+$intheelectrolyteupontheinitialchargeisthehostforH$^{+}$.Basedonthiselectrodemechanism,combinedwithfabricatinghierarchicallystructuredmesoporous\alpha -Mn$_{2}$O$_{3}$microrodarraymaterial,anunprecedentedratecapabilitywith103mAhg-1at5.0Ag-1aswellasanappealingstabilityof2000cycles(at2.0Ag$^{-1}$) with a capacity decay of only ≈0.009% per-cycle are obtained.