Interface regulated MnO2/Mn2+ redox chemistry in aqueous Zn ion batteries

Abstract

Due to the rapid development of energy storage systems from the goal of carbon neutrality, rechargeable aqueous Zn-MnO2 batteries have attracted growing attention. While the controversy surrounding various mechanisms, such as Zn2+ insertion, Zn2+/H+ co-insertion and Mn dissolution/deposition, leads to limitation of MnO2 cathodes, especially for the β-MnO2. Though showing promising performance in recent works, the reaction process and influence factors of β-MnO2 cathodes are still under debate. In this work, a complete MnO2/Mn2+ redox chemistry is proposed to explain the abnormal electrochemical behaviors of β-MnO2 cathodes, which indicates the reversible dissolution/deposition of layered manganese oxides appears after the initial MnO2 dissolution reaction. The revealed effects of interfacial environment in regulating the electrochemical reactions also provide a new perspective for studying the working mechanism of aqueous Zn-MnO2 batteries. Besides, the high specific capacity shown in the MnO2/Mn2+ redox chemistry also contributes to designing high-performance cathodes for AZIBs.