Counter‐ion insertion of chloride in Mn3O4 as cathode for dual‐ion batteries: A new mechanism of electrosynthesis for reversible anion storage

Abstract

Abstract Irreversible reductive insertion of Zn2+ transforms Mn3O4 such that the resulting Zn0.2Mn3O4 exhibits highly reversible storage properties of chloride ions, thus rendering Zn0.2Mn3O4 an excellent cathode of aqueous dual‐ion batteries. With Zn2+ trapped, Zn0.2Mn3O4 delivers the chloride‐storage capacity over 200 mAh/g at an average potential of 1.6 V vs Zn2+/Zn by reversibly forming a new ionic compound equivalent to Zn0.2Mn3O4Cl1.7. Electrochemical quartz crystal microbalance results suggest chloride as the primary charge carrier in the reversible oxidative anion insertion. The Mn3O4 anion‐hosting cathode couples with Zn metal anode in a full‐cell dual‐ion battery, demonstrating stable cycling in practical pouch cells with an energy density of 150 Wh/kg based on the mass of both electrodes.

Keywords

• anion insertion
• counter‐ion insertion
• dual‐ion battery
• metal oxide cathode
• Zn batteries