Proton Inserted Manganese Dioxides as a Reversible Cathode for Aqueous Zn-Ion Batteries

Recent achievements of aqueous Zn-ion batteries have aroused widespread attention and call for an urgent demand on the development of potential cathode materials. In this work, we developed the proton inserted manganese dioxides (HxMn2O4) as a cycle-stable cathode material for aqueous Zn-ion batteries. The porous HxMn2O4 microspheres were derived from the ZnMn2O4 templates via a cation exchange method. Material characterization revealed the distinctive crystal structure with extensive insertion of H+ ions inside the tunnel of Mn0 6 octahedrons. Compared with the ZnMn2O4, the HxMn2O4-based Zn-ion batteries delivered an initial capacity of 281.0 mAh/g at 100 mA/g and maintained at 133.4 mAh/g after 1000 cycles at 1000 mA/g. Moreover, a high energy density of 391.6 Wh/kg was realized at 139.4 W/kg. Ex-situ XRD investigation demonstrated the synergistic and reversible insertion/extraction of H+ and Zn2+ ions in the HxMn2O4 cathode during the charge/discharge process. GITT measurement further verified the fast diffusion kinetics of the Zn2+ ions in the HxMn2O4 microspheres. The application of the spinel-type HxMn2O4 cathode would promote the follow-up research on advanced electrode materials for long-life span Zn-ion batteries.