Oxygen vacancies-enriched Mn3O4 enabling high-performance rechargeable aqueous zinc-ion battery

The development of high-energy cathode for rechargeable aqueous zinc-ion batteries (ZIBs) is highly attractive. However, the disproportionation effect of Mn2+ seriously affects the capacity retention of ZIBs during cycling. Defect engineering provides efficient methods to enhance conductivity and structural stability of active materials. Here, a novel in situ generated bulk oxygen deficient Mn3O4 nanoframes cathode for rechargeable aqueous ZIBs is reported, with high capacity and good electrochemical stability. The oxygen-deficient Mn3O4 spheres display an excellent gravimetric capacity of 325.4 mAh g−1 and a high energy density of 423 Wh kg−1 at a power density of 2257.2 W kg−1. Ex situ X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) characterization demonstrate the initial Mn3O4 is converted to ramsdellite MnO2 for insertion and extraction of H+ and Zn2+. Theoretical modeling reveal that numerous edge sites and oxygen vacancies act as preferential intercalation sites for the zinc ions, leading to a much greater capacity than that of defect-free Mn3O4. These results highlight the potentials of defect engineering as a strategy of improving the electrochemical performance of Mn3O4 in aqueous rechargeable batteries.