Magnetic field-assisted synthesis of Co-doped Mn3O4/MnOOH multiphase manganese oxides for high-performance cathodes in aqueous rechargeable zinc-ion batteries

As a promising candidate for aqueous zinc-ion batteries (AZIBs), manganese-based oxides are recognized as suitable cathode materials. However, the cycling stability and rate performance of AZIBs are significantly hindered by inadequate electronic conductivity and sluggish ion migration rates, thereby limiting their practical applications. In this study, we synthesized Co-Mn3O4/MnOOH materials through a straightforward magnetic element induction method. The incorporation of cobalt markedly altered the microstructure of the pristine MnOOH, resulting in the formation of a distinctive multiphase manganese oxide system. Within this system, the coexistence of manganese ions in varying valence states establishes an efficient network for electron transport and substantially accelerates the charge transfer rate, leading to a significant enhancement in the conductivity of Co-Mn3O4/MnOOH. This transformation not only improves the zinc storage capacity but also effectively mitigates the Jahn-Teller distortion typically associated with Mn3+ ions during the electrochemical reaction, thereby positively influencing both the long-term cycling stability and the high energy storage capacity of the battery. In a pioneering revelation, the storage mechanism of the Co-Mn3O4/MnOOH material was elucidated as Zn2+/H+ co-insertion, confirmed through ex-situ X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) characterizations. This discovery paves the way for innovative two-phase or multiphase manganese-based composites for AZIBs.