Defect-Rich Manganese–Iron Oxides Nanoarchitecture Delivered High Specific Capacity and Synergetic Zn²⁺ Redox Storage/ZSH-Assisted Deposition–Dissolution Mechanism

Rechargeable aqueous Zn–Mn batteries have attracted significant attention for their potential as high-safety energy storage systems in the next generation. However, the main limitation of Mn-based cathodes lies in their low practical capacity and unclear energy storage mechanism. In this study, a core–shell manganese–iron oxide nanoarchitecture (FMFO@C) cathode was introduced for the first time. This cathode not only possesses a robust structure and high conductivity but also enables three-dimensional (3D) transport of Zn ions, resulting in a significantly enhanced specific capacity, superior rate performance, and prolonged cycle life. Consequently, the evaluated aqueous Zn//FMFO@C battery demonstrates an impressive specific capacity of 441 mA h g–1 at 0.1 A g–1 and excellent capacity retention of 118 mA h g–1 at 2 A g–1 over 3000 cycles. Combined with density functional theory (DFT) calculations, the core–shell FMFO@C cathode allows for a reversible insertion of Zn2+ into the redox-active FMFO and reversible deposition–dissolution of Zn4SO4(OH)6·xH2O (ZSH) on the amorphous carbon skeleton. The proposed strategy exhibits significant merits in terms of overall practical capacity and cycling stability, which can be extended to the elaborately modifying design of cathode materials for reliable and cost-effective energy storage.