Structural Regulation of ZnMn2O4 cathode material by K, Fe-Double doping to improve its rate and cycling stabilityfor rechargeable aqueous zinc-based batteries

In aqueous zinc-based batteries (ZBBs), manganese-based materials are considered to be potential cathode materials. However, sluggish electrochemical reaction kinetics and problems with manganese dissolution have limited their further development. Herein, K and Fe double-doped ZnMn2O4 (K, Fe-ZMO) is demonstrated to be effective in solving the above problems. The doping of K and Fe can form oxygen defects to enhance the conductivity of the material and the diffusion of Zn2+. Interestingly, the K, Fe-doped ZnMn2O4 shows a high specific capacity of 221.2 mA h g−1 (0.1 A g−1) after 50 cycles, more than the pure ZnMn2O4 (137.3 mA h g−1). The capacity retention (≈88.1% 500 cycles at 1.0 A g−1) is also better than ZnMn2O4 cathode (≈27.5% 370 cycles at 1.0 A g−1). Density functional theory (DFT) calculations prove that double doping and oxygen defects can facilitate electronic rearrangement to enhance the conductivity, which finally improves the reaction kinetics and electrochemical performance of the K, Fe-ZMO. Furthermore, the modifications can also reduce the formation energy so as to effectively stabilize the Mn-O bond and Fe-O of K, Fe-ZMO, which alleviates the dissolution of manganese. We believe that the strategy proposed in this work will provide another example for the practical application of manganese-based materials in aqueous zinc-based batteries.