Research on Doping Modification of Mn₂O₃ Cathode Materials for Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries (AZIBs) show great promise for large-scale energy storage due to their high safety, low cost, and environmental friendliness. However, their cathode materials, especially manganese-based oxides, still face challenges such as inadequate cycling stability and rate capability. In this study, pristine and iron-, cobalt-, nickel-doped Mn₂O₃ materials were synthesized via a Mn-organic framework (MOF) template method. The effects of different doping elements and their concentrations on structure, morphology, and electrochemical performance were systematically investigated. The results indicate that nickel (Ni) doping at a 5% level exhibits the optimal modification effect. It delivers a discharge specific capacity of 201.7 mA h g^–1 at a current density of 0.1 A g^–1 after 100 cycles and retains a reversible capacity of 61.3 mA h g g^–1 after 500 cycles at 0.5 A g^–1. Its cycling stability and rate performance are significantly superior to those of others. In-depth analysis reveals that the introduction of Ni²⁺ promotes the oxidation of some Mn³⁺ to Mn⁴⁺, helping to maintain charge balance and suppress manganese dissolution. Simultaneously, Ni doping effectively reduces the charge transfer resistance of the electrode and increases the bulk diffusion coefficient of Zn²⁺. Considering both performance and cost, a 5% Ni doping level represents an effective modification strategy for Mn₂O₃ cathode materials.