Ni2+-doped ZnMn2O4 with enhanced electrochemical performance as cathode material for aqueous zinc-ion batteries.

Manganese-based materials are considered as potential cathode materials for aqueous zinc-ion batteries due to the advantages of high voltage platform, non-toxic, and environmental protection. However, the rapid decline capacity due to the dissolution of manganese and the low conductivity restrict its further development. In this paper, Ni²⁺-doped ZnMn₂O₄ nanoparticles were prepared and used as cathode materials for aqueous zinc-ion batteries. The Ni²⁺-doping effectively improves its electrochemical performance. The Ni²⁺-doped ZnMn₂O₄ cathode shows a discharge-specific capacity of 175 mAh g⁻¹ after an activation process at current density of 100 mA g⁻¹. At a high current density of 1A g⁻¹, the cathode displays a specific capacity of 120 mAh g⁻¹, and the Coulombic efficiency of above 97% can be maintained throughout the cycles except for the first cycle, indicating a high reversibility of charging/discharging. The Ni²⁺-doping increases the conductivity and zinc-ion diffusion coefficient of the material electrode through destroying the periodic potential field generated by the material. It shows that the synergistic effect of manganese and transition metal ions provides a possible direction for the future development of cathode materials for aqueous zinc-ion batteries. [ABSTRACT FROM AUTHOR]