Boosting High Energy Density for Aqueous Ni–Zn Batteries by Synergetic Engineering of Bimetal Doping and Se Vacancy in Ni₃Se₂

Developing transition metal selenide materials with high capacity, excellent rate capability, and satisfactory durability presents significant challenges due to their sluggish electrochemical kinetics, limited electrical conductivity, and detrimental volume change. To address these challenges, we have prepared four Ni3Se2-based cathode materials, named as Ni3Se2, Mo-Ni3Se2, V-Ni3Se2, and MoV-Ni3Se2, with selenium vacancies through a one-step hydrazine-hydrothermal process. Co doping with Mo and V demonstrates the synergistic effects of the bimetallic dopants and induces the generation of a higher density of selenium vacancies. The incorporation of Mo/V codoping and rich selenium vacancies confers upon MoV-Ni3Se2 obvious advantages, such as improved electrical conductivity, enhanced structural flexibility, sufficient redox reaction sites, and reduction of charge-transfer resistance. Consequently, the MoV-Ni3Se2 electrodes achieve a peak specific capacity of 1.78 mAh cm–2 at a current density of 2 mA cm–2 and sustain a high rate capability of 0.96 mAh cm–2 at 50 mA cm–2. The MoV-Ni3Se2//Zn battery delivers an impressive surface energy density of 2.93 mWh cm–2 and a remarkable power density of 51.55 mW cm–2 with outstanding cycling stability (capacity retention of 87.44% at 20 mA cm–2 after 3000 cycles). This study provides valuable insights for the development of high-performance cathode electrodes by synergetic engineering of doping and defects for aqueous nickel–zinc batteries.