Enhancing Zn²⁺-Storage and Stability in Aqueous Zinc-Ion Batteries by Nickel and Cobalt Co-Doping in NH₄V₄O₁₀...

Aqueous zinc-ion batteries (AZIBs) are promising for energy storage due to their high safety, low cost, and environmental friendliness. However, their practical use is limited by the low specific capacity and poor cycling stability of cathode materials. NH₄V₄O₁₀ (NVO), a layered material, offers high theoretical capacity and open zinc-ion transport channels but suffers from poor intrinsic conductivity and structural instability. This study investigates the impact of Ni²⁺ and Co²⁺ single and co-doping on the zinc-storage performance of layered NH₄V₄O₁₀. The synergistic co-doping of Ni²⁺ and Co²⁺ expands interlayer channels, increases oxygen-defect concentration, reduces the Zn²⁺ diffusion barrier, and reinforces interlayer stability against structural collapse, thereby improving reaction kinetics and long-term cycling stability. Benefiting from these advantages, the co-doped NVO exhibits a capacity of 440 mAh g^-1 at 0.1 A g^-1 and maintains 265 mAh g^-1 over 2000 cycles at 2 A g^-1, far outperforming pristine and singly ion-doped NVO. This work provides new insights into the synergistic modification of vanadium-based cathode materials and supports the development of high-performance, long-life AZIBs.