Synergistic co-preintercalation of nickel and aluminum ions into vanadium oxide hydrate as positive electrode material in ultrahigh-rate and high-capacity aqueous zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) are a promising alternative to lithium-ion batteries (LIBs) due to the high capacity, low cost, safety, and durability of metallic zinc in aqueous environments. However, challenges such as the low Zn²⁺ mobility, which limits ion transport and influences battery performance, and the lack of well-established energy storage mechanisms of ZIBs necessitate the development of novel positive electrode materials. In this study, Al³⁺- and Ni²⁺-co-preintercalated hydrated vanadate (NiAlVOH) nanowires were successfully synthesized via a hydrothermal method and utilized as positive electrode material in AZIBs. The synthesized nanowires demonstrated a high capacity of 440 mA h g⁻¹ at 0.1 A g⁻¹ and an exceptional rate retention, maintaining 202 mA h g⁻¹ at a high current density of 20 A g⁻¹. Moreover, NiAlVOH exhibited excellent cycling stability, retaining 81% of its maximum capacity at 5 A g⁻¹ after 1000 cycles, and exhibited a high Zn²⁺ diffusion coefficient in the range of 8.2 × 10⁻⁸–5.7 × 10⁻¹⁰ cm² s⁻¹. Operando X-ray absorption spectroscopy and X-ray diffraction analyses, employed to investigate the energy storage mechanism in NiAlVOH, revealed a highly reversible energy storage mechanism. NiAlVOH exhibits outstanding electrochemical properties arising from the synergistic co-preintercalation of Ni²⁺ and Al³⁺ ions, which stabilize the layered vanadium oxide framework, enlarge interlayer spacing, and accelerate Zn²⁺ diffusion kinetics. These combined effects deliver high specific capacity, ultrafast rate performance, and long-term cycling stability, positioning NiAlVOH as a promising cathode material for AZIBs with considerable potential for grid-scale energy storage applications.