Nickel Vanadate Cathode Induced In Situ Phase Transition for Improved Zinc Storage by Low Migration Barrier and Zn²⁺/H⁺ Co-Insertion Mechanism

Designing cathode materials that exhibit excellent rate performance and extended cycle life is crucial for the commercial viability of aqueous zinc (Zn)-ion batteries (ZIBs). This report presents a hydrothermal synthesis of stable Ni_0.22V₂O₅·1.22H₂O (NVOH) cathode material, demonstrating high-rate performance and extended cycle life. A successful in situ phase transformation yields Zn₃(OH)₂V₂O₇·nH₂O (ZVO), which undergoes an irreversible phase transition and exhibits exceptional energy storage properties. The procedure maintains the lattice structure of ZVO and ensures high structural stability throughout the phase transformation. The NVOH cathode material exhibits the discharge capacities of 399 mA h g⁻¹ at a rate of 1 A g⁻¹ after 400 cycles and 303 mA h g⁻¹ at 10 A g⁻¹ after 2000 cycles. Density functional theory calculations indicate that the material is protected by electrostatic forces and exhibits structural stability, with a Zn-ion migration barrier of 0.32 eV across the host lattice and the electrode–electrolyte interface. Due to these properties, NVOH also exhibits high energy/power densities of 395 Wh kg⁻¹/406 W kg⁻¹ at 0.5 A g⁻¹ and 288 Wh kg⁻¹/8830 W kg⁻¹ at 10 A g⁻¹. Ex situ characterizations indicate structural modifications and irreversible phase changes of NVOH, highlighting the potential of H⁺ intercalation and in situ phase transitions for high-performance aqueous ZIBs.