Oxygen vacancy defect engineering of porous single-crystal VO2 nanobelts for aqueous zinc ion battery cathodes

Aqueous zinc ion batteries (AZIBs) have received considerable attention due to their high safety, low cost, environmental friendliness, and high theoretical capacities. However, the energy/power density and cost efficiency of AZIBs are still limited by cathode materials, so the exploration of advanced cathode materials plays a key role in their further practical development. Herein, porous single-crystal VO2 nanobelts with adjustable oxygen vacancy defects (Od-VO2 NBs) are obtained by precise regulation of chemical synthesis. Collective results reveal that the defect engineering designed Od-VO2-2 NBs as the optimized cathode exhibit excellent electrochemical performance due to the suitable oxygen vacancy defects, showing a high discharging capacity of 202.8 mAh g–1 after 500 cycles at 0.5 A g–1, durable cycling stability over 1000 cycles at 1.0 A g–1, and impressive rate performance. The electrode design can effectively improve the electrical conductivity and structural stability of Od-VO2 cathodes to accelerate reaction kinetics, and provide more activated sites for reversible Zn2+ storage. Besides this, the porous single-crystal structure favors rapid ions/electrons transport and buffering the volume change. This work demonstrates a simple method to design vanadium-based cathodes for high-performance AZIBs, making it a promising candidate for next-generation energy storage devices.