Rod-like anhydrous VO assembled by tiny nanosheets as a high-performance cathode material for aqueous zinc-ion batteries.

Aqueous zinc-ion batteries offer a low-cost and high-safety alternative for next-generation electrochemical energy storage, whereas suitable cathode materials remain to be explored. Herein, rod-like anhydrous VO derived from a vanadium-based metal-organic framework is investigated. Interestingly, this material is assembled by tiny nanosheets with a large surface area of 218 m g and high pore volume of 0.96 cm g. Benefiting from morphological and structural merits, this material exhibits excellent performances, such as high reversible capacity (449.8 mA h g at 0.1 A g), good rate capability (314.3 mA h g at 2 A g), and great long-term cyclability (86.8% capacity retention after 2000 cycles at 2 A g), which are significantly superior to the control sample. Such great performances are found to derive from high Zn ion diffusion coefficient, large contribution of intercalation pseudocapacitance, and fast electrochemical kinetics. The measurements unveil that the intercalation of Zn ion is accompanied by the reversible V reduction and HO incorporation. This work discloses a direction for designing and fabricating high-performance cathode materials for zinc-ion batteries and other advanced energy storage systems.