Oxygen-deficient ZnVOH@CC as high-capacity and stable cathode for aqueous zinc-ion batteries

Vanadium oxides have become promising cathodes for aqueous zinc ion batteries (AZIBs) due to their low cost and high theoretical capacity. However, vanadium oxides suffer from the problems of low electrical conductivity and structural instability. To address the challenges, Zn_xV₂O₅·nH₂O with oxygen-rich vacancies was synthesized in situ on carbon cloth (ZnVOH@CC) via a one-step hydrothermal method. The introduction of Zn²⁺ and oxygen vacancies is beneficial to enhance the structural stability and improve the Zn²⁺ diffusion rate. The pre-intercalated Zn²⁺/H₂O acts as “pillars” to increase the interlayer spacing of vanadium pentoxide (V₂O₅), weakening the electrostatic interactions between Zn²⁺ and the ZnVOH host lattice. Benefiting from the above advantages, the ZnVOH@CC composite was used as the cathode for AZIBs, which showed a high capacity of 464.9 mAh/g at 0.1 A/g, a large capacity of 208.1 mAh/g at 1.0 A/g after 1,000 cycles, and a good cycling stability at a high current density of 5.0 A/g after 10,000 cycles. In addition, the assembled ZnVOH@CC//Cu₂Se full cell by matching ZnVOH@CC with Cu₂Se also exhibits a high reversible capacity of 68 mAh/g at 1.0 A/g and 92.5 % capacity retention after 260 cycles.