K0.39V2O5·0.52H2O Nanostructures with Oxygen Vacancies as Cathodes for Aqueous Zinc-Ion Batteries

Abstract

Aqueous zinc-ion batteries (AZIBs) are considered a promising option for large-scale energy storage because of their low cost and high safety. However, the lack of suitable cathode materials has limited their development. Vanadium-based oxides have been widely studied due to their layered crystal structures and high theoretical specific capacities. Nevertheless, they are prone to vanadium dissolution and have a limited cycle life during cycling. Pre-embedding of K⁺ in V₂O₅ by the hydrothermal method increases the layer spacing and stabilizes the crystal structure. Oxygen vacancies are introduced to provide more sites for Zn storage. The results show that the K_0.39V₂O₅·0.52H₂O nanostructures exhibit stable cycling performance. The capacity is 552 mAh g^–1 at 0.1 A g^–1, and the capacity retention is 90% for 11,000 cycles at 10 A g^–1. When the electrolyte is changed from Zn(CF₃SO₃)₂ to ZnSO₄, the capacity retention rate is 98% after 200 cycles at 1 A g^–1 and nearly 100% after 2400 cycles at 10 A g^–1. This study highlights the potential of ion doping and oxygen defects in modifying cathode electrodes and provides a guide for exploring the working mechanisms of aqueous zinc-ion batteries.