Harnessing oxygen vacancy in V₂O₅ as high performing aqueous zinc-ion battery cathode

Rechargeable aqueous zinc-ion batteries (ZIBs) have attracted considerable attention for large-scale energy storage systems due to their high energy density, low cost, and inherent safety. However, ZIBs suffer from limited cyclic stability with the use of the current cathode materials (such as V₂O₅) due to the strong electrostatic ion–lattice interactions with the diffusing divalent Zn²⁺, usually leading to a limited cyclic duration (<400 h). Herein, oxygen vacancies are introduced into V₂O₅ lattice to promote Zn²⁺ diffusion kinetic, thus enhancing the storage capacity and Zn²⁺ (de)intercalation processes, so as to high reversibility. In this work, the oxygen-deficient V₂O₅ displays improvements in electrochemical performances over the pristine V₂O₅. The as-assembled Zn//oxygen-deficient V₂O₅ battery shows an impressive stability of 90% capacity retention over 1000 cycles as compared to Zn//pristine V₂O₅ with 59% capacity retention over 680 cycles at a current density of 2 A g⁻¹. It is also able to attain a high reversible specific capacity of approximately 406 mAh g⁻¹ at 0.1 A g⁻¹, which is 33% higher as compared to the capacity of pristine V₂O₅ (307 mAh g⁻¹). More importantly, the Zn//oxygen-deficient V₂O₅ battery reaches an ultra-long cyclic duration of 620 h at 0.2 A g⁻¹ without any significant capacity fading, which is, to the best of our knowledge, one of the best cyclic performance reported for V₂O₅ system. Thus, based on these encouraging results, harnessing oxygen vacancies in V₂O₅ may help to further enhance the electrochemical performance of the cathodes towards high performing ZIBs.