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.