Revealing the impacts of oxygen defects on Zn2+ storage performance in V2O5

Vanadium pentoxide (V2O5) featured with open-framework structure and various oxidation states is regarded as the most promising cathode of aqueous zinc-ion batteries (ZIBs), whereas sluggish Zn2+ diffusion kinetics and poor structural stability plague its further application. Herein, the oxygen defects have been introduced into V2O5 (V2O5-Od), the experimental studies and first-principles calculations reveal the oxygen defects can enlarge the interlayer spacing (7.58 Å) and significantly lower the Zn2+ diffusion energy barrier (0.72 eV), leading to favorable Zn2+ migration path and fast reactive kinetics. Moreover, a narrower bandgap (0.45 eV) and lower charge transfer resistance are obtained in V2O5-Od, thus accelerating the electron transportation and improving the Zn2+ storage performance (427.3 mAh/g at 0.1 A/g). In addition, the internal structure of V2O5 is well-maintained owing to the greatly reduced formation energy of V2O5-Od (55.04 eV), contributing to outstanding cycling stability (92.1% after 5,000 cycles at 20 A/g), outperforming numerous reported cathodes. Moreover, the pouch cell with V2O5-Od delivers admirable electrochemical performance and modular integration capabilities, suggestive of its excellent practical viability. Therefore, this research highlights the great potential of oxygen defects in designing advanced electrodes and offers a guideline for exploring the working mechanism of defective electrode materials.