Oxygen-Related Defect Engineering of Amorphous Vanadium Pentoxide Cathode for Achieving High-Performance Thin-Film Aqueous Zinc-Ion Batteries

Thin-film aqueous zinc-ion batteries are expected to serve as next-generation energy storage devices that are both low-cost and safe. However, to realize practical energy storage devices based on zinc-ion batteries, it is necessary to develop reliable, high-capacity cathode materials. In this study, we prepared a V2O5- based thin-film electrode and investigated the effect of varying the Ar pressure during radio frequency magnetron sputtering of V2O5, a representative cathode material in thin-film zinc-ion batteries, to control the number of oxygen vacancies in the oxide lattice. The optimized V2O5 thin-film electrode exhibited enhanced electro-chemical activities, low degree of polarization, improved ion diffusion, and increased electrical conductivities. Specifically, an oxygen-deficient V2O5-x thin-film prepared by sputtering under high pressure exhibited a high rate capability (57.2 mAh g-1 at 20 C) and superior electrochemical performance (105.2 mAh g-1 for up to 1000 cycles at a current density of 5 C). The mechanism for the performance enhancement was revealed by density functional theory calculations, which showed that the oxygen-deficient V2O5-x had a lower Zn2+-ion diffusion energy barrier than that of pristine V2O5. This defect engineering strategy for tuning the oxidation state should aid in designing high-performance cathodes for advanced thin-film aqueous battery chemistry.

Automated summary

In this study, an optimized V2O5 thin-film electrode was prepared by controlling the oxygen pressure during the sputtering process. The electrode exhibited enhanced electrochemical activities, low polarization, improved ion diffusion, and increased electrical conductivities. Density functional theory calculations revealed that the oxygen-deficient V2O5-x had a lower Zn2+-ion diffusion energy barrier than pristine V2O5, contributing to its superior electrochemical performance.