Adjusting the Valence State of Vanadium in VO2(B) by Extracting Oxygen Anions for High-Performance Aqueous Zinc-Ion Batteries

VO2 generally has a higher theoretical capacity and layered structure suitable for the intercalation/extraction of zinc ions. However, Zn2+ ions with high charge density interact with the crystal lattice and limit further improvement in electrochemical performance. Defect engineering is a potential modification method with very promising application prospects, but the established procedures for preparing defects are complicated. In this study, VO2-x(B) with oxygen deficiency is prepared by a simple solution reaction with NaBH4. The presence of oxygen deficiencies is confirmed by positron annihilation lifetime spectroscopy, UV/Vis absorbance spectroscopy and others. Owing to the presence of oxygen defects, the aqueous Zn/VO2-x(B) battery exhibits improved specific capacity, excellent reversibility, and structural stability. Ex situ characterization techniques are employed to demonstrate the reversible insertion-extraction mechanism of Zn2+ ions from and into the host material. In addition, the Zn/VO2-x(B) batteries still exhibit considerable electrochemical performance, even with high-loading electrodes (about 4 mg cm(-2)).

Automated summary

In this study, oxygen-deficient VO2-x(B) is prepared by a simple solution reaction and shows improved electrochemical performance and structural stability, making it suitable for aqueous Zn/VO2-x(B) batteries. The reversible insertion-extraction mechanism of Zn2+ ions is demonstrated using ex situ characterization techniques, even with high-loading electrodes.