Manipulating the d-band center of bimetallic molybdenum vanadate for high performance aqueous zinc-ion battery.

Vanadium-based oxides have good application prospects in aqueous zinc ion batteries (AZIBs) due to their structures suitable for zinc ion extraction and intercalation. However, their poor conductivity limits their further development. The d-band center plays a key role in promoting adsorption of ions, which promotes the development of electrode materials. Here, a series of MoV₂O₈ compounds with oxygen defect (O_d-MoV₂O₈) were synthesized by a simple hydrothermal process and a subsequent vacuum calcination process through strict control of the deoxidation time. Theoretical calculations reveal that the abundant oxygen vacancies in MoV₂O₈ effectively regulate the d-band center of the zinc ion adsorption site. This precise control of the d-band center enhances the zinc ion adsorption energy of MoV₂O₈, lowers the migration energy barrier for zinc ions, and ultimately significantly boosts zinc storage performance. The specific capacity is as high as 282.4 mAh/g after 100 cycles at 0.1 A/g, and it also shows excellent performance and outstanding cycle life. In addition, the maximum energy density of O_d-MVO-0.5 (MoV₂O₈ sample deoxidized for 0.5 h) is 343.3 Wh kg^-1. Importantly, the mechanism of Zn²⁺ storage in O_d-MoV₂O₈ was revealed by the combination of in situ and ex situ characterization techniques.