In situ synthesis of VO2 containing high-valent vanadium via surface oxidation of V2C MXene for robust near-interface reactions in aqueous zinc-ion batteries

Abstract

Vanadium-based materials are promising candidates for cathodes in aqueous zinc-ion batteries (AZIBs), but balancing high capacity with long-term stability remains a challenge. High-valent vanadium enhances conductivity but is unstable, while low-valent vanadium improves stability but lacks sufficient conductivity and capacity. In this study, we improved the overall capacity and stability of the electrodes by in-situ growing VO₂ containing high-valent vanadium on V₂C to suppress structural degradation, and by dispersing the VO₂/V₂C heterostructure nanosheets onto carbon nanofibers (CNF) to reduce V₂C restacking and expose more active sites. Density Functional Theory (DFT) calculations suggest that the interface of the VO₂/V₂C heterostructure optimizes electron cloud distribution, highlighting the role of V₂C in enhancing the reaction kinetics of VO₂. Furthermore, the coordination effect between V₂C and VO₂ enables stable near-interface reactions on V₂C, further improving the electrochemical performance of the electrode. The optimized VO₂/V₂C@CNF-2 electrode achieves a discharge-specific capacity of 549 mAh g⁻¹ at 0.1 A g⁻¹ after 100 cycles and retains 300 mAh g⁻¹ after 5000 cycles at 10 A g⁻¹. These findings provide new insights into enhancing AZIB cathode electrochemical performance and expand the application potential of V₂C in aqueous batteries.