Asymmetric orbital hybridization at the MXene–VO2−x interface stabilizes oxygen vacancies for enhanced reversibility in aqueous zinc-ion batteries†

Abstract

Modulating the storage kinetics of Zn²⁺ through oxygen vacancy (O_v) manipulation represents a promising approach for developing cathode materials in aqueous rechargeable zinc-ion batteries (ZIBs). However, recent studies have shown that these O_vs can undergo migration and refilling during electrochemical cycling, leading to severe structural degradation and rapid capacity fading. Therefore, developing technologies to stabilize O_vs is critical for maximizing their efficiency, although it presents a significant challenge. Herein, we demonstrate a covalent heterostructure design that pushes the cycling performance of a vanadium dioxide (VO₂) cathode to an unprecedented level. The rationale lies in the chemical growth of VO₂ nanowall arrays on MXene nanosheets that leads to Ti–O–V asymmetric orbital hybridization (AOH) at the interface, which remarkably enhances the stability of O_vs on VO₂. Due to this advanced cathode design, the prepared ZIBs exhibit highly reversible aqueous Zn²⁺ storage capacities and maintain a robust structure over 30 000 cycles at 20 A g⁻¹, without any significant capacity loss (1.4%). Detailed experimental and theoretical analyses indicate that Ti–O–V AOH facilitates a charge transfer pathway at the interface, allowing electrons to migrate from VO₂ to the MXene surface, thereby stabilizing the O_vs both thermodynamically and kinetically. Our work offers an inspiring design principle for developing sustainable cathode materials for high-performance aqueous ZIBs and beyond, leveraging the synergistic effects of O_vs and interfacial orbital engineering.