Asymmetric Orbital Hybridization at MXene-VO2-x Interface Stabilizes Oxygen Vacancies for Enhanced Reversibility in Aqueous Zinc-ion Battery

Abstract

Modulating the storage kinetics of Zn2+ through oxygen vacancy (Ov) manipulation represents a promising approach for developing cathode materials in aqueous rechargeable zinc-ion batteries (ZIBs). However, recent studies have shown that these Ov can undergo migration and refilling during electrochemical cycling, leading to severe structural degradation and rapid capacity fading. Therefore, developing technologies to stabilize Ov 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 rational lies in the chemical growth of VO2 nanowall arrays on MXene nanosheets to form Ti-O-V asymmetric orbital hybridization (AOH) at the interface, which remarkably enhances the stability of Ov 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 analysis indicate that the Ti-O-V AOH facilitates a charge transfer pathway at the interface, allowing electrons to migrate from VO2 to MXene surface, thereby stabilizing the Ov 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 Ov and interfacial orbital engineering.