Orbital-Modulated Cu-Doped VO2 Nanoflowers via Glucose-Assisted Synthesis: Structural Optimization and Electronic Coupling Engineering for High-Capacity Aqueous Aluminum Ion Batteries

Vanadium oxide cathode materials in aqueous aluminum-ion batteries (AAIBs) have an exceptional potential for development because of their high valence and fast electron transfer capability. However, the strong electron–electron Coulomb repulsion in vanadium and its associated electrostatic interactions severely hinder the feasibility of vanadium oxides in AAIBs. The glucose-assisted hydrothermal reduction of monoclinic VO 2 combined with Cu ion doping effectively promotes the self-assembly of VO 2 into nanoflower architectures, enabling precise control over morphology and crystalline structure. When integrated with a 5 m Al(OTF) 3 electrolyte and an Ionic liquid （IL ）-treated Al sheet anode, this full battery demonstrates outstanding electrochemical performance, achieving an initial discharge capacity of 642 mAh·g −1 at 0.4 A·g −1 . Moreover, introducing Cu 3d orbitals effectively enhances the hybridization and electronic coupling effects between the V 3d and O 2p orbitals. Ex situ characterization and diffusion kinetic provide insights into the embedding/de-embedding mechanism of Al 3+ . This work significantly improves the application potential of VO 2 in AAIBs through structural optimization and mechanism studies and provides systematic scientific guidance for the development of vanadium oxide cathode materials.