Hollow spinel ZnV₂O₄ cathodes with enhanced Zn^2 + diffusion kinetics for aqueous zinc-ion batteries

The development of cathode materials with robust architectures and fast ion-transport pathways is critical for addressing the key challenges of aqueous zinc-ion batteries (AZIBs), including sluggish Zn²⁺ diffusion kinetics and structural degradation during cycling. Herein, a one-step solvothermal strategy is developed for the synthesis of monodisperse spinel ZnV₂O₄ hollow nanospheres (ZVO-HNs). By regulating precursor stoichiometry, solvent composition, and reaction time, uniform hollow structures with well-defined internal cavities are successfully obtained. The hollow structure evolves through an Ostwald-ripening-assisted aggregation process followed by diffusion driven void formation, which is consistent with a Kirkendall mechanism. The unique spinel hollow architecture enables the ZVO-HNs cathode to deliver a reversible capacity of 363.2 mAh g⁻¹ at 0.1 A g⁻¹ and retain 84.3% of its capacity after 1500 cycles at 5 A g⁻¹. Ex situ XPS and TEM analyses reveal an activation induced structural reconstruction and reversible Zn²⁺ storage behavior, while kinetic analysis indicates a pseudocapacitive dominated charge storage process. This work demonstrates an effective strategy for constructing hollow spinel cathodes and provides useful insight into the structure kinetics stability relationship of vanadium-based cathode materials for AZIBs.