Vanadium-based cathodes for aqueous zinc-ion batteries: From fundamental mechanisms, methodological design to future directions

The static intrinsic properties of cathode materials and their dynamic evolution during cycling profoundly affect the performance of aqueous zinc-ion batteries (AZIBs). Vanadium-based materials have emerged as preeminent candidates due to their multivalent redox chemistry (V 2 + -V 5+ ), structural polymorphism, and superior theoretical capacities. This review systematically analyzes electrochemical mechanisms and structural engineering strategies for optimizing vanadium cathodes while delineating prospective research directions. The currently mainstream vanadium-based cathodes are categorized into three major classes, focusing on their microscopic spatial structure: one-dimensional tunnels, two-dimensional layers, and three-dimensional frameworks, to elucidate the correlation between lattice symmetry and ion-transport pathways deeply. We summarize and critically evaluate past zinc storage mechanisms, particularly the conversion reaction mechanisms that have long been considered correct, and identify critical bottlenecks, including active material dissolution, structural degradation, and sluggish zinc ion diffusion kinetics. To overcome these limitations, key methodological designs are summarized, such as interlayer engineering, morphological nano-structuring, defect and doping engineering, interfacial modification, and electrolyte optimization. Finally, future directions are proposed, emphasizing mechanistic insights via advanced operando characterization, computational modeling, novel phase innovation, and system-level optimization for high-areal-capacity electrodes. The review aims to provide a methodological framework for designing high-performance vanadium cathodes, accelerating the application of AZIBs in grid-scale energy storage systems.