Revealing Diffusion-Dominated Charge Storage in Ultrathin V2O5 Electrodes for Aqueous Zn-Ion Batteries

In this work, we report the development of an additive-free and electrolyte/electrode interface-sensitive vanadium pentoxide (V₂O₅) cathode for aqueous zinc-ion batteries (ZIBs), fabricated via alternating current electrophoretic deposition (AC-EPD) onto stainless steel foil. X-ray diffraction analysis confirms the formation of highly crystalline, phase-pure orthorhombic V₂O₅ with preferential orientation. Electrochemical testing shows stable and reversible Zn²⁺ intercalation, with the electrode delivering ∼120 mAh/g at 0.5 C and excellent rate performance within a narrower 1.0–1.5 V window, instead of the typical 0.1–1.5 V range. Scan rate-dependent cyclic voltammetry and b-value analysis reveal that the charge storage in the ultrathin V₂O₅ film is predominantly governed by diffusion-controlled processes. This behavior aligns with the intrinsic layered crystal structure of V₂O₅, which facilitates bulk Zn²⁺ intercalation rather than surface-limited capacitive reactions. This study shows that ultrathin V₂O₅ electrodes made by AC-EPD deliver high capacity and stable Zn-ion storage. Despite their thinness, charge storage is mainly diffusion-controlled due to the layered structure. To our knowledge, this is the first report demonstrating that diffusion-controlled Zn²⁺ intercalation remains the dominant mechanism in ultrathin, binder-free V₂O₅ electrodes, thereby establishing a definitive baseline for structure–function analyses in layered oxides. This provides new insight into bulk intercalation behavior in interface-sensitive systems.