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 (V 2 O 5 ) 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 V 2 O 5 with preferential orientation. Electrochemical testing shows stable and reversible Zn 2+ 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 V 2 O 5 film is predominantly governed by diffusion-controlled processes. This behavior aligns with the intrinsic layered crystal structure of V 2 O 5, which facilitates bulk Zn 2+ intercalation rather than surface-limited capacitive reactions. This study shows that ultrathin V 2 O 5 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 Zn 2+ intercalation remains the dominant mechanism in ultrathin, binder-free V 2 O 5 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.