Interfacial Electrochemical Media‐Engineered Tunable Vanadium Zinc Hydrate Oxygen Defect for Enhancing the Redox Reaction of Zinc‐Ion Hybrid Supercapacitors

Abstract Zinc‐ion hybrid supercapacitors (ZIHCs) are promising electrochemical energy storage system candidates owing to their eco‐friendliness, low‐cost, reliable safety, and high‐power density. Of particular note, ZIHCs are desirable alternatives to lithium‐ion batteries (LIBs) because they can overcome the disadvantages of LIBs, such as the explosion hazard and the complex manufacturing process. Nevertheless, the low specific capacity of ZIHCs caused by their limited active sites and poor cycling stability because of their low wettability and irreversible Zn dendrite formation at the electrode has hindered their commercial application. Herein, for the first time, the fabrication and interfacial engineering of ZIHCs using vanadium (IV) oxide sulfate (VOSO 4 ) as an additive chemistry agent is described, and the effect of the additive on the electrochemical performance is demonstrated. After the activation process, the resultant supercapacitor exhibits a zinc vanadium hydrate (ZVO) layer on both the anode and cathode. The electrochemical role of the ZVO layer on the electrodes are as follows: i) improved active sites for Zn‐ion intercalation at the cathode, ii) enhanced wettability between electrolyte and electrodes, and iii) buffer layer for the suppression of undesirable and irreversible Zn dendrites at the anode.