High Energy Density Hybrid Supercapacitor: In-Situ Functionalization of Vanadium-Based Colloidal Cathode

A novel and creative in-situ electrochemical activation method to transform vanadium ions to highly electroactive colloidal cathode in KOH solution under electric field has been designed. After undergoing electrochemical reaction, the in-situ-functionalized vanadium-based colloidal cathode can adapt their geometrical structure to the high pseudocapacitive activity. The vanadium-based colloids//activated carbon asymmetric supercapcitor displays a high energy density of 50.4 Wh/kg at a power density of 250 W/kg, which is higher than most reported vanadium-based supercapacitors. The main advantage of this system is that the materials synthesis and the device operation are performed in the same reactive environment. The obtained vanadium-based colloids can display high V³⁺ cation utilization ratios of about 100% for one-electron redox reactions. The present results highlight a new area of research on in-situ formation of reactive electrode materials under realistic environments, which can bring new chemistry and new structures of materials that are only present under the current in-situ reactive conditions.