3.3-V-Rated EDLC Performance with an Alternative Conducting Agent (nc-RuO2·nH2O/KB)

Nano-crystalline hydrous RuO2 particles that are hyper-dispersed within Ketjen Black (KB) matrix have been added as an alternative-conducting agent. In the present study, the authors succeeded in enhancing the EDLC’s withstanding voltage from 2.7 to 3.3 V by addition of small amount of MOx/KB (MOx = RuO2) composite. Addition of 4 wt% RuO2/KB only in the positive activated carbon electrode dramatically increased the voltage limitation up to 3.3 V. To date 3.3-V-rated EDLC (activated carbon based electrochemical capacitor) has never been attained. The test EDLC cell demonstrated a high energy density (18 Wh kg−1) with prolonged charge-discharge cycling up to 9000 times in the voltage range of 0–3.3 V. In this study, the critical factors enabling such a high voltage operation have been investigated in relation to the mechanism that efficiently prevents consecutive water-induced chained failure mode reactions.