Simply incorporating an efficient redox additive into KOH electrolyte for largely improving electrochemical performances

In this work, a novel redox additive of calcon carboxylic acid sodium salt (abbr. CS) has been implemented for the first time in KOH electrolyte for largely improving the electrochemical performance of a supercapacitor . By directly carbonizing potassium citrate monohydrate at 800   °C, giving rise to the Carbon-800 sample, and the resulting specific capacitance can reach up to 128.4   F   g −   1 at 3   A   g −   1 when measured in a three-electrode system with the conventional 6   mol   L −   1 KOH electrolyte. To further elevate these capacitances, certain amount of CS as a redox additive is introduced into KOH electrolyte. Remarkably, the Carbon-800-15 sample by adding CS 15   mmol   L −   1 into 6   mol   L −   1 KOH electrolyte displays a highly improved specific capacitance of 237.0   F   g −   1 at 3   A   g −   1 in a three-electrode system, which is almost the 2.1 times than that of the pristine one. In addition, the Carbon-800-15 sample also possesses an elevated energy density of 11.4   Wh   kg −   1 at the power density of 1.5   kW   kg −   1 when measured in a two-electrode system, much larger than the 7.3   Wh   kg −   1 of the Carbon-800 sample. The improved performance incurred by CS additive is attributed to the fast redox reactions at the electrolyte/electrode interface. Apparently, the present efficient and low-cost redox additive of CS is expected to be implemented for largely improving the performances of a supercapacitor.