Improved performance of a CoTe//AC asymmetric supercapacitor using a redox additive aqueous electrolyte.

Cobalt telluride (CoTe) nanosheets as supercapacitor electrode materials are grown on carbon fiber paper (CFP) by a facile hydrothermal process. The CoTe electrode exhibits significant pseudo-capacitive properties with a highest of 622.8 F g at 1 A g and remarkable cycle stability. A new asymmetric supercapacitor (ASC) is assembled based on CoTe (positive electrode) and activated carbon (negative electrode), which can expand the operating voltage to as high as 1.6 V, and has a specific capacitance of 67.3 F g with an energy density of 23.5 W h kg at 1 A g. The performance of the ASC can be improved by introducing redox additive KFe(CN) into alkaline electrolyte (KOH). The results indicate that the ASC with KFe(CN) exhibits an ultrahigh specific capacitance of 192.1 F g and an energy density of 67.0 W h kg, which is nearly a threefold increase over the ASC with pristine electrolyte.