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 C _m of 622.8 F g^-1 at 1 A g^-1 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^-1 with an energy density of 23.5 W h kg^-1 at 1 A g^-1. The performance of the ASC can be improved by introducing redox additive K₄Fe(CN)₆ into alkaline electrolyte (KOH). The results indicate that the ASC with K₄Fe(CN)₆ exhibits an ultrahigh specific capacitance of 192.1 F g^-1 and an energy density of 67.0 W h kg^-1, which is nearly a threefold increase over the ASC with pristine electrolyte.