High performance hybrid supercapacitors by using para-Benzoquinone ionic liquid redox electrolyte

A solution of 0.4M para-Benzoquinone (p-BQ) in the ionic liquid N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide (PYR 14 TFSI) was used as a redox electrolyte in hybrid supercapacitors. Two carbons with very different textural properties, Pica carbon and Vulcan carbon, were used as electrode material. Electrochemical performance of these energy storage systems was investigated by cyclic voltammetry (CV) and galvanostatic charge-discharge (CD). Unlike SCs with pure IL electrolyte, new battery-like features appeared in the CV curves and CD profiles. This electrochemical performance, associated with the faradaic contribution of the redox electrolyte, results in a significant improvement of the electrochemical performance of the hybrid system. For Vulcan carbon with low specific surface area (S BET = 240 m 2 g -1 ), specific capacitance (C s ) and specific real energy (E real ) values as high as 70 Fg -1 and 10.3 WhKg −1 were obtained at 5 mAcm −2 with hybrid SC operating at 3 V. This represents an increment of 300% in C s and E real with respect to the SC based on pure PYR 14 TFSI. For high surface area carbon such as Pica (S BET = 2410 m 2 g -1 ), the addition of the redox quinone molecule resulted in a moderate enhancement reaching values of 156 Fg -1 and 30 WhKg −1 under the same experimental conditions (36% and 10% increment, respectively).