Addition of Redox Additive to Ionic Liquid Electrolyte for High-Performance Electrochemical Capacitors of N-Doped Graphene Aerogel

Abstract

To enhance the specific energy of electrochemical capacitors, several methods have been introduced including complex electrode modification as well as asymmetric cell development. Herein, an alternative approach to enhance both specific energy and power of N-doped reduced graphene oxide aerogel electrochemical capacitor via the introduction of hybrid redox electrolyte is proposed. The electrochemical properties of the hybrid electrolyte composing of 1-butyl-1-methylpyrrolidinium dicyanamide ionic liquid with 100 mM ferrocene methanol redox additive were studied via cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The combination between a unique nanostructure of N-doped reduced graphene oxide aerogel and novel hybrid electrolyte results in an excellent specific capacitance and specific energy of 112.1 F g−1 and 34.2 Wh kg−1, respectively, as compared to 76.7 F g−1 and 23.5 Wh kg−1 of the neat 1-butyl-1-methylpyrrolidinium dicyanamide electrolyte. The remarkable improvements can be explained by the emerging of the Faradaic-redox activity of the ferrocene methanol at the electrode-electrolyte interface. This simple approach could demonstrate another feasible route to improve the performance of ionic liquid-based electrochemical capacitors.