Electrolyte-mediated assembly of graphene-based supercapacitors using adsorbed ionic liquid/non-ionic surfactant complexes

Abstract

Supercapacitors are increasingly being used in energy management systems due to their ability to operate efficiently at high power densities. To boost supercapacitor performance, high surface area electronically conducting materials like graphene in combination with room temperature ionic liquids are a promising combination capable of increasing cell voltage and specific capacitance, respectively – requirements for higher energy density. To overcome challenges associated with graphene aggregation and restacking, we present an electrolyte-mediated, electrode fabrication strategy where a commonly used ionic liquid (IL) is complexed with a non-ionic surfactant to design a surface active spacer that adsorbs to the surface of reduced graphene oxide in dispersion and acts as the electrolyte in the final consolidated electrode composite. We find a general trend that the gravimetric capacitance scales linearly with surfactant plus IL content reaching values as high as 243.8 F g⁻¹ at 5 mV s⁻¹ after which the electrodes are not solid enough to process. While this is amongst the highest reported for IL-based supercapacitors, the maximum in volumetric capacitance (80 F cm⁻³) is achieved at intermediate spacer fractions due to challenges associated with achieving fully dense composites.