Fabrication of high performance supercapacitors based on ethyl methyl imidazolium bis(trifluoromethylsulfonyl) imide (EMIMTFSI)-decorated reduced graphene oxide (rGO)

Abstract

In this paper, we outline the construction of symmetric supercapacitors comprised of reduced graphene oxide (rGO) and hydrophobic ionic liquid (IL) (1-ethyl-3-methylimidazolium bis(trifluoromethyl sulfonyl)imide (EMIMTFSI) acting as physical spacer and electrolyte between rGO plates. To increase the porosity and interlayer spacing between the graphene plates, different solvents are analyzed by Hansen solubility parameters’ approach (HSP). Accordingly, the solubility performances of two solvents, namely Tween 80 and N, N-dimethylformamide (DMF), coupled with rGO and IL, are deemed to offer the most beneficial results, and they are the solvents used in this study to develop rGO/Tween 80/IL and rGO/DMF/IL electrodes. The comparison of the electrodes’ performances shows that the consumption of 80 wt percent IL would deliver the optimum electrochemical performance and capacitance results. At room temperature, the prepared rGO/Tween 80/IL80% and rGO/DMF/IL80% deliver capacitances of 375 and 213 F/g, respectively. The maximum energy density of rGO/Tween 80/IL electrode is 187.5 Wh/kg at a power density of 1125 W/kg, while for the rGO/DMF/IL electrode the maximum energy density reaches 106.5 Wh/kg at a power density as high as 639 W/Kg. The supercapacitors prepared based on rGO/Tween 80/IL80% and rGO/DMF/IL80% electrodes show capacitance retention of 90% and 84% after 10,000 charge-discharge cycles, respectively. This design approach eliminates the need for the prevalant stand-alone type of electrolyte in supercapacitors, and instead, the electrolyte is incorporated as a component of electrode’s structure.