Mesoporous graphene nanoflakes for high performance supercapacitors with ionic liquid electrolyte

Mesoporous graphene nanoflakes (GNFs) of different thickness with a specific surface area of 660-1720 m(2)/g were produced by the template synthesis via hexane pyrolysis over MgO. The structure and morphology of GNFs were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy and low-temperature N-2 physisorption. The electrochemical performance of GNF-based supercapacitors was tested in ionic liquid electrolyte (1.2 M N+Et4TFSI- in CH3CN) by cyclic voltammetry and galvanostatic charge - discharge measurements. The assembled symmetric supercapacitors with a wide voltage window of 3 V delivered specific capacitance of 112 F/g at 5 mV/s and 105 F/g at 0.5 A/g with a high rate capability of similar to 81% at a current density of 15 A/g. The energy density reached 32.8 Wh/kg corresponding to the power density of 0.7 kW/kg. Furthermore, even at a high power density of 19.9 kW/kg, GNFs still showed an energy density of 24.3 Wh/kg, which made them promising for application in supercapacitors.