Outstanding room-temperature capacitance of biomass-derived microporous carbons in ionic liquid electrolyte

A remarkable capacitance of 180 F.g(-1) (at 5 mV.s(-1)) in solvent-free room-temperature ionic liquid electrolyte, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, was achieved in symmetric supercapacitors using microporous carbons with a specific surface area of ca. 2000 m(2).g(-1) calculated from gas sorption by the 2D-NLDFT method. The efficient capacitive charge storage was ascribed to textural properties: unlike most activated carbons, high specific surface area was made accessible to the bulky ions of the ionic liquid electrolyte thanks to micropores (1-2 nm) enabled by fine-tuning chemical activation. From the industrial perspective, a high volumetric capacitance of ca. 80 F.cm(-3) was reached in neat ionic liquid due to the absence of mesopores. The use of microporous carbons from biomass waste represents an important advantage for large-scale production of high energy density supercapacitors.