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

A remarkable capacitance of 180F·g−1 (at 5mV·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. 2000m2·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 (1–2nm) enabled by fine-tuning chemical activation. From the industrial perspective, a high volumetric capacitance of ca. 80F·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. [Display omitted] •Biomass derived microporous carbons exhibit high capacitance in ionic liquids.•Ionic liquid exhibits low in-pore resistance in mesopore-free activated carbon.•Micropore size above 0.7nm is required for high capacitance and low resistance.