Biomass-derived microporous carbon with large micropore size for high-performance supercapacitors

Large micropore with a pore size of 1–2 nm can allow high charge storage capability while ensure fast ions transport, which serves to improve the energy density of supercapacitors without sacrificing high power density. Herein, we report a large micropore dominant microporous carbon derived from a biomass waste, flaxseed residue from the edible oil industry, for high-performance supercapacitors. The reported material exhibits a large specific surface area of up to 3230 m2 g−1, and more than 70.1% of micropore volume is contributed by large micropores. The specific capacitance of the obtained material reaches up to 369 and 398 F g−1 in KOH and H2SO4 electrolyte, respectively. Meanwhile, the assembled supercapacitor device based on the obtained material exhibits excellent rate and cycle performance. Over 92.7% of the initial capacitance is retained even under a large current density of 20 A g−1 and the capacitance retention is more than 98.1% after 10000 times cycle in KOH electrolyte. The energy density of the assembled supercapacitor device reaches 61.2 Wh kg−1 at a power density of 468.8 W kg−1, and a high energy density of 43.5 Wh kg−1 is retained at a large power density of 13.3 kW kg−1 in ionic liquid EMIMBF4 electrolyte.