Honeycomb carbon obtained from coal liquefaction residual asphaltene for high-performance supercapacitors in ionic and organic liquid-based electrolytes

Rational design of electrode material with high specific surface area (SSA) and hierarchical porous structure is significant for supercapacitor. Herein, 3D honeycomb carbon was prepared from coal liquefaction residual asphaltene by a template-assisted method. The activated 3D honeycomb carbon (C-SiO2) exhibits high SSA and hierarchical porous structure, including microporous, mesoporous, and microporous. These merits enhance the contact area between the electrode material and the electrolyte, and offer more active sites. The C-SiO2 shows an excellent specific capacitance (247 F g−1/1 A g−1) and superior rate capability (134 F g−1/100 A g−1). Meanwhile, the assembled symmetric supercapacitors also exhibit high specific capacitance (188 F g−1/1 A g−1, 133 F g−1/100 A g−1) and excellent cycle stability with a specific capacity of 153 F g−1 after 20,000 cycles at 5 A g−1. Moreover, this device presents a remarkable energy density of 21.1 Wh kg−1 and 23.7 Wh kg−1 at the power density of 10,000 W kg−1, when the aqueous electrolyte is replaced by ionic liquid or organic electrolyte. At the same time, a LED bulb can be powered by the symmetrical supercapacitors, further verifying its high energy densities for future practical applications.