Dual-Role Salt-Assisted Construction of Hierarchically Porous Carbon for Supercapacitors with High Energy and Power Density

Hierarchically porous carbons (HPCs) have attracted much attention because of their potential application in carbon-based supercapacitors. Here, we list a facile and green method to obtain HPCs by annealing a coal tar pitch with sodium bicarbonate. The produced gases and sodium carbonate template can guide the formation of carbon products with a multiscale pore structure. Further activation by KOH endows HPC with a surface area of 2851.7 m2 g–1 and a total pore volume of 2.4 cm3 g–1. Accordingly, such an HPC electrode achieves a specific capacitance of 321.5 F g–1 (0.5 A g–1) and retains 230.0 F g–1 (100.0 A g–1). Moreover, the HPC-based symmetric supercapacitor exhibits superior cyclic stability (1.1% capacity decay after 30,000 cycles) in an aqueous electrolyte. In the TEABF4/acetonitrile electrolyte, the assembled device displays a high energy density of 53.0 Wh kg–1 and still retains 77.9% even when the power density is increased from 750.0 to 15,000.0 W kg–1. We believe that the salt-assisted synthesis strategy for HPC paves a green way to developing high-performance supercapacitors.