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.