Lamellar Hierarchical Porous Carbon Prepared from Coal Tar Pitch through a Lamellar Hard Template Combined with the Precarbonization and Activation Method for Supercapacitors

The lamellar porous carbon favors the diffusion and penetration of electrolyte ions and presents a fantastic advantage as an energy storage electrode material. In this work, the lamellar Mg5(OH)4(CO3)2·4H2O template is synthesized via a simple precipitation method in the low-temperature hydrothermal condition. Lamellar hierarchical porous carbon (LHPC) is successfully synthesized through the Mg5(OH)4(CO3)2·4H2O hard template and the KOH activation method using coal tar pitch (CTP) as the carbon source. The effects of activation temperature and activator dosage on the morphology, microstructure, and supercapacitor performance are researched at length. LHPCs-1–700 displays a good lamellar structure and an abundant mesoporous structure, so as to exhibit superior capacitive performance compared with other carbon electrodes. The specific capacitance for LHPCs-1–700 reaches 298 F g–1 at 1 A g–1 and still maintains 234 F g–1 at 50 A g–1 with a high capacitance retention of 78.5% in the three-electrode system. The kinetic behavior of the LHPCs-1–700 electrode was also analyzed according to the CV data obtained at different scan rates, and it was found that the fast kinetic capacitance contribution was up to 87% at 200 mV s–1. The assembled LHPCs-1–700 symmetric supercapacitor delivered an energy density of 16.73 W h kg–1 with a power density of 859.4 W kg–1 in 1 M Na2SO4 solution. Besides, the specific capacitance retention rate could still reach 95.8% after 8000 cycles.