Heteroatom-doped layered hierarchical porous carbon electrodes with high mass loadings for high-performance supercapacitors

Electrodes with high mass loadings are the impetus for improving the energy density of supercapacitors. However, such electrodes have poor charge and ion kinetics in most cases, and rationally designing them which have high electron and ion transport rates is a major challenge. In this work, a new heteroatom-doped hierarchical porous carbon material, called LPC-2, was developed with longan shell and KOH as its precursor and an activator, respectively, through heteroatom self-doping and architecture design integration, in which heteroatoms of nitrogen, oxygen and sulfur were found. Its frequency response was excellent at a scan rate up to 5 and 0.3 V s-1 when the mass loading was set to be 1.0 and 12 mg cm-2, respectively. At a high mass loading of 12 mg cm-2, LPC-2 had gravimetric and areal specific capacitances of 171 F g-1 and 2052 mF cm-2, respectively. The assembled LPC-2//LPC-2 symmetric supercapacitor can complete charge and discharge in 0.4 s, showing a high energy density of 10.8 Wh kg-1 at a high power density of 97.4 kW kg- 1 in 6 M KOH. In addition, 99.5 % of the original capacitance was retained after 20,000 cycles at 10 A g-1, which embodies the application value of biomass-derived carbon in supercapacitors.