Nitrogen-and-sulfur-enriched interconnected hierarchical porous carbon derived from green radish for high-mass-loading supercapacitors

Abstract

It is still enormously challenging to design carbon-based electrode materials with good performance under a high mass loading to satisfy the demand for lightweight supercapacitors in applications. Herein, interconnected hierarchical porous carbon materials with an appropriate content of heteroatoms (O, S, and N) are synthesized using a green radish precursor. The prepared porous carbon is approximately spherical with a size range of 35–95 nm and a microporous-mesoporous structure. The corresponding specific surface area and total pore volume are 2415 m2/g and 1.386 cm3/g, respectively. The electrochemical behavior, capacitance sources, and reaction kinetics mechanisms of the prepared material were carefully studied. As a result of its structural properties, the porous carbon in a three-electrode system with a 6 M KOH electrolyte exhibited a high areal capacitance of 3.55 F/cm2 at 0.5 A/g and 2.97 F/ cm2 at 20 A/g under a high mass loading of 10 mg/cm2. In a coin cell, the capacitance and the energy density of the porous carbon reached 258 F/g (at 1 A/g) and 9.2 Wh/kg (at a power density of 247.5 W/kg), respectively. The hierarchical pore distribution and heteroatom-enriched structure of the porous carbon result in a large ion-accessible surface, fast charge/mass diffusion channels, and excellent wettability. Thus, the porous carbon exhibits high specific capacitance, good rate performance, and superior energy density at a high mass loading.