Self-assembly of biomass derivatives into multiple heteroatom-doped 3D-interconnected porous carbon for advanced supercapacitors

The rational design of the pore structure of carbon materials is of great significance for solving the low specific capacitance and poor rate performance of supercapacitors. Herein, we propose a multiple heteroatom-doped three-dimensional (3D) interconnected carbon material obtained from the self-assembly of biomass derivatives including chitosan and sodium lignosulfonate with the assistance of boric acid. The amino group of chitosan protonated by boric acid can form electrostatic adsorption and hydrogen bonding with the sulfonic acid group of sodium lignosulfonate to form a carbon network structure. Boric acid also acts as a template, and in combination with KOH activation, further promotes the formation of the hierarchical porous structure, resulting in the as-prepared carbon possessing a high specific surface area of 2700.65 m2 g−1. As the electrode material in 6 M KOH electrolyte, it manifests a decent specific capacitance of 332 F g−1 at 1 A g−1 in the three-electrode system, while the symmetric electrode achieves a high energy density of 17.7 W h kg−1 at 166.4 W kg−1. Moreover, the contribution rate of the fast and slow kinetic process, as well as the fast diffusion of electrolyte ions are deeply revealed through the ultrafast charge/discharge and the ion diffusion kinetics analysis, respectively. The symmetric electrode in PVA/KOH gel electrolyte maintains 97% capacitance retention and 100% Coulombic efficiency over 10000 cycles, indicating excellent cycling stability.