Winter-jujube-derived carbon with self-doped heteroatoms and a hierarchically porous structure for high-performance supercapacitors

Abstract

Novel biomass-derived carbon materials have attracted a lot of attention for application in supercapacitors due to their low cost and environmental friendly properties. Herein, we report a novel winter-jujube-derived carbon material (JC) prepared via a pre-carbonization and KOH activation strategy. The physical and chemical properties of JC were characterized by field-emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, and nitrogen adsorption–desorption isotherms. The electrochemical characteristics are measured using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS). The as-obtained carbon skeleton possesses a hierarchical porous structure, abundant heteroatom groups, and good electrical conductivity. It is notable that the use of KOH significantly influenced the properties of JC. When the KOH to carbon weight ratio is 3.5 : 1, the as-prepared sample (JC-3.5) possesses an ultra-huge specific surface area (SSA) of 2286.2 m² g⁻¹. In addition, the electrochemistry results show that JC-3.5 exhibits a high specific capacitance up to 341 F g⁻¹ at 0.5 A g⁻¹ and a considerable rate capability of 76% retention when the current density increases to 20 A g⁻¹. After 5000 cycles at 5 A g⁻¹, the capacitance still has 96.5% retention. In addition, the JC-3.5-based symmetric supercapacitor device possesses an energy density of 30.9 kW h⁻¹ at 0.1 A g⁻¹ and power density of 8.9 kW at 5 A g⁻¹. Therefore, it is quite feasible to make the winter-jujube-derived carbon material into a high performance supercapacitor electrode material.