Large-surface-area activated carbon with high density by electrostatic densification for supercapacitor electrodes

Although activated carbon has been widely used for supercapacitors, the unsatisfactory volumetric capacitance and rate performance caused by the well-developed porous structure severely hinder its application in minimized and high-power devices. Herein, we develop an electrostatic densification method to prepare large surface area (ca. 3359 m² g⁻¹) and high density activated carbon materials by using the positively charged chitosan and negatively charged graphene quantum dots (GQDs) as the precursors. The strong molecular electrostatic attraction makes the GQDs embedded activated carbon an improved compaction density of 0.75 g cm⁻³ than the activated carbon without GQDs (3245 m² g⁻¹, 0.67 g cm⁻³) and commercial activated carbon (1600 m² g⁻¹, 0.45 g cm⁻³). The highly crystallized GQDs can also improve the electrochemical kinetics by constructing the entire conductive networks. Therefore, the sample shows high capacitances of 341 F g⁻¹/256 F cm⁻³ at 1 A g⁻¹ and remarkable rate performance with 70% capacitance retention at 100 A g⁻¹ in three-electrode system. Moreover, the outstanding capacitive performance can maintain at the commercial mass loading of 10 mg cm⁻², demonstrating great potential for practical application.