Self-Supporting Lignin-Based Carbon Material Flexible Supercapacitor Prepared by the Microwave Method

In this study, lignin carbon materials were prepared by the simple and rapid microwave method and carbon felt containing nitrogen atoms was used as the current collector. Different concentrations of KOH not only activate lignin but also cause its dissolution in the solution and adsorption on carbon felt without a binder. The structure, surface elements, and chemical states of the materials were tested by SEM and XPS. The capacitance of modified lignin reached 394.8 F g–1 (1 A g–1). When circulating after 100,000 times under 10 A g–1, the retention rate of the capacitor was 83.69% of the initial value. In addition, the outstanding energy density and power density of the assembled flexible supercapacitor can reach 15.062 W h kg–1 and 750 W kg–1, respectively. When circulating for 15,000 times under 3 A g–1, the retention rate of the capacitor is 74.45% of the initial value.