Cotton fiber-derived ultrafine activated carbon fiber for supercapacitor electrode: The effect of fibrillation.

Activated carbon fiber (ACF) is a fibrous activated carbon (AC) characterized by high specific surface area (SSA), abundant micropore structure, and excellent machinability, making it an ideal electrode material. This work provided a theoretical basis for the sustainable and large-scale production of high-performance ACF from natural cellulose through fibrillation treatment, papermaking techniques, and CO activation. The effect of fiber fibrillation degree on ACF's structure and electrochemical performance was investigated in detail. The results indicated that with the increase of cotton fiber fibrillation, the SSA and beating degree increased gradually, and the air permeability of cotton paper decreased rapidly. The pore volume, SSA, and specific capacitance of ACF all displayed a trend of increasing first and then reducing slowly. Among them, 40°SR ACF had the largest SSA (1267 m/g) and specific capacitance (0.5 A/g, 129.9 F/g), which were 1.47 and 1.45 times higher than those of ACF without fibrillation treatment. In addition, compared with coconut shell-based AC prepared under the same activation conditions, ACF had a more developed microporous structure, higher SSA, and specific capacitance, making it a preferred raw material for fabricating supercapacitor electrodes. This paper provides a theoretical basis for the application of natural fibers in supercapacitors.