High-performance fibre supercapacitors based on ball-milled activated carbon nanoparticles mixed with pen ink

A flexible coaxial fibre supercapacitor based on ball-milled activated carbon nanoparticles mixed with pen ink as electrode materials was successfully fabricated. With the ball-milling time prolonging, the size distribution of the activated carbon particles became gradually narrowed and the average particle size decreased into tens of nanometres from tens of microns, and some Fe₂O₃ phases were introduced. The specific capacitance of the ball-milled activated carbons improved. Furthermore, an activated carbon ball-milled for 24 h with a higher specific capacitance was selected to mix with commercial ink in a ratio of 1:20 to prepare a new active material for high-performance coaxial fibre supercapacitors. Consequently, the specific capacitance for the fibre supercapacitor reached 14.5 mF cm⁻¹, which was 16 times more than that using commercial ink alone as the active layer material, and four times than that using ink mixed with the original activated carbon.