Highly electroconductive mesoporous activated carbon fibers and their performance in the ionic liquid-based electrical double-layer capacitors

The development of supercapacitors with high energy density calls for multi-functional electrode materials without obvious drawbacks in capacitance performance and in device processing. The highly electroconductive mesoporous activated carbon fibers (MACFs) for 4 V supercapacitors in ionic liquids are proposed. Preparing by the controlled carbonization and activation of polyacrylonitrile-based fibers by CO2 at high temperature, MACFs exhibit high special surface area (2404 m2/g), large mesopore volume (2.3 cm3/g), large packing density (0.25 g/cm3), high electrical conductivity of 57–195 S/cm, good chemical stability at high voltage and low liquid intake ability. As tested in EMIMBF4 electrolyte at 4 V, MACFs exhibit high capacitance (204 F/g at 0.5 A/g), high energy density (113 Wh/kg) and excellent capability of capacitance retention. Such excellent capacitance performance is also due to the one-dimensional structure of MACFs, with the long carbon in-plane length for electron transfer in axial direction and the short radial diffusion distance for ions of ionic liquids. To the best of our knowledge, the obtained MACFs are the first material combining all advantages of conventional electrode material (activated carbon) and new generation electrode materials (mainly carbon nanotubes and graphene) together, as well as minimizing their major drawbacks.