Abstract:
Supercapacitors have been widely studied and applied in hybrid vehicles, new energy generation, aerospace and other fields due to their high power density, high charge/discharge speed, long cycle life and environmental friendliness. Carbon materials have become popular in the field of supercapacitor electrode materials, because of their high conductivity, stable chemical properties and low cost. As a type of microporous carbon, activated carbon fiber (ACF) is a good supercapacitor electrode material because of its large specific surface area, high adsorption rate and concentrated pore size distribution. As most carbon materials, the porous structure and microstructure of ACF will change significantly after heat-treatment, which affects the performance of supercapacitor. At present, there are few studies on the changes of surface structure and properties of ACF during heat-treatment. In this work, three typical ACFs (cellulose, pitch and polyacrylonitrile-based ACFs were treated at different temperatures ranging from 700 ℃ to 2 800 ℃. The effects of temperature on porous structure, micro-structure, elemental composition and conductivity of ACFs were investigated by nitrogen adsorption, X-ray diffraction, elemental analysis and resistivity test. In the meantime, ACFs were used as supercapacitor electrode materials to study the electrochemical performance in inorganic and organic systems. It was shown that after heat-treatment, the BET specific surface area increased first and then decreased with the increase of heat-treatment temperature and the capacitance performance of ACFs showed variations in inorganic and organic systems.