Hypercoal-derived Activated Carbon For Electric Double Layer Capacitor Electrode

High specific surface area activated carbons(ACs) were prepared from Hyper Coal by carbonization-activation method and direct activation methods, and were used as electrodes in electric double layer capacitors(EDLC). The effects of preparation conditions on pore structure and electrochemical performance of ACs were investigated in this study. The relationship between specific surface areas, pore size distributions and the specific capacitance of ACs was discussed. The SEM, XRD and N2 adsorption were used to characterize the surface properties and pore structure of ACs. The electrochemical performance of electrode materials was tested by constant current charge-discharge.Firstly, the ACs electrode materials with high specific surface area were successfully prepared by carbonization-activation method and KOH as activating agents. The effects of carbonization temperature, activation temperature and activation time on yields, pore structure and electrochemical performance of ACs were investigated systematically. The AC with yield of 53.3%, specific surface area of 2540.2 m2 g-1 and total pore volume of 1.65 cm3 g-1 was achieved at carbonization temperature of 500 oC, activation temperature of 800 oC and activation time of 2 h and the specific capacitance reached 46.0 F g-1 in 0.5 M TEABF4/PC electrolyte. The constant current charge-discharge tests suggest that ACs electrodes prepared under different conditions can exhibit good electrochemical properties. Secondly, ACs electrode materials were prepared by direct activation methods and KOH as activating agents and the effects of activation temperature and activation ratio on yields, pore structure and electrochemical performance of ACs were investigated. It was found that the specific surface area, total pore volume and specific capacitance increased with raising activation temperature and activation ratio. The yield, specific surface area, total pore volume and specific capacitance of AC were achieved 38.3%, 2440.2 m2 g–1, 1.48 cm3 g–1 and 44.4 F g-1 under the condition of an activation temperature of 800 oC and an activation ratio of 4.0. Thridly, for Na OH activating, high specific surface area ACs electrode materials were prepared by carbonization-activation method and the effect of activation temperature on yields, pore structure and electrochemical performance of ACs were investigated. The best condition of preparing AC with yield of 45.4%, specific surface area of 3110.2 m2 g-1 and total pore volume of 1.77 cm3 g-1 is activation temperature and activation ratio being 700 oC and 4.0. The specific capacitance of the electrode reached 43.9 F g-1 and it showed good electrochemical characteristics. The results showed that the ACs with developed pore structure and excellent capacitive properties can be obtained under appropriate preparation conditions when Na OH as activating agents.