Carbon-based Materials For Supercapacitor Electrodes

Supercapacitor is a new kind of energy storage devices between batteries and capacitors, which have many merits such as high power density, short charging time, durable cycle life and so on. However, not only its energy density is low, but also the realization of the large capacity is more difficult. Electrode material is pivotal for our research to improve the electrochemistry performance of supercapacitors. Currently, it is natual to take activated carbon for granted as supercapacitor electrode materials. Activated carbon need many requirements like high specific surface area, corrosion and elevated temperature resistance, good electrical conductivity, tunable porous structure, etcHuolinhe lignite in Inner Mongolia is used as raw materials for electrode materials, lignite resources in Inner Mongolia is rich and its price is low, and all those advantages make it be good raw material for activated carbon. According to its different reaction conditions, electrical properties are compared. The results show that prepared activated carbon has better electrochemical properties and porous structure. Activated carbon is manufactured by a more mature neutral activator activation method.The optimum activation temperature, active time, activator concentration are selected in single factor experiment, under different activation temperatures,the specific surface area of resultant product is758-1024m2g-1, and micropore dominates, about65%to78%of total volume. Specific capacitance reached207.5Fg-1at0.5A g-1when the activation temperature is650℃, and specific capacitance is102F/g even at20Ag-1. So capacitance remain is49.2%. Activation temperature is650℃to get the best performance. Activation temperature has certain influence to the activated carbon. At low activation temperature, the pore structure form is incomplete; specific surface area is low; the electrochemical performance is not stable; when the activation temperature is too high, it will lead to excessive pore structure ablation, poor electrochemical performance. Active carbon is prepared under different active time. The specific capacitance is up first and then down when active time is prolonged by constant charge-discharge test.. So the results show that the best time is90min in our experiment. Activation time has a certain effect on activated carbon pore forming, under short activation time, activation is not complete, while longer activation time introduces excessive activation, thus activation time has a larger effect on the electrochemical properties.Active carbon is manufactured under different activator concentration. The specific capacitance is up first and then down when current density is promoted under0.5A g-1and the variation tendency remains. So the concentration is3M. Activator concentration has a role in promoting pore forming in respect to active carbon. The activator concentration is too high, inhibiting the generation of pore structure, poor electrochemical performanceOrthogonal experimental results show that the activation temperature of, the activator concentration of, the activation time of115min of activated carbon in the current density of0.5Ag-1, the specific capacitance can reach220F/g when the activation temperature, the activator concentration and the activation time are650℃,4M and115min separately. The poor analysis shows that the factors are ordered as follow according to the influence of the specific capacitance:activator concentration> activation time> activation temperature.