Preparation And Electrochemical Performances Of Activated Carbon And Carbon-Based Materials Used In Supercapacitor

Supercapacitor has attracted much attention in the electrochemical research area because of its high specific power, long life, wide use temperature and safety. In this paper, physical and chemical activation was used for preparing activated carbon with high specific surface area, and the electrochemical properties were investigated. Some other methods were explored to improve the specific capacitance. The main content is summarized as following.The activated carbon with high specific surface area and considerable mesopore rate were prepared from bamboo plotsam by phosphoric acid-carbon dioxide activation. The effect of preparation parameters on the pore structure and electrochemical performance of activeated carbon were discussed. The results show that higher specific surface area and greater pore volume can be obtained by impregnating phosphoric acid. With the increase of impregnation ratio and concentration of phosphoric acid, the specific surface area and total pore volume of activated carbon increased. And with the increasing of the activation temperature, activation time and impregnation time, the specific surface area and total pore volume of activated carbon first increased and then decreased.The activated carbon was then modified by nitric acid, sulfuric acid and hydrochloric acid, respectively, followed bythermal treatment in nitrogen atmosphere. The influence of surface function groups on the performance of carbon electrodes were investigated in details. The results showed that the modification caused a slight decrease in specific surface area and average pore size, and the pore structure had few changes. XPS results show that the surface chemical states of activated carbon were changed obviously. The contents of C-C and O-C=O functional groups were decreased, while the C-O and C=O functional groups were increased. The galvnostatic charge/discharge, cyclic voltammetry and impedance detection were used to study its electrochemical performance. The results show that the capacitance of modified carbon materials increased with the trend of nitric acid> sulfuric acid> hydrochloric acid. Moreover, the internal resistance all decreased, indiating the improvements of the hydorphilicity and wettability of modified carbon.MnO2/C and MnO2/CNTs have been prepared by liquid method. And then MnO2/C and MnO2/CNTs/C capacitors were assembled. The influence of MnO2content on the electrochemical performance was studied expecially. The galvanostatic charge/discharge cyclic, voltammetry and alternate current impedance were employed to found that the specific capacitance of complex capacitors was improved, which reached435F/g and528F/g respectively. Moerover, the specific capacitance first increased and then decreased with the increasing of MnO2content. The internal resistance of MnO2/C was increased compared with pure active carbon capacitor by testing of alternate current impedance, while the MnO2/CNTs/C’s remain unchanged.Nanosized nickel oxide particles have been prepared by chemical bath depositon method with NiSO4as materials and NH3H2O as the precipitating agent. X-ray diffraction, scanning electron microscope and transmission electron microscope were used to study showed the performance of the nickel oxide, the morphology and crystal type of the product. And an asymmetric capacitor with activated carbon as negative electrode and nickel oxide as position electrode respectively were assembled and characterized. The results show that the asymmetric capacitor can improve the specific capacitance effectively. When at current density of25mA/g, the capacitance with nickel oxide calcining at300℃reached1039F/g, and it decreased with the increasing of calcinate temperature.