| With the continuous progress of the energy industry, supercapacitors, as a new electrochemical energy storage device, began to receive widespread attention. Activated carbon material are actually the most widely used supercapacitors electrode material, because current well-established activation technology allows the low production costs of porous carbons with high surface areas. However, when activated carbon material are used as electrodes of supercapacitors, the slow electrolytic ions transport in such narrow pores almost inevitably engenders poor performance of capacitors. Hierarchically porous carbon possessing well-defined macropores and interconnected meso- and micropores, are promising high-performance electrode materials. Currently, one of the most important method of preparing porous carbon materials is templating-activation method by using polymer(phenolic resin, glucose, etc.) as a precursor. The key of this study was to find a suitable template for introducing large pores into activated carbon. However, the current templates such as silica, F127 and metal oxides have many disadvantages including complicated and costly process, serious pollution and limited performance. Therefore, we try to explore new templates for preparing the high-performance hierarchically porous carbon electrode materials cheaply. The main content and conclusion of this thesis are as follows:(1) In order to obtain low-cost and high-performance super-capacitor electrode material, we mixed phenolic resin used as a carbon source and ammonium chloride used as a template in aqueous solution. The mixture solution was freezing-dried followed by calcination and finally transformed into porous carbon material. Herein, ammonium chloride can be crystallized into smaller particles dispersed in the resin via rapid cooling under the induction of the resin. During calcination, ammonium chloride particles are brokendown into gas and then removed, which generates large pores in the resol. Adjusting the proportion of the resin with ammonium chloride can effectively regulate the morphology of the material. The obtained porous carbon materials, after activation using potassium hydroxide for introducing mesopores and micropores, became hierarchically porous carbon. Besides, it has a specific surface area of up to 2441 m2/g,and thus could become used as excellent ultracapacitor electrode material. Compared to the blank sample,the capacitance of the obtained hierarchically porous carbon material have an increases of 54 F/g at a current density of 0.1 A/g. At 10 A/g, the capacitance of the material can still reach 217 F/g.(2) To further optimize the pore structure of the above porous material for improving the capacitive performance, we chose one-dimensional organic tubular structure with a diameter of 100 nm as templates in preparation process. This organic tubular structure always appears in the dilute lithocholic acid solution under the addition of ammonium chloride. From a structural point, lithocholic acid was added in order to fill the gaps between macroscope pore structure constructed using ammonium chloride as a template and micro-and meso-pores introduced by activation, which could improve electrolytic ions transport within activated carbon electrode. At the same time, the introduction of these 100 nm pore structure makes activation efficiently improved the surface area of the material. Because of the cholesteric group,lithocholic acid should be able to improve the conductivity of the obtained carbon material. Owing to the above advantages, carbon material shows excellent capacitive properties, especially the high rate performance current densities in the two-electrode system. |
