The Research On Preparation Of Carbon Electrode Materials By Microwave Radiation For Supercapacitors

Supercapacitors have been recognized as unique energy storage devices between conventional electrostatic capacitors and secondary batteries. Because they integrate many advantages, such as the high power density, the high energy density, the long cyclic life and no pollution. Supercapacitors are widely used in the fields of communication, electronics, dynamoelectric car, aviation aerospace and national defense. With high specific surface area carbon prepared by microwave radiation as electrode materials for supercapacitor, this dissertation has investigated preparation, structure and capacity property. Main research contents are as follows:1. High specific surface area activated carbon for supercapacitors has been prepared from petroleum coke by activation with potassium hydroxide through microwave radiation. The mass ratio of KOH to petroleum coke, microwave radiation power and microwave radiation time have important effects on the structure and the capacitance characteristic of the activated carbon. The BET specific surface area of activated carbon can reach 1951 m²/]g, and the specific capacitance can reach 288F/g while the mass ratio of KOH to petroleum coke is 3.5: 1 and the radiation power and time of microwave are 800 W and 7 minutes respectively. Using this activated carbon as electrode materials, the supercapacitor has good charge/discharge properties. It can discharge not only at the small current condition in long time, but also at the large current condition in short time. It also has excellent cycle stability. The capacity of supercapacitors drops no more than 5 percent after 100 cycles.2. Activated carbon for supercapacitors has been prepared from petroleum coke by activation with potassium hydroxide through common high temperature heating method. The mass ratio of KOH to petroleum coke,activation temperature and activation time have important effects on the structure and the capacitance characteristic of the activated carbon. The specific capacitance can reach 256F/g while the mass ratio of KOH to petroleum coke is 4: 1 and activation temperature and activation time are 800℃and 1 hour respectively. Using this activated carbon as electrode materials, The capacity of supercapacitors drops no more than 8 percent after 100 cycles.3. Activated carbon for supercapacitors has been prepared from petroleum coke by activation potassium hydroxide with common high temperature heating method and microwave radiation. Compared to the structure of activated carbon which is prepared by the common high temperature heating method, the structure of the activated carbon which is prepared by microwave radiation has more graphitized structure and more bigger C_dl(specific double-layer capacitance). That is why the activated carbon which is prepared by microwave radiation has bigger specific capacitance.The specific double-layer capacitance of activated carbon which prepared by microwave radiation can reach 14.8μF/cm². The specific double-layer capacitance of activated carbon which prepared by the common high temperature heating method can reach 10.8μF/cm².