Preparation And Capacitive Performance Of Activated Mesocarbon Microbeads By Compound Activation

Supercapacitors are new energy storage devices with intermediate performance between batteries and dielectric capacitors, which have high power density, long cyclic life and high charge/discharge capability, etc. They have multiple applications including aeronautics and astronautics, electronic communication, automobiles, military, etc. Energy density plays a key role in improving the performance of supercapacitor, and the volumetric specific capacities have a significant effect on energy density of supercapacitor. In this paper, Activated mesocarbon microbeads (A-MCMBs) with high volumetric specific capacitance were prepared from mesophase pitch microbeads (MPMBs) by electrical furnace heating (EF), which activated by KOH/NaOH compound activating agents. With the analysis of the micro structure and capacitance of the electrode materials, preparation of porous carbon and its effect on pore structure and the formation of high volumetric specific capacitance were systematically studied. Main research contents are as follows:A-MCMBs with high volumetric specific capacitance has been prepared from MPMBs by activation with potassium hydroxide and sodium hydroxide and heating with EF. The results show that the capacitance performances of A-MCMBs are influenced by the ratio of KOH/NaOH, the activating temperature, activating time, etc. and when (KOH/NaOH)/MPMBs weight ratio, activating temperature and activating time increased, the capacitance increase firstly and then decrease, what is more, the optimization activating process is:KOH:NaOH:MPMBs=5:1:1, activating temperature at850℃and activating time for60min. At the optimun process conditions mentioned above, the yield of A-MCMBs is47%, the tap density is0.29g/cm3, the specific capacitance is306F/g, and the volumetric capacitance is94F/cm3.This paper also studies the differences of the A-MCMBs which are activated separately by compound activating agents and KOH at conventional resistance furnace heating method using MCMBs as precursor. Through analyzing two kinds of activated mesocarbon microbeads (A-MCMBs) tapping density and capacitance, and testing by XRD, SEM and BET specific surface area analyzers, it was obtained that MCMBs prepared by compound activating agents have a higher tap density, which is0.37g/cm3, and have a higher degree of graphitization, what is more, its volumetric capacitance increases from53F/cm3to81F/cm3. These A-MCMBs are benefit for using as electrode materials of EDLC. This EDLC has good cycle performances, It can charge-discharge not only under the small current and long time, but also under the large current and short time. In addition, its internal resistance and drain current are very small, so can suit with different practical application.