Preparation Of Coal-based High-Surface-Area Porous Carbon And Its Utilization Of Supercapacitors

The volatility of the operation of new energy power generation systems,the rapid start and stop of electric vehicles and the energy saving requirements of their operation processes all place urgent demands on high power density energy storage.Supercapacitor is an ideal high-power density energy storage system through ion electrochemical adsorption energy storage.Carbon-based materials have the advantages of abundant resources,easy to control,and are important choices for supercapacitor energy storage materials.Supercapacitors require high activity and stability of carbon-based materials.The development of porous carbon with high specific surface area and good crystallite structure is the key to improving the performance of supercapacitors.Rich in coal reserves and low in price,it is a complex carbon-based macromolecule composed of aromatic structure and fatty structure bridging.It has high carbon content and is an ideal carbon-based material precursor.The development of coal to high activity and stability of porous carbon conversion methods is of great significance in the field of coal utilization and supercapacitor energy storage.Based on the characteristics of typical coal types,this paper studies the preparation method of coal-based porous carbon and its supercapacitor energy storage characteristics.In this paper,porous carbon was prepared by high-activity Zhundong coal as carbonaceous precursor by physicochemical coupling activation.The physical and chemical structures of porous carbon were analyzed by means of SEM,TEM,N₂adsorption,XRD and Raman spectroscopy.The influence of ash on pore development was investigated and the energy storage characteristics of supercapacitors were evaluated.The results show that the physical coupled chemical activation method can obtain high specific surface area graded porous carbon with specific surface area of2308 m² g^-1 and pore volume of 1.51 cm³ g^-1.Compared with ash-free coal,ash-containing coal is more conducive to the development of pore structure.The ash rich in alkali metals and alkaline earth metals has catalytic gasification and promotes the development of pores.Porous carbon exhibits high specific capacitance and good rate performance in supercapacitor energy storage.In the aqueous three-electrode system with KOH as electrolyte,the specific capacitance at 1A g^-1 is 308F g^-1,100A g^-1.The capacitance is still up to 202 F g^-1.In order to further enhance the activation effect,high specific surface area porous carbon was prepared by KOH activation method.The effects of coal-based precursor coalification degree and activation temperature on the development of pores and crystallites were investigated.The specific surface area of porous carbon prepared by KOH activation was above 3000 m² g^-1.With the deepening of coalification,the yield increased from 13.6%to 41.7%.When the activation temperature is increased to1000°C,the specific surface area of anthracite can reach 3214 m² g^-1,and the tap density is in line with the requirements of the supercapacitor national standard.As the temperature increases,the graphite crystallites gradually grow and the conductivity can reach more than 8 times that of commercial activated carbon.In the symmetric supercapacitor of the organic electrolyte system,the specific capacitance at 1A g^-1 is 170.8F g^-1,and the specific capacitance at 30A g^-1 is still 149.3F g^-1.In order to further optimize the microcrystalline structure of porous carbon prepared by KOH activation,this paper explored the effects of carbonation pretreatment and external catalytic medium on pore structure and microcrystalline structure with quasi-east coal as carbonaceous precursor.Pre-carbonization promotes the growth and ordering of the microcrystalline structure.The porous carbon exhibits a certain crystalline state,and the carbon-based precursor with higher original hydrogen content has better crystallite quality.The addition of catalytic medium during the activation of KOH can promote the development of graphite crystallites,and the existence of KOH is the key to the development of crystallites under the activation conditions of 900°C.Compared to direct KOH activation,the conductivity of the microcrystalline crystals which are further developed can be increased by¹ times.