Study On Preparation Of Activated Carbon For Supercapacitor By Physical Activation

With the rapid socio-economic development and the massive consumption of fossil fuels,the shortage of resources and serious environmental pollution bring about by the problem have aroused great concern.The development of new energy storage technologies has become particularly important,and supercapacitors,as new energy storage elements,have attracted widespread attention for their advantages of high power density,long service life,and environmental friendliness.Porous carbon material is the most widely used electrode material for supercapacitors.It has the advantages of wide sources,large specific surface area,better chemical stability,and low cost.The development of green preparation technology of activated carbon is in line with the requirements of modern society.In this paper,porous activated carbon for supercapacitor was prepared by using coconut shell as raw material and then activated by carbon dioxide（CO₂）and water vapor.The effects of physical parameters such as activation temperature,activation time and activation gas flow rate on the pore structure and electrochemical properties of activated carbon were studied by using argon physical adsorption and desorption,constant current charging and discharging techniques.The main research of the paper is as follows.（1）Graded porous activated carbon with high electrochemical performance and large specific surface area is prepared by adjusting the ratio of carbon dioxide to carbonized material,activation time,activation temperature and other parameters using coconut shell carbonized material as raw material and CO₂ as activator.The development of pore structure of porous activated carbon is largely dependent on the activation conditions.Therefore,with reasonable regulation of process parameters,microporous activated carbon with rich pore structure and large specific surface area as well as pore size distribution mainly concentrated in 0.5-1.5 nm can be manufactured.The pore structure of biomass activated carbon determines the capacitive characteristics of the electrode material,and the change trend of the pore structure and capacitive characteristics of the material is basically the same as the activation time of CO₂ increases and the temperature increases.When activated with CO₂ at 900℃for 3 h,the structure and capacitance performance of the activated carbon obtained are optimized.The specific surface area is 1245 m²·g^-1,the total pore volume is 0.58 cm³·g^-1 and the specific capacitance is prepared.Activated carbon which is 162 F·g^-1and has high cycle stability.（2）The graded porous activated carbon with excellent electrochemical properties and large specific surface area was prepared by using coconut shell carbonization material as raw material and water vapor as activator,and by adjusting the parameters of water vapor activation time and activation temperature under the condition of excess water vapor.The activation temperature of water vapor and the activation time have a very strong influence on the pore structure of porous activated carbon.Therefore,the activation process parameters can be reasonably controlled to prepare porous activated carbon with rich pore structure,high specific surface area and pore size distribution concentrated in the range of0.5-1.5 nm.With the increase of water vapor activation time and temperature,the pore structure and capacitance characteristics of the material changed in the same trend.The specific surface area,total pore volume and specific capacitance were 994 m²·g^-1,0.48cm³·g^-1 and 132 F·g^-1and the cycling stability was also high.