Preparation And Capacitance Performances Of Activated Carbon Materials With Alkali

Supercapacitors have been widely investigated in recent years on account of their high power denisities,long cycle lifetimes and high charge/discharge.The electrode is an important part of a supercapacitor and can greatly impact its performance.Porous carbon electrodes are promising electrode materials owing to their high specific surface area,good conductivity and abundance.In this paper,porous carbon materials with high specific surface area were prepared by carbonization and activation with low cost biomass materials as carbon sources.Their surface chemical characteristics,pore structure parameters and electrochemical properties were studied.The main research contents and results are as follows:(1)Phenolated calcium lignosulfonate-based phenol formaldehyde resin activated carbon were prepared by the crosslinking and polycondensation of phenolated calcium lignosulfonate with formaldehyde,followed by carbonization and activation.When KOH/char ratio was 6,the sample carbon with good morphological structure and electrochemical properties was prepared by activation at 800 °C for 2 h,its specific surface area is 1320.13 m2/g.In 6 M KOH electrolyte,the mass specific capacitance is 204.88 F/g when the current density is 0.5 A/g.At the same time,the sample also showed good cyclic stability.Under the current density of 2 A/g,the capacitance retention rate is 97.55%after 100 constant current charge discharge.The carbon sample with high micropore content has a higher area specific capacitance,which shows that microporous structure can significantly affect the capacitance of the electrode.(2)The extraction residue of larch bark was used carbon source,using its natural stricture,a high specific surface area activated carbon was prepared by carbonization and KOH activation.The results show that when KOH/char ratio was 6,the sample carbon with high specific surface area(1811.69 m2/g)was prepared by activation at 700 °C for 1.5 h.In 6 M KOH electrolyte,the mass specific capacitance is 204.40 F/g when the current density is 0.5 A/g,the capacitance retention rate is reach to 99.00%after 100 charge-discharge cycles at the current density of 2 A/g.The carbon sample with abundant pore structure and higher nitrogen and oxygen content has larger area specific capacitance.Through comparison,it is found that the micropore structure and nitrogen and oxygen content have a significant influence on the increase of capacitance.(3)Amur corktree leaves with rich transfusion tissue were used as the raw material,4 kinds of porous activated carbon were prepared by activation with KOH,K2C03 and H3P04,respectively.The results show that when KOH/char ratio was 4,the sample carbon with high specific surface area(2011.39 m2/g)and rich pore structure was prepared by activation at 700 °C for 25 h.In 6 M KOH electrolyte,the mass specific capacitance is 239.32 F/g when the current density is 0.5 A/g,the capacitance retention rate is reach to 96.98%after 100 charge-discharge cycles at the current density of 2 A/g.