Preparation Of Porous Carbon Materials From Coal Tar Pitch For Supercapacitors

In this paper,porous carbons?PCs?were prepared with coal tar pitch?CTP?from Inner Mongolia as carbon precursor using KOH and K₂CO₃ as activators.The effect of activation temperature on the structure of PCs was studied,and the relationship among the microstructure,surface properties and electrochemical performance was analyzed.The effects of activation time and the amount of activator on the electrochemical performance of PCs were also investigated.In addition,the characteristics of PCs activated by KOH and K₂CO₃ were compared by the microstructure,surface morphology and electrochemical performance of PCs.The pore structure of PCs was controlled by CaCO₃ template strategy to improve the electrochemical performance.The structure of PCs was characterized by N₂ adsorption and desorption test,X-ray diffraction?XRD?,Fourier transform infrared spectroscopy?FTIR?,transmission electron microscope?TEM?,scanning electron microscope?SEM?,and Raman test?Raman?.Electrochemical tests included galvanostatic charge-discharge?GCD?,cyclic voltammetry?CV?and electrochemical impedance spectroscopy?EIS?.The results show that different porous structures were generated through the process of activation KOH and K₂CO₃.More micropores were produced in KOH activation,while more open tremella-like structures and more mesopores were formed in K₂CO₃ activation.The PCs prepared by KOH activation and K₂CO₃ activation both stored energy in the form of an electric double layer without apparent pseudo capacitance.PCH-T700 and PCC-T700,with KOH and K₂CO₃ as activator respectively,prepared at 700 ^oC for 60 min with a mass ratio of activator to CTP of 2:1 showed the best electrochemical performance compared with other samples.In the button capacitors representing practical applications,the specific capacitances of PCH-T700were 226.01 F g^-1 at 0.5 A g^-1 and 207.94 F g^-1 at 4 A g^-1 with a high energy density of7.22 W h kg^-1 at a power density of 999.69 W kg^-1.And its specific capacitance reached216.24 F g^-1 after 5000 GCD tests at 1 A g^-1,which was 98.20%of the initial value.Furthermore,the specific capacitances of PCH-T700 were 225.51 F g^-1 at 0.5 A g^-1 and216.03 F g^-1 at 4 A g^-1 with a high energy density of 7.5 W h kg^-1 at a power density of1038.46 W kg^-1.And its specific capacitance reached 230.39 F g^-1 after 5000 GCD tests at 1 A g^-1,which was 103.77%of the initial value.Compared with PCH-T700,PCC-T700 had more excellent rate characteristics and cycle life,and could give better consideration to high power density and high energy density,which mean higher practical value.More mesopores with diameters of 2-4 nm were produced in PCs via CaCO₃ template to improve their electrochemical performance.For example,PCC-T900-0Ca prepared at 900 ^oC for 60 min with a mass ratio of K₂CO₃ to CTP of 2:1showed 234.80 F g^-1 at 1 A g^-1,and the specific capacitance of PCC-T900-0.5Ca adjusted by adding CaCO₃ according to 0.5:2:1 of m?CaCO₃?:m?K₂CO₃?:m?CTP?was285.99 F g^-1.In addition,there is a synergistic effect of CaCO₃ template and KOH activation on the formation of micropores.In the button capacitors,PCC-T900-0.5Ca exhibited more outstanding performance with specific capacitances of 245.79 F g^-1 at0.5 A g^-1 and 232.02 F g^-1 at 4 A g^-1,as well as a high energy density of 8.06 W h kg^-1at a power density of 1000.55 W kg^-1.Moreover,PCC-T900-0.5Ca was electrochemically activated and its specific capacitance reached 244.21 F g^-1 after 5000GCD tests at 1 A g^-1,which was 101.76%of the initial value.The test results show that PCC-T900-0.5Ca was more suitable for practical use.In this work,relatively cheap CTP was used to prepare PCs for supercapacitors,which is expected to achieve high value-added conversion of CTP.There are 83 pictures,26 tables,and 89 references in this paper.