Preparation And Electrochemical Properties Of Coal Tar Pitch-based Porous Carbon

Our coal tar pitch resources are rich,the annual output has exceeded 10 million tons,but its high value-added effective utilization rate is low,and serious pollution to the environment.With the implementation of the national strategy of"carbon peak,carbon neutral",people pay more attention to the high value clean utilization of coal tar pitch resources.In recent years,porous carbon prepared from coal tar pitch has been widely studied in the field of energy storage.However,due to the complex composition of coal tar pitch and the many factors affecting the preparation of porous carbon,the reported properties of porous carbon are different or even very different.Therefore,a systematic study of the effects of tar pitch type,composition and preparation conditions on the properties of porous carbon is helpful for the development of high-performance energy storage carbon.In this thesis,the modified tar pitch（oxidized tar pitch OP,thermo-polymerized tar pitch TP）was prepared by air oxidation method and thermal polymerization method.Then,the toluene soluble components(TS_MP,TS_OP,TS_TP)and insoluble components(TI_MP,TI_OP,TI_TP)of three kinds of tar pitch were prepared by hot solution extraction.Nine kinds of raw materials were used as precursors to prepare porous carbon.Their chemical bond structure and pyrolysis properties were studied by FTIR and TG-DTG respectively.The KOH activation method was used to prepare the bituminous porous carbon.The effect of the preparation conditions on the capacitive properties of the porous carbon was investigated by single factor experiment.On this basis,the optimum preparation process of porous carbon was optimized by response surface method.The structural morphologies of porous carbon prepared by nine kinds of raw materials under optimal conditions were studied by XRD,Raman,BET,SEM and TEM,and their electrochemical properties were tested by three electrode system and two electrode system respectively.The results are as follows:（1）The chemical structure of the nine precursors of raw materials is similar.Aromatic hydrogen structure adjacent to 3H/4H is dominant in the aromatic ring,and the alkyl side chain is short.The order of aromatic degree is insoluble component>raw tar pitch>soluble component,and the content of residual carbon at 750℃is consistent with this order.（2）The optimum preparation conditions of coal-bituminous porous carbon optimized by response surface method are as follows:activation temperature 677.8℃,alkali-carbon ratio 2.4,activation time 2.0h.Under these conditions,the maximum specific capacitance predicted by the model is 423.5 F/g,which is equivalent to the measured 420.0 F/g.The quadratic regression linear equation of the model is:Y=417.65-65.21A+9.71B-13.42C+26.47AB+14.82AC+10.13BC-81.78A²-34.23B²+0.52C².（3）In the three-electrode system,the order of capacitance of nine kinds of porous carbon is:raw tar pitch porous carbon>soluble component porous carbon>insoluble component porous carbon.Among the raw bituminous porous carbon,medium temperature bituminous porous carbon（MPC）has the best capacitive performance,with A high specific capacitance of 418.0 F/g at 0.5 A/g current density and 295.5F/g specific capacity at 20 A/g.（4）In the two-electrode system,the order of capacitance size of the nine kinds of porous carbon is:porous carbon of soluble component>porous carbon of raw tar pitch>porous carbon of insoluble component.Among the soluble component porous carbon,the medium temperature tar pitch soluble component porous carbon(TSC_MP)has the best capacitance performance,with A specific capacitance value of 129.9 F/g at the current density of 1 A/g.After 1000 cycles of constant current charge-discharge test,its capacity retention rate reaches 97%.When the power density is 448.9W/kg,it can provide 16.2Wh/kg energy density.