| Supercapacitors,also referred to as electrochemical capacitors,as a new type of environmentally friendly energy storage device,because of its fast charge and discharge,high energy density,high power density and good cycle stability.The research shows that the super capacitor electrode material is the key factors affecting its performance.A coal tar pitch,which is the by-product of coking enterprises processing process,is used as supercapacitor electrode materials because of high carbonization yield,low molecular weight,abundant resources and low price.In this paper,coal tar pitch was used as the carbon source to study the incorporation of potassium hydroxide activator and the ratio of magnesium oxide template and the addition of nitrogen to the pore structure of the prepared carbon electrode and the change of electrochemical performance.Firstly,coal tar pitch was used as the carbon source and KOH as the activator.The porous carbon materials were prepared by grinding method and impregnation method and different activation ratio respectively.Among them,the carbon material prepared by the impregnation method uniformly disperses a large number of pores on the surface of the carbon material,while the surface of the carbon material prepared by the grinding method has many irregular holes and a small amount of large pores,which indicates that the impregnation method can make the asphalt react with KOH agent to achieve the maximum effect of maximum mixing.When the activation ratio is 1:2,the specific surface area of the sample was 1012 m2g-1 and the average pore size was 2.68 nm.The electrochemical test showed that in the 6 mol L-1 KOH electrolyte,1 A g-1The specific capacitance of the asphalt-based microporous carbon electrode material is 331 F g-1 at the current density.With the increase of the current density,the specific capacitance is 240 F g-1 at a current density of 20 A g-1,and the specific permittivity is 72.5%,and has good rate performance.It can be seen that the impregnation method is the best way to prepare the carbon material by the KOH activator mixed asphalt.Secondly,magnesium chloride was reacted with urea to form basic magnesium carbonate.The pyrolysis of magnesium oxide was carried out.MgO was used as template and mixed with asphalt and KOH activator to prepare multi-stage pore carbon with microporous,mesoporous and macroporous material.The carbon material is laminated by a layer of thin film,the overall layered structure.When the asphalt/KOH is 1:2 and the calcination temperature is 800?,the specific surface area of the sample is 1330 m2 g-1 and the average pore size was between 4.93?6.55 nm,the specific capacitance of 290 F g-1.When the current density is increased to 20 A g-1,the capacitance is maintained at 250 F g-1,and the retention rate can reach 86%.The electrochemical performance of the two-electrode system in the alkaline electrolyte and the neutral electrolyte is slightly different,at a current density of 1 A g-1,the power density of the carbonaceous material in the alkaline electrolyte is 493.2 W kg-1 and the energy density is 8.58 Wh kg-1.The power density in the neutral electrolyte is 873.6 W Kg-1 with an energy density of 20.28 Wh kg-1.Finally,nitrogen-doped porous carbon was prepared from melamine as nitrogen source.The effects of different activator dosage and calcination temperature on the pore structure and chemical properties of carbonaceous materials were investigated.By observing the scanning electron microscopy,it was found that the unactivated carbon material was formed by stacking a layer of lamellae and containing a small amount of micropores.And the activated carbon material is rich in mesopores and macropores,and the pores connected with the hole.When the calcination temperature is 700 ?and the amount of KOH activator is 0.4 g,the specific surface area increases to 687 m2g-1.At a current density of 1 A g-1,the specific capacitance is 290 F g-1. |
PDF Full Text Request