Preparation?Assembly And Properties Of Coal Based Electrode Materials For Supercapacitors

In recent years,Supercapacitor,as a new type of energy storage devices between conventional capacitors and batteries,have attracted significant attention,mainly due to their high power density,long lifecycle,wide operating temperature range etc.In many application areas,some of the most effective and practical technologies for electrochemical energy conversion and storage are hybrid gasoline-electric power,mobile communications and solar/wind power generation.As we know,the supercapacitor consists of three major components:electrode materials,separators and electrolytes,among which the electrode material is one of the key factors that determine the performance of capacitor.In this thesis,the preparation,assembly and design of coal based electrode materials for supercapacitors were investigated.The main contents are as follows:TanHei(TH),TaiXi coal(TX)and Bituminous coal(YM)were employed as precursors to prepare carbon quantum dots(CQDs)by simple chemical oxidation and centrifugation method.The as-prepared samples were characterized by XRD,SEM,FTIR,TEM.The specific capacitances of TH-24-GO,TX-24-GO,YM-24-GO can reach 93.47 F/g,83.26 F/g,40.33 F/g at a scan rate of 10 mV/s in 1 mol/L Na2SO4 solution,respectively.The higher carbon content of raw materials,the better electrochemical properties of CQDs,probably due to higher conductivity.The result shows that the CQDs from TX coal have higher capacitance than those from YM coal.The influence of different reduction process(chemical reduction,labeled as-C and thermal reduced method,labeled as-T)on the electrochemical properties was investigated.The specific capacitances of TX-CQDs-C,TX-CQDs-T can reach 157.4 F/g?141.5 F/g at a scan rate of 10 mV/s in 1 mol/L Na2S04 solution,respectively.As the scan rate increase to 100 mV/s,the specific capacitance drop to 1 18.4 F/g,100 F/g,respectively.The TX-CQD-C sample was chosen as electrode to assemble into a two electrode cell and test by LAND battery test system,and an excellent cycling stability was achieved after 200 cycle tests at 5 A/g.Three kinds of CQDs/Mn3O4 electrode material for supercapacitor were prepared by solvothermal methods.The as-obtained samples were characterized by XRD,FTIR,TEM,SEM.The results showed that the specific capacitances of TH-CQDs/Mn3O4?TX-CQDs/Mn3O4?YM-CQDs/Mn3O4 can reach 218.7 F/g,223.5 F/g,192.3 F/g at a scan rate of 10 mV/s in 1 mol/L Na2SO4 solution,respectively.Capacitance retention rates were 36.6%,63.9%,36.5%at the range of 10 to 100 mV/s,respectively.CQDs/Mn3O4 electrode composites showed much higher specific capacitance(223.5F/g)than that of either pure CQDs(157.4F/g)or pure Mn3O4(57.4F/g).