The Preparation And Capacitive Performance Of Biomass Derived Carbon Materials

Supercapacitor,is a new type energy device between the capacitor and the battery,having the advantages of fast charge and discharge rate,high power density,long cycle life,and maintenance-free.Biomass derived carbon materials are currently the most promising supercapacitor electrode materials owing to their cheap raw materials and easy preparation process.However,derived carbon based sueprcapacitors still have a certain gap in enenrgy density compared to batteries.According to the energy density formula E=1/2CV2,this thesis mainly starts with the promotion of C.The specific work is as follows:First,potassium hydroxide(KOH)and thiourea(CH4N2S)are used to treat the biomass to prepare N,S co-doped biomass-derived carbon.Comparing the one-step method and two-step method,it is found that thiourea has a triple action of doping,auxiliary activation and reduction in one-step method,and the specific capacitance of the derived carbon was as high as 317 F g-1 at 1 A g-1.Then,potassium ferricyanide(K3Fe(CN)6)and thiourea(CH4N2S)are selected as graphitization catalysts and dopants,respectively,to prepare N,S co-doped bamboo fiber-derived carbon NSGFC.The derivatized carbon exhibits a large specific surface area,a suitable degree of graphitization,excellent electrical conductivity,and excellent electrolyte wettability due to the synergistic effect of thiourea and K3Fe(CN)6.Based on these advantages,it shows excellent rate performance(specific capacitance is 328 F g-1 at 1 A g-1,and its capacitance retention rate is 61.3%at 15 A g-1).Finally,a nickel-based compound/derived carbon composite was constructed to introduce a redox reaction and increase the specific capacity C.Firstly,N,S co-doped derived carbon(DC)was prepared in a one-step method,and MnO2 was grown on the surface of DC.Then,DC@Ni(OH)2/NiOOH composite was prepared by hydrothermal reaction,and the DC/MnO2 was used as an intermediate product through an etching displacement reaction.The nickel-based compound in the composite material has a sheet-like morphology,which can be in fill contact with the electrolyte,thereby shortening the ion transmission path.In addition,the conductivity of the material and the volume change caused by the phase change have been improved based on the presence of NiOOH,thereby improving the rate performance and cycle stability of the composite material.The specific capacitance of the composite material is1109 F g-1 1 A g-1,and the capacity retention rate is still 60.1%at 10 A g-1.After assembling an asymmetric hybrid capacitor,at a high power density of 12800 W kg-1,an energy density of 12.1 Wh kg-1 is still achieved,indicating that the application potential of DC@Ni(OH)2/NiOOH//DC is in the supercapacitors.