Preparation And Performance Study Of Graphene And CuO Composites As Supercapacitor Materials

Supercapacitor is a new kind of energy storage device, it has been thought as themost important energy storage device because of high power density, excellent cycleability and environment protection. Supercapacitors have been used in industrial UPSpower supply, electric vehicle, aerospace and so on. In this paper, the authorinvestigated the research of supercapacitor and selected CuO and graphene asresearch object.In this thesis, graphene oxide is prepared from nature graphite via a way ofmodified Hummer‘s method, and then reduced by pyrolytic deoxidation method.Graphene sheets with different reduction levels have been produced through thermalreduction of graphene oxide in the temperature range of200–900°C. The structureand electrochemical performance of graphene nanosheets (GNS) are systematicallyinvestigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy(FTIR), Energy dispersive X-ray spectroscopy (EDS), Raman diffraction spectrumand a variety of electrochemical testing techniques. The effects of interlayer spacing,oxygen content, specific surface area and disorder degree on their specific capacitancewere explored systematically. The variation of oxygen-containing groups was shownto be a main factor influencing the electrochemical double layer capacitorsperformances of the pyrolytic graphene. The highest capacitance of260.5F/g at acharge/discharge current density of0.4A/g was obtained for the sample thermallyreduced at about200°C.In this paper, a leaf-like porous CuO/graphene nanostructure is synthesized byhydrothermal method. The author tried to improve the specific capacitance of CuOand to improve the energy density. We try to synthesis a new two-dimension structurecomposite to improve electrical conductivity, wetting quality, then improve thespecific capacitance, rate ability and cyclic ability. The as-prepared composite ischaracterized using XRD, Raman, SEM, TEM and nitrogen adsorption/desorption. The composite material is formed by self-assembly mechanism and this2-D structurecan effectively avoid the agglomeration of material. Electrochemical characterizationdemonstrate that the leaf-like CuO/graphene are capable of delivering specificcapacitance of331.6F/g at the current density of0.6A/g. A capacity retention of95.1%can be maintained after1000continuous charge-discharge cycles, whichshould be attributed to the improvement of electrical contact by graphene andmechanical stability by layer-by-layer structure.In this thesis, CuO/carbon nanotube (CNT) nanomicrospheres have beensuccessfully synthesized by hydrothermal method and investigated with SEM,BET,XRD, and electrochemical experiments. It benefits from an as-formed CNT,which should be attributed to the improvement of electrical contact by carbonnanotube and mechanical stability. Electrochemical characterization demonstrate thatthe CuO/CNT are capable of delivering specific capacitance of96F/g at the currentdensity of2A/g,and the capacity of92F/g after1000continuous charge-dischargecycles.