Research On Preparation Of Graphene Aqueous Solution And Its Applications

Graphene is an inorganic material with one atom thickness,0.335 nm,and honeycomb crystal structure,formed by sp~2 hybridization of carbon atoms.Other novel carbon material,such as fullerenes,carbon nanotubes and graphite,can be constituted by this basic hexatomic unit.On account for its unique structure,graphene possesses many outstanding properties,for example,transmittance,electron mobility,thermal conductivity,mechanical strength,and large surface area.Due to these properties,it shows abundant application potential in microelectronics,organic optoelectronics,energy storage,biomedicine and composite materials.As a result,graphene has been attracting attention of academic circle for a decade.However,current preparation methods of graphene(such as mechanical exfoliation,reduction of graphene oxide,chemical vapor deposition,epitaxial growth on silicon carbide,incision of carbon nanotube method),have their weak points or disadvantages,in one way or another.Therefore,it is necessary to find a simple graphene preparation method with low cost and high-quality.However,graphene cannot displays supposed characteristics in most of situation,because uneven distribution and agglomeration tendency for the van der Waals forces between graphene sheets.To tackle this problem,electrochemical modification is introduced to anchor some oxygen-contained hydrophilic functional groups on the surfaces or edges of graphene.Precisely,these functional groups not only can maintain the hydrophilic properties,but also can increase the distance between the graphene layers,resulting in less agglomeration and stability in aqueous solvent.Moreover,this technic is capable of upgrading performance of graphene in practice.Contains of this paper shows as following:(1)In the first stage of this research,the laboratory-made liquid poly acrylonitrile(LPAN)is used as raw material,followed by pre-oxidization at 260℃in air,and crashing.After that,this precursor is sintered to 650℃,ball-milled,heated to 1400℃and refined by high-energetic ball-milling.Finally,graphene samples is obtained by thermo-treated in 2200℃and 3000℃.Such graphene were characterized by Raman spectroscopy,scanning electron microscopy(SEM),transmission electron microscopy(TEM)and X-ray photoelectron spectroscopy(XPS).The result meets the ideal expectation.(2)Using the prepared graphene powder as a raw material,electrochemical modified graphene oxide(EGO)aqueous solution was prepared by effective and controllable electrochemical method.Parameters of oxidation degree of the prepared product are investigated and optimized,which includes voltage,and electrolyte concentration.EGO solution with such parameter compare to graphene oxide(GO)solution made by novel Hummer method,which includes Raman spectroscopy,SEM,TEM,XPS,Fourier transform infrared spectroscopy(FTIR),ultraviolet spectroscopy(UV-vis),atomic force microscopy(AFM),and thermogravimetric analyzer(TGA).As a result,EGO solution possesses superior qualities.(3)EGO prepared by optimal conditions is utilization in many parts of lithium ion battery,including corrosion inhibitor of aluminum current collector,separator,and anode material.These batteries was tested by electrochemical performance,cyclic voltammetry,AC impedance test and the likes.The results show that EGO has played a role in restraining corrosion in aluminum current collector,so that extend the cycle life of lithium-ion battery.Additionally,EGO applied membrane can reduce the impedance and increase the safety of the lithium ion battery.Lastly,EGO,acting as anode material,displays a high specific capacity in the beginning,but followed by serious deterioration based on a larger specific surface area of EGO.