Study On The Doping And Compounding Of Graphene Films

Since graphene was found,its unique two-dimensional structure and excellent performance have received extensive attention.The study on doping and compounding of graphene films is one of the most rapidly growing research fields,in order to apply graphene film material in real life.Doping can make graphene into a semiconductor of n-or p-type,which can effectively improve the electrical properties of graphene nanoelectronics.Meanwhile,compositing cannot only improve the conductivity and thermal stability of the graphene films,but also sharply improve the mechanical properties.Therefore,the study on the doping and compositing of graphene films will promote the commercial application and development of graphene materials.In our work,the doped graphene films and composite graphene films were prepared by chemical vapor deposition.By optimizing process parameters,the quality of graphene films was improved,which will lay the foundation for its commercial application.Choosing ethylboronic acid as the sole source of carbon and boron and copper foil as catalytic substrate,boron-doped graphene films with large area,high quality and good uniformity are successfully prepared by chemical vapor deposition.The molecular structure of ethylboronic acid determines it can grow boron doped graphene films under a lower reaction temperature compared to the gas source.Moreover,it is low in toxicity as well as in cost and simplifies the preparation process.To explore different growth conditions on the quality of the boron doped graphene films,the pre-treatment and post-annealing of the copper foils were introduced to the growth process and proved to have great influence on the quality of boron doped graphene.High temperature pretreatment on copper foil can reduce the surface defects,promote the growth of crystal grains of copper foil,and then help to improve the quality of the graphene films.The content of B in boron doped graphene film prepared by the pre-treatment of copper foil is about 2.3%.The electrical properties are improved to some extent.In comparison,the electrical properties of boron doped graphene films with annealing treatment were more excellent.However,the content(1.8%)of B in boron doped graphene films with the post-annealing copper foil,is lower than that in boron doped graphene films with preheated copper foil.The possible reason is that the excessively high temperature causes the fractures of the combined B-C bonding,which leads to the decrease in B content.Then using the carbon nanomaterials,such as graphene,as the carbon matrix,copper foil as the catalytic substrate and methane as the carbon source,the silicon nanoparticles/graphene composites were directly grown on the copper foil by chemical vapor deposition method.The effective contact between the silicon nanoparticles / graphene composite films and the copper foil collector was achieved without the use of binder,which will improve the energy density of lithium-ion batteries.We investigated the effects of the structure of graphene carbon nanomaterial and silicon nanoparticles on the dispersion of silicon nanoparticles and the effects of different preparation processing of silicon nanoparticles on the surface morphology of the composite film.When graphene films were composited with the silicon nanoparticles only,the constant increase of the silicon nanoparticles' dispersion concentration can do harm to the quality of composite graphene films.High concentrations of silicon nanoparticles on graphene films can cause the agglomeration of silicon nanoparticles,which will seriously affect the cycle stability of the composite materials.However,the addition of carbon nanotubes cannot only effectively disperse silicon nanoparticles on graphene,but improve the electrical conductivity and cycle stability of the composite materials.By continuous optimizing the experimental conditions and process parameters,the composite graphene films were successfully applied to the anode of lithium ion batteries,and it has good electrochemical performance and excellent cycle stability,which will further promote the application of graphene and silicon nanoparticles composite films in the lithium-ion battery anode materials.