The Production Of Graphene Sheets And The Electrochemical Properties Of Graphene Based Composite Materials As Anode Material In Lithium-ion Batteries

Graphene sheets are two-dimensional carbon nanomaterials. For its excellent performance in both material science and physics science, graphene sheets have the important scientific research value and extremely wide application prospect. In this paper, high quality graphene sheets are synthesized through efficient oxidation process followed by rapid thermal expansion and reduction by H2. The lithium storage performance of graphene sheets and composite is also researched.The product in each stage of the process is characterized by elemental analysis, thermo-gravimetric analysis, scanning electron microscopy, and fourier transform infrared spectroscopies. During the preparation of graphite oxide, the oxidant promoted the increase of the oxidation of graphite oxide. In addition, the graphite particles of smaller particle size were more easily oxidized. In the production of expansion graphene, the expansion temperature can not affect the extent of expansion but reduce the oxidation degree of expansion garphene. In fact, the high temperature expansion is the process of pyrolysis reduction. When the H2 was used for the reduction of expansion graphene sheets, the reductive degree is promoted by the increase of reaction temperature. However, the reduction efficiency at 500℃is similar with that at 700℃. So it is benefit for reducing the energy loss and easily implementing to use a lower reaction temperature.The number of graphene layers is controlled by tuning the oxidation degree of GOs. The higher the oxidation degree of GOs is getting, the fewer the numbers of graphene layers can be obtained. The graphene sheets with fewer layers as the lithium battery anode material have higher reversible capacity.The graphen/graphite composite as anode electrode materials for lithium-ion batteries were prepared by the method of simple mixed. The electrochemical properties of graphen/graphite composite are also discussed. The results show that the graphen/graphite composites combine the advantages of graphite and graphene. It is helpful for increasing the capacity of batteries to add the graphene sheets. The formation of the voltage platform is promoted by the increase of the graphite ratios in the graphen/graphite composites.