Study On Preparation And Electrochemical Properties Of Carbon-Coated Ferroferric Oxide Graphene Composite Materials

The technologies of energy storage have been developed much today, lithium batteries are the most common-used devices now. Many devices have reached a quite high current density, however, they still not satisfied consumers' needs, so some new materials are extremely urgent. Recently, metal oxides have shown some desirable properties such as their high theoretical capacity,500-1000 mA h/g, compared with conventional graphite ?372 mA h/g?. But most of the transition metal oxides usually have poor electronic conductivity, so Fe₃O₄ gradually come into people's views, with their high capacity, low cost, economic friendly and low toxic. Despite all this, as a electrode, Fe₃O₄ has suffer from varieties of problems such as volume expansion, crack of electrode, agglomeration of materials. To solve these problems, this work used some methods, carbon-coated and RGO added, to promote the material's electrochemical properties. Some details of our research are presented as follows:1. Prepared Fe₃O₄ nanoparticles with hydrothermal method and H2 reduction. After electrochemical characterization, we found that their reversible capacity was 335.4 mA h/g after 100cycles at the current density of 100 mA/g, which showed a relatively good electrochemical property.2. Successfully prepared carbon-coated Fe₃O₄ with hydrothermal method, using glucose as carbon source. Carbon was not only the reduction of the chemical reaction, but also protect matrix and act as a volume buffer during the electrochemical tests. Besides, the existence of carbon promotes the conductivity of the materials. These effects together advanced the electrochemical properties of the materials.3. The thickness of outer surface carbon also influences the electrochemical properties of the materials. A moderate carbon layer's thickness leads a higher electrochemical property. At the current density of 100 mA/g, the reversible capacity of carbon-coated Fe₃O₄-1200 is 900 mA h/g, which is 2.73 times of Fe₃O₄ ?335 mA h/g?. Moreover, carbon-coated Fe₃O₄ nanocomposites are also shown a gradual increase in cycle performance.4. By solvent vaporization process, carbon-coated Fe₃O₄@RGO was prepared. Graphene can improve the conductivity of the material through two aspects. The first aspect is the conductivity of graphene itself. The another one is that the carbon coated Fe₃O₄ nanoparticles can distribute homogeneously on the surface of graphene and lead a conductive network which is benefit to electrons' transfer.