The Preparation And Electrochemical Preformance Of Graphene-metal Oxide Nanocomposites

Lithium-ion batteries have been an important power source at present, because of its high energy, high voltage, long life, no memory effect and little self-discharge characteristics. On the one hand, the graphene shows special advantages as a support with application in anode material of lithium-ion batteries, due to its unique physicochemical properties including large surface area, superior electronic conductivity and high chemical stability; on the other hand, metal oxides show high theoretical storage capacity as an anode material for lithium-ion batteries. Therefore, we prepared graphene-metal oxides composites including Fe₃O₄/graphene, SnO₂–TiO₂/graphene and MoO₂–Fe₃O₄/graphene nanocomposites, and characterized their microstructural and electrochemical properties through a variety of testing methods.Fe₃O₄/graphene nanocomposite was prepared via a hydrothermal method using FeSO₄ and graphite oxide as raw materials and sodium gluconate as the auxiliary addition. After the hydrothermal process, the graphite oxide was reduced to graphene and nano Fe₃O₄ particles were evenly distributed on the surface of graphene sheets. The as-prepared Fe₃O₄/graphene nanocomposite exhibits excellent electrochemical properties. The initial discharge and charge capacities were 1456 mAh g^-1 and 739.9 mAh g^-1 at high current density of 500 mA g^-1. Additionally, the charge capacity was also retained at 698.3 mAh g^-1 after 200 cycles.SnO₂–TiO₂/graphene ternary nanocomposite was prepared via a simple reflux method. First, the SnCl2·2H2O and graphite oxide mixed solution was refluxed; then, Ti?OC4H9?4 was added into the above mixed solution and refluxed again. After 100 cycles, the reversible discharge capacity of the SnO₂–TiO₂/graphene nanocomposites was still maintained at 1159.4 mAh g^-1 at a current density of 100 mA g^-1, showing high reversible capacity and long cycle life.MoO₂–Fe₃O₄/graphene nanocomposite was prepared by a hydrothermal-reflux method. In the hydrothermal process, MoO₂/graphene composite was prepared via adding ammonium molybdate, graphite oxide and ascorbic acid into a Teflon-lined stainless steel autoclave. In the reflux process, MoO₂–Fe₃O₄/graphene ternary nanocomposite was prepared using the MoO₂/graphene and FeSO₄ as raw materials. The ultrafine MoO₂ nanoparticles and nanosized Fe₃O₄ were homogeneously distributed on the surface of graphene sheet. After 100 cycles, the initial charge specific capacity of Mo O₂–Fe₃O₄/graphene nanocomposite is 1154.9 mAh g^-1 at 200 mA g^-1, which is 125% comparing to the initial charge capacity.