Fabrication Of VO₂-rGO Nanosheets And Their Performance For Lithium Ion Battery

Energy crisis forced people to the development and utilization of new energy, wind energy, solar energy, nuclear power and other new energy sources need to be converted into secondary energy before use due to their characteristics. Electricity energy has become the first choice for it's easy to use, clean and pollution-free advantages. However, a steady supply of electricity has become a major issue for power applications, a simple and effective solution is to use the power storage device. Lithium-ion batteries has been widely used because of its high energy density in storage areas, however, the common electrode materials have a poor stability and conductivity which limiting its development. In this paper, we prepared vanadium oxide-graphene nanosheets, by coating the graphene to improve conductivity and stability of vanadium dioxide, thereby increasing its lithium-ion battery cycle life and specific capacity. The main contents are as follows:(1) Preparation of nanosheets ammonium vanadate. It is divided into two steps: ? Vanadium pentoxide is reduced by urea under molten state, by controlling the reaction time and temperature we can regulate the ratio of vanadium in different valence states, and thus synthesis of (NH4)V3O8 with a cube morphology. ?reparation of (NH4)2V4O9 nanosheet by hydrothermal reaction of (NH4) 2V3O8 and Li2CO3. The study found that during the hydrothermal process, lithium ions can be inserted into the lamellar structure of (NH4) 2V3O8 Which leads stripped of (NH4) 2V3O8, Pentavalent vanadium dissolved from the (NH4) 2V3O8 nanosheets and the remaining tetravalent vanadium restructuring form into (NH4)2V4O9 nanosheets in alkaline solution.(2) Preparation of vanadium dioxide nanosheets. Prepared of vanadium dioxide nanosheets by calcined (NH4)2V4O9 nanosheets under a nitrogen atmosphere. Research shows that with the increase of the calcination temperature, Metastable monoclinic vanadium dioxide is gradually transformed into Monoclinic vanadium dioxide.(3) Preparation of VO2-RGO nanosheets. (NH4)2V4O9 nanosheets and graphene oxide can be better dispersed in aqueous ethanol, when adding strong cationic electrolyte, (NH4)2V4O9 and graphene oxide will be coprecipitation through electrostatic interaction, reduced by hydrazine we can be obtained (NH4)2V4O9-RGO nanosheets, when calcination at high-temperature VO2-RGO nanosheets is obtained.(4) Lithium-ion battery properties. Prepare of button batteries with vanadium oxide, VO2-RGO nanosheets and lithium as the cathode and anode material respectively, then analyzing it's lithium-ion properties, explore the impact of coated graphite.