Copper Sulfide And Vanadium-Based Compound:Solvothermal Synthesis And Applications In Lithium Lon Batteries

The increasingly serious crises of the energy and environment in the21st century make people have a higher demand on the production and conversion of energy. Due to its high selectivity and high efficiency, nanomaterial is one of the most optimal choices. For example, choosing nanomaterial as the electrode material in the lithium ion battery has become a very popular research subject in the whole world. As we all know, the products of solvothermal synthesis method have a lot of unique merits such as high crystallinity, high purity, less aggregation and so on. The goal of this dissertation is to synthesis transition metal oxides and sulfides with different morphologies controllably, such as3D micro-nanostructures and2D graphene-like structures. According to the characteristics of material itself, we discuss the influences of temperature and time on the morphologies and compositions of these micro-nanostructures, study their electrochemical behaviors in the lithium ion battery, in the further, contrast the properties of materials having different morphologies. The main points are summarized briefly as follows:1. We successfully synthesized monodispersed CuS nanospheres with a diameter of about200nm consisted of nanoplates with the thickness of10nm by a hydro/solovthermal strategy without any surfactant. The PL and UV-Vis absorption spectrums both exhibit some degree blue shift attributed to the quantum confinement of the CuS nanoplates. The electrochemical performances of CuS nanospheres were studied both in organic and aqueous lithium-ion batteries. There have two discharging platforms, one of which is in the window of aqueous solution on the electrochemical reaction. It may be a promising candidate of cathode material in aqueous lithium-ion batteries.2. Vanadyl ethylene glycolate (VEG) spherical microstructures composed of nanocube-based with an average diameter of-400nm were solvothermally prepared at180℃. The influence of temperature in solvothermal process was investigated. When the temperature rised to250℃, the products transformed from VEG (IV) spheres to (NH4)2V6O16(V) flakes.The electrochemical properties of vanadyl ethylene glycolate in rechargeable lithium batteries were firstly investigated. At a current density of60mA/g the initial specific discharge capacity is1826mA/g and even after200cycles the discharge capacity is still maintained at477mA/g,which exbits high discharge capacity and good cycling stability. V2O3with different morphologies were also prepared by a simple top-down precursor-pyrolyzation strategy, which is also a promising electrode material in lithium-ion batteries.3. Without any surfactant, V2O3graphene-like structures by the top-down precursor-pyrolyzation strategy had been synthesized controllably. Interestingly enough, these ultrathin V2O3nanosheets which should exist temperature-induced reversible metal insulator transition represents a brand new two-dimensional material having metallic behavior. Meanwhile, we successfully realized controllable synthesis of3D flower-like structure precursor composed of nanaosheets having different diameter, packing density, and thickness of nanosheets by adjusting temperature and time. Using different gases, the V2O3and V2O3/C with the perfect inheritance of the morphology of their precursors were prepared by top-down precursor-pyrolyzation strategy. Compared with the V2O32D ultrathin sheets,3D flower-like structures and their composites with carbon coating, at the current density of200mA/g, the discharge capacity of V2O3/C3D flower-like micro-nanostructures is still maintained at360mAh/g after80cycles, which exbits excellent discharge capacity and superior cycling stability.4. Graphene nanosheets (1-3graphite layers)had been solvothermally synthesized through reducing hexachloro-1,3-butadiene (C4Cl6) by Metallic sodium in polyethylene glycol (PEG-600) at300℃...