Preparation And Electrochemical Properties Of Three Dimensional Hierarchical Structure V₂O₅

The international maritime organization issued a new requirement in 2020:the sulfur content of ship fuel worldwide will be reduced from 3.5%to 0.5%.The new policy means that vessels sailing on a global scale will use regulated low-sulfur fuels or gaseous fuels such as liquefied natural gas and liquefied petroleum gas.It is urgent to develop a new type of ship energy saving and emission reduction device in the future,which can be used in the engineering field of ship and vehicle.As a new generation of energy storage device,lithium ion battery is widely used in small electrical appliances.However,with the rapid development of electric vehicles and large energy storage equipment,higher expectations have been put forward for the energy density and power density of lithium ion batteries.Nevertheless,V2O5 electrode material is a kind of positive electrode material with bright application prospect because its specific capacity is significantly higher than other traditional positive electrode materials.In view of V2O5 material conductivity low and lithium ion diffusion poor performance and other shortcomings.In this paper,the electrode materials with high electrochemical properties are obtained by means of microstructure regulation and element doping,so as to meet the performance requirements of dynamic lithium ion batteries.Study on the performance of one-dimensional and two-dimensional V2O5.In chapter three,the V2O5 materials with one-dimensional micro-nano rod structure and two-dimensional micro-nano sheet structure were prepared through hydrothermal method by controlling the addition of raw materials(vanadium source)and surfactants.The rod-shaped V2O5 sample has a diameter of about 50-200nm and a length ranging from tens of nanometers to several micrometers.The thickness of V2O5 sample is about 50nm.The capacity of V2O5 rod and V2O5 sheet was 255.9 and 296.2mAh/g,respectively,and the capacity retention rate of V2O5 sheet was 60.5%after 50 cycles,showing good cycling performance..Preparation and properties of three dimensional hierarchical structure V2O5.Three-dimensional hierarchical structure not only has the high specific surface area of one-dimensional and two-dimensional materials,but also has the good self-support of three-dimensional materials,which is not easy to occur agglomeration.In chapter four,V2O5 electrode materials with different morphologies were prepared by using different solvent systems and self-made vanadium solution(VOC2O4)with different reactant concentrations.When the solvent was isopropanol,the V2O5 electrode materials prepared with 0.1mol/L reactant concentration were microspheres with a diameter of 1-2 μm composed of nanosheets,and the morphology of V2O5 electrode materials prepared with 0.2mol/L reactant concentration and 0.3mol/L reactant concentration were microspheres with a diameter of 2-3μm composed of nanowires and nanoparticles,respectively.When the concentration of reactant is 0.3mol/L,the electrochemical properties of the material obtained are optimal.Under the condition of 0.1C,the specific capacity of the first discharge was 300.1mAh/g,and the capacity retention rate was 63.5%after 100 cycles.Under the condition of 4C discharge,the discharge specific capacity was maintained at 143.2mAh/g.The electrochemical properties of the material are better than that of commercial V2O5.At 0.1C,the first discharge specific capacity of commercial V2O5 material is 228.1mAh/g,and the capacity retention rate after 100 cycles is only 40.4%.In order to further improve the lithium ion diffusion ability of V2O5 electrode materials,La and Ce were doped,respectively.After element Ce doping,the lattice volume of the material is increased.The material has a multi-stage spherical structure of micro-nano structure and consists of nano particles with particle size of about 2-5 μm microspheres.The electrochemical properties of doped Ce0.1V2O5 were the best.At 10C,the discharge specific capacity was maintained at 163.1 mAh/g,showing excellent rate performance.It is believed that Ce doping increases the lattice volume and the diffusion coefficient of lithium ions.Moreover,after 200 cycles,the retention rate of the material is as high as 88.9%,with excellent cycling stability.