Synthesis Of Cathode Material For Li-ion Batteries Via Sol-Gel And Electrospinning Methods

Experimental devices with different electric field distribution were designed for software simulation. The effect of electric field distribution on the electrospinning was investigated by the electric field simulation combined with the experimental results. The nanostructured fibers with different morphologies were prepared by the electrospingning combined with the sol-gel method and characterized by a variety of means. The fibers were used as a kind of new cathode materials for micro-batteries and their electrochemical properties were detailedly investigated in order to increase electrochemical performance. The contents include the preparation of the fibers and the control of fiber morphology, the investigation of electrochemical performance as the cathode materials for lithium ion batteries.In the chapter one of this thesis, the electrospinning was introduced briefly. The contents include historical development, basic principles and processes. It focuses on the theory of the electrospinning, which provides theoretical guidance for the application of the electrospinning technology. In the below content, the application of the fibers was presented and the development of the electrospinning technology opens up a broad space for the applications of the nanofibers. In the sencond, the sol-gel process was introduced briefly. The contents include the phylogeny, character and principle of the sol-gel process. A great deal of attention had been paid for the influence of the processing parameters on every step. At last, the application and development of sol-gel combined with the electrospinning in the preparation of nanofibers were introduced.We design multi-nozzle electrospinning equipments which have different electric field distribution, one is conventional needle equipment and another is auxiliary-plate needle equipment. The impact of the spacing of multi-nozzle on the maximum electric field strength at the tip of the nozzles in multi-nozzle arrangement was investigated via finite element method (FEM), and the results were compared with single-nozzle system. It can be seen that the maximum electric field of multi-nozzle arrangement has been significantly weakened due to the influence of another needle in the arrangement, and the field varied very little as a function of needle spacing for the range used in this study. Experimental results showed that the multi-nozzle electrospinning head performed much better than single-nozzle system, and the spacing of multi-nozzle had some relationship with the diameter and discrete distribution of the spun fiber.In the third chapter, Hierarchical structures of Li1+xV3O8nanorods growing on electrospun fibers were successfully synthesized by electrospinning and calcinations. The products were characterized by field-emission scanning election microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectra. The formation mechanism of the hierarchical structures was investigated, showing that the morphology of the hierarchical structures was mainly determined by the calcined conditions. Electrochemical properties of the Li1+xV3O8hierarchical structures were investigated by cyclic voltammetry and charge-discharge experiments, and the results demonstrated that the Li1+xV3O8hierarchical structures exhibited a high discharge capacity and excellent cycling stability.The Mg, B-doped LiFePO4nanostructured fibers were prepared by the electrospinning with the sol-gel method. The doping of Mg effectively increased the conductivity of the material, thereby improving its charge-discharge capacities. On the other hand, the doping of B effectively improved the micro-structure of the fibers, thus contributing to the improved stability of the electrochemical cycle. Mg, B-dopedLiFePO4nanostructure fiber will effectively improve the performance of the lithium-ion battery electrode materials, is a very promising cathode material.Hollow BaFe12O19/Fe2O3composite fibers were prepared by co-electrospinning related sol-gel method. The organic additives were added into the BaFe12O19sols to adjust the properties of the sols. During the calcined process, the properties of sols obviously affected the desiccation and sinter of xerogel fibers, which resulted in hollow BaFe12O19/Fe2O3composite fibers. The heating rate had also an important influence on the morphologies of BaFe12O19/Fe2O3fibers, the decrease of surface tension of the sol and appropriate heating rate were favorable for the hollow structure.In the chapter6, a metal-organic compounds were prepared through a self assembled reaction between a novel ligand (three iodine benzene acid) and the lanthanide metal ion Sm. We analysized their structures, and found the compounds have stronger thermal stability, and better fluorescence properties.