| Summary: | 碩士 === 國立臺南大學 === 綠色能源科技學系碩士班 === 103 === This research focuses on the tin-modified titanium dioxide synthesized by chemical plating hydrothermal method. We aim to use the Nano-sized (Ti/Sn)O2 composites as electrode materials which can be blended with the water system instead of the organic system. The results show that the first-cycle irreversible capacity can be reduced using the Nano-sized (Ti/Sn)O2 composites. We also utilize X-ray diffraction analyzer to investigate its crystal structure of the Nano-sized (Ti/Sn)O2 composites before and after charge/discharge electrochemical reactions. The investigations include two parts, the first part examines the crystal structure of the electrode material in different charge capacity by Ex-situ X-ray diffraction. The initial structure of the material belongs to a low-angle Rutile crystal phase. With increasing the amount of the inserted lithium ions, the Rutile crystal phase changes to a high-angle Anatase crystal phase. The second part examines the crystal structure of the electrode in different charging and discharging states by In-situ X-ray diffraction analyzer. The results show the initial state of the material is identical with that analyzed by the Ex-situ method. It is also found that the high-angle Anatase (011) crystallizing layers (D-space) is stretched by continuously inserting lithium ions, resulting in the emergence of a new diffraction peak of Li-Anatase (011). When the capacity increases, the low-angle peak significantly shifts to a higher-angle Li-Anatase (011) diffraction peak. This indicates that a structural change occurs in the Nano-sized (Ti/Sn)O2 composite. In addition, the surface layer of stannide for the uncharged cell disappears after several days. The Cyclic Voltammetry (CV), Impedance analysis (EIS) and X-ray photoelectron spectroscopy (XPS) analysis can prove some of the results obtained. The cell itself will proceed low chemical reaction without going through the electrochemical reaction. Our results propose a direct evidence that the stannide will react to form Solid Electrolyte Interphase membrane. Because the membrane can prevent the unexpected reaction of the active material with electrolyte, the cell can have better stability.
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