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Electrochemical Performance of Si-based Material : C Composite Anode for Lithium ion Batteries
http://hdl.handle.net/10076/13065
http://hdl.handle.net/10076/13065740e5043-1560-4453-bf08-e751abf38063
| 名前 / ファイル | ライセンス | アクション |
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2011D008.pdf (2.4 MB)
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| Item type | 学位論文 / Thesis or Dissertation(1) | |||||||
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| 公開日 | 2013-06-11 | |||||||
| タイトル | ||||||||
| タイトル | Electrochemical Performance of Si-based Material : C Composite Anode for Lithium ion Batteries | |||||||
| 言語 | en | |||||||
| 言語 | ||||||||
| 言語 | eng | |||||||
| 資源タイプ | ||||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_46ec | |||||||
| 資源タイプ | thesis | |||||||
| 著者 |
Si, Qin
× Si, Qin
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| 抄録 | ||||||||
| 内容記述タイプ | Abstract | |||||||
| 内容記述 | The volume effects of silicon upon Li insertion and extraction can be effectively suppressed by designing a composite microstructure containing ultrafine silicon which is uniformly dispersed in a ductile conducting carbonaceous matrix with electron/ion conductivity. By this way, in the part 1, several types of Si-based composites have been developed by means of pyrolysis process in accompany with adjunction of CNF in the liquid electrolyte. After only the pyrolysis process, obtained Si/C composite shows fairly rapid capacity decay, although the Si/C composite have better capacity retention than only Si during cycling. The pyrolized carbon matrix alone is not sufficient to accommodate the large volume change of silicon during the cycling, which leads to the cracking and crumbling of the Si/C particles. The loss in electronic contact with the Si particles therefore results in the gradual degradation of the electrode. We found that the CNFs homogeneously dispersed on the Si/C mixture surface form a secondary conductive matrix due to the ability of the CNFs to wrap the Si/C particles, thus holding them together and keeping the electronic contact. With the formation of the secondary conductive matrix, these Si particles are kept in contact within two-layer matrixes of the disordered carbon and the CNFs and thus the capacity of the electrode is largely maintained. Moreover, a new type of the composite was also prepared through the other route, where CNF was covered with pyrolytic carbon derived from PVC. CNF, Si and PVC were mixed and then heated, so that Si and CNF were covered with the PVC-derived pyrolytic carbon. The new composite material has a porous structure. Such a structure offers more free space to buffer the volume changes of LixSi during the Li insertion and extraction process. However, when the particle size is down to below 100nm, silicon active particles are very easy to reunion during the Li-insertion and extraction to form the electrochemical sintering. Moreover, nanometer silicon powder shows a large surface area, so the increase in direct contact with the electrolyte leads to a large irreversible capacity and reduces the coulomb efficiency. In addition, nanometer silicon powder is produced mainly by the laser method, so the preparation costs are very high. An inexpensive micron size of SiO powder was pulverized using HEMM and then mixed with CNF. The electrode performance of the SiO/CNF composite anode was investigated as a function of the milling time and was discussed with respect to the change of the Si valence by the milling time. The high irreversible capacity at the first cycle was compensated by chemically precharging with a lithium thin film attached to the composite electrode. The SiO was ball-milled for 12 h with CNF to produce a composite electrode material that exhibited excellent cycling performance. A reversible capacity of approximately 700 mAh g-1 was observed after 200 cycles. Several factors were considered for the contribution of the improved cycling performance. Firstly, by the micro articulation, the best particle size distribution was obtained for better lithium ion diffusion. Secondly, the flexible CNF may function as a good electronic conductor and formed a good morphology properties effectively acted as a buffering matrix and greatly alleviated the volume changes of Si upon cycling. Finally, the content ratio of Si4+ is not too high, which makes it possible to ensure a certain amount of Si0 capable of reaction and thus to more reliably hold a capacity. Solid-state rechargeable lithium ion batteries are principle and promising power sources for a wide variety of electronics. However, graphitic carbon that is currently used as negative electrode material in the commercial Li-ion batteries appears to be unsatisfied due to low theoretic capacity and poor thermal stability under lithiated state. Therefore, there is even-increasing research in the feasibility of the replacement of graphitic anodes. Part 2 is described the carbon coated nano-Si composite with CNF electrode in PEO (polyethylene oxide) electrolytes. The lithium insertion and extraction performance of a Si/C@CNF composite electrode for a solid-polymer lithium secondary battery was examined. The electrode showed a high reversible capacity and good cycling performance, although the first cycle irreversible capacity was very high. In order to increase the availability of the Si/C@CNF anode, a “precharged” method using lithium sheet was applied. The coulombic efficiency of the precharged electrode for the first cycle was as high as 112% and after the third cycle, the lithium insertion and extraction efficiency reached almost 100%. A reversible capacity of more than 1000mAh g-1 was maintained after 40 cycles. The Si/C@CNF electrode with the PEO-based electrolyte was revealed to have suitable safety characteristics for practical application. These results should contribute to the development of silicon-based anode materials for solid-polymer lithium-ion batteries. | |||||||
| 言語 | en | |||||||
| 内容記述 | ||||||||
| 内容記述タイプ | Other | |||||||
| 内容記述 | 三重大学大学院工学研究科博士後期課程材料科学専攻 | |||||||
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| 内容記述タイプ | Other | |||||||
| 内容記述 | 87p | |||||||
| 書誌情報 |
発行日 2011-01-01 |
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| フォーマット | ||||||||
| 内容記述タイプ | Other | |||||||
| 内容記述 | application/pdf | |||||||
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| 出版タイプ | VoR | |||||||
| 出版タイプResource | http://purl.org/coar/version/c_970fb48d4fbd8a85 | |||||||
| 出版者 | ||||||||
| 出版者 | 三重大学 | |||||||
| 修士論文指導教員 | ||||||||
| 姓名 | 今西, 誠之 | |||||||
| 言語 | ja | |||||||
| 資源タイプ（三重大） | ||||||||
| 値 | Doctoral Dissertation / 博士論文 | |||||||
