Processing of Mesophase Coal-Tar Pitch to be used in Lithium Secondary Batteries
| Autor: | Jung-Chi Chao, 趙榮麒 |
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| Rok vydání: | 2003 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 91 In this study electrochemical characteristics of various carbon electrodes made from mesophase coal-tar pitch, used as the anode of the lithium ion batteries have been investigated. The relationship between the capacity of lithium ion batteries and the microstructure and properties of carbon anodes were carefully examined. The X-ray diffraction and Raman spectra were used to examined the structures of mesophase pitch carbon. Elemental analysis to determine the compositions after different heat treatments, the BET method for analyzing the surface area and the density of this carbon material was also measured. Moreover, charge-discharge cyclic tests and cyclic voltammograms were employed to get the electrochemical properties of the batteries and correlated to the different parameters of carbon materials. Discharge capacity of carbons were found to be influenced by the values of Lc, La and BET specific surface area of materials. Synthesizing graphite from mesophase coal-tar pitch was performed by different heating rate during the graphitization process. To study the charge-discharge capacity and reversibility between the carbonized and graphitized mesophase pitch, the mixture of coke and graphite produced from mesophase coal-tar pitch were also used. Different ratios of the carbon materials for the electrode affect the electrochemical behavior of the battery. The mixture of coke and graphite with weight ratio of 5:5 gave to a remarkable change in reducing irreversible electrical capacity to about 165mAh/g, and mentained a high reversible capacity of about 354 mAh/g, with a cyclic efficience of about 68.21%, and a slow decay in discharge capacity. The hysteresis in the voltage profile of mixture was also decreased. Therefore, mixture of coke and graphite material with good electrochemical properties may will be the future material for anodes in the lithium ion batteries. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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