LiFePO4 Incorporated Mesoporous Carbon used as Cathode Materials for Lithium Ion Battery

• Main Authors: Chih-chao Hsu, 許智超
• Other Authors: Bing-Joe Hwanh
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/34305930136708624145

碩士 === 國立臺灣科技大學 === 化學工程系 === 96 === The purpose of the study is to synthesize LiFePO4 materials in the nanochannels of CMK-3 by the previously developed hydrophobic encapsulation route for Li ion battery cathodes. By employing the developed route, nano-sized LiFePO4 could be deposited in the confined space of CMK-3, which could compensate the poor electronic conductivity of LiFePO4 with the aid of continuous carbon mesostructure. Further, the synthesized LiFePO4 could be restricted in the confined space as well, resulting in reduction of the particle size. It would help to reduce the path for Li+ ions during intercalation/de-intercalation process. On the other hand, increase of LiFePO4 in LiFePO4/CMK-3 composite materials was examined by reducing the sucrose concentration during the preparation process. It would be helpful for increase of specific energy density of the composite materials. The crystalline structure of the synthesized composite materials was determined to be Olivine-type structure, indicating the success of LiFePO4 in the composite materials. The observation also shows the broadening of the peaks, exhibiting degrees of LiFePO4 in the confined space. The content of LiFePO4 can be increased up to 81 wt % by reduction of the sucrose concentration during process, but, the carbon nano-rods in the CMK-3 shows no ordering, which may resulted from lowing the sucrose concentration. In addition, the degree of graphitization for all the composite materials shows no difference. The charge-discharge cycling performances of the LiFePO4/CMK-3 composite materials were demonstrated by using coin cells. After 30 cycles, it was found that no obvious degradation was shown for the specific capacity even cycling at high C-rate (degradation rate of LiFePO4/CMK-3(60%) at 2C is only 1.64 %. The discharge capacity of 1st and 30th cycles are 116.2 and 114.3 mAh/g, respectively), indicating possible application in practice.