纳米碳管的电化学贮锂性能

用透射电镜、高分辩透射电镜、X射线衍射和拉曼光谱表征了用催化热解法制备的纳米碳管的结构,研究了纳米碳管的电化学嵌脱锂性能.以纳米级铁粉为催化剂热解乙炔气得到的纳米碳管石墨化程度较低,结构中存在褶皱的石墨层、乱层石墨和微孔等缺陷,具有较高的贮锂容量,初始容量为640mAh/g,但循环稳定性较差.而以纳米级氧化铁粉为催化剂热解乙烯得到的纳米碳管结构比较规则,循环稳定性较好,但贮锂容量较低,初始容量为282 mAh/g.讨论了纳米碳管的结构对其温度特性和不同电流密度下的充放电容量的影响.

Characteristics of Electrochemical Insertion Lithium of Carbon Nanotubes

The microstructure of the carbon nanotubes were characterized by means of transmis-sion electron microscope, high-resolution transmission electron microscope, X-ray diffraction and Raman spectra. The effects of the microstructure on their properties of electrochemical insertion were investigated. The carbon nanotube, which preparaed by catalytic decomposition of acetylene using iron nanoparticles as catalyst, showed a low degree of graphitization. There were large amount of the defects such as wrinkled graphite sheets, interstitial carbon atoms, unorga-nized graphitic structure and microcavities in this nanotube and lead to a higher specific capacity, which is 640mAh/g at first cycle. But the defect structure resulted in a low cycling stability. After 40 cycles, its capacity was degraded to 58% of the original one. The carbon nanotube, which prepared by the pyrolysis of ethylene catalyzed by iron oxide nanoparticales, showed a high degree of graphitization and a rule microstructure. The well-graphitized carbon nanotube exhibited a low electrochemical storage lithium capacity, which is 282mAh/g at first cycle. But it showed a good cycling stability. After 40 cycles, the capacity maintained 86% of the original capacity. The influences of the temperature and charge/discharge current densities on their electrochemical storage lithium capacities were also discussed.