Surface fluorination and electrochemical behavior of petroleum cokes graphitized at medium and high temperatures for secondary lithium battery
Surface fluorination and electrochemical behavior of petroleum cokes graphitized at medium and high temperatures for secondary lithium battery
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DOI：
10.1016/j.jfluchem.2005.03.016
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发表时间：
2005-07-01
影响因子：
1.9
通讯作者：
Iwata, H
中科院分区：
文献类型：
--
作者：
Li, JL;Naga, K;Iwata, H
研究了2100℃和2600℃热处理的石油焦（简称PC2100和PC2600）以及200℃和300℃氟元素氟化的石油焦的表面结构和电化学性能。XPS研究表明，表面氟与碳以共价键结合，表面氟含量在4.9-17.8 at.%范围内。通过氟化减少表面氧。氟化前后的BET表面积几乎相同。氟化增强了在15 80 cm(-1)（G带）和1360 cm(-1)（D带）处观察到的两个拉曼位移中的D带强度，表明表面无序性增加。在 150 mA/g 的高电流密度下，观察到在 200 摄氏度氟化的 PC2100 以及在 200 和 300 摄氏度氟化的 PC2600 的容量增加。最有趣的结果是表面氟化提高了第一库仑效率。在 300 摄氏度下氟化的 PC2600 的首次库伦效率在 60 mA/g 和 150 mA/g 下分别提高了 12.1% 和 25.8%。阻抗测量表明，碳电极表面薄膜的电阻因氟化而增加，然而，200℃氟化的PC2100的电荷转移电阻降低了12.3%，200℃和300℃氟化的PC2600分别降低了27.5%和6.4%。对于在 200 摄氏度下氟化的 PC2100 以及在 200 和 300 摄氏度下氟化的 PC2600，电荷转移电阻的降低与电荷容量的增加一致。(c) 2005 Elsevier B.V. 保留所有权利。
The surface structure and electrochemical performance have been investigated of petroleum cokes heat-treated at 2100 and 2600 degrees C (abbreviated to PC2100 and PC2600) and those fluorinated by elemental fluorine at 200 and 300 degrees C. XPS study indicated that surface fluorine was covalently bonded to carbon and surface fluorine contents were in the range of 4.9-17.8 at.%. Surface oxygen was reduced by fluorination. BET surface areas were nearly the same before and after fluorination. Fluorination enhanced D-band intensity in two Raman shifts observed at 15 80 cm(-1) (G-band) and 1360 cm(-1) (D-band), indicating the increase in the surface disordering. At a high current density of 150 mA/g, the capacity increase was observed for PC2100 fluorinated at 200 degrees C and for PC2600 fluorinated at 200 and 300 degrees C. The most interesting result was the increase in first coulombic efficiencies by surface fluorination. First columbic efficiencies for PC2600 fluorinated at 300 degrees C were increased by 12.1% at 60 mA/g and by 25.8% at 150 mA/g, respectively. The impedance measurements showed that the resistances of surface films on carbon electrodes were increased by fluorination, however, the charge transfer resistances were decreased by 12.3% for PC2100 fluorinated at 200 degrees C, and by 27.5 and 6.4% for PC2600 fluorinated at 200 and 300 degrees C, respectively. The reduction of the charge transfer resistances was consistent with increase in the charge capacities for PC2100 fluorinated at 200 degrees C and PC2600 fluorinated at 200 and 300 degrees C. (c) 2005 Elsevier B.V. All rights reserved.