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哟哟william

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虫号: 1254368
注册: 2011-04-03
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专业: 固体与表面物理化学

[求助] 小段英文翻译，求助。各路大神速来呀！！！

To understand the reason for the superior electrochemical performance
of the sulfur–carbon composite synthesized by the in
situ sulfur-deposition route, EIS measurements were carried out
with the coin cells. The Nyquist profiles of the pure sulfur and
sulfur–carbon composite cathodes and the equivalent circuits are
shown in Fig. 8. Re refers to the resistance of electrolyte, Rct refers
to the charge transfer resistance between the interfaces of carbon/
sulfur/electrolyte, Wo refers to the Warburg impedance, and
CPE refers to the constant phase element [23]. The resistance of
electrolyte was estimated from the intersection of the front end of
semicircles with the Z axis, which is similar for both the cathodes.
The diameter of the impedance semicircles is related to the charge
transfer resistance, which is a measure of the difficulty involved
for charges crossing the boundary between the electrode and electrolyte.
Before cycling, the sulfur–carbon composite cathode has
a slightly lower charge transfer resistance value than the pure sulfur
cathode, which is expected considering its higher first discharge
capacity compared to that of the pure sulfur cathode. The close contact
between the conductive carbon black and the insulating sulfur
lowers the resistance for electrons transferring across the interface
between them. In the subsequent cycles (1st, 25th, and 50th), the
charge-transfer resistance of the pure sulfur cathode grows much
larger than that found with the sulfur–carbon composite cathode.
The main reason for this is the porous structure of the cycled pure
sulfur cathode. Electrons passing across the boundary between conductive
carbon and active material are impeded by the irreversible
formation of the Li2S layer in the pores [10]. The EIS measurements
thus reveal that the sulfur–carbon composite cathode exhibits better
electronic conductivity and lithium-ion transport than the pure
sulfur cathode due to the stable network structure of carbon black
wrapping around the sulfur. The impedance of the sulfur–carbon
composite after 50th cycles does not increase much, suggesting that
the network structure maintains its integrity during the cycling
process.

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1楼 2013-04-26 21:19:39

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南京工大

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哟哟william: 金币+10, 翻译EPI+1, ★有帮助 2013-04-26 22:42:55

为了更好的理解通过原位硫沉积法制备的硫-碳复合物电极具有良好电化学性能的原因，我们使用扣式电池进行了电化学阻抗谱的测试。图8中所表示的是纯的硫，硫碳复合物电极，以及对应电路的尼奎斯特图像。其中，Re代表电池液的电阻，Rct代表碳/硫/电池液界面间电荷转移的阻力，Wo代表瓦尔堡阻抗，CPE代表常相角元件。电池液以及阴极的电阻通过图线中半圆形曲线的前端与Z轴的交点确定。阻抗曲线的直径与电荷转移的阻力相关，通过该值可以测定电荷穿越电极和电池液界面的难易。在循环前，硫碳复合物电极的电荷传递阻力值略小于单纯硫电极，考虑到它与单纯硫电极相比较高的首次放电能力，这一点是可以理解的。导电炭黑与绝缘体硫的紧密接触减小了两者界面上电子传递的阻力。在后面的循环中（第一次，第25次，第50 次），单纯硫电极的电荷传递阻力增大程度要远大于硫碳复合物电极。单纯硫电极的多孔结构导致了这一现象的出现。电子在穿过导体碳和活性材料之间的界面时，被孔中不可逆生成的Li2S层阻碍。电化学阻抗谱的测试结果显示，硫碳复合物电极中，炭黑包裹在硫的表面生成稳定的网络结构，使其与单纯硫电极相比具有更好的电子传导性能以及锂离子传输性能。硫碳电极在50次循环后，阻抗并没有明显的增加，显示了其网络结构在循环过程中保持了很好的完整性。