Si/C复合材料电极首次嵌锂过程的电化学阻抗谱研究

Electrochemical Impedance Spectroscopic Studies of the First Lithiation of Si/C Composite Electrode

采用球磨法制备了Si/C复合材料,X射线衍射(XRD)和扫描电子显微镜(SEM)测试结果显示Si/C复合材料中硅保持着良好的晶体结构且均匀的分散于炭黑基体中.充放电测试结果表明Si/C复合材料首次放电容量高达3393 mAh/g,4周之后可逆容量均保持在1000 mAh/g左右,表现出较好的循环性能.电化学阻抗谱测试结果显示,Si/C复合材料电极在首次嵌锂过程中分别出现了代表接触阻抗、固体电解质相界面界面膜(SEI膜)阻抗、电荷传递阻抗和相变阻抗的圆弧,并详细分析了它们的变化规律.

The Si/C composite materials were prepared by bail milling method, and characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The result displayed that Si in the Si/C com- posite materials still maintained a good crystal structure and uniformly dispersed in carbon black matrix. The first discharge capacity was 3393 mAh/g, and 4 cycles later still retained 1000 mAh/g, showing better charge-discharge cycle performance. Electrochemical impedance spectroscopy test indicated that there appeared three semicircles respectively representing the impedance of contact problems, solid electrolyte interface film （SEI film）, charge transfer and phase transformation in the first lithiation, and their evolutive principles were also investigated.