Towards a Fundamental Understanding of the Improved Electrochemical Performance of Silicon–Carbon Composites
Towards a Fundamental Understanding of the Improved Electrochemical Performance of Silicon–Carbon Composites
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DOI：
10.1002/adfm.200600937
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发表时间：
2007-07
影响因子：
19
通讯作者：
J. Saint;M. Morcrette;D. Larcher;L. Laffont;Shane Beattie;Jean-Paul Pérès;David Talaga;Michel Couzi
中科院分区：
文献类型：
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作者：
J. Saint;M. Morcrette;D. Larcher;L. Laffont;Shane Beattie;Jean-Paul Pérès;David Talaga;Michel Couzi
以聚氯乙烯(PVC)和硅粉为原料，在900℃、氮气气氛下进行热解，制备了由镶嵌在致密、无孔碳基质中的硅颗粒组成的硅碳复合材料。与微米级(1-10μm)和纳米级(10-100 nm)的纯Si粉末相比，这种粉末的循环性能较差，15次循环后几乎没有剩余容量，而复合材料的织构大大提高了Si与Li合金化反应的可逆性。例如，对于含有纳米硅颗粒的硅-碳复合材料，20次循环(0-2.0V vs.Li+/Li)的容量可达到约1000 mA/g-1。我们还证明，即使没有释放游离的硅，温和的手工研磨处理也会将复合材料的循环性能降低到与母体硅一样低的水平。结合拉曼光谱数据进行的电化学测量表明，原位生成的碳对硅电畴施加了很大的应力。这种碳诱导应力在球磨过程中消失，表明碳诱导压力以及随之而来的电连接性的改善是改善Si与Li循环行为的关键参数。
Silicon–carbon composites consisting of Si particles embedded in a dense and non‐porous carbon matrix are prepared by the pyrolysis of intimate mixtures of poly(vinyl chloride) (PVC) and Si powder at 900 °C under a flow of N2. In contrast to bare micrometer‐sized (1–10 μm) and nanometer‐sized (10–100 nm) Si powders, which show poor cycling behavior with almost no capacity remaining after 15 cycles, the texture of the composite is seen to greatly enhance the reversibility of the alloying reaction of Si with Li. For instance, a capacity of ca. 1000 mA h g–1 is achieved for 20 cycles (0–2.0 V vs. Li+/Li) for a silicon–carbon composite containing nanometer‐sized Si particles. We also demonstrate that a mild manual grinding treatment degrades the cycling performance of the composites to levels as low as the parent Si, even though free Si is not released. The electrochemical measurements in conjunction with Raman spectroscopy data indicate that a huge stress is exerted on the Si domains by the in situ formed carbon. This carbon‐induced stress is found to disappear during the milling of the composites, indicating that the carbon‐induced pressure, along with the accompanying improvement in electrical connectivity, are the key parameters for the improved cycling behavior of Si versus Li.