Pyrolyzed Polysiloxanes for Use as Anode Materials in Lithium‐Ion Batteries
Pyrolyzed Polysiloxanes for Use as Anode Materials in Lithium‐Ion Batteries
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DOI：
10.1149/1.1837828
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发表时间：
1997-07
影响因子：
3.9
通讯作者：
W. Xing;A. Wilson;K. Eguchi;G. Zank;J. Dahn
中科院分区：
文献类型：
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作者：
W. Xing;A. Wilson;K. Eguchi;G. Zank;J. Dahn
合成了60多种含不同有机官能团的硅氧烷聚合物。合成的硅氧烷聚合物在1000℃的惰性气体中热解，化学分析表明，热解产物分布在Si-C-O-Gibbs相图上明确的区域内。分别用硬币形测试电池和X射线粉末衍射仪测试了材料的电化学性质和结构性能。最有趣的材料在连接碳和SiO 1.3的Si-C-O Gibbs三角形中的线附近找到。锂的可逆比容量最大的材料(约900毫安/克)就在这条线上，其碳含量约为43%，氧含量约为32%，硅含量约为25%(原子百分比)。几乎为纯碳的材料表现出无序碳的特征的衍射图。在从碳到SiO 1.3这条线上，样品结构可以描述为单组或小组石墨烯薄片与Si-C-O非晶态玻璃区域的混合。玻璃的数量和成分根据总体样品成分的不同而变化。从碳到SiO 1.3，可逆容量首先从纯碳的约340mAhg上升到接近50%碳的最大值900mAhg，然后在碳含量为0%时下降到接近于零的mAhg。这表明，非晶态玻璃可以与锂发生可逆反应，前提是碳的存在为电子和锂离子提供了一条路径。然而，电压分布中的滞后(充放电电压之差)和不可逆容量沿这条线路几乎是线性增加的。这些材料的不可逆容量和磁滞与其含氧量有明显的相关性。沿着连接碳和硅的线，可逆容量从纯碳的340mAhg增加到含约15%Si的样品的约600mAhg。然后，当成分接近碳化硅时，它下降到接近零。在C-SiC线上，不可逆容量保持在200mAh/g以下。我们确信，优化后的含硅碳可以作为锂离子电池负极材料的良好替代品
More than sixty siloxane polymers containing various organofunctional siloxane units were synthesized. The synthesized siloxane polymers were pyrolyzed in inert gas at 1000°C. Chemical analysis showed that the products of pyrolysis were distributed over a well-defined region in the Si-C-O Gibbs phase diagram. The electrochemical and structural properties of these materials were measured using coin-type test cells and x-ray powder diffraction, respectively. The most interesting materials are found near the line in the Si-C-O Gibbs triangle connecting carbon to SiO 1.3 . Materials with the largest reversible specific capacity for lithium (about 900 mAh/g) are on this line and were at about 43% carbon, 32% oxygen, and 25% silicon (atomic percent). Materials which were almost pure carbon showed diffraction patterns characteristic of disordered carbons. Along the line from carbon to SiO 1.3 the sample structure can be described as a mixture of single or small groups of graphene sheets mixed with regions of Si-C-O amorphous glass. The amount and composition of the glass changed according to the overall sample composition. Moving from carbon to SiO 1.3 , the reversible capacity first rises from about 340 mAh/g for pure carbon, to a maximum of 900 mAh/g near 50% carbon, and then falls to near zero mAh/g at 0% carbon. This suggests that the amorphous glass can reversibly react with lithium, provided the carbon is present to provide a path for electrons and Li ions. However, the hysteresis in the voltage profile (difference between charge and discharge voltages) and the irreversible capacity increase almost linearly along this line. There is a clear correlation between both the irreversible capacity and hysteresis in these materials with their oxygen content. Along the line connecting carbon to silicon, the reversible capacity rises from 340 mAh/g for pure carbon to about 600 mAh/g for samples with about 15 atomic percent Si. It then decreases to near zero as the composition nears SiC. Along the C-SiC line, the irreversible capacities remain below about 200 mAh/g. We are quite convinced that optimized silicon-containing carbons can be good alternatives to pure carbons as anode materials in lithium-ion batteries