Knowledge Management System Of Institute of process engineering,CAS
硅由于其极高的理论比容量(4200mAh/g)、较低的嵌锂电压、资源丰富等优点，被认为是最有希望替代石墨的下一代锂离子电池负极材料。但是硅负极在嵌脱锂过程存在较大的体积膨胀问题，导致电池的循环性能变差，从而制约了硅负极在锂离子电池中的实际应用。本论文通过使用不同的工艺方法和调控手段制备出了新型硅基负极材料。负极材料中的二维材料构建成了导电网络，硅被可控地嵌入二维材料网络框架之中，合理的材料结构有效的缓解了硅在循环过程中的膨胀问题。同时应用大量的表征手段对制备的材料进行表征，探究复合材料在循环充放电中的形貌变化和储锂机制。主要研究内容和结果如下：1.利用超临界二氧化碳超高的渗透性能，石墨首先被剥离成具有高机械强度的可折叠二维石墨片。同时利用超临界流体高扩散性的特点，纳米硅粉和碳纳米管被均匀地分散在可折叠石墨层间。所有的组分在超临界流体的帮助下被可控的组装成具有多层级导电网络结构的硅基负极材料。二维的折叠石墨和碳纳米管构建的导电网络，加快了整体电极的载流子传输速率，并在一定程度上缓解了纳米硅粉的膨胀问题。对制备出的材料进行电化学性能测试，结果表明该材料具有优异的循环性能和倍率性能。2. 二维材料MXene因为具有金属级导电性、丰富的表面化学等特点而在储能领域受到广泛的关注。该工作将纳米硅粉用PDDA改性使其表面带上正电荷。从MAX中刻蚀得到的MXene表面附有多种基团，所以MXene表面带有负电荷。将MXene与改性的到的纳米硅粉在液相条件下通过静电自组装制备出具有三维导电网络的MXene-Si复合材料，电化学表征证明制备获得的材料具有优异电化学性能。;Silicon is considered to be the most promising next-generation lithium-ion battery anode material because of its high theoretical specific capacity (4200 mAh/g) low lithium insertion voltage and abundant resources. However, silicon anode has a large volume expansion problem during the electrochemical charge/discharge cycle process, which causes the problem of unstable cycling performance and further limits its practical application in lithium-ion batteries.In this thesis, new silicon-based anode materials were prepared by different process methods and control methods. A two-dimensional material conductive network framework was constructed and silicon is controllably embedded in the two-dimensional material network framework。 The reasonable material structure effectively alleviates the problem of silicon expansion during the charge/discharge process. At the same time, many characterization methods were applied to test the prepared materials. The morphological changes and lithium-ion storage mechanism of the anode materials during the cycling process were explored. The main research contents and results are as follows:1. With the super-permeability of supercritical carbon dioxide, graphite was first stripped into two-dimensional foldable graphite sheet with high mechanical strength. Meanwhlie, supercritical fluids with the high diffusivity is used to uniformly disperse nano-silicon powder and carbon nanotubes between foldable graphite layers. With the help of supercritical fluid, all the components were controllably assembled into a silicon-based anode material with a multi-level conductive network. The conductive network constructed by two-dimensional folded graphite and carbon nanotubes accelerates the electrons and ions transmission rate in the overall electrode and alleviates the expansion problem of nano-silicon powder. The electrochemical performance test of the prepared material shows that the material has excellent cycle performance and rate performance.2. The two-dimensional material MXene is widely concerned in the field of energy storage because of its metal-level conductivity and rich surface chemistry. In this work, the nano-silica powder was modified with PDDA to make the surface positively charged. The surface of MXene etched from MAX has a variety of groups attached to it, so the surface of MXene is negatively charged. MXene and modified nano-silica powder were prepared by electrostatic self-assembly in liquid-phase conditions. The prepared MXene-Si composite material has three-dimensional conductive network. The electrochemical characterization proved that the prepared material had excellent electrochemical performance.
|王晓阳. 二维材料/纳米硅多层级复合负极材料的制备及其电化学性能研究[D]. 中国科学院大学,2020.|
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