硅银碳纳米杂化锂离子电池负极材料的制备及性能研究

发布时间：2018-01-01 18:14

本文关键词：硅银碳纳米杂化锂离子电池负极材料的制备及性能研究　出处：《中北大学》2017年硕士论文　论文类型：学位论文

【摘要】：硅的质量比容量高、充放电平台低、资源丰富、安全性好等优点使其成为了最有潜力的锂离子电池负极替代材料。但硅本身存在两大缺陷:体积膨胀和导电性差。导致其寿命短、循环性差。目前,改善硅基负极的锂电性能的措施包括:纳米化,复合化以及合理的结构设计。纳米化是通过将硅的尺寸减小到纳米级别,从而减少硅在循环过程中的绝对体积膨胀和破碎。如硅纳米颗粒、硅纳米管等。复合化是将硅与碳、金属、非金属等缓冲基质复合,缓解体积膨胀,增强硅基负极的导电性。合理的结构设计指的是通过对硅基负极构筑多层次结构来容纳硅的体积膨胀,抑制SEI膜形成。其中金属银单质由于具有良好的机械性能和导电性而被广泛研究。但金属银属于贵金属,银的大量使用会导致生产成本的加大不利于产业化。另外在锂离子电池充放电的过程中银的嵌锂能力及其有限。所以银的大量使用还会导致负极材料容量的降低。为了解决这一系列问题,本论文从以下几个方面入手:第一,通过制备硅银碳纳米杂化材料引入碳基质,不仅有利于降低材料的成本,同时有利于形成连续的导电基质,缓解硅基负极在循环过程中的体积膨胀。第二:制备超小的银纳米粒子,银纳米粒子的减小有利于刺激诱导电场的产生,从而增强碳基质的导电性。第三:制备不同形貌的银纳米粒子如银纳米棒,有利于形成三维交联导电网络。本论文中重要研究结果如下:(1)通过超声分散法制备硅银负极并对其锂电性能进行研究,我们发现通过与银纳米粒子进行复合,可以显著改善硅基负极的锂电性能。但是随着银含量的增多,硅银负极的整体比容量有所下降。说明大量的银的存在会导致硅基负极的容量的降低。(2)通过简单的固化煅烧法制备银碳负极并对其锂电性能进行研究,我们发现少量的银纳米粒子的存在可以显著改善热解碳负极的锂电性能。(3)通过简单的固化煅烧法制备硅银碳负极并对其锂电性能进行研究,我们发现实验所制备的碳基质为氮参杂的碳。通过对纳米杂化材料负极的锂电性能进行表征,我们发现在硅碳负极中引入银纳米粒子可以显著改善其倍率性能,尤其是在大电流密度下,硅银碳负极表现出了优异的性能。这说明银的加入显著改善了碳基质的导电性。(4)通过引入形貌调控剂,我们得到了含有银纳米棒的硅银碳纳米杂化材料。在对所制备的复合材料进行锂电性能表征之后,我们可以发现含有银纳米棒的硅银碳纳米杂化材料表现出了最佳的倍率性能,可能由于银纳米棒的加入有利于形成交联的导电网络从而极大地改善锂离子电池的倍率性能。
[Abstract]:The quality of silicon is high, the charging and discharging platform is low, and the resources are abundant. The advantages of good safety make it the most potential anode substitute for lithium ion batteries. However, silicon itself has two major defects: volume expansion and poor electrical conductivity, resulting in its short life, poor cycling. At present. Measures to improve the lithium electrical properties of silicon-based negative electrodes include nanocrystalline, composite and reasonable structural design. Nanocrystalline is achieved by reducing the size of silicon to the nanometer level. In order to reduce the absolute volume expansion and breakage of silicon in the process of cycling, such as silicon nanoparticles, silicon nanotubes, etc., the composite is to compound silicon with buffer matrix such as carbon, metal, non-metal and so on, so as to alleviate volume expansion. Reasonable structure design is to build multi-layer structure of silicon based negative electrode to accommodate the volume expansion of silicon. Silver is widely studied because of its good mechanical properties and electrical conductivity, but silver is a precious metal. The large use of silver will lead to the increase of production cost which is not conducive to industrialization. In addition, during the charging and discharging process of lithium ion batteries, the lithium intercalation capacity of silver is limited. Therefore, the large use of silver will also lead to the reduction of the capacity of negative electrode materials. To solve this series of problems. This paper starts from the following aspects: first, by preparing silver-carbon nano-hybrid materials to introduce carbon matrix, not only to reduce the cost of materials, but also to form a continuous conductive matrix. Second, ultrasmall silver nanoparticles were prepared. The reduction of silver nanoparticles was helpful to stimulate the generation of electric field. In order to enhance the electrical conductivity of the carbon matrix. Third: the preparation of different morphology of silver nanoparticles such as silver nanorods. In this paper, the main results are as follows: 1) Silicon-silver negative electrode was prepared by ultrasonic dispersion method and its lithium electrical properties were studied. We found that the lithium electrical properties of silicon-based anode can be significantly improved by compounding with silver nanoparticles, but with the increase of silver content. The overall specific capacity of silver-silver anode has been decreased. It shows that the presence of a large amount of silver will lead to the reduction of silicon-based anode capacity. 2) Silver-carbon negative electrode was prepared by simple curing calcination method and its lithium electrical properties were studied. We found that the presence of a small amount of silver nanoparticles can significantly improve the lithium electrical properties of pyrolytic carbon anode. We found that the carbon matrix prepared by the experiment is nitrogen-doped carbon. Through the characterization of lithium electrical properties of the negative electrode of nano-hybrid materials, we found that the introduction of silver nanoparticles into the silica carbon anode can significantly improve its rate performance. Especially at high current density, silver-silicon carbon anode exhibits excellent performance, which indicates that the addition of silver significantly improves the conductivity of carbon matrix. The silver-silver-carbon nanohybrid materials containing silver nanorods were obtained and the lithium electrical properties of the composites were characterized. We can find that silver-carbon nano-hybrid materials containing silver nanorods exhibit the best rate performance. It is possible that the addition of silver nanorods is conducive to the formation of a cross-linked conductive network which greatly improves the performance of lithium-ion batteries.
【学位授予单位】：中北大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM912;TB383.1

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