锂离子电池硅碳复合负极材料的制备及其性能研究

发布时间：2018-05-27 07:25

本文选题：锂离子电池 + 3D结构石墨烯　；参考：《东华大学》2014年硕士论文

【摘要】：锂离子电池由于具有比能量大、工作电压高、安全性好、环境污染小等优点,在各种便携式电子设备、电动汽车等方面有着广泛的应用前景。最近几年,随着对高能电源需求的增长,围绕如何开发高能密度、快速大功率充放电的锂离子电池展开了大量研究。一般来说,锂离子电池的总比容量是由组成电池的各元件共同决定的,而负极材料作为储锂的主体,是提高锂离子电池总比容量、循环寿命、充放电性能等相关参数的关键。硅具有非常高的理论比容量和较低的嵌/脱锂电位,被认为是最具有潜力实现下一代高能量密度锂离子电池的新型负极材料之一。但在充放电过程中,体积过度膨胀粉化导致容量衰减快,成为其作为商业负极材料的最大障碍。而碳材料作为负极材料虽然比容量小,但不仅具有一定的电化学活性,结构也较稳定,可以作为硅电极的“缓冲基体”。因此,结合两者的性能有可能制备出具有高容量和优良循环性能的硅-碳复合负极材料。本论文是与法国圣戈班集团上海研发中心合作,拟开发出一种具有高容量和优良循环性能的锂离子电池硅碳复合负极材料。主要研究内容有,通过SiO发生歧化反应,在不同的热处理条件下制备多种Si-SiOx复合物,并将其与用真空抽滤法制备的三维网络结构石墨烯进行自组装,得到不同种类的Si-SiOx-C复合负极材料。用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和蓝电电池测试系统分别对Si-SiOx复合物、石墨烯及Si-SiOx-C复合材料的形貌、结构和电化学性能进行了表征。实验结果表明,真空抽滤法可以成功制备空间网络结构十分明显的3D结构石墨烯。其电化学测试结果显示,石墨烯首次循环充电比容量为311.2mAh/g,与纯炭材料的理论比容量372mAh/g相差较少,且库伦效率高达84.9%；经过100次循环后充电比容量为134.1mAh/g,虽然相比首次充电比容量有所减少,但是比容量仍然较高,且整个充放电过程的稳定性也较好,第100次循环的库伦效率也高达97%,充分说明3D结构石墨烯用作锂离子电池负极材料时具有较好的电化学性能。通过SiO的歧化反应成功制备了Si-SiOx复合物。制备过程中由于热处理条件不同得到的Si-SiOx复合物的性能也不同。其电化学测试结果显示,随着反应过程中的热处理温度的升高,Si的结晶度也随之升高,相应的Si-SiOx复合物的首次循环充放电比容量却越来越低,这是因为热处理温度越高,Si的结晶度越大,Si的颗粒尺寸越大,尺寸较大的Si颗粒不利于锂离子嵌入和脱出,从而导致比容量下降。而在Si-SiOx复合物的多次循环性能测试中,复合物的比容量急剧下降,这是由于歧化反应过程中生成了大量的单质硅,虽然硅具有非常高的理论比容量和较低的嵌/脱锂电位,但其体积过度膨胀粉化导致容量衰减快,因而循环数次之后其容量大大衰减。说明较低的热处理温度有利于制备出比容量更高的Si-SiOx复合物电极材料。当Si-SiOx复合物与石墨烯自组装之后,得到的Si-SiOx-C复合材料的首次循环充放电比容量大大提高,充电比容量由152.24mAh/g上升到811.3mAh/g,不可逆容量也大大减少,且电池的库伦效率由14%增加到52%。在循环100次之后,其充放电比容量也大大提高,稳定性很好,从第5次循环开始,充放电比容量都维持在一个稳定的水平,约为150mAh/g左右,基本不再衰减；不可逆容量也大大减少,而库伦效率也大大提高,基本达到100%。这表明石墨烯与Si-SiOx复合物组装之后能够大大提高比容量、循环稳定性和库伦效率,说明石墨烯能够有效限制Si颗粒的体积膨胀效应,提高Si-SiOx复合物的电化学性能。
[Abstract]:Because of the advantages of high energy, high working voltage, good safety and small environmental pollution, lithium ion batteries have a wide application prospect in all kinds of portable electronic equipment and electric vehicles. In recent years, with the increase in the demand for high energy power supply, lithium ion batteries with high energy density and high power charge and discharge are around. In general, the total specific capacity of the lithium ion battery is determined by the components of the battery. As the main body of the lithium storage, the negative electrode is the key to improve the total specific capacity, the cycle life, the charge discharge performance and other related parameters of the lithium ion battery.
Silicon has a very high theoretical specific capacity and low embed / delithium potential. It is considered to be one of the most potential new anode materials for the next generation of high energy density lithium ion batteries. However, during the charge and discharge process, the volume of excessive expansion of the powder leads to the capacity attenuation and the biggest obstacle to be used as a commercial anode material. As a negative material, although its specific capacity is small, it not only has a certain electrochemical activity, but also has a stable structure, which can be used as a "buffer matrix" for silicon electrode. Therefore, it is possible to prepare a silicon carbon composite negative material with high capacity and excellent cycling performance by combining the performance of the two.
In this paper, in cooperation with the Shanghai R & D center of Saint Gobain group, France, a kind of silicon carbon composite anode material with high capacity and excellent cycling performance is developed. The main research contents include the preparation of multiple Si-SiOx complexes under different heat treatment conditions through SiO disproportionation and the vacuum extraction method. The prepared three-dimensional network structure graphene is self-assembled, and different kinds of Si-SiOx-C composite negative materials are obtained. The morphology, structure and electrochemical properties of Si-SiOx complex, the morphology, structure and electrochemical properties of the composites of Si-SiOx, stone and Si-SiOx-C are respectively used by the X ray diffractometer (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and the blue electric battery test system. It was characterized.
The experimental results show that the vacuum pumping method can successfully prepare the 3D structure graphene with very obvious spatial network structure. Its electrochemical test results show that the first cycle charge specific capacity of graphene is 311.2mAh/g, and the theoretical specific capacity of carbon materials is less than that of 372mAh/g, and the efficiency of Kulun is up to 84.9%; after 100 cycles, the charge ratio is compared. The capacity is 134.1mAh/g, although the specific capacity of the first charge is reduced, but the specific capacity is still higher, and the stability of the whole charging and discharging process is better. The efficiency of the 100th cycle of Kulun is also up to 97%. It fully shows that the 3D structure graphene has good electrochemical performance when it is used as anode material for lithium ion battery.
The Si-SiOx complex was successfully prepared by the disproportionation reaction of SiO. The properties of the Si-SiOx complex obtained from different heat treatment conditions were different during the preparation process. The electrochemical test results showed that the crystallinity of Si increased with the increase of heat treatment temperature during the reaction process, and the corresponding Si-SiOx complex was recharged for the first time. The electrical specific capacity is getting lower and lower, because the higher the heat treatment temperature, the greater the crystallinity of Si, the larger the size of Si particles, the larger size Si particles are not conducive to the insertion and removal of lithium ion, which leads to the decrease of the specific capacity. And the specific capacity of the composite decreases sharply in the multiple cycle performance testing of the Si-SiOx complex, which is due to disproportionation. A large number of mono silicon is generated during the reaction, although silicon has very high theoretical specific capacity and low potential for inlaying / removing lithium, but its volume overexpansion pulverization leads to rapid capacity attenuation, so its capacity greatly attenuates after several cycles. It shows that the lower heat treatment temperature is advantageous to the preparation of Si-SiOx complex electricity with higher specific capacity. Polar materials.
When the Si-SiOx complex and graphene are self assembled, the initial cyclic charge discharge capacity of the Si-SiOx-C composite is greatly increased, the charge specific capacity is increased from 152.24mAh/g to 811.3mAh/g, and the irreversible capacity is greatly reduced, and the Kulun efficiency of the battery is increased from 14% to 52%. after 100 cycles, and its charge discharge ratio is also great. To improve, the stability is very good, from the fifth cycle, the charge discharge specific capacity is maintained at a stable level, about 150mAh/g, basically no longer attenuating, the irreversible capacity is greatly reduced, and the efficiency of Kulun is greatly improved, basically reaching the 100%.. Ring stability and Kulun efficiency indicate that graphene can effectively limit the volume expansion effect of Si particles and enhance the electrochemical performance of Si-SiOx composites.
【学位授予单位】：东华大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM912

【参考文献】