锂离子电池用硅基复合负极材料的制备及电化学性能研究

发布时间：2018-04-21 02:18

本文选题：锂离子电池 + 硅/聚苯胺复合材料　；参考：《重庆大学》2014年硕士论文

【摘要】：硅因具有高的理论容量（4200mAh/g）和丰富的资源有望成为替代石墨负极的候选材料之一。但是硅负极材料低的导电率、严重的体积效应和差的循环稳定性等缺点，严重制约了其商业化应用。碳材料是离子和电子的混合导体，在充放电过程中体积变化小，且具有良好的延展性和弹性，可以作为硅负极材料的“缓冲基体”。此外，两者的嵌锂电位相近，因此，结合两者的优点有望制备出具有高容量和良好循环性能的新型锂离子电池材料。本研究分别采用苯胺和淀粉为碳源，纳米硅为硅源，并通过不同的制备方法制备硅/碳复合负极材料。（1）以纳米硅和苯胺为原料，通过乳液聚合和高温热解两步法制备硅/碳复合负极材料，研究中采用扫描电镜、红外光谱和X-射线衍射对复合材料结构进行表征，并将其作为锂离子电池负极材料探讨硅/苯胺质量比和负电极片制备工艺对其电化学性能的影响。研究表明：纳米硅表面成功包覆了聚苯胺，且在高温碳化过程中纳米硅与碳之间没有生成电化学惰性的碳化硅；复合负极材料制备过程中硅/苯胺质量比为1:2，负电极片制备过程中复合负极材料/导电剂（Super p）/粘结剂（羧甲基纤维素钠，CMC）的比例为85:5:10且采用pH=3的柠檬酸/氢氧化钾缓冲液作为调浆溶剂时，所制备复合负极材料表现出高的比容量和良好的循环性能，经20次循环后可逆容量仍为1013mAh/g。（2）以纳米硅和马铃薯淀粉为原料，通过高温热解和球磨两步法制备硅/碳复合负极材料，并将其作为锂离子电池负极材料探讨制备过程中球磨时间、硅石墨比例、调浆液pH值及粘结剂等因素对复合材料电化学性能的影响机制。结果表明：硅/石墨比为4:8，球磨时间为10小时，复合材料：导电石墨：CMC=85:5:10，pH=3的柠檬酸/氢氧化钾缓冲液作为调浆溶剂时，复合材料的首次充放电比容量分别是1347mAh/g、934mAh/g，20次循环后充放电比容量仍高达1034.08mAh/g、985.34mAh/g，该复合材料显示出良好的电化学性能。这是由于淀粉基炭包覆能够有效地缓解由于硅在充电过程中体积膨胀而引起的电极粉化和剥落问题，另一方面复合材料中裸露的Si颗粒表面形成的羟基与CMC中之间形成了酯键，，这使电极片在充放电过程中保持了很好的完整性。
[Abstract]:Silicon is expected to be one of the candidate materials for graphite anode because of its high theoretical capacity of 4200mAh/ g) and abundant resources. However, the low conductivity, serious volume effect and poor cycle stability of silicon negative materials seriously restrict its commercial application. Carbon material is a mixed conductor of ions and electrons. It has little change in volume during charge and discharge, and has good ductility and elasticity, so it can be used as a "buffer matrix" for silicon anode materials. In addition, the lithium intercalation potential of the two materials is similar. Therefore, it is expected that a new type of lithium ion battery material with high capacity and good cycling performance can be prepared by combining the advantages of the two. In this study, aniline and starch were used as carbon source, nano-silicon as silicon source, and silicon / carbon composite anode materials were prepared by different preparation methods. Silicon / carbon composite anode materials were prepared by emulsion polymerization and high temperature pyrolysis from nano-silicon and aniline. The structure of the composite was characterized by scanning electron microscopy, infrared spectroscopy and X-ray diffraction. The effect of the mass ratio of silicon to aniline and the preparation process of negative electrode on the electrochemical performance of lithium ion battery was studied. The results showed that Polyaniline was successfully coated on the surface of nano-silicon and no electrochemical inert silicon carbide was formed between nano-silicon and carbon during high temperature carbonization. The mass ratio of silicon to aniline is 1: 2 in the preparation of composite negative electrode material. The ratio of composite anode material / conductive agent / binder is 85:5:10 and the citric acid / hydrogen oxidation of pH=3 is used in the preparation of negative electrode sheet. When potassium buffer is used as sizing solvent, The composite anode material showed high specific capacity and good cycling performance. After 20 cycles, the reversible capacity was still 1013mAh/ g. Using nano-silicon and potato starch as raw materials, silicon / carbon composite anode materials were prepared by high-temperature pyrolysis and ball milling, and used as anode materials for lithium ion batteries to discuss the milling time and the ratio of silicon to graphite. The influence of pH value of sizing fluid and binder on the electrochemical properties of composites. The results show that the ratio of silicon to graphite is 4: 8, and the milling time is 10 hours. When the conductive graphite: CMC: 85: 5: 5: 10 pH 3 buffer solution is used as the sizing solvent, The first charge-discharge capacity of the composite is 1347 mg / g 934 mg / g respectively. The charge-discharge capacity is still up to 1034.08 mg / g 985.34 mg / g after 20 cycles. The composite shows good electrochemical properties. This is due to the fact that the starch based carbon coating can effectively alleviate the problem of electrode pulverization and exfoliation caused by the volume expansion of silicon during the charging process. On the other hand, the hydroxyl groups formed on the surface of exposed Si particles in the composite materials form ester bonds between the hydroxyl groups formed on the surface of the bare Si particles and the CMC particles. This makes the electrode sheet in charge and discharge process to maintain a good integrity.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：O613.72;TM912

【参考文献】