摘 要

锂离子电池在当今崇尚绿色清洁能源的时代发挥着重要的作用,而清洁能源和电子设备的发展需要更高的能量密度,这其中负极材料对于整个锂离子电池体系能量密度的提高至关重要。硅基负极材料中硅具有自身理论容量大、嵌锂电位合适、地表资源丰富、无污染等特点，逐渐脱颖而出。但是单质硅作为负极材料充放电过程中伴有巨大的体积效应，在锂离子嵌入/脱嵌过程中巨大的体积膨胀会导致颗粒的粉化和破碎，电极结构崩坏，造成电子转移通道和离子转移通道受阻，严重影响电池的安全性和循环性能。此外由于硅本身极低的电导率，也难以实现高功率输出。基于此，本工作主要是建立均匀的的硅/石墨烯网络，一方面缓冲硅的体积膨胀，一方面改善材料导电通道，为未来发展高循环稳定性、高实用性的硅基负极材料奠定基础。

本研究利用溶液复合法在水溶液中复合氧化石墨和纳米硅制得硅/石墨烯复合材料应用于锂离子电池负极，采用将硅颗粒束缚于石墨烯三维网络中以限制硅在充放电过程中的体积效应，同时碳良好的力学性能尤其是韧性可以作为缓冲材料进一步限制硅的膨胀；另外碳材料本身是良好的导体，碳的引入可以解决硅的电导率问题。纳米粒径的复合材料比表面积大的特点，也为锂离子的快速嵌入/脱嵌提供了可能。在测试过程中循环稳定性得到了明显的提升证明了复合负极材料结构对性能的改善。但由于反应机制或材料配比等缺陷，导致材料微观出现局部团聚的现象，制备工艺仍需要进一步提高。

关键词：硅负极；石墨烯；氧化石墨；锂离子电池

Abstract

Lithium ion battery plays an important role in this era in which electric equipment becomes gradually tiny and portable， and the green energy is highly advocated. The anode material, key of the lithium ion battery, has a big influence to the safety and quality of the battery. Silicon is a promising new generation anode material for its high theoretical capacity, appropriate insertion voltage, and high element abundance, and low pollution. However, silicon has a big volume effect during the process of battery charging and discharging. The over 300% expansion will cause the crumbing and pulverization of electrode particles, leading to the collapse of the structure of battery, and the safety and circulation quality are not ensured. At the same time, silicon is hard to undertake the role of battery material due to its low conductivity. The favorable way to solve the above mentioned problem is to construct composite silicon materials.

This research is using liquid phase method to complete the synthesis of silicon/graphene composite from oxidation graphite and nano-silicon, and then apply it to the anode of lithium ion battery. Bounding the silicon particles into graphene matrix structure is a possible way to limit the volume effect during the charging/discharging process. On the other hand, graphene is a kind of excellent conductor, the import of carbon element may solve the problem of silicon’s low- conductivity and make it a well material for the anode. In addition, limiting the composite into nanometer size enlarge the specific electrochemical surface area, making it possible to let lithium ion intercalation/de-intercalation more quickly. During the test, the obvious improvement in the cycling stability shows the composite structure makes the electrochemical quality improved. However, agglomeration among the nano-particles can also be observed, suggesting that preparation technologies and reaction mechanism also should be improved.

Key Words：silicon anode； graphene； oxidation graphite； lithium ion battery

目 录

第1章 绪论 1

1.1 引言 1

1.2锂离子电池的发展历史 1

1.3 锂离子电池的工作原理 2

1.4 锂离子电池负极材料的现状和发展方向 3

1.5 本文研究目的和主要研究内容 5

第2章 实验部分 7

2.1 实验试剂与仪器 7

2.1.1 实验试剂 8

2.1.2 实验仪器 8

2.2 材料物理性质表征 8

2.2.1 X射线衍射分析（X-ray Diffraction，XRD） 8

2.2.2 扫描电子显微镜(Scanning Electron Microscopy, SEM) 9

2.3 材料的电化学性质表征 9

2.3.1 恒电流充放电测试 9

2.3.2交流阻抗测试 9

2.4 硅/石墨烯复合锂离子电池负极材料的制备流程 10

2.4.1 氧化石墨的制备 10

2.4.2 硅的表面改性 11

2.4.3 硅与氧化石墨的复合 11

2.4.4 电极片的制备及装配电池 12

第3章 硅/石墨复合负极材料的性能表征 14

3.1 硅/石墨复合锂离子电池负极材料的物理性能表征 14

3.1.1 硅/氧化石墨复合材料的物相分析 14

3.1.2 硅/石墨烯复合负极材料的微观形貌分析 14

3.2 硅/石墨烯复合负极材料的电化学性能表征 15

3.2.1 硅/石墨烯复合材料的循环充放电曲线特征 15

3.2.2 硅/石墨烯复合材料的交流阻抗测试 17

3.3 本章小结 18

第4章 结论与展望 19

参考文献 21

致 谢 23

第1章 绪论