论文总字数：22210字

摘 要

锂离子电池（LIBs）在所有的二次电池中由于充放电容量高，成本较低，商业化程度高，绿色环保污染小而受到世界研究者的青睐。然而传统的LIBs负极（石墨）由于能量密度较低已经不能满足高耗能设备的使用。如今越来越多的研究者青睐于导电率和比容量高的金属硫化物。而在金属硫化物中，CoS性能更优异。这种材料可以储存300-800 mAh/g之间的锂离子，具有更高的理论比容量和循环稳定性。但是CoS在长时间充放电过程中电极体积膨胀会很明显，甚至电极结构发生极大变化。这会出现导电性变差，倍率能力降低，循环次数降低以及容量衰减变快等问题，阻碍了其作为LIBs新负极材料实际应用，本文将着重解决该问题。

复合材料具有复合组分性能耦合增效的机制。所以将CoS与具有稳定性和导电性的材料复合，可以极大改善其电化学性能。本文将设计一种硫化钴@碳/碳纤维布复合材料，使用水热法在CFC上自支撑生长硫化钴纳米片，并在硫化钴纳米片上包覆由聚多巴胺碳化而成的碳膜。由于层状纳米片结构具有很大的比表面积，电解质将会更容易进入电极表层，电子迁移率和离子传输性能进一步提升，电极的体积膨胀效应也由于纳米片上的碳膜而得到减缓。

实验通过简单两步水热法制备了生长在碳布上并包覆碳的致密片状CoS（CoS NS@C/CFC）。通过XRD表征分析证明了CoS NS@C/CFC被成功合成。当所制备的CoS NS@C/CFC复合材料作为LIBs负极时， CoS NS@C/CFC复合材料表现出高比容量（在0.1 A /g时为710 mAh/g）、优异的倍率性能（0.1 A/g时为710 mAh/g和2 A/g 时为440 mAh /g）和改善的循环稳定性（200次循环后83%的容量保持率）。原因在于硫化钴与碳布复合能一定程度解决锂离子在不断嵌入和脱离过程中引起的电极膨胀问题。这样可以提升LIBs的电子迁移率和比容量。

关键词：锂离子电池 硫化钴 碳布 水热法 循环性能 碳包覆

Preparation of CoS NS@C/CFC composite and research on its lithium storage properties

Abstract

All researchers like Lithium batteries, because of their high charge and discharge capacity, low cost, easy commercialization, and low environmental pollution. However, due to the low energy density, the traditional LIBS anode (graphite) can not withstand the use of tall power consumption equipment. Because of its higher conductivity and theoretical specific capacity, now more and more researchers prefer metal sulfides with high conductivity and specific capacity.Among the metal sulfides, CoS has better properties. This material can store lithium ions between 300-800 mAh/g, which has higher theoretical specific capacity and cycle stability. However, similar to most oxides and alloys, CoS electrode volume expansion will be obvious during long-term charge and discharge, and even the electrode structure will change greatly. This will cause problems such as poor conductivity, reduced rate capability, reduced cycle times, and faster capacity decay, which hinder its practical application as a new anode material for lithium battery. This paper will focus on solving this problem.

The composite material has the mechanism of coupling and enhancing the performance. Therefore, CoS combined with materials of stability and conductivity can greatly improve its electrochemical performance. In this paper, a cobalt sulfide @carbon / carbon fiber cloth composite material will be designed. Cobalt sulfide nanosheets are self-supported to grow on carbon fiber cloth by hydrothermal method, and the cobalt sulfide nanosheets are coated with carbonized polydopamine.Because the layered nanosheet structure has a large specific surface area, the electrolyte will more easily enter the electrode surface layer, which can improve the electron mobility and ion transport performance. The volume expansion effect of the electrode is also slowed down by the carbon film on the nanosheet.

In the experiment, a simple two-step hydrothermal method was used to prepare dense sheet-like CoS grown on carbon cloth and coated with carbon, the name is CoS NS@C/CFC. XRD characterization analysis proved that CoS NS@C/CFC was successfully synthesized. When the prepared CoS NS@C/CFC composite material is used as a negative electrode of LIBs, the CoS NS@C/CFC composite material exhibits a high specific capacity (710 mAh/g at 0.1 A/g) and excellent rate performance (710 mAh/g at 0.1 A/g and 440 mAh/g at 2 A/g) and improved cycle stability (83% capacity retention after 200 cycles). The reason is that the combination of cobalt sulfide and carbon cloth can solve the electrode expansion problem caused by the continuous insertion and detachment of lithium ions to a certain extent. In this way, the electronic mobility and specific capacity of LIBs can be promoted.

Keywords: Lithium-ion battery; cobalt sulfide; carbon cloth; hydrothermal method; cycle performance; carbon coating

目录

摘要 I

Abstract II

第一章 绪论 1

1.1前言 1

1.2锂离子电池简述 2

1.2.1 锂离子电池的发展 2

1.2.2锂离子电池结构 3

1.2.3锂离子电池原理 3

1.3 LIBs 相关正极材料进展 4

1.3.1 Li_xM_nO₂（M=Co、Ni）层状材料 4

1.3.2尖晶石结构材料 4

1.3.3聚阴离子化合物 4

1.4 LIBs负极材料的要求及成果 5

1.4.1碳类负极材料 5

1.4.2过渡金属化合物 5

1.4.3合金类材料 6

1.5硫化钴相关合成方法 6

1.6 本课题的主要研究意义以及选题意义 7

第二章 实验方法 8

2.1 实验设备 8

2.2 实验药品 8

2.3 电极材料的制备 9

2.4纽扣电池的组装过程 11

第三章 材料表征与分析 12

3.1 X射线衍射分析 12

3.2 扫描电子显微镜分析 13

3.3 X射线光子能谱分析 14

第四章 电化学性能分析 16

4.1 充放电性能 16

4.2 循环性能 17

4.3 交流阻抗 18

第五章 结论与展望 20

5.1 结论 20

5.2 展望 20

参考文献 22

致谢 25

第一章 绪论

1.1前言

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