论文总字数：31334字

摘 要

随着锂离子二次电池的不断发展，目前商业化使用的碳类负极材料已逐渐不能满足需求，人们对高比容量负极材料的需求越来越高。硅具有4200mAh/g的理论比容量，已受到人们的广泛关注，但是硅负极材料在实际充放电循环过程中会发生巨大的体积膨胀，导致电极结构崩塌从而失效，因此难以生产应用^[2]。为了解决此问题，本文在研究不同硅粉粒径所制备负极组装电池的性能影响的基础上，优化选择合适的Si粉粒径，采用化学刻蚀法制备出多孔硅，通过研究不同刻蚀液成分及含量，以及刻蚀温度、时间等对多孔硅微观结构及其所制备负极锂硅电池性能影响的基础上，得出最佳制备工艺参数；并通过研究固定刻蚀工艺参数下多孔硅粉的微观结构的演化，初步探索其化学刻蚀机制。本文的主要工作和得到的主要结论如下：

1. 不同硅粉粒度对所制备负极组装电池的性能影响研究表明：采用200nm硅粉制备出的多孔硅比表面积较大，团聚不严重，能与电解液充分接触发生反应，有效解决体积膨胀问题，有良好的电池比容量和循环容量保持率。
2. 不同刻蚀温度对所制备负极组装电池的性能影响研究表明：随着温度的升高，多孔硅孔径变大，孔隙率增加，孔隙分布也更加均匀；但温度过高时，孔洞结构会受到破坏。合适的孔径和孔隙率有助于获得优良的电化学性能，推荐刻蚀温度为20℃。
3. 不同刻蚀液浓度是影响样品孔径分布的主要因素，保持HF浓度为15.6%，硝酸浓度为5.2 % 时，样品为中孔材料，孔径分布更为均匀。
4. 不同刻蚀时间对所制备负极组装电池的性能影响研究表明：随着刻蚀时间的增加，孔径减小，孔的数量增加，深度减小，比表面积增加，但超过一定时间所制备的样品无法投入应用。推荐刻蚀时间为120min。
5. 固定刻蚀参数下多孔Si粉微观结构随时间的演化规律研究表明，其刻蚀机制主要是HNO₃和NaNO₂将硅粉在其表面氧化形成SiO₂层，HF腐蚀SiO₂，腐蚀过程先纵向发展，进行到一定程度后再横向发展，使孔壁变薄，刻蚀时间过长，孔壁则会崩塌。

关键词：锂离子电池 负极材料 多孔硅 化学刻蚀法 电化学性能

Preparation and electrochemical performance of porous silicon powder for lithium-silicon battery

ABSTRACT

With the continuous development of lithium-ion secondary batteries, the carbon-based anode materials used currently have gradually failed to meet the commercially demand, and the demand for anode materials with high specific capacity is increasing. Silicon has a theoretical specific capacity of 4200mAh/g^[2], which has been widely concerned, but the silicon anode material will undergo huge volume expansion during the actual charge and discharge cycle, causing the electrode structure to collapse and fail, making it difficult to produce and application. In order to solve this problem, this paper uses chemical etching method to prepare porous silicon, by studying the composition and content of different etching solutions, as well as the effects of etching conditions such as temperature and time on the microstructure of porous silicon (such as pore size and porosity, etc.), and assemble to form a battery, determine the best preparation conditions. The results obtained are as follows:

1. The effect of different silicon powder particle size on the performance of the assembled negative battery shows that the specific surface area of porous silicon prepared with 200nm silicon powder is large, the agglomeration is not serious, it can react with the electrolyte in full contact, and effectively solve the volume expansion The problem is that there is a good battery specific capacity and cycle capacity retention rate.
2. The effect of different etching temperatures on the performance of the assembled negative battery shows that as the temperature increases, the pore size of porous silicon becomes larger, the porosity increases, and the pore distribution is more uniform; but when the temperature is too high, the pore structure will destroy. Proper pore size and porosity help to obtain excellent electrochemical performance. The recommended etching temperature is 20℃.
3. The concentration of different etching solutions is the main factor affecting the pore size distribution of the sample. When the HF concentration is maintained at 15.6% and the nitric acid concentration is 5.2%, the sample is mesoporous and the pore size distribution is more uniform.
4. The effect of different etching times on the performance of the assembled negative battery shows that with the increasing of corrosion time, the pore size decreases, the number of pores increases, the depth decreases, and the specific surface area increases, but samples prepared over a certain period of time can not be put into application. The recommended etching time is 120min.
5. The study of microstructure evolution of porous Si powder with time under fixed etching parameters shows that the etching mechanism is mainly HNO₃ and NaNO₂ to oxidize the silicon powder on its surface to form a SiO₂ layer. HF corrodes SiO₂, and the corrosion process first develops longitudinally. When it reaches a certain level, it will develop laterally, so that the hole wall becomes thinner, and if the corrosion time is too long, the hole wall will collapse.

Key words: Lithium-ion Batteries； Anode material； Porous silicon； Chemical corrosion method；Electrochemical performance

目 录

摘 要 I

ABSTRACT III

第一章 绪 论 1

1.1论文研究目的及意义 1

1.2锂离子电池基础 2

1.2.1锂离子电池发展历史 2

1.2.2锂离子电池的特点和工作原理 2

1.3锂离子电池正负极材料研究现状 3

1.3.1正极材料研究现状 3

1.3.2负极材料研究现状 5

1.4锂离子电池硅基负极材料简介 6

1.4.1硅基负极材料的嵌锂机制和存在问题 7

1.4.2硅基负极材料的研究进展 9

1.5多孔硅的制备方法 10

第二章 实验原料、设备及方法 12

2.1 实验原料及设备 12

2.1.1实验原料 12

2.1.2实验设备 12

2.2实验方法 13

2.2.1 控制刻蚀参数制备多孔硅粉 13

2.3材料物化性能表征 14

2.3.1 X射线衍射分析（XRD） 14

2.3.2激光粒度分析仪 14

2.3.3扫描电子显微镜（SEM ） 14

2.3.4透射电子显微镜（TEM） 14

2.5.5 松装密度 14

2.3.6比表面积测定 14

2.3.7 孔隙率、孔径分布测定 15

2.4 锂硅电池的制备及组装 15

2.5 材料电化学性能测试 16

2.5.1充放电性能测试 16

2.5.2循环伏安测试 16

第三章 实验结果与讨论 17

3.1 硅粉粒径的优化 17

3.1.1 硅粉粒径的选择 17

3.1.2 不同粒径制备的多孔硅粉的TEM表征 17

3.1.3 多孔硅粉电化学性能表征 18

3.2刻蚀温度对多孔Si微观结构及电化学性能的影响 18

3.2.1 刻蚀温度对多孔Si微观结构的影响 18

3.2.2 刻蚀温度对多孔Si负极电化学性能的影响 20

3.3刻蚀液浓度对多孔Si微观结构及电化学性能的影响 20

请支付后下载全文，论文总字数：31334字