论文总字数：27079字

摘 要

锂离子电池作为目前移动设备、电动汽车、电动工具等移动电源在工业电力储能方面有着巨大的商业价值和研究价值。锂离子电池作为当今时代能源领域的热点研究项目。其中，提高其电池容量、电池稳定性、循环效率和安全性都是广大学者研究的方向，而高容量硅负极电极因具有最高理论比容量受到研究者的广泛关注，但是由于其物理-电化学特性，在锂离子与硅负极的嵌合和脱嵌过程中会发生巨大的结构变形现象，使形态改变无法稳定地进行电池循环。

目前有两种方式来进行锂离子硅负极电池的优化和性能测试，分别是理论和实验。理论主要是从力学、电化学、分子模拟以及物理数学模型建立上面获取结果，并且分析锂离子电池硅负极的电化学性能和力学性能，基于物理和力学相关基础进行电池负极所受应力分析的推导和计算，进而解释其电充电过程中高容量负极材料问题。

由于此项实验所需营造的实验环境极其苛刻，并且成本相对较高，所以在实验中获取各个参数是十分困难的，而且锂离子电池硅负极在实验过程中存在严重的体积效应，因此选择建立力学模型来研究物理扩散和电化学反应过程。

根据力学模型可以推导出理论本构方程、锂离子在不同充电条件下的浓度方程、恒压充电条件下锂离子电池硅负极材料所受扩散应力的计算方程、恒流充电条件下锂离子电池硅负极材料所受扩散应力的计算方程。并且通过Mathematic软件进行计算和图像绘制。

根据数值模拟所演算出的图像，可以得出相应的结论：在恒定电流充电条件下，球形的锂离子电池硅负极内部中心沿直径方向所受应力最大，然后所受应力向外不断递减，直到球形电极表面的径向扩散应力值为0，全部表现为拉应力。同样的，随着时间的增加，负极材料内部切向扩散应力值的绝对值在不断增加，但是电极中心所受应力表现为拉应力，电极外表面所受的切应力表现为压应力。在恒定电压充电条件下，由球型电极内部向外，电极所受的径向应力不断减小，球形电极中心径向应力最大，在电极表面所受的径向应力最小，根据边界条件设置为零。锂离子电池溶质扩散到电极中心时，电极中心所受切向应力仍表现为拉应力，但是电极外表面所受的切应力在锂离子嵌入电极时表现为压应力。是在恒定压力条件下，锂离子电池硅负极中所产生的径向、切向应力比恒定电流充电情况下所产生的径向、切向应力更大。

本论文主要分析充电情况下的锂离子电池中离子浓度和扩散应力（DIS）。在应力演化分析的基础上，探讨硅负极材料在电化学—力学耦合情况下锂离子的嵌合与脱嵌情况。再进行数值模拟来研究出恒定电流充电情况与恒定电压充电情况下的扩散应力。

关键词：锂离子电池 硅负极材料 扩散应力 离子浓度。

Abstract

As a mobile power source for mobile devices, electric vehicles and power tools, lithium-ion batteries have great commercial value and research value in industrial power storage. Lithium-ion batteries are a hot research project in the energy field of today's era. Among them, improving its battery capacity, battery stability, cycle efficiency and safety are the research directions of many scholars, and high-capacity silicon negative electrode has received extensive attention from researchers because of its highest theoretical specific capacity, but due to its physical-electrochemistry The characteristic is that a large structural deformation phenomenon occurs during the process of fitting and deintercalating lithium ions and a silicon negative electrode, so that the morphological change cannot stably perform the battery cycle.

There are currently two ways to optimize and test the performance of lithium-ion silicon negative batteries, which are theoretical and experimental. The theory mainly obtains the results from the establishment of mechanics, electrochemistry, molecular simulation and physical mathematical model, and analyzes the electrochemical performance and mechanical properties of the silicon negative electrode of lithium ion battery. Based on the physical and mechanical basis, the derivation of the stress analysis of the negative electrode of the battery is carried out. And calculations to explain the problem of high-capacity anode materials during electrical charging.

Because the experimental environment required for this experiment is extremely demanding and the cost is relatively high, it is very difficult to obtain various parameters in the experiment, and the lithium-ion battery silicon negative electrode has serious volume effect during the experiment, so choose to establish Mechanical models to study physical diffusion and electrochemical reaction processes.

According to the mechanical model, the theoretical constitutive equation, the concentration equation of lithium ion under different charging conditions, the calculation equation of the diffusion stress of the silicon anode material of lithium ion battery under constant voltage charging condition, and the silicon ion battery of lithium ion battery under constant current charging condition can be derived. The calculation equation for the diffusion stress of the negative electrode material. Calculations and image rendering are performed using Mathematical software.

According to the numerical simulation, the corresponding conclusion can be drawn: under the constant current charging condition, the inner center of the silicon negative electrode of the spherical lithium ion battery is subjected to the maximum stress in the diameter direction, and then the stress is continuously decreased until the stress is applied. The radial diffusion stress value of the surface of the spherical electrode is 0, and all of them are tensile stresses. Similarly, with the increase of time, the absolute value of the tangential diffusion stress value inside the anode material is increasing, but the stress at the center of the electrode is the tensile stress, and the shear stress on the outer surface of the electrode is the compressive stress. Under constant voltage charging conditions, the radial stress of the electrode is reduced from the inside of the spherical electrode, the radial stress of the spherical electrode is the largest, and the radial stress on the surface of the electrode is the smallest. zero. When the solute of the lithium ion battery diffuses to the center of the electrode, the tangential stress at the center of the electrode still exhibits tensile stress, but the shear stress on the outer surface of the electrode exhibits compressive stress when the lithium ion is embedded in the electrode. Under constant pressure conditions, the radial and tangential stresses generated in the silicon negative electrode of a lithium ion battery are greater than the radial and tangential stresses generated under constant current charging.

This paper mainly analyzes the ion concentration and diffusion stress (DIS) in lithium ion batteries under charging conditions. On the basis of stress evolution analysis, the chimerization and deintercalation of lithium ion in the electrochemical-mechanical coupling of silicon anode materials were discussed. Numerical simulations were then carried out to study the diffusion stress in the case of constant current charging and constant voltage charging.

Keywords: lithium ion battery silicon anode material diffusion stress ion concentration.

目录

摘要 Ⅰ

Abstract Ⅱ

第一章 绪论 1

1.1背景及意义 1

1.1.1国内外进展 1

1.1.2锂离子电池的分类 3

1.1.3锂离子电池的基本结构 3

1.1.4锂离子电池负极种类 3

1.1.5锂离子电池工作原理 4

1.2高容量硅基负极材料 5

1.3综述小结 6

1.4课题研究目的和内容 6

1.5课题研究方法 7

1.6本章小结 7

第二章 充电过程硅负极材料力学模型 8

2.1锂离子电池充电过程 8

2.1力学本构方程 8

2.1.1硅颗粒负极材料计算模型 8

2.1.2力学方程 10

2.3充电过程硅负极材料应力 11

2.4 本章小结 13

第三章 恒流充电条件下锂离子电池硅负极中扩散应力分析 14

3.1采用计算参数 14

3.2恒流充电条件下浓度分析 14

3.3恒流充电条件扩散应力分析 16

3.4本章小结 18

第四章 恒压充电条件下锂离子电池硅负极中扩散应力分析 19

4.1恒压计算参数 19

4.2恒压充电条件下硅负极浓度方程 19

4.3恒压充电条件下硅负极中扩散应力 21

4.4本章小结 23

第五章 论文总结和展望 25

5.1论文总结 25

5.2展望 26

参考文献： 28

致谢 30

绪论

1.1背景及意义

电池是实现化学能转化为电能的储能设备，由电解液和一对耦合的电极构成。人们早在公元初始就对储能设备开始了研究并且不断发展壮大^[1]。意大利的Volta在十八世纪研究出了最类似与电池的储能设备，从此人们开始了解并且尝试在各个领域加以利用^[1,2,4]。在之后的两个世纪中，电池行业蓬勃发展，先后发明了铅系列电池、干电池、镍电池、燃料电池，锂电池充电电池在上个世纪九十年代被提出，如今已经投入生产。

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