锂离子电池电极材料的热—力—化耦合理论及有限元分析
发布时间：2019-04-22 09:35
【摘要】：锂离子电池电极材料是决定其工作电压和使用寿命的关键材料。锂离子电池的研究主要集中在电极材料的结构设计、工艺改善和电化学性能等方面,近年来研究人员逐渐关注锂离子电池充放电过程中电极材料的变形与电化学性能的关系,其中电极材料的应力主要是由锂离子的扩散和温度分布的不均匀而引起的。锂离子电池的能量密度、循环寿命等主要性能表征量都与电极材料的应力有着紧密地联系,应力过大就会导致电极材料的破坏,最终导致锂离子电池的失效。为了从本质上认识和理解电极材料锂化过程中的锂离子浓度场和应力场的演变规律,本论文基于温度场的基本理论,通过理论分析和有限元数值模拟,建立锂离子电池及其关键电极材料化-力作用下的浓度场和应力场的理论模型。本论文的研究内容主要包括以下三个方面:(1)建立锂离子电池充放电过程中电极材料的温度场的理论模型。利用有限元软件研究电极材料表面与外界的热传导系数和表面热辐射率对其温度场的影响,发现随着表面与外界的热传导系数和表面热辐射率的增加,电极材料的温度会降低。(2)建立电极材料化-力作用下的浓度场和应力场的理论模型。利用有限元软件研究各向同性与各向异性对空心核-壳和薄膜结构Si负极材料相变锂化过程中的浓度场和应力场的影响,发现空心核-壳结构Si负极材料各向异性时环向拉应力大于各向同性的情况,这更容易导致Si负极材料的破坏。(3)建立电极材料热-力-化耦合时的浓度场和应力场的理论模型。利用有限元软件研究不同充电方式对空心核-壳结构LiyMn2O4正极材料热-力-化耦合锂化过程中的浓度场和应力场的影响。发现在恒定流量下,随着曲率a/b的减少,LiyMn2O4材料的环向拉应力不断增加,这更容易导致LiyMn2O4材料的破坏;在恒定浓度下,随着曲率a/b的增加,LiyMn2O4材料的环向拉应力不断增加,这更容易导致LiyMn2O4材料的破坏。然后分析两球形LiyMn2O4正极颗粒相接触下其热-力-化耦合时的锂离子浓度场和应力场。发现两球形LiyMn2O4正极颗粒相接触的区域压应力很大,导致其锂离子浓度明显低于其它区域的锂离子浓度。
[Abstract]:The electrode material of Li-ion battery is the key material to determine the working voltage and service life of lithium-ion battery. The research of Li-ion battery mainly focuses on the structure design, process improvement and electrochemical performance of electrode material. In recent years, researchers have paid more and more attention to the relationship between the deformation of electrode material and electrochemical performance in charge-discharge process of Li-ion battery. The stress of electrode materials is mainly caused by the diffusion of lithium ions and the uneven temperature distribution. The energy density and cycle life of lithium-ion batteries are closely related to the stress of electrode materials. Too much stress will lead to the destruction of electrode materials and ultimately lead to the failure of lithium-ion batteries. In order to understand and understand the evolution of lithium ion concentration field and stress field in lithium electrode material in essence, this paper is based on the basic theory of temperature field, through theoretical analysis and finite element numerical simulation. The theoretical models of concentration field and stress field of Li-ion battery and its key electrode are established. The main contents of this thesis are as follows: (1) the theoretical model of the temperature field of electrode materials during charge-discharge process of Li-ion battery is established. The influence of thermal conductivity coefficient and surface thermal emissivity on temperature field of electrode material is studied by using finite element software. It is found that the thermal conductivity coefficient and surface thermal emissivity of electrode material increase with the increase of surface and exterior heat conduction coefficient and surface thermal emissivity. The temperature of electrode material will decrease. (2) the theoretical model of concentration field and stress field of electrode material will be established. The effects of isotropy and anisotropy on the concentration field and stress field in the lithium phase transition of hollow core-shell and thin-film Si negative materials are studied by using finite element software. It is found that the circumferential tensile stress of hollow core-shell Si negative material is greater than that of isotropy when the material is anisotropic. This is more likely to lead to the destruction of Si negative materials. (3) the theoretical model of concentration field and stress field of electrode materials under thermal-mechanical-chemical coupling is established. The effect of different charging modes on the concentration field and stress field of LiyMn2O4 cathode materials with hollow core-shell structure in the process of thermal-mechanical-chemical coupling lithium is studied by using finite element software. It is found that the circumferential tensile stress of LiyMn2O4 materials increases with the decrease of curvature at constant flow rate, which leads to the destruction of LiyMn2O4 materials more easily. At constant concentration, the circumferential tensile stress of LiyMn2O4 increases with the increase of curvature a _ (b), which leads to the destruction of LiyMn2O4 materials more easily. Then the concentration field and stress field of lithium ion in the thermal-mechanical-chemical coupling of two spherical LiyMn2O4 positive particles are analyzed. It is found that the compressive stress in the contact region between the two spherical LiyMn2O4 positive particles is very large, which leads to a lower lithium ion concentration in the two spheres than in the other regions.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM912
[Abstract]:The electrode material of Li-ion battery is the key material to determine the working voltage and service life of lithium-ion battery. The research of Li-ion battery mainly focuses on the structure design, process improvement and electrochemical performance of electrode material. In recent years, researchers have paid more and more attention to the relationship between the deformation of electrode material and electrochemical performance in charge-discharge process of Li-ion battery. The stress of electrode materials is mainly caused by the diffusion of lithium ions and the uneven temperature distribution. The energy density and cycle life of lithium-ion batteries are closely related to the stress of electrode materials. Too much stress will lead to the destruction of electrode materials and ultimately lead to the failure of lithium-ion batteries. In order to understand and understand the evolution of lithium ion concentration field and stress field in lithium electrode material in essence, this paper is based on the basic theory of temperature field, through theoretical analysis and finite element numerical simulation. The theoretical models of concentration field and stress field of Li-ion battery and its key electrode are established. The main contents of this thesis are as follows: (1) the theoretical model of the temperature field of electrode materials during charge-discharge process of Li-ion battery is established. The influence of thermal conductivity coefficient and surface thermal emissivity on temperature field of electrode material is studied by using finite element software. It is found that the thermal conductivity coefficient and surface thermal emissivity of electrode material increase with the increase of surface and exterior heat conduction coefficient and surface thermal emissivity. The temperature of electrode material will decrease. (2) the theoretical model of concentration field and stress field of electrode material will be established. The effects of isotropy and anisotropy on the concentration field and stress field in the lithium phase transition of hollow core-shell and thin-film Si negative materials are studied by using finite element software. It is found that the circumferential tensile stress of hollow core-shell Si negative material is greater than that of isotropy when the material is anisotropic. This is more likely to lead to the destruction of Si negative materials. (3) the theoretical model of concentration field and stress field of electrode materials under thermal-mechanical-chemical coupling is established. The effect of different charging modes on the concentration field and stress field of LiyMn2O4 cathode materials with hollow core-shell structure in the process of thermal-mechanical-chemical coupling lithium is studied by using finite element software. It is found that the circumferential tensile stress of LiyMn2O4 materials increases with the decrease of curvature at constant flow rate, which leads to the destruction of LiyMn2O4 materials more easily. At constant concentration, the circumferential tensile stress of LiyMn2O4 increases with the increase of curvature a _ (b), which leads to the destruction of LiyMn2O4 materials more easily. Then the concentration field and stress field of lithium ion in the thermal-mechanical-chemical coupling of two spherical LiyMn2O4 positive particles are analyzed. It is found that the compressive stress in the contact region between the two spherical LiyMn2O4 positive particles is very large, which leads to a lower lithium ion concentration in the two spheres than in the other regions.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM912
【参考文献】
相关期刊论文 前5条
1 马增胜;周益春;刘军;薛冬峰;杨庆生;潘勇;;锂离子电池硅负极材料衰退机理的研究进展[J];力学进展;2013年06期
2 何亮明;杜，
本文编号：2462727
本文链接：https://www.wllwen.com/kejilunwen/dianlidianqilunwen/2462727.html
