【摘要】：鋰離子電池電極材料是決定其工作電壓和使用壽命的關(guān)鍵材料。鋰離子電池的研究主要集中在電極材料的結(jié)構(gòu)設(shè)計、工藝改善和電化學(xué)性能等方面,近年來研究人員逐漸關(guān)注鋰離子電池充放電過程中電極材料的變形與電化學(xué)性能的關(guān)系,其中電極材料的應(yīng)力主要是由鋰離子的擴散和溫度分布的不均勻而引起的。鋰離子電池的能量密度、循環(huán)壽命等主要性能表征量都與電極材料的應(yīng)力有著緊密地聯(lián)系,應(yīng)力過大就會導(dǎo)致電極材料的破壞,最終導(dǎo)致鋰離子電池的失效。為了從本質(zhì)上認(rèn)識和理解電極材料鋰化過程中的鋰離子濃度場和應(yīng)力場的演變規(guī)律,本論文基于溫度場的基本理論,通過理論分析和有限元數(shù)值模擬,建立鋰離子電池及其關(guān)鍵電極材料化-力作用下的濃度場和應(yīng)力場的理論模型。本論文的研究內(nèi)容主要包括以下三個方面:(1)建立鋰離子電池充放電過程中電極材料的溫度場的理論模型。利用有限元軟件研究電極材料表面與外界的熱傳導(dǎo)系數(shù)和表面熱輻射率對其溫度場的影響,發(fā)現(xiàn)隨著表面與外界的熱傳導(dǎo)系數(shù)和表面熱輻射率的增加,電極材料的溫度會降低。(2)建立電極材料化-力作用下的濃度場和應(yīng)力場的理論模型。利用有限元軟件研究各向同性與各向異性對空心核-殼和薄膜結(jié)構(gòu)Si負(fù)極材料相變鋰化過程中的濃度場和應(yīng)力場的影響,發(fā)現(xiàn)空心核-殼結(jié)構(gòu)Si負(fù)極材料各向異性時環(huán)向拉應(yīng)力大于各向同性的情況,這更容易導(dǎo)致Si負(fù)極材料的破壞。(3)建立電極材料熱-力-化耦合時的濃度場和應(yīng)力場的理論模型。利用有限元軟件研究不同充電方式對空心核-殼結(jié)構(gòu)LiyMn2O4正極材料熱-力-化耦合鋰化過程中的濃度場和應(yīng)力場的影響。發(fā)現(xiàn)在恒定流量下,隨著曲率a/b的減少,LiyMn2O4材料的環(huán)向拉應(yīng)力不斷增加,這更容易導(dǎo)致LiyMn2O4材料的破壞;在恒定濃度下,隨著曲率a/b的增加,LiyMn2O4材料的環(huán)向拉應(yīng)力不斷增加,這更容易導(dǎo)致LiyMn2O4材料的破壞。然后分析兩球形LiyMn2O4正極顆粒相接觸下其熱-力-化耦合時的鋰離子濃度場和應(yīng)力場。發(fā)現(xiàn)兩球形LiyMn2O4正極顆粒相接觸的區(qū)域壓應(yīng)力很大,導(dǎo)致其鋰離子濃度明顯低于其它區(qū)域的鋰離子濃度。
[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.
【學(xué)位授予單位】：湘潭大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TM912

【參考文獻(xiàn)】

相關(guān)期刊論文 前5條

1 馬增勝;周益春;劉軍;薛冬峰;楊慶生;潘勇;;鋰離子電池硅負(fù)極材料衰退機理的研究進(jìn)展[J];力學(xué)進(jìn)展;2013年06期

2 何亮明;杜，

本文編號：2462727