發(fā)布時(shí)間：2018-04-16 19:17

  本文選題：鋰離子電池 + 熱應(yīng)力　； 參考：《北京有色金屬研究總院》2014年碩士論文

【摘要】：鋰離子電池已經(jīng)成為發(fā)展電動(dòng)汽車(chē)的關(guān)鍵。鋰離子電池在充放電過(guò)程中伴隨著電極材料的脫嵌鋰和溫度升高,從而引起電池厚度的變化和熱應(yīng)力的產(chǎn)生。一方面厚度和應(yīng)力的改變可能引起電池性能的變化,對(duì)電池的壽命和可靠性造成不利的影響。另一方面也制約了電池的成組設(shè)計(jì)。因此研究鋰離子電池厚度變化和熱應(yīng)力分布特征既可以提高對(duì)電池性能變化規(guī)律的認(rèn)識(shí),也可以為電池成組設(shè)計(jì)提供依據(jù),具有重要的科學(xué)意義和實(shí)用價(jià)值。 本論文根據(jù)鋰離子電池結(jié)構(gòu)特點(diǎn)將其簡(jiǎn)化成具有儲(chǔ)能功能的疊層材料,采用疊層材料細(xì)觀力學(xué)模型和有效熱膨脹理論計(jì)算得到相關(guān)力學(xué)參數(shù)。然后依據(jù)熱平衡方程和傳熱邊界條件,通過(guò)理論計(jì)算得到了鋰離子電池穩(wěn)態(tài)溫度場(chǎng)方程。最后根據(jù)穩(wěn)態(tài)溫度場(chǎng)方程和阻止應(yīng)變法計(jì)算得到電池的熱應(yīng)力方程,并使用ANSYS模擬了在常規(guī)使用條件下鋰離子電池的穩(wěn)態(tài)溫度場(chǎng)和熱應(yīng)力場(chǎng)。論文最后使用線(xiàn)性位移傳感器原位測(cè)量了鋰離子電池充放電過(guò)程中厚度的變化,分析其變化規(guī)律和影響電池厚度變化的因素,并推導(dǎo)了鋰離子電池厚度變化與SOC的關(guān)系。主要結(jié)論有： (1)方形鋰離子電池穩(wěn)態(tài)溫度場(chǎng)為橢球方程,等溫面為橢球面。電池幾何中心位置溫度最高,最高溫度與對(duì)流換熱系數(shù)呈反相關(guān)、與生熱速率呈線(xiàn)性相關(guān)。最大溫差與電池的生熱速率和電池尺寸的平方成正比。當(dāng)生熱速率Q=8500W/m3,環(huán)境溫度為20℃時(shí),電池中心最高溫度為23.4℃,最大溫差為0.6℃。 (2)鋰離子電池?zé)釕?yīng)力分布不均勻,電池中心高溫區(qū)域熱膨脹受到抑制承受壓應(yīng)力,側(cè)邊低溫區(qū)域受拉應(yīng)力,側(cè)邊中心處出現(xiàn)熱應(yīng)力集中。沿x方向最大壓應(yīng)力為15.0KPa,最大拉應(yīng)力為31.4KPa,最大拉應(yīng)力約為最大壓應(yīng)力的兩倍。von miss應(yīng)力最大為29.7KPa,最小為0.56KPa。剪切應(yīng)力在對(duì)稱(chēng)面上近似為零,在長(zhǎng)度和寬度的2/3處出現(xiàn)極小值,為-5.4KPa。 (3)軟包裝鋰離子電池在充放電過(guò)程中厚度的變化與SOC狀態(tài)、電池初始厚度、電極材料的種類(lèi)和配比、充放電制度、溫升等因素有關(guān)。1/3C、1/2C和1.0C循環(huán)時(shí)電池厚度變化規(guī)律相似,變化的幅度分別為0.061mm、0.061mm和0.069mm,充電時(shí)電池厚度變厚,放電時(shí)厚度減小,厚度變化可逆。充電時(shí)SOC從0%增加到40%時(shí)電池厚度增加了0.040-0.050mm,占總變化量的70-80%,SOC在50%附近電池厚度基本保持不變。放電電流大于1.0C時(shí),電池的溫升較大,電池厚度因溫升引起的變化也較大。放電電流為2.0C時(shí)電池表面溫升達(dá)到9.2℃,引起電池厚度的變化為0.013mm,計(jì)算得電池沿厚度方向的熱膨脹系數(shù)為1.9×10-4/℃。
[Abstract]:Lithium ion battery has become the key to the development of electric vehicles. The lithium ion battery during charging and discharging with electrode materials of lithium intercalation and temperature, causing the battery thickness change and thermal stress. On the one hand, the thickness and stress change may cause changes in the performance of battery, resulting in adverse effects on the battery life and reliability. On the other hand also restricted the design of battery group. So the study on lithium-ion battery thickness change and thermal stress distribution can not only improve the understanding of the changes of battery performance, can also provide the basis for the design of battery meter group, has important scientific significance and practical value.
In this paper the simplified with laminated material storage function according to the structural characteristics of lithium ion battery, calculate the mechanical parameters of the laminated composite micromechanics model and thermal expansion theory. Then based on the heat balance equation and heat transfer boundary conditions obtained by theoretical calculation equation for the steady-state temperature field of lithium ion batteries. At last according to the steady-state temperature field equation and prevent strain calculated battery thermal stress equation, and use ANSYS to simulate the steady-state temperature field and thermal conditions in the routine use of lithium ion batteries. The stress field at the end of the paper, the thickness change in the charge discharge process of lithium ion battery was measured using a linear displacement sensor in situ, factor analysis the variation and influence of battery thickness change, and the relationship between the thickness of lithium ion battery with the change of SOC. The main conclusions are derived:
(1) the steady temperature field of square lithium ion battery for ellipsoid equation, the isothermal surface for an ellipsoid. The highest cell geometry center temperature, maximum temperature and heat transfer coefficient had a negative correlation with linear correlation. The heat rate of heat generation rate and battery size and the maximum temperature difference is proportional to the square of the battery. When the heating rate of Q=8500W/m3 and the ambient temperature is 20 degrees centigrade, battery center highest temperature is 23.4 DEG, the maximum temperature of 0.6 degrees.
(2) lithium ion battery thermal stress distribution is not uniform, the cell center area of high temperature thermal expansion was inhibited under compressive stress, the side zone of tensile stress, the thermal stress concentration occurs at the center. The side along the X direction of the maximum compressive stress is 15.0KPa, the maximum tensile stress is 31.4KPa, the maximum tensile stress is about two times the maximum compressive stress of.Von Miss stress and maximum 29.7KPa, minimum 0.56KPa. shear stress on the symmetric plane is approximately zero, the minimum value is 2/3 at length and width, -5.4KPa.
(3) the change in the thickness of the soft packing lithium ion batteries during charge and discharge the battery with SOC status, initial thickness, type and ratio of electrode material, charge discharge system, the temperature rise is related to the factors such as.1/3C, 1/2C and 1.0C cycle variation in the magnitude of the change is similar to the thickness of the battery, respectively 0.061mm, 0.061mm and 0.069mm when the thickness of the battery, charging, discharge when the thickness decreases, the thickness change is reversible. When charging increases from 0% SOC to 40% 0.040-0.050mm when the battery thickness increases, the total changes in the amount of 70-80%, SOC remained unchanged in the vicinity of 50%. The thickness of the battery discharge current is more than 1.0C, the battery temperature is larger and larger battery because of the temperature rise caused by the thickness change. The discharge current of 2.0C battery surface temperature reached 9.2 degrees, caused by the change of the thickness of the battery is 0.013mm, the calculated cell along the thickness direction of the thermal expansion coefficient of 1.9 x 10-4/ C.

【學(xué)位授予單位】：北京有色金屬研究總院
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類(lèi)號(hào)】：TM912

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