锂离子电池热应力分析及厚度变化的研究

发布时间：2018-04-16 19:17

本文选题：锂离子电池 + 热应力　；参考：《北京有色金属研究总院》2014年硕士论文

【摘要】：锂离子电池已经成为发展电动汽车的关键。锂离子电池在充放电过程中伴随着电极材料的脱嵌锂和温度升高,从而引起电池厚度的变化和热应力的产生。一方面厚度和应力的改变可能引起电池性能的变化,对电池的寿命和可靠性造成不利的影响。另一方面也制约了电池的成组设计。因此研究锂离子电池厚度变化和热应力分布特征既可以提高对电池性能变化规律的认识,也可以为电池成组设计提供依据,具有重要的科学意义和实用价值。本论文根据锂离子电池结构特点将其简化成具有储能功能的叠层材料,采用叠层材料细观力学模型和有效热膨胀理论计算得到相关力学参数。然后依据热平衡方程和传热边界条件,通过理论计算得到了锂离子电池稳态温度场方程。最后根据稳态温度场方程和阻止应变法计算得到电池的热应力方程,并使用ANSYS模拟了在常规使用条件下锂离子电池的稳态温度场和热应力场。论文最后使用线性位移传感器原位测量了锂离子电池充放电过程中厚度的变化,分析其变化规律和影响电池厚度变化的因素,并推导了锂离子电池厚度变化与SOC的关系。主要结论有： (1)方形锂离子电池稳态温度场为椭球方程,等温面为椭球面。电池几何中心位置温度最高,最高温度与对流换热系数呈反相关、与生热速率呈线性相关。最大温差与电池的生热速率和电池尺寸的平方成正比。当生热速率Q=8500W/m3,环境温度为20℃时,电池中心最高温度为23.4℃,最大温差为0.6℃。 (2)锂离子电池热应力分布不均匀,电池中心高温区域热膨胀受到抑制承受压应力,侧边低温区域受拉应力,侧边中心处出现热应力集中。沿x方向最大压应力为15.0KPa,最大拉应力为31.4KPa,最大拉应力约为最大压应力的两倍。von miss应力最大为29.7KPa,最小为0.56KPa。剪切应力在对称面上近似为零,在长度和宽度的2/3处出现极小值,为-5.4KPa。 (3)软包装锂离子电池在充放电过程中厚度的变化与SOC状态、电池初始厚度、电极材料的种类和配比、充放电制度、温升等因素有关。1/3C、1/2C和1.0C循环时电池厚度变化规律相似,变化的幅度分别为0.061mm、0.061mm和0.069mm,充电时电池厚度变厚,放电时厚度减小,厚度变化可逆。充电时SOC从0%增加到40%时电池厚度增加了0.040-0.050mm,占总变化量的70-80%,SOC在50%附近电池厚度基本保持不变。放电电流大于1.0C时,电池的温升较大,电池厚度因温升引起的变化也较大。放电电流为2.0C时电池表面温升达到9.2℃,引起电池厚度的变化为0.013mm,计算得电池沿厚度方向的热膨胀系数为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.

【学位授予单位】：北京有色金属研究总院
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM912

【参考文献】