层叠式锂离子电池展向温度分布的分析解及基于分析解的热设计优化

大型锂离子动力电池的热相关问题是限制其在电动汽车上大规模应用的主要问题之一.单体电池的热模型是进行电池热设计、改善电池热特性的重要工具.根据热模型的求解方法,可分为数值解和分析解两类.在现有文献的研究中,数值解占据了主要地位.但是,分析解因具有计算量小、可实现设计变量的全局优化等优点,在电池热设计和电池组热管理系统中可发挥重要作用.例如,在电池热设计中,分析解可全面考察多个设计参数连续变化下对电池热特性的影响,以进行多设计参数下的全局优化.本文首先对一款大型层叠式锂离子电池进行了数值热模拟和实验验证,数值热模拟的结果与多枚热电偶的实验测量结果吻合良好;然后,基于数值热模拟的结果提取了层叠式电池温度分布和产热率分布的主要特点,进而假设温度呈展向平面分布、产热率均匀分布;针对简化后的电池热问题,利用双重积分变换方法提出了分析解;最后,使用分析解开展了电池的热设计优化工作,讨论了不同电芯尺寸和极耳布置方案下的电池热特性.

Thermal design optimization of laminated lithium ion battery based on the analytical solution of planar temperature distribution

Thermal issues constitute a major barrier to the deployment of large-format lithium ion batteries on electrical vehicles. Thermal modeling is a powerful tool to investigate the thermal design and improve the thermal performance of the battery. There are two methods to solve thermal models, the numerical simulation and the analytical solution. Most of the thermal modeling works reported in the literature are based on the numerical simulation. However, the analytical solution is highly desirable for optimization as it allows the effects of mutiple thermal parameters to be evaluated simultaneouly, thanks to its low computational cost. This work firstly proposes and validates a numerical thermal model for a 25 Ah laminated lithium ion battery. The simulated temperatures agree well with the experiment results from multiple thermocouples. Secondly, an analytical solution to the planar temperature distribution is deduced using the integral transform technique, assuming that the temperature distribution is two-dimensional and the heat generation rate is uniform. These assmuptions are justified from the simulation results. Finally, the analytical solution is used to optimize the battery thermal design, including the optimal core aspect ratio and the tab displacement.