基于液冷策略的锂离子电池组安全管理研究

发布时间：2018-06-09 01:54

本文选题：锂离子电池 + 热管理系统　；参考：《中国科学技术大学》2017年硕士论文

【摘要】：锂离子电池的容量、内阻以及电压对所处的工作温度十分敏感。因此,电池组内部温度的不均一性会明显降低电池组的性能并且缩短电池的寿命周期。此外,锂离子电池在高度集成后,电池产生的热量在电池组内积聚,由于自身结构抗滥用性较差,容易发生热失控进而引起火灾或者爆炸事故。本文通过有限元数值模拟方法和小尺寸的实验对锂离子电池的液冷管理以及安全防护技术进行研究,旨在提出锂离子电池组优化设计方法,建立灭火-冷却一体化系统,为电池组均衡管理与消防灭火提供技术支撑。在开放环境下分别对单电池、自然对流电池组以及使用液冷策略的电池组进行动态充放电测试,并研究电池的温度分布、电压以及电流的变化规律。结果表明,锂离子电池在动态循环中至少存在2个温度峰,随着电流倍率的增加,电池温度相应升高,温度峰发生了兼并。搁置工况一定程度上对电池升温过程进行缓冲,优化电池使用性能。在锂离子电池成组后,每个测点的波峰与波谷的出现存在时间差,温度极值以及温度波动呈现不同程度的增加。在0.5C、1C和3C循环倍率下系统中最高温度分别为27.4℃、38.5℃和62.9℃,最大温升分别为8.9℃、16.3℃和37.7℃,最大温差分别为4.9℃、4.2℃和13.7℃。使用液冷方案时,在同样的动态循环工况下,每个测点的时间差现象出现了明显的改善,系统的热均衡能力得到提高。在0.5C、1C和3C循环倍率下系统中最高温度分别为31.8℃、38.5℃和 56.2℃,最大温差分别为 1.6℃、3.5℃和 29.5℃。基于经典的传热理论以及电化学模型中提供的数学物理方法,利用多物理场仿真软件构建模型,对在开放环境中动态循环的单电池以及基于液冷策略动态循环的电池组进行了模拟与验证。结果表明,在动态循环过程中实验得到的单电池温度分布与模拟结果吻合较好,但模拟的充电电压比实验值偏高,最大值之间相差0.15V,同时在充电阶段模拟得到的温度峰也宽于实验温度峰。基于液冷策略,模拟得到的电池组温度分布与实验值变化趋势相同。由于热物性参数和动力学参数都是温度的函数,而模拟中所使用的为常量,导致模拟温度值低于实验值。在0.5C、1C和3C循环倍率下系统中模拟温度与实验温度最大误差分别为1.79℃、4.44℃和23.09℃。电池模组中外侧电池的模拟温度值与实验值相似。在0.5C、1C和3C循环倍率下的外侧电池模拟温度与实验测量值最大误差分别为1.1℃、3.09℃和 7.15℃。研究了火探管自身的热响应行为以及火探管灭火系统对锂离子电池火灾的灭火效率,根据实验结果提出火探管复合灭火系统方案。结果表明,火探管处于火焰区时响应时间较短,破裂降温较明显。当火探管灭火系统直接布置在电池正上方时,能在起火后的5.6s内有效控制火情,随着灭火剂用量增加体系温度将显著降低。火探管灭火系统是点式灭火系统,在灭火剂喷放后仅能冷却局部区域的电池单元,当覆盖区域外的电池发生失控后将作为热源继续加热临近电池,引发连锁热失控,也可能引起灭火区域内电池的复燃,造成灭火系统失效。根据实验结果,提出灭火技术与热均衡技术耦合的方法。
[Abstract]:The capacity, resistance and voltage of a lithium ion battery are very sensitive to the working temperature of the battery. Therefore, the inhomogeneity of the internal temperature in the battery group can obviously reduce the performance of the battery and shorten the life cycle of the battery. In addition, after the lithium ion battery is highly integrated, the heat generated by the battery is accumulated in the battery group, because of its own structure resistance. In this paper, the liquid cooling management and safety protection technology of lithium ion batteries are studied by the finite element numerical simulation method and small size experiment. The aim of this paper is to put forward the optimization design method of lithium ion battery group and establish an integrated fire extinguishing and cooling system, which is a battery pack. The dynamic charge and discharge test of single battery, natural convection battery group and liquid cooling strategy are carried out in the open environment, and the temperature distribution, voltage and current change law of the battery are studied. The results show that there are at least 2 temperatures in the dynamic cycle of the lithium ion battery. With the increase of the current ratio, the temperature of the battery increases and the temperature peak is annexed. The heating process of the battery is buffered to a certain extent, and the performance of the battery is optimized. After the lithium ion battery is set up, the time difference exists between the peak and the trough of each test point, the temperature extreme value and the temperature fluctuation show different range. The maximum temperature of the system at 0.5C, 1C and 3C cycles is 27.4, 38.5 and 62.9, respectively 8.9, 16.3 and 37.7, and the maximum temperature difference is 4.9, 4.2 and 13.7, respectively. When the liquid cooling scheme is used, the time difference phenomenon of each point in the same dynamic cycle is obviously changed. The thermal equilibrium ability of the system is improved. The maximum temperature of the system at 0.5C, 1C and 3C cycles is 31.8, 38.5 and 56.2, respectively 1.6, 3.5 and 29.5, respectively. Based on the classical heat transfer theory and the mathematical and physical methods provided in the electrochemical model, the model is constructed using the multi physical field simulation software. The simulation and verification of the single cell and the battery group based on the dynamic cycle of the liquid cooling strategy in the open environment are simulated and verified. The results show that the temperature distribution of the single cell obtained in the dynamic cycle is in good agreement with the simulation results, but the simulated charge voltage is higher than the actual test value, and the difference between the maximum values is 0.15V, and at the same time, The temperature peak of the simulation is also wider than the experimental temperature peak. Based on the liquid cooling strategy, the simulated temperature distribution of the battery group is the same as the experimental value. Because the thermal physical parameters and the kinetic parameters are the functions of the temperature, the simulated temperature is lower than the experimental value. The simulation temperature is lower than the experimental value. It is in 0.5C, 1C and 3C. The maximum error of simulated temperature and experimental temperature in the system is 1.79, 4.44 and 23.09. The simulated temperature of the battery module in the battery module is similar to the experimental value. The maximum error between the simulated temperature and the measured value at 0.5C, 1C and 3C cycle ratio is 1.1, 3.09 and 7.15. According to the experimental results, the thermal response behavior of the fire detection system and the fire extinguishing system for the lithium ion battery fire are proposed. The results show that the response time is shorter and the fracture temperature is more obvious when the fire probe is in the flame area. The temperature of the fire in the 5.6S after the fire will be effectively controlled, with the increase of the temperature of the system with the increase of the amount of fire extinguishing agent. The fire detection system is a point type fire extinguishing system. After the fire extinguishing agent is sprinkled, it can only cool the cell unit in the local area. When the battery outside the covering area is out of control, it will continue to heat near the battery as a heat source and cause the chain heat loss. The control may also cause the re ignition of the battery in the fire extinguishing area, resulting in the failure of the fire extinguishing system. Based on the experimental results, the coupling method of the fire extinguishing technology and the thermal equalization technology is put forward.
【学位授予单位】：中国科学技术大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM912

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