锂离子电池失控机理模拟

Thermal Runaway Mechanism of Lithium Ion Batteries

锂离子电池由于存在热失控风险,安全性不能得到保障,在实际应用中仍存在局限。因此,了解热失控触发后电池的温度场变化规律,分析影响温度变化的因素是很有必要的。使用ANSYS FLUENT对锂离子电池进行模拟,建立了单体锂离子电池三维瞬态生热模型,通过模拟发电端不稳定导致的不同充放电波动功率输入下电池的温度场变化来研究电池内部热扩散规律;模拟锂离子电池局部内短路触发热失控后的温度场变化来分析热扩散规律。结果表明,锂离子电池的温度和壁面热流密度随输入电流的波动而波动。锂离子电池局部内短路触发后,热失控沿着电极纵向扩展的速率大于沿径向向外扩散的速率,增加对流换热系数能有效降低电池温度升温速率和幅度,降低电池触发热失控的可能性。研究热扩散规律对于实际应用中预测热失控、提高安全性、改善电池冷却工艺等提供了研究依据。

As an important technical form of electrochemical energy storage,lithium ion battery is still limited in practical application due to the possibility of thermal runaway.Therefore,it is necessary to understand the variation rule of battery temperature field after thermal runaway trigger and analyze the factors affecting temperature change.In this paper,ANSYS FLUENT is used to simulate the lithium ion battery,and the internal thermal diffusion law of the battery is studied by simulating the temperature field change of the battery under different charge and discharge fluctuation power input caused by the instability of the generator end.The thermal diffusion law is analyzed by simulating the temperature field after the thermal runaway triggered by local short circuit in lithium ion battery.The results show that the temperature and wall heat flux of the lithium-ion battery fluctuate with the input current.When triggered by local short circuit,the rate of thermal runaway extending lengthwise along the electrode is greater than that of radially spreading outwards.Increasing convective heat transfer coefficient can effectively reduce the rate and amplitude of battery temperature rise,reducing the possibility of thermal runaway of battery.The study of thermal diffusion law provides a basis for predicting thermal runaway in practical application,improving safety,and improving battery cooling technology.