基于电化学-热耦合模型的21700型锂离子电池充放电过程热行为分析

Thermal behavior analysis of 21700 type lithium ion battery during charge-discharge cycles based on electrochemical-thermal model

锂离子电池具有比能量高、循环寿命长、输出功率大、可承受较宽充放电倍率等特点,已成为电动汽车领域电池开发的研究热点.锂离子电池在循环过程中的热行为对其性能、循环寿命和安全性有着较大的影响.本文基于21700圆柱形锂离子电池建立电化学-热耦合模型,并通过实验验证模型的精确性.分析了充电过程中的热行为,包含温度和产热分布.结果表明,充电过程中的温升主要受恒流充电过程的影响,电池平均温度和总产热均呈先上升后下降的趋势,且电池不可逆热占比高于可逆热.通过对比充放电过程的温度分布和产热变化可知,恒流充电过程中的产热和温度均大于恒流放电过程,充电过程具有温度提升时间短、变化速度快、产热峰值高等特点.

Lithium ion batteries have become a hotspot in the field of electric vehicles due to their excellent performance of high specific energy,long lifespan,high output power,and wide range of charge-discharge rates.The thermal behavior of the batteries during the charge-discharge cycle has a large impact on their performance,life cycle and safety.In this work,an electrochemical-thermal model is established based on a 21700 type cylindrical lithium ion battery,and corresponding experiments are conducted to validate the model.The thermal behavior during the charge process is analyzed,including the temperature and heat generation distribution.The results show that temperature rise in the charging process is mainly affected by the constant current charging process,the average temperature and heat generation of the battery both exhibit a trend of ascending first and descending later,and the irreversible heat shares a larger proportion of the total heat generation.The thermal behavior is contrasted between the charge and discharge process,and it is found that compared with the discharge process,the thermal behavior at the charge process has the characteristics of quick temperature change and high heat generation peaks.