低温循环老化锂离子电池热失控特性研究

Study on thermal runaway characteristics of low-temperature cyclic aging Li-ion batteries

锂离子电池在低温环境下工作会不可避免地发生循环老化,导致电池容量下降、阻抗增加等性能衰退,更会加剧电池发生热失控的风险。文章搭建了热失控试验平台,进行锂离子电池低温环境下循环老化热失控特性研究,分析老化程度、荷电状态及其耦合条件对锂离子电池热失控特性的影响。研究发现:在-10℃的低温环境下,电池发生燃爆的时间提前,喷射更加剧烈,温升速率上升更为明显,但电池表面上部(近泄压阀)温度随循环圈数的增加而降低。由于电池下部没有喷射口,热量聚集导致电池下部温度略高于上部。试验同时给出了不同老化程度及荷电状态下电池发生热失控时的电压及质量损失演变规律。研究结果有助于提高对老化锂离子电池热失控特性的认识,为低温环境下运行的锂离子电池安全性提供理论依据及数据支撑。

Lithium-ion batteries working at low temperatures will inevitably experience cyclic aging,resulting in performance declines such as reduced battery capacity and increased impedance,which will exacerbate the risk of thermal runaway of the battery.In this study,a thermal runaway experiment platform was built to study the thermal runaway characteristics of lithium-ion batteries after cyclic aging at low temperature,and the effects of different aging degrees,charging states and coupling conditions on the thermal runaway characteristics of lithium-ion batteries were analyzed.It is found that under-10℃low temperature environment,the time of thermal runaway explosion is advanced,the injection is more intense,and the temperature rise rate of the battery is more obvious,but the temperature on the upper part of the battery surface(near the pressure relief valve)decreases with the increase of the number of cycles.Since there is no jet port in the lower part of the battery,the heat accumulation causes the lower part of the battery to be slightly warmer than the upper part.At the same time,the evolution law of voltage and mass loss of the battery under different aging degree and charged state is given.This work helps to improve the understanding of thermal runaway characteristics of aging lithium-ion batteries,and provides theoretical basis and data support for the safety of lithium-ion batteries operating in low temperature environment.