低压环境下不同三元圆柱锂电池热失控危险特性对比研究

Comparative study on thermal runaway hazardous characteristics of different ternary cylindrical lithium battery under low-pressure environment

为研究21700和18650新旧2型多用途锂离子电池在航空运输低压环境下的热失控特性差异,采用动压变温实验舱搭建实验平台开展实验。将实验环境压力设定为飞机巡航时的环境压力30 kPa,对比常压101 kPa,使用外部热源加热的方式触发锂电池热失控,利用热传播引发相邻电池热失控,分别从热失控温度变化特性、热释放速率和热解气体组分浓度变化进行分析。研究结果表明:能量密度更高的21700电池热失控峰值温度更高,高温危险性要高于18650电池,但触发热失控所需的热量更多,电池间热传播时间会延长;低压环境有利于降低锂电池热失控燃爆峰值温度,减小燃爆热释放速率,但会产生更多CxHy和CO等具有燃爆性的热解气体,可能会在有限空间内与氧气混合引起二次燃爆。

In order to study the difference in the thermal runaway characteristics of two types of multi-purpose new and old lithium-ion batteries including 21700 and 18650 lithium-ion battery under the low-pressure environment of air transportation,an experimental platform was set up by using the experiment module with variable pressure and temperature to conduct the experiments.The experimental environment pressure was set to be 30 kPa where the aircrafts are cruising,compared with normal pressure of 101 kPa,the external heat source was used to trigger the thermal runaway of the lithium battery,and the heat propagation was used to cause the thermal runaway of adjacent batteries.The characteristics of thermal runaway temperature change,heat release rate(HRR)and concentration of pyrolysis gas components were mainly analyzed.The results showed that the 21700 battery with higher energy density had a higher thermal runaway peak temperature and a higher high-temperature hazard than the 18650 battery.However,more heat was required to trigger the thermal runaway,so the time of heat propagation between the batteries would be prolonged.The low-pressure environment was beneficial to reduce the thermal runaway blasting peak temperature of lithium battery,decrease the HRR of blasting,but generate more pyrolytic gases with blasting properties such as CxHy and CO,which may cause secondary blasting when mixing with O2 in the confined space.