Fire forensic investigators are challenged to determine in what scenarios can lithium ion batteries initiate a fire, and what post-fire signatures exist to determine if the battery was more likely the cause of the fire or a victim of the fire. Towards this goal, this study experimentally characterizes the ignition characteristics of cylindrical format 18650 cells and the post-failure properties of the cells. First, failure tests of individual 18650 cell were used to quantify the temperature of vented gases and heat fluxes from these gases to cold objects for battery thermal failure at various states-of-charge (SOC) in either inert or normal oxygen environments. Experiments were then conducted with 18650 cells failed on composite cushion materials to evaluate how failures from different SOC cells ignite common fabric materials. Finally, laptop tests were conducted to investigate the effect of a common appliance package on the propagation of individual cell thermal runaway within the power bank of a common laptop configuration. The experimental results show that in the event of a thermal runaway, batteries can either explode or release a jet flame. The ignition behavior of fabric materials varies with varying SOCs with more vigorous ignition occurring at larger SOC. It was observed that the final mass of failed batteries is lower for higher SOC cells. Finally, propagation of thermal runaway inside a laptop power bank can be facilitated by having the failure take place at the center location of the power bank and can be hindered if the SOC is sufficiently low.

消防取证调查员面临挑战，要确定锂离子电池在什么情况下会引起火灾，以及存在哪些火灾后信号来确定电池是否更可能是引起火灾的原因或火灾的受害者。为了达到这个目标，本研究通过实验表征了圆柱形18650型电池的着火特性和电池的失效后特性。首先，使用单个18650电池的故障测试来量化排出气体的温度以及从这些气体到冷物体的热通量，以在惰性或正常氧气环境中以各种荷电状态（SOC）进行电池热故障。然后对18650个在复合垫材上失效的电池进行了实验，以评估不同SOC电池的失效如何点燃普通织物材料。最后，进行了笔记本电脑测试，以研究通用设备封装对通用笔记本电脑配置的电源组中单个电池热失控传播的影响。实验结果表明，在热失控的情况下，电池可能会爆炸或释放出喷射火焰。织物材料的着火行为随SOC的变化而变化，在更大的SOC下会发生更剧烈的着火。观察到，对于较高的SOC电池，失效电池的最终质量较低。最后，通过使故障在移动电源的中心位置发生，可以促进笔记本电脑移动电源内部的热失控传播，如果SOC足够低，则可以阻止故障的发生。