A semi-quantitative analysis of infrared characteristics of thermal runaway ejection behaviour of lithium-ion battery

Lithium-ion battery (LIB) thermal runaway at elevated temperatures generates heat, smoke, and a jet fire and high-temperature mixture (JFHM) of gases, vapours, and particles. The ejection of the JFHM may damage the surrounding humans and facilities. In this study, an 18650 battery was heated at different State of Charges (SOCs) or heating powers to have a thermal runaway, and the ejection process was captured by a high-speed infrared camera. The evolution of the JFHM was obtained in the experiment in a semi-quantitative way. The vertical ejection of the JFHM presented a clear V-shape, and the horizontal ejection appeared more dispersed from the front side. A semi-quantitative analysis to evaluate the high temperature scope of the ejection was developed. The results indicate that the ejection has positive correlation with the SOC or heating power. The vertical flame length of the JFHM peaks at 79.33 mm, and the longest horizontal flame length is 68.82 mm. Based on the analysis results, new calculation method was developed to predict the ejection dimensions. A better understanding of the thermal runaway ejection can contribute to the design of devices with LIBs.