Thermal runaway and jet flame features of 314 Ah lithium iron phosphate battery: Mechanism exploration and safety assessment

In the field of energy storage, safety has emerged as a paramount concern due to its growing importance. The prevailing trend is to enhance the capacity of individual batteries, which unfortunately heightens the risk when thermal runaway (TR) occurs. In this study, we examine the TR and jet flame characteristics of a 314 Ah lithium iron phosphate (LFP) battery subjected to overheating abuse. We comprehensively analyze the impacts of heating power and state of charge (SOC) on parameters such as temperature, voltage, venting pressure, mass loss, expansion force, and flame area and height. Findings indicate that an increase in SOC results in the safety valve opening earlier and a sooner TR initiation. The peak battery temperature correlates linearly with SOC. Higher SOC also leads to increased expansion force change rates, gas pressure, and exhaust speed. We identify four phases-initial jet flame, stable combustion, secondary jet flame, and flame abatement-based on distinct flame characteristics. Specifically, both flame area and height enlarge as SOC rises. Furthermore, we established a TR hazard assessment model, revealing that a 25% SOC battery exhibits the lowest TR hazard, while a 100% SOC cell presents the highest. This research enhances the understanding of TR and fire behavior in large-capacity LFP batteries, offering valuable insights for fire prevention design and emergency management.