Thermal runaway and jet flame features of LIBs undergone high-rate charge/discharge: An investigation

In this work, a series of experiments are carried out to investigate the effect of charge/discharge rates (1, 2, 3 and 4 C) and state of charges (SOCs, namely 0%, 50%, 75% and 100%) on thermal runaway (TR) and fire behavior of lithium iron phosphate (LFP) batteries. The TR process caused by overheating LFP batteries is usually divided into four stages, with high temperatures and fire risks. High-rate charge and discharge damage the internal morphology and structural stability of materials seriously. The TR behavior of battery is fully aggravated, which is further manifested by the advanced opening of the safety vent, release of gas and occurrence of TR. With the increase of charging rate, the deteriorated TR characteristics can be discerned, such as the lower TR temperature, the shorter TR time, and the more serious TR consequences. Such changes can be assigned to the decline of battery stability. In addition, the battery SOC greatly impacts safety, especially the flame temperature and the severity of consequences. As for the 100% SOC battery cycled at 4 C, there is still a high risk of thermal runaway propagation at the position 1 m far away from the battery. This work helps to realize the TR and fire features of battery in-depth, enlightening the safety protection of battery.