Modeling the propagation of internal thermal runaway in lithium-ion battery

The trend toward high capacity and huge size in lithium-ion batteries has made it necessary to investigate the internal thermal characteristics. In this study, a thermal runaway model was developed to describe lithium-ion batteries' internal thermal characteristics. Moreover, triggering energy was proposed as a critical feature for evaluating and characterizing the thermal runaway under diverse thermal abuse situations, with large differences among characteristic temperatures. Finally, the effects of battery configuration on thermal runaway behaviors were investigated. The modeling results showed that internal temperature distribution can be divided into four characteristic stages with two jelly rolls, and the application of more numerous and thinner cells inside a battery can accelerate the propagation of thermal runaway. The experimental results showed that the ratio of triggering energy of self-heat onset to total self-heat generation remained consistent in an adiabatic environment. The mean value of the ratio was 24.5%, indicating that lithium iron phosphate batteries obtain most of the energy (generally 80%) from internal exothermic reactions during adiabatic thermal abuse. The triggering energy of thermal runaway remained constant when various heating powers were applied to one of the batteries' laterals (about 20.8% of theoretical energy contained inside lithium iron phosphate batteries). Triggering energy can provide new insights into the modeling of thermal runaway mechanisms and propagation.