Numerical Model of the Heat-Wait and Seek and Heating Ramp Protocol for the Prediction of Thermal Runaway in Lithium-Ion Batteries

Interest in Battery-Driven Electric Vehicles (EVs) has significantly grown in recent years due to the decline of traditional Internal Combustion Engines (ICEs). However, malfunctions in Lithium-Ion Batteries (LIBs) can lead to catastrophic results such as Thermal Runaway (TR), posing serious safety concerns due to their high energy release and the emission of flammable gases. Understanding this phenomenon is essential for reducing risks and mitigating its effects. In this study, a digital twin of an Accelerated Rate Calorimeter (ARC) under a Heat-Wait-and-Seek (HWS) procedure is developed using a Computational Fluid Dynamics (CFD) framework. The CFD model simulates the heating of the cell during the HWS procedure, pressure build-up within the LIB, gas venting phenomena, and the exothermic processes within the LIB due to the degradation of internal components. The model is validated against experimental results for an NCA 18650 LIB under similar conditions, focusing on LIB temperature and domain pressure. The CFD model effectively captures the heat released by the LIB undergoing TR through convection and radiation to the surrounding air while providing temporal and spatial resolution of gas composition before and after the safety-vent collapse. This tool is, therefore, useful for calibrating TR models under controlled conditions and assessing flammability in future studies. The study is completed by analyzing various heating conditions to understand their impact on key parameters, revealing an influence on the maximum temperature reached by the LIB and the temporal evolution of gas composition but showing a lower TR trigger temperature and a faster TR trigger time.