The electrification of mobility is a major inflection point for reducing greenhouse gas emissions and air pollutants from the transportation sector. In this context, the Li-ion battery is currently the technology shared by automakers to provide the energy storage needed to deploy electrified vehicles.
However, Li-ion batteries can undergo incidents with dramatic consequences, referred to as thermal runaway (TR). This can result from abnormal conditions: excessive temperature, mechanical deformation, electrical overcharge, internal short circuit. TR is characterized by a violent reaction, that is, difficult to control and can release hazardous gases. This issue is today a crucial safety concern that strongly impacts the design and the battery management strategies.
The objective of this study is to contribute to the understanding of the phenomena by focusing on the variability of the battery cell (BC) TR induced by thermal initiation. The commercial BC used is an 21700 cylindrical LG M50LT with state-of-the art active materials: NMC811 for the positive electrode and silicon graphite composite for the negative electrode.
The variability of the TR phenomenon is analyzed experimentally using two different devices: the first is Accelerating Rate Calorimeter (an ARC) with the specific Heat Wait and Search protocol and, the second, is a high-pressure/high-temperature vessel, based on constant heating ramps, using specific instrumentation with optical access to visualize the combustion phases.
The variability of the TR phenomenon is subsequently examined through essential key parameters as cell self-heating onset, venting event and accelerated TR temperature.
Finally, a calibrated and validated TR model for the BC studied allows the observed phenomena to investigating by confronting the experimental results with a sensitivity analysis of the model.
The results allow to highlight the interest of considering the variability of the TR phenomenon by thermal initiation for numerical calibration.
