Thermal Runaway Propagation—Critical Variables and Protocols

Abstract This study describes the efforts taken to determine the variables that are critical to obtain consistent and repeatable results to initiate thermal runaway in Li-ion multicell packages and modules. In this study, lithium primary cells were also studied under similar conditions. A series of tests was conducted to evaluate the effects of various parameters that need to be considered when designing experimental studies to investigate the thermal runaway behaviors of Li-ion batteries. The results show that a heating rate of 5–10 °C/min produced the most stable and consistent results compared to higher or lower heating rates, but 10 °C/min was chosen as the standard for a majority of the tests. The control thermocouple positioned 5 mm from a heater provided more accurate measurements of the heating rate of the cell avoiding excessively high temperatures near the heater. The comparison between two heating methods, a heater and an oven, showed that the heater offered better control of the heating rate but can be the cause of other unexpected reactions due to venting of semisolids from the cell if the temperatures exceeded a certain limit, whereas the oven heating provided uniform heating across the cell surface by convective heating. The states-of-charge (SOCs) greatly affected the propagation of thermal runaway between Li-ion cells. The results highlight the importance of test configuration and settings which may impact the outcome of the tests.