One of the lesser-known but critical aspects of Thermal Runaway (TR) in lithium-ion batteries is the 'Ejection of Particles'. These particles, depending on their size, composition, and deposition location, can significantly influence the propagation of TR within a battery pack. For instance, if particles settle on or near other cells, they can induce short circuits or block cooling pathways, thereby exacerbating or spreading the thermal event to adjacent cells.
A recent study takes an innovative approach to measuring these ejected particles during TR, providing insights that could be pivotal in designing safer battery systems. This research introduces a novel experimental setup that mimics real-world conditions within EV battery modules during TR episodes.
The experimental setup employed involves integrating a single prismatic lithium-ion cell into an environment that closely represents a typical section of an EV battery pack. The setup included 86 weighing plates placed within the path of the vented gases and particles. This arrangement allowed researchers to capture and quantify the spatial mass distribution of particles as they were ejected from the cell during TR. Such detailed measurement is critical because it helps identify which particles are likely to contribute to the propagation of TR by settling on neighboring cells or in pathways critical for the battery's thermal management systems.
To test the effectiveness of their setup, the researchers Hoelle S et. al. conducted two proof-of-concept experiments. These experiments varied the distance between the cell vent and the module cover, a key variable that could influence how particles are dispersed within a battery module. The findings from these experiments were revealing; they showed that different configurations significantly affect the deposition patterns of the ejected particles. For example, a shorter distance tended to concentrate particle deposition closer to the vent, suggesting that in a tightly packed battery module, such configurations could increase the risk of TR propagation.
Furthermore, the study also analyzed the particle size distribution and the specific heat capacity of both the ejected particles and the remains of the jelly roll (the burnt residue inside the cell post-TR). These measurements are essential for refining simulation models used to predict the behavior of batteries under fault conditions. By improving the accuracy of these models, engineers can better design battery packs that are not only more resistant to thermal runaway but also better at containing its effects should it occur.
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