Understanding the Fundamental Mechanisms of Battery Thermal Runaway Propagation and Mitigation

The increased prevalence of larger and more energy-dense battery packs for transportation and grid storage applications has resulted in an increasing number of severe battery thermal events. The implications on product reliability, consumer safety, and the surrounding environment are significant. While there are many potential root causes for battery thermal runaway, these events often start within a single battery cell or group of cells that cascade to neighboring cells and other combustible materials, rapidly increasing the hazard profile of the battery pack as more stored energy is released. Reducing these hazards requires preventing severe thermal runaway scenarios by mitigating cell-to-cell propagation through the improved design of both individual cells and battery packs.

This work provides a fundamental understanding of how thermal runaway events can start in large-format battery packs, the mechanisms for thermal runaway propagation between individual cells, and the mitigation strategies currently available on the market. Understanding these mechanisms and implementing appropriate mitigation strategies into battery packs can enable the design of less hazardous and more reliable battery systems. There is an interplay between mitigation strategies and the ever-increasing energy density of cells toward enabling improved duration and longer-range applications, which will be highlighted below.