Understanding Battery Thermal Runaway Propagation

Three Exponent scientists explain mechanisms and mitigation strategies for battery thermal runaway events in a technical paper published by the Society of Automotive Engineers

As the energy density of battery packs for vehicles and grid energy storage increases, how can we make high-density energy systems less hazardous and more reliable?

That's the question explored by three Exponent scientists — Nicholas Faenza, Ryan Spray, and Michelle Kuykendal — in their new technical paper, "Understanding the Fundamental Mechanisms of Battery Thermal Runaway Propagation and Mitigation." The authors explain how severe thermal runaway scenarios can occur and outline the tenets of successful mitigation to reduce these hazards.

Thermal runaway events often begin with the failure of a single battery cell or group of cells, cascading to other neighboring cells, and increasing in severity as the stored energy of the battery pack is released. To reduce the likelihood and severity of these scenarios, the scientists discuss design strategies that can impede propagation of thermal runaway events between cells.

To implement these design strategies and moderation measures, the authors suggest that design engineers first develop a deep understanding of the mechanisms that drive battery thermal runaway propagation. To start, the authors outline a number of the factors that drive many cell failures and runaway events such as acute exposure of a cell to high temperatures, mechanical abuse, and flaws in the construction of either individual cells or the battery pack.   

The paper then discusses the mechanisms by which thermal runaway propagation can occur between cells and provides details on the fundamentals of these methods. In addition, the authors provide an overview of potential mitigation approaches to prevent thermal runaway propagation that are currently used in industry and commentary on pathways for developing an effective protection strategy.

The technical paper was released and discussed at The Energy & Mobility Conference & Expo by SAE International, which took place in Cleveland, Ohio, Sept. 12-15, 2023.

From the publication: "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."