High-Speed Imaging for Investigating Battery Failure Mechanisms

As the EV and battery market continues to grow, understanding and mitigating battery thermal runaway remains a critically important area of research. Under controlled experimental conditions, researchers have employed a range of different techniques to initiate battery fires and understand both how and why they occur. These tests give important information about how a battery cell catastrophically fails under abuse conditions. However, recognizing the changes in the internal structure of the cell is vital to understanding the mechanisms of thermal runaway which enables the development of effective mitigation strategies. During the last decade, X-ray imaging has emerged as an important diagnostic tool for battery degradation, electrochemical performance, and safety diagnostics. Researchers use X-ray imaging to directly observe the internal changes in the cell during all stages of thermal runaway. Depending on the initiation method, it can sometimes take minutes, hours, or days for a cell to undergo failure. However, the actual final reactions that cause thermal runaway occur over fractions of a second. High-speed cameras, operating at up to 40,000 frames per second, can capture the interactions between electrodes at the final moments of thermal runaway. In this article, the basics of high-speed X-ray imaging and how this technique has been applied to investigating battery thermal runaway are discussed.