Failure Analysis of Large Battery Systems - Challenges and Lessons

Learning from our mistakes is a defining characteristic of human existence and a cornerstone of scientific advancement. For as long as humans have been building things, we have puzzled over why they fail and have used failure analysis to improve subsequent designs. The lithium-ion battery industry is no exception to this rule. Failure analysis has been an important driver for safety and performance improvements since before Sony released the first commercial lithium-ion cell in 1991. Additionally, failure analysis can be pivotal to decisions made during legal actions involving lithium-ion batteries. However, the increasing complexity and size of lithium-ion batteries and the destructive power of large lithium-ion battery packs severely challenges conventional failure analysis techniques. In this presentation we will explore advanced techniques for understanding failures in large lithium-ion battery packs, such as those used in marine electrification applications. The implementation of computed tomography X-ray imaging (CT scanning), physical testing and incident reconstruction will be examined through the lens of a failure analysis investigation conducted on a large, rack-based lithium-ion battery pack that suffered thermal runaway creating an air-fuel deflagration event that severely injured four first responders.