Battery failure can happen due to electric short-circuits, overheating or through impact or penetration. This can ultimately lead to a process known as ‘thermal runaway’. Now a team led by Paul Shearing, professor of chemical engineering at University College London, has come up with an effective way to quantify thermal runaway within batteries. The results are published in Energy and Environmental Science.

For the last 10 years, Shearing and collaborators at the National Renewable Energy Laboratory in the United States and the European Synchrotron Radiation Facility (ESRF) have been developing improved battery safety testing methods using the ESRF’s beamline ID19. The team has now produced a toolbox to assess and quantify safety features of batteries, and have quantified, for the first time, the rate of propagation of battery failure mechanisms revealed by high-speed X-ray radiography. The team uses a unique combination of Gabor filtering and cross-correlation, which enables the toolbox to track selectively the internal structure at the onset of failure. Thermal runaway propagation within batteries by nail penetration has been shown to occur more slowly than previously thought, which may have safety consequences when compared to other types of failure that stem from instantaneous short-circuiting or thermally induced degradation events.

This tool can not only validate existing theoretical mechanical models, but also standardise battery failure testing procedures. In this way, manufacturers could track where and how failure starts in the battery. Most of the data collected by the team over years of research has been made open source via the Battery Failure Databank

Image: 2D spatiotemporal cross-correlation mapping as a quantitative technique to track failure propagation; this image shows the spatiotemporal map where a ball compresses the electrode structure. The map indicates that the centre of the ball, x ≈ 3.45 mm, starts displacing the electrodes from t ≈ 0.04 s, where the extent of displacement reduces radially due to the circular profile of the ball.

Case study published December 2022.