German institute’s X-ray system sees inside batteries during thermal runaway

A high-speed X-ray system developed by the Fraunhofer Institute for High-Speed Dynamics Ernst-Mach-Institut (EMI) has shown researchers what happens inside a vehicle battery cell when it fails, according to an institute press release.

“Until now, cell manufacturers and vehicle integrators have had to rely on simulations, destructive testing methods, and indirect measurements,” a Fraunhofer EMI press release states.

The release notes that a key engineering milestone is a protective chamber that reliably shields sensitive X-ray components from the extreme conditions generated during lithium-ion cell thermal runaway.

The X-ray system makes dynamic processes inside large-format prismatic cells visible in real time for the first time and is designed as a modular platform, according to the release. Researchers say the system can be scaled to different cell formats and new cell chemistries, which Fraunhofer EMI notes is an important advantage for future battery development.

Along with German cell manufacturer PowerCo, a Volkswagen Group company, Fraunhofer EMI is now bringing the technology into industrial use, the release states.

“The system combines high-performance X-ray technology with a specially designed battery test chamber and advanced sensor systems that simultaneously capture temperature, pressure, voltage, and gas flow,” the release states. “Recording up to 1,000 images per second, it reveals processes such as gas formation, material displacement, and crack propagation inside the cell at extremely high resolution…”

Sebastian Schopferer, Fraunhofer EMI head of battery safety, adds that the institute’s in-situ method allows researchers to see what happens inside a cell in fractions of a second, in real time, and in high resolution.

“This fundamentally changes how we understand battery design and safety,” he said in the release.

Fraunhofer EMI says it has already used the system for several German car manufacturers, including Volkswagen and Audi, “to characterize material ejection during thermal runaway and propagation behavior in multi-cell configurations.”

“The resulting data enables engineers to assess cell designs based on directly observed processes and refine simulation models with greater precision—delivering direct added value for product development and certification processes,” the release states.

In the next phase of development, Fraunhofer EMI and PowerCo plan to transfer the technology into industrial use. The release notes that Fraunhofer EMI brings expertise in materials research, battery abuse testing, and high-speed imaging while PowerCo contributes production requirements and access to real-world cell types.

“Initial results from the collaboration are already feeding into the development of optimized production cells at PowerCo, accelerating the path from research to industrial implementation,” the release states. “The system is scheduled for installation at PowerCo’s Salzgitter site in 2028.”

HW Vassen, PowerCo chief technology officer, adds that in-situ high-speed X-ray imaging takes battery research to a new level.

“For the first time, we can make the dynamic processes inside cells visible in real time and in slow motion,” he said in the release. “This unprecedented depth of insight allows us to optimize battery cell safety and design in a highly targeted way and bring innovations into industrial use much faster. Together with Fraunhofer EMI, we are advancing high technology made in Europe and are strengthening Europe’s role in the battery industry.”

Images

Featured image: Research being conducted by the Fraunhofer Institute for High-Speed Dynamics Ernst-Mach-Institut (EMI).

A still image taken from an X-ray video recorded during a nail penetration test of a prismatic lithium-ion cell.

Fraunhofer EMI’s laboratory test setup for in-situ visualization of thermal runaway in lithium-ion cells. 

All photos provided by Fraunhofer EMI.