Synchrotron CT: From brilliant images to innovative approaches for battery development and recycling

When it comes to particle accelerators, most people first think of their use in the discovery of new elementary particles or in nuclear energy research. But accelerators can do so much more: computer tomography, for example. Synchrotrons – particle accelerators in which electrons are accelerated to almost the speed of light – are used specifically for this purpose. In this interview, we explain how this technology can help make electric powertrains and batteries for electric vehicles safer in the development process, how it can make recycling more precise and efficient, and how it can map even the tiniest defects in objects with micrometer precision.

Prof. Zabler, how should we picture a synchrotron?

A synchrotron is a particle accelerator like those used at CERN, for example, only much smaller. We use the European Synchrotron (ESRF) in Grenoble, France, which has a specialized X-ray source with specific properties for computed tomography. With the help of accelerated electrons, we can create extremely brilliant X-rays – up to one million times brighter than a lab anode of the latest generation. This lets us produce highly detailed images.

The online magazine series Battery Research focuses in particular on sustainability and electromobility. What role can this technology play in sustainability?

In X-ray inspection, sustainability refers primarily to closed material cycles. This is based on the realization by policymakers that nowadays, a market economy based on the belief in the infinite availability of raw materials is no longer viable. What that means is that this market economy calculation must factor in the disposal of those raw materials. We have a responsibility to society to enable a shift toward a closed material cycle, in which a material or component – such as a battery – is completely recycled at the end of its service life. Unfortunately, we’re not there yet. That’s why we’re conducting intensive research into synchrotron CT technology.

In synchrotron CT, we can digitally record and analyze very high-resolution, razor-sharp 3D images of component pieces or material samples in order to determine various properties. What alloy, what kind of steel are we looking at? What is the average fiber length of this carbon fiber composite material? What does this electronic component look like at the micrometer level? With these and similar analyses, material can be sorted by type and returned to a closed cycle after its first life cycle. Materials tend to get recycled in mixed form today, which reduces the quality of the recyclate. 

“We can create extremely brilliant X-rays – up to one million times brighter than a laboratory anode of the latest generation. This means we can create highly detailed images.”

How is synchrotron CT helping to expand electromobility?

I define electromobility as the broad introduction of all-electric powertrains and energy storage systems for road passenger transportation. I’ve deliberately left out rail transport, as electrification is already widespread there. 

Regarding vehicle powertrains, we’d like to use synchrotron CT first and foremost to test components that can be damaged quickly. These could be parts from electrical powertrain technology, coils, magnets, stators, which we examine for potential faults or signs of wear. 

The other aspect of electromobility is the battery systems in electric cars. Here, there’s still a need for reverse engineering – in other words, drawing conclusions about individual components from the finished system. That’s because at the moment, the majority of energy storage systems are bought from Asia and installed here in Europe. Efforts are underway to bring production of these systems closer to home. Synchrotron CT can support this by mapping the state of the art in three dimensions with micrometer precision, thus shortening the corresponding development cycles. Another advantage of synchrotron CT is that it makes time-resolved imaging possible, too. This means we can also examine batteries and battery systems over their service life without restricting their use. That lets us carry out long-term studies – for example, by cycling batteries to accelerate their aging so we can investigate any problems that arise. 

What advantages does synchrotron CT offer customers? What problems can it solve?

In most cases, customers come to us for troubleshooting or to run accuracy tests. In other words, are the dimensions of the manufactured components within their defined tolerances? In principle, we can even check both things at the same time. Our imaging methods achieve 10–100 times higher contrast resolution and/or spatial resolution than conventional methods. This means we can take a much closer, much better look inside to find even the smallest defects or check the dimensional accuracy in detail. Here we’re talking about individual particles in the micrometer range, which become visible in high resolution thanks to this technology. Only the synchrotron can achieve that kind of accuracy.

Prof. Zabler, thank you for talking to us today.

Interview conducted by Lucas Westermann, editor, Fraunhofer IIS Magazine