Inline X-ray computed tomography (CT) is a powerful inspection technique that can further reduce the risk of defects and recalls, compared with today’s 2D X-ray inspection techniques. However, to achieve the levels of inspection coverage, throughput and resolution necessary for high-volume battery production, a high-power X-ray source with a micrometer-sized X-ray spot is necessary. The Excillum MetalJet E1+ 160 kV source makes this possible, achieving a full scan with micrometer resolution in just one second.
When it comes to energy production – such as solar cells, fuel cells or water splitting – an understanding of a material’s physiochemical properties is essential to efficient energy conversion. Excillum X-ray sources boost both throughput and resolution in X-ray based techniques including XRD, SAXS, XRF, XAS/XES, HAXPES and more, enabling researchers to gain deeper understanding of the relations between a material’s macroscopic performance and microscopic properties.
In-line microCT of EV battery cells
An internal feature to be inspected during manufacturing of a battery is the anode overhang. The anode should be dimensioned to overlap the cathode. To produce this with repeatability puts high demands on the manufacturing and process precisions. To inspect this with precision in prismatic battery cells, X-ray CT is a pre-requisite. Furthermore, to have a 3D model of each produced battery cell can be very helpful for forensics in case a battery cell would fail in the field – in order to minimize a recall to an as small volume as possible.
With the MetalJet E1+, Excillum is looking to enable high-speed 3D X-ray inspection of industrial samples, such as batteries. In this video, you’ll see an example of how we achieve a full CT-scan with micrometer resolution of an electrolyte filled battery cell, taken from a VW Golf GTE, in only 1 second.
100 % 3D X-ray inspection, or 3D complement to 2D inspection in unclear cases, is a promising path to satisfactory quality control. But, in order to achieve 100 % 3D X-ray inspection, a high-power X-ray source with a micrometer-sized X-ray spot is needed – something previously not available on the market.
The experiments were performed at Excillum’s facilities in Sweden using our MetalJet E1+, a high-performance detector from Direct Conversion (Thor FX20.256 CdTe) and a high-speed, high-precision rotation stage.
A NanoCT system with the Excillum NanoTube has been designed, developed and commissioned at Fraunhofer IIS, Würzburg, Germany. Together with an EIGER2 CdTe detector, the system has been optimized for materials characterization and NDT applications.
The image shows a 3D rendering of the NanoCT of a lithium ion battery cathode (NCA/LCO-E), showing particles of different sizes. Voxel sampling 140 nm.
Challenging high entropy oxide samples
Researcher at Karlsruhe Institute of Technology utilized a STOE Stadi MP goniometer powered by a MetalJet D2+ to investigate challenging high entropy oxide (HEO) samples. The challenge was to measure a large number of samples and that for every type of sample only a small amount was available. By illuminating the powder samples with a focused bright and small beam of quasi monochromatic Gallium K β radiation, a good signal to noise ratio was obtained with an acceptable measurement time. Powder XRD data sets of a HEOs with varying composition are illustrated here.
For more details, please see the references:
Wang et.al.: Spinel to Rock-Salt Transformation in High Entropy oxides with Li Incorporation. Electrochem 2020, 1, 60–74;doi:10.3390/electrochem1010007
Wang et.al.: Multi-anionic and –cationic compounds: new high entropy materials for advanced Li-ion batteries. Energy Environ. Sci. 2019; doi: 10.1039/c9ee00368a
Performance improvements of solar cells
In the laboratory at Meiji University, led by Professor Atsushi Ogura, the objective is to improve the performance of solar cells and electronics devices based on semiconductor nanotechnology. A significant improvement in material characterization capability was achieved when a Scienta Omicron HAXPES-Lab system was installed. The HAXPES-Lab is a home laboratory-type hard X-ray photoelectron spectroscopy (HAXPES) system with the key components: monochromator, high energy analyzer and a 9 keV X-ray source, the Excillum MetalJet D2+.
The non-destructive technique of HAXPES opens up a window to the bulk, as the technique can characterize the element-specific chemical states sub surface of materials, e.g. at buried interfaces or in the bulk. Previously, 9 keV photoemission had only been possible at synchrotron beamlines but with the introduction of the HAXPES-Lab system experiments in the home laboratory became possible, 24 hours a day, 365 days a year.
Investigation of bulk heterojunction solar cells
GISAXS and GIWAXS are X-ray methods used to give insight into the order and orientation of thin films on a substrate, typical examples include solar cells, long range order of block copolymers, nanoparticles and nanoparticle composites, membranes and lithographic patterning.
Using a high intensity X-ray source such as the MetalJet for these experiments enables in-situ investigation of materials. One example of such an in-situ study is that of Vegso at al. from the institute of physics of the Slovak academy of science. They used a laboratory GISAXS/GIWAXS setup with a MetalJet emitting Ga Kα X-ray radiation to investigate the phase separation of the polymer and the fullerene phase in a bulk heterojunction solar cell.
The size and intermixing of domains of the electron acceptor (polymer) and the electron donor (fullerene) are key determinants of the efficiency with which solar energy is converted to electrical power. The combination of GISAXS and -WAXS give unprecedented insight into the real-time structural evolution of the polymer:fullerene phase separation in terms of polymer crystallization and fullerene agglomeration. GISAXS patterns were collected with 10 second intervals and GIWAXS patterns with 2.5 second intervals. These short exposures were sufficient to follow the kinetics of the bulk heterojunction formation of the spin-coated polymer: fullerene mixture by means of tracking the ratio of assembled material versus non-assembled material (φ) as depicted in the picture to the right, the radius of gyration (Rg) of the fullerene phase and the d100 spacing of the lamellar polymer phase.
Ratio of assembled versus not assembled polymer-fullerene mixture as calculated from grazing incidence scattering measurements.