Contacts: yves.kayser@cec.mpg.de
Web-site: https://www.cec.mpg.de/en/research/inorganic-spectroscopy/dr-yves-kayser
The in-house X-ray spectroscopy group at the MPI CEC operates several stand-alone instruments for high-energy-resolution spectroscopy. Depending on the design of the instrument, either X-ray absorption spectroscopy experiments in transmission mode or X-ray emission spectroscopy experiments can be performed. The standout property of X-ray spectroscopy as an analytical technique is its element sensitivity, which enables the electronic structure of a selected element to be investigated in detail. Changes in the X-ray absorption or emission spectra can reveal information about the coordination, spin state, oxidation state, atomic weight, and distance to neighboring atoms. X-ray emission spectroscopy can be realized in the energy range from 2.3 keV to 20 keV (K-lines of S to Ru), and X-ray absorption spectroscopy can be realized in the energy range from 0.2 keV to 1.0 keV (K-edge of C, N, O and F, and L-edge of 3d transition metals), and from 5 keV to 15 keV (K-edge of 3d transition metals heavier than V, and L-edge of heavy metals).
X-ray emission spectrometer at MPI CEC
A full cylinder von Hamos geometry X-ray emission spectrometer with an integrated glovebox for handling samples under inert conditions is available for ex situ and post mortem investigations of electrodes. Changes in the electronic structure of 3D transition metals can be targeted to monitor changes in pristine materials and during battery cycling. The spectrometer was developed in collaboration with the Berlin Laboratory for Innovative X-ray technologies and is equipped with highly annealed pyrolytic graphite optics, which, in combination with the full-cylinder configuration, optimizes the instrument's detection efficiency. A liquid metal jet coupled with polycapillary optics is used to efficiently excite a selected element, making valence-to-core transitions accessible. These transitions are characterized by low probability, but provide insight into ligand identity and bond length.
EXAFS spectrometer
An X-ray absorption spectrometer based on the von Hamos geometry and optimized for extended X-ray absorption fine structure analysis in transmission mode is available to explore the local structure around the metals used in cathodes. This will improve our understanding of the changes that occur in batteries after cycling. The instrument has a large energy bandwidth, making the energy range around the ionization threshold of several elements accessible simultaneously. Spectra are obtained by integrating the signal over time, with typical measurement times of the order of hours (minutes for foils) and no need for scanning through positions. This instrument was developed in collaboration with the Berlin Laboratory for Innovative X-ray Technologies.
X-ray absorption and emission spectrometer at MPI CEC
An X-ray spectrometer based on the Johann geometry that can flexibly be used for X-ray absorption measurements in transmission mode or X-ray emission spectroscopy experiments will be explored for in situ investigations coupled with impedance spectroscopy. Unlike the other instruments, this instrument keeps the samples under ambient conditions, allowing for a more straightforward combination with any complementary analytical technique, such as impedance spectroscopy, for a hybrid in situ or operando analysis of batteries. The instrument can be easily reconfigured from X-ray absorption spectroscopy to X-ray emission spectroscopy, or vice versa, by simply rotating the X-ray source and repositioning the sample.
Researcher at MPI CEC
Yves Kayser graduated with a degree in physics in 2007 and received his PhD in 2011 from the University of Fribourg in Switzerland. His dissertation explored combining grazing emission fluorescence with high-energy-resolution X-ray spectroscopy for depth profiling applications. Following a postdoctoral fellowship at the University of Fribourg, during which he integrated a micro-focused X-ray source with an existing X-ray emission spectrometer, Yves Kayser worked as a postdoctoral researcher at the Swiss Light Source of the Paul Scherrer Institute from 2012 to 2016. He focused on the metrology of X-ray optics at synchrotron radiation sources and X-ray free electron lasers, using grating interferometry. However, it also included activities relating to scanning-free grazing emission spectroscopy and resonant X-ray emission spectroscopy. From 2016 to 2022, he was part of the X-ray spectrometry group at the Physikalisch-Technische Bundesanstalt (PTB). There, he continued to work on grazing X-ray fluorescence techniques and X-ray emission spectrometry using radiometrically calibrated instrumentation, which the group had established to allow reference-free quantification. During this time, he was involved in several European projects covering topics ranging from semiconductor technologies to environmental and battery research. In 2022, he joined the Max Planck Institute for Chemical Energy Conversion, working in the Department of Inorganic Spectroscopy headed by Serena DeBeer. He is in charge of the in-house X-ray spectroscopy group, which operates stand-alone instrumentation for high-energy-resolution X-ray spectroscopy. The group operates X-ray emission and X-ray absorption spectrometers for laboratory-based measurements of samples relevant to the storage or release of energy from chemical bonds. The group is continuously developing its instrumentation capabilities to meet the requirements of samples of interest within the department, as well as expanding the scope of measurements that can be performed.