Benchtop, High-Resolution XAFS and Xes Spectrometers As Tools for Electrochemical Research

Advanced x-ray spectroscopies allow the direct and element-specific interrogation of local electronic structure, yet their scientific impact is necessarily constrained by access limitations. This is particularly evident for x-ray absorption fine structure (XAFS) and x-ray emission spectroscopy (XES) techniques. Here, the technical capability afforded by a synchrotron x-ray facility allows researchers to answer basic or applied research questions and push the forefront of science. These national-lab scale sources often provide the only means to perform these techniques, consequently slowing progress on critical projects, and also largely excluding routine analytical characterization. Over the last four years, our group at the University of Washington has been developing several new families of lab-based instruments to expand the accessibility of advanced x-ray spectroscopies. [1-5] It is now possible to identify the electroactive element in a material and assess its oxidation state, spin state, and coordination chemistry – all with benchtop XAFS and XES. The feasibility of these studies is established by comparing performance of our benchtop instruments with various synchrotrons in the context of several electrochemical systems. From the standpoint of materials inquiry, we will present a variety of measurements of lithium ion batteries, valence-to-core XES results from a series of oxides, and preliminary efforts toward solution-phase measurements will be presented. The latter will be done with an eye toward future electrolyte analyses. William M. Holden, et al. “A Compact Dispersive Refocusing Rowland Circle X-ray Emission Spectrometer for Laboratory, Synchrotron and XFEL Applications”, Rev. Sci. Instrum 88, 073904 (2017). [DOI: 10.1063/1.4994739] T. Seidler, et al., “A Laboratory-based Hard X-ray Monochromator for High-Resolution X-ray Emission Spectroscopy and X-ray Absorption Near Edge Structure Measurements,” Review of Scientific Instruments 85, 113906 (2014). [DOI: 10.1063/1.4901599] T. Seidler, et al., “A Modern Laboratory XAFS Cookbook,” Journal of Physics: Conference Series 712, 012015 (2016). [ http://iopscience.iop.org/article/10.1088/1742-6596/712/1/012015] R. Mortensen, et al., “Benchtop Nonresonant X-ray Emission Spectroscopy: Coming Soon to Laboratories and Beamlines Near You,” Journal of Physics: Conference Series 712, 012036. (2016) [http://iopscience.iop.org/article/10.1088/1742-6596/712/1/012036] G.T. Seidler, “The Case for Analytical XAFS”, https://www.linkedin.com/pulse/case-benchtop-analytical-xafs-gerald-seidler