Development of a two-dimensional imaging system of X-ray absorption fine structure

Abstract

A two-dimensional imaging system of X-ray absorption fine structure (XAFS) has been developed at beamline BL-4 of the Synchrotron Radiation Center of Ritsumeikan University. The system mainly consists of an ionization chamber for I(0) measurement, a sample stage, and a two-dimensional complementary metal oxide semiconductor (CMOS) image sensor for measuring the transmitted X-ray intensity. The X-ray energy shift in the vertical direction, which originates from the vertical divergence of the X-ray beam on the monochromator surface, is corrected by considering the geometrical configuration of the monochromator. This energy correction improves the energy resolution of the XAFS spectrum because each pixel in the CMOS detector has a very small vertical acceptance of ∼0.5 µrad. A data analysis system has also been developed to automatically determine the energy of the absorption edge. This allows the chemical species to be mapped based on the XANES feature over a wide area of 4.8 mm (H) × 3.6 mm (V) with a resolution of 10 µm × 10 µm. The system has been applied to the chemical state mapping of the Mn species in a LiMn(2)O(4) cathode. The heterogeneous distribution of the Mn oxidation state is demonstrated and is considered to relate to the slow delocalization of Li(+)-defect sites in the spinel crystal structure. The two-dimensional-imaging XAFS system is expected to be a powerful tool for analyzing the spatial distributions of chemical species in many heterogeneous materials such as battery electrodes.

Local atomic structure inheritance in Ag50Sn50 melt

“…AIMD simulation results and the experimental ones. and Sn in the alloy melt,[28][29][30][31][32][33] which agrees well with the PDOS results. Combined with Ref.…”

Ionic Conduction in Lithium Ion Battery Composite Electrode Governs Cross-sectional Reaction Distribution

“…S3 ). Mapping the absorption energy as a function of pixel position provides the information about cross-sectional reaction distribution of the electrodes 20 . Sample for this mesurement is explained in Fig.…”

“…The rate performance, the cross-sectional reaction distribution and electronic/ionic conductivity in various porous composite electrodes are experimentally measured. To investigate the cross-sectional reaction distribution occurring in composite electrodes, two-dimensional (2D) imaging X-ray absorption spectroscopy (XAS) technique is applied 20 . For the measurement of electronic/ionic conductivity in composite electrodes, we have developed a method for simultaneous measurement of electronic and ionic conductivities in composite electrodes.…”

Electrochemical Evaluation of Active Materials for Lithium Ion Batteries by One (Single) Particle Measurement

“…This is due to current (potential) distribution in the porous electrode. 18,19 One of useful method to eliminate the effect of porous nature is a utilization of thin electrode which should be less than 10 µm. In this case, the current distribution (potential) distribution is not so large, so that the electrochemical properties of active materials can be evaluated more precisely.…”