X-Ray Absorption Fine Structure Imaging of Lithium Ion Secondary Battery

Abstract

  The X-ray absorption fine structure (XAFS) imaging with two-dimensional detector is a powerful tool to analyze the reaction distribution of lithium ion secondary battery. We have achieved the distribution analysis of transitional metal elements in the active material of lithium ion secondary battery by analyzing their XAFS spectra, which represent the chemical state of the transition metal element directly related to the existence of the lithium ion. The appearance of reaction channels caused by the electron conduction network was evaluated for the LiFePO₄ electrode. The distribution maps of the lithium ion during the charging/discharging processes were thus identical for the LiFePO₄ electrode, whereas the map for the LiNiO₂ electrode during the charging process was opposite to that during the discharging process. It is considered that the reaction distribution of the LiNiO₂ electrode is generated by the disturbed lithium ion diffusion due to the generated side products, which cover the electrode surface.