Chemical state analysis of Li and Si for Si negative electrode of solid-state lithium ion battery, using combination of windowless EDS and SXES on a SEM
Silicon (Si) negative electrode material has problems such as volume expansion and decrease of charging efficiency during charging-discharging, but it has a large theoretical capacitance of 4200 mAh/g and is attracting attention as a new material for Lithium (Li) ion secondary battery (LIB) to replace graphite which is widely used. Therefore, a chemical state analysis method using soft X-ray emission spectroscopy (SXES) has been reported for the purpose of structural analysis of the Si negative electrode active material in the charged state. However, since elemental mapping by SXES takes at least a few hours of processing time, it is not easy to compare the chemical state of each Si particle across the entire negative electrode layer. In this study, we combined a newly designed windowless EDS and SXES, and tried to establish a simple method to analyze the chemical state of Si negative electrodes in charged states.
The Schottky FE-SEM, JSM-IT800 (JEOL), combined with the SXES-LR, SS-94000SXES (JEOL), and the windowless EDS, Dry SDTM Gather-X (JEOL), was used for this study.