(Invited) Operando Analysis for Charge/Discharge Reaction Mechanism of Graphite Anode of Li Ion Battery

The first preparation of Li-graphite intercalation compound (Li-GIC) was attempted by Hérold et al. in 1955. Since then, a lot of reports have been made mainly by the research groups in France, and with regard to the stage I and II compounds, it is clarified that they take the in-plane structures called by P(√3×√3)R30°. Though there have been many reports since 1970s, the detail discussion has not been done so far concerning the intercalation mechanism and in-plane structure of higher stage compounds. The first reason is that the concentration of Li species becomes smaller in the higher stages. The second reason is the strong preferred orientation of graphite. Such reasons make difficult to clarify the intercalation mechanism and in-plane structure. In order to improve the performance of Li-ion battery, it is essential to investigate the detail structure change of graphite electrode during the charge/discharge process. In this study, in order to elucidate the intercalation mechanism and structure change not only along c-axis, but also along the a,b-axes, we traced dynamically the intercalation reaction in Li-ion battery negative electrode by Operando measurement with synchrotron radiation diffraction.