Synchronized Operando Analysis of Graphite Negative Electrode of Li-Ion Battery

Abstract

Since the rechargeable Li-ion battery was invented in the early 1990s, its performance has evolved continually and Li-ion batteries are now installed in most mobile devices. In these batteries, graphite is used as a negative electrode material. However, the detailed reaction mechanism between graphite and Li remains unclear. Here we apply synchrotron X-ray diffraction, 7Li-nuclear magnetic resonance and Raman spectroscopy to operando analysis of the charge/discharge mechanism of a graphite electrode. The spectrum of the graphite electrode is measured repeatedly during the reaction. The operando dataset obtained is then analyzed synchronously with the composition of x in LiCx estimated from the charge/discharge curves. We propose a synchronized operando analysis method that provides useful information about the behavior of the C-C bond vibration mode and the interactions between Li and carbon atoms due to structural change during the charge/discharge reaction. In addition, we determine details of the intercalation mechanism.