Lithium intercalation into graphite: In operando analysis of Raman signal widths

Abstract

The mechanism of reversible lithium intercalation in graphite anodes is still not fully understood. In operando Raman spectroscopy provides a sensitive means to monitor structural changes during the intercalation process. Analysis of the D-band to G-band intensity ratio (D/G ratio) is a common method to study the structure of carbon materials. However, this approach is complicated for the investigation of graphite anodes during battery cycling, as the D-band disappears with the onset of lithium intercalation. To circumvent this issue, the D/G ratio can be replaced by using the G-band full-width-at-half-maximum (FWHM). In this study, an investigation of the G-band FWHM during battery cell cycling is demonstrated as an alternative to monitor the intercalation of lithium into a graphite electrode. It was observed that lithium intercalation already occurs to a small extent during solid–electrolyte interphase (SEI) formation and that the formation of staged intercalation compounds leads to a continuous deformation of the boundary graphene layer.