Operando Raman Spectroscopy Insights into the Electrochemical Formation of F-Graphite Intercalation Compounds

This study presents the first observation of the electrochemical formation of graphite-F intercalation compounds (GICs) within LiF-containing organic liquid electrolytes. As determined by operando Raman spectroscopy measurements, the peaks corresponding to the G band (i.e., in-plane mode of sp(2) bonded carbon with a planar configuration) in highly oriented pyrolytic graphite (HOPG) are separated during the process of electrochemical oxidation, indicating that F-GIC is electrochemically formed in the HOPG electrodes. Furthermore, the rate of reaction and the reversibility of the electrochemical intercalation/deintercalation of F- are notably enhanced in HOPG electrodes endowed with a LiF-based surface layer. This enhancement suggests that augmenting the activity of F- ions, coupled with the suppression of side reactions, is pivotal for the successful electrochemical synthesis of F-GICs.