Vanadium Oxide Fluoride‐Graphite Intercalation Compounds: Structural Characteristics and Electrochemical Insertion of Lithium Cations

Graphite intercalation compounds of vanadium oxide fluoride, , were synthesized in a fluorine atmosphere. Fourier transform infrared spectroscopy, x‐ray photoelectron spectroscopy, and x‐ray diffraction measurements were used for their structural characterization. These experiments have suggested that cointercalation of fluorine and in the carbon occurs involving local structural modifications and that excess oxygen was present in the graphite layers. The study of electrochemical insertion of lithium was carried out at 25°C in a ‐propylene carbonate electrolyte by chronopotentiometry and ac impedance measurements. The interfacial charge‐transfer process, associated to the half‐reaction occurring during the intercalation, was found to be independent of the intercalation ratio of lithium cations, y . The chemical diffusion coefficient, D Li , and the conductivity, σ Li , obtained were deduced from impedance data by considering the geometric surface area. Both are roughly constant for all the y ‐range: and for and for .