The Effect of Carbon Starting Material on Carbon Fluoride Synthesized at Room Temperature: Characterization and Electrochemistry

A series of carbon fluorine compounds (C x F) was prepared by catalyzed, room-temperature reactions of natural graphite, petroleum coke, and coal-tar-pitch coke with fluorine in the presence of HF and IF 5 . Elemental analysis indicated that most of the compounds had carbon-to-fluorine ratios between 1 and 2. X-ray diffraction, X-ray photoelectron spectroscopy, and infrared spectroscopy suggest that carbon-fluorine bond strengths were intermediate between ionic and covalent. The C x F materials exhibit higher reduction potentials when compared to commercially available CF x . Although the discharge capacities were lower for C x F compounds, their greater discharge voltage yielded higher energy densities than for analogous CF x cells. Discharge capacities for C x F increased slightly when prepared from petroleum coke heated to 1700°C compared with coke heated to 2600°C. This suggests that better discharge performance may be achieved from carbons with lower degrees of graphitization. C x F synthesized from natural graphite with particle sizes x F prepared from natural graphite with particle sizes between 20 and 40 µm. Materials prepared from coal-tar-pitch coke exhibited poor discharge capacities.