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

Abstract

International audienceA series of carbon fluorine compounds (C_<i>x</i>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 IF₅. 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_<i>x</i>F materials exhibit higher reduction potentials when compared to commercially available CF_<i>x</i>. Although the discharge capacities were lower for C_<i>x</i>F compounds, their greater discharge voltage yielded higher energy densities than for analogous CF_<i>x</i> cells. Discharge capacities for C_<i>x</i>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_<i>x</i>F synthesized from natural graphite with particle sizes <10 µm had a greater discharge capacity on a mass basis but a lower discharge efficiency based on F content when compared to C_<i>x</i>F prepared from natural graphite with particle sizes between 20 and 40 µm. Materials prepared from coal-tar-pitch coke exhibited poor discharge capacities

Model Passivated Carbon Electrodes for Fluorine Generation in Molten KF-2HF Electrolyte

“…This is believed to be related to the amount and type of impurities present in the material used as a binder for these kinds of electrodes, e.g., coal-tar pitch in TT amorphous carbon (Figure 3). This is consistent with the findings by Root et al (13) who found that pure coal-tar pitch was poorly fluorinated even by direct chemical fluorination using gaseous F 2 at elevated temperatures. Thus, the coal-tar pitch may confer a beneficial effect of helping the carbon material resist the formation of stable carbonfluorine (C-F) bonds.…”

Advanced Carbon Fluorides For Primary Lithium Batteries

“…The voltage initially drops and then increases steadily to reach the main voltage plateau after few minutes; such a behavior has been already observed for graphite fluorides. [4,5] The average potential is stable during the discharge in agreement with the unique C-F bonding (determined by 13 C and 19 F solid state NMR), which is still covalent whatever the fluorination conditions. The most unexpected observation is that the experimental capacity (Qexp) significantly exceeds the theoretical value (Qtheo), for those two materials.…”

Enhanced electrochemical activity of rechargeable carbon fluorides–sodium battery with catalysts

“…For the pristine electrode, the peaks at 284.3 and 291.8 eV in C 1s spectrum correspond to C-C and C-F in CF x , respectively, while the peak at 287.6 eV is assigned to C-F in PVDF. In F 1s spectrum, the peaks at 688.6 and 686.8 eV can be assigned to C-F in CF x and Fe-F in FeF 3 , respectively [15]. The relative intensity ratio of the first to the second peak is about 1.25:1.…”