Rate Capability and Electrochemical Stability of Carbon Fluorine Compounds in Organic Electrolytes

Polarization measurements of cathodes containing various carbon fluorine compounds, CF n ( n = 0.24 – 1.5 ) , as the active depolarizer material were made in 1 M LiClO 4 ‐ propylene carbonate at 298°K. The polarization (free of ohmic iR drop) was measured, using the periodically interrupted sine wave pulse current technique. The open‐circuit potentials and polarization data were analyzed, considering their mixed potential character. The two major factors that influenced the data were the C / F ratio and the electrode compression pressure. With graphite fluorides, activation polarization was prevalent and Tafel behavior was observed ( b = 0.12 ) . The exchange currents were low, peaking at n = 0.93 with 10 −22 A. From the exchange currents, the cathodic currents at the mixed potentials were computed. For n = 0.93 , a value of about 7 · 10 − 10 A was obtained, indicating a depolarizer shelf life of about 10 6 years. Compounds with higher rate capabilities, such as polymeric, perfluorinated, and polycyclic hydrocarbons, show a very short shelf life by oxidizing rapidly the organic solvent. The experimental behavior of such compounds can be explained by the mixed potential theory. Shifts in open circuit, mixed potentials to more positive values are predicted for compounds with higher rate capability and can be observed experimentally.