Low operational temperature Li-CF x batteries using cathodes containing sub-fluorinated graphitic materials
Commercial lithium/polycarbon monofluoride batteries [Li-(CF) n] are typically current-limited and are therefore not implemented in high-rate or low-temperature applications. Recent results suggest, however, that CF-based cathodes that use sub-fluorinated CF x (SFCF x) active materials in a thin electrode form factor are able to support very high currents (up to 5 C) while still providing a significant fraction of their specific capacity. In this work, the low temperature efficacy of these materials is examined in a -40 °C environment. CF 0.54 and CF 0.65 powders were characterized using X-ray diffraction, scanning electron microscopy, and X-ray energy dispersive spectroscopy. These materials were then implemented in a spray-deposited electrode using a 1-mil (∼25 μm) aluminum foil current collector and PVDF as a binder. Electrochemical tests showed that these materials were able to deliver specific capacity values up to five times greater than commercial CF 1.08 powder inserted into identically fabricated test cells tested at -40 °C. Testing also indicated that a room-temperature pre-discharge step was necessary to condition the electrode materials before exposure to the low-temperature test environment.