Radiation Effects on Lithium CFX Batteries for Future Spacecraft and Landers

Future landers to the moons of the outer planets will be enabled by higher specific energy primary batteries to support exploration of the surface. Batteries based on the lithium carbon monofluoride (Li/CFx) cell chemistry provide ~50% higher specific energy than heritage cells (Li/SO2 or Li/SOCl2) in relevant conditions. Radiation tolerance is a major concern due to the high radiation environment surrounding Jupiter and its moons. Gamma radiation exposure may also become the sterilization technique (a critical step for any lander to planetary bodies where life may survive) of choice because the alternative thermal technique (prolonged exposure to high temperature) results in significant capacity loss for Li/CFx cells. Several D-sized Li/CFx and Li/CFx-MnO2 cells have been exposed to up to 10 MRad of gamma radiation from a 60Co source. The energy and capacity of the cells decreases by less than 2% following radiation and trends regarding the open circuit voltage and impedance spectroscopy are reported. To better understand the effects of radiation, samples of individual materials have been exposed to radiation as well as three-electrode cylindrical Li/CFx cells. These component level tests along with the experimental cells reveal that the interaction between the electrolyte and the electrodes in a fully assembled cell is the likely cause of increased impedance and decreased energy/capacity, following exposure to ionizing radiation.