High Temperature Primary Batteries for Venus Surface Missions

Abstract

Because of the hostile environments of high temperature and pressure, previous Venus probes survived for just two hours. Future Venus surface missions need to survive for much longer durations of several days, in order to return useful science. NASA’s LISSE lander concept has been proposed to operate on the surface of Venus for 60 days. Operating at a temperature of 465 °C and an ambient (CO2) pressure of 92 bar for up to 60 days is a significant challenge and requires new battery chemistries and cell designs. With this objective, we have been investigating high temperature lithium primary batteries with lithium alloy anodes, transition metal sulfide cathodes and molten salt electrolytes. Various cathode materials were screened for thermal stability at high temperature, in contact with the molten salt. Among these cathodes, FeS exhibited the highest stability and laboratory cells were fabricated and tested at 475 OC at various discharge rates to demonstrate long-term operational capability. Initial single cell designs have been shown to be operational for up to 15 days, with the cathode utilization decreasing at the low rates of discharge. Factors determining selection of cathode material, electrolyte composition, separator, etc. will be discussed, along with plans to achieve a full 60 day discharge.