Performance characteristics of lithium-ion cells for Mars sample return Athena Rover

Future planetary exploration missions, especially Landers and Rovers, will utilize lithium ion rechargeable batteries, due to their advantages of reduced mass and volume compared with nonlithium systems. In addition to the usual requirements of high specific energy and energy density, some applications, e.g., Mars Landers and Rovers, require the batteries to be functional over wide range of temperatures, i.e., -20 to +40/spl deg/C. Several prototypes with modified chemistries commensurate with these mission needs were built by US Battery manufacturers, in conjunction with a NASA-DoD Interagency developmental effort and are being tested at JPL in the last couple of years. The proposed Mars Rover will have three lithium ion batteries (with one serving the purpose of redundancy) connected in parallel, each with four 6-9 Ah cells in series, to augment the solar array. The charger for these Rover batteries is being designed and built in-house. In this paper, we present several performance characterization tests, including cycle life at different temperatures, rate capability at various charge/discharge rates and temperatures and real time and accelerated storage, which were carried out on these prototype cells in support of the Mars exploration missions.