Cycling and low temperature performance of Li ion cells

Lithium-ions cells, of DD and D size, are being developed under a contract with the USAF for NASA's Mars Rover missions. The cells contain spirally wound electrodes of LiNiO/sub 2/ positive electrode material and graphite anode in cylindrical stainless steel hardware. The electrolytes were selected based on the mission needs of good low temperature (-20/spl deg/C) performance, combined with adequate stability at ambient temperature. The cells are being subjected to 100% DOD cycling at -20/spl deg/C as well as at ambient temperature. In addition, the cells are being tested in 30% depth of discharge (DOD) low Earth orbit (LEG) regime and 60% DOD geosynchronous Earth orbit (GEO) regime. The cells have so far completed 5000 accelerated LEO cycles and about 500 accelerated GEO cycles. In this paper, the results of these on-going tests are presented.