NASA requires lightweight rechargeable batteries for future missions to Mars and the outer planets that are capable of operating at low temperatures. Due to the attractive performance characteristics, lithium-ion batteries have been identified as the battery chemistry of choice for a number of future applications, including Mars Rovers and Landers. Under an Interagency program, lithium-ion cells of varying capacity are being developed for NASA and DOD applications. JPL, in collaboration with Wright Patterson Laboratory (Air Force), is currently evaluating a number of lithium-ion cells varying in capacity from 3 Ah to 50 Ah for future aerospace applications. The Mars Lander and Rover applications require a rechargeable, high energy density system capable of operation at temperatures as low as -20°C. To assess the viability of lithium-ion cells for these applications, a number of performance characterization tests have been performed, including: assessing the room temperature cycle life, low temperature cycle life (-20°C), rate capability as a function of temperature, pulse capability, self-discharge and storage characteristics, as well as, mission profile capability.