Rechargeable Li ion batteries are perceived as likely substitutes for conventional nickel systems in an effort to minimize the mass and volume of the power subsystems in aerospace applications. The on-going consortium of NASA and DoD, after 2 years of existence, has propelled the advancement of aerospace Li ion technology in the US. Prototype cells of different sizes have been built by domestic manufacturers and are being evaluated both by NASA and Air Force. The early versions of these prototypes catered to needs of imminent NASA missions, i.e. Mars landers and rovers. Developmental efforts are underway to further improve the technology to meet the demands of long calendar life, as in the geosynchronous earth orbit (GEO) and the outer planets missions, and long cycle life as in the low earth orbit (LEO) missions. In this paper, we will briefly describe the objective and progress of this joint effort.