High energy density batteries operable in various space environments are needed for space exploration missions (2015 NASA Technology Roadmap; TA3.2). Additionally, technologies that leverage in-situ resources to dramatically reduce launch mass and cost of human exploration missions are also desirable. (2015 NASA Technology Roadmap TA7.1) We propose to evaluate a novel in-situ resource utilization (ISRU) energy concept which efficiently utilizes abundant CO2 in the Mars atmosphere as the cathode reactant for lithium-based batteries (Li-CO2 batteries). This rechargeable energy storage system will enable significant weight savings for Mars exploration missions. The MAB is expected to achieve a cell level specific energy >1000 Wh/kg, in comparison to ~260 Wh/kg for SOA lithium ion cells. Because a large amount of the total reactant mass (~80%) comes from the Martian CO2 atmosphere, the energy density benefit in terms of system cargo weight is substantial. Significantly, the MAB may also function effectively in an oxygen-rich environment (internal to habitats, spacesuits, etc.) with no loss in battery performance. This provides the potential to design multi-use, cross-functional battery systems. While Li-CO2 batteries may have a significant impact on mass reduction of Mars surface energy storage, their relatives, Li-air and Li-O2 systems, are of significant interest on the aeronautics side for the same reason. Even if the anticipated results are not achieved under this project, the understanding of parasitic energy demands and how they trade with cell efficiency will increase our understanding of these systems and the impact they may have on other aerospace systems.