PSI proposes to develop a rechargeable lithium metal cell with energy density >400Wh/kg. This represents a >70% increase as compared to similarly constructed cells using commercial off the shelf components. Further, the use of lithium metal eliminates the need to produce the anode material and electrode, simplifying cell construction and thus reducing cost. The Phase I work will build upon PSI's previous efforts focused on forming a high power cell design. These efforts have demonstrated the ability to construct pouch sized cells that charge and discharge without the formation of dendrites. During Phase I, PSI will build high energy pouch cells and demonstrate the cycling efficiency of its lithium metal cell design. A specialized electrolyte will be developed that maximizes the cycle life and offers comparable performance to conventional electrolytes designed for graphite cells. A composite separator tailored to efficiently operate with the electrolyte will be used to provide a reduced diffusion distance between the anode and cathode. Phase I testing will demonstrate each component can be scaled to allow stable cycling of Ah pouch cells. Phase II will focus on building multi amp hour cells that achieve the targeted energy density, 400Wh/kg.