Robert Bosch, LLC
Li-metal based cells, including Li/air, are attractive due to their high gravimetric energy density, but safely recharging Li metal over hundreds of cycles remains a significant challenge. This is due in part to the fact that Li metal electrodes are chemically and morphologically unstable in most, if not all, liquid electrolytes and must be protected with a solid electrolyte, for which there are few working prototypes. Here we examine the principle requirements of such a protection layer from a systems perspective. In addition to possessing high ionic conductivity, mechanical strength, and chemical stability against both lithium and the positive electrode constituents, these materials must be thin (< 50 µm,) cheap (< $100/m2), and defect free. We conclude that further fundamental materials and processing research and development are needed to attain these objectives.