High Energy Density Lithium-Sulfur Batteries for NASA and DoD Applications

Abstract

We have been successfully using Li-ion batteries in several NASA missions since 2000, including the Mars Exploration Rovers (Spirit and Opportunity), Mars Science Laboratory (MSL), Phoenix Lander, JUNO, Aquarius, Keppler Rovers and SMAP. Being compact, lightweight and durable, these batteries have contributed to a significant enhancement or even enablement of these missions. However, NASA’s future missions, e.g., Astronaut’s Portable Life Support System (PLSS) for Extra-Vehicular Activities (EVA), small planetary rovers, planetary probes, CubeSats etc., require more advanced battery technologies with higher energy densities. The lithium-sulfur system emerges as the most promising technology, because of its high theoretical specific energy (3-4x) compared to Li-ion cells. However, despite many significant developmental efforts over the last few years, Li-S technology hasn’t matured yet, mainly due to the challenges from the soluble polysulfides forming a redox shuttle and also poisoning the lithium anode. Several attempts are being reported in the literature to develop novel cathode designs, e.g., hierarchical porous carbon structures to sequester sulfur and its reduction products, and also electrolyte solutions to minimize their solubility. 1-5 Good cycle life was reported in some of these cases with nanostructured sulfur cathodes in both organic electrolytes containing suitable additives (LiNO3) and in ionic liquids, but the sulfur loadings are much lower (below 4 mg/cm2), while high loadings of >12 mg/cm2 are essential for high specific energy Li-S cells. In this context, we have developed new sulfur composite cathodes blended with transition metal sulfides (e.g., titanium and molybdenum disulfide), which not only provided adequate electronic and ionic conductivity, but also facile electrochemical activity at sulfur reduction potentials to function as redox mediators.6 With such blended cathodes, we have been able to realize high specific capacities of ≥800 mAh/g at C/3 rates with high material loadings. In this paper, we will describe the performance of these composite sulfur cathodes in different electrolytes, and also in conjunction with a polymer-protected Li anode. Y. Yin, S. Xin, Y. Guo and L. Wan, Angew. Chem. Int. Ed. 2013, 52, 13186 (2013).S. Evers, L. F. Nazar, Acc. Chem. Res., 46, 1135 (2013);X. Ji, K. T. Lee, L. F. Nazar, Nat. Mater. 8, 500 (2009).A. Manthiram, S.-H. Chung, C. Zu, Adv. Mater. 27, 1980 (2015).S. S. Zhang, Front. Energy Res. 1, 1 (2013).Ratnakumar Bugga, Simon Jones, Jasmina Pasalic, Dan Addison and Ramanathan Thillaiyan, 228th ECS Meeting, Phoenix, AZ, Oct. 11 (2015)