Lithium-Sulfur (Li-S) batteries represent one of possible development pathways of Lithium based batteries, which are expected to provide benefits of high volumetric energy density, various safety features and low production cost ¹. Already nowadays, one can find demonstrated applications, which heavily depend on unique attributes of Li-S batteries, e.g. high-altitude long-endurance unmanned aerial vehicles capable to endure for an extended periods of time in air (currently proofed for 14 day without landing) ². However, wide commercialization of Li-S batteries is still hindered mainly by their limited performance and short lifetime ³.

Both, cycling and storage, influence the Li-S battery lifetime. The degradation is often assigned to the irreversible relocation of polysulfides, which results into the corrosion of lithium metal anode, degradation of sulfur cathode and surface passivation of both electrodes ⁴. These degradation aspects were studied and discussed in literature into a certain degree; however, as pointed out in Ref. 3, some observations are possible to be done only at commercial-size cells, instead at coin cells, which determines the further focus of this work on a larger format cells, specifically pouch cells. The Li-S pouch cells were previously studied for an effect of cycling degradation on sulfur cathodes ⁵ and lithium metal anodes ⁶. The current study brings an experimental investigation of a capacity fade and a self-discharge with a periodic one month checking for storage of Li-S cells at various conditions of state-of-charge and temperature. The methodology presented in Ref. ⁷ is used for evaluation of the battery performance during the degradation in terms of capacity, resistance, power capability and shuttle current.

1. M. Wild, L. O’Neill, T. Zhang, R. Purkayastha, G. Minton, M. Marinescu, and G. J. Offer, Energy Environ. Sci., 8, 3477–3494 (2015).
2. http://defence.airbus.com/portfolio/uav/zephyr/, accessed at 20^th November 2017.
3. T. Cleaver, P. Kovacik, M. Marinescu, T. Zhang, and G. Offer, J. Electrochem. Soc., 165, A6029–A6033 (2018).
4. S.-H. Chung and A. Manthiram, ACS Energy Lett., 1056–1061 (2017).
5. S.-E. Cheon, S.-S. Choi, J.-S. Han, Y.-S. Choi, B.-H. Jung, and H. S. Lim, J. Electrochem. Soc., 151, A2067 (2004).
6. X. B. Cheng, C. Yan, J. Q. Huang, P. Li, L. Zhu, L. Zhao, Y. Zhang, W. Zhu, S. T. Yang, and Q. Zhang, Energy Storage Mater., 6, 18–25 (2017).
7. V. Knap, D. I. Stroe, R. Purkayastha, S. Walus, D. J. Auger, A. Fotouhi, and K. Propp, ECS Trans., 77, 479–490 (2017).