Comparative study on sulfur cathode preparation methods for industrial scale-up of metal-sulfur batteries

Kurzfassung

Metal-sulfur batteries are an important building block for the successful realization of the energy transition. The transformation of preparative laboratory methods into industrially relevant, scalable processes is essential for a successful market launch. In the present work, the efficient production and performance of the cathode with sulfur (S) infiltrated in microporous carbon aerogel (Vp,micro 0.27 to 0.45 cm³/g) is investigated. This sort of composite was in-depth evaluated in the past progress.[1-3] For the purpose of advancing production readiness, (i) infiltration methods were evaluated, (ii) industrially applicable suspension were formulated and the (iii) performance of the resulting batteries was compared on a single-layer pouch scale level. To optimize the (i) production of sulfur-carbon composites, infiltration methods are required that increase the material throughput while reducing processing time and energy consumption are necessary. Various methods, from complex, non-scalable with outstanding performance and economically efficient with moderate performance were analyzed. When developing the obtained composites into electrodes, using wet coating application, a common lab method is doctor blade, as this is an easy batch fabrication, relatively undemanding to the parameters of the suspension. To transfer electrode design into a continuous, production-ready process (ii), slot die coating is a relevant, industrial scalable coating process. Among others, rheological parameters turned out to be of utmost relevancy for ensuring a homogeneous coating quality. To ensure matching its parameter frame, suspension guide formulation was carefully examined and influence of key-parameters determined. To evaluate the efficiency of scaled up material and coatings development (iii) LiS batteries were applied and evaluated in terms of composite preparation, electrolyte composition and transfer to pouch cell level. The results indicate that the highest S-loadings could be achieved using gas, extruder and melt infiltrations, with the S predominantly present in the micropores. The composites produced with gas [4] and extruder infiltrations [5] exhibit good cycle stability and high discharge capacity. In comparison, open gas infiltration, microwave infiltration and infiltration in the solvent show low S-loading and insufficient performance in the cell. References: [1] M. Nojabaee, B. Sievert, M. Schwan, et al., J. Mater.Chem. A. 2021, 9, 6508-6519 [2] M. Gerle, M.Nojabaee, et al., SOC. JES, 2022. 169(3): p. 030505. [3] B. Sievert, M.Nojabaee et al, J. Mater. Chem. A, 2024,12, 9002-9016 [4] B. Milow, M. Schwan, N. Wagner and F. Warth (2018). DLR. Germany. DE 10 2018 123 285.3 [5] B. Milow, M. Schwan, J. Kröner, I. Milow (2023). DE 10 2023 111 810.2