Carbon Matrix Optimization: A Key to Enhancing Sulfur-Carbon Cathode Performance in Solid-State Lithium-Sulfur Batteries
Mahsa Hokmabadi1,2, Daniel Vogt1,2, Peter Michalowski1,2, Arno Kwade1,2
1 Institut für Partikeltechnik, TU Braunschweig, Volkmaroder Str. 5, 38104 Braunschweig
2 Battery LabFactory Braunschweig, TU Braunschweig, Langer Kamp 19, 38106 Braunschweig
Solid-state lithium-sulfur batteries have been considered as a potentially remarkable development in energy storage technology, especially for aviation applications and stationary storage [1]. By combining the potential high specific capacity of sulfur-based cathodes with the stability and safety of solid-state electrolytes, these batteries promise enhanced performance, including longer cycle life and a more compact form factor. However, the challenges caused by sulfur’s low electrical conductivity and the polysulfide shuttle effect result in capacity fading and low efficiency [2]. A well-designed conductive network within the sulfur cathode is critical for guaranteeing effective electron transport and maintaining the electrode’s structure. Therefore, determining the appropriate SSA and porosity of the carbon host is essential for enhancing cathode performance [3].
Taking these considerations into account, this study aims to explore the impact of various carbon structures on the performance of lithium-sulfur batteries. To achieve this, four commercially available carbon materials including Ketjen Black (KB), Carbon Super C65, Black Pearls, and Nanoplate Carbon were selected to fabricate sulfur-carbon composites. This research focuses on the design and production of sulfur-carbon cathodes with varying carbon matrix compositions, combined with a polymer electrolyte made of poly(ethylene oxide) (PEO) and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI).
To evaluate the performance of the prepared materials, various characterization techniques were employed. SEM images revealed that Black Pearls provided a uniform sulfur distribution without agglomeration, contributing to improved cycling stability. Ketjen Black, despite ensuring full sulfur coverage, exhibited cracks and weaker adhesion, which could affect long-term stability. Nanoplate Carbon and KB delivered high initial capacity, but suffered from significant capacity loss over 50 cycles. This study also evaluated porosity and tortuosity, finding that all tested cathodes had porosity above 30%, which can reduce electronic conductivity and energy density. However, lower tortuosity in well-structured cathodes allowed for better ion transport, improving performance. Electrical conductivity measurements showed that C65 exhibited the highest conductivity, ensuring superior electron transport, while the other carbons displayed similar but lower values.

[1] Sun, Zhenjie, et al, Journal of Power Sources 285. 2015, 478-484. [2] Niu, Xiao-qing, et al, Journal of Materials Chemistry A 3.33. 2015, 17106-17112. [3] Schmidt, Florian, et al, Energy Technology 11.10 (2023): 2300518.