Influence of Carbon Blends for Cathode Active Material Pre-Treatment on Battery Performance

Solid state batteries show significant potential. Specifically, the lithium-sulfur system shows significant potential thanks to its large gravimetric capacity and the lack of the problematic sulfur-shuttle effect as encountered in liquid cells. To achieve sufficient utilization of the active material, appropriate solid conductors for both ionic and electronic conduction have to be added to the cathode material mixture. While solid electrolytes are studied intensively in regards to optimizing their ionic conductivity, influences of electron conductors are studied more sparsely. Somewhat structured carbons such as carbon fibers are often used with the idea to provide prefabricated conductive pathways, but without in-depth investigation of the interactions between the individual components of the solid cathode composites during mixing.<br/>In this study, we show how already simple mixing of two basic carbons in solid sulfur cathode composites alters significantly the cycling behavior in half-cells. For this purpose, we analyzed two mixtures of two different carbon species in different ratios. For both systems, cathode composites prepared with pure carbons results in vastly different performance than achieved by simple blending of the two carbons. It can be shown, that rather than utilizing purely one sort of carbon, improvements in performance can be achieved by application of specific carbon mixtures, although the exact ratio depends strongly on the type of the added carbons. This means that it is already possible to make significant improvements to the solid lithium-sulfur battery system by mixing simple, inexpensive carbons rather than using complex-structured, expensive carbons, which is particularly interesting in terms of advances in industrial applications and commercialization.