The lithium–sulfur battery is among the most promising next-generation energy storage technologies. Particularly carbon nano-composites display an important “piece of the puzzle” to enhance their performance. This short review addresses five major challenges the research field is currently confronted with. It discusses new developments of advanced carbon nanostructures and highlights strategies to improve the performances by cathode functionalization. It outlines current ambitions to gain a deeper understanding of carbon cathode chemistry by in situ characterization techniques, highlights the beneficial role of carbon nanostructures in anode and interfacial components and closes with recommendations for comprehensive and mandatory electrochemical characterization of Li–S cells.