context: Lithium–sulfur batteries have low material costs and high energy densities, which have attracted considerable research interest for application in next-generation energy-storage systems. However, the practical applications of Li–S batteries face challenges owing to their poor sulfur utilization, service lifetimes, and rate capability. Recently, great progress has been made in the design, synthesis, and application of micro/nanostructured metal sulfides to address obstacles facing Li–S batteries. This review aims to highlight valuable concepts from the latest reports. Major approaches to improve sulfur cathodes and strategies for preparing metal sulfide-based materials are first summarized with a particular focus on their main functions and useful properties. Then, the electrochemical activities of metal sulfides are classified and their applications in Li–S batteries are introduced to provide a fundamental understanding of the material interactions involved. In parallel, advancements in the use of interlayers, modification of separators, and protection of lithium anodes that involve metal sulfides are surveyed. Finally, special attention is paid to the general design principles, future prospects, and challenges facing metal sulfides for high-energy-density Li–S batteries.
answer: sulfur 