The lithium-sulfur technology is cheaper than the other chemistries considered in the previous chapters. However, in order to be competitive with other LiBs, Li–S batteriesBatteriesLi-S must have a high mass loadingMass loading of sulfur and high sulfur utilization, as well as a long cycle lifeCycle life, which means that theLithium-sulfur batteries (Li-S)shuttle effect shuttle effectShuttle effect of the polysulfides is suppressed. These conditions have only recently been met, which explains the recent commercialization of Li–S batteriesBatteriesLi-S. This chapter is dedicated to the progress made in the last decade, and reviews the state of the art of their electrochemical performance. The first sections recall the principleLithium-sulfur batteries (Li-S)principles of Li–S chemistry and the challengesLithium-sulfur batteries (Li-S)challenges. The next sections are dedicated to the optimization of the different parts of the batteries: the sulfur cathode, its design, including electrocatalysts, heterostructures, pore structure; the separators, the bindersBinders. Emphasis is placed on polymers used as electrolytes or in cathodes. Due to their importance, separate sections are devoted to sulfur-derived cathodes: sulfurized polyacrylonitrile (SPAN)Sulfurized polyacrylonitrile (SPAN) and Li2S. The results are discussed in the last section.