Practical Lithium–Sulfur Batteries: Beyond the Conventional Electrolyte Concentration

Advances in electrolyte chemistry and the development of electrolyte systems have revealed that electrolyte concentration significantly affects battery performance. However, the relationship between electrolyte concentration, polysulfide formation, and lithium–sulfur (Li–S) battery performance remains unclear, which hinders the developmental progress of practical Li–S batteries. In this study, we compared the electrolyte structures and performance of Li–S batteries with various electrolyte concentrations and developed a method that links microscopic interactions, apparent electrolyte parameters, and battery performance. The relationship between polysulfides and the electrolyte system was analyzed at various concentrations, which revealed that systems with a low lithium-salt concentration, especially below 1 M, are better suited to practical Li–S batteries and that polysulfides play crucial roles in ion-transport processes under practical conditions. This study supports the development of electrolytes for practical Li–S batteries and provides guidance for controlling ion-transport processes in liquid electrolytes for other secondary batteries.