Separators for lithium–sulfur batteries

As an integral part of batteries, separators function primarily to separate two electrodes to avoid short-circuit, reserve electrolytes, and maintain electrochemical inertness in the potential battery window. Separators are characterized by their porosity, dimensional stability, thickness, chemical inertness, wettability, melting point, etc. For lithium–sulfur (Li–S) batteries, the functions of separators are somewhat extended due to redox chemistry and polysulfide dissolution problems. Separators should also restrict polysulfide migration to the electrolyte and thus minimize polysulfide shuttle. This chapter provides a systematic discussion of separators on recent developments of Li–S battery separators. This review includes separators of different forms like porous, nonwoven, single-layer, multilayer, polymer blends, and composites as forming materials and functionally modified separators exploiting physisorption, chemisorption, electrical charging, etc. In addition, safety features and long cycle life are technological challenges to achieve high-performance separators for next-generation Li–S batteries.