Recent progress of separators in lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries have attracted considerable attention due to their advantages, such as high specific capacity, high energy density, environmental friendliness, and low cost. Therefore, Li-S batteries are one of the most promising electrochemical energy storage systems. However, the practical application of Li-S batteries is limited by some severe faults, such as the dissolution and migration of polysulfides, the insulation and volume expansion during the cycling of elemental sulfur. Considerable research efforts have been dedicated to solving these difficulties from every parts of Li-S batteries, including separators. By rationally designing and optimizing of separators, the reversible capacity, coulombic efficiency, and cycling stability of the Li-S batteries can be effectively improved. This article mainly reviews the research progress of separator modification materials in Li-S batteries, and summarizes the methods and characteristics of separator modification including carbon materials, polymer materials, inorganic compound materials, metal organic framework, and covalent organic framework materials and other metal compounds. From the anode side, the mechanism through the modification of separators can help to stabilize lithium metal anode is also discussed. Finally, the perspectives and challenges of separator modification in Li-S batteries are pointed out.