Review and prospect on Metal-organic framework-based Separators for Lithium–Sulfur Battery

With the continuous advancement of technology, wearable smart devices and electric vehicles (EVs) have become an integral part of our daily lives. The increasing demand for energy from these devices and vehicles has driven the pursuit of high-performance rechargeable battery technology. In particular, the widespread adoption of electric vehicles has set higher standards for the energy density and cycle life of batteries. However, the energy density of the widely used lithium-ion batteries is currently limited by the theoretical capacity of commercial cathode materials, and there are certain challenges in terms of safety and cost-effectiveness. Therefore, the development of a new generation of rechargeable batteries with higher energy density, better safety, and more economical cost is particularly urgent. Lithium-sulfur batteries, due to their high energy density, high economic benefits, and high environmental friendliness, are considered to be one of the most promising successors to the widely used lithium-ion batteries. However, in practical applications, the electrochemical performance of lithium-sulfur batteries still needs to be improved. In particular, the poor conductivity of sulfur/lithium and the shuttle effect of polysulfides make the cycle life of the battery less than ideal, and lithium-sulfur batteries (LSB) are still far from achieving large-scale commercialization. The separator used in lithium-sulfur batteries plays a crucial role in its cycle performance and safety. The current commercial separator lacks the ability to effectively regulate the shuttle of polysulfides and is prone to thermal runaway at high temperatures. Therefore, to improve these issues, various functional materials have been used to modify the separator. Among them, as a new type of porous coordination polymer, metal organic frameworks (MOFs) have become a promising material for modifying separators due to their large specific surface area and highly ordered tunable nano-holes.At the same time, their rich inorganic nodes and designable organic ligands allow for the customization of pore chemistry at the molecular level, which can interact with the electroactive components in lithium-sulfur batteries in a tunable manner. This article reviews the reaction mechanism of lithium-sulfur batteries and the structural advantages of MOFs in terms of pore chemistry and morphology and briefly introduces the research progress of MOF-based interfacial layers for the functionalization of LSB separators in recent years. It elaborates on the mechanisms by which various modified separators improve electrochemical performance and provides a prospect for the development prospects of the field.