Multi-functional separator/interlayer system for high-stable lithium-sulfur batteries: Progress and prospects

The development of advanced energy storage systems is of crucial importance to meet the ever-growing demands of electric vehicles, portable devices, and renewable energy harvest. Lithium-sulfur (Li-S) batteries, with the advantages in its high specific energy density, low cost of raw materials, and environmental benignity, are of great potential to serve as next-generation batteries. However, there are many obstacles towards the practical application of Li-S batteries such as the electrical insulating nature of sulfur, the volume expansion during lithium insertion, and the shuttle of soluble polysulfide intermediates that induces severe degradation of the cell performance. In this review, the progresses of multi-functional separators/interlayers in Li-S batteries are highlighted. The introduction of multi-functional separators/interlayers with unexpected multiple functionalities is beneficial for better sulfur utilization, efficient polysulfide diffusion inhibition, and anode protection. Multi-functional separator system with ion selective/electrical conductive polymer, sp² and porous carbon, metal oxide modified separators, as well as interlinked free-standing nanocarbon, micro/mesoporous carbon, and other conductive interlayers have been proposed. The biomass derived materials was also included as interlayer for advanced Li-S batteries. These novel Li-S cell configurations with multi-functional separators/interlayers are especially suitable for Li-S batteries with high capacity, high stability, and high-rate performance. The opportunities of high-performance separators/interlayers and their applications in next-generation Li-S batteries were also involved. New insights on the role of working separators/interlayers in practical Li-S cells should be further explored to obtain the principle and process for advanced components for energy storage devices based on multi-electron conversion reactions.