The surface binding and energy issues in the rational design of separators for Li||S batteries

Lithium-sulfur batteries (LSBs) represent a next-generation energy storage technology, but widespread applications are restricted by the shuttle of lithium polysulfides (LiPSs). The rational design of separators has been demonstrated to be one of the most efficient and cost-effective strategies to curb the shuttle effect, and tremendous research progress has been achieved. The efficiency of a separator depends on its interaction with LiPSs, which is governed by the surface energy and binding strength. Despite several review works that have been reported to advance the separators, most of them primarily focus on active material innovation and construction. The most crucial issues of surface binding energy have not been systematically reviewed, limiting the precise design of efficient separators. In this review, fundamentals related to surface energy and binding interactions with LiPSs are comprehensively analyzed and discussed. With surface binding and energy main lines, the advancements in separator engineering strategies are elaborately summarized and discussed. Moreover, techniques for evaluating affinity to LiPSs are thoroughly analyzed to avoid any ambiguities in measurement. Based on the research context, valuable research directions are suggested to construct efficient separators. This work provides guidelines to regulate the surface binding and energy of separators for high-performance LSBs.