Mechanistic understanding of the role separators playing in advanced lithium-sulfur batteries

The lithium-sulfur battery is considered one of the most promising candidates for portable energy storage devices due to its low cost and high energy density. However, many critical issues, including polysulfide shuttling, self-discharge, lithium dendritic growth, and thermal hazards need to be addressed before the commercialization of lithium-sulfur batteries. To this end, tremendous efforts have been made to explore battery configurations and components, such as electrodes, electrolytes, and separators, among which the separator plays an especially critical role in addressing aforementioned issues. Thus, this review analyzes the mechanisms and interactions of these critical issues and summarizes both the function of separators and recent progress made towards remedying such issues. Additionally, promising directions for the development of separators in lithium-sulfur batteries are proposed.