Defect Engineering for Expediting Li–S Chemistry: Strategies, Mechanisms, and Perspectives

Abstract Lithium–sulfur (Li–S) batteries have stimulated a burgeoning scientific and industrial interest owing to high energy density and low materials costs. The favorable reaction kinetics of sulfur species is a key prerequisite for pursuing their commercialization. Recent years have witnessed a wealth of investigations in terms of boosting sulfur redox via rationalizing redox mediators. Defect engineering, which allows for the effective exposure of active sites and optimization of electronic structure, has emerged expeditiously as an essential strategy to enhance polysulfide modulation, and hence expedite Li–S chemistry. Nevertheless, a comprehensive overview of defect engineering in Li–S realm is still lacking. This review emphasizes the recent advances in the rational design and polysulfide modulation strategies of different types of defective mediators. Their unique morphological configuration, superb electrochemical activity, and underlying catalytic mechanism are comprehensively summarized, aiming to deepen the understanding of defect‐mediated Li–S chemistry. Moreover, in situ evolution of defective mediators is discussed to identify the true active sites under aprotic reaction conditions. Opportunities and an outlook of this fast‐developing frontier that may lead to practical implementations of Li–S batteries are proposed.