Emerging redox kinetics promoters for the advanced lithium-sulfur batteries

Lithium-sulfur batteries encounter substantial limitations in actual energy density due to the kinetic constraints of lithium polysulfides conversion. Various approaches have been proposed to facilitate the multi-phase and multi-electron cathodic redox reactions involving sulfur, lithium polysulfides, and lithium sulfides. The widespread adoption of redox kinetics promoters has been instrumental in achieving high energy density, outstanding rate performance, and long cycle life in lithium-sulfur batteries. A comprehensive and timely understanding of these promoters is crucial for a profound grasp of the unique electrochemistry of lithium-sulfur batteries. This article summarizes the latest advancements in the design of heterogeneous, homogeneous, and semi-immobilized promoters, elucidating catalytic mechanisms, strategies for activity regulation, and advanced electrochemical kinetics measurements to offer guidance for rational design. Importantly, the structure-activity correlations and electrocatalytic mechanisms have been proposed to deepen the understanding of this field. Finally, a development roadmap is outlined, discussing future research directions aimed at achieving favorable redox kinetics and ultimately bridging the gap between the actual and ideal mechanisms in practical lithium-sulfur batteries. This review aims to enhance and propel the understanding of sulfur electrochemistry, thereby guiding further advancements in excellent lithium-sulfur batteries and similar rechargeable battery systems.