Electrochemical Kinetic Modulators in Lithium–Sulfur Batteries: From Defect-Rich Catalysts to Single Atomic Catalysts

Lithium–sulfur batteries exhibit unparalleled merits in theoretical energy density (2600 W h kg⁻¹) among next-generation storage systems. However, the sluggish electrochemical kinetics of sulfur reduction reactions, sulfide oxidation reactions in the sulfur cathode, and the lithium dendrite growth resulted from uncontrollable lithium behaviors in lithium anode have inhibited high-rate conversions and uniform deposition to achieve high performances. Thanks to the “adsorption-catalysis” synergetic effects, the reaction kinetics of sulfur reduction reactions/sulfide oxidation reactions composed of the delithiation of Li₂S and the interconversions of sulfur species are propelled by lowering the delithiation/diffusion energy barriers, inhibiting polysulfide shuttling. Meanwhile, the anodic plating kinetic behaviors modulated by the catalysts tend to uniformize without dendrite growth. In this review, the various active catalysts in modulating lithium behaviors are summarized, especially for the defect-rich catalysts and single atomic catalysts. The working mechanisms of these highly active catalysts revealed from theoretical simulation to in situ/operando characterizations are also highlighted. Furthermore, the opportunities of future higher performance enhancement to realize practical applications of lithium–sulfur batteries are prospected, shedding light on the future practical development.