Mechanistic roles and design criteria for catalysts in lithium–sulfur batteries

Catalysis is widely explored in lithium–sulfur (Li–S) batteries to address challenges related to limited capacity and cycle durability. Despite extensive research, catalyst development has often focused on materials without a clear understanding of the mechanistic landscape underlying the complex, multi-step, multi-electron sulfur redox pathway. In fact, our understanding of the thermodynamic, kinetic, and mass transport framework in Li–S systems is still evolving, particularly with respect to the reaction pathways during charge and discharge, and the dynamic evolution of materials in both liquid and solid phases. These evolving insights may fundamentally shift the requirements for catalyst design and future research priorities. Therefore, this perspective aims to establish the fundamental roles of catalysts in Li–S batteries, providing a mechanism-based reference applicable to both existing and emerging material systems. The discussion is organized around four core catalytic functions: LiPS adsorption, ion and electron transport, conversion of intermediate species, and decomposition of discharge products. For each, representative catalytic strategy, structure–property relationships, and the underlying physical and electrochemical principles are discussed. By decoupling catalytic function from specific material classes, this conceptual framework identifies unifying design principles and highlights critical knowledge gaps with the goal to guide the rational design of next-generation catalysts with mechanism-informed, function-specific performance in Li–S systems. Catalysis in lithium-sulfur batteries can address issues related to limited capacity and cycle durability. This Perspective discusses the mechanisms behind the role catalysts play in LiPS adsorption, ion and electron transport, conversion of intermediate species, and decomposition of discharge products.