Dual-atom catalysts for lithium-sulfur battery cathodes: Synthesis, characterization, and catalytic mechanisms

Lithium-sulfur batteries (LSBs) stand out as premier next-generation energy storage technologies due to their exceptional theoretical specific capacity and energy density. However, their commercial viability is severely hindered by the ''shuttle effect'' of lithium polysulfides (LiPSs), poor sulfur utilization, and sluggish redox kinetics. Dual-atom catalysts (DACs) have emerged as a transformative solution, offering maximized atomic utilization and unique electronic structures. In particular, the inter-site synergistic effects and modulated charge redistribution in DACs effectively immobilize LiPSs and accelerate their conversion. Crucially, this dual-site configuration enables a unique ''relay catalysis'' mechanism, in which the two coupled yet distinct active sites sequentially process different reaction intermediates, achieving efficient functional compartmentalization. This review systematically outlines the design principles, synthesis methods, and advanced characterization techniques for DACs in LSB cathodes. The structure-activity relationships are thoroughly analyzed, with particular attention to how dual-site architectures modulate the anchoring and catalytic conversion of sulfur species. Furthermore, the critical roles of DACs in enhancing rate capability, cycling longevity, and sulfur utilization are evaluated. Special emphasis is placed on operando/in situ characterization techniques (e.g., in situ XRD, Raman, and synchrotron-based methods) to reveal the real-time evolution of active sites and complex reaction pathways under practical operating conditions. Finally, we address current challenges in catalytic durability and scalable fabrication, and propose future directions for the rational design of high-performance DAC-based LSBs.