Unraveling the site-dependent mechanisms of bimetallic catalysts from atomic to nanoparticles for high performance lithium–sulfur batteries

Nanoparticle-sized, atomically distributed bimetallic catalysts have attracted extensive attention in lithium–sulfur batteries (LSBs) due to their abundant active sites, tunable electronic structures, and superior catalytic performance. However, the relationship between active-site distribution and battery performance, particularly its effect on polysulfide conversion and cycling stability, remains unclear. Here, x NiCo@CNF (0.125 ≤  x  ≤ 1.0) bimetallic catalysts with tunable active-site distributions were synthesized via electrospinning, constructing NiCo bimetallic with nanoparticle-to-atomic-scale distribution and diverse attachment site configurations. Systematic studies reveal a site-dependent mechanism: large nanoparticles offer strong polysulfide adsorption but limited active sites, slowing reaction kinetics; atomically dispersed particles provide numerous sites, enhancing conversion efficiency; an intermediate active-site density achieves an optimal balance between adsorption strength and site density, promoting uniform electron transfer, accelerating LiPS redox reactions, and facilitating Li 2 S nucleation. As a result, atomically uniformly distributed 0.25NiCo@CNF exhibits optimal performance, delivering a higher initial discharge capacity of 1175.6 mAh g −1 at 0.1C and excellent rate capability (650.8 mAh g −1 at 5.0C). While maintaining stable cycling under high sulfur loading and wide temperature ranges (−30–50 °C). Overall, this work elucidates the site-dependent catalytic mechanism of bimetallic alloys in LSBs, providing a guideline for the rational design of high-performance sulfur cathodes.