Transition metal anchoring on porous carbon for enhanced polysulfide stability and accelerated redox dynamics in Li–S and Al–S batteries

Metal–Sulfur (M–S) batteries, including lithium‑sulfur (Li–S) and aluminum‑sulfur (Al–S) systems, are promising next-generation energy storage technologies due to their high theoretical energy density, cost-effectiveness, and inherent safety. However, their practical application is severely limited by challenges including metal polysulfides shuttle effect, and their sluggish redox conversion kinetics, leading to rapid capacity degradation and short cycle life. To address these limitations, it is crucial to develop cathode materials with robust structural stability, high electrical conductivity, strong polysulfide anchoring capability, and superior catalytic activity. In this work, density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations are employed to investigate the potential of nitrogen-doped porous graphitic carbon (NPGC) embedded with single-atom 3 d transition-metal (TM) catalysts as advanced cathode materials for Li–S and Al–S batteries. These computational findings confirm that all TM@NPGC configurations exhibit excellent thermodynamic stability, high electrical conductivity, and intrinsic magnetic properties. The incorporation of TM single-atom sites markedly strengthens polysulfide adsorption and promotes catalytic conversion, offering a dual strategy to mitigate the shuttle effect and improve sulfur redox kinetics. First-principles calculations reveal a pronounced chemistry-dependent catalytic response governed by the identity of the TM center. In Li–S chemistry, Mn and Fe achieve the most favorable balance between polysulfide anchoring and sulfur-reduction thermodynamics, facilitating conversion toward Li 2 S. By contrast, Al–S chemistry preferentially benefits from Co and Ni sites, which provide an advantageous interplay between intermediate binding and conversion energetics. Kinetic analysis using climbing-image nudged elastic band (CI-NEB) calculations further differentiates these candidates, identifying Mn@NPGC and Co@NPGC as the kinetically preferred catalysts for Li–S and Al–S systems, respectively, owing to their lower Li 2 S and Al 2 S 3 decomposition barriers relative to their Fe- and Ni-based counterparts. Collectively, these results establish that optimal catalytic performance arises from a delicate balance among polysulfide affinity, reaction thermodynamics, and kinetic accessibility, providing an atomistic basis for the rational selection of TM single-atom active centers in high-performance metal–sulfur battery cathodes.