Ferromagnetic Atomic d-p Orbital Hybridization for Promoting Al-S Batteries

Rechargeable aluminum-sulfur batteries (Al-S) are emerging as a promising alternative energy storage system beyond lithium-ion batteries due to their high energy density, abundant material resources, and economic efficiency. However, their practical application remains challenged by sluggish conversion kinetics, polysulfide shuttling, and low sulfur cathode utilization. While extensive studies have focused on enhancing polysulfide adsorption through catalytic strategies, the roles of electronic structure in dictating catalytic performance remain underexplored. Here, this work unveils the critical effect of unpaired electronic structure on the catalytic performance of single atom ferromagnetic transition metals through a systematic evaluation of three typical atomically dispersed ferromagnetic single atoms-Fe, Co, and Ni-supported on porous carbon (denoted as PC-SAFAs). Comprehensive characterizations and density functional theory (DFT) calculations reveal that the PC-SAFe catalysts, exhibiting the highest spin polarization arising from unpaired electrons, demonstrate the strongest interactions with polysulfide, thereby facilitating rapid and reversible polysulfide conversion reactions. Consequently, Al-S batteries incorporating the optimized PC-SAFe cathode achieve an impressive specific capacity of 508.8 mAh g^-1 at 1.0 A g^-1 after 500 cycles, along with much improved rate capability. This work provides a deeper understanding of the role of electronic structure in catalytic chemistry, and offers new insights for developing high-performance Al-S batteries.