Boosting Polysulfide Conversion on Fe‐Doped Nickel Diselenide Toward Robust Lithium–Sulfur Batteries

Abstract Sulfur offers a high‐energy‐density, low‐cost, and sustainable alternative to traditional battery cathodes, but its practical use is limited by sluggish and uneven reaction and polysulfide dissolution, necessitating electrocatalytic additives to enhance conversion efficiency. Generating unpaired spin electrons has proven effective in enhancing performance in Co‐based electrocatalysts. These unpaired electrons increase polysulfide conversion by enhancing adsorption and weakening S─S bonds, facilitating their cleavage during sulfur reduction reactions. This work extends the strategy to Fe–Ni‐based catalysts. The synthesis of NiSe ₂ and Fe‐doped NiSe ₂ particles is reported and investigate the impact of Fe doping on the electronic structure, catalytic activity, and performance of NiSe ₂ is introduced as a coating on the cathode side of the Li–S battery (LSB) separator. Experimental analyses and first‐principles calculations reveal that Fe‐rich cores and surface doping in NiSe ₂ enhance the density of states at the Fermi level and introduce unpaired electrons, boosting LiPS adsorption and catalytic conversion. These synergistic effects significantly improve the catalytic performance, cycling stability, and overall performance of LSB cells. Specifically, LSB cells based on Fe‐doped NiSe ₂ ‐based separators achieve specific capacities of 1483 mAh g⁻¹ at 0.1C and 1085 mAh g⁻¹ at 1C, along with remarkable cycling stability, retaining 84.4% capacity after 800 cycles. High sulfur‐loading tests further validate the multifunctional membrane's effectiveness, showing significant capacity retention and reduced polysulfide loss.