Magnetopyrite Fe1−xS modified with N/S-doped carbon as a synergistic electrocatalyst for lithium-sulfur batteries

Rational design of effective cathode host materials is an effective way to solve the problems of serious shuttle and slow conversion of polysulfides in lithium-sulfur batteries (LSBs). However, the redox reaction of sulfur differs from conventional “Rocking chair” type batteries and involves a cumbersome phase transition process, so a single-component catalyst cannot consistently and steadily enhance the reaction rate throughout the redox process. In this work, a hybrid composed of magnetopyrite Fe_1−xS catalyst-modified with N/S-doped porous carbon spheres (Fe_1−xS@NSC) is proposed as a novel sulfur host to synergistically promote the adsorption and redox catalysis conversion of polysulfides. In this hybrid, the NSC skeleton provides excellent electrical conductivity and abundant adsorption sites for the physical immobilization of polysulfides; the magnetopyrite Fe_1−xS nanoparticles promote the fast conversion reaction from Li₂S₂ to Li₂S, affording strong adsorption and catalytic conversion. The optimal LSB with Fe_1−xS@NSC manifests a high initial capacity of 971 mAh g⁻¹ at 0.2 C (1 C = 1675 mAh g⁻¹) and a retention rate of up to 75 % after 100 cycles. This work can provide a new approach for rationalizing the novel transition metal sulfide/porous carbon-based composite hosts with efficient lithium polysulfides (LiPSs) adsorption and catalytic conversion in high-performance lithium-sulfur batteries.