Bimetallic sulfide Fe₅Ni₄S₈ nanoparticles modified N/S co-doped carbon nanofibers as anode materials for...

Transition metal sulfides (TMSs) have garnered significant attention owing to high theoretical capacities, favorable environmental compatibility, abundant natural resources, and suitable discharge/charge voltage platform in the field of anode materials for sodium-ion batteries (SIBs). However, the sluggish reaction rates and significant volume alteration during the process of sodiation/desodiation restrict the practical application of TMSs for SIBs. Herein, a novel bimetallic sulfide Fe₅Ni₄S₈ nanoparticles modified nitrogen/sulfur co-doped carbon nanofibers (NSCFs) composite is successfully synthesized using a straightforward electrostatic spinning and sulfurization treatment. As an anode material for SIBs, Fe₅Ni₄S₈/NSCFs exhibits a high reversible specific capacity of 686.34 mAh g^-1 at 0.1 A/g and a capacity of 607.26 mAh g^-1 after 120 cycles at 1.0 A/g with a capacity retention rate of 96.9 %. Even at 10.0 A/g, it still maintains a capacity of 481.14 mAh g^-1 after 800 cycles, indicating an excellent electrochemical energy storage performance. Density functional theory calculations demonstrate that the Fe₅Ni₄S₈ exhibits enhanced binding with NSCFs, promoted electron transfers, improved Na⁺ adsorption ability, and decreased Na⁺ diffusion barrier energy compared to those of monometallic sulfide FeS. Additionally, the three-dimensional network skeleton of NSCFs can effectively enhance the electrical conductivity and relieve the volume change during the discharge and charge process. The innovative multicomponent design and nanostructural configuration provide a promising strategy to develop high-performance anode materials based on bimetallic sulfide for SIBs.