Tuning Solid-State Reaction Pathways Using Molecular Sulfur Precursors to Synthesize FeS Anodes of Li-Ion Batteries for Boosted Electrochemical Performance

The solid-state reactions between Fe2O3 and molecular sulfur sources could produce FeS nanoparticles efficiently, while the functions of these molecules have been ignored except for the role as sulfur sources. In this work, thioacetamide and thiourea were employed as sulfur sources for the solid-state reactions with Fe2O3 to explore their effects on the microstructure and electrochemical performance of the produced FeS. Despite the slight difference in one functional group for two molecules (−CH3 against −NH2), thiourea leads to a more complex reaction pathway with FeS2 as the intermediate phase, while no such an intermediate phase is observed in the reaction with thioacetamide. The former yields FeS of 2D nanoflakes as the final products, compared with the aggregated nanoparticles in reactions with thiourea. As a result, the nanoflakes exhibit a higher discharge capacity with enhanced stability (388.9 mAh∙g−1 vs. 374.7 mAh∙g−1 above 1 V). According to the reaction pathways, the formation of FeS nanoflakes and superior electrochemical performance were addressed, paving a route for the solid-state reactions with molecules to develop high-performance sulfide electrode materials.