Microstructured Sulfur-Doped Carbon-Coated Fe7S8 Composite for High-Performance Lithium and Sodium Storage

From the perspective of resource reserves, environmental effects, and production costs, direct utilization of natural ores as electrode materials for rechargeable batteries after mineral processing is of more practical significance than chemosynthetic materials. While the corresponding investigation is relatively insufficient, herein phenolic resin (PR)-coated natural pyrite composite (FeS2@PR) is successfully fabricated using natural pyrite and oligomeric phenolic resin as starting materials. Subsequent oligomer polymerization and calcination process convert FeS2@C into sulfur-doped carbon-coated Fe7S8 (FS@C). Benefiting from the good electric and ionic conductivity of Fe7S8, abundant sulfur active sites, and porosity on carbon shell and effective carbon buffering, FS@C exhibits impressive electrochemical performance as anodes for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). It delivers high reversible capacities of 1319 and 796 mAh g–1 after 100 cycles at 0.1 A g–1 for LIBs and SIBs, respectively. Even at a high current density of 2.0 A g–1, considerable capacities of 771 mAh g–1 after 1000 cycles and 545 mAh g–1 after 400 cycles are retained for LIBs and SIBs. This work provides a promising prospect toward scalable production of high-capacity iron sulfide anode for lithium-ion and sodium-ion batteries.