Interface Engineering of Space-Confined Fe3O4/FeS Heterostructures: Synergistic Effect and Ultrastable Li Storage

Iron-based compounds, which feature the advantages of high specific capacity and inexpensive fabrication, are widely studied as promising anode candidates for the purpose of facilitating their electrical conductivity and structural integrity. Interface engineering and structural confinement are verified as effective methods to improve the sluggish charge transfer kinetics and rapid structural failure during the repeated lithiation/delithiation processes. In this work, we proposed a simple synthesis strategy to construct a space-confined Fe3O4/FeS heterostructure embedded in pyrolytic carbon (Fe3O4/FeS@C). The Fe3O4/FeS heterogeneous interface facilitates combination of the advantages of each component (Fe3O4 and FeS) and constructs a built-in electric field to promote the charge transport in the Fe3O4/FeS@C anode. The space-confined structure contributes to maintaining the structural stability by buffering the volumetric variation and suppressing the aggregation of active particles. Profiting from the synergism of the engineering of heterogeneous interfaces and the feature of confined structure, Fe3O4/FeS@C manifests an excellent rate capability (913.74 mA h·g–1 at 200 mA·g–1 and 535.79 mA h·g–1 at 6400 mA·g–1) and a stable cycling performance (439.8 mA h·g–1 after 1000 cycles at 3200 mA·g–1) as a competitive anode for lithium-ion batteries. The density functional theory (DFT) calculations demonstrate that the introduction of a heterogeneous interface enhances the adsorption of Li-ions, improves the electrical conductivity, as well as promotes interfacial electron/ion transfer kinetics.