Three-dimensional (3D) carbon-wrapped iron sulfide interlocked graphene (Fe7S8@C-G) composites for high-performance
sodium-ion storage are designed and produced through electrostatic interaction and subsequent sulfurization. The ironbased
metal-organic frameworks (MOFs, MIL-88-Fe) interact with graphene oxide sheets to form 3D networks, and
carbon-wrapped iron sulfide (Fe7S8@C) nanoparticles with high individual-particle conductivity are prepared following a
sulfurization process, surrounded by interlocked graphene sheets to enhance the interparticle conductivity. The prepared
Fe7S8@C-G composites not only have the improved individual-particle and interparticle conductivity to shorten
electron/ion diffusion pathways, but also have the enhanced structural stability to prevent the aggregation of active
materials and buffer large volume charges during sodiation / desodiation. As a sodium-ion storage material, the Fe7S8@CG
composites exhibit a reversible capacity of 449 mA h g-1 at 500 mA g-1 after 150 cycles and a retention capacity of 306
mA h g-1 under a current density of 2000 mA g-1. The crucial factors related to the structural changes and stability during
cycles have been further investigated. These results demonstrate that the high-performance sodium-ion storage
properties are mainly attributed to the unique designed three-dimensional configuration.