Ultrasmall Iron Fluoride Nanoparticles Embedded in Graphitized Porous Carbon Derived from Fe-Based Metal Organic Frameworks as High-Performance Cathode Materials for Li Batteries

Iron-based metal organic framework (MOF) MIL-53 is used as a precursor and self-template to synthesize a 3D porous carbon/FeF ₃ ⋅ 0.33 H ₂ O composite in situ. We find that the organic ligands in iron-containing MOFs can convert into highly graphitized carbon with the catalysis of central Fe atoms. The FeF ₃ ⋅ 0.33 H ₂ O nanoparticles formed after fluorination and dehydration are surrounded by highly graphitized carbon. In the composite, the graphitized 3D porous carbon can provide passageways for electron transport and ultrasmall FeF ₃ ⋅ 0.33 H ₂ O nanoparticles facilitate the diffusion of Li ions. The composite shows excellent performance for the Li storage. A capacity of 86 mAh g ⁻¹ can be reached at an ultra-high rate of 20 C. Even after 300 charge−discharge cycles at 5 C, the capacity remains at 113 mAh g ⁻¹ .