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 .