Nanostructured Iron Fluoride Derived from Fe-Based Metal-Organic Framework for Lithium Ion Battery Cathodes

A comprehensive strategy for the morphological control of octahedral and spindle Fe-based metal-organic frameworks (Fe-MOFs) via microwave-assisted adjustment is proposed in this research. Afterward, in situ copyrolysis under N₂ atmosphere contributes to the fabrication of two shape-maintained FeF₃·0.33H₂O nanostructures (named O-FeF₃·0.33H₂O and S-FeF₃·0.33H₂O, respectively) with confined hierarchical porosity and graphitized carbon skeleton. The lithium storage performances for the MOF-derived octahedral O-FeF₃·0.33H₂O and spindle S-FeF₃·0.33H₂O composites are investigated, and the prospective lithium storage mechanism is discussed. As a result, the main product of the porous O-FeF₃·0.33H₂O structure is found to be a promising cathode material for lithium ion batteries owing to its advantageous electrochemical capability. Even after being cycled over 1000 times at 2 C (1 C = 237 mAh g^-1), the capacity attenuation rate of the as-prepared O-FeF₃·0.33H₂O electrode is as low as 0.039% per cycle. The combination of proper octahedral morphology and highly graphitized carbon modification can not only enhance the conductivity of the cathode but also promote the diffusion of Li⁺ effectively. The remarkable performance of octahedral O-FeF₃·0.33H₂O can be confirmed by the Li-ion diffusion coefficient (D_Li⁺) calculation analysis and kinetics analysis of lithium storage behavior.