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 N 2 atmosphere contributes to the fabrication of two shape-maintained FeF 3 ·0.33H 2 O nanostructures (named O-FeF 3 ·0.33H 2 O and S-FeF 3 ·0.33H 2 O, respectively) with confined hierarchical porosity and graphitized carbon skeleton. The lithium storage performances for the MOF-derived octahedral O-FeF 3 ·0.33H 2 O and spindle S-FeF 3 ·0.33H 2 O composites are investigated, and the prospective lithium storage mechanism is discussed. As a result, the main product of the porous O-FeF 3 ·0.33H 2 O 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-FeF 3 ·0.33H 2 O 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-FeF 3 ·0.33H 2 O can be confirmed by the Li-ion diffusion coefficient ( D Li + ) calculation analysis and kinetics analysis of lithium storage behavior.