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 (DLi+) calculation analysis and kinetics analysis of lithium storage behavior.