Preparation and performance of spherical FeF2.5·0.5H2O nanoparticles wrapped by MWCNTs as cathode material of lithium ion batteries

Spherical FeF2.5·0.5H2O-MWCNTs nanocomposites are synthesized via an ionic liquid (IL) based on precipitation route as a high performance cathode material for lithium ion batteries (LIBs), in which the BMMimBF4 is used as environmentally friendly fluorine source, appropriate solvent and binder. The addition of MWCNTs can not only increase the conductivity of the active material, but also play a role in designing a especial morphology where nano-sized FeF2.5·0.5H2O particles grew up. The structure, morphology and electrochemical performance of the as-prepared samples have been characterized by X-ray diffraction (XRD), Rietveld refinement of XRD pattern, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and charge/discharge tests. The results show that the spherical FeF2.5·0.5H2O-MWCNTs nanocomposites present the cubic crystal structure with the cell volume of 1.13293 nm3. Furthermore, it can deliver a high initial discharge capacity of 324.7 mA h g-1 and stable cycle performance of 175.2 mA h g-1 after 50 cycles at 40 mA g-1 between 1.5 V and 4.5 V. Especially, even at a high current density of 500 mA g-1, the as-prepared material can still display a high discharge capacity of 136.0 mA h g-1.