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

Abstract

Spherical FeF_2.5·0.5H₂O–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 FeF_2.5·0.5H₂O 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 FeF_2.5·0.5H₂O–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.