Mechano-chemical synthesis of nanostructured FePO4/MWCNTs composites as cathode materials for lithium-ion batteries

Abstract

Nanostructured iron phosphate/multi-walled carbon nanotubes (FePO₄/MWCNTs) composites have been synthesized by a mechano-chemical process using 1-butyl-3-methylimidazolium tetrachloroferrate (bmimFeCl₄) and (NH₄)₃PO₄·3H₂O as precursors in the presence of 1-butyl-3-methylimidazolium chloride (bmimCl). The bmimFeCl₄ serves not only to provide the necessary Fe-ion source, but also as a co-dispersant for the MWCNTs and as a soft co-template for structure control of the FePO₄ nanoparticles, together with the bmimCl. The obtained FePO₄/MWCNTs composites were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric and differential scanning calorimetry analysis (TG-DSC). As cathode materials for rechargeable lithium-ion batteries, the composites exhibited a capacity of 171 mA h g⁻¹ at a current density of 40 mA g⁻¹, which is close to theoretical capacity for this material, and good cycle performance with a reversible capacity of 135 mA h g⁻¹ after 100 cycles at a rate of 50 mA g⁻¹.