Preparation and electrochemical properties of LiFePO_4/C nanocomposite using FePO_4·2H_2O nanoparticles by introduction of Fe_3(PO_4)_2·8H_2O at low cost

摘要

A LiFePO_4/C composite was synthesized by a simple solid-state reaction method using stearic acid as reductive agent and carbon source and nano-sized FePO_4·2H_2O as precursor which was prepared from intermediate Fe_3(PO_4)_2·8H_2O using industrial FeSO_4·7H_2O and industrial NH_4H_2PO_4 at a low cost. The structure, morphology and electrochemical performance of LiFePO_4/C were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), galvanostatic charge-discharge tests, cyclic voltammogram (CV) and electrochemical impedance spectroscopy (EIS). The results indicate that the LiFePO_4/C has an olivine-type structure with nano-size and exhibits excellent electrochemical properties. The discharge capacities are 159mAh g~(-1), 148 mAh g~(-1) and 113 mAh g~(-1) at 0.1 C, 1 C and 10C, respectively. Furthermore, the capacity retention rate is higher than 99% after 100 cycles at 1 C and 10 C. The excellent electrochemical performances of LiFePO_4/C composite should be attributed to spherical nanoparticles as well as less impurity in FePO_4·2H_2O precursor.