Enhanced performance of LiFePO4 through hydrothermal synthesis coupled with carbon coating and cupric ion doping

A hydrothermal reaction has been adopted to synthesize pure LiFePO4 first, which was then modified with carbon coating and cupric ion (Cu2+) doping simultaneously through a post-heat treatment. Xray diffraction patterns, transmission electron microscopy and scanning electron microscopy images along with energy dispersive spectroscopy mappings have verified the homogeneous existence of coated carbon and doped Cu2+ in LiFePO4 particles with phospho-olivine structure and an average size of 400 nm. The electrochemical performances of the material have been studied by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge-discharge measurements. The carbon-coated and Cu2+-doped LiFePO4 sample (LFCu5/C) exhibited an enhanced electronic conductivity of 2.05 x 10(-3) S cm(-1), a specific discharge capacity of 158 mAh g(-1) at 50 mAg(-1), a capacity retention of 96.4% after 50 cycles, a decreased charge transfer resistance of 79.4 Omega and superior electrode reaction reversibility. The present synthesis route is promising in making the hydrothermal method more practical for preparation of the LiFePO4 material and enhancement of electrochemical properties. (C) 2011 Elsevier Ltd. All rights reserved.