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

Highlights: → Hydrothermal reaction has been adopted to synthesize LiFePO4 with a narrow size distribution. → LiFePO4 was modified with carbon coating and cupric cation (Cu2+) doping simultaneously. → Electrochemical properties of LiFePO4 were improved by carbon coating and cupric cation doping. - Abstract: 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. X-ray 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 mA g-1, a capacity retention of 96.4% after 50 cycles, a decreased charge transfer resistance of 79.4 Ω 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.