Abstract:

Cu–C co-coated LiFePO₄ (LiFePO₄/(C + Cu)) cathode material was successfully prepared through solid state reduction reaction. The optimized additive amount of CuO was determined by electrochemical test of series content-dependent samples. Electrochemical performances of LiFePO₄/(C + Cu) cathode material were investigated. Crystalline structure, morphology and electrochemical performance of the samples were characterized by X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), charge–discharge tests and AC impedance techniques. Results showed that crystal structure of the bulk material was not destroyed after Cu particles distributed on the surface of LiFePO₄/C. With 5 wt% CuO additive, the LiFePO₄/(C + Cu) cathode material showed improved electrochemical performance especially at high rates and low temperature. At 25 °C and 0.1 C current rate, specific capacity of the Cu-coated sample reaches 161.3 mA h/g. The result was 47 mA h/g higher than that of the un-coated one. At −20 °C, the discharge capacity of Cu-coated materials was 113.4 mA h/g at 0.1 C rate and 83.8 mA h/g at 5 C rate, which reached about 70% of that at room temperature, respectively.

Key words: LiFePO₄/(C D Cu), Cu-coated, Low temperature performance, Li-ion batteries, Electrochemical performances, Materials synthesis