Ammonia Assisted Hydrothermal Synthesis of Monodisperse LiFePO4∕C Microspheres as Cathode Material for Lithium Ion Batteries

In order to obtain high tap density LiFePO 4 /C with excellent electrochemical performance, the monodisperse LiFePO 4 /C microspheres were synthesized by a ammonia assisted hydrothermal method using inexpensive Fe(NO 3 ) 3 and LiOH as raw materials. The structure, morphology and electrochemical properties of the sample were examined by X-ray diffraction (XRD), scanning electron microscope (SEM), charge/discharge tests and electrochemical impedance spectroscopy (EIS). The results showed that the morphology and size of particle can be availably controlled due to the addition of ammonia. Besides, the as-prepared monodisperse LiFePO 4 /C microspheres exhibited a favorable spherical morphology, a quite uniform particle size distribution of about 2 μ m, relatively high tap density (1.3 g/cm 3 ) and excellent electrochemical performance. Simultaneously, the monodisperse LiFePO 4 /C microspheres presented a high discharge capacity of 153.9 mAh·g −1 at the first cycle as well as stable cycling performance (the capacity was not almost changed till 100 cycles) at 1 C (170 mA·g −1 ). Especially, the sample showed a good rate capability, it delivered still a high discharge capacity of over 125 mAh·g −1 even at 5 C. Therefore, it was concluded that the addition of ammonia not only improved efficiently the morphology and size distribution of LiFePO 4 /C, but also enhanced markedly electrochemical performance of LiFePO 4 /C.