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

In order to obtain high tap density LiFePO4/C with excellent electrochemical performance, the monodisperse LiFePO4/C microspheres were synthesized by a ammonia assisted hydrothermal method using inexpensive Fe(NO3)(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 LiFePO4/C microspheres exhibited a favorable spherical morphology, a quite uniform particle size distribution of about 2 mu m, relatively high tap density (1.3 g/cm(3)) and excellent electrochemical performance. Simultaneously, the monodisperse LiFePO4/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 LiFePO4/C, but also enhanced markedly electrochemical performance of LiFePO4/C. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.095112jes]