The effect of ammonia concentration on the morphology and electrochemical properties of LiFePO4 synthesized by ammonia assisted hydrothermal route

The LiFePO4/C composites with different morphology are synthesized by an ammonia assisted hydrothermal method at various ammonia concentrations (from 0 to 1.6 mol L-1) using inexpensive Fe(NO3)(3) and LiOH as raw materials. The influences of the ammonia concentration on the structure, morphology and electrochemical properties of the LiFePO4/C composite are investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), galvanostatic charge/discharge tests and electrochemical impedance spectroscopy (EIS). The results demonstrate that the ammonia concentrations markedly impact the morphology and electrochemical properties of the LiFePO4/C. With the change of ammonia concentrations, the LiFePO4/C synthesized with 0.4 mol L-1 ammonia shows the smallest average particle size, the most uniform microsphere particle distribution and relatively high tap density (1.27 g cm(-3)). In addition, the sample appears a high discharge capacity of 153.9 mAhg(-1) at the first cycle as well as stable cycling performance (the capacity was not almost changed till 100 cycles) at a rate of 1C (170 mA g(-1)). Moreover, it exhibits a good rate capability and still shows a high discharge capacity of over 125 mAh g(-1) even at a rate of 5C. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.