Characteristics of lithium iron phosphate (LiFePO4) particles synthesized in subcritical and supercritical water

The effect of temperature, pH, time, and reactant concentrations on the size and morphology of lithium iron phosphate (LiFePO4) particles synthesized in a batch hydrothermal reactor was investigated in this work. It was found that LiFePO4 could only be synthesized at neutral or slightly basic pH in both subcritical and supercritical water. Synthesis in subcritical water resulted in micron-sized particles of high crystallinity, whereas synthesis in supercritical water produced submicron particles. A more uniform particle size distribution was obtained at low reactant concentrations, irrespective of the synthesis temperature. Qualitative explanations for these observations are provided in terms of nucleation, growth, and agglomeration phenomena at subcritical and supercritical conditions.