Preparation and Characterization of Spherical-like Ferric Phosphate Precursors by Co-precipitation--Spray-drying Method.

The preparation of spherical-like battery-grade ferric phosphate by co-precipitation--spray-drying method was investigated using ferrous sulfate heptahydrate (FeSO₄, • 7H₂O) and ammonium dihydrogen phosphate (NH₄ H₂ PO₄) as raw materials. The effects of the addition of the surfactant cetyltrimethyl ammonium bromide (CTAB), reaction time, and solution pH on the physical phase and particle size of ferric phosphate were examined. The products were characterized by a laser particle sizer, X-ray powder diffractometer, thermogravimetric analyzer, and field emission scanning electron microscope. The results indicate that under the conditions of a Fe/P molar ratio of 1/1.01, CTAB addition of 0.04 g, reaction time of 1 h, and solution pH of 3.0, the ferric phosphate exhibits the smallest particle size distribution, ranging from 300 to 500 nm, and displays more uniform spherical morphology. Moreover, lithium iron phosphate is prepared by ball milling, mixing and sintering, using the spherical-like ferric phosphate as the precursor iron source. The specific discharge capacity of lithium iron phosphate is 150.14 mAh/g at 0.1 C and the retention rate is 98.9% after 200 cycles at 1 C, the performance is good. [ABSTRACT FROM AUTHOR]