Cathode properties of amorphous and crystalline FePO4

FePO4 is an attractive rare-metal-free cathode active material. Simple and inexpensive new synthesis routes obtained from solution were investigated. P2O5 and Fe metal powders, both of which react in water at room temperature, were selected as inexpensive starting materials. Amorphous powders obtained through ball milling were annealed at various temperatures (100-650 degrees C) in air. IR spectra showed that PO4 tetrahedra units existed even in the amorphous matrix. XRD peaks of the trigonal FePO4 phase appeared above 500 degrees C. Reversible Fe3+/Fe2+, redox reactions in the amorphous and crystalline FePO4 were confirmed by Fe-57 Mossbauer spectroscopy. The heating temperature dependence of the cathode properties is reported. (c) 2005 Elsevier B.V. All rights reserved.