Iron Phosphate Materials as Cathodes for Lithium Batteries by Pier Paolo Prosini

Author:Pier Paolo Prosini
Language: eng
Format: epub, pdf
Publisher: Springer London, London

5.2 Physical and Electrochemical Characterization of Amorphous and Crystalline FePO4

In the previous chapter it was shown that a mixture of amorphous 3Fe2O3•2P2O5•10H2O, prepared by air oxidation of iron(II)phosphate, exhibited good electrochemical properties as cathode of a lithium cell [1]. However, two different types of iron were formed during the heating treatment of iron(II)phosphate, namely iron(III)phosphate and iron(III)oxide. Since the latter form is electrochemically non-active for lithium intercalation in the investigated voltage range (4.0–2.0 V) [2], the electrochemical properties of such material was only due to the amorphous iron(III)phosphate phase. For this reason we investigated a new synthetic route to prepare pure amorphous iron(III)phosphate [3]. Amorphous iron(III)phosphate was synthesized by spontaneous precipitation from equimolar aqueous solutions of Fe(NH4)2(SO4)2·6H2O and NH4H2PO4, using hydrogen peroxide as an oxidizing agent as described in Eq. 5.1:

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