Electrochemical Properties of Lithium Iron Oxides Prepared by Low Temperature Synthesis

Two lithium iron oxides r-Li(0.8)H(0.2)FeO(2) (ramsdellite-type) and o-Li(0.7)H(0.3)FeO(2) (orthorhombic structure) have been synthesised by an ion exchange reaction between respectively alpha-FeOOH and gamma-FeOOH, and C(2)H(5)OLi at 170 degrees C and 140 degrees C The reaction products were characterised through elemental analyses, infrared spectroscopy, density measurements and X-ray diffraction. The refinement of the powder XRD patterns of r-Li(0.8)H(0.2)FeO(2) and o-Li(0.7)H(0.3)FeO(2) has been performed by the Rietveld method and the results show that the products are isostructural to their precursors. Electrochemical measurements of Li(1-x)H(x)FeO(2)/Li have been made in lithium cells in the 1.5 - 5 V range. Their elemental analyses and the study of X-ray diffraction results and Mossbauer spectroscopy measurements show the instability of Fe(4+) in the electrochemically produced species in the electrochemical cell, and therefore the difficulty of cycling on the couple Fe(IV)/Fe(III).