Cationic distribution in the Li1 − z(Ni1 − yFey)1 + zO2 electrode materials

Various Li1 − z(Ni1 − yFey)1 + zO2 materials (0 < y ≤ 1) were prepared and characterized by XRD. Phases with a quasi-lamellar O3 type structure are obtained only for y ≤ 0.30. In order to precisely determine the cationic distribution in the layered phases, a combined analysis by X-ray and neutron diffraction, magnetic measurements and also Mössbauer spectroscopy was performed. The Rietveld refinement of the XRD patterns shows that a significant amount of 3d cation is always present in the lithium site leading to the formation of ferrimagnetic clusters. A comparative 57Fe Mössbauer study of iron substituted lithium and sodium nickelate showed that the quadrupolar splittings are very sensitive to the nature of the iron site. For the largest y and z values iron ions are simultaneously present in the slab and in the interslab space.