Cationic distribution in the Li1-z(Ni1-yFey)(1+z)O-2 electrode materials

Various Li1-z(Ni1-yFey)(1+z)O-2 materials (0<y<less than or equal to>1) wer e prepared and characterized by XRD. Phases with a quasi-lamellar O3 type s tructure are obtained only for y less than or equal to0.30. In order to pre cisely determine the cationic distribution in the layered phases, a combine d analysis by X-ray and neutron diffraction, magnetic measurements and also Mossbauer spectroscopy was performed. The Rietveld refinement of the XRD p atterns shows that a significant amount of 3d cation is always present in t he lithium site leading to the formation of ferrimagnetic clusters. A compa rative Fe-57 Mossbauer study of iron substituted lithium and sodium nickela te 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 simultaneous ly present in the slab and in the interslab space.