Mixed cobalt and iron substituted lithium nickelate: a structural and electrochemical study

Layered Li1−z(Ni1−yFey/2Coy/2)1+zO2 phases were obtained by high temperature synthesis. A Rietveld characterization of their XRD patterns shows that the presence of cobalt ions leads to a decrease of the amount of 3d cations in the lithium site vs. the Li1−z(Ni1−yFey)1+zO2 phases. This result is confirmed by a magnetic properties characterization. A Mössbauer spectroscopy study shows that there are no iron ions in the lithium site and that a very small amount of iron ions occupies a very distorted tetrahedral site. The electrochemical behavior of these materials in lithium batteries was studied. The XRD characterization of the cycled materials shows a very good cycling reversibility without any change in the structure.