Electrochemical Behavior of Iron-Substituted Lithium Nickelate

Abstract

Lamellar phases with nominal composition Li(Ni1-yFey)O2(y?0.30) were synthesized and characterized by Rietveld refinement of their X-ray diffraction (XRD) patterns. These materials exhibited the formula Li1-z(Ni1-yFey)1+zO2 with 0.06?z?0.08 and were used as positive electrodes in lithium batteries. Their electrochemical performances decreased with increasing iron content. The Lix(Ni0.90Fe0.10)1.06O2 phases were characterized by XRD and Mossbauer spectroscopy. A solid solution appeared in the entire deintercalation domain 0.28?x?0.94, and Rietveld refinement of the XRD patterns allowed us to characterize the variation of structural parameters upon lithium deintercalation. 57Fe Mossbauer spectroscopy showed that nickel and iron ions were oxidized simultaneously. The fraction of high-spin Fe4+ was related to the strong ligand field resulting from the presence of the prevailing Ni3+ and Ni4+ ions which lead to a lattice contraction. The behavior upon deintercalation of the Li(Ni0.90Fe0.10)O2 phase was compared to that of two-dimensional LiFeO2.