Electrochemistry and structure of Li2-xCryMn2-yO4 phases

The synthesis of phases in the solid state solution series Li2CryMn2-yO4 where 0 < y < 2 and their use as cathodes in lithium ion cells was reported previously. This paper reports the results of electrochemical evaluations with metallic lithium anodes and on Rietveld refinements of X-ray and neutron powder diffraction data for these phases. Although these materials are prepared at moderately high temperatures, the refinements show that the have a structure similar to the monoclinic layered form of LiMnO2 prepared by soft chemistry at low temperatures by Armstrong and Bruce and by Delmas and Capitaine. The degree of monoclinic distortion in the initial materials has an effect on the structural changes that occur on charging. The phases with a small monoclinic distortion change to an undistorted hexagonal structure on their first charge while those with a large monoclinic distortion change to a spinel-like structure on cycling.NRC publication: Ye