Preparation by a ‘chimie douce’ route and characterization of (LiNizMn1 –zO2)(0.5⩽z⩽1) cathode materials

Abstract

LiNi_zMn_{1 –z}O₂ cathode materials have been prepared using a ‘chimie douce’ route for 0.5 ⩽z⩽1 Coprecipitation of hydroxides is followed by drying and heating at 700 °C for 5 h under oxygen flow. Because of the high reactivity of the coprecipitates, the preparation time is shorter than for the classical powder mixing and heating methods used generally, and materials with 0.5⩽z⩽1 are obtained easily. DTA-TG and XRD studies have been performed for each composition. The LiNi_zMn_{1 –z}O₂ crystallinity deteriorates progressively when the manganese content is increased, but in contrast to the pure LiNiO₂ compound, partial manganese substitution removes the lithium deficiency. Moreover, owing to the ease of oxidation of manganese ions, partially substituted compounds can be obtained at lower temperature than for pure LiNiO₂. However, manganese substitution in LiNiO₂ deteriorates the electrochemical capacity and reversibility of this compound. This is probably due to the large difference between the structures of nickel and manganese lithium oxides, which produces increasing disorder between layers when the Mn content is increased.