Powder properties of partially substituted LiM xMn 2− xO 4 (M = Al, Cr, Fe and Co) synthesized by ultrasonic spray pyrolysis

Abstract

Powders of spinel lithium manganese oxide LiMn 2O 4 and its substituted forms LiM x Mn 2− x O 4 ( x = 0.05, 0.1, 0.2 and 0.3; M = Al, Cr, Fe and Co) have been successfully synthesized using an ultrasonic spray pyrolysis technique. The effect of Al, Cr, Fe and Co substitution on the powder properties of spinel lithium manganese oxides was examined by X-ray diffraction (XRD), the Brunauer–Emmett–Teller (BET) surface area method, field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). All the samples exhibited a pure cubic spinel structure without any impurities in the XRD patterns. The morphology changes from spherical and porous to spherical and dense with increasing metal (Al, Cr, Fe and Co) substitution. The powder properties of lithium manganese oxide, such as geometric mean diameter, crystallite size, and specific surface area, were strongly affected by the composition, x, and substituted metal M (= Al, Cr, Fe and Co) in LiM x Mn 2− x O 4. Spherical, dense particles with the larger crystallite size and smaller specific surface area could be synthesized using ultrasonic spray pyrolysis technique when the manganese was partially substituted by Cr at the composition x ≥ 0.1 in LiCr x Mn 2− x O 4 and by Fe at the composition x ≥ 0.2 in LiFe x Mn 2− x O 4, respectively.