Evidence of a cationic substitution domain in lithium-manganese spinels

Abstract

Magnetic susceptibility measurements and electron paramagnetic resonance spectra of samples prepared from the reactive system MnO/Li2CO3 with different starting Li cationic fraction cursive Greek chi are analyzed, taking into account the structural and compositional information provided by x-ray diffraction. Parent phases, as Mn2O3, Mn3O4 and Li2MnO3, arise together with the lithium-manganese spinel as a result of Li-deficiency or Li-excess with respect to the cursive Greek chi = 0.33 composition pertinent to the stoichiometric LiMn2O4 spinel. The data show that the spinel phase can sustain a partial Li-Mn substitution in the cation sites, according to compositional models described, for cursive Greek chi > 0.33, by Li1+yMn3+1-3yMn4+1+2yO4 (Li-rich spinel) and, for cursive Greek chi < 0.33, by Li1-|y|Mn2+|y|Mn3+1+|y|Mn4+1-|y|O4 (Li-poor spinel). Paramagnetic resonance data of the Li-poor spinel phase are analyzed to discuss the possible oxidation state of Mn in the tetrahedral site.