Structural change of the LiMn2O4 spinel structure induced by extraction of lithium

Abstract

A structural change of the LixMn2O4 spinel induced by extraction of lithium was investigated using the Rietveld refinement method for its X-ray diffraction pattern change. Two cubic phases of the spinel LixMn2O4 were observed in the range 0.5> x >0.13 and their lattice parameters were found to decrease with decreasing x. If both phases were thermodynamically stable, the lattice parameters should not change during the extraction of lithium. Therefore, our X-ray diffraction (XRD) patterns suggest the destruction of the rigid LixMn2O4 spinel structure which provides a high reversibility for the insertion and extraction of lithium. The possible mechanisms corresponding to this structural degradation are the compositional change of Mn or O atoms in LixMn2O4 through the extraction of lithium. On the other hand, the separation of Mn2+ ions from LixMn2O4(0.5> x >0.13) was detected by electron paramagnetic resonance (EPR). From these results, it is concluded that LixMn2O4 decomposes through the extraction of lithium to form Mn2+ compounds as a separate phase.