High-resolution X-ray diffraction, DIFFaX, NMR and first principles study of disorder in the Li2MnO3-Li[Ni1/2Mn1/2]O-2 solid solution

摘要

X-ray diffraction patterns of Li[Li(1-2x)/3NixMn2/3-x/3]O-2 show reflections between 20 degrees and 35 degrees, 20 (CuK alpha) due to Li2MnO3-like ordering of the transition metal (Ni, Mn and Li) layers. The ordering is rarely perfect, resulting in characteristic broadening and changes in the intensities of these reflections. Li-6 MAS NMR studies of Li2MnO3 show that the [Li1/3Mn2/3] layers are well ordered, the disorder arising from the stacking of the layers in the c-direction. DIFFaX was used to model the Li2MnO3 XRD data and extract the stacking fault frequency. The results show that even well-ordered cation layers may show only weak or no superstructure reflections, if there is no or little ordering in the c-direction. (c) 2005 Elsevier Inc. All rights reserved.