Structural disorder along the lithium diffusion pathway in cubically stabilized lithium manganese spinel I. Synchrotron X-ray studies

Electron density distribution, EXAFS, and transmission electron microscope studies on stoichiometric Li(Mg1/6Mn11/6)O-4 have revealed that: (1) the structure is essentially of spinel-type with slight diffuse scattering, (2) the Li atoms are not all located at the ideal 8a site of the Fd (3) over barm spinel structure, but are partially tetrahedrally distributed along the 8a-16c tie line, (3) the 0 atoms also exhibit a statistical distribution about their ideal positions and (4) the Mn 3d electrons are squeezed out toward the open space of the coordinating octahedra with D-3d distortion. The present results indicate the possible existence of many metastable Li positions in the structure. suggestive of complicated Li atom hopping routes in conjunction with a local distortion of neighboring atoms at least up to the second shell. (C) 2003 Elsevier Inc. All rights reserved.