Structural determination of Li1-yNi0.5Mn0.5O2 (y=0.5) using a combination of Rietveld analysis and the maximum entropy method

The crystal structures and electron density distributions of the layered oxide Li1-yNi0.5Mn0.5O2 (y=0.5) were studied using a combination of Rietveld analysis of high-resolution synchrotron powder X-ray diffraction data and the maximum entropy method (MEM). Structural analysis revealed that Li1-yNi0.5Mn0.5O2 (y=0.5) has the lattice parameters a=4.934 Angstrom, b=2.852 Angstrom, c=5.090 Angstrom, beta=108.8degrees and adopts the space group C2/m. The chemical formula can be expressed as [Ni-0.0815](2a){Li0.5Ni0.0115}(4i)-[Mn(0.5)Ni(0.407)square(0.093)](2d)O-2. The electron density map obtained using MEM clearly shows that most of the Li ions migrate from the octahedral 2a site to the tetrahedral 4i site during Li de-intercalation.