Abstract
In this study, we extensively establish unique relationships between the chemical compositions of LiNi0.5-xMn1.5+xO4 (LNMO) spinel-type positive electrode materials and the degree of Mn/Ni ordering, which influences their electrochemical performance. To achieve this, in situ temperature-controlled neutron powder diffraction experiments were performed under air or oxygen atmospheres to track the Mn/Ni ordering process during annealing of LNMO samples that contain different Mn/Ni ratios. Systematic in-depth structural analysis of a large number of samples, using both neutron and synchrotron X-ray powder diffractions, revealed clear correlations between the variations in the voltage-composition profiles and the distribution of Mn and Ni atoms between the 4b and 12d crystallographic sites of ordered LNMO. Additionally, we employed high-resolution scanning transmission electron microscopy combined with fast Fourier transform analysis that enabled us to visualize the distribution and sizes of Mn/Ni ordered domains at the particle level in excellent agreement with the Rietveld refinement from neutron powder diffraction data.