Bond pathway analysis of NMR spectra for Li$_{1.2}$Mn$_{0.4}$Co$_{0.4}$O$_{2}$: pristine material

NMR has been applied extensively to lithium ion battery cathode materials, of which layered-layered composites $x$Li$_{2}$MnO$_{3}\cdot(1-x)$Li$M$O$_{2}(M=$Mn,Co,Ni) are of particular interest, owing to their high energy density. In this work, NMR spectra are measured for the model layered-layered system $x$Li$_{2}$MnO$_{3}\cdot(1-x)$LiCoO$_{2}$ and Bond-Pathway-model analysis is applied to elucidate the atomic arrangement and domain structure of this material (in its pristine state, before electrochemical cycling). The simplest structural element of a domain consists of a stripe of composition LiMn2 parallel to an in-layer crystallographic axis in a metal layer of the composite. A simple model of the composite structure may be constructed by a superposition of such stripes in an LiCoO background. We show that such a model can account for most of the features of the observed NMR spectra. Support from the Vehicle Technologies Program U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy.