Bond Pathway Analysis of NMR Spectra for Li1.2Mn0.4Co0.4O2: Pristine Material

NMR has been applied extensively to lithium ion battery cathode materials, of which layered-layered composites xLi₂MnO₃•(1-x)LiMO₂ (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 xLi₂MnO₃•(1-x)LiCoO₂  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 LiCoO₂ 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.