The performance of LiNi1/3Mn1/3Co1/3O2 depends largely on the distribution of transition-metal (TM) ions over the available lattice sites within the layered rocksalt structure. Despite predictions that the TM ions take on an ordered arrangement described by a root 3 x root 3R30 degrees supercell, little experimental evidence is available to confirm this model. However, the observed cation distribution likely depends on synthesis conditions. Here, we present a study of commercially produced LiNi1/3Mn1/3Co1/3O2 synthesized at 1000 degrees C before and after charge-discharge cycling. Electron diffraction shows that in-plane ordering is observed to small extents. After charge-discharge cycling, a transformation toward the cubic spinel structure and significant morphology changes are observed. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3424884] All rights reserved.