Effects of Stacking Fault Defects on the X-ray Diffraction Patterns of T2, O2, and O6 Structure Li2/3[CoxNi1/3-xMn2/3]O2

During the preparation of Li2/3[CoxNi1/3-xMn2/3]O2 from Na2/3[CoxNi1/3-xMn2/3]O2 by low-temperature ion exchange, the MO2 sheets slide so the alkali coordination can change from prismatic in the Na compound to octahedral or tetrahedral in the Li compound. All Li-containing samples show stacking faults, some with very high densities of faults, based on broad mixed index peaks in their diffraction patterns. Here, we calculate simulated diffraction patterns using the DIFFaX program developed by Treacy et al. We have considered intergrowths of the T2 and O2 structures and stacking faults in both O2 and O6 structures and have compared the results with experimental X-ray diffraction patterns of Li2/3[CoxNi1/3-xMn2/3]O2 (x = 0, 1/24, and 1/12). The stacking fault models are consistent with the experimental data. Furthermore, we suggest that Li2/3[CoxNi1/3-xMn2/3]O2 (x = 1/12) is actually a stacking faulted O6 structure, not a stacking faulted O2 structure as we claimed previously.