Lithium has been chemically extracted from the layered oxide solid solutions Li[Li1/3Mn2/3]O-2(z)Li[ Mn0.5-yNi0.5-yCo2y]O-2 (0 <= y <= 1/2 and 0.25 <= z <= 0.75) and characterized by X-ray diffraction. The weak super lattice reflections that occur in the parent samples at around 2 theta = 20-25 degrees vanish on extracting a significant amount of lithium due to the removal of lithium from the transition metal layer and a consequent loss of the ordering between the Li+ and the transition metal ions. Additionally, the chemical delithiation process results in an incorporation of some protons from the chemical delithiation medium into the layered lattice, which has an influence on the structure of the delithiated samples. While the incorporation of a higher concentration (similar to 0.4 per formula unit) of protons results in the formation of O1 or P3 phases, delithiated samples with <0.2 protons maintain the initial O3 structure. However, the electrochemically charged samples maintain the initial O3 structure. (C) 2008 Elsevier B.V. All rights reserved.