The structural and thermal properties of the delithiated LixNi1/3Co1/3Mn1/3O1 (0 < x <= 1) Material have been investigated by using diffraction and thermoanalytical techniques such as XRD and TG-DSC methods. XRD result shows that the delithiated materials maintain the O3-type structure with defined stoichiometric number at the range of 0.24 < x <= 1, exhibiting good crystal structural stability. The cobalt and nickel ions in the delithiated materials change their valence state (i.e. Co3+ to Co4+ and Ni3+ to Ni4+) when x < 0.49; the irreversible changes of the transformation may affect the first cycle of charge-discharge efficiency of the materials. A comparison of the results of TG-DSC with TPD-MS shows that the irreversible change of oxygen species during the delithiation process of LixNi1/3Co1/3Mn1/3O2 have great influence on the structural and thermal stability and reversibility of the materials. (c) 2006 Published by Elsevier B.V.