The Li1.2-xMn0.54Ni0.13Co0.13O2 were synthesized by chemical or electrochemical delithiation. The characterization by using the XRD, ICP, synchrotron XRD and thermodynamic measurements were performed for pristine and delithiated compounds. The measured lithium compositions for chemically delithiated Li1.2-xMn0.54Ni0.13Co0.13O2 showed the values of x = 0.31, 0.43, and 0.88, and were nearly the same as the electrochemically delithiated cathodes at 4.3 V, 4.5 V, and 4.8 V, respectively. The crystal and electronic structures for pristine and delithiated samples were analyzed by the Rietveld method using synchrotron X-ray diffraction. As a result, many structural parameters resembled between chemically and electrochemically delithiations up to x = 0.5. Above x = 0.5, the distortion parameters, lambda and sigma(2), and the electronic structures for electrochemically delithiated materials were not coincide with those for corresponding chemically delithiated one. Thermodynamic stabilities of the materials about x approximate to 0.9 were enhanced for electrochemically delithiation. The chemically delithiation of the Li1.2-xMn0.54Ni0.13Co0.13O2 enabled the reproduction of the charged active materials up to 4.5 V by using the NO2BF4 oxidizer. (C) 2016 Elsevier B.V. All rights reserved.