The electronic structural changes during lithium-ion intercalation/de-intercalation process of nickel substituted lithium manganese spinet oxides have been investigated by using X-ray absorption near-edge structure (XANES) spectra of O K-edges as well as Ni L-3-edges and Mn L-3-edges. The results of the XANES spectra indicate that the electronic structure of both manganese and oxygen atoms contribute on the redox reaction at 0.06 <= x < 1, and only that of nickel atom affect the redox reaction at 1 < x <= 1.78 in LixNi0.5Mn1.5O4. Thus, the electronic structural change of oxygen atom is also crucial for considering redox reaction at intercalation/de-intercalation process, and the contribution of the oxygen atom on redox reaction differs in various redox cation species. (C) 2013 Elsevier B.V. All rights reserved.