A long and irreversible plateau is observed for Li1.12(Ni0.425Mn0.425Co0.15)0.88O2. The layered Liy(Ni0.425Mn0.425Co0.15)0.88O2 (y=0.93 and 0.73) materials were prepared by discharging to 3.2 V Li//Liy(Ni0.425Mn0.425Co0.15)0.88O2 cells charged up to 4.4 V (beginning of the plateau) and 4.8 V (end of the plateau), respectively. The structure was investigated using the combination of X-ray and electron diffraction experiments to study a possible structural evolution upon cycling of the superstructure observed for the pristine material. The disappearance of the superlattice lines in the 19.5–34° (2fCu) range in the X-ray diffraction pattern as well as that of the diffuse disorder scattering lines (or the extra spots) in the electron diffraction patterns were clearly observed for Li0.73(Ni0.425Mn0.425Co0.15)0.88O2...