The nickel–manganese compounds were synthesized by redox reactions in aqueous solutions using potassium permanganate as an oxidizing agent at ambient temperature. Also, a layered Li–Ni–Mn–O system was synthesized by using a nickel–manganese compound as precursor for electrode materials. X-ray diffraction patterns of the lithiated Li1.296Ni0.056Mn0.648O2 sample were indexed to a layered structure based on hexagonal α-NaFeO2 (space group: R-3m, 166) with signs of monoclinic-related peaks indicating the existence of monoclinic Li2MnO3 phase. The lithiated Li1.296Ni0.056Mn0.648O2 electrode provides the initial discharge capacity of 108mAhg−1 and the maximum discharge capacity of 192mAhg−1 between 2.0 and 4.8V versus Li/Li+ at 0.2mAcm−2.