Synthesis of Li1+xNi0.5Mn0.5O2+delta (x = 0, 0.3) cathode materials for secondary lithium batteries was performed by freeze-drying method using various chemical precursors. Electrochemical performance of materials demonstrates considerable dependence on their chemical prehistory and Li stoichiometry. Increase in duration of the final annealing at 900degreesC since 1-12 h results in decreasing capacity values for all x and chemical prehistories. Observed capacity fall is explained by smaller grain size and, therefore, shorter Li diffusion pathways in the samples obtained using short time annealing. (C) 2004 Elsevier B.V. All rights reserved.