Li1+xNi0.5Mn0.5O2 (x <= 0.4) powders are synthesized from coprecipitated (Ni,Mn) hydroxides with different intermediate synthesis steps and under the same conditions of final annealing. It is shown that the variation of the Li introduction temperature allows the grain size to be modified from 800 nmto 200-250 nm that could be attributed to the LiOH influence on the zonal isolation processes. The appearance of NiMn2O4 and NiMnO3 intermediates was accompanied by the enhancement of cation mixing in Li1+xNi0.5Mn0.5O2 from 4.5 to 9%. According to XPS data, the variations of synthesis conditions have no influence on the oxidation states of Ni and Mn (2+/3+ and 4+, respectively). The grain size decrease of Li1+xNi0.5Mn0.5O2 promotes the corresponding decrease in charge transfer resistance at the electrode-electrolyte boundary. Lithium diffusion coefficients calculated both from cyclic voltammetry data and from electrochemical impedance spectroscopy demonstrate the corresponding enhancement from 10 (18) to 10 (14) cm(2)s (1). The degradation of electrochemical performance of Li1+xNi0.5Mn0.5O2 during cycling can be attributed to the progressive cationic disorder in the layered LiMeO2 lattice. (C) 2014 Elsevier Ltd. All rights reserved.