Single phase LiCo(1-y)Ni(y)O(2) (y=0.4 and 0.5) with fine particles and high homogeneity was synthesized by ``chimie douce'' assisted by citric acid as the polymeric agent and investigated as positive electrodes in rechargeable lithium batteries. The long-range and short-range structural properties are investigated with experiments including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and superconducting quantum interference device magnetometry. The physicochemical properties of the powders (crystallinity, lattice constants, grain size) have been investigated in this composition. The powders adopted the alpha-NaFeO(2) structure as it appeared from XRD and FTIR results. Magnetic measurements shows signal at low temperature attributed to the magnetic domains in the nanostructure sample from which we estimated that the cation mixing are 3.35 and 4.74% for y=0.4 and 0.5 in LiCo(1-y)Ni(y)O(2), respectively. LiCo(0.5)Ni(0.5)O(2) cathode yields capacity (135 mAh g(-1)) compared to LiCo(0.6)Ni(0.4)O(2) cathode (147 mAh g(-1)) when discharged to a cutoff voltage of 2.9 V vs. Li/Li(+). Lower capacity loss and higher discharge efficiency percentage are observed for the cell of LiCo(0.6)Ni(0.4)O(2) cathode.