A nanocrystalline Li[Li(0.12)Ni(0.32)Mn(0.56)]O(2) powder was synthesized via the pyrolysis of polyacrylate salt precursors prepared by in situ polymerization of the metal salts and acrylate acid. The pyrolysis mechanism of the polymeric precursor is discussed by use of thermal analysis. Layered crystalline structure of the resulting compound was characterized by powder X-ray diffraction and high-resolution transmission electron (TEM) micrographs. The results revealed that the Li[Li(0.12)Ni(0.32)Mn(0.56)]O(2) as prepared has nanosized morphology and good crystallinity even if calcined at 900 degrees C, and the electrodes made from these nanoparticles exhibited high-rate characteristics and can deliver stable discharge capacity (163 mA.h/g) with excellent capacity retention at appropriate charge-discharge voltage interval. Since this preparation method is simple and particularly suitable for preparation of mixed metal oxides, it can be used for industrial production of highly homogeneous metal oxide cathode materials of the lithium-ion batteries.