Substituting mechanical stirring by ultrasonic irradiation in co-precipitation method, cathode material LiNi0.5Mn0.5O2 for lithium batteries with better layered structure and crystallinity has been successfully synthesized. The physicochemical and electrochemical properties of ultrasonic co-precipitation (UCP) prepared material were compared with those of the mechanical stirring co-precipitation (MSCP) prepared material by thermogravimetery analysis (TGA), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), and galvanostatic charge-discharge testing in detail. UCP prepared LiNi0.5Mn0.5O2 presents better rate discharge capability, cyclic stability and reversibility, resulting from smaller electrochemical polarization during electrode reaction and easier lithium ion insertion/desertion. Application of ultrasonic irradiation during the co-precipitation preparation process is beneficial to produce samples with better physicochemical and electrochemical properties. (c) 2007 Elsevier B.V. All rights reserved.