To overcome the difficulty of orthorhombic LiMnO2 synthesis, we employed an emulsion-drying method that can intermix cations homogeneously in atomic scale and quite effective to synthesize fine single-crystallite oxide electrode material. The orthorhombic LiMnO2 was easily prepared from calcination of Li-Mn-O emulsion-dried precursor. That is, firstly, the as-received was oxidized at relatively low temperature. Then, the oxidized powder was simply calcined at 925 degreesC using Ar gas without controlling oxygen partial pressure. Finally, the resultant showed a well-ordered orthorhombic LiMnO2 single-crystallite particle oxide, as observed by transmission electron microscopy and electron diffraction pattern. Li/LiMnO2 Cell showed the highest capacity of about 173 mA h (g oxide)(-1) and more than 155 mA h g(-1) over 300 cycles at 25 degreesC. Chemical delithiation of LiMnO2 resulted in increased capacity in the initial several cycles. Several cycles at elevated temperature and subsequent cycling at 25 degreesC led to a much higher capacity as well as good cyclability. The orthorhombic LiMnO2 from the emulsion-dried powder precursor demonstrated much more enhanced battery performance than those by other synthetic routes.