Synthetic optimization of orthorhombic LiMnO2 by emulsion-drying method and cycling behavior as cathode material for Li-ion battery

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 °C 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 °C. Chemical delithiation of LiMnO2 resulted in increased capacity in the initial several cycles. Several cycles at elevated temperature and subsequent cycling at 25 °C 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.