Abstract:The monoclinic and orthorhombic ordered-rocksalt polymorphs of LiMnO↓2 are of interest as high-capacity cathode materials for rechargeable Li batteries. LiMnO₂ and LiMn_1-xCr_xO₂ were prepared by a high temperature solid-state route. In comparison with undoping Cr orthorhombic LiMnO₂, monoclinic LiMnO₂ was preserved with Cr doping. The volume of m-LiMnO₂ decreasing with increasing Cr confirms that the length of bond around Cr ion decreases with Mn substituted by Cr ion. A phase transformation mechanism was proposed for understanding the structure relationship between the LiMnO₂ and chromium-substituted LiMnO₂ oxides.

Key words: LiMnO₂; Cr doping; phase transformation mechanism