SYNTHESIS OF LIMNO2 WITH ALPHA-NAMNO2-TYPE STRUCTURE BY A MIXED-ALKALINE HYDROTHERMAL REACTION

A metastable form of LiMnO2 with alpha-NaMnO2-type structure (layered- LiMnO2) was synthesized directly from Mn2O3 by hydrothermal reaction a t 220 degrees C using aqueous mixed-alkaline solutions such as LiOH . H2O-KOH or LiCl-KOH. Relatively highly crystallized samples could be o btained by a one-step process, compared with that of an ion-exchanged sample obtained previously. Magnetization data between 83 and 500 K sh ow that manganese ions ate present as 3+ in high-spin state and a broa d maximum is observed ca. 250 K, suggesting a yield of antiferromagnet ic ordering below room temperature. Preliminary electrochemical tests using coin-type cells in which lithium metal was used as negative elec trode material show that about 100 mAh/g specific capacity remained at the eighth cycle between 2.0 and 4.3 V, whereas the initial charge ca pacity reached ca. 210 mAh/g up to 4.3 V.