Soft-Mechanochemical Synthesis of LiMnO_2 for Better Cathodes of Lithium-Ion Batteries

摘要

Single phase orthorhombic (o-) LiMnO_2 was synthesized via a soft-mechanochemical route from a stoichiometric powder mixture comprising Li_2CO_3 and Mn_2O_3. Mechanical stressing was exerted in N_2 by a newly developed horizontal type multi-ring milling machine, Mechano-MICROS~(~R). While crystalline reactants remain in a starting mixture even after milling for 7h, they quickly disappear after heating in air. When the starting mixture was milled for more than 1h, single phase o-LiMnO_2 was obtained after linear heating at 10?/min up to 1000°C in N_2 atmosphere. In contrast, heating the same sample under the same program but in air resulted in LiMn_2O_4 as a sole product. When the maximum temperature was below 800°C, second phase was not fully eliminated. The temperature of decarboxylation was observed as an endothermic DTA peak at 730°C from the intact mixture, but at 430°C for the mixture milled for 60min. Likewise, the crystallization of o-LiMnO_2 were observed at 750°C for intact and at 580°C for the sample preliminarily milled for 60min. Thus, the soft-mechanochemical process is quite beneficial to obtain fine-grained and well-crystallized single phase o-LiMnO_2.