Uyama Takeshi, Mukai Kazuhiko, Yamada Ikuya
Toyota Central Research and Development Laboratories, Inc. Nagakute Aichi 480-1192 Japan
Department of Materials Science, Graduate School of Engineering, Osaka Prefecture University 1-2 Gakuen Sakai Osaka 599-8590 Japan.
RSC Adv. 2018 Jul 24;8(46):26325-26334. doi: 10.1039/c8ra03722a. eCollection 2018 Jul 19.
Tetragonal structured LiMnO (t-LiMnO) samples were synthesized under pressures above 8 GPa and investigated as a positive electrode material for lithium-ion batteries. Rietveld analyses based on X-ray diffraction measurements indicated that t-LiMnO belongs to a γ-LiFeO-type crystal structure with the 4/ space group. The charge capacity during the initial cycle was 37 mA h g at 25 °C, but improved to 185 mA h g at 40 °C with an average voltage of 4.56 V Li/Li. This demonstrated the superiority of t-LiMnO over other lithium manganese oxides in terms of energy density. The X-ray diffraction measurements and Raman spectroscopy of cycled t-LiMnO indicated an irreversible transformation from the γ-LiFeO-type structure into a Li MnO spinel structure by the displacement of 25% of the Mn ions to vacant octahedral sites through adjacent octahedral sites.
四方结构的LiMnO（t-LiMnO）样品在8 GPa以上的压力下合成，并作为锂离子电池的正极材料进行了研究。基于X射线衍射测量的Rietveld分析表明，t-LiMnO属于具有I4/mmm空间群的γ-LiFeO型晶体结构。初始循环期间在25°C时的充电容量为37 mA h g，但在40°C时提高到185 mA h g，平均电压为4.56 V（Li/Li）。这证明了t-LiMnO在能量密度方面优于其他锂锰氧化物。循环后的t-LiMnO的X射线衍射测量和拉曼光谱表明，通过25%的Mn离子通过相邻八面体位置位移到空的八面体位置，从γ-LiFeO型结构不可逆地转变为Li₂MnO₃尖晶石结构。
