Synthesis of Li[(Ni0.5Mn0.5)1 - x Li x ]O2 by Emulsion Drying Method and Impact of Excess Li on Structural and Electrochemical Properties

• Published in: Chemistry of materials 2006-03, Vol.18 (6), p.1658-1666
• Main Authors: Myung, Seung-Taek, Komaba, Shinichi, Kurihara, Koutarou, Hosoya, Kiyoharu, Kumagai, Naoaki, Sun, Yang-Kook, Nakai, Izumi, Yonemura, Masao, Kamiyama, Takashi
• Format: Article
• Language: English
• ISSN: 0897-4756; 1520-5002
• DOI: 10.1021/cm052704j

Layered Li[Ni0.5Mn0.5]O2 (R3̄m space group) was synthesized with controlling the Li/(Ni + Mn) ratio by employing an emulsion drying method, and the effect of Li on the transition-metal layer was investigated. Structural analyses of the final products were done by X-ray diffraction, neutron diffraction, and X-ray absorption near-edge spectroscopy. From the structural studies, we found that an excess amount of Li is located at the transition-metal layer and the presence of Li in the transition metal significantly improved structural ordering in the crystal structure. High capacity with good cyclability, faster Li+ chemical diffusivity, less changes in the host structure by Li+ de-/intercalation, and higher thermal stability were achieved for the Li-excess Li[(Ni0.5Mn0.5)0.94Li0.06]O2 compound relative to Li[Ni0.5Mn0.5]O2. It is believed that such enhanced electrochemical properties are related to the improved physical and structural properties of Li-excess Li[(Ni0.5Mn0.5)0.94Li0.06]O2.