Advanced Manufacturing Research Institute, National Institute of Advanced Industrial Science and Technology (AIST)
○Yasuhiko Takahashi Junji Awaka Norihito Kijima Junji Akimoto

Lithium cobalt dioxide, LiCoO₂, has been used industrially as the positive electrode material for lithium-ion rechargeable batteries. In almost of the experimental studies reported to date, sintered or pressed powder samples or the corresponding polycrystalline thin films are used. In an experiment using such samples, much of information on the anisotropy is lost. In the recent of our study, we have succeeded in the growth of LiCoO₂ single crystals and determined the crystal structure by single-crystal X-ray diffraction method. In this study, the structural and physical properties of Li_xCoO₂ were investigated using the chemically and electrochemically oxidized Li_xCoO₂ single crystal samples. Compositional dependence of the in-plane electrical resistivity in Li_0.5CoO₂ has been clarified. Metallic conductivity in Li_0.5CoO₂ single crystal has been successfully measured for the first time. The lithium-ion and vacancy ordering structure and electron density distribution in Li_0.5CoO₂ has been precisely determined by single-crystal X-ray diffraction and Maximum Entropy Method using program PRIMA (Fig.). And also calculate the electronic structure of Li_xCoO₂ using DFT calculations and the results were compared with the experimental results.