Single-crystal synthesis, structure refinement and electrical properties of Li0.5CoO₂

Single crystals of Li0.5CoO2 were synthesized for the first time by means of a chemical lithium-ion deintercalation process using LiCoO2 single crystals as a parent compound. A single-crystal x-ray diffraction study revealed an ordered superstructure with monoclinic symmetry, that could be assigned to the space group P 2/m. The crystal structure, including anisotropic displacement parameters for each atom, was refined to the conventional values R 1 = 3.1%, wR 2 = 10.9%, and S = 1.16 using 2385 independent reflections in the range sinθ/λ<1.3 A−1. The lithium-ion and vacancy ordering structure in Li0.5CoO2 was clearly revealed in the electron density distribution analyzed by the maximum entropy method (MEM) using the single-crystal x-ray diffraction data. The in-plane electrical resistivity in Li0.5CoO2 measured using the single-crystal specimen was around 2 mΩ cm and approximately temperature independent, suggesting metallic conduction. These findings were very consistent with those obtained by the FLAPW calculations.