Fabrication and Electrical Properties of Bulk Textured LiCoO2

In order to study the orientation dependence of the electrical properties of layered structure cathode materials used in lithium-ion thin-film microbatteries, a typical composition, LiCoO2, has been hot-press sintered in bulk with a strong crystallographic texture. Microstructural characterization using X-ray diffraction, scanning electron microscopy, and Raman spectroscopy showed that the degree of LiCoO2 texture depended upon the precise hot-press conditions used. There was a pronounced orientation of the polycrystalline LiCoO2 c-axis in the pressing direction with a high Lotgering factor (f=0.96) for sintering at 950 degrees C. The pronounced texture led to a remarkable anisotropy in electronic conductivity between directions parallel (sigma(parallel to)) and perpendicular (sigma(perpendicular to)) to the pressing direction in the temperature range 190-400 K, with sigma(perpendicular to)/sigma(parallel to) =187 at 300 K. The results suggest that texture can be used to tune not only the well-known electrochemical performance of all-solid-state lithium-ion thin-film batteries, but also their electronic conductivity.