Intrinsic Electrochemical Characteristics in the Individual Needle-like LiCoO₂ Crystals Synthesized by Flux Growth

Abstract

The intrinsic electrochemical characteristics of needle-like LiCoO₂ crystals with a hexagonal cylindrical shape were studied by the single particle measurement technique. The needle-like LiCoO₂ crystals were synthesized by the flux growth method. Single-particle Raman spectroscopy and galvanostatic charge-discharge tests at different electrical contact points in one needle-like LiCoO₂ crystal revealed that the crystal has homogeneous intercalation/deintercalation characteristics throughout the long axis. This suggests that the electron conductivity is high on a 100 µm scale along that axis and that lithium ions are efficiently transferred from the electrolyte to the layer structure of the crystal. The charge rate characteristics of the needle-like LiCoO₂ crystals were also evaluated and compared to those of powdered LiCoO₂. The polarization curve analysis indicates that the needle-like LiCoO₂ particles had almost same exchange current density, i₀, as powdered LiCoO₂, which has a much smaller volume. These excellent electrochemical characteristics are considered to be due to the orientation of the {104} crystal face on the crystal sides, which is the preferential face for lithium ion transfer, and the larger effective surface area of the particles.