Preparation of Highly Oriented Porous LiCoO2 Crystal Films via Li-Vapor Crystal Growth Method

To construct better Li-ion-based batteries, highly oriented porous LiCoO2 crystal film is urgently needed for an active positive electrode. In this study, we prepared such a crystal film via the Li-vapor crystal growth method, which involves a simple reaction between the CoO substrate and Li vapor. Highly crystalline LiCoO2 particles 2-3 mu m in size were grown on the CoO substrate surface with strong relation of their orientation. The < 110 >- and < 018 >-oriented LiCoO2 particles, which are preferable for Li-ion conduction, were generated on the CoO(110) substrate. On the CoO(111) substrate, LiCoO2 particles were grown with not only the < 003 > orientation but also the < 012 > orientation, suggesting that the crystal growth should follow the three-dimensional structure of the CoO and LiCoO2 lattice. Both the prepared LiCoO2 films from the CoO(110) and CoO(111) substrates exhibited stable and superior electrochemical properties for Li-ion battery cycling, indicating that the films will be useful for high-performance Li-ion-based batteries.