The Effect of Al[sub 2]O[sub 3] Coating on the Cycle Life Performance in Thin-Film LiCoO[sub 2] Cathodes

Abstract

The electrochemical stability of LiCoO2LiCoO2 films is improved by an ∼10 nm Al2O3∼10 nm Al2O3 coating on top of the thin-film cathode material. Galvanostatic charge/discharge experiments showed enhanced electrochemical properties in the Al2O3Al2O3 -coated LiCoO2LiCoO2 films than the bare ones. This phenomenon is related to the faster Li diffusion rate in the Al2O3Al2O3 -coated samples, as evidenced by cyclic voltammograms. This provides easier pathways for Li-ion migration by forming a thin-film solid solution layer (LiCo1−xAlxOz).(LiCo1−xAlxOz). Similar results were observed in LiCoO2LiCoO2 powders, showing enhanced cycle performance after coating with a thin-film metal-oxide coating. However, unlike the powder geometry, both bare and Al2O3Al2O3 -coated LiCoO2LiCoO2 thin films showed negligible cc axis expansion. © 2002 The Electrochemical Society. All rights reserved.