The effect of Al2O3 coating on the cycle life performance in thin-film LiCoO2 cathodes

The electrochemical stability of LiCoO2 films is improved by an similar to10 nm Al2O3 coating on top of the thin-film cathode material. Galvanostatic charge/discharge experiments showed enhanced electrochemical properties in the Al2O3-coated LiCoO2 films than the bare ones. This phenomenon is related to the faster Li diffusion rate in the Al2O3-coated samples, as evidenced by cyclic voltammograms. This provides easier pathways for Li-ion migration by forming a thin-film solid solution layer (LiCo1-xAlxO2). Similar results were observed in LiCoO2 powders, showing enhanced cycle performance after coating with a thin-film metal-oxide coating. However, unlike the powder geometry, both bare and Al2O3-coated LiCoO2 thin films showed negligible c axis expansion. (C) 2002 The Electrochemical Society.