Influence of Two-Step Heat Treatment on Sputtered Lithium Cobalt Oxide Thin Films

A crack-free LiCoO(2) thin film with a preferred oriented crystalline structure is obtained by adopting a two-step heat treatment with a combination of substrate heating at 300 degrees C during sputtering and a rapid thermal annealing (RTA) process. The performances of cells deposited at room temperature and at 600 degrees C with and without the RTA process are also compared. The LiCoO(2) cathode thin film deposited at 300 degrees C with RTA shows a high specific discharge capacity of 65 mu Ah/cm(2)-mu m at a 1C rate and excellent reversibility of the dQ/dV curve in a half cell using liquid electrolyte. In a Li/Lipon/LiCoO(2) structure, a specific discharge capacity of 63.5 mu Ah/cm(2)-mu m is demonstrated, corresponding to 92% of its theoretical value. During charge and discharge the first specific discharge capacity of 60 mu Ah/cm(2)-mu m is observed even at a 5 C rate, demonstrating superior cycling performance over 500 cycles with no capacity degradation. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.036112jes] All rights reserved.