Fabrication of LiCoO2 thin-film cathodes for rechargeable lithium microbatteries

Polycrystalline thin films of lithium cobalt oxide were grown by pulsed-laser deposition (PLD) technique. Films of LiCoO2 were deposited onto Si substrates heated at temperature lower than 300°C from a sintered composite target (LiCoO2+Li2O) irradiated with a Nd:YAG laser. The structural characterizations of these films were carried out by X-ray diffraction and Raman scattering spectroscopy, which probe the local environment of cations in the LiCoO2 framework. Raman spectra of PLD LiCoO2 films were investigated as a function of various growth conditions as substrate temperature, partial oxygen pressure in the deposition chamber, and target composition. PLD LiCoO2 films obtained with a polycrystalline morphology were successfully used as cathode materials in lithium microbatteries. The Li//LiCoO2 cells were tested by cyclic voltammetry and galvanostatic charge–discharge techniques in the potential range 2.0–4.2 V. Specific capacity as high as 195 mC cm−2 μm was measured on polycrystalline films.