Fabrication of LiCoO2 thin film cathodes by DC magnetron sputtering method

LiCoO2 thin films were fabricated on Al substrate by direct current magnetron sputtering method. The effects of Ar/O2 gas rates and annealing temperatures were investigated. Crystal structures and surface morphologies of the deposited films were investigated by X-ray diffraction, Raman scattering spectroscopy and field emission scanning electron microscopy. The as-deposited LiCoO2 thin films exhibited amorphous structure. The crystallization starts at the annealing temperature over 400 °C. However, the annealed films have the partially disordered structure without completely ordered crystalline structure even at 600 °C annealing. The electrochemical properties of the LiCoO2 films were investigated by the charge–discharge and cycle measurements. The 500 °C annealing film has the highest capacity retention rate of 78.2% at 100th cycles.