Preparation and characterization of LiFePO4 thin films as cathode materials for lithium ion battery

LiFePO4 thin films were prepared by sol-gel technique. The phase and surface morphology were characterized by X-ray diffraction and scanning electron microscopy. The electrochemical properties ofthe thin films were measured by cyclic voltammetry, galvanostatic charge-discharge experiments and electrochemical impedance spectroscopy in 1 mol/L LiPF6/EC-DMC solution using lithium metal as both counter and reference electrodes. The films prepared by this method are ofpure LiFCPO4 phase. The capacity of the film annealed at 700 degrees C for 30 min is 145 mA-h/g, and the capacity loss per cycle is 0.06% after being cycled 50 times. The electrochemical impedance spectroscopy shows that the diffusion rate of lithium ion in LiFePO4 thin film is 5.1 X 10(-14)cm(2)/S.