Li-ion diffusion kinetics in LiFePO4 thin film prepared by radio frequency magnetron sputtering

LiFePO4 thin films were prepared by radio frequency (RF) magnetron sputtering and were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and atomic force microscope (AFM). Li-ion chemical diffusion coefficients, D˜Li, were measured by potentiostatic intermittent titration technique (PITT), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). The effects of Ag content, film thickness, and film orientation on the electrochemical performance and Li-ion chemical diffusion coefficients of the LiFePO4 thin films were investigated. D˜Li values were measured using the liquid electrolyte and the solid electrolyte, and the obtained values were discussed. The D˜Li values by PITT and EIS were in the range of 10−14 to 10−12 and 10−15 to 10−12 cm2 s−1, respectively and that by CV was in the order of 10−14 cm2 s−1.