Orientation dependence of Li–ion diffusion kinetics in LiCoO 2 thin films prepared by RF magnetron sputtering

Abstract

LiCoO 2 thin films with different orientations were prepared by radio frequency (RF) magnetron sputtering. The Li–ion chemical diffusion coefficients, D̃ Li, were measured using cyclic voltammetry (CV), galvanostatic intermittent titration technique (GITT), potentiostatic intermittent titration technique (PITT), and electrochemical impedance spectroscopy (EIS). It was found that the LiCoO 2 thin film orientation depends on the thickness of the film. A LiCoO 2 thin film with a thickness of 0.31 μm shows a high (003) orientation and that with 1.35 μm thickness exhibits high (104) orientation. The (104) oriented thin film exhibits a larger D̃ Li value than that of the (003) oriented thin film. The lithium ion conductivity of LiCoO 2 was measured with the help of a Li/lithium ion conducting polymer/Li 1 − δ CoO 2/lithium ion conducting polymer/Li cell. The ionic conductivity obtained was compared with that obtained from the chemical diffusion coefficient of the thin films. The ionic conductivity estimated from the PITT results was a close comparison with that measured by the electron blocking method.