Determination of Li-ion diffusion coefficient in amorphous Zn and ZnO thin films prepared by radio frequency magnetron sputtering

Amorphous Zn and ZnO thin films have been prepared by radio frequency magnetron sputtering on Cu substrates and have been characterized by X-ray diffraction, scanning electron microscope, and Raman spectroscopy. The electrochemical performance of the thin films has been studied by galvanostatic cycling and cyclic voltammetry. The voltage dependence of Li-ion chemical diffusion coefficients, D˜Li, of the films has been determined by galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy (EIS). It is found that the amorphous Zn and ZnO films exhibit almost the same D˜Li values ranging from 10− 14 to 10−12 cm2 s− 1 and similar Li-ion transport characteristics determined both by GITT and by EIS methods.