The electrochemical reaction of zinc oxide thin films with lithium

The electrochemical and spectroelectrochemical properties of ZnO thin films prepared by reactive pulsed laser deposition in oxygen ambient have been investigated. The as-deposited and lithiated ZnO thin films were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy techniques. The discharge and charge measurement indicates that the reversible capacities of the as-deposited ZnO thin-film electrodes are more than one Li per Zn atom with an initial capacity of less than 2.75 Li per Zn atom, and more than 0.75 Li per Zn atom could not be explained by the alloying process of ZnO reaction with Li. The evolution of the in situ absorbance spectra exhibits a marked boundary of lithiating 2Li per Zn atom and provides a hint about two different lithiation reactions occurring during charging of the ZnO/Li cell. A new reaction mechanism of lithium with ZnO involving both the classical alloying process and the oxidation/reduction of nanosized metal is proposed. (C) 2003 The Electrochemical Society.