Fabrication and Electrochemical Characterization of Copper Selenide Thin Films by Pulsed Laser Deposition

Abstract

Copper selenide, Cu2 Se, CuSe, and Cu Se2, thin films have been successfully fabricated using pulsed laser ablation of mixed targets of Cu and Se. The substrate temperature was a key factor in preparing high-quality thin films of the copper selenides, with different crystalline structures and stoichiometries. Although these three kinds of compounds (Cu2 Se, CuSe, and Cu Se2) all form thin films with the same anion and cation in their chemical formula, their electrochemical properties clearly differ from each other, evidently associated with their various compositions and structures. The galvanostatic cycling measurement indicates that a Cu2 SeLi cell has the best cycling performance when compared to the other two possible cells, Cu Se2 Li and CuSeLi. The conversion reaction mechanism between Cu2+ (CuSe and Cu Se2) and Cu+ (Cu2 Se) are proposed for Cu Se2 Li and CuSeLi cell, while the Cu2 SeLi cell may undergo a "displacement" reaction mechanism according to X-ray diffraction, transmission electron microscopy, and selected area electron diffraction data. These complex and unique mechanisms make copper selenides interesting materials for rechargeable lithium batteries.The Electrochemical Society © 2006 The Electrochemical Society.