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

Copper selenide, , CuSe, and , 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 ( , CuSe, and ) 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 cell has the best cycling performance when compared to the other two possible cells, and . The conversion reaction mechanism between (CuSe and ) and are proposed for and cell, while the 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.