Nanocolumnar Structured Porous Cu-Sn Thin Film as Anode Material for Lithium-Ion Batteries

Two nanocolumnar structured porous Cu-Sn films were produced by tuning the duration of the process using an oblique angle deposition (OAD) technique of electron beam coevaporation method. The structural and morphological properties of these porous Cu-Sn films are characterized using thin film X-ray diffraction, scanning electron microcopy (SEM) and atomic force microscopy (AFM). Galvanostatic half-cell electrochemical measurements were conducted in between 5 mV to 2.5 V using a Li counter electrode, demonstrating that the Cu rich Cu6Sn5 thin film having homogenously distributed nanocolumns achieved a good cycleability up to 100 cycles with a high capacity retention, whereas the Cu6Sn5 nanostructured porous thick film with inhomogeneous morphology showed only a very short cycle life (<25 cycles). The difference in the electrochemical performances of the thin and thick nanocolumnar structured porous Cu-Sn films resulting from different evaporation duration was evaluated on the basis of X-ray photoelectron spectroscopy (XPS) analysis on the cycled samples.