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The helical array (with 10 atom % Cu) exhibits 3130 mAh g(-1) with 83% columbic efficiency and retains 83% of its initial discharge capacity after 100th cycle. Homogeneously distributed interspaces between the helical arrays accommodate high volumetric changes upon cycling and copper atoms form a conductive network to buffer the mechanical stress generated in the electrode while minimizing electrochemical agglomeration of Si. Also, ion assistance is believed to enhance the density of the helices at the bottom thus increasing the adhesion.

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.

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