Well-aligned, ordered, nanocolumnar, Cu-Si thin film as anode material for lithium-ion batteries

Nanocolumnar composite Cu-Si films were produced as anodes using an oblique angle electron beam co-evaporation method. Two evaporation durations were used to yield different film thicknesses: thin (<250 ± 100 nm) and thick (>400 ± 100 nm). The structural and morphological properties of these Cu-Si films were characterized using X-ray diffraction and scanning electron microcopy. Galvanostatic half-cell electrochemical measurements were conducted over a voltage range of 50 mV-2.5 V using Li as a counter electrode and the Cu-Si films as anodes. The results demonstrated that the thin film has homogeneously distributed nanocolumns and yielded good cyclability upto 100 cycles with high capacity retention; by contrast, the thick film has an inhomogeneous porous structure and exhibited poor cyclability. The reason for the better electrochemical performance of the thin film was determined by X-ray photoelectron spectroscopy (XPS) at different states of charge. Moreover, in-situ electrodilatometric analysis during the galvanostatic test of the thin films measured the ongoing volumetric changes upon cycling.