Si-Cu alloy nanowires grown by oblique angle deposition as a stable negative electrode for Li-ion batteries

Thin films having nanocolumnar arrays made of various Si-Cu atomic ratios (90-10, 80-20, 70-30 %) are fabricated by an ion-assisted oblique angle co-deposition technique to produce stable negative electrodes for lithium-ion batteries. Cu is added into the electrode because of its ductility and electron conductivity. Cu plays a crucial role in holding the electrode together, minimizing overall capacity loss and enabling faster electron transfer. Plus, Cu is inactive versus Li+; therefore, Si-Cu variation is expected to affect the electrochemical performances of the electrodes. In this work, the effect of Si-Cu atomic ratios on the morphologies and the structures of the electrodes are studied. Plus, the uses of these nanocolumns with different Cu contents are evaluated as anodes by electrochemical tests. The morphological analyses demonstrate that an increase in Si-Cu atomic ratio affects the width of the nanocolumns and the homogeneity of the thin film morphology. The increase in Cu content dramatically improves the capacity retention of Si-Cu anodes, whereas it decreases the initial discharge capacity.