Evaluation of composite helices used as anodes for rechargeable lithium ion batteries

Helices made of varying Cu-Si atomic ratios (10-90, 20-80, 30-70%) are fabricated by an ion-assisted glancing angle codeposition technique. Cu is added into the electrode because of its ductility and electron conductivity. Thus, Cu holds the electrode together, minimizing overall capacity loss and enabling faster electron transfer. Plus, Cu is inactive versus Li⁺; therefore, Cu/Si variation in the films is expected to affect the physical and electrochemical performances of the electrodes. The morhological analyses demonstrate that an increase in Cu/Si atomic ratio affects the width of the helices and the homogeneity in the thin film morphology. The galvanostatic tests show that Sample 1 (with 30%at. Cu) performs 3389 mAh g^-1 with 49% capacity retention where as Samples 2 (with 20%at. Cu) and 3 deliver 1885 and 1680 mAh g^-1 as initally discharge capacities and retain 77% and 53% of their first discharge capacities after 100^th cycle.