Optimizing the composition of the Cu/Si thin film anodes produced via magnetron sputtering

The reversible cyclability of Si based composite anodes is greatly improved by optimizing the atomic ratio of Cu/Si in the films fabricated via magnetron sputtering. The galvanostatic test results show that the thin film anode made of 20%at. Cu delivers 1950 mAhg^-1 as the initial discharge capacity with 80% coulombic efficiency. Then, after the 50^th cycles 80% of the initial discharge capacity is retained, with 99.5 % coulombic efficiency. This remarkable performance can be explained by small crystalline sizes, amorphous structures of the thin film and its enhanced physical and mechanical properties due to the 20 %at. Cu content. High specific capacities achieved in this study prove that magnetron sputtering deposition might be a good alternative production technique to fabricate high performance anode materials. Furthermore, this one step, environmentally friendly process enables one to control the film composition, structure as well as adhesion which minimizes delamination and pulverization.