Sputtered Ge/Si Nanocomposite Films as High Performance Anode Materials for Lithium-Ion Battery

Abstract

In this paper, we report a kind of laminated Ge/Si thin film used for stabilizing the electrochemist properties of lithium ion batteries (LIBs) prepared by magnetron sputtering technique. Due to the deposition of extra-thin Ge film on Si surface, the capabilities of discharge power and rate performance are improved obviously in the lithium insertion and extraction processes. It indicates that the optimal thickness of Si and Ge film in LIBs are 75 and 27 nm, respectively. The Ge/Si electrode exhibits excellent performance that the capacity retention of 78% after 500 cycles at a 4 A/g current density in the voltage range of 0.01–2.0 V, and the average lost of capacity is as low as 0.53 mAh/g per cycle. Our results suggest that the buffer effect and lithium ions diffusion coefficient is enhanced approximately three times induced by introducing Ge film are responsible for this achievement. The Li2O and Li4SiO4 are the major irreversible products for whole processes. Our work provides a method for improving the stability of Si-based film electrodes in LIBs. Diagrams of the fading per capacity and SEM images of Si electrode and Ge/Si electrode.