Influences of Composition on the Electrochemical Performance in Immiscible Sn-Al Thin Films as Anodes for Lithium Ion Batteries

Immiscible Sn-Al alloy films with various Sn contents were prepared by electron beam deposition to construct the matching of composition and electrochemical performance as anodes in lithium ion batteries. It was found that the Sn-rich film electrodes deliver relatively lower discharge capacities and present poor cycleability, whereas the Al-x wt % Sn (40 <= x <= 60) film electrodes show a good balance among cycling ability, fast Li+ diffusion, and acceptable capacity of about 600 mA h g(-1). This is because they have unique microstructure features that were revealed by XRD, SEM, and TEM analysis. There are two types of Sn particles in the Al-40 wt % Sn alloy film, which are the faceted big Sn particles with a (100) [001] preferential orientation and the Sn nanocrystals homogenously dispered in the Al matrix. The influences of composition of electrodes on their cycle performance were discussed from the viewpoint of volume change and Li+ diffusion kinetics in the film electrodes.