The immiscible Al-Sn alloy thin films prepared by electron-beam deposition were first investigated as possible negative electrodes for lithium ion batteries. In the complex structure of the Al-Sn thin films, tiny Sri particles dispersed homogeneously in the At active matrix. Their electrochemical characteristics were tested in comparison with the pure At and Sri films. Cyclic voltammetry results indicated that the Li+-transport rates in these Al-Sn alloy films were significantly enhanced. Charge-discharge tests showed that the Al-Sn alloy film anodes had good cycle performance. The electrode with high Al content (Al-33 wt%Sn) delivered a high initial discharge capacity of 752 mAh g(-1) while the electrode with high Sn content (Al-64 wt%Sn) had better cycleability with a stable specific capacity of about 300 mAh g-1 under 0.8C rate. The good performance of these immiscible Al-Sn alloy film anodes was attributed to their unique microstructure. The mechanism of lithiation and delithiation reaction had been proposed based on cyclic voltammograms and impedance response of the Al-Sn alloy thin film electrodes. Our preliminary results demonstrate that the Al-Sn immiscible alloy is a potential candidate negative material for Li-ion battery. (C) 2008 Elsevier B.V. All rights reserved.