Microstructure and electrochemical performance of thin film anodes for lithium ion batteries in immiscible Al–Sn system

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 Sn particles dispersed homogeneously in the Al active matrix. Their electrochemical characteristics were tested in comparison with the pure Al and Sn 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 0.8 C 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.