Electrochemical performance of SiAlSn films prepared by combinatorial sputtering

Amorphous alloys of Si and Sn exhibit large specific and volumetric capacities when cycled electrochemically vs. lithium. To improve the electrochemical performance of these materials, we explore here the effect of Al additions to the alloys. Combinatorial films of Si1-x-yAlxSny were prepared by magnetron sputtering and then analyzed for structure, composition, and electrochemical performance. If the film is amorphous, the voltage-capacity behavior of the Li/Si1-x-yAlxSny cell is smooth and the differential capacity vs. potential shows no sharp peaks, indicating homogeneous insertion of lithium. If the film contains crystalline material, the voltage-capacity relation shows plateaus and peaks are seen in the differential capacity, indicating inhomogeneous insertion of lithium. If the film is amorphous, capacity retention is generally good, while films containing crystalline material have poor capacity retention. A summary of specific capacity and reversible capacity as a function of composition is presented. (C) 2003 The Electrochemical Society.