Si-Cu Thin Film Electrode with Kirkendall Voids Structure for Lithium-Ion Batteries

Si-Cu thin film electrodes supported on Ti were fabricated by magnetron sputtering. The electrodes were annealed at 200, 400, and 600 degrees C and characterized by X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectroscopy, and Raman spectroscopy. The void structure caused by the Kirkendall effect was observed in the electrode after 600 degrees C annealing. Cu3Si was detected after heat-treatment at 600 degrees C. Cycling and rate behavior of the electrodes were enhanced with an increased annealing temperature. However, the initial capacity of the electrodes decreased with an increase in annealing temperature because of the formation of inactive Cu-silicides. The characterization of cycled electrodes indicated that the Kirkendall voids alleviate the volume expansion of Si, and the Cu-silicides formed during the process of annealing act as an inactive matrix, which stabilizes the electrode during. cycling. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.073212jes] All rights reserved.