In Situ AFM Measurements of the Expansion of Nanostructured Sn-Co-C Films Reacting with Lithium

The volume changes vs lithium content of nanostructured Sn(1-x-y)Co(x)C(y) thin films with different compositions have been measured using in situ atomic force microscopy (AFM) experiments. For the films studied, the Co content, x, varied 0.18 < x < 0.5 and the carbon content, y, varied 0 < y < 0.79. In all cases the volume varied linearly with lithium content, and the maximum volume expansion ranged from 142 to 204%, depending on the initial composition, for compositions with y < 0.5. The experimental values have been compared with theoretical estimates calculated based on 8.9 +/- 0.5% cm(3)/mol for the alloyed Li atoms as proposed by Obrovac [J. Electrochem. Soc., 154. A849 (2007)]. The agreeement is excellent except for the sample that has y = 0.79, or 79% carbon. (C) 2009 The Electrochemical Society.