Structure and Performance of Tin-Cobalt-Carbon Alloys Prepared by Attriting, Roller Milling and Sputtering

Samples of (Sn50Co50)(1-y)C-100y for 0 <= y <= 0.8 have been prepared in increments of y = 0.1 using a vertical-axis attritor and a horizontal roller mill. The effect of the carbon content on the structure and performance as a negative electrode material of the Sn-Co-C composites was examined by X-ray diffraction (XRD), small angle neutron scattering (SANS) and electrochemical methods. These results were compared to similar alloys prepared by magnetron sputtering. XRD experiments of all of the prepared samples show diffraction patterns characteristic of nanostructured materials except for the samples made without carbon which show broad Bragg peaks of Co3Sn2. The nanostructured samples were best described as Co-Sn grains surrounded by a carbon matrix. SANS results showed that samples prepared by roller milling and by attriting had Co-Sn grains of about 45 angstrom and 75 angstrom, respectively, while those prepared by sputtering were either amorphous or had Co-Sn grains of about 10 angstrom. Excellent charge-discharge capacity retention was observed for samples with y >= 0.3. It is believed that this concentration marks the point at which the Co-Sn grains become isolated in the matrix of carbon. (C) 2014 The Electrochemical Society. All rights reserved.