(Sn0.5Co0.5)1-yCy Alloy Negative Electrode Materials Prepared by Mechanical Attriting

Samples of (Sn0.5Co0.5)(1-y)C-y for 0 <= y <= 0.8 were prepared in increments of y = 0.1 using a vertical-axis attritor. The effect of the carbon content on the structure and performance of the Sn-Co-C nanocomposites was examined by X-ray diffraction (XRD), Sn-119 Mossbauer effect spectroscopy, and electrochemical methods. Thermal stability aspects of these nanocomposites were inferred from differential scanning calorimetry (DSC) and surface area measurements. XRD experiments show diffraction patterns characteristic of nanostructured materials, except for the sample without carbon, which shows broad Bragg peaks of Co3Sn2. Mossbauer effect spectroscopy shows that the samples are best described as Sn-Co grains surrounded by a carbon matrix. DSC of the samples in air showed crystallization of CoSn for samples with low carbon content and combustion of carbon for samples with high amounts of carbon. The specific surface area of the samples was less than 1 m(2)/g for samples with y <= 0.6. Excellent charge-discharge capacity retention was observed for samples with y >= 0.3. Samples with acceptable electrochemical performance and low reactivity with air at elevated temperature were found in the range 0.3 <= y <= 0.6. (C) 2009 The Electrochemical Society.