Effect of annealing on nanostructured Sn30Co30C40 prepared by mechanical attrition

Sn30Co30C40 prepared by mechanical attriting is nanostructured with grains of amorphous CoSn dispersed in a disordered carbon matrix. The effects of annealing on the structure of the material were examined using X-ray diffraction (XRD), differential scanning calorimetry (DSC) and Mössbauer effect spectroscopy. XRD experiments show that the X-ray amorphous diffraction pattern is basically unchanged up to 300 °C and that crystallization of the amorphous CoSn grains occurs between 350 and 400 °C. DSC experiments show a sharp exothermic feature near 360 °C associated with this crystallization as well as a broad exothermic signal between 100 and 360 °C thought to be caused by changes in short-range order in the amorphous CoSn grains, prior to crystallization. Mössbauer effect spectroscopy shows evidence for the changes in short-range order (SRO) below the crystallization temperature. The Mössbauer effect spectrum above the crystallization temperature changes with temperature as the Co and Sn site occupations approach the expected values in crystalline Co–Sn, which are reached near 600 °C. A study of the impact of these structural changes on the performance of nanostructured Sn30Co30C40 negative electrodes for Li-ion batteries is underway.