Effect of annealing on Sn(30)Co(30)C(40) prepared by mechanical attriting

Samples of Sn(30)Co(30)C(40) prepared by vertical-axis attriting were annealed at different temperatures up to 500 degrees C. The effects of annealing Sn(30)Co(30)C(40) were studied by X-ray diffraction (XRD) and by electrochemical testing. The XRD pattern of the as-milled sample shows an amorphous-like diffraction pattern. Crystallization of the Sn(30)Co(30)C(40) occurs as evidenced by the appearance of Bragg peaks of crystalline CoSn in the diffraction pattern of the sample annealed at 300 degrees C. Samples annealed above 350 degrees C show only Bragg peaks of crystalline CoSn and no amorphous or nanostructured components. Electrochemical results show a significant decrease in first cycle reversible capacity from room temperature (525 mA h/g) to the sample annealed at 500 degrees C (125 mA h/g). The decrease in capacity can be related to the poor electrochemical performance of crystalline CoSn and to the increase in size of the CoSn grains in the carbon matrix. (C) 2008 The Electrochemical Society.