Nanostructured Ag-Fe-Sn/carbon nanotubes composites as anode materials for advanced lithium-ion batteries

Nanostructured Ag-Fe-Sn/C composites were synthesized by mechanical milling Ag-Fe-Sn alloys with carbon nanotubes (CNTs). The milled composites were characterized by X-ray diffraction, high-resolution transmission electron microscopy, energy dispersive X-ray spectrometry, and selected area electron diffraction techniques. These analyses revealed that, except for residual CNTs segments protruding from the edges of the composite particles, most CNTs were converted to an amorphous structure that formed a shell around alloy particles during mechanical processing. The electrode behaviors of the synthesized materials were examined and compared with those of their unmilled counterparts as well as the original alloys. It was demonstrated that the formed amorphous carbon shell around the alloy particles significantly improved the cycling performance of the composite electrodes, though the initial irreversible capacity loss was increased. For instance, the milled Ag36.4Fe15.6Sn48/CNTs electrode provided a discharge capacity of similar to 530 mAh/g in the second cycle, maintaining a rechargeable capacity of similar to 420 mAh/g after 300 cycles. (c) 2005 The Electrochemical Society. All rights reserved.