Co-Sn alloys as negative electrode materials for rechargeable lithium batteries

We have prepared three kinds of Co-Sn intermetallic compounds, i. e., Co3Sn2, CoSn, and CoSn2, by mechanical alloying followed by heat-treatment. The results of ex situ X-ray diffraction analysis and charge/discharge tests indicate that the electrochemical reaction of lithium with crystalline intermetallic CoSn2 results in the formation of Li-rich tin phase (Li4.4Sn), whereas the crystalline Co3Sn2 and CoSn alloys only partly form LixSn. All three alloys in the low-crystalline obtained by further mechanical milling show improved capacity. Co3Sn2 shows the best cycling performance among the three alloys, but delivers small capacity. The cycling ability of CoSn2 was also improved by partly introducing Co and C into the alloy. (c) 2006 The Electrochemical Society.