Co-Sn Alloys as Negative Electrode Materials for Rechargeable Lithium Batteries

We have prepared three kinds of Co - Sn intermetallic compounds, i.e., Co 3 Sn 2 , CoSn , and CoSn 2 , 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 CoSn 2 results in the formation of Li-rich tin phase ( Li 4.4 Sn ) , whereas the crystalline Co 3 Sn 2 and CoSn alloys only partly form Li x Sn . All three alloys in the low-crystalline obtained by further mechanical milling show improved capacity. Co 3 Sn 2 shows the best cycling performance among the three alloys, but delivers small capacity. The cycling ability of CoSn 2 was also improved by partly introducing Co and C into the alloy.