Abstract
Zn-Al and Sn-Al alloys were used as the anode materials to explore the possible high capacity electrode for lithium batteries. Selective etching, by which the different phases show different etching rate, was utilized to prepare porous Zn and Sn powders to increase their reactive area and thus higher lithium intercalation capacity.It was found that 88at%Sn-12at%Al or 77.5at%Zn-22.5at%Al powders show the most porosity of all studied Sn-Al, Zn-Al alloys, respectively. As manifest from the SEM micrographs, the pores are bigger, around 2□m, and more irregular in digested Sn-Al alloys as compared with those of the Zn-Al alloys that have pores smaller than 0.5□m and sharper.Electrochemically, the digested alloy powders show much improved capacity than those of pure Sn or Zn powder. However, the Sn-Al powders tend to be disintegrated during charging due to very high expansion during Li intercalation. This leads to a problem of high irreversible loss. The Sn-12%Al charged capacity reaches 1077mAh/g and 658mAh/g, the first irreversible capacity being 419mAh/g, while after 10 cycles, it becomes 78mAh/g, 73mAh/g. Zn-Al powders suffer less expansion during Li intercalation. The irreversible loss at the first cycle is less than those of Sn-Al alloys. The Zn-22.5%Al alloy shows charged capacity 736mAh/g and 117mAh/g with the first irreversible capacity 619mAh/g, that becomes 400 mAh/g after 10 cycles.