Lithium Insertion in Nanostructured Si1-xTixAlloys

Nanostructured Si1-xTix alloys (0 ≤ x ≤ 0.3) prepared by ball milling were studied as negative electrode materials in Li cells. The alloys comprised a nanocrystalline and amorphous Si phase and a nanocrystalline C49 TiSi2 phase. When x ≥ 0.15 the nanocrystalline Si phase was completely eliminated and such alloys consisted only of amorphous Si and the C49 TiSi2 phase. The alloys with x ≥ 0.15 also completely suppressed the formation of Li15Si4 during cycling, resulting in good capacity retention, and, unlike other Si transition metal alloys, without introducing noticeable cell polarization. The observed capacity of the Si1-xTix alloys suggested that the TiSi2 is an inactive phase toward Li. The Si0.85Ti0.15 composition had a high capacity of 1710 Ah/L with 96% capacity retention after 50 cycles, making it attractive for use in Li-ion batteries.