Influence of catalyst layer thickness on the growth of nickel silicide nanowires and its application for Li-ion batteries

• Correlation of nickel silicide nanowire phase and morphology based on amount of free catalyst.
• Creation of a novel heterogeneous NiSi2 crystalline core Ni doped SiO amorphous shell nanowire.
• Displaying high capacity and high retention performance of heterogeneous nanowire when used as an anode for Li-ion battery.
• Displaying surface passivating characteristics during full charging of a Si based anode.

We report the influence of nickel catalyst layer thickness when growing nickel silicide alloy nanowires below the liquefaction temperature through metal induced growth. Three different catalyst layer thicknesses show three different nanowire growth results that vary significantly the performance when used as an anode in a lithium ion solution. The thicker catalyst layers (70 nm) show pure NiSi nanowires which have an initial capacity of 1300 mAh g−1 that degrades to 550 mAh g−1 within 90 cycles. The thinner (30 nm thick) layer shows a heterogenous nanowire morphology comprising of a multicrystalline NiSi2 inside core and a Ni doped SiO amorphous shell with initial Li-ion capacity of 1727 mAh g−1 capacity that increases to 2468 mAh g−1 after 90 cycles. Samples with no catalyst layers were shown to grow pure silicon nanowires with poor surface coverage having an initial capacity of 1779 mAh g−1 that falls to 242 mAh g−1 after 90 cycles.