Tin-containing nanometric and amorphous intermetallics and alloys are envisaged as negative electrodes for high-capacity lithium ion batteries. Nanocrystalline FeSn2 has been prepared by reduction of Sn2+ and Fe3+ in tetraethylene glycol at 185°C. Microcrystalline FeSn2 has been prepared at 490°C. The properties of nano-FeSn2 and micro-FeSn2 have been observed to be very different. The small particles size hinders the long-range magnetism and consequently the Mössbauer spectra are modified. The nanocrystalline particles of FeSn2 show exothermal effects in the DTA experiment that are not observed in the micrometric particles. Nanocrystalline FeSn2 exhibits a much better electrochemical behavior and electrode stability than microcrystalline FeSn2.