The performances and mechanisms of two types of anodes formed by FeSn2 microparticles and nanostructured FeSn2, respectively, were studied by Mössbauer spectroscopy and electrochemical testing. The specific capacity, which is within the range 400–600mAhg−1 even at high C-rate, did not vary with cycle number over 50–60 cycles for the microparticles but progressively decreased for the nanostructured material. In the two cases, the first discharge consists in the irreversible transformation of FeSn2 into Fe/Li7Sn2 nanocomposite. The capacity fade is attributed to the growth and/or coalescence of the particles during cycling.