Electron Paramagnetic Resonance, X-ray Diffraction, Mossbauer Spectroscopy, and Electrochemical Studies on Nanocrystalline FeSn2 Obtained by Reduction of Salts in Tetraethylene Glycol

Nanocrystalline FeSn2 was prepared by chemical reduction of Sn-Fe chlorides in tetraethylene glycol using a one-pot method. Structural characterization is carried out by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and Sn-119 Mossbauer spectroscopy. The electrochemical reaction of nanocrystalline FeSn2 with Li was examined by electron paramagnetic resonance (EPR) and Fe-57 Mossbauer spectroscopy. Nanocrystalline FeSn2 delivers reversible capacities of about 600 mAhg(-1) vs lithium after 20 cycles. The mechanism of the electrochemical reaction involves the conversion of FeSn2 into LixSn phases and superparamagnetic iron (or tin-doped iron) nanoparticles. The composition and the dimensions of the superparamagnetic particles depend on the depth of discharge. The electrochemically formed superparamagnetic particles are preserved in the course of the reverse electrochemical reaction.