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

Nanocrystalline FeSn 2 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 119 Sn Mössbauer spectroscopy. The electrochemical reaction of nanocrystalline FeSn 2 with Li was examined by electron paramagnetic resonance (EPR) and 57 Fe Mössbauer spectroscopy. Nanocrystalline FeSn 2 delivers reversible capacities of about 600 mAhg −1 vs lithium after 20 cycles. The mechanism of the electrochemical reaction involves the conversion of FeSn 2 into Li x Sn 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.