Structural and electrochemical properties of the binary silicides Eu5Si3 and EuSi

The crystal structures of Eu5Si3 and EuSi were studied in detail by X-ray single-crystal diffraction. The single crystals were selected from arc-melted and annealed samples. X-ray diffraction was performed at room temperature on an Oxford Diffraction X'calibur Atlas four-circle diffractometer (MoK alpha radiation). Eu5Si3 adopts the tetragonal Cr5B3-type: space group I4/mcm (# 140), Pearson code tI32, Z = 4, alpha = 7.9339(6), c = 15.308(2) angstrom. The compounds with equiatomic composition EuSi crystallize in the structure type TM space group Cmcm (# 63), Pearson code oS8, Z = 4, alpha = 4.6955(6), b = 11.1528(13), c = 3.9845(4) angstrom. The silicides Eu5Si3 and Li2Si form during electrochemical lithiation (charge process) of EuSi. The electrochemical process 5EuSi + 4Li(+) + 4e(-) <-> Eu5Si3 + 2Li(2)Si is reversible, and the discharge specific capacity at 1C rate reached 140 mAhg(-1) and the Coulombic efficiency is 93%.