CuLi 2 Sn and Cu 2 LiSn: Characterization by single crystal XRD and structural discussion towards new anode materials for Li-ion batteries.

The stannides CuLi ₂ Sn (CSD-427095) and Cu ₂ LiSn (CSD-427096) were synthesized by induction melting of the pure elements and annealing at 400 °C. The phases were reinvestigated by X-ray powder and single-crystal X-ray diffractometry. Within both crystal structures the ordered CuSn and Cu ₂ Sn lattices form channels which host Cu and Li atoms at partly mixed occupied positions exhibiting extensive vacancies. For CuLi ₂ Sn, the space group F-43m. was verified (structure type CuHg ₂ Ti; a =6.295(2) Å; wR ₂ ( F ²)=0.0355 for 78 unique reflections). The 4( c ) and 4( d ) positions are occupied by Cu atoms and Cu+Li atoms, respectively. For Cu ₂ LiSn, the space group P 6 ₃ / mmc was confirmed (structure type InPt ₂ Gd; a =4.3022(15) Å, c =7.618(3) Å; wR ₂ ( F ²)=0.060 for 199 unique reflections). The Cu and Li atoms exhibit extensive disorder; they are distributed over the partly occupied positions 2( a ), 2( b ) and 4( e ). Both phases seem to be interesting in terms of application of Cu-Sn alloys as anode materials for Li-ion batteries.