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)(F²)=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 P6(3)/mmc was confirmed (structure type InPt(2)Gd; a=4.3022(15) Å, c=7.618(3) Å; wR(2)(F²)=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.