Li9Al4Sn5as a new ordered superstructure of the Li13Sn5type

Abstract

Alloys from the ternary Li–Al–Sn system have been investigated with respect to possible applications as negative electrode materials in Li-ion batteries. This led to the discovery of a new ternary compound, a superstructure of the Li13Sn5binary compound. The ternary stannide, Li9Al4Sn5(nonalithium tetraaluminium pentastannide; trigonal,P\overline{3}m1,hP18), crystallizes as a new structure type, which is an ordered variant of the binary Li13Sn5structure type. One Li and one Sn site have \overline{3}m. symmetry, and all other atoms occupy sites of 3m. symmetry. The polyhedra around all types of atoms are rhombic dodecahedra. The electronic structure was calculated by the tight-binding linear muffin-tin orbital atomic spheres approximation method. The electron concentration is higher around the Sn and Al atoms, which form an [Al4Sn5]m−polyanion.