Synthesis, structure, and ionic conductivity of Na5Li3Ti2S8

摘要

The compound Na(5)Li(3)Ti(2)Sg has been synthesized by the reaction of Ti with a Na/Li/S flux at 723 K. Na5Li3Ti2S8 crystallizes in a new structure type with four formula units in space group C2/c of the monoclinic system. The structure contains three crystallographically independent Na+ cations and two crystallographically independent Li+ cations. Na5Li3Ti2S8 possesses a channel structure that features two-dimensional (2)(infinity)[LiTiS43-] layers built from Li(1)S-4 and TiS4 tetrahedra. The layers, which are stacked along c, comprise eight-membered rings and sixteen-membered rings. Na(3)(+) cations are located between the eight-membered rings and Na(1)(+), Na(2)(+.), and Li(2)(+) cations are located between the sixteen-membered rings. These cations are each octahedrally coordinated by Six S2- anions. The ionic conductivity sigma(T) of Na5Li3Ti2S8 ranges from 8.8 x 10(-6) S/cm at 303 K to 3.8 x 10(-4) S/cm at 483 K. The activation energy E-a is 0.40 eV. (C) 2008 Elsevier Inc. All rights reserved.