LiBi3S5—A lithium bismuth sulfide with strong cation disorder

Abstract

Terms of Use AbstractAmong chalcogenide semiconductors for thermoelectric applications, alkali-metal bismuth compounds occur in many complex compositions favorable for high performance. Although LiBi 3 S 5 had been announced in 1977, the potential 1D lithium-ion conductor has hitherto eluded selective synthesis and structure determination. In this study, we present a solid-state route to phase-pure LiBi 3 S 5 powder starting from LiBiS 2 and Bi 2 S 3 . Neutron diffractograms and lithium-NMR spectra reveal its crystal structure to be a cation-disordered variety of the

Nanostructured Ceramics: Ionic Transport and Electrochemical Activity

“…From the atomic scale point of view the elementary hopping processes have to be characterized in many cases by 3D diffusion unless diffusion of the ions is preferred along a special direction of the crystal structure. Apart from such anisotropic movements in materials offering 3D diffusion there are layer-structured and channel-structured ion conductors with significantly constraint migration pathways [30,65,[79][80][81][82][83][84]. Lithium transition metal dichalcogenides represent a typical class of materials that offer 2D diffusion in their van-der-Waals gaps [83].…”

Solid-State NMR to Study Translational Li Ion Dynamics in Solids with Low-Dimensional Diffusion Pathways

“…From a structural point of view we can explain this finding because of cation disorder. Our structural analyses [34] has shown that immobile Bi 3+ ions may easily block the Li diffusion pathways, thus hindering ion migration along the channels of the sulfide. In such a case, Li ion diffusion is expected to be largely mediated by defects in the various sub-lattices enabling the ions to diffuse via non-regular lattice sites.…”

“…LiBi 3 S 5 also crystallizes with a channel-like structure and the Li ions residing inside the channels have, thus, access to a spatially rather restricted diffusion pathway (see Figure 11b). We followed a solid-state route to prepare phasepure gray-black LiBi 3 S 5 powder starting from LiBiS 2 and Bi 2 S 3 [34]. Neutron diffractograms and lithium NMR spectra reveal its crystal structure to be a cation-disordered variety of the AgBi 3 S 5 type (synthetic pavonite; monoclinic, C2/m).…”

“…Whereas earlier investigations put emphasis on 2D diffusion in Li x TiS 2 and the quasi 1D diffusion in β-eucryptite (LiAlSiO 4 ), for example see Refs. [7,11,[20][21][22][23][24][25][26][27], the present collection comprises, on the one hand, layer structured materials such as hexagonal LiBH 4 [12,28], Li x NbS 2 [29,30] [33], LiBi 3 S 5 [34] and ramsdellite-type Li 2 Ti 3 O 7 [35][36][37] the ions are expected to move inside the channels, the stacked Si 5 rings in Li 12 Si 7 [38][39][40] guide the ions outside the channels to follow quasi 1D diffusion.…”

Diffusion Pathways and Activation Energies in Crystalline Lithium-Ion Conductors

“…With LiBi 3 S 5 (monoclinic, C2/m), we were able to selectively synthesize and characterize an announced, but hitherto elusive compound [65]. The material had been deemed a potentially fast one-dimensional lithium-ion conductor; to our dismay, NMR studies showed it to be moderate at best.…”