Diffusion-induced 7Li NMR relaxation of layer-structured tin disulphide — Li diffusion along the buried interfaces in Li0.17SnS2

• Bulk Li diffusion in layered tin-disulphide was measured via NMR relaxometry.
• Complex Li diffusion behaviour that manifests itself in multiple NMR rate peaks has been revealed.
• The diffusivity found is lower than that of Li in tin disulphide or niobium disulphide.
• We report on the effect of annealing on the Li diffusion behaviour.

7Li NMR relaxation has been used to study lithium-ion diffusion in layer-structured SnS2. Keeping the Li intercalation degree in LixSnS2 below x = 0.49, the Li ions preferentially occupy sites in the van der Waals gap between the SnS2 sheets. In contrast to conventional NMR spin-lattice relaxation (SLR) rate measurements in the laboratory frame of reference, which are sensitive to rather fast Li exchange processes, with the help of spin-locking SLR NMR slower Li motions were extracted from characteristic diffusion-induced rate peaks. The latter contain information on both Li+ activation energies Ea and Li ion jump rates τ− 1 characterizing the elementary steps of Li+ hopping. Our results point to two different diffusion processes (Ea(I) = 0.38 eV; Ea(II) = 0.28 eV), a slower and a faster one, observable directly after chemical Li insertion. Interestingly, the diffusion behaviour irreversibly changes when the sample has been exposed to temperatures as high as 573 K. Diffusion-induced NMR rates and corresponding line shapes are discussed with respect to an inhomogenous distribution of Li ions in SnS2, which seems to be present directly after Li intercalation.

Figure optionsDownload as PowerPoint slide