Lithium-Ion Transport in Nanocrystalline Spinel-Type Li[InxLiy]Br4 as Seen by Conductivity Spectroscopy and NMR

Abstract

Currently, a variety of solid Li + conductors are being discussed that could potentially serve as electrolytes in all-solid-state Li-ion batteries and batteries using metallic Li as the anode. Besides oxides, sulfides and thioposphates, and also halogenides, such as Li 3 YBr 6 , belong to the group of such promising materials. Here, we report on the mechanosynthesis of ternary, nanocrystalline (defect-rich) Li[In x Li y ]Br 4 , which crystallizes with a spinel structure. We took advantage of a soft mechanochemical synthesis route that overcomes the limitations of classical solid-state routes, which usually require high temperatures to prepare the product. X-ray powder diffraction, combined with Rietveld analysis, was used to collect initial information about the crystal structure; it turned out that the lithium indium bromide prepared adopts cubic symmetry (Fd3m). The overall and electronic conductivity were examined via broadband conductivity spectroscopy and electrical polarization measurements. While electric modulus spectroscopy yielded information on long-range ion transport, 7 Li nuclear magnetic resonance (NMR) spin-lattice relaxation measurements revealed rapid, localized ionic hopping processes in the ternary bromide. Finally, we studied the influence of thermal treatment on overall conductivity, as the indium bromide might find applications in cells that are operated at high temperatures (330 K and above).

Toward Understanding of the Li-Ion Migration Pathways in the Lithium Aluminum Sulfides Li3AlS3 and Li4.3AlS3.3Cl0.7 via 6,7Li Solid-State Nuclear Magnetic Resonance Spectroscopy

“…7 Li VT NMR spectra can also provide qualitative insights into ion mobility in solids by identifying the sites contributing to long-range ion mobility and the pathways involved. For instance, a number of previous works − have shown that static VT NMR spectra can support the presence of both mobile and immobile ions on the NMR timescale, which is evidenced by the superposition of resonances with different linewidths from ions moving at different rates. VT diffusion-induced 7 Li NMR SLR rate constants in both the laboratory ( T 1 –1 ) and rotating ( T 1ρ –1 ) frames allow access to quantitative information on the Li diffusion process.…”