From Micro to Macro: Access to Long‐Range Li⁺ Diffusion Parameters in Solids via Microscopic ^6, 7Li Spin‐Alignment Echo NMR Spectroscopy

Abstract

The development of highly conductive solids is a rapidly growing research area in materials science. In particular, the study of Li-ion conductors is driven by the ambitious effort to design powerful lithium-ion batteries. A deeper understanding of Li dynamics in solids requires the availability of a large set of complementary techniques to probe Li self-diffusion on different length and time-scales. We report on (7)Li as well as (6)Li spin-alignment echo (SAE) nuclear magnetic resonance (NMR) spectroscopy, which is capable of probing long-range diffusion parameters from a microscopic, that is, atomic-scale, point of view. So far, variable-temperature SAE NMR spectroscopy has been applied to a number of polycrystalline and glassy Li-ion conductors. The materials investigated serve as model systems to unravel the interesting features of the technique in determining reliable Li jump rates and hopping activation energies. In particular, the latter are compared with those probed by macroscopic techniques such as dc-conductivity measurements that are sensitive to long-range translational motions.

In-Channel and In-Plane Li Ion Diffusions in the Superionic Conductor Li10GeP2S12 Probed by Solid-State NMR

“…c is a stretched exponential factor. 18 By measurement, but the low-temperature activation energies derived from these two measurements coincide. This implies that SAE and line width methods probe the same Li ionic motion but in different time scales, which will be discussed later.…”

Ion dynamics in solid electrolytes for lithium batteries

“…In the case of fast ion conductors these regions often block long-range ion transport is not only restricted to measure short-range motions but is also able to get access to long-range ion transport parameters [18]. This simply depends on the temperature window and on the effective resonance frequency used to monitor any changes in magnetization [66,70,96].…”

“…To study ion dynamics in promising ceramics on the angstrom length scale, that is, from an atomic scale point of view, nuclear magnetic resonance (NMR) can be applied [18,66,67]. NMR plays on the various interactions of the Li spins with external and internal magnetic fields.…”

Extremely slow Li ion dynamics in monoclinic Li2TiO3—probing macroscopic jump diffusion via7Li NMR stimulated echoes

“…[29][30][31][32][33] As we have pointed out quite recently, when applied to Li ion conductors, SAE NMR is sensitive to slow, long-range Li diffusion processes although the corresponding jump rates are probed from an atomic-scale point of view. 8,28 Hence, results extracted from variable-temperature stimulated echoes are predisposed to be compared with dc-conductivity values reflecting the charge carrier transport through successful ion jump processes occurring on approximately the millisecond time scale.…”