The development of safe and long-lasting all-solid-state lithium-ion batteries needs electrolytes with exceptionally good transport properties. Here, we report on the combination of several solid-state nuclear magnetic resonance (NMR) techniques which have been used to precisely probe short-range as well as long-range Li + dynamics in Li 6 PS 5 Br from an atomic-scale point of view. NMR data clearly reveal an extraordinary high Li diffusivity. This manifests in so-called diffusion-induced spin−lattice relaxation NMR rate peaks showing up at temperatures as low as 260 K. From a quantitative point of view, at ambient temperature the Li jump rate is of the order of 10 9 s −1 which corresponds to a Li + conductivity in order of 10 −3 to 10 −2 S/cm, thus, indicating "liquid-like" Li + diffusion behavior in Li 6 PS 5 Br.

Lithium tantalum oxide, LiTaO 3 , with an average particle size in the µm range is known as a very poor Li ion conductor. It is shown here that its Li conductivity can be drastically increased by ball milling. The so-obtained nanostructured powder with an average particle size of about 20 nm shows a dc conductivity, σ dc , of about 3 × 10 -6 S cm -1 at T ) 450 K (σ dc T ) 1.4 × 10 -3 S cm -1 K) which is about 5 orders of magnitude larger than that of the corresponding microcrystalline powder at the same temperature. The activation energy E A is reduced by about one-third, i.e., it decreased from E A ) 0.90(1) eV to about E A ) 0.63(1) eV. The effect of different milling times on the ionic conductivity is studied. Furthermore, the thermal stability of the nanocrystalline materials against grain growth has been examined by in situ impedance spectroscopy. Interestingly, the Li conductivity of a sample milled for 16 h does not change much even when the material is exposed to about 700 K for several hours. Moreover, the Li self-diffusion in the nanostructured as well as the coarse grained materials has been investigated by various solid-state 7 Li NMR techniques.

Conductivity spectroscopy and 7Li spin-locking NMR relaxometry reveal enhanced ion dynamics in nanocrystalline Li2O2 prepared by high-energy ball milling.

All-solid-state batteries with ceramic electrolytes and lithium metal anodes represent an attractive alternative to conventional ion battery systems. Conventional batteries still rely on flammable liquids as electronic insulators. Despite the great efforts reported over the last years, the optimum solid electrolyte has, however, not been found yet. One of the most important properties which decides whether a ceramic is useful to work as electrolyte is ionic transport. The various time-domain nuclear magnetic resonance (NMR) techniques might help characterize and select the most suitable candidates. Together with conductivity measurements it is possible to analyze ion dynamics on different length-scales, i.e., to differentiate between local, within-site hopping processes from long-range ion transport. The latter needs to be sufficiently fast in the ceramic, in the best case competing with that of liquid electrolytes. In addition to conductivity spectroscopy, NMR can help understand the relationship between local structure and dynamic parameters. Besides information on activation energies and jump rates the data also contain suggestions about the relevant elementary steps of ion hopping and, thus, Support by the Deutsche Forschungsgemeinschaft (DFG) is highly appreciated (FOR 1277 diffusion pathways through the crystal lattice. Recent progress in characterizing ion dynamics in ceramic electrolytes by NMR relaxometry will be briefly reviewed. Focus is put on presently discussed solid electrolytes such as garnets, phosphates and sulfides, which have so far been studied in our lab.