Nanostructured materials for energy storage

Atomic-scale measurement of ultraslow Li motions in glassyLiAlSi2O6by two-timeL6Wilkening1, Kuhn2, Heitjans3 2008Phys. Rev. B594500View full textAdd to dashboardCite

“…Problem ͑ii͒, however, is still not solved for 7 Li as it requires a phase cycling which is experimentally very difficult to realize for a spin-3/2 nucleus. 39 Fortunately, in the case of 6 Li, multitime SAE NMR experiments are possible which are in principle identical to those realized earlier for the 2 H nucleus which has also a spin quantum number of I =1. [43][44][45] It is worth mentioning that 2 H SAE NMR has developed into one of the most powerful NMR methods to study rotational as well as translational deuteron dynamics.…”

“…In the course of developing powerful secondary Li batteries [1][2][3][4][5][6][7][8] being promising for future energy storage, disordered ion conductors, i.e., highly defective crystalline ͑e.g., nanocrystalline͒ or amorphous materials, will increasingly be considered as solid electrolytes or electrodes. This is due to the often found observation that structurally disordered Li conductors exhibit exceptionally fast ionic diffusivity as compared to their low-defective crystalline counterparts.…”

“…Advantageous over already well-established Li NMR methods [15][16][17][18][19] is the use of 7 Li stimulated echo, or more precisely, spin-alignment echo ͑SAE͒ NMR which has so far been applied mainly to crystalline Li conductors. 17,[20][21][22][23][24][25][26][27][28][29][30][31][32] Similar to modern twodimensional 6 Li and 7 Li exchange NMR spectroscopy, 33-38 7 Li SAE NMR is sensitive to extremely slow cation exchange processes and gives access to diffusion parameters from a microscopic point of view. Thus, it is possible to record single-particle motional correlation functions, 39 from which the atomic jump rate can be directly obtained, i.e., without the help of a diffusion model.…”

“…Thus, it is possible to record single-particle motional correlation functions, 39 from which the atomic jump rate can be directly obtained, i.e., without the help of a diffusion model. [21][22][23][24][25][26][27] In some cases the use of 6 Li ͑spin quantum number I =1͒ is advantageous over 7 Li ͑I =3/ 2͒ SAE NMR. In particular, this is true when ͑i͒ strong 7 Li homonuclear dipole-dipole interactions 30 largely influence the generation of pure spinalignment order necessary to record a single-particle twotime correlation function or ͑ii͒ if three-or four-time phase correlation functions have to be measured ͑see, e.g., Refs.…”

“…The latter would provide, e.g., information about possible dynamical heterogeneities. Problem ͑i͒ can be overcome in 7 Li NMR by using 6 Li enriched samples in order to separate the 7 Li spins spatially. The natural abundance of the latter is about 92.5%.…”