Multinuclear Solid-State NMR Study of Local Structure and Dynamics in Li0.7Nb3S4

The present work focuses on channel-structured Li0.7Nb3S4, where, among others, the question of the dimensionality of the diffusion pathway arises

NMR and LDA evidence for spiral magnetic order in the chain cuprate LiCu2O2

We report on {6,7}Li nuclear magnetic resonance measurements of the spin-chain compound LiCu2O2 in the paramagnetic and magnetically ordered states. Below T about 24 K the NMR lineshape presents a clear signature of incommensurate (IC) static modulation of the local magnetic field consistent with an IC spiral modulation of the magnetic moments. {7}Li NMR reveals strong phason-like dynamical fluctuations extending well below 24 K. We hypothesize that a series of phase transitions at 24.2, 22.5, and 9 K reflects a "Devil's staircase" type behavior generic for IC systems. LDA based calculations of exchange integrals reveal a large in-chain frustration leading to a magnetical spiral.Comment: 4 pages, 4 figure

Energetically preferred Li+ ion jump processes in crystalline solids: Site-specific hopping in β-Li3VF6 as revealed by high-resolution 6Li 2D EXSY NMR

The visualization of atomic or ionic jump processes on the Ångström length scale is important to identify the preferred diffusion pathways in solid electrolytes for energy storage devices. Two-dimensional high-resolution 6Li nuclear magnetic resonance (NMR) spectroscopy is highly suited to yield unprecedented site-specific insights into local Li+ exchange processes within a single measurement. Here, the beta-modification of Li3VF6 is used as a model system for such an investigation as it provides a range of important Li+ geometric environments in one and the same crystal structure useful to elucidate qualitatively a ranking of energetic preferences of the Li+ exchange processes. In Li3VF6 the Li+ ions are subject to diffusive exchange processes among five crystallographically and magnetically inequivalent Li sites: LiFn (n = 6, 4). By using a sample with a natural concentration of the 6Li isotope, we suppressed unwanted spin-diffusion processes and visualized the various exchange processes on the ms time scale. We were able to verify the following ranking experimentally: Li+ ion jumps between face-shared polyhedra are preferred, followed by Li+ exchange between edge-shared configurations for which interstitial sites are needed to jump from site to site. Surprisingly, Li+ exchange between corner-shared polyhedra and Li+ hopping involving almost isolated LiF4 polyhedra do contribute to overall Li+ self-diffusion as well. In this sense, the current study experimentally verifies current predictions by theory but also extends our understanding of ion dynamics between corner-shared Li-bearing polyhedra

NMR and Impedance Spectroscopy Studies on Lithium Ion Diffusion in Microcrystalline γ-LiAlO2

In this work nuclear magnetic resonance (NMR) and impedance spectroscopy (IS) studies on Li ion dynamics in microcrystalline γ-LiAlO2 are presented. The sample was prepared by solid state synthesis between Li2CO3 and Al2O3 in air, followed by a quenching procedure. The presence of phase-pure γ-LiAlO2 was confirmed by X-ray powder diffraction including Rietveld refinement. Further structural characterization was done with 6Li, 7Li and 27Al NMR. Several NMR techniques such as spin-lattice relaxation measurements, motional narrowing experiments, as well as spin-alignment echo were employed for the investigation of Li ion diffusion. The measurements were carried out at high temperatures (up to 970 K) in order to access the regime of Li ion motion being very slow. The dc conductivities measured by IS in the temperature range from 680 K to 870 K were converted to diffusion coefficients being compatible with those obtained by NMR. © 2015 Walter de Gruyter

Structure Determination of the Crystalline LiPON Model Structure Li5+xP2O6-xN1+x with x approximate to 0.9

Non-crystalline lithium oxonitridophosphate (LiPON) is used as solid electrolyte in all-solid-state batteries. Crystalline lithium oxonitridophosphates are important model structures to retrieve analytical information that can be used to understand amorphous phases better. The new crystalline lithium oxonitridophosphate Li5+xP2O6-xN1+x was synthesized as an off-white powder by ampoule synthesis at 750-800 degrees C under Ar atmosphere. It crystallizes in the monoclinic space group P2(1)/c with a=15.13087(11) angstrom, b=9.70682(9) angstrom, c=8.88681(7) angstrom, and beta=106.8653(8)degrees. Two P(O,N)(4) tetrahedra connected by an N atom form the structural motif [P2O6-xN1+x]((5+x)-). The structure was elucidated from X-ray diffraction data and the model corroborated by NMR and infrared spectroscopy, and elemental analyses. Measurements of ionic conductivity show a total ionic conductivity of 6.8x10(-7) S cm(-1) at 75 degrees C with an activation energy of 0.52 +/- 0.01 eV

Synthesis of ternary transition metal fluorides Li 3MF 6via a sol-gel route as candidates for cathode materials in lithium-ion batteries

A sol-gel route for ternary lithium fluorides of transition metals (M) is presented allowing the synthesis of Li 3MF 6-type and Li 2MF 5-type compounds. It is based on a fluorolytic process using transition metal acetylacetonates as precursors. The domain size of the obtained powders can be controlled by modifying the conditions of synthesis. 6Li and 7Li magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy is used to study local environments of the Li ions in orthorhombic and monoclinic Li 3VF 6 as well as Li 2MnF 5. The number of magnetically inequivalent Li sites found by MAS NMR is in agreement with the respective crystal structure of the compounds studied. Quantum chemical calculations show that all materials have high de-lithiation energies making them suitable candidates to be used as high-voltage battery cathode materials. © 2012 The Royal Society of Chemistry