Lithium-doped spinels could function as solid state electrolytes in batteries in which all components have the spinel structure. In this study we prepared lithium-doped MgAl 2 O 4 and ZnAl 2 O 4 . Advanced solid state 7 Li, 25 Mg, and 27 Al NMR have been used to investigate the structure of these spinels and the structural changes that take place therein upon lithium doping. The spinel structure is well retained, although the amount of tetrahedral aluminum increases with increased lithium content. Using MQMAS experiments, the presence of two tetrahedral sites is discovered in both doped and undoped spinels. It is shown that the spinel structure of MgAl 2 O 4 is heterogeneous, which leads to distributions in chemical shift and quadrupolar parameters. The heterogeneity is also shown in 25 Mg spectra obtained with the quadrupolar Carr−Purcell−Meiboom−Gill (QCPMG) and sideband selective Double Frequency Sweep-QCPMG (ssDFS-QCPMG) pulse sequences. Lithium mobility is measured using static variable temperature 7 Li NMR experiments. A low fraction of mobile lithium was found (3−4%) for magnesium spinels. The lithium doped ZnAl 2 O 4 sample shows practically no mobility. This sample has significantly less disorder and less cation site inversion than the magnesium samples. ■ INTRODUCTIONLithium-ion batteries nowadays dominate the market for portable devices. For their automotive applications there are, however, significant improvements to make, which include improving safety, recyclability, and reducing mass. Solid state batteries show potential in these properties. In solid state batteries the liquid electrolyte has been replaced by a solid electrolyte. Much research has been performed in finding new solid electrolyte materials with high conductivity. The current focus is on lithium-ion materials, ranging from crystalline materials to polymers, amorphous composites, and glasses. 1,2 LiPON is an example of a solid state electrolyte that is being used for commercial applications, 3 but its performance is limited by the low ionic conductivity (ca. 10 −6 S/cm at 300 K).Research on new solid electrolytes is focused on two fields: sulfide-based and oxide-based materials. Sulfide materials such as the Li 2 S−P 2 S 5 glass-ceramics, 4 Li 10 GeP 2 S 12 and its derivatives, 5,6 or Argyrodite-type compounds 7−9 have shown excellent conductivity, up to 10 −2 S/cm at room temperature. While these materials are attractive, their preparation is complicated, as it needs to be carried out in protected atmosphere, and the resulting powders are not stable in contact with certain oxide cathode materials, requiring costly and complex coatings. 10 Oxide-type solid electrolytes have the advantage of being more easily synthesized, but their conductivity is in general lower than that of sulfides. Examples include the LATP or LAGP materials with Nasicon-type structure, 11,12 the A-site deficient perovskites such as Li 3x La (2/3)-x □ (1/3)−2x TiO 3 (LLTO), 13 or the large family of garnet-type materials. 14−16 All these compounds exhibit high con...

MgCl2 is a vital component of Ziegler-Natta catalysts for olefin polymerization. Here we:synthesized anhydrous MgCl2 using different drying protocols and exploited H-1 NMR to quantify the proton content. We report on our study of neat and ball-milled MgCl2 samples by means of Mg-25 and Cl-35 solid-state NMR. DFT calculations of the quadrupole tensor aid in analysis of the spectra. The results show that, due to the morphology of the neat particles, a preferred Orientation is induced which manifests itself in unusual powder line shapes. Ball Milling reduces particle size, which subsequently leads to a small distribution of quadrupole parameters for the bulk. Surface sites, highly relevant for catalysis, are not directly observed, due to their broad lines of low intensity

Ziegler–Natta catalysis is a very important industrial process for the production of polyolefins. However, the catalysts are not well-understood at the molecular level. Yet, atomic-scale structural information is of pivotal importance for rational catalyst development. We applied a solid-state NMR/density functional theory tandem approach to gain detailed insight into the interactions between the catalysts’ support, MgCl2, and organic electron donors. Because of the heterogeneity of the samples, large line widths are observed in the carbon spectra. Despite this, good agreement between experimental and computational values was reached, and this shows that 1,3-diether based donors coordinate at (110) surface sites, while phthalates are less selective and coordinate at both (104) and (110) surface sites.

Ziegler−Natta catalysts are one of the most important industrial catalysts for the production of isotactic polypropylene, yet they are still not properly understood at the molecular level. We explore the potential of 35,37 Cl and 47,49 Ti solid-state NMR to study the formation of catalytically relevant titanium sites. First, a systematic study of titanium chlorides (TiCl 2 , TiCl 3 , and TiCl 4 ) is undertaken to gain insight into the spectral characteristics for different titanium coordinations. For these materials, chlorine spectra can be relatively straightforwardly obtained, despite their strongly broadened quadrupolar line shapes. The sensitivity of titanium NMR to its local environment is exemplified by the TiCl 4 spectrum, for which a small quadrupolar interaction is found despite the nearly symmetric Ti coordination. Upon wet impregnation of MgCl 2 with TiCl 4 , TiCl 4 is immobilized at the surface, retaining its tetrahedral coordination. For a ball-milled binary MgCl 2 /TiCl 2 adduct, a ternary system where donors are added, and a ternary system where Al-alkyl cocatalysts are added, we obtain broad 47,49 Ti spectra after extensive signal averaging, showing that the local environment of Ti is substantially perturbed. The span of the signal is similar for all three samples, suggesting that most of the donor and the cocatalyst do not directly bind to the titanium. Nevertheless, the signal loss from reduction to Ti 3+ is obvious, indicating that a fraction of the titanium sites is activated.

The most commonly used cocatalyst species in Ziegler-Natta catalysts are aluminium alkyls. In this study we aim to find the interaction between aluminium centres of these activators and other components in the ZNC system. Initially we look at binary systems of Al-alkyl/MgCl and ternary systems of Al-alkyl/MgCl/TiCl, followed by donor containing systems. The aluminium alkyls prove to be very reactive species and only in the case of trimethylaluminium the alkyl is strongly present in the sample. This species appears to convert, however, over time. H NMR proves to be an efficient method to detect the presence of the Al-alkyl species. The use of high magnetic field strengths andAl MQMAS NMR alleviates signal overlap and gives insight in the dominant line broadening mechanisms thus providing an in-depth view of the cocatalyst. Various Al species with different coordinations can be identified in the samples. The heterogeneity of the samples turns out to have a larger effect on the Al NMR spectra than the quadrupolar interaction, which argues against the presence of highly distorted sites with mixed coordinations. Nevertheless for the samples indicating the presence of alkyls in theH NMR spectra, we observe an aluminium site at 97 ppm in the Al spectra that might be coordinated to an organic group.