Room-Temperature Solid-State Transformation of Na4 SnS4 ⋠14H2 O into Na4 Sn2 S6 ⋠5H2 O: An Unusual Epitaxial Reaction Including Bond Formation, Mass Transport, and Ionic Conductivity.

A highly unusual solid-state epitaxy-induced phase transformation of Na4 SnS4 ⋅ 14H2 O (I) into Na4 Sn2 S6 ⋅ 5H2 O (II) occurs at room temperature. Ab initio molecular dynamics (AIMD) simulations indicate an internal acid-base reaction to form [SnS3 SH]3- which condensates to [Sn2 S6 ]4- . The reaction involves a complex sequence of O-H bond cleavage, S2- protonation, Sn-S bond formation and diffusion of various species while preserving the crystal morphology. In situ Raman and IR spectroscopy evidence the formation of [Sn2 S6 ]4- . DFT calculations allowed assignment of all bands appearing during the transformation. X-ray diffraction and in situ 1 H NMR demonstrate a transformation within several days and yield a reaction turnover of ≈0.38 %/h. AIMD and experimental ionic conductivity data closely follow a Vogel-Fulcher-Tammann type T dependence with D(Na)=6×10-14  m2 s-1 at T=300 K with values increasing by three orders of magnitude from -20 to +25 °C.

Photo-Cross-Linked Single-Ion Conducting Polymer Electrolyte for Lithium-Metal Batteries.

Polymer electrolytes are considered potential key enablers for lithium-metal batteries due to their compatibility with the lithium-metal negative electrode. Herein, cross-linked self-standing single-ion conducting polymer electrolytes are obtained via a facile UV-initiated radical polymerization using pentaerythritol tetraacrylate as the cross-linker and lithium (3-methacryloyloxypropylsulfonyl)-(trifluoromethylsulfonyl)imide as the ionic functional group. Incorporating propylene carbonate as charge-transport supporting additive allowed for achieving single-ion conductivities of 0.21 mS cm-1 at 20 °C and 0.40 mS cm-1 at 40 °C, while maintaining a suitable electrochemical stability window for 4 V-class positive electrodes (cathodes). As a result, this single-ion polymer electrolyte featured good cycling stability and rate capability in Li||LiFePO4 and Li||LiNi0.6 Mn0.2 Co0.2 O2 cells. These results render this polymer electrolyte as potential alternative to liquid electrolytes for high-energy lithium-metal batteries.

Poly(ionic liquid) Based Composite Electrolytes for Lithium Ion Batteries.

Polymerized ionic liquids (PIL) are an interesting substance class, which is discussed to transfer the outstanding properties and tunability of ionic liquids into a solid material. In this study we extend our previous research on ammonium based PIL and discuss the influence of additives and their usability as polymer electrolyte membranes for lithium ion batteries. The polymer electrolyte is thereby used as replacement for the commercially widespread system of a separator that is soaked with liquid electrolyte. The influence of the material composition on the ionic conductivity (via electrochemical impedance spectroscopy) and the diffusion coefficients (via pulsed-field-gradient nuclear magnetic resonance spectroscopy) were studied and cell tests with adapted membrane materials were performed. High amounts of the additional ionic liquid (IL) MPPyrr-TFSI (1-methyl-1-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide) increased the ionic conductivity of the materials up to 1.3·10-4 S·cm-1 but made the usage of a cross-linker necessary to obtain mechanically stable membranes. The application of liquid electrolyte mixtures with ethylene carbonate (EC) and MPPyrr-TFSI decreased ionic conductivity values down to the 10-9 S·cm-1 range, but increased 7Li diffusion coefficients with increasing amounts of EC up to 1.7·10-10 m2·s-1. Cell tests with two membrane mixtures proofed that it is possible to build electrolyte membranes on basis of the polymerized ionic liquids, but also showed that further research is necessary to ensure stable and efficient cell cycling.

Structure-Property Relationship of Polymerized Ionic Liquids for Solid-State Electrolyte Membranes.

Eight new polymerized ammonium-based ionic liquids were prepared as thin membrane films and evaluated within the scope of their usage in lithium-ion batteries. The focus of this work is to get a better understanding of the influence of structural modifications of the monomers on the polymerized materials. Further, different concentrations of a lithium-ion conducting salt were applied in order to receive an optimized combination of monomer structure and lithium salt concentration. It was found that an increased side chain length of the studied ammonium-based polymerized ionic liquids leads to a reduction in glass transition temperatures and increased ionic conductivity values. As a result of the addition of conducting salt to the PIL membranes, the glass transition temperatures and the ionic conductivity values decreases. Nevertheless, PFG-NMR reveals a higher lithium-ion mobility for a sample with higher conducting salt content.

Garnet to hydrogarnet: effect of post synthesis treatment on cation substituted LLZO solid electrolyte and its effect on Li ion conductivity.

We investigated why commercial Li7La3Zr2O12 (LLZO) with Nb- and Ta substitution shows very low mobility on a local scale, as observed with temperature-dependent NMR techniques, compared to Al and W substituted samples, although impedance spectroscopy on sintered pellets suggests something else: conductivity values do not show a strong dependence on the type of substituting cation. We observed that mechanical treatment of these materials causes a symmetry reduction from garnet to hydrogarnet structure. To understand the impact of this lower symmetric structure in detail and its effect on the Li ion conductivity, neutron powder diffraction and 6Li NMR were utilized. Despite the finding that, in some materials, disorder can be beneficial with respect to ionic conductivity, pulsed-field gradient NMR measurements of the long-range transport indicate a higher Li+ diffusion barrier in the lower symmetric hydrogarnet structure. The symmetry reduction can be reversed back to the higher symmetric garnet structure by annealing at 1100 °C. This unintended phase transition and thus a reduction in conductivity is crucial for the processing of LLZO materials in the fabrication of all-solid state batteries.

Organic Liquid Crystals as Single-Ion Li+ Conductors.

The development of new materials for tomorrow's electrochemical energy storage technologies, based on thoroughly designed molecular architectures is at the forefront of materials research. In this line, we report herein the development of a new class of organic lithium-ion battery electrolytes, thermotropic liquid crystalline single-ion conductors, for which the single-ion charge transport is decoupled from the molecular dynamics (i. e., obeys Arrhenius-type conductivity) just like in inorganic (single-)ion conductors. Focusing on an in-depth understanding of the structure-to-transport interplay and the demonstration of the proof-of-concept, we provide also strategies for their further development, as illustrated by the introduction of additional ionic groups to increase the charge carrier density, which results in a substantially enhanced ionic conductivity especially at lower temperatures.

Li7GeS5Br-An Argyrodite Li-Ion Conductor Prepared by Mechanochemical Synthesis.

In recent years, the search for glassy and ceramic Li+ superionic conductors has received significant attention, mainly due to the renaissance of interest in all-solid-state batteries. Here, we report the mechanochemical synthesis of metastable Li7GeS5Br, which is, to the best of our knowledge, the first compound of the Li2S-GeS2-LiBr system. Applying combined synchrotron X-ray diffraction and neutron powder diffraction, we show Li7GeS5Br to crystallize in the F4̅3m space group and to be isostructural with argyrodite-type Li6PS5Br, but with a distinct difference in the S2-/Br- site disorder (and improved anodic stability). Electrochemical impedance spectroscopy indicates an electrical (ionic) conductivity of 0.63 mS cm-1 at 298 K, with an activation energy for conduction of 0.43 eV. This is supported by temperature-dependent 7Li pulsed-field gradient-nuclear magnetic resonance spectroscopy measurements. Overall, the results demonstrate that novel (metastable) argyrodite-type solid electrolytes can be prepared via mechanochemistry that are not accessible by conventional solid-state synthesis routes.

Correction: Influence of residual water and cation acidity on the ionic transport mechanism in proton-conducting ionic liquids.

Correction for 'Influence of residual water and cation acidity on the ionic transport mechanism in proton-conducting ionic liquids' by Jingjing Lin et al., Phys. Chem. Chem. Phys., 2020, 22, 1145-1153.

Influence of residual water and cation acidity on the ionic transport mechanism in proton-conducting ionic liquids.

Proton-conducting ionic liquids (PILs) are discussed herein as potential new electrolytes for polymer membrane fuel cells, suitable for operation temperatures above 100 °C. During fuel cell operation, the presence of significant amounts of residual water is unavoidable, even at these elevated temperatures. By using electrochemical and NMR methods, the impact of residual water on 2-sulfoethylmethylammonium triflate [2-Sema][TfO], 1-ethylimidazolium triflate [1-EIm][TfO] and diethylmethylammonium triflate [Dema][TfO] is analyzed. The cationic acidity of these PILs varies by over ten orders of magnitude. Appropriate amounts of the PIL and H2O were mixed at various molar ratios to obtain compositions, varying from the neat PIL to H2O-excess conditions. The conductivity of [2-Sema][TfO] exponentially increases depending on the H2O concentration. The results from 1H-NMR spectroscopy and self-diffusion coefficient measurements by 1H field-gradient NMR indicate a fast proton exchange process between [2-Sema]+ and H2O. Conversely, [1-EIm][TfO] and [Dema][TfO] show only very slow or non-significant proton exchange, respectively, with H2O during the time-scale relevant for transport. The proton conduction follows a combination of vehicle and cooperative mechanisms in highly acidic PIL, while a mostly vehicle mechanism in medium and low acidic PIL occurs. Therefore, highly acidic ionic liquids are promising new candidates for polymer electrolyte fuel cells at an elevated temperature.

Li15P4S16Cl3, a Lithium Chlorothiophosphate as a Solid-State Ionic Conductor.

Tremendous efforts have been devoted to the design of solid Li+ electrolytes and the development of all-solid-state batteries. Compared with conventional Li-ion batteries, which use flammable liquid organic electrolytes, all-solid-state batteries show significant advantages in safety. In this work, a novel lithium chlorothiophosphate compound, Li15P4S16Cl3, is discovered. The crystal structure and electrochemical properties are investigated. Li15P4S16Cl3 can be synthesized as a pure phase via a facile solid-state reaction by heating a ball-milled mixture of Li2S, P2S5, and LiCl at 360 °C. The crystal structure of Li15P4S16Cl3 was refined against neutron and synchrotron powder X-ray diffraction data, revealing that it crystallizes in the space group I4̅3d. The Li+ transport in Li15P4S16Cl3 was also investigated by multiple solid-state NMR methods, including variable-temperature NMR line-shape analysis, NMR relaxometry, and pulsed-field-gradient NMR. Li15P4S16Cl3 shows good thermodynamic stability and can be synthesized at relatively low temperature. Although it exhibits a low ionic conductivity at room temperature, it can serve as a new motif crystal structure for the design and development of new solid-state electrolytes.

A Crosslinked Polyethyleneglycol Solid Electrolyte Dissolving Lithium Bis(trifluoromethylsulfonyl)imide for Rechargeable Lithium Batteries.

Replacing liquid electrolytes with solid ones can provide advantages in safety, and all-solid-state batteries with solid electrolytes are proposed to solve the issue of the formation of lithium dendrites. In this study, a crosslinked polymer composite solid electrolyte was presented, which enabled the construction of lithium batteries with outstanding electrochemical behavior over long-term cycling. The crosslinked polymeric host was synthesized through polymerization of the terminal amines of O,O-bis(2-aminopropyl) polypropylene glycol-block-polyethylene glycol-block-polypropylene glycol and terminal epoxy groups of bisphenol A diglycidyl ether at 90 °C and provided an amorphous matrix for Li+ dissolution. This composite solid electrolyte containing Li+ salt and garnet filler exhibited high flexibility, which supported the formation of favorable interfaces with the active materials, and possessed enough mechanical strength to suppress the penetration of lithium dendrites. Ionic conductivities higher than 5.0×10-4  S cm-1 above 45 °C were obtained as well as a wide electrochemical stability window (>4.51 V vs. Li/Li+ ) and a high Li+ diffusion coefficient (≈16.6×10-13  m2 s-1 ). High cycling stability (>500 cycles or 1000 h) was demonstrated.

Hybrid particles derived from alendronate and bioactive glass for treatment of osteoporotic bone defects.

Osteoporosis is the most widespread metabolic bone disease which represents a major public health burden. Consequently, novel biomaterials with a strong capacity to regenerate osteoporotic bone defects are urgently required. In view of the anti-osteoporotic and osteopromotive efficacy of alendronate and 45S5 bioactive glass, respectively, we investigated the feasibility to synthesize novel hybrid particles by exploiting the strong interactions between these two compounds. Herein, we demonstrate the facile preparation of a novel class of hybrid particles of tunable morphology, chemical composition and structure. These hybrid particles (i) release alendronate and various inorganic elements (Ca, Na, Si, and P) in a controlled manner, (ii) exhibit a strong anti-osteoclastic effect in vitro, and (iii) stimulate regeneration of osteoporotic bone in vivo. Consequently, this novel class of hybrid biomaterials opens up new avenues of research on the design of bone substitutes with specific activity to facilitate regeneration of bone defects in osteoporotic patients.

Inducing High Ionic Conductivity in the Lithium Superionic Argyrodites Li6+ xP1- xGe xS5I for All-Solid-State Batteries.

Solid-state batteries with inorganic solid electrolytes are currently being discussed as a more reliable and safer future alternative to the current lithium-ion battery technology. To compete with state-of-the-art lithium-ion batteries, solid electrolytes with higher ionic conductivities are needed, especially if thick electrode configurations are to be used. In the search for optimized ionic conductors, the lithium argyrodites have attracted a lot of interest. Here, we systematically explore the influence of aliovalent substitution in Li6+ xP1- xGe xS5I using a combination of X-ray and neutron diffraction, as well as impedance spectroscopy and nuclear magnetic resonance. With increasing Ge content, an anion site disorder is induced and the activation barrier for ionic motion drops significantly, leading to the fastest lithium argyrodite so far with 5.4 ± 0.8 mS cm-1 in a cold-pressed state and 18.4 ± 2.7 mS cm-1 upon sintering. These high ionic conductivities allow for successful implementation within a thick-electrode solid-state battery that shows negligible capacity fade over 150 cycles. The observed changes in the activation barrier and changing site disorder provide an additional approach toward designing better performing solid electrolytes.

Gelatin Nanoparticles with Enhanced Affinity for Calcium Phosphate.

Gelatin nanoparticles can be tuned with respect to their drug loading efficiency, degradation rate, and release kinetics, which renders these drug carriers highly suitable for a wide variety of biomedical applications. The ease of functionalization has rendered gelatin an interesting candidate material to introduce specific motifs for selective targeting to specific organs, but gelatin nanoparticles have not yet been modified to increase their affinity to mineralized tissue. By means of conjugating bone-targeting alendronate to biocompatible gelatin nanoparticles, a simple method is developed for the preparation of gelatin nanoparticles which exhibit strong affinity to mineralized surfaces. It has been shown that the degree of alendronate functionalization can be tuned by controlling the glutaraldehyde crosslinking density, the molar ratio between alendronate and glutaraldehyde, as well as the pH of the conjugation reaction. Moreover, it has been shown that the affinity of gelatin nanoparticles to calcium phosphate increases considerably upon functionalization with alendronate. In summary, gelatin nanoparticles have been developed, which exhibit great potential for use in bone-specific drug delivery and regenerative medicine.

Slow motions in microcrystalline proteins as observed by MAS-dependent 15N rotating-frame NMR relaxation.

(15)N NMR relaxation rate R1ρ measurements reveal that a substantial fraction of residues in the microcrystalline chicken alpha-spectrin SH3 domain protein undergoes dynamics in the µs-ms timescale range. On the basis of a comparison of 2D site-resolved with 1D integrated (15)N spectral intensities, we demonstrate that the significant fraction of broad signals in the 2D spectrum exhibits the most pronounced slow mobility. We show that (15)N R1ρ's in proton-diluted protein samples are practically free from the coherent spin-spin contribution even at low MAS rates, and thus can be analysed quantitatively. Moderate MAS rates (10-30 kHz) can be more advantageous in comparison with the rates >50-60 kHz when slow dynamics are to be identified and quantified by means of R1ρ experiments.

Internal protein dynamics on ps to µs timescales as studied by multi-frequency (15)N solid-state NMR relaxation.

A comprehensive analysis of the dynamics of the SH3 domain of chicken alpha-spectrin is presented, based upon (15)N T1 and on- and off-resonance T1ρ relaxation times obtained on deuterated samples with a partial back-exchange of labile protons under a variety of the experimental conditions, taking explicitly into account the dipolar order parameters calculated from (15)N-(1)H dipole-dipole couplings. It is demonstrated that such a multi-frequency approach enables access to motional correlation times spanning about 6 orders of magnitude. We asses the validity of different motional models based upon orientation autocorrelation functions with a different number of motional components. We find that for many residues a "two components" model is not sufficient for a good description of the data and more complicated fitting models must be considered. We show that slow motions with correlation times on the order of 1-10 µs can be determined reliably in spite of rather low apparent amplitudes (below 1 %), and demonstrate that the distribution of the protein backbone mobility along the time scale axis is pronouncedly non-uniform and non-monotonic: two domains of fast (τ < 10(-10) s) and intermediate (10(-9) s < τ < 10(-7) s) motions are separated by a gap of one order of magnitude in time with almost no motions. For slower motions (τ > 10(-6) s) we observe a sharp ~1 order of magnitude decrease of the apparent motional amplitudes. Such a distribution obviously reflects different nature of backbone motions on different time scales, where the slow end may be attributed to weakly populated "excited states." Surprisingly, our data reveal no clearly evident correlations between secondary structure of the protein and motional parameters. We also could not notice any unambiguous correlations between motions in different time scales along the protein backbone emphasizing the importance of the inter-residue interactions and the cooperative nature of protein dynamics.

The relation of the X-ray B-factor to protein dynamics: insights from recent dynamic solid-state NMR data.

In addressing the potential use of B-factors derived from X-ray scattering data of proteins for the understanding the (functional) dynamics of proteins, we present a comparison of B-factors of five different proteins (SH3 domain, Crh, GB1, ubiquitin and thioredoxin) with data from recent solid-state nuclear magnetic resonance experiments reflecting true (rotational) dynamics on well-defined timescales. Apart from trivial correlations involving mobile loop regions and chain termini, we find no significant correlation of B-factors with the dynamic data on any of the investigated timescales, concluding that there is no unique and general correlation of B-factors with the internal reorientational dynamics of proteins.

Microsecond time scale mobility in a solid protein as studied by the 15N R(1rho) site-specific NMR relaxation rates.

For the first time, we have demonstrated the site-resolved measurement of reliable (i.e., free of interfering effects) (15)N R(1rho) relaxation rates from a solid protein to extract dynamic information on the microsecond time scale. (15)N R(1rho) NMR relaxation rates were measured as a function of the residue number in a (15)N,(2)H-enriched (with 10-20% back-exchanged protons at labile sites) microcrystalline SH3 domain of chicken alpha-spectrin. The experiments were performed at different temperatures and at different spin-lock frequencies, which were realized by on- and off-resonance spin-lock irradiation. The results obtained indicate that the interfering spin-spin contribution to the R(1rho) rate in a perdeuterated protein is negligible even at low spin-lock fields, in contrast to the case for normal protonated samples. Through correlation plots, the R(1rho) rates were compared with previous data for the same protein characterizing different kinds of internal mobility.