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Solid-state-batteries employing lithium metal anodes promise high theoretical energy and power densities. However, morphological instability occurring at the lithium/solid–electrolyte interface when stripping and plating lithium during cell cycling needs to be mitigated. Vacancy diffusion in lithium metal is not sufficiently fast to prevent pore formation at the interface above a certain current density during stripping. Applied pressure of several MPa can prevent pore formation, but this is not conducive to practical application. This work investigates the concept of ionic liquids as “self-adjusting” interlayers to compensate morphological changes of the lithium anode while avoiding the use of external pressure. A clear improvement of the lithium dissolution process is observed as it is possible to continuously strip more than 70 μm lithium (i. e., 15 mAh cm$^{−2}$ charge) without the need for external pressure during assembly and electrochemical testing of the system. The impedance of the investigated electrodes is analyzed in detail, and contributions of the different interfaces are evaluated. The conclusions are corroborated with morphology studies using cryo-FIB-SEM and chemical analysis using XPS. This improves the understanding of the impedance response and lithium stripping in electrodes employing liquid interlayers, acting as a stepping-stone for future optimization.

Large-scale industrial application of all-solid-state-batteries (ASSBs) is currently hindered by numerous problems. Regarding thiophosphate-based ASSBs, interfacial reactions with the solid electro...

Summary Li7La3Zr2O12 (LLZO)-based garnet materials are recently being investigated as suitable electrolytes for solid-state batteries with lithium-metal electrodes. Unfortunately, lithium-metal penetration through polycrystalline garnet-type electrolytes limits the electric current density during cell charging. In this study, we introduce an electrochemical operando approach that is well suited to get insights into the early stage of lithium-metal penetration that was yet only accessible with very elaborate neutron measurements. Combined with in situ as well as ex situ electron microscopic techniques, we investigate the morphological instability of the lithium-metal anode on garnet-type solid electrolytes under cathodic load and demonstrate the inter-relationship between microkinetic aspects and lithium-penetration susceptibility.

All-solid-state batteries promise to enable lithium metal anodes and outperform state-of-the-art lithium-ion battery technology. To achieve high battery capacity, utilization of the active material...

Interface strain and its influence on the ionic transport along hetero-interfaces has gained a lot of attention over the last decade and is controversially discussed. We investigate the relaxation of mismatch induced interfacial strain as a function of the degree of orientation/texture of the columnar crystallites and assess the impact on the oxygen ion conductivity in Er2O3/YSZ multilayer systems. Results from X-ray diffraction clearly show, that the width of the strained hetero-interface region increases with an increasing degree of orientation of the crystallites. The combined impact of film texture and strain at the hetero-interfaces of the film on the ionic conductivity however is not easily deduced from these measurements. The samples with the highest degree of orientation, i.e. with only one azimuthal variant, show strong anisotropic electrical properties. In samples with a lower degree of orientation, i.e. samples with a fiber texture, anisotropic properties cannot be detected, possibly due to a geometrical averaging of the electrical properties. The expected strain induced monotonic increase of the ionic conductivity with decreasing layer thickness and thus increasing interfacial influence could only be detected for samples with a fiber texture and a considerable degree of crystallite misorientation. This leads to the important conclusion that the texture and therefore the nature of the grain boundaries and their network influence the ionic conductivity of the multilayer thin films in the same order of magnitude as the misfit induced interface strain. Thus, the potential design of strain-controlled ionic conductors requires additionally the control of the microstructure in terms of grain orientation.

Drug functionalization of biomaterials is a modern and popular approach in biomaterials research. Amongst others this concept is used for the functionalization of bone implants to locally stimulate the bone healing process. For example strontium ions (Sr2+) are administered in osteoporosis therapy to stimulate bone growth and have recently been integrated into bone cements. Based on results of different analytical experiments we developed a two-phase model for the transport of therapeutically active Sr2+-ions in bone in combination with Korsmeyer-Peppas kinetics for the Sr2+ release from bone cement. Data of cement dissolution experiments into water in combination with inductively coupled plasma mass spectrometry (ICP-MS) analysis account for dissolution kinetics following Noyes-Whitney rule. For dissolution in ??-MEM cell culture media the process is kinetically hindered and can be described by Korsmeyer-Peppas kinetics. Time of flight secondary ion mass spectrometry (ToF-SIMS) was used to determine the Sr2+ diffusion coefficient in healthy and osteoporotic trabecular rat bone. Therefore, bone sections were dipped in aqueous Sr2+-solution by one side and the Sr2+-profile was measured by classical SIMS depth profiling. The Sr2+ mobility can be described by a simple diffusion model and we obtained diffusion coefficients of (2.28??2.97)???10-12cm2/s for healthy and of (1.55??0.93)???10-10cm2/s for osteoporotic bone. This finding can be explained by a different bone nanostructure, which was observed by focused ion beam scanning electron microscopy (FIB-SEM) and transmission electron microscopy (TEM). Finally, the time and spatially resolved drug transport was calculated by finite element method for the femur of healthy and osteoporotic rats. The obtained results were compared to mass images that were obtained from sections of in vivo experiments by ToF-SIMS. The simulated data fits quite well to experimental results. The successfully applied model for the description of drug dispersion can help to reduce the number of animal experiments in the future.Copyright ?? 2017 Elsevier B.V. All rights reserved.

One limiting phenomenon for the cycle life of metal–oxygen batteries is the growth of dendrites during metal plating (cell charging). For the relatively new sodium–oxygen cell, this subject has been scarcely investigated, until now. Therefore, dendrite formation is systematically investigated herein, with the aim of gaining a more detailed understanding of the underlying mechanisms and relevant control parameters. Electrochemical impedance spectroscopy, cycling experiments, and optical characterization techniques are applied in situ and ex situ; sodium dendrite growth is directly visualized, for the first time, by means of a tubular glass cell. The growth of instable surface morphologies is discussed from a theoretical perspective to comprehend the experimentally observed dendrite growth. Furthermore, countermeasures against issues with dendrites are discussed, with the aim of increasing the cycle life of sodium–oxygen batteries.

Within thermoelectric generators, the chemical diffusion of a contact material into the active thermoelectric material is a potential cause for degradation, which has rarely been discussed in literature. Frequently, this degradation phenomenon leads to major problems in developing new modules and achieving long-term stability. In this study, copper as one of the standard contact materials and lead telluride as the state-of-the-art active material in the mid-temperature range are investigated. Chemical diffusion experiments of copper in lead telluride were carried out between 375 K and 795 K and the copper diffusion profiles were obtained by Secondary Ion Mass Spectrometry (SIMS). The evaluated chemical diffusion coefficient is lower than 10 −13 cm 2 /s in the respective temperature range.

We report a novel method for the direct synthesis of mono- and bis-arylated alkynes utilizing catalytically activated CaC2 as the alkyne component. This fluoride-activated cross coupling reaction provides advantages over existing methods regarding operational simplicity, use of readily available starting materials, and low cost.

Herein X-ray tomography of cycled symmetric sodium cells with Na-β-alumina is used to validate the success of a protective layer. X-ray imaging after cell failure reveals that the solid electrolyte unexpectedly broke apart alongside a crack. The crack might have acted as the nucleation site for sodium dendrite growth, which ended in short-circuiting and cell failure.

Li₇La₃Zr₂O₁₂ (LLZO) based garnet materials are recently investigated as suitable electrolytes for solid state batteries with lithium metal electrode. Unfortunately, lithium metal penetration through polycrystalline garnet type electrolytes limits the electric current density during cell charging. In this study, we introduce an electrochemical operando approach that is a well suited to get insights into the early stage of lithium metal penetration that was yet only accessible with very elaborate neutron measurements. Combined with in situ as well as ex situ electron microscopic techniques, we investigate the morphological instability of the lithium metal anode on garnet type solid electrolytes under cathodic load and demonstrate the interrelationship between microkinetic aspects and lithium penetration susceptibility.

Sodium cobaltate (NaxCoO2, NCO) is a model type thermoelectric material for high temperature applications, which is representative for the class of non-stoichiometric and mixed ion-electron conducting thermoelectrics (e.g., Cu2 – xSe). The present study deals with the kinetic instability of the originally homogeneous chemical composition when a temperature gradient is applied – a common situation in thermoelectric materials with a mobile component (element), but rarely considered in thermoelectric materials research so far. In order to investigate a well reproducible system, highly epitaxial thin films of NaxCoO2 with an atmosphere protective capping layer of alumina are prepared via pulsed laser deposition on sapphire (001) and lanthanum aluminate (111). A self-designed non-isothermal set-up allows the precise determination of the heat of transport for mobile sodium as 8.3 kJ mol−1 and, therefore, the quantification of thermodiffusion (i.e., the Ludwig-Soret effect in the stationary state). The experiments also allow to estimate the chemical diffusion coefficient of sodium at 422 K as about = 5 × 10−4 cm2 s−1.

Drug functionalization of biomaterials is a modern and popular approach in biomaterials research. Amongst others this concept is used for the functionalization of bone implants to locally stimulate the bone healing process. For example strontium ions (Sr

Copper sulfides are attractive electrode materials as their reaction with lithium offers high capacity and energy density. However, the reversibility is poor and (nano)structuring is considered necessary to achieve moderate improvements. In contrast, we show in this study that the electrolyte is a major factor that governs the reversibility of the cell reaction. All our experiments were done with commercially available copper sulfides (CuS and Cu2S) without any special nanostructure. Different electrolyte compositions were tested among LiPF6 in EC/DMC and LiTFSI in DOL/DME. While rapid capacity fading is found in cells containing carbonate-based electrolytes, cells with ether-based electrolytes show a much better electrochemical performance. For a mixture of 1 M LiTFSI in DOL/DME, Cu2S can be cycled with capacities of around 200 mAh g−1 for more than 150 cycles with coulombic efficiencies >98.4%, for example. The improved stability in the ether-based electrolyte further allowed us to study how the discharge and charge voltage change during prolonged cycling. Our study underlines that improvements in the Li/CuS and Li/Cu2S system are still possible by very simple measures, but further studies on the complex Li–Cu–S phase behavior are necessary to understand the discharging and especially the charging mechanisms.

The lithium-ion solid electrolyte “Li7La3Zr2O12” (LLZO) and the tantalum substituted analogue Li7−xLa3Zr2−xTaxO12 (LLZTO) with varying Ta content 0.375 I a 3 ¯ d ). Phase formation was studied by X-ray powder diffraction. While Al doping was necessary for the preparation of dense LLZO ceramics crystallizing in the high lithium ion conductive cubic garnet modification, dense cubic tantalum substituted LLZTO ceramics could be prepared without Al doping. Ta substitution was found to facilitate the formation of the cubic garnet modification at lower synthesis temperature. The temperature dependence of the ionic conductivity and lithium metal electrode kinetics were studied by ac impedance spectroscopy and cyclic voltammetry, respectively. The ionic conductivity of cubic LLZTO was found to increase by Al doping. The highest room temperature conductivity of 5 × 10−4 S cm−1 with an activation energy of Ea = 0.41 eV was found for the sample Li6.625La3Zr1.625Ta0.375O12 with 28 mol% Al content. Lithium electrode kinetics was studied on LLZO and LLZTO samples. The electrode activation energies of all investigated samples showed similar values between Ea = 0.41 eV and 0.46 eV close to the activation energies for lithium ion migration in the bulk electrolyte. Thus, the Ta substituted and Al-doped material Li6.625La3Zr1.625Ta0.375O12 (29 mol% Al) showed a more than one order of magnitude higher exchange current density of i0 = 240 μA cm−2 than Ta-free LLZO with i0 = 18 μA cm−2.

Functional materials are often exposed to high temperatures and inherent temperature gradients. These temperature gradients act as thermodynamic driving forces for the diffusion of mobile components. The detailed consequences of thermodiffusion depend on the boundary conditions of the non-isothermal sample: Once the boundaries of the sample are inert and closed for exchange of the mobile components, thermodiffusion leads to their pile-up in the stationary state (the so called Soret effect). Once the system is open for an exchange of the mobile component, chemical diffusion adds to the Soret effect, and stationary non-zero component fluxes are additionally observed in the stationary state. In this review, the essential aspects of thermodiffusion and Soret effect in inorganic functional materials are briefly summarized and our current practical knowledge is reviewed. Major examples include nonstoichiometric binary compounds (oxides and other chalcogenides) and ternary solid solutions. The potential influence of the Soret effect on the long term stability of high temperature thermoelectrics is briefly discussed. Typical Soret coefficients for nonstoichiometric compounds are found to be of the order of (dδ/dT) ≈ 1%/K.

The structures and properties of silver selenide samples strongly depend on the method of preparation. Thin films prepared by pulsed laser deposition (PLD) contain lamellae of two low-temperature m...

Dispersions of very small non-magnetic metal particles or inclusions in a non-magnetic semiconductor matrix are well known to produce unusually large and linear magnetoresistance effects. So far these materials were limited to the binary silver-rich chalcogenides Ag2Se and Ag2Te. In this contribution Ag3AuTe2 was selected as a first candidate for a ternary matrix material, thus offering enhanced capabilities for the generation of heterogeneous microstructure and spatially varying composition on the nanoscale. In gold-rich Ag3Au1.1Te2 two kinds of inhomogeneities are present, namely Au deposits with a size on the micron scale and an inhomogeneous distribution of Au and Ag within the matrix. The matrix consists of micron-sized grains with the structure type of Ag3AuTe2 as studied by electron microscopy. Like the binary silver chalcogenide phases, the material also shows a large and linear magnetoresistance effect. The transversal magnetoresistance effect was measured between 20 K and 270 K in magnetic fields up to B = 5 T. The results are discussed on the basis of existing models for a large and linear positive MR effect.

Thin films of silver selenide with varying composition have been deposited on magnesium oxide substrates with pulsed laser deposition and were investigated via micro-XRF. A calibration procedure was designed to determine the absolute thicknesses of the films. The lateral homogeneity was investigated by elemental mapping, thus delivering information about the deposition process. Wet chemical analysis was performed on the dissolved layers with ICP-OES and ICP-MS to determine the stoichiometry of the Ag x Se y . The results suggest a correlation between the composition of the layers and their thicknesses by showing a silver enrichment for thinner layers.

For the purpose of preparing TCCs (= transparent and electrical conducting coatings), metallic and ferromagnetic nano-additives were dispersed into a transparent varnish and the obtained dispersions were coated on transparent plastic substrates. During hardening of the dispersion the magnetic nano-additives were aligned by a magnetic field. The resulting coatings have electrical pathways along lines of nano-additive chains and are highly transparent in the areas between the lines. Therefore, the electrical conductivity is anisotropic, and it depends on the alignment of the nano-additives (i.e. on the distance between the nano-additives within the chains and the length of the lines) as well as on the thickness of an oxide and/or solvent shell around the nano-additives. The transparency depends also on the alignment and here especially on the thickness and the distance between the formed lines. The quality of the alignment in turn, depends on the magnetic properties and on the size of the particles. We used commercial plastic varnishes, which form electrically isolating (≥ 10 − 12 S/m) and transparent (about 90% transparency) coatings, and the following magnetic additives: Co-, Fe-, CoPt 3 , CoPt 3 @Au- and Fe@Au-nanoparticles as well as CoNi-nanowires. Coatings with Fe@Au-nanoparticles show the best results in terms of the electrical conductivity (10 − 5 S/m–10 − 6 S/m) at transparencies above 70%. Furthermore, in addition to the magnetic nano-additives, transparent additives (Al 2 O 3 -particles) and non-magnetic, but better conducting additives (carbon-nanotubes) were added to the varnish to increase the transparency and the electrical conductivity, respectively.

FeS polycrystalline films were prepared on float glass by radio-frequency reactive sputtering. X-ray diffraction, scanning electron microscopy, Rutherford backscattering, and secondary ion mass spectroscopy were used to characterize the films. The effects of the deposition parameters, such as sputter power and substrate temperature, on the morphological structure and on the metal–semiconductor phase transition of FeS films were investigated. It has been found that the films show a substrate temperature dependent preferential orientation and phase-transition temperature.

Bandgap-bowing has been observed in many of the zinc-group-VI compounds, when the anion is substituted with an isovalent element. Recently new results on the ZnO1–xSx and ZnO1–xSex system have been presented, but so far only one report on ZnO1–xTex is known. We examine the possibility of substituting tellurium by oxygen in sputter-deposited polycrystalline ZnTe thin-films and the effects on bandgap energy and crystal structure. A first approximation of the bowing curve with a lower limit of the bowing parameter of 2.7 eV is performed. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The magnetoresistance (MR) effect of the low temperature phase of silver selenide ( α -Ag 2+ δ Se) is studied with both bulk and thin film samples within a wide range of composition, i.e. metal content. Homogeneous bulk silver selenide shows the ordinary magnetoresistance (OMR) effect, which can be explained by the two-band model of a classical semiconductor. Heterogeneous silver selenide forms a semiconductor/metal dispersion which shows completely different MR effects, depending on the microstructure of the samples. XRD and TEM studies of thin film samples prove the two-phase character of the silver-rich material, and also offer new insights into the microstructure of the low temperature phase of silver selenide: Two selenide phases appear and form a “nano-parquet” of two coexisting selenide phases with both coherent twin boundaries and incoherent large angle grain boundaries. This microstructure is discussed as the possible reason for the observed MR effects.

In the nonstoichiometric low-temperature phase of silver selenide a very small silver excess within the semiconducting silver selenide matrix in the order of 0.01% is sufficient to generate a linear magnetoresistance (LMR) of more than 300% at 5 T, which does not saturate at fields up to 60 T. Different theoretical models have been proposed to explain this unusual magnetoresistance (MR) behavior, among them a random resistor network consisting of four-terminal resistor units. According to this model the LMR and the crossover field from linear to quadratic behavior are primarily controlled by both the spatial distribution of the charge-carrier mobility and its average value, being essentially functions of the local and average compositions. Here we report measurements on silver-rich thin ${\text{Ag}}_{x}\text{Se}$ films with a thickness between 20 nm and $2\text{ }\ensuremath{\mu}\text{m}$, which show an increasing average mobility in conjunction with an enhanced MR for increasing film thickness. We found a linear scaling between the size of the transverse LMR and the crossover field, as predicted by the theory. For films thinner than about 100 nm the MR with field directed in the sample plane shows a breakdown of the LMR, revealing the physical length scale of the inhomegeneities in thin ${\text{Ag}}_{x}\text{Se}$ devices.

The preparation of Ag 2+x Se thin films with thicknesses between 4 nm and 3000 nm by pulsed laser deposition on single crystalline NaCl and MgO substrates is reported. The films are perfectly dense and show a good lateral uniformity with a small number of defects. The microstructure of the films corresponds to a nanoparquet, being composed of two different phases of silver selenide. One phase is identified as the Naumannite low temperature phase of silver selenide, the structure of the other phase has not been reported in detail before and probably represents a metastable phase. Silver-rich films contain silver precipitates with typical sizes on the nanoscale. Their presence and their size appears to be responsible for the large and linear magnetoresistance effect of silver-rich silver selenide.

FeS polycrystalline thin films were prepared on float glass at 500°C by radio-frequency reactive sputtering. The influence of vacuum annealing on the metal-semiconductor transition of FeS films was investigated. It has been found that with the increase of the annealing temperature from 360to600°C, the metal-semiconductor transition temperature of FeS films first decreases and then increases, associated with first a reduction and then an enhancement of hysteresis width. The thermal stress is considered to give rise to the abnormal change of the metal-semiconductor transition of the FeS film during annealing.

In the present study, we investigated the galvanomagnetic transport properties of polycrystalline AgxSe thin films with silver excess in the range from x=1.5 to 18. The results prove that the silver excess controls the transition from linear magnetoresistance (MR) behavior to the quadratic ordinary MR and the temperature for the metal–semiconductor transition. Analyzing the MR effect by Kohler’s rule and comparing the results with the field-free resistivity we observe for 2