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Organic electrochemical transistors (OECTs) have emerged as a promising platform for biosensing, electrophysiology, and neuromorphic devices. However, OECTs are often limited by the stability of the channel materials. Here, we systematically investigate the stability of OECT channels under varied operating voltage ranges. We find that OECT materials can be operated with high stability when the voltage range is reduced. We show that repeated full voltage cycling degrades device performance. The results indicate that to maximize stability, OECTs should either be operated in the saturation regime to maximize current gain (transconductance) or in the subthreshold regime to maximize the on/off ratio. [ABSTRACT FROM AUTHOR]

Argyrodites, Li6PS5X (X=Cl, Br, I), have piqued the interest of researchers by offering promising lithium ionic conductivity for their application in all-solid-state batteries (ASSBs). However, other than Li6PS5Cl (651Cl) and Li6PS5Br (651Br), Li6PS5I (651I) shows poor ionic conductivity (10−7 S cm−1 at 298 K). Herein, we present Al-doped 651I with I−/S2− site disordering to lower activation energy (Ea) and improve ionic conductivity. They formed argyrodite-type solid solutions with a composition of (Li6−3xAlx)PS5I in 0⩽x⩽0.10, and structural analysis revealed that Al3+ is located at Li sites. Also, the Al-doped samples contained anion I−/S2− site disorders in the crystal structures and smaller lattice parameters than the non-doped samples. Impedance spectroscopy measurements indicated that Al-doping reduced the ionic diffusion barrier, Ea, and increased the ionic conductivity to 10−5 S cm−1; the (Li5.7Al0.1)PS5I had the highest ionic conductivity in the studied system, at 2.6×10−5 S cm−1. In a lab-scale ASSB, with (Li5.7Al0.1)PS5I functioned as a solid electrolyte, demonstrating the characteristics of a pure ionic conductor with negligible electronic conductivity. The evaluated ionic conduction is due to decreased Li+ content and I−/S2− disorder formation. Li-site cation doping enables an in-depth understanding of the structure and provides an additional approach to designing better-performing SEs in the argyrodite system. [ABSTRACT FROM AUTHOR]

Deep eutectic solvent (DES)-based gels, with their biocompatibility, non-volatility, low cost, and electrochemical stability, have attracted widespread interest as novel solid-state ionic conductor for flexible devices. However, fabrication of tough and stretchable DES gels is challenging due to the insufficient understanding of the interactions between polymers and DES. The development of tough DES gels based on hydrogen bonding is attractive but also challenging due to the possible competitive hydrogen bonds between the hydrogen bond-rich choline chloride-based polar DES and polymers. Herein, tough copolymer-supported DES gels with dual-cross-linked dissipative network were fabricated through copolymerization of methacrylic acid and N, N-dimethylacrylamide monomers with good and poor compatibility with DES to promote the formation of stable hydrogen bonds between polymers in the DES. The resulting DES gels were stiff, tough, stretchable, and self-recoverable, with tensile strength, breaking strain, Young's modulus, toughness, and recovery ratio being 2.08 MPa, 792%, 1.76 MPa, 12.88 MJ m−3, and 76%, respectively. The mechanical properties of DES gels could be widely tuned by varying the monomer ratio and solvent structure changes. The carbon-based supercapacitor based on the DES gel shows stable voltage window to 2 V and exhibits the specific capacitance of 93.25 F g−1 at 2 A g−1. An ultratough and stretchable copolymer-supported DES gel ionic conductor with high tensile strength of 2.08 Mpa, high toughness of 12.88 MJ m−3, stretchability of 792%, and excellent recovery properties are facile fabricated for flexible electronics through copolymerization of two monomer pairs of methacrylic acid and N, N-dimethylacrylamide that can form stable hydrogen bonds in the DES environment with a small amount of chemical cross-linker to form a dual-crosslinked dissipative network. [ABSTRACT FROM AUTHOR]

The sodium ion–based materials have interesting physical properties which make them suitable for industrial applications. In this paper, we focus our work on sodium ytterbium phosphate NaYbP2O7, prepared by the solid-state method. It is found that NaYbP2O7 crystallizes in the monoclinic system with P121/n1 space group. Impedance analysis shows that this compound exhibits semiconductor behavior and that the conduction mechanism is thermally activated. AC conductivity measurements show that NaYbP2O7 can be a good ionic conductor with an activation energy value up to 0.94eV. The frequency dependence of conductivity is probably caused by the jump of Na ions between octahedral sites of the olive framework. Such properties of NaYbP2O7 make it suitable as an ionic conductor. [ABSTRACT FROM AUTHOR]

The mixed alkali-diphosphate materials are among the widely used commercial materials due to their outstanding physical properties. The Li2Na2P2O7 (LNOP1) and Li3NaP2O7 (LNOP2) compounds have been synthetized by the conventional solid-state method. The structural and morphological analysis, optical properties, electrical and dielectric measurements were taken on the obtained compounds. Their powder X-ray diffraction analysis indicates that they crystallize in the monoclinic system with non-centrosymmetry P12/m1 and P121/m1 space group, respectively. The morphological images show that the two compounds are consisting of irregular block-shaped aggregates. The UV–Vis absorbance spectra show that the cutoff edges for compounds (LNOP1) and (LNOP2) are below 400 nm. The optical gaps of the both compounds are found indirect type with a value of 3.39 eV and 3.42 eV, respectively. The electrical data are investigated using the complex impedance spectroscopy technique in the range of frequency (0.1 Hz–1 MHz) and through large temperature scale (373–673 K). The AC conductivity evolution increases rapidly with appearance of a dispersive behavior, which obeys to Jonscher's law. Furthermore, the complex impedance analysis shows the contribution of only the grains in the conduction mechanism. The complex modulus diagrams confirmed the existence of only the contribution of the grain effect. Finally, the dielectric behavior of both compounds shows a non-Debye relaxation type. [ABSTRACT FROM AUTHOR]

The mixed alkali-diphosphate materials are among the widely used commercial materials due to their outstanding physical properties. The Li2Na2P2O7 (LNOP1) and Li3NaP2O7 (LNOP2) compounds have been synthetized by the conventional solid-state method. The structural and morphological analysis, optical properties, electrical and dielectric measurements were taken on the obtained compounds. Their powder X-ray diffraction analysis indicates that they crystallize in the monoclinic system with non-centrosymmetry P12/m1 and P121/m1 space group, respectively. The morphological images show that the two compounds are consisting of irregular block-shaped aggregates. The UV–Vis absorbance spectra show that the cutoff edges for compounds (LNOP1) and (LNOP2) are below 400 nm. The optical gaps of the both compounds are found indirect type with a value of 3.39 eV and 3.42 eV, respectively. The electrical data are investigated using the complex impedance spectroscopy technique in the range of frequency (0.1 Hz–1 MHz) and through large temperature scale (373–673 K). The AC conductivity evolution increases rapidly with appearance of a dispersive behavior, which obeys to Jonscher's law. Furthermore, the complex impedance analysis shows the contribution of only the grains in the conduction mechanism. The complex modulus diagrams confirmed the existence of only the contribution of the grain effect. Finally, the dielectric behavior of both compounds shows a non-Debye relaxation type. [ABSTRACT FROM AUTHOR]

MgO-doped partially stabilized zirconia (xMgPSZ, with x = 8 or 10 mol%) materials sintered at 1700°C, were characterized with respect to structure, microstructure, thermal expansion and electrical performance. The monoclinic (M) phase content is almost vestigial in 10MgPSZ, unlike in 8MgPSZ. Combined powder XRD and customized thermal expansion data analysis, allowed a separation between M and tetragonal (T) particles, outside or imbedded in cubic grains. Combination of thermal expansion and impedance spectroscopy data provided novel insights on the totally distinct roles of fine and dispersed T or M particles within the PSZ cubic matrix grains. [ABSTRACT FROM AUTHOR]

The design and production features of a solid oxide fuel cell greatly impact its microstructure and performance; however, these factors are frequently omitted in related studies. In this work, the influence of the design and formation factors of a solid oxide fuel cell on its performance and long-term stability is studied. The sintering process of multilayer half-cells is studied by heating microscopy and the optimal sintering strategy is identified. We show here the importance of the sintering strategy and suggest an approach for SOFC design that results in a stable in time performance. The electrochemical performance is evaluated by impedance spectroscopy and the distribution of relaxation times (DRT) technique. It is shown that the absence of the barrier layer leads to a decrease in the SOFC performance by 22.5% as-sintered and continues to drop down during the exposure of 850 °C for 400 h. The impregnation of the cathode and anode by Pr(NO3)3 and Ce(NO3)3 improves electrochemical performance by 15% and this increase withstands a heat treatment at least for 215 h without any noticeable degradation. The most stable in time performance of the cell with impregnated electrodes and the barrier layer is 515.3 mW × cm−2 (H2 + 3% H2O used as fuel, air + 3% H2O as oxidizer). [ABSTRACT FROM AUTHOR]

Reactive flash synthesis simplifies the processing of complex ceramics such as alumina doped lithium lanthanum zirconate. Low temperatures and short processing times obviate the loss of lithium while producing dense single-phase ceramics. Here we show the synthesis of non-stoichiometric compositions of this ceramic which increases the ionic conductivity by a factor of more than three. The non-stoichiometry refers to non-equilibrium lithium/lanthanum ratio, and to the addition of boron to produce excess lithium-ion vacancies. The results open the possibility of using non-stoichiometry as a concept, and RFS as the tool, for the discovery of new compositions that enhance lithium-ion conductivity. [ABSTRACT FROM AUTHOR]

Due to its high capacity and low density, lithium metal is considered as one of the most promising anodes for next-generation lithium batteries. However, the problems of dendrite and volume change are the main obstacles to limit its further development. Therefore, it is of great significance to realize the stable plating and stripping of lithium metal. The stability of lithium metal can be improved by compositing lithium with conductor materials, but the effect of conductor materials on lithium composite anode needs to be further studied. Herein, ionic or electronic conductor powders are introduced into the interior of lithium metal by hot-melt mixed coating method; Li/Cu, Li/Zn, and Li/Li3N composite anodes are prepared; and their electrochemical performances in solid and liquid batteries are studied. The results show that plating and stripping of lithium in composite anodes will take place preferentially around electronic or ionic conductor, rather than around lithium itself. For liquid batteries, the introduction of electronic conductor in lithium composite anode will make the electric field distribution more uniform and thus make the lithium deposition more stable, while the introduction of ionic conductor in composite anodes can improve the electrochemical stability of composite anodes in solid-state batteries. The capacity of the Li/Cu-LFP battery was 42.5 mAh g−1 after 500 cycles at 10 °C, corresponding to the 77% retention of its initial capacity. [ABSTRACT FROM AUTHOR]

To improve the stability and performance of the cathode materials, an ionic conductor layer was coated successfully on the surface of Li1.2Mn0.54Ni0.13Co0.13O2 (LMNC) microspheres. The structural analysis confirmed that LiV3O8 coating did not change the basic structure of LMNC, and all obtained materials are solid solutions with a good-layered structure and a good crystallinity. The microscopy measurement showed that the thickness of the coating layer for the LV-3 sample is about 2.5 nm. This appropriate layer is helpful for improving the surface stability of LMNC and the diffusion of lithium, leading to an obvious enhancement of the electrochemical performance. Our result confirmed that the average discharge specific capacities for LV-3 sample at 0.1 C, 0.2 C, 0.5 C, 1 C, and 3 C are respectively 265.9, 219.1, 188.0, 156.3, and 121.5 mAh g−1, which are much larger than the values of other samples. After 50 cycles at a 1 C rate, the capacity retentions for different samples are 60.7%, 74.0%, 87.6%, and 70.4%, indicating that LV-3 sample exhibits the best performance. Furthermore, EIS measurements showed that the diffusion coefficient for LV-3 sample is calculated to be 1.26 × 10−15 cm2 s−1, which is also the largest value among all considered samples. Our experiments identified that coating an ionic conductive layer on the cathode material surface will significantly improve their rate capacity and cycling stability. [ABSTRACT FROM AUTHOR]

Soft electronic materials are key elements for realizing wearable, attachable, and stick-on electronics. The development of deformable and stretchable electrodes is a key research area as they are one of the most important components for soft electronic devices. Recently, significant progress in the development of deformable and stretchable electrodes has been achieved with organic materials offering electrical tunability, simple mechanical implementation, and desirable chemical and optical properties. In this review, we present recent progress in the design of stretchable electronics based on deformable conducting materials, including their fabrication and conductivity properties and the methods that are employed to enhance performance. In addition, we review the development status of organic- and carbon- based conductive materials and their hybrid composites being used for electronic applications, including carbon nanotubes, graphene, metal composites, conductive polymers, hybrid composites, and ion gel composites. The structural aspects, such as wavy or mesh configurations, of stretchable electrodes and other high-performance conducting materials are investigated intensively. Many stretchable electrodes show great potential for use in future electronics such as electronic skin (e-skin) and stretchable displays, which require reversible deformation and a high degree of operational stability. [ABSTRACT FROM AUTHOR]

Technologies for detecting and analyzing a single molecule help us understand and engineer numerous phenomena observed in nature. Carbon nanotubes (CNTs) are highly efficient molecular conduits due to their atomically smooth surface. Because of their small diameters, comparable to the size of a single molecule, even a single blocking molecule can obstruct CNT fluidic channels. Analyzing these pore-blocking events in CNTs therefore enables single-molecule studies. The high-aspect ratios of CNT channels, which extend the time scale of transport, allow for studying molecular transport that is too fast to record in other systems. Both theoretical studies and ensemble experimental measurements have verified the enhanced flow of various ions and molecular species in CNTs. Experimental measurements of a single-CNT fluidic channel, however, have only recently begun, demonstrating the detection of individual DNA, polymer, and alkali-metal ions. This article reviews recent advances in single-nanotube fluidic channels with a focus on experimental measurements. [ABSTRACT FROM PUBLISHER]

Glass-ceramics have gained considerable importance for applications in high-energy technology. Li- and Na-superionic ion-conducting ceramics find widespread use in lithium- and sodium-ion batteries as separators, solid electrolytes, and cathode materials. The ionic conductivity of these materials is influenced by crystal chemical parameters and can be further optimized via microstructural control using glass-ceramic processing. This article summarizes the most promising glass-ceramic material systems currently in use, detailing recent progress in understanding their structure–property–performance relationships. We also highlight the power and potential of solid-state nuclear magnetic resonance techniques for providing quantitative knowledge about structure, phase composition, and ion dynamics in these materials. [ABSTRACT FROM AUTHOR]

Materials designed and engineered for technical applications must invariably meet or exceed multiple key specifications. Even if commercial realization is not intended, scientific interest is piqued if a challenging combination of properties is achieved, particularly if they are mutually exclusive for certain classes of materials. For example, the combination of mechanical toughness, chemical durability, and high thermal-shock resistance, with pore-free, smooth, aesthetically beautiful surfaces simultaneously realized in certain glasses that are crystallized in a controlled manner—glass-ceramics—have enabled two distinct, decades-long applications, cookware and flat cooktop panels. Other special glass-ceramic materials have been developed for electronic, photonic, dental, and biomedical applications. No other class of material could combine these properties in such an advantageous and economically feasible manner. This issue highlights six very different innovative applications of glass-ceramics, all of which owe their importance and continuing interest to “hard-to-combine” properties. [ABSTRACT FROM AUTHOR]

Bulk specimens of CeGdO prepared with powders within a range of specific surface area were sintered in oxidizing, inert, and reducing atmospheres. The aim of this work is to investigate the effects of the sintering atmosphere on the microstructure and grain and grain boundary conductivities of the solid electrolyte. The lattice parameter determined by Rietveld refinement is 0.5420(1) nm, and the microstrain was found negligible in the powder materials. Specimens sintered in the Ar/4 % H mixture display larger average grain sizes independent on the particle size of the starting powders. The grain and grain boundary conductivities of specimens sintered under reducing atmosphere are remarkably lower than those sintered under oxidizing and inert atmospheres. The activation energy (∼0.90 eV) for total electrical conductivity remains unchanged with both the initial particle size and the sintering atmosphere. [ABSTRACT FROM AUTHOR]

A complex of lithium tetrafluoroborate (LiBF) and N-methylacetamide was prepared and investigated. Both LiBF and N-methylacetamide are solid at room temperature, but their mixture has liquid- or solid phase at room temperature, depending on the composition. When the complex is liquid, the complex has ionic conductivity. But if the complex is solid, it has electric conductivity. The room temperature ionic conductivities of some compositions in propylene carbonate of the complex exceed 6mS/cm. Room temperature electric conductivity of the complex is 5.025×10 mS/cm. In addition, supercapacitors were constructed and tested using the above-mentioned complex electrolyte. The electrochemical properties of the complex and the supercapacitors were evaluated with cyclic voltammetry, ac impedance spectroscopy, etc. The supercapacitors with this complex show good electrochemical properties in specific capacitance, cycling performances. [ABSTRACT FROM AUTHOR]

In the past decade, the research in designing fast oxygen conducting materials for electrochemical applications has largely shifted to microstructural features, in contrast to material-bulk. In particular, understanding oxygen energetics in heterointerface materials is currently at the forefront, where interfacial tensile strain is being considered as the key parameter in lowering oxygen migration barriers. Nanocrystalline materials with high densities of grain boundaries have also gathered interest that could possibly allow leverage over excess volume at grain boundaries, providing fast oxygen diffusion channels similar to those previously observed in metals. In addition, near-interface phase transformations and misfit dislocations are other microstructural phenomenon/features that are being explored to provide faster diffusion. In this review, the current understanding on oxygen energetics, i.e., thermodynamics and kinetics, originating from these microstructural features is discussed. Experimental observations, theoretical predictions and novel atomistic mechanisms relevant to oxygen transport are highlighted. In addition, the interaction of dopants with oxygen vacancies in the presence of these new microstructural features, and their future role in the design of future fast-ion conductors, is outlined. [ABSTRACT FROM PUBLISHER]

The magnitude and character of conductivity were studied for Y(WO) ceramics synthesized by the ceramic (from oxides) and organic-nitrate procedures. Investigation of the dependence $$\sigma \left( {{\alpha _{{o_2}}}} \right)$$ and measurements of the ion transport numbers of charge carriers by the EMF method showed that Y(WO) is basically an ion conductor. The conductivity is largely determined by the sample preparation conditions related to the dependence of the specific surface area and powder grain size on the synthetic procedure. The maximum high-temperature conductivity of Y(WO) was 2.51 × 10 S/cm, which roughly corresponds to the conductivities of Sc(WO) and In(WO) measured under the same conditions. It was confirmed that Y(WO) crystallizes as a mixed monoclinic-orthorhombic structure at 1000°C. The character of water incorporation in hydrated Y(WO) crystals was studied by thermogravimetry and diffuse reflectance IR spectroscopy. A qualitative model of water intercalation was suggested. [ABSTRACT FROM AUTHOR]

The physics underlying operation of cold (room-temperature) ionic-liquid emitter sources for use in propulsion shows that such thrusters are advantaged relative to all other “rockets” because of the direct scaling of power with emitter array density. Nanomaterials and their integration through nano- and microfabrication can propel these charged-particle sources to the forefront and open up new applications including mass-efficient in-orbit satellite propulsion and high-thrust-density deep-space exploration. Analyses of electrostatic, fluid-dynamic, and electrochemical limits all suggest that arrays of such ionic-liquid thrusters can reach thrust densities beyond most in-space propulsion concepts, with a limit on nanoporous thruster packing density of ∼1 μm due to ionic-liquid viscous flow and electrochemistry. Nanoengineered materials and manufacturing schemes are suggested for the implementation of microfabricated and nanostructured thruster arrays. [ABSTRACT FROM PUBLISHER]

As an ionic conductive functional layer of intermediate temperature solid oxide fuel cells (ITSOFC), samarium-doped ceria (SDC)-LiNaSO nano-composites were synthesized by a sol-gel method and their properties were investigated. It was found that the content of LiNaSO strongly affected the crystal phase, defect concentration, and conductivity of the composites. When the content of LiNaSO was 20 wt%, the highest conductivity of the composite was found to be, respectively, 0.22, 0.26, and 0.35 S cm at temperatures of 550, 600, and 700 °C, which are much higher than those of SDC. The peak power density of the single cell using this composite as an interlayer was improved to, respectively, 0.23, 0.39, and 0.88 W cm at 500, 600, and 700 °C comparing with that of the SDC-based cell. Further, the SDC-LiNaSO(20 wt%)-based cell also displayed better thermal stability according to the performance measurements at 560 °C for 50 h. These results reveal that SDC-LiNaSO composite may be a potential good candidate as interlayer for ITSOFC due to its high ionic conductivity and thermal stability. [ABSTRACT FROM AUTHOR]

Considerable interest in understanding interfacial phenomena occurring across nanostructured solid oxide fuel cell (SOFC) membrane electrode assemblies has increased demand for in situ characterization techniques with higher resolution. We briefly outline recent advancements in atomic force microscopy (AFM) instrumentation and subsystems in realizing real time imaging at high temperatures and ambient pressures, and the use of these in situ, multi-stimuli probes in collecting local information related to physical and fundamental processes. Here we demonstrate direct probing of local surface potential gradients related to the ionic conductivity of yttria-stabilized zirconia (YSZ) within symmetric SOFCs under intermediate operating temperatures (500–600 °C) via variable temperature scanning surface potential microscopy (VT-SSPM). The conductivity values obtained at different temperatures are then used to estimate the activation energy. These locally collected conductivity and activation energy values are subsequently compared to macroscopic electrochemical impedance results and bulk literature values, thus supporting the validity of the approach. [ABSTRACT FROM PUBLISHER]

Nanoparticles of lanthanide (Ln)-based zirconates have been prepared through the autoignited combustion technique. The structure of the system was analyzed by powder x-ray diffraction and vibrational spectroscopic tools. The compounds with Ln = Ce, Pr, Nd, Sm, and Gd have pyrochlore cubic structure, whereas those with Ln = Dy, Er, and Yb possess anion-deficient disordered cubic fluorite structure. The optical properties of the powder were analyzed using ultraviolet-visible spectroscopy. Pellets of the compounds were sintered in the range from 1325°C to 1530°C for 2 h. The surface morphology of sintered NdZrO was analyzed by scanning electron microscopy. Impedance spectroscopic studies of the samples were carried out at different temperatures. The conductivity increased to the order of 10 S/m at 750°C, and the highest conductivity of 13.21 × 10 S/m was obtained for ErZrO. All samples of this system are suitable candidates for fabrication of electrolytes for use in solid oxide fuel cells, particularly at moderate temperatures. [ABSTRACT FROM AUTHOR]

Nanoparticles of platinum were dispersed on an oxygen ionically conducting support, Yttria-Stabilized Zirconia (YSZ), on non-doped zirconia and on silica. The role of the support oxygen lattice in the mechanism of propane deep oxidation was investigated by using O Temperature-Programmed Desorption, catalytic activity measurements using isotopic oxygen, and isotopic exchange experiments. The results emphasize that the propane combustion mechanism on Pt/YSZ presents a different pathway compared with that involved on Pt/SiO and Pt/ZrO because, propane is preferentially oxidized by lattice YSZ oxygen species on Pt/YSZ. Strong Pt nanoparticles/YSZ interactions generate a promoted state similar to that observed on polarizations during electrochemical promotion of catalysis. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Solid-oxide fuel cells (SOFCs) are unique in their ability to directly convert the chemical energy of a wide variety of fuels to electric power with unmatched energy conversion efficiency. The articles in this issue of MRS Bulletin highlight the enormous potential of, and recent progress toward, operating SOFCs at lower temperatures (<650°C). Lower temperatures dramatically increase the number of potential applications for this technology as well as provide the opportunity to incorporate a wider variety of materials in SOFC power generation systems with greater reliability and lower cost. The articles in this issue describe materials development and processing for low-temperature SOFCs, including the enabling of nanotechnology and microelectromechanical systems-based cell designs, the development of highly active electrodes and their three-dimensional microstructural characterization, as well as the use of novel proton-conducting electrolytes, all of which provide new avenues of research. New fabrication methods are also being applied in the development of micro-SOFCs and microtubular SOFCs with higher power densities. Finally, advances in lowering performance degradation rates, a critical commercialization issue, are described. [ABSTRACT FROM AUTHOR]

Solid-oxide fuel cells (SOFCs) are an energy conversion technology with unique potential to have the highest energy conversion efficiency with the least environmental impact, as well as broad fuel flexibility from renewable to conventional fuels. Lowering the SOFC operating temperature will further lower system and operational costs, increase long-term durability, and allow more rapid start-up, providing feasibility for load following and transportation applications. Unfortunately, at reduced temperatures, the thermally activated nature of ionic conduction and electrochemical reactions increase polarization resistances, thus decreasing cell and system performance. However, lower operating temperatures also create the opportunity to employ nanostructured materials with higher surface area-to-volume ratios and greater interphase and interfacial regions, which can greatly enhance electrochemical performance. Here, we review recent progress in the development of various nanostructured electrodes and electrolytes and discuss their effects on the enhancement of the electrocatalytic activity of oxygen reduction and fuel oxidation, as well as oxygen-ion conduction, in order to achieve high-performance low-temperature SOFCs. [ABSTRACT FROM AUTHOR]

The need for reducing the operating temperature of solid-oxide fuel cells (SOFCs) imposed by cost reduction has pushed significant progress in fundamental understanding of the individual components, as well as materials innovation and device engineering. Proton-conducting oxides have emerged as potential alternative electrolyte materials to oxygen-ion conducting oxides for operation at low and intermediate temperatures. This article describes major recent developments in electrolytes, electrodes, and complete fuel cell performance for SOFCs based on proton-conducting electrolytes. Although the performance of such fuel cells is still relatively modest, significant improvements in the power density output have been made during the last couple of years, and this trend is expected to continue. [ABSTRACT FROM AUTHOR]

Solid oxide fuel cells (SOFCs) offer an efficient energy conversion technology for alleviating current energy problems. High temperature proton-conducting (HTPC) oxides are promising electrolytes for this technology, since their activation energy is lower than that of conventional oxygen-ion conductors, enabling the operating temperature reduction at 600 °C. Among HTPC oxides, doped BaZrO3 materials possess high chemical stability, needed for practical applications. Though, poor sinterability and the resulting large volume of highly resistive grain boundaries hindered their deployment for many years. Nonetheless, the recently demonstrated high proton conductivity of the bulk revived the attention on doped BaZrO3, stimulating research on solving the sintering issues. The proper selection of dopants and sintering aids was demonstrated to be successful for improving the BaZrO3 electrolyte sinterability. We here briefly review the synthesis strategies proposed for preparing BaZrO3-based nanostructured powders for electrolyte and electrodes, with the aim to improve the SOFC performance. [ABSTRACT FROM PUBLISHER]

The new field of nano-ionics is expected to yield large improvements in the performance of oxide-based energy generation and storage devices based on exploiting size effects in ion conducting materials. The search for novel materials with enhanced ionic conductivity for application in energy devices has uncovered an exciting new facet of oxide interfaces. With judicious choice of the constituent materials, oxide heterostructures can exhibit enhanced ion mobility compared to the bulk counterparts. Here we review recent experimental and theoretical progress on enhancement of oxide-ion conductivity arising in oxide ultrathin layers and at their interfaces, and describe the different scenarios, space-charge effects, epitaxial strain, and atomic reconstruction at the interface, proposed to account for the observed conductivity enhancement. [ABSTRACT FROM PUBLISHER]

The considerable potential of model-type thin film electrodes for the investigation of oxygen exchange pathways is demonstrated for different electrode materials on yttria-stabilized zirconia (YSZ). In particular, a correlation of voltage-driven 18O tracer experiments and electrical ac and dc measurements has proven to be helpful when aiming at mechanistic conclusions. For Pt electrodes, two different parallel reaction pathways can be identified under equilibrium conditions. At lower temperatures, a diffusion limited path through the electrode is dominant, whereas at higher temperatures, an electrode surface path with oxygen incorporation at the three-phase boundary determines the electrochemical activity. In addition, for high cathodic polarization, an electrolyte surface path with electron transfer via YSZ outperforms both other pathways. The oxygen incorporation zones of the bulk path as well as the electrolyte surface path can be visualized by 18O tracer incorporation experiments in combination with time-of-flight secondary ion mass spectrometry (ToF-SIMS) analysis. A successful separation of surface and bulk path can also be obtained for La0.8Sr0.2MnO3−δ (LSM) electrodes by means of 18O tracer incorporation at different cathodic overpotentials. Under lower polarization, a surface path with oxygen incorporation at the three-phase boundary is dominant, whereas at higher cathodic overpotential, the bulk path becomes significantly more pronounced. These changes are discussed in terms of polarization-induced changes of the ionic conductivity in the LSM electrode. Measurements on the acceptor-doped perovskite-type materials La0.6Sr0.4CoO3−δ (LSC) and La0.6Sr0.4FeO3−δ (LSF) illustrate the limitations of the tracer incorporation method. In the case of highly active LSC electrodes with low polarization resistances, the tracer distribution is determined by the electrolyte, and thus the active sites of the electrodes can no longer be visualized. The effect of polarization-induced changes of the electrode's electronic conductivity is demonstrated for LSF. Only a region close to the current collector remains electrochemically active owing to limited lateral electron transport. [ABSTRACT FROM AUTHOR]

This paper deals with the preparation and ion transport characteristics of a series of compositions in the solid-state mixed system [(SbI)-(AgSO)] where x = 10, 20, 30, 40, 50, 60, 70, 80, and 90 mol%, respectively. These samples have been characterized by powder X-ray diffraction, differential scanning calorimetry, Fourier transform infrared spectroscopy, ionic transport number, and impedance spectroscopic measurements. Among various compositions investigated, significant ones have possessed AgI as one of the constituent phases. Detailed electrical conductivity studies have shown that the observed ionic conductivity attains a maximum value of 2.1 × 10 S cm at room temperature (298 K) for the typical composition containing x = 60 mol%, whereas the corresponding values of transport number of silver ion as determined by Wagner's and EMF methods are found to be nearly unity. Interestingly, the enhanced ionic conduction of the chosen composite system may be attributed to the feasibility of formation of AgI in several compositions as a consequence of ion exchange reaction between SbI and AgSO. [ABSTRACT FROM AUTHOR]

We have investigated protic ionic liquids (PILs) as proton conductors for non-humidified intermediate-temperature fuel cells. PILs exhibit proton conductivity and activity in fuel cell electrode reactions, as seen in acidic aqueous solutions and acidic polymer membranes. The wide molecular designability of PILs enabled the finding of a promising candidate, diethylmethylammonium trifluoromethanesulfonate ([dema][ TfO]), which exhibits favorable bulk properties and electrochemical activity. Solid thin films containing [dema][ TfO] were fabricated using sulfonated polyimide as a matrix polymer. By using the composite membrane, non-humidifying fuel cell operation at 120°C succeeded. The fuel cell performance can be further improved by the optimization of the catalyst layer and with further research on PILs. [ABSTRACT FROM AUTHOR]

The proton conducting perovskite MZr1−xLnxO3−δHz ceramics are promising electrolytic membranes for fuel cell and water steam electrolyser applications. Simultaneous elastic/quasielastic and diffraction neutron studies were performed in a wide temperature range (25–1150 °C) on protonated Yb-modified BaZrO3 ceramics: dense (97% of theoretical density) and ultradense (99%) using the triple axis spectrometers. The results allowed us to determine: (i) the real content of bulk protonic species ∼1–5 10−3 mol/mol, (ii) the structural modifications caused by the proton doping, and (iii) the bulk proton dynamics. The quasielastic neutron scattering (QNS) results are discussed in the light of neutron diffraction, conductivity, Raman, thermogravimetric, and thermal expansion measurements. The highest bulk proton motion appears in the temperature range where the structural modifications and the energy activation changes are detected. This allows defining the optimum temperature range for the proton dynamics between 400 and 560 °C. [ABSTRACT FROM PUBLISHER]

Atomic force microscopy (AFM)-based impedance spectroscopy provides localized impedance information of materials and interfaces at the nanoscale by utilizing the conductive AFM tip as a moving electrode to detect current response as a function of time and frequency under controlled environments. This capability enables AFM-based nanoscale impedance measurements to play a unique role in enhancing our understanding of many electronic and electrochemical devices. This article introduces the central concepts of AFM-based impedance measurement and reviews recent examples applying this technique to a variety of functional materials systems, in particular focusing on fuel cells, lithium-ion batteries, photoactive biomembranes, as well as other application examples. [ABSTRACT FROM PUBLISHER]

The design and control of materials properties, often at the nanoscale, are the foundation of many new strategies for energy generation, storage, and efficiency. Scanning probe microscopy (SPM) has evolved into a very large toolbox for the characterization of properties spanning size scales from hundreds of microns to nanometers. Recent advances in SPM involve properties and size scales of precise relevance to energy-related materials, as presented in this issue. These advances are put into the general context of energy research, and the general principles are summarized. [ABSTRACT FROM PUBLISHER]

A range of material systems exist in which nanoscale ionic transport and redox reactions provide the essential mechanisms for memristive switching. One class relies on mobile cations, which are easily created by electrochemical oxidation of the corresponding electrode metal, transported in the insulating layer, and reduced at the inert counterelectrode. These devices are termed electrochemical metallization (ECM) memories, also called conductive bridge random access memories. The memristive characteristics of the ECM cells provide opportunities for circuit design and computational concepts that go beyond those in traditional complementary metal oxide semiconductor (CMOS) technology. Passive memory arrays open up paths toward ultradense and 3D stackable memory and logic gate arrays. Furthermore, the multivalued conductance characteristics allow for potential exploitation of the cells as synapses in neuromorphic circuits in future energy efficient high-performance computer architectures. Despite exciting results obtained in recent years, many challenges have to be met before these physical effects can be turned into competitive industrial technology. Here, we briefly review the basic working principle, the different possible and potential material combinations, and the fundamental electrochemical processes in ECM cells and their implications for device operations. The prospects of ECM-based resistive random access memory as an emerging memory technology are also reviewed in terms of switching speed and scalability. [ABSTRACT FROM PUBLISHER]

Ionic motion and electrochemistry in bulk materials and at their surfaces have long been studied for their relevance in several areas of science and technology, ranging from ionic conductors to batteries to fuel cells. The ability to engineer materials at the nanometer scale, however, has made these concepts even more relevant. This is due to the large surface-to-volume ratios typical of nanostructures. This implies, for instance, that chemical reactivity and defect motion at surfaces or interfaces are enhanced or may be fundamentally different compared to their bulk counterparts. In addition, nominally modest voltages or differences in chemical potential when applied across nanoscale distances can produce large electric fields and diffusive forces. While all of this may complicate the interpretation of experimental results, it also presents us with new opportunities for materials engineering. In this article, we will briefly review the current research status of several systems where ionic motion and electrochemical effects are of particular importance. These include resistive switching systems, oxide heterostructures, ferroelectric materials, and ionic liquids. We will report on experimental results and also emphasize open questions regarding their interpretation. We will conclude by discussing future research directions in the field. [ABSTRACT FROM AUTHOR]

The nanocrystalline samarium doped ceria powder of phase CeSmO was pelletized and sintered at about 1,623 K for the study of relaxation process. The impedance measurements were done within the frequencies from 1 Hz to 1 MHz for wide temperature range of 529-673 K. The temperature-dependent relaxation frequency found to be shifted towards higher frequency region from 17.26 to 707.96 KHz and the corresponding relaxation time for oxygen ions transport was varied from 9.22 to 0.22 μS. The temperature dependent conductivity and relaxation frequency revealed Arrhenius nature, showing activation energies 1.18 and 1.01 eV, respectively. This difference was attributed to pronounced interference due to the grain boundaries. The effect of sintering on microstructure of the sample was studied by using SEM and X-ray diffractometer (XRD). The structural and phase stability study was done by high-temperature (HT)-XRD. The thermal expansion coefficient of the samarium doped ceria powder determined from HT-XRD was found to be 13.9 × 10 K. [ABSTRACT FROM AUTHOR]

A new method of preparation of high performance fluoride ion conductor, BaSnF4, by water leaching of newly discovered barium tin(II) chloride fluorides, has been designed, and the materials have been studied and compared to the solid prepared by the usual dry method. The unit-cell parameters and crystallite dimensions were found to vary with the method of preparation. In addition, the crystallite dimensions were found to be highly anisotropic for the samples obtained by the wet method. The Mössbauer spectrum is made of a large tin(II) quadrupole doublet, and a broad tin(IV) oxide peak due to surface oxidation. The tin(II) spectrum is in agreement with covalently bonded tin(II) having a strongly stereoactive lone pair. An unusually high dependence of the quadrupole splitting at low temperatures was observed (5.8 times larger than for α-SnF2). [ABSTRACT FROM AUTHOR]

The elaboration of Na+ super-ionic conductor (NaSICON) ceramics is studied in this work. These solid electrolytes can be used as sensor for detection of polluted gases in air. Two sorts of ceramics with different chemical compositions are synthesised by soft chemistry route: a zirconium-based NaSICON and a hafnium-based NaSICON. DTA-TG and temperature depending X-ray diffractometry were used to follow the thermal decomposition of the precursor phases. The electrical properties of these ceramic sodium ionic conductors are investigated by complex impedance spectroscopy (CIS). The substitution of the zirconium by the hafnium increases the ceramic conductivity and decreases the activation energy E a (from 0.29 to 0.12 eV). [ABSTRACT FROM AUTHOR]

Organic-inorganic hybrid lithium ion conductors were prepared by the sol-gel process. The hybrid ion conductor will be used as the electrolyte for Li based high-energy density batteries. The hybrid ion conductor was prepared from a mixture of tetramethyl orthosilicate (TMOS), polyethylene glycol 200 (PEG200), lithium perchlorate (LiClO4) and water. A wet gel was prepared at room temperature. The gels dried at 80°C under vacuum did not contain water. The dried hybrid ion conductor gel had homogeneity and high transparency. Ionic conductivity of the hybrid sample was measured by the complex impedance method and it increased with increasing PEG200 content. The dried hybrid gel that contained no LiClO4 did not show ion conduction. Conductivity on the order of 10−5 S·cm−1 at room temperature was obtained. Structural characterization was done by Fourier Transform Infrared Spectra (FTIR) and NMR measurement of 13C and 1H, and the thermal stability and glass transition properties were studied by DSC. Glass transition temperature decreased with increasing PEG200 content and increased with increasing [Li]/[O] ratio (the oxygen considered is from the polyethylene glycol). Existence of the Si–O–(C2H4O) n–bond and the C–OH bond in the framework of the organic and inorganic phases was confirmed. TMOS and PEG200 were hydrolyzed and condensed. The organic and inorganic phases were chemically bonded and the microstructure of the hybrid matrix was shaped as comb. The comb shape leads to high ionic conduction. [ABSTRACT FROM AUTHOR]

AgI-AlO composites were fabricated by precipitating Agl grains within micropores of porous alumina pellets utilizing reaction between AgF and Nal solutions supplied from separately held containers. The effect of temperature of the Nal solution on the texture and morphology of the composites was studied. With respect to all the composites examined in this study, the initially formed part did not show grain orientation, while the subsequently formed part showed significant grain orientation, and the crystallite sizes along [001] and [hh0] at the initially formed part almost agreed with each other. With an increase in distance from the initially formed part, the crystallite size along [001] as well as that along [hh0] changed and the degree of the change depended on the temperature of the solution. A growth mechanism based on the experimental results is proposed. [ABSTRACT FROM AUTHOR]

Two groups of hybrid organic-inorganic composites exhibiting ionic conduction properties, so called ORMOLYTES (organically modified electrolytes), have been prepared by the sol-gel process. The first group has been prepared from mixture of a lithium salt and 3-isocyanatopropyltriethoxysilane(IsoTrEOS),O,O′-bis(2-aminopropyl)polypropyleneglycol. These materials produce chemical bonds between the organic (polymer) and the inorganic (silica) phases. The second group has been prepared by an ultrasonic method from a mixture of tetraethoxysilane (TEOS), polypropyleneglycol and a lithium salt. The organic and inorganic phases are not chemically bonded in these samples. The Li+ ionic conductivity, σ, of all these materials has been studied by AC impedance spectroscopy up to 100°C. Values of σ up to 10−6 Ω−1 · cm−1 have been found at room temperature. A systematic study of the effects of lithium concentration, polymer chain length and the polymer to silica weight ratio on σ shows that there is a strong dependence of σ on the preparation conditions. The dynamic properties of the Li+ ion and the polymer chains as a function of temperature between −100 and 120°C were studied using 7Li solid-state NMR measurements. The ionic conductivity of both families are compared and particular attention is paid to the nature of the bonds between the organic and inorganic components. [ABSTRACT FROM AUTHOR]