Ion-conducting Phase Research Articles

A Solid-Liquid Bicontinuous Fiber with Strain-Insensitive Ionic Conduction.

Stretchable ionic conductors are crucial for enabling advanced iontronic devices to operate under diverse deformation conditions. However, when employed as interconnects, existing ionic conductors struggle to maintain stable ionic conduction under strain, hindering high-fidelity signal transmission. Here, it is shown that strain-insensitive ionic conduction can be achieved by creating a solid-liquid bicontinuous microstructure. A bicontinuous fiber from polymerization-induced phase separation, which contains a solid elastomer phase interpenetrated by a liquid ion-conducting phase, is fabricated. The spontaneous partitioning of dissolved salts leads to the formation of a robust self-wrinkled interface, fostering the development of highly tortuous ionic channels. Upon stretch, these meandering ionic channels are straightened, effectively enhancing ionic conductivity to counteract the strain effect. Remarkably, the fiber retains highly stable ionic conduction till fracture, with only 7% resistance increase at 200% strain. This approach presents a promising avenue for designing durable ionic cables capable of signal transmission with minimal strain-induced distortion.

Facile Al2O3 coating suppress dissolution of Mn2+ in Mn-substituted Na3V2(PO4)3 with outstanding electrochemical performance for full sodium ion batteries

Na3V2(PO4)3 (NVP) encounters significant obstacles, including limited intrinsic electronic and ionic conductivities, which hinder its potential for commercial feasibility. Currently, the substitution of V3+ with Mn2+ is proposed to introduce favorable carriers, enhancing the electronic conductivity of the NVP system while providing structural support and stabilizing the NASICON framework. This substitution also widens the Na+ migration pathways, accelerating ion transport. Furthermore, to bolster stability, Al2O3 coating is applied to suppress the dissolution of transition metal Mn in the electrolyte. Notably, the Al2O3 coating serves a triple role in reducing HClO4 concentration in the electrolyte, inhibiting Mn dissolution, and functioning as the ion-conducting phase. Likewise, carbon nanotubes (CNTs) effectively hinder the agglomeration of active particles during high-temperature sintering, thereby optimizing the conductivity of NVP system. In addition, the excellent structural stability is investigated by in situ XRD measurement, effectively improving the volume collapse during Na+ de-embedding. Moreover, the Na3V5.92/3Mn0.04(PO4)3/C@CNTs@1wt.%Al2O3 (NVMP@CNTs@1wt.%Al2O3) possesses unique porous structure, promoting rapid Na+ transport and increasing the interface area between the electrolyte and the cathode material. Comprehensively, the NVMP@CNTs@1wt.%Al2O3 sample demonstrates a remarkable reversible specific capacity of 122.6 mAh/g at 0.1 C. Moreover, it maintains a capacity of 115.9 mAh/g at 1 C with a capacity retention of 90.2 mAh/g after 1000 cycles. Even at 30 C, it achieves a capacity of 87.9 mAh/g, with a capacity retention rate of 84.87 % after 6000 cycles. Moreover, the NVMP@CNTs@1wt.%Al2O3//CHC full cell can deliver a high reversible capacity of 205.5 mAh/g at 0.1 C, further indicating the superior application potential in commercial utilization.

Enhancing Fast-Charge Capabilities in Solid-State Lithium Batteries through the Integration of High Li0.5La0.5TiO3 (LLTO) Content in the Lithium-Metal Anode.

Solid-state batteries (SSBs), which have high energy density and are safe, are recognized as an important field of study. However, the poor interfacial contact with high resistance, the dendrite problem, and the volume change of the metallic lithium anode prevent the use of SSBs. Li0.5La0.5TiO3 (LLTO) particles and molten lithium were used to create a high-performance LLTO-Li composite lithium with a sequential ion-conducting phase. With garnet electrolytes, this lithium has better wettability and reduced surface tension. To compensate for the lithium depletion that occurs during stripping, the Li-Ti phase with a high ionic diffusion coefficient that forms in the anode can rapidly transport lithium from the bulk to the solid-state interface, ensuring tight interface contact, preventing the formation of gaps, and homogenizing the current and Li+ flux. The LLTO-Li| LLZTO| LLTO-Li symmetric cell exhibits a good cyclic stability of 1000 h at room temperature, a low interfacial resistance of 22 Ω cm2, and a high critical current density of 1.2 mA cm-2. Furthermore, fully built cells with a LiFePO4 cathode showed outstanding cycling performance, maintaining 95% of their capacity after 900 cycles at 1 C and 92% capacity retention after 100 cycles at 2 C.

Lanthanide element variation in rare earth doped ceria – FeCo2O4 dual phase oxygen transport membranes

The increased interest in dual-phase membrane materials for oxygen separation leads to the continuous optimization of their composition. Rare-earth doped ceria is a promising candidate as the ion-conducting phase in the membrane. Spinel-structured FeCo2O4 was investigated as an electronic conducting phase forming an additional electronic conducting perovskite-structured phase during sintering when combined with Ce1−xLnxO2−δ. The influence of rare-earth lanthanide elements, i.e., Gd and Sm, as well as their concentration, i.e. x = 0.1 and 0.2, on the final phase composition and microstructure as well as its related functional properties in particular oxygen permeation is analyzed. 20 mol.% doping of either Gd or Sm reveals a multi-phase microstructure after sintering. Moreover, segregation of Gd/Sm, iron, and cobalt is found at the ceria-ceria grain boundaries in Ce0.8Sm0.2O2−δ- and Ce0.9Gd0.1O2−δ-based composites. In contrast, 10 mol.% Gd–doping leads to a dual-phase membrane material without the formation of any other phase. In all cases, the percolation threshold is reached at approx. 20 vol% of the electron-conducting phase in the system leading to similar maximum permeation rates determined by the ionic conductivity of the ceria phase.

Structural, morphological and photocatalytic properties of nanostructured TiO2/AgI photocatalyst

Nanostructured TiO2/AgI photocatalyst under the action of ultraviolet or visible electromagnetic radiation effectively neutralizes organic pollutants in the aqueous environment. It is a nanostructure in which micro- and small mesopores of anatase TiO2 are filled with silver iodide in the superionic state. The content of the α-AgI ion-conducting phase in the volume of ТіО2 pores can be ~20 wt %.
 To obtain a photocatalyst, titanium dioxide is synthesized by the sol-gel method, using a titanium aquacomplex solution [Ti(OH2)6]3+•3Cl- and a Na2CО3 modifier additive as a precursor. The modifying additive during synthesis ensures the fixation of =О2СО carbonate groups on the surface of oxide material particles. The presence of these groups leads to an increase in both the pore volume and the specific surface area of ТіО2. The specific surface area of carbonized titanium dioxide is 368 m2•g-1, the pore volume is 0.28 cm3•g-1, and their size is 0.9-4.5 nm.
 To fill the micro- and small mesopores of TiO2 with the superionic α-AgI phase, Ag+ cations are first adsorbed from the AgNO3 solution on the titanium dioxide surface, and then the oxide material is contacted with the KI solution.
 Compared to the Evonik P25-TiO2 photocatalyst, the nanostructured TiO2/AgI photocatalyst demonstrates a significantly higher efficiency of photodegradation of organic dyes Congo Red and Methyl Orange in visible and ultraviolet radiation. The most active ТіО2/40AgI sample achieved complete degradation of the CR dye in 6 minutes of UV irradiation, while the efficiency of commercial Р25-TiO2 over the same time was only 42%.

Temperature and pressure sensitive ionic conductive triple-network hydrogel for high-durability dual signal sensors

In this work, the fabrication of strengthened triple network hydrogels was successfully achieved based on in-situ polymerization of polyacrylamide by combining both chemical and physical cross-linking methods. The ion conductive phase of lithium chloride (LiCl) and solvent in the hydrogel were regulated through soaking solution. The pressure and temperature sensing behavior and durability of the hydrogel were investigated. The hydrogel containing 1 mol/L LiCl and 30 %v/v glycerol displayed a pressure sensitivity of 4.16 kPa−1 and a temperature sensitivity of 2.04 %/oC ranging from 20 to 50 °C. The durability results reveal that the hydrogel could maintain water retention rate of 69 % after 20 days of ageing. The presence of LiCl disrupted the interactions among water molecules and made it possible for the hydrogel to respond to changes in environment humidity. The dual signal testing revealed that the delay of temperature response over time (about 100 s) is much different from the rapidity of pressure response (in 0.5 s). This leads to the obvious separation of the temperature–pressure dual signal output. The assembled hydrogel sensor was further applied to monitor human motion and skin temperature. The signals can be distinguished by different resistance variation values and curve shapes in the typical temperature–pressure dual signal performance of human breathing. This demonstrates that this ion conductive hydrogel has the potential for application in flexible sensors and human–machine interfaces.

Topological Data analysis of Ion Migration Mechanism.

Topological data analysis based on persistent homology has been applied to the molecular dynamics simulation for the fast ion-conducting phase (α-phase) of AgI to show its effectiveness on the ion migration mechanism analysis. Time-averaged persistence diagrams of α-AgI, which quantitatively record the shape and size of the ring structures in the given atomic configurations, clearly showed the emergence of the four-membered rings formed by two Ag and two I ions at high temperatures. They were identified as common structures during the Ag ion migration. The averaged potential energy change due to the deformation of the four-membered ring during Ag migration agrees well with the activation energy calculated from the conductivity Arrhenius plot. The concerted motion of two Ag ions via the four-membered ring was also successfully extracted from molecular dynamics simulations by our approach, providing new insight into the specific mechanism of the concerted motion.

Composite lithium with high ionic conducting Li3Bi alloy enabled high-performance garnet-type solid-state lithium batteries

Solid-state lithium metal batteries (SSLMBs) are regarded as an important development direction due to their high energy density and safety. Nevertheless, the application of SSLMBs is hampered by the poor interfacial contact with large resistance and dendrite issue, as well as volume variation of metallic lithium anode. Here, a high-performance Li-BiF3 composite lithium having successive ion-conducting phase was constructed via the conversion reaction between commercial BiF3 powders and molten lithium, which shows reduced surface tension of lithium and improved wettability toward Li6.4La3Zr1.4Ta0.6O12 electrolytes. The as-formed Li3Bi in the anode with high ionic diffusion coefficient can quickly transport lithium from the bulk to the solid-state interface to compensate for the lithium depletion during stripping, thus ensuring tight interface contact, inhibiting the generation of gaps, and homogenizing current and Li+ flux. The Li-BiF3/LLZTO/Li-BiF3 symmetric cells present small interfacial resistance (7.4 Ω cm2), large critical current density (1.1 mA cm−2) and superior cyclic stability of 850 h under 0.3 mA cm−2 at 25 °C. In addition, full cells assembled together with LiFePO4 and LiNi0.8Co0.1Mn0.1O2 cathodes demonstrate exceptional cyclic performance with 92.9% and 86.5% capacity maintenance upon 100 cycles under 0.5 C.

Boosting the performance and durability of heterogeneous electrodes for solid oxide electrochemical cells utilizing a data-driven powder-to-power framework

Solid oxide electrochemical cells (SOCs) hold potential as a critical component in the future landscape of renewable energy storage and conversion systems. However, the commercialization of SOCs still requires further breakthroughs in new material development and engineering designs to achieve high performance and durability. In this study, a data-driven powder-to-power framework has been presented, fully digitizing the morphology evolution of heterogeneous electrodes from fabrication to long-term operation. This framework enables accurate performance prediction over the full life cycle. The intrinsic correlation between microstructural parameters and electrode durability is elucidated through parameter analysis. Rational control of the ion-conducting phase volume fraction can effectively suppress Ni coarsening and mitigate the excessive ohmic loss caused by Ni migration. The initial and degraded electrode performances are attributed to the interplay of multiple parameters. A practical optimization strategy to enhance the initial performance and durability of the electrode is proposed through the construction of the surrogate model and the application of the optimization algorithm. The optimal electrode parameters are determined to accommodate various maximum operation time requirements. By implementing the data-driven powder-to-power framework, it is possible to reduce the degradation rate of Ni-based electrodes from 2.132% to 0.703% kh−1 with a required maximum operation time of over 50,000 h.

A continuum theory of organic mixed ionic-electronic conductors of phase separation

Organic mixed ionic-electronic conductors (OMIECs) are the core functioning component in the emerging flexible, bio-, and optoelectronics owning to their unique capability of mixed conduction. Of all types, two-phase OMIECs exhibit exceptional performance due to their high stretchability and balanced ionic-electronic conduction. However, the electron-conducting phase may segregate from the ion-conducting phase in a two-phase OMIEC, changing the conducting path and eventually leading to degraded performance and dysfunction of the devices. In this work, we formulate a continuum theory following the thermodynamics framework of a two-phase OMIEC undergoing phase separation. The free energy consists of contributions from the deformation of the polymer chains, the mixing of the polymer with salts and solvents, the electrostatic field, and the two-phase interfaces. The equilibrium conditions and kinetics equations are derived with the constraint of mass conservation, thermodynamics laws, and electrostatics. We implement the theory into a finite element model and study the mechanics and electrochemistry of the OMIEC channel in an electrolyte-gated organic electrochemical transistor (OECT) device. The computational model captures the concurrent transport of charge carriers, mechanical swelling, and phase separation in the OMIEC and replicates the transfer curves of an OECT which agree well with the experiments. More specifically, we reveal the origin of the volumetric capacitance as the accumulation of charge carriers at the two-phase interfaces. We examine the parametric space to elucidate experimental observations such as molecular size-dependent conductivity and substrate-dependent phase separation. The swelling behavior and the transfer curves of OECTs under stretched, free, and constrained states are compared, demonstrating the effects of deformation on the phase dynamics and the electron-conducting behavior. We show that, for volumetric swelling and the electrochemical transfer curves, the effect of stress-transport coupling dominates while the effect of the Maxwell stress is negligible. This work provides a theoretical basis for the mechanics and electrochemistry of two-phase OMIECs.

High-resolution patterning of silica nanoparticle-based ionogels by reverse-offset printing and its characterization

In this study, nanoparticle-based, high-resolution patternable ionogels are presented to provide a route for realizing printed solid-state ionic devices. By incorporating an ionic liquid (IL) into a spherical silica nanoparticle suspension, a quasi-solid ionogel layer compatible with reverse-offset printing (ROP) with a spatial resolution of approximately 5 μm was realized. In situ near-infrared (NIR) spectroscopic analysis revealed the drying kinetics of the ionogel ink during printing, and a temporal margin for successful patterning in relation to its dry state was provided. In contrast to polymer-based gels, the present ionogel can be regarded as a porous medium of silica filled with ionic liquids with a certain degree of saturation. By optimizing the ink formulations, ROP patterning was successful for saturation up to 102%, indicating the nanoscale pores between silica nanoparticles can be fully used as an ion-conductive phase in the proposed patternable gel. The conductivity depends drastically on saturation, with a saturation exponent of approximately −7 according to Archie’s law. From a complementary scratch test, an ionogel at a saturated condition still exhibited fragile but solid-like characteristics. As a demonstration, planar micro-supercapacitors fully printed with reverse-offset printable ionogel and carbon inks were fabricated. A comparison with a drop-casted IL showing a similar capacitance indicates a limited ability of the carbon nanoparticle material used here, while a relatively high resistance of the silica-nanoparticle-based ionogel hinders a fast cyclic voltammetry response.

Increasing the performance of all-solid-state Li batteries by infiltration of Li-ion conducting polymer into LFP-LATP composite cathode

Polymer-ceramic composites combine the benefits of polymers and ceramics. In particular, the infiltration of the ceramic cathode with a Li-ion-conducting polymer in an all-solid-state Li battery enhances the utilization of the cathode active material (CAM) and enables the application of thicker cathodes with higher storage capacity. This concept has already been validated in our earlier work, in which a porous LiCoO2–Li6.45Al0.05La3Zr1.6Ta0.4O12 (LLZO:Al:Ta) composite cathode was fabricated by spark plasma sintering (SPS) technique. However, its performance stability was low. In the present work, the concept is modified using an LFP-LATP cathode with LiFePO4 as the CAM, Li1.5Al0.5Ti1.5(PO4)3 as the ion-conducting phase, and tape-casting with free sintering instead of SPS. Both tape-casting and free sintering are more relevant for large-scale production. The sintered LFP-LATP cathode is infiltrated with the MEEP polymer and LiC2NO4F6S2 ion-conducting salt. A full cell with the polymer-infiltrated cathode, LLZO:Al:Ta separator, and Li anode shows nearly full LFP utilization in the 100 μm thick cathode with an excellent area-specific storage capacity of above 3 mAh cm−2. However, after a few dozen cycles, a Li dendrite penetrates the separator leading to abrupt capacity fading. The prevention of Li dendrite formation remains a challenge for our future work.

Точечные дефекты висмута в кристаллах TlInTe-=SUB=-2-=/SUB=-, электрофизические и диэлектрические свойства твердых растворов

In this work, to determine the solubility of bismuth in TlInTe2 crystals by the methods of physicochemical analysis, we studied the phase diagram of TlInTe2 - Bi in the concentration range of 0-10 at.% Bi and studied the electrical and dielectric properties of (TlInTe2)1-x Bix solid solutions. Analyzing the obtained experimental data, we assume that bismuth atoms, penetrating into the TlInTe2 lattice, form interstitial solid solutions, occupying octahedral voids between thallium atoms in the crystallographic direction 001 (z = 0.5). The influence of bismuth impurities on the dielectric properties of TlInTe2 crystals is also observed, while forming barriers to the movement of thallium ions, bismuth impurities increase the temperature of the phase transition to the ion-conductive phase (Ti): in the crystallographic direction 001-69 K, and in the direction 110-87 K.

Composite of Ca-Cobaltite with Pr-Doped Ceria as Oxygen Electrode for Solid Oxide Electrochemical Cells

A growing interest in the development of solid oxide electrochemical systems, including solid oxide fuel cell (SOFC) and solid oxide electrolyser cells (SOEC) has increased the demand for new electrode materials that can offer superior electrochemical performance. The misfit-layered Ca cobaltite ([Ca2CoO3-δ]0.62[CoO2], C349) has emerged as a potential oxygen electrode for solid oxide cells (SOCs), in recent years, due to its optimal electrical conductivity (~100 S cm-1, from room temperature to 800 °C), excellent thermal compatibility with typical electrolyte materials, its low cost and its avoidance of Sr surface segregation issues that can deplete the electrochemical performance in more common oxygen electrodes 1,2. Its structure consists of two monoclinic subsystems of layers of Ca2CoO3 (three-layered rock salt-type block, CaO-CoO-CaO) and CoO2 (triangular lattice), stacked along the c-axis 3. This compound offers mixed ionic and electronic conduction (MIEC), where the first subsystem is responsible for the ionic conductivity, due to its higher oxygen deficiency, while the second subsystem is responsible for the electronic behaviour. Nonetheless, the level of ionic conductivity of C349 is, comparatively, low, and this factor has prevented it from attaining a competitive electrode performance 4, to date when compared to peak electrode materials, such as La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF). For this reason, we overcome this limitation in this study by the addition of a predominately ion-conducting phase with a minor p-type electron-conductivity, Ce0.8Pr0.2O1.9 (CPO) to the C349 material. This new composite electrode is compared against the standard, high performing, electrode material LSCF in terms of microstructure, film thickness, and subsequent electrochemical properties.Symmetrical cell assemblies were fabricated by a cheap and simple screen-printing technique using Ce0.9Gd0.1O1.95 electrolytes and repeated depositions were performed to investigate the electrode thickness effect.A minimum R p value can be found for the C349-based electrodes with 5 depositions (70 – 85 μm). By comparison to the state-of-the-art LSCF electrode, C349 has been shown to require a higher solid volume fraction close to the electrolyte/electrode interface for continuing to maximise the penetration of the ionic current into the electrode bulk and for extending the electrochemically active region for oxygen exchange at the gas/electrode interface. The presence of a higher solid fraction of material benefits the oxygen exchange/reaction processes, with additional surface diffusion. Furthermore, the addition of CPO to the C349 electrode is shown to dramatically lower its polarisation resistance, allowing this composite to achieve a competitive electrochemical performance to that of the state-of-the-art LSCF electrode (0.37 and 0.52 Ω·cm2, at 700 °C in oxygen atmosphere, respectively). Overall, a Gerischer contribution can explain the experimental R p of the electrodes (except in the case of the C349 sample with just one deposition). These results are further supported by a detailed mechanistic study, based on a Distribution Function of Relaxation Times (DFRT) analysis, to understand the origin of this improvement as a function of electrode morphology and composition.The successful outcome of this work is extremely important as it provides not only a highly competitive new electrode composition, but also valuable insight into future optimisation methods for similar new mixed ionic-electronic conducting electrodes that intrinsically suffer from low levels of oxygen diffusion. AcknowledmentsThis study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001. Allan J. M. Araújo acknowledges the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq/Brazil, reference number 200439/2019-7). João P. F. Grilo, Carlos A. Paskocimas and Daniel A. Macedo also thank CNPq/Brazil (482473/2010-0, 446126/2014-4, 308548/2014-0, 307236/2018-8, 431428/2018-2 and 309430/2019-4). Laura I. V. Holz acknowledges Fundação para a Ciência e Tecnologia (FCT) for the PhD grant PD/BDE/142837/2018. The authors also acknowledge the projects, PTDC/CTM-CTM/2156/2020, PTDC/QUI-ELT/3681/2020, POCI-01-0247-FEDER-039926, POCI-01-0145-FEDER-032241, UIDB/00481/2020 and UIDP/00481/2020 and CENTRO-01-0145-FEDER-022083 - Centro Portugal Regional Operational Programme (Centro2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF). References1 K. Nagasawa, S. Daviero-Minaud, N. Preux, A. Rolle, P. Roussel, H. Nakatsugawa and O. Mentré, Chem. Mater., 2009, 21, 4738–4745.2 S. P. Simner, M. D. Anderson, M. H. Engelhard and J. W. Stevenson, Electrochem. Solid-State Lett., 2006, 9, A478–A481.3 M. Schrade, H. Fjeld, T. G. Finstad and T. Norby, J. Phys. Chem. C, 2014, 118, 2908–2918.4 V. Thoréton, Y. Hu, C. Pirovano, E. Capoen, N. Nuns, A. S. Mamede, G. Dezanneau, C. Y. Yoo, H. J. M. Bouwmeester and R. N. Vannier, J. Mater. Chem. A, 2014, 2, 19717–19725.

Solvothermal synthesis high lithium ionic conductivity of Gd-doped Li1.3Al0.3Ti1.7(PO4)3 solid electrolyte

NASICON-type [Formula: see text][Formula: see text][Formula: see text]([Formula: see text] (LATP) solid electrolytes have been widely studied because of its stability in the air, low material price and high ionic conductivity. Gd-doped [Formula: see text]Al[Formula: see text][Formula: see text][Formula: see text]([Formula: see text] ([Formula: see text]= 0, 0.025, 0.05, 0.075 and 0.1) with high ionic conductivity was successfully synthesized by solvothermal method for the first time in this work. The effect of Gd doping content on the structure and electrochemical performance of solid electrolytes was systematically studied. The optimal doping content of Gd is [Formula: see text]= 0.075. With the Gd doping content of 0.075, the solid electrolyte has the highest ionic conductivity of 4.23 × 10[Formula: see text] S cm[Formula: see text] at room temperature, the lowest activation energy of 0.247 eV and the highest relative density of 94.89%. This is because the fact that when [Formula: see text]= 0.075, it is the maximum content of Gd[Formula: see text] to replace Al[Formula: see text] and can completely enter the lattice of LATP, and does not emerge too much non-lithium ion conductive GdPO4 phase.

Synergistic electron doping and ion conductive phase incorporating of SrCoO3-δ as desirable cathode materials for intermediate-temperature solid oxide fuel cells

Mixed conducting perovskite-structured oxides are desirable catalysts toward the oxygen reduction reaction (ORR) process. Pure cubic perovskite-structured SrCoO3–δ is a promising class of mixed conductors with high ORR activity. However, it suffers from structural instability and thermal incompatibility at elevated temperatures, thereby impeding its practical application in intermediate-temperature solid oxide fuel cells (IT-SOFCs). In this work, A-site electron doping in SrCoO3–δ was conducted to chemically compensate for the loss of lattice oxygen, thus improving the structural stability of SrCoO3–δ. Among the as-prepared Y-doped Sr1−xYxCoO3−δ (x = 0.05–0.20) samples, 10 mol% Y-doping of Sr0·9Y0·1CoO3–δ (SYC10) experimentally exhibits desirable electrical conductivity and lowest area specific resistance (ASR) while maintaining structural stability at elevated temperatures. The results are confirmed by first-principles calculations that involve density of states and oxygen vacancy formation energy. In addition, Gd0.1Ce0·9O1.95 incorporation further improves the thermal compatibility and cell performance, where the measured thermal expansion coefficients between 30 °C and 1000 °C decrease from 23.3 × 10−6 K−1 for SYC10 to 19.0 × 10−6 K−1 for SYC10–40GDC, and the corresponding ASRs with La0·9Sr0.1Ga0.8Mg0·2O3–δ electrolyte decrease from 0.080 Ω cm2 to 0.044 Ω cm2 at 700 °C. Results suggest that SYC10–40GDC is a desirable cathode material for IT-SOFCs.

The tortuosity factor effect on solid oxide fuel cell performance

In this work, the three-dimensional (3-D) microstructure of Solid Oxide Fuel Cell (SOFC) composite electrode is reconstructed by a random particle packing procedure and a geometrical dilating process, based on which the different tortuosity factors (τ) are calculated by solving the steady state charge conservation equation in different percolated networks. After that, the effects of the different τ on cell performance are analyzed by a one-dimensional (1-D) SOFC performance simulation model, in which the electrochemical reactions and the gas/ion/electron transport are coupled. The results indicate that the tortuosity factor of the ion-conducting phase in SOFC cathode (τio,c) plays the most important role and up to 62% SOFC performance improvement can be expected by decreasing τio,c. In addition, by decreasing the tortuosity factor of the gas phase (τgas,a) and the ion-conducting phase in SOFC anode (τio,a), 1.7% and 17% performance improvement can be achieved, respectively. This work could help improving SOFC performance by modifying the tortuous transport paths in SOFC porous electrodes.

Humidity-Controlled Water Uptake and Conductivities in Ion and Electron Mixed Conducting Polythiophene Films.

Mixed conducting polymer films are of great interest in applications where an interface between electronic and ionic charge transport is needed, e.g., in bioelectronics, electrochemical energy applications, and photovoltaic device interfaces. The role of water on charge transport is of high relevance not only for aqueous environments but also for devices that are manufactured at ambient conditions with varying relative humidities. In this contribution, we present our results on the influence of controlled humidity changes on the mixed conductivity and correlation to the concomitant water uptake in the films. Two sulfonate-bearing polythiophene systems are studied: a self-made conjugated polyelectrolyte, poly(6-(thiophen-3-yl)hexane-1-sulfonate)-sodium (PTS-Na), and poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) with different ratios of PEDOT and the polyelectrolyte PSS. Our data give clear evidence of the similarities between the aforementioned polythiophene systems and pure ionic membranes such as Nafion used in fuel cells. As such, a phase separation between the hydrophobic electronically conducting polythiophene phase and the hydrophilic water-swellable ion-conducting phase is proposed. Changing the humidity from dry conditions up to ∼90% relative humidity results in extremely high water uptakes of more than 90 wt %, which corresponds to ∼13 water molecules per sulfonate unit at maximum water uptake. Conversely, the electronic conductivity is less sensitive to increasing humidity, which is due to percolation pathways. The ionic conductivity strongly increases from 10-10 S/cm at dry conditions to 10-3 S/cm at around 30 wt % water content and then levels off at maximum conductivities of 10-3-10-2 S/cm up to water contents of 90 wt %.

Exploring Ni(Mn1/3Cr2/3)2O4 spinel-based electrodes for solid oxide cells

The alkaline earth element- and cobalt-free Ni(Mn1/3Cr2/3)2O4 spinel is used to form composite electrodes with an oxygen ion conductive phase for symmetrical solid oxide cells, and applied successfully in both solid oxide fuel cell and solid oxide electrolysis cell modes.

Impact of Morphological and Structural Changes on Performance of Solid Oxide Cells

The durable performance of solid oxide cells (SOCs) is of great importance in their large-scale utilization. However, the degradation processes, especially the degradation of electron and ion conductive phase interface impair SOCs performance. Significant sources of such interfaces degradation represent morphological and structural changes of materials. To minimize these processes, their detailed understanding is necessary. Therefore, a series of SOCs were fabricated from commercial powders to study mechanisms of these changes under different operation conditions. Each cell was examined by electrochemical as well as by spectroscopic methods. Degradation processes were observed at electron and ion conductive phases contacts and their origin discussed.