Thin Film Electrolyte Research Articles

(Invited) Effect of Anode Thickness on Thin-Film Solid Oxide Fuel Cells Deposited on Nanoporous Substrates

In this study, low-temperature solid oxide fuel cells having different thin-film anode thicknesses were fabricated, and their characteristics were studied. Since the low-temperature solid oxide fuel cells (LT-SOFCs) have the advantages of a low-cost fuel cell system and a wide selection of components’ materials, many researchers have made efforts to lower the operating temperature range. Naturally, thin-film electrolyte technology has been improved to reduce the exponentially increasing ohmic resistance of oxygen conduction when the working temperature is lowered. Various substrates or even no substrate were used to fabricate thin-film solid oxide fuel cells (TF-SOFCs). However, free-standing TF-SOFCs have poor mechanical strength, and the active area was limited to tens of square micrometers. A nanoporous substrate such as Anodic aluminum oxide (AAO) has been a great platform on which TF-SOFCs were stably deposited and operated. AAO has well-arranged and straight pores from its bottom to the top but no electrical conductivity. Due to the resistance characteristics of TF-SOFCs based on AAO, the anode’s thickness and the nanostructure significantly influence the overall performance of the fuel cell. According to previous studies, the performance tends to increase as the thickness increases with well-maintained porosity in the thin-film anode. To confirm this tendency and further improve cell performance, AAO substrates with 250nm-size pores and relatively rough surfaces were used. On the AAO substrate, nickel gadolinium-doped-ceria (Ni-GDC) mixed ionic and electronic conductor (MIEC) was introduced as the anode material, which increased hydrogen oxidation reaction (HOR) reactivity at the anode. In addition, the glancing angle deposition (GLAD) of the sputtering method was applied to maintain porosity better than the conventional method. With this method, thickening the thin-film anode improved the current collecting performance while the pores were well connected to the anode-electrolyte interface. Following that, the yttria-stabilized zirconia (YSZ) electrolyte was densely deposited, and the porous deposited platinum cathode completed the entire cell. The fabricated cells were tested at 500C and electrochemically analyzed by i-V-P curves and the EIS method. Also, the anode’s nanostructures were revealed by various analyzing methods such as surface FESEM, FIB cross-sectional SEM, TEM-EDS, and 4-probe conductivity measurement. Each cell’s stable structure and the uniformity of some fuel cell components such as the electrolyte and the cathode were confirmed. We found that the electrochemical performance increases as the anode thickness increases while its porosity is well-maintained. About 550mW/cm2 was measured as the highest maximum power density, which is more than a 20% increased result than the other fabricated cells. Those investigations also enabled the anode nanostructure to be identified, such as the anode thin-film porosity, conductivity, and three-dimensional morphology. The correlation between the anode nanostructure and the fuel cell performance was discussed, and the optimized cell structure was found. This study enlarged the understanding of nanoporous substrate-based TF-SOFC manufacturing and their expandability.

Review on the preparation of electrolyte thin films based on cerate-zirconate oxides for electrochemical analysis of anode-supported proton ceramic fuel cells

Proton ceramic fuel cells (PCFCs) are a better alternative to the combustion-based electrical generators because of their high energy conversion efficiency and low carbon emission at relatively low operating temperatures. The electrochemical performance of PCFCs in terms of conductivity, cycling stability, and power density is heavily influenced by the morphological and compositional characteristics of the electrolyte materials. These characteristics can be controlled during the synthesis and fabrication processes. Microstructural modification of the proton ceramic electrolyte can further optimize the electrochemical performance and enhance the efficiency of PCFCs. The well-known electrolyte materials derived from cerate–zirconate ceramic perovskite-type oxides show incredibly high proton conductivity in hydrogen- and/or water-containing atmospheres. This review aims to discuss the influence of electrolyte synthesis and fabrication techniques on the electrochemical properties of PCFCs. Results and findings from different studies are explored and analyzed to examine the effects of grain size, sample density, sintering temperatures, and the addition of metal oxides on the electrolyte performance of PCFCs. • Electrolyte based on cerate-zirconate oxides for PCFCs application is reviewed in the context of fabrication techniques. • Selection of the aright fabrication technique can produce the required microstructure of the targeted proton conductor. • The microstructure of the electrolytes has remarkable impacts on the PCFCs performance.

Monolithic All-Solid-State High-Voltage Li-Metal Thin-Film Rechargeable Battery.

The substitution of an organic liquid electrolyte with lithium-conducting solid materials is a promising approach to overcome the limitations associated with conventional lithium-ion batteries. These constraints include a reduced electrochemical stability window, high toxicity, flammability, and the formation of lithium dendrites. In this way, all-solid-state batteries present themselves as ideal candidates for improving energy density, environmental friendliness, and safety. In particular, all-solid-state configurations allow the introduction of compact, lightweight, high-energy-density batteries, suitable for low-power applications, known as thin-film batteries. Moreover, solid electrolytes typically offer wide electrochemical stability windows, enabling the integration of high-voltage cathodes and permitting the fabrication of higher-energy-density batteries. A high-voltage, all-solid-state lithium-ion thin-film battery composed of LiNi0.5Mn1.5O4 cathode, a LiPON solid electrolyte, and a lithium metal anode has been deposited layer by layer on low-cost stainless-steel current collector substrates. The structural and electrochemical properties of each electroactive component of the battery had been analyzed separately prior to the full cell implementation. In addition to a study of the internal solid–solid interface, comparing them was done with two similar cells assembled using conventional lithium foil, one with thin-film solid electrolyte and another one with thin-film solid electrolyte plus a droplet of LP30 liquid electrolyte. The thin-film all-solid state cell developed in this work delivered 80.5 mAh g–1 in the first cycle at C/20 and after a C-rate test of 25 cycles at C/10, C/5, C/2, and 1C and stabilized its capacity at around 70 mAh g–1 for another 12 cycles prior to the start of its degradation. This cell reached gravimetric and volumetric energy densities of 333 Wh kg–1 and 1,212 Wh l–1, respectively. Overall, this cell showed a better performance than its counterparts assembled with Li foil, highlighting the importance of the battery interface control.

Magnetron sputtered LSC-GDC composite cathode interlayer for intermediate-temperature solid oxide fuel cells

The paper investigates the influence of the La0.6Sr0.4CoO3-δ-Gd0.1Ce0.9O1.95 (LSC-GDC) composite cathode interlayer on the operation of solid oxide fuel cells (SOFCs). Thin composite layers with the different GDC content are obtained by the reactive magnetron sputtering. The impact of the high-temperature annealing on the LSC-GDC phase composition is studied by the X-ray diffraction instrument using additionally a synchrotron radiation. The NiO-YSZ anodes with the YSZ electrolyte thin film and GDC barrier layer are used for the SOFC fabrication. The current-voltage curves and impedance spectra of SOFCs are obtained in the temperature range of 700–800°С. It is shown that not annealed composite layers with ∼50 vol% GDC content possess the most efficient electrochemical activity. The maximum power density of the SOFC with the LSC-GDC interlayer is 1322, 1041 and 796 mW/cm2 at 800, 750 and 700 °C, respectively, which is 20–35% higher than that of the cell without cathode interlayer.

The Properties of Intermediate-Temperature Solid Oxide Fuel Cells with Thin Film Gadolinium-Doped Ceria Electrolyte.

Mixed ionic-electronic conducting materials are not used as a single-layer electrolyte of solid oxide fuel cells (SOFCs) at relatively high operating temperatures of ~800 °C. This is because of a significant decrease in the open-circuit voltage (OCV) and, consequently, the SOFC power density. The paper presents a comparative analysis of the anode-supported SOFC properties obtained within the temperature range of 600 to 800 °C with yttria-stabilized zirconia (YSZ) electrolyte and gadolinium-doped ceria (GDC) electrolyte thin films. Electrolyte layers that are 3 µm thick are obtained by magnetron sputtering. It is shown that at 800 °C, the SOFC with the GDC electrolyte thin film provides an OCV over 0.9 V and power density of 2 W/cm2. The latter is comparable to the power density of SOFCs with the YSZ electrolyte, which is a purely ionic conductor. The GDC electrolyte manifests the high performance, despite the SOFC power density loss induced by electronic conductivity of the former, which, in turn, is compensated by its other positive properties.

Effect of Sputtering Pressure on the Nanostructure and Residual Stress of Thin-Film YSZ Electrolyte

Solid oxide fuel cells are energy conversion devices that contribute to carbon neutrality, with the advantages of high efficiency, clean emissions production, and distributed power generation. However, the high operating temperature of the solid oxide fuel cells causes system stability and material selection problems. In this study, we aimed to lower the operating temperature of a solid oxide fuel cell by reducing the thickness of the electrolyte via sputtering. The deposition process was conducted under various pressure conditions to find the optimal sputtering process for a gas-tight YSZ thin-film electrolyte. The gas-tightness of the YSZ electrolytes was evaluated by observing the nanostructure and cell performance. As a result, the YSZ thin-film deposited at 3 mTorr showed the best gas-tightness and cell performance. At 500 °C, 1.043 V of OCV and a maximum power density of 1593 mW/cm2 were observed. Then, X-ray diffraction was used to calculate the residual stress of the YSZ films. As a result, it was confirmed that the gas-tight film showed compressive residual stress. Through this study, we were successful in developing a room-temperature YSZ electrolyte fabrication process with excellent gas-tightness and performance. It was also proven that there is a strong relationship between the gas-tightness and residual stress. This study is expected to contribute to cost reductions and the mass production of solid oxide fuel cells.

Preparation of an yttria-stabilized zirconia electrolyte on a porous Ni-based cermet substrate by laser chemical vapor deposition

This work investigated the use of laser chemical vapor deposition (LCVD) to apply an yttria-stabilized zirconia (YSZ) thin film electrolyte to a porous Ni metal/YSZ substrate. Using this process, a dense YSZ film having a columnar structure and small grain sizes was successfully fabricated on a porous cermet substrate at a relatively low temperature of approximately 700 °C. A 15 µm thick film was obtained following a deposition time of only 20 min. Solid oxide fuel cell (SOFC) power generation tests were performed using the sample on which YSZ was deposited and stable power generation was observed. However, the open circuit voltages were lower than the theoretical values and the ohmic loss of the specimen was significantly higher than that estimated from the conductivity of YSZ. These inferior performance parameters can possibly be attributed to the formation of cracks in the electrolyte film during the SOFC test, and thus enhanced performance could be obtained by suppressing crack formation. In addition, the reason for the crack formation was also discussed in this work.

Infiltrated nano-CeO2 and inserted Ni-Fe active layer in a tubular cathode substrate for high temperature CO2 electrolysis on solid oxide cells using La0.9Sr0.1Ga0.8Mg0.2O3−δ thin film electrolyte

A tubular type solid oxide cell which consists of a NiO-Y 2 O 3 stabilized ZrO 2 (YSZ) tubular cathode substrate, a La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3−δ (LSGM) electrolyte film and a Sm 0.5 Sr 0.5 CoO 3-δ (SSC) anode was prepared by dip-coating for CO 2 electrolysis at 800 °C. Since Ni in Ni-YSZ substrate is easily re-oxidized under a pure CO 2 electrolysis atmosphere, co-feeding a reductive gas was essential for avoiding Ni re-oxidation and achieving a stable and large CO 2 electrolysis current under high temperature operation. It was found that co-feeding H 2 is more effective for preventing re-oxidation of Ni compared with CO, however, the CO formation rate was slightly lower than that estimated amount by Faraday`s law due to a water shift reaction when H 2 was used as a reductive gas. Deposition of a thin Ni-Fe cathode active layer and CeO 2 nano-particles obtained by infiltration were effective for increasing the CO 2 electrolysis current because of the decrease in the cathodic overpotential. In spite of the low concentration of Ce was infiltrated by using a 1 M solution with a dip process, the volume change in substrate caused by the CO 2 oxidant was also measured. The CO formation rate almost corresponded to the amount estimated by Faraday`s law and the coke deposition was hardly observed in Ni-YSZ substrate after CO 2 electrolysis, when 10% or 5% of CO was co-fed.

Composite Polymer Electrolytes for Lithium Batteries

AbstractThe flexible and less flammable solid polymer electrolytes are attractive candidates for high specific energy density lithium batteries. However, the use of polymer electrolytes in rechargeable batteries for EVs is hindered because of their low lithium‐ion conductivity at room temperature and lithium dendrite formation during lithium deposition at high current density. To improve the room temperature conductivity of polymer electrolytes, composite lithium‐ion conductors consisting of polymer and ionic liquids or inorganic solid lithium ion conductors have been examined over the past two decades. The polymer electrolyte with ionic liquid showed ionic conductivity of more than 10−4 S cm−1at room temperature, but lithium dendrite‐free composite electrolytes have not yet been reported at room temperature and a high current density. The flexible composite electrolytes of polymers and lithium‐ion conductive solid electrolytes showed high ionic conductivity of more than 2×10−4 S cm−1and no dendrite short‐circuit was observed at room temperature and 1.0 mA cm−1for long cycling. The suppression of lithium dendrite formation in the composite electrolyte is due to the formation of a stable interface layer between the lithium electrode and composite electrolyte. At present, no room temperature all‐solid‐state batteries have been developed with performance comparable to conventional lithium‐ion batteries with liquid electrolytes. One of the disadvantage of the lithium batteries with the composite polymer electrolyte is higher mass of the electrolyte than that of a liquid electrolyte with a porous separator. The specific energy density of the batteries depends on the thickness of the electrolyte and the specific area capacity. At present, the thickness of the polymer composite electrolytes is in a range of 50–200 μm. The specific energy density of the lithium battery with a 100 μm thick composite electrolyte is 430 Wh kg−1at 10 mAh cm−2, which is 1.4 times higher than that of the conventional Li‐ion battery. A high specific area capacity battery with a thin polymer composite electrolyte should be developed to obtain a high energy density battery. We are anxiously expecting a mechanically stable composite polymer electrolyte thin film of less than 100 μm thick with high Li‐ion conductivity more than 10−3 S cm−1at room temperature and low interface resistance with Li electrode. The addition of small amount of a low molecular weight additive into the composite electrolytes is effective to improve the interface resistance between the lithium electrode and composite electrolyte, which results in no dendrite formation at high current density and room temperature.

The electrochemical measurement of salt diffusion coefficient, apparent cation transference number and ionic conductivity for a thin-film electrolyte.

Further development of the electrochemical measurement procedure, namely the Symmetric Polarization Procedure (SPP), is described. The SPP allows for an additional verification of measurement assumptions through a quick and simple inspection of a symmetry between the procedure outcomes. It also improves the precision of estimated transport properties. A considerable emphasis was also put on detailed outcomes analysis. In particular, a newly developed approach to the analysis of restricted diffusion data is proposed. This approach is based on a power law which is a common form for the rate equation, therefore it allows for a precise estimation of the salt diffusion coefficient and, innovatively, the diffusion domain. Importantly, as a result of this approach, the subdiffusive-like response is recognized in every electrolyte examined herein. The viscoelastic relaxation of polymer matrix is given as most probable cause of such response. Additionally, four approaches that lead to a quantification of the apparent cation transference number are also extensively discussed. It has been demonstrated, how a knowledge about the salt diffusion coefficient, the apparent cation transference number and the ionic conductivity can be used to evaluate the electrochemical performance of an electrolyte. It is also shown, how these properties can be utilized to approximate the diffusion-limited current and the deviation from Nernst-Einstein equation.

The Atmospheric Corrosion of Trivalent Cr Metal / Cr Oxide Coatings for Packaging Steels

The superior mechanical properties associated with steel mean that it is heavily utilized in many industries including automotive, and construction (1). Although steel offers desirable mechanical properties such as toughness and tensile strength, it is known to corrode, this having cost implications and raising safety concerns, for instance within the food packaging industry. Thus, steel is often used in conjunction with a coating as a preventative measure for corrosion.Within the food packaging industry, steel is often coated with a thin (~20 nm thick) chromium metal-chromium oxide coating, the product being referred to as electro chromium coated steel (ECCS), which is produced during a continuous electrodeposition process whereby a low carbon steel strip passes through baths of chromic acid electrolyte containing hexavalent chromium, Cr(VI). The final coating consists of two distinct layers; a 20-110 mg.m-2 chromium underlayer and a 2-20 mg.m-2 native (hydr)oxide outer layer (2). REACH, a regulation associated with the restriction of chemicals that are harmful to human health and the environment, have made a legislation that has imposed a restriction on the use of Cr(VI) due to its carcinogenic nature (3). This impact has resulted in the drive of the steel packaging industry to find a suitable, non-toxic replacement for ECCS.Coatings made with Trivalent Chromium Coatings Technology (TCCT®) are currently being developed as a potential replacement for ECCS. TCCT® production has developed to consist of a two-electrolyte process involving an aqueous solution of Cr(III) sulphate, sodium sulphate, sodium formate and sulphuric acid leading to the formation/application of a bilayer coating. Various issues including coating inhomogeneity have previously been reported (4).Due to the low coating weights involved, packaging products such as ECCS and TCCT® are also used in conjunction with an organic coating. Thus, they could be susceptible to various modes of organic coating failure including corrosion-driven cathodic delamination, whereby a coating becomes physically separated from the underlying substrate, a key failure process that affects organically coated metal products in high humidity, such as those experienced during storage in the packaging industry. Cathodic delamination occurs when an electrolyte comes into contact with the metallic substrate at a flaw in the organic coating at which anodic metal dissolution occurs. This is coupled to the cathodic oxygen reduction reaction which takes place at the delamination front. The hydroxide ions produced during the cathodic reduction of oxygen, or a reaction intermediate, disturb the bonds between the substrate and coating leading to adhesion failure and delamination of the coating (5).To ensure that new products such as TCCT® are successfully incorporated into the market it is important that they are comparable in performance to existing products. For example, TCCT® must provide sufficient delamination resistance. The scanning kelvin probe (SKP) is a technique which measures corrosion potential under a thin electrolyte film and organic coatings, which can be used to create a surface potential map (6).This study makes use of the SKP to investigate the rate of cathodic delamination as a function of TCCT® Cr(III) oxide (varying from 1.8 mg.m-2 to 23.35 mg.m-2). The results will help to determine the minimum satisfactory chromium oxide coating weight needed for commercial TCCT®.It was found that higher Cr(III) oxide coating weights had a positive effect on inhibiting cathodic delamination, confirming the mechanism. The results were explained using complementary electrochemical data including OCP measurements as well as potentiodynamic polarisation which showed that higher TCCT® Cr(III) oxide coating weights were acting to supress the cathodic reaction.The results also highlighted that a TCCT® Cr(III) oxide coating weight of around 7 mg.m-2 is sufficient with regards to resisting cathodic delamination completely. This work has determined that the Cr(III) oxide coating weight value is very important with regards to improving coating coverage and resisting cathodic delamination.References Singh MK. Application of Steel in Automotive Industry Application of Steel in Automotive Industry. Int J Emerg Technol Adv Eng. 2016;6(7):2250–459.Wijenberg J, Steegh M, Penning JP, Portegies Zwart I. Wo 2014/079909 2014.Petry T, Knowles R, Meads R. An analysis of the proposed REACH regulation. 2007;44(2006):24–32.Allman A, Whiteside J, Jewell E, Griffiths C, McMurray N, de Vooys A. Surface modification of Cr(III) packaging substrates for enhanced adhesion via citric acid processing. Surfaces and Interfaces. 2020 1;20:100545.Øystein O, Knudsen AF. Corrosion Control Through Organic Coatings. Second. Schweitzer PA, editor. New York: Taylor & Francis; 2017.Stratmann M, Streckel H, Feser R. A new technique able to measure directly the delamination of organic polymer films. Corros Sci. 1991;32(4):467–70.

Metal Supported Thin Film SOFC Fabrication Via RF Sputtering

Thin film solid oxide fuel cell (TF-SOFC) has been studied for past few decades to lower its operating temperature to intermediate temperature range (400℃-700℃). However, it is a challenge to deposit a pinhole free electrolyte thin film on a conventional porous ceramic support. In the case of the Ni-Fe based metal support, even if NiO-Fe2O3 is manufactured as a dense structure, it is reduced to Ni-Fe in a hydrogen atmosphere and forms pores. In this study, Ni-Fe based metal support has been introduced as TF-SOFC support to deposit pinhole free electrolyte. Metal support was fabricated as 290㎛ thick porous bulk(34% porosity) with 10㎛ thick dense layer(<1% porosity) by using tape casting process. Ni-Fe ratio (9:1. 7:3, 5:5, 3:7) and sintering condition (1300℃-1500℃) of metal support were optimized to minimize a mismatch of TEC with thin film and improve microstructure stability of support. After that, NiO-YSZ anode functional layer (AFL) and YSZ electrolyte were continuously deposited on metal support through RF sputtering. By tailoring sputtering condition (substrate temperature, operating pressure, reactive gas flow), 39vol%NiO-YSZ composition AFL and 8.6mol%YSZ pinhole free electrolyte were deposited. Annealing was performed at a temperature of 1100℃ or less to improve the crystallinity of the thin film and suppress Ni agglomeration of Ni-YSZ AFL while minimizing diffusion of Fe in the AFL. In cell operating condition (600℃-H2 atmosphere), the dense layer of metal support and NiO-YSZ AFL formed 28% and 24% of pores, respectively. By using LSM-YSZ cathode through the screen printing process, Metal support (300㎛) / Ni-YSZ (1.3㎛) / YSZ (0.8㎛) / LSM-YSZ (20㎛) button cell was fabricated, and electrochemical analysis was performed. Key wards: Sputtering, Thin film, Metal Support, Ni-Fe, YSZ, Ni-YSZ

A review on the preparation of thin-film YSZ electrolyte of SOFCs by magnetron sputtering technology

Solid oxide fuel cells (SOFCs) have become one of the most attractive energy conversion devices due to their fuel flexibility, environmental friendliness and promising energy conversion efficiency. However, the high operating temperature (typically above 800 °C) of SOFCs poses some challenges concerning stability, sealing integrity and safety. Reducing the operating temperature of SOFCs to 600 °C or lower is currently an important research topic in the field. One effective strategy is to reduce the thickness of the electrolyte with high stability and high performance at lower temperatures. Among the thin-film preparation technologies, magnetron sputtering is gaining attention due to the advantages in scaling up and commercialization. Here we compare and analyze various electrolyte preparation methods and present a comprehensive review of the preparation of oxygen-ion-conducting electrolyte thin films by magnetron sputtering technology. The yttria-stabilized zirconia (YSZ) electrolyte and YSZ-based bilayer or multilayer electrolyte are employed as examples due to their high stability and high ionic conductivity. The effects of processing parameters on the microstructures and properties of the electrolyte thin films, the relevant interfaces and full SOFCs are reviewed and discussed. Finally, we present some perspectives and directions for developing high-performance SOFCs with thin-film electrolytes prepared by magnetron sputtering technology.

Electrical Conductivity Properties of Solid Polymer Electrolytes PEO-PVP-NaIO4 Filled with TiO2 Nanoparticles

Frequency-dependent conductivity and conduction relaxation in nanocomposite solid polymer electrolyte films consisting of poly(ethylene oxide) and polyvinyl pyrrolidone blend as host matrix, NaIO4 as ions dopant, and titanium dioxide (TiO2) nanoparticles of average size 10 nm, were studied. The films were characterized using measurements of complex electrical impedance spectra in the frequency range from 1 Hz to 1 MHz, at room temperature. The concentration of the salt NaIO4 was 10 wt%, the TiO2 percentage varied from 1 wt% to 5 wt%. The frequency spectra of both alternating-current (AC) conductivity and electric modulus were analyzed in order to elucidate the effect of TiO2 nanoparticles on the electrical transport properties of the examined electrolyte thin films with a thickness of 150 μm.

Direct Electrophoretic Deposition and Characterization of Thin-Film Membranes Based on Doped BaCeO3 and CeO2 for Anode-Supported Solid Oxide Fuel Cells.

In this work, a technology was developed for the formation of BaCe0.8Sm0.2O3+1 wt% CuO (BCS-CuO)/Ce0.8Sm0.2O1.9 (SDC) thin-film electrolyte membranes for intermediate-temperature solid oxide fuel cells (IT-SOFCs) on porous NiO-BCS-CuO anode substrates using direct electrophoretic deposition (EPD). The effect of increasing the zeta potential when modifying the base suspension of a micro-sized SDC-gn powder (glycine–nitrate method) with the addition of a SDC-lec nanopowder (laser evaporation–condensation) was investigated. Dependences of the current strength on the deposition time and the deposited weight on the EPD voltage were obtained, and evolution of the morphology of the coatings during the modification of the SDC-gn suspension and a suspension of BCS-CuO powder was studied. The compatibility of the shrinkage kinetics of the SDC, the BCS-CuO electrolyte coatings and the NiO-BCS-CuO anode substrate was studied during the high-temperature sintering. Dense BCS-CuO/SDC films of different thicknesses were obtained for the first time on porous NiO-BCS-CuO anode substrates and comprehensive microstructural and electrochemical studies were carried out. The developed technology can be applied to the formation of anode-supported SOFCs with thin-film electrolyte membranes.

Influence of Deposition Modes and Thermal Annealing on Residual Stresses in Magnetron-Sputtered YSZ Membranes.

Thin-film electrolyte made of 8-mol% yttria stabilized zirconia (8YSZ) for solid oxide fuel cells (SOFCs) was fabricated on anode substrates using reactive magnetron sputtering of Zr-Y targets in a mixture of Ar and O2 gases. The deposition of 4–6 µm thin-film electrolyte was in the transition or oxide modes differing by the oxygen concentration in the sputtering atmosphere. The half-cell bending of the anode-supported SOFCs was measured to determine the residual stresses in the electrolyte films after the deposition and thermal annealing in air. The dependences were studied between the deposition modes, residual stresses in the films, and the SOFC performance. At 800 °C, the maximum power density of SOFCs ranged between 0.58 and 1.2 W/cm2 depending on the electrolyte deposition mode. Scanning electron microscopy was carried out to investigate the surface morphology and structure of the YSZ electrolyte films after thermal annealing. Additionally, an X-ray diffraction analysis of the YSZ electrolyte films was conducted for the synchrotron radiation beam during thermal annealing at different temperatures up to 1300 °C. It was found that certain deposition modes provide the formation of the YSZ electrolyte films with acceptable residual stresses (<1 GPa) at room temperature, including films deposited on large area anodes (100 × 100 mm2).

Galvanic corrosion protection of Al-alloy in contact with carbon fibre reinforced polymer through plasma electrolytic oxidation treatment

Al-alloy/carbon fibre reinforced polymer (CFRP) joint systems offer exceptionally lightweight, superior fatigue behaviour and impact resistance for aerospace applications. Nevertheless, the galvanic corrosion at the joint interfaces accelerates the adhesive failure and strength damage. In this work, oxidation of Al 7075 alloy was studied by employing plasma electrolytic oxidation (PEO) and thin film sulphuric acid anodizing (TFSAA) methods, addressing their galvanic corrosion (GC) protection performance in contact with CFRP. Structural and electrochemical characterisations were carried out in tandem with varied oxidation process parameters, revealing that high voltage PEO resulted in crystallized compact ceramic coating and thus improved GC protection. A decrease in the GC current by ~ 90% has been achieved by using the PEO coating at 700 V compared with the ~ 12% current reduction of commercial TFSAA coating. Further microstructure studies revealed that the improved GC protection of the crystallized PEO coating was realized by suppressing the initiation and propagation of localized pitting due to the improved electrical isolation between the Al-alloy/CFRP interfaces. A high voltage PEO process provides sufficient energy to produce uniform and crystalline ceramic coating consisting of Al2O3 and mullite, which give rise to improved corrosion protection.

Advances in Inkjet‐Printed Solid Oxide Fuel Cells

AbstractSolid oxide fuel cells (SOFCs) are high temperature galvanic devices able to electrochemically convert chemical energy of fuels to electrical energy at remarkably high efficiencies. However, several challenges, associated with the complexity, scalability, and cost of the current fabrication processes, remain to be resolved for their large‐scale deployment. Additive Manufacturing (AM) methods are proposed to address such fabrication‐related issues, with Inkjet Printing (IJP) being one of the most promising. In this review, the use of IJP is examined as a potential AM method to deposit electrode and electrolyte thin films for SOFCs. The most important aspects of IJP for SOFCs fabrication processes, including ink formulation of active materials, inkjet deposition, printing optimization, and characterization of inkjet‐printed thin films, are described in detail. Additionally, the effect on electrochemical performance of inkjet‐printed SOFCs highlights the overall potential of this fabrication technique. Challenges and opportunities for the future development of the topic are also discussed.

Enhanced Performance of Protonic Solid Oxide Steam Electrolysis Cell of Zr-Rich Side BaZr0.6Ce0.2Y0.2O3-δ Electrolyte with an Anode Functional Layer.

Proton-conducting solid oxide electrolysis cells (H-SOEC) containing a 15-μm-thick BaZr0.6Ce0.2Y0.2O3−δ (BZCY622) electrolyte thin film, porous cathode cermet support, and La0.6Sr0.4Co0.2Fe0.8O3−δ anodes were fabricated using a reactive cofiring process at approximately 1400 °C. Steam electrolysis was conducted by supplying wet air to the anode at a water partial pressure of 20 kPa. The performance was evaluated using electrochemical measurements and gas chromatography. At 600 °C, the cells generated an electrolysis current of 0.47 A cm–2 at a 1.3 V bias while the Faradaic efficiency reached 56% using 400 mA cm–2. The electrolysis performance was efficiently improved by introducing a 40-nm-thick La0.5Sr0.5CoO3−δ (LSC) nanolayer as an anode functional layer (AFL). The cells with LSC AFL produced an electrolysis current of 0.87 A cm–2 at a 1.3 V bias at 600 °C, and the Faradaic efficiency reached 65% under 400 mA cm–2. Impedance analysis showed that the introduction of the AFL decreased the ohmic resistances and improved interfacial proton transfer across the anode/electrolyte interface and polarization resistances related to the anode reaction. These results demonstrate opportunities for future research on AFL to improve the performance of H-SOECs with Zr-rich BaZrxCe1–x–yYyO3−δ electrolytes.

Emulation of synaptic functions with low voltage organic memtransistor for hardware oriented neuromorphic computing

Here, various synaptic functions and neural network simulation based pattern-recognition using novel, solution-processed organic memtransistors (memTs) with an unconventional redox-gating mechanism are demonstrated. Our synaptic memT device using conjugated polymer thin-film and redox-active solid electrolyte as the gate dielectric can be routinely operated at gate voltages (VGS) below − 1.5 V, subthreshold-swings (S) smaller than 120 mV/dec, and ON/OFF current ratio larger than 108. Large hysteresis in transfer curves depicts the signature of non-volatile resistive switching (RS) property with ON/OFF ratio as high as 105. In addition, our memT device also shows many synaptic functions, including the availability of many conducting-states (> 500) that are used for efficient pattern recognition using the simplest neural network simulation model with training and test accuracy higher than 90%. Overall, the presented approach opens a new and promising way to fabricate high-performance artificial synapses and their arrays for the implementation of hardware-oriented neural network.