bluuebunny/crossref_metadata_2025 huggingface dataset:
Laser-Structured Electrodes for Lithium-Ion Batteries
Authors: Li Jianlin , Smyrek Peter , Wood Marissa , Zheng Yijing , Sheng Yangping , Rakebrandt Jan-Hendric , Du Zhijia , Pfleging Wilhelm , Wood David L
Published: February 2020

Insufficient energy density is one of the barriers for widespread application of lithium-ion batteries (LIBs). Increasing energy density relies on developing novel active materials with higher energy density and/or increasing the active material ratio via electrode engineering [1].

One natural strategy is to increase the energy density by increasing the electrode thickness, which reduces the fraction of some inactive components such as current collectors and separators. However, thick electrodes suffer from electrolyte depletion under high discharge rates and low power density. As a result, electrodes are divided into two categories—thin electrodes (ca. 50 µm) for high power application and thick electrode (> 100 µm) for high energy application [2]. This work reports a design in thick electrodes with 3D micro-structures enabled by laser processing, which minimizes the electrode tortuosity and improves the lithium ion diffusion kinetics. This novel design enables high energy and high power densities for LIBs.

References:

[1] Z. Du, D.L. Wood, C. Daniel, S. Kalnaus, J. Li, Journal of Applied Electrochemistry 47 (3), (2017) 405-415

[2] P. Smyrek, J. Proll, H. J. Seifert, and W. Pfleging, Journal of the Electrochemical Society, 163 (2), (2016) A19-26.

Acknowledgements

This research at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) under contract DE-AC05-00OR22725, was sponsored by the Office of Energy Efficiency and Renewable Energy (EERE) Vehicle Technologies Office(VTO) (Deputy Director: David Howell) Applied Battery Research subprogram (Program Manager: Peter Faguy).

This work at Karlsruhe Institute of Technology (KIT) received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement no. 644971. Finally, the support for laser materials processing by the Karlsruhe Nano Micro Facility (KNMF, http://www.knmf.kit.edu/) a Helmholtz research infrastructure at KIT is gratefully acknowledged.
Alignment and Size Control of TiO2(B) for Fast Lithium Storage
Authors: Sugimoto Wataru , Yoshida Tomohiro , Tanaka Ryo , Makino Sho , Ayato Yusuke , Mochizuki Dai
Published: February 2020

TiO2(B) has attracted much interest as a fast and safe anode for lithium ion batteries as well as lithium ion capacitors owing to its high theoretical capacity (335 mAh g-1), fast Li intercalation/de-intercalation properties and favorable electrode potential. TiO2(B) can be synthesized by thermal treatment of layered titanate. We have shown that TiO2(B) thin films can be prepared by utilizing electrophoretic deposition (EPD) of TiO2 nanosheets [1]. Such methods afford TiO2(B) film with the (0k0) planes lying perpendicular to the substrate.

In this study, the influence of the orientational structure (horizontal, vertical, random alignment) on the kinetics of Li+ storage in TiO2(B) was studied by fabricating TiO2(B) electrodes with the same mass loading by different orientation.

Vertically aligned TiO2(B) films were prepared by a combination of EPD and freeze-drying. Randmoly stacked TiO2(B) films was prepared by flocculation of nanosheets. Furthermore, the effect of the TiO2(B) size was studied by using TiO2 nanosheets with different lateral size. Electrochemical lithiation/de-lithiation studied in 1 M LiPF6/EC-DEC by cyclic voltammetry and galvanostatic charge/discharge revealed that the orientation of TiO2(B) had a large influence on Li+ storage kinetics. Perpendicularly aligned TiO2(B) showed much faster Li+ intercalation/de-intercalation behavior compared to vertically aligned TiO2(B) with the same mass loading. Randomly stacked TiO2(B) possesed similar performance to vertically aligned TiO2(B). High power capability was further improved by using smaller-sized TiO2(B).

[1] W. Sugimoto, O. Terabayashi, Y. Murakami, Y. Takasu, J. Mater. Chem., 12, 3814-3818 (2002).
A New Type of Supercapacitor Oxide ZnMn2O4 Showing Combined Pseudocapacitance and Battery Behaviors
Authors: Wu Nae-Lih , Abdollahifar Mozaffar
Published: February 2020

Supercapacitors have attracted great attention due to their rapid charge-discharge rates, long cycle life and high power density. Binary metal oxides, specially spinel structures as supercapacitor have been investigated to show better electrochemical performances than single component oxides owing to their available multiple oxidation states. In this paper, a simple and scalable process has been developed for synthesizing ultrafine ZnMn2O4/carbon nanostructures through a solution combustion method. Effect of polyethylene glycol (PEG) weight percentage with low and high molecular weights, as carbon source and pore size controller, on the structure and physical properties of the ZnMn2O4/carbon were investigated in details and well characterized using XRD, FESEM, TEM, HRTEM and N2 adsorption/desorption. Electrochemical characterization of the oxide electrode indicated unique combination of pseudocapacitance and battery behaviors, exhibiting large capacitances (> 150 F/g) and an intriguing dependence on electrolytes. The charge-transfer mechanisms have been characterized by in-situ XRD and X-ray absorption analyses.
Combining Battery-like and Pseudocapacitive Charge Storage in 3D MnOx–Carbon Electrode Architectures for Zinc-Ion Cells
Authors: Ko Jesse S. , Sassin Megan B. , Rolison Debra R. , Long Jeffrey W.
Published: February 2020

The ability of manganese oxides to exhibit charge-storage behavior characteristic of either batteries or electrochemical capacitors (ECs) offers an intriguing opportunity to design electrode materials that innately deliver both high power and high capacity. We previously demonstrated that lamellar birnessite-type MnOx, when expressed in carbon nanofoam–based electrode architectures (MnOx@CNF), amplifies charge storage by pseudocapacitance in aqueous electrolytes (e.g., Na2SO4; Li2SO4). Herein, we extend the functionality of these established electrode materials by varying the ionic composition of the electrolyte in which they are cycled. For example, cycling MnOx/C nanofoam electrodes in aqueous 1 M ZnSO4 yields battery-like voltammetric features reminiscent of those previously reported for “rechargeable Zn-ion batteries.” When cycling in mixed Na2SO4:ZnSO4 electrolytes, we retain Zn2+ redox peaks, but now superimposed on a pseudocapacitive background arising from the presence of Na2SO4. The Zn2+ redox provides high capacity (up to 230 mAh g–1 normalized to MnOx) at low rates (<5 mV s–1), while pseudocapacitance mechanisms take over at high rates to mitigate the effects of slow kinetics for Zn2+ insertion. Fundamental electrochemical properties are established using a three-electrode half-cell configuration. We apply peak-current kinetic analyses (for CV data) and AC impedance to deconvolve the complex mechanisms that give rise to battery-like and pseudocapacitive charge-storage features. On the basis of three-electrode studies, we down-select electrolyte compositions for testing MnOx@CNF, paired against Zn metal, in two-electrode Swagelok cells that are subjected to galvanostatic cycling at challenging C-rates (1C–20C).
Redox-Active Organic Positive Electrodes for Li- and Na-Ion Capacitors
Authors: Liu Tianyuan , Lee Byeongyong , Park Jinho , Lee Seung Woo
Published: February 2020

Li-ion capacitors employ capacitive positive electrodes from electrochemical capacitors (ECs) and intercalation negative electrodes from Li-ion batteries (LIBs), bridging the performance gap between ECs and LIBs. However, the low capacity of capacitive positive electrodes limits the energy density of the Li-ion capacitors. Incorporating pseudocapacitance (surface redox reaction) into the carbon materials is a promising strategy to enhance the capacity of the carbon-based positive electrodes. We have been investigating the redox reactions of various organic materials with Li- and Na-ions for hybrid capacitor applications. We have revealed that the organic electrodes, which are prepared from pyrene derivatives,1 hydrothermally synthesized carbon from glucose,2 and polymerized dopamine,3 have redox reactions with Li- and (or) Na- ions. In this study, we further reveal that the organic electrodes can store high capacities in both Li- and Na-cells in the high voltage region by utilizing the redox reactions between oxygen functional groups and metal ions. Finally, we demonstrate the high-performance Li-ion capacitors by combining the organic positive electrode and high-energy battery negative electrode.

References

1. J. C. Bachman, R. Kavian, D. J. Graham, D. Y. Kim, S. Noda, D. G. Nocera, Y. Shao-Horn and S. W. Lee, Nature Communications, 6:7040 (2015).

2. T. Y. Liu, R. Kavian, Z. M. Chen, S. S. Cruz, S. Noda and S. W. Lee, Nanoscale, 8, 3671 (2016).

3. T. Liu, K. C. Kim, B. Lee, Z. Chen, S. Noda, S. S. Jang and S. W. Lee, Energy & Environmental Science, 10, 205 (2017).
Hybrid Composite Electrodes for Asymmetric Full Cell Supercapacitors
Authors: Mokkelbost Tommy , Tolchard Julian Richard , Jayasayee Kaushik , Barnett Alejandro Oyarce , Hanetho Sidsel Meli , Svensson Ann Mari , Montemor M. F
Published: February 2020

Supercapacitors, which can store energy by a combination of electrostatic (double layer capacitance) and electrochemical (pseudocapacitance) storage of electrical energy, are an important energy storage device applicable for a variety of uses and technologies, especially in applications which requires rapid charge/discharge cycles and several thousands of cycles, e.g. short term energy storage and high powder delivery. The asymmetric electrode configuration which allows for the use of aqueous electrolytes are a promising route to low-cost and environmentally friendly supercapacitors without compromising power and energy density.

Here we present a novel approach based on easy synthesis methods to prepare hybrid electrode materials consisting of mixed transition metal oxides for the redox contribution together with carbonaceous materials contributing to the double layer response. The synthesis methods used are possible to scale up and results in nanosized, high surface area hybrid electrode materials. Different methods have been selected which results in significant different morphologies and characteristics. The electrode materials have been characterized by standard physical techniques, e.g. SEM, TEM, EDX and XRD. To prepare final electrode materials, inks using PTFE, ketjen black and H2O/isopropanol, was spray coated on carbon paper with different loading to be able to balance a asymmetric cell. The electrodes were tested for electrochemical performance as capacitors, such as cyclic voltammetry and charge and discharge curves, as a function of electrode composition, time and type of water based electrolyte, and compared with e.g. electrodeposition. Some of the composite electrode demonstrated specific capacitances of 300 Fg-1. Asymmetric cells were prepared using electrodes of metal oxide/carbon and pure "capacitor grade" carbon with tailored loading for balancing the cell and mounted in a El-cell using aqueous electrolytes.

The project is funded through the m-ERA.net program and financial support from Research Council of Norway and Fundação para a Ciência e a Tecnologia is appreciated.
Pseudocapacitive Polycationic Oxides for Supercapacitors Operating in Aqueous Electrolytes
Authors: Crosnier Olivier , Goubard-Brétésché Nicolas , Buvat Gaëtan , Douard Camille , Iadecola Antonella , Favier Frederic , Brousse Thierry
Published: February 2020

Electrochemical double-layer capacitors (EDLCs) represent the most important family of today’s commercially available Electrochemical Capacitors (ECs). Such systems store charges electrostatically in the electrochemical double-layer that arises from the separation of charges at the electrode / organic electrolyte interfaces when polarizing the electrodes, and exhibit an excellent cycling stability combined with fair gravimetric and volumetric energy densities. Other types of ECs use “pseudocapacitive” materials, i.e. materials that use fast and reversible surface redox (faradic) reactions to store energy. To combine the advantages of both organic EDLCs and aqueous symmetric systems, the design of aqueous asymmetric supercapacitors was proposed. These devices comprise either two pseudocapacitive materials, or a pseudocapacitive and a capacitive carbon-based material which exhibit complementary electroactive windows. As a result, operating cell voltages approaching 2 V can be obtained, leading to competitive energy densities without the disadvantages of using an organic electrolyte [1].

Both specific energy and power densities have to be increased and improving the volumetric capacitance of supercapacitors, which is one of the limiting factors of today’s stationary applications, is essential [2]. In order to meet those requirements, solid state chemistry is an extremely powerful tool to design new materials. Our strategy was based on the study of materials that are electrochemically active in aqueous media, with transition metals and/or high density elements, with the possibility to use low-temperature synthesis methods in order to get nanosized particles with high specific surface areas, and the possibility to have several redox couples that could be involved in the charge storage mechanism. Among the studied materials, our interest has focused on different materials such as transition metal oxides (MnO2, Fe3O4,…) and polycationic oxides MWO4 (M=Fe, Mn, Co,…) [3]. Synthesis conditions and materials characterizations of the electrodes and also of full devices will be detailed in the presentation, highlighting the crucial role of the electroactive elements, the crystallographic structure, and the morphology of the synthesized materials on their electrochemical performance.

J.W. Long et al., MRS Bulletin., 36, 513 (2011).

N. Goubard-Bretesché et al., Electrochem. Commun., 57, 61 (2015).

N. Goubard-Bretesché et al., Electrochim. Acta
206, 458 (2016).
Utilization of Engineered Iron Oxide and Industry Waste Red Mud in High Performance Supercapacitor
Authors: Bhattacharya Gourav , Roy Susanta Sinha
Published: February 2020

Development of high performance energy storage materials is still an important topic to the researchers as there is a rapid depletion of non-renewable energy resources and a continuous demand for electrical power sources. In this work, at first, by utilizing electrochemical technique, supercapacitor behavior of a novel hybrid nanocomposite encompassed of engineered iron oxide (Fe3O4) nanoparticles and reduced graphene oxide (RGO) was investigated. The synergistic effect between the Fe3O4 and RGO components accomplished a high sp. capacitance (576 F g−1) a high energy storage density ( 75 W h kg−1 at a current density of 6 A g−1) and a promising long term stability [1]. The engineered coating not only enhances the pseudo-capacitive charge transfer process but also felicitates enhanced surface area which boosts double layer capacitance. Motivated by the above results, the potential use of red mud (an aluminum industrial waste material) as supercapacitor electrode was further explored. Red mud, a natural source of iron oxide (Fe2O3) was mechanically processed. The nanoparticle exhibits a promising energy density, a moderate specific capacitance and a remarkable cyclic stability, where ~ 98% of the initial capacitance was retained even after 5000 cycles for a high sp. current density (6 A g-1) (Fig. 1). This study shows that waste red mud can effectively be utilized in energy harvesting.

References

[1] Gourav Bhattacharya et al. RSC Advances 7.1 (2017): 327-335.

Figure 1
CVD Synthesis and Functionalization of Boron-Doped Graphene
Authors: Ion-Ebrasu Daniela , Enache Adrian , Enache Stanica , Soare Amalia , Carcadea Elena , Varlam Mihai , Stefanescu Ioan
Published: February 2020

We report in this paper the development of Boron-doped Graphene via chemical vapor deposition (CVD) that can serve as an efficient metal-free electrocatalyst for hydrogen evolution reaction (HER) in both alkaline and acidic media. Graphene growth is carried out by the flow of methane and hydrogen gasses, and with a borazine precursor over Ni foil and foam substrates at atmospheric pressure. The characterization is performed with scanning electron microscopy (SEM/EDS) and Raman/AFM spectroscopy. Electrochemical characterization of HER is performed by cyclic voltammetry (CV) measurements in 1 M KOH and 1M H2SO4 respectively, at room temperature, and 10 mV s–1 scan rate. Electrochemical tests are performed with an in-house designed cell with 1 cm2 surface area. The catalytic activity towards the HER of catalysts is determined from Tafel plots obtained from galvanostatic current-voltage measurements.
Microporous Carbon Hybrid Nanostructure for Supercapacitors
Authors: Dorvilien Valerio , Santa Cruz Neida , Rojas Carolina Valeria , LopezdeVictoria Monica , Rivera Kevin , Mendoza Frank , Limbu Tej B. , Morell Gerardo , Weiner Brad R.
Published: February 2020

Through this work we report an efficient way to produce high specific capacitance in supercapacitors devices based on zeolite template and by controllable oxidation percentage of high-quality graphene oxide. We discuss the fabrication of complex hybrid nanostructures by growing carbon-compounds on pre-synthesized nanostructured zeolites templates by chemical vapor deposition (CVD) and then etching away the zeolites, controlling the oxygen percentage in the structure. We study two types of zeolites structures, NaX and NaY to explore the side effects. Systematically, all roles of different parameters were studied, such as the composition, morphology and crystallinity of the Zeolites, as well as the CVD growth temperature and different carbon precursors to grow carbon-compound on Zeolites. Furthermore, the selection of a zeolite is also important, as type X are shown to be more resistant to thermal damage than their type Y. Finally, we could successfully remove the zeolite templates to form free-standing carbon-based nanostructures. The results presented in this analysis demonstrate the long lifespan that this type of material offers to improve capacitance.
Chemical Purification of Gd3N@C88 Metallofullerene Using Alcohols and Lewis Acids
Authors: Thompson Hannah R. , Stevenson Steven
Published: February 2020

This project addresses the paucity of literature on trimetallic nitride fullerenes possessing carbon cages larger than C80. Herein, we present our chemical isolation of Gd3N@C88, which was selected based on the (1) few reports describing its fundamental chemistry and (2) curiosity of its candidacy as an effective MRI contrast agent. To date, MRI contrast agent development for metallic nitride fullerenes has focused on the more ubiquitous and smaller-cage Gd3N@C80 species. Excitement for Gd3N@C88 is predicated, in part, on the projected increased reactivity of its C88 cage. The higher reactivity could, in principle, allow more attached hydrophilic groups, which in turn would translate into better water-solubility and improved clearance from the body in biological systems. Prior to any application, though, the fundamental science must first be performed. We demonstrate that the unique chemical reactivity of Gd3N@C88 can be strategically manipulated into a separation strategy for its isolation from complex extract mixtures containing more than 50 different species of fullerene and metallofullerene contaminant species. We describe the use of amino alcohols and Lewis acids to obtain highly enriched samples of greater than 90% purity. For subsequent studies (e.g., medical) demanding a higher purity (>99%), the appropriate HPLC parameters and fraction collection are also discussed.
Electrochemical Evaluation of the Influence of Surface Treatment Used on the AA6063T5 Alloy
Authors: Teixeira Dilton Gonçalves , Suegama Patricia Hatsue , Fugiwara Cecílio Sadao , Benedetti Assis Vicente
Published: February 2020

Three AA6063T5 alloy samples were investigated: as received, trimmed and polished mechanically and chemically treated. The mechanical treatment was performed using sandpaper SiC of sizes 320 to 4000 and the chemical was performed using an aqueous solution containing a mixture of hydroxide, sulfate and sodium chloride. All samples were physically characterized by X-ray diffractometry (XRD), hardness measurements, scanning electron microscopy (SEM) and optical microscopy (OM), and by open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) in 3.5% NaCl solution. The SEM images showed that the presence of intermetallic particles on the alloy surface decreases after the chemical treatment compared to the mechanical treatment. The EIS results showed that the chemical treatment offers higher resistance to corrosion than those submitted to the other treatments, because the alkaline attack used dissolved most precipitates containing Fe or Cu, elements responsible for cathodic sites. Washing with HNO3 through which the chemically treated sample passed probably reinforced the oxide layer, making the surface of the alloy more resistant to attack by chloride.
The Efficiency of Hexamethylenetetramine ((CH2)6N4) and Thiourea (CH4N2S) in Protection of Coating Layer
Authors: Al zoubi Wail
Published: February 2020

In the present study, a synergistic effect on the corrosion protection properties of plasma electrolytic oxidation and thiourea as inhibitor has been investigated by microstructure surface, polarization, and basic computational. To achieve this purpose, a PEO coating was performed under an alternating current condition in aluminate electrolytes containing hexamethylenetetramine. The structural observations on the coating layer exhibited that chemical additive would generate lower level of porosity than that without this additive, which was attributed to favorable formation of MgAl2O4 and carbon with the additions of (CH2)6N4. On the other hand, when CH4N2S was added to the coating surface, the results revealed that the structural surface defects of the PEO coatings were sealed by inhibitor-treatments resulting in decreases in micro-cracks and open micro-pores. Thus, it was found that the CH4N2S acts a good corrosion inhibitor for magnesium corrosion in aqueous solution. This adsorption of thiourea on the surface may be due to a weak interaction between an electron donor from thiourea that has a sufficiently low ionization potential and an acceptor such as oxide coating surface that has a sufficiently high electron affinity. Besides that, the inhibition efficiencies and the global chemical reactivity relate to total energy, EHOMO, ELUMO and gap energy (∆E). Potentiodynamic polarization method was used to evaluate the corrosion behavior of these coatings in 3.5% NaCl solution. On this basis, the results revealed that electrochemical corrosion results indicated that the treated PEO coatings with inhibitor showed better corrosion resistance than the untreated PEO coatings.
Effect of Tail Length of Surfactant-like Corrosion Inhibitors on Chemical Mechanical Planarization Slurry
Authors: Ho Lin-Chen , Tsai Wei-Wen , Lee Cheng-Bin , Hsu Yao-Hsin , Wang Jiun-Fang , Zhou Wenjia
Published: February 2020

Integrated circuits (IC) are produced by deposition and modification of different dielectric and metal layers on a silicon wafer. Because of the continuing miniaturization of the device dimensions and the requirements of interconnecting an increasing number of devices on a chip, building multilevel interconnections on planarized levels has become an essential part of IC production. Chemical mechanical planarization (CMP) is a process of smoothing the dielectric and metal films in the process of integrated circuit fabrication with the combination of chemical and mechanical forces. For a metal CMP slurry, the key components and steps are as follows: 1. Oxidizing agent is added to the slurry to oxidize the metal surface. 2. Nano-scaled abrasives subsequently remove the dielectric and oxidized metal layer by mechanical force. 3. Inhibitors are added to prevent or minimize undesired corrosion thus controlling the surface quality.

A group of surfactant-like inhibitors have been investigated in this study. Their structures differed by the length of their hydrophobic tails (alkyl groups having 4 to 16 carbon atoms). The molecules were absorbed on metal wafer surface through hydrophilic head and the hydrophobic tail wriggled on top and around. Thus, adjusting the length of tail may change the behavior of the adsorbing layer on metal films, which provided a viable route to interrupt the interactions between slurry components and the metal surface. We found that adjusting the length of tail affected the CMP slurry properties (such as suppression of static etching rate, see Figure 1), longer tail lengths led to better etching inhibition, and also caused distinct modification on the surface of abrasive (mean particle size and zeta potential). Polishing performances including removal rates and topography were also affected by the tail length, but the results with various feature sizes were more complex due to the combined net effect of etching inhibition and modified abrasive properties. The tail length demonstrated an important role on slurry stability and polishing performance.

Figure 1. The decay of etching rates with inhibitors. The indicate-axis tail numbers designate the carbon atoms in hydrophobic tails.

Figure 1
Modelling Microstructural and Chemical Degradation of Ferritic Stainless Steels for SOFC Interconnects
Authors: Oum Melissa , Andrews James , Steinberger-Wilckens Robert
Published: February 2020

Ferritic Fe-based (FeCrX) alloys forming a protective chromium oxide film are used for providing electrical interconnection in high temperature Solid Oxide Fuel Cells (SOFC) are susceptible to degradation mechanisms in the presence of high temperatures (>600oC), and humid air. These translate by the increase in interconnect electrical contact resistance and the formation of volatile chromium species causing poisoning of the adjacent cathode.

 

Modelling tools and techniques are increasingly becoming popular to gain better understanding of the degradation mechanisms that lead to the formation of volatile chromium species. This research work examines the oxidation behaviour of uncoated ferritic stainless steels system operated at temperature of 700oC in both wet (3% humidity) and dry conditions.

 

A model is presented based on the physical processes involved. The model is able to predict the weight gain of the samples upon oxidation, the oxide film thickness, the volatilization of chromium and the useable lifetime of interconnects based on chromium depletion. Parameter determination from standard experiments is discussed along with the physical and design insights from the model. Perhaps most importantly the model provides recommendations regarding accelerated testing of FeCrX interconnects and control of the Chromia film thickness.

 

Acknowledgements: This work was supported by the European FCH JU in project SCORED 2:0 under contract no. 325331 and the EPSRC.
Composite LSF-YSZ and LSCrF-YSZ Electrode Scaffolds for Infiltrated SOFC Cathodes
Authors: Cheng Yuan , Oh Tae-Sik , Rahmanipour Morteza , Wilson Rachel , Gorte Raymond J , Vohs John M.
Published: February 2020

Conductive scaffolds were investigated for use in fabrication of SOFC cathodes in order to reduce the number of perovskite infiltration steps required to achieve sufficient conductivity. Initial work involved composites of Sr-doped LaFeO3 (LSF) and YSZ. Although no new phases form when LSF-YSZ composites are calcined to 1623 K, shifts in the lattice parameters indicate Zr can enter the perovskite phase. Measurements on dense, LSF-YSZ composites show that the level of Zr doping depends on the Sr:La ratio. Because conductivity of undoped LSF increases with Sr content but both the ionic and electronic conductivities of Zr-doped LSF decrease with the level of Zr in the perovskite phase, there is an optimum initial Sr content corresponding to La0.9Sr0.1FeO3 (LSF91). Although scaffolds made with 100% LSF had a higher conductivity than scaffolds made with 50:50 LSF-YSZ mixtures, the 50:50 mixture provided better interfacial structure with the electrolyte and sufficient conductivity, providing the better cathode performance upon infiltration of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF). To minimize Zr doping, we also examined scaffold composites made from La0.8Sr0.2CrxFe1-zO3-δ (LSCrF) and YSZ. For intermediate Cr contents, it was possible to prevent Zr doping and maintain reasonable performance of cathodes made from LSCrF-YSZ composites.
Fabrication of Nanoparticle Networked La0.6Sr0.4Co0.2Fe0.8O3-δ Thin Film Layer between the Cathode and Electrolyte of Solid Oxide Fuel Cell by Using a Spin Coating Method
Authors: Jang Inyoung , Kim Chanho , Kim Sungmin , Yoon Heesung , Paik Ungyu
Published: February 2020

In this study, nanoparticle network of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) thin film layer was coated via spin-coating using metal-nitrate solution to enhance the connectivity between cathode layer and electrolyte. The layer was annealed at 500oC after coated and then LSCF- gadolinium doped ceria (GDC) cathode layer was screen printed. The layer showed amorphous phase after 500oC annealing, and it changed to crystallized phase after sintering at 1050oC. The fabrication of LSCF layer on the GDC electrolyte was confirmed by energy dispersive X-ray spectroscopy (EDS) measurement. The crystallite size and thickness of the LSCF layer were measured by Scanning electron microscopy (SEM). The results were 20 to 50nm and 200 to 300nm, respectively. The I-V performance of the cell was improved as a function of the coating times. Electrochemical impedance spectroscopy (EIS) data of the cells showed that ohmic resistance and cathode polarization were lower than the cell without thin film layer.
eCOs - A Commercial CO2 Electrolysis System Developed by Haldor Topsoe
Authors: Küngas Rainer , Blennow Peter , Heiredal-Clausen Thomas , Holt Tobias , Rass-Hansen Jeppe , Primdahl Søren , Hansen John Bøgild
Published: February 2020

This paper will cover the technical and commercial features of Haldor Topsoe’s CO from CO2
technology. Haldor Topsoe’s eCOs® is a solid oxide electrolysis cell (SOEC) technology that allows the safe, efficient, and cost-competitive production of carbon monoxide directly at the site of facilities where the gas is needed. The CO-generation device uses feedstock carbon dioxide and electrical power to produce CO in quantities ideal for most operations that today rely on cylinder or tube trailer supply.

An eCOs plant is delivered as a stand-alone unit with power, CO2 and product gas connections. Furthermore, the plant ensures high levels of purity, producing CO at 99.5% assay with minimal contaminants and CO2 as the main contaminant. An eCOs solution can also be customized to produce CO at 99.999% purity. One eCOs plant is able to deliver between 10 and 100 Nm3 CO gas per hour.

The patented eCOs technology ensures security of supply, eliminates the need to transport hazardous gas, and drastically reduce costs related to storage, rentals and connections. In the longer run, this technology opens up for a whole new segment of green and sustainable chemicals from renewable carbon sources.

Field test results from the 12-kW demonstration-unit located in Houston, Texas will be reported, as well as progress towards the 400-kW commercial unit to be delivered in 2018. Results from a 50-kW H2O electrolysis unit located in Foulum, Denmark used for biogas upgrading will also be presented.
Characteristics of New Nickel Porous Alloy for Cathode Current Collector in Solid Oxide Fuel Cells
Authors: Hiraiwa Chihiro , Tawarayama Hiromasa , Higashino Takahiro , Okuno Kazuki , Majima Masatoshi
Published: February 2020

Introduction

A Nickel (Ni) porous metal is used for anode current collector in solid oxide fuel cells (SOFCs)[1]. However, it is difficult to be applied as cathode current collector due to its large oxidation resistance at high temperature. In this work, we investigated characteristics and applicability of a new Ni-Sn porous alloy as the cathode current collector for SOFCs.

Experimental

The Ni porous alloy was prepared by electroplating process. Sn was deposited continuously by electroplating onto the surface of the Ni porous metal. Then, heat treatment was performed under hydrogen atmosphere to obtain the Ni-Sn porous alloy [2]. Figure 1(A) shows a SEM image of three-dimensional structure of the as-prepared sample.

Oxidation resistances were evaluated by measuring weight increase due to the heat treatment, and the area-specific resistance at high temperature. The crystalline phases of the specimens before and after heat treatment were identified by XRD. Mechanically polished cross-sections of the specimens were observed via SEM-EPMA. Finally, the prototype SOFCs were fabricated using the Ni-Sn porous alloy as the cathode current collector.

Results and Discussion For Ni-Sn porous alloys with various Sn contents, figure 1(B) shows the weight increase due to the heat treatments in air at 800 °C for 1,000 hours and at 600 °C for 3,000 hours. In the case of the heat treatment at 800 °C for 1,000 hours, the weight of Ni-Sn porous alloys increased regardless of the Sn content. And the weight increased more than 1.7 mg/cm2, revealing a noticeable level of oxidation. In contrast, for Ni-Sn porous alloy with Sn content of 5 wt% or more, the oxidation was noticeably retarded in spite of a long-term heat treatment at 600 °C for 3,000 hours. Figure 1(C) shows the distribution of oxygen by using EPMA-EDS to analyze the cross-section area of the Ni-10wt%Sn porous alloy before and after heat treatment at 600 °C in air for 1,000 hours. After heat treatment, one can see a clear existence of oxygen in the depth about 1 μm from the surface, indicating the oxidation of this region.

 The IV relationship and the power output characteristics of SOFCs with the cathode current collectors made of Pt mesh or the Ni-10wt%Sn porous alloy. Both the behavior of the IV relationship and the output power of the SOFC with the Ni-10wt%Sn porous alloy were almost equivalent to that using the Pt mesh.

Conclusions

 The Ni-Sn porous alloy has relatively low electrical resistance after the heat-treatment in oxygen, and also high electric conductivity at 600 °C. Thus, this new Ni porous alloy has promising perspective to be applied as the cathode current collector for SOFCs operating in an intermediate temperature range. And such demand is expected to grow in near future.

[1] W. Guan, et al., Fuel Cells, 12(2012), 1085-1094

[2] K. Okuno, et al., SEI Technical Review, 75(2012), 137-140

Figure 1
Diesel Based SOFC Demonstrator for Maritime Applications
Authors: Nehter Pedro , Wildrath Barbara , Bauschulte Ansgar , Leites Keno
Published: February 2020

Emission regulations for ships are forcing ship-owners and shipyards to drastically reduce harmful species for the Emission Control Areas (ECA) along the US coast, Baltic Sea and North Sea. SOFC systems are seen as most efficient and clean alternative to conventional diesel engines. In this context, the project SchIBZ has been initiated to develop a fuel cell based generator set for seagoing ships. A consortium of industrial and academic partners has been joined to develop a diesel based SOFC demonstrator with a rated power of around 50 kW. Adiabatic prereforming of diesel is one of the most efficient type of fuel processing for SOFC systems. The feasibility of adiabatic prereforming of commercial ultra-low sulphur diesel has successfully been tested with one of Haldor Topsoe’s catalyst.

The demonstrator was built to demonstrate the feasibility of the process and the robustness of the SOFC. It consists of 2 submodules supplying each 27 kW gross power. The key feature of the process is the anode gas recirculation that allows us to handle the diesel within the adiabatic prereformer without any deep desulphurization technologies on the one hand side and to increase the overall fuel utilization on the other hand side. Furthermore, an additional anode off-gas blower is used to levelize the pressure between the anode and the cathode, which reduces the risk of oxidation of the anode in case of leakages. The demonstrator was started on commercial road diesel containing 11 ppm_wt sulphur, 6.2%_vol FAME and 24%_wt aromatics. An electrical gross efficiency of 55% and fuel utilization of 73% could be demonstrated already during the first hours of operation.
Preparation of Freeze Cast T-SOFCs and a Universal Electrochemical Testing Fixture
Authors: Emley Benjamin , Woodson Theo , Bose Anima , Du Yanhai
Published: February 2020

Direct Internal Reforming (DIR) has potential to increase the value proposition of Solid Oxide Fuel Cells (SOFCs) by improving the electrical conversion efficiency, simplifying the SOFC system, and reducing manufacturing costs. Utilizing DIR in SOFCs, however, presents technical challenges. These challenges include balancing the thermal-mechanical stress present along a dynamic fuel pathway; avoiding carbon build-up on the anode surface; anchoring the reforming catalysts to the anode without reducing electrochemical active area; and maintaining efficient and selective reformation of the hydrocarbon fuels. Deactivation of catalysts typically starts with build-up of excessive carbon that cascades into more severe problems that damage the cell and eventually lead to system failure. We believe the solution for achieving stable and efficient DIR in the SOFC requires an optimized anode microstructure that is tuned specifically for DIR. Conventional ceramic manufacturing processes for SOFCs are limited with regards to microstructural optimization such as providing a hierarchical fuel pathway while maintaining high surface area. In this research, we have characterized and optimized a manufacturing process referred to as freeze casting of tubular SOFCs (T-SOFCs). The freeze casted anode was modified as a function of processing conditions and then was examined with techniques such as B.E.T. surface area measurements, scanning electron microscopy, and X-ray diffraction. The processing conditions that were optimized included changes in the slip formulation, casting temperatures, and freeze drying conditions. Electrochemical evaluation of the tubular SOFCs made via the freeze cast process revealed state-of-art performance and while creating an optimized surface for anchoring DIR catalysts. A universal electrochemical performance testing fixture for T-SOFCs is also discussed.
Effect of YSZ Coatings as Diffusion Barrier between Glass Sealing and Steel
Authors: Spotorno Roberto , Fracchia Elisa , Schiller Guenter , Piccardo Paolo
Published: February 2020

In solid oxide fuel cell (SOFC) stacks the sealing is a critical element which has to ensure gas tightness between different gas streams as well as electrical insulation in several parts of the system depending on its design. It has therefore to establish stable interfaces with different materials such as the ferritic stainless steel (FSS) used for interconnects frame or gas manifolds and the ceramic materials of the cell electrolytes. Therefore, sealants have to be chemically and mechanically stable in contact with such materials at the SOFC working conditions in terms of temperatures, thermal and stress gradients, and exposition to different gas compositions.

Glasses are widely used as sealing material because of their thermal expansion characteristics, mechanical properties, the possibility to obtain gas tight structures and ease of application. However, due to the operating temperatures, reactions and diffusion processes can occur at the interfaces resulting in the formation of undesirable phases that could compromise the glass properties increasing the risk of failures. The application of a barrier layer between the two components is considered as suitable countermeasure avoiding the migration of elements at the interfaces. In this work the barrier properties and compatibility at the interfaces of Yttria-stabilized zirconia (YSZ) has been investigated. YSZ layers have been applied by means of plasma spraying on as-rolled FSS substrates. Several glass compositions, applied on substrates with and without YSZ coating, have been tested at 780°C in static air up to 1000 h to investigate the barrier layer effects, the compatibility of the materials and the stability of the interfaces. Microstructural changes and migration of elements have been characterized post-experiment in cross-section by means of scanning electron microscopy- energy dispersive X-ray analysis.
Reactive-Element-Free, Silver-Based Brazes for SOFC Applications
Authors: Zhou Quan , Bieler Thomas R. , Nicholas Jason D.
Published: February 2020

The current go-to braze for SOFC applications is the Ag-CuO reactive air braze (RAB). As with other RAB brazes, the ability to use this braze with ceramic materials (such as yttria stabilized zirconia (YSZ) and oxide-protected stainless steel (SS)) is enabled by a braze component (in this case Cu) reacting with the brazing atmosphere to form a surface oxide that facilitates wetting. [1-3]. Although Ag-CuO provides an easy way to join YSZ and SS for SOFC applications, the insufficient ~45° wetting angle of the conventional Ag-4 wt.% Cu braze [1, 2] often leads to braze joint manufacturing defects (Type I pores). Further, the reduction of CuO during dual atmosphere (H2/O2) SOFC operation results in porosity (Type II pores) that: i) mechanically weaken the braze/SS and braze/YSZ interfaces and ii) facilitates H2invasion into the center of the braze, which in turn, hastens the development of gaseous water pockets within the braze (Type III pores) caused by dissolved oxygen and hydrogen meeting.

This poster will present a new method for silver brazing YSZ and SS without the need for reactive air elements. As shown in Figure 1, this procedure (which is performed under SOFC electrode compatible oxygen partial pressures ≥ 1x10-10atm) produces a braze that wets both the YSZ and SS. In addition, this procedure also produces Ag-YSZ bonding which has been shown by Kuhn et. al [4] to have a fracture energy two times higher than conventional Ag-CuO braze joints. It is expected that the elimination of Type I and Type II pores enabled by this new brazing method will increase SOFC braze joint lifetimes.

References

1. Kim, J.Y., J.S. Hardy, and K.S. Weil, Effects of CuO Content on the Wetting Behavior and Mechanical Properties of a Ag-CuO Braze for Ceramic Joining. Journal of the American Ceramic Society, 2005. 88(9): p. 2521-2527.

2. Kim, J.Y., J.S. Hardy, and K.S. Weil, Silver-Copper Oxide Based Reactive Air Braze for Joining Yttria-Stabilized Zirconia. Journal of Materials Research, 2005. 20(3): p. 636-643.

3. Chatzimichail, R., et al., Interfacial properties of (Ag plus CuO) brazes used as sealing materials in SOFC stacks. Journal of Materials Science, 2014. 49(1): p. 300-313.

4. Kuhn, B., et al., Mechanical Performance of Reactive-Air-Brazed (RAB) Ceramic/Metal Joints for Solid Oxide Fuel Cells at Ambient Temperature. Journal of Power Sources, 2009. 193(1): p. 199-202.

Figure 1. Back scattered electron cross-sectional images of a) the entire joint sandwich, b) the SS/braze interface and c) the braze/YSZ interface.

Figure 1
Prediction of Performance Degradation Due to Grain Coarsening Effects in Solid Oxide Fuel Cells
Authors: Mason Jerry Hunter , Celik Ismail Bektas , Lee Shiwoo , Abernathy Harry , Hackett Gregory A
Published: February 2020

Long term degradation of solid oxide fuel cells is one of the biggest impediments to commercialization. Due to the inordinate amount of time required to properly test degradation experimentally, physics based models which can predict long term degradation can be crucial time and money saving tools. At the cell level, one of the primary modes of degradation comes from grain coarsening and the resulting changes in microstructure properties. In this study a multi-physics model of a single fuel cell is presented which aims to predict performance loss as a function of time caused by coarsening in the electrodes of an LSM/YSZ/Ni SOFC. Microstructural properties are changed as a function of time from their initial values using functional relations derived from data from experiments and phase field models. Specie and charge transport equations are solved using these parameters to predict performance changes with time which result from the aforementioned microstructural changes. The model is first calibrated such that it correctly captures the performance and impedance response of a particular button cell at a given time without any degradation. This same model is run for a duration of 750 hours with performance data being measured for the same cell including impedance measurements being taken intermittently. Performance change over time predicted by the model are compared to experimental data. It is found that the model predicts a slower degradation rate than the rate which occurs experimentally. This is deemed reasonable as other forms of degradation are not being accounted for. The model is then used to make long term predictions of cell performance loss due to grain coarsening. The resulting degradation rate is considered to be the theoretical minimum which occurs when all other modes of degradation are not present. Work is underway to include other forms of degradation in the model so that a complete and robust degradation prediction tool is available for design analysis without the need for costly long term degradation measurements.
Evaluation of Impurity Levels in Cathodes of Seven Different SOFC Stacks and Modules before and after Long-Term Operation
Authors: Yamaji Katsuhiko , Ishiyama Tomohiro , Bagarinao Katherine Develos- , Kishimoto Haruo , Horita Teruhisa , Yokokawa Harumi
Published: February 2020

NEDO project “Fundamental Study on Rapid Evaluation Method of SOFC Durability” (FY 2013- 2017) focuses on a life time of 90,000 h with a degradation rate of 0.1 % / 1,000 h. Here, in addition to the three companies (Kyocera, MHPS, TOTO) which participated in the previous project on durability of SOFCs), three more ceramics manufacturers (NTK, NGK, Murata) have joined, and with the addition of Denso in December 2015, brings the total to 7 participating companies involved in the improvement of durability of SOFC cells/stacks. AIST, as a neutral research institute, is continuously carrying out dissectional analyses using secondary ion mass spectroscopy (SIMS) of cell stacks from each stack manufacturer before and after long-term operation in order to clarify the cumulative effect on degradation of trace impurities, which would be difficult to detect using conventional analyses. In this paper, we evaluate Impurity levels in cathodes of 7 different SOFC stacks and modules before and after long term operation.
Long-Term Test of a Solid Oxide Fuel Cell Stack with External Manifold Structure
Authors: Yang Jiajun , Yan Dong , Huang Wei , Pu Jian , Chi Bo , Li Jian
Published: February 2020

A 5-cell solid oxide fuel cell (SOFC) stack with external manifold structure is assembled and has undergone a long-term test for nearly 3500h at a current of 60A at 750 °C.Cells used in the stack are anode supported cells with yttria-stabilized zirconia (YSZ) electrolytes, Ni/YSZ hydrogen electrodes and YSZ based composite cathode. The size of the cell is 15×15 cm (active area: 13×13cm). Ceramic-glass sealant is used in the stack to keep the gas tightness between cells, interconnects and manifolds. In the test, pure hydrogen is used as fuel. Due to device limitations, the stack only got a maximum output of 350W at 95A. During the long-term test, the stack shows a degradation of 1.8% per 1000h. The stack is still running and shows a good stability. The applicability of stack with an external manifold structure in planar intermediate temperature SOFC has been demonstrated.