bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Three-Dimensional Freestanding Nanofiber Electrodes for Electric Double Layer and Pseudo-Capacitors
Authors: Kalra Vibha 
Published: February 2020

Fabrication of novel three-dimensional material architectures is essential for development of energy storage devices that allow high rate operation with sufficient energy capacity. In this talk, I will present our work on development of freestanding nanofiber-based electrodes using a simple electrospinning methodology for application in supercapacitors (EDLC/Pseudocapacitors)
We have developed porous carbon nanofibers (PCNF) that exhibit specific surface area of >1500 m2/g and multi-levels of pore sizes in the range of micro (< 2 nm), meso (< 50 nm) and macropores (> 50 nm). We studied these materials as freestanding electrodes in 1) electric double layer capacitors (EDLC) using liquid (aqueous and ionic liquid), as well as solid-state electrolytes and 2) as platforms for polyanilene (PANi) electrodeposition to develop hybrid supercapacitors that integrate electric double layer and pseudocapacitive energy storage. The unique combination of pores at different length scales allows us to achieve a battery-like energy density of up to 80 Wh/kg, while retaining high power and cycle life in EDLCs. In-operando infrared spectroelectrochemistry was conducted to understand the transport of ions through the carbon electrode pores and its effect on performance in ionic liquid-based EDLCs. In the hybrid supercapacitor devices, we demonstrated that the PCNF mats retain their EDLC behavior post PANi coating providing a 366 F g–1 gravimetric capacitance, 140 F cm–3 volumetric capacitance, and up to 2.3 F cm–2 areal capacitance at 100 mV s-1 scan rate based on the weight, volume and area of the complete hybrid electrode – polyaniline coating and carbon substrate.
Ionic Liquid Mixtures As Electrolytes for Electrochemical Capacitors
Authors: Van Aken Katherine L , Beidaghi Majid , Gogotsi Yury 
Published: February 2020

While known for a higher power density than batteries, electrochemical capacitors are limited by their energy density for some energy storage applications. Since the energy density of the device is proportional to the square of operating potential window, an effective way to increase energy density of the device is by increasing this voltage window. Ionic liquid electrolytes are beneficial for this reason since they can theoretically operate at up to 6 V, though experimentally, the value is between 3-4 V, depending on the properties of electrode materials. Electrode materials can be made from high surface area carbons that contain a network of pores (activated carbon, carbide-derived carbon) or lower surface area carbons that consist of an outer surface where charging and discharging takes place. Though they boast a large operating potential window, ionic liquids are known to contain large and bulky ions. This can make it difficult to use an ionic liquid on a porous carbon with a range of pore sizes, some being very small, even though the specific surface area of the electrode material is higher. It has also been shown that the capacitance of porous electrodes is maximized when the ion size and pore size are equal.1 In this case, the ion is small enough to fit inside the pores while still large enough to take advantage of the surface area within the pore walls. While the outer surface materials allow a more accessible surface for adsorbing large ions, their capacitance is limited by their specific surface area. By designing an electrolyte based on mixed ionic liquids, 2 we can match the ions in the mixture to the multiple pore sizes of the electrode material. Imidazolium-based ionic liquids are chosen based on their variable alkyl chain length which alters the cation size and the TFSI is chosen as the anion for all ionic liquids. Different porous carbons with varying pore size distributions are used to illustrate the effect of ionic liquid mixture electrolytes.
1. Lin, R. et al. Solvent effect on the ion adsorption from ionic liquid electrolyte into sub-nanometer carbon pores. Electrochim. Acta
54, 7025–7032 (2009).
2. Van Aken, K. L., Beidaghi, M. & Gogotsi, Y. Formulation of Ionic-Liquid Electrolyte to Expand the Voltage Window of Supercapacitors. Angew. Chemie
127, 4888–4891 (2015).
Electrochemical Performance of Solid Oxide Cell Oxygen Electrodes Under Pressurization
Authors: Hughes Gareth , Railsback Justin , Butts Danielle , Barnett Scott A 
Published: February 2020

Pressurized operation is of interest for solid oxide fuel cells used in combined cycle applications, and for solid oxide electrolysis cells to influence the chemical constitution of the fuel produced. Here we present results on the effect of oxygen pressure on the electrochemical performance of a number of solid oxide cell (SOC) oxygen electrodes, studied in symmetrical cells by impedance spectroscopy. Electrodes investigated include single-phase (La0.8Sr0.2)0.98MnO3-δ (LSM), LSM - Zr0.84Y0.16O2-γ (YSZ) composite, LSM-infiltrated YSZ, single-phase La0.6Sr0.4Fe0.8Co0.2O3-d (LSCF), and LSCF-Ce0.8Gd0.2O1.95 (GDC) composite. All electrodes exhibited reduced electrode resistance with increasing oxygen pressure, with all but the single-phase LSM showing a resistance decrease of around pO2
-0.18. The single-phase LSM electrode displayed a pO2
-0.28 dependence. Two primary features were found in the impedance spectra equivalent model fits. A higher frequency peak around 103 Hz had around a pO2
-0.25 dependence and was attributed to charge transfer reaction limitations. Of all the electrodes, only the single-phase LSM sample did not exhibit the higher frequency peak. A lower frequency peak around 102 Hz had around a pO­2
-0.15 dependence, which was attributed to either ionization of an adsorbed oxygen atom or oxygen ion transport from the electrode material to the electrolyte material. Only the LSM-infiltrated electrode did not display the lower frequency peak. Overall, these results indicated that performance losses due to oxygen electrode resistance can be reduced by operating a SOC at elevated pressure.
Design and Fabrication of a 600W Anode Supported Flat Tubular SOFC Stack
Authors: Ji Weijie , Zhang Lei , Ming Li , Jiang Yousong , Xie Bin 
Published: February 2020

Keywords: SOFC stack, flat tube, metallic support, Ag-Cu air braze,
Introduction
Recently, great interests are focused on Solid Oxide Fuel Cells for future energy economy. In order to reduce the cost and increase the lifetime of SOFCs, lowering the working temperature is necessary. To meet the demands, new stack structures and materials are developed. Among them, flat tubular stacks are shown to be promising for their performance and fabrication techniques, and also metallic materials are applied as interconnect and support for their characteristics [1].
In this work, we design and fabricate a 600W anode supported flat tubular SOFC stack. The stack is composed of 36 flat tubular cassettes made by FeCrAl alloy. Cells composed of NiO-YSZ (anode)/ YSZ (electrolyte)/LSM-YSZ (cathode) are sealed on cassettes by Ag-Cu air braze. Experimental
The schematic diagram of stack structure is shown in Fig 1. A short stack is composed of several metallic cassettes made by FeCrAl (a commercial product: 1Cr21Al4). Five frames are located on the surface of the cassette, on which cells are sealed on the anode side by Ag-Cu air brazing. Ag-Cu brazes also serve as the electrical connect to the anode. FeCrAl interconnects with Ag mesh serve as the electrical connect to the cathode. Ag wires connect th e Ag-Cu braze with interconnects. Fuel inlet pipe is located at one end of the cassette and outlet is on the other end. Pipes are sealed by Ag rings with ceramic tubes. Fuel flows along the pipes and the ceramic tubes.
Cells of 5x5cm2 are produced as described in previous results [2]. Anode substrates of NiO-YSZ are produced by conventional tape casting and sintering methods. YSZ electrolytes of 15 um are produced by spray and cathodes of 4x4cm2 LSM/YSZ are produced by screen printing.
Results and Discussion
Stack of 36 cassettes are produced and tested. Humidified H2(2-3% H2O) is applied as the fuel and air as the oxidant. A mean open circuit voltage of 1.03V per cassette is obtained under working temperature 750 centigrade. The stack has been tested for 1000 hours. Ag-Cu braze and FeCrAl show good stability and reliability.
Fig.2 shows the performance of the 36-cassette stack under different fuel flow. When 15slm H2 is supplied to the stack, a maximum output of 614W and an average power density of 213mw/cm2are obtained. The fuel utilization efficiency is 51%.
Conclusions
An anode supported flat tubular stack is designed and produced. Stack of 36 cassettes are produced and tested with humidified H2 as fuel. An average power density of 213mw/cm2is obtained, higher than those reported results of the stacks [1].
References
[1] Ludger Blum etc, Int. J. Appl. Ceram. Technol., 2 [6] 482–492 (2005).

[2] Lei Zhang etc, Journal of Alloys and Compounds 586 (2014) 10–15

Figure 1
Development of Modelling and Testing for Analysis of Degradation in Solid Oxide Fuel Cells
Authors: Maillard John Geoffrey , Steinberger-Wilckens Robert 
Published: February 2020

The ability to predict the lifetime performance of an SOFC can give guidelines for where improvements and alterations can be made in terms of production, operating parameters and cell design. Multiple attempts have been made to implement models which can respond to all the varying parameters to give their characteristic performances over longer operational lifetimes than is feasible to physically test.
This study focuses on continuous degradation mechanisms and the impact they have on the components of a single repeating unit level, i.e. the anode, cathode, electrolyte, metal interconnect and sealants. Currently the model being developed deals specifically with anode and electrolyte degradation. Depending on operating conditions, SOFC cells suffer from Ni particle agglomeration, coarsening, and volatilisation which lead to increased overpotential in the anode. A loss in the ionic conductivity in the electrolyte is also observed.
Using models derived for these degradation mechanisms combined with percolation models, Matlab ® coding has been developed to outline the loss of performance in a single repeating unit for a given set of operating parameters. These equations will be tested against real life data to establish their validity and, where necessary, adjusted for accuracy. Further progress will allow for accelerated testing of components and cells to determine the long term performance of a given material alteration or design change.
Fabrication of Large-area Multi-scale-architectured Thin-Film SOFC via Commercially Viable Thin-film Technology
Authors: Noh Ho-Sung , Hong Jongsup , Kim Hyoungchul , Yoon Kyung Joong , Kim Byung-Kook , Lee Jong-Ho , Son Ji-Won 
Published: February 2020

We have reported the ultimate performance level that the anode-supported solid oxide fuel cell (SOFC) can reach by employing thin-film electrolytes and nano-structure electrodes, without drastically changing the component materials. Based on the platform named as multi-scale-architectured thin-film SOFC (TF-SOFC), thin-film electrolytes of thickness less than 1 micron and electrodes with particle size in nm scale are successfully realized on NiO-YSZ anode supports, and a peak power density exceeding 500 mWcm-2 at 500 oC is obtained.
Although this approach proves the potential of the thin-film technology to significantly improve the low-temperature performance of the SOFC, it is highly questionable that this platform can be transferred to the commercial sector because pulsed laser deposition (PLD) is employed to fabricate the cells. PLD is the best thin-film deposition research tool for the oxide with complex composition and has a high deposition rate, which is tremedous advantages for the thin film components in the TF-SOFC. Nevertheless, PLD has a small deposition area which cannot be larger than several cm by several cm in general, which is the most critical disadvantage of PLD to be employed as a commerciallization processing technique.
Therefore, to be employed in the commercial sector, it is the prerequisite that the multi-scale-architectured TF-SOFC should be realized by commercially viable techniques other than PLD. In this regard, the present study deals with the realization of the same platform by using other technique, specifically sputtering. Several key issues, such as nano-composite deposition, stoichiometry transfer, crystallinity of the thin films, etc., will be identified and the possible solutions to resolve these issues in sputtering will be suggested. A larger area (~ 5 cm by 5 cm) TF-SOFC using a 2-inch sputtering system will be fabricated to check the fesibility and its chracteristics will be compared with that of the cell fabricated using PLD.
Thermo-Mechanical Reliability of SOFC Stacks during Combined Long-Term Operation and Thermal Cycling
Authors: Greco Fabio , Nakajo Arata , Wuillemin Zacharie , Van herle Jan 
Published: February 2020

Thermo-mechanical issues in planar solid oxide fuel cells (SOFC) must be understood and overcome to meet the reliability standards for market implementation. This study presents a modelling framework constituted by a thermo-mechanical and electrochemical model of a SOFC stack. Rate-independent plasticity and creep of the component materials have been considered. Modified periodic boundary conditions have been implemented to simulate the behaviour of a single repeating unit (SRU) in a stack.
The analysis starts with the simulation of stack conditioning procedures, which aims at capturing the stress build-up/relaxation throughout the several steps in the stack components production and assembly.
The simulated stresses after the initialisation sequence provide the initial stress state for the simulation of stack operation, which consists in importing into Abaqus software the temperature profiles from thermo-electrochemical simulations. The study includes long-term steady-state operation in both co-flow and counter-flow configuration, interrupted by thermal cycling. The temperature profiles implemented in the long-term operation cases correspond to operation under internal steam-methane reforming.
The simulation results show that the contact pressure is significantly lower at room temperature, after a first thermal cycle after stack qualification. The contact pressure is lost in large regions, which is expected to alter in the long-term the electrical conductivity of the interface. It also progressively decreases during long-time operation. Thermal cycling after long-term operation worsens the extent of loss of contact pressure at room temperature. Most of the active area is close to no-contact pressure.
No critical stresses were found in the sealant joining the cell to the SRU. In contrast, the stresses in the manifold sealants were found to be relevantly high. Similarly to the evolution of contact pressure, long-term operation increases the risks of sealant failure during thermal cycling.
Figure 1: On the top side, temperature field in co-flow configuration plotted on the deformed shape of a short stack (deformation along the z-axis magnified by 300:1), state: “Start Operation”. On the bottom side, contact pressure at the interface anode/GDL fuel along the symmetry line of the SRU. Lines 3b, 4 and 5 are referred to the case of long-term operation in co-flow configuration.

Figure 1
Development of Electrolyte Supported Cells Based on a Thin 3YSZ Substrate: Through Optimized Contact Layer to High Power Density
Authors: Trofimenko Nikolai , Kusnezoff Mihails , Klemm Denis , Schimanke Danilo 
Published: February 2020

The 3YSZ substrates with thickness between 90-200 μm are excellent from mechanical and economical points of view, but its main disadvantage is rather low ionic conductivity when compared with scandia-doped zirconia or fully stabilized 8YSZ. With decreasing electrolyte thickness between 40-60 μm, it is possible to significantly improve the electrochemical performance of the 3YSZ based electrolyte-supported cell (ESC) thereby fully utilizing the available mechanical stability. Development and progress in manufacturing of high power density electrolyte supported cell based on a thin (50 µm) 3YSZ substrate is presented. The cells with improved cathode based on LSMM’/ScSZ and the multilayer anode based on Ni/GDC cermet show very good electrochemical performance. The maximum power density increases up to 750 mW/cm2 for developed cell without additional contact layer at 0.7V@860 °C and is greater than one of the commercial cells based on partially scandia stabilized zirconia electrolytes as well as 95 µm 3YSZ. The changes in polarization resistance of tested cells under different operating conditions as well as during redox-cycling and durability tests are discussed on basis of analysis of impedance spectra. The developed cells show a good long-term stability (proved for >1300 h) under high current density (500 mA/cm²@850 °C, N2:H2:H2O=55:40:5, air). The estimated power degradation rate is lower than 0.5%/1300 h. By using Ni/GDC anode the redox cycle ability of cell under real operating conditions is considerably improved. To reduce the contacting losses in stack different contacting layers have been tested and optimized in test bench. The influence of different parameters on electrochemical performance of the cell as well as first results for cells integration in stack are presented and discussed.
Status of Light Weight Cassette Design of SOFC
Authors: Margaritis Nikolaos , Blum Ludger , Batfalsky Peter , Bohmann Dirk , Ceschini Sergio , Fang Qingping , Federmann Dirk , Kroemer Joachim , Peters Roland , Steinberger-Wilckens Robert 
Published: February 2020

Lightweight SOFC stacks are currently being developed for stationary applications such as residential CHP units, for automotive applications such as APU and for portable devices. Within the EU funded project the so-called Jülich CS-design has been improved for lightweight SOFC stacks using glass-ceramic sealings that decouple the thermal stresses within the stack and at the same time allows optimal sealing and contacting. The design is highly suitable for industrial low-cost manufacturing and automated assembly. To determine the effect on the thermomechanical behaviour of the fuel cell stack, modelling and coupled thermomechanical analysis have been performed. Based on the analysis results in combination with the manufacturing experience, test results, and post-test analysis from previous stack design, substantial changes have been made to the CS-design in order to improve mechanical robustness of the stack.
The manufacturing of single parts, particularly due to the improved design of sheet metal interconnects, as well as the assembling processes are suitable for low-cost mass manufacturing. The novel decal concept of glass-ceramic sealant screen printed on foil in order to produce green tapes is used for joining the stack layers offering an enormous potential for cost savings in industrial assembly process. The new design CSV(D2.0 in the MMLCR=SOFC project) furthermore has extended the process window of the laser welding joining process.
First CSV–design stack tests showed a comparable electrochemical performance to the previous CSIV design. The good adhesion of the glass sealant applied on steel sheet by screen printed tape and good contacting behaviour between cells and interconnects were furthermore confirmed by post-test analysis.
Thermodynamic Evaluation of Integrated Heat-Pipe Reformer SOFC System
Authors: Herrmann Stephan , Jimenez Arreola Manuel , Gaderer Matthias , Spliethoff Hartmut 
Published: February 2020

In the presented work a medium-sized integrated system based on a sodium heat pipes powered allothermal fluidized bed gasification and SOFC is introduced, simulated and validated in Aspen Plus. Suitable feedstocks for such fluidized bed gasification systems are for example waste and biomass, especially wood. The concept development and evaluation have been conducted as part of the EU FCH-JU project SOFCOM.
During the allothermal heat pipes gasification process heat for the endothermic gasification reactions is transported into the gasification chamber via the heat pipes. The heat pipes allow low temperature differences using mainly latent heat transport. Inside the heat pipes sodium is evaporated on the hot side by a heat source (i.e. combustion chamber) and condensed on the cold side (i.e. gasification chamber). Heat pipes based gasification has proven to be a reliable technology at different installations by the company Agnion energy GmbH and others. The gasifier model has been validated against data from this type of gasifier. The SOFC model applied is a thermodyamic model, which has been developed in the frame of SOFCOM and already described in detail in other works.
In the presented system configuration the product gas from the gasifier is cleaned during several process steps at an intermediate temperature of 350°C. After the cleaning procedure the gas is introduced into the SOFC anode where it is converted into electricity and high temperature heat at a fuel utilization rate of 80%. At the same time preheated air is fed to the cathode of the SOFC. The SOFC exhaust is fed into a fluidized bed post combustion chamber where residual fuel is burned with residual oxygen. Heat is extracted via the heat pipes from the combustion chamber, as well as the SOFC itself. Combustion exhaust gases are used to preheat the cathode air. Residual exhaust heat is used to generate high pressure superheated steam, which in turn is expanded in a steam turbine. At this point, the steam necessary for the fluidization of the gasifier and gasification agent is not produced in a separate steam generator but instead extracted from the steam turbine. Especially by means of utilization of excess heat from the SOFC and its exhaust gases via the heat pipes and full integration of the steam cycle the electrical efficiency of the combined system reaches up to 62%LHV.

Figure 1