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This review discusses the groundbreaking advancements in electric current-assisted sintering techniques, specifically Flash Sintering (FS) and Ultrafast High-Temperature Sintering (UHS), for their application in Solid Oxide Fuel Cells (SOFCs). These innovative sintering methods have demonstrated remarkable potential in enhancing the efficiency and quality of SOFC manufacturing by significantly lowering sintering temperatures and durations, thereby mitigating energy consumption and cost. By providing a detailed overview of the mechanisms, process parameters, and material characteristics associated with FS and UHS, this paper sheds light on their pivotal role in the fabrication of SOFC components such as electrolytes, electrodes, multilayered materials, and interconnect coatings. The advantages, challenges, and prospective opportunities of these sintering technologies in propelling SOFC advancements are thoroughly assessed, underlining their transformative impact on the future of clean and efficient energy production technologies. [ABSTRACT FROM AUTHOR]

In this study, a numerical framework for microstructure design of functionally graded (FG) electrodes of solid oxide fuel cells (SOFCs) is developed using a number of mesoscale numerical simulations. The "multi-sphere" discrete element method, kinetic Monte Carlo method and lattice Boltzmann method are used sequentially to model the powder packing, powder sintering, and electrochemical reaction in the cathode. In the current FG electrode concept, porosity gradients with linear and nonlinear profiles are considered for La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) FG-cathodes. It is shown that in a porosity graded cathode, the concentration overpotential can be mitigated by improving the gas transport. However, when the porosity of the cathode is higher than approximately 0.40, the porosity gradient design contributes little to reduce the concentration overpotential but it rather increases the activation and ohmic overpotentials. In all cases, the porosity gradient design can suppress sintering, hence the thermal stability of the cathode can be improved. For cathode with an initial thickness of 25 μm and density range of 0.40–0.65, an optimal exponential factor of P = 1.5 is found for the best performance of the cathode. [Display omitted] • A numerical framework for lifetime simulation of the porosity graded cathode is developed. • Realistic shapes of the particles are considered for particle packing modeling of the cathode. • Influences of the microstructure on the activation, concentration and ohmic overpotentials are modeled. • Optimal graded microstructure is determined from the beginning of the cathode fabrication. [ABSTRACT FROM AUTHOR]

In this work, a deep learning accelerated homogenization framework is developed for prediction of elastic modulus of porous materials directly from their inner microstructures. The finite element method (FEM) and the homogenization theory are used to obtain the macroscopic properties of materials based on their microstructures. Based on a large dataset consisting of various microstructures and corresponding elastic properties via FEM, a deep convolutional neural network (CNN) is trained to capture the nonlinear functional relationship between the microstructure features and their macroscopic elastic properties. The deep learning model is finally well validated against extra new samples with excellent predictive performances. This demonstrates that the CNN deep learning model can be trusted as a surrogate model for the FEM based homogenization method, with the computation time being reduced by several orders of magnitude. The proposed deep learning framework is highly extendable for prediction of various macroscopic properties from microstructures. [Display omitted] • Meso scale finite element model (FEM) is built for calculation of anisotropic elastic properties of a porous SOFC cathode. • Convolutional neural network based deep learning model is built on basis of the large simulation data by FEM. • The deep learning framework is highly extendable for linking more macroscopic material properties to microstructures. [ABSTRACT FROM AUTHOR]

[Display omitted] • First 3D open-source pore-scale modeling of pure and composite MIEC cathodes. • Well validated pore-scale electrochemical open-source model framework is developed. • Evaluation under high current density, low operating temperature, and low P O2. • Local TPB/DPB current densities analysis at the pixel level. • Composite LSCF/GDC cathode with 20–40 μm thickness is recommended. Composite engineering is one of the most practical strategies for mitigating thermo-mechanical instability in state-of-the-art cobalt-based mixed ionic-electronic conducting electrodes for solid oxide cells. Nevertheless, the mechanism underlying improved performance and durability of composite electrodes is not substantially examined and understood. Pore-scale modeling can effectively bridge the gap between material property, microstructure discovery, and performance evaluation. However, most of the previous pore-scale models are built on in-house codes or commercial software that is closed-source to the public, limiting customization and community involvement. Here we report for the first time a microstructure-resolved 3D pore-scale model based on an open-source Lattice Boltzmann library, implementing a well-validated electrochemical module that considers gas, ion and electron transport, as well as electrochemical reaction at triple-phase-boundary (TPB) and double-phase-boundary (DPB). The pure La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) and 50/50 vol% composite LSCF/GDC (Gd-doped ceria) cathodes are reconstructed using focused ion beam-scanning electron microscopy and then are investigated under various current densities, temperatures, oxygen concentrations, and thicknesses. Results reveal the advantages of boosted TPB density and ionic conductivity outweigh the disadvantages of lower DPB density and electronic conductivity for the composite cathode. Furthermore, the composite cathode performs better at low temperatures and low oxygen concentrations due to the presence of more macropores, the stable bulk ion conductivity of GDC, and higher TPB density. Local current distribution at active sites indicates a thickness of 20 to 40 μm is favorable for reduced overpotential and moderate reaction homogeneity. [ABSTRACT FROM AUTHOR]

Microstructural properties such as relative density, triple phase boundary length, specific surface area, tortuosity factors are often calculated for microstructure-based analysis and modeling of solid oxide fuel cells (SOFCs). A realistic representation of the microstructure is a challenging and important issue for both experiments and modeling. In the present study, statistical correlation functions and a volume expansion method are used to determine the representative volume element size for the analyses of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ cathode microstructures in SOFCs. [ABSTRACT FROM AUTHOR]

Microstructural parameters such as triple phase boundary (TPB) density, surface area density, connectivity and tortuosity of different phases strongly influence the performance of solid oxide fuel cells (SOFCs). In this study, the effect of the powder morphology on the microstructural parameters of a La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 (LSCF) cathode is comprehensively examined using Kinetic Monte Carlo (KMC) simulations. A number of numerical samples consisting of spheres or clumped spheres are created using a Discrete Element Method (DEM), taking into account the powder morphology such as particle size, particle size distribution, particle aspect ratio and sphericity, and particle orientation. The DEM-generated numerical structures with different particle morphologies are submitted to the KMC simulations. Their effects on relative density, densification rate, surface area density, tortuosity factor of LSCF phase and tortuosity factor and connectivity of the pore phase are compared and analyzed. [ABSTRACT FROM AUTHOR]

The Potts Kinetic Monte Carlo (KMC) model, proven to be a robust tool to study all stages of sintering process, is an ideal tool to analyze the microstructure evolution of electrodes in solid oxide fuel cells (SOFCs). Due to the nature of this model, the input parameters of KMC simulations such as simulation temperatures and attempt frequencies are difficult to identify. We propose a rigorous and efficient approach to facilitate the input parameter calibration process using artificial neural networks (ANNs). The trained ANN reduces drastically the number of trial-and-error of KMC simulations. The KMC simulation using the calibrated input parameters predicts the microstructures of a La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 cathode material during sintering, showing both qualitative and quantitative congruence with real 3D microstructures obtained by focused ion beam scanning electron microscopy (FIB-SEM) reconstruction. [ABSTRACT FROM AUTHOR]

In this study, nano-sized Al 2 O 3 and Gd 0.1 Ce 0.9 O 1.95 (GDC) particles are added to La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) cathode material as sintering inhibitors for solid oxide fuel cells (SOFC) to improve the stability of the cell performance. Studies reveal that as the amount of the inhibitors increases, the sintering activation energy of the composite LSCF sample increases, resulting in retarded sintering kinetics indicated by the suppressed grain size of the sintered composite LSCF cathode. Long-term durability tests show that due to the enhanced stability of the microstructure of the composite LSCF cathode, the composite cathode exhibits improved performance stability. Furthermore, both the Al 2 O 3 and GDC additions can improve the hardness and elastic modulus of the cathode, while the electrical conductivity of both cathodes exceed 100 S/cm and can still meet the requirements for the SOFC in the operation temperature range of 600–800 °C. In light of the boosted electrochemical durability of the Al 2 O 3 -added LSCF cathode and much lower cost of Al 2 O 3 compared to the rare-earth element based GDC materials, LSCF cathode with a proper amount of the nano-sized Al 2 O 3 inhibitors is a good solution to enhance the mechanical property, electrochemical durability of LSCF cathode for the SOFCs at low cost. [ABSTRACT FROM AUTHOR]

The ohmic resistance in solid oxide fuel cells (SOFCs) mainly comes from the electrolyte, which can be reduced by developing novel electrolyte materials with higher ionic conductivity and/or fabricating thin-film electrolytes. Among various kinds of thin-film fabrication technology, the physical vapor deposition (PVD) method can reduce the electrolyte thickness to a few micrometers and mitigate the issues associated with high-temperature sintering, which is necessary for wet ceramic methods. This review summarizes recent development progress in thin-film electrolytes fabricated by the PVD method, especially pulsed laser deposition (PLD) and magnetron sputtering. At first, the importance of the substrate surface morphology for the quality of the film is emphasized. After that, the fabrication of thin-film doped-zirconia and doped-ceria electrolytes is presented, then we provide a brief summary of the works on other types of electrolytes prepared by PVD. Finally, we have come to the summary and made perspectives. Electrolytes strategy for lowering the operating temperature. [Display omitted] • The application of physical vapor deposition in the preparation of SOFCs electrolytes is summarized systematically. • The effects of deposition process and film configuration on thin-film electrolytes are carefully discussed. • The challenges and prospects of thin-film electrolytes fabricated by physical vapor deposition are pointed out. [ABSTRACT FROM AUTHOR]

High-performance durable commercial size, 12×12 cm2, electrolytes with GDC|YSZ|GDC tri-layer configuration are fabricated with less than 2.5-h reactive sputtering and followed by annealing at 1000 °C. SOFCs with sputtered electrolytes and LSCF single-phase cathodes show open circuit voltages close to the theoretical values and excellent electrochemical performances. The performance shows no sign of degradation during the 300-h stability test at 650 °C under 0.8 V. [Display omitted] • Durable large-area electrolytes are fabricated with facile reactive sputtering. • The sputtered GDC|YSZ|GDC tri-layer electrolytes require annealing at only 1000 °C. • Excellent performances are obtained incorporating LSCF single-phase cathodes. • The performance shows no sign of degradation during the 300-h stability test. Scalable and facile fabrication of large-area electrolytes by physical vapor deposition (PVD) for efficient and durable solid oxide fuel cells (SOFCs) is a promising way to tackle the issues such as elemental diffusion and warpage of cells resulted from high-temperature sintering in conventional wet ceramic methods. Herein, high-performance industrial size, 12 × 12 cm2, electrolytes are successfully fabricated by reactive sputtering on commercially obtained nickel oxide-yttria-stabilized zirconia (NiO-YSZ) anode without any pretreatment. Electrolytes of 6-μm-thick with gadolinium-doped ceria (GDC)|YSZ|GDC tri-layer configuration are fabricated with less than 2.5-h sputtering and followed by annealing at 1000 °C, much lower than that adopted in traditional wet process. In combination with traditional La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) cathodes, SOFCs with sputtered electrolytes show open circuit voltages close to the theoretical values, excellent electrochemical performances and long-term stability. The initial peak power densities of such cells reach 1.80, 1.24, 0.75 and 0.42 W cm−2 at 800, 750, 700 and 650 °C, respectively. The performance increases slightly in the initial stage and then stabilizes without degradation during the 300-h stability test under a constant voltage of 0.8 V at 650 °C. The scaled-up deposition area and the high deposition rate (∼2.5 μm h−1) show promising opportunities in the mass production of SOFCs using reactive sputtering. [ABSTRACT FROM AUTHOR]

[Display omitted] • A standalone diesel-fueled SOFC distributed power generation system is proposed. • With a steam/carbon ratio of 3.5, the proposed system shows an efficiency of 52.4%. • Higher steam/carbon ratio and higher SOFC temperature increase the efficiency. • Condensing the steam content in the raw syngas will improve the system efficiency. • S-based content negatively affects the system efficiency and needs to be removed. Solid oxide fuel cell (SOFC) recently emerges as a promising technology for distributed power generation with high energy efficiency. While H 2 production and delivery are still the hurdles, diesel can be accessed easily. Thus, it would be of great advantage to generate electricity through an SOFC-based power generation system fueled with diesel. In this work, a standalone diesel-fueled SOFC distributed power generation system combining a steam reformer, a water condenser, a desulfurizer, an SOFC, and a burner is proposed and analyzed thermodynamically. C 16 H 34 is used as a diesel surrogate fuel in the analysis. To realize independent operation of the system, all the heat required by the reformer is supplied by the combustion of the unreacted flue gas from SOFC. With a steam to carbon ratio of 3.5, a reformer temperature of 800 ℃, and an SOFC temperature of 800 ℃, the fuel utilization is determined to be 0.72, and the system presents an energy efficiency of 52.4%. The water condenser is of great importance to improve the system efficiency by eliminating fuel-dilution effect attributing to the existence of H 2 O, without which the energy efficiency decreases to 50.6%. Further, to add a desulfurization unit or to use pre-desulfurized fuel is of great importance as the existence of H 2 S will cause an immediate drop of the system efficiency of ∼ 5% and may lead to irreversible damage. A parametric study is performed and presented and the implications for future research focus are discussed. [ABSTRACT FROM AUTHOR]