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Solid oxide electrochemical cells (SOCs) have attracted increasing attention as energy conversion devices due to their high efficiency. The microstructures of SOCs play a critical role in their electrochemical performance, however, characterizing them is challenging due to their heterogeneous microstructure. This paper describes a quantitative analysis of SOC microstructures via 3D reconstruction technique using a focused ion beam-scanning electron microscope (FIB-SEM) dual beam system. The reconstructed SOC electrodes offer microstructural characteristics, including particle and pore size, tortuosity, connectivity, and triple-phase boundary (TPB) density. These in-depth analyses contribute to better understanding of the electrochemical behavior of SOCs.

Low-temperature solid oxide fuel cells (LT-SOFC) operating below 650 °C have attracted attention as a next-generation fuel cell. Although much effort has been paid to develop such fuel cells, it still remains challenging to satisfy all the requirements ensuring practical operation, such as power output and durability. Here we demonstrate 4 cm × 4 cm multiscale structured LT-SOFCs having a record high power output of 13 W per single cell at 500 °C via a large-area ceramic micropatterning and thin-film depositions. Our cell exhibits excellent long-term stability with performance degradation of less than 0.05% per 500 h. Quantitative microstructure and electrochemical analyses reveal that the proposed cell significantly lowered both ohmic and polarization losses than the reference planar cells. This work features a facile and powerful tool to implement robust and large-area 3D architectures in LT-SOFCs, which opens up opportunities to produce practical LT-SOFC systems satisfying both power and durability.

Herein, for the first time, we demonstrate ultra-fast fabrication of a tape casted NiO-yttria stabilized zirconia (YSZ) anode support for solid oxide fuel cells (SOFCs) using resonant acoustic mixing (RAM) technology. Due to its characteristics of non-contact and high-intensity acoustic field-assisted mixing, NiO-YSZ tape-cast slurry is prepared via a RAM process within ∼0.5 h, > 140 times faster than use of a conventional ball-milling (BM) process (∼72 h). During the RAM process, liquid binders more effectively penetrate into soft agglomerated ceramic powders and covered larger surface area than the case of BM process. The optimization of RAM procedure requires more subdivided mixing sequence and higher content of binders and plasticizers compared to that of the BM. Despite drastically reduced mixing time, the microstructures of RAM Ni-YSZ anode, quantified via a 3D reconstruction, are statistically identical to that of BM Ni-YSZ. The SOFC employing RAM Ni-YSZ anode support achieves 0.55 W/cm2 at 750 °C in peak power density and exhibits high durability for 300 h without noticeable degradation. Thus, our results demonstrate that the RAM process is a highly effective and ultra-fast mixing technology to produce high performance SOFC components.

The key challenge in all-solid-state batteries is to construct well-developed ionic and electric conductive channels within an all-solid-state electrode, with an extensive contact area between electrode components. Hence, a new design methodology is proposed for all-solid-state electrodes utilizing a 3D geometry interpretation tool and electrochemical simulator. Firstly, the 3D structures of all-solid-state electrodes are generated using the voxel array formation. Secondly, with these structures, not only physical properties such as the specific contact area of the active materials, but also conductivity values can be identified. Subsequently, the main parameters derived from the 3D structures are utilized to build an electrochemical model to predict the cell performance. This three-step process will provide key insights on how 3D structures of all-solid-state electrodes must be constructed by predicting their preliminary physical and electrochemical properties with the help of computational simulations.

Conversion of CO2 into useful chemical products by solid oxide electrolysis cells (SOECs) is a promising technology capable of reducing CO2 concentration for a carbon-neutral society [1]. This electrochemical device has several advantages such as high-energy efficiency and fast electrode kinetics due to its high operating temperature. Conventionally, Ni/YSZ cermet has been widely used as the cathode material of CO2 electrolysis system. However, they are prone to degrade under CO2 atmosphere due to the oxidation of nickel, particle agglomeration, and carbon deposition. Therefore, the development of alternative cathode materials with high electrocatalytic activity and good long-term stability for CO2 reduction reaction (CO2RR) is highly needed. The perovskite-type mixed ionic and electronic conducting (MIEC) oxides are widely investigated as the promising alternatives to the Ni/YSZ cermet cathode. Among them, double perovskite oxides PrBaCo2O5+d(PBCO) material is attracting attention because of high oxygen surface exchange, diffusion coefficients and adequate mixed ionic and electronic conductivity. However, this material is easily degraded in the presence of CO2 impurity, with the formation of BaCO3 nanoparticles [2]. To overcome this issue, doping the B-site Co cations with transition metals and tailoring the cation mismatch by controlling A-site dopant ratio in PBCO were selected as a novel strategy. As a result, it was proved that co-doping was an effective way to improve both electrochemical and surface chemical stability. Our design strategy could benefit the preparation of highly active and stable cathodes for direct CO2 reduction for SOECs. References [1] Lee, Seokhee, et al. Advanced Energy Materials (2021): 2100339. [2] Zhu, Lin, et al. Applied Surface Science 416 (2017): 649-655.

Formulating knowledge of structure-function relationships in heterogeneous catalysis is central to the rational design of highly efficient catalysts, yet the elucidation of dominant reaction sites has remained as a grand challenge for researchers. Here, we present a novel methodology that can be used to visualize metal-gas and metal-oxide-gas interfaces in three dimensions and to quantify their catalytic activity levels. As a case study, CH4 oxidation occurring in a Pt/CeO2 system is chosen. By employing thermally robust Pt@CeO2 model catalysts with size-tunable and monodisperse cores, and gas-permeable shells, we reconstruct a series of heterogeneous structures in 3D via electron tomography and match the information precisely to catalytic activity data and theoretical calculations. This strategy reveals that the two different interfaces concurrently catalyze the CH4 oxidation and that their contribution to the overall reaction rate changes dynamically with respect to the Pt size, temperature, and gas atmosphere. Our results provide a new analytic platform on which to explore reaction pathways and mechanisms applicable to multiple reactions and materials.

Composite cathodes comprising nanoscale powders are expected to impart with high specific surface area and triple phase boundary (TPB) density, which will lead to better performance. However, uniformly mixing nanosized heterophase powders remains a challenge due to their high surface energy and thus ease with which they agglomerate into their individual phases during the mixing and sintering processes. In this study, we successfully synthesized La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF)–Gd0.1Ce0.9O1.95 (GDC) composite cathode nanoscale powders via an in situ sol–gel process. High-angle annular dark field scanning transmission electron microscopy analysis of in situ prepared LSCF–GDC composite powders revealed that both the LSCF and GDC phases were uniformly distributed with a particle size of ∼90 nm without cation intermixing. The in situ LSCF–GDC cathode sintered on a GDC electrolyte showed a low polarization resistance of 0.044 Ω cm2 at 750 °C. The active TPB density and the specific two phase (LSCF/pore) boundary...

To lower the carbon emission from the rising consumption of fossil fuels, electrochemical devices such as fuel cells and batteries, which can produce or store electricity from renewable resources, are attracting attention. Both systems require an electronically insulating solid membrane, which separates the cathode and anode to prevent short-circuiting. To improve the performance of porous electrodes, researchers have focused on tuning the electrode microstructure. The addition of highly ionic conducting materials to the electrode is commonly used to maximize the reaction site density. However, microstructural features, such as particle size distribution, electrochemically active site density and connectivity of each phase, are difficult to quantify only using conventionally used characterization methods such as scanning electron microscopy (SEM). One well-established method for obtaining three-dimensionally interconnected microstructural information is serial sectioning using a FIB/SEM dual beam system. Using this technique, more reliable and accurate quantification of the SOFC and ASSLIB electrodes microstructure are available. Also, the quantified features will be reflected in the responses of electrochemical impedance spectroscopy (EIS) measurements. These results can provide a link between them. Therefore, the aim of this study is to three-dimensionally reconstruct the microstructure of solid-state energy devices via FIB/SEM dual beam system and to quantify their microstructural features. Also, these results will be combined with the electrochemically analyzed properties to further understanding their relationship with microstructural properties.

We present a fast 3-D scattering center extraction algorithm using the shooting and bouncing ray technique. The proposed algorithm generates a 3-D inverse synthetic aperture radar image from which a set of 3-D scattering centers is then extracted using the CLEAN algorithm. In the conventional extraction algorithm, computation time is improved using the fast Fourier transform (FFT)-based scheme. However, the memory requirement is greatly increased because of the high oversampling required to mitigate the interpolation error. Evaluation of memory-time tradeoffs indicates that the conventional algorithm is still too time consuming given the constraints of practical memory. Thus, a modified FFT-based scheme is proposed to improve computation time without increasing the memory requirement. Through modifying the ray spread function, the distortion from the interpolation error is mitigated without the use of high oversampling. Implementation based on the proposed FFT-based scheme accelerates the image formation process significantly. Numerical simulations of realistic targets are presented to demonstrate the performance of the proposed algorithm.

Solid oxides are attractive electrolyte materials for all-solid-state lithium batteries (ASSLBs) owing to their high stability and pure Li-ion conductivity. Nevertheless, the electrochemical performance of ASSLBs employing solid oxide-based electrolytes cannot compete with ASSLBs with sulfide or polymeric electrolytes due to poor interfacial contact and high boundary resistance between the active materials and solid oxide electrolytes. To overcome this hurdle, elaborate microstructural analysis of the interface of the active material/solid oxide electrolyte in ASSLBs is essentially required since the interfacial contact area dominantly acts as the ion pathway and the electrochemical reaction site in the electrode. Although recent attempts on interfacial structure analysis of ASSLBs have provided simple 2D or semi-3D microstructural features, the results have not yielded deep insights. Herein, we investigated the interfacial defects in an all-solid-state electrode with a solid oxide electrolyte via a 3D digital twin technology combining 3D structural quantification and physico-electrochemical simulations to unravel the intrinsic limitations of solid oxide electrolytes. The in-depth results can be used to design materials and optimize electrode design parameters for ASSLBs.

Since the introduction of a fast Fourier transform (FFT)-based convolution scheme between an impulse train and a ray spread function for the inverse synthetic aperture radar (ISAR) image formation using shooting and bouncing ray (SBR), remarkable progress has been made in reducing calculation time. However, because of an interpolation algorithm, which is essential to the FFT process, it necessarily causes the distortion of image. The present work is an attempt to generate an accurate image without loss of calculation time efficiency. Specifically, by removing dominant interpolation error contribution from the prior ray spread function, the distortion is prevented without the use of the time-consuming higher-order interpolation or high oversampling. The proposed scheme is simulated for several 3-D CAD models and demonstrated by comparing the image using the proposed and existing scheme under the same conditions.

When a receiving antenna array operates on a complex environment, the ideal phase differences of the receiving voltages of the antenna array are significantly distorted by both mutual coupling and platform scattering. This distortion causes performance degradation of the direction of arrival (DOA) algorithms. For estimating and compensating for the phase distortion, an analysis of the receiving voltages of the receiving antenna array on the platform is required. In this paper, we propose a hybrid UTD-ACGF technique for modeling port voltages of the receiving antenna array on a complex environment. The complex environment is modeled by UTD technique, and the antenna array is modeled by ACGF. In order to explain the coupling effect between the complex environment and the antenna array, we use the first perturbation series approximation based on the exact mutual coupling perturbation series. The hybrid UTD-ACGF results are verified through comparison to MoM results. Finally, we statistically define a distortion matrix that has a relation between the distorted port voltages and the ideal port voltages. The distorted port voltages are evaluated using the hybrid UTD-ACGF technique as a backbone. In order to enhance the performance of the DOA algorithm, we efficiently estimate and compensate for the distortion matrix. A DOA simulation using the MUSIC algorithm is performed to confirm the compensatory effect of the distortion matrix.

Accurate and fast inverse synthetic aperture radar (ISAR) image formation using the shooting and bouncing ray (SBR) technique has been examined in order to facilitate precise and fast signature prediction for a known target in target recognition. A fast Fourier transform (FFT)-based convolution scheme has been used to accelerate the image formation using the SBR technique. The scheme represents an image domain ray-tube integration formula, which consists ray-sum procedure, through a convolution operation between an impulse train and a ray spread function. However an interpolation algorithm, which is entailed in the scheme, distracts the image, therefore, a FFT-based accurate convolution scheme is proposed to improve in accuracy of the image formation. The accurate scheme utilizes a modified ray spread function to minimize the distortion. In this paper, we demonstrate the accurate convolution scheme based on the linear interpolation for a complex and realistic 3D CAD model.