Anode Microstructure Research Articles

Co‐Generation of Electricity and Chemicals From Methane Using Direct Internal Reforming Solid Oxide Fuel Cells

AbstractThe co‐generation of electricity and chemicals via direct internal reforming solid oxide fuel cells (DIR‐SOFCs) offers a promising route to carbon‐neutral energy solutions. However, challenges such as inadequate performance and fast degradation, particularly when using hydrocarbon fuels like CH4, hinder the deployment of DIR‐SOFC technology. This study addresses three critical issues: the effect of fuel composition on electrochemical properties, the mechanisms and microstructural impacts of carbon deposition, and the practical feasibility of DIR‐SOFCs at an industrial scale. First, comprehensive polarization and impedance analyses are conducted to assess the impact of varying fuel compositions—specifically p(CH4) and p(H2O)—on DIR‐SOFC performance. Second, advanced morphological characterization, machine learning‐assisted 3D reconstructions, and numerical simulations are utilized to reveal carbon deposition behavior and its effects on anode microstructures. Quantitative analysis of carbon's impact on pores, Ni, and YSZ phases provides novel insights into carbon‐induced microstructural changes. Finally, the industrial‐scale co‐generation of electricity and chemicals is validated, emphasizing both energy efficiency and operational stability. This study enhances the understanding of electrochemical and microstructural mechanisms, offering crucial insights for optimizing DIR‐SOFC design and operation, and laying the groundwork for their broader adoption in a carbon‐neutral future.

Effects of La addition on the microstructure, corrosion behavior and discharge performance of the as-casted AP63 anodes for Mg–air batteries

Effects of La addition on the microstructure, corrosion behavior and discharge performance of the as-casted AP63 anodes for Mg–air batteries

The effect of the nature of pore former on the microstructure of SOFC anodes based on NiO and 10YSZ formed by hybrid 3d printing

The effect of the nature of pore former on the microstructure of SOFC anodes based on NiO and 10YSZ formed by hybrid 3d printing

Crystal Step‐Induced Uniform and Rapid Deposition on Zinc Anodes

AbstractAqueous Zn‐ion batteries have emerged as promising candidates for large‐scale energy storage owing to their high safety and low cost. However, dendrite growth and side reactions compromise the stability of the Zn anode in practical applications. Here, a novel Zn anode featuring well‐designed crystal steps along the (002) facets, referred to as Step‐Zn is introduced. The intersections of the (002) and (100) planes in these crystal steps create preferential adsorption sites for Zn2⁺ ions, promoting initial electro‐epitaxial growth of Zn that uniformly covers the crystal steps. This process effectively regulates subsequent Zn deposition, ensuring fast reaction kinetics and smooth morphology without dendrite formation. Consequently, the unique Step‐Zn anode exhibits excellent cycle life over 6000 times at 3 mA cm−2 and low greatly reduced polarization voltage under high areal currents and capacities. Integrated with activated carbon (AC) cathode, the Step‐Zn||AC full cell demonstrates excellent durability over 10 000 cycles at 5 A g−1. This work offers valuable insights into controlling Zn deposition modes by engineering the surface microstructure of Zn anodes with greatly extended cycling stability.

Degradation analysis of plasma sprayed metal-supported solid oxide fuel cell: The evolution of electrode processes under polarization

Metal-supported solid oxide fuel cells (MS-SOFCs) prepared by plasma spraying exhibit promising potential for scale-up applications, where the key lies in breaking through the challenges of limited lifetime and durability. Although electrochemical impedance spectroscopy (EIS) has been widely used to unfold the complex electrode processes in electrochemical reactions, there are still some concerns concerning the in-depth understanding and scientific evaluation of the degradation mechanism of cell long-term performance. In this study, the contribution of each resistance to the overall performance degradation is separately determined by coupled equivalent circuit model (ECM) based on the deconvolution of recorded EIS data at different DC biases. It is found that the deterioration of cathode surface oxygen exchange and O2− conduction causes more than 64 % of the total resistance increase, followed by the anode charge transfer reaction and gas-phase transport (24.91 %), and then the ohmic resistance (9.73 %). However, the correlation between the output voltage drop of MS-SOFC under load and the gas-phase diffusion resistance gradually increases, indicating a shift in the cell degradation mechanism. Combined with the post-test characterization of the aged cell, it can be inferred that the degradation is mainly attributed to the densification of the anodic microstructure and the cathodic elemental segregation. Additionally, attention should be paid to the effects of the thickening of the metal substrate oxide layer and thermal mismatch on the structural stability of MS-SOFC.

Microstructure Characterizations of Electrodeposited Magnesium after Discharge/Charge Cycles for Rechargeable Magnesium Battery

Rechargeable magnesium (Mg) batteries attract lots of attention owing to their high theoretical volumetric energy density and low cost from the natural abundance of Mg. Additionally, Mg is less prone to dendrite growth during charging, improving the battery safety. While most studies of rechargeable Mg batteries focus on developing new electrolytes and their performances, the microstructure of the Mg metal anodes during discharge/charge cycles is not fully characterized. Therefore, in this report, we investigated the microstructure evolution of electrodeposited Mg after discharge/charge cycles on both a bulk Mg metal anode and a copper (Cu) current collector in an all phenyl complex (APC) electrolyte.The electrodeposited Mg on both the Mg anode and the Cu current collector at a current density of 2.25 mA/cm2 with a capacity of 1.5 mAh/cm2 show uniform distributions of Mg grains with an average grain size of about 1 to 2 μm. Subsequent Mg stripping with intermediate current density (0.75 mA/cm2) results in non-uniform discharge holes and possible local exposure of the substrate underneath, which could deteriorate the anode integrity. In contrast, the stripped electrodeposited Mg at relatively large (2.25 mA/cm2) and small (0.25 mA/cm2) discharge current densities show dense and uniform discharged holes on the surface. The microstructure evolution of the electrodeposited Mg on different substrates will be discussed based on the plating/stripping overpotentials and the interfacial impedances of the electrodeposited Mg under different conditions.

Automated Microstructural Analysis of Anodic Catalyst Layers in Proton Exchange Membrane Water Electrolyzers (PEMWEs) Using Python-Based Image Processing Framework

Adverse climatic conditions caused by greenhouse gas (GHG) emissions from non-renewables have led to increased focus on utilization of clean alternative fuels such as hydrogen (H2). Clean H2 can be obtained via electrochemical reaction of water splitting through proton exchange membrane water electrolyzers (PEMWEs). However, challenges to its widespread commercialization lie with the high H2 production cost, a large portion of which comes from use of expensive anodic catalyst materials. To improve anodic catalyst utilization to attain better performance at reduced cost, a thorough understanding of anodic catalyst layer microstructure is needed. In-depth characterization through scanning transmission electron microscopy with energy dispersive spectroscopy (STEM/EDS) can provide a comprehensive dataset, which can be processed further to extract structural parameters and correlate to electrochemical performance. However, extracting relevant information from these datasets can be very challenging and time-consuming.In this study, an automatic python-based image processing framework is implemented to quantify compositional and microstructural parameters for different IrO2 based catalyst inks and their corresponding catalyst layers. The code can provide areal density of catalyst materials, pore/agglomerate size distribution, connectivity of phases, coverage of catalyst particles by ionomer, and its content percentage and distribution. Quantified parameters are then correlated with the electrochemical performance of the PEMWEs. The results provide adequate pointers to not only help capturing microstructural details of catalyst layers but also provide a basis to predict electrochemical behavior and performance of the inks and catalyst layers being studied.

A Novel Approach to Continuum FE Multiphysics Simulation of Batteries via Heterogeneous Homogenization

Advancements in modern technology necessitate batteries that can be safely charged and discharged at high rates with minimal aging. A promising strategy to achieve these ends is through optimization of porous microstructures of existing electrode materials to promote better electrical and ionic transport without compromising energy density, as has been shown experimentally by introducing laser ablation channels to the electrodes. The present work proposes a microstructure up-scaling methodology that efficiently accounts for material heterogeneity by assigning a porosity field to a continuum scale finite element mesh, effectively homogenizing materials while maintaining the heterogeneous porosity distribution inherent to the original microstructure. Constitutive relationships relating solid electric conductivity and pore tortuosity to local porosity are directly computed from fully resolved anode, cathode, and separator microstructure 3D models and assigned in the continuum as material properties of a finite element mesh. This allows for utilization of the computationally efficient, homogenized Newman model while maintaining dependency on the heterogeneous local porosity. Then, coupled electrochemical-thermal-mechanical-pore pressure finite element simulations are performed on the battery cell model with this heterogeneous porosity field, and associated local variations on transport properties are prescribed as material properties by the precomputed constitutive relationships. Performance metrics and lithium plating potential are compared to the results of simulations of the fully homogenized cell with the same constitutive relationships and to the base case of a fully homogenous cell with typical modelling assumptions applied to porosity dependent constitutive relationships. These comparisons are made both as a means of validating the methodology and to demonstrate the vast differences that arise when simplifying assumptions are used instead of the constitutive relationships of the actual material microstructure. Finally, the methodology is used in its intended optimization application to compare the performance of a typical battery microstructure to a similar porous microstructure with micro holes added via laser ablation. The results indicate that differences in the microstructure of materials with identical average porosities and similar constitutive relationships can have significant differences in both cell performance and aging that would typically be impossible to detect using fully homogeneous continuum modeling. Figure 1

Evaluation of anode support microstructure in solid oxide fuel cells using virtual 3D reconstruction: A simulation study

In this study, the impact of microstructural properties of the anode support layer (ASL) composed of catalyst, electrolyte and pore phases on the performance of solid oxide fuel cell (SOFC) is investigated. Synthetic SOFC anode microstructures, comprising two layers including the anode functional layer (AFL), where electrochemical reactions take place, are generated using an open-source software. Different configurations of the anode support layer with various particle sizes and volume fractions of the catalyst and electrolyte phases for different porosities are combined with a consistent AFL to isolate the effect of ASL microstructural parameters. The triple phase boundary (TPB) density, chosen as a useful metric monitoring the anode performance, is then quantitively determined for each anode layer and entire anode in all reconstructed microstructures. The results demonstrate that the microstructure of ASL significantly influences the anode and thus cell performance by impacting reactant gas supply and current collection, emphasizing the necessity for meticulous design. Specifically, ASL microstructures with low volume fractions of Ni and the pore phase, and/or substantial differences between the volume fractions of the phases, are observed to result in discontinuous phase networks, which deactivate TPBs in AFL.

Regulating the active hydroxyl group of starch: Revealing the evolution of hard carbon structure and sodium storage behavior

The active hydroxyl group of starch has a crucial effect in regulating the microstructure of hard carbon anodes for sodium-ion batteries. By optimizing the chemical structure of starch and controlling the pyrolysis process, high-performance hard carbon materials can be obtained. These active hydroxyl groups are primarily located on the terminal and ring structures of glucose units, exerting significant influence on the formation and performance of hard carbon. Our results demonstrate that low-temperature oxidation treatment effectively modifies the terminal hydroxyl groups in precursor materials, facilitating chain cross-linking and leading to a more robust hard carbon structure. This cross-linking effect helps suppress excessive foaming during pyrolysis, thereby enhancing the stability of the hard carbon structure. Furthermore, by modifying the hydroxyl group on the ring structure of precursors, we can control the pyrolysis process, promote pore closure, and further improve the low plateau capacity of hard carbon anode materials from 153.95 to 219.58 mAh g −1. This study offers novel insights into harnessing and understanding starch's active hydroxyl groups in preparing hard carbon materials—a significant contribution towards optimizing their performance as anode materials.

Investigation of calendaring parameters on the microstructure of graphite anodes within lithium-ion batteries: Insights from ultrasonic testing

The study explores the application of ultrasonic testing to analyse the impact of the calendaring process on the microstructure of graphite anodes within a lithium-ion battery. It examines the correlation between calendaring parameters such as roll gap and line speed, and their impacts on ultrasonic signal characteristics.Our study reveals that different sample thicknesses responded differently to the calendaring process. Specifically, the amplitude of the first peak increased for thinner samples (<45 μm) post-calendaring, indicating improved material uniformity, whereas thicker samples (>50 μm) demonstrated increase in Time of Flight with reduced attenuation in acoustic signal. Notably, thinner electrodes (45 μm) exhibit a substantial density increase from 0.95 to 1.6 gr/cm³, surpassing the density gain in thicker electrodes (100 μm) which rise from 1.0 to 1.3 gr/cm³ under identical calendaring conditions.This initial study confirms that a clear correlation exists between the properties of the acoustic waveform and variations in the calendaring process parameters. These results will form the basis of a future study investigating the possible in-line sensing, process control and quality assessment of electrode manufacture. The data obtained from this study's characterisation process has the potential to underpin a data-driven model to predict calendaring performance using machine-learning methods.

Unraveling the intercorrelation between pseudo-graphitic phase and Li+/Na+ migration behavior in semicoke-based carbon anodes

Microstructural engineering is regarded as a promising option for fabricating high-performance carbon anodes. Hence, a facile solvothermal-assisted low-temperature calcination strategy was employed to modulate the microstructure of semicoke-derived carbon anodes. Owing to the effective pseudo-graphite phase modulation, the modified carbon anode exhibited a significant increase in capacity, cycling stability and ion kinetics in both lithium-ion batteries and sodium-ion batteries. Kinetic analysis and in-situ X-ray diffraction confirmed the “adsorption and intercalation” energy storage mechanism of the obtained carbon electrodes. In addition, by investigating the energy storage mechanism, we found that increasing the pseudo-graphite phase proportion played different roles in lithium and sodium ions storage. For lithium-ion storage, the pseudo-graphitic phase preferentially promotes lithium-ion transport kinetics. Conversely, during sodium-ion storage, this particular structure markedly augments the embedding capacity of sodium. Theoretical calculations demonstrate that different patterns of variation in the activation energy with the carbon layer spacing of lithium/sodium intercalation compounds lead to differences in performance enhancement. This study not only offers a low-cost approach for preparing carbon anodes enriched with a pseudo-graphitic phase, but also provides new insight into the discrepancy between lithium ion and sodium ion storage.

Tuning the microstructure of biomass-derived hard carbons by controlling the impurity removal process for enhanced Na ion storage performance

Biomass-derived hard carbons are promising anode materials of sodium-ion batteries (SIBs) due to their low cost, renewability and high specific capacity. However, there are inevitably some impurities in biomasses that may not only affect the purity, but microstructure and electrochemical performance of hard carbons. Although the impurities can be removed by appropriate treatments after carbonization, the microstructure of hard carbons can hardly be changed. In this work, taking ficus macrophylla leaves (FMLs) as the model biomass, the effects of impurities and their removing process on the microstructure and Na ion storage performance of hard carbons are investigated. It is found that the presence of Ca and Si-bearing impurities in FMLs results in more graphite-like structure in hard carbons because of their catalytic graphitization effect. The acid and base washing processes after carbonization can mostly get rid of the inorganic impurities is unable to increase the plateau region capacities associating to Na ion insertion in the interlayer of graphitic microcrystals and Na metal filling in micropores. By contrast, by stepwisely removing the Ca and Si-bearing impurities from raw materials before carbonization, hard carbons with high purity, larger interlayer space and more micropores are produced, which exhibit a high reversible specific capacity of 336 mAh g−1 at 20 mA g−1, a high initial Coulombic efficiency of 93 %, excellent rate capability (245 mAh g−1 at 2 A g−1) and robust cycle stability. This study implies that controlling the impurity removal process can simultaneously tune the microstructure of hard carbon anodes derived from biomasses towards high performance Na ion storage.

Research on effect of anode microstructures on mass transfer and electrochemical reaction in SOFCs based on a fractional Brownian motion model

Research on effect of anode microstructures on mass transfer and electrochemical reaction in SOFCs based on a fractional Brownian motion model

New strategy for Mg-air battery voltage-efficiency synergy by engineering protective film with cation vacancies on Mg anode surface

Although the Mg-air battery with high theoretical energy density is desirable for the energy supply of marine engineering equipment, its applications remain limited due to the low actual discharge voltage and inferior Mg anode utilization rate. In addition to the microstructure of Mg alloy anodes, the properties of discharge product films are of great importance to the discharge performance. Herein, the discharge behaviors of Mg-Y-Zn alloys are first studied mainly from the perspective of film properties. Through contrastive analysis, it is found that the sufficient Y3+ produced during the discharge process can substitute Mg2+ in Mg(OH)2 to introduce effective cation vacancies. The Mg-Y-Zn anode with profuse cation vacancies in the product film shows a synergy of potential and efficiency, and this can be attributed to an increase in the migration pathway for Mg2+, reducing the diffusion over-potential caused by the protective product film. This study is expected to provide a new strategy from the perspective of cation vacancy design of discharge film for developing high-performance Mg-air batteries.

Enhancing multi-channel electrode structures in ceramic fuel cells: Influence of channel geometry on mass transport and electrochemical performance

Solid oxide fuel cell (SOFC) is a promising electrochemical power generation technology that contributes to the decarbonization of the energy field. The electrode-supported design enables the use of thinner electrolytes, but inevitably brings additional gas diffusion resistance, which in turn leads to higher anodic concentration polarization. Therefore, additional structural design of the electrodes is necessary to ensure efficient operation and mass transport resistance minimization. In this study, anode-supported micro-tubular SOFCs with different multi-channel geometries have been attempted, during which samples with 4 channels exhibit unique elliptical structure due to meticulous manipulation. In addition, the 4-channel samples have been compared to the single-channel and 7-channel counterparts, exploring the influential mechanism of the anode micro-structure on gas transfer and electrochemical performances. The study found that the 4-channel cell has the best geometric controllability, with its minimum gas diffusion path reduced to below 50 μm, such thin electrochemical active region (EAR) accounts for >50 % of the entire external surface. Efficient utilization of the geometric surface area considerably facilitates the fuel transport to reach anode/electrolyte interface. By enhancing the mass transport efficiency, the maximum power density of the 4-channel cell reached 1.40 W cm−2 (750 °C), which is 22.8 % and 102.9 % higher than that of the 7-channel and single-channel cells under the same conditions. The highly efficient anode design additionally exhibited exceptional structural integrity and mechanical robustness, thereby ensuring the steady operation of the cell.

Analyzing the degradation mechanism of solid oxide fuel cell during different time periods

Improving the lifetime and robustness of solid oxide fuel cells (SOFCs) is crucial for their commercial viability. This study aims to elucidate the degradation mechanism of SOFCs during galvanostatic tests and understand the internal and external factors influencing the cell degradation. Three nominally identical cells underwent galvanostatic testing for different durations to illustrate the evolution mechanism of SOFCs degradation at different stages. The electrochemical impedance spectroscopy (EIS) measurements under the open circuit voltage (OCV) and the direct current (DC) bias at different periods were carefully analyzed. By combining distribution of relaxation times (DRT) with equivalent circuit model (ECM) fitting, the contribution of each electrode process to cell performance degradation during galvanostatic testing was quantified. The polarization impedance, primarily associated with the charge transfer reactions in the anode, exhibited continuous increase under DC bias, contributing more than 80 % to the increase overall polarization impedance. Conversely, the cathode, related to O2 dissociation and diffusion process, contributed 7.2 %. The rapid degradation in the early stage was attributed to the degeneration of the anode microstructure, resulting from the formation of numerous isolated micron Ni particles and a subsequent decrease in three phase boundary (TPB) density. The anode microstructure after galvanostatic testing was characterized, revealing a novel Ni migration evolution mechanism. This mechanism involves the rapid agglomeration of Ni crystal particles at the beginning test, subsequent diffusion as micro-particles within 25 h, and eventual coarsening into dispersive agglomerates over time. The proposed mechanism of anodic microstructure evolution offers insights for optimizing anodic structures and lays the foundation for enhancing the long-term stability of SOFCs.

Effect of Low Plasma Spraying Power on Anode Microstructure and Performance for Metal-Supported Solid Oxide Fuel Cells

Effect of Low Plasma Spraying Power on Anode Microstructure and Performance for Metal-Supported Solid Oxide Fuel Cells

Quantifying Microstructure Features for High-Performance Solid Oxide Cells.

The drive for sustainable energy solutions has spurred interest in solid oxide fuel cells (SOFCs). This study investigates the impact of sintering temperature on SOFC anode microstructures using advanced 3D focused ion beam-scanning electron microscopy (FIB-SEM). The anode's ceramic-metal composition significantly influences electrochemical performance, making optimization crucial. Comparing cells sintered at different temperatures reveals that a lower sintering temperature enhances yttria-stabilized zirconia (YSZ) and nickel distribution, volume, and particle size, along with the triple-phase boundary (TPB) interface. Three-dimensional reconstructions illustrate that the cell sintered at a lower temperature exhibits a well-defined pore network, leading to increased TPB density. Hydrogen flow simulations demonstrate comparable permeability for both cells. Electrochemical characterization confirms the superior performance of the cell sintered at the lower temperature, displaying higher power density and lower total cell resistance. This FIB-SEM methodology provides precise insights into the microstructure-performance relationship, eliminating the need for hypothetical structures and enhancing our understanding of SOFC behavior under different fabrication conditions.

Topological Defect-Regulated Porous Carbon Anodes with Fast Interfacial and Bulk Kinetics for High-Rate and High-Energy-Density Potassium-Ion Batteries.

Carbonaceous materials are regarded as one of the most promising anodes for potassium-ion batteries (PIBs), but their rate capabilities are largely limited by the slow solid-state potassium diffusion kinetics inside anode and sluggish interfacial potassium ion transfer process. Herein, high-rate and high-capacity PIBs are demonstrated by facile topological defect-regulation of the microstructure of carbon anodes. The carbon lattice of the as-obtained porous carbon nanosheets (CNSs) with abundant topological defects (TDPCNSs) holds relatively highpotassium adsorption energy yet low potassium migration barrier, thereby enabling efficient storage and diffusion of potassium inside graphitic layers. Moreover, the topological defects can induce preferential decomposition of anions, leading to the formation of high potassium ion conductive solid electrolyte interphase (SEI) film with decreased potassium ion de-solvation and transfer barrier. Additionally, the dominant sp2-hybridized carbon conjugated skeleton of TDPCNSs enables high electrical conductivity (39.4 S cm-1) and relatively low potassium storage potential. As a result, the as-constructed TDPCNSs anode demonstrates high potassium storage capacity (504mA h g-1 at 0.1 A g-1), remarkable rate capability (118mA h g-1 at 40 A g-1), as well as long-term cycling stability.