Journal articles on the topic 'Gas-Solid interface stability'
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1
Zhang, Di. "Investigation of the Zeta Adsorption Model and Gas-Solid Adsorption Phase Transition Mechanism Using Statistical Mechanics at Gas-Solid Interfaces." Adsorption Science & Technology 2023 (November 15, 2023): 1–16. http://dx.doi.org/10.1155/2023/8899160.
Abstract:
This review examines the significance of the zeta adsorption model in physics and its integration with statistical mechanics within the field of interface adsorption. Through a comprehensive analysis of existing research, this study presents the collective findings and insights derived from the reviewed literature. The zeta adsorption model, proposed by Ward, has gained recognition for its seamless extension into the thermal disequilibrium region without encountering singularities. By incorporating principles from quantum mechanics and statistical thermodynamics, this model offers fresh perspectives on the adsorption of gas molecules on solid surfaces. Notably, it demonstrates enhanced accuracy in describing the adsorption performance of mesoporous materials and nanomaterial surfaces, surpassing the limitations of traditional models such as the BET isotherm. Additionally, this review explores the behavior of cluster formation under varying temperature and pressure conditions. It highlights the correlation between increasing pressure ratios and the decreased availability of empty adsorption sites, resulting in the formation of larger clusters within the adsorbate. Ultimately, this process leads to a transition from adsorption to condensation, where the liquid phase wets the solid surface. Moreover, the zeta adsorption model provides a solid theoretical foundation for understanding crucial aspects of gas-solid interface adsorption. It enables the determination of the distribution of adsorbate clusters on gas-solid interfaces, facilitates the identification of wetting pressure ratios during phase transitions, and allows for the calculation of solid surface tension under conditions of zero adsorption. Noteworthy parameters such as the bonding strength (β) between the solid surface and adsorbed atoms significantly influence the overall strength of the solid-fluid interaction. Furthermore, the phenomenon of surface subcooling, which necessitates sufficient energy for the transformation from adsorbed vapor to condensate liquid, plays a pivotal role in studying interface phase transitions. Additionally, this review investigates the thermodynamic stability of the adsorbate through an analysis of molar latent heat. It reveals that beyond a critical adsorbate coverage, the formation of critical-sized clusters and the ensuing interactions among these components render the adsorbate unstable. This instability prompts a transition from the interface to a liquid phase, followed by subsequent adsorption onto the surface. In summary, this literature review highlights the significant contributions of the zeta adsorption model to the field of physics, particularly in the context of interface adsorption. It serves as a valuable tool for studying various materials and cluster formation, thanks to its seamless extension into the thermal disequilibrium region and its incorporation of principles from quantum mechanics and statistical thermodynamics. By presenting a synthesis of existing research, this review sheds light on the advantages of the zeta adsorption model and paves the way for further investigations into gas-solid interface adsorption phenomena.
2
Kang, Seul-Gi, Dae-Hyun Kim, Bo-Joong Kim, and Chang-Bun Yoon. "Sn-Substituted Argyrodite Li6PS5Cl Solid Electrolyte for Improving Interfacial and Atmospheric Stability." Materials 16, no. 7 (March 29, 2023): 2751. http://dx.doi.org/10.3390/ma16072751.
Abstract:
Sulfide-based solid electrolytes exhibit good formability and superior ionic conductivity. However, these electrolytes can react with atmospheric moisture to generate H2S gas, resulting in performance degradation. In this study, we attempted to improve the stability of the interface between Li metal and an argyrodite Li6Ps5Cl solid electrolyte by partially substituting P with Sn to form an Sn–S bond. The solid electrolyte was synthesized via liquid synthesis instead of the conventional mechanical milling method. X-ray diffraction analyses confirmed that solid electrolytes have an argyrodite structure and peak shift occurs as substitution increases. Scanning electron microscopy and energy-dispersive X-ray spectroscopy analyses confirmed that the particle size gradually increased, and the components were evenly distributed. Moreover, electrochemical impedance spectroscopy and DC cycling confirmed that the ionic conductivity decreased slightly but that the cycling behavior was stable for about 500 h at X = 0.05. The amount of H2S gas generated when the solid electrolyte is exposed to moisture was measured using a gas sensor. Stability against atmospheric moisture was improved. In conclusion, liquid-phase synthesis could be applied for the large-scale production of argyrodite-based Li6PS5Cl solid electrolytes. Moreover, Sn substitution improved the electrochemical stability of the solid electrolyte.
3
Zakaria, K. "Kelvin--Helmholtz instability of a horizontal interface between a finite subsonic gas and a finite magnetic liquid." Canadian Journal of Physics 76, no. 5 (May 1, 1998): 361–74. http://dx.doi.org/10.1139/p98-006.
Abstract:
The nonlinear Kelvin-Helmholtz instability of a horizontal interface between a magnetic inviscid incompressible liquid and an inviscid laminar subsonic gas is investigated. The gas and the liquid are assumed to have finite thicknesses. The applied magnetic field is parallel to the solid surfaces of the considered system. The method of multiple scales is used to obtain two nonlinear Schrodinger equations describing the behaviour of the perturbed system. The stability of the progressive waves is discussed theoretically. The nonlinear cutoff wave number is obtained, where the stability conditions of the standing waves are obtained. A numerical example is applied to discuss the stability diagrams.PACS Nos.: 51.60 and 47.20
4
Zheng, Miaozi, Renjie Yang, Jianmin Zhang, Yongkai Liu, Songlin Gao, and Menglan Duan. "An Interface Parametric Evaluation on Wellbore Integrity during Natural Gas Hydrate Production." Journal of Marine Science and Engineering 10, no. 10 (October 18, 2022): 1524. http://dx.doi.org/10.3390/jmse10101524.
Abstract:
Based on the whole life cycle process of the economic exploitation of natural gas hydrate, this paper proposes the basic problem of stabilizing the wellbore for the basic conditions that must be met to ensure the integrity of the wellbore for exploitation: revealing the complex mechanism of fluid–solid–heat coupling in the process of the physical exchange of equilibrium among gas, water, and multiphase sand flows in the wellbore, hydrate reservoir, and wellbore, defining the interface conditions to ensure wellbore stability during the entire life cycle of hydrate production and proposing a scientific evaluation system of interface parameters for wellbore integrity.
5
Shao, Xiaohan, Qianhong Zhu, Ting Wang, Mourin Jarin, Xing Xie, and William Abraham Tarpeh. "Probing Bubble Properties during Hydrogen Evolution Reaction on Platinum Micropatterns Using Scanning Electrochemical Microscopy." ECS Meeting Abstracts MA2023-02, no. 54 (December 22, 2023): 2634. http://dx.doi.org/10.1149/ma2023-02542634mtgabs.
Abstract:
Many electrochemical reactions involve gas bubble consumption and generation at liquid-solid interfaces, creating a three-phase interfacial zone (e.g., solid electrode, liquid electrolyte, gaseous products). For example, hydrogen and oxygen evolution reactions (HER, OER) generate gas, the nitrate reduction reaction (NO3RR) makes gaseous and aqueous products, and the carbon dioxide reduction reaction (CO2RR) consumes gas while making gaseous and aqueous products. These reactions correlate gas bubbles to important energy and sustainability applications such as aqueous electrolysis, photoelectrochemical energy storage, environmental catalysis, and water treatment. In electrochemical water treatment, gas bubbles have been shown to catalyze chemical reactions and enhance the efficiency of water treatment by degrading organic pollutants and reducing fouling of water treatment components (e.g., membranes). However, gas bubbles grow into macroscopic sizes after nucleating on solid surfaces, which interferes with chemical processes by blocking the reactants from reaching the liquid-solid interface and impedes reaction rate and energy efficiency. The liquid-solid interface is a critical zone that dictates the performance of electrochemical processes. Bubble formation at the liquid-solid interface also presents a major challenge for establishing molecular understanding of reaction mechanisms, kinetics, stability, and selectivity toward desired products, and therefore complicates process designs that leverage gas bubble properties to facilitate electrochemical reactions. Questions such as how surface bubbles form and grow on surfaces, how they impact chemical reactivity at surfaces, and how electrode geometries (e.g., the size, shape, and arrangement of the catalysts for reactions) guide bubble formation and transport should be answered to inform rational design of electrochemical processes to efficiently utilize the bubbles. In this study, we use HER as a model reaction to probe bubble properties using scanning electrochemical microscopy (SECM) and optical microscopy to gain understandings of the fate and dynamics of bubbles (i.e., nucleation, aggregation, transport, and dissolution). Specifically, we developed and fabricated micro-scale platinum patterned substrates that vary in Pt pattern size (20-200 µm diameter), gap spacing (1-10x diameter apart), and angle (60° and 90°between Pt patterns) to facilitate bubble nucleation. The patterns (120 nm in height) were deposited on n-type silicon wafer (525 µm thickness) using photolithography and electron beam evaporation. We then identified the locations of bubble nucleation on the patterned substrates with optical microscopy. We correlated the locations of bubble formation with the distribution of Pt patterns on the electrode by deconvoluting the measured currents due to bubble aggregation from conductivity of Pt patterns via SECM, a powerful tool to acquire spatial and electrochemical activities for various use cases (e.g., corrosion, catalysis, gas evolution). In addition, we investigated the effects of current densities and reaction time on the nucleation and stability of the bubbles on the fabricated patterned substrates. Furthermore, the lifetime of the patterned substrates was examined, which will provide insights into future engineering design of robust and effective substrates that leverage bubble properties to advance electrochemical water treatment. The results of this study are generalizable to other reactions involving gas bubble generation to enhance optimization and sustainability of other industrial electrochemical processes.
6
Jiang, Shi-Kai, Sheng-Chiang Yang, Wei-Hsiang Huang, She-huang Wu, Wei-Nien Su, and Bing Joe Hwang. "Basicity and Stability of Argyrodite Sulfide-Based Solid Electrolytes." ECS Meeting Abstracts MA2023-02, no. 8 (December 22, 2023): 3278. http://dx.doi.org/10.1149/ma2023-0283278mtgabs.
Abstract:
Argyrodite-type sulfide-based solid electrolyte Li6PS5Cl (LPSC) holds immense promise for solid-state battery applications. This is attributed to its stable structure and high ionic conductivity. Nonetheless, the persistent challenges involving the instability at the electrode/electrolyte interface and susceptibility to moisture present significant obstacles in material preparation and cell manufacturing processes. Our research has unveiled a noteworthy finding: the sulfur of the PS4 3− moiety is a Lewis-base active site to adsorb Lewis acid. It is found that the adsorption of CO2 on the sulfide electrolytes can enhance both the interfacial and electrochemical stability of the lithium and sulfide electrolyte interface. The formation of new S–CO2 bonds, confirmed using various analytical techniques, plays a pivotal role in modifying the interfacial behaviors of the sulfide electrolytes. Moreover, the LijCO2@LPSCjLTO shows an amazing result, with 62% capacity retention and ultra-high coulombic efficiency of 99.91% after 1000 cycles. Interestingly, the same concept was also applied to the high ionic conductivity sulfide-based superionic conductor Li10GeP2S12 (LGPS) system, which also has the PS4 3− moiety. A novel approach is also developed by utilization of the BBr3 gas as a Lewis base indicator to probe the strength of Lewis basicity of the sulfur sites of sulfide electrolytes. The basicity of the sulfide electrolytes can be correlated to the shift of 11B NMR peak. This correlation is further supported by the H2S generation rate when the electrolyte is exposed to a moisture atmosphere. This work not only provides a new pave towards enhancing stability at the sulfide electrolyte/lithium interface but profound insights into the basicity and moisture stability of sulfide electrolytes.
7
Li, Xuefeng, Baojiang Sun, Baojin Ma, Hao Li, Huaqing Liu, Dejun Cai, Xiansi Wang, and Xiangpeng Li. "Study on the Evolution Law of Wellbore Stability Interface during Drilling of Offshore Gas Hydrate Reservoirs." Energies 16, no. 22 (November 15, 2023): 7585. http://dx.doi.org/10.3390/en16227585.
Abstract:
The study of wellbore stability in offshore gas hydrate reservoirs is an important basis for the large-scale exploitation of natural gas hydrate resources. The wellbore stability analysis model in this study considers the evolution of the reservoir mechanical strength, wellbore temperature, and pressure parameters along the depth and uses plastic strain as a new criterion for wellbore instability. The wellbore stability model couples the hydrate phase transition near the wellbore area under the effect of the wellbore temperature and pressure field and the ‘heat–fluid–solid’ multifield evolution characteristics, and then simulates the stability evolution law of the wellbore area during the drilling process in the shallow seabed. The research results show that, owing to the low temperature of the seawater section and shallow formation, the temperature of the drilling fluid in the shallow layer of the wellbore can be maintained below the formation temperature, which effectively inhibits the decomposition of hydrates in the wellbore area. When the wellbore temperature increases or pressure decreases, the hydrate decomposition rate near the wellbore accelerates, and the unstable area of the wellbore will further expand. The research results can provide a reference for the design of drilling parameters for hydrate reservoirs.
8
Safiullin, A. R. "Acoustic stability of a superheated liquid with vapor–gas bubbles." Multiphase Systems 18, no. 1 (May 2023): 32–36. http://dx.doi.org/10.21662/mfs2023.1.005.
Abstract:
It is known that the physicochemical properties of liquids in a metastable state are mainly determined by the presence of various inclusions in their composition, for example, gas bubbles or solid particles, and it has been established that, under mechanical and thermal equilibrium, the state of a liquid with gas bubbles distributed over the volume due to the action of capillary forces at the interface, always overheated. In this paper, we consider the propagation of weak perturbations in a superheated water-air bubbly medium, when, in addition to water vapor, the bubbles contain an inert gas (for example, air) that does not participate in phase transitions. To describe the problems under consideration, a system of equations is used, which consists of the laws of conservation of mass, the number of bubbles, momentum equations, the Rayleigh–Lamb equation, the equation of heat conduction and diffusion. The solution is sought in the form of a damped traveling wave. Based on the solution of the dispersion equation, maps of the stability zones of the systems under consideration were constructed depending on the magnitude of the liquid overheating on the plane ”volume content — bubble radius“.
9
Pham, Anh Tuan. "(Invited) Multiscale Modeling of Heterogeneous Interfaces for Hydrogen Production." ECS Meeting Abstracts MA2023-02, no. 48 (December 22, 2023): 2409. http://dx.doi.org/10.1149/ma2023-02482409mtgabs.
Abstract:
Improving performance of hydrogen production devices requires a detailed understanding of physicochemical processes at solid-gas and solid-liquid interfaces. However, probing behavior of these interfaces under working conditions remain a significant challenge for both simulations and experimental techniques. In this talk, I will provide an overview of our strategy for simulating heterogeneous interfaces within the HydroGEN Advanced Water Splitting Materials Consortium, ranging from first-principles calculations of chemical reactivity to machine learning approaches for accelerating theory-experiment integration and continuum methods for understanding microstructure effects. In particular, I will discuss how computational models can be used to elucidate mechanisms of interface chemical reactions and mass transport, as well as the formation of new phases and their impacts on materials stability and performance. I will also show how simulations have been integrated with experimental probes, such as X-ray spectroscopy, to obtain new understanding of materials interfaces under operating conditions. Finally, I will discuss how this understanding is being used to guide new strategies for improving materials functionality for hydrogen production. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
10
Guo, Weibin, Yinggan Zhang, Liang Lin, Wei He, Hongfei Zheng, Jie Lin, Baisheng Sa, et al. "Enhancing cycling stability in Li-rich Mn-based cathode materials by solid-liquid-gas integrated interface engineering." Nano Energy 97 (June 2022): 107201. http://dx.doi.org/10.1016/j.nanoen.2022.107201.
11
Zhu, Mingze, Zexuan Zhu, Xiaoyong Xu, and Chunxiang Xu. "Surfactant Improved Interface Morphology and Mass Transfer for Electrochemical Oxygen-Evolving Reaction." Catalysts 13, no. 3 (March 11, 2023): 569. http://dx.doi.org/10.3390/catal13030569.
Abstract:
The surface microstructure of a catalyst coating layer directly affects the active area, hydrophilicity and hydrophobicity, and the high porosity is desirable especially for solid–liquid–gas three-phase catalytic reactions. However, it remains challenging to customize catalyst distribution during the coating process. Here, we report a simple strategy for achieving ultrafine nanocatalyst deposition in a porous structure via introducing the surfactant into coating inks. For a proof-of-concept demonstration, we spin-coated the nanoscale IrO2 sol with a surfactant of sodium dodecyl sulfate (SDS) onto the glassy carbon (GC) electrode for oxygen evolution reaction (OER). Due to the surfactant action, the deposited IrO2 nanocatalyst is evenly distributed and interconnected into a highly porous overlayer, which facilitates electrolyte permeation, gas bubble elimination and active-site accessibility, thus affording high-performance OER in alkaline media. Particularly, the SDS-modified electrodes enable the industrial-level high-current-density performance via enhanced mass transfer kinetics. Such manipulation is effective to improve the coating electrodes’ catalytic activity and stability, and scalable for practical applications and suggestive for other gas-evolving electrodes.
12
McCaughan, F., and H. Bedir. "Marangoni Convection With a Deformable Surface." Journal of Applied Mechanics 61, no. 3 (September 1, 1994): 681–88. http://dx.doi.org/10.1115/1.2901514.
Abstract:
Double diffusive convection is considered in a semi-infinite domain, bounded below by a solid surface and above by a gas interface. Temperature and concentration gradients are imposed normal to the free surface and the linear stability of the fluid is examined. Traditional analyses are extended to include the effects of a deformable free surface. The governing equations are nondimensionalized and the parameter groupings are identified. We particularly focus on the effects of the capillary number, the Nusselt number and the Marangoni temperature and concentration numbers.
13
Chandra-ambhorn, Somrerk, Patthranit Wongpromrat, Thammaporn Thublaor, and Walairat Chandra-ambhorn. "CHAPTER 5 Effect of Water Vapour on the High Temperature Oxidation of Stainless Steels." Solid State Phenomena 300 (February 2020): 107–34. http://dx.doi.org/10.4028/www.scientific.net/ssp.300.107.
Abstract:
This chapter primarily reviews the nature of water vapour when it presents in bulk gas. The change in a ratio between water vapour and corresponding dissociated hydrogen, which determine the thermodynamic stability of the oxide formation, is analysed when the oxidation kinetics are linear and parabolic. When water vapour reaches the solid/gas interface, chromium species volatilisation and oxidation controlled by surface reaction can occur. The adsorbed water vapour can be further incorporated into the oxide possibly in the form of hydrogen defects. The role of these defects on altering the defect structure of the oxide is discussed. Finally, characteristics of the oxide scale on stainless steels formed in the atmosphere containing water vapour are reviewed.
14
Ospanova, Zh B., S. Toktagul, A. Tasmagambetova, and M. Asadov. "Preparation of foaming agents for dust suppression of coal particles." Chemical Bulletin of Kazakh National University, no. 3 (September 30, 2019): 12–18. http://dx.doi.org/10.15328/cb1071.
Abstract:
The results of the study of foams stabilized by solid coal particles are given. The method of sedimentation analysis determined the most likely radius of coal particles equal to 20.28 microns. Foaming ability was determined by the height of the foam column obtained by the method of bubbling within 1 min. Foam stability was determined by the time of complete destruction of the foam column. Foams stabilized by the compositions of anionic surfactants – sodium dodecyl sulfate (DDSNa) and sulfonol (SF) with polyvinyl alcohol (PVA) in the presence of hydrophobic solid particles of coal showed greater foaming capacity and stability compared to foams from individual surfactants. The surface tension isotherms of aqueous solutions of surfactants, PVA, and their mixtures were obtained. An increase in the stability of foams in the presence of coal particles corresponds to a decrease in the surface tension at the liquid-gas interface. The stability of foams obtained from surfactant-PVA compositions is explained by the combined influence of thermodynamic (reduction of surface tension) and structural-mechanical (increase in viscosity of inter-membrane fluid) of stability factors. These properties of foams can be used to suppress dust in coal mining.
15
Jo, Eunchan, Byungmoon Kim, and Oh-Young Song. "Lattice-Boltzmann and Eulerian Hybrid for Solid Burning Simulation." Symmetry 11, no. 11 (November 14, 2019): 1405. http://dx.doi.org/10.3390/sym11111405.
Abstract:
We propose a new hybrid simulation method to model burning solid interactions. Unlike gas fuel, fire and smoke interactions that have been relatively well studied in the past, simulations of solid fuel combustion processes remain largely unaddressed. These include pyrolysis/smoldering, interactions with oxygen and flow inside porous solid. To advance this simulation problem, we designed a new hybrid of the Lattice-Boltzmann method (LBM) and a Eulerian grid based Navier-Stokes equation (NSE). It uses the LBM, which has symmetrical directions of particle velocities in a cell, for inside the solid fuel and the NSE, which has a representative velocity in a cell, for outside the solid. At the interface where the two methods join, we develop a novel method to exchange physical quantities and show a natural transition between the two methods. Since LBM allows us to directly manage the quantity of exchanges from the microscopic perspective, that is, between lattice points, we can easily simulate the burning speed and the shape change of burning an inhomogeneous solid. Also, we derive an LBM version of the previously proposed porous Navier-Stokes equation to simulate gas flow inside the porous solid. In addition, we use the NS solver outside the solid where macroscopic behavior is much more dominant and, hence, LBM is less efficient than NS solver. Our results show us the physical stability and accuracy and visual realism.
16
Xie, Jiamiao, Jingyang Li, Wenqian Hao, and Fenghui Wang. "Influence of Interface Morphology on the Thermal Stress Distribution of SOFC under Inhomogeneous Temperature Field." Energies 16, no. 21 (October 31, 2023): 7349. http://dx.doi.org/10.3390/en16217349.
Abstract:
Excessive thermal stress can cause the failure of a solid oxide fuel cell (SOFC), and an inhomogeneous temperature field is one of the reasons for thermal stress in the cell. In the present work, the bi-dimensional thermo-mechanical coupling models of SOFCs with different interface morphologies including planar and corrugated cells are proposed. The temperature distribution of two types of cells under the action of heat conduction is analyzed. Further, the inhomogeneous temperature field caused by gas flow is used as the thermal load to compare the thermal stress distribution of planar and corrugated cells. The influence of interface morphology on the temperature distribution, stress distribution and the contribution of the temperature gradient to stress distribution are investigated. This research provides a reference for reducing thermal stress and improving the stability of SOFC.
17
Liatard, Sébastien, Marine Soler, Vasily Tarnopolsky, Céline Barchasz, Frédéric Le Cras, Anass Benayad, and Eric De Vito. "Sulfide-Based Solid-State Lithium-Sulfur Batteries: An in-Depth Study of the Li-Electrolyte Interface." ECS Meeting Abstracts MA2023-02, no. 4 (December 22, 2023): 551. http://dx.doi.org/10.1149/ma2023-024551mtgabs.
Abstract:
The development of solid-state batteries has gained significant attention in recent years, owing to their potential to enhance the temperature range and energy density of energy storage devices. Sulfide-based electrolytes are some of the most promising candidates for solid-state batteries, thanks to their high ionic conductivity and low processing temperature. For lithium-sulfur (Li-S) batteries, the transition from liquid to solid electrolytes holds even greater promise. Sulfur is a readily available cathode material known for its high specific capacity, which endows Li-S batteries with remarkable specific energy and favourable environmental and economic impact. In liquid electrolytes however, the solubility of sulfur and lithium polysulfide causes a multitude of issues that hamper the performance of the Li-S system: rapid self-discharge, redox shuttle mechanism during charging, and loss of active sulfur and lithium material due to direct chemical reactivity. Solid-state Li-S cells are not prone to these issues, but they have, of course, issues of their own. Amongst them, the stability of the interface between the electrolyte and the lithium is of crucial importance to allow the use of this very high energy density negative electrode. In the present study, we compare two sulfide electrolytes, Li6PS5Cl and Li7P3S11, and assess their respective stability against lithium. We used innovative methods to characterize the interphase between the sulfide and the lithium without damaging it upon dismantling the cell. The nature and the properties of this interphase was characterised via EIS, XPS and ToF-SIMS. The EIS study showed that Li6PS5Cl forms a much more stable interphase with lithium than Li7P3S11, which is in accordance with most recent results in the literature. The XPS study confirmed the chemical composition of the interphase. Li2S and Li3P were present for both electrolytes. In the case of Li6PS5Cl, LiCl was also identified as expected. Gas cluster ion beam (GCIB) assisted abrasion of the interphase followed by in-situ XPS and ToF-SIMS suggested a separation of the components of the interphase depending on the depth of the abrasion. The interphase was found to be organised as Li2S-, Li3P- or LiCl-rich discrete layers, with the Li2S-rich layer being consistently the closest to lithium. This result confirms and completes the most recent research in the field published by Otto et al. in 2022 (doi: 10.1002/admi.202102387). To establish solid-state batteries as a practical energy storage option, it is essential to fully understand and effectively manage the Li-electrolyte interface. These findings suggest that thanks to the relative stability of its interface with lithium, Li6PS5Cl is the better option for solid-state lithium metal cells. It also sheds light on the reasons why this interface is more stable. The self-assembled lamellar structure of the interphase could also inspire strategies to better control the stability of solid electrolytes versus lithium.
18
Kirkinis, E., and A. V. Andreev. "Odd-viscosity-induced stabilization of viscous thin liquid films." Journal of Fluid Mechanics 878 (September 4, 2019): 169–89. http://dx.doi.org/10.1017/jfm.2019.644.
Abstract:
Thin viscous liquid films sitting on a solid substrate support nonlinear capillary waves, driven by surface shear stresses at a liquid–gas interface. When surface tension is spatially dependent other mechanisms, such as the thermocapillary effect, influence the dynamics of thin films. In this article we show that in liquids with broken time-reversal symmetry the character of the aforementioned waves and of the thermocapillary effect are significantly modified due to the presence of odd or Hall viscosity in the liquid. This is because odd viscosity gives rise to new terms in the pressure gradient of the flow thus modifying the evolution equation of the liquid–gas interface accordingly. These terms in turn break the reflection symmetry of the evolution equation leading the system to evolve from a pitchfork to a Hopf bifurcation. The odd-viscosity incipient waves can stabilize unstable thin liquid films. For instance, we show that they can suppress the thermocapillary instability. We establish the parameter ranges that odd viscosity has to satisfy in order to initiate those waves that will lead to stability.
19
Han, Chao, Xinyue Dong, Leiyi He, Jin Xu, Pengxiang Li, and Jiakang Li. "Research on SOFC Properties of Low Concentration Gas Fuel and SFM-GDC Reforming." E3S Web of Conferences 385 (2023): 03015. http://dx.doi.org/10.1051/e3sconf/202338503015.
Abstract:
When gas fuel is used in solid oxide fuel cells, methane cracking occurs at high temperature in the Ni-based anode, forming granular carbon deposition in the active site of the anode, and finally completely wrapped Ni metal, greatly losing the electrochemical performance. Therefore, it is very necessary to add a reforming catalytic layer in the anode of the battery. The methane is reformed into CO and H2 fuel before entering the anode, and the place where methane cracking occurs is mostly transferred to the reforming layer, which reduces the catalytic reforming burden of the Ni-based anode, so as to effectively improve the battery performance. In this paper, Sr2Fe1.5Mo0.5O6 with double perovskite structure was synthesized and prepared, which maintained very good stability in high temperature REDOX atmosphere and had high electrical conductivity. The combination of GDC and SFM can increase the reaction site of the three-phase interface of the reforming layer, and also help to improve the thermal expansion matching between the reforming layer and anode. In this paper, the electrochemical performance of straight cell coated with SSFM-GDC reforming layer has been studied. Low concentration gas in coal mine contains methane, oxygen, nitrogen, and water hydrogen sulfide, etc., and its reaction process in solid oxide fuel cells is complicated. Therefore, studying the reaction mechanism of low concentration gas in solid oxide fuel cells has important practical significance for promoting its application.
20
Tolganbek, Nurbol, Zhumabay Bakenov, and Almagul Mentbayeva. "Degradation Prevention of Latp Towards Li Metal and Interface Improvement By Layer-By-Layer Polymer Assembly Technique." ECS Meeting Abstracts MA2022-02, no. 7 (October 9, 2022): 2489. http://dx.doi.org/10.1149/ma2022-0272489mtgabs.
Abstract:
Abstract Degradation of Li1.3Al0.3Ti1.7(PO4)3 (LATP), NASICON-types solid electrolyte (Figure 1) towards Li metal creates a dramatic issue, as materials itself is very promising due to its stability towards air and moisture and facile fabrication methods. Figure 1. Illustration of Li1.3Al0.3Ti1.7(PO4)3 degradation towards Li metal Solid electrolytes containing titanium, germanium suffer from reduction while contacting with Li metal. Reduction of Ti4+ to Ti3+ in LATP leads to a formation of mixed conductive interphase, a secondary phase that hinders lithium ion conduction between the solid electrolyte and electrode. In the majority cases, this problem can be solved by applying artificial interlayer that prevents the direct contact of these components. In addition, the protective interlayer also helps to reduce interfacial impedance that present between electrolyte and electrodes. In our research, we resolved it by applying thin composite gel polymer electrolyte (GPE) as interlayer using layer by layer (LbL) technique. Despite preventing the side reaction, the simultaneous coating on both sides of LATP pellets improved interfacial contact between cathode and electrolyte, anode and electrolyte. The effect of this modification was characterized by physical, chemical and electrochemical analyses. Acknowledgement This research was supported by the research grants #021220CRP0122 “Development of highly sensitive MOS based nano-film gas sensors” from Nazarbayev University. Figure 1
21
Huneault, Justin, David Plant, and Andrew J. Higgins. "Rotational stabilisation of the Rayleigh–Taylor instability at the inner surface of an imploding liquid shell." Journal of Fluid Mechanics 873 (June 25, 2019): 531–67. http://dx.doi.org/10.1017/jfm.2019.346.
Abstract:
A number of applications utilise the energy focussing potential of imploding shells to dynamically compress matter or magnetic fields, including magnetised target fusion schemes in which a plasma is compressed by the collapse of a liquid metal surface. This paper examines the effect of fluid rotation on the Rayleigh–Taylor (RT) driven growth of perturbations at the inner surface of an imploding cylindrical liquid shell which compresses a gas-filled cavity. The shell was formed by rotating water such that it was in solid body rotation prior to the piston-driven implosion, which was propelled by a modest external gas pressure. The fast rise in pressure in the gas-filled cavity at the point of maximum convergence results in an RT unstable configuration where the cavity surface accelerates in the direction of the density gradient at the gas–liquid interface. The experimental arrangement allowed for visualisation of the cavity surface during the implosion using high-speed videography, while offering the possibility to provide geometrically similar implosions over a wide range of initial angular velocities such that the effect of rotation on the interface stability could be quantified. A model developed for the growth of perturbations on the inner surface of a rotating shell indicated that the RT instability may be suppressed by rotating the liquid shell at a sufficient angular velocity so that the net surface acceleration remains opposite to the interface density gradient throughout the implosion. Rotational stabilisation of high-mode-number perturbation growth was examined by collapsing nominally smooth cavities and demonstrating the suppression of small spray-like perturbations that otherwise appear on RT unstable cavity surfaces. Experiments observing the evolution of low-mode-number perturbations, prescribed using a mode-6 obstacle plate, showed that the RT-driven growth was suppressed by rotation, while geometric growth remained present along with significant nonlinear distortion of the perturbations near final convergence.
22
Lim, Jungwoo, Rory Powell, and Laurence J. Hardwick. "Gas Evolution from Sulfide-Based All-Solid-State Batteries." ECS Meeting Abstracts MA2022-01, no. 2 (July 7, 2022): 231. http://dx.doi.org/10.1149/ma2022-012231mtgabs.
Abstract:
The demand for high-performance batteries for electrical vehicles (EV) and large-scale energy storage systems have accelerated the development of all-solid-state batteries. Switching from organic liquid electrolyte to solid electrolyte (SE) ensures, not only the high energy density (Wh/L), but also an intrinsic improvement to safety from the removal of flammable solvent in the liquid electrolyte. However, for the development of all-solid-state batteries, still many problems exist toward commercialisation. One challenge is their chemical/electrochemical stability. In case of Li6PS5Cl argyrodite, their electrochemical decomposition was proposed as following reaction. [1] Li6PS5Cl → Li4PS5Cl + 2Li+ + 2e → Li3PS4 + Sx + LiCl → P2Sx + Sx + LiCl + 3Li+ + 3e (1) However, this proposed reaction is bulk electrochemical decomposition of argyrodite. To understand the decomposition in actual cell, layered oxide cathode/argyrodite composite were analysed by in situ Raman microscopy, X-ray photoelectron spectroscopy and Time-of-flight secondary ion mass spectrometry. [2, 3] This research reports actual solid decomposition product formed by active material and solid electrolyte such as POx or (S2)2- compound. Not only for solid decomposition product, but also gaseous decomposition product can be generated from the interface between cathode materials and SE. Previously, much work has demonstrated that O2 and CO2 gases are released from the positive electrode material within the lithium-ion cell. [4] These exothermic surface reactions are important not only for cell swelling in the long-term usage, but also for cell combustion. However, the gas releasing behaviour of positive electrode mixture in all-solid-state batteries are still not well recognised. In this research, we focused on the gas releasing behaviour of all-solid-state batteries. LiNi0.6Mn0.2Co0.2O2 was selected for cathode materials in this research. For the solid electrolyte itself and LiNi0.6Mn0.2Co0.2O2/SE mixture were analysed by Differential Electrochemical Mass Spectroscopy (DEMS). Furthermore, to understand the importance of surface chemistry, air stored LiNi0.6Mn0.2Co0.2O2 and Al2O3 coated LiNi0.6Mn0.2Co0.2O2were prepared. Since air contamination (H2O and CO2) is detrimental for Ni-rich cathode and battery [5], we propose role of surface chemistry in all-solid-state batteries by comparing different LiNi0.6Mn0.2Co0.2O2 composites. As shown in Figure 1, CO2 and O2 gas evolution is observed within an all-solid-state cell as it is charged up to 5 V, with evolution beginning at ca. 4 V highlighting the requirement of stabilising interfaces even when a solid-state electrolyte is used. Figure 1. Comparison of O2 and CO2 gas evolution from (a) Li6PS5Cl and (b) LiNi0.6Mn0.2Co0.2O2/ Li6PS5Cl composite when charged to 5 V vs. Li/Li+. [1] L. Zhou, N. Minafara, W. G. Zeier, L. F. Nazar, Innovative Approaches to Li-Argyrodite Solid Electrolytes for All-Solid-State Lithium Batteries, Acc. Chem. Res., 54, (2021) 2717–2728 [2] Y. Zhou, C. Doerrer, J. Kasemchainan, P. G. Bruce, M. Pasta, L. J. Hardwick, Observation of Interfacial Degradation of Li6PS5Cl against Lithium Metal and LiCoO2 via In Situ Electrochemical Raman Microscopy, Batter. & Supercaps, 3, (2020) 647 –652 [3] F. Walther, R. Koerver, T. Fuchs, S. Ohno, J. Sann, M. Rohnke, W. G. Zeier, J. Janek, Visualization of the Interfacial Decomposition of Composite Cathodes in Argyrodite-Based All-Solid-State Batteries Using Time-of-Flight Secondary-Ion Mass Spectrometry, Chem. Mater, 31, (2019), 3745-3755 [4]S. Sharifi-Asl, J. Lu, K. Amine, R. Shahbazian-Yassar, Oxygen Release Degradation in Li-Ion Battery Cathode Materials: Mechanisms and Mitigating Approaches, Adv. Energy Mater., 9, (2019) 1900551 [5] H. Kim, A. Choi, S. W. Doo, J. Lim, Y. Kim, K. T. Lee, Role of Na+ in the cation disorder of [Li1-xNax] NiO2 as a cathode for lithium-ion batteries, J. Electrochem. Soc., 165, (2018), A201 Figure 1
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Zhang, Zhenying, Yixuan Wang, Yuehua Fang, Xiufeng Pan, Jiahe Zhang, and Hui Xu. "Global study on slope instability modes based on 62 municipal solid waste landfills." Waste Management & Research: The Journal for a Sustainable Circular Economy 38, no. 12 (October 2, 2020): 1389–404. http://dx.doi.org/10.1177/0734242x20953486.
Abstract:
This study summarized global examples of landfill slope instability over the past 40 years, then selected 62 cases from 22 different counties to analyse the primary factors causing landfill instability. Three slope instability modes in landfill were categorized according to the position of the slip surface: (1) slip surfaces generated inside the waste pile; (2) slip surfaces that pass through the foundation soil; and (3) slip surfaces that occur along the interface between the bottom liner and the municipal solid waste (MSW) pile. These three types of slope instability modes account for 69.4%, 19.32% and 11.28% of all slope instability, respectively. Moreover, five primary causes of landfill instability were identified. A high landfill leachate level was the dominant cause, accounting for 40.32% of cases. This was followed by inadequate compaction of MSW, which accounted for 22.58% of cases, and insufficiently bearing capacity of the foundation, which accounted for 19.35% of cases. Moreover, low shear strength of the liner–MSW interface and rapid release or deflagration of landfill gas were critical factors affecting landfill stability. Factors of safety were calculated using GeoStudio software for selected landfills in China (Maoershan and Xiaping) and Sri Lanka (Meethotamulla). Results from this study are expected to contribute to the prevention and control of landfill failure.
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Kirkinis, E., and A. V. Andreev. "Healing of thermocapillary film rupture by viscous heating." Journal of Fluid Mechanics 872 (June 10, 2019): 308–26. http://dx.doi.org/10.1017/jfm.2019.338.
Abstract:
Thin liquid films sitting on a heated solid substrate and surrounded by a colder ambient gas phase are strongly affected by surface-shear stresses induced by surface tension and temperature gradients, as well as by viscous and capillary forces. The temperature dependence of surface tension may lead to thinning of liquid-film depressions promoting instability which takes place when a critical temperature difference $\unicode[STIX]{x0394}\unicode[STIX]{x1D717}_{cr}$ between the substrate and the ambient gas phase is exceeded. In this article we show theoretically that viscous heating, previously neglected in related literature, may delay or suppress the thermocapillary instability and leads to film healing. The viscous heating effect, by inhibiting heat transfer, prevents the system from reaching the critical value $\unicode[STIX]{x0394}\unicode[STIX]{x1D717}_{cr}$ required to bring about instability. As a consequence, the system remains within the stability region, suppressing film rupture. The presence of the viscous heating effect leads to a persistent circulating motion of two counter-rotating vortices lying diametrically opposite to a depression of the liquid–gas interface reducing the wavelength of disturbances to one half of its initial value. This effect has yet to be observed in experiment.
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Wu, Junwen, Wenfeng Jia, and Chenggang Xian. "Foaming Agent Developed for Gas Wells with Liquid Loading Problem Using New Surfactant and Nanotechnology." SPE Journal 25, no. 06 (July 13, 2020): 3138–44. http://dx.doi.org/10.2118/201249-pa.
Abstract:
Summary Liquid buildup in the wellbore is one of the major causes of production decline in gas wells, in which case additional energy is needed to drain off the liquid to solve this problem. Foaming agents offer a method to reduce the liquid density to make it easier to be lifted with the gas flow, unloading the accumulated liquid in gas wells. The main ingredient of foaming agents are surfactants. Foam stability is influenced by several factors, such as salinity, temperature, and pressure, so a foaming stabilizer is usually needed for a foam system. A foaming agent should be developed to form stable foams in the presence of a salt or sweet-water hydrocarbon phase at a given temperature and pressure. Recently, various kinds of foaming agents have been developed and discussed. Previous studies mainly focused on the complex interaction between an anionic surfactant and amphoteric ion surfactant; however, stability of the foam system formed by these foaming agents needs to be further improved (Nikolai et al. 2009). Therefore, development of a novel foaming agent with improved stability is necessary, especially for the application under downhole conditions. The complex interaction between the anionic and cationic surfactants is neglected in previous research. For example, the synergies between the anionic and cationic surfactants with appropriate methods can greatly improve the foam stability compared with the one-component system. A complex phase behavior and microstructure that has a high surface activity and foam stability can be obtained by the strong electrostatic interaction between the opposite charge ionic head groups and the hydrophobic interaction between the hydrocarbon groups. A gemini surfactant with a spacer can make the molecules pack tighter and increase the surfactant cohesion within the monolayer, which can greatly enhance the foam stability. The liquid film of foam formed by the surfactant is dynamically unstable because the liquid film cannot prevent the diffusion of gas, and the foam will burst quickly. However, solid films with particles adsorbed in the gas/water interface can weaken the foam drainage speed, so that the foam stability is greatly enhanced. In summary, a robust foaming agent is developed with the introduction of an anionic-nonionic surfactant complexed with a gemini cationic surfactant; moreover, nanoparticles with a certain hydrophilicity and size are also adopted as stabilizers.
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Fatin Hana Naning, Syed Abdul Malik, and Hafizul Fahri Hanafi. "Isotherm Behaviour of P3OT, P3HT and PCBM Langmuir Layer on Ionic Subphase." Journal of Advanced Research in Applied Sciences and Engineering Technology 29, no. 3 (February 8, 2023): 168–74. http://dx.doi.org/10.37934/araset.29.3.168174.
Abstract:
Isotherms are generally curves that depict the phenomena that govern a substance’s mobility at a constant temperature and pH. In this study, the Langmuir layer of P3OT, P3HT and PCBM were characterised by computing their surface pressure as a function of the surface area available to the molecules at the interface to obtain a curve called surface pressure – area (Π-A) isotherm. All three polymers were spread on two types of subphases - DI water and water containing bivalent metal ions, Pb2+. None of the Langmuir layers exhibits discrete gas-liquid-solid phase transitions on the water subphase. However, more stable Langmuir layers formed when lead ions were added to the water subphase. The stability enables the capping of lead ions between the polymer chain or within the balls, which can be implemented in flexible electronic devices.
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Indacochea, J. E., J. Beres, and A. Polar. "Interface Development in Joining Yttria Stabilized Zirconia to Stainless Steel by In Situ Alloying with Ni/Ti Filler Metals." Solid State Phenomena 127 (September 2007): 19–24. http://dx.doi.org/10.4028/www.scientific.net/ssp.127.19.
Abstract:
There is need for efficient energy conversion systems based on domestic fossil or biofuels. Solid Oxide Fuel Cells (SOFC's) are attractive in this case, however sealing is a critical issue in SOFC development. The purpose of this investigation is to find a procedure to seal yttria stabilized zirconia (YSZ) electrolyte to the stainless steel electrical interconnect or gas manifold. The seal is usually exposed to high temperatures in the range of 500 to 1000°C. Brazing by in-situ alloying of nickel and titanium foils was performed to braze zirconia to 444- stainless steel. Different combinations of nickel/titanium foils were used; brazing was done in vacuum at 6 x 10-6 torr at 960°C, 1010, and 1030°C for different brazing times. The braze and interfacial microstructures were characterized by optical microscopy, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). This paper assesses the effect of process parameters on the development and stability of the braze metal and the interactions of the filler metal with the two substrates.
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Nejati, Iman, Mathias Dietzel, and Steffen Hardt. "Conjugated liquid layers driven by the short-wavelength Bénard–Marangoni instability: experiment and numerical simulation." Journal of Fluid Mechanics 783 (October 13, 2015): 46–71. http://dx.doi.org/10.1017/jfm.2015.544.
Abstract:
The coupled dynamics of two conjugated liquid layers of disparate thicknesses, which coat a solid substrate and are subjected to a transverse temperature gradient, is investigated. The upper liquid layer evolves under the short-wavelength Bénard–Marangoni instability, whereas the lower, much thinner film undergoes a shear-driven long-wavelength deformation. Although the lubricating film should reduce the viscous stresses acting on the up to one hundred times thicker upper layer by only 10 %, it is found that the critical Marangoni number of marginal stability may be as low as if a stress-free boundary condition were applied at the bottom of the upper layer, i.e. much lower than the classical value of 79.6 known for a single film. Furthermore, it is experimentally verified that the deformation of the liquid–liquid interface, albeit small, has a non-negligible effect on the temperature distribution along the liquid–gas interface of the upper layer. This stabilizes the hexagonal pattern symmetry towards external disturbances and indicates a two-way coupling of the different layers. The experiments also demonstrate how convection patterns formed in a liquid film can be used to pattern a second conjugated film. The experimental findings are verified by a numerical model of the coupled layers.
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Promdirek, Piyorose, Gobboon Lothongkum, Yves Wouters, Somrerk Chandra-ambhorn, and Alain Galerie. "Effect of Humidity on the Corrosion Kinetics of Ferritic Stainless Steels Subjected to Synthetic Biogas." Materials Science Forum 696 (September 2011): 417–22. http://dx.doi.org/10.4028/www.scientific.net/msf.696.417.
Abstract:
Ferritic stainless steels have nowadays been used as materials for interconnectors in solid oxide fuel cells (SOFCs) at intermediate temperatures (800°C). Their degradation in contact with dry synthetic biogas used instead of other fuel gas has already been studied. In such biogas atmosphere, humidity may play an important role. The objective of this study is therefore to understand the effect of H2O on the corrosion kinetics of the ferritic stainless steels type AISI441 (18CrTiNb) under synthetic biogas (70%CH4and 30%CO2) mixed with 3%H2O. The thermodynamic analysis by FactSage was used to determine the partial pressure of oxygen and the activity of carbon in the humid biogas. The results showed that the partial pressure of oxygen is in the range 10–24.8to 10–21.2bar for temperatures between 600-800°C and that the formation of solid carbon can occur in these conditions. This was not different compared with the conditions in dry biogas. These conditions lead to the stability of some important oxides such as Cr2O3and Cr-Mn spinel and to carbon deposition and/or carbide formation. The surface morphology of 441 subjected to humid biogas showed oxide scale composed mainly of Cr2O3topped with Cr-Mn spinel. Some carbide such as Cr7C3was found in chromia scale. Kinetic experiments under both dry and humid biogas at temperatures between 600 and 800°C showed linear weight changes. Arrhenius law was followed and the rate-determining steps were identified as parallel oxidation and carburization limited by oxide-gas interface reactions.
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Muravev, Anton, Tatiana Gerasimova, Robert Fayzullin, Olga Babaeva, Ildar Rizvanov, Ayrat Khamatgalimov, Marsil Kadirov, et al. "Thermally Stable Nitrothiacalixarene Chromophores: Conformational Study and Aggregation Behavior." International Journal of Molecular Sciences 21, no. 18 (September 21, 2020): 6916. http://dx.doi.org/10.3390/ijms21186916.
Abstract:
Achieving high thermal stability and control of supramolecular organization of functional dyes in sensors and nonlinear optics remains a demanding task. This study was aimed at the evaluation of thermal behavior and Langmuir monolayer characteristics of topologically varied nitrothiacalixarene multichromophores and phenol monomers. A nitration/azo coupling alkylation synthetic route towards partially O-substituted nitrothiacalixarenes and 4-nitrophenylazo-thiacalixarenes was proposed and realized. Nuclear magnetic resonance (NMR) spectroscopy and X-ray diffractometry of disubstituted nitrothiacalix[4]arene revealed a rare 1,2-alternate conformation. A synchronous thermal analysis indicated higher decomposition temperatures of nitrothiacalixarene macrocycles as compared with monomers. Through surface pressure/potential-molecular area measurements, nitrothiacalixarenes were shown to form Langmuir monolayers at the air–water interface and, through atomic force microscopy (AFM) technique, Langmuir–Blodgett (LB) films on solid substrates. Reflection-absorption spectroscopy of monolayers and electronic absorption spectroscopy of LB films of nitrothiacalixarenes recorded a red-shifted band (290 nm) with a transition from chloroform, indicative of solvatochromism. Additionally, shoulder band at 360 nm was attributed to aggregation and supported by gas-phase density functional theory (DFT) calculations and dynamic light scattering (DLS) analysis in chloroform–methanol solvent in the case of monoalkylated calixarene 3. Excellent thermal stability and monolayer formation of nitrothiacalixarenes suggest their potential as functional dyes.
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Franco, T., Z. HoshiarDin, P. Szabo, M. Lang, and G. Schiller. "Plasma Sprayed Diffusion Barrier Layers Based on Doped Perovskite-Type LaCrO3 at Substrate-Anode Interface in Solid Oxide Fuel Cells." Journal of Fuel Cell Science and Technology 4, no. 4 (May 2, 2006): 406–12. http://dx.doi.org/10.1115/1.2756846.
Abstract:
In the thin-film solid oxide fuel cell (SOFC) concept of the German Aerospace Center (DLR) in Stuttgart, the entire membrane electrode assembly (MEA) is deposited onto a porous metallic substrate by an integrated multistep vacuum plasma spray (VPS) process. This concept enables the production of very thin and stable electrodes and electrolyte layers with a total cell thickness of only 100–120μm. In this concept, the porous ferrite substrate material predominantly acts as mechanical cell support and as fuel gas distributor. In general, ferrite substrate alloys with high chromium and low manganese content show both excellent corrosion stability and adequate thermal expansion behavior. Nevertheless, at the high process temperature in the SOFC of ∼800°C, atomic transport processes can show a detrimental effect on cell performance, at least at the required long-term operation. Problems arise, in particular, through diffusion processes of Fe-, Cr-, and Ni-species between the Ni/8YSZ anode and the ferrite steel-based substrate material. This can induce significant structure changes both in the anode and the substrate. As a reliable solution of this key problem, a plasma sprayed thin diffusion barrier layer is seen at the interface between anode and substrate, which consists of an electrically conductive and chemically stable ceramic component. For this purpose, some doped perovskite-type LaCrO3, such as La1−xSrxCrO3−δ, La1−xCaxCrO3−δ, or La1−xSrxCr1−yCoyO3−δ were investigated and tested carefully at DLR. These types of perovskites show a high potential to fulfill all the required properties that are needed for the applicability as an anode-side diffusion barrier layer. The paper focuses on basic investigations of differently doped LaCrO3 compounds under SOFC-relevant conditions concerning thermal expansion, electrical conductivity, chemical stability, etc. Furthermore, first results of electrically and electrochemically characterized half cells carried out with some qualified doped LaCrO3 are shown. Finally, the diffusion barrier layer is demonstrated as a new SOFC component that is effective at cell operating conditions.
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Wakamatsu, Katsuhiro, Takaaki Yasuda, Yuji Okada, and Teppei Ogura. "First-Principles Studies for Optimal Model of the Ni/YSZ Triple Phase Boundary in Solid Oxide Cells." ECS Meeting Abstracts MA2023-01, no. 54 (August 28, 2023): 207. http://dx.doi.org/10.1149/ma2023-0154207mtgabs.
Abstract:
Non-Faradaic electrochemical modification of catalytic activity (NEMCA) with electric field applications in solid oxide cells (SOCs) is thought to be induced by spillover effects of lattice oxygen from the bulk, although the detailed mechanism has not still been clear. In SOCs, important phenomena such as fuel decomposition, charge transfer, etc. occur at the triple phase boundary (TPB) as a highly active site that consists of catalyst, electrolyte, and gas phases. NEMCA is expected to be also induced strongly by the surface mechanism on TPB, and understanding surface reactions on TPB is essential for improving catalyst and cell performances. However, the reliable TPB model has not been still uniquely defined to discuss the property of TPB although various studies have been reported. Therefore, in this study, we have focused on the TPB model comprising Ni catalyst cluster; YSZ electrolyte; and gas phase, and aimed to identify a reliable TPB model for theoretical studies by using first-principles calculations as an initial step. In concrete, we identified firstly the stable structures of YSZ surface models by using DFT calculations taking into account oxygen vacancy positions, yttrium atom arrangements, yttria concentration, and other factors. Thereafter, we discussed a reliable Ni/YSZ interface model based on the most stable YSZ model proposed above results by evaluating the Ni structure, interface stability, and so on. In this study, DFT calculations with a plane-wave basis set were implemented using CASTEP, and GGA-PBE exchange-correlation functional was used. The plane-wave cutoff energy was set as 489.8 eV, the OTFG-ultrasoft was used as the pseudopotentials, and the spin-polarization is considered because YSZ is a ferromagnetic substance. In YSZ surface models, yttria concentrations are set to 4.35 mol% and 9.1 mol% which shows the maximum ion conductivity of ZrO2. The three-layer YSZ (111) slabs with 15 Å vacuum layer with 2×2 and 2×4 unit cells were used for repeated slab models. The DFT+U method is used to obtain the correct electric structure of metal oxides with partially filled d or f-orbital shells, and k-points were set to 4×2×1. In Ni/YSZ interface models, we considered Ni cluster and Ni belt type models based on the most stable 2×4 YSZ surface model (9.1 mol%) proposed in this study. We also considered both cases of (111) and (100) facets for the contact interface. In the case of Ni/YSZ interface models, the DFT+U method was not considered to improve the calculation convergence and k-points were set to 4×2×1. A schematic diagram of the Ni/YSZ interface model is shown in the attached Figure. In the case of the 2×2 YSZ model with the yttria concentration of 9.1 mol%, the YSZ model is stabilized when oxygen vacancy is on the second O atom layer and the second neighbor to Y atoms, indicating that improvement in the geometry instability of ZrO2 for 8-coordination is more important than keeping local electron neutrality. We have also found that oxygen vacancy positions are more sensitive to the YSZ surface stability than Y atom arrangements. In the case of the 2×4 YSZ model with the yttria concentration of 4.35 mol%, the YSZ model where there are Y atoms on the first layer is stabilized. The crystal structure achieves a more stable structure by varying bond lengths when Y3+ with the larger ionic radius is replaced with Zr4+. Therefore, the structure is easier to stabilize when the Y atom exists on the surface than in the bulk due to the higher degree of freedom of the Y atom. The most stable structure of the 2×4 YSZ model with the yttria concentration of 9.1 mol% given based on the above results is 0.18 eV more stable than the previously reported structure [1]. This is because the number of Y atoms on the first layer with the second neighbor from oxygen vacancy is larger than the previously reported structure. We evaluated then the structural stability of the Ni/YSZ interface model based on the above YSZ model. As a result, we have found that adhesion energy between Ni and YSZ is independent of the relative position of Ni atoms. In addition, the larger the number of Ni atoms is, the more stable the structure is. This is because the electronic property of Ni atoms approaches the metal as increasing the number of Ni atoms. Other results and a detailed discussion will be reported in our meeting publications (ECS Transactions) and the presentation. [1] M. Shishkin and T. Ziegler, Phys. Chem. Chem. Phys., 16, 1798-1808 (2014). Figure 1
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VLACHOMITROU, M., and N. PELEKASIS. "Nonlinear interaction between a boundary layer and a liquid film." Journal of Fluid Mechanics 638 (October 7, 2009): 199–242. http://dx.doi.org/10.1017/s0022112009990644.
Abstract:
The nonlinear stability of a laminar boundary layer that flows at high Reynolds number (Re) above a plane surface covered by a liquid film is investigated. The basic flow is considered to be nearly parallel and the simulations are based on triple deck theory. The overall interaction problem is solved using the finite element methodology with the two-dimensional B-cubic splines as basis functions for the unknowns in the boundary layer and the film and the one-dimensional B-cubic splines as basis functions for the location of the interface. The case of flow above an oscillating solid obstacle is studied and conditions for the onset of Tollmien–Schlichting (TS) waves are recovered in agreement with the literature. The convective and absolute nature of TS and interfacial waves is captured for gas-film interaction, and the results of linear theory are recovered. The evolution of nonlinear disturbances is also examined and the appearance of solitons, spikes and eddy formation is monitored on the interface, depending on the relative magnitude of Froude and Weber numbers (Fr, We), and the gas to film density and viscosity ratios (ρ/ρw, μ/μw). For viscous films TS waves grow on a much faster time scale than interfacial waves and their effect is essentially decoupled. The influence of interfacial disturbances on short-wave growth in the bulk of the boundary layer bypassing classical TS wave development is captured. For highly viscous films for which inertia effects can be neglected, e.g. aircraft anti-icing fluids, soliton formation is obtained with their height remaining bounded below a certain height. When water films are considered interfacial waves exhibit unlimited local growth that is associated with intense eddy formation and the appearance of finite time singularities in the pressure gradient.
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Pateli, Ioanna Maria, Mihkel Vestli, and John Irvine. "Interfacial Chemical Stability of Doped Li7-XLa3Zr2 -X(Nb/TaX)O12 with LiCoO2 Electrode Material." ECS Meeting Abstracts MA2023-02, no. 4 (December 22, 2023): 565. http://dx.doi.org/10.1149/ma2023-024565mtgabs.
Abstract:
Garnet-type oxide solid state electrolytes (SEs) are promising candidates due to their potential high ionic conductivity and chemical stability with Li for the replacement of flammable liquid electrolytes used in the current Li-ion batteries. Intense research has been focused on optimising the interface of garnets with Li, with the positive side to be somehow neglected. A significant issue of oxide SEs, hurdling their industrial application, is their poor contact with positive materials due to their rigidity. Poor interfacial contact leads to the need of co-sintering at high temperatures (> 400 °C), which enables side reactions and unwanted processes like cation intermixing, diffusion of elements and formation of non-conductive secondary mixed phases. In this work the chemical stability of Ta and Nb doped LLZO garnet SE was tested in contact with LiCoO2, a common positive material used in the battery industry. Initially, mixed powders of SE and active material were heat treated and studied using Raman spectroscopy and scanning electron microscopy to observe side reactions. In order to improve contact between the two materials, instead of already synthesized crystalline powder, nitrate precursors were also used for in-situ synthesis of LiCoO2 material in contact with the garnet. Mixtures of the SE powder and nitrate precursors for LiCoO2 were also heat-treated at various temperatures for different time periods in different gas atmospheres. The heat-treated materials were then analysed extensively using scanning electron microscopy coupled with energy dispersive X-Ray element mapping and with Raman microscopy to prove the existence or absence of secondary mixed phases at given conditions. Additionally, the optimized heat-treatment conditions were adapted for layered garnet SE/LiCoO2 samples to study the actual electrolyte/electrode interface at the same conditions used for powder mixtures. Based on the results the symmetrical LiCoO2/garnet SE/LiCoO2 cells will be prepared and tested electrochemically.
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Yoon, Kyungho, Hwiho Kim, Sangwook Han, Ting-Shan Chan, Kun-Hee Ko, Sugeun Jo, Jooha Park, et al. "Detrimental effect of high-temperature storage on sulfide-based all-solid-state batteries." Applied Physics Reviews 9, no. 3 (September 2022): 031403. http://dx.doi.org/10.1063/5.0088838.
Abstract:
The all-solid-state battery (ASSB) has become one of the most promising next-generation battery systems, since the aspect of safety has emerged as a crucial criterion for new large-scale applications such as in electric vehicles. Despite the recent remarkable progress in the performance enhancement, the real-world implementation of the ASSB still requires full comprehension/evaluation of its properties and performance under various practical operational conditions. Unlike batteries employed in conventional electronic devices, those in electric vehicles—the major application that the ASSB is expected to be employed—would be exposed to wide temperature variations (−20 to ∼70 °C) at various states of charges due to their outdoor storage and irregular discharge/rest/charge conditions depending on vehicle drivers' usage patterns. Herein, we investigate the reliability of a Li6PS5Cl-based ASSB system in practically harsh but plausible storage conditions and reveal that it is vulnerable to elevated-temperature storage as low as 70 °C, which, in contrast to the common belief, causes significant degradation of the electrolyte and consequently irreversible buildup of the cell resistance. It is unraveled that this storage condition induces the decomposition of Li6PS5Cl in contact with the cathode material, involving the SOx gas evolution particularly at charged states, which creates a detrimental porous cathode/electrolyte interface, thereby leading to the large interfacial resistance. Our findings indicate that the stability of the solid electrolyte, which has been believed to be failsafe, needs to be carefully revisited at various practical operational conditions for actual applications in ASSBs.
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Seo, Jongmin, Ricardo García-Mayoral, and Ali Mani. "Turbulent flows over superhydrophobic surfaces: flow-induced capillary waves, and robustness of air–water interfaces." Journal of Fluid Mechanics 835 (November 27, 2017): 45–85. http://dx.doi.org/10.1017/jfm.2017.733.
Abstract:
Superhydrophobic surfaces can retain gas pockets within their microscale textures when submerged in water. This property reduces direct contact between water and solid surfaces and presents opportunities for improving hydrodynamic performance by decreasing viscous drag. In most realistic applications, however, the flow regime is turbulent and retaining the gas pockets is a challenge. In order to overcome this challenge, it is crucial to develop an understanding of physical mechanisms that can lead to the failure of superhydrophobic surfaces in retaining gas pockets when the overlying liquid flow is turbulent. We present a study of the onset of failure in gas retention by analysing direct numerical simulations (DNS) of turbulent flows over superhydrophobic surfaces coupled with the deformation of air–water interfaces that hold the gas pockets. The superhydrophobic surfaces are modelled as periodic textures with patterned slip and no-slip boundary conditions on the overlying water flow. The liquid–gas interface is modelled via a linearized Young–Laplace equation, which is solved coupled with the overlying turbulent flow. A wide range of texture sizes and interfacial Weber numbers are considered in this study. Our analysis identifies flow-induced upstream-travelling capillary waves that are coherent in the spanwise direction as one mechanism for failure in retention of gas pockets. To confirm physical understanding of these waves, a semianalytical inviscid linear analysis is developed; the wave speeds obtained from the space–time correlations in the DNS data were found to match with the predictions of the semianalytical model. The magnitude of the pressure fluctuations due to these waves was found to increase with decreasing surface tension, and increase with a much stronger dependence on the slip velocity, when all numbers are reported in wall units. Based on a fitted scaling, a threshold criterion for the failure of superhydrophobic surfaces is developed that is based on estimates of the onset condition required for the motion of contact lines. The second contribution of this work is the development of boundary maps that identify stable and unstable zones in a parameter space consisting of working parameter and design parameters including texture size and material contact angle. We provide a brief description of previously identified failure modes of superhydrophobic surfaces, namely the stagnation pressure and shear-driven drainage mechanisms. In an overlay map, the stable and unstable zones due to each mechanism are presented. For various input conditions, we provide scaling laws that identify the most critical mechanism limiting the stability of gas retention by superhydrophobic surfaces.
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Kalutara Koralalage, Milinda, Varun Shreyas, William Richard Arnold, Sharmin Akter, Arjun Thapa, Jacek Bogdan Jasinski, Gamini Sumanasekera, Hui Wang, and Badri Narayanan. "Quasi-Solid-State Lithium-Sulfur Batteries Consist of Super P – Sulfur Composite Cathode." ECS Meeting Abstracts MA2022-02, no. 4 (October 9, 2022): 541. http://dx.doi.org/10.1149/ma2022-024541mtgabs.
Abstract:
Lithium-Sulfur (Li-S) batteries stand out to be one of the most promising candidates to meet the current energy storage requirement, with its natural abundance of materials, high theoretical capacity of 1672 mAhg-1, high energy density of 2600 Whkg-1, and low cost and lower environmental impact. Sulfur itself (S8), Li2S2 and Li2S formed during the discharge process, are electrical insulators and hence reduce the active material utilization and the electronic conductivity of the cathode affecting the battery performance. Combining of Carbon Super P (SP) with sulfur in cathode formulation is used to overcome these issues. In Liquid electrolyte batteries, polysulfides formed while charging and discharging, easily dissolve in liquid electrolyte and the resulting polysulfide shuttling leads to poor coulombic efficiency and cyclability. Liquid electrolytes used in the conventional Li-S batteries are easy to flow and become flammable. Further, Lithium dendrites piercing through separator causing short circuit paths leads to safety concerns. Replacement of the liquid electrolyte by a solid-state electrolyte (SSE) proves to be a strategy to overcome above mentioned issues. Sulfide based solid electrolytes have received greater attention due to their higher ionic conductivity, compatible interface with sulfur-based cathodes, and lower grain boundary resistance. Novel Li6PS5F0.5Cl0.5 due to its remarkable ionic conductivity of 3.5 x 10-4 S cm-1 makes it an excellent candidate for use in a Li-S solid state battery. However, the interface between SSEs and cathodes has become a challenge to be addressed in all solid-state Li-S batteries due to the rigidity of the participating surfaces. A hybrid electrolyte containing of SSE coupled with a small amount of ionic liquid at the interface, has been employed to improve the interface contact of the SSE with the electrodes. Cathode formulation consisting of sulfur as the active material, Super P as the conductive carbon black, acetylene carbon black as conductive carbon additive, with water based carboxymethyl cellulose (CMC) solution and Styrene butadiene rubber (SBR) as the binder was successfully developed. Thermo gravimetric analysis (TGA) studies of the cathode were carried out by the thermo gravimetric analyzer TA 2050 under N2 gas flow of 100 ml/min. Cathode surface morphology was characterized using the Field emission gun scanning electron microscope (FEI), TESCAN scanning electron microscope with energy dispersive X-ray spectroscopy (EDAX). Using a solvent-based process, Li6PS5F0.5Cl0.5 and Li6PS5F0.5Cl2 SSE were synthesized via the introduction of LiF into the argyrodite crystal structure, which enhances both the ionic conductivity and interface-stabilizing properties of the SSE. Relevant Ionic Liquids (IL) were prepared using Lithium bis(trifluoromethyl sulfonyl)imide (LiTFSI) as salt, with premixed pyrrolidinium bis(trifluoromethyl sulfonyl)imide (PYR) as solvent and 1,3-dioxolane (DOL) as diluent. SP-S cathode with 0.70 mgcm-2 sulfur loading was punched into disks of 2.0 cm2. SSE was pressed into 150 mg pellets using a stainless-steel tank. During the assembly, SSE was wetted with total of 40 μl of IL (LiTFSI dissolved in PYR and DOL solution) from both ends using a micropipette. 2032 type coin cells of Quasi-solid-state Li-S batteries (QSSLSB) consisting of SP-S based composite cathodes, Li anodes and novel Li6PS5F0.5Cl0.5 SSE were tested with an ionic liquid wetting both electrode-SSE interfaces. All the QSSLSB were cycled at 30 °C between 1.0 V and 2.8 V using an 8 channel Arbin battery testing system. Effect of IL dilution, co-solvent amount, LiTFSI concentration and C rate at which the batteries are tested, were systematically studied and optimized to develop a QSSLSB with higher capacity retention and cyclability. Optimum batteries had initial discharge capacity >1100 mAh/g and discharge capacity >400 mAh/g after 100 cycles at the C rate of C/10 with a significant coulombic efficiency. 40 μl of LiTFSI (2M) dissolved in PYR:DOL(1:1) IL was found to be optimum for high performance QSSEBs with low sulfur loading of 0.7 mg/cm2. From the C rate performance study QSSEBs have shown improved stability with the higher current rates. Next, cathodes with higher sulfur loading were studied and for sulfur loading > 4 mgcm-2, initial discharge capacity >950 mAh/g and 400 mAh/g after 60 cycles at C/20 rate were achieved with 40 μl of IL consisting of LiTFSI (3M) dissolved in PYR:DOL(1:3) for the SSE Li6PS5F0.5Cl2. Further testing is underway to improve the performance at high C rate for higher loading by incorporating SSE in the cathode to realize QSSLSB with higher capacity with improved cycle retention.
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Moridis, George J., Michael Brendon Kowalsky, and Karsten Pruess. "Depressurization-Induced Gas Production From Class-1 Hydrate Deposits." SPE Reservoir Evaluation & Engineering 10, no. 05 (October 1, 2007): 458–81. http://dx.doi.org/10.2118/97266-pa.
Abstract:
Summary Class 1 hydrate deposits are characterized by a hydrate-bearing layer underlain by a two-phase zone involving mobile gas. Two kinds of deposits are investigated. The first involves water and hydrate in the hydrate zone (Class 1W), while the second involves gas and hydrate (Class 1G). We introduce new models to describe the effect of the presence of hydrates on the wettability properties of porous media. We determine that large volumes of gas can be readily produced at high rates for long times from Class 1 gas-hydrate accumulations by means of depressurization-induced dissociation using conventional technology. Dissociation in Class 1W deposits proceeds in distinct stages, while it is continuous in Class 1G deposits. To avoid blockage caused by hydrate formation in the vicinity of the well, wellbore heating is a necessity in production from Class 1 hydrates. Class 1W hydrates are shown to contribute up to 65% of the production rate and up to 45% of the cumulative volume of produced gas; the corresponding numbers for Class 1G hydrates are 75% and 54%. Production from both Class 1W and Class 1G deposits leads to the emergence of a second dissociation front (in addition to the original ascending hydrate interface) that forms at the top of the hydrate interval and advances downward. In both kinds of deposits, capillary pressure effects lead to hydrate lensing (i.e., the emergence of distinct banded structures of alternating high/low hydrate saturation, which form channels and shells and have a significant effect on production). Introduction Background. Gas hydrates are solid crystalline compounds in which gas molecules (referred to as guests) are lodged within the lattices of ice crystals (called hosts). Gas-hydrate deposits occur in two distinctly different geologic settings where the necessary favorable thermodynamic conditions exist for their formation and stability: in the permafrost and in deep ocean sediments. Because of different formation processes, these two types of accumulations have distinctly different attributes. Although there has been no systematic effort to map and evaluate this resource, and current estimates vary widely the consensus is that the worldwide quantity of hydrocarbon-gas hydrates is vast (Sloan 1998). Even the most conservative estimate surpasses by a factor of two the energy content of the total fossil-fuel reserves recoverable by conventional methods. The sheer magnitude of this resource commands attention as a potential energy resource, even if only a limited number of hydrate deposits are attractive production targets and/or only a fraction of the trapped gas may be recoverable. As current energy economics make gas production from unconventional resources increasingly appealing (or, at a minimum, less prohibitive), the potential of hydrate accumulations clearly demands technical and economic evaluation. The attractiveness of hydrates is further augmented by the environmental desirability of gas (as opposed to solid and liquid) fuels. Gas from hydrates is produced by inducing dissociation by one of the following three main methods (Sloan 1998) (or combinations thereof):depressurization, which involves pressure lowering below the equilibrium hydration pressure at the prevailing temperature;thermal stimulation, in which the temperature is raised above the equilibrium hydration temperature at the prevailing pressure; andthe use of hydration inhibitors (such as salts and alcohols).
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Tenhaeff, Wyatt. "(Invited) Lithium Battery Interfacial Engineering with Thin Conformal Polymer Coatings." ECS Meeting Abstracts MA2023-02, no. 1 (December 22, 2023): 78. http://dx.doi.org/10.1149/ma2023-02178mtgabs.
Abstract:
Coupled chemical and mechanical phenomena at electrode interfaces largely govern the reversibility and long term stability of lithium ion and lithium metal batteries. A well-known example in lithium ion batteries is the formation of the electrically insulating, ionically conductive, continuous solid electrolyte interface (SEI) on graphitic anodes, which passivates the electrode against further electrochemical reduction of the electrolyte. Unfortunately, this stable passivation does not occur in Si and Li metal anodes. High voltage cathodes are also prone to detrimental interfacial processes, resulting in electrolyte oxidation, gas formation, and transition metal dissolution. In response, a myriad of coating technologies has been developed to mitigate and control these interfacial phenomena and enable next-generation electrodes. These technologies must provide thin, conformal coatings over the entire electrochemically active surface area of the electrode; the coatings must also possess the requisite mechanical properties to accommodate volume dilation due to lithium insertion/extraction. This presentation will describe the development of conformal, compliant polymer thin film coatings for lithium battery electrodes. The polymer thin films are prepared by initiated chemical vapor deposition (iCVD), which provides exquisite control over film composition and morphology by facilitating heterogeneous free-radical polymerization of vinyl monomers with thickness precision on the order of 1 nm. Poly(1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane) (pV4D4) was deposited onto silicon thin film electrodes using iCVD. 25 nm-thick pV4D4 films on Si electrodes improved initial coulombic efficiency by 12.9% and capacity retention over 100 cycles by 64.9% relative to untreated electrodes. PV4D4 coatings also improved rate capabilities, enabling higher lithiation capacity at all current densities. Post-cycling FTIR and XPS showed that pV4D4 inhibited electrolyte reduction and altered the SEI composition, with enrichment in LiF. In another example, thin conformal coatings of perfluorinated polymer were deposited onto battery-grade Cu current collectors to function as an artificial solid electrolyte interface. The effect of the film thickness on Li cycling reversibility was characterized. By galvanostatically cycling Li in an asymmetric Li||Cu cell using 1M LiFSI in a 1:1 (v/v) mixture of dioxolane:dimethoxyethane at 30°C, it was shown that the average coulombic efficiency averaged over 50 cycles increased from 98.36% for bare, untreated Cu to 99.08% for Cu coated with 25 nm of the fluoropolymer. Moreover, the 25 nm coating suppressed interfacial impedance growth on the current collector; the resistance of the coated Cu was 40% lower than the untreated Cu after 100 cycles. The mechanism by which the polymer coating enhances coulombic efficiency and suppresses side reactions will be discussed, along with discussion of the performance in practical anode-free lithium metal batteries.
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Evrensel, Cahit A., Md Raquib U. Khan, Shahram Elli, and Peter E. Krumpe. "Viscous Airflow Through a Rigid Tube With a Compliant Lining: A Simple Model for the Air-Mucus Interaction in Pulmonary Airways." Journal of Biomechanical Engineering 115, no. 3 (August 1, 1993): 262–70. http://dx.doi.org/10.1115/1.2895485.
Abstract:
The respiratory tract of mammals is lined with a layer of mucus, described as viscoelastic semi-solid, above a layer of watery serous fluid. The interaction of these compliant layers with pulmonary airflow plays a major role in lung clearance by two-phase gas-liquid flow and in increased flow resistance in patients with obstructive airway diseases such as cystic fibrosis, chronic bronchitis and asthma. Experiments have shown that such coupled systems of flow-compliant-layers are quite susceptible to sudden shear instabilities, leading to formation of relatively large amplitude waves at the interface. Although these waves enhance the lung clearance by mobilizing the secretions, they increase the flow resistance in airways. The objective of this paper is to understand the basic interaction mechanism between the two media better by studying airflow through a rigid pipe that is lined by a compliant layer. The mathematical model that has been developed for this purpose is capable of explaining some of the published experimental observations. Wave instability theory is applied to the coupled air-mucus system to explore the stability of the interface. The results show that the onset flow speed for the initiation of unstable surface waves, and the resulting wavelength, are both very sensitive to mucus thickness. The model predicts that the instabilities initiate in the form of propagating waves for the elastic mucus where the wave speed is about 40 percent of the flow speed. The wavelength and phase speed to air velocity ratio are shown to increase with increasing mucus thickness. Also, results show that the mucus viscosity causes the onset air velocity to increase and the wave speed to decrease. The predictions of the model for the viscoelastic case are in good qualitative and quantitative agreement with some of the published experimental observations.
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Wang, Rong-Tsu, Horng-Yi Chang, and Jung-Chang Wang. "An Overview on the Novel Core-Shell Electrodes for Solid Oxide Fuel Cell (SOFC) Using Polymeric Methodology." Polymers 13, no. 16 (August 18, 2021): 2774. http://dx.doi.org/10.3390/polym13162774.
Abstract:
Lowering the interface charge transfer, ohmic and diffusion impedances are the main considerations to achieve an intermediate temperature solid oxide fuel cell (ITSOFC). Those are determined by the electrode materials selection and manipulating the microstructures of electrodes. The composite electrodes are utilized by a variety of mixed and impregnation or infiltration methods to develop an efficient electrocatalytic anode and cathode. The progress of our proposed core-shell structure pre-formed during the preparation of electrode particles compared with functional layer and repeated impregnation by capillary action. The core-shell process possibly prevented the electrocatalysis decrease, hindering and even blocking the fuel gas path through the porous electrode structure due to the serious agglomeration of impregnated particles. A small amount of shell nanoparticles can form a continuous charge transport pathway and increase the electronic and ionic conductivity of the electrode. The triple-phase boundaries (TPBs) area and electrode electrocatalytic activity are then improved. The core-shell anode SLTN-LSBC and cathode BSF-LC configuration of the present report effectively improve the thermal stability by avoiding further sintering and thermomechanical stress due to the thermal expansion coefficient matching with the electrolyte. Only the half-cell consisting of 2.75 μm thickness thin electrolyte iLSBC with pseudo-core-shell anode LST could provide a peak power of 325 mW/cm2 at 700 °C, which is comparable to other reference full cells’ performance at 650 °C. Then, the core-shell electrodes preparation by simple chelating solution and cost-effective one process has a potential enhancement of full cell electrochemical performance. Additionally, it is expected to apply for double ions (H+ and O2−) conducting cells at low temperature.
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Nguyen, Xuan Dong, Seok hee Lee, Hyung Tae Lim, and Tae Ho Shin. "Boosting the Stability and Performance of SOFCs: A New Approach to Oxygen Storage Capacity Using Lanthanum-Doped Ceria Interlayer Technology." ECS Meeting Abstracts MA2023-02, no. 46 (December 22, 2023): 2208. http://dx.doi.org/10.1149/ma2023-02462208mtgabs.
Abstract:
Being carbon neutral is one of the world's most important objectives. More than 65 percent of the countries that emit harmful greenhouse gases have committed to achieving net-zero emissions by the middle of the century.[1] There are numerous essential ways to gather energy for worldwide missions, including fuel cells, solar power, wind power, etc. The growing marketplace of fuel cells is following the trend of green-energy demand. Solid oxide fuel cells (SOFCs) are gaining popularity in the next-generation energy industry due to their high energy conversion efficiency, fuel flexibility, and low emissions.[2] The main challenges for the commercialization of SOCs that need to address are high performance, long-term durability, and effective cost. Stabilized zirconia such as Yttria-stabilized zirconia (YSZ) and Scandia-stabilized zirconia (ScSZ) is commonly used as a self-standing electrolyte support. The inability of zirconia-based electrolytes to react with Sr-rich cathode materials like LSC, LSCF, BSCF, etc. Therefore, the electrodes and the zirconia-based electrolyte must have the best-interlayered buffer structure. Optimizing interlayer microstructures to make them more effective at high-performance ESCs is of great interest. Several Rare-earth doped ceria (RDC) materials, including (Gd, Ce)O2, (Sm, Ce)O2, and (La, Ce)O2, have been used as efficient interlayers to lessen reactivity and preserve ionic conductivity in the interface. However, the difference in the thermal expansion coefficient (TEC) between the GDC and the YSZ poses a significant problem for starting and halting SOCs. In the present work, we focus on the commercial lanthanum-doped ceria (Ce0.6La0.4O1.8 - LDC) as a buffer layer between the YSZ electrolyte and the LSCF cathode because of its higher oxygen storage capacitance. The reactivity of the YSZ/GDC composite was higher than that of the YSZ/LDC composite. And the total conductivity of the LDC/YSZ composite is higher than GDC/YSZ composite even though LDC has lower conductivity than GDC. Moreover, the mismatching of TEC was reduced by replacing the GDC with the LDC bilayer. Consequently, the maximum power density for the electrolyte-supported cell SOFC with LDC interlayer was ~0.55 W.cm−2 at 1073 K. A variety of additives (Co, Mn, and Cu) was added to the LDC buffer layer to examine the sintering properties. The addition of copper not only obtained the highest microstructural density but also improve mechanical stability under cost-effective processes. References [1] M. Meinshausen, N. Meinshausen, W. Hare, S.C. Raper, K. Frieler, R. Knutti, D.J. Frame, M.R.J.N. Allen, Greenhouse-gas emission targets for limiting global warming to 2 C, 458 (2009) 1158-1162. [2] C. Graves, S.D. Ebbesen, S.H. Jensen, S.B. Simonsen, M.B.J.N.m. Mogensen, Eliminating degradation in solid oxide electrochemical cells by reversible operation, 14 (2015) 239-244.
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Price, Robert, Aida Fuente Cuesta, Holger Bausinger, Gino Longo, Jan Gustav Grolig, Andreas Mai, and John Irvine. "Evaluation and Upscaling of Impregnated La0.20Sr0.25Ca0.45TiO3 Fuel Electrodes for Solid Oxide Electrolysis Cells Under H2O, CO2 and Co-Electrolysis Conditions." ECS Meeting Abstracts MA2023-01, no. 54 (August 28, 2023): 141. http://dx.doi.org/10.1149/ma2023-0154141mtgabs.
Abstract:
As a result of a successful collaboration between the University of St Andrews and HEXIS AG over the past >10 years, an alternative solid oxide fuel cell (SOFC) fuel electrode material (to the state-of-the-art Ni/CGO fuel electrode) has been intensively researched and developed 1 at a button cell scale (1 cm2 active area), 2 tested under harsh operating conditions and upscaled to short stack scale (5 cells each of 100 cm2 active area), 1,3 in addition to being integrated into full combined heat and power units (60 cells each of 100 cm2 active area) with nominal 1-1.5 kW power outputs. 3,4 This highly robust fuel electrode comprises a La0.20Sr0.25Ca0.45TiO3 (LSCTA-) ‘backbone’ with cerium gadolinium oxide (CGO) and Rh impregnates, offering stability toward redox/thermoredox/thermal cycling, overload or stress testing, degradation comparable to the state-of-the-art SOFCs and exposure to sulphurised natural gas. 1 This material, therefore, addresses many of the challenges presented by the Ni/CGO fuel electrodes. Given the success of this material as a SOFC fuel electrode and the growing demand for production of ‘green’ hydrogen and synthesis gas through high-temperature electrolysis, 5 it is also desirable to assess its performance in solid oxide electrolysis cells (SOECs). In this paper, the authors present a comprehensive study of the performance of SOECs containing the aforementioned titanate-based fuel electrodes. Firstly, testing of button cell scale SOECs (1 cm2 active area) in pure CO2 and H2O/H2 mixtures, carried out at the University of St Andrews and HEXIS AG, will be outlined, including promising initial test data from VI curves and AC impedance spectroscopic analysis. Subsequently, information on durability testing of the aforementioned SOECs will be provided. This data indicates that high degradation is observed during testing in H2O/H2/N2 mixtures when employing a LSM-YSZ/LSM air electrode, most likely due to delamination caused by oxygen evolution at the triple phase boundary between LSM and YSZ particles and at the air electrode-electrolyte interface, which is significantly minimised by replacement with a LSCF-CGO air electrode. Finally, upscaling of this technology to a 5 x 5 cm footprint SOEC (16 cm2 active area) containing the aforementioned fuel electrode, a stabilised zirconia electrolyte and a LSCF-CGO air electrode will be outlined. Encouraging results from a ~600 hour test at 850 °C will be presented, including operation in 54 % H2O:46 % CO2 and pure CO2 at 1.47 V, as well as in 51 % H2O:49 % N2 at 1.29 V (without the use of a reducing gas). References 1 R. Price, M. Cassidy, J. G. Grolig, G. Longo, U. Weissen, A. Mai and J. T. S. Irvine, Advanced Energy Materials, 2021, 11, 2003951. 2 R. Price, M. Cassidy, J. G. Grolig, A. Mai and J. T. S. Irvine, J. Electrochem. Soc., 2019, 166, F343–F349. 3 M. C. Verbraeken, B. Iwanschitz, E. Stefan, M. Cassidy, U. Weissen, A. Mai and J. T. S. Irvine, Fuel Cells, 2015, 5, 682–688. 4 R. Price, H. Bausinger, G. Longo, U. Weissen, M. Cassidy, J. G. Grolig, A. Mai and J. T. S. Irvine, In Preparation, 2022. 5 J. B. Hansen, Faraday Discuss., 2015, 182, 9 – 48.
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Amin, Adil, Moritz Loewenich, Hartmut Wiggers, Fatih Özcan, and Doris Segets. "Towards a Higher Energy Density for Lithium-Ion Battery Anodes Via Hierarchically Structured Silicon/Carbon Supraparticles Using Spray Drying." ECS Meeting Abstracts MA2023-02, no. 2 (December 22, 2023): 236. http://dx.doi.org/10.1149/ma2023-022236mtgabs.
Abstract:
Silicon has a high potential to replace commercial graphite anodes in lithium-ion batteries (LiBs). It can facilitate achieving excellent energy densities because of its high theoretical specific lithiation capacity (Chan et al. 2008). However, major challenges such as rapid capacity fading and low Coulombic efficiency due to the huge volume change (∼300 %) during cycling have seriously hindered its commercialization (Wu et al. 2013). Although nanostructuring has been successful in minimizing volume expansion issues, the electrochemical performance of nano-sized silicon is still limited due to unstable solid-electrolyte interphase, low coating density and overall poor electrical properties due to the higher interparticle resistance (Liu et al. 2014). To tackle those challenges, here we introduce a new concept of post-synthesis spray drying to produce hierarchically structured micro-agglomerates from silicon/carbon (Si/C) composite nanoaggregates synthesized in the gas phase (Amin et al. 2023; Adil Amin et al.). The resulting agglomerates were characterized i) on the powder level by scanning electron microscopy (Fig. 1a) and N2 sorption, ii) on the dispersion level by rheometry and analytical centrifugation, iii) on the electrode level by atomic force microscopy for structure and iv) via electrochemical testing on half-cells for electrochemical performance (Fig. 1b). These results show that electrodes from Si/C supraparticles with the highest concentration of stabilizer exhibit better redispersion stability and excellent first cycle specific discharge capacity as well as better cycling stability as compared to the Si/C composite nanoaggregates (4 wt.% carbon content). Furthermore, compared to the reference electrodes made of nanoaggregates, the more stable supraparticles (3 wt.% stabilizer) showed the highest first Coulombic efficiency. This is due to the reduction of their surface to volume ratio which helps in forming less volume of solid electrolyte interface. To conclude, our investigation suggests how an established industrial process (gas phase synthesis of nanoparticle in a hot-wall reactor) can be combined with scalable one-step spray drying to get dense active materials for LiBs. This enables to fully utilize the new materials’ potential by the right packaging into optimum electrode structures with high performance and longevity. Furthermore, we are of the opinion that this pioneering method can be utilized as a broadly relevant design principle to enhance other (anode) materials that encounter analogous problems of volume expansion. Publication bibliography Amin, Adil; Özcan, Fatih; Loewenich, Moritz; Kilian, Stefan O.; Wiggers, Hartmut; Segets, Doris; Wassmer, Theresa; Bade, Stefan; Lyubina, Julia: Hierarchically Structured Si/C Agglomerates by Spray-Drying. Patent no. PCT / EP 2022/ 052453. Amin, Adil; Loewenich, Moritz; Kilian, Stefan O.; Wassmer, Theresa; Bade, Stefan; Lyubina, Julia et al. (2023): One-Step Non-Reactive Spray Drying Approach to Produce Silicon/Carbon Composite-Based Hierarchically Structured Supraparticles for Lithium-Ion Battery Anodes. In J. Electrochem. Soc. 170 (2), p. 20523. DOI: 10.1149/1945-7111/acb66b. Chan, Candace K.; Peng, Hailin; Liu, Gao; McIlwrath, Kevin; Zhang, Xiao Feng; Huggins, Robert A.; Cui, Yi (2008): High-performance lithium battery anodes using silicon nanowires. In Nature nanotechnology 3 (1), pp. 31–35. DOI: 10.1038/nnano.2007.411. Liu, Nian; Lu, Zhenda; Zhao, Jie; McDowell, Matthew T.; Lee, Hyun-Wook; Zhao, Wenting; Cui, Yi (2014): A pomegranate-inspired nanoscale design for large-volume-change lithium battery anodes. In Nature nanotechnology 9 (3), pp. 187–192. DOI: 10.1038/nnano.2014.6. Wu, Hui; Yu, Guihua; Pan, Lijia; Liu, Nian; McDowell, Matthew T.; Bao, Zhenan; Cui, Yi (2013): Stable Li-ion battery anodes by in-situ polymerization of conducting hydrogel to conformally coat silicon nanoparticles. In Nature communications 4, p. 1943. DOI: 10.1038/ncomms2941. Figure 1
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Hagen, Anke, Davide Tasca, Agathe De-Faria, Federico Capotondo, Riccardo Caldogno, Bhaskar Reddy Sudireddy, and Xiufu Sun. "Reversible Metal Supported Solid Oxide Cells." ECS Meeting Abstracts MA2023-01, no. 54 (August 28, 2023): 362. http://dx.doi.org/10.1149/ma2023-0154362mtgabs.
Abstract:
Solid oxide fuel cells (SOFCs) excel by high efficiencies in fuel cell as well as electrolysis modes, and by being able to operate in both modes as a reversible cell (solid oxide cell – SOC). This allows for production of electricity and heat from a green fuel, and for storage of electricity as gas or use as fuel. Lifetime and costs are major factors enabling such reversible SOCs to enter green energy systems. Metal supported SOCs (MSCs) provide cost-competitive materials within the cell. Furthermore, targeting the lower operating temperatures around 650 oC, MSCs will allow for cheaper stack and balance of plant components as well. Lowering operating temperatures leads to a reduction of thermally activated degradation processes, thereby prolonging the lifetime. The present study investigates the option to operate MSCs, fabricated at DTU Energy by tape casting, lamination, and screen-printing, in reversible mode between fuel cell (FC) and electrolysis (EC). Emphasis is on the effect of reversible operation on performance and durability of the MSC, compared to steady state operation in either mode, and to the behavior of state-of-the-art (SoA) fuel electrode supported SOC with Ni/YSZ fuel electrode. The MSCs are composed of a FeCr support, a Ni/GDC (gadolinium-doped ceria) infiltrated LSFNT (lanthanum-doped strontium iron nickel titanate) fuel electrode, a YSZ (yttria-stabilized zirconia) electrolyte, a GDC barrier layer, and an in situ sintered LSC (lanthanum-doped strontium cobaltite) air electrode. The reversible operation was carried out by switching between FC and EC modes at current densities of 0.25 and -0.25 A/cm2, respectively, at 650 oC using a gas mixture of 50/50 H2O/H2 to the fuel electrode and air to the oxygen electrode. Figure 1 shows the evolution of the cell voltages for the SoA cell and the MSC. The degradation rate of the SoA cell was larger during operation in EC as compared to FC mode. Similar observations were made previously, even though these tests were typically carried out at temperatures higher than 650 oC as in this work [1]. Furthermore, the degradation rate decreases over time, more particularly in EC mode, which is also a known phenomenon at this type of cells [2, 3]. In the final ca. 200 h, both degradation rates are in the range of 3%/1000 h, which is an interesting observation, i.e., the longer-term degradation rates are similar in both modes (EC and FC). The analysis of electrochemical impedance spectroscopy (EIS) recorded under current allowed to conclude that the main contribution to the degradation is the increase of polarization resistance, i.e., related to electrodes degradation. In the initial ca. 400 h hundred hours, the cell voltage degradation on the MSC is larger in fuel cell mode, while there is nearly no degradation in electrolysis mode. The good stability in EC mode over a few hundred hours confirms the findings of steady-state electrolysis tests with the same type of cells [4]. In the final period from ca. 600 h, both degradation rates increase but stay fairly constant with ca. 4%/1000 h in EC and ca. 16%/1000 h in FC mode, when calculated as linear increase. EIS reveals that both, the serial and the polarization resistances increase in parallel, which indicates a combination of degradation of electrode and probably corrosion and/or interface attachment. Details will be presented, including comprehensive EIS evaluation combined with micro-structural characterization. Figure 1. Cell voltage vs. operating time under current in reversible mode at 650 oC, 0.25 A/cm2 in fuel cell and -0.25 A/cm2 in electrolysis mode, 50/50 H2O/H2 fuel and air to the oxygen electrode, (a) SoA cell, (b) MSC, gaps in the cell voltage are interruptions of operation due to technical issues in the lab References [1] X. Sun, B.R. Sudireddy, X. Tong, M. Chen, K. Brodersen, A. Hauch, Optimization and Durability of Reversible Solid Oxide Cells, ECS Trans. 91 (2019) 2631. [2] A. Hagen, R. Barfod, P.V. Hendriksen, Y.-L. Liu, S. Ramousse, Degradation of anode supported SOFCs as a function of temperature and current load, J. Electrochem. Soc. 153(6) (2006) A1165. [3] A. Hauch, K. Brodersen, M. Chen, C. R. Graves, S. H. Jensen, P. S. Jørgensen, P. V. Hendriksen, M. B. Mogensen, S. Ovtar, X. Sun, A Decade of Solid Oxide Electrolysis Improvements at DTU Energy, ECS Transactions, 75(42) (2017) 3. [4] A. Hagen, R. Caldogno, F. Capotondo, X. Sun, Metal Supported Electrolysis Cells, Energies 15 (2022) 2045. Figure 1
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Lu, Dong Qi, Li Cui, Hong Xi Chen, Yao Qing Chang, Zhi Bo Peng, and Ding Yong He. "Laser-MIG Hybrid Keyhole Welded 6mm Steel/Aluminum Butt Joints." Materials Science Forum 944 (January 2019): 581–92. http://dx.doi.org/10.4028/www.scientific.net/msf.944.581.
Abstract:
At present, the connection of steel/aluminum joints has been widely used in industrial fields such as aerospace, marine and automotive.Although the joints with excellent performance can be obtained by the solid phase welding methods such as explosion welding and friction welding, the production process is complicated and the efficiency is low, and the practical application is limited.Laser welding has attracted a lot of attention from researchers because of its advantages of high energy density, small welding deformation and fast welding speed.However, in the single-beam laser welding process, there are problems such as high joint assembly precision, excessive energy density, and easy formation of depressions in the weld.The newly developed laser-MIG (Metal Inert Gas) hybrid welding not only retains the advantages of laser welding, but also fully exploits the advantages of MIG welding, improves weld formation, improves the stability of the welding process, and helps solve the single-beam laser welding problems.In this paper, the laser deep penetration welding process of 5.5 mm thick E36 steel and 6 mm thick 5083 aluminum alloy butt joint was studied by laser-MIG composite welding heat source. Compared with the single laser welding process, the influence of wire feed speed on the welded steel/aluminum joint, joint interface structure and joint mechanical properties was studied.The results show that the laser-MIG composite deep-melt welding can obtain good steel/aluminum butt joint performance. At a laser power of 3.25 kW, a wire feed speed of 1.5 m / min, a laser offset of 0.5 mm and a defocus of 0 mm, the tensile strength of the steel/aluminum butt joint is as high as 85.0 MPa.Laser-MIG hybrid welding can improve the dent defects of a single laser welded steel/aluminum butt joint. The amount of acicular Fe4Al13 phase in the intermetallic compound was significantly reduced, and the resistance of the steel/aluminum joint was increased from 8.6 kN to 12.7 kN.
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Wu, Zhenrui, Evan Hansen, and Jian Liu. "An in-Depth Study of How Zinc Metal Surface Morphology Determines Aqueous Zinc-Ion Battery Stability." ECS Meeting Abstracts MA2022-01, no. 1 (July 7, 2022): 14. http://dx.doi.org/10.1149/ma2022-01114mtgabs.
Abstract:
In order to achieve the net-zero world initiative and combat the climate crisis, a global consensus of marching towards a sustainable energy structure has been built, where developing reliable, affordable, and sustainable energy storage devices, the medium of storing intermittent surplus electricity from clean and inexhaustible renewable energy sources, such as wind power and solar energy, and transferring to the smart electric grid system, is of great significance [1]. Besides lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs), the two dominant technologies having been developed substantially in the energy storage industry, researchers started pioneering studies on multivalent-ion systems of Ca [2, 3], Mg [4], Al [5, 6], and Zn [7-9] with competitive advantages, especially the ones as non-flammable economic substitutes, to ease manufacturing burden and enrich practical solutions for widespread application scenarios [10]. Especially, zinc metal with benefits of aqueous compatibility, commensurate capacity (820 mAh/g), and crust abundance, a resurgence of rechargeable zinc-ion batteries (ZIBs) is happening. This battery system with water-based electrolyte chemistries is born with eye-catching benefits of safety and affordability; Zn/MnO2 with an improved energy density of 409 Wh/kg at 1.9 V is considered a promising candidate for grid-scale energy storage [11]. This revolutionary cheap and safe solution empowers the global energy structural transformation and enriches the public’s awareness of sustainable development. However, like most reactive metals, zinc exposed in the air naturally evolves a dense passivation layer of Zn5(CO3)2(OH)6 to discontinue the corrosion by oxygen and humidity, which, in batteries, can passivate the molecular dynamics at the interface between zinc and the electrolyte and demonstrate enormous electron transfer resistance due to the inferior conductivity [12]. Thus, wearing off this passivation layer is considered a facile approach to revitalize the frozen kinetics of zinc ions [13]. Exposing fresh zinc to the electrolyte is also conductive of forming a functional solid-electrolyte interphase (SEI). Studies present that ZnF2-rich SEI plays a pivotal role in elongating the cycling life of zinc symmetric cells by effectively screening zinc from electrolyte solvents and reducing their sequence of side reactions [14]. Additionally, a tactful change of zinc’s surface roughness before electrochemical operations should impact electron distribution, zinc nucleation and growth, and SEI formation. Especially, dendrites are often considered guilty of internal short-circuiting of batteries; similar to lithium, the far-end of zinc dendrites can become dead zinc, whose accumulation brings in issues of electrolyte depletion, anodic capacity loss, internal resistance growth, and cell polarization [15]. In this work, a simple method was developed to change the surface of Zn anode to create more nucleation sites with lowered energy barriers (nucleation over-potentials), thus alleviating their dendrite growth. The cycling programs for zinc symmetric cells are standardized by fixing either the depth of cycling (DOC) or the areal current density in accordance with the constant energy or constant power supply in full batteries. In order to enunciate the battery degradation mechanism and shed light on the gas emission problems, we operate a careful electrochemical analysis cooperated with the differential electrochemical mass spectrometry (DEMS) technique. The preliminary data demonstrate an evident impact of initial zinc surface morphology on sequential zinc plating/stripping profiles and eventual lifespans at serial DOCs and current densities.
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Zhang, Lijuan, Chunlei Wang, Renzhong Tai, Jun Hu, and Haiping Fang. "The Morphology and Stability of Nanoscopic Gas States at Water/Solid Interfaces." ChemPhysChem 13, no. 8 (February 28, 2012): 2188–95. http://dx.doi.org/10.1002/cphc.201100742.
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Cox, Dalton, and Scott A. Barnett. "Microstructural Changes in Ni-YSZ Electrodes Operated in Fuel Cell and Electrolysis Modes: Effect of Gas Diffusion Limitations." ECS Meeting Abstracts MA2023-01, no. 54 (August 28, 2023): 295. http://dx.doi.org/10.1149/ma2023-0154295mtgabs.
Abstract:
Lifetime performance stability is a key issue for the commercialization of solid oxide cells. Ni migration in Ni-YSZ electrode supported cells is an important degradation mechanism. Here we present the results of life tests on symmetric Ni-YSZ electrode-supported cells. These symmetric cells have similar processing and microstructure as conventional Ni-YSZ-supported cells, but the symmetric structure provides information on the Ni-YSZ electrode operating as both an anode and a cathode in the same test. Life tests of up to 1000 h were carried out at 800 ˚C in 50-50 H2-H2O at current densities of 0, 0.75, 1.00, and 1.50 A/cm2. Total applied voltage to each cell was tracked over the lifetime, and small portions of the cells were removed during the life tests to study the time-dependent changes in microstructure. Figure 1 summarizes the microstructural results from a Ni-YSZ cell operated at 1.0 A/cm2, observed at 100, 500, and 1000 h. 2D and 3D microstructure characterization was used to show the volume fractions of pore and active (electrically connected) Ni versus position. Somewhat surprisingly, the cathode microstructure remains relatively unchanged compared to a non-polarized cell, with no evidence of Ni migration or isolation. In contrast, Ni migration and isolation was observed to increase with time at the anode in polarized cells, with the thickness of the Ni deactivated region growing from ~5 mm at 500 h to ~15 mm at 1000 h for 1.0 A/cm2 and ~2 μm at 500 h and ~8 μm at 1000 h for 0.75 A/cm2. In addition, total cleavage at the anode-electrolyte interface occurs at 1.5 A/cm2 by 100 h, and at 1.0 A/cm2 by 1000 hr. The increase of porosity in the altered zones clearly shows where Ni is depleted. There is no evidence of Ni enrichment adjacent to the depleted region, as might be expected if Ni was moving via surface diffusion. Although there have been numerous recent reports of Ni migration/isolation in Ni-YSZ cathodes during electrolysis cell operation1, Ni migration has also been reported in Ni-YSZ fuel cell anodes2,3. Here we suggest that such results can be explained by a relatively high steam content in the Ni-YSZ anode functional layer. Conversely, the lack of Ni migration in the electrolysis cathode can be explained by a relatively low steam content in the cathode functional layer. To quantitatively assess the gas compositions, one-dimensional modeling of the electrochemical and gas diffusion processes of these cells was performed using a finite difference method (FDM) with modified Butler-Volmer kinetics and the dusty-gas model respectively. Using diffusivity values calculated via electrochemical impedance spectroscopy and microstructural measurements, the modeling reveals that electrochemically active Ni sees significantly different gas composition than the inlet, creating steam-rich anodes (PH2O = 0.73, 0.8, and 0.95 atm for 0.75, 1.0 and 1.5 A/cm2 respectively) and steam-depleted cathodes (PH2O = 0.27, 0.2, and 0.05 atm for 0.75, 1.0 and 1.5 A/cm2 respectively). This is in accord with results and models suggesting that Ni migration is important mainly under high steam conditions, probably due to vapor transport. Note that these effects are exacerbated by the relatively low porosity and small pore size in the present electrodes that lead to asymmetric Knudsen diffusion, wherein H2O diffuses at ~1/3 the rate of H2. These results suggest that the nature of the porosity in Ni-YSZ supports can lead to significant variations in the extent and directionality of Ni migration. Figure 1: (a, b, c) Polished cross sectional backscatter electron (BSE) images and (d,e,f) low voltage secondary electron (LV-SE) images of an electrode-supported symmetric Ni-YSZ cell at 100, 500, and 1000 h of galvanostatic operation at 1.00 A/cm2 in 50-50 H2-H2O and T = 800 ˚C. BSE images reveal a depletion of total Ni at the anode-electrolyte interface (AEI) by a net increase in porosity, and eventual cleavage at that line. LV-SE images reveal that near total deactivation of Ni occurs near the AEI as well. (g,h,i) Quantitative image analysis reveals the extent of porosity increase (via Ni depletion) and Ni deactivation at 100, 500, and 1000 hours. The regimes for both events exactly overlap, with the depletion/deactivation extending 0, 5, and 15 μm from the AEI, respectively. M. B. Mogensen et al., Fuel Cells, 21, 415–429 (2021). J. Geng et al., J. Power Sources, 495, 229792 (2021). Z. Jiao and N. Shikazono, J. Power Sources, 396, 119–123 (2018). Figure 1
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Luong, Samantha, Anand Chandra Singh, Xia Tong, Dayna Wiebe, and Viola Ingrid Birss. "N-Doped Colloid Imprinted Carbons As Promising ORR Catalysts for Alkaline Applications." ECS Meeting Abstracts MA2022-01, no. 7 (July 7, 2022): 632. http://dx.doi.org/10.1149/ma2022-017632mtgabs.
Abstract:
The oxygen reduction reaction (ORR) has long been of interest in relation to its many energy applications and interesting multi-pathway mechanisms. The ORR is a key reaction in a range of electrochemical energy conversion and storage devices, such as hydrogen fuel cells and metal-air batteries, respectively. These devices are expected to play an ever-increasing role in the global transition to net zero emissions. Metal-air batteries, such as Zn/air batteries, can operate at room temperature, use recyclable materials, are environmentally friendly, and are preferred in relation to consumer safety than batteries relying on organic solvents and reactive electrode species.1 High rates of the ORR are crucial for the development of high performance Zn/air batteries and catalysts play a significant role, with lowering of the catalyst cost also of increasing importance. The costs of conventional Pt-based ORR catalysts are high. Therefore, metal-free carbon-based ORR electrocatalysts are viewed as increasingly promising alternatives, especially as they are lower in cost due to the availability of the precursor materials. Carbon is also a good electrical conductor and support material, is chemically stable, and can have large surface areas. However, the ORR kinetics are sluggish on carbon and chemical and physical modifications are required to enhance its activity. In typical Zn/air batteries, the ORR occurs at the three-phase boundary (TPB) formed between the solid electrode, liquid electrolyte, and gaseous oxygen. The porosity of the catalyst layer, the wettability of the catalyst/electrolyte interface, and the gas permeability and hydrophobicity of the gas diffusion layer (GDL) are thus also important, significantly influencing the cathode performance and durability. The catalyst layer (CL) must therefore be constructed with both a high-performance catalyst and an optimized TPB length to provide high performance without compromising durability. In the current work, we have doped nitrogen into the lattice of a family of nanoporous colloid imprinted carbon (CIC) powders to increase its ORR activity. The CICs are unique for their versatility in terms of pore size control and ease of surface functionalization.2 Pore sizes in the range of 12 to 100 nm were examined and their effect on the ORR activity and mass transport limitations were investigated. To carry out N-doping, the CICs were exposed to ammonia at 800 ˚C for 7 hr. Catalyst inks were then prepared by mixing the CICs with a binder in an isopropyl alcohol/water solution. Aliquots of the ink were drop-casted on the disc of an RRDE system, or were spray coated or drop-casted on a GDL to determine the ORR performance in an in-house Zn/air battery testing cell, with the N-doped CIC catalyst layer sandwiched between an electrolyte chamber and a graphite current collector. In this setup, O2 gas was flowed through the pores in the GDL to the catalyst/electrolyte interface, a Zn wire installed in the electrolyte chamber was used as the reference electrode, and a Ni sponge was used as the counter electrode. The RRDE experiments showed that, after N doping of the CIC powders, the production of peroxide decreased significantly and the ORR onset potential increased to a very respectable value of ca. 0.9 V vs RHE, indicating the successful activation of the ORR. Electron transfer numbers were found to be greater than 3.5, indicating that either a direct or pseudo- 4 electron transfer ORR pathway is dominant. In agreement with the literature, the ORR currents in the kinetic regions increased linearly with mass loading, expected to be proportional to the total active N-doped CIC surface area.3 The N-doped CIC samples retained excellent performance up to a loading of 0.350 μg/cm2 without losing mechanical stability. Similar N-doped CICs and binders of different hydrophobicity were tested in the Zn/air battery testing system. Electrodes made with a hydrophobic NCS microporous layer (MPL) showed much better ORR performance and durability than hydrophilic NCS MPLs. Although electrodes made using hydrophobic polytetrafluoroethylene (PTFE) as the binder in the catalyst layer showed a similar initial performance to those made using hydrophilic Nafion binders, the PTFE based electrodes exhibited better durability. Furthermore, the temperature and pressure used during electrode fabrication were also found to have a significant impact on the binder distribution and ORR performance. Once optimized, a very good correlation was obtained between the N-doped CIC catalyst performance in the RRDE setup and in the Zn/air battery testing system. References J. Pan et al., Adv. Sci., 5, 1700691 (2018). X. Li et al., ACS Appl. Mater. Interfaces, 10, 2130–2142 (2018). N. Gavrilov et al., J. Power Sources, 220, 306–316 (2012).