bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gas-Transport Resistances in Fuel-Cell Catalyst Layers
Authors: Schuler Tobias , Tucker Michael C , Weber Adam Z 
Published: February 2020

The commercialization of PEFCs depends significantly on reduction of the costly precious metal content in fuel-cell electrodes. To achieve this goal, a high-performance low-loaded electrode must be utilized; and there is a need to understand the key transport resistances and processes within such a structure. The catalyst layer represents the most complex system in a PEFC due to the existence of multiple phases and a heterogeneous structure. Within catalyst layers, gas transport dominates the performance at high current densities, resulting in mass-transport limitations. To quantify these resistances, limiting-current measurements can be used. In this talk, we report on such mass-transport resistances utilizing a hydrogen-pump limiting current under various operating conditions including gas pressure and gas chemical identity for various low-loaded catalyst structures. In this fashion, one can separate the various resistances into molecular versus Knudsen diffusion and bulk versus non-bulk resistances.
The in-situ method based on H2limiting current measurements was used for the characterization of catalyst-layer resistances in porous Pt/C based electrodes. The parameters studied were the ionomer to carbon ratio, the platinum loading, and the influence of different carbon supports. The effect of platinum loading on hydrogen transport resistance shows that the catalyst-layer resistance is inversely proportional to the roughness factor of the electrode as shown in the figure. The dominant transport mechanism is estimated to be Knudsen diffusion for vulcan-based catalyst layers. An increase of molecular diffusion can be observed by diluting Vulcan black by Ketjen black. Overall, the technique allows for quantification of the local transport resistances within the catalyst layer using a simplified experiment, thereby suggesting that the ionomer film is key in controlling the resistance. Furthermore, the observed trends can be used to guide optimization of novel low-loaded fuel-cell electrodes.

Acknowledgements

This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Fuel Cell Technologies Program of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 and by CRADA agreement LB08003874 between Lawrence Berkeley National Laboratory and Toyota Motor Company.
Figure 1. Total cell resistance as a function of inverse roughness factor at 40°C, 0.5psi. The catalyst layer resistance is inversely proportional to the roughness factor of the electrode, as represented by the linear regression function.

Figure 1
Electrochemical Impedance Spectroscopy Study of Alkali-Metal Insertion Processes on Hard Carbon Electrodes
Authors: Väli Ronald , Jänes Alar , Kanarbik Rait , Lust Enn 
Published: February 2020

Sodium-ion batteries have attracted great deal of attention due to sodium’s abundance and lower price compared to lithium and cobalt. A major obstacle that prevents sodium-ion batteries from going into mass-scale production is the negative electrode (anode during discharge). Graphite is currently the safest negative electrode material for lithium-ion batteries, but does not intercalate sodium reversibly, because sodium ions prefer prismatic or octahedral coordination sites [1].
Our previous work [2] focused on the synthesis and electrochemical characterization of glucose-derived hard carbon negative electrodes for sodium-ion batteries. The results inspired us to conduct a more detailed impedance study of the electrode processes.
Hard carbons have shown to absorb/insert and desorb/de-insert sodium reversibly [2,3]. However, the exact mechanism is difficult to understand without detailed studies which apply different physical and electrochemical methods. Therefore, electrochemical impedance analysis with equivalent circuit fitting (Figure 1a, b) was conducted to analyse surface processes at various potentials. ICP-MS, SEM-EDS (Figure 1c) and TOF-SIMS confirmed alkali-metal absorption in the carbon structure.

Acknowledgements

This research was supported by the EU through the European Regional Development Fund TK141 “Advanced materials and high-technology devices for energy recuperation systems”, Estonian target research project IUT20–13 and personal research grant PUT55. The authors thank Dr. Kalle Kirsimäe for ICP-MS analysis.

References

1. J. Qian, X. Wu, Y. Cao, X. Ai, and H. Yang, Angew. Chem. Int. Ed., 52, 4633 (2013).
2. R. Väli, A. Jänes, T. Thomberg, and E. Lust, J. Electrochem. Soc.(2016), under review.
3. S. Prabakar, J. Jeong, and M. Pyo, Electrochim. Acta, 161, 23 (2015).

Figure 1
Path Dependence in Lithium-Ion Batteries Degradation - a Comparison of Cycle and Calendar Aging
Authors: Dubarry Matthieu , Devie Arnaud 
Published: February 2020

The Hawai‘i Natural Energy Institute (HNEI) is leading research efforts to understand the degradation of lithium-ion batteries under two distinct projects. The first research project is focused on grid-scale battery energy storage systems (BESS) while the second project is targeting electric vehicles (EVs) and their synergy with the grid.
Both applications require a combination of long cycle-life (1000 cycles or more) and long shelf-life (10 to 20 years in operation) to meet the expectations of the customers. To determine whether these durability goals are realistic or not, we performed accelerated testing of different lithium-ion battery technologies in the laboratory. For each technology, we conducted a series of cycle and calendar aging experiments. The results of these studies will be used to develop predictive performance models.
The concept of accelerated aging is only valid if the degradation the cell underwent is the same than of the one it experienced in real life. In this presentation, we want to share our preliminary observations regarding the differences between cycle aging and calendar aging across the different chemistries and across the industries (EVs, BESS). Our primary objective is to showcase the different degradation pathways, whether calendar-driven or cycle-driven, which can lead to identical capacity losses. This concept is better known as path dependence and this talk will highlight its implications for the design of long-life battery systems, the laboratory testing it requires and the validity of accelerated testing strategies.
[1] M. Dubarry, N. Vuillaume and B. Y. Liaw, J. Power Sources 186(2), (2009) 500-507.
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[3] https://www.soest.hawaii.edu/HNEI/alawa/
[4] M. Dubarry, C. Truchot, A. Devie and B. Y. Liaw, J. Electrochem. Soc 162(6), (2015) A877-A884.
Modeling Volume Change and Battery Performance Due to Intercalation in Porous Electrodes
Authors: Garrick Taylor Reed , Dai Yiling , Higa Kenneth , Huang Xinyu , Srinivasan Venkat , Weidner John W. 
Published: February 2020

In order to accurately predict the behavior or electrochemical devices, it is necessary to develop sophisticated models that take into consideration transport processes, electrochemical phenomena, mechanical stresses, and structural deformations on the operation of an electrochemical system. Many different models exist that can predict the electrochemical performance of these devices under a variety of operating and design conditions.[1-7] However, many of these models assume constant porosity and do not take into consideration the effects of a variable porosity on the porous electrode during cycling and what effects that may have on performance. In recent years, electrodes have been developed that show a significant volume change during intercalation and deintercalation, which are unable to be accurately predicted using these constant porosity models.
Porosity and dimensional changes in an electrode can significantly affect the resistance of the battery during cycling and cause premature failure of the battery due to generated stresses. Previously, we have shown the ability to incorporate dimensional and porosity changes in a porous electrode into a model to predict volume changes in the active material during intercalation through the coupling of porous rock mechanics and porous electrode theory.[6] However, that model incorporated many assumptions in order to obtain an analytical solution, including the assumption of bulk stress, strain, and porosity. Here, we present a model that removes those assumptions and illustrates the coupling of porous electrode theory and rock mechanics in order to predict stress, strain, and porosity gradients across a porous electrode during cycling.
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3. P. M. Gomadam and J. W. Weidner, J Electrochem Soc, 153, A179 (2006).
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5. J. Christensen and J. Newman, J Solid State Electr, 10, 293 (2006).
6. T. R. Garrick, K. Kanneganti, X. Y. Huang and J. W. Weidner, J Electrochem Soc, 161, E3297 (2014).
7. K. Higa and V. Srinivasan, J Electrochem Soc, 162, A1111 (2015).
Disulfonated Copolymer Membranes with Improved Selectivity and Lifetime for Vanadium Redox Flow Batteries
Authors: Kara Kenan , Sankir Mehmet , Demirci Sankir Nurdan , Agar Ertan 
Published: February 2020

One of the critical needs to increase the widespread implementation of vanadium redox flow batteries (VRFBs) is identifying reliable and cost-effective membranes with improved lifetime. Among ion exchange membranes, Nafion® has been the most thoroughly studied and widely used material in VRFB applications due to its good proton conductivity, chemical stability and durability. However, the low vanadium selectivity of Nafion®, which leads to significant crossover and related capacity fade with cycling, hinders the use of this type of membrane for commercial VRFB applications [1].
In order to solve this problem, several post-sulfonated hydrocarbon polymers such as poly(sulfone) [2] and poly(benzimidazole) [3] have been studied to explore their effectiveness for use in VRFBs. Although these post-sulfonated membranes have been shown to provide improved proton conductivity and vanadium selectivity, one major limitation of the post-sulfonation method is that the amount of sulfonation and related ion exchange capacity (IEC) cannot be controlled precisely [4]. Especially, the sulfonation of polysulfone with strong acids (e.g. sulfuric and chlorosulfuric) often leads to undesirable side reactions (e.g. cross-linking) and chain cleavage, making the control of sulfonation even more difficult, thereby degrading the mechanical integrity of the final membrane [4]. One potential approach to precisely control the degree of sulfonation of an ion exchange membrane is using direct sulfonation by copolymerization [5]. With this technique, the sulfonic acid groups can be positioned on the more stable and more acidic deactivated sulfone unit, which results in more precise control of ionic group concentration in the final product.
In this talk, we will discuss the performance evaluation of disulfonated copolymer membranes for use in a VRFB application. Basic membrane properties and the results of charge/discharge cycling analysis with respect to various degrees of sulfonation and fluorination will be reported and then compared with Nafion® 212. The study will be presented with emphasis on tailoring the membrane properties of directly disulfonated copolymers and establishing the structure-property-performance relation for these membranes.

References:

[1] E. Agar, K.W. Knehr, D. Chen, M.A. Hickner, E.C. Kumbur, Electrochim. Acta,98, 66-74 (2013).
[2] D. Chen, S. Kim, L. Liyu, G. Yang, M.A. Hickner, RSC Adv., 2, 8087-8094 (2012).
[3] T. Luo, O. David, Y. Gendel, M. Wessling, J. Power Sources, 312, 45-54 (2016).
[4] F. Wang, M.A. Hickner, Y.S. Kim, T.A. Zawodzinski, J.E. McGrath, J. Membr. Sci., 197, 231-242 (2002).
[5] L. Semiz, N.D. Sankir, M. Sankir, J. Membr. Sci., 468, 209-215 (2014).
Characterization of Fluid Flow Dispersion in Electrodes By Means of Computed Tomography and Lattice-Boltzmann Simulations
Authors: Maggiolo Dario , Trovo' Andrea , Picano Francesco , Carmignato Simone , Guarnieri Massimo 
Published: February 2020

Lattice-Boltzmann simulations of fluid flow in fully reconstructed porous materials are performed in order to characterized the macroscopic behavior of fluid flow and dispersion in porous media for flow batteries applications [1]. The material quantitative reconstruction has been performed by means of X-ray microtomography and the obtained data have been used as input geometry in the Lattice-Boltzmann algorithm. The Lattice-Boltzmann model is coupled with a Lagrangian Particle Tracking algorithm in order to better understand the complex dispersion behavior of species induced by the medium microstructure that conforms a superdiffusive behavior [2].
Different materials have been investigated, including typical carbon felt used as electrodes in redox flow batteries and innovative carbonized rigid materials. The anisotropic behavior due to the fiber orientation has been taken into account and its effects have been investigated (Fig. 1).
For each material and microstructure, the flow behavior and particle trajectories have been computed extracting the flow resistance and dispersion features (Fig 2). These analyses have allowed identifying the optimal material and its arrangement, which involve minimal drag and maximized mixing. These conditions ensure an increase of the performance of the redox flow cell, in terms of reduced diffusion losses in the electrochemical reaction as well as reduced pressure drop and pumping needs of the electrolyte solutions and of the overall efficiency of flow batteries.

References

[1] Wang B., Kuo J., Bae S.C. and Granick S., Nature Materials, 2012, 11(6): 481-5.
[2] Maggiolo D., Picano F., Marion A., Guarneri M., “Application of the Lattice-Boltzmann Method for Modeling All-Vanadium Redox Flow Batteries”, Proc.
IV International Conference on Particle-based Methods – Fundamentals and Applications - Particle 2015, pp. 579-589, Barcelona, Spain, Sept. 28-30, 2015.

Figure 1
New Redox Polymer Hybrids: Bridging the Gap Between Li-Ion Batteries and Supercapacitors
Authors: Gohy Jean Francois 
Published: February 2020

A rational management of the energy resources and consumption is at the center of the preoccupations of a world in constant development. In this context, a sustainable development and exploitation of the energetic resources is asked, necessitating practical and quick solutions to direct the economy towards an energetic autonomy. This presentation is centered on the development of novel energy storage systems with enhanced performances through original organic electroactive material chemistry and engineering approaches. Deciphering the fundamental flaws and building better organic batteries is the primary target, the long-term goal of this research being the development of sustainable all-carbon-based batteries. Based on this, we focus on three complementary yet, distinct directions with specific goals: improve and develop new organic radical materials for pseudo-capacitive energy storage by engineering high energy density nitroxide radical containing block copolymer architectures [1,2]; design and synthesize hybrid macromolecular architectures displaying both, electroactive and electron conductive properties [3-5]; and develop hybrid organic-inorganic electrochemical energy storage materials and technologies that combine best-of-both worlds characteristics [6]. Accordingly, this research aims the design and development of novel electroactive organic materials and architectures and, by doing so, develop faster, safer & longer-lasting organic batteries, capacitors and their hybrids.
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Tandem Cell-Based Vanadium Redox Flow Battery Stack
Authors: Jin Chang-Soo , Park Se-Kook 
Published: February 2020

Today about two-thirds of the world’s total electric power is generated from fossil fuels and nuclear based energy. Globally accelerating concerns regarding environmental pollution from the burning fossil fuels in combination with increasing energy shortages have provoked great interest in the generation of electrical energy from renewable sources such as wind and solar [1-3]. However, the random and intermittent nature of these power sources induces low-quality output in electricity, which affects the stability of the grid. Given that energy storage system (ESSs) can be efficiently balanced between power generation and the consumption of renewable energy sources through load-leveling and peak-shaving strategies, they have emerged as a key technological challenge [4-5].
Among various types of ESSs, the all-vanadium redox flow battery (VRFBs) is a promising technology for large scale electrical energy storage systems. These batteries utilize the reduction and oxidation reaction of two active species in the electrolytes for charge and discharge processes. VRFBs can independently be the scalable application which shows power and energy capacity component of the system [6,7].
In this study, we report in detail our investigation of Tandem electrode structure for VRFB system and its effect on long-term stability and electrochemical performance.
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(Invited) Effect of Heat Treatment Conditions on Crystallization of Anodic Alumina Membrane Formed in Phosphoric Acid
Authors: Asoh Hidetaka , Shigehara Yoshihito , Hashimoto Hideki , Ono Sachiko 
Published: February 2020

Porous-type anodic aluminum oxide films have attracted considerable attention as a key material in the fabrication of several types of devices owing to their potential technological applications. However, conventional anodic alumina films have low chemical resistance because the anodic oxide films obtained by typical anodizing processes are amorphous. Expanding the application of alumina films necessitates enhancement of the chemical resistance of alumina.
Previously, we identified the optimized anodizing conditions and the detachment method for suppressing thermal deformation, such as curving and cracking, during heat treatment of the alumina membrane (1-4). In our previous study, anodizing was conducted under an applied voltage of 25 V–185 V, which resulted in the formation of an anodic porous alumina film with pore diameters tunable over a wide range of approximately 30-350 nm. When oxalic acid was used as an electrolyte, the fabrication of a crack-free and flat α-alumina membrane with a diameter of 25 mm, a thickness of 50 μm and a pore diameter of approximately 60 nm was fabricated using the optimized anodizing conditions in oxalic acid at 40 V, followed by subsequent detachment from the substrate and heat treatment (2). In the case of phosphoric acid, the fabrication of α-alumina membrane with a pore diameter of 350 nm was achieved through optimization of various conditions (3).
In the present study, the chemical composition and morphological changes of the alumina membrane formed in phosphoric acid during heat treatment were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermogravimetry-differential thermal analysis (TG-DTA). The results of analyses clearly showed that the alumina membrane formed in phosphoric acid has unique characteristics such as coexistence of crystalline alumina and aluminum phosphate at high temperature region above around 1100 oC. Therefore, we focused on the effect of heat treatment conditions (e.g., temperature, heating rate and holding time) on the morphological changes of alumina cell wall in comparison with alumina films formed in sulfuric acid and oxalic acid. By controlling of heating conditions, alumina membrane with hierarchically porous structures consisted of main macropores and smaller textural mesopores in the cell walls could be fabricated. Through-hole structure of heated alumina membrane was maintained even at high temperature, and additional mesopores were formed by the selective removal of aluminum phosphate from alumina cell wall.
[1] F. Rashidi, T. Masuda, H. Asoh, S. Ono, Surface and Interface Analysis, 45, 1490-1496 (2013)
[2] T. Masuda, H. Asoh, S. Haraguchi, S. Ono, Electrochemistry, 82, 448-455 (2014)
[3] T. Masuda, H. Asoh, S. Haraguchi, S. Ono, Materials, 8, 1350-1368 (2015)
[4] H. Asoh, T. Masuda, S. Ono, ECS Transactions, 69, 225-233 (2015)
Contribution of Hydrogen to the Intergranular Corrosion Damage in a 2024 T351 Aluminum Alloy
Authors: de Bonfils-Lahovary Marie-Laetitia , Lafouresse Manon , Laffont Lydia , Blanc Christine 
Published: February 2020

In aeronautic industry, lifetime prediction of structural elements is a capital issue, in particular for the parts exposed to atmospheric corrosion processes. Tests exist to detect corrosion defects but only a few predictive tests allowing the corrosion defects propagation kinetics to be determined are developed and they need to be optimized. In this framework, tensile tests on pre-corroded samples are assumed to be useful. First results were obtained for AA 2024 samples pre-corroded by continuous immersion in a 1M NaCl solution for times ranging from 6h to 1200h. Results from tensile tests evidenced a decrease of the mechanical properties with the exposure time. Propagation depths of the corrosion defects were then derived from the results of mechanical tests. However, depending on the exposure conditions, a volume damage related to the corrosion-induced hydrogen absorption seemed to contribute to the loss of mechanical properties of the pre-corroded samples. To better understand, hydrogen content of pre-corroded samples was measured using an Instrumental Gas Analysis on a Horiba EMGA-621 W analyzer. Moreover, AA-2024 samples were hydrogenated by cathodic polarization in H2SO4solution to model the corrosion defect tip. Samples were then corroded by continuous immersion in 1 M NaCl solution. First, observations using optical microscope and scanning electron microscope allowed the morphology of the corrosion defects to be studied for the hydrogenated samples. Then, electrochemical characterizations of the hydrogenated samples were performed in order to determine the influence of hydrogen on the corrosion defect propagation kinetics.
This work is supported by ANR-14-CE07-0027-01 – M-SCOT: Multi Scale COrrosion Testing.