bluuebunny/crossref_metadata_2025_split huggingface dataset:
Strategies to Facilitate the Electron Transfer in Li-O2 Battery Charging Process
Authors: Shen Yue 
Published: February 2020

Lithium-oxygen battery has the highest theoretic energy density among all rechargeable batteries. But its discharge product Li2O2 is difficult to be oxidized back in the charge process because it is difficult to transfer electron from Li2O2 to the cathode material (mostly carbon). Here, we introduce 3 strategies to facilitate the electron transfer during charging process: 1. To use redox mediators as redox shuttles between carbon and Li2O2; 2. To use electrolyte which can dissolve Li2O2 (or other peroxide species) so that the dissolved Li2O2 can be oxidized at the carbon surface; 3. To use some highly elastic polymer network to push the Li2O2 to the carbon surface, so that the carbon-Li2O2 contact can be improved. The third strategy was firstly developed in our group and is very suitable to make high loading thick air cathodes with areal capacity > 12 mAh cm-2. These methods were all found to be effective, but not perfect. Especially when the Li metal anode problems are considered. The pros and cons of these strategies will be exhibited, compared and explained. It is also possible to combine these strategies with other advanced cathode architectures and catalysts to further improve the performance. Our study is helpful to design high energy density Li-O2 prototype cells with REAL reversibility.
References:

Sun, D.;Shen, Y.; Zhang, W.; Yu, L.; Yi, Z.; Yin, W.; Wang, D.; Huang, Y.; Wang, J.; Wang, D.; Goodenough, J. B. J. Am. Chem. Soc.
2014, 136, 8941.

Zhang, W.;Shen, Y.; Sun, D.; Huang, Z.; Zhou, J.; Yan, H.; Huang, Y. Nano Energy
2016, 30, 43.

Zhang, W;Shen, Y. ; Sun, D.;Huang, Z.; Huang, Y. Adv. Energy Mater.
2017,1602938

Shen, Y.; Zhang, W.; Chou, S.-L.; Dou, S.-X. Science
2016, 352, 667.
High Volumetric Energy Density Li-Air Battery; Cell Scale Design, Modeling and Simulation
Authors: Lee Heung Chan 
Published: February 2020

Ever been higher demands for energy storage systems that can exceed the energy density of current Li-ion battery encourage researchers to investigate new battery chemistries that are beyond the limitation of the current intercalation mechanism based battery chemistry.1–3 Among many candidates for the beyond-intercalation batteries, Li-air battery, also known as Li-O2 battery, got enormous research attention owing to their ultra-high theoretical gravimetric energy density of 3,458 Wh/kg.
Althogh high volumetric energy density is desired for transportation applications due to the space limitation in a vehicle, its volumetric energy density (Wh/L) with actual cell scale evaluation has been rarely discussed.4 It may be due to the theoretical maximum value, 2,040 Wh/L of Li-O2 battery with lithium anode, is not much superior than Li-ion battery with LiCoO2 cathode with carbon anode, 1,940 Wh/L.5

Here, we demonstrate the Li-O2 battery cells perfuming 700 Wh/kg and 610 Wh/L of complete cell level gravimetric and volumetric energy density, respectively, by seamless integration of all the best performing components. To understand transport phenomena inside of the cell and predict maximum performances, specifically designed modeling and simulation was conducted by combining physics of oxygen gas flow into the GDL, dissolution of O2 into the electrolyte, electrochemistry across the whole cell components, and dynamically changing carbon surfaces and porosity by Li2O2 formation.
References
1. Freunberger, S. A. True performance metrics in beyond-intercalation batteries. Nat. Energy
2, 17091 (2017).
2. Lu, J. et al. Aprotic and Aqueous Li–O2 Batteries. Chem. Rev.
114, 5611–5640 (2014).
3. Grande, L. et al. The Lithium/Air Battery: Still an Emerging System or a Practical Reality? Adv. Mater.
27, 784–800 (2015)
4. Gallagher, K. G. et al. Quantifying the promise of lithium-air batteries for electric vehicles. Energy Environ. Sci.
7, 1555–1563 (2014).
5. Lu, Y.-C. et al. Lithium-oxygen batteries: bridging mechanistic understanding and battery performance. Energy Environ. Sci.
6, 750–768 (2013).
Cryogenic Focused Ion Beam Characterization of Alkali Metal Anodes
Authors: Lee Jungwoo Z. , Wynn Thomas Andrew , Alvarado Judith , Hirsh Hayley S , Meng Ying Shirley 
Published: February 2020

There is significant effort to enable lithium metal anodes for rechargeable batteries due to its low electrode potential (-3.04 V vs. standard hydrogen electrode) and high theoretical specific capacity (3860 mAhg-1). However, despite nearly a half-century of research efforts, several challenges still exist that prevent widespread adoption, such as the high reactivity with the electrolyte preventing the formation of a stable solid electrolyte interphase (SEI) and lithium metal dendrite formation. While various techniques have been used to characterize lithium-ion batteries, there are limitations to characterizing lithium metal because of its intrinsic high chemical reactivity, low thermal stability, and low atomic number making it prone to contamination and melting, while exhibiting weak scattering characteristics for electrons and x-rays [1].
Recently, cryogenic transition electron microscopy (cryo-TEM) techniques have proven to be powerful for observing the fundamental structure and SEI composition of nanoscale electrochemically deposited lithium metal [2-3]. However, this technique alone is limited to very thin specimens, so cannot be applied to traditional bulk battery materials. Therefore, we explore the ability of cryogenic focused ion beam (cryo-FIB) to mill bulk lithium metal structures while minimizing local heating damage and gallium ion reactions. Using cryo-FIB, we observe notably different features from those of room temperature FIB milled cross-sections of electrochemically deposited lithium metal and solid-state thin-film lithium metal batteries. With this technique we demonstrate the ability to investigate cross-sections of plated lithium metal to observe nucleation, morphology, and density. Further, we demonstrate the ability to cryo-FIB prepare TEM lamellae of solid-state thin-film lithium metal batteries for more comprehensive chemical and structural analyses.
[1] D. Lin et al. “Reviving the lithium metal anode for high-energy batteries,” Nature Nanotechnology. 13 (2017) 194-206.
[2] X. Wang et al. “New insights on the structure of electrochemically deposited lithium metal and its solid electrolyte interphases via cryogenic TEM,” Nano Letters. 10.1021/acs.nanolett.7b03606.
[3] Y. Li et al. “Atomic structure of sensitive battery materials and interfaces revealed by cryo–electron microscopy,” Science. 358 (2017) 506-510.
Controllable Synthesis of Low-Platinum Oxygen Reduction Catalysts By Modified Atomic Layer Deposition Process
Authors: Higgins Drew Christopher , Xu John , Kim Yongmin , Orazov Marat , Lee Daniel , Wang Zhaoxuan , Schladt Thoams , Graf Tanja , Jaramillo Thomas F , Prinz Fritz 
Published: February 2020

The widespread deployment of polymer electrolyte membrane fuel cells (PEFCs) is still limited by cost and durability challenges that arise from the oxygen reducing cathode catalysts. Current state of the art catalysts are platinum (Pt) or Pt-alloy nanoparticles deposited on high surface area carbon supports. Lowering the Pt loading of PEFC cathodes requires the development of catalysts that combine good oxygen reduction activity and high Pt dispersion (i.e., electrochemically active surface area, ECSA) to achieve sufficient high-power performance [1]. It is therefore highly desirable to develop synthetic techniques that provide careful, atomic level control over the deposition of Pt onto catalyst supports.
In this talk, we will report on a modified atomic layer deposition (ALD) process that provides excellent control over the nucleation and growth of Pt onto different substrate materials. This technique was leveraged to prepare catalysts for the ORR, which were found to show excellent activity that significantly surpasses that of state-of-the-art Pt/C catalysts through rotating disc electrode evaluation. Furthermore, this ALD process provides the ability to deposit Pt on substrates that generally have very poor interactions with Pt precursors, enabling the preparation of uniform, highly dispersed Pt nanoparticles on these materials. Strong catalyst-support interactions resulted from this synthetic technique, with prepared catalysts showing excellent activity and ECSA retention following stability testing, with very little changes observed to the Pt nanoparticle size and morphology. This provides opportunity to use non-traditional catalyst support materials that can potentially overcome corrosion challenges associated with high surface area carbon. Catalyst formulation optimization as well as membrane electrode (MEA) integration is currently underway.
[1] Kongkanand, Mathias, Journal of Physical Chemistry Letters (2016) 7, 1127-1137.
Self-Supported Hierarchical Porous Metallic Aerogels Synthesized Via Spontaneous Methods As High Performance Electrocatalysts
Authors: Liu Wei 
Published: February 2020

Metal nanomaterials are one major class of enablers for clean technology. For example, they play vital roles as electrocatalysts in fuel cells and electrochemical sensors. Despite great efforts from world-wide, the commercialization of metal electrocatalysts based devices still meet critical challenges including high cost, insufficient activity, and low durability. Therefore, it is of great interests to explore the factors that influence the electrocatalytic activity and durability of the metallic electrocatalysts, and to develop simple strategies to generate high performance metallic electrocatalysts.
We have developed facile spontaneous methods including one-step spontaneous gelation method in combination with galvanic replacement reaction and fabricated a series of self supported metallic aerogels with extended metal backbone nanostructures of nanowire or nanotubular networks and very high surface area and large porosity.[1-5] In addition, supported metal nanostructure have been also obtained and self-assembled on electrodes.[6,7] These materials were utilized as high performance electrocatalysts in fuel cell anode and cathode reactions and in electrochemical sensors. Our results show that porous structure, metal composition and support material have great influences on the electrocatalytic activity of metal nanomaterials.

Acknowledgements

The authors acknowledge the financial supports from the 100Top Talents Program - Sun Yat-sen University (P.R. China), theEuropean Commission (Brussels) for the Marie Curie Research Fel-lowship for Transfer of Knowledge (No. MTKD-CT-2006-042637)and from the Finnish Cultural Foundation. Financial supportsfrom the Alexander von Humboldt Foundation and the EuropeanResearch Council (ERC-2013-AdG AEROCAT) a gratefully acknowl-edged.

References

W. Liu, A.-K. Herrmann, D. Geiger, L. Borchardt, F. Simon, S. Kaskel, N. Gaponik and A. Eychmüller, Angew. Chem. Int. Ed.
51, 5743 -5747 (2012).

A. Eychmüller, W. Liu, J. Yuan, N. Gaponik, A.-K. Herrmann, T. J. Schmidt, P. Rodriguez, A. Rabis, A. Foelske-Schmitz, R. Kötz, European Patent EP000002690693(A1) (2014)

W. Liu, P. Rodriguez, L. Borchardt, A. Foelske, J. Yuan, A.-K. Herrmann, D. Geiger, Z. Zheng, S. Kaskel, T. J. Schmidt, and A. Eychmüller, Angew. Chem. Int. Ed.
52, 9849 -9852 (2013).

W. Liu, A.-K. Herrmann, N. C. Bigall, P. Rodriguez, D. Wen, M. Oezaslan, T. J. Schmidt, N. Gaponik, A. Eychmüller, Acc. Chem. Res.
48, 154-162 (2015).

W. Liu, D. Haubold, B. Rutkowski, M. Oschatz, R. Hübner, M. Werheid, C. Ziegler, L. Sonntag, S. Liu, Z. Zheng, A.-K. Herrmann, D. Geiger, B. Terlan, T. Gemming, L. Borchardt, S. Kaskel, A.Czyrska-Filemonowicz, and A. Eychmüller, Chem. Mater.
28, 6477-6483 (2016).

W. Liu, E. Repo, M. Heikkilä, M. Leskelä, M. Sillanpää, Nanotechnology 21, 395604 (2010).

W. Liu, K. Hiekel, R. Hübner, H. Sun, A. Ferancova, M. Sillanpää, Sens. Actuators B: Chem. 255, 1325-1334 (2018).

Figure 1
Changes in Proton and Electron Transfer Resistance in Cathode Catalyst Layer of PEM Fuel Cell By Carbon Corrosion
Authors: Cho Seonghun , Park Gu-Gon , Lee Won-Yong , Yim Sung-Dae 
Published: February 2020

The structural robustness of the catalyst layer controlled by the morphology of the carbon support is closely related to the durability of the fuel cell. Electrochemical corrosion of the carbon support leads to the structural collapse of the cathode catalyst layer, decreasing the catalyst layer thickness. The collapse of the catalyst layer causes the increase in the oxygen diffusion resistance, which has been accepted as the major mechanism of the performance degradation of the fuel cell by carbon corrosion. However, little attention has been paid on the possibility of the damage of proton and electron pathway in the cathode catalyst layer by carbon corrosion and the resultant performance decay by the pathway damage. In this study, we introduce the fuel cell performance degradation mechanism in terms of the changes in proton and electron transfer resistance that is induced by the structural change of the cathode catalyst layer by carbon corrosion.
Two types of cathode catalyst layer were prepared by adding electrically conductive carbon nanoparticles (Vulcan carbon) and electrically nonconductive silica nanoparticles into the typical Pt/C catalyst layer, respectively, as a model catalyst layer. The cathode catalyst layer consisted of a Pt/C (TEC10E50E) catalyst and long-side chain (Nafion IEC 1.00) ionomer binder. The electrolyte membrane was NRE211 (25 μm). Membrane electrode assemblies (MEAs) were fabricated by decal transfer process and their electrochemical characteristics were measured in a single cell. The accelerated stress test of the carbon corrosion was evaluated by applying a high potential of 1.4 V, and the change of the characteristics of the MEA was confirmed through electrochemical evaluation, before and after the carbon corrosion.
The addition of nanoparticles to the cathode catalyst layer enhanced the structural stability of the catalyst layer regardless of the type of nanoparticles, which led to better durability in the catalyst layers added with nanoparticles after carbon corrosion. After carbon corrosion test, the cathode catalyst layer added with nanoparticles revealed a smaller decrease of catalyst layer thickness and a less increase of ohmic resistance than that of the catalyst layer without the nanoparticles. The different behavior of ohmic resistance change between the catalyst layers with and without the nanoparticles was closely related to the degree of damage in electron pathway in the cathode catalyst layer by carbon corrosion. The degree of proton resistance change in the catalyst layer was also dependent on the presence and the type of nanoparticles added to the catalyst layers.
Modeling Water Management and Carbon Dioxide Contamination Effects in Anion-Exchange Membrane Fuel Cells
Authors: Gerhardt Michael R. , Pant Lalit M. , Weber Adam Z. 
Published: February 2020

Anion-exchange membrane fuel cells (AEMFCs) offer a potential advantage over their traditional proton-exchange membrane counterparts in that many non-precious metal catalysts are chemically compatible with the alkaline environment in an AEMFC [1]. Recently, high-power operation of AEMFCs has been demonstrated, including achieving 1 W/cm2 using silver metal cathode catalysts [2], [3]. The performance of AEMFCs, however, can be highly sensitive to small changes in relative humidity, as water is a reactant in the alkaline oxygen reduction reaction. Additionally, performance degradation due to carbon dioxide contamination remains a major issue. The absorption of carbon dioxide and subsequent conversion to carbonate anions reduces membrane conductivity and worsens fuel cell performance.
In this work, we use our previously developed two-dimensional model [4] to illustrate and explore the effects of membrane and ionomer properties, relative humidity changes, and absorption of carbon dioxide on AEMFC performance. A 2+1D modeling approach is used, where an external stepping model is used to move along the gas channels. At each step, the 2D cross-section model [4] is used to simulate cell performance. Mass and energy balances are performed at each step to obtain the channel conditions, such as concentration, relative humidity, and temperature, for the subsequent step. The 2+1D model accounts for the performance changes due to concentration and relative humidity changes along the channel, especially at integral cell conditions. Finally, we show how performance limitations from carbon dioxide absorption, flooding, and dry-out could be alleviated through changes in operating parameters or ionomer properties.

Acknowledgements

The work was funded under the Fuel Cell Performance and Durability Consortium (FC-PAD), by the Fuel Cell Technologies Office (FCTO), Office of Energy Efficiency and Renewable Energy (EERE), of the U.S. Department of Energy under contract number DE-AC02-05CH11231. We thank Bryan Pivovar and the members of the Fuel Cells group of the National Renewable Energy Laboratory for helpful discussion and model validation data.
[1] J. R. Varcoe et al., “Anion-exchange membranes in electrochemical energy systems,” Energy Environ. Sci., vol. 7, pp. 3135–3191, 2014.
[2] D. R. Dekel, “A mini-review on cell performance in anion exchange membrane fuel cells,” J. Power Sources, p. submitted, 2017, 2017.
[3] L. Wang and J. R. Varcoe, “The first anion-exchange membrane fuel cell to exceed 1 W cm-2 at 70 °C with a non-Pt cathode,” Chem. Commun., pp. 1–3, 2017.
[4] H.-S. Shiau, I. V. Zenyuk, and A. Z. Weber, “Elucidating Performance Limitations in Alkaline-Exchange- Membrane Fuel Cells,” J. Electrochem. Soc., vol. 164, no. 11, pp. E3583–E3591, 2017.
Monolayer Graphene Based Membrane to Replace Nafion in PEM Fuel Cells
Authors: Sahoo Madhumita , Perez-page Maria , Kalangi Vasu , Nair Rahul Raveendran , Holmes Stuart 
Published: February 2020

Low temperature, proton exchange membrane fuel cells (PEMFC) are one of the promising and much investigated electrochemical energy conversion devices as a solution to the enormous world energy consumption demand. Hydrogen and methanol fuelled cells are of particular interest because of their high efficiency and low emission. However commercialization of these cells is hindered by their high cost, which mostly comes from the noble platinum catalyst and conventional Nafion membrane electrolyte. Research to reduce the amount of Pt by dispersing onto, high surface area support materials or to replace with non-precious catalysts have been studied widely to achieve minimal (~ µgPt/cm2 loading) expenditure in this area. However, an alternative to expensive Nafion is still a challenge.
In our previous work [1], we have shown that the incorporation of monolayer graphene (grown on copper foil by chemical vapour deposited (CVD) method) on the membrane electrode assembly (MEA) reduces the problematic methanol crossover in a direct methanol fuel cell by 26 % without affecting the proton conductivity [2]. 45 % improvement in the fuel cell performance for the single layer graphene (SLG) fused cell was achieved in comparison to the cell without SLG [1].
Herein we report two approaches as an alternative to completely replace the solid Nafion membrane in PEMFC. In the first method, SLG incorporated direct membrane deposited [3] MEA is used in the cell. The thickness of the modified electrolyte layer was controlled and optimized by varying the quantity of used Nafion ionomer and scanning electron microscope (SEM) image analysis. Cheaper polybenzimidazole (PBI) membrane is used as the mechanical backing support for the SLG and used to assemble the MEA in conventional method for the second route. Polarization curve, linear sweep voltammetry, impedance spectroscopy and durability testing is implemented to test the practical fuel cell performance for the systems. Obtained results are analysed, compared and discussed with respect to thickness, fuel crossover and membrane resistance for the modified electrolyte cells over conventional solid membrane cell.

References

[1] Stuart M. Holmes, Orabhuraj Balakrishnan, Vasu. S. Kalangi, Xiang Zhang, Marcelo Lozada-Hidalgo, Pulickel M Ajayan, Rahul R. Nair., 2D Crystals Significantly Enhance the Performance of a Working Fuel Cell. Advanced Energy Materials 7 (2017) 1601216.
[2] S. Hu, M. Lozada-Hidalgo, F. C. Wang, A. Mishchenko, F. Schedin, R R. Nair, E. W. Hill, D. W. Boukhvalov, M. I. Katsnelson, R. A. W. Dryfe, I. V. Grigorieva, H. A. Wu, A. K. Geim, Proton transport through one-atom-thick crystals. Nature 516 (2014) 227-230.
[3] M. Klingele, M. Breitwieser, R. Zengerle, S. Thiele, Direct deposition of proton exchange membranes enabling high performance hydrogen fuel cells. Journal of Materials Chemistry A 3 (2015) 11239-11245.
Estimation of Cation Contamination Level in Polymer Electrolyte Membrane Fuel Cells By Electrochemical Impedance Spectroscopy
Authors: Shibata Masao , Kitano Naoki , Shinohara Akihiro , Asaoka Takahiko , Takeuchi Norimitsu , Morita Touru , Kumei Hideyuki 
Published: February 2020

One of the fundamental hurdles for further commercialization of fuel cell vehicles (FCV) using polymer electrolyte membrane fuel cells (PEMFC) is their upper limitation of operating temperature. Operating temperature of current PEMFC is much lower than that of internal-combustion engines and it makes FCV require huge radiators for high power operation. Raising operating temperature is beneficial for downsizing and cost reduction for FCV system because it downsizes not only cooling system but also PEMFC stack.
One of the root causes of this limitation is the decrease in proton conductivity of the membrane during long term operation. In order to avoid the decrease in proton conductivity, reducing the contamination of metal cations in the membrane is an effective way. Metal cations, which contaminate into the membrane during operation, reduce the proton conductivity of the membrane due to decrease in the proton path in the membrane. Proton conductivity loss by contamination of metal cations is critical for the high temperature performance.
In order to reduce cation contamination into the membrane, it is necessary to understand its mechanism. An in-situ measurement for the amount of metal cations should be helpful to understand the phenomena. For this reason, we propose an in-situ quantitative measurement for cation contamination ratio in PEMFC.
Electrochemical impedance spectroscopy (EIS) was adapted to the measurement because cation transport inside the membrane was expected to be detectable with EIS. Experimental results showed that EIS spectrum under a certain condition reflects metal cation contamination ratio strongly, which was proposed to be an indicator of cation contamination ratio. The mechanism of EIS spectrum change is explained theoretically by a numerical simulation using a simple model of cation and water transport. Detail of the measurement will be shown in the conference.
Therefore this EIS measurement is proposed for the analysis of metal cation contamination mechanisms in PEMFC. Further study will elucidate the impact of catalyst layer, membrane and metal cation species against the EIS spectrum.