bluuebunny/crossref_metadata_2025 huggingface dataset:
Operando
57 Fe Mössbauer Spectroscopy of Fe-N-C Catalysts during Oxygen Reduction Reaction
Authors: Ni Lingmei , Gallenkamp Charlotte , Kübler Markus , Theis Pascal , Bill Eckhard , Krewald Vera , Kramm Ulrike I.
Published: November 2022

Proton exchange fuel cells (PEFCs) are a clean technology for efficient conversion of chemical into electrical energy and are specifically promising for the decarbonization of heavy duty vehicles [1]. Currently, the drawback of PEFCs is the high cost of Pt-based catalysts used for cathode and anode, which hinders their commercialization. [2] The rapid development of FeNCs holds promise for replacing Pt-based catalysts for the oxygen reduction reaction (ORR). The nature and characterization of the FeNC active sites is a challenging subject of research, and the exact structure of intrinsic active center for FeNC catalysts is still under debate. [3-6]

57Fe Mössbauer Spectroscopy is powerful in obtaining knowledge of iron sites, with respect to structural composition, electronic states as well as magnetic environment [3,7-9]. To solve the debate, 57Fe Mössbauer experiments were carried out under ex situ, in situ, or operando conditions to identify iron signatures and their changes induced by different conditions. On the basis of our in situ results of three differently prepared catalysts, two transitions between the oxygenated and deoxygenated state were found and assigned to sites involved in the direct and indirect ORR. [10-11] In order to gain an in-depth understanding of active sites operando conditions (thus during ORR) were performed for the FeNC catalyst that exhibited the strongest change during in situ testing. One iron signature (D4) gets exclusively formed under ORR conditions and its intensity scales with the ORR current. Together with density functional theory calculations the overall set of data enables us to make important conclusions on the ORR mechanism on FeNC catalysts.

Literature:

[1] M. K. Debe, Nature. 486, 2012, 43−51.

[2] C. Sealy, Mater.Today.11, 2008, 65.

[3] S. Wagner, H. Auerbach, et al. Angew. Chem. 131.31, 2019, 10596-10602.

[4] A. Zitolo, V. Goellner, et al. Nat. Mater. 14.9, 2015, 937.

[5] X.,Li, C. Cao, et al. Chem. 6, 2020, 3440–3454.

[6] J. Li, M. T. Sougrati, et al. Nat. Catal. 4, 2021, 10–19.

[7] U.I. Kramm, M. Lefèvre, et al. J. Am. Chem. Soc. 136, 2014, 978-985.

[8] U.I. Kramm, J. Herranz, et al. Phys. Chem.Chem.Phys. 14, 2012,11673-11688.

[9] U.I. Kramm, L. Ni, et al. Adv. Mater.31.31, 2019, 1805623.

[10] L. Ni, C. Gallenkamp, et al. Adv. Energy Sustainability Res. 2, 2021, 2000064.

[11] L. Ni, P. Theis,et al. Electrochim. Acta. 395, 2021, 139200.
Redox Behavior and ORR Catalytic Activity of Fe-N-C Electrocatalysts in Various Electrolytes and in the Presence of Probe Molecules
Authors: Wang Xiaoping , Park Jaehyung , Ferrandon Magali , Zeng Yachao , Zhang Hanguang , Wu Gang , Zelenay Piotr , Myers Deborah J.
Published: November 2022

Materials in the Fe-N-C family are the most promising platinum group metal-free (PGM-free) catalysts for the oxygen reduction reaction (ORR) in polymer electrolyte fuel cells (PEFCs). Significant progress has been made in recent years in improving both the ORR activity and durability of the Fe-N-C catalysts. However, further improvements are needed, especially in long-term performance durability in hydrogen-air PEFCs, to enable use of these catalysts in practical applications, such as powering light and heavy-duty vehicles. One of the major factors that hinder the further enhancement of the catalysts is the lack of clear understanding of the nature of the active sites in the Fe-N-C catalysts that catalyze the ORR reaction, due to the complexity of the Fe-N-C catalysts composition and structure. The most active Fe-N-C catalysts have been synthesized by pyrolyzing iron salts or other iron-containing compounds with zinc-based zeolitic imidazolate frameworks (ZIFs) and/or phenanthroline (as carbon and nitrogen sources), or by heat treating iron-substituted ZIFs. It has been shown that many synthesis variables, such as type of iron precursors, the metal and carbon-nitrogen macrocycle ratio, the heat treatment temperature, atmosphere, and temperature profile, all affect the properties and structure and thus the activity and stability/durability of the resulting catalysts. In order to further improve the Fe-N-C catalysts, it is critical to gain insights into the origins of ORR activity and the reaction mechanism. In this work, the redox behavior of different Fe-N-C catalysts, synthesized by a variety of techniques mentioned above, and correlation of this redox behavior with ORR catalytic activity in different electrolytes will be discussed and the effect of nitric oxide gas-phase adsorption on the catalyst redox feature and ORR activity will be presented. The implication of these results on the identity or identities of the ORR active sites of the Fe-N-C catalysts will be discussed.

This work was supported by the U.S. Department of Energy (DOE), Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office (HFTO) under the auspices of the Electrocatalysis Consortium (ElectroCat 2.0). This work utilized the resources of the Advanced Photon Source, a U.S. DOE Office of Science user facility operated by Argonne National Laboratory for DOE Office and was authored by Argonne, a U.S. Department of Energy (DOE) Office of Science laboratory operated for DOE by UChicago Argonne, LLC under contract no. DE-AC02-06CH11357.
(Invited) Decoupling the Contributions of Different Instability Mechanisms to the Fuel Cell Performance Decay of Fe-Based O2-Reduction Catalysts
Authors: Herranz Juan , Ünsal Secil , Saveleva Viktoriia , Ebner Kathrin , Kübler Markus , Theis Pascal , Lee Jongmin , Artiglia Luca , Schmidt Thomas J. , Boillat Pierre , Kramm Ulrike I.
Published: November 2022

The last decade of research on Fe-based O2-reduction single atom catalysts (SACs) has led to the development of SACs with an initial polymer electrolyte fuel cell (PEFC) performance close to that of Pt-based catalyst layers (CLs). However, these inexpensive materials generally suffer from a fast performance decay that has been ascribed to several mechanisms that can be simultaneously at play during device operation. These include (i) the demetallation of the SACs’ active sites; (ii) the potential-induced corrosion of the carbonaceous matrix that hosts these active centers; and/or (iii) the chemical degradation of the CL-ionomer, active sites and/or carbon support by radicals derived from the H2O2 produced as an O2-reduction by-product. Unfortunately, little is known regarding the relative contributions of these mechanisms to the overall PEFC-performance loss and as a function of the operative conditions – a missing understanding of pivotal importance for the design of strategies to mitigate this instability.

With this motivation, this contribution will start with a comparison between the device stability in the course of 30 min holds at various currents of two type of SACs featuring similar beginning-of-life PEFC-performance. Particular attention will be paid to the effect of the catalyst loading on the observed degradation, which will be linked to the operando mapping of the distribution of liquid water within these materials’ CLs based on neutron imaging. In a subsequent step, we will present the results derived from a stability protocol in which the combination of different cathode gas feeds (i.e., air vs. N2) and potential hold durations allow decoupling the relative contributions of the above deactivation mechanisms to the overall performance decay. This requires a careful assessment of the kinetic, ohmic and mass transport overpotentials (and changes thereof in the course of the stability measurements) based on Tafel analyses and electrochemical impedance spectroscopy measurements. Moreover, these results are again complemented by an assessment of the protocol-induced changes in catalyst morphology and surface chemistry based on transmission electron microscopy and X-ray photoelectron spectroscopy measurements.

In summary, this contribution will showcase our efforts to deconvolute the relative effects of various deactivation mechanisms to the overall PEFC-performance loss of SAC-CLs.
Degradation Acceleration-Factor Analysis for Platinum Group Metal (PGM)-Free Polymer Electrolyte Fuel Cell Cathodes
Authors: Beltran Diana , Zeng Yachao , Wu Gang , Li Xianglin , Litster Shawn
Published: November 2022

This work explores designs and methods that can mitigate degradation and can be used to expand models to predict PGM-free fuel cell degradation due to voltage cycling during accelerated stress tests (AST) and constant potential holds, specifically current density loss over time. The motivation behind investigating degradation mechanisms is that most of the recent advances have mostly focused on enhancing initial electrocatalytic activity, and not on catalyst stability. Advancements in catalyst stability are less substantial and are well below the level for commercialization. The objective is to determine the impact of the operating point on degradation rate in membrane electrode assemblies (MEAs) and to perform time-efficient evaluation of degradation acceleration factors on a single MEA. The preliminary AST cycling results show that reducing temperature and upper potential cycling limit considerably reduces degradation rates. This work can help identify operating points that optimize between performance and durability using empirical data. Ultimately, the correlations extracted from this work can be applied into drive-cycle models for PGM-free catalysts for simulation-based lifetime performance forecasting.

This work was partially supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy under grant DE-0008440 (Prime: University of Kansas).
Synthesis and Characterisation of High Performing Heteroatom Doped Carbon Catalyst for Oxygen Reduction Reaction (ORR) in Alkaline Fuel Cells
Authors: Baburajan Aravind B , Ramya Krishnan , Chandrabose A
Published: November 2022

Alkaline fuel cell (AFC) routing platinum-free electrocatalysts are one of the potential frontiers to enable its use in widespread applications. PGM catalysts have alwaysbeen preferred andwidely utilised due to their enhanced intrinsic activity and superior performance. Its high cost and less abundance brought attention to heteroatom doped carbon-based electrocatalysts that offer comparable performance, tunable selectivity and simple synthesis route. The lack of efficient catalysts hampers the performance, peak power density and longevity of the cell due to sluggish ORR activity.

In this article, Heteroatom-doped carbon (F, N/F and N/S/F) is prepared using PVDF-HFP polymer as a precursor. The polymer is mixed with urea or ThioUrea concerning the required dopant and pyrolyzed at 900 ºC for 3 hours at a heating rate of 5 deg per min in an inert atmosphere. The enhanced performance is obtained from the N/F- doped carbon which shows an onset potential (E = 1.04V vs. RHE), a diffusion-limited current density(j) of 6.12 mA/cm2 in 0.1M KOH, which is comparatively better than the F-doped and N/S/F-doped carbon. The number of electrons (n) involved in the ORR activity was calculated to be 3.99, 3.98, 3.85 for N/F-C, N/S/F-C and F-C respectively. This suggests a 4e- pathway indicating efficient operation for the Alkaline electrochemical cell. The systematic studies exhibit an increased ORR activity in the case of the N/F-doped carbon electro-catalyst due to a combined synergistic effect of hetero-atoms and high surface area. Heteroatom doping and the activity in the carbon material were confirmed by all the necessary physical and electrochemical characterisations.

Keywords: Hydrogen, Alkaline Fuel cell, AFC, Oxygen reduction reaction, ORR catalyst
(Digital Presentation) Electrocatalytic Oxidation of Methanol over Silver Based Electrocatalysts Synthesized By Solution Combustion Technique
Authors: Logade Khulood , Shafath Sadiyah , Kumar Anand , Abu Reesh Ibrahim
Published: November 2022

Herein, we report the electrocatalytic properties of Ag-M/C (M=Cu, Zn, Fe, Cr, Mn) catalysts produced using solution combustion synthesis (SCS) method for methanol oxidation reaction (MOR). The morphological properties of the synthesized catalysts were studied using SEM, EDX, TEM, XRD and XPS techniques. The characterization results indicated that out of all catalysts, AgCu/C had the most porous surface, small and well distributed particles with high surface area making it a good choice for electrocatalytic experiments. The XPS results showed a shift in peak in the AgCu/C sample due to the charge transfer between Ag and Cu indicating a strong interaction between Ag and Cu. The electrochemical properties of the catalysts were studied at 1 M methanol concentration and 1 M KOH (electrolyte) concentration by performing Cyclic Voltammetry (CV) and Linear Sweep Voltammetry (LSV) experiments. It was observed that AgCu/C exhibited a greater electrocatalytic activity and was therefore, found to be a more viable catalyst for MOR. Following this, further concentration studies were conducted on AgCu/C for methanol concentrations of 0.5M, 1M, 1.5M, 2.5M to evaluate the rate dependency of the catalyst on MeOH concentration. The CV and LSV curves depicted a linear increase in current density proportional to the increase in methanol concentration, indicating power-law dependency. The catalyst also displayed long-term stability when chronoamperometry test was performed for 20 hours.
(Digital Presentation) Multifunctional Lanthanum Perovskite Electrocatalysts (LaMnxCo1-xO3 (0≤x≤1)) for Alkaline Medium Methanol Oxidation and Oxygen Catalysis
Authors: Shafath Sadiyah , Logade Khulood , Kumar Anand , Abu Reesh Ibrahim
Published: November 2022

Lanthanum-based synthetic perovskites (LaMnxCo1-xO3 (0≤x≤1)) were synthesized using a solution combustion synthesis technique with variable ratios of Co and Mn to investigates the surface and electrocatalytic property (activity and stability of catalysts) for methanol oxidation reaction (MOR), oxygen reduction reaction (ORR), oxygen evolution reaction (OER) under alkaline medium (KOH). The structural and morphological characterizations of the synthesized catalyst were performed by XRD, FTIR, SEM, TEM and XPS techniques. The structural and chemical properties systematically changed by varying the Mn to Co ratio in the perovskite structure. To observe the completion of combustion and temperature characteristics during the synthesis process, which are known to impact structural qualities, the time temperature profile during the combustion process was monitored. SEM/EDX and XPS analysis confirmed the formation of targeted ratio of Mn and Co on the catalyst. Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) results revealed that all perovskite samples with different Co:Mn ratios were active for ORR, OER and MOR. The LaMnxCo1-xO3 perovskite with x=0.4 showed the highest current density compared to other samples towards all the investigated electrocatalytic reactions (MOR, ORR and OER) under alkaline reaction conditions.
Development of Li Metal Batteries with Improved Safety
Authors: Zhang Ji-Guang , Cao Xia , Xu Wu , Kim Ju-Myung
Published: November 2022

Development of Li metal batteries (LMBs) has attracted worldwide attention in recent years due to their much higher theoretical energy densities than those of conventional Li ion batteries. LMBs with high energy density and long cycle life have been demonstrated by several institutions and companies recently.1,2 LMBs may be safe in their early stage of cycling due to the small geometric surface area of Li metal anode. However, after long term cycling, mossy/dendritic/“dead Li” will form eventually. They will not only lead to the increase of cell thickness, but also lead to powdered Li which pose a safety concern when exposed to air in the extreme case of mechanical damage, especially for their large scale applications.3 Thus, a paradigm change in the electrolyte design is required to minimize the formation of “dead Li” and improve the thermal stability of the batteries. In this work, several approaches have been used to improve the thermal stability of LMBs. (1) Use of electrolyte with high coulombic efficiency to minimize the formation of “dead Li” or mossy Li; (2) use of non-flammable solvent in electrolyte; (3) use of solvent with high boiling point and high flash point. (4) use of electrolyte enabling formation of large size of Li deposition with minimal surface area. This will enable the formation of a lithiophobic SEI layer which can accommodate stress/strain during large volume changes. (5) Screening additives to improve Li CE and safety. The electrolytes with improved safety/stability at extreme conditions will also be reported in this work.

1 Niu, C. et al. Balancing interfacial reactions to achieve long cycle life in high-energy lithium metal batteries. Nature Energy, (2021).

2 Hu, Q. Li-metal batteries, https://s29.q4cdn.com/695431818/files/doc_presentation/2022/03/March-2022-Investor-Presentation.pdf (2022).

3 Louli, A. J. et al. Diagnosing and correcting anode-free cell failure via electrolyte and morphological analysis. Nature Energy
5, 693-702, (2020).
Rational Design of 3-Dimensional Carbon Architectures with Controlled Interfacial Activity for Reversible Li Metal Storage
Authors: Shin Hong Rim , Kim Siwon , Lee Jong-Won
Published: November 2022

Three-dimensional (3D) host architectures for Li metal storage have emerged as promising strategies for resolving the critical issues of Li metal anodes: severe volume changes and dendritic growth of Li during charge–discharge processes. However, the ionic resistance of electrolyte-filled pores causes the preferential deposition of Li on top of the 3D architecture (i.e., top plating), resulting in early cell failure. To realize Li metal anodes with high capacity and cyclability, herein, we report 3D-architectured electrodes with controlled interfacial activity based on metal–organic framework (MOF)-derived carbon hosts. Electrochemical simulations of Li plating processes in the 3D-architectured electrode suggest that the top plating can be effectively suppressed by increasing the interfacial activity across the thickness toward bottom of the electrode. MOF nanoparticles are pyrolyzed to form highly porous carbon hosts, and then, atomic Ag clusters are incorporated into the host by a galvanic displacement reaction to enhance the interfacial activity. A bi-layered carbon electrode with controlled interfacial activity is fabricated via sequential electrophoretic deposition of the host materials: i.e., as-pyrolyzed carbon on top and Ag-incorporated carbon on bottom. In comparison with the conventional electrode with uniform interfacial activity, the bi-layered electrode exhibits reduced overpotentials for Li plating and enhanced cyclability during galvanostatic Li plating–stripping. The combined computational and experimental studies further demonstrate that the bottom layer with atomic Ag clusters acts as a preferential site for Li nucleation even in the presence of kinetic limitations of ionic transport. As a result, Li deposits are confined in the bi-layered carbon electrode, thereby enhancing the reversibility of Li metal storage. This work provides an effective strategy to develop long-cycling, high-capacity Li metal anodes by controlling the interfacial activity of 3D carbon architectures.
The SEI on Lithium Metal Anodes: From Understanding to Enhancement
Authors: Kühn Sebastian Paul , Weintz Dominik , Winter Martin , Cekic-Laskovic Isidora
Published: November 2022

Lithium metal batteries (LMB) have risen back into focus of battery research in resent years, due to the high theoretical specific capacity of the lithium metal anodes (3860 mAh g-1).[1] However, the utilization of lithium metal as an anode material requires an in depth understanding of the solid electrolyte interphase (SEI) on lithium metal electrodes, since its formation, composition and electrochemical characteristics significantly impact important LMB lifetime parameters, e.g. lithium stripping/plating behaviour, dendrite growth and in operando electrolyte consumption.[2]

Lithium metal electrode performance is influenced by a variety of different, however often overlooked factors, e.g. the native passivation layer, inevitably present on each lithium metal electrode surface, which has only recently gathered more attention as an influencing factor in respect to SEI characteristics.[3] The presented research utilizes the preformation of an uncontaminated SEI on the lithium metal electrode surface to circumvent the influence of native lithium metal passivation. A systematic study of different preformed SEIs resulted in a better understanding of the influence by different electrolyte components on relevant SEI characteristics, namely, selected conducting salts (LiFSI, LiPF6) and functional additives (VC, FEC). Analyses of the SEIs electrochemical properties, composition, morphology and dynamics were conducted via stripping/plating experiments as well as in operando EIS, SEM (incl. cryogenic cross section and post mortem) and XPS (post mortem) measurements. Finally, careful tailoring of the preformed SEI was shown to have an enhancing effect on NMC811||Li cells, increasing the LMB lifetime by up to 25%. Furthermore, the application of a tailored preformed SEI has also shown a positive impact on the performance of solid state LMBs.

The presented results highlight the importance of an in depth understanding regarding the cause and effect of varying electrolyte components on the SEIs characteristics. This understanding will ultimately have a significant impact on the research towards enhanced and reliable LMB performance and future applicability.

References:

[1] D. Jin, J. Park, M. H. Ryou, Y. M. Lee, Adv. Mater. Interfaces
2020, 7, 1–17.

[2] B. Horstmann, J. Shi, R. Amine, M. Werres, X. He, H. Jia, F. Hausen, I. Cekic-Laskovic, S. Wiemers-Meyer, J. Lopez, D. Galvez-Aranda, F. Baakes, D. Bresser, C.-C. Su, Y. Xu, W. Xu, P. Jakes, R.-A. Eichel, E. Figgemeier, U. Krewer, J. M. Seminario, P. B. Balbuena, C. Wang, S. Passerini, Y. Shao-Horn, M. Winter, K. Amine, R. Kostecki, A. Latz, Energy Environ. Sci.
2021, 14, 5289–5314.

[3] S. Otto, T. Fuchs, Y. Moryson, C. Lerch, B. Mogwitz, J. Sann, J. Janek, A. Henss, Appl.
Energy Mater.
2021, 4, 12798–12807.
Electrochemical-Piezoelectric Mechanism for Dendrite Growth
Authors: Gao Tianhan , Lu Wei
Published: November 2022

On immersing two lithium metal electrodes in a solution containing lithium salt and applying a voltage, lithium metal will deposit on the electrode connected to the lower voltage. This process is known as electrodeposition. It has been widely observed that under moderate currents, lithium ions do not deposit to a flat surface but rather spontaneously form sharp needle shapes known as dendrites. Dendrite formation is a major barrier for realizing the lithium metal battery, which not only causes capacity loss but also leads to internal short circuit and safety hazard [1].

We report a discovery that the use of a soft piezoelectric film as separator can effectively suppress the formation of lithium dendrite and stabilize the lithium surface during electrodeposition system [2, 3]. When the film is deformed by any local protrusion because of surface instability of the deposited lithium, a local piezoelectric overpotential is generated to suppress lithium deposition on the protrusion. We have established a theory that integrates electrochemistry, piezoelectricity and mechanics. We developed multiphysics computations to simulate dendrite growth in contact with a piezoelectric film. We find that the dendrite-suppression capability is over 6 orders stronger than the limit of mechanical blocking by any separators or solid-state electrolytes. Simulations show that the mechanism ensures deposition to form a flat surface even if the initial substrate surface has significant protrusions, suggesting its robustness and effectiveness against manufacturing defects. We show that the mechanism is so strong that even a weak piezoelectric material is highly effective, opening up a wide range of materials.

REFERENCES

Liu, G. and Lu, W. A model of concurrent lithium dendrite growth, SEI growth, SEI penetration and regrowth. Electrochem. Soc.(2017) 164: A1826.

Liu, G., Wang, D., Zhang, J., Kim, A. and Lu, W. Preventing dendrite growth by a soft piezoelectric material. ACS Mater. Lett.(2019) 1: 498-505.

Gao, T., Rainey, C. and Lu, W. Piezoelectric mechanism and a compliant film to effectively suppress dendrite growth. ACS Appl. Mater. Interfaces. (2020) 12: 51448–51458.
(Invited) U.S. DOE Lithium Metal Solid-State Battery R&D
Authors: Thompson Simon T. , Smith Patricia H. , Duong Tien Q.
Published: November 2022

Decarbonizing transportation through electrification requires less expensive, higher energy density batteries made from earth-abundant materials to displace internal combustion engines. Suitable solid-state electrolytes (SSEs) that facilitate lithium metal anodes by blocking Li dendrite formation represent a promising pathway to high-energy density cells. In a similar manner, SSEs that block the polysulfide shuttle could facilitate sulfur cathodes with even higher energy density that avoid issues of critical materials and supply chain constraints coupled to transition metal oxide-based cathodes.

Interest in solid-state batteries has increased rapidly in recent years. There are examples of solid-state batteries (SSBs) in commercial automotive applications; however, achieving wider adoption requires SSBs operating without the need for heating or excessive applied cell pressure. Several solid-state electrolyte chemistries (e.g., sulfides, ceramics, polymers, halides) are under development, but key issues remain unresolved in the case of each electrolyte chemistry.

The U.S. Department of Energy Vehicle Technologies Office supports R&D encompassing all of these candidate electrolytes for solid-state batteries through the Advanced Battery Materials Research program. The R&D portfolio prioritizes: improving electrolytes through modified composition or synthesis to increase room-temperature Li+ conductivity and mitigate Li dendrite penetration; improving interfaces to address chemical or electrochemical reactivity, to decrease impedance, and to improve Li plating and stripping; and improving suitability for high-volume manufacturing of solid-state lithium metal batteries by improving mechanical properties and demonstrating thin, defect-free, large-area SSE layers.

This presentation comprises solid-state lithium metal battery R&D priorities and accomplishments in the context of meeting DOE targets for energy density, cycle life, and cost. It will also emphasize the importance of SSBs to U.S. DOE strategy for increasing domestic lithium-based battery manufacturing and securing the U.S. position in next-generation battery innovation.
Mechanism of Void Formation in Lithium Metal Solid-State Batteries
Authors: Banerjee Sourim , Vishnugopi Bairav Sabarish , Naik Kaustubh Girish , Mukherjee Partha P.
Published: November 2022

Solid-state batteries (SSBs) with lithium metal anodes promise higher energy and power density over conventional lithium-ion batteries. But the development of SSBs faces fundamental challenges related to the electro-chemo-mechanics and stability of solid-solid interfaces. Among these, the formation and growth of voids at the lithium metal-solid electrolyte interface during stripping persists to be a major limitation. In this work, we analyze the nature of metal electro-dissolution and its critical implication on the evolution of solid-solid point contacts. The competing nature of lithium self-diffusion, reaction kinetics and ionic transport at the solid-solid interface, dependent on factors such as temperature and surface roughness are examined. Hotspots in the dissolution morphologies are identified and systematically connected to the electrochemical signature and onset of failure in SSBs.
Insights into the Crystal Structure of Halide Solid Electrolytes and Li Diffusion
Authors: Liu Zhantao , Chien Alex , Wang Shuo , Lin Zihao , Liu Jue , Mo Yifei , Chen Hailong
Published: November 2022

Lithium halides with general formula Li3MX6 (M = metals such as Y, In, Yb or Sc; X = Cl or Br) have attracted significant attention because of their promising room temperature conductivities and high oxidative stability[1]. Li-ion mobility in these halides is strongly affected by the synthesis method and parameters. In Li3YCl6 with a hexagonal-close-packed (hcp) anion framework, the ionic conductivity is commonly observed to decrease with increased crystallinity. While in Li3YBr6 with a face-centered-cubic (fcc) anion framework, the ionic conductivity increases with increased crystallinity. So far there is no clear explanation for such opposite trends in these two otherwise very similar crystal structures. Ab initio molecular dynamics (AIMD) simulation[2] suggested higher ionic conductivity and lower activation energy in Li3YCl6 than inLi3YBr6, which also does not agree well with the experimental observation that Li3YBr6 commonly shows higher conductivity than Li3YCl6. Above-mentioned unexplained observations and inconsistencies imply that likely some critical structural features of these halides that strongly impact ionic diffusion are not yet explored nor taken into consideration. Here, we report our recent findings in the crystal structure of Li3YCl6 and Li3YBr6 and the design, synthesis and electrochemical testing of a few new halide compounds designed based on the new findings. The crystal structures are investigated with using ex situ and in situ synchrotron X-ray diffraction (XRD) and neutron diffraction (ND). Our study[3] demonstrated that the discrepancies between simulated and experimental results in Li3YBr6-type structure is partly caused by the grain boundary. Through PDF data analysis, we provide experimental evidences of cation local ordering in ab plane and stacking fault along c-direction in Li3YBr6-type structure. The lower ionic conductivity in low crystallinity is owing to the blockage of Li diffusion channel along c-direction caused by the stacking fault. Moreover, a new tetrahedral Li-site is identified, which may be critical in understanding the Li diffusion behaviors. Via rationally tuning Li occupancies at the tetrahedral and octahedral sites, low Li diffusion barriers can be achieved, which is in consistence with theoretical calculation results.

[1] T. Asano, A. Sakai, S. Ouchi, M. Sakaida, A. Miyazaki, S. Hasegawa, Advanced Materials
2018, 30, 1803075.

[2] S. Wang, Q. Bai, A. M. Nolan, Y. Liu, S. Gong, Q. Sun, Y. Mo, Angewandte Chemie International Edition
2019, 58, 8039-8043.

[3] Z. Liu, S. Ma, J. Liu, S. Xiong, Y. Ma, H. Chen, ACS Energy Letters
2021, 6, 298-304.
Elucidating MnO2 Reaction Mechanism By Multi-Modal Characterization in Aqueous Zn-MnO2 Batteries
Authors: Kankanallu Varun , Zheng Xiaoyin , Lin Cheng-Hung , Zmich Nicole , Ge Mingyuan , Chen-Wiegart Yu-chen Karen
Published: November 2022

Aqueous Zn-ion batteries has attracted great attention in recent years, as a promising candidate for grid energy storage applications. An aqueous system offers intrinsic safety, high ionic conductivity contributing improved power capability and raw materials that are more earth abundant and environment friendly. Numerous promising reports haven been focusing on the Zn/MnO2 system owing to its low cost, moderate discharge potentials and with improved reversibility in the mild aqueous electrolyte. However, many questions remain unanswered regarding its reaction mechanism. The different reaction mechanisms including Zn+2 insertion, H+ insertion, chemical conversion reaction including the combined intercalation and conversion reaction mechanism, and the dissolution-deposition of the manganese oxide.

In this work, we aim to unravel the reaction mechanism by a systematic multimodal synchrotron characterization. This work discusses the galvano-static charge-discharge process of aqueous Zn-MnO2 batteries using operando measurements, which provides us with a direct insight into the phenomenon and can be directly correlated to the battery's electrochemical response. The multimodal techniques include operando X-ray diffraction to study the structural phase change of the cathode active material, operando X-ray absorption spectroscopy to probe the local structure changes and transmission X-ray microscopy studies to observe the key morphological events. Overall, this multimodal approach gives us an insight into the reaction mechanism enabling us to better design Zn-MnO2 batteries for practical applications.
A Sulfone-Based Crystalline Organic Electrolyte for 5 V Solid-State Potassium Batteries
Authors: Kang Seokbum , Jeon Boosik , Hong Seung-Tae , Lee Hochun
Published: November 2022

Solid-state potassium batteries are promising energy storage systems, but their wide use requires suitable solid electrolytes to ensure high ionic conductivity, electrochemical stability, and contacting ability with composite electrodes. For this purpose, this study introduces sulfone-based crystalline organic electrolytes (SCOEs) consisting of dimethyl sulfone (DMS) and potassium bis(fluorosulfonyl)imide (KFSI). One solid-state SCOE, KFSI/DMS 1:9 by mol, exhibits high ionic conductivity (4.0 × 10−4 S cm−1 at 25 °C), oxidation stability (~5.8 V vs. K+/K), and negligible flammability. Moreover, owing to its optimal melting point (94 °C), the SCOE enables seamless contact with the composite electrodes through the melt-casting process, which has been challenging for other solid-state electrolytes. K||KVPO4F cells filled with this SCOE show improved cycle performance (capacity retention 88.8% after 100 cycles vs. 77.6% after 74 cycles at 25 °C) with high Coulombic efficiency (asymptotic value 99.6% vs. 92.0%) compared to cells with a conventional carbonate electrolyte. With these results, the developed SCOE paves the way to room-temperature operable, 5 V solid-state potassium batteries.

Figure 1
Spectroscopic Studies of Solution Structure and Ion Conduction in Concentrated Aqueous Electrolytes
Authors: Koo Bonhyeop , Lee Hochun
Published: November 2022

Aqueous Li-ion batteries have been spotlighted because they are potentially low in cost, safe, and environmentally friendly. However, they suffer from low energy density due to limited cell voltage. Concentrated aqueous electrolytes have been attracting alternatives to aqueous electrolytes because they enable a wide electrochemical stability window. Although many studies have reported excellent cell performance, employing concentrated aqueous electrolytes, the solvation structure and dynamic role of water in concentrated aqueous electrolytes still remain elusive. To reveal solution structure and Li-ion transport mechanism in concentrated aqueous electrolytes, we employed dielectric relaxation spectroscopy, and pulsed-field gradient NMR. We found concentrated aqueous electrolytes still contain a non-negligible amount of bulk water which shows fast rotational dynamics, not interacting with ions. Our experimental results support that concentrated aqueous electrolytes have a heterogeneous solvation environment, and the presence of a microscopic water-rich region with high mobility could facilitate the vehicular migration of Li-ions through highly viscous electrolytes. The molecular understanding of concentrated aqueous electrolytes in this study would shed some light on designing solvation structures to overcome the limit of dilute LIB electrolytes.
Effect of Hydrogenation on the Electrochemical Performance of Anatase and Rutile TiO2 As Anode for Sodium-Ion Batteries
Authors: Panda Ananya , Patra Jagabandhu , Chang Jeng-Kuei
Published: November 2022

Defect engineering, such as manipulating oxygen vacancies (OVs), which can alter the local structure and electronic properties of metal oxides, has attracted increasing attention for improving the charge-storage performance of electrode materials. In this work, a high-pressure hydrogenation method was developed to fabricate oxygen-deficient TiO2. Two TiO2 phases, namely rutile (TiO2-R) and anatase (TiO2-A), and their hydrogenated phases (denoted with the prefix “H”) are investigated as sodium-ion battery (SIB) anodes. The charge-discharge properties of both phases can be significantly enhanced via the hydrogenation treatment. The introduction of OVs increases the electronic and ionic conductivity of TiO2, and the disordered TiO2 provides more electro-active sites for sodiation/desodiation reactions. For the first time, electrochemcial properties of the H-TiO2-R and H-TiO2-A electrodes are systematically compared. The H-TiO2-A electrode exhibits an excellent high-rate capacity of 100 mAh g–1 at 10000 mA g–1 and great cycling stability of 80% capacity retention after 4500 cycles. The superior performance is well supported by a generalized gradient approximation Perdew-Burke-Ernzerhof density functional calculation. The proposed anode and material modification strategy have great potential for high-power and high-durability SIB applications.
Atomic Dispersed Ce/Ti Onto Layered Double Hydroxide Substrate Via Atomic Layer Deposition for Efficient Oxygen Evolution Reaction
Authors: Liu Ziqi , Lee Min Hwan , Garcia ThomasJae , Li Haoyu
Published: November 2022

Recently, transition metal based layered double hydroxides (LDHs) based materials have attracted attention for the enhancement of oxygen evolution reaction (OER) performances due to their unique structural property, high specific capacitance, facile synthesis process and low cost. [1,2] Atomic layer deposition (ALD) is a powerful technique for realizing highly dispersed nano-species at the atomic level with a precise control over the size, shape, and composition by leveraging its self-limiting nature of surface reactions. ALD precursors could be readily combined with LDH structures due to the abundant hydroxy group on the surface of LDH structure. The additional ALD-derived doping can regulate the electronic structures of original LDH and further strength the synergetic effects between the host and doped metals for enhancing electrocatalytic activities.[3]

In this study, a simple and effective method of introducing Ce as a third metal was used to prepare high-performance Ni/Co-LDH based electrodes: hydrothermal approach followed by an ALD process, using Ni foam as the substrate to achieve the growth of Ni/Co nanostructures. Smooth 2D LDH plates of a uniform structure with high surface area and abundant active sites were synthesized. The resultant CoNi-LDH@5Ce and CoNi-LDH@5Ti exhibit optimal activity and stability toward OER. In particular, CoNi-LDH@5Ce exhibits excellent OER performance with a small overpotential of 270 mV to reach 50 mA cm-2. ALD-treated samples exhibit a decreased charge transfer resistance, indicating a more efficient OER. Furthermore, both CoNi@5Ti and CoNi@5Ce show lower ohmic resistance of 1.5 Ω, which is additionally beneficial to OER performance. The enhanced performance could be attributed to a synergic effect between the doped elements (Ce, Ti) and base transitional metals (Co, Ni). Furthermore, metal oxides – especially cobalt oxide – generated on the surface during ALD process is conjectured to have contributed to an acceleration of O-O bond formation during OER process.

References

[1] Z. Jiang, Z. Li, Z. Qin, H. Sun, X. Jiao, D. Chen, .

[2] T. M. Masikhwa, M. J. Madito, D. Y. Momodu, J. K. Dangbegnon, O. Guellati, A. Harat, M. Guerioune, F. Barzegar, N. Manyala, .

[3] L. Lv, Z. Yang, K. Chen, C. Wang, Y. Xiong, Adv. Energy Mater.
2019, 9, 1803358.
Utilizing 3D Electrolysis Models to Link Transport to Cell Design and Performance
Authors: Lopata Joseph Steven , Weidner John W. , Cho Hyun-Seok , Shimpalee Sirivatch
Published: November 2022

Computational fluid dynamics (CFD) has been employed extensively for modeling fuel cells, but electrolysis has lacked this degree of attention in literature. As electrolysis commercialization advances, the desire to use numerical methods to aid the engineering process grows. The work described in this presentation aims to link channel/manifold geometry, porous media design, and operating conditions to cell performance in the context of mass transport and identify important unknown input quantities to which models are particularly sensitive. CFD is applied to electrolysis systems to quantify the impact of two-phase flow patterns and porous media properties on energy losses, primarily those linked directly to the presence of the gas phase.

3D models for proton exchange and alkaline electrolysis devices are summarized. For proton exchange electrolysis, a homogeneous two-phase model was built in order to estimate the species composition at the anode and how operating conditions and porous transport layer (PTL) properties influence distributions. The model suggests that cell performance is particularly sensitive to the evaporation rate and PTL permeability when the contribution of the gas-phase reaction is considered. A similar model was applied to alkaline diaphragm electrolysis to study effects of the manifolds on the flow distribution and thereby local performance. Current and gas crossover were correlated with cell geometry and altered by the cell potential and feed rate.

Figure 1
Voltage Loss Analysis of Proton Exchange Membrane Water Electrolyzers
Authors: Pasmay Fausto N , Ferner Kara , Litster Shawn
Published: November 2022

Proton exchange membrane water electrolyzers (PEMWEs) present a promising hydrogen production alternative to common methods like steam methane reforming, particularly for producing green hydrogen from renewable sources. However, scaling up PEM electrolyzers is challenged by the high cost of their platinum group metal catalysts (Ir & Pt) for the oxygen and hydrogen evolution reactions (OER & HER). This study focused on the performance of PEM electrolyzers and its subsequent volage loss breakdown analysis. Current voltage loss breakdown analyses separate voltage losses into three categories: kinetic, ohmic, and mass transport overpotentials. Current models explain the first two but lack proper phenological description of the latter. To better separate and ascribe the mass transport losses due to electrode and PTL dry-out, a new electrolyzer galvanostatic intermittent titration technique (eGITT) was developed in this work. The time-series data from this pulse-based transient diagnostic evaluated through time-scale analysis and basic physical models to extract key transport properties that can be used to quantify the efficacy of different electrode and PTL materials. Results from this method were compared to current model predictions and evaluated against literature values.
Optimal Dynamic Operation of Grid-Integrated Hydrogen Energy System: A Techno-Economic Analysis
Authors: Haggi Hamed , Brooker Paul , Sun Wei , Fenton James M.
Published: November 2022

Rapidly decreasing costs of solar energy and policies that encourage decarbonization are driving solar photovoltaic (PV) farms to be paired with large scale and longer duration energy storage. Hydrogen generation from renewable energy can provide long-term, clean energy storage and can be used in the power industry through fuel cells or combustion turbines, used as chemical feedstock for industry, or as a fuel for transportation. Production costs of hydrogen via electrolytic methods mainly depends on the electricity price, capital costs, and equipment capacity factors. To be cost effective with other types of energy storage, a desired hydrogen price of $1/kg by 2030 will be needed. This study focuses on a techno-economic analysis of a grid-integrated microgrid that includes hydrogen systems (i.e. electrolyzer, compressor, storage tank, and stationary fuel cell), high penetration of solar PV, and battery energy storage systems. The microgrid is operated in a way to minimize the total operation and investment costs and maximize the revenue of the microgrid owner by exchanging power with the grid. While previous work [1] (one hour steady-state time steps) considered a fixed conversion efficiency for the electrolyzer, this study focuses on dynamic operation of the electrolyzer using polarization curves and non-linear conversion efficiency (modeled based on actual cell voltage, cell current, and Faraday efficiency) for more realistic results.

Simulation results show that the hourly conversion efficiency of the electrolyzer highly depends on stack operating conditions (cell voltage and current density, the size of the electrolyzer, the temperature, hydrogen demand, etc.). This results in different microgrid optimization and scheduling of energy assets, and consequently the hydrogen production cost. Sensitivity analysis on the PV penetration, current density of the electrolyzer, and changes in asset capital costs will be presented.

[1] Hamed Haggi, Paul Brooker, Wei Sun, James M. Fenton, “Hydrogen and Battery Storage Technologies for Low-Cost Energy Decarbonization in Distributed Networks”, arXiv, 11 (2022). https://doi.org/10.48550/arXiv.2202.02711
(Invited, Digital Presentation) Electrocatalyst and Electrolyte Engineering for Oxygen Evolution in Acidic Media
Authors: Escudero-Escribano Maria
Published: November 2022

The slow kinetics of the oxygen evolution reaction (OER) limits the performance of proton exchange membrane (PEM) electrolysers. Only iridium-based oxides are both reasonably active and stable for the OER in acidic electrolytes [1], and high amounts of Ir are needed at the anode of PEM electrolysers. In addition, the lack of stable support materials limits the utilisation of Ir. Designing novel electrocatalysts with enhanced OER activity and stability in acidic media remains a great challenge. In this talk, I will present some recent strategies aiming to understand and engineer the interfacial structure and properties for oxygen evolution electrocatalysis. We have developed self-supported high surface area nanostructured Ir-based networks as highly active electrocatalysts for OER [2]. These networks, prepared by alternating sputtering of Ir and Co, followed by selective Co leaching, show a unique morphology and combine excellent mass activity with promising stability [2]. In addition, our group is working in the development of an easy and affordable method to prepare IrOx catalysts by controlled electrodeposition of Co and Ni in a deep eutectic solvent followed by galvanic displacement [3]. By controlling the conditions during the galvanic displacement, we tune the morphology and thus the electrocatalytic properties for OER. Finally, we have investigated the role of both composition and concentration of the acidic electrolyte (perchloric and sulphuric acid) on the OER electrocatalytic performance of Ir nanoparticles [4]. Our work highlights the key role the electrolyte plays in the performance of Ir-based electrocatalysts during rotating disc electrode measurements.

REFERENCES

[1] M. Escudero-Escribano et al., Journal of Physical Chemistry B
2018, 122, 947.

[2] A.W. Jensen, G.W. Sievers, K.D. Jensen, J. Quinson, J.A. Arminio-Ravelo, V. Brüser, M. Arenz, M. Escudero-Escribano, Journal of Materials Chemistry A
2020, 8, 1066.

[3] F.B. Holde, K.N. Dalby, H. Falsig, P. Sebastián-Pascual, M. Escudero-Escribano, in prep., 2022.

[4] J.A. Arminio-Ravelo, A.W. Jensen, K.D. Jensen, J. Quinson, M. Escudero-Escribano, ChemPhysChem
2019, 20, 2956.