bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Understanding the Structure and Interfacial Chemistry of High Temperature Molten Salts
Authors: Britt Phillip F. , Mahurin Shannon
Published: December 2020

There has been a renewed interest over the past decade in the use of molten salts as coolants and fuels in next-generation nuclear reactors that are used for electricity generation and to supply high-temperature, low-pressure heat. For solid-fuel salt-cooled reactors, molten salts are used as the coolant for solid-fueled reactors that operate at high temperatures (>500 °C) while for liquid salt fueled reactors, fissile, fertile, and fission products are dissolved in a homogeneous molten salt which serves as both the fuel matrix and the primary coolant. Two key challenges with a liquid salt fueled reactor is to manage the solubility and oxidation state of the materials dissolved in the molten salt and to manage the interfacial interactions of the molten salt with the reactor materials to limit corrosion. To understand how the structure and dynamics of molten salts impact their physical and chemical properties, such as viscosity, solubility, and thermal conductivity, as well as chemical reactivity, it is necessary to determine the structure and speciation of the molten salt at the atomic/molecular scale. The Molten Salts in Extreme Environments (MSEE) Energy Frontier Research Center is addressing these challenges through a coordinated experimental and theoretical effort to elucidate the atomic and molecular basis of molten salt behavior, including interactions with solutes and interfaces and under coupled extremes of temperature and radiation. The structure of bulk salt mixtures, such as MgCl2/KCl, and solute speciation in molten salts has been studied to better understand behavior in these complex environments using combined X-ray scattering and spectroscopy, neutron scattering, optical spectroscopy and computational modeling. The chemical and morphological evolution of metal/molten salt interfaces has been examined using X-ray tomography and electron microscopy to better understand corrosion processes in molten salt systems. This presentation will discuss the challenges in molten salt chemistry for nuclear energy applications and highlight recent results in understanding the structure, properties and reactivity of high temperature molten salts.
Corrosion Resistant Cold Sprayed Cladding for Molten Salt Reactors
Authors: Lu Pin
Published: December 2020

The bimetallic structure concept consisting of a corrosion resistant surface layer joined on top of an ASME code-approved substrate becomes a promising solution to address the corrosion issue of ASME substrate materials in molten salt environment. Specifically, refractory materials such as molybdenum, tungsten, and alloys containing them are found to be most resistant in molten salt environment and hence they have great potential to be used as the protective salt-facing surface layer. Due to the well-recognized difficulties of welding/3D-printing refractory materials (i.e., oxidation, brittle phase formation, cracking, etc.), cold spray, a deposition technology that minimizes material heating, avoids undesired thermal effects and maintains dimension stability, is an ideal approach for fabricating the bimetallic components. A corrosion resistant cladding material that is also amenable to cold spray process is desired and has been developed. Promising cladding structure has been designed, and tested by both molten salt corrosion and cold spray trials for down-selection. Prototyping for clad adhesion test will also be conducted as proof-of-concept validation. This program is sponsored by DOE Office of Nuclear Energy.
Corrosion of Metallic Materials in 3LiCl-2KCl and 3LiCl-2KCl-UCl3
Authors: Alimgulov Ruslan , Trubcheninova Anastasia I. , Abramov Aleksandr , Zhilyakov Arkadiy Yu. , Belikov Sergey V. , Rebrin Oleg I. , Polovov Ilya B.
Published: December 2020

High-temperature molten salts are widely used in production and refining of non-ferrous and rare metals, in nuclear technology and solar storage systems. However, application of such technologies is limited by the problem of finding suitable corrosion resistant materials capable of withstanding a prolonged contact with molten salts.Current study is focused on the corrosion of metallic materials in 3LiCl-2KCl-based melts.

Metallic tantalum and molybdenum, nickel-chromium-molybdenum alloys (VDM Alloy C-4, Hastelloy G-35 and specially designed KhN62M alloy) were chosen as the objects of the investigation. Corrosion tests were performed in 3LiCl-2KCl and 3LiCl-2KCl-UCl3 (5 wt. % U) melts. The corrosion tests run for 100 h, and the temperature was varied from 450 to 750 °C. The corrosion rates were determined by both gravimetric technique and chemical analysis of quenched melts. The last technique is very useful in case of alloys formation on the surface of tested samples.

It was found that all the above metallic materials can be used in 3LiCl-2KCl melts at 450 and 550 °C. Increasing working temperature led to intensification of corrosion processes. This effect was more pronounced for nickel-based alloys where increasing temperature to 650 °C also resulted in changing character of the corrosion. The undesirable intergranuluar corrosion was noticed for the nickel-based alloys at 750 °C and this was induced by the formation of secondary phases at the grain boundaries.

Metallic tantalum and molybdenum were subjected to only gradual etching even at 750 °C. Their corrosion rates did not exceed 0.01 mm/year and these materials can be recommended for the application in contact with molten chlorides at 750 °C.

Addition of uranium(III) chloride to the melt led to increasing corrosion rate for all the materials studied. The corrosion mechanism, however, did not change much with temperature. The presence of oxidant (U3+) resulted in acceleration of corrosion etching. The rate of the exchange reaction between uranium chlorides and components of the materials can be accelerated by the formation of U-Ni alloys. Formation of metallic uranium-containing layers on the surface of nickel-based samples deserves a separate attention as an element of possible currentless protection coatings.

The corrosion resistance of tantalum and molybdenum is also sufficient at 750 °C in 3LiCl-2KCl-UCl3 (5 wt. % U). However, it should be remembered that their mechanical properties, weldability, and high-temperature resistance in air are noticeably worse compare to the nickel-based alloys.
Al Electrodeposition in Molten CaCl2 with Various Calcium Aluminates
Authors: Iwai Yuta , Morishige Taiki , Takenaka Toshihide
Published: December 2020

An innovative production process of Al metal is desired to reduce CO2 and perfluorocarbon gas generation. Our previous study showed that calcium titanate and silicate dissolved in molten CaCl2. Ti and Si metals could be electrodeposited, and it was indicated that Ti and Si reductions depended on the molar ratio of CaO to TiO2 or SiO2. In this study, direct production of liquid Al metal was attempted in molten CaCl2 with various calcium aluminates.Molten CaCl2 at 1373 ~ 1573K in an Ar atmosphere was used as a bath. Calcium aluminate (molar ratio of CaO to Al2O3, RCaO/Al2O3 =1.0, 12/7 or 3.0) was prepared by sintering a molded mixture of CaO and Al2O3, and it was added in CaCl2 beforehand. Mo and graphite rods were used a working and counter electrode, respectively. Mo wire was used as a quasi-reference electrode. The cathodic reaction was investigated by cyclic voltammetry, and potentio-static electrolysis was carried out. The electrodeposit was analyzed by XRD and SEM-EDX.Although no sharp current peak was seen, cathode current increased overall with calcium aluminate addition. The shape of CVs slightly changed with RCaO/Al2O3, but RCaO/Al2O3 seemed not to affect Al reduction significantly.Al and Al-Mo alloy were detected in the electrode after the electrolysis at -1.8V at 1573K regardless of RCaO/Al2O3, but the Al amount was very small. So, a Mo cathode with BN receiver in the bottom shown Fig.1 was used to prevent deposited Al metal from running down from the cathode. Al metal covered the surface by electrolysis, and a thick Al-Mo alloy layer was found in its cross section. It was shown that calcium aluminate dissolved in molten CaCl2 above 1573K, and that Al metal could be deposited electrochemically. The molar ratio of CaO to Al2O3 slightly affected the Al deposition though its influence have not clarified well.
Kinetics of Reaction of Oxygen with Uranium(IV) Chloride in Alkali Chloride Melts
Authors: Volkovich Vladimir A. , Ivanov Alexander B. , Ryzhov Alexander A. , Maltsev Dmitry , Griffiths Trevor R.
Published: December 2020

Alkali chloride melts have numerous potential applications in nuclear fuel cycle including pyrochemical reprocessing of spent nuclear fuels, uranium electrowinning and electrorefining. Oxygen is a common technological impurity that can affect uranium speciation and behavior in fused salts. The present work was devoted to studying the reactions of oxygen with solutions of uranium tetrachloride in molten alkali chlorides. The experiments were performed in LiCl–KCl, NaCl–KCl–CsCl and NaCl–CsCl eutectic based melts at 450–750 oC. Pure oxygen and argon–oxygen mixtures (containing ca. 1 and 10 % O2) were used. Amount of oxygen passed through the melt varied from less than one to over 100 moles per mole of uranium present. Effect of moisture (0.4–2.5 % H2O) presence in oxygen or Ar–O2 mixtures was also investigated. The course of the reaction was followed by in situ electronic absorption spectroscopy measurements with the spectra recorded at the certain time intervals.

Depending on temperature, cationic melt composition and oxygen-to-uranium molar ration the reaction resulted in oxidation of uranium(IV) to soluble uranyl chloride and/or precipitation of uranium dioxide. Analysis of the spectra provided the information on kinetics of U(IV) concentration change. Increasing temperature, O2 : U(IV) molar ratio or decreasing mean radius of alkali cations of the solvent melt resulted in faster decrease of U(IV) concentration in the melt.

Under certain conditions U(IV) can be oxidized to UO2Cl4
2– without precipitation of UO2. Therefore sparging the melt with oxygen can be used as a way of separating uranium from certain fission products, for example rare earth elements. Rare earth chlorides react with oxygen yielding oxychlorides or oxides insoluble in alkali chloride melts. Interaction of oxygen with melts containing a mixture of uranium and rare earth chlorides was therefore also investigated and an example of the spectra recorded in LiCl–KCl–UCl4–NdCl3 melt is shown in Fig.

Fig. Spectra recorded in the course of reaction of O2 with LiCl–KCl–UCl4–NdCl3 melt at 550 oC. Arrows show the direction spectra changed.

Figure 1
Molten-Salt Synthesis of Metal Oxide Nanoparticles
Authors: MAO Yuanbing
Published: December 2020

The search for synthesis methods which are simple, green, reliable, scalable and generalizable for functional metal oxide nanoparticles has been an area of interest for many researchers in recent years. Because of its meritorious features including environmental friendliness, low cost, simple to operate, easy to scale-up, etc., molten-salt synthesis (MSS) method becomes an excellent bottom-up synthesis technique of nanomaterials with various chemical compositions and morphologies. In this talk, I will start with the status, potential and challenges of MSS for the synthesis of nanomaterials to give a concise flavor on the importance of synthesis on the properties and application of nanomaterials. I will discuss different aspects of MSS such as the role of used molten salt, the choice of desirable molten salt, the effect of various synthesis parameters, typical oxosalts and their electrochemical aspects. More importantly, I will cover the recent progress of MSS for inorganic metal oxide nanoparticles. Other than the nanomaterials of a few binary oxides synthesized by the MSS, I will highlight how the MSS method has been successful in synthesizing complex metal oxide nanoparticles, such as AMO2 delafossites, AMO3 perovskites, AM2O4 spinels, and A2M2O7 pyrochlores. Specifically, in the past few years, we have focused on the studies of lanthanide and actinide doped pyrochlore AIII
2MIV
2O7 nanoparticles (where A = trivalent rare earth ions, and M = Zr4+, Hf4+, etc.) useful for solid-state lighting, X-ray scintillators, thermometry, bioimaging, and radioactive waste containment. We have achieved substantial tunability of their particle size, crystal phase, and more importantly, luminescence properties. We have gained a clear understanding of the influences of synthesis conditions, particle morphology and composition on their photoluminescence and radioluminescence. Therefore, MSS opens a new avenue for making size and shape tunable nanomaterials for various catalytic, optoelectronic, magnetic and electrical applications.
Utilizing X-Ray Absorption Spectroscopy to Investigate Solute-Solvent Interactions in Molten Salt Environments
Authors: Dias Elaine , Gill Simerjeet , Huang Jiahao , Mausz Julia , Gakhar Ruchi , Roy Santanu , Topsakal Mehmet , Phillips William C. , Layne Bobby H. , Mahurin Shannon , Halstenberg Philip , Dai Sheng , Wishart James F. , Bryantsev Vyacheslav , Frenkel Anatoly
Published: December 2020

Molten Salt Reactors (MSRs) are the leading candidates out of the six-generation IV advanced nuclear power reactor designs chosen for deployment for nuclear energy in US. MSR technology is particularly attractive due to better passive safety, operation at atmospheric pressure, high thermal efficiency, lower spent fuel per unit energy and increased solubility of fission products in molten salts.

To facilitate robust and economical design of such systems, accurate knowledge and fundamental understanding of the structure and speciation of salts and metals in and near molten salt environments is necessary. Speciation of solutes is important because it determines how chemical behavior in solution and complex speciation from fission and corrosion products impact kinetic, thermodynamic, and transport properties of the molten salt systems. Investigating effects of radiation on metallic species and radiation-induced nucleation and growth of metallic nanoparticles under ionizing radiation is crucial for predicting the stability and reactivity of molten salts.

Molten Salts in Extreme Environments (MSEE) EFRC aims to investigate speciation of metals and radiation-induced reactions in molten salt systems by utilizing synchrotron based XAS methods. In our work, Extended X-ray Absorption Fine Structure (EXAFS) and X-Ray Absorption Near Edge structure (XANES) are used to investigate local coordination environment and chemical structure of metal species such as Nickel in Zinc Chloride based molten salt systems. In addition, the effect of metal concentration and temperature on changes in local and chemical structure of metal is studied. XAS studies are complemented by optical ultra-violet spectroscopy studies of molten salts, enabling a direct correspondence between UV-Vis peak shape and coordination geometry and number, determined by EXAFS. Such knowledge of speciation of metals and radiation-induced nanoparticles in molten salt environments will provide critical understanding needed to predict and control the physical and chemical properties of molten salts and corrosion mechanisms in molten salt systems. This work was supported as part of the Molten Salts in Extreme Environments, Energy Frontier Research Center, funded by the U.S. Department of Energy Office of Science.
Corrosion of Metallic Materials in the Molten FLiNaK
Authors: Polovov Ilya B. , Abramov Aleksandr , Alimgulov Ruslan , Zolotarev Daniil A. , Trubcheninova Anastasiya I. , Gibadullina Alfiya F. , Volkovich Vladimir A. , Zhilyakov Arkadiy Yu. , Khotinov Vladislav A. , Belikov Sergey V.
Published: December 2020

Molten ﬂuoride salts can be used as the fuel and coolant for molten salt reactors (MSR) and electrolytes for spent nuclear fuel (SNF) reprocessing. 46.5%LiF-11.5%NaF-42%KF (FLiNaK) melt is the prospective media for these purposes due to their desirable thermophysical and nuclear properties. Finding construction materials with sufficient corrosion and mechanical resistance is the most challenging task for practical implementation of MSR concept.

In the present study the corrosion and mechanical properties of different types of construction materials were investigated. The materials included various low carbon Ni-Cr-Fe-Mo, Ni-Cr-Mo, and Ni-Mo alloys, and metals with relatively positive electrode potentials.

The corrosion experiments were performed in FLiNaK melt at different temperatures (from 550 to 750 °C) in the specially designed stainless steel cells under high-purity argon atmosphere. Corrosion properties of studied materials were investigated under static conditions, and the duration of each test was 100 h to enable the comparison of the experimental data. In a special series of experiments fluorides of typical fissile nuclides and fission products were added to the salt electrolyte to estimate the influence of the red-ox potential on the corrosion resistance of the materials.

Corrosion rates were determined from the weight loss measurements and chemical analysis of quenched melts. Surface and microstructure of corroded samples was examined by various microscopic techniques. Mechanical properties of investigated materials were also studied at the ambient temperature and at 600 °C.

Advantages and limitations of different types of construction materials were evaluated on the basis of data obtained. The effect of temperature on corrosion and mechanical properties of the studied materials were determined. Possible mechanisms of corrosion of various materials in fluoride melts were proposed.

The alloys based on Ni-Cr-Mo and Ni-Mo systems, and molybdenum and its alloys were selected for further long-time tests under dynamic conditions to determine the resource of materials in contact with molten fluorides for MSR and SNF recycling technologies.
(Invited) Evolution of Structural, Transport and Electrical Properties of Binary Ionic Liquids in the Presence of Graphite
Authors: Shah Jindal
Published: December 2020

The flexibility to manipulate various interactions in ionic liquids by changing the cation, anion, or the various functional groups on the ions has drawn researchers to design tailor-made ionic liquids for a given application. Another approach that is gaining importance in tuning the properties of ionic liquids is to form binary, ternary, and reciprocal ionic liquid mixtures. Results from molecular simulations conducted in our research group have demonstrated that the binary ionic liquid mixtures in which two anions are combined in different molar ratios for a given cation can lead to either native or non-native structures in the bulk depending on the difference between the hydrogen bonding ability of the participating anions. The non-native structures differ markedly from those for the pure ionic liquid analogues and impact the physical dissolution mechanism for gases such as CO2.

Given the importance of ionic liquids as electrolytes in the next-generation of batteries, it is likely that such ionic liquid mixtures will increasingly be investigated for their ability to transport ions to and from charged surfaces. However, very little is currently known regarding how the presence of a surface or an interface affects the local and long-range structures of binary ionic liquids. In this talk, we will present our findings from molecular simulation studies by examining the structural response of binary ionic liquid mixtures comprised of a single cation in combination with two anions when presented with a graphite surface. We will compare and contrast these structures to those obtained when binary ionic liquid mixtures are formed with a single anion and two cations and a graphite surface is introduced. Additionally, we will elucidate the influence of graphite on the transport and electrical properties of binary ionic liquids.
Advancing Low Temperature Molten Sodium Batteries By Interfacial Engineering of Ceramic Electrolytes
Authors: Gross Martha , Peretti Amanda , Small Leo J. , Percival Stephen , Rodriguez Mark , Spoerke Erik D.
Published: December 2020

Molten sodium batteries show remarkable promise as large-scale energy storage systems, but their widespread deployment has been limited by high operating temperatures (~300°C), which impacts their lifetime, cost, and reliability. Lowering the battery operating temperature promises substantial improvements in these areas, but the lower temperature introduces new challenges to the battery chemistry, especially related to the solid state ion-conducting separators used in these batteries. Traditionally, the high temperature operation has been required to not only maintain high Na+-ion conductivity of solid electrolytes, such as β”-Al2O3 or NaSICON, but also to improve the liquid-solid interfacial wetting of molten sodium on the solid electrolyte. We are focused on drastically reducing the operating temperature to near the melting temperature of sodium (97.8oC), which leads to poor interfacial wetting of the molten sodium. Poor wetting and ineffective charge transfer can dominate battery resistances resulting in a cell-limiting interface. Here, we will describe the rational design of engineered coatings to improve wetting of the molten sodium on NaSICON at low temperatures near 100°C, and therefore improve charge transfer across this critical interface. Enhanced mating of the separator-sodium interface by means of engineered coatings is demonstrated to result in lower interfacial resistance and higher battery performance at increased current densities. This strategy promises substantial advances in the operation of molten sodium batteries at low temperatures and opportunities to expand the utility of these batteries to meet emerging grid-scale needs.

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.
On the Dependence of Ionic Transport on Crystal Orientation in Nasicon-Type Solid Electrolytes
Authors: Ladenstein Lukas , Lunghammer Sarah , Wang Yan Eric , Miara Lincoln J. , Wilkening Martin , Redhammer Günther , Rettenwander Daniel
Published: December 2020

The dependence of ionic transport on crystal orientations in NaSICON-type solid electroytes is studied on flux-grown M3Sc2(PO4)3 (M = Na, Ag) single crystals with well-defined facets. Herein, we provide the first impedance spectroscopy study to characterize ion conduction along different crystallographic orientations in this important class of materials for electrochemical energy storage systems. Moreover, we used single crystal X-ray diffraction, differential scanning calorimetry, 23Na NMR spin-lattice relaxation measurements, and ab initio molecular dynamics simulations to study the interplay of structure and ion transport taking place at different length scales. We conclude that the phase behavior in NaSICON-type materials is strongly linked to ion diffusion. At room temperature, ionic conductivity is slightly anisotropic along the crystallographic orientations [001] and [100]. The slightly different activation energies are related to diffusion bottlenecks solely changing along [001]. This change is caused by anisotropic thermal lattice expansion. With increasing temperature, ion transport increasingly becomes isotropic finally resulting in an order-disorder phase transition from C2/c to R−3c. This phase transition is associated with a clear change in activation energy solely along [001]; it can be traced back to the increasing jump distance along this crystal orientation with temperature. Astonishingly, changing the ionic charge carrier, i.e., when going from Na+ to Ag+, shifts the phase transition temperature by 140 K toward lower temperature. The Arrhenius behaviour remains, however, similar. This finding is related to the higher mobility of Ag+ in the NaSICON framework leading to isotropic ion diffusion at much lower temperatures. Overall, flux-grown M3Sc2(PO4)3 allowed us to show that ionic transport parameters and phase stability sensitively depend on crystal chemistry.
Mitigating Interfacial Issues in All-Solid-State Batteries
Authors: Liao Jared , Kirner Joel , Zhao Feng
Published: December 2020

All Solid-State Batteries (ASSB), by replacing liquid electrolyte with solvent-free solid electrolyte, have the potential to ultimately resolve the safety issues of Li-ion batteries (LIBs). Although inorganic lithium-ion conductors are available, their practical applications have been mainly hindered by interfacial issues, since it is very challenging to construct intimate contact between the solid electrode and solid electrolyte due to their rigidity in conventional ASSBs, leading to high polarization and low utilization of active materials. Herein, we developed a solid polymer electrolyte (SPE) that exhibits high Li+ conductivity of >1.2 mS/cm at room temperature and wide electrochemical window (~4.8 V vs. Li/Li+), and we also demonstrate a simple but effective interfacial engineering approach to mitigate the poor interfacial contact via in-situ polymerization process. The investigation revealed that the polymerization process of SPE plays a significant role in interfacial resistance between electrodes and electrolytes in large format pouch cells. Complete characterization of ASSBs with two SPE systems (in-situ polymerization vs. ex-situ polymerization) will be compared and presented, as well as the cell lifetime under galvanostatic cycling.
Interfaces and Interphases of All Solid State Battery
Authors: Banerjee Abhik , Wang Xuefeng , Meng Ying Shirley
Published: December 2020

All-solid-state batteries (ASSBs) have attracted enormous attention as one of the future critical technologies for safe and high energy batteries. With the emergence of several highly conductive solid electrolytes (SEs) in recent years, the bottleneck is no longer Li ion diffusion within the SEs. Rather, most ASSBs still suffer from low Coulombic efficiency, poor power performance, and short cycling life, due to the high resistance from the interfaces in ASSBs. Due to the varied chemical/physical/mechanical properties of different solid components in ASSBs as well as the nature of solid-solid contact, many kinds of interfaces are present in ASSBs: these involve loose physical contact, grain boundaries, chemical and electrochemical reactions, to name a few. All of these contribute to increasing resistance at the interface. Here, we will present the distinctive features of the typical interfaces and interphases in ASSBs and summarize the recent work on identifying, probing, understanding and engineering them. We will highlight the complicated but important nature of interphases, namely the composition, distribution, electronic, and ionic properties of the CEI on the cathode side and SEI on the anode; understanding these properties are the key to achieving a stable interface. In addition, conformal coatings to prevent side reactions and their selection criteria are reviewed. We emphasize the significant role of the mechanical properties of the interface as well as the mechanical property of all components, especially when the soft Li metal anode is used under constant stacking pressure. Finally, we provide full-scale (energy, spatial, and temporal) characterization methods to explore, diagnose and understand the dynamic buried interfaces and interphases.
(Invited) Interface Stability in All-Solid-State Batteries
Authors: Battaglia Corsin
Published: December 2020

All-solid-state batteries combining an alkali metal anode and a high-voltage cathode have the potential to achieve high energy density. However, interface stability remains a major challenge. On the anode side, dendrite formation limits the maximum plating current density and prevents fast charging, while on the cathode side the limited oxidative stability of most solid electrolytes is a major challenge, especially when the battery is charged beyond 4 V.

Here we demonstrate that the critical current density for dendrite formation in the archetypical ceramic solid electrolyte Na-β”-alumina is ten times higher than that measured on a garnet-type Li7La3Zr2O12 electrolyte under equivalent conditions and reaches up to 12 mA/cm2 at room temperature [1]. Further, we show that above the melting temperature of sodium, a cumulative capacity of >10 Ah of sodium can be plated and stripped at an enormous current density of 1000 mA/cm2 without dendrite formation [2].

On the cathode side, we have been developing hydroborate solid electrolytes reaching ionic conductivities >1 mS/cm at room temperature [3]. We already demonstrated the integration of these electrolytes with a 3 V class cathode [4, 5], but recently managed to obtain stable cycling with a 4 V class cathode through the formation of a passivating interface [6]. Combined with their low gravimetric density <1.2 g/cm3, low toxicity, high thermal and chemical stability, stability vs lithium and sodium metal anodes, soft mechanical properties enabling cold pressing [4], compatibility with solution infiltration [7], and potential for low cost [8, 9], hydroborate electrolytes represent a promising option for a competitive future all-solid-state battery.

[1] M.-C. Bay, M. Wang, R. Grissa, M. V. F. Heinz, J. Sakamoto, C. Battaglia, Adv. Energy Mater. 2019, 201902889

[2] D. Landmann, G. Graeber, M. V. F. Heinz, S. Haussener, C. Battaglia, submitted

[3] L. Duchêne, A. Remhof, H. Hagemann, C. Battaglia, Energy Storage Mater. 2020, 25, 782

[4] L. Duchêne, R.-S. Kühnel, E. Stilp, E. Cuervo Reyes, A. Remhof, H. Hagemann, C. Battaglia, Energy Environ. Science 2017, 10, 2609

[5] R. Asakura, L. Duchêne, R.-S. Kühnel, A. Remhof, C. Battaglia, ACS Appl. Energy Mater. 2019, 2, 6924

[6] R. Asakura, D. Reber, L. Duchêne, A. Remhof, H. Hagemann, C. Battaglia, submitted

[7] L. Duchêne, D. H. Kim, Y. B. Song, S. Jun, R. Moury, A. Remhof, H. Hagemann, Y. S. Jung, C. Battaglia, Energy Storage Mater., 2020, 26, 543

[8] A. Gigante, L. Duchêne, R. Moury, M. Pupier, A. Remhof, H. Hagemann, ChemSusChem 2019, 12, 4832

[9] S. Payandeh, R. Asakura, P. Avramidou, D. Rentsch, Z. Lodziana, R. Cerny, A. Remhof, C. Battaglia, Chem. Mater. 2020, 32, 1101
Effects of Synthesis Method and Parameters on Electrochemical Performance in Li-Conducting Garnets
Authors: Weller Jon , Chan Candace K.
Published: December 2020

Lithium conducting garnets such as lithium lanthanum zirconate (Li7La3Zr2O12, LLZO) are of great interest as ceramic solid electrolytes for solid-state lithium-metal batteries. Various synthetic approaches have been investigated for LLZO such as sol-gel, co-precipitation, thin film deposition, spray pyrolysis, combustion, and molten salt synthesis (MSS), not to mention the standard solid-state reaction (SSR) method. Most of the aforementioned methods have been used to form LLZO electrolytes with high ionic conductivity and density, each with benefits as well as some drawbacks such as cost, high processing temperatures, complexity, or difficulty of producing fine powders for thin films of LLZO. Further, there are many discrepancies between important performance parameters such as ionic conductivity reported in the literature, implying that achieving the highest performance is not completely straightforward and that the details of the synthetic route have substantial effects on the resultant materials properties. Herein, Ta-doped LLZO of nominal composition Li6.4La3Zr1.4Ta0.6O12 is investigated as a representative example, and is synthesized by various MSS routes as well as SSR for comparison, covering a wide temperature range (as low as 400 °C for MSS and up to 1000 °C for SSR). By using different synthesis methods for the same target material, the differences in ionic conductivity, sinterability, and other properties as a result of the peculiarities of individual synthetic approaches are investigated. Interestingly, elemental inhomogeneity on the order of individual LLZTO grains is observed to varying degrees in each of the synthesis methods investigated, with more inhomogeneity correlated with reduced performance in sintered LLZTO, implying that strict control over garnet phase formation is required to achieve optimal performance. Some advantages of MSS for LLZTO are presented and the thermodynamic and kinetic origins of compositional inhomogeneity are discussed, as are solutions and strategies to mitigate this inhomogeneity.
Integrated Modeling Framework for Investigating Multiscale Microstructural Impacts on the Ionic Conductivity of Garnet Solid Electrolytes
Authors: Heo Tae Wook , Grieder Andrew , Akhade Sneha A , Wan Liwen , Adelstein Nicole , Wood Brandon C.
Published: December 2020

Although recent years have seen the emergence of several solid electrolyte candidates with intrinsically high ionic conductivities for all-solid-state batteries, practical processing and synthesis routes often generate grain boundaries and other interfaces that can perturb primary conduction channels. In this talk, we will present our development of a multiscale modeling framework for predicting the effective ionic conductivity through a solid electrolyte with a complex polycrystalline microstructure, which allows us to address challenges associated with directly probing these effects. We first demonstrate an efficient mesoscopic computational method for predicting the effective ionic conductivity through a solid electrolyte with a complex polycrystalline microstructure. By considering the interplay between concurrent grain boundary and bulk conduction modes, this method surpasses simplified circuit descriptions to account for realistic, nontrivial networks of conduction channels. Using the Li7-x
La3Zr2O12 (LLZO) garnet solid electrolyte as a technologically relevant model system, we then parameterize our simulation framework using a multiscale approach that connects synthetic microstructures from phase-field simulations with diffusivity tensors from molecular dynamics simulations of ordered and disordered systems. Systematically designed simulations of the effective ionic conductivity of polycrystalline LLZO are applied to elucidate the relationship between relevant microstructural features and overall ionic transport properties, with a focus on topological features of grains and grain boundary networks. In particular, we will discuss atomistic and mesoscopic tunability of grain boundary and microstructure, respectively, controlling mass transport in LLZO. We identify specific instances in which competition between conduction modes results in a high sensitivity to microstructural features, highlighting the need to account for the detailed microstructural information when assessing mass transport in LLZO and related solid electrolyte materials, while simultaneously offering design guidance for achieving desired ionic transport properties in processed polycrystalline LLZO.

This work of was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
(Keynote) Transport and Mechanical Property Targets for Enabling Solid State Batteries
Authors: Barai Pallab , Kim Hong-Keun , Srinivasan Venkat
Published: December 2020

Solid state batteries have become a popular topic of research in the past few years, driven by recent discoveries of solid ion conductors with high ionic conductivity. With these developments, the old problems of dendrite growth and the new problems related to interface delamination between the cathode and the solid electrolyte have become a focus of the research. While new materials are being researched that show promise, they suffer from a combination of low ionic transport properties to provide the necessary rate capability and/or from insufficient mechanical strength to prevent dendrites.

Over the past several years, we have been developing mathematical methods that combine electrochemical effects (kinetics, mass transfer and ohmic) with mechanical interactions (elastic deformation, plastic deformation, and fracture) to understanding the role of material properties and operating conditions on the chemo-mechanics at the interface of both Li-metal anode and of the oxide cathode. These models have provided deep insights into the present status of polymers when used in electric vehicle applications and the targets to achieve the necessary energy and power requirements. In addition, these models have helped understand the reason for the formation of dendrites and interface delamination on the cathode/solid electrolyte interface and the targets to prevent these detrimental phenomena. Studies provide insights into the role of soft and hard materials, impact of cell pressure, and the importance of transference number on cell behavior.

In this talk, we will summarize the research efforts around solid state batteries and call attention to the controlling factors that need to be the focus of future material innovations.
Quantifying the Influence of the Electrode Porous Structure on Lithium-Ion Battery Performance
Authors: Gulsoy Begum , Atalay Selcuk
Published: December 2020

The growing demand of lithium-ion batteries (LIBs) on portable electronics, electric vehicles urgently requires higher energy density, longer cycling life, and better safety to satisfy the needs of environmental factors and economics. In order to have higher energy density, simply increasing the volume of the single electrodes of LIB results in poor capacity due to inefficient mass transport of Li ions through the irregular microstructure of the electrode. Since understanding the influence of geometrical properties electrodes is of considerable significance to battery performance, we investigate two basic cells: (i) an irregular microstructure intercalation host and (ii) a periodically aligned microchannel intercalation hosts. Our in-house developed simulation tool solves Nernst-Planck and electron conduction equations with proper interfacial reactions by considering experimentally verified ageing mechanism (2-layered SEI and lithium-plating) into account and compute the associated characteristic voltage vs. state of charge curves under various geometric and design parameters. The proposed model is parameterized and optimised for mass transport based on fresh cell and validated against experimental results available on the literature. We show that the nanostructured electrode design yields better battery performance because the uniformity of electrodes yields elimating the nonuniform intercalation and side reactions on active material electrode surface. This work presents a design concept for higher energy and power densities that are not limited to LIBs.

*This work has been supported by The Warwick Research Development Fund, UK, through the Grant No. RDF19035.

Figure 1
Electrolyte Effects on Single Crystal Cyclic Voltammograms
Authors: Jensen Kim Degn , Bagger Alexander , Petersen Amanda Schramm , Wan Hao , Rossmeisl Jan , Escudero-Escribano María
Published: December 2020

Insights into the governing mechanisms relevant for electrocatalytic energy conversion is of fundamental interest for future energy schemes aimed at combating fossil dependence and anthropogenic CO2 emissions.1 Electrocatalytic reactions occur at an electrode’s surface-electrolyte interface (see figure 1a). In this interface both geometric and electronic effects determine the selectivity and efficiency of the electrocatalytic reaction.2,3 Simultaneously, the structure and properties of the electrochemical interface are affected not only by the potential applied to the electrocatalyst, but also the pH of the solute4 as well as the cations/anions present in the electrolyte.3,5

Given recent advances on the generalized computational hydrogen electrode (GCHE)6 it is now possible to predict the most probable surface structure using ab initio molecular dynamics (AIMD) and density functional theory (DFT). These structures can be represented as 2D phase diagrams of the interface at any given potential. Herein, we present the basic methodology for creating such diagrams and how to correlate these with experimental cyclic voltammograms (CVs).7 CVs of Pt(111) under different electrolyte conditions (see figure 1b) have been investigated using a rotating disk electrode (RDE) setup and compared with DFT calculations. Our work addresses the impact cations, anions and pH have on the surface of Pt(111) electrodes and what one may extrapolate when contemplating real fuel cell devices.

We herein show that combining experimental model studies with theoretical calculations through the GCHE framework opens up for a new and powerful tool for interpreting CVs of well-ordered metallic M(hkl) interfaces8 for a wide range of electrocatalytic reactions.

References

S. Chu, and A. Majumdar, Nature, 488, 294–303 (2012);

K. D. Jensen, J. Tymoczko, J. Rossmeisl, A. S. Bandarenka, I. Chorkendorff, M. Escudero-Escribano, and I. E. L. Stephens, Angew.
Chemie Int. Ed., 57, 2800–2805 (2018);

D. Strmcnik, M. Escudero-Escribano, K. Kodama, V. R. Stamenkovic, A. Cuesta, and N. M. Marković, Nat. Chem.,
2, 880–885 (2010);

A. Bagger, L. Arnarson, M. H. Hansen, E. Spohr, and J. Rossmeisl, JACS, 141, 1506–1514 (2019);

R. Rizo, E. Herrero, and J. M. Feliu, PCCP, 15, 15416 (2013);

J. Rossmeisl, K. Chan, R. Ahmed, V. Tripkovic, and M. E. Björketun, PCCP,
15, 10321 (2013);

J. Rossmeisl, K. D. Jensen, A. S. Petersen, L. Arnarson, A. Bagger, and M. Escudero-Escribano, Submitted-under review, (2020);

A. Bagger, R. M. Arán‐Ais, J. H. Stenlid, E. Campos dos Santos, L. Arnarson, K. D. Jensen, M. Escudero‐Escribano, B. R. Cuanya, and J. Rossmeisl, ChemPhysChem, 20, 3096-3105 (2019);

Figure 1
Mechanistic Insights on Enhanced Activity of Cu-Deposited Fibrous Electrocatalyst for Oxygen Evolution Reaction
Authors: Morinaga Asuka , Uchiyama Shunsaku , Tsutsumi Hiromori , Katayama Yu
Published: December 2020

Water electrolysis is an ideal method for producing hydrogen, which is expected as a next-generation energy carrier. However, the sluggish reaction kinetics of the oxygen evolution reaction (OER) limits the overall energy efficiency.1,2 Therefore, designing efficient electrocatalyst for the OER is crucial and has been studied extensively for more than a few decades.3 Precious metal catalysts such as RuO2 and IrO2 exhibit high activity,4,5 but are expensive, and transition metals have been attracted as alternative catalysts.6

In this study, a fibrous Cu catalyst was synthesized as a highly active and low-cost OER catalyst. An electrospinning method was selected to synthesize a fibrous polymer substrate, which was subsequently coated with Cu by electroless deposition. We applied Cu, which is a low cost and has excellent electrical conductivity as an electrocatalyst. As a geometric structure, fiber shape was adopted to increase the specific surface area and improving the diffusion efficiency of the catalyst. We selected PVdF-HFP as catalyst support, to promote the diffusion of the ions in the electrolyte and enhance the activity as a catalyst by its ferroelectricity.

In order to clarify the effect of geometric structure on the OER activity, Cu catalysts were synthesized by various methods, including drop-casting, impregnation, and electrospinning. It was found that the fibrous Cu catalyst exhibited the best OER activity amongst all the geometric structures tested in this study, probably due to the increased active surface area as well as better mass transport and diffusion. Furthermore, the effect of the dielectric properties of PVdF-HFP on the OER activity was clarified. The molecular orientation of PVdF-HFP was evaluated by infrared (IR) spectroscopy, which indicates that the stretching and annealing treatment can effectively increase its electric polarizability. Linear sweep voltammetry (LSV) confirmed that the fibrous Cu catalyst with stretching and annealing treatment showed superior OER activity compared to the pristine fibrous Cu catalyst, indicating the large electric polarizability also enhanced the OER.

Based on these results, it was clarified that the improvement of the OER activity of the fibrous Cu catalyst was due to the following reasons; (i) improvement of mass transport by fibrous structure, and (ii) optimization of the OER reaction energetics by catalyst(Cu)-support(PVdF-HFP) interaction. Optimizing both geometry and electronic structure of the electrocatalyst provides a new design strategy to achieve improved activity towards oxygen evolution reaction.

1 Seh, W. Z. et al., Science.
2017, 355, eaad4998.

2 Fabbri, E. et al., Catal. Sci. Technol.
2014, 4, 3800–3821.

3 Jiao, Y. et al., Chem. Soc. Rev.
2015, 44, 2060–2086.

4 Lee, Y. et al., J. Phys. Chem. Lett.
2012, 3, 399–404.

5 Paoli, A. E. et al., Chem. Sci.,
2015, 6, 190–196.

6 Hong, T. W. et al., Energy Environ. Sci.
2015, 8, 1404–1427.
Development of Anode Wicks for Liquid Metal Sodium Batteries
Authors: Kim Hwa-Jung , Choi Hanul , Park Inchul , Park Yoon-Cheol , Moon Jiwoong , Yang Choongmo , Sprenkle Vincent , Li Guosheng , Jung Keeyoung
Published: December 2020

One of the major technical hurdles in developing liquid metal sodium batteries, such as sodium beta-alumina batteries (NBBs), is designing an anode wick which is responsible for facile shuttling of liquid metal and electrons upon cycling. The anode wicks utilize either or both principles of the capillary effect via sophisticated design of its geometry, and the surface tension between the wick and liquid metal via surface treatment of the wick material. It's geometry and surface treatment should be carefully selected because its shuttling capability strongly depends on the travel distance of liquid metal, ranging from tens of microns to over a centimeter, and cell operation temperature especially when the operation current is high.

In this study, different types of anode wicks are devised based on the two principles. The wicks are implemented to one of the most promising liquid metal batteries with Na-NiCl2 chemistry, and their performances are evaluated by varying current densities upon cell cycling.
Comparison of Machine Learning Methods in SOC Estimation of Lithium-ION Batteries
Authors: Miao Shan , Katayama Noboru
Published: December 2020

In recent years, demand for fuel cells and storage batteries is increasing. In particular, lithium ion batteries are very popular as batteries of small electronic devices such as mobile phones and laptop computers because they have very high energy density and can easily output high voltage. As effects of temperature, charging / discharging cycle and degradation, It is difficult to accurately determine the SOC (State of Charge) of the battery under use. Equivalent circuit model is usually used as the SOC estimation method. Although it has high robustness, it has the drawback that design of equivalent circuits and calculations are complicated and difficult. In this study, the impedance of the lithium ion battery was measured by AC impedance method. The measured impedance locus was used as the input layer, and the output layer was SOC. Machine learning methods such as SVM(Support Vector Machine) and SVR(Support Vactor Regerssion) were used to estimate the SOC. It is well proved that the estimation of SOC is possible by the machine learning method. According to the comparation of the result of each method, an optimum method was obtained.