bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigating a Novel Layer-By-Layer Coating Electrode Manufacturing Process for High Energy Batteries
Authors: Wu Qiang , Zheng J.P.
Published: February 2020

Within the decades, there has been immense effort focused on reducing the cost and increasing energy density of energy storage devises. Optimizing cell engineering through tuning the electrode architecture is a straightforward approach to meet the cost and performance requirements of different application.

Layer-by-layer architectures have been proposed to provide precise control over the spatial arrangement of electrode materials, as well as tailoring various electrode components or formulations in each layer for specific purpose [1]. This facile multi-layer of the electrode structure can be created by layer-by-layer coating process, which can enable lower the cost and increase the energy density by manufacturing of thick battery electrodes.

Here we present a systematic study where the layer-by-layer coating process is investigated in order to identify the best possible combination of multi-layer low cost and high energy density electrodes. The silicon and graphite based materials are evaluated for the multi-layer anode. Both wet and dry methods are used to make multi-layer anode electrode including conductive layer, silicon-based anode layer and graphite anode layer. Free standing graphite anode sheet made by our advanced dry coating electrode technology [2] provide the facile way for the layer-by-layer coating process. In addition, the electrochemical performance of electrode with various binders such as CMC, PAA and Na alginate are also compared.
Manufacturing Method for Large-Format, Rechargeable Zn-Sponge Electrodes
Authors: Hopkins Brandon J. , Chervin Christopher N. , Parker Joseph F. , Long Jeffrey W. , Rolison Debra R.
Published: February 2020

Rechargeable zinc (Zn) batteries are safe, sustainable, and energy-dense alternatives to Li-ion batteries. Recent advances, such as monolithic Zn-sponge electrodes, have enabled long cycle lives by suppressing the formation of short-circuiting dendrites even after deep levels of discharge and charge. A substantial barrier, however, to their widespread adoption has been their poor mechanical integrity. Our previous Zn-sponge electrodes had uniaxial compressive strengths near 0.01 MPa. With such a compressive strength, the sponge electrode can break under its own weight if cantilevered with planar dimensions beyond 1 cm with a thickness of 0.2 cm. If the mechanical strength were enhanced while preserving electrochemical performance, Zn-sponge electrodes could be used in next-generation grid-storage, electric-vehicle, and personal-electronic batteries. Here, we present a manufacturing process that optimizes the reinforcing zinc-oxide shell over the fused zinc-sponge core. The presence of the oxide shell boosts the compressive strength of the sponge with respect to our previous version by 9,900%, yielding a plateau stress of 1 MPa. This increase in strength enables the fabrication of large, thin Zn-sponge electrodes (12×12×0.2 cm) for large-format applications. When paired with a nickel electrode, the reinforced Zn-sponge electrode displays rechargeability and high system energy density.
A Facile and Scalable Processing Method for 3-D Nanostructured Copper Current Collectors to Enable High Energy Li-Metal Batteries
Authors: Ma Yifan , Ma Xuetian , Chen Hailong
Published: February 2020

Lithium metal is a promising anode for high-energy-density batteries owing to its high theoretical capacity and highly negative electrochemical potential. However, its commercial application is stalled by the undesired dendritic growth of lithium during cycling.[1]Among all kinds of promising approaches (e.g. electrolyte engineering, interfacial engineering, use of solid electrolyte and use of 3-D structured current collectors, etc. )
[2], 3-D structured current collectors represent some new promises as they can effectively increase Li nucleation sites and reduce local current. However, most of these successes are at lab-scale with coin cells and most of the methods are sophisticated and expensive, not scalable and compatible with the roll-to-roll manufacturing processes of current Li-ion battery industry.

Here we report a facile electrodeposition process for low- cost, scalable fabrication of copper current collectors with 3-D architected porous structures composed of interconnected Cu nanoparticles.[3]Compared to flat foil current collectors, the deposited 3-D nanostructured Cu current collector has much larger active surfaces area, thus effectively reduces the actual current density for the same apparent current and lowers the possibility of triggering dendritic growth. During Li plating process, Li can be accommodated in the porous structure and on the top surface of the 3-D nanostructured Cu current collector, which effectively suppresses Li dendrite formation and provides a very high practical Li storage areal capacity. The nanoporous electrodeposition coated Cu foil can be produced with very low cost and this foil can be seamlessly incorporated into current Li-ion battery production with no major modifications required. The electrodeposition method also provides great flexibility and tunability of the deposited structure, which suggests more Li may be accommodated and ultrahigh energy density batteries may be developed along this promising approach.

Harry, K.J., et al., Detection of subsurface structures underneath dendrites formed on cycled lithium metal electrodes.Nat. Mater., 2014. 13(1): p. 69-73.

Lin, D., Y. Liu, and Y. Cui, Reviving the lithium metal anode for high-energy batteries.Nat. Nanotechnol, 2017. 12(3): p. 194-206.

Ma, X., Z. Liu, and H. Chen, Facile and scalable electrodeposition of copper current collectors for high-performance Li-metal batteries.Nano Energy, 2019. 59: p. 500-507.
Scalable Porous Metals from Lithium Alloys
Authors: Han Sang Yun , Boebinger Matthew G , Yeh David , McDowell Matthew T
Published: February 2020

Nanoporous metals are often fabricated from bimetallic alloys via selectively dissolving one of the chemical elements of the alloy. Porous metals can feature superior mechanical properties per unit mass, as well as high surface areas. Because of the unique mechanical and structural properties, porous metals have a variety of applications, including radiation shields, electrocatalysts, sensors, and as electrode materials for batteries. Recently, An et al. found that dealloyed silicon with a nanoporous structure can overcome mechanical degradation during cycling in lithium batteries, resulting in significantly improved capacity retention of the electrode during cycling [1]. Although this finding is useful and attractive for energy storage devices, scaled production of porous materials has remained a challenge because of fabrication difficulties such as fracture of the monolith and diffusion limitations. Here, we examine the dealloying process of lithium metal alloys, and we show the controlled chemical dealloying can lead to the large-scale fabrication of a variety of different porous metals (in particular, Sn and In). Lithium is chemically alloyed with different low-melting point metals at relatively low temperature (< 300 °C), and the lithium is then removed by controlled exposure to different solvents for various times. Because Li-rich alloys contain 60-75 atomic % lithium, removal of lithium results in the formation of porous structures with continuous ligaments a few microns in size for the cases of In and Sn. X-ray diffraction showed that the lithium was completely removed after dealloying, and crystalline oxide formation was minimal. Interestingly, other lithium alloys (ex. Li-Bi, Li-Sb) do not form continuous ligaments under similar conditions; instead, the metal structures collapse and pulverize to form particles. The porous metals fabricated here were used as anodes in different types of lithium-based batteries, and overall volume changes of the electrodes were found to be less substantial than pure metals, with promising cycling performance. This work demonstrates a simple chemical method for creating porous metals that may find beneficial use for battery electrodes, as well as other applications.

An, W. et al. Scalable synthesis of ant-nest-like bulk porous silicon for high-performance lithium-ion battery anodes. Nat. Commun. 1–11 (2019). doi:10.1038/s41467-019-09510-5
(Invited) Towards Scalable Manufacturing of Solid State Batteries
Authors: Doeff Marca , Yi Eongyu , Shen Hao , Chen Guoying , Sofie Stephen
Published: February 2020

The use of ceramic electrolytes like LLZO (variants of Li7La3Zr2O12) hold great promise for improving safety and increasing practical energy densities of batteries with lithium metal anodes. However, the thin film configurations that are currently employed in devices based on ceramic components are not readily scalable, limiting the applications for which these batteries can be used. Moreover, practical energy densities fall far short of the theoretical values because of the low areal capacities of the cathodes. We are currently exploring an alternate approach to the fabrication of solid state batteries based on a low-cost, eco-friendly, and continuous processing method known as freeze tape casting (FTC). In this method, an aqueous slurry of LLZO (or any other ceramic electrolyte of interest) is tape cast over a cold surface. If the conditions are selected correctly, columnar ice crystals form in such a way as to exclude particles. The ice is then removed by freeze-drying, resulting in a porous green body, which then can be sintered to strengthen the pore walls. By changing formulations, temperatures, and other experimental parameters, the thicknesses, porosities, and pore sizes of the scaffolds can be varied. The resultant porous scaffolds can then be infiltrated with active material and other components to make composite cathodes. The low tortuosity of the pores (approaching t=1) in a typical FTC scaffold is beneficial for the infiltration process and also shortens lithium diffusion pathways.

A goal is to make electrodes similar in thicknesses and loadings to what is used for cathodes in conventional lithium ion batteries (~100 mm, >75 vol.% porosity), to maximize energy density. Freestanding scaffolds this thin are somewhat fragile. Supporting the porous layer on a thin, dense electrolyte layer results in a more robust configuration. A lithium foil can then be attached to this bilayer to form the cell. A porous/dense/porous trilayer has additional manufacturing advantages. In this sort of configuration, lithium metal or another anode material is infiltrated into one of the porous layers, and a cathode material (and other components) into the other.

For this talk, we will discuss the challenges of fabricating solid state cells for large scale applications like electric vehicles, and show examples of FTC components and cells made in our labs.
Large Enhancement of Oxygen Surface Exchange Kinetics in Ruddlesden–Popper Thin Films By Thickness Controlled Strain
Authors: Zhu Shiyue , Yang Gene , Jung Wonsang , Lee Yueh-Lin , Huang Kevin , Lee Dongkyu
Published: February 2020

The design of highly active catalysts for the oxygen reduction reaction (ORR) that leads to the majority of efficiency loss is a critical requisite in the needs of intermediate temperature solid oxide fuel cells (SOFCs). Introducing the lattice strain of an epitaxial film induced by lattice mismatch with a substrate enables a new way to enhance the ORR at elevated temperatures. However, very limited available electrolytes to induce strains in high temperature electrochemical applications, in which yttria-stabilized zirconia (YSZ) uniquely satisfies both the growth requirements (i.e. lattice mismatch) and the electro-chemical requirements (i.e. ionic conductor and electronic insulator) impose a constraint on applying the lattice strain. The limited choice of substrates imposes a constraint on the range of lattice strains, which suggests the need to develop a new strategy to modulate the epitaxial strain for designing catalytically active materials.

In this work, we explore the dramatically enhanced ORR kinetics in the Ruddlesden–Popper oxide, LaSrCoO4 (LSC214), which have been highlighted as alternative cathode materials for intermediate temperature SOFCs grown on (001) YSZ substrates using film thickness to control the epitaxial strain. Pulsed laser deposition (PLD) is employed to deposit LSC214 thin films with four different film thicknesses. Electrochemical impedance spectroscopy (EIS) results demonstrate that the oxygen surface exchange coefficient (k
q) values of ~ 15 nm LSC214 thin film with only ~1 % in-plane tensile strain can be dramatically enhanced by up to two orders of magnitude compared to fully relaxed thicker films (~70 and 140 nm). We find that this enhancement is strongly associated with a change of the surface chemistry revealed from Auger electron spectroscopy (AES), which can lead to a change of the electronic structure, the oxygen 2p band center relative to the Fermi energy level. In addition, we also show no discernible change in the k
q values at low oxygen partial pressures regardless of the film thickness. This result suggests that the rate-limiting step for the oxygen surface exchange in LSC214 thin films changes depending on the oxygen partial pressure. Our work illustrates that controlling thickness is a new strategy to design highly active oxide materials for applications of complex oxides in the solid-state electrochemistry.
Catalyst-Coated PrBa0.8Ca0.2Co2O5+Δ Cathode with High Cr-Poisoning Tolerance for Intermediate-Temperature Solid Oxide Fuel Cells
Authors: Niu Yinghua , Chen Yu , Zhang Weilin , He Weidong , Liu Meilin
Published: February 2020

Intermediate-temperature solid oxide fuel cells (IT-SOFCs) have potential to be a very promising technology for direct conversion of a wide variety of fuels to electricity. However, the commercialization of IT-SOFCs is hindered by several technical challenges. For example, volatile chromium species from interconnect materials often accumulates on the cathode surface or the cathode/electrolyte interface[1], resulting in degradation in electro-catalytic activity for oxygen reduction reaction (ORR) of the cathode. Further, the presence of water vapor can exacerbate the effect of Cr poisoning[2]. Thus, the development of a cathode material with high resistance to Cr poisoning in the presence of water is urgently needed. Recently, a double perovskite PrBa0.8Ca0.2Co2O5+δ (PBCC) cathode with high ORR activity and excellent tolerance against CO2 has attracted much attention[3]. However, its tolerance to Cr poisoning and long-term durability under realistic operating conditions are yet to be characterized. Inspired by our previous studies [4], a number of catalysts are used to modify the surface of PBCC cathode in order to enhance its tolerance to Cr poisoning. As shown in Figure 1a, the measured apparent ORR activation energy is ~1.09 eV for the bare PBCC cathode, as determined from the slope of the Arrhenius plots of kinetics studies. The apparent activation energies for PBCC cathode infiltrated with Ce0.8Sm0.2O1.9 (SDC), La2NiO4 (LN), Ba0.5Co0.5Ox (BaCo), PrOx, and PrNi0.5Mn0.5O3 (PNM) are 0.98 eV, 0.86 eV, 0.87 eV, 0.91 eV, and 0.91 eV, respectively. PBCC coated with La2NiO4 shows the lowest activation energy. As shown in Figure 1b, PBCC cathodes coated with La2NiO4 and Ba0.5Co0.5Ox also show better durability than bare PBCC and other cathodes towards Cr-poisoning (even when the water content was ~7 v%). For instance, the polarization resistance (Rp) of the bare PBCC cathode increased from 0.056 Ω·cm2 to 0.235 Ω·cm2 after operation at 650℃ for ~220 hours in air with 3 v% H2O and then for 140 hours in air with 7 v% H2O; in contrast, the Rp for the Ba0.5Co0.5Ox-coated PBCC cathode remained less than 0.050 Ω·cm2 under the same testing conditions. Among all electrodes studied, La2NiO4 and Ba0.5Co0.5Ox coated PBCC cathodes show the best durability against Cr-poisoning.

Figure 1
Rapid Reactive Laser Processing of Protonic Ceramics
Authors: Mu Shenglong , Huang Hua , Zhao Zeyu , Zou Minda , Hong Yuzhe , Lei Jincheng , Kuzbary Patrick , Wan Nathan , Brinkman Kyle S , Peng Fei , Xiao Hai , Tong Jianhua
Published: February 2020

Protonic ceramics possess low transport activation energies, which allow for high ionic conductivity at low operating temperatures (250–600°C). The protonic ceramic energy devices such as protonic ceramic fuel cells, protonic ceramic electrolyzers, solid state ammonia synthesis cells, hydrogen or water sensors, steam permeable membrane reactors, and hydrogen permeable membrane reactors, etc., have attracted significant attention recently. It has been recognized that the processing of protonic ceramics with high phase purity and controlled microstructure is equally significant compared with the development of new materials. Though the recently discovered solid state reactive sintering method has been proven as an effective method for processing of protonic ceramics from cost-effective raw materials such as oxides and carbonates, the traditional long-term (more than 10 hours) furnace sintering at high temperatures (>1400°C) is still inevitable. In this work, by combining the selective laser sintering/melting technique and the solid state reactive sintering technique, we developed a new rapid laser reactive processing method for selectively and instantaneously processing protonic ceramics with well-engineered microstructures and high phase purity. More than 10 perovskite oxides and cermets have been successfully fabricated for using as the protonic electrolyte and highly porous protonic electrode scaffolds.
Multi-Scale Modeling of Anode-Supported Solid Oxide Fuel Cell
Authors: Jeon Dong Hyup
Published: February 2020

Three-dimensional comprehensive model of micro-scale transport in positive electrode/ electrolyte/negative electrode(PEN) and macro-scale transport in gas channel of anode supported SOFCs (solid oxide fuel cells) is developed in object-oriented CFD code Open Field Operation and Manipulation (OpenFOAM). The numerical procedure consists of calculations of complex phenomena which are fully coupled together with electrochemical reaction kinetics, mass balance, and energy balance, interacting between porous PEN structure and fluid gas channel. Computational fluid dynamics (CFD) was performed in flow channels with calculations of mass balance and continuum micro-scale model were used to predict the electrochemical characteristics in PEN. The distributions of current density and mass fraction are employed to suggest a dependency. To validate our numerical model, we compare the simulated results with experimental data at intermediate temperatures. This study provides detailed information of heat and mass transport phenomena with electro-chemical characteristics for intermediate temperature SOFCs.

References

[1] OpenFOAMⓇ, 2016, User and
Programmer’s Guide, OpenCFD Ltd., available from http://www.openfoam.com.
Yb Doping Effects on Structure and Performance of BaCo0.7Fe0.3-XYbxO3-Δ Perovskite
Authors: Yang Chunyang , Gan Yun , Lee Myongjin , Ren Chunlei , Xue Xingjian
Published: February 2020

Fe partial substitution for Co on B-site may tradeoff stability-activity for BaCoO3-δ perovskite. However, large radius mismatch between Ba and Co/Fe favors the formation of a low symmetric hexagonal phase BaCo1-xFexO3-δ, which may experience phase structural transitions with varying temperatures and could induce structural reliability issue of associated devices. The B-site doping with high valence elements may facilitate to form cubic BaCo1-xFexO3-δ perovskite, it could also significantly deteriorate their catalytic property. The Yb3+ with ionic radius being larger than those of Co4+ and Fe4+ could be used as B-site dopant to tune Goldschmidt tolerance factor of BaCo1-xFexO3-δ to 1 and therefore stabilize its cubic structure. Additionally, the electronegativity of Yb is lower than that of Co and Fe. This would induce a slightly lower valance of Co and/or Fe when Yb is used as B-site dopant, facilitating oxygen vacancy generation and electrochemical kinetic process. In this research, Yb-doping effects on crystal structure and performance of BaCo0.7Fe0.3-xYbxO3-δ (x = 0.05, 0.10 and 0.15) are systematically evaluated. The results indicate that Yb partial substitution for Fe on B-site is able to effectively stabilize crystal structure with highly cubic symmetry and BaCo0.7Fe0.2Yb0.1O3-δ is among the best as cathode material for intermediate temperature SOFCs.
3D Hierarchical SnO2@Carbon Cloth for Selective Electrochemical Reduction of CO2 to Formate
Authors: Zhang Qi , Qiao Jinli
Published: February 2020

Electrochemcial reduction of CO2 (CO2RR) into the industrial feedstocks and low carbon fuels could be a promising strategy to alleviate the excessive emission of CO2. In CO2RR, C1 products are more feasible due to their low electron transfer and relative fast kinetics. A flexible SnO2@CC catalyst electrode was synthesized by one-step hydrothermal method in alkaline condition and annealing in air at high temperature using CC as supporting material, SnCl2 2H2O as SnOx precursor and sodium citrate as stabilizer. The electrocatalytic performance of catalytic electrode compared with that of traditional gas diffusion electrodes (GDE). Pure SnO2/GDE and commercial SnO2/GDE were prepared by traditional spraying technology. Among different GDEs, the 3D layered SnO2@CC catalyst electrode had more catalytic active sites and faster charge transfer rate, which resulted in higher electrocatalytic activity and formic acid selectivity. The maximum current density at -1.45 V vs. SHE is -46.4 mA cm-2, and the Faraday efficiency for HCOO- is 73.4% at -1.3 V vs. SHE.
Investigation of Metallic Dendrite Growth in Electrolytes
Authors: Lei Chong , Sparks Taylor D , Virkar Anil V.
Published: February 2020

The formation of the metallic dendrite in the electrolyte under electrolytic mode can contribute to the failure of the battery, which may result in dramatic fires. Under electrolytic conditions often degradation occurs which manifests as electrode delamination and formation of cracks. In this work, both solid and liquid electrolytes were used to investigate the in-situ metallic dendrite growth.

Sodium sulfur batteries have been widely used for energy storage. Also, sodium ion batteries operating at room temperature are under development. One of the modes of failure of these devices is the formation of metallic sodium dendrites. In this work, a two-phase material Na-β”-alumina+3YSZ has been used to investigate the sodium dendrite growth under electrolytic conditions. The mixed Na+ ion and O2- ion electrolyte was fabricated by the vapor phase process. The sample was sintered and converted with an embedded hole, which was achieved by a wax coated copper wire during the initial uniaxial pressing stage. Subsequently, a small plastic tube with 1M NaNO3 solution was put on the surface of the obtained disc. Silver wires were put into the NaNO3 solution and the embedded hole, they were connected with an amperemeter, a resistor, and a voltage generator. The disc was put under the microscope, and a voltage of 3.5V was applied. In-situ formation of sodium dendrites was observed. The current response and the voltage between the sample were recorded, and EIS was measured every 20 min.

Furthermore, the silver nitrate solution was used to investigate the formation of sharp silver dendrites. Several drops of silver nitrate solution were placed onto the surface of the glass slide, and a cover glass was used for protection. Two silver wires were immerged inside of the solution. By applying the voltage, the silver dendrites shoot out from the tip of the silver wire and also grow along the silver wire. The current response and voltage between the sample were recorded. EIS was measured every 10 min to get the Nyquist plots.
New Mixed Glass Former Glassy Solid Electrolytes: A New Compositional Tool to Optimize the Performance of Glassy Solid Electrolytes
Authors: Martin Steve W
Published: February 2020

So far, sodium batteries operate at elevated temperatures due to the low Na+ ion conductivity in solid electrolytes. For this reason, higher conductivity Na+ ion conducting solid electrolytes are of interest and we are exploring new glass compositions with very high conductivities. In this talk, the Na+ ion conduction in and its relation to the structure of a series of previously well studied sodium borosilicate mixed glass former glassy solid electrolytes will be reported. B and Si MASS NMR measurements have been combined with IR and Raman vibrational spectroscopies to develop detailed models of the structures of these glasses. These models have been combined with measurements of both the Na+ ion conductivity and the physical properties to develop understandings of the unique role of boron in these glasses. Such new studies are able to yield new insights into the mechanisms of Na+ conduction in glassy solid electrolytes.
(Invited) Development of High-Performance Lithium-Ion Batteries in the 21st Century
Authors: Li Yangxing
Published: February 2020

Development of High-Performance Lithium-ion Batteries in the 21st Century

Yangxing Li, Ph.D., Chief Scientist

Watt Lab, Central Research Institute, Huawei Technologies Co.,Ltd.

li.yangxing@huawei.com

High-performance lithium batteries are desirable in the modern society, especially on enhanced safety, improved energy density, increased rate capability and high temperature performance. In order to achieve high energy density for battery, significant efforts have been taken to develop high-capacity electrode materials, high-cut-off voltage cathode, and increased loading density. Some specific technical approaches to achieve high-performance lithium-ion batteries will be discussed here.
(Invited) Sputtered Thin Films for Very High Power, Efficient, and Low-Cost Commercial SOFCs
Authors: Li Yue , Gore Colin M. , Pan Ke-Ji , Hartmann Johanna , Correa Luis , Blackburn Bryan M. , Bishop Sean R.
Published: February 2020

Sputtering of thin electrolyte layers has been demonstrated to increase solid oxide fuel cell (SOFC) performance in very small-scale, e.g., button cells. The few cases where thin film techniques were brought in to early stages of commercialization (e.g., Lilliputian and SiEnergy) showed remarkable low temperature SOFC performance, but required sophisticated cell designs processed with Si and MEMs type technologies. This work takes advantage of low cost, conventional ceramic processing to build large format (10 cm x 10 cm) half-cells upon which the sputtered layers above are added to dramatically increase SOFC performance. In this work, an electron-blocking layer which increases the open circuit cell voltage of the GDC electrolyte based cell and a Gd doped ceria (GDC) buffer layer which mitigates reactions between the cathode and electron blocking layer are deposited by sputtering. This presentation will present progress towards developing increased SOFC performance using this sputtering technology at the commercial-scale. Challenges encountered or expected with thin film development for SOFC commercialization will be discussed.
Difference in Oxide Ion Conduction Properties of Oxide Ion Excess and Cation Deficient PbWO4s and Oxide Ion Deficient CaWO4
Authors: Takai Shigeomi , Sano Toshifumi , Yabutsuka Takeshi , Yao Takeshi
Published: February 2020

Introduction

When lanthanum ions are partly substituted for lead in PbWO4 with sheelite-type structure, high oxide ion conduction appeared at elevated temperature [1]. From the density measurement, it has been reported that oxide ion interstitials are formed for the substitution as Pb1-xLaxWO4+x/2, while Pb1-xLa2/3WO4 shows the defect structure of cation deficiency. While the former system exhibits a little higher oxide ion conduction, both systems show approximately unity of the oxide ion transport number. In recent years, it is also found that CaWO4 with the mineral name of scheelite also exhibit the oxide ion conduction by partly substituting potassium ions for calcium site as Ca1-xKxWO4-x/2. In addition to the electrochemical measurements, we have investigated the high-temperature neutron diffraction on these experiments to clarify the oxide ion conduction paths at high-temperatures. We have reported these results separately and have not compared with concerning defect structure. In the present study, we compare the conduction paths between three types of scheelite-type structured oxide ion conductors from the results of high-temperature neutron diffraction.

Experimental

Pb1-xLaxWO4+x/2 (x = 0.2), while Pb1-xLa2/3WO4 (x = 0.1) and Ca1-xKxWO4-x/2 (x = 0.2) were prepared by conventional solid-state reaction method started from PbO, La2O3, H2WO4, CaCO3 and K2CO3. The sintering temperatures were selected as 900ºC for PbWO4-based materials and 1000ºC for CaWO4s. The crystalline phase of the obtained samples was confirmed by X-ray diffraction. The sintered samples with the amount of c.a. 10 g are set into a vanadium holder with a thin quartz tube to prevent the reaction of sample with holder, which was mounted to the neutron diffractometer SHRPD in J-PARC. Diffracted neutrons were collected at various temperatures up to 800ºC. Structure analyses were performed by using Z-Rietveld, and the trace of nuclear density was calculated by Z-MEM. BVS calculations were also carried out based on the refined structure data.

Results and Discussions

Fig. 1 exhibits the nuclear density map of (a) Pb1-xLaxWO4+x/2, (b) Pb1-xLa2/3WO4 and (c) Ca1-xKxWO4-x/2 deduced by maximum entropy method based on the neutron diffraction data collected at 800ºC. For Pb1-xLaxWO4+x/2 with the oxide ion interstitials, nuclear density seems to be distributed to the interstitial site, while the latter two systems without oxide ion interstitials, much less amount of nuclear density is observed at the interstitial sites. Therefore, Pb1-xLaxWO4+x/2 system possess the three-dimensional conduction path allowing higher oxide ion conductivity at elevated temperatures. We will also discuss the conduction path in terms of the bond valence sum.

References

[1] T. Esaka et al., Solid State Ionics, 52 319-325 (1992).

Figure 1
The Effect of Oxygen Partial Pressure and Composition on the Oxygen Reduction Reaction Properties of Ba0.5Sr0.5Fe1-XCuxO3-δ as a Cathode for Solid Oxide Fuel Cells
Authors: Abubaker Orrsam Aadil , Singh Kalpana , Thangadurai Venkataraman
Published: February 2020

Solid oxide fuel cells (SOFCs) face hurdles in market acceptability due to their high operating temperatures, which typically ranges from 750 oC – 1000 oC. Thus, current research is moving towards lowering the operating temperature to an intermediate temperature range from 500 oC - 700 oC by developing intermediate temperature (IT)-SOFCs. However, during IT operation, conventional cathodes show sluggish oxygen reduction reaction (ORR) kinetics. Till now, perovskite-type oxides have been at the forefront because of their mixed ionic electronic conductive (MIEC) nature. Additionally, Co-based perovskites have shown high catalytic activity for ORR in IT-SOFC cathodes. However, Co-leads to additional cost, high thermal expansion coefficient and toxicity.

In this study, ORR properties of the Co-free perovskite-type Ba0.5Sr0.5Fe1-x
Cu
x
O3-δ (x = 0.05 and 0.2) (BSFCu) cathodes were investigated by utilizing electrochemical impedance spectroscopy (EIS). BSFCu powders were synthesized through the sol-gel method with a final sintering temperature of 1050 °C. Powder X-ray diffraction was used test chemical compatibility between BSFCu and La0.8Sr0.2Ga0.8Mg0.2O3-δ (LSGM) powders up to 1100 °C in air. Symmetrical cells of the following configurations BSFCu-LSGM/LSGM/BSFCu-LSGM were prepared for electrochemical measurements using varying ratios of cathode to electrolyte. Using a well-controlled set up, the effect of pO2
on the area specific resistance (ASR) for ORR of symmetrical cells was studied. BSFCu0.05-LSGM/LSGM/BSFCu0.05-LSGM showed the lowest ASR of 0.03 Ω/cm2 under ambient air at 800 °C, when sintered at 1000 °C. These ASR values are competitive with typical values for Co-based cathodes as reported in the literature. Thermo-gravimetric analysis, under O2/Ar atmospheres showed reversible oxygen intake/release capability of BSFCu powders, making them potential candidates for applications in oxygen-storage technologies.
Boosting the Oxygen Electrode Performance of Reversible Protonic Ceramic Electrochemical Cells By Interfacial Engineering
Authors: Zou Minda , Zhao Zeyu , Huang Hua , Mu Shenglong , Tong Jianhua
Published: February 2020

Reversible protonic ceramic electrochemical cell (RePCEC) is one of the most promising energy conversion and storage devices. Because of the low to intermediate operating temperatures (300-650oC), RePCECs demonstrated great potential for simultaneously achieving high performance, long-term durability and low cost of materials 1,2. However, the state-of-the-art RePCECs still cannot satisfy with practical demand, which is significantly ascribed to the high polarization resistance from oxygen (O2) electrode 3. Modification of the phase interfaces in the composite O2 electrodes played vital roles in enhancing the performance by extending active sites, which were extensively investigated in the field of oxygen-ion conducting solid oxide electrochemical cells (O-SOECs) 4,5. However, the engineering of the interfaces in the composite O2 electrode, especially in nanoscale, has not been extensively studied for RePCECs 6. In this work, O2 electrode scaffolds based on the barium cerate-zirconate co-doped with ytterbium and yttrium (BaCe0.7Zr0.1Y0.1Yb0.1O3-δ) are decorated by dual phase triple (e-/O2-/H+) conducting oxide (TCO) nanoparticles of BaCeFeCoO, BaCeFeO and BaCeYCoFeO, respectively. The low O2 electrode polarization resistance, excellent power output and water electrolysis performance were achieved below 600℃.

References

Duan, C., Kee, R., Zhu, H., Sullivan, N., Zhu, L., Bian, L., Jennings, D. and O’Hayre, R., 2019. Highly efficient reversible protonic ceramic electrochemical cells for power generation and fuel production. Nature Energy, 4(3), p.230.

Duan, C., Tong, J., Shang, M., Nikodemski, S., Sanders, M., Ricote, S., Almansoori, A. and O’Hayre, R., 2015. Readily processed protonic ceramic fuel cells with high performance at low temperatures. Science, 349(6254), pp.1321-1326.

Fabbri, E., Pergolesi, D. and Traversa, E., 2010. Materials challenges toward proton-conducting oxide fuel cells: a critical review. Chemical Society Reviews, 39(11), pp.4355-4369.

Dai, H., He, S., Chen, H., Yu, S. and Guo, L., 2015. Performance enhancement for solid oxide fuel cells using electrolyte surface modification. Journal of Power Sources, 280, pp.406-409.

Chao, C.C., Hsu, C.M., Cui, Y. and Prinz, F.B., 2011. Improved solid oxide fuel cell performance with nanostructured electrolytes. ACS nano, 5(7), pp.5692-5696.

Bi, L., Shafi, S.P., Da'as, E.H. and Traversa, E., 2018. Tailoring the Cathode-Electrolyte Interface with Nanoparticles for Boosting the Solid Oxide Fuel Cell Performance of Chemically Stable Proton‐Conducting Electrolytes. Small, 14(32), p.1801231.
Deposition of Conformal Catalyst Coatings on Porous Electrodes Using a Layer-By-Layer Surface Sol-Gel Process
Authors: Kane Nicholas John , Liu Meilin
Published: February 2020

The state-of-the-art cathode of solid oxide fuel cells suffers from accelerated degradation and slow reaction kinetics for the oxygen reduction reaction (ORR). Surface modification of the cathode has been widely investigated and shown to greatly improve catalytic activity and prevent the formation of insulating phases. However, there is a need to improve the quality of the surface modification coatings while reducing the cost. In this presentation, we report a novel surface modification technique, coined layer-by-layer surface sol-gel (LbL SSG), for deposition of BaO and Pr2O3 on a porous La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) cathode, greatly increasing the catalytic activity for ORR and tolerance against contaminants. This low-cost, liquid phase deposition technique produces conformal coatings with precise thickness control by utilizing alternating self-limiting reactions between chemisorbed metal alkoxides and water on hydroxyl-rich surfaces. The availability of many different metal alkoxide precursors previously proved in traditional sol-gel processes, capability to deposit at room temperature, and lack of expensive vacuum equipment make this technique extremely promising over other conformal deposition techniques such as atomic layer deposition. LbL SSG is shown to produce much more conformal coatings throughout the entire porous cathode and further reduce degradation over similar coatings produced via solution infiltration. Electrochemical impedance spectroscopy analysis shows a great reduction in polarization resistance of symmetrical cells with electrodes modified by catalyst coatings. Utilizing the precise thickness control of the layer by layer process via deposition cycle count, the optimum thickness is determined to be about 8 nm (derived from 30 cycles). Thinner films are shown to be instable, breaking down and degrading over the first 30 hours, while thicker films increase the polarization resistance due to the lower ionic conductivity of the catalyst coatings. The process also demonstrates excellent scalability and versatility by coating larger cathodes (one inch in diameter) and depositing various oxides using different metal alkoxide precursors.

Figure 1. SEM images of bare and coated porous electrodes showing the conformal BaO film deposited via LbL SSG. The polarization resistance versus time for various deposition cycle counts showing greatly improved stability for coated cells.

Figure 1
(Invited) Developing Carbon Catalysts for Selective Electro-Reduction of Carbon Dioxide into Target Products
Authors: Wu Jingjie , Zhang Tianyu
Published: February 2020

Electrocatalytic reduction of CO2 into value added chemicals or fuels is a promising technique towards a carbon-neutral chemical process. The electrochemical reduction of CO2 is a complicated process involving multiple protons coupled electron transfer, theoretically resulting in a variety of products (e.g. CO, HCOOH, CH4, C2H4 and C2H5OH). Therefore, the major challenge in CO2 reduction lies in the manipulation of the selectivity towards a specific product as demanded. However, the study on CO2 reduction has not substantially advanced primarily because of the lack of fundamental understanding of the reaction mechanism and the challenge of discovering efficient and robust catalysts for the various multi-electron transfer processes. Researchers have screened a wide range of metal-based materials for electrochemical reduction of CO2, and found only copper-based metals exhibit selectivity towards formation of hydrocarbons and oxygenates at fairly high efficiencies while most others favor production of carbon monoxide or formate.

Here we present the development of carbon materials as an alternative to Cu for efficient and high-rate electro-reduction of CO2 into hydrocarbons and oxygenates. We will discuss the key structural and electronic factors that govern the selectivity of carbon catalysts towards production of CO, CH4 and C2 products (e.g. C2H4 and C2H5OH). Three categories of carbon catalysts were developed based on the primary products of CO, CH4 and C2H4 in our group. The first carbon catalyst featuring the metal-nitrogen-carbon structure exclusively catalyzes CO2 electro-reduction into CO. The second catalyst called functionalized carbon nanostructure can selectively reduce CO2 into CH4 with Faradaic efficiency up to 90% while the third one namely doped carbon nanostructure (e.g. N-doped graphene quantum dots) can yield C≥2 products with a Faradaic efficiency up to 70%. Both carbon nanostructure can achieve partial current density at the scale of 100 mA cm-2 for target product at fairly low overpotentials. This study provides in-depth insights into developing high-performance carbon-based catalysts for electrochemical reduction of CO2.
Mixed Electronic and Protonic Conducting Membrane for Non-Oxidative Dehydrogenation
Authors: Sun Shichen , Huang Kevin
Published: February 2020

Non-oxidative dehydrogenation of hydrocarbons (NODHHCs) has drawn increasing interests in recent years due to its great potential to achieve high conversion rate, high selectivity, low energy consumption and low CO2 emission. However, coking and thus degradation issues are currently hindering the commercial demonstration of the NODHHC technology. We here present a single-phase membrane reactor for NODHHC reaction for efficient and selective conversion of hydrocarbons. The membrane is consisted of a mixed electronic and protonic conductor, BaCo0.4Fe0.4Zr0.1Y0.1O3 (BCFZY). The conversion study was carried out in a temperature range of 600-800oC free of catalyst or electrical field. With ethane/steam as a feed gas, a single-pass ethane conversion rate of 70%, ethylene selectivity of 90% and ethylene yield of 67% has been demonstrated by the reactor from 650 to 750oC with a steam/ethane ratio of 1.25. This performance is superior to the benchmark steam cracking technology. Long-term stability test has also shown that there is no significant degradation for more than 100 hours under the selected operating conditions.
(Invited) Computational Modeling of Grain Boundary Electrostatic Effect Inpolycrystalline SrTiO3 Thin Film
Authors: Cao Ye
Published: February 2020

Understanding the leakage current caused by charge transport and local accumulation in dielectric oxides is critical for predicting and extending the lifetime of dielectric‐based electronic devices. The internal interfaces such as grain boundaries (GBs) inside a dielectric induce local strain and charge segregation and thus further influence the charge transport behavior. In this work, we employ computational modeling based on the Schottky barrier model and nonlinear Nernst-Planck transport equation is used to study the oxygen vacancy transport and leakage current evolution in a SrTiO3 thin film under a DC bias with planar electrodes. It is found that in polycrystalline SrTiO3, the GB‐bounded donors create an electric potential barrier and a local depletion region near the GBs, impeding the oxygen vacancy transport and suppressing the leakage current increase compared to a single crystal SrTiO3 thin film. The effects of temperature, the magnitude of an applied field, the number density of GBs, the GB‐bounded donor concentration, and the depletion layer width on the leakage current evolution are systematically investigated. The simulation results are compared with the analytical solutions, as well as with existing theoretical and experimental reports. This work thus helps shed light to the grain‐structure dependent electrostatic behaviors in dielectric thin films under different intrinsic and extrinsic conditions.
Understanding of Solid Oxide Electrolysis Cell Degradation: The Role of the Electrode Overpotential
Authors: Park Beom-Kyeong , Zhang Qian , Liu Qinyuan , Voorhees Peter W , Barnett Scott A
Published: February 2020

Solid oxide electrolysis cells (SOECs) can produce hydrogen, an increasingly important energy carrier, with considerably higher efficiency than other electrolysis technologies. A critical hurdle for the market penetration of SOECs is to ensure that degradation rates are sufficiently low to allow long-term operation. Degradation of the oxygen electrode has been shown to increase with increasing current density; however, the effects of other parameters such as temperature, electrode overpotential, and electrode composition have not been fully quantified. Moreover, significant degradation within the electrolyte as well as fuel electrode is observed during electrolysis operation, but the mechanisms are still not fully understood. Here, we report an experimental life test study of both full and symmetric cells with YSZ electrolytes along with various oxygen electrode materials including Sr(Ti0.3Fe0.7)O3 (STF), Sr(Ti0.3Fe0.63Co0.07)O3, (La0.6Sr0.4)(Co0.2Fe0.8)O3 (LSCF), and Ni-YSZ fuel electrodes. The observed dependences on temperature, current density, and electrode composition indicate that the electrode overpotential is the factor determining the electrode/electrolyte degradation and eventual cell failure. A theory that determines the electric potentials and oxygen partial pressure across the electrolyte is used to model the results, and can determine the condition for fracture or oxygen bubble formation. For example, fracture at the oxygen-electrode/electrolyte interface is observed when the electrode overpotential exceeds ~200 mV, corresponding to a critical oxygen partial pressure of 7410 atm; the model shows that the pressure is near its peak at this interface, and is sufficient to cause fracture because of the relatively low fracture toughness of the perovskite electrode.
Developing Data Driven Models to Study Electrocatalytic CO2 Reduction on Ceria
Authors: Mejia Alejandro , Zhu Jiaxin , Nonnenmann Stephen S. , Mebane David S
Published: February 2020

As the rates of carbon dioxide emissions have continually increased on a global scale, mainly due to high demand of fossil fuel burning for transportation and generating electricity, an inevitable interest in managing and recycling the CO2 byproducts has emerged. New solutions are focusing on sustainable reduction of CO2 to CO, which can be conveniently converted to useful hydrocarbon liquid fuel products, such as methane, using existing technologies and infrastructure, as well as renewably generated electricity. Of particular interest in this field is the development and improvement of effective CO2 reduction catalysts, which ceria-based materials have been shown to be suitable for intermediate temperature solid oxide fuel cells. However, understanding the physical mechanisms by which ceria-based catalysts reduce CO2 has posed a challenging problem. In this work, recently-developed continuum approaches for the near-surface chemistry of high-temperature mixed conductors and data driven model-building routines have been combined to gain a quantitative understanding of the physical phenomenon of high-temperature CO2 reduction on ceria catalysts. The main insights pertain to the surface and near-surface defect structure of these materials, where the presence of oxygen vacancies is linked to the enhanced catalytic activity. The experimental data is in-operando scanning surface potential probe measurements performed on specially-designed patterned and thin-film test cells at temperature and under polarization. Preliminary results of data-driven model building will be presented and discussed.
(Invited) Co-Doping for Solving a Short-Hole Diffusion Length Issue of Hematite in Water Splitting
Authors: Jang Ji-Hyun , Ahn Hyo-Jin , Yoon Ki-Yong
Published: February 2020

Titanium and boron hetero-doped hematite photoanodes with an n-n+ homo-junction showed significantly increased photoelectrochemical (PEC) water splitting activity. The Ti and B co-doping in hematite not only suppresses the number of Ti4+and Sn4+ions that cause electron hole pair (EHP) recombination at the hematite surface but also generates an internal electric field for easy hole extraction. The Ti:B-Fe2O3 with a 890 nm height and 70 nm diameter converted the incident photons to EHPs with much reduced recombination and exhibited an excellent photocurrent density of 1.92 mA/cm2at 1.23 VRHEand 2.83 mA/cm2at 1.50 VRHE.Our co-doping strategy provides a straightforward way of addressing the chronic short-hole diffusion length issue that causes a high electron hole recombination rate and thus the critical length limitation of an ideal hematite photoanode, to potentially improve the performance of PEC devices.