bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Drying Patterns from Nanofluid Droplet Evaporation
Authors: Duan Fei
Published: February 2020

Droplet evaporation has received more attention for the applications including concentrating chemicals, coating, printing, spraying, drying, painting, biomedical sampling, etc. Deposition pattern form the evaporative colloidal droplet has many applications in the industrial applications. The process to form the configuration in the drying droplet has been investigated with simulation and experiments. Experimentally, the suspensions of colloidal droplet with the particle size at nano- and micro-scale nanoparticles in the deionized water were prepared. The suspensions are carried out by well stirring first and then putting in an ultrasonication bath to ensure the even initial dispersion of the particles in the water. The clean silicon wafer was used as a substrate for the colloidal sessile droplet drying. Right after the suspensions were prepared, we placed a tiny sessile droplet to dry in the open conditions. The drying patterns were directly recorded with the optical microscope. The formation of branched particle aggregation structures was observed during the droplet evaporation. The experiments demonstrated the dried patterns such as finger, coffee ring, uniform coverage and the combined structures. We have applied the kinetic Monte Carlo model and the diffusion-limited aggregation simulation to explain the self-assemble processes. A lattice-gas Kinetic Monte Carlo (KMC) is developed to explain the of the finger structure while the diffusion-limited aggregation simulation is development to explain the transition from the coffee ring to uniform coverage. The mathematical models control the variables which indicate the presence of liquid, particle or substrate in cells of the cubical lattice. The simulation domain mimics the shape of a sessile nanofluid droplet. The particle, liquid, vapor interaction, and the other factors are considered. The experiments can be reflected by the simulations.
Numerical Simulations of Electrical Double Layer and Electroosmotic Flow in a Nanopore By Openfoam
Authors: Ye Jian , Chen Dilin , Xu Li , Kang Xin , Li Jie
Published: February 2020

The microfluidic chip transfers the pretreatment, chemical reaction, separation, detection, and other functions of the sample to a chip of several square centimeters, which embodies the characteristics of miniaturization, integration, automation, and simplicity. The drive and control of microfluidic have become the key problems in the research of microfluidic chip. In this work, numerical simulation of the electrical double layer (EDL) formed next to a charged planar surface and an electroosmotic flow (EOF) in a nanopore is demonstrated using OpenFOAM. The electrostatics and the ionic mass transport are governed by the Poisson–Nernst –Planck (PNP) equations without considering fluid motion in the model for EDL. The numerical predictions of the electric field and ionic concentrations are in good agreement with the analytical solution. The model for EOF includes the modified Stokes equations for the flow field, the Poisson equation for the electrostatics, and the Nernst–Planck equations with the convective term for the ionic mass transport. The predicted EOF velocity quantitatively agrees with the analytical solution.
In-Operando Observation of Lithium-Silicon Alloy Phase Propagation in Particle-Based Electrodes Using Nanoscale X-Ray Computed Tomography
Authors: Choi Paul , Litster Shawn
Published: February 2020

Silicon (Si) is considered to be one of the most promising anode materials for next-generation lithium-ion batteries primarily due to its high theoretical specific capacity of up to 4200 mAh g-1 and its abundance in nature. However, the irreversible capacity loss and poor cycle life caused by the dramatic volumetric expansion of Si upon alloying with lithium (Li) (>300%) prevents practical implementation of anodes with high Si loading. A better understanding of the interactions between the electrochemistry and mechanical behavior of Si anodes during cycling is therefore needed to develop novel materials and electrode design that can efficiently accommodate the volumetric expansion. In addition, there are significant questions regarding the interactions of the Si with the surrounding carbon materials.

In this work, we use nano-resolution x-ray computed tomography (nano-CT) and an in-house micro-capillary sample cell to directly observe the cycling (lithiation/delithiation) process of Si particle-based electrodes as a function of time. We will show preliminary results on the effects of the electrode composition (Si particle size distribution, particle proximity, etc.) on the Li-Si alloy phase nucleation and propagation.

This material is based upon work supported by the National Science Foundation under Grant No. CBET-1705321. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
(Invited) The Paradox of High-Energy Density Materials for Li-Ion Batteries
Authors: Doublet Marie-Liesse , Saubanere Matthieu , Vergnet Jean
Published: February 2020

Increasing the energy density of cathode materials is a central goal of the ongoing research in Li-ion batteries. This implies improving simultaneously the capacity and the potential of the materials used at the positive electrode of the electrochemical device. While the electrochemical potential is well controlled through an appropriate choice of the redox centre involved in the Li-driven electrochemical reactions, the increase of capacity appears more difficult to achieve without penalizing the material structural stability.[1-3] So far, materials showing the highest energy densities are the Li-rich layered transition metal oxides (LLOs) for which a cumulative cationic and anionic redox activity has been demonstrated. Ever since, numerous materials have been synthesized with various combinations of 3d, 4d, 5d or non transition metals [4-6] and different mechanisms have been proposed to rationalize their electrochemical activity vs. Li or Na with no real consensus about the directions to follow to overcome the structural instability that often comes along with the anionic process. In this paper, we review the different interpretations proposed in the literature to address the fundamental questions of increasing both the potential and the capacity of current positive electrodes with the hope that a common language will help in clarifying the relationship between the material electronic structure, the potential, the (extra)-capacity and the consequences of high-energy-density on the material structural stability. This unified picture highlights that a trade-off needs to be found for the development of high-energy-density materials for alkali-ion batteries.

References:

[1] Zhao, C., Wang, Q., Lu, Y., Hu, Y.-S., Li, B. & Chen, L. Review on anionic redox for high-capacity lithium- and sodium-ion batteries. J. Phys. Appl. Phys. 50, 183001 (2017).

[2] Yabuuchi, N. Solid-state Redox Reaction of Oxide Ions for Rechargeable Batteries. Chem. Lett. 46, 412

(2017).

[3] Li, B. & Xia, D. Anionic Redox in Rechargeable Lithium Batteries. Adv. Mater. 1701054 (2017).

[4] Yabuuchi, N., et al.. High-capacity electrode materials for rechargeable lithium batteries: Li3NbO4-based system with cation-disordered rocksalt structure. Proc. Natl. Acad. Sci. 112, 7650 (2015). Takeda N. et al. Journal of Power Sources 367, 122 (2017).

[5] House, R. et al. Lithium manganese oxyfluoride as a new cathode material exhibiting oxygen redox, Energy & Envir. Sci. Accepted (2018).

[6] Maitra, U; Oxygen redox chemistry without excess alkali-metal ions in Na2/3[Mg0.28Mn0.72]O2 Nat. Chem. 10 (2018) online.

[7] a) Saubanère, M., McCalla, E., Tarascon, J.-M. & Doublet, M.-L. The intriguing question of anionic redox in high-energy density cathodes for Li-ion batteries. Energy Env. Sci 9, 984–991 (2016).

[8] Xie, Y., Saubanère, M. & Doublet, M.-L. Requirements for reversible extra-capacity in Li-rich layered oxides for Li-ion batteries. Energy Env. Sci 10, 266–274 (2017).
Outgassing of Ni- and Li-Rich Li Ion Battery Cathode Materials: The Importance of Impurities
Authors: Renfrew Sara E , McCloskey Bryan D.
Published: February 2020

Outgassing of active materials in Li-ion batteries provides a route to quantitatively study degradation processes that occur during cycling. In particular, we are primarily interested in quantifying the individual and coupled decomposition/transformations of the cathode – a lithiated transition metal oxide (TMO) – and the electrolyte – most commonly carbonate blends (ethylene carbonate, diethyl carbonate, etc.) with lithium hexafluorophosphate (LiPF6) as the salt. Previous observations of high-voltage instabilities include TMO surface reconstruction, transition metal dissolution, electrolyte decomposition, and formation of surface species. However, this picture is still incomplete, with the dependence on electrolyte and TMO composition not yet fully understood. We will present results in which isotopic labeling of 18O in Ni-rich and Li/Mn-rich NMCs is combined with quantitative gas evolution analysis to show that residual solid lithium carbonate (Li2CO3) on the surface of TMOs predominantly accounts for CO2 and CO evolved. Furthermore, O2 evolution from the TMO lattice is related to Li2CO3 present in the cathodes. These results indicate that electrolyte degradation negligibly contributes to gas evolution up to 4.8 V vs. Li/Li+ on the first charge.
Energy-Tuned Photoelectron Spectroscopy of Lithium-Ion Battery Cathodes: Revealing Oxygen Redox Activity and Investigating New Materials
Authors: Naylor Andrew , Maibach Julia , Källquist Ida , Makkos Eszter , Roberts Matthew R. , Younesi Reza , Hahlin Maria , Brandell Daniel , Islam M. Saiful , Bruce Peter G. , Edström Kristina
Published: February 2020

With the quest to find better performing electrode materials for Li-ion batteries becoming hotter by the day, advanced spectroscopic techniques are being employed to better understand the processes at interfaces of the battery components and deeper in the bulk of the active materials. One of those techniques is energy-tuned photoelectron spectroscopy (XPS), typically performed at synchrotron facilities, which offers the possibility to irradiate a sample with soft or hard X-rays and detect electrons with kinetic energies up to 10,000 eV. This builds up a true surface vs. bulk picture including formation of solid electrolyte interphases on anodes, oxidation products on cathodes and redox activity in the bulk of particles, such as that of transition metals or oxygen.

A class of cathode materials which are of particular interest are those exhibiting oxygen redox activity, providing capacity beyond that of the traditional transition metal redox. We have investigated a number of such lithium-excess Ni, Co, or Mn oxide materials, which are known to exhibit oxygen redox, by energy-tuned XPS. The analysis reveals important details of the differences between surface and bulk, which DFT calculations have helped rationalise.

Lithium-rich oxyfluorides (Li2MO2F where M = V, Fe, Mn etc.) are another class of material that have gained increased attention in recent years. These cathode materials have promising potential with high theoretical capacities (420 mA h g-1 for Li2VO2F) at ~2.5 V with minimal volume expansion, but suffer from local structural instabilities. We are using energy-tuned XPS (Figure 1) to study their degradation mechanisms and how they might be mitigated using transition metal doping or coatings.

Figure 1. O 1s and V 2p XPS spectra of a Li2VO2F electrode for the EU H2020 ‘LiRichFCC’ project, at two photon energies: 2005 eV (black, top), 6015 eV (red, bottom).

Figure 1
Surface-Modified Ni-Rich Layered Cathode Materials Via Li-Reactive Inorganic Coatings
Authors: Becker Dina , Schmuch Richard , Winter Martin , Placke Tobias
Published: February 2020

In recent years, the demand for lithium ion batteries (LIBs) significantly increases due to the wide range of application, from consumer electronics to automotive industry. The improvement of the LIB’s energy density is one of the key factors to the mass market penetration of electric mobility. Currently, LIBs are applied in hybrid (HEV), plug-in hybrid (PHEV) and fully electric (EV) vehicles. Particularly, layered lithium Ni-Co-Mn oxides LiNixCoyMnzO2 (NCM, x + y + z = 1) cathode materials are the most promising candidates for LIBs due to their high capacity, lower cost and enhanced stability compared with LiCoO2.[1]

Although the state-of-the-art NCM cathode material is NCM-523, the trend is going towards a higher energy density. Recently, the focus of research is on the cathode materials with high nickel content. For example NCM-811 with a Ni content of 80% can deliver a discharge capacity of 200 mAh/g at 4.3 V. At the same time, the high Ni content causes some disadvantages, such as an unstable electrode structure and rapid capacity fading.

One of the challenges is the synthesis and stabilization of Ni-rich materials. In order to avoid cation mixing, an excess of lithium must be ensured. Consequently, the unreacted lithium on the surface of the active material can react with water and CO2 from the air. As a result of the contamination, LiOH and L2CO3 are formed on the surface of the active material. These residues can form an insulating layer of LiF in contact with the electrolyte, which leads an increased internal resistance of the electrode. Furthermore, the highly reactive Ni4+ ions in the delithiated state of the electrode of Ni-rich cathode materials can oxidize the electrolyte and result in active material loss.[2]

In this contribution, we investigate the effect of surface modification of NCM-811 via an inorganic coating on the electrochemical performance. The inorganic coating acts as protective layer on the surface of the active material, preventing the direct contact of the cathode material with the electrolyte. Moreover, it suppresses the side reactions on the particle surface. The effect of the coating on the structural and electrochemical properties was investigated in NCM-811/graphite full cells. The cells with coated electrodes were significantly improved with respect to their long-term cycling performance compared to the uncoated electrodes (Figure 1).

[1] S.-K. Jung, H. Gwon, J. Hong, K.-Y. Park, D.-H. Seo, H. Kim, J. Hyun, W. Yang and K. Kang, Advanced Energy Materials, 2014, 4, 1300787.

[2] W. Liu, P. Oh, X. Liu, M.-J. Lee, W. Cho, S. Chae, Y. Kim and J. Cho, Angewandte Chemie International Edition, 2015, 54, 4440-4457.

Figure 1: Cycling performance of uncoated and coated NCM-811/graphite LIB full cells at room temperature using a voltage window of 2.5 – 4.3 V. Three formation cycles at 0.1C and following cycling at 0.5C rate.

Figure 1
Synthesis of Nanocellulose Based Metal Oxide Nanostructure for Li-Ion Battery Applications
Authors: Youn Chulmin , Lee Joonbong , Choi Taekjib
Published: February 2020

Nanocellulose is considered as the sustainable materials due to renewability, affordability and non-toxicity in nature. As a chemical raw material, nanocellulose can for flexible or strong networks that are suitable templates for artificial nanostructure with enhanced electrochemical performances. Here, we prepared nanocellulose-metal oxide hybrid nanostructure from cellulose nanofibrils and oxide nanobelt via hydrothermal method using transition metal oxide precursor and TEMPO oxidized cellulose nanofibers. Oxide nanobelts with high aspect ratio are structurally uniform and single crystalline. Nanocellulose-metal oxide hybrid nanostructure presented fast charging and discharging capability with high capacity and long cycle performances. Our hybrid nanostructure can provide a new route into the development of high capacity, unique architecture, and suitable electrode potential for promising electrode materials.
Study on Separator / Lithium Metal Integration for Improving Performance of Lithium Metal Battery
Authors: Choi Junyoung , Oh Jeonghun , Jin Dahee , Kim Seokwoo , Park Jinkyu , Yoon Byeolhee , Jo Hearin , Ryou Myung-Hyun
Published: February 2020

Recently, as the exhaustion of fossil fuels and the pollution of the environment have accelerated, interest in electric vehicles(EV) and energy storage systems(ESS) has increased, so that research on the battery materials for increasing the energy density of lithium secondary batteries is actively being carried out. In particular, lithium metal (3860mAh g-1), which is one of anode materials, has a higher energy density than graphite (372mAh g-1), which is currently being commercialized, and has attracted attention as a anode material suitable for use in Li-Air and Li-Surfer cells However, lithium metal has a problem in that dendrite and dead lithium are generated in repeated charging and discharging processes, resulting in deterioration of lifetime characteristics, and explosion and ignition may occur due to an internal short circuit when exposed to a harsh environment In order to solve this problem, studies have been reported to coat the organic / inorganic composite layer on the surface of lithium metal to suppress the lithium dendrite by physical force and greatly improve the lifetime characteristics. However, there is a problem that the thick coating layer is not suitable for manufacturing a high capacity battery Therefore, in this study, we intend to improve the performance of cell by integrating separator and lithium metal by using electrochemically stable thin polymer adhesive layer. The new battery manufacturing method and electrochemical and physical properties are presented through this.
Lithium Ion Carbon Electrodes from Virtual Cathode Deposition
Authors: Murphy Carmen , Petrucco Enrico A. , Kumar R Vasant , Tomov R I , Yarmolich Dmitry
Published: February 2020

Commercial graphite electrodes exhibit insufficient energy density to meet future automotive battery targets. Herein we explore the electrochemical characteristics of a stable high energy density carbon battery anode layer directly prepared by PVD related Virtual Cathode Deposition technique. The novel form of carbon prepared by VCD enables access to a specific capacity much higher than the graphite theoretical value of 375mAhg-1 while having high coulombic efficiency and lifetime. Lithium ion diffusion was derived from a range of electrochemical methods and compared with ex-situ results. Our ex-situ analysis provides further insight into the differences between VCD prepared carbon and conventional graphite anodes.
Luminescent Properties of Twelve Novel MOFs Based on 2,7-Bis(4-benzoic acid)-N-(4-benzoic acid)Carbazole and Their Application in Ni2+ Ions Concentration Sensing and Vis-NIR Fluorescent Materials
Authors: Chen Dong-Hui , Wu Xin-Tao
Published: February 2020

I will present twelve novel luminescent metal-organic frameworks, TCZ-001 – TCZ-005 and TCZ-M (M = Nd, Sm, Eu, Gd, Tb, Dy, Ho). All of the twelve MOFs were assembled from a novel luminescent carbazole-based ligand, 2,7-bis(4-benzoic acid)-N-(4-benzoic acid)carbazole. TCZ-001, TCZ-003 and TCZ-004 show a remarkable response to the Ni2+ concentration in DMA, H2O or EtOH. Some of Zn2+ ions were replaced by Ni2+ ions and the rate of the transmetalation depended on the concentration of Ni2+ ions. Also, changing part of the metal node would transform the colour of emitted light. Additionally, the colour of the luminescence displays a linear correlation with the Ni2+ concentration range from 0.005 M to 0.35 M (mol·L−1). Besides selective sensing of Ni2+, TCZ-004 can also be utilized to detect Eu3+ ions in DMA solution. Thus, several potential sensory probe materials for Ni2+ and Eu3+ detection in DMA solution have been obtained. As to TCZ-M (M = Nd, Sm, Eu, Gd, Tb, Dy, Ho), X-ray crystallography showed that all of them are isomorphous and possess a 3,6-connected three-dimensional (3D) framework with a point symbol of {4·62}2·{42·610·83}. The photoluminescence measurement indicates that TCZ-Eu shows reddish-orange emission bands and TCZ-Sm shows both visible and near-infrared (NIR) emission bands. In addition, the isomorphous structure of TCZ-M (M = Nd, Sm, Eu, Gd, Tb, Dy, Ho) provide the potential to fabricate multicolour luminescent materials.

[1] D.-H. Chen, L. Lin, T.-L. Sheng, Y.-H. Wen, S.-M. Hu, R.-B. Fu, C. Zhuo, H.-R. Li and X.-T. Wu, CrystEngComm, 2017, 19, 2632.

[2] D.-H. Chen, L. Lin, T.-L. Sheng, Y.-H. Wen, X.-Q. Zhu, L.-T. Zhang, S.-M. Hu, R.-B. Fu and X.-T. Wu, New J. Chem., 2018, 42, 2830.
Local Conductivity Measurements of Metal-Organic Layers By Conductive AFM on Micropatterned Electrodes Produced By Metal Polymer Blend Lithography
Authors: Walheim Stefan , Redel Engelbert , Wöll Christof , Schimmel Th.
Published: February 2020

The electronic characterization of thin metal-organic layers like SURMOFs is often difficult, since transport contributions in global measurements may be dominated by pin holes with direct electrical contact of top and bottom electrodes. In addition, these measurements average over a wide surface area and no local information can be derived.

Using an AFM with a metalized tip, local measurements of the conductivity and I-V characteristics can be extracted. But these measurements have three important draw backs: (I.) the small contact area in the 20-nm-range restricts the range of measureable conductivity due to a limited sensitivity of the electronic amplifiers, (II.) the electric field underneath the AFM Tip is rather inhomogeneous and current contributions in-plane and off-plane are mixed and (III.) the contact area varies individually from tip to tip and with the applied force.

With our approach of polymer blend lithography (PBL) we produce billions of small metal islands with diameters in the range of a few hundred nanometers up to a few microns with a simple process (Metal-PBL) [1]. These Islands serve as planar top electrodes, which we can address individually with the AFM-tip in a highly reproducible way. Using a set of AFM scans in the same region, a manifold of data sets concerning conductivity and I-V characteristic can be extracted, since many individual islands are measured simultaneously.

1.: Polymer blend lithography for metal films: large-area patterning with over 1 billion holes/inch2: C. Huang, A Förste, S. Walheim, and Th. Schimmel: Beilstein Journal of Nanotechnology 2015, 6, 1205–1211
Polymer Electrolyte Membrane Fuel Cells (PEMFCs) Catalyst Layer Based on the Triple-Phase Separated Nanostructure
Authors: Seo Dongjun , Kim Hansung , Kim Tae-Young
Published: February 2020

The eco-friendly power generation mechanism and high energy density of polymer electrolyte membrane fuel cells(PEMFCs) have been steadily researched in many institutions and countries that are aiming for sustainable development and have improved to a commercially available level of performance. However, electrode production using platinum has high price and supply problem, so research is being carried out to achieve high performance using small amount Pt catalyst. In order to produce MEA that meet these requirements, this study understands the three phase boundary, which is the basis of the catalytic reaction, and aims to design an electrode layer suitable for a polymer electrolyte membrane fuel cell and suggest a production method.

In the conventional electrode manufacturing process, the mixed liquid slurry is used, so the ionomer is randomly distributed in the electrode layer after drying. Therefore, it was difficult to adjust to exist in the optimal position favorable to the reaction. Especially, the thick ionomer on carbon supports is located in the catalyst layer inevitably has a structure that is difficult to reach the Pt surface because the reaction gas supplied through the pores is diffused. In the case of cathodes, Pt surface is known to form a low oxygen fraction of 1/20 compared to pores, which indicates the limit of performance with high mass transfer resistance.

In this study, Ionomer was coated on a carbon support and then solidified. After that, the electrode was made by mixing with the commercial catalyst at the optimal ratio, so that the movement path of the proton and the electron could be separated independently. We are trying to suggest a new recipe to make a catalytic layer that can induce high oxygen pressure on the surface of the catalyst and introduce a pore distribution that is effective for electrochemical reactions.

In addition, the catalytic layer produced by this method was able to realize an independent path because the contact of each part was maintained well. As a result, the pores effective for electrochemical reactions were widened to achieve the performance of commercial electrodes even at a low level of 0.2mgPt/cm2. Moreover, this method can be used to produce high-performance electrodes at a low price using a small amount of expensive platinum catalysts, and especially in the related industries, because all materials used in the manufacturing method are commercially used and do not require specially manufactured equipment.
Carbon Corrosion on the Wettability Change of Cathode Catalyst Layers of PEM Fuel Cells
Authors: Fang Zhengyuan J , Fuller Thomas F
Published: February 2020

It is well-known that water management plays a critical role in operation of PEM fuel cells especially under the dynamic operating conditions and relatively low temperatures, in which both liquid and gaseous water is present. In this study, the wettability of the cathode catalyst layer (CL) on MEAs is characterized by ex-situ sessile-drop method. The method was applied on ten cathode CLs with varying carbon loss (0 to 13 wt% of the cathode) under both potential cycling and holds. The apparent contact angles of the cathode CL decreased from 143.5° to 130° after severe corrosions. Atomic Force Microscopy and X-ray Photoelectron Spectroscopy were used to elucidate structural and compositional changes that account for the decrease in apparent contact angles.
(Invited) Non-Precious Metal Catalysts with Designed Nanostructures and Controlled Active Sites for Oxygen Reduction Reaction in Fuel Cells
Authors: Lee Jinwoo
Published: February 2020

In the low temperature fuel cells, it is of great importance to overcome a sluggish oxygen reduction reaction (ORR) by employing the highly effcient electrocatalysts. Due to high cost of the representative Pt based catalysts, it is highly required to develop non-precious metal or metal-free catalysts with high perforamance. In this sense, we developed N,P co-doped large pore sized ordered mesoporous carbons with high activity for ORR. A large pore sized N, P co-doped ordered mesoporous carbon with precisely controlled doping site position exhibited a remarkable on-set potential and produced 70% of the maximum power density obtained using Pt/C. We also developed an ordered mesoporous Fe/N/C catalyst for oxygen reduction reaction in fuel cells. By simple ‘one-pot’ process, we combined two necessary factors for the high performance of Fe/N/C catalyst in cathode of practical-level fuel cell. The ORR kinetic activity of the single Fe-Nx/C active site was increased by a new and versatilely applicable strategy. The incorporated electron withdrawing/donating functionalities changed the strength of the electronic effect, resulting in the change of ORR activity.
High Conductivity and Low Permeability Alkaline Fuel Cell Membrane with Ordered Interpenetrating Network Morphology By Electric Field Poling
Authors: Chu Peter Po-Jen , Huang Yiyun , Fang Yu-shin , Tseng Yu-Cheng , Chen PinHaw
Published: February 2020

A new category of hydroxide ion exchange membrane bearing ordered interpenetrating network (semi-IPN) structure established by electric field poling during membrane formation, lead to balanced property where high ion conductivity and low alcohol (methanol and ethanol) permeability co-existed. Success of this membrane preparation scheme is illustrated with the semi-IPN membrane formed by dendritic modified bismaleimide (mBMI) and polyvinyl alcohol (PVA) hydrogel casted together under applied electric field (E-field> 2000V/cm, Ac=1-20Hz,). Detailed morphology and water diffusion studies shows electric field poling establishes higher ordered amorphous domains that induces preferentially oriented conducting path that raised ion conductivity. On the other hand, semi-IPN network effectively reduces methanol and ethanol permeation and improves membrane toughness. When PVA:mBMI equals 2 to 3 weight ratio, the membrane delivered impressive room temperature OH ion conductivity of 38.2 mS/cm and a substantially reduced ethanol permeation of 7.7x10-8 cm2/s; giving exceedingly high ethanol selectivity ratio (~106) with electric field poling preparation. Ordering in the semi-IPN structure by electric field poling also causses densification of the amorphous domain that leads to improved chemical stability (99wt% mass retention in 6M KOH for nearly a month) and mechanical toughness (Tensile strength increased from 3.5 MPa to 7.0 MPa, and elongation at break raised from 60% to 92%). The study concludes the application of an external electric field initiated reorganization of membrane morphology where high performance fuel cell membrane bearing high ion conductivity; low fuel permeation; high membrane strength; and high chemical stability can be established, simultaneously.
Ru-Functionalized Mo2c Nanoparticles in-Situ Grown on Biomass-Derived 3D Porous Carbon Framework for Catalytic Hydrogen Evolution
Authors: Zhang Zhen , Feng Qi , Li Hui , Wang Haijiang
Published: February 2020

Developing highly efficient and long-durable electrocatalysts toward the hydrogen evolution reaction (HER) is highly desirable for implementation of the water-splitting to produce high-purity H2 at large scale.[1] Although Pt-group metals so far have been proven to be superior electrocatalysts for HER, the high-cost and scarcity heavily inhibit their widespread application. To date, a series of HER electrocatalysts based on transition metal carbides have been developed. However, in most of these cases, their catalytic activity and durability still need to be improved to compete with Pt-based electrocatalysts.[2, 3] As a cheaper alternative to Pt, Ru possesses similar bond strength with hydrogen, guaranteeing the promise for catalytic hydrogen evolution.[4, 5] In this study, we demonstrate a novel strategy for the preparation of Ru-functionalized Mo2C nanoparticles embedded in popcorn-derived three-dimensional (3D) porous carbon framework.

The synthesis mainly involves two steps: (i) the activation of popcorn by KOH and the co-assembly with Ru and Mo precursors. With the help of activation treatment, the popcorn can easily disperse in the solution and absorb Ru and Mo precursor. (ii) freeze-drying followed by in situ annealing treatment. The crystallization of Ru nanoparticles, in-site growth of Mo2C nanoparticles and the carbonization of porous popcorn were simultaneously performed during annealing process. Due to the synergistic effects between Ru and Mo2C nanoparticles, the composite catalyst showed higher HER activity.

Figure 1. a) A schematic diagram showing the organization of the Mo2C@Ru. b) HER polarization curves of Mo2C, Ru and Mo2C@Ru with the iR drop correction, acquired at a scan rate of 5 mV s-1 in 0.5 M H2SO4.

References

[1] Q. Feng, X.Z. Yuan, G. Liu, B. Wei, Z. Zhang, H. Li, H. Wang, Journal of Power Sources, 366(2017) 33-55.

[2] K.-H. Liu, H.-X. Zhong, S.-J. Li, Y.-X. Duan, M.-M. Shi, X.-B. Zhang, J.-M. Yan, Q. Jiang, Progress in Materials Science, 92 (2018) 64-111.

[3] M. Miao, J. Pan, T. He, Y. Yan, Y. Xia Bao, X. Wang, Chemistry – A European Journal, 23 (2017)10947-10961.

[4] J. Mahmood, F. Li, S.-M. Jung, M.S. Okyay, I. Ahmad, S.-J. Kim, N. Park, H.Y. Jeong, J.-B. Baek,Nature Nanotechnology, 12 (2017) 441.

[5] J. Su, Y. Yang, G. Xia, J. Chen, P. Jiang, Q. Chen, Nature Communications, 8 (2017) 14969.

Figure 1
(Invited) On Deconvoluting the Contributions of the Cathode and Anode to SOFC Electrode Performance
Authors: Zhou Xiao-Dong , Wang Yudong , Wilson Joshua A.
Published: February 2020

In SOFC research, it is well know that deconvoluting the contributions of the cathode and anode to the total electrode performance is of significant importance, but is also extremely challenging because of the overlap of reaction time constants from both electrodes. Due to the difficulty in placing a reference electrode, currently there are two approaches to address this challenge. The first approach is to use the distribution of relaxation times (DRT) to analyze the spectra acquired from electrochemical impedance spectroscopy (EIS). The second method is to measure the SOFC performance by changing the oxygen partial pressure while other operating parameters are fixed. In doing so, one assumes that the changes in EIS spectra are resulted from the change of cathode performance. In this presentation, a theoretical model is developed to show what the requirements are for this assumption. Various cathode- and anode- materials are then utilized to validate our theoretical analysis. DRT analysis is used to cross validate this model. Criteria on deconvoluting electrode performance will be provided.
(Invited) Poisson-Cahn: A Space Charge Theory for Dilute and Concentrated Systems
Authors: Mebane David S
Published: February 2020

The Poisson-Boltzmann theory, used almost exclusively in the description of space charge zones in solid electrolytes and mixed conductors, is strictly valid only in the dilute limit. Although it is useful for dilute systems, a host of experimental results in different materials, from different groups using different techniques, confirm the failure of the theory in concentrated systems, in that the thickness of charge accumulation zones are consistently an order of magnitude larger than that predicted by Poisson-Boltzmann. Poisson-Cahn adapts the Cahn-Hilliard theory of inhomogeneous systems to systems containing charged particles near surfaces and interfaces. The result is a theory that reproduces the experimental findings on space charge in concentrated systems, while preserving the dilute-case limiting behavior predicted by Poisson-Boltzmann. An overview of the theory along with applications to grain boundaries and surfaces in pure and acceptor-doped ceria will be presented, along with comparisons to experimental results in those systems.
Role of Microstructure on Disorder and Transport in Pyrochlore Oxides
Authors: Kreller Cortney R. , Parker Nia , Valdez James Anthony , Holesinger Terry , Wang Yongqiang , Tang Ming , Uberuaga Blas
Published: February 2020

Crystalline disorder in complex oxides can have a pronounced effect on mass transport, but the role of disorder within the complex landscape of material and microstructural defects is not uniquely understood. Dopants or substitutions are commonly used to introduce disorder, but this inherently convolutes chemical composition and structure. In this work, we use irradiation damage not to study the fundamental damage response, but rather to induce and control the extent of disorder in oxide materials of a single composition in order to explore the relationship between intrinsic disorder and oxygen ion conduction. Prior work showed that the transition from ordered pyrochlore to disordered fluorite in Gd2Ti2O7 (GTO) with increasing fluence of He irradiation was accompanied by an orders-of-magnitude increase in conductivity. This work examines the role of grain/grain-boundary microstructure on irradiation-induced damage and its corresponding impact on conductivity.
Study on Mechanical Behavior of Metal-Supported Solid Oxide Fuel Cell (MS-SOFC) in Wet Chemical Coating Process
Authors: Lee Jaeseok , Lee Kunho , Bae Joongmyeon
Published: February 2020

Metal-supported solid oxide fuel cell (MS-SOFC) requires not only high electrochemical performance and durability but also high volumetric and gravimetric power density to be applied to portable and transportation fields. However, reducing the thickness of the metal substrate, which generally occupies the most portion of the volume and mass among components of the MS-SOFC, may cause mechanical deformation during fabrication processes. In this study, mechanical behavior of the MS-SOFC, especially consists of a thin metal substrate (~100 µm) and thin-film electrolyte deposited through wet chemical coating processes, was addressed. First of all, thermal surface stress generated during the wet chemical coating processes and mechanical deformation caused by the thermal surface stress were measured by thermomechanical analysis and surface profiler, respectively. Furthermore, after quantifying the mechanical deformation of the MS-SOFC, a novel method of introducing magnets in the wet chemical coating processes to suppress mechanical deformation was proposed and evaluated. As a result, vertical deformation of the MS-SOFC was successfully suppressed from approximately 160 µm to 30 µm without significant defects of the electrolyte such as cracks, pinholes or residual stresses.
New Structure of Large-Sized Protonic Ceramic Fuel Cell with Porous Alloy
Authors: Hiraiwa Chihiro , Tawarayama Hiromasa , Higashino Takahiro , Okuno Kazuki , Han Donglin , Uda Tetsuya , Majima Masatoshi
Published: February 2020

Introduction

Some perovskite oxides, such as doped BaCeO3 and BaZrO3 electrolyte-based protonic ceramic fuel cell (PCFC) have received increasing attention as electrolytes of reduced temperature to operate [1,2]. Furthermore, PCFC leads to the production of water vapor at the cathode side, which helps to improve the conversion efficiency of SOFC system. And it is possible to reduce the cost of the stack because inexpensive metal materials can be used for interconnectors in stacks. However most of the previous researches on PCFC are small-sized cell and it is necessary to further improve the power density. In this work, we reported that a cell stack of a new structure was designed and made with large-sized PCFC and porous alloys for anode and cathode current collector to improve power density, and the characteristics were evaluated.

Experimental

2.1 Preparation of large-sized PCFC

BaCe0.8Y0.2O3-δ(BCY20) and BaZr0.8Y0.2O3-δ(BZY20) were prepared by solid state reaction method and were mixed with NiO by a ball-mill to prepare an anode powder. The powder was pressed uniaxially under 40 MPa into anode pellet. On anode pellet BCY20 and BZY20 electrolyte layer were deposited by a screen printing and co-sintered at 1450 ºC for 10 hours. LSCF cathode powder was also deposited and sintered at 1000 ºC. Figure 1(A) shows an optical image of a large-sized PCFC.

2.2 Preparation of Ni and Ni-Sn porous metals

A polyurethane foam with interconnected cells was treated to become electrically conductive. This was followed by the application of a predetermined amount of nickel via electrodeposition. The base material, or plastic foam, was removed through heat treatment at 800 ºC. The remaining nickel was reduced in a reducing gas at approximately 1000 ºC to become a nickel porous metal. Next, the Ni porous metal was coated with a predetermined amount of Sn by electrodeposition. Additionally, this was heat-treated in a reducing gas at approximately 1000 ºC to become a Ni-Sn porous alloy by means of Sn diffusion into Ni. Figure 1(B) shows an SEM image of the surface of the Ni-Sn porous alloy [3].

Result

The power generating characteristics of a single-PCFC in which Ni-Sn porous alloy and Ni porous metal were applied as a cathode and anode collector was evaluated at the operating temperature of 600 ºC. Peak power densities of 500 mW/cm2 and 333 mW/cm2 were achieved, respectively, at 600 ºC and 500 ºC operating on hydrogen fuel.

[1] H. Iwahara, et al., Solid State Ionics, 61, 65 (1993)

[2] J. Dailly, et al., Journal of Power Sources, 240, 323 (2013)

[3] C. Hiraiwa, et al., International Journal of Hydrogen Energy, 42, 12567 (2017)

Figure 1
(High Temperature Materials Division Outstanding Achievement Award) Recent Advances in Intermediate-Temperature Fuel Cells: Surface Modification and In Situ/Operando Characterization
Authors: Liu Meilin
Published: February 2020

The performances of electrochemical systems are often limited by the charge and mass transfer along surfaces and across interfaces. Fundamental understanding of these electrochemical processes, especially the rate-limiting steps, is vital to achieving rational design of a new generation of intermediate-temperature fuel cells powered by a wide variety of readily available fuels. Also, surface modification has been successfully used to dramatically enhance electro-catalytic activity and durability of electrode materials. This presentation will highlight some recent advances in surface modifications and characterization of electrodes in energy storage and conversion systems. Surface enhanced Raman spectroscopy (SERS) has been used for probing and mapping new phases and reaction intermediates on electrode surfaces under or near operating conditions. It has also been demonstrated that SiO2 shell isolated Ag nanoparticles have excellent chemical and thermal robustness and stability for in situ SERS study of electrode materials under in situ or operando conditions, providing valuable information on reaction intermediates or structural changes that critically influence the performance and stability of the electrodes. Further, synchrotron-based X-ray absorption spectroscopy (XAS) and XPS have been used to characterize the local atomistic structure and oxidation state of electrode surfaces and interfaces, which may critically affect the activation or degradation processes of electrodes. These experimental studies, together with modeling and simulation, have helped us to gain important insights into the mechanisms of chemical and energy transformation, electro-catalytic reactions, and degradation processes, providing valuable guidelines for rational design of new electrode materials, surfaces, and interfaces with desired functionalities.
Synergy Effect of Mixed Precursor Infiltrated Cathode on Solid Oxide Fuel Cell Performance
Authors: Kim Jinhyeon , Shin Sung Soo , Choi Jiwoo , Lee Channyung , Shin Hyunho , Choi Mansoo
Published: February 2020

The Solid oxide fuel cells (SOFCs) are promising alternative to combustion technology for electric energy production due to no emission and high efficiency in chemical to electric energy conversion. However, the commercialization of SOFCs is hindered by the high operating temperature, resulting in few of main problems, such as expensive system cost and short lifetime. Thus, while reduced-temperature SOFCs has been a long lasting interest in SOFC community, the sluggish oxygen reduction reaction (ORR) occurring at cathode at intermediate temperature is the most critical challenge for enhanced overall performance of SOFCs. In recent years, the surface modification of cathode materials by infiltration process shows outstanding performance. In this process, it is important to select the proper infiltrate materials since which play important role in enlarging active sites for ORR. However, the existing infiltration processes have limiting effect on performance of SOFC due to coarsening of particles at high temperature. Therefore, the selection of appropriate infiltrate materials along with the suppression of particle growth is the key requirement for enhanced ORR, dominating overall SOFC performance.

In this paper, we attempt to systemically investigate the various metal oxide as infiltrate material and extend active site for ORR by controlling the size of infiltrated oxide. The nitrate precursor of corresponding oxide was infiltrated into the cathode, La0.6Sr0.4Co0.2Fe0.8O3 (LSCF), in symmetric cell to test the effect of each infiltrated oxide on ORR. Among the tested samples, Pr infiltrated LSCF show lower polarization resistance (Rp) at 500 °C; 40 % lower Rp for Pr infiltrated LSCF than that of bare LSCF. Furthermore, mixed precursor of two different oxides, chemically inactive each other, were infiltrated. This process can effectively suppress particle growth at high temperature, resulting in more active site for ORR due to increased surface area. To confirm the morphology of infiltrated oxides anchored on the cathode surface, scanning electron microscope (SEM) and transmission electron microscopy (TEM) are performed.Also, electrochemical impedance spectroscopy (EIS), thermogravimetric analysis (TGA) and iodometric titration are conducted to understand correlation between produced oxygen vacancy by infiltrated oxide and ORR. In conclusion, this study shows that mixed precursor-infiltrated cathode has significant influence on ORR in SOFCs.
Effects of External Pressure on the Performance of Lithium Anode Cells
Authors: Nagpure Shrikant C. , Dufek Eric J. , Wood Sean M. , Dickerson Charles C , Liaw Boryann
Published: February 2020

Rechargeable lithium metal anode batteries (RLB) have the potential to meet the Department of Energy’s 500 Wh/kg goal [1]. However, higher cycling efficiency and safety of these cells is challenged by the dendritic Li plating morphology. Li surface protective coating or electrolyte that can promote growth of stable solid electrolyte interphase from the reduction products can prevent dendritic growth of Li during plating. Another way to suppress the dendritic growth and facilitate more uniform Li surface morphologies is by applying the external pressure to the cell [2].

The external cell pressure can influence the Li plating conditions and modify Li surface. The growth of Li dendrites can be suppressed due to the Li surface strain field under external cell pressure. Also the loss due to dead lithium can be minimized by maintaining a good electrochemical contact between Li deposits. A dendrite-free uniform mossy Li surface with good electrochemical contact will improve the cycling efficiency and safety of the cells.

The effect of external cell pressure was studied in cells with nickel rich LiNi0.6Mn0.2Co0.2O2 cathode and Li metal anode. The cycling performance was analyzed with electrochemical diagnostics tools. The Li surface morphology was characterized with scanning electron microscopy. The effects of various external pressure on cycling efficiency and the Li surface morphology will be illustrated and discussed.

References:

[1] Battery500 Consortium to Spark EV Innovations: Pacific Northwest National Laboratory-led, 5-year $50M effort seeks to almost triple energy stored in electric car batteries, in Office of Technology Transitions Energy.gov (2016).

[2] Gireaud, L., Grugeon, S., Laruelle, S., Yrieix, and B., Tarascon, J. –M., Electrochem. Comm.
8, 1639–1649 (2006)