bluuebunny/crossref_metadata_2025 huggingface dataset:
Measuring Li+ Inventory Losses in LiCoO2/C Cells Using Ex-Situ Raman Spectroscopy
Authors: Snyder Chelsea Marie , Duquette David , Apblett Christopher A. , Grillet Anne M. , Beechem Thomas E.
Published: February 2020

For the future progress of lithium ion batteries, identifying and understanding degradation mechanisms that affect the cycle-life are of major interest. Beyond identification, it is necessary to assess the relative influence of individual mechanisms to the totality of capacity fade [1-3
]. Specifically, comparisons between the relative impact of several mechanisms—primary active material loss (Li+ inventory), secondary active material loss (LiCoO2 and/or Graphite), and increased internal cell resistance (caused by surface films)—remain the topic of continued investigation [1].  Such effort is complicated by the dependence of these mechanisms to several parameters as it has been shown that their relative significance can vary based upon: the physical and chemical nature of the system, cycle rate [1], and testing temperature [2].  

Owing to this complexity, multiple means of characterization are necessary to link global performance to the local mechanisms belying such performance. Most often electrochemical techniques are employed to link capacity fade to the aforementioned mechanisms [2-4]. Such techniques are unable, however, to specify local, crystal structure, alterations to this fade.  In response, ex-situ Raman and electrochemical techniques are combined here to link local structural information of active particles to capacity loss. The Raman spectrum of LiCoO2 is sensitive to the state of lithiation and can therefore be leveraged to quantify the state of lithiation. Specifically, we investigate the Raman response of LiCoO2 cathode particles in full cells subject up to 80 cycles at slow rates (C/10), see Fig. 1. Cycle dependent changes in Raman spectra are compared to bulk electrochemical behavior – and hence capacity loss- demonstrating that such loss is linked to reductions in Li+ inventory commensurate with SEI formation and growth.

Acknowledgment

Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

References

G. Ning, B. Haran, and B. N. Popov, Journal of Power Sources, 117 (1-2), p. 160-169, 2003

M. Safari, and C. Delacourt, Journal of The Electrochemical Society, 158 (10), p. A1123-A1135, 2011

B. Stiaszny, J. C. Ziegler, E. E. Krauss, M. Zhang, J. P. Schmidt, and E. Ivers-Tiffée, Journal of Power Sources, 258, p. 61-75, 2014

J. Cannarella, and C. Arnold, Journal of Power Sources, 245, p. 745-751, 2014

Figure 1
Investigation of the Solid Electrolyte Interphase (SEI) in Polysulfide-Containing Glyme-Based Electrolytes
Authors: Agostini Marco , Shizhao Xiong , Matic Aleksandar , Hassoun Jusef
Published: February 2020

The massive employment of non-renewable fossil fuels has resulted in a rapid increase of greenhouse gas emission and global warming. The consequent excessive climate changes have triggered a new energy policy, mainly focused on clean and renewable sources.
1
Solar and wind energy conversion systems are the most suitable for large-scale diffusion, in particular in view of recent advances reflecting in cost reduction and economic advantages.
1
However, these discontinuous energy sources require side systems for energy storage and electrical grid stabilization.
2
Furthermore, electrified vehicles using high-energy storage systems matching the automotive market requirements may effectively mitigate the environmental pollution in large urban areas.
2
Thus, there is a large push for the development of high capacity energy storage technologies.

Lithium−sulfur battery appears as one of the most promising technologies due to its high theoretical capacity and energy density, i.e. 1672 mAh g−1 and 3500 Wh kg−1 basing on the sulfur weight, respectively, the natural abundance, the low toxicity of elemental sulfur, and the expected low cost.
3
However, a sulfur electrode in a lithium battery shows several drawbacks, including poor electronic conductivity, high solubility of the polysulfides formed during the electrochemical process, large volume changes (approximately 80%) by operation, and precipitation of insoluble Li−S intermediates formed during the discharge process in the electrolyte solution. These remarkable issues, leading to severe capacity fading and Li−S cell deterioration upon cycling, have been already investigated in terms of the reaction mechanism.
4

Herein, we reported a detailed study of an important aspect, i.e., the chemical−physical and electrochemical characterization of the electrode−electrolyte interphase. Indeed, we comparatively investigate the properties of the SEI film formed at the lithium electrode surface in tetraethylene glycol dimethyl ether (TEGDME)-based electrolytes containing different polysulfide species, namely Li2S2, Li2S4, Li2S6, and Li2S8, added within a constant concentration of 5% w/w.
5

References

(1) Armand, M.; Tarascon, J.-M. Nature
2008, 451, 652−657.

(2) Bruce, P. G.; Freunberger, S. A.; Hardwick, L. J.; Tarascon, J.-M. Nat. Mater.
2012, 11, 19−29.

(3) Ji, X.; Nazar, L. F. J. Mater. Chem.
2010, 20, 9821−9826.

(4) Ryu, H.-S.; Guo, Z.; Ahn, H.-J.; Cho, G.-B.; Liu, H. J. Power Sources
2009, 189, 1179−1183.

(5) Agostini, M.; Shizhao, X.; Matic, A.; Hassoun, J. Chem. Mater
2015, 27, 4604−4611.
Development and Novel Characterization of All-Solid-State Thin Film Batteries
Authors: Wynn Thomas Andrew , Wang Ziying , Lee Jungwoo Zema , Rustomji Cyrus Sam , Meng Ying Shirley
Published: February 2020

All-solid-state batteries are looked to for their high energy density and reduced capacity fade, and are a safer alternative to the conventional liquid electrolyte batteries currently being manufactured. However, few solid electrolytes are currently known. Amorphous lithium phosphorus oxynitride (LiPON) is a well-established solid electrolyte and is currently the only viable solid-state electrolyte for thin film batteries. LiPON is stable in contact with Li metal, but exhibits a relatively low ionic conductivity (10-6 S/cm2) [1]. A variety of other solid electrolytes with higher ionic conductivities are currently being explored, such as lithium lanthanum titanate (LLTO), achieving high lattice ionic conductivity of >10-3 S/cm2 [2]. We aim to enable LLTO as an electrolyte for thin film batteries via pulsed laser deposition. Additionally, performance of all-solid-state batteries is largely influenced by interfacial impedance and phase evolution during charge and discharge. The thin film geometry provides an ideal platform for analyzing the various electrode/electrolyte interfaces. Using novel focused ion beam and dynamic in situ transmission electron microscopy techniques, we have fabricated electrochemically active nanobatteries and observed their cycling behavior in situ. These techniques have been demonstrated on the layered lithium cobalt oxide (LCO)/LiPON interface, elucidating the mechanism of interfacial impedance which was previously unknown via ex-situ cycling experiments [3].

[1] N.J. Dudney, “Solid-state thin film rechargeable batteries,” Materials Science and Engineering: B, 116 (2005) 245-249.

[2] O. Bohnke, “The fast lithium-ion conducting oxides Li3xLa2/3 − xTiO3 from fundamentals to application,” Solid State Ionics, 179 (2008) 9-15.

[3] Z. Wang, D. Santhanagopalan, W. Zhang, F. Wang, H. Xin, K. He, J. Li, N. Dudney and Y.S. Meng, “In situ STEM/EELS Observation of Nanoscale Interfacial Phenomena in All-Solid-State Batteries,” Submitted.
The Role of the F Anion in the Spinel Structure for the Enhancement of High Rate Capability and Cyclability in LiNi0.5 Mn1.5 O4-XFx Crystals
Authors: Kim Dae-wook , Shiiba Hiromasa , Zettsu Nobuyuki , Teshima Katsuya
Published: February 2020

Lithium ion secondary batteries are one of the most important energy storage systems because of their higher energy density and power density. In particular, many different types of cathode materials are studied for increasing capacity and cell potential. Spinel-type LiNi0.5Mn1.5O4 (LNMO) have been attracting significant attention due to higher redox potential, lower cost and low environmental load. The LNMO is possibly sorted into two type of spinel structure with different space group, ordered and disordered phase, which is typically identified due to formation of oxygen deficient, which cause reduction of Mn4+ to Mn3+ based on charge valance.     

Disordered spinel structures could also lead to improved rate capability due to higher electronic conductivity and Li-ion diffusive of Mn3+ ion, However, too much concentration of Mn3+ lead to structural distortion and disproportionation, and which can be reduce cyclability. Thus, Mn cation adjustment is one of important factor for advanced LNMO electrode.  

Therefore, in order to control efficiently Mn cation, fluorine was considered for substitution within LNMO. Because fluorine can easily control cation distribution due to charge valance and, which can adjust the degree of disorder. Besides, strong M-F bonding can be maintains spinel structure during long-term operation. In present work, we have demonstrated the flux growth of idiomorphic LiNi0.5 Mn1.5O4-xFx crystals and the effect of fluorine substitution on their LIBs characteristics, including rate capability and cyclability.
On Lithium Transference Number in Liquid-Solid Electrolytes
Authors: Popovic Jelena , Maier Joachim
Published: February 2020

The application of high lithium transference number electrolytes in lithium ion batteries is greatly beneficial as they would prevent the occurrence of salt concentration gradients which may limit battery cell lifetime and energy density. In “soggy sand” electrolytes (insulating oxide nanoparticles dispersed in typically organic lithium salt solution), lithium transference number close to unity is expected to be achievable at high volume fractions as a consequence of disappearing bulk conductivity.[1] Such a trend has already been observed in the 1 M LiTf/PEGDME-150 containing mesoporous MSU-H nanoparticles.[2] A convenient way of circumventing particle network reproducibility and stationarity is by infiltration of monolithic hierarchically porous SiO2 (with various surface modifications) or Al2O3 with 1 M LiTf/PEGDME-150 leading to liquid-solid electrolytes with very high lithium transference number (0.75 to 0.89) without compromising high room temperature ionic conductivity (0.32 to 0.48 mS cm-1).[3] Additionally, importance of indirect (vehicular) transport mechanism of lithium and deconvolution of contributions of free ions and ion pairs to the overall conduction in LiTf/PEGDME-150 liquid electrolyte by a combination of experimental techniques (impedance spectroscopy, dc polarization, pulse field gradient NMR) will be discussed.[4] The pertinence of liquid/solid electrolytes is remarkable as they could make lithium battery separators dispensable offering form stability and excellent contact with high power nanostructured electrodes.     

C. Pffafenhuber, M. Göbel, J. Popovic, J. Maier, 
Physical Chemistry Chemical Physics, 15(42), 18318–18335, 2013.

C. Pfaffenhuber, F. Hoffmann, M. Fröba, J. Popovic, J. Maier, Journal of Materials Chemistry A, 1(40), 12560–12567, 2013.

J. Popovic, G. Hasegawa, I. Moudrakovski, J. Maier, Advanced Materials, submitted

J. Popovic, C. Pfaffenhuber, J. Melchior, J. Maier, Electrochemistry Communications, 60, 195–198, 2015.
(Invited) Advanced Cathode Material for High Energy Sodium-Ion Batteries
Authors: Sun Yang-Kook
Published: February 2020

Rechargeable sodium batteries due to the almost infinite supply of the metal, are the most appealing as immediate alternatives to lithium batteries. Despite of cost advantages, sodium ion batteries still have some drawbacks of cathode, anode and electrolyte. In response, we have developed a sodium-ion battery that has an electrolyte of NaClO4 in a mixture of ethyl methanesulfonate electrolyte (EMS) and fluoroethylene carbonate (FEC) additive for increasing the stability and conductivity, along with an anode of carbon-coated Fe3O4 and a cathode of O3-type layered Na[Ni0.25Fe0.5Mn0.25]O2. Additionally, we proposed the high energy cathode material that having unique nano-rod structured with varied chemical composition. This novel concept cathode show the outstanding electrochemical activity and structural stability of high-Ni systems. We believe that the suggested concepts can be used as the cathode material for high energy and high power sodium batteries. These batteries should be able to compete with lithium batteries in terms of cost, battery performance and safety.
Preparation of LiCoO2/Li3BO3/Li6.75La3Zr1.75Nb0.25O12 composite Electrodes By Using Flux Growth and Characterization of Their Electrochemical Properties for All-Solid-State Libs
Authors: Zettsu Nobuyuki , Onodera Hitoshi , Kaneko Sakina , Teshima Katsuya
Published: February 2020

We performed flux growth of LiCoO2/Li3BO3/Li6.75La3Zr1.75Nb0.25O12 composites with various composite ratio. Powder XRD profiles and cross-sectional SEM images revealed that individual LiCoO2 and Li6.75La3Zr1.75Nb0.25O12 single crystals were homogeneously dispersed in amorphous Li3BO3 matrix without formation of any sub-phase at the interphase even though the crystal growth process was performed under 1000 oC for 5h. The each crystals size and the relative density of the composite was increased as increasing time and temperature. The relative density was maximally 92%. Indicating that small amount of Li3BO3 plays a key rule for insulating the direct contact of LiCoO2 with Li6.75La3Zr1.75Nb0.25O12 as well as for assisting the enhancement of relative density of composites relied on liquid-state sintering principle. The Li ion conductivity of the composite with ca. 700 mm thick was 1.1×10-4 S/cm at room temperature, as evaluated by AC-impedance spectroscopy. We also characterized their all-solid-state LIBs properties.
Bacteria-Assisted Synthesis of Electrode Materials for Li or Na Batteries
Authors: Mirvaux Boris , Recham Nadir , Miot Jennyfer , Courty Matthieu , Guyot François , Larcher Dominique , Tarascon Jean Marie
Published: February 2020

The production of materials for high-energy Li-ion batteries is generally associated with negative environmental footprints, due to high temperatures required and chemical toxicity of their components [1]. Our goal is to explore new bio-assisted low-temperature routes of synthesis in order to reduce this environmental impact and possibly improve their electrochemical performances.

Bacteria are easy to grow; able to mineralize transition metals and other elements [2], with controlled morphology, crystal structure and texture; they also constitute a potential source of conductive carbon. For these reasons, bacteria assisted synthesis caught our attention, especially as exceptional power performances were already shown for biomineralized hollow shells of hematite (α-Fe2O3) [3] when compared to those of non-textured material.

Hydrated amorphous ferric phosphate (a-FeIIIPO4·~3H2O) was precipitated from aqueous solution at 30°C under air at the contact of bacteria (Sporosarcina pasteurii). The resulting materials were investigated using various techniques (e.g. thermal analysis, mass spectrometry, infrared spectroscopy, electron microscopy) and consist of dead bacteria (2-3 µm x 0.5 µm) coated by a 70 nm thick layer of interconnected a-FeIIIPO4·~3H2O particles (40-80 nm), as presented by the following microscopy image. Surface chemistry of the bacterial cell wall plays a key role in the nucleation process thereby controlling particle size. After a mild temperature treatment, a 90 mAh/g capacity has been achieved versus Li (at 3.0 Volts mean voltage) with an excellent cyclability, constant coulombic efficiency (~100%) and interesting power performances. This approach allows overcoming the intrinsic poor conductivity of Fe phosphate without any use of harsh mixing treatments with conductive additive, or complex synthetic procedure.

Bacteria are capable of many things and we are now applying this strategy for other materials and other metals like manganese. We will also address the positive attributes of these bio-assisted synthesis for application in Na-based batteries.

[1] Samaras C., Meisterling K., Environmental Science & Technology. 42, 3170 (2008).

[2] Dupraz S. et al., Chemical Geology. 265, 54 (2009).

[3] Miot J. et al., Energy & Environmental Science. 7, 451 (2014).

Figure 1
The Influence of Blood Proteins on the Mobility of Self-Propelled Electrodeposited Microtubes
Authors: Wang Hong , Zhao Guanjia , Pumera Martin
Published: February 2020

Self-propelled micromotors have attracted considerable interests recently due to the potential to address problems in biomedical and environmental problems. One of the most promising types of micromotors is tubular micromotors, which are microtubes with platinum inner surface to catalyze the decomposition of hydrogen peroxide. Propulsion by oxygen bubbles provides microtubes with high velocity, robust performance and large towing power. The microtubes are prepared using a modified membrane template electrodeposition method. The high density of relative homogenous pores in the membrane allows mass electrodeposition of microtubes. The microtubes we used in the study are conical bimetallic microtubes with a copper outer surface and a platinum inner surface. Proteins are common in biomedical environment where the electrodeposited microtubes are envisioned to perform tasks. Therefore, we examined the effect of blood proteins on the mobility of the electrodeposited microtubes. The presence of blood proteins at physiological concentrations has been found to be able to reduce the mobility of the electrodeposited microtubes. These findings may provide important implications for employment of electrodeposited microtubes in biomedical field.
(Invited) Graphene Plane Electrode for Low Power 3D Resistive Random Access Memory
Authors: Lee Seunghyun , Sohn Joon , Jiang Zizhen , Chen Hong-Yu , Wong H. -S. Philip
Published: February 2020

The central theme of the “Internet of Things” is a societal and technological movement towards ubiquitous, abundant-data computing. Such transformation requires real-time analytics on enormous quantities of data collected by a vast network of sensors and other autonomous sources feeding into the data cloud. Current computing technology, however, cannot satisfy such applications with the required throughput and necessary energy efficiency. The next technology frontier will be monolithically integrated chips with 3-dimensionally interleaved memory and logic for unprecedented data bandwidth with reduced energy consumption. In this work, we exploit the atomically thin nature of the graphene plane to assemble a resistive memory stacked in a vertical 3D structure. Compared to the same architecture that uses conventional metal (Pt) as an RRAM electrode, the atomically thin graphene edge electrode was able to reduce power consumption by ×300 while producing a highly localized electrical field for oxygen anion migration. The switching energy of this device is one of the lowest reported compared to existing alternative memory technologies. Importantly, circuit analysis of the 3D architecture using experimentally measured device properties show higher storage potential for graphene devices compared that of metal based devices.
(Electronics and Photonics Division Award) High Power Nitride Based Field Effect Transistors
Authors: Shur Michael
Published: February 2020

Nitride semiconductors have a great potential for high power applications because of a high breakdown field, a very large density of polarization induced two-dimensional electrons, high electron saturation and overshoot velocities, a relatively high mobility, excellent thermal properties, chemical inertness, and radiation hardness. GaN power transistors grown on silicon substrates are already being commercialized. However, while their performance characteristics are competitive or even surpass the best silicon based power transistors, the full potential of the nitride materials for power applications is still to be achieved and will require dramatic changes in the device design that account for the materials properties of wide band gap materials. Such new features include the use of diamond substrates for a better heat removal, adding a low conducting passivation in the high field region between the gate and drain, changing the gate geometry to the perforated channel with perforations extending beyond the gate, using AlInN for lattice matching design to improve stability and reach a high temperature operation and employing lateral-vertical designs and cascade solutions. This presentation will review of the state-of-the –art power GaN based transistors and project the potential improvements in their performance
ZnSe Nanowires Synthesis and Characterization
Authors: Hung Yu Chen , Wang Chiu-yen
Published: February 2020

ZnSe nanowires (NWs) were synthesized by using a thermal evaporation method in a vacuum-sealed quartz tube inside a tube furnace. NWs were used ZnSe powder as a precursor to grow. ZnSe NWs grow on silicon (100) substrates coated with different thickness 2, 5, and 10 nm Au catalysts film. The growth mechanism of NWs is vapor-liquid-solid (VLS) mechanism. It will help us to get the good crystallinity and less defect in the NWs. Moreover, we will observe the different condition of NWs by controlling the temperature of precursor, temperature of growth area, pressure, carrier gas, thickness of Au film, position of substrate and growth time of NWs. The temperature of precursor decides the amount of the ZnSe vapor. As the temperature is higher the vapor will come out more and quickly. The temperature of growth area controls the precipitate condition of NWs. Also, pressure is one of the important condition of growing NWs. It controls the growth environment, such as the magnitude of vapor pressure. In this work, the pressure is kept around 0.4 to 1 Torr to observe the variation of NWs. Carrier gas in this work mainly affects the position of the NWs growth. However, in this work different thickness of Au film cannot be observed the obviously different dimeter. Position of substrate can show the growth area of the NWs, namely the distribution of NWs. It combines above conditions such like pressure and carrier gas. NWs in different position can grow verity of configuration or distribution. At last, growth time of NWs determine the density and length of NWs. As the time is longer, NWs will become longer and more density. Combination of above conditions, the length of appropriate NWs we need is about 20-50 μm, and the dimeter is around 80 nm. Furthermore, the morphorlogy of NWs is uniform and straight. ZnSe NWs were characterized by field-emission scanning electron microscope (FE-SEM), X-ray diffractometer (XRD), and transmission electron microscope (TEM) about the morphology and crystal structure.
A Novel and Robust Packaging Technology for Miniaturized FET-Based Biosensors with Microfluidic Channels
Authors: Hsu Chen-Pin , Chen Pei-Chi , Wang Yu-Lin
Published: February 2020

FET devices are extensively used for sensors, including gas sensors and biosensors. In contrast to traditional resistive devices, FET has transconductance gain, which can significantly improve the S/N ratio. Recently, more and more applications in biosensors combine microfluidic channels and the FET system. In FET-based biosensors, the wafer manufacturing process always requires a lot of cost, and most of the chip area is used for metal lines as interconnect. Miniaturized chip plays a key role in reducing the manufacturing cost. However, simultaneously integrating the sensor chip and microfluidic channels on one chip is challenging. In this study, a novel and robust packaging method has been developed, to effectively reduce the size of the sensor chip and thereby the cost. 1 mm x 1 mm FET sensor chip has been fabricated and embedded in epoxy. Photolithography and metal deposition were done followed by lift-off process for metal interconnect. The FET-embedded chip was passivated and covered by the microfluidic channel made of PDMS. Figure 1 shows the schematic of the system and the final package size is 1cm x 1cm. Electrical measurement is also proceeded with liquid sample to confirm the usability.

Figure 1
Tellurium Nanowire Arrays-Based Nanogenerators for Thermal Energy Harvesting
Authors: Li Ying-Chun , Lin Zong-Hong
Published: February 2020

Semiconductor nanorods and nanowires are interesting nanomaterials and have been applied in sensor and energy applications. Tellurium is a typical p-type semiconductor having bandgap energy of 0.35 eV and has already been recognized as an interesting material for fabricating nanodevices. For examples, tellurium nanowires have shown great potential in the applications of nanogenerators, supercapacitor, lithium battery, and biosensors. In this paper, we developed a thin, light-weight, and flexible thermoelectric nanogenerator based on the nanocomposite of tellurium nanowire arrays and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). The Seebeck coefficient of the nanocomposite was determined to be 235 μV/K. A linear relationship between the output voltage and the temperature difference across the thermoelectric nanogenerator was observed. We demonstrated that the thermoelectric nanogenerator can be integrated with fiber fabric and harvested the thermal energy from human body temperature. Not only for the purpose of energy harvesting, the thermoelectric nanogenerator can also function as a self-powered sensor for water temperature measurement.
(Invited) Graphene Plasmonics: Plasmon-Plasmon Hybridization and Chemical Sensing
Authors: Farmer Damon , Avouris Phaedon , Han Shu-Jen
Published: February 2020

Graphene has emerged as an interesting material for plasmonic applications in the terahertz to mid-infrared, the spectral region where its plasmonic resonance typically resides.  The coupling behavior of graphene plasmons with both molecular vibrations and other plasmons will be presented.  Plasmon energy dispersion with the number of stacked graphene layers allows for the creation of multi-mode plasmonic structures, where unconventional plasmon-plasmon hybridizations arise, resulting in an increased infrared absorption bandwidth.  Interaction of graphene plasmons with molecular vibrations results in electromagnetically induced transparency phenomena in plasmon light absorption, thereby increasing the effective infrared absorption cross section of the molecular vibrations.  As both bandwidth enhancement and detection sensitivity enhancement have practical value, potential technological implications of these results will also be discussed.
(Invited) Synthesis and Applications of Novel Two-Dimensional Nanomaterials
Authors: Zhang Hua
Published: February 2020

In this talk, I will summarize the recent research on synthesis, characterization and applications of two-dimensional nanomaterials in my group. I will introduce the synthesis and characterization of novel low-dimensional nanomaterials, such as  graphene-based composites including the first-time synthesized hexagonal-close packed (hcp) Au nanosheets (AuSSs) on graphene oxide, surface-induced phase transformation of AuSSs from hcp to face-centered cubic (fcc) structures, the synthesis of ultrathin fcc Au@Pt and Au@Pd rhombic nanoplates through the epitaxial growth of Pt and Pd on the hcp AuSSs, respectively, the first-time synthesis of 4H hexagonal phase Au nanoribbons (NRBs) and their phase transformation to fcc Au RNBs as well as the epitaxial growth of Ag, Pt and Pd on 4H Au NRBs to form the 4H/fcc Au@Ag, Au@Pt and Au@Pd core–shell NRBs, and the epitaxial growth of metal and semiconductor nanostructures on solution-processable transition metal dichalcogenide (TMD) nanoshees at ambient conditions, single- or few-layer metal dichalcogenide nanosheets and hybrid nanomaterials, the large-amount, uniform, ultrathin metal sulfide and selenide nanocrystals, other 2D nanomaterials, nanodots prepared from 2D nanomaterials, and self-assembled 2D nanosheets and chiral nanofibers from ultrathin low-dimensional nanomaterials. Then I will demonstrate the applications of these novel nanomaterials in chemical and bio-sensors, solar cells, water splitting, hydrogen evolution reaction, electric devices, memory devices, conductive electrodes, other clean energy, etc.
(Invited) A Systematic Approach to Develop and Validate Models for the Design of Membrane Electrode Assemblies
Authors: Putz Andreas Michael Vincent , Secanell Marc
Published: February 2020

The modeling and simulation landscape for fuel-cells has increased dramatically over last years. A number of commercial and OpenSource (e.g. OpenFCST,  FAST-FC, DuMux) software packages are available to the aspiring researcher or engineer in academia and industry.

The complexity ranges from purely analytic models with O(1) number of parameters to fully numerically models with O(100) input parameters. However, despite the apparent abundance on model and simulation tools, their practical use for the design of next generation MEA components like the catalyst layers or porous transport layers has been very limited and progress has been mainly driven by large, slow and expensive experimental studies. This stands in stark contrast to combustion engine design where virtual prototypes are built, tested and optimized through numerical simulations before a physical prototype is built. In the fuel-cell community this lack of application tends to be explained by the large number of equations and the corresponding computational resources needed to tackle the problem. The fact that combustion engineering does not suffer this problem, despite an equally high level of complexity, seems to indicate that numerical complexity is not the root cause.

Browsing the numerical codes and the modeling literature shows little consensus about the correct description of the individual physical effects. A few of the topics of disagreement are:

Gas transport: Fickian diffusion,  Maxwelll-Stefan diffusion, Dusty Gas models, ...

Membrane water transport: concentration driven, liquid pressure driven, ...

Reaction at the catalyst surface: macro-homogeneous models, ionomer filled agglomerate models, water filled agglomerate models,thin film models, ...

Electrochemical reaction mechanisms: Tafel,  Butler-Volmer, Double-Trap, Dual-Path, ...

...

In this tutorial, a consistent validation strategy with a focus on gas mass transport is outlined and demonstrated. We will take AFCCs baseline MEA model platform OpenFCST through a

validation with ex-situ experiments: Permeability and Diffusivity

validation through in-situ experiments:

Limiting current methods

Polarization curves under different operating conditions

Thickness variations

validation through imaging techniques:

Diffusion simulations on reconstructed catalyst layers

The impact of different model configurations will be studied and we will investigate if a validation strategy like this can pinpoint the weaknesses or strengths of the model configuration chosen.

References

OpenFCST (www.openfcst.org)

M. Bhaiya, A. Putz and M. Secanell, "Analysis of non-isothermal effects on polymer electrolyte fuel cell electrode assemblies", Electrochimica Acta, 147C:294-309, 2014. DOI: 10.1016/j.electacta.2014.09.051

Figure 1
(Invited) Coupling of Mechanical and Transport Phenomena in Ionomers
Authors: Goyal Priyamvada , Monroe Charles W
Published: February 2020

In a polymer-electrolyte membrane (PEM) within a fuel cell, water transport can be driven by diffusive, electro-osmotic, and permeative mechanisms. The equilibrium thickness of a PEM is also known to change substantially with respect to both water content and applied pressure. Most physical models treat hydraulic permeation or diffusion/osmosis in isolation; those that account for both phenomena in parallel do not always incorporate the pressure in a way that permits the analysis of all possible boundary conditions. Kusoglu and Weber have recently highlighted the need for models that handle situations involving simultaneous gradients of both pressure and water activity across constrained, swelling membranes [1].

This talk will focus on our recent efforts to reconcile all the transport modes within a rigorous multicomponent transport formalism that incorporates standard diffusive properties such as ionic conductivity, water activity coefficient, water diffusivity, and electro-osmotic drag coefficient alongside elastic properties such as the bulk modulus and Poisson ratio. The key ideas are that a volume-explicit equation of state needs to be incorporated along with the typical governing equations that describe the membrane bulk, and that a momentum balance needs to be included to determine how stress is distributed within the membrane. Information embodied in the stress tensor is, in some sense, independent of the information in the diffusion driving force that accounts for molecular and pressure diffusion. Thus hydraulic and diffusive modes can be handled in parallel without any additional simplifications.

We will present a macroscopic model that describes the volume change of or water redistribution within vapor-equilibrated ionomers in freely swelling or constrained geometries. The model will be used to underpin simulations that show how strain arises (and is distributed) during typical water-flux measurements across vapor-equilibrated membranes [2]. Values of the key parameters will be discussed in light of literature data as well. An experimental program will be suggested through which the most important properties can be probed.

References

[1] A. Kusoglu and A.Z. Weber, “Electrochemical/Mechanical Coupling in Ion-Conducting Soft Matter,” The Journal of Physical Chemistry Letters
6(2015) 4547-4552.

[2] C.W. Monroe, T. Romero, W. Mérida, and M. Eikerling, “A vaporization-exchange model for water sorption and flux in Nafion,” Journal of Membrane Science
324 (2008) 1-6.
(Science for Solving Society’s Problems Challenge Grant Winner) Sustainable Water Treatment Using an SOFC-Based Combined Heat and Power System
Authors: Hays Thomas H , Wachsman Eric D
Published: February 2020

Without adequate sanitation and a reliable supply of potable water, it can be very difficult for individuals in developing nations to pursue education or other activities that would improve themselves or their communities. Addressing this problem at the local level with a strategy of distributed water purification powered by local fuel resources will be very effective. Using methane derived from agricultural waste, durable small scale SOFC units can generate significant amounts of electricity and heat. By leveraging both electrical and thermal energy, very high system efficiency is possible. The fuel flexibility, modularity, and the all solid state nature of SOFCs make them ideal for operation in remote areas.

Electrical and thermal outputs from a biogas fueled SOFC are measured and total cell efficiency is calculated to inform design criteria for the proposed power units. Stability to sulfur contamination is determined by measuring voltage drop during operation at the current density corresponding to maximum power. Using the information gathered from these tests, a basic analysis of the system size and fuel requirements necessary for community level use is presented.
A Coupled Experimental/Numerical Approach for Tuning High-Performing SOFC-Cathode
Authors: Celikbilek Ozden , Jauffres David , Dessemond Laurent , Burriel Mónica , Martin Christophe L , Djurado Elisabeth
Published: February 2020

The present study concerns the influence of the micro/nano-structural properties of LSCF (La0.6Sr0.4Co0.2Fe0.8O3−δ) and 60:40 vol.% LSCF/CGO (Ce0.9Gd0.1O2-δ) composite cathode films on their electrochemical behavior. Electrostatic spray deposition technique is used to deposit 10 μm-thick functional films (Fig. 1). Contrary to expectations, pure LSCF showed a better response compared to the composite material. It exhibits Area Specific Resistance (ASR) values as low as 0.021 and 0.068 Ω.cm2 at 650 ˚C and 600 ˚C respectively. These values are, to the best of our knowledge, one of the lowest reported to date for LSCF-6428 composition in open circuit voltage (OCV) condition.1 To better comprehend the complex relationships between material properties, processing, micro/nano structure and electrode performance, a simplified geometry representing the typical 10x10x10 μm3 porous columns of the electrodes is modelled by 3D finite element (FEM).2 ASR is computed with real microstructural parameters obtained from 3D FIB/SEM technique. On the other hand, it is also calculated by a simple volume-averaged analytical model (1D-ALS model)3 within an assumed macrohomogeneous geometry. The computed ASRs with these two relatively simple models are compared to experimental results and the relevance of such models for inhomogeneous microstructures like ‘columnar’ is discussed.

Figure 1: Microstructural characterization of the films a-c) LSCF, e-g)  60/40 vol.% LSCF/CGO composite films observed by SEM. 3D reconstructed images by FIB/SEM technique of  (d) LSCF and (h) 60:40 LSCF/CGO composite.

Celikbilek, O., Jauffres, D., Dessemond, L., Burriel, M., Martin, C.L., Djurado, E.,(2015), to be submitted to J. Mat. Chem. A

Haffelin, A., Joos, J., Ender, M., Weber, A., Ivers-Tiffee, E. (2013). J. Electrochem. Soc. 160, F867–F876

 Adler, S. B., Lane, J. A. & Steele, B. C. H. (1996). J. Electrochem. Soc. 143, 3554–3564

Figure 1
Electrochemical Performance and Durability of (Pr1-xNdx)2NiO4 As the Cathode for Solid Oxide Fuel Cells
Authors: Dogdibegovic Emir , Guan Wanbing , Wright Christopher J. , Zhou Xiao-Dong
Published: February 2020

Single phase (Pr1-xNdx)2NiO4 powders (x=0, 0.25, 0.50, 0.75, 1) were synthesized via glycine-nitrate combustion process. Rietveld refinement shows that the unit cell volume decreases linearly with an increase of x. This volume contraction is mainly driven by a decrease in c parameter which follows Vegard’s Law. Reproducible performance was obtained for each cathode composition providing the wealth of data for quantitative studies. The overall cell performance decreases with an increase in Nd content between 650 and 850 °C, based on analysis of area specific resistance and i-E measurements. Performance stability was studied at 750 °C and 0.8 V. In comparison to the parent compound Pr2NiO4, the total polarization increases by 29% in (Pr0.5Nd0.5)2NiO4 and by twofold in (Pr0.25Nd0.75)2NiO4. Although exhibiting the highest peak performance, Pr2NiO4-based cells show 4% performance degradation within 500 hours, while the degradation is negligible in other compositions. Dynamic dependency of EIS spectra, as function of current density, is in agreement with dc measurements.
Thermodynamically and Electrochemically Activated Oxygen Surface Exchange Process in Lscf As Solid Oxide Fuel Cathode
Authors: Zhang Xinxin , Liu Xingbo
Published: February 2020

In this paper, the thermodynamically (oxygen partial pressure) and electrochemically (overpotential) activated oxygen surface exchange process for LSCF were investigated. The oxygen surface (La0.6Sr0.4)0.995Co0.2Fe0.8O3-δ(LSCF) dense layer was successfully coated on Gd-doped CeO2(GDC) electrolyte by air brush spraying and pressing method with thickness 5-20µm. The electrochemical properties of the three electrode cells (LSCF/GDC/Pt) were characterized by electrochemical impedance spectrum under difference oxygen partial pressure and bias voltage conditions. One main arc under lower frequency was shown in the EIS pattern, which indicates that the rate limiting step focus on the surface oxygen reduction reaction. The surface oxygen exchange coefficients calculated based on the cathode polarization resistance is 0.25-3.5×10-7 cm/s for LSCF at 700oC in the range of 0.0002-0.2 atm, and decrease with increasing the oxygen partial pressure.  Similar tendency was observed in the variation of the bias voltage from -0.1-0.1 V, corresponding withk values 0.75-1.8×10-7 cm/s. However,the uncoordinated relationshipon k values was obtained between oxygen partial pressure and bias voltage based on the Nernst equation, where the slope for the variation of bias voltage is lower than that for the variation of oxygen partial pressure. The theoretical defect concentration and electrostatic potential in the cathode were analyzed under different oxygen partial pressure and bias voltages. It indicates thatboth surface oxygen vacancy concentration influenced by thegradient of the oxygen vacancy in bulk electrode under bias voltage and the surface over-potential relating with the charged oxygen species coverage work on  this deviation.
Effect of Thermal Treatment on Structural/Electrical Properties of Protective Oxides for SOFC Metallic Interconnects
Authors: Tsai Shu-Yi , Fung Kuan-Zong , Ni Chung-Ta
Published: February 2020

For intermediate temperature SOFC applications, metallic interconnects, such as Crofer 22H, have been used to replace ceramic interconnects in SOFC stacks because they are less expensive, more conductive and able to form complex shapes. Most metallic interconnects use chromium-containing alloy that form chromia scales at high temperatures. Since chromia may react with cathode and cause degradation, a protective oxide may be used to suppress the growth of chromia. Several techniques have been adopted to deposit oxides on metallic interconnects, thermal spray is found to be an appropriate technique. Thermal spray coating process has been used to produce a high quality coating by a combination of high temperature, high energy heat source, a relatively inert spraying medium, usually argon, and high particle velocities. This process allows the spraying of various types of metallic or ceramic coatings on to a wide range of substrate materials. As a result, uniform coating layer with excellent bond strength to substrate is obtained without noticeable distortion.

However, the temperature during thermal spraying may be high enough to change the crystal structure and conductivity of protective oxides. The heat treatment is believed to be an appropriate method to obtain adequate properties for protective oxide.

In this study, conducting oxides were deposited on metallic interconnect using plasma spray technique. However, the deposition temperature for thermal spray coating may be high enough to change the crystal structure and conductivity of protective oxide. The post annealing at elevated temperature is found to be an appropriate method to obtain adequate properties for protective oxide. Thus, the objective of this work is to investigate the effect of annealing on the crystal structure and conductivity of the sprayed oxide. The crystal structure, morphology and electrical conduction of interconnect with sprayed oxide films will be examined by using XRD, FESEM and resistance measurement.
Internal Partial Pressure and Durability of Bcy Based Protonic Ceramic Fuel Cells As a Function of Electrolyte Thickness
Authors: Lim Hyung-Tae
Published: February 2020

Internal partial pressure in BCY based solid oxide fuel cells were measured as a function of electrolyte thickness. The measurements of internal  ΔΦ were conducted on the thin (~ 10 µm) and thick (~ 50 µm) BCY electrolyte using an embedded Pt probe, and it was observed that  ΔΦ depends on the electrolyte thickness. Using the values of internal ΔΦ, internal hydrogen and oxygen partial pressure were calculated, and it was found that the internal partial pressure changes with electrolyte thickness. Thin BCY cells are dominated by the near-cathode gases rather than the near-anode gases, indicating it is more vulnerable to water vapor produced at the cathode during fuel-cell operation. The correlation between internal partial pressure profile and performance durability were also investigated. CC tests were conducted on a thin (~ 10 µm) BCY-electrolyte cell with BCY + LSCF cathode, and on a thick (~ 35 µm) BCY electrolyte cell with BZY + LSCF cathode, at positive and negative cell voltage. The former showed a rapid rate of voltage drop under all operating conditions, while the latter showed much more stable performance, even when operating at a negative voltage. No changes in microstructure and composition were detected in the thick BCY electrolyte or the BZY + LSCF cathode. Thus, the present work shows the effect of the electrolyte thickness and cathode-material selection on the durability of BCY based cells, in terms of internal partial pressure.
Conductivity of La0.9M0.1NbO4(M=Sm, Gd, Yb) As High Temperature Proton Conductors
Authors: Cao Yong , Duan Nan-Qi , Xiong Chuanyan
Published: February 2020

La0.9M0.1NbO4-
d (M=Sm, Gd, Yb) were prepared via a solid reaction route and single phase was attained by calcining constituent oxides at 1200 ˚C for 5 h. Their phase crystal structure, microstructure and conductivity were investigated. The total conductivity of LaNbO4 was improved by Sm, Gd, Yb doping, which was mainly attributed to the introduction of oxygen vacancy, and followed the order as La0.9Sm0.1NbO4-
d > La0.9Gd0.1NbO4-
d >La0.9Yb0.1NbO4-
d, as shown in the figure acttached. The highest conductivity (1.76×10-4 S cm-1) was achieved for La0.9Sm0.1NbO4-
d at 800 ˚C in wet air, more one order higher than that of LaNbO4.

Figure 1
Development of the Oxide Ion Conductor Na0.5Bi0.5TiO3 (NBT) for Solid Oxide Cells
Authors: Tumilson Christopher , Hardacre Chris , Jacquemin Johan , Elder Rachael H , Sinclair Derek C
Published: February 2020

Na0.5Bi0.5TiO3 (NBT) is a well-known lead-free piezoelectric material with potential to replace lead zirconate titanate (PZT),1 however high leakage conductivity for the material has been widely reported.2 Through a combination of Impedance Spectroscopy (IS), O2- ion transference (EMF) number experiments and O18 tracer diffusion measurements, combined with Time-of-flight Secondary Ion Mass Spectrometry (TOFSIMS), it was identified that this leakage conductivity was due to oxygen ion conductivity. The volatilization of bismuth during synthesis, causing oxygen vacancies, is believed to be responsible for the leakage conductivity.3 The oxide-ion conductivity, when doped with magnesium, exceeds that of yttria-stabilized zirconia (YSZ) at ~500 °C,3 making it a potential electrolyte material for Intermediate Temperature Solid Oxide Cells (ITSOCs). Figure 1 shows the comparison of bulk oxide ion conductivity between 2 at.% Mg-doped NBT and other known oxide ion conductors.

As part of the UK wide £5.7m 4CU project, research has concentrated on trying to develop NBT for use in Intermediate Temperature Solid Oxide Cells (ITSOCS). With the aim of achieving mixed ionic and electronic conduction, transition metals were chemically doped on to the Ti-site. A range of experimental techniques was used to characterize the materials aimed at investigating both conductivity and material structure (Scanning Electron Microscopy (SEM), IS, X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Spectroscopy (XAS)). The potential for NBT as an ITSOC material, as well as the challenges of developing the material, will be discussed.

(1)  Takenaka T. et al. Jpn. J. Appl. Phys
1999, 30, 2236.

(2)  Hiruma Y. et al. J. Appl. Phys
2009, 105, 084112.

(3)   Li. M. et al. Nature Materials
2013, 13, 31.

Figure 1