bluuebunny/crossref_metadata_2025 huggingface dataset:
Novel Gradient-Porosity Structure Cathode for Intermediate-Temperature Solid Oxide Fuel Cells
Authors: Li Jin , Jia Lichao
Published: February 2020

A-site cation ordered double perovskite cathode, especially LnBaCo2O5+δ series, have drawn great interests due to their faster oxygen ion diffusion and higher electrical conductivity[1-3].As a promising SOFC cathode with highest oxygen diffussion coefficient (D*) among the mixed ionic and electronic conductor (MIEC)[4], PrBaCo2O5+
δ exhibits great oxygen reduction reaction(ORR) catalytic activity and electrochemical performance[5] .Here we proposed a gradient-porosity PrBaCo2O5+
δ SOFC cathode. The top-layer of the cathode was highly porous while the sub-layer much denser. Gases’ adsorption plays important roles in ORR process, thus pores’ distribution has great influence on cathode’s performance[6]. Higher porosity means more ORR active regions but less ions paths, and vice versa. There is a trade-off between gases path and ions path. And gradient-porosity cathode aiming at increasing gases adsorption region at gas-contacted surface of cathode about 3-5um depth, at the meantime ensure ions’ fast transfer by enlarge cathode-electrolyte contacted regions. This targeted modification will enhanced cathode’s ORR activity and can be adopted in SOFC’s practical application. 

[1] Q. Zhou, T. He, Y. Ji, J. Power Sources, 185,754-758 (2008) .

[2] A. Chang, S.J. Skinner, J.A. Kilner, Solid State Ion, 177,2009-2011 (2006) .

[3] S. Choi, S. Yoo, J. Kim, S. Park, A. Jun, S. Sengodan, J. Kim, J. Shin, H.Y. Jeong, Y. Choi, Sci. Rep, 3 (2013).

[4] A. Tarancón, M. Burriel, J. Santiso, S.J. Skinner, J.A. Kilner, J. Mater. Chem, 20,3799-3813 (2010) .

[5] D. Chen, R. Ran, K. Zhang, J. Wang, Z. Shao, J. Power Sources, 188,96-105 (2009) .

[6] S. Skinner, J. Kilner, Solid State Ion, 135,709-712 (2000) .
Effect of SrZrO3 Formation at Lscf-Cathode/GDC-Interlayer Interfaces on the Electrochemical Properties of Solid Oxide Fuel Cells
Authors: De Vero Jeffrey Centeno , Bagarinao Katherine Develos- , Ishiyama Tomohiro , Kishimoto Haruo , Horita Teruhisa , Yamaji Katsuhiko , Yokokawa Harumi
Published: February 2020

Formation of oxide scales such as SrZrO3 (SZO) at the gadolinia-doped ceria (GDC)-interlayer/yttria-stabilized zirconia (YSZ) electrolyte interface during fabrication and operation negatively affects the electrochemical properties and long-term stability of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) cathode/GDC/YSZ based solid oxide fuel cells (SOFCs). In this work, we investigated the effect of SZO formation at LSCF-cathode/GDC-interlayer interfaces on the electrochemical properties of LSCF/GDC/YSZ using scanning electron microscopy and electrochemical impedance spectroscopy. The GDC interlayers were grown on YSZ by pulsed laser deposition and fired using a multi-step heat treatment in air at 1400ºC for 1.5 h followed by 1000ºC for 10 h. The obtained GDC interlayer is dense with minimal cracks and pores avoiding the complexity arising from the porosity of the interlayer and cation diffusion via gas phase. The porous LSCF cathode layer with 12.0 µm-thickness was then screen-printed on top of GDC surface and fired at 1080ºC for 3.5 h in air. Cells consisting of LSCF cathode/GDC interlayer/YSZ electrolyte/Pt electrode was tested under open-circuit voltage and -0.3A cathodic polarization conditions at 800ºC for 300 h in air. It has been found that both cells showed an initial formation of nanosized SrZrO3 (SZO) particles along the LSCF/GDC due to the fast Zr transport in PLD-grown GDC interlayers after the tests. However, the size and distribution of SZO differ between the OCV and cathodically polarized interface. The SZO particles on the LSCF/GDC interface are substantially smaller and are highly distributed across the GDC surface in OCV as compared to cathodically polarized interface characterized by larger localized SZO grains. From this result, we infer that the SZO grains may have impaired the O2 reduction and oxidation reactions at the O2/LSCF/GDC triple-phase boundary (TPB) areas responsible for the observed increase in polarization resistances as a function of time. However, the formation and subsequent growth of larger localized SZO grains on the cathodically polarized LSCF/GDC interface may have led to oxygen permeable TPB areas corresponding to no apparent cell performance degradation. Our results show that the morphology, size, and distribution of SZO along the LSCF/GDC interface influenced the electrocatalytic activity of LSCF cathode affecting electrochemical cell performance.
SrZrO3 Formation in SOFCs : Microstructural Characterization and Cell Performance
Authors: Kanae Shu , Toyofuku Yasuhiro , Kawabata Tsutomu , Inoue Yuko , Matsuda Junko , Chou Jyh-Tyng , Shiratori Yusuke , Taniguchi Shunsuke , Sasaki Kazunari
Published: February 2020

One of the major phenomena to shorten SOFC durability is the formation of insulated phases, such as SrZrO3, between the cathode and the electrolyte. It is known that SrZrO3 is formed and grown during sintering processes as well as during long-term operation. A systematical study is therefore desired to clarify the SrZrO3 formation mechanisms and their influence on electrochemical properties.

In this study, four parameters are considered and systematically varied: sintering temperatures of cathode, electrolyte, and buffer layer, and buffer layer thickness. The cells tested consist of yttria stabilized zirconia (YSZ) as the electrolyte, Ni-yttria stabilized zirconia (Ni-YSZ) as the anode, La(Sr)Co(Fe)O3（LSCF）as the cathode, and Ce0.9Gd0.1O2 (GDC) as the buffer layer. The GDC layer was sintered at 1300oC with 5μm in thickness, while the YSZ electrolyte was sintered at 1400oC. Cathode sintering temperature and time were varied. The electrochemical performance of the cells was tested under various conditions of testing temperature, current density, and testing time by feeding humidified fuel: H2 (97 cc/min) and H2O (3 cc/min). Microstructure of model cells after sintering and testing was observed in details by FE-SEM (Field Emission Scanning Electron Microscope) and STEM (Scanning Transmission Electron Microscope).

Microstructural observation has been revealed (1) no SrZrO3 formation during sintering LSCF at 1000oC, and (2) a partial formation of SrZrO3 between the cathode and the electrolyte after sintering LSCF at 1100oC. (3) After the sintering of the LSCF cathode at 1200oC, the interface was fully covered by the SrZrO3 layer, clarified by the microstructural observation with EDX elementary mapping. This shows that cathode sintering temperature depends on SrZrO3 formation. Microstructure of model cells after sintering for (a) 0.5h, (b) 1h, (c) 2h, (d) 16h was observed in details by STEM. Figure 1 shows that sintering time of cathode depends on SrZrO3 formation. Figure 1 indicates SrZrO3 formation mechanisms that SrZrO3 was partially formed between the YSZ and the GDC by grain boundary diffusion or surface diffusion along pore walls and covered fully the interface. Such SrZrO3 formation led to a decrease in electrochemical performance (Figure 2). These results indicate the importance of the SrZrO3 formation controlling the SOFC performance.

Figure 1
Biomass Integrated Gasification Fuel Cell in CO2 Atmosphere
Authors: Kim Jong-Pil , Jeon Chung-Hwan
Published: February 2020

Biomass energy is carbon neutral and its net life-cycle emissions are zero because the biomass removes as much CO2 as is emitted into the atmosphere from its combustion. In a fuel cell, direct utilization of biomass can lead to performance degradation by clogging the anode porous structure because of ash and tar in biomass. In this study, biomass gasification derived fuel gas was used as a renewable fuel in high temperature fuel cell. Biomass powder was first gasified in the gasifier reactor in CO2 atmosphere, the syngas was fed into a fuel cell. The gaseous product resulting from gasification was an energy rich mixture composed of CO, CH4 and H2, as major constituents; 36% CO, 24% CH4, 15% H2, 20% CO2, 5% others(N2, O2, etc.) at 800
ºC.
A cathode-supported tubular SOFC was employed to convert directly the chemical energy of syngas into electricity. Cell performance indicated peak power density of 30 mW/cm2.
Effect of the Stabilized Bismuth Oxide Interlayer on Oxygen Reduction Reaction at the Cathode/Electrolyte Interface
Authors: Joh Dong Woo , Kim Do Yeub , Park Jeong Hwa , Lee Kang Taek
Published: February 2020

Solid oxide fuel cells (SOFCs) are one of the most efficient electric power generating technologies through electrochemical reactions. However, conventional SOFCs based on yttria-stabilized zirconia (YSZ) electrolytes operate at high temperatures over 800 ºC, leading to high system cost and insufficient long-term stability. Reducing the operating temperature below 700 ºC brings significant reduction of system cost via scope expansion of material’s availability for stacks and balance of plants (BOPs), faster start-up time, as well as higher mechanical and chemical stability. However, the cathodic polarization loss at the electrolyte and cathode interface is significantly increased at reduced temperatures, due to the thermally activated nature of oxygen reduction reactions (ORRs).

At below 700 oC, the erbia- stabilized bismuth oxide (ESB) is a promising electrolyte material due to exceptionally high oxygen ion conductivity. Moreover, recent studies showed that ESB improves the cathode performance via enhancing ORR rate at the electrolyte/cathode interface at lower temperatures (450 ~ 700 ºC)1,2.

In this study, we employed an ESB interlayer at the interface between LSM-ESB cathode and YSZ electrolyte. The effect of the stabilized-bismuth oxide phase on ORR at reduced temperatures was systematically investigated by electrochemical impedance spectroscopy. Furthermore, I-V characterization was carried out to evaluate the performance of YSZ/ESB bilayered electrolyte SOFCs.

Acknowledgement

This research was supported by (1) Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2014R1A1A2057681), (2) the DGIST R&D Program of the Ministry of Science, ICT and Future Planning of Korea (1501- HRLA-01) and (3) the Global Frontier R&D on Center for Multiscale Energy System funded by the National Research Foundation under the Ministry of Science, ICT & Future Planning, Korea (2014M3A6A7074784).

Reference

1. K. T. Lee, D. W. Jung, H. S. Yoon, A. A. Lidie, M. A. Camaratta and E. D. Wachsman, J. Power Sources, 220 (2012) 324–330.

2. K. T. Lee, A. A. Lidie, S. Y. Jeon, G. T. Hitz, S. J. Song and E. D. Wachsman, J. Mater. Chem. A, 1 (2013) 6199

Figure 1
(Invited) Structure and Properties of Electrolyte Solutions Based on Fluorinated Alkylphosphates As Nonflammable Solvents for Lithium-Ion Batteries
Authors: Todorov Yanko , Fujii Kenta , Aoki Masahiro , Mimura Hideyuki , Yoshimoto Nobuko , Morita Masayuki
Published: February 2020

It has become more important to establish safety and reliability in lithium-ion battery (LIB) technology, especially for developing large-scale and higher energy density systems. Nonflammable organic solvents are considered to be safer components in LIBs [1]. Fluorinated ethers, carbonates and phosphates have been examined as possible candidates that consist of nonflammable electrolyte solutions. Among them, fluorinated alkylphosphates (FAPs) show excellent nonflammability as well as good compatibility with materials used in LIBs [2, 3]. In the present paper, ionic structure and basic characteristics of the electrolyte solutions composed of FAPs dissolving lithium salts are reported.

Tris(2,2,2-trifluoroethyl) phosphate (TFEP) and bis(2,2,2-trifluoroethyl)-ethyl phosphate (BTEP) as FAP were used as the nonflammable solvent. Triethylphosphate was also used for comparison. Ionic conductivity and viscosity were measured for the electrolytic solutions dissolving lithium salts with different anions. The Walden’s product (conductivity ´ viscosity) of the electrolytic solution was analyzed to discuss the ionic structure depending on the combination of the solvent and the salt (anion). Although the most of lithium salts dissolve with considerable concentration, eg. ~0.6 mol dm-3 (M) for LiPF6 in TFEP and > 0.6 M for other LiX/FAP combinations, the conductance behavior of the solution suggested that rather strong ionic interactions, or ion-association, will exist over wide salt-concentration range. The ionic structure of each electrolyte system, including the coordination of solvent and anion to Li+ cation (solvation), was further examined by spectroscopic measurements (ATR-IR and Raman). The analyses of the spectroscopic data gave different solvation structures that are strongly dependent on the combination of the solvent and the salt.

Thermal analyses of the electrolyte systems consisting of FAP solvents were conducted by DSC. Conventional alkylcarbonate-based electrolyte solution showed highly exothermic behavior above ca. 200 °C under the contact with charged (oxidized) positive electrode, whereas the TFEP-based electrolyte solution behaved stably up to 310 °C and gave smaller quantity of total exothermic heat than alkylcarbonate solution did. The above experimental results proved that FAP-based solvents give safer electrolyte system for larger-scale LIBs.

 

[1] M. Ue, et al., in “Modern Aspects of Electrochemistry, Vol 58; Electrolytes for Lithium and Lithium-ion Batteries” (T. R. Jow, et al., editors), Ch. 2, p.93, Springer (2014).

[2] T. R. Jow, et al., J. Electrochem. Soc., 149, A1489 (2002); 150, A161 (2003); 150, A171 (2003).

[3] H. Nakagawa, et al., J. Electrochem. Soc., 161, A480 (2014).

Figure 1
(Invited) Electrolyte Additives for High-Voltage Lithium-Ion Battery Cathodes
Authors: Passerini Stefano , Birrozzi Agnese
Published: February 2020

In order to increase the energy density of lithium-ion batteries, novel cathode materials have attracted much attention due to their high operating voltage [1]. However, their practical application is still limited due to the poor stability of the cathode / alkyl carbonate-based electrolyte interface. In fact, the working potential of many high voltage cathode is beyond the electrochemical stability window of the conventional carbonate-based electrolytes (< 4.3 V vs. Li+/Li), thus leading to the electrolyte oxidative decomposition [2]. This phenomenon, besides reducing the energy stored in the cell, might even results in the formation of decomposition products (e.g., HF) leading to metal dissolution, and hence material capacity fading.

Many strategies, such as the use of alternative electrolyte system or the coating of the material, have been proposed in order to enable the use of high-voltage cathodes [3]. However, using electrolyte additives is one of the most efficient and economic strategy for alleviating the undesired reactions among cathode and electrolyte [4]. In fact, electrolyte additives can be sacrificially decomposed to form a protective layer on cathode surface, thus avoiding further electrolyte decomposition reactions. In addition, electrolyte additives can even scavenge water or other impurities and/or stabilize the lithium salt, extending therefore the cycle life of the high-voltage cathodes.

In this study, the investigation of additives’ effects in enhancing the cathode cycling stability and efficiency will be presented via a combination of electrochemical techniques, such as impedance spectroscopy and ex-situ analytical techniques, i.e. XRD, XPS and RAMAN. The feasibility of the electrolyte additives employment for practical application will be demonstrated showing full-cell studies with graphite as anode.

[1] A. Kraytsberg, Y. Ein-Eli, Advanced Energy Materials, 2 (2012) 922-939.

[2] S. Tan, Y.J. Ji, Z.R. Zhang, Y. Yang, ChemPhysChem, 15 (2014) 1956-1969.

[3] N.-S. Choi, J.-G. Han, S.-Y. Ha, I. Park, C.-K. Back, RSC Advances, 5 (2015) 2732-2748.

[4] S.S. Zhang, J. Power Sources, 162 (2006) 1379-1394.
In Situ Electrochemical Measurements of Deposition and Dissolution of Lithium in Li[N(CF3SO2)2]-Glyme Solvate Ionic Liquids
Authors: Tachikawa Naoki , Hosoda Shin , Ishida Takuya , Yoshii Kazuki , Watanabe Masayoshi , Katayama Yasushi
Published: February 2020

The equimolar mixture of lithium bis(trifluoromethylsulfonyl)amide (LiTFSA)-tetraglyme (G4) has been known as a solvate ionic liquid consisting of [Li(G4)]+ and TFSA–. This solvate ionic liquid contains lithium ions in high concentration (ca. 3 mol dm–3) and has negligible vapor pressure at ambient temperature. It has been reported that the solvate ionic liquid is compatible with sulfur cathode because of the low solubility of lithium polysulfides [1]. To achieve the high energy density of the rechargeable Li-S batteries, it is required to investigate anode materials having high specific capacity such as a lithium anode. In this study, the initial stage of deposition of lithium was investigated in the solvate ionic liquids with different compositions using electrochemical quartz crystal microbalance (EQCM) and optical microscope.

LiTFSA-G4 solvate ionic liquids were prepared by mixing LiTFSA and G4 at different molar ratios of LiTFSA (X
LiTFSA) in an Ar filled glove box. The potentials of Li(I)|Li were evaluated using a Ag|Ag(I) reference electrode, which consisted of a silver wire immersed in 50.0-50.0 mol% LiTFSA-G4 containing 0.1 mol dm–3 AgCF3SO3. EQCM measurement was performed with an airtight three-electrode cell. A Cu coated quartz crystal electrode was used as a working electrode. Lithium was used as a reference and counter electrode.

[Li(G4)]+ is considered a major lithium species in LiTFSA-G4 solvate ionic liquid at X
LiTFSA = 50 mol%. On the other hand, both [Li(G4)]+ and [Li(TFSA)2]– are expected to exist in LiTFSA-G4 solvate ionic liquid at X
LiTFSA > 50 mol%. It was found that the potential of Li(I)|Li in the LiTFSA-G4 solvate ionic liquid at X
LiTFSA > 50 mol% was given by an equilibrium, [Li(TFSA)2]– + e– = Li + 2TFSA–, indicating the active lithium species is [Li(TFSA)2]– rather than [Li(G4)]+. Li was deposited at a current density of –0.01 mA cm–2. The electric charge for deposition was –0.05 C cm–2. In the case of 54.5-45.5 mol% LiTFSA-G4 solvate ionic liquid, Li was deposited sparsely on the Cu electrode surface and grew as a whisker-like shape. On the other hand, whisker-like Li deposit was not observed in 50.0-50.0 mol% LiTFSA-G4 solvate ionic liquid where Li nuclei were uniformly generated on the electrode surface. These results suggest that the nucleation and crystal growth of Li are affected by the composition of the solvate ionic liquids, resulting in the morphology change of Li deposits.

Acknowledgment

This study was supported by the Advanced Low Carbon Technology Research and Development of Program (ALCA) of the Japan Science and Technology Agency (JST).

Reference

[1] K. Dokko et al., J. Electrochem. Soc., 160, A1304 (2013).
Novel Carbonate-Based Polymer Electrolytes for All-Solid-State Li Batteries
Authors: Tominaga Yoichi
Published: February 2020

Solid polymer electrolytes (SPE) such as poly(ethylene oxide) (PEO)-metal salt complexes are of great interest to replace typical liquid electrolytes for batteries because of their flexibility and lightweight. However, the ionic conductivity of PEO-based electrolytes is limited to approximately 10-5 S/cm at room temperature, and it is extremely difficult to enhance the lithium (cation) transference number. So we consider polycarbonates that can be obtained by the alternating copolymerization of CO2 with epoxides and comprise novel polymer candidates for SPE. This CO2/epoxide copolymer is a remarkable macromolecule because it utilizes CO2 as a raw material and has excellent properties; it is biodegradable, easily processed and colored, and has high transparency and low oxygen permeability. We have focused on the chemical structure of the copolymer, which has one alternating carbonate group (-O-(C=O)-O-) in each repeating unit of the main chain. The carbonate group has a large dipole moment, and it may dissolve many types of salts. Carbonate-based organic solvents, such as dimethyl carbonate, are used as the electrolyte solution in Li-ion batteries because of their high dielectric constant. We therefore consider that the carbonate-based polymer can be a suitable framework for SPE and can provide suitable polar environment for dissolved ions. In this study, we used commercial polycarbonates such as poly(ethylene carbonate) (PEC) and novel polycarbonates having side groups synthesized in our laboratory. We found extraordinary and unique properties of carbonate-based electrolytes that the conductivity of PEC-Li salt electrolytes increases with increasing salt concentration and the Li transference numbers were extremely higher than those of typical polyether system. Polycarbonates having short oxyethylene (OE) side chains were synthesized, and we revealed that the LiFSI electrolytes having longer OE groups have high conductivity at low salt concentrations, and the conductivity increases dramatically at high salt concentrations. A Li|PEC-LiFSI|LiFePO4 cell with 3DOM polyimide membrane delivered a reversible charge-discharge capacity around 120 mAh g-1 at 30 oC and C/20 rate.

This study was supported financially by the Specially Promoted Research for Innovative Next Generation Batteries of the Advanced Low Carbon Technology Research and Development Program (ALCA-SPRING) of JST and the Grant-in-Aid for Scientific Research (B) of JSPS KAKENHI (No. 25288095, 16H04199), Japan. The 3DOM polyimide matrix was kindly donated from Prof. Kiyoshi Kanamura and Dr. Hirokazu Munakata of Tokyo Metropolitan University, Japan.

References: Electrochem. Commun., 66, 46 (2016), Polymer, 84, 21 (2016), Macromol. Chem. Phys., 216, 1660 (2015), J. Electrochem. Soc., 162, A3133 (2015), Chem. Commun., 50, 4448 (2014), Polym. J., 44, 1155 (2012), Electrochim. Acta, 57, 36 (2011), Polymer, 51, 4295 (2010).
(Invited) in Situ Functional Imaging of Electrodes for All-Solid-State Batteries
Authors: Leite Marina S.
Published: February 2020

To date, the development of higher performance Li-ion all-solid-state batteries still entails the complete understanding of how the electrolyte and electrode materials change upon lithiation/delithiation. While macroscopic voltammograms are extremely informative, they do not provide information about how the material composing the active layers of the battery is changing upon lithiation/delithiation. Thus, to probe the mesoscale behavior of the batteries we combine real-time scanning electron microscopy in ultra-high vacuum with electrochemical cycling, in addition to ex situ characterization of the morphological, chemical, and electrical changes of the anodes and electrolyte upon lithiation. In particular, we will discuss the results using LiCoO2 (cathode), LiPON (electrolyte, deposited via sputtering), and Al and Si (anode) [1,2]. In the anode, Li ions are trapped by an AlLi alloy capped by a stable Al-Li-O is formed, leading to a rapid capacity fade, from 48.0 to 41.5 μ.Ah/cm2 in two cycles [1]. Surprisingly, the addition of a Cu protective layer is insufficient to avoid the device degradation because of the ultra fast Li diffusion within Al. Nevertheless, the Si anodes present extremely stable cycling: >92% of capacity retention after 100 cycles, with average Coulombic efficiency of 98% [2]. The in situ functional imaging platform presented here paves the way to diagnosing in real-time the changes that take place in all-solid-state batteries.

[1] M. S. Leite et al., J. Mater. Chem. A. 2, 20552 (2014). Inside Cover.

[2] C. Gong et al., ACS Appl. Materials and Interfaces. 7, 26007 (2015). Cover.
Quasi-Solid State Electrolytes for Li-Ion Battery Applications
Authors: Honma Itaru , Matsuo Takahiro , Unemoto Atsushi , Gambe Yoshiyuki
Published: February 2020

High energy density secondary batteries are key devices for mobile industrial applications such as electric vehicles, drones and robots. Among attractive new device concepts such as lithium- air, lithium- sulfur, Na/Mg ion and all solid state battery (ASSB), ASSB has been considered to be most promising due to their higher energy density, higher cell output voltage and superior chemical/thermal safety. In this paper, our original approach to electrolyte materials are reported, which are synthesized by hybridization of ionic liquid and nanoparticles. In fact, the quasi-solid state electrolytes have been made by solidification of Li ion conducting ionic liquid by mixing with SiO2 nanoparticles due to strong interaction between ionic liquid molecules and SiO2 surface, which resulted in the electrolytes having liquid-like ionic conductivities in their solid state matrix. All solid state Li battery cell consisting Li metal anode/quasi-solid state electrolytes/LiFePO4 cathode have been successfully fabricated and demonstrated stable charge /discharge cycles more than a thousand under 1.0C-rates in spite of their solid state cell design. More importantly, it has been demonstrated for the first time, bipolar stacked tripled cells with multiple voltages up to 10V are successfully demonstrated on the coin cell CR2032 devices.

references

[1] Seitaro Ito, Atsushi Unemoto, Hideyuki Ogawa, Takaaki Tomai, and Itaru Honma, J. Power Sources, 2012, 208, 271

[2] Atsushi Unemoto, Hideyuki Ogawa, Seitaro Ito and Itaru Honma, J. Electrochemical Society, 2013, 160, A138

[3] Takaharu MATSUO, Yoshiyuki GAMBE and Itaru HONMA, Scientific Reports,2014,4,6084

[4] Yoshiyuki Gambe, Yan Sun and Itaru Honma, Scientific Reports, 2015, 5, 8869

Figure 1
Activity and Selectivity of Ni-Fe Layered Double Hydroxide Electrocatalyst for Seawater Electrolysis
Authors: Dionigi Fabio , Reier Tobias , Gliech Manuel , Kühl Stefanie , Strasser Peter
Published: February 2020

Electrochemistry will play a critical role in the development of future sustainable energy storage and conversion technologies, where new functional nanocatalyst materials are the key components for application in fuel cells and electrolyzers. In this context, the generation of hydrogen and oxygen from seawater electrolysis is an attractive process for fuel production since the majority of liquid water available to mankind at the earth's surface is salty water [1]. Unfortunately, chlorine evolution reaction (CER) is a competing reaction to oxygen evolution reaction (OER) when seawater is used as electrolyte.

Although OER is thermodynamically favored over CER, the poor kinetics of the OER makes CER the dominant reaction in many catalytic systems. NiFe layered double hydroxide (LDH) has been reported to catalyze the OER reaction in alkaline media at low overpotentials comparable with the performance of noble metals catalysts [2]. In our study, its activity and stability for seawater oxidation have been investigated with a rotating disk electrode in chloride containing electrolytes with basic and slightly basic pH. The electrochemical experiments are combined with products analysis (Figure 1) in order to estimate the selectivity for oxygen evolution. In particular, CER and hypochlorite formation are investigated by an in-line quadrupole mass spectrometer (QMS) and iodometric titration respectively.

NiFe LDH shows a high selectivity for OER in alkaline electrolytes (pH 13) containing 0.5 M NaCl, a chloride ions concentration typical of seawater. In 0.3 M borate buffer (pH 9.2) with 0.5 M NaCl the electrochemical experiments show degradation in performance at current densities approaching 10 mA/cm2, despite the high selectivity at lower current densities. This degradation of the anodic current is not observed in pH 13 (0.1 M KOH) in the presence of the same concentration of NaCl.

References

[1] H.K. Abdel-Aal, K.M. Zohdy, M. Abdel Kareem, Hydrogen Production Using Sea Water Electrolysis, The Open Fuel Cells Journal, 3 (2010) 1-7.

[2] M. Gong, Y.G. Li, H.L. Wang, Y.Y. Liang, J.Z. Wu, J.G. Zhou, J. Wang, T. Regier, F. Wei, H.J. Dai, An Advanced Ni-Fe Layered Double Hydroxide Electrocatalyst for Water Oxidation, J Am Chem Soc, 135 (2013) 8452-8455.
Electrochemical Membrane Reactor for Hydrogen & Syn Gas Fabrication
Authors: Yoon Sung Pil , Han Jonghee , Nam Suk Woo , Ham Hyung Chul
Published: February 2020

Energy conversion & storage from renewable sources is an issue because of their unstable supply. The production of hydrogen from renewable resources is one of the candidates, becoming a highly researched field around the world. However, water electrolytic hydrogen is so far the most practical and promising technology for large-scale renewable hydrogen production. Among the water electrolytic hydrogen productions, solid oxide electrolyzer cells (SOECs) are the most promising technology because SOEC can produce hydrogen at a higher chemical reaction rate with a lower electrical energy requirement. For example, SOECs can produce about 40% more hydrogen from a given energy input than a conventional water electrolysis system. One of the technical hurdles is to maintain the high operating temperature due to the high endothermic reaction of water electrolysis. Recently, in order to improve the hydrogen production efficiency, SOECs has considered using heat from nuclear energy and geothermal energy.

In this experiment, we have tried to develop an electrochemical membrane reactor for both hydrogen & syn-gas fabrication. In this system, water can be electrolyzed at the SOFC anode part and methane can be partial oxidized at the opposite electrode to produce syn-gas. The advantages of this system can reduce the need of additional heat because of exothermic reaction of methane POX. Also, the methane POX with pure oxygen from the electrolyzer cell can produce the syn-gas with a H2/CO ratio of 2, which is suitable for methanol GTL process. We can further discuss operating results of the system at the meeting.

Figure 1
3D Printed Reversible Solid Oxide Electrochemical Reactors
Authors: Farandos Nicholas Michael , Kleiminger Lisa , Kelsall Geoff H.
Published: February 2020

The increasing penetration of intermittent energy sources into electricity grids worldwide necessitates deployment of large-scale energy storage facilities to ensure that the balance between energy supply and demand can be managed over a range of time scales. Reversible, high-temperature solid oxide electrochemical reactors with oxide ion-conducting electrolyte, such as yttria-stabilized zirconia (YSZ), can convert electrical energy to chemical energy, and vice versa, with roundtrip efficiencies of ca. 70 %,[1] depending on current densities, for splitting of CO2 and H2O to CO and H2, respectively, and oxygen.

Electrolysis at high current densities over long times necessary for inter-seasonal energy storage results in severe microstructural degradation at the oxygen electrode, lanthanum strontium manganite (LSM)| YSZ | pore interface, the so called triple phase boundary (TPB). This is due to delamination, as a result of pressures associated with O2 accumulation in non-percolating voids.[2] Therefore, greater control over microstructure could eliminate these non-percolating voids, decreasing degradation rates.

We are investigating inkjet printing to fabricate oxygen-electrode architectures with exquisitely controlled microstructures, in order to minimise the probability of non-percolating pores. The first step was formulation of a printable YSZ ink that was printed to form the sintered scaffold structures, shown in Figure 1. A printable LSM ink was formulated, printed into the pillar-scaffold structure and subsequently heat-treated to form the composite electrode, comprised of a close-packed cylinder array (Figure 2a). Electrochemical performance data of the resulting cell in electrolyser mode will be presented, and compared with model predictions (Figure 2b).

References

1. S. H. Jensen, C. Graves, M. Mogensen, C. Wendel, R. Braun, G. Hughes, Z. Gao, S. A. Barnett, Energy Environ. Sci.,
8, 2471. (2015).

2. C. Graves, S. D. Ebbesen, S. H. Jensen, S. B. Simonsen, M. B. Mogensen, Nat. Mater.
14, 239. (2015).

3. B. Kenney, K. Karan, Solid State Ionics,
178, 297. (2007).

Figure 1
(Invited) Reverse Electrodialysis for Unique Devices
Authors: Kwon Seung-Ryong , Baek Seol , Kim Ji Tae , Jeon Joohee , Seo Daye , Chung Taek Dong
Published: February 2020

Reverse electrodialysis (RED) is emerging as one of the promising process for generating electrical power from renewable energy sources. Production of electrical power was demonstrated by mixing the fresh and salt water which are inexhaustible resources at the mouth of river for the first time in early 1950s. This idea had not been receiving keen attention, however,  before we seriously faced the depletion crisis of natural power resources. Recently, a couple of European countries, including Netherland, Sweden, and Italy, have been interested in the study and development of salinity gradient power-based electricity production systems. For instance, Wetsus center in Netherland built up experimentally and theoretically optimized RED systems to obtain maximum electrical power for sustainable water technology with given materials and mechanical engineering resources. They are developing the pilot RED plant capable of 200 MW electricity production and ultimately planning to supply local public/private housing. Meanwhile, some scientists paid attention to unique applications based on eco-friendly RED systems. As an application, Logan group at Pennsylvania State University showed significantly increased electricity production with simultaneous purification of waste water using the hybrid system of RED and microbial cell. They also reported the hydrogen production strategy by generating electricity in the same combinations. In this talk, a few unique applications based on RED system as a new electrical power source are introduced and discussed.
(Invited) Photoluminescence Properties of ZnO Nanostructures Growth Vertically on Transparent and Conductive Al-Doped ZnO Substrates
Authors: LI Chaoyang , Hou Shengwen
Published: February 2020

ZnO nanostructures were fabricated on transparent conductive Al-doped ZnO films by a novel multi-annealing process in which the reducing annealing and oxidization annealing were carried out in turn to achieve the re-crystallization of ZnO film on AZO film. As the result, ZnO nanostructures with good alignment were fabricated vertically on the AZO film with the high transmittance over 80%. The photoluminescence properties of ZnO nanostructures were influenced significantly by the annealing processes. An intense blue-green emission centered at 491nm in the visible range was observed from obtained ZnO nanostructures. The growth mechanism of the ZnO nanostructures was investigated in detail.
Microelectrode-Less Control of Semiconducting Fluorescent Nanoparticles By Dielectrophoretic (DEP) Force for High Degree of Freedom
Authors: Kim Jinsik , Kim Hyejin , Hwang Kyo Seon
Published: February 2020

In previous our research, we introduced attachment or detachment of 25nm diameter quantum dots (QDs) manipulating method and 100nm diameter polystyrene (PS) nano-beads at nano sized metal structures by dielectrophoretic (DEP) force. The metal nano-structures were connected with micro electrode to apply the DEP force for trapping the nanoparticles. The DEP force is easily controllable by frequency and intensity of applied electric field. And the DEP force is very sufficient to manipulate the fluorescent nanoparticles at specific nanostructures, due to the large difference of electric fields inducement around nanostructures. The trapped fluorescent nanoparticles at nano metal structures which can be considered and called as a composited structure of photon emitting nanoparticles and nano structures could be utilized in study of coupling photons to plasmon waveguides as a real single photon generator. And the nanoparticle manipulating method could accomplish the additional composite structures without any chemical reactions as a lithographic method of fluorescent nanoparticles which can be used in QD display. The QDs are the most important and remarkable candidates nanoparticles to produce photon-emitting in quantum devices and display. However, the previous research had limitations such as limiting the variety of nanostructure, degree of freedom, and attaching sites due to the connected microelectrodes. And additional fabrication steps should be needed after the manipulation of nanoparticles to metal structures.

 In this paper, we introduced the manipulation of QD which is composed with cadmium selenide, the semiconducting materials at the nanostructures by DEP force for plasmonic applications and QD display. For the high degree of freedom, the nanostructures didn’t connect with microelectrodes. Various shapes of nano structures which is made of gold are accomplished between the micro electrodes. The microelectrodes were not connected with the nano-structures. Wire, Y-branch and vertex shape of nanostructure were fabricated with e-beam lithography and lift-off process. The distance between microelectrodes and nanostructures was also calculated to optimize the condition of QD trapping with multiphysics simulation. Possibility of selective manipulation of QDs was also performed through the theoretical approaches at various shape of nanostructures by using the DEP force. Each shape of structures was considered to manipulate the QDs at the nanostructures. The selective manipulation which is attaching-side, position, end-facet selective in nanostructures provide the three degrees of freedom in attachment in the same structure. Consequently, the semiconductor materials based fluorescent nanoparticles, QDs, are successfully manipulated at nano-structures without any connecting with microelectrodes.
Direct Visualization of Stress Distribution Related to Adhesive through Mechanoluminescence
Authors: Terasaki Nao , Fujio Yuki , Sakata Yoshitaro , Uehara Masato , Tabaru Tatsuo
Published: February 2020

Elasticoluminescent material is a novel ML functional ceramic powder (controllable size: 10 nm―100 μm, representative and the most efficient ML material: SrAl2O4:Eu2+) and it can emit intensive light repeatedly accompanied by mechanical stress such as deformation, friction, impact, even in elastic deformation region. The ML intensity is proportional to strain energy of the material. Thus, when dispersedly coated onto a structure, each particle acts as a sensitive mechanical sensor, while the two-dimensional (2D) emission pattern of the whole assembly reflects the dynamical strain/stress distribution inside the structure and the mechanical information around the defect and crack or the in-visible tip. This ML visualization technique provides a novel way of diagnosing the structural health, especially in early detection for safe & security measure. Actually, the ML sensor has been applied to real social infra-structure such as bridge, building, welding point of pipeline and high pressure vessel, and successfully demonstrated the ability to detect active crack including likelihood for growth, real crack propagation and mechanically weak points etc.

Meanwhile, recently NEW advanced material such as CFRP, high tensile strengthen steel and non-steel metal for light weight vehicle are strongly required from the viewpoint of energy saving and environment. Accordingly, joint & adhesive technologies especially for different kinds of materials and the non-destructive evaluation have been investigating for application of these materials and the reliability in use. Especially, as to adhesion, kissing bond and weak bond, in which strengthen of the bonding is nothing or weak respectively without void and crack, have been remaining as challenge for the application and has been vigorously investigated in the field of non-destruct evaluation so far.

In the presentation, we would like to report on suitability of the ML sensing for diagnosing (1) a stress distribution in adhesive, (2) visualization of mechanical distribution related to adhesive condition. In fact, as the result of (1), we succeeded to directly visualize stress distribution in adhesive for the first time through mechanoluminescence. We will discuss the results with the result of conventional FEM analysis, simulation of mechanical stress distribution. In addition, as the result of (2), we succeeded to visualize strass/strain distribution of adherend, clearly find out the stress/strain distribution are related to adhesion condition and also find out the area of pseud kissing bond through mechanoluminescence for the first time.

[Acknowledgement] The research was partially supported by Innovative Structural Materials Association (ISMA), program for the promotion of scientific research with a view to creating intellectual resources through New Energy and Industrial Technology Development Organization (NEDO), AIST Strategic budget 2015 and KAKENHI, Grant-in-Aid for Scientific Research (B).
(Invited) Impact of LED Implementation on Rare-Earth Usage in Lighting
Authors: Ku Anthony , Setlur Anant A
Published: February 2020

Several rare earth elements are used in phosphors for fluorescent lighting: a significant fraction of global demand for yttrium, europium, and terbium have beenfrom lighting applications. Solid-state lighting products based on InGaN light emitting diodes (LEDs) are in the process of taking over the general illumination market due to their higher energy efficiency, lifetime, and packaging flexibility. . While LED phosphors also use yttrium and europium, the quantities required are much lower than what is needed to produce an equivalent amount of light using fluorescent bulbs. This dynamic suggests that rare earth oxide demand for lighting will peak and then decline off of current usage levels. This paper presents a simple order of magnitude analysis to estimate when this peak is expected to occur, based on projected LED adoption rates in different regions. We also discuss some of the implications for the supply-demand balance for rare earth elements.
Self-Supporting Gel Electrolyte Material for Electrochemiluminescent Sticker Display
Authors: Hong Kihyon
Published: February 2020

Nowadays, there has been an increasing demand to develop low-cost, disposable or reusable display devices to meet and maximize short-term user convenience. However, the disposable device has unfortunately not materialized yet due to the light-emitting materials and fabrication process issues. Here, we report sticker-type electrochemiluminescent (ECL) cell using self-supporting, light-emitting gel electrolytes. The self-supporting ion gels were formulated by mixing a network-forming polymer, ionic liquid, and metal complex luminophore. The resulting ion gels exhibit excellent mechanical strength to form free-standing rubbery light-emitting electrolyte films, which enables the fabrication of sticker-type display by simple transfer and lamination processes on various substrates. The sticker-type ECLs can be operated under an AC bias and exhibit a low operating voltage of ± 2 V with a maximum luminance of 90 cd/m2. It is notable that the result is the first work to realize sticker displays based on electrochemical light emitting devices and can open up new possibilities for flexible or disposal display.
Both Directional Organic Light-Emitting Diodes Using Thin Film Electrodes
Authors: Lee Jong-Lam , Lee Illhwan
Published: February 2020

Recently, transparent organic light-emitting diodes (TOLEDs) have attracted much interest, because they can open new applications for bi-directional displays, transparent displays, wearable displays, smart glass, and window lighting. Typically, the device structure of TOLEDs needs to consist of an ITO bottom anode, emitting layer, and a thin metal cathode. To protect underlying organic layer from sputtering damage, a thin metal-based semi-transparent cathode was necessarily used by thermal evaporation. In this system, there were many problems in application of ITO electrodes to high efficient TOLEDs.

First, these TOLEDs usually have a preferential one-sided emission due to differences in reflection between ITO and Ag electrodes. In particular, the ITO-side emission ratio has a strong intensity which is more than 70% of the total emission ratio because of the relatively low reflection of ITO compared with Ag film. Second, the majority of the light generated in the organic layers is confined in the ITO anode and glass substrates due to the large difference in the refractive index between their layers. This results in out-coupling efficiencies of around only 20% due to the total internal reflection at the ITO / glass and glass / air interfaces. These problems can be solved by employing a thin metal (Ag) electrode as an ITO alternative. However, it is very difficult to form smooth and very thin Ag layers for transparent anode. Ag layers exhibit three-dimensional island growth as a result of the poor wettability of Ag on the substrate. A discrete Ag film consisting of an island structure exhibits strong absorption and scattering of incident light, because of localized surface plasmon resonance. Thus, thin Ag film was not considered as a transparent electrode for TOLED.

Here, we demonstrate an innovative method to make transparent and high performance OLEDs on substrates using only ultra-thin Ag electrodes as both the top and bottom transparent electrodes. We show that merely a minute-plasma treatment on the glass before the deposition of Ag layer leads to significantly improved growth homogeneity of the Ag layer. The ultra-thin Ag film is formed after oxygen plasma treatment, leading to improved visible range transmittance and sheet resistance. By designing the weak micro-cavity structure with the ultra-thin Ag electrodes, waveguide modes could be suppressed and optical transmittance of TOLEDs could be improved. According to FDTD simulation, waveguide modes in ITO and glass substrate can be remarkably extracted because of weak micro-cavity effect. Consequently, the luminance of TOLED could be improved by 47 %. In addition, the transmittance of TOLED with the ultra-thin Ag electrode showed a high transmittance (73.84 %), which was similar than that of ITO (73.19%). The optimized weak micro-cavity structured shows the high optical transmittance, identical emission rate and reduced wave-guided mode were achieved, enhancing the luminance of devices.
Luminescence Properties of Nd-Doped Strontium Aluminate with Six Coordination Sites
Authors: Matsui Takafumi , Nakanishi Takayuki , Kitagawa Yuichi , Fushimi Koji , Higuchi Mikio , Hasegawa Yasuchika
Published: February 2020

Neodymium-doped phosphors have been applied to laser materials due to their potential for high efficiency and compactness. Among them, neodymium-doped yttrium aluminum garnet (Nd:YAG) was widely used as a medium material for near-infrared solid-state lasers. In this study, we focused on a novel neodymium-doped strontium aliminate phosphor, Nd:Sr3Al2O6. This crystal, which has cubic system (Pa-3), has the potential as a transparent polycrystalline ceramic. Additionally, the phosphor contains six Sr2+ sites that neodymium ions substitute. We prepared this phosphor by conventional solid state reaction using SrCO3 (99.9%), γ-Al2O3 (99.9%), and Nd(NO3)3・6H2O (99.9%). These starting materials were mixed in an alumina mortar, and all mixtures were sintered under air atmosphere. The crystal structure of a prepared sample was characterized by using X-ray diffraction. The diffraction pattern of the sample agreed with that of JCPDS for Sr3Al2O6 (24-1187). Luminescence properties were estimated by using emission spectrum and lifetime. The 4f-4f emission of Nd3+ was broad compared with that of Nd:GdVO4, which has a broader emission band than that of Nd:YAG. Nd:Sr3Al2O6 is potentially applicable to Nd-doped solid-state laser with a broad emission band.