bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Corrosion Behavior and Hydrogen Permeation of Steel Materials Under Wet-Dry Cyclic Environment
Authors: Katayama Hideki , Katsumura Toshiki , Akashi Takaya
Published: December 2020

Higher strength steels have been required from the viewpoint of safety and energy saving in the fields of transportation equipment and infrastructure. However, it is known that the higher the strength of steels, the higher the risk of hydrogen embrittlement. It has been reported that hydrogen embrittlement occurs even in atmospheric corrosive environment, and solving the problem of hydrogen embrittlement will be the key to the future hydrogen energy society. For that purpose, it is necessary to clarify the hydrogen embrittlement behavior due to atmospheric corrosion. We focused on surface potential measurement as a technique to visualize permeated hydrogen. The purpose of this study is to clarify the hydrogen permeation behavior of steel materials under atmospheric corrosive environment.

A 50 x 50 x 0.5t mm of pure iron plate was used as the sample. After grinding both surfaces of samples and degreasing with ethanol, nickel plating was applied to the hydrogen detective side of the sample. Hydrogen penetration was accelerated by a wet-dry cyclic corrosion test using a droplet of 0.5 M NaCl solution. The distilled water was added after second cycles to avoid the accumulation of NaCl. The potential of the hydrogen detective surface was measured with time in the drying process by surface potential device. The surface potential probe is set on the XY stage and the surface potential distribution can be obtained by scanning the probe. In this study, the surface potential of the copper plate in contact with the sample was adjusted at 0V as the reference potential.

Although the corrosion occurred on the surface in the drying process after dropping the NaCl solution, no surface potential change was observed on the hydrogen detective side of the sample in that process. The surface potential started to change in a part of the surface of the sample immediately after the droplet was completely dried, and after 1hour, the size and shape of the potential changed area became almost the same as those of the corrosion products. No corrosion occurred on the hydrogen detective side of samples during the surface potential measurement, indicating that the surface potential change is attributed to the atomic hydrogen penetrated through the samples. The surface potential changed area gradually disappeared, and almost no potential change was observed on the surface after 72 hours. The change in surface potential after the second cycle of wet and dry cyclic corrosion test showed the same tendency as in the first cycle, and a potential distribution close to the shape of corrosion products was observed.
Evaluation of Corrosion Resistance of Steel Materials By Hyperspectral Analysis of Corrosion Products
Authors: Kobayashi Ryo , Katayama Hideki , Akashi Takaya
Published: December 2020

Direct visual inspection at short range and hammering test every five years are obligatory for inspection and evaluation of bridges in Japan. However, simple and quantitative inspection techniques are required due to issues such as a shortage of bridge inspectors and a lack of inspection cost. We focused on the spectrum analysis by a hyperspectral camera as a new tool to evaluate corrosion resistance. The purpose of this study is to investigate the feasibility of evaluating the corrosion resistance of steel materials by hyperspectral analysis of corrosion products.

α-FeOOH, β-FeOOH, γ-FeOOH and Fe3O4 were used as the samples of standard iron corrosion products. These corrosion products were set on the sample holder, and the spectra were taken by a hyperspectral camera using halogen lamps as a source of irradiation light. The average spectrum obtained at almost the center of the sample was analyzed.

The reflection spectra were observed at 595 nm and 770 nm for α-FeOOH, 745 nm for β-FeOOH, and 790 nm for γ-FeOOH, respectively, and Fe3O4 showed a low reflection spectrum. This means that different corrosion products can be identified from the reflection spectrum. In addition, the spectrum analysis was conducted for the corrosion products formed on the sample exposed in coastal area for six months. The peaks in the spectrum were correspondent with them observed in the spectra of the standard iron corrosion products. The spectrum analysis by a hyperspectral camera can be powerful tool to evaluate the corrosion performance of steel materials.
Modeling, Validation, and Application of Finite Element Models for the Galvanic Corrosion of Aluminum Alloy 6061-T6 Coupled to Non-Passivating and Passivating Alloys
Authors: Wohner Natalie , Smith Cody Troy , Hihara Lloyd H.
Published: December 2020

Galvanic corrosion of aluminum alloys coupled to non-passivating and passivating alloys exposed in corrosive environments can cause severe corrosion damage in marine structures. The aim of this study is the development of a finite element model using COMSOL Multiphysics to predict the galvanic interaction of aluminum alloy AA6061-T6 coupled to noble materials.

The numerical model is based on anodic dissolution kinetics of AA6061 and cathodic kinetics of Ti6Al4V, 316 stainless steel, and copper determined with potentiodynamic polarization. The model predicts that the cathodic material and the geometry of the galvanic couple both influence the corrosion rate of AA6061, and that the solution composition locally changes over time.

In order to account for the time-dependent change in solution chemistry a thorough experimental investigation of the effect of pH and chloride ion (Cl-) concentration on the corrosion kinetics of AA6061 is presented using potentiodynamic polarization. Corrosion kinetics were obtained in sodium sulfate and sodium chloride solutions as a function of pH and chloride ion concentration and implemented in the numerical model.

The validation of the model is in progress and will be compared to data of actual galvanic couples exposed in the laboratory and in different atmospheric environments.

Acknowledgement:

This material is based on research sponsored by the USAFA and University of Hawaii under agreement number FA7000-18-2-0004. The U.S. Government is authorized to reproduce and distribute reprints for Governmental purposes notwithstanding any copyright notation thereon.
Understanding the Mechanisms of Early Stage Aluminum Corrosion
Authors: Stavila Vitalie , Sen-Britain Shohini Tanuka , Weitzner Stephen Eric , Keilbart Nathan Daniel , Sugar Joshua D , Friddle Raymond William , Heo Tae Wook , Pham Tuan Anh , Wood Brandon C. , Allendorf Mark D.
Published: December 2020

Aluminum alloys are widely used in many applications due to their inherent corrosion resistance, which is attributed to the formation of a protective oxide layer. However, the strength and durability of many Al-based materials is reduced in humid environments. Consequently, detailed mechanistic understanding of corrosion reactions over time is necessary to predict the cost, safety, and performance. Most of the current knowledge of atmospheric aluminum corrosion is built on response relationships upon extensive corrosion and typically involve a first-order correlation of corrosion data with environmental conditions. However, mechanistic understanding of corrosion processes is still limited, particularly at the early stages of exposure to humid environments. In addition, the effects of electrolytes such as sodium chloride present in the environment are still not fully understood. This presentation will focus on our recent efforts to reveal the mechanistic dependence of electrochemical aluminum corrosion in humid air in the presence of NaCl. The rate of corrosion is explored through complimentary experimental and theoretical analyses relating corrosion rate to electrolyte chemistry, mass uptake and corrosion products. As an experimental platform, we use quartz crystal microbalance (QCM) electrodes coated with aluminum and sodium chloride using sputtering techniques. Structure, composition, and surface morphology of the samples were characterized by grazing-incidence X-ray diffraction, FTIR spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy, scanning transmission electron microscopy, and electron energy loss spectroscopy. The QCM provides operando data with nanogram resolution on the formation of the corrosion product layer, from which we can derive rate constants for aluminum surface reactions. We find that the reaction rate in dry air is negligible, but a dramatic acceleration is observed at 50% RH and above. In addition, this study provides additional insight into: 1) the influence of the sodium chloride film thickness on the rate and reaction products; 2) the role of surface termination and roughness on aluminum oxide/hydroxide formation; and 3) the electrochemical corrosion reaction rate acceleration as a function of temperature. Finally, based on the interplay between theory and experiment we achieved preliminary understanding of the rate-limiting steps, which we will use to develop validated computational models of early-stage (hours to several days) aluminum corrosion.

Figure 1
Corrosion Behavior of Rusted Carbon Steel Coated with Reactive Paint Under Wet and Dry Cyclic Condition
Authors: Takahashi Masamitsu , Tsuchiya Hiroaki , Hanaki Koushu , Yamashita Masato , Fujimoto Shinji
Published: December 2020

Degradation of steel infrastructure built in 20th century is seriously progressing. This deterioration is mainly caused by corrosion of steel in atmospheric environments that contain O2 and H2O. To ensure long-term reliable service of steel infrastructures, some measures to retard the atmospheric corrosion of steel structures must be applied.

Among several measures, paint coating is widely employed for corrosion protection of steel infrastructures. However, paint coating layers applied over steel infrastructures are subjected to degradation, and therefore need to be repaired by reapplication of the paint coating. Even after the reapplication, steel substrate under the coating is prone to corrode, accompanied with formation of rust layer which accelerates corrosion even under the coating since rust layer acts as an oxidant. Therefore, simple reapplication of a conventional paint coating over the rusted steel is insufficient. It is desired to reduce the corrosion acceleration effect of rust, and moreover to increase the protectiveness of rust layer underneath the coating.

In the atmospheric corrosion environment, four types of crystalline rusts can be produced; alpha-FeOOH, beta-FeOOH, gamma-FeOOH, and Fe3O4. The composition of the rust layer is acknowledged to exert a significant influence on corrosion resistance of steels. Thus, it is an interesting challenge to enhance corrosion protectiveness of the rust layer by reapplication of a sophisticated paint coating to the rusted steel structure. In this study, corrosion protection performance of the reactive paint coating, which is designed so as to modify the protectiveness of rust layer, applied over a rusted carbon steel is discussed.

It was found that the reactive paint coating worked well to reduce corrosion damage of the rusted carbon steel. After 4,320 h cyclic corrosion test according to JIS K5600-7-9, a large amount of rust flow and swelling of the paint coating layer around the crosscut damage made in advance in the coated surface were detected for the conventional heavy-duty coating specimen. In contrast, very small flow of rust or swelling around the crosscut damage was detectable for the reactive paint coating specimen, implying that corrosion propagation from the residual rust on the steel surface was effectively suppressed by the reactive paint.

Electrochemical analyses revealed that the reactive paint coating applied over the rusted carbon steel greatly reduced corrosion current density of the steel, compared to the conventional heavy-duty coating. This low corrosion rate of the rusted steel covered with the reactive paint is found to be attributed to the modification of rust structure.
(Invited) Thick-Cathode All Solid High Energy Batteries with Improved Interphases
Authors: Yang Jihui
Published: December 2020

Solid-state batteries (SSBs) could significantly improve safety and energy density over the conventional liquid cells. One key enabling technology is solid electrolytes. NASICON-type Li1.3Al0.3Ti1.7(PO4)3 is a very attractive solid-state electrolyte for the cathode side due to its high oxidation potential and high ionic conductivity. The usage, however, is limited by its large interfacial resistances against most of the cathode materials as well as the thermodynamic instability during high temperature sintering needed to achieve high mass density. I will report our recent effort to construct a thin, percolative, and mixed conductive interphases through in-situ low melting-point liquid sintering. These mixed conductive interphases drastically improve the kinetics, leading to high-loading cathodes and potentially more than 400 Wh/Kg SSBs.
(Invited) How Well Cathode Materials are Being Used in Rechargeable Li Batteries
Authors: Zhang Yulun , Dufek Eric J. , Li Bin , Liaw Boryann (Bor Yann)
Published: December 2020

How efficient a cathode active material (CAM) that is being used in an electrode is a vital issue for rechargeable Li battery (RLB) performance. Such utilization efficiency is a key parameter in the cell design for high energy and high power RLB. Here, we present a unique method to determine the utilization of CAM, such as NMC, in charge-discharge cycles in RLB and show the implications of this utilization of CAM can reveal the true efficiency of utilization of CAM due to the impacts from other components (e.g. electrolyte and Li anode) and conditions of use (e.g. charging and discharging conditions).
(Battery Division Technology Award Address) Exploring Stable Manganese-Based Oxides As Cathodes for Na-Ion Batteries
Authors: Yang Yong , Zuo Wenhua , Liu Xiangsi
Published: December 2020

Sodium ion batteries (SIBs) promise the potential for large-scale grid storage, due to the high abundance and wide distribution of Na sources as compared to their lithium counterparts.1-3 Among various sodium storage cathodes, layered sodium transition metal oxides (NaxMnO2) have gained significant attention owing to their great variety of compositions, ease of scalable preparation and high reversible specific capacity.

In the last several years, we have utilized different strategies such as alivovalent doping, ALD coating and controlled thermal treatments to synthesize several series of P2-type Mn-based cathodes materials and obtained promising results for future development[2-5]. For example, we propose an effective and synergetic strategy in combination of liquid N2 quenching and aliovalent doping to get new layered cathode materials [5]. As evidenced by X-ray diffraction, neutron diffraction and solid-state 23Na nuclear magnetic resonance techniques, the results reveal the significance of manipulating transition metal ions vacancies and valences to the electrochemical performance of P2-type Mn-based materials. Our results demonstrate that such a new structure significantly enhances the deliverable capacity, Na+ mobility and electronic conductivity of the materials. Furthermore, the effects of aliovalent doping elements and cooling approach on the long-range structure, local environment and electrochemical performance are comprehensively studied by comparing 15 sets of Na0.67MxMn1-xO2 materials (M = Al, Fe, Mg, Li ). The optimized Na0.67Al0.1Fe0.05Mn0.85O2 material exhibits a remarkably high initial capacity of 202 mAh g-1 among ever reported P2-type layered oxides within 2-4 V, a stable capacity retention of 81% after 600 cycles and outstanding rate capability of the specific capacity up to 122 mAh g-1 at 1200 mA g-1. In addition, some work about the air-stability of these oxides materials will be also presented.

References:

N. Yabuuchi, K. Kubota; M. Dahbi, S. Komaba, Chemical Reviews
2014,
114 (23), 11636-11682

X.H.Wu, Y. Yang et al; J Power Sources, 2015，281，18-26

X.S. Liu, W. H. Zuo, Y. Yang, et al, Angrew Chemie.; 2019，58，18086

W.H. Zuo, J.Q. Qiu, Y. Yang, et al; Energy Storage Materials; 2020，26，503-512

Xiangsi Liu, et al; submitted
(Invited) Elucidation of Electrochemical Reactions in Li2MnO3 Using Thin-Film Solid-State Battery
Authors: Kanno Ryoji , Hikima Kazuhiro , Shimizu Keisuke , Kiuchi Hisao , Hinuma Yoyo , Suzuki Kota , Hirayama Masaaki
Published: December 2020

All-solid-state is an ideal form of batteries. The all-solid-state batteries are also suitable system for elucidating battery reaction using spectroscopic methods. The present study focuses on the reaction mechanism study of lithium excess cathode materials using all-solid-state batteries. The lithium manganese oxide, Li2MnO3, is a model system of the lithium excess layered rock-salt structure. In the present study, the epitaxial and polycrystalline films with 30 nm-thick with various compositions and morphologies were fabricated using pulsed laser deposition and sputtering methods. These electrodes showed charge-discharge capacity ranging from 150 to 300 mAh g-1 with different degradation characteristics depending on the compositions and morphologies. The reaction mechanisms were studied by in-situ and operando methods using surface X-ray diffraction and operando HAXPES analyses. The Li2MnO3 shows a transformation to a high-capacity phase after activation process by the first charge and the degradation during subsequent cycling depends on the sample stoichiometry and morphology. The transition to the high capacity phase is related the phase change from O3 to O1 type, together with interlayer cation disordering on the Li/Mn layer. The activation process is related to the oxidation of oxygen and a formation new oxygen species. The activation process and the reversible reactions of the lithium-rich layered rock-salt materials are elucidated.
Plasmonic Ag/N-doped Graphene Nanoflakes as Electrocatalyst for Oxygen Reduction Reaction Enhanced by Solar Energy
Authors: Wang Zhihuan , Chen Yingjie , Gong Chong , Sui Lina , Yu Liyan , Dong Lifeng
Published: December 2020

Oxygen reduction reaction (ORR) is a crucial cathodic reaction for fuel cells. Due to its sluggish kinetics, various ORR electrocatalysts have been designed and extensively investigated. Traditionally, Pt-based materials serve as efficient ORR catalysts. However, Pt’s low abundance, high cost and poor durability have compelled people to explore other materials. For example, silver (Ag) is comparatively well-stocked and low-cost, which has drawn great attention. Although Ag shows exceptional anti-poisoning property, it is not good as Pt. Recently, enhanced electrochemical behavior of plasmonic nanostructures under illumination has been examined through both theoretical modeling and experimental investigations. As a green and sustainable energy source, solar energy can be efficiently introduced into fuel cells and metal-air batteries. Plasmonic Ag nanoparticles have strong spectral absorption in the ultraviolet and visible light bands due to unique localized surface plasmon resonance effects. Meanwhile, nitrogen-doped graphene (NG) incorporates nitrogen (N) atoms into graphene skeleton through a hydrothermal process, thereby providing active ORR sites. Also, the vacancies and defects generated by the N-doping allow silver nanoparticles to be better dispersed on the graphene as well as maintain silver nanoparticles during the reaction.

Herein, plasmonic Ag nanoparticles decorated N-doped graphene (Ag/NG) were synthesized and utilized as ORR catalysts. The ORR performance of Ag/NG greatly exceeded that of pure Ag nanoparticles and NG. For instance, the half-wave potential was 0.86 V, exceeding that of commercial Pt/C (20 wt. %). Under the AM1.5G simulated sunlight, Ag/NG demonstrated photo-enhanced electrocatalytic performance with right shifting of onset potential and enhanced current density. Therefore, the Ag/NG composite provides a potential strategy for the development of solar-enhanced electrocatalysts for fuel cells and metal-air batteries.
The Process Challenge and Optimization of Self-Aligned Contact Etch
Authors: Zheng ErHu , Chen Zhuofan , Zhang Hai-Yang
Published: December 2020

The self-aligned contact (SAC) is a key process in developing the next generation ultra-large scale integrated (ULSI) devices because its advantage on providing an efficient reduction of active array areas, decreasing the transistor gate features, and alignment margin improvements in photolithography (1-2). With the transistor gate feature size continuously scaled down, pattern density and aspect ratios continuously increase, conversely. It requires a robust etch process to solve the multiple issues such as hard mask (HM) loss loading between different patterns (trench, hole, etc.), HM shoulder profile, sidewall profile control (3). In this work, we examined the impact of various technologies on the extremely high aspect ratio SAC etch process, including source pulsing, bias pulsing, synchronous pulsing and the atomic layer etch (ALE) methods. Results indicate the introduction of pulsing function could significantly reduce the nitride loss while avoid the contact open. The synchronous pulsing and ALE scheme shows its superior capability on improving the trade-off between HM loss and profile control. To further improve the process margin, we also introduced a novel HM shape engineering. Finally we achieved a manufacturable SAC process without any side effect.

Acknowledgments

The authors gratefully acknowledge support from Shanghai Sailing Program.

References

Kim, J. Vac. Sci. Technol. A 23(4), 7(2005).

Kim, J. Vac. Scl. Technol. B 20(5), 9(2002)

H. Zheng, A study of self-aligned contact etch of NOR flash
, China Semiconductor Technology International Conference (2015).
Capacitance Measurement of Cerium Oxide Thin Film Capacitors
Authors: Kusafuka Kazuki , Kakushima Kuniyuki
Published: December 2020

Introduction

Cerium oxide (CeOx) is an attractive material for large volume on-chip decoupling capacitors, owing to its high dielectric constant (k) of 28. Commonly, a definite frequency dispersion in the small-signal capacitance measurement is observed in the frequency sweep, and larger capacitance values can be obtained at low frequency in the kHz range. The dielectric relaxation is reported to originate from the interface polarization between the polycrystalline grains in the films. In this work, the thickness-dependent polarization and the capacitance measurement under a DC voltage application are characterized.

Fabrication process

CeOx films with thicknesses from 8 to 20 nm were deposited by e-beam evaporation on an n+Si substrate with a W layer atop. Another W layer was deposited on CeOx layers and patterned to form electrodes. After the Al back contact formation, the samples are annealed at 420oC.

Results

Fig. 1 shows the frequency dispersion of the capacitors with different CeOx thicknesses measured at 0 V. The dielectric relaxation frequency shifts to higher frequency while thinning the thickness, which is useful for capacitor application. The transient current upon 1 V application is shown in fig. 2. After a high charge current, one can observe a decay in the transient current, indicating the delay in the polarization. The capacitance of the samples can be obtained by taking the integral of the charge current and is shown in fig. 3. Comparable capacitance values were obtained with the small-signal measurements. 2 to 3 times higher capacitance values can be achieved with respect to the ionic polarization.

Conclusion

High capacitance values measured in the small-signal setup were confirmed by direct current measurement by DC voltage application. An even higher capacitance can be obtained with the thinner film.
(Invited) Composition and Interfacial Engineering of Lithium Iron Orthosilicate Cathodes with Superior Intercalation Properties
Authors: Demopoulos George P. , Zeng Yan , Rasool Majid , Zaghib Karim
Published: December 2020

The quest for Li-ion batteries (LIBs) delivering higher energy density while being safer and sustainable has intensified recently. This work presents our advances towards improving the intercalation properties of an important cathode material, Li2FeSiO4(LFS), in order to take advantage of its attractive properties in terms of sustainability and safety. LFS theoretically has 330 mAh g-1capacity (2 Li+ per formula unit), however, inherently it exhibits relatively poor Li-ion intercalation kinetics, interfacial reactivity and complex phase transitions resulting in lower than one Li+ storage and poor capacity retention.In this work, we apply a multi-prong strategy to overcome these obstacles making use of compositional engineering to tune the electronic and crystal structures of LFS in concert withmechanochemical processing and polymer coating to provide a stabilizing interphase. We take advantage of the versatility of hydrothermal synthesis [1a] and mechanochemical activation and synthesize various cation-substituted and non-stoichiometric LFS nanomaterials with annealed orthorhombic Pmn21structure. Firstly, mechanochemical annealing leads to activation of Li-ion diffusion (DLi) by one order of magnitude enhancement [2a,b]. Secondly, partial substituting Co for Fe is found to allow faster phase transformation from pristine Pmn21to inverse Pmn21with important positive ramifications in its cycling performance [1b]. Thirdly, we boost the capacity of LFS, bydesigning Fe-rich (and not Li-rich!) LFS materials that deliver higher capacity within a reasonable voltage window [1c]. Lastly, PEDOT coating and near the surface composition alteration allows for stable cycling performance with >1.2 Li capacity [2c].

Acknowledgments:This research was supported by a NSERC grant and the McGill Sustainability Systems Initiative (MSSI).

References:

[1] Yan Zeng et al., (a) Hydrothermal Crystallization of Pmn21Li2FeSiO4Hollow Mesocrystals for Li-Ion Cathode Application,Chem. Eng. J., 359 (2019), 1592-1602; (b) Unveiling the mechanism of improved capacity retention in Pmn21Li2FeSiO4 cathode by cobalt substitution, J. Materials Chem. A2019, 7, 25399 – 25414; (c) Defect Engineering of Fe-Rich Orthosilicate Cathode Materials with Enhanced Li-Ion Intercalation Capacity and Kinetics, ACS Applied Energy Materials, 2020, 3, 675−686

[2] Majid Rasool et al., (a) Mechanochemically-tuned structural annealing: a new pathway to enhancing Li-ion intercalation activity in nanosized βIILi2FeSiO4
, J Mater. Chem. A 2019, 7, 13705 – 13713; (b) Unusual Li-ion intercalation activation with stepwise capacity increase in orthosilicates, J. Phys. Chem. C;DOI: 10.1021/acs.jpcc.9b11896; (c) PEDOT encapsulated and mechanochemically engineered silicate nanocrystals for high energy density cathodes, Advanced Materials Interfaces, 2020, 2000226; DOI: 10.1002/admi.202000226
Thermodynamics and Kinetics of LiCoO2/Graphite Commercial Battery
Authors: Mao Jing , Liu Xin
Published: December 2020

With the energy density increase of lithium-ion batteries in electric vehicles, people pay more and more attention to safety issues. The heat generation is the main factor affecting the safety. When the lithium-ion battery is overcharged, the so-called thermal runaway will occur in the battery system. In the process of thermal runaway, the temperature of battery increases due to exothermic reaction. In turn, the increased temperature accelerates these degradation reactions and makes the system unstable.

In this paper, we use LiCoO2/graphite commercial battery with assumed uniform heating to study the relationship between the kinetics and thermodynamics of electrode reaction and the function of magnification and temperature by means of electrochemical test. The results are used to estimate the heat production rate, which is related to the ohmic resistance of the LCO electrode, the charge transfer and transfer limitation of SEI film, and the entropy of the electrode reaction. After that, the kinetic and thermodynamic characteristics of the electrode are given. Then, the dependence of different heat sources on magnification and temperature are shown. Finally, the total heating rate of LCO electrode is calculated, and the importance of different individual contributions is discussed.

The results show that all the individual heat sources contribute significantly to the total heat in the electrode. The heat source is a function of magnification, temperature and lithium concentration in the active material. Compared with IR drop, the heat generated due to transfer restriction has a greater impact on irreversible heat. When the concentration of lithium ion is small, the irreversible heat accounts for the main part of the total heat. When the concentration of lithium ion is large, the reversible heat accounts for a large proportion of the total heat, but the difference between the reversible heat and the irreversible heat is not significant.
Study of Cu Replacement in Na2Ti1-XTMXO3 Na-Rich Cathode Material for High Capacity and Superior Stability
Authors: Ganesan Bala Krishnan , Balasubramaniam Ramkumar , DongWook Kim , Moorthy Megala , Seol Jaechang , Lee Seon Yeong , Lee Yun-Sung
Published: December 2020

Sodium ion batteries are considered as a cost effective and promising alternative to lithium ion batteries for next generation large scale energy storage applications. However, the sluggish intercalation kinetics and poor stability plagues the efficient applications.[1] Recently sodium rich cathode materials are emerging as a promising system to retain high specific energy with improved durability. Benefiting from the stabilizing property of other transition metal [TM = Cu, Cr] , the same is used as a substitute in Ti site and improved stability have been achieved. [2] In this work, we developed a high performing doped cathode of Sodium Titanium Oxide (Na2TiO3) as a battery positive electrode. The highly favorable architecture in both the electrodes showed an enhanced capability towards ion storage. A high energy retention at high power condition along with high stability have been achieved.

References:

[1] J. R. Miller, P. Simon, Science
2008, 321, 651.

[2] R. Thangavel, B. Moorthy, D. K. Kim, Y. S. Lee, Adv. Energy Mater. 2017, 1602654

Keywords : Sodium Ion Capacitors; Graphene; Energy Density; Stability; Ragone Plot
Preparation of xLiFePO4·yLi3V2(PO4)3/C Composite Cathode Materials Using Simple Physical Blending Process
Authors: Chien Wen-Chen
Published: December 2020

In this study, lithium iron phosphate/carbon (LiFePO4, LFP) and lithium vanadium phosphate/carbon (Li3V2(PO4)3, LVP) cathode materials were synthesized by solid-state method. Then, the prepared LFP and LVP were physical blending by spray drying followed a carbon coating calcination process to obtain the lithium iron phosphate-lithium vanadium phosphate/carbon composite cathode materials (xLiFePO4·yLi3V2(PO4)3/C, xLFP·yLVP/C) under different molar ratio (x:y =1:0, 3:7, 4:6, 5:5, 6:4, 7:3, 0:1) ) of LFP and LVP. The results showed that the initial discharge capacity of LFP and LVP at 0.1C/0.1C was 147.92 mAh/g (2.4-3.8 V) and 124.51 mAh/g (2.4-4.3 V), respectively. For the composite cathode materials with different molar ratio of LFP and LVP, the initial discharge capacity at 0.1C/0.1C (2.8-4.3 V) was 121.43 mAh/g for 3LFP·7LVP/C, 122.63 mAh/g for 4LFP·6LVP/C, 130.38 mAh/g for 5LFP·5LVP/C, 137.05 mAh/g for 6LFP·4LVP/C, 137.53 mAh/g for 7LFP·3LVP/C , respectively. The results showed that 0.7LFP·0.3LVP/C composite cathode materials delivered the best initial discharge capacity of 137.53 mAhg-1 at 0.1C/0.1C, 126.98 mAh/g at 0.2C/0.2C, 123.81 mAh/g at 0.2C/0.5C, 118.58 mAh/g at 0.2C/1C, and 69.55 mAh/g at 0.2C/3C, respectively. For the cyclic stability testing, the discharge capacity of 0.7LFP · 0.3LVP/C composite cathode material decreased from 135.02 mAh/g to 129.28 mAh/g after 50 cycles at 0.1C/0.1C and room temperature (25℃), the capacity retention rate was 95.75%. Moreover, the discharge capacity of 0.7LFP·0.3LVP could be maintained 105.16 mAh/g after 50 cycles at 0.1C/1C and low temperature (-20℃). No obvious capacity fading could be observed. The results showed that prepared 0.7LFP·0.3LVP/C composite cathode materials prepared from a simple physical blending by spray drying followed a calcination had a good electrochemical properties as compared with those of pure LFP/C and LVP/C cathode materials.
Improving Mass Transport of Titanium Hollow Fibre Electrodes through Gas Flow Stimulated Hydrodynamics
Authors: Jong Ronald P.H. , Krzywda Piotr M. , Mul Guido
Published: December 2020

Hollow fiber electrodes, also known as porous tube electrodes, creatively address common gas related challenges in electrochemistry. By purging gas through the electrode wall an intense three phase contact can be established along the entire electrode-electrolyte interface. The electrochemical behavior of the hollow fiber electrode has been hypothesized based on the CO2 reduction reaction on a copper hollow fiber electrode 1. It was however not studied to any significant extent. The electrochemical behavior of the hollow fiber electrode and it’s relevant parameters have now been clarified and studied in more detail.

In this study highly conductive titanium hollow fiber electrodes are used, since it is an attractive base electrode material for a great variety of electrochemical applications 2. These titanium based hollow fibers have an electrical resistivity (4.1-9.6 μΩ·m) 3 that is orders of magnitude lower than those previously reported in literature 4. This results from utilization of the two-step thermal decomposition of the polymer, which is required for the construction of an inorganic hollow fiber in a dry-wet spinning process 3.

The investigation of platinum electrodeposition onto titanium hollow fiber electrodes with different flow rates has proven exceptionally insightful with regard to understanding the electrochemical behavior of the hollow fiber electrodes. The effect of volumetric gas flow rate on the resulting platinum deposit is visualized through the platinum electrochemical surface area and SEM images (Figure 1). Looking beyond the volumetric gas flow rate it is found that the exerted pressure and the pore size distribution relate to the area depended flow rate and bubble frequency at a pore, which affect the platinum distribution. In order to deconvolute the mass transfer during the platinum electrodeposition process, the hydrogen evolution reaction and an Fe2+/3+-redox couple have been investigated. These experiments isolate mass transport as an electrical current response to flow rate in the cases of gas evolution and electron transfer in solution respectively. By drawing on analogues with the proven methods of porometry and rotating disk electrodes it was found that many aspects of the electrochemical behavior of hollow fiber electrodes can be explained. The Young-Laplace equation helps in matching pressure fluctuation to the chemical state of the electrode surface and following the principles of the Koutecký-Levich equation it is possible to describe the current changes resulting from gas flow rate.

Kas, et al. (2016). Nat. Commun., 7. DOI: 10.1038/ncomms10748

Devilliers & E. Mahé. (2007). Trends in Electrochemistry Research., 1. ISBN: 1-59454-457-3

P. H. Jong, et al. (2020). To be submitted.

David, et al. (2014). J. Membr. Sci., 139. DOI: 10.1016/j.memsci.2014.03.010

Figure 1
Adatom Surface Modification of Metal Nanoparticle Electrodes Though Underpotential Deposition for CO2 Electroreduction Catalysis
Authors: Carroll Mike
Published: December 2020

The electrocatalytic CO2 reduction reaction to form higher order carbon-coupled products is a complex interplay of CO binding energies, kinetic rate-constant branching ratios, CO2 solubility, and pH gradients. The result of this wide, and often uncontrolled parameter space is a distribution of CO2RR products, especially in carbon-coupled reactions. Designing electrocatalysts that promote any of these parameters individually is an attractive route to not only build selective CO2RR catalysts, but also to provide the framework of design principals for selective electrocatalysis. To this end, systematically varying the electrode kinetics of CO2 reduction reactions on model system substrates through minor surface modifications is an informative approach for understanding this complicated reaction and how certain products can be expressed or suppressed.

Metal nanoparticle electrocatalysts are an interesting model system as recent advances in synthetic methods enable a large degree of size, shape, and facet control which allow systematic investigations of several well controlled parameters. Palladium nanoparticles are particularly interesting as Pd alloys with hydrogen prior to electroreduction catalysis in aqueous media. This alloying provides a continuous supply of reducing hydrogen equivalents for electrocatalysis. Pd surfaces can also be modified with submonolayer amounts of metal adatoms through underpotential electrodeposition. This surface modification can, in principal, tune both the binding energies of CO and the kinetic rate constants of the hydrogen evolution reaction, both critical parameters for CO2RR. This wide parameter space presents opportunities for applied and fundamental research. I will discuss recent results aimed at modifying the electrode kinetics of palladium nanocubes with 100 surface termination by modifying the surface with various metal adatoms in different amounts. I will show how Pd nanocube surface modification influences not only the surface, but bulk, hydrogen alloying properties of the nanocube as well.
Electrochemical Study on the Reduction of Si and Ti from Molten TiO2 - SiO2 - Al2O3 - MgO - CaO Slag
Authors: Martin-Treceno Samuel , Allanore Antoine , Bishop Catherine , Marshall Aaron Timothy , Watson Matthew
Published: December 2020

Recently, the electrochemical recovery of metals from molten TiO2 - SiO2 - Al2O3 - MgO - CaO slag has been proven feasible. The use of the largest by-product of the ironmaking process as an electrolyte has the potential of producing titanium metal in a more sustainable and environmentally friendly manner than the current Kroll process. However, a more extensive understanding of the electrochemical behaviour of this complex oxide system in its molten state is paramount for the design of industrial electrolytic cells. In this work, we present the results from molten oxide electrolysis experiments performed above 1500 °C, and we discuss the effect of the experimental processing conditions on the reduction of Si and Ti ions from the melt.
Nickel Phosphide Electrocatalyst Prepared By Pulse Electrodeposition for Proton Exchange Membrane Water Electrolyzer
Authors: Yeon Kyurim , Kim Junhyeong , Ahn Sang Hyun
Published: December 2020

Hydrogen is one of the main attractions for fossil fuels because it has several advantages. Since the combustion products are pure water, hydrogen is free from environmental pollution problems. And raw materials also use water, which is an infinite material on the earth, so there is no risk of exhaustion.

One of the ways to make high purity hydrogen is water electrolysis. Of the known elements, platinum is the most active material as an electrocatalyst in the hydrogen evolution reaction (HER). Platinum and platinum group elements have excellent activity, but there are several drawbacks such as low supply stability and high price due to its scarcity.

Considering industrial and economic aspects, electrocatalysts based on inexpensive and abundant transition metals such as Nickel, Copper and Molybdenum have been studied. Pure transition metals have weakness of poor activity and stability in HER. Various types of compounds, such as phosphide, carbide, nitride, and chalcogenide, were prepared to compensate for this.

In this study, a nanoparticle-type nickel phosphide (np/Ni-P) electroplated on carbon paper (CP) was used as the cathode of HER. When nickel phosphide is fabricated by electrodeposition, metallic nickel is deposited as well as nickel phosphide. If it is used intactly as an electrode catalyst, the performance and life of the catalyst are reduced as metallic nickel is oxidized in the HER process. So, additional leaching process was added to remove the metallic nickel over-plated.

In this study, nickel phosphide on nanoparticles with a large surface area was fabricated using a pulsed electroplating method that alternates electroplating and selective leaching. This makes it possible to produce a catalyst having a wider shape than that of which the surface area was electroplated and leached for the same time. In addition, this altenating process makes it possible to greatly reduce the amount of metallic nickel present in the catalyst, so helps increase the intrinsic activity of the catalyst because the proportion of phosphorus in the catalyst increases.

The finally produced catalyst was used as a cathode of a proton exchange membrane water electrolyzer (PEMWE) to investigate the results of a single cell, which showed reasonable activity.
(Invited) Fluorinated Hybrid Solid-Electrolyte-Interphase for Dendrite-Free Lithium Deposition
Authors: Pathak Rajesh , Chen Ke , Qiao Qiquan , Zhou Yue
Published: December 2020

Lithium (Li)-metal anode has attracted extensive attention owing to its high theoretical specific capacity (3860 mAh/g), which is more than ten times to that of graphite anode (372 mAh/g). However, the notorious reactivity of Li-metal prevents their practical applications due to undesired Li dendrite growth and unstable solid electrolyte interphase (SEI) formation. Here, we developed a facile, cost-effective and one-step approach for creating an artificial Li-metal/electrolyte interface by treating Li metal anode with an electrolyte containing SnF2. As a result, the artificial SEI composed of LiF, Sn and Sn-Li alloy was formed with higher ionic conductivity and increased Young’s modulus. The higher ionic conductivity and larger Young’s modulus of the artificial layer facilitate fast Li-ion diffusion and suppress Li dendrite growth, respectively. The hybrid artificial SEI showed a synergistic effect of storing Li by a reversible Sn-Li alloy formation and Li plating underneath the SEI. The artificial SEI treated Li symmetrical cells showed outstanding plating/stripping cycles (~2325 hrs) with reduced overpotential compared to the bare Li. Coupled with a high-loading (11.88 mg.cm-2) LiNi1/3Co1/3Mn1/3O2 (NMC111) cathode, the SEI protected Li full cells exhibited remarkable performance such as longer stable cycling, higher capacity retention and higher capacity at higher rates compared to the bare Li anode.
Electrodeposited Transitional Metal-Based Electrocatalysts for Hydrogen Evolution Reaction
Authors: To Dung , Park Sun Hwa , Seyedmahmoudbaraghani Saba , Myung Nosang Vincent
Published: December 2020

As the fossil fuel is continuously declining, the necessity of a sustainable and clean source of energy is increasing. Hydrogen has been considered as a potential alternative due to its “zero emission” when reacting with oxygen in electrochemical cells. In addition, hydrogen is also a promising energy carrier/ storage to compensate the intermittent nature of other renewable energy sources (e.g. sunlight, wind, and tides). However, majority of hydrogen production comes from the combustion of fossil fuel which doesn’t make hydrogen a practical sustainable energy. Electrocatalytic hydrogen evolution reaction (HER) in water electrolysis therefore has drawn considerable attention owing to water and oxygen as the “green” reactant and by-product respectively.

Early works with electrocatalytic HER involved noble metals (e.g. Pt) which is not cost-effective for industrial scale production. Therefore, transitional metal-based electrocatalysts (TMEs) have been intensively studied owing to the affinity of unpaired d-band electrons for chemisorption of hydrogen atoms. Among different strategies to improve the intrinsic properties of TMEs, coupling with other materials synergistically promotes the kinetics of HER. Nickel with minimum energy for hydrogen adsorption among various nonprecious metals exhibits the most efficient catalytic activities as a binary alloy with molybdenum in alkaline HER. Hydrogen spillover and averaging effect between the hydrogen adsorption energies of nickel and molybdenum facilitate the catalytic activity of nickel molybdenum alloy. On the other hand, transitional metal phosphides, especially cobalt with similar energy for hydrogen adsorption as nickel, have been considered as promising TMEs for acidic HER. With high electronegativity, phosphorus atoms can trap the positively charged protons and consequently enhance the dissociation of hydrogen. Moreover, dissolution of phosphorus-doped cobalt is less thermodynamically favored than that of cobalt, resulting in better electrocatalytic stability. To further enhance the HER catalytic performance, both types of electrocatalysts are synthesized at non-equilibrium by electrodeposition techniques to introduce chemical disorders and metaphases as well as to widen the range of composition. Different properties of deposits (e.g. composition, morphology, and grain size) can be tuned by controlling electrolyte composition and electrodeposition parameters.
Hybrid Electrodeposition of Ag-Graphene Composite Films on Cu Alloys for High-Conductive and Wear-Resistive Automotive Connectors
Authors: Sakaida Shizuka , Kure-Chu Songzhu , Matsubara Takashi , Liu Jiacheng , Hihara Takehiko , Yashiro Hitoshi
Published: December 2020

In recent years, plug-in hybrid electric vehicles (PHEV) and plug-in hybrid vehicles (PHV) have become popular due to depletion of fossil fuels. At the tip of the wire harness, which is said to be the nerve of automobiles, there are numerous terminal connectors that are connected to various electronic devices, and the demand for their reliability is every increasing with the progress of PHEVs and PHVs. Considering the conductivity and heat generation, Cu alloys that plated with a highly conductive Ag film are commonly used. However, in addition to the problem of soaring costs due to the increased use of noble Ag, which is a, there is an important problem that the wear resistance of Ag is insufficient because of its adhesiveness during sliding and/or its soft nature, which has been unsolved yet.

In this study, we are aimed at fabricating a novel Ag-graphene composite films on Cu alloys though a facile hybrid electrodeposition. Here, graphene is used to function as an effective solid lubricant, while maintaining the conductivity of Ag matrix plating films that are indispensable to various automotive connectors. A commercial Cu alloy sheet was used as the base material. Graphene was produced by electrolytically exfoliating Graphite. A cyan-free Ag plating solution containing home-made graphene nano-flakes was adopted in electrodeposition. The thickness of the deposited films was designed to be 5 mm and controlled by depositing conditions. The resultant specimens were investigated by FE-SEM, EDX, GD-OES, Raman spectroscopy. The properties such as hardness, resistivity, and wear resistance were also evaluated.

Fig.1 shows the surface FE-SEM images of as-deposited pure Ag and Ag-graphene films. Both the pure Ag and the Ag-graphene composite film were smooth, consisting of nano-sized fine particles. It can be seen in the Ag-graphene composite film that, there were some areas where the particle size was slightly larger, and moreover, a hazy film-like material was observed on them, which was examined as C by EDS analysis. Fig. 2 shows the Raman spectroscopic measurement results of the pure Ag film and the Ag-graphene composite films. Compared to peak-less spectrum of pure Ag film, three typical peaks were detected in Ag-graphene composite film. The detected peaks are indexed to be D-band, G-band, and 2D-band from graphene, thus indicating the co-deposition of Ag and graphene flakes during the hybrid Ag electrodeposition and graphene electrophoretic deposition. Moreover, it was also found that the Ag-graphene composite films exhibited higher hardness and lower friction coefficient compared to the pure Ag film, thus confirming a promising candidate material for high-conductive and wear-resistive automotive connectors.

Figure 1