bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of Diffusion Coefficient of Li+ Ions in Porous Electrodes from Rate Capability Tests
Authors: Suzuki Rikuya , Ariyoshi Kingo
Published: December 2020

To apply lithium-ion batteries as a power source of an electric vehicle, it requires high input- and output-power capability. Our previous study revealed that the decrease in capacity on rate capability tests is due to the migration process of Li ions in a porous electrode [1]. Specifically, solid state diffusion of Li ions in an active material is much faster than diffusion of Li ions in liquid phase. This indicates that transportation of Li ions in an electrolyte within porous electrode is a rate determining step.

In this paper, the diffusion coefficient of Li ions in porous electrode was determined from the results of rate capability tests by means of electrochemical simulation program (Dualfoil 5.1 [2-4]), because the mass transport of lithium ions in the electrolytic solution within porous electrode occurs by the diffusion process. The discharge behavior of Li/LAMOF cells was calculated with changing the electrode thickness of the LAMOF electrode. The results showed that the area-specific capacity (ASC) per geometrical electrode area on discharge was correlated to the discharge current density based on the geometrical electrode area (J
a) in the high current density region, whereas ASC was constant in the low current density region. The linear relationship between the two can be expected from Sand’s equation described as follows,

Jτ½CR
*-1 = nFADR
½π½ 2-1

The above equation ca be transformed in the following equation,

JτA-1 = (DRn²F²πCR
*²4-1) × (J A-1)-1

From this equation, diffusion coefficient of Li ions (D
R) can be determined from the slope of the linear relation.

From the results on rate-capability tests with changing various electrode structure, thickness and porosity, the relationship between the diffusion coefficient and the rate characteristic is discussed.

[1] K. Ariyoshi et al., J. Electrochem. Soc., 165, A3965-A3970 (2018).

[2] M. Doyle et al., J. Electrochem. Soc., 140, 1526-1533 (1993).

[3] T. F. Fuller et al., J. Electrochem. Soc., 141, 1-10 (1994).

[4]T. F. Fuller et al., J. Electrochem. Soc., 141, 982-990(1994).

Figure 1
Effect of State of Charge on Physical Properties of Vanadium Redox Flow Battery Electrolytes
Authors: Chace Wyndom M. , Lawton Jamie S. , Arruda Thomas M
Published: December 2020

Vanadium redox flow batteries (VRFB)s consist of two half-cells separated by an electrolyte/membrane through which ions migrate in order to maintain charge balance.1 Nafion, a perfluorinated polymer with sulfuric acid functional groups that facilitate proton transport, is a widely utilized membrane for both flow battery and fuel cell technologies. Parasitic vanadium crossover measurements can take into account the correlation between the composition of electrolyte solutions and the membrane properties. In the case of VRFB based on vanadium sulfate, vanadium concentration, sulfuric acid concentration, and state of charge (SOC) are three main factors describing electrolyte composition. Electrolyte solutions with higher H2SO4 concentration have been found to corresponded to lower VO2+ membrane permeability.2 In previous crossover-diffusion experiments,3 the permeability of VO2+ with respect to the counter ion followed the trend H+ > VO2
+ > VO2+. Absorption of vanadium species in the membrane followed the order V3+ ≈ VO2+> VO2
+ at all concentrations of H2SO4.

The state of charge (SOC) of the electrolyte, expressed as a percentage from 0% to 100%, describes the extent of oxidation that has occurred in each electrolyte. In the case of this study, 0% SOC consists of all VO2+ and 100 % SOC consists of all VO2
+ while the intermediate SOCs consist of mixtures of the two and probe the electrochemical reactions of the positive electrode in the VRFB. The characterization of mass transfer in the operating VRFB has yet to fully investigate the role of SOC on diffusion and other properties. Here, we study the relationship between SOC and properties of the electrolyte solutions using electron paramagnetic resonance spectroscopy4,5
6, cyclic voltammetry,7 and gravimetrics.

References

M. Skyllas-Kazacos, L. Cao, M. Kazacos, N. Kausar, and A. Mousa, ChemSusChem, 9 (2016).

J. S. Lawton, A. Jones, and T. Zawodzinski, J. Electrochem. Soc., 160, 697–702 (2013).

J. S. Lawton, A. M. Jones, Z. Tang, M. Lindsey, and T. Zawodzinski, J. Electrochem. Soc. , 164, A2987–A2991 (2017) http://jes.ecsdl.org/content/164/13/A2987.abstract.

J. S. Lawton, E. S. Smotkin, and D. E. Budil, J. Phys. Chem. B, 112, 8549–8557 (2008).

J. S. Lawton and D. E. Budil, J. Phys. Chem. B, 113, 10679–10685 (2009).

J. S. Lawton and D. E. Budil, Macromolecules, 43, 652–661 (2009).

J. S. Lawton, S. M. Tiano, D. J. Donnelly, S. P. Flanagan, and T. M. Arruda, Batteries, 4, 1–14 (2018).
Hydrogen Storage Properties of Melt Spun Mg-Based Alloy through Electrochemical Method for Ni-MH Batteries
Authors: Bhatt Priyanka , Hazan Joseph , Huot Jacques
Published: December 2020

Magnesium-based alloys have attracted much attention and extensive research as negative electrode materials for Ni/MH batteries. Magnesium alloys are low cost and they have high discharge capacity in electrochemical processes1. However, corrosion behaviour severely limits their utilization. Magnesium alloys are also considered as hydrogen storage materials due to their high hydrogen capacity. In this communication, the crystallographic, morphology and electrochemical properties of melt spun Mg74Zn22Nd4 will be reported. It was found that, despite the ribbon being very thin (0.10 mm), the microstructure on each side of the ribbon is different. The surface touching the wheel is showing a much higher crystallinity and texture than the other face of the ribbon. In the same way, morphology on both faces are different. The electrochemical hydrogen storage behaviour in addition to gas phase absorption/desorption will be discussed.

[1] Li-FangJiao, Hua-TangYuan, Yi-JingWang, Yong-MeiWang, International Journal of Hydrogen Energy. 34 (2009) 1476–1482
Synthesis of Reduced Quinone - Alkali Metal Cation Pairs
Authors: Ganapathi Devi , Baclig Antonio C , Penn Emily E , Chueh William C.
Published: December 2020

Quinone-based molecules are currently being widely studied for use as electrolytes in redox flow batteries. Upon discharge (if used as the positive electrolyte), quinones accept 2 electrons to form a doubly reduced species. In aqueous solutions, this reduced species is typically a hydroquinone, due to the abundance of protons in solution. However, in non-aqueous and/or solvent-free electrolytes, the counterion is not necessarily a proton - it depends on the identity of the negative electrolyte. We aim to synthesize these compounds so that they may be studied directly. We investigate synthesis routes for these reduced quinones paired with alkali metal cations (Na+ and K+), as would be produced in a flow battery with NaK (a eutectic liquid metal) as the negative electrolyte. An ion-exchange procedure based on an existing synthesis route [1], starting from the desired hydroquinone, has been developed to synthesize these compounds. The products of these syntheses have been characterized via 1H NMR and other techniques.

References:

[1] G. Valulescu, L. Gavrila, S. C. Patrascu, M. N. Vasiliu, D. Jitaru, Rom. 1994, RO 107949 B1 9940131

Figure 1. Generic (oxidized) quinone species (left) discharging to reduced quinone-alkali pair species (right). This can be done with potassium (pictured), lithium, sodium, or another alkali metal ion. Replacing K with H yields a hydroquinone. Xn represent arbitrary side groups.

Figure 1
All-Solid-State Lithium-Ion Batteries Fabricated by Screen-Printing and Its Electrochemical Impedance Measurement
Authors: Kamei Arisa , Watanabe Hikari , Hoshi Yoshinao , Shitanda Isao , Itagaki Masayuki
Published: December 2020

Lithium ion batteries (LIBs) show the excellent cycle characteristics, however, the flammable organic solvent is used for the electrolyte. To solve this problem, all-solid-state lithium-ion batteries, in which the oxide-based solid electrolytes are used, are expected to be an attractive next-generation battery. However, the large interface resistance at positive electrode/solid electrolyte interface is one of the critical issues for the development of high performance all-solid-state lithium-ion batteries 1)2)
. In the present study, all-solid-state lithium-ion batteries were fabricated by screen printing to investigate the suitable design of the positive electrode/solid electrolyte interface. We applied the electrochemical impedance spectroscopy to the investigation of interface resistance at positive electrode/solid electrolyte interface of screen-printed all-solid-state lithium-ion batteries.

The LLZ target (Li6.25La3Zr2Al0.25O12) was used as the solid electrolyte. The size of LLZ target was φ2 cm × 0.05 cm. The LiCoO2 and Li4Ti5O12 were screen-printed on each side of the LLZ target as the positive and negative electrodes, respectively. The solvent of NMP, in which LiCoO2, solid electrolyte of LICGC, conductive auxiliary agent acetylene black (AB), and binder PVDF were dispersed, was used as the slurry of positive electrode. The slurry of negative electrode was prepared in the same manner. The current collector was an Al sheet coated with the solvent of NMP in which the AB and PVDF were dispersed. An electrochemical impedance measurement was carried out by using a three-electrode cell (Toyo system co. ltd.) at room temperature in an argon atmosphere. In the present study, arbitrary addition rate of LICGC in the positive electrode was selected to investigate the impedance at positive electrode/solid electrolyte interface.

The impedance spectrum of the screen-printed all-solid-state battery was measured by a two-electrode system. It was confirmed that a part of large loop was observed on the Nyquist plane. This partial large loop was composed of time constants related to the positive electrode/solid electrolyte interface and the negative electrode/solid electrolyte interface. The partial large loop became small when the addition rate of LICGC in the positive electrode was increased. This result indicated that impedance at positive electrode/solid electrolyte interface become small due to the increase of addition rate of LICGC. In the present study, the relationship between the addition rate of LICGC and the charge transfer resistance estimated from impedance spectrum was discussed.

References:

1) Narumi Ohta et al., Adv. Mater, 18, 2226-2229 (2006).

2) Ting Liu et al., J. Power Sources, 324, 349-357 (2016).
Reduced Graphene Oxide By Modified Hummer’s Method Under Appropriate Drying Temperatures As Anode Material for Rechargeable Li, Na and K Batteries
Authors: Lee Indeok , Kim Seokhun , Lee Seulgi , Alfaruqi Muhammad Hilmy , Kim Jaekook
Published: December 2020

We have successfully synthesized Reduced graphene oxide (rGO) sheets by modified Hummer’s method without additional reducing procedures, such as chemical and thermal treatment, by using appropriate drying temperatures under ambient atmosphere. The rGO sample dried at the optimum temperature of 250 has the most increased specific surface area and porosity as evidenced by SEM and BET analysis, leading to improved lithium-ion, sodium-ion and potassium-ion storage properties. We confirmed the use of a moderate drying temperature led to electrodes’ enhanced cyclability and good electrochemical performance at high current densities. The dimensions of the sheets ranged from nanometers to micrometres and these were entangled with each other to form aggregates. These morphological features of rGO facilitates the movement of guest ions larger than Li-ions, however there were slight instability during repeated cycling. To improve the electrochemical properties, we adopted simple chemical strategies using surfactant/solvent-assisted ultrasonication or mechanical or thermal methods. Our results will be useful for improving the full cell characteristics, and especially for preventing potential drop in sodium-ion batteries and potassium-ion batteries, which are expected to replace the lithium-ion battery system.
Nanosized-LiMn2O4/C Cathode with Enhanced Lithium Storage Properties Prepared By One-Pot Synthesis Technique
Authors: PARK Sunhyeon , Kim Seokhun , Mathew Vinod , Lee Jun , Alfaruqi Muhammad Hilmy , Kim Jaekook
Published: December 2020

A facile method with one-pot polyol-assisted pyro-technique has been adopted to synthesize highly crystalline, carbon-coated LiMn2O4 (LMO/C) nanoparticles for using as a cathode material in rechargeable Li-ion battery (LIB) applications. this study shows the efficacy of a simple and low-cost pyro-synthesis to realize high performance nano-sized particle electrodes with uniform carbon coating for useful energy storage applications. As using X-ray techniques, we confirmed The phase purity, structure and stoichiometry of the prepared cathode. Electron microscopy studies established that the synthetic technique facilitated the production of nano-sized LMO particles with uniform carbon coating. LMO/C cathode demonstrates excellent electrochemical properties (cycling stabilities of 86% and 77.5% and high rate capabilities of 79% and 36% within the potential windows of 3.3–4.3V and 2.5–4.3V, respectively). The high electrochemical performance of the LMO/C cathode is attributed to the nano-size of the LiMn2O4 particles enabling high surface area and hence greater lithium insertion and also the uniform amorphous carbon coating facilitating effective reduction in manganese dissolution and volume expansion during the lithium de-intercalation/intercalation reactions
Cotton-Candy-like Na4VMn0.9Cu0.1(PO4)3/C Cathode Via Rapid Pyrosynthesis Technique for Long-Life Sodium-Ion Battery
Authors: Soundharrajan Vaiyapuri , Kim Seokhun , Kim Jaekook
Published: December 2020

Over the last decade, there is an inviting grace for sodium-ion batteries (SIBs) as a like-for-like equivalent for Lithium-ion batteries (LIBs), that supplies high voltage and superior energy, due to the low battery-manufacturing cost and extensive availability of sodium resources. NASICON-type Na4MnV(PO4)3 (NMVP) cathode explored for SIBs proven to be encouraging because of the high operating voltage, high specific capacity, and three-dimensional framework. However, the inherent conductivity issue limits the rate-performance and complete utilization of the specific capacity of the cathode material. In this study we demonstrated the preparation of Cu-doped NVMP or (Na4Mn0.9Cu0.1PO4)3) with cotton-candy-like architecture wrapped by a thin layer of uniform carbon NVMCP/C/CC by a rapid pyro-synthesis technique. In situ synchrotron XRD and GITT studies revealed the two-phase reaction mechanism upon electrochemical Na-ion extraction/insertion process, while DFT analysis entrenched the critical reasons behind the improved electronic conduction of the NVMCP/C/CC cathode. The superior electrochemical properties of the NVMCP/C/CC cathode at low (79 mAh g-1 after 450 cycles at 1.5 C) and high current rates (68 mAh g-1 after 3000 cycles at 30 C) demonstrate that the combination of a three-dimensional nanoarchitecture, uniform carbon-coating, and Cu-doping is favorable for improving the electrochemical properties of NVMP cathodes
Hybrid Effect of Micro-Patterned Lithium Metal and Three Dimensionally Ordered Macroporous Polyimide Separator on the Cycle Performance of Lithium Metal Batteries
Authors: Kim Dohwan , Munakata Hirokazu , Park Joonam , Roh Youngjoon , Jin Dahee , Ryou Myung-Hyun , Kanamura Kiyoshi , Lee Yong Min
Published: December 2020

Short cycle life of the lithium metal secondary battery (LMSB) is largely ascribed to the dendritic growth of lithium metal during the charging process followed by continuous electrolyte decomposition. To make up for this intrinsic drawback of lithium metal, two pioneering techniques, micropatterning on lithium metal and three dimensionally ordered microporous polyimide (3DOM PI) separator, are combined to ascertain their hybrid effect on the cycle performance of LMSB. When a unit cell consisting of LiNi0.6Mn0.2Co0.2O2/3DOM PI separator/patterned lithium metal is cycled at the charging and discharging c-rates of 0.3C and 1C (1C = 2.5 mA), respectively, above 80% of the initial discharge capacity is maintained even after 400 cycles, while a control cell with polyethylene separator survives only for 130 cycles. This tremendous improvement is ascribed to the combination effect of inducing preferential lithium electrodeposition reaction into the micropattern and the uniform distribution of lithium ions on the nonpatterned lithium surface region by the 3DOM PI separator. Thus, combining these two technologies is very promising for LMSB commercialization in the future.
Analysis of Mechanical Properties of Composite Electrode with Different Binder Molecular Weights
Authors: Byun Seoungwoo , Roh Youngjoon , Lee Yong Min
Published: December 2020

In order to improve the energy density of the lithium ion battery, the loading level of the electrode is continuously increasing. As a result, the presence of inactive materials such as conductive materials / binders in the electrodes is also highlighted. In particular, securing the mechanical properties of the electrode according to the distribution and composition of the binder is becoming more important in terms of long-term reliability. However, increasing the composition of the binder of the electrode can ensure the mechanical properties of the electrode at the same loading level and density, but increases the resistance of the electrode. This increase in resistance may reduce the lifetime of the electrode, apart from the mechanical properties of the electrode. Therefore, in order to minimize the resistance increase rate of the electrode and to secure mechanical properties, the mechanical properties and resistance of the electrode according to the molecular weight of the binder in the electrode were analyzed.

In this presentation, three LiCoO2 electrodes with different PVDF binder molecular weights of 500,000 / 630,000 / 1,000,000 were prepared, and the adhesion and volume resistivity of the electrodes were measured using SAICAS and Electrode Resistance Meter. Although the adhesion of the electrodes was different according to the molecular weight of the PVdF binder, the increase in the volume resistivity of the electrode was not large. This is because the behavior of the binder and the active material / conductive material in the electrode are different from each other as the molecular weight of the binder increases, and the mechanical properties of the binder are also different according to the molecular weight. In order to confirm this more intuitively, the battery was fabricated and the behavior of the electrode was observed. Furthermore, the physical properties of the polymer were analyzed according to the molecular weight of the binder in order to clarify the cause.
Saponin: Multifunctional Additive Toward Advanced Lithium-Sulfur Batteries
Authors: Kim Soochan , Cho Misuk , Lee Youngkwan
Published: December 2020

Saponin, comprising abundant hydroxyl groups and hydrophobic aglycone moieties, is firstly introduced as a multi-functional additive for sulfur cathodes. The hydroxyl groups efficiently suppress the lithium polysulfide shuttle effects and prepare sites that can strengthen the mechanical properties of cathode through heat treatment. The amphiphilic structure of saponin also helps to disperse active electrode materials in the sulfur cathode. Through the synergistic effects due to its unique structure, the addition of a small amount (1 wt.%) of saponin into the sulfur cathode allows a 300% increase in the specific capacity of the cathode with a capacity decay of 0.012% per cycle at 2 C over 1,000 cycles.
Highly Mesoporous Carbon Derived from Silica-Embedded Zeolitic Imidazolate Framework As a Potential Reservoir of Metallic Li
Authors: Choi Seung Hyun , Kim Junyoung , Park Min-Sik
Published: December 2020

During the last decade, lithium ion batteries (LIBs) have shown great promise as a potential power source for various applications such as portable electronic devices and electric vehicles (EVs) [1]. Responding to the growing demand for high-energy LIBs, it is crucial to develop advanced materials which provides a higher energy density than commercial materials currently available. Li metal has long been considered as a future anode material for LIBs because of its extremely high theoretical capacity (~3,860mAh/g) and low potential for electrochemical reactions (-3.04V vs. standard hydrogen electrode). Despite these advantages, the practical use of Li metal is hindered by several technical issues as follow; i) unavoidable dendritic growth of Li and ii) infinite volume changes during cycling. Such issues are still regarded as main drawbacks of Li metal causing rapid performance fading and safety hazards [2]. Recently, the feasibility of various porous materials with a well-defined pore structure has been examined as potential reservoirs for Li storage to suppress unfavorable dendritic growth as well as volume changes of Li metal [3-4]. Herein, we design a highly mesoporous carbon (MC) as a potential Li storage material, based on the dual-phase reaction mechanism (i.e. lithiation and metallization). It can be synthesized via a direct carbonization of silica-embedded zeolitic imidazolate frameworks (SiO2@ZIFs) combined with a chemical etching process. Colloidal silica nanoparticles (~20nm) are employed as a mesopore former during the synthesis of ZIFs and then completely removed by a hydrofluoric acid. The formation of mesopores is effective for accommodating a large amount of metallic Li, showing a stable cycle performance over 100 cycles. It is confirmed that Li can be reversibly stored in the structure without significant dendritic growth of Li and volume changes based on various electrochemical and structural analyses. Furthermore, we thoroughly investigate a correlation between pore structure and Li storage behavior of MC as the next generation anode for high-energy LIBs.

References:

[1] N. Nitta, F. Wu, J. T. Lee, G. Yushin, Mater. Today. 18 (2015) 252-264.

[2] W. Xu, J. Wang, F. Ding, X. Chen, E. Nasybulin, Y. Zhang, J. -G. Zhang, Energy Environ. Sci. 7 (2014) 513-537.

[3] A. Li, Y. Tong, B. Cao, H. Song, Z. Li, X. Chen, J. Zhou, G. Chen, H. Luo, Sci. Rep. 7 (2017) 40574.

[4] A. Vu, Y. Qian, A. Stein, Adv. Energy Mater. 2 (2012) 1056-1085.
Modeling to Predict the Cycle Life of a Lithium-Ion Battery
Authors: Lee Dongcheul , Lee Jaewoo , Kim Byungmook , Shin Chee Burm
Published: December 2020

The lithium-ion battery (LIB) is the primary choice for many applications such as mobile electronics, electric vehicles, and stationary energy storage solutions due to its high energy density, high voltage and low self-discharge rate. The service life of LIB for such applications is generally limited by aging, although it depends strongly on the usage conditions. The aging of LIB manifests itself in the variation of electrical and thermal behaviors such as capacity fade, cell voltage drop under load, and peak temperature rise during cycling. It is of intense interest to predict accurately the cycle life of the commercial LIB by including the effect of aging.

In this work, a modeling is performed to predict the cycle life of an LIB cell during cycling over a long time. This work adopts a simple modeling approach by considering Ohm’s law and charge conservation on the electrodes based on the simplified polarization characteristics of the electrodes. By not computing the potential distribution of electrolyte phase and the transport phenomena of ionic species, the modeling method in this work cuts down considerable computation time in comparison with rigorous electrochemical models. The validation of the modeling approach is provided through the comparison of the modeling results with the experimental measurement data.
Bifunctional Additive with Smoothing and Protecting Effects for Stable Lithium Metal Anode
Authors: Jiang Zhipeng , Zeng Ziqi , Han Zhilong , Hu Wei , Xie Jia
Published: December 2020

Practical applications of lithium metal anodes are gravely impeded by inhomogeneous lithium deposition, which results in dendrite growth. Electrolyte additives are proven to be effective in improving performance but usually serve only a single function. Herein, nitrofullerene is introduced as a bifunctional additive with a smoothing effect and forms a protective solid electrolyte interphase (SEI) layer on stable lithium metal anodes. By design, nitro-C60 can gather on electrode protuberances via electrostatic interactions and then be reduced to NO2
− and insoluble C60. Next, the C60 anchors on the uneven groove of the lithium surface, resulting in a homogeneous distribution of Li ions. Finally, NO2
– anions can react with metallic Li to build a compact and stable SEI with high ion transport. With a 5 mM nitro-C60 additive, Li−Li symmetric cells show superior cycle stability in both carbonate and ether electrolytes, Li−sulfur batteries with a high cathode loading (10.6 mg cm−
2 , 6 mAh cm−
2) can achieve improved cycle retention of 63.2% over 100 cycles in a carbonate electrolyte, and full cells paired with a high-areal-capacity LiNi0.6Co0.2Mn0.2O2 cathode (3.5 mAh cm−
2) exhibit a significantly enhanced cycle lifespan even under lean electrolyte conditions. This work not only develops a new insight into the application of fullerene but also provides a novel design strategy for electrolyte additives with multiple functions for stable lithium metal anodes.

Reference:

Jiang, Z.; Zeng, Z.; Yang, C.; Han, Z.; Hu, W.; Lu, J.; Xie, J. Nano Lett.
2019, 19, 8780−8786.

Figure 1
Low Temperature Sealing of Anodized Aluminum for Enhancing Corrosion Resistance
Authors: Lee Junghoon , Kim Wangryeol , Hyunbin Jo , Kim Hyunsik
Published: December 2020

Aluminum and it alloys has various advantages for industrial and application fields, such as high specific strength, thermal conductivity and machinability. However, due to its relatively high reactivity, the low corrosion resistance should be improved for practical uses. In order to improve the corrosion resistance of aluminum, various technologies have been employed to passivate against corrosion. Especially, anodic oxidation (or anodizing) is one of the most effective method to create passive layer on aluminum, which enhance the corrosion resistance. The anodic oxidation creates a thick oxide layer with nanoscale high-aspct-ration cylindrical pores on aluminum substrate, and the pores provide paths of corrosive media to aluminum substrate causing the corrosion. Therefore, the pores in the oxide layer should be sealed to inhibit the absorption of corrosive media in the pores. Hot sealing methods requires relatively short time for process, but there is a energy cost for boiling water during the sealing. Cold sealing doesn’t need to heat the solution, but the processing time is longer and some expensive chemicals are required, such as nickel fluoride. In this study, we designed a new solution for cold sealing of anodized aluminum as an alternative of cold nickel fluoride sealing. We mixed ammonium based chemicals and nicke based chemicals, so that the active ion spices will be similar with nickel fluoride. With respect to the concentration of mixed solution, we could reduce the processing time to maximize the corrosion resistance. Moreover, the corrosion resistance of the anodized aluminum sealed with mixed solution showed better corrosion resistance than previous cold sealing and hot sealing.
Phase-Field Simulation of Stress Corrosion Cracking in Stainless Steel
Authors: Hirose Hotaka , Abe Yousuke , Yamanaka Akinori
Published: December 2020

Stress corrosion cracking (SCC) sometimes occurs in stainless steels, which are used for steam turbines of geothermal power plants. In order to prevent SCC that causes serious accidents in the plants, understanding the SCC behavior through experiments and numerical simulations is essential. Phase-field (PF) method is one of the widely used numerical simulation methods to analyze various microscale-material phenomena including electrochemical reactions such as corrosion. In this study, we have developed a new PF model for simulating a SCC behavior in a stainless steel, which includes the stress concentration at the propagating crack tip, diffusion and electrophoresis of ions in the liquid solution. The PF model is based on the PF model for general and pitting corrosion in a pure iron [C. Tsuyuki et al., Scientific Reports, Vol. 8 (2018), 12777.], which incorporates the Butler-Volmer equation. The stress evolution during the SCC is calculated by solving the mechanical equilibrium equation by means of fast Fourier transform. The diffusion and electrophoresis of ions are analyzed by solving the Nernst-Planck equation. Through the numerical simulations of SCC in a polycrystalline stainless steel which have a notch, we revealed that the crack growth rate increase in accordance with the stress intensity factor. The results have proved the crack proceeds through the grain when the elastic strain energy at the crack tip is high, and it propagate through the grain boundary when the low energy.
Uncovering the Rate Equation for the Electrochemical Hydrogenation and Hydrogenolysis of Furfural in Acidic Media over Copper
Authors: May Andrew , Biddinger Elizabeth
Published: December 2020

Electrochemical methods can be used to produce chemicals with the benefits of using intermittent renewable electricity and avoiding the use of external hydrogen gas. In addition, electrochemical methods can operate at room temperature and ambient pressure. One process that can be done electrochemically is the electrochemical hydrogenation and hydrogenolysis (ECH) of furfural, a biomass derived species. The hydrogenation and hydrogenolysis products are furfuryl alcohol and 2-methylfuran, respectively, and are produced in parallel. These products are used as a binder and as a fuel, respectively. The kinetics and mechanism of the parallel reactions involved in furfural ECH were investigated and the development of possible mechanisms are presented.

The kinetics were investigated by changing the furfural concentration between 10 and 120 mM and the applied potential between -500 and -800 mV vs RHE. In addition, the activation energies were found by changing the temperature between 15°C and 45°C. Three mechanisms are proposed based on the results from changing the concentration of furfural: non-competitive Langmuir-Hinshelwood, competitive Langmuir-Hinshelwood, and Eley-Rideal and their development will be presented.
Effect of Electrode Overpotential in Secondary Solution on Lithium Recovery Rate for Electrodialysis with Two Power Supplies and Three Electrodes
Authors: Shin-mura Kiyoto , Tokuyoshi Ryoya , Sasaki Kazuya
Published: December 2020

Demand for lithium-ion batteries (LIB) is rapidly increasing with the electrification of automobiles and the spread of new energy management systems. It is desired to recover lithium resources, whose supply and demand are tight, from spent LIB and seawater. Lithium for LIB must have a high purity of 99.9% or higher. The electrodialysis method using a lithium ion electrolyte has a high potential for recovering such high-purity lithium. Kunugi et al. [1] reported that only lithium ions could be recovered from LiCl-NaCl-KCl mixed aqueous solution by electrodialysis using La0.55Li0.35TiO3 as an electrolyte. Hoshino [2] demonstrated the possibility of using lithium ion conductive glass ceramics (LICGCTM). However, in either method, the lithium recovery rate is too low for practical use. We have devised an electrodialysis system with two power sources and three electrodes, which is different from a general electrodialysis cell consisting of two electrodes and one power source, and experimentally confirmed a large lithium recovery rate. In this study, we investigate the effect of electrode overvoltage in the secondary solution on the lithium recovery rate by this new electrodialysis method.

An anode (primary solution side) and a cathode (secondary solution side) were formed on both sides of the La0.57Li0.29TiO3 (LLTO) by firing a Pt paste. As a third electrode, a Ni mesh electrode was placed in the secondary solution at a position apart from the cathode. A constant DC voltage was applied between the anode and the cathode. A constant DC voltage of another magnitude was also applied between the cathode and the Ni mesh electrode. The electric resistance of the solution between the cathode and the third electrode was changed by changing the lithium concentration in the secondary side solution or the distance between the cathode and the third electrode. The change in the lithium recovery rate due to this change in electrical resistance was investigated. The recovery rate was calculated using the lithium concentration in the secondary side solution measured by inductively coupled plasma optical emission spectroscopy.

The electrical resistance of the solution between the cathode and the third electrode decreased due to the increase of the lithium-ion concentration in the secondary side solution, and the overpotential for the electrochemical reaction on the cathode and the third electrode increased. As a result, the lithium recovery rate was increased.

[1] S. Kunugi, Y. Inaguma and M. Itoh, Solid State Ionics, 122, 35-39 (1999).

[2] T. Hoshino, Desalination, 359, 59-63 (2015).
Investigation of Electroless Plated Magnetic Thin Film for Application to Medical Magnetic Devices
Authors: Kikuchi Shun
Published: December 2020

Recently, pandemics due to new viruses and pathogens have occurred worldwide. New species of viruses and pathogens are less effective than conventional drugs, so more effective treatments are needed. A tailor-made drug discovery research has been actively investigated. Human immune cells have cells called B lymphocytes. If we can analyze the immune mechanism by stimulating B-lymphocytes with antigens, identifying and capturing cells that respond to B-lymphocytes, we can develop highly efficient and low side effect drugs that are effective only against the causative pathogens. Therefore, a method to capture B lymphocytes modified with magnetic beads on magnetic micro-spot arrays by magnetic force is proposed. This method has been shown to be one of the most promising candidates for obtaining accurate genomic data because it can capture cells more rapidly than conventional capture methods. However, this method requires a perpendicular residual magnetic flux density (Mr⊥) in the perpendicular magnetic field that does not allow the B lymphocytes to flow out, because, although it is possible to capture B lymphocytes when a magnet is installed, there is a problem that the B lymphocytes flow out during the subsequent rinsing process. In this study, the plating conditions were investigated to improve the perpendicular magnetic anisotropy of cobalt (Co) based magnetic thin films. Alkaline degreasing and acid-activated copper (Cu) plates were used as substrates for the experiments. CoNiP, CoNiMnP and CoNiMnReP thin films were prepared by electroless plating under the plating bath composition and plating conditions as shown in Table 1. Vibrating sample magnetometer (VSM), X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDS) were used for the evaluation. Fig. 1 shows the hysteresis curves of thin films plated with different bath compositions. Perpendicular residual magnetic flux density (Mr⊥) was 25 emu/cc for the CoNiP thin film and 219 emu/cc for the CoNiMnP thin film.The CoNiMnP thin film was found to improve Mr⊥ more than 8 times compared to the CoNiP thin film.It was found that the addition of MnSO4 5H2O improved the Mr⊥.The addition of MnSO4 5H2O may have enhanced Mr⊥ due to the effect of crystal magnetic anisotropy due to the vertical orientation of the c-axis of hcp Co.The perpendicular saturation magnetic flux density (Ms⊥) values were 818 emu/cc and 612 emu/cc for the CoNiMnP and CoNiMnReP thin films respectively.The results showed that the addition of NH4ReO4 reduced the Ms value with maintaining a high Mr⊥ values.

Figure 1
Friction and Wear of Ni-P Electroless Plating By Adding for WO3 Particles
Authors: Choi Byeong-Chan , Lee Sang Joon , Kim Byung-Jun , Moon Hyoung-Seok , Kim Byoung-Koo , Kim Yang Do , Kim Hyoung Chan
Published: December 2020

Electroless Ni (nickel) plating is known as an industrially unique wet plating. In particular, nickel plating is widely used for precision mechanical parts, pipes, bearings, cylinders, etc. due to its corrosion resistance, excellent hardness, and uniform plating properties. However, depending on the use environment, due to the low thermal stability, the grain growth and recrystallization of the plating layer reduce the corrosion prevention properties. For the purpose of improving thermal stability, elements such as W (Tungsten) and Mo (Molybdenum) can be added to improve mechanical properties. The composite plating containing W shows excellent heat resistance, and hardness and abrasion resistance can be improved. In addition, there is a trend to study composite plating of PTFE (Polytetrafluoroethylene) and MoS2 (Molybdenum disulfide) to improve lubricity and non-adhesion. In this study, Ni-P-PTFE-WO3 was plated using WO3 (Tungsten trioxide) powder to improve thermal stability, abrasion resistance, and lubricity. The experiment was plated at 90 ° C for 1 hour in the plating solution, and the heat treatment process was performed at 300 ° C for 1 hour. We analyzed the change in crystallinity before and after heat treatment using XRD (X-ray Diffraction), and observed the plating thickness and surface using SEM (Scanning Electron Microscope). By using wear test, the change of abrasion resistance and lubricity with and without WO3 plating will be compared.
Building Block Design for Rapid Mass Transport in Quasi-Solid-State Solar Cells
Authors: Cui Lingling , Zhang Xiao LI
Published: December 2020

Mesoscopic solar cells have rapidly emerged as a promising alternative to conventional silicon photovoltaics due to the combined benefits of low-cost, simple fabrication and competitive solar energy conversion efficiency. Recent success in low light absorption cobalt (II/III) polypyridyl complexes has led to encouraging solar energy conversion efficiencies in excess of 13%. Moreover, as one-electron redox mediators, cobalt (II/III) complexes based DSC systems also show a lower overpotential for dye regeneration and better compatibility with flexible metal substrates than iodide/tri-iodide. Such efforts open up great possibilities towards commercial applications.

In contrast to the conventional organic liquid electrolytes that commonly have challenges durable encapsulation of the devices due to solvent evaporation, gel electrolytes have exhibited an impressive long-term stability, especially for outdoor applications where temperature of the DSC system can reach 80-85 oC under sunlight. Improvement on mass transport of the considerably large sized cobalt (II/III) complexes, particularly in high viscosity electrolyte, is crucial for solid-state dye-sensitized solar cells (SS-DSCs) to reach a reliable high efficiency toward practical applications.

In this work, titania nanorod aggregates (TNA) with a great specific surface area and well-developed crystalline network were synthesized through a solvothermal approach and utilized as photoanode building blocks for application in cobalt (II/III) tris(2′2-bipyridine) complexes based solid-state electrolyte. An initial efficiency excess 7.1% and a long term stable efficiency of approximately 8.0% were achieved at full sun illumination by freshly assembled and aged TNA SS-DSCs, respectively. This represents dramatic enhancements of nearly 35% and 100% against the SS-DSCs prepared from two standard TiO2 nanoparticle samples – CCIC (approx. 5.9%) and Degussa P25 (approx. 4.0%), correspondingly. The TNA is characterised by a combination of mesopores within each aggregate and macro inter-aggregates voids, a high specific surface area and a great light scattering ability; such features make the aggregates superior photoanode building blocks for the application in bulky cobalt redox mediator based SS-DSCs system.
Growth and Characterization of CuInGaSe2 Single Crystal
Authors: Harayama Koudai , Nagaoka Akira , Masuda Taizo , Nishioka Kensuke , Yoshino Kenji
Published: December 2020

The chalcopyrite Cu(In,Ga)Se2 (CIGS) alloy system has received strong interest in recent years because of its potential for the development of high efficiency and low cost solar cells. The bandgap energy can be varied between 0.9 and 1.68 eV by composition ratio of In and Ga and the absorption coefficient is very high of abobe 105 cm-1. In our previous work1, I-III-VI2 chalcopyrite compound Cu(In0.2, Ga0.8)Se2 (CIGS) single crystal was successfully grown by traveling heater method (THM). The powder X-ray diffraction (XRD) pattern showed preferred orientations of (112), (220) and (312) planes, confirming the chalcopyrite structure. In Raman spectra, the A1 mode peaks expected for CIGS were observed, and no secondary phases were observed. The full-width at half-maximum (FWHM) of the X-ray rocking curve (XRC) for the (112) oriented CIGS single crystal is 103 arcsec. The good-quality single-phase CIGS single crystal can be obtained1). In this work, Ga-rich composition ratio CIGS single crystals could be also successfully grown by THM. At the ratio of Ga / (Ga + In) > 0.3, the CIGS changed from n-type conduction to p-type conduction. It was assumed that Se vacancies are reduced with increasing Ga ratio from the results of Energy dispersive X-ray spectroscopy.

1)Nagaoka, et al., Renewable Energy 2015, 79, 127-130.
Oxygen Reduction Reaction Activity of Iron (II) Phthalocyanine Monolayers in Acidic Media Studied Using a Rotating Disk Electrode Technique
Authors: Toyama Tatsuya , Motobayashi Kenta , Ikeda Katsuyoshi
Published: December 2020

Metal complexes such as metalloporphyrins and metallophthalocyanines are widely studied in various research fields due to their unique physical and chemical properties. Especially, their catalytic activities for oxygen reduction reaction (ORR) are of great interest because this reaction plays an important role in energy conversion or biological redox processes. Among various metal complexes, Iron (II) phthalocyanine (FePc) is expected as a candidate for four-electron ORR catalysts. However, most of the kinetic studies for ORR have been carried out using heat-treated catalysts of FePc. Unfortunately, their chemical structures become ill-defined after the heat treatment, and thus, the nature of active sites is still unclear. Actually, there is a possibility that four-electron ORR activity is induced by dimeric FePc. The intrinsic activity of monomeric FePc, especially in acidic media, is still under discussion. In this study, well-defined monolayers of monomeric FePc complexes were fabricated on chemically modified Au surfaces using two-step assembly [1]. Their ORR activity was quantitatively measured in acidic media using a rotating disk electrode (RDE) technique. The catalytic behavior of FePc was compared with that of Cobalt (II) tetraphenylporphyrins (CoTPP), which is known as two-electron ORR catalyst.

The monolayers of FePc or CoTPP were fabricated on Au surfaces as follows. First, an Au disk electrode with diameter of 10 mm was modified with self-assembled monolayers of pyridine-4-thiol (PySH) or 1,6-diisocyanohexane (C6DI). Next, metal complexes of FePc or CoTPP were immobilized on top of these molecular monolayers through axial ligation with their different terminal groups. The ORR activity of these samples was measured in O2-saturated 0.05 M H2SO4 aqueous solution using the RDE method.

Figure shows rotation rate dependences of RDE polarization curves for CoTPP and FePc on C6DI-modified Au. According to the Koutecky-Levich analysis of these curves at 0 V vs. RHE, the electron transfer number was estimated to be 1.9 for CoTPP, indicating that CoTPP indeed catalyzed only two-electron ORR. On the other hand, the estimated transfer number for FePc was 2.4, suggesting that this complex was indeed able to catalyze the four-electron ORR in the acidic condition. Interestingly, the catalytic behavior of FePc on C6DI-modified Au was apparently different from that on PySH-modified Au. In the poster, we will present details about the ORR activities of FePc measured on various monolayer-modified Au electrodes.

Reference

[1] Toyama T, Sato S, Motobayashi K, Uosaki K, Ikeda K. J Solid State Electrochem. DOI: 10.1007/s10008-019-04461-9.

Figure. Rotation rate dependence of RDE polarization curves for FePc/C6DI/Au and CoTPP/C6DI/Au measured in 0.05 M H2SO4 solution, where FePc/C6DI/Au and CoTPP/C6DI/Au denote FePc and CoTPP monolayers immobilized on C6DI-modified Au, respectively.

Figure 1
Electropolishing of Type 304 Stainless Steel in an Amide Type Ionic Liquid Containing Chloride Ion
Authors: Yuza Nitaro , Serizawa Nobuyuki , Katayama Yasushi
Published: December 2020

Electropolishing of stainless steel (SUS) has been commercially performed in such aqueous acid solutions as phosphoric and sulfuric acid. The current process shows low current efficiency due to the oxygen evolution reaction. Amide type ionic liquids with wide electrochemical windows are expected as an alternative electrolyte for electropolishing of metals with high current efficiency. Although electropolishing of Ti, Cu, Pt, and Sn has been reported in amide type ionic liquids, there is no report for SUS. In addition, previous studies on electropolishing of SUS in nonaqueous electrolytes have suggested that chloride ions are necessary to promote the breakdown of the oxide film on SUS. In the present study, the anodic dissolution mechanism of type 304 SUS was investigated in an amide type ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl) amide (BMPTFSA), containing chloride ions.

BMPTFSA containing Cl- was prepared by dissolving BMPCl. The anodic behavior of SUS was investigated by linear sweep voltammetry. The surface morphology and roughness of SUS before and after the anodic dissolution were evaluated by scanning electron microscopy and laser scanning microscopy.

A smooth and shiny surface was obtained by the anodic dissolution with optimum conditions in BMPTFSA containing Cl-. The surface roughness decreased after the anodic dissolution. On the other hand, no anodic current corresponding to the anodic dissolution of SUS was observed in BMPTFSA without Cl-, indicating the presence of Cl- is necessary for the anodic dissolution of SUS in an amide type ionic liquid. The dissolved metal ion species in the ionic liquid were identified to be the chlorocomplexes of Fe, Cr, and Ni by ultraviolet-visible spectroscopy. The current efficiency of anodic dissolution was estimated to be 93 to 100% from the mass change of the electrode and electric charge, suggesting that electropolishing with high current efficiency is possible.

The present work was partially supported by the Kato Foundation for Promotion of Science.