bluuebunny/crossref_metadata_2025 huggingface dataset:
Advanced Na Batteries Using β″-Alumina Solid-State Electrolytes
Authors: Li Guosheng , Chang Hee Jung , Lu Xiaochuan , Sprenkle Vincent
Published: February 2020

Developing advanced and reliable electrical Energy Storage Systems (ESS) is critical to stimulate the growth of renewable electricity generation from wind and solar power resources and improve the reliability of the electric power grid. Lithium (Li)-based batteries have dominated the current rechargeable battery markets for portable electronics and now expanded to ESS. However, the present Li battery industry has encountered critical problems, such as high cost, safety concerns, and limited resources, which are obstacles to fulfilling the increasing demand for ESS application. In the last few years, high-temperature Na batteries (HT-Na batteries), such as Na-S and Na-NiCl2 batteries, have been considered attractive candidates for next-generation ESS owing to naturally abundant Na resources (1000 times greater than Li) and a suitable redox potential of Na metal (-2.7 V for Na vs. -3.0 V for Li). However, the application of HT Na batteries for ESS use has not yet been widely accepted by earlier markets up to date. This is because of (1) high operating temperatures (280°C for Na-NiCl2 and 350°C for Na-S battery), (2) safety concerns associated with catastrophic cell failure in the conventional HT Na-S cell, (3) high manufacturing costs of solid-state electrolytes and battery packs, (4) limitation on cell design, etc.

Over the years, we have been actively developing new technologies to improve the battery performance, reliability and cost effective cell designs for NBBs.  In here, we report an advanced intermediate temperature (IT) NBBs, which is operated at a temperature much lower than that of conventional HT-NBBs. Our results indicate that lowering operating temperature could obtain substantial benefits by slowing down the battery degradation, reducing the cost of cathode materials and manufacturing process. Hence, IT-NBBs presented in here could bring new paradigms to Na β″-alumina batteries for its practical applications in ESS.
Battery Degradation and Cost Analysis of a Lithium Ion Battery System for a 1 MW Green Energy Hub (GEH)
Authors: Morris Larry , Weatherspoon Mark H
Published: February 2020

Studying higher renewable energy penetrations during the electricity generation phase, the Future Renewable Electric Energy Delivery and Management (FREEDM) Systems Center has focused on supporting the battery degradation and cost analysis portion of a commercial 1 MW green energy hub (GEH). Cost analysis and battery degradation modeling will be used as part of a coupled approach and consist of the following software applications: NREL's System Advisor Model (SAM) - for identification of load requirement and summarization of PV productions; COMSOL Multiphysics - for determination of efficient electrochemical battery energy storage system (BESS); and MATLAB – for the implementation of state of charge (SOC), state of health (SOH), and peak shaving algorithms. The GEH will provide for various grid services using 20% renewable energy penetration and a Lithium ion based (Li-ion) BESS. Preliminary results using a LiFePO4 based BESS are presented below.

Technical Approach with Preliminary Results

The LiFePO4 battery was cycled to determine SOC and SOH using the Versastat 4 Potentiostat with the measured data being used as a baseline for the development of the COMSOL model.

SAM

The System Advisor Model (SAM) is a model developed by the U.S. Department of Energy and National Renewable Energy Laboratory to analyze sustainable energy systems. The SAM was used to determine the photovoltaic footprint capable of supporting 20% penetration.

Fig 1.

COMSOL

COMSOL Multiphysics is a general-purpose software platform, based on advanced numerical methods, for modeling and simulating physics-based problems. COMSOL was used to model battery degradation and the affect of multiple cycling characteristics in a LiFePO4 cell.

Fig 2.

MATLAB

MATLAB is matrix-based software that uses programming language for numerical computation. MATLAB was used for computation and data analysis of the peak shaving algorithm.

Fig 3.

Acknowledgement

This work was supported by the FREEDM ERC program of the National Science Foundation under award number EEC-08212121.

References

Dubarry, Matthieu, Liaw, Bor Y. (2009). Identify capacity fading mechanism in a commercial LiFePO4 cell Journal of Power Sources Vol 194, pg 541-549.

Kim, Jae-Hun, Woo, Sang C., Park, Min-Sik, Kim, Ki J., Yim, Taeeun, Kim, Jeom-Soo, Kim, Young-Jun. (2013). Capacity Fading Mechanism of LiFePO4 Based Lithium Secondary Batteries for Stationary Energy Storage, Journal of Power Sources Vol 229, pg 190-197.

Yang, Ye, Li, Hui, Aichhorn, Andreas, Zheng, Jianping, Greenleaf, Michael. (2014). Sizing Strategy of Distributed Battery Storage System With High Penetration of Photovoltaic for Voltage Regulation and Peak Load Shaving. IEEE Transaction on Smart Grid, Vol 5, No2, pg 982 – 991.

Figure 1
A New Process to Synthesize the Rh2S3 Precursor for RhxSy Catalyst for HER/HOR in HBr Solution
Authors: Li Yuanchao , Nguyen Trung Van
Published: February 2020

With the development of distributed renewable energy resources such as wind and solar power, there has been growing interest in electrical energy storage. The hydrogen-bromine (H2-Br2) reversible fuel cell system serves as one of the promising technologies because of its high round-trip conversion efficiency and low cost. For the highly corrosive HBr/Br2 environment, alternative catalysts to platinum, which was shown to be rapidly corroded and poisoned in this environment, is needed for the HER/HOR reactions at the hydrogen electrode. RhxSy catalysts have been found to be stable in the HBr/Br2 environment.1,2 In the current synthesis process, the source of sulfur ions in RhxSy is provided by (NH4)2S2O3.
3 In the new process, the use of Na2S as a source of sulfur ions was explored. This presentation will discuss the new synthesis process of RhxSy catalyst and the characteristics and performance of this catalyst.

References

 

1. J. Masud, T. Van Nguyen, N. Singh, E. McFarland, M. Ikenberry, K. Hohn, C. J. Pan and B. J. Hwang,, Journal of the Electrochemical Society, 162, F455–F462 (2015).

2. A. Ivanovskaya, N. Singh, R.-F. Liu, H. Kreutzer, J. Baltrusaitis, T. Van Nguyen, H. Metiu and E. McFarland,, Langmuir, 29, 480–492 (2013).

3. A. F. Gulla and R. J. Allen, Carbon supported metal sulphide catalyst for electrochemical oxygen reduction, Google Patents, (2008).

Acknowledgement

The work presented herein was funded by the National Science Foundation under Grant No. EFRI-1038234.
Copper Bromide Chemistry Analysis for Use in Large Scale Energy Storage and Beyond
Authors: Stricker Elizabeth A. , Wainright Jesse S. , Savinell Robert F.
Published: February 2020

Copper redox flow batteries have been recently studied in a high halide environment [1, 2]. The halide chemistry allows for the stabilization of the copper I oxidation state and the complexation also prevents the disproportionation reaction from taking place [3]. Historically, the copper halide chemistry has been used for electrowinning. Although the chemistry has been used for many years, little has been done to characterize the diffusion of bromide ion in the presence of high concentrations of bromide, the diffusion of the copper bromide complexes, and the kinetic parameters of electrodeposition from the copper I bromide complex. We have conducted charge and discharge experiments on the copper redox flow battery in a bromide electrolyte. It was observed that the battery is able to charge at higher current densities than it can discharge. During charging experiments, the battery was able to achieve a geometric current density over 200mA/cm2. However, during discharging experiments the battery was not able to achieve 125mA/cm2as shown in Figure 1. This is most likely due to an intermediate insoluble complex formed during discharge that passivates the surface. In this study, bromide ion diffusion, copper I diffusion, and copper I kinetics have been explored. A preliminary model, based on these precepts, has been developed and the applicability of these results to redox flow batteries and other systems are discussed.

[1] L. Sanz, D. Lloyd, E. Magdalena, J. Palma, K. Kontturi, Journal of Power Sources, 268 (2014) 121-128.

[2] D. Lloyd, E. Magdalena, L. Sanz, L. Murtomäki, K. Kontturi, Journal of Power Sources, 292 (2015) 87-94.

[3] H. Zhao, J. Chang, A. Boika, A.J. Bard, Analytical Chemistry, 85 (2013) 7696-7703.

Figure 1
Understanding Speciation in Ionic-Liquid Electrolytes for Non-Aqueous Redox Flow Batteries
Authors: Miller Mallory A. , Gaudet Jason , Thompson Levi T , Wainright Jesse S. , Savinell Robert F.
Published: February 2020

Conventional aqueous redox flow batteries (RFB) are limited by low energy and power densities; thus, recent focus has been on development of non-aqueous electrolytes. Although organic solvents allow for increased voltage windows, they possess a several drawbacks, including sensitivity to moisture, low solubility of active species, and high flammabilities and toxicities. Ionic liquids (IL) offer a “greener” alternative to volatile organic electrolytes as they are non-toxic and nonflammable [1, 2].

Iron chloride based IL electrolytes containing up to 6.3 M iron have been synthesized. It was found that electrolyte conductivity and viscosity, as well as the nature of the electroplated iron, are greatly influenced by electrolyte composition. An electrolyte containing iron chloride, choline chloride, and ethylene glycol in a 1:1:4 molar ratio was attractive due to its high plating efficiencies, fast kinetics, and acceptable conductivity [3]. Electrochemical reactivity of the solute ions as well as the physical properties of the electrolyte are controlled by speciation of the metals in solution. To understand what ions are responsible for the observed properties in these iron IL electrolytes, chemical speciation was investigated using x-ray absorption spectroscopy (XAS) as well as x-ray photoelectron spectroscopy (XPS). The two techniques indicate the presence of organometallic compounds which may hinder the electrokinetics as well as the fluid properties. For example, the conductivity is a function of the mole fraction of iron as well as the iron to chloride ratio (Fig 1 below). Complexes such as [FeCl4]-have been shown to exhibit enhanced fluid properties [4], however, when the iron:chloride ratio is less than 1:4, di-iron species have been known to form [5]. The properties of these iron IL electrolytes as a function of composition coupled with results from XAS and XPS to explain observed trends will be presented.

[1] M. J. Earle and R. K. Seddon, Pure Appl. Chem., vol. 72, p. 1391, 2000.

[2] K. N. Marsh, A. Deev, A. C.-T. Wu, T. E., and A. Klamt, Korean J Chem. Eng. , vol. 19, 2002.

[3] J. S. W. M. A. Miller, and R. F. Savinell, "Iron Ionic Liquid Electrolytes for Redox Flow Battery Applications," Journal of The Electrochemical Society, vol. 163, pp. A578-A579, 2016.

[4] I. M. H. C. A. Angell, P. A. Cheeseman, "Physico-chemical and computer simulation studies of the role of cation coordination numbers on melt physical properties," Electrochemical Society Proceedings, p. 138, 1976.

[5] M. S. Sitze, E. R. Schreiter, E. V. Patterson, and R. G. Freeman, "Ionic Liquids Based on FeCl3 and FeCl2. Raman Scattering and ab Initio Calculations," vol. - 40, pp. - 2304, 2001.

Figure 1
Understanding Hydrogen Peroxide Decomposition Activity of Transition Metal Oxide Catalysts in Oxygen Reduction Reaction
Authors: Trinh Phong , Malkhandi Souradip , Manohar Aswin K , Manivannan A. , Prakash G. K. Surya , Narayanan S. R.
Published: February 2020

Energy storage is essential for large-scale integration of renewable energy such as solar and wind into the electricity grid. Fuel cells and metal-air batteries are promising technologies for grid-scale energy storage owing to their high energy densities and environmental friendliness. However, it is well known that the slow kinetics of the oxygen reduction reaction (ORR) at the cathode limits the efficiency of these fuel cells and metal-air batteries. Among transition metal oxides, calcium-doped lanthanum cobalt oxide is one of the promising catalysts for ORR because of the ability of these materials to support both oxygen evolution and oxygen reduction reactions [1]. In previous work, we demonstrated that in transition metal oxide–carbon composites catalysts, carbon is the primary electrocatalyst for the two electron electro-reduction of oxygen to hydrogen peroxide and the transition metal oxide decomposes the hydroperoxide to generate additional oxygen [2]. Therefore, we have focused on understanding the role of mixed metal oxides on decomposition of hydrogen peroxide for designing more active carbon-based catalyst systems. Specifically, we have studied the effect of manganese substitution of cobalt in calcium-doped lanthanum cobalt oxide on the hydrogen decomposition rate of the catalysts.

Manganese-substituted compounds of the formula La0.6Ca0.4Co1-xMnxO3 compound with x value = 0.0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1 were synthesized by the sol-gel method using the Pechini process. As previously described [3], a two-step heat treatment was employed for the synthesis of these compounds. In the first step the material subjected to controlled combustion at 120-170 oC, then the material was collected, ground and heat-treated in a second step sintering process at 700oC for 2 hours.

The decomposition characteristics of hydrogen peroxide on various transition metal oxides was measured by oxygen reduction studies on rotating-ring-disk (coated glassy carbon) electrode, and by steady state polarization studies of the oxidation and reduction of hydrogen peroxide.

We have demonstrated that the mixed potential of the oxide electrode under open circuit conditions could be predicted from the kinetics of the conjugate reactions of peroxide oxidation and reduction. We also find that the higher rate of oxidation of hydroperoxide correlated directly with the improved oxygen reduction activity in the composite catalyst. The presentation will discuss these findings.

Figure 1
Nanostructured Organic Positive Electrodes for Sustainable Energy Storage
Authors: Liu Tianyuan , Lee Byeongyong , Lee Seung Woo
Published: February 2020

Lithium-ion battery has become the major power source for various applications owing to its high efficiency, high energy density, and small form factor. Despite these advantages, the high cost of electrode materials, including transition metal oxides, limits their penetration for large-scale applications, such as electrical grid and renewable energy storage. Therefore, developing low-cost, sustainable, and high-performance electrode materials could be the critical enabling factor. Recently, organic electrode materials, which can be prepared from earth-abundant and sustainable sources, have attracted intensive attention due to their high energy density per cost.

We also have reported on the nanostructured carbon based electrodes that were assembled from organic molecules, such as pyrene derivatives1 or glucose.2 In this study, we further investigate the redox-active properties of these organic molecules with lithium ions, enabling those materials to be the active electrode components for lithium-ion batteries or capacitors. We show that these organic electrodes can deliver high specific capacities over 150 mAh/g with high redox potentials over 3 V vs. Li/Li+, proposing to be the promising positive electrodes for both lithium-ion batteries and capacitors. In addition, these nanostructured organic electrodes can significantly improve their rate-performance and cycling stability by employing the conductive carbon substrates, such as carbon nanotubes or reduced graphene oxides. These high-performance organic electrodes provide a new opportunity to developing low-cost and sustainable large-scale energy storage devices.

References

1. J. C. Bachman, R. Kavian, D. J. Graham, D. Y. Kim, S. Noda, D. G. Nocera, Y. Shao-Horn and S. W. Lee, Nature Communications, 6:7040 (2015).

2. T. Y. Liu, R. Kavian, Z. M. Chen, S. S. Cruz, S. Noda and S. W. Lee, Nanoscale, 8, 3671 (2016).
Electrochemical Characterization of Cu2s Cathode Prepared By Spray Pyrolysis with Heat Treatment
Authors: Kalimuldina Gulnur , Taniguchi Izumi
Published: February 2020

Introduction

In the modern society, the requirements for the capability of existing LIBs are not satisfying and motivates researchers for the development of the more powerful energy storage systems. In response to the urgent environmental and energy issues, the cathode materials’ improvement is considered as one of the solutions in the way of fulfilling the demand for high capacity and sufficient energy density rechargeable batteries [1-2].

Copper sulfides became a topic of considerable interest and importance because of their theoretical capacity 337 mAh g-1 for Cu2S and 560 mAh g-1 for CuS with flat and prolonged charge/discharge plateaus [3].

In this work, we have synthesized Cu2S with Cu/S≈2 elemental ratio by spray pyrolysis followed by heat treatment and physical and electrochemical characterizations of the material were investigated.

Experimental part

The preparation of Cu2S powder was carried out by dissolving copper (II) nitrate trihydrate (Cu (NO3)2·3H2O) and thiourea (CS (NH2)2) in the molar ratio range of Cu: S from 2 to 0.5. The sprayed droplets carried by N2+3%H2 gas inside the reactor and the reactor temperature was varied from 400 to 700 ºC. Afterwards samples were sintered in the temperature range from 400 to 600 ºC in a N2+3%H2 gas atmosphere for 2 h.

The cathode slurry was prepared by mixing 80:10:10 wt.% of Cu2S, polyvinylidene fluoride (PVdF) and acetylene black (AB) in 1-methyl-2-pyrrolidinone (NMP). The coin-type cells (CR2032) were assembled with 1 M LiTFSI in 1:1 w/w in DOL/DME electrolyte and lithium metal foil used as a reference electrode in a high purity Ar gas atmosphere (99.9995% purity). The cell performance test was performed for charge/discharge cyclability in a voltage range of 1.0-3.0 V where 1C was used as 337 mA g-1.

Results and discussion

In Fig. 1 the rate capability of Cu2S is presented. Stoichiometric Cu2S prepared at SP 400 ºC and further annealing at 460 ºC for 2h of Cu:S=1 molar ratio solution revealed the 1st discharge capacity of 330 mAh g-1 (98% of its theoretical capacity) at 0.1C. Upon cycling, the cell capacity kept at 270 mAh g-1. With the increase of the C-rate the capacity gradually decreased to 220 mAh g-1 at 30C. The Coulombic efficiency was retained at about 100% value from 0.1C to 10C rate and dropped to 95% at 30C. The prepared Cu2S demonstrated relatively stable capacity value between 0.1C and 30C without severe decay and with good charge/discharge reaction reversibility.

References

[1] B. Scrosati, J. Garche, J. Power Sources, 195 (2010) 2419-2430.

[2] B. Jache, B. Mogwitz, F. Klein, P. Aldelhelm, J. Power Sources, 247 (2014) 703-711.

[3] X. Meng, S.C. Riha, J.A. Libera, Q. Wu, H.-H. Wang, A.B.F. Martinson, J.W. Elam, J. Power Sources, 280 (2015) 621-629.

Figure 1
Self-Polymerized Dopamine As an Organic Cathode for Lithium-Ion Batteries
Authors: Liu Tianyuan , Lee Byeongyong , Lee Seung Woo
Published: February 2020

The redox-active organic materials have been intensively investigated as promising candidates for replacing the inorganic cathodes in lithium-ion batteries (LIBs). In particular, quinone-based organic molecules, such as benzoquinone, naphthoquinone, and anthraquinone, have received considerable attention owing to their high redox potential, high theoretical capacity (up to 500 mAh g−1), and possibility of being synthesized from earth-abundant resources. However, these quinone derivatives cannot be directly used in common LIBs because of their high solubility in non-aqueous electrolytes.

Dopamine, which has a similar molecular structure with adhesive proteins in mussel, can be self-polymerized on various types of substrates. It is interesting to note that one of the oxidation intermediates of dopamine, 5, 6-indolequinone, resembles the structures of benzoquinone and naphthoquinone, having a high theoretical capacity of 364 mAh/g. Despite its intrinsic redox characteristic of the quinone groups,1 the redox-active properties of the polydopamine (PDA) with lithium ions have not been reported yet. Here, we first demonstrated PDA as a promising organic cathode in LIBs. PDA showed a specific capacity of ~235 mAh/g at 0.14 C and ~140 mAh/g at ~27.4 C. We also investigated the energy storage mechanism in PDA and confirmed the existence of both electrical double-layer capacitance and pseudocapaitance. By using carbon nanotubes (CNTs) as 1D templates for the polymerization of dopamine, we prepared flexible PDA and CNT composite films. The composite films exhibited enhanced rate capability and excellent cycling stability owing to the unique combination of redox-active PDA and superior electrical conductivity of CNT.

References:

(1) M. D. Hawley, S. V. Tatawawadi, S. Piekarski, and R. N. Adams, J. Am. Chem. Soc., 89, 447 (1967).
Characteristics Analysis of NaNiCl2 Battery for Applying to Ships
Authors: Ahn Jong-Woo , Roh Gill-Tae , Park Ki-Do , Kim Kyung-Hwa
Published: February 2020

Marine equipment and shipping industries have done research to develop high efficient and environment-friendly ship technology to deal with IMO's air pollutant regulation from ships. Nowadays research on marine power generation and propulsion system based on the secondary battery, which is enable to charge and discharge and has high energy density, has been spotlighted in the world. Among the secondary batteries, NaNiCl2 battery is used in buildings, transportation by land due to high efficiency and safety. To apply the NaNiCl2 battery to ships, its safety in marine environment condition has to be proved. In this paper, the testbed developed for inclining and vibration experiments and test results are introduced.
CV Measurement of New Redox Flow Battery Electrolyte Using Single Fiber Electrode
Authors: Narita Ayumi , Sato Yukari , Kaneko Yuji , Negishi Akira , Nozaki Ken , Kato Tohru
Published: February 2020

Redox flow batteries (RFB) are one of the candidates for large-scale energy storage systems to solve the issues of power variation with renewable energy. All-vanadium RFBs have strongly developed up to now [1], because their electrolyte includes only vanadium ions in both half-cells as active materials, avoiding cross-contaminations. In order to supply RFBs to the world, it is required to lower the production costs and use the material which is rich in natural resources.

In last year, Sumitomo Electric Industries, Ltd. published new type of RFBs using titanium (Ti) and manganese (Mn) as active materials [2]. This RFB have been expected to lower the costs, and avoid the cross-contamination by using Ti (IV) and Mn (II) mixed aqueous electrolyte in both positive and negative electrodes. Moreover, they presented that the mixed electrolyte prevents the precipitation of MnO2 in the electrolyte. However, details of electrode reactions between Ti (IV) and Mn (II) electrolyte and the carbon fiber have not been understood, yet. To improve the performance of this new RFBs, it is significantly important to reveal how the reaction occurs on the surface of the electrode.

In previous study, we reported the characterization of all-vanadium RFB electrodes using single fiber electrodes [3]. The results showed the differences of electrochemical property each one of the carbon fibers, and the observation of the electrode reaction for vanadium ions. In the presentation, we demonstrate CV results in Ti (IV) and Mn (II) electrolyte using the single fiber electrode.

Acknowledgments

This work was supported by a grant from Ministry of Economy, Trade and Industry (METI) which is re-entrustment from Sumitomo Electric Industries, Ltd. The authors wish to thank them deeply.

References

[1] T. Shigematsu, SEI Technical Review, 73, 1 (2011).

[2] Y. R. Dong, H. Kaku, K. Hanafusa, K. Moriuchi and T. Shigematsu, ECS Trans. 69, 59 (2015).

[3] A. Narita, Y. Kaneko, Y. Sato, A. Negishi, K. Nozaki and T. Kato, ECS Trans. 68, 89 (2015).
Nitrogen-Doped Porous Carbon with High Degree of Graphitization Derived from Silk Cocoon for Lithium-Sulfur Batteries
Authors: Xiang Ming Wu , Liu Heng
Published: February 2020

Lithium/sulfur batteries (Li/S) are receiving significant attention due to its high theoretical specific capacity (1675 mA·h/g) and high theoretical specific energy (2600 W·h/kg), and inexpensive sulfur. However, the practical applications of Li/S batteries are still greatly hindered because of the low coulombic efficiency, poor cycle life and rate capability. To enhance the inherent insulating property of sulfur and insoluble discharge products and alleviate the shuttling effect of soluble polysulfides, here, a new type of nitrogen-doped porous carbon (NPC) derived from renewable silk cocoon has been successfully prepared via simultaneously activation and graphitization using metal salts FeCl3 and ZnCl2. Interestingly, the as-prepared NPC exhibits an extremely high degree of graphitization and possesses a high specific surface area of 1058 m2 g-1 and a large pore volume of 0.9026 cm3 g-1. The NPC/S composite with encapsulated sulfur content of 63% was prepared by a facile melt-diffusion method. The NPC/S electrode delivered a high initial discharge capacity of 1499 mAh g-
1 at 80 mA g-1 and coulombic efficiency of over 98%. Especially, the NPC/S composite still show excellent cycle life when the rate recover to 800 mA g-1 after cycling at various rates from 80 to 2560 mA g-1. Taking into account the low-cost of renewable biomass carbon resource and facile strategy, this work is an effective approach to increase the utilization of sulfur and improve the electrochemical performance of Li/S batteries.
Podiform Graphene-Sulfur Composite for Lithium Sulfur Battery
Authors: Guo Yi , Zhang Yun
Published: February 2020

A podiform graphene and sulfur composite is prepared by a facile lyophilization method followed by low-temperature heat treatment for high-performance lithium sulfur battery. SEM, EDS, XRD and TG are used to characterize the morphology and structure of the material. Sulfur nanoparticles are physically trapped inside the podiform graphene like beans. Graphene serve as a conductive framework for electrode material. Meanwhile, the podiform structure not only constrain the dissolution of polysulfide, but also accommodate the volume expansion during the charge/discharge process. As a consequence, the as-designed graphene-sulfur electrode deliver an initial specific discharge capacity of 1538 mAh g-1 at 0.05C. It still can exhibit a capacity of 674 mAh g-1 at 2C after 100 cycles. Good performance of the graphene-sulfur composite can attribute to the unique podiform structure.
Electrochemical Charge-Discharge Properties of Co-S/x Wt.% AB5 Composite Materials in Nickel-Based Batteries
Authors: Li Jiajia , Zhao Xiangyu
Published: February 2020

The Co-S/x wt.% AB5 (x=0, 10, 20, 30) composite materials were prepared by simply mixing Co-S material fabricated by hydrothermal method and AB5 alloy. The structure and morphology of the composite materials were characterized by XRD and SEM, respectively. The electrochemical properties of the composite electrodes were studied by the galvanostatic charge, discharge test and electrochemical impedance spectroscopy. The results showed that the Co-S/20 wt.% AB5 composite electrode showed the highest discharge capacity and the best cycling stability. The existence of the AB5 alloy improved the electrochemical activity of composite electrodes, reduced the electrochemical polarization resistances and promoted the electrochemical conversion reaction between Co and Co(OH)2. In order to improve the utilization rate of active materials, 0.01 mol/L Na2S2O3 was added into the electrolyte. The electrochemical properties of the composite electrode were significantly enhanced. After fifty cycles, the discharge capacity of the composite electrode increased from 407 to 481.7 mAh/g and the capacity retention increased from 79.7% to 91.2%.
The Kinetics of the Metastable Pit Nucleation on Metal Surfaces
Authors: Lu Pin , Engelhardt George , Macdonald Digby D.
Published: February 2020

The theory for kinetics of nucleation of metastable pits in terms of the Point Defect Model (PDM) has been applied the first time to describing the evolution of the nucleation rate of metastable pits on a variety of metallic substrates. The PDM successfully accounts for the experimental data that have been reported in the literature on stainless steel, carbon steel, iron, aluminum, and Alloy-22, and which are judged to be reliable and reproducible. Important fundamental parameters related to metastable pitting such as total number density of pitting nucleation sites, dissolution time of the cap over the pit, energy related to absorption of the aggressive ions into oxygen vacancies in the surface of the barrier layer, vacancy condensation rate, and the time at which the nucleation rate of metastable pits is maximum were obtained from the optimization of the PDM on the experimental data, as reported in the present paper. The values obtained for those parameters are in good agreement with values and observations reported elsewhere. The present work successfully demonstrates the capacity of the PDM in accounting for experimental observations of metastable pitting and that the PDM can be applied as an underlying theory for studying and understanding metastable pitting on metal surfaces.
(Keynote) Anodic Oxide Films As Electron Spectrometer
Authors: Diesing Detlef , Meyburg Jan Philipp
Published: February 2020

Anodic oxide films formed by electrochemical oxidation of Al, Ti and Ta can act as spectrometer for excited electrons. The oxide films can be used as interstitial layer of so-called metal-insulator-metal systems. These systems show a device current without any applied voltage, when one of the metal’s temperature or electron distribution deviates from equilibrium. A deviation from the equilibrium for example of the top metal electrode occurs when the top metal is a catalytic metal and the device is mounted in a chemical reactor. Oxidation reactions in CO+O2 atmosphere on the catalyst surface lead to a heating of the catalyst surface and subsequently to a current from the hotter catalytic top metal to the cooler non catalytic base metal. The application of bias voltage between the non catalytic base metal and the catalytic top metal in the course of the chemical surface reaction allows a spectrometer like study of the top electrode’s state. The spectroscopic function of three different oxide films (AlOx, TiOx, TaOx) will be discussed.
(Invited) Anodic Oxide Formation and Oxygen Evolution on Metals Such As Al and Ta - Experiment and Simulation
Authors: Lohrengel Manuel M.
Published: February 2020

This presentation recalls the peculiarities of anodic polarization valve metals namely aluminium and Tantalum. Both metals are very unnoble and react immediately with oxygen or water. They form an anodic oxide that hinders further transport of anions and cations through this film. Upon higher polarization the electrical field in the oxide exceeds the critical value of oxide formation field strength enabling metal cations and oxygen anions to migrate within the high field gradient in a thermally activated and field supported hopping process. This mechanism that is known as the high field mechanism of oxide formation nicely explains the most important aspects of oxide formation but some of the kinetic observations require a more sophisticated description that is called the extended high field model. As a result of the ions injected into the adjacent phases through the interface, a space charge is formed that drastically changes the local field strength. Since the potential drop over the entire film thickness remains constant, other regions of the film must compensate the reduced interface potential drop. This leads to a temporal imbalance of the driving forces within the oxide. For a limited time the charge carrier concentration can become extremely high, resulting in an experimentally observed maximum in current density named overshoot. This overshoot is not only observed in potentiostatic experiments but also in potentiodynamic scans. Both types of experiments can be satisfyingly simulated on the basis of this model. Under specific conditions however, oxide formation is not the only occurring process, meaning that the current efficiency in terms of oxide formation is below 100%. There are at least two different charge transport mechanism leading to oxygen evolution. The first one is the more obvious one in which the oxide breakdown field strength is exceeded resulting in a, at least temporal and/or local, destruction of the oxide film, that allows charge flow into this side reaction. The second one is less obvious since direct elastic tunnelling of electrons is not possible over a range of a few nm. A large number of defects in the insulating oxide film which can also be described as states in the band gap may allow charge transport in an unexpected way. The importance of these findings, the model behind, and the industrial applications will be discussed.
Direct Measurement of the Dissolution of Valve Metals Under High Field Anodisation Conditions
Authors: Hassel Achim Walter , Kollender Jan Philipp
Published: February 2020

Valve metals such as Ti, Nb and Ta react spontaneously with water or oxygen forming dense oxide layers on their surface. These thin passive layers are protecting the metals from further corrosion. Anodisation can be used to increase the thickness of the passive layers for an improved corrosion and wear resistance. Oxide growth during anodisation occurs via ion transport through the oxide film under high field conditions.

The oxide growth process during anodisation of valve metals has been investigated in detail in the past. Most widely used for the description of the oxide growth mechanism during anodisation is the high field model [1]. However, there is one parameter that cannot be described by the high field model or any other existing model that is the metal dissolution during oxide growth. To date the metal dissolution during anodisation of Nb, Ta and Ti has also never been experimentally observed or quantified. In an attempt to study this phenomenon a flow-type scanning droplet cell microscope (FT-SDCM) [2] which is directly coupled to inductively coupled plasma mass spectrometry (ICP-MS) [3] was used. By means of this technique it was possible to investigate the time and potential dependent metal dissolution during anodisation. Additionally the influence of the pH value of the used electrolyte was investigated.

All experiments showed an overshoot in metal dissolution during the initial stage of oxide growth. The dissolution rate stabilized into a constant plateau (stationary dissolution) after this initial period for all investigated materials.

In acidic electrolytes a constant increase of the overall amount of dissolved metal was observed when increasing the anodisation potential. For neutral electrolytes on the other hand the exact opposite was observed. Higher formation potentials were leading to lower dissolution rates. Furthermore, a direct potential - independent proportionality between the amount of charge carriers crossing the electrolyte-oxide interface and the amount of dissolved metal during anodisation was observed. The measured dissolution rates were highest for Ti and lowest for Ta under all investigated pH values. Interestingly almost exactly one order of magnitude difference in dissolution rate between each of the three investigated materials was found.

For a better understanding of the observed dissolution behaviour electrochemical impedance spectroscopy was performed under oxide formation conditions for each investigated material. Differences were significant in the film resistance depending on the pH value of the electrolyte. They could be used to rationalise the observed dissolution behaviour.

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[1] M. M. Lohrengel, Mater. Sci. Eng. R. 11 (1993) 243

[2] J. P. Kollender, A. I. Mardare, A. W. Hassel et al., J. Electroanal. Chem. 740 (2015) 53

[3] A. I. Mardare, J. P. Kollender, A. W. Hassel et al., Electrochem. Comm. 59 (2015) 5
pH Sensing Electrochemical Cell to Investigate Anodic Dissolution of Magnesium
Authors: Miyazawa Kei , Hoshi Yoshinao , Shitanda Isao , Itagaki Masayuki
Published: February 2020

Magnesium (Mg) is widely used as the automobile parts and biomedical materials because it is lightweight and high strength material. However, it is well known that Mg has large corrosion rate, which limits the application of Mg. The hydrogen evolution rate on Mg increases with noble potential from corrosion potential. This phenomenon is called the Negative Difference Effect (NDE).1-8) The effect of pH on the Mg dissolution and hydrogen evolution during the anodic dissolution is one of the key issue for understanding of NDE phenomenon.4) In the present study, we developed the pH sensing electrochemical cell to investigate the pH changes near the Mg electrode due to the anodic dissolution.

Schematic of the pH sensing electrochemical cell developed in the present study is shown in Fig. 1. The electrochemical cell was constructed using transparent acrylic plates. The working electrode and the counter electrode were placed in compartments separated by a glass filter to avoid the pH changes due to the gas generation on each electrode. Tungsten/tungsten oxide electrode was set closed to the working electrode. Tungsten/tungsten oxide electrode was prepared by the anodic oxidation. The diameter of tungsten electrode was 3 mm. The anodic oxidation of tungsten electrode was performed at 0.52 V vs. SSE in 1 mol dm-3 phosphate buffer solution (pH=1) for 1 min. This electrode was immersed in the buffer solution adjusted to arbitrary pH to evaluate the performance as the pH sensor. The distance between the tungsten/tungsten oxide electrode and the working electrode was 1 mm. The anodic polarization curve measurement of Mg was conducted by three electrode system. The working electrode was the Mg electrode and the counter electrode was Pt wire. The saturated potassium chloride/silver/silver chloride electrode (SSE) was used as the reference electrode. The 1 mol dm-3 sodium sulfate solution was used as the electrolytic solution.

The pH was monitored using the tungsten/tungsten oxide electrode during the anodic polarization curve measurement of Mg electrode. The relation between pH and anodic current of Mg was discussed in the present study.

 

Reference

[1] G. Song, A. Atrens, D. Stjohn, J. Nairn, and Y. Li, Corros. Sci., 39, 855 (1997).

[2] R.L. Petty, A.W. Davidson, J. Am. Chem. Soc., 76, 363-366 (1954).

[3] G. Song, A. Atrens, D. Stjohn, X. Wu, and J. Nairn, Corros. Sci., 39, 1981 (1997).

[4] L. Rossrucker, A. Samaniego, J.-P. Grote, A. M. Mingers, C. A. Laska, N. Birbilis, G. S. Frankel, K. J. J. Mayrhofer, J. Electrochem. Soc., 162, C333-C339 (2015).

[5] G. S. Frankel, A. Samaniego, and N. Birbilis, Corros. Sci., 70, 104 (2013).

[6] G. Williams, N. Birblis, and H. N. McMurray, Electrochem. Commum., 36, 1 (2013).

[7] G. L. Song and A. Atrens, Ave. Eng. Mater., 1, 11 (1999).

[8] G. L. Song and A. Atrens, Ave. Eng. Mater., 5, 837 (2003).

Figure 1
Development of Empirical Charge Transfer Interatomic Potential for Tantalum Oxide Nanostructures from First Principle Calculations
Authors: Sasikumar Kiran , Narayanan Badri , Sankaranarayanan Subramanian K. R. S.
Published: February 2020

There has been considerable interest over the years in metal oxides and their nanostructures owing to their exotic properties making them ideal candidates for several applications, notably in electronics, thermal management, catalysis and biochemistry. In particular, mesoporous (2-50 nm pore sizes) tantalum oxide nanostructures can be used for photocatalytic decomposition of water, thermal insulation and molecular adsorption, while Ta2O5nanoparticles have applications in bio-imaging due to their inertness and non-toxicity. It is essential to obtain a clear fundamental understanding of the structure and chemistry of metal oxide nanostructures to optimize the material performance in these applications.

Atomistic molecular dynamics (MD) simulations provide an ideal tool to investigate the underlying mechanisms at play in the nanoscale processes around these nanostructures and to decode the structure-property relationship. The key to a reliable MD simulation is the underlying empirical force field that describes the interatomic interactions. While robust interatomic potentials have been developed for several metal oxides, namely, alumina, titanium oxide, iridium oxide etc., there is no available empirical charge transfer force field to simulate the behavior of tantalum oxide nanostructures and metal-oxide interfaces. This is primarily due to a lack of comprehensive structural and energetics information, both experimental and ab initio theory, on the different polymorphs of Ta2O5.

In this talk, we present a detailed tabulation of ab initio density functional theory (DFT) calculations of structure, cohesive energies and elastic properties for the three main experimentally observed polymorphs of Ta2O5, namely, hexagonal, orthorhombic and monoclinic. The DFT-generated dataset is used to parameterize an EAM+QEQ (Streitz-Mintmire) charge transfer interatomic potential for tantalum oxide via evolutionary algorithms.

Streitz-Mintmire force field is a variable charge potential, which can account for dynamic charge transfer, and has been demonstrated to be a reasonable potential for single-metal oxides. In particular, oxidation of metallic nanoparticles can be investigated using this charge transfer formalism. The developed force field can also be used to investigate Ta/TaO interfaces, the properties of which are significantly affected by the nanostructure of the interface.

In this work, the developed interatomic potential is used to investigate the oxidation of tantalum thin films and nanoparticles. The thermal and mechanical stability of tantalum oxide nanoparticles and mesoporous nanostructures, and the atomic scale processes (oxidation and sintering) that occur in the vicinity of these nanoclusters are also investigated.
Influence of Alkali Metal Oxide on CMAS Damage Progression in Air Plasma Sprayed Thermal Barrier Coatings
Authors: Hayashi Yuki , Lokachari Siddharth , Yamagishi Satoshi , Okazaki Masakazu
Published: February 2020

Thermal barrier coatings (TBCs), which typically comprised of a yittria-stabilized zirconia (YSZ) ceramic top coat, a bond coat and a metallic substrate, have been widely used to protect the hot-section metallic components of gas turbine engines. More recently at high temperatures exceeding 1200℃, the TBCs can be damaged by calcium-magnesium-alumino-silicates (CMAS) resulting from the ingestion of siliceous minerals with the intake air and from unclean fuels. The chemical composition of CMAS is mainly comprised of CaO, MgO, Al2O3 and SiO2. In addition to that, alkali metal oxides can be interblended into CMAS constituents under some operating environments. In this study, the effect of alkali metal oxide (K2O) on CMAS damage progression on air plasma sprayed (APS) YSZ TBC specimens was investigated through simulating the CMAS damage at lab-scale employing synthetic CMAS products. Two types of synthetic CMAS products both with and without K2O were prepared. The synthetic CMAS was spread on the APSed TBC specimen, followed by isothermal exposure at different temperatures up to 1300℃ for various times. It was found that the infiltration of CMAS into the top coat was observed in the both CMAS compositions. However, the infiltration rate was significantly decreased due to the presence of K2O. In the case of CMAS without K2O, the reaction between CMAS and YSZ was significant resulting in the change in microstructural morphology, whereas it was little occurred on the CMAS including K2O. These results suggest that the addition of K2O to YSZ top coat can mitigate the CMAS damage progression.
Evaluation of Corrosion Resistance of Materials for Supercritical Carbon Dioxide Power Plant
Authors: Lee Soo Yeol , Chae Hobyung , Seo Sukho , Jung Yongchan
Published: February 2020

The Supercritical Carbon Dioxide Brayton Cycle has drawn much attention due to its high efficiency and stability in the power plants. Evaluation of the corrosion behavior and mechanical properties as an essential part of the power plant is of great importance for structural integrity assessment. In this work, the three types of possible candidate materials were chosen to examine high-temperature thermal stability and corrosion resistance under the high-temperature carbon dioxide environment: i) ferritic-martensitic steels (T92), ii) austenitic steels (304L & 316L), and iii) Ni-based alloys (Alloy 600 and 738LC). The experiments were performed during 1000 hours at temperatures ranging from 500 to 800°C. The corrosion behaviors of the tested materials were evaluated from weight change, composition and thickness of oxide scale, and analyses of surface and cross-section morphologies. The results show that Ni-based alloys and austenitic steels have better corrosion resistance than ferritic-martensitic steels at the temperatures tested. The corrosion resistances of the tested materials were compared with those from other publications.
In Situ Optical Investigation of H2s Impact on Carbon Oxidation in Operating Solid Oxide Fuel Cells
Authors: Kirtley John D , Qadri Syed Noorullah , Steinhurst Daniel A , Owrutsky Jeffrey C
Published: February 2020

While solid oxide fuel cells (SOFCs) promise efficient electricity production and high fuel flexibility, trace sulfur and chlorine constituents commonly found in desirable fuel sources such as syngas and biogas pose challenges. Sulfur poisoning is a well-established phenomenon that can lead to rapid loss of electrochemical performance in SOFCs that operate at high temperatures (650 – 800 °C). State-of-the-art Ni/YSZ (yttrium stabilized zirconia) anodes lose significant catalytic activity upon exposure to even ppm-levels of H2S, but details regarding how the catalyst degrades and the specific effects on electro-catalytic processes remain unclear. One approach to solving this shortcoming is to understand the degradation mechanisms through real time correlation of electrochemical performance with in situ, molecular specific observations. This current study uses infrared emission from the Ni/YSZ anode surface of an operating SOFC to simultaneously characterize 1) gas species using Fourier transform infrared emission spectroscopy (FTIRES) and 2) temperature changes using near infrared (NIR) thermal imaging. These data are collected with electrochemical potential when the SOFC is operated at 75% maximum current at 700 °C using CH4, with and without 170 ppm H2S added. In situ FTIRES measurements show that the CO2 oxidation product and the CO electrochemical intermediate are suppressed when cell potential deteriorates with H2S present. Simultaneous NIR thermal imaging measurements of surface temperatures show that cooling also reflects evolving processes at the anode. After each trial, electrochemical oxidation of deposited carbon showed that H2S also hindered carbon accumulation. These results together have begun to provide direct insight into how sulfur poisoning affects electrochemical processes in SOFCs through correlations of electrochemical potential, surface temperature changes, and gas species at the anode.