bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study of HF-Free Pulse Reverse Electropolishing of Nb Surface with an Alkaline Electrolyte
Authors: Tian Hui , Taguchi Junji , Reece Chalies E , Namekawa Akihiro , Saeki Takayuki , Hayano Hitoshi 
Published: February 2020

Chemical etching or electropolishing of Nb superconducting radio-frequency (SRF) cavities to achieve a clean and smooth internal surface require the removal of the passive Nb2O5 film. Typically, an aggressive chemical, such as hydrofluoric acid is included in the solution to accomplish this. The problem with using HF is that it is dangerous both to people and to the environment. As an alternative, in order to depassivate the surface, cathodic pulses may be interspersed between anodic pulses which passivate the Nb surface forming Nb2O5 film, in place of or in conjunction with off-times. Use of such cathodic pulses eliminates the need for HF and/or fluoride salts or other chemicals to actively remove the surface oxide. A present understanding of a pulse reverse electropolishing of Nb in alkaline electrolyte-sodium hydroxide will be reported. In this study, 10~30 % concentration of NaOH has been used as the electrolyte. In order to better understand the mechanism of a pulse reverse electropolishing of Nb with sodium hydroxide, and optimize the process parameters for Nb cavity process, the effect of cathodic pulse duration and amplitude, off time, and anodic pulse duration have been systematically studied, the surface of Nb samples have been characterized chemically and morphologically. We expect the results will enable application of this safer and greener process to future accelerator projects using Nb SRF cavities.
In Search of an Alternative Solar Grade Silicon Production By Electrochemical Reduction of SiO2
Authors: Akpinar Bengisu , Ergul Emre , Erdogan Metehan , Karakaya Ishak 
Published: February 2020

Silicon plays an important role in fabrication of solar cells and solar chips. Metallurgical grade silicon (98 to 99 % Si) demands further purification such as zone refining [1, 2], metallothermic reduction [3] and Siemens process [4] to convert it to solar grade. A promising method, based on direct electrochemical reduction of oxides by FFC Cambridge Process [5], was adopted to form silicon from porous SiO2 pellets in molten CaCl2 and CaCl2–NaCl salt mixture [6]. The contamination of silicon powder by iron and nickel originating from stainless steel cathode was reported to disqualify the product from solar applications. SiO2 pellets, sintered at 1300oC for 4 hours, were sandwiched between pure silicon wafer plates to minimize contamination of silicon. The promising results indicated a potential alternative method of direct solar grade silicon production for expanding solar energy industry.
[1] P.R. Mei, S.P.Moreira, E.Cardoso, A.D.S.Cortes, F.C.Marques, “Purification of metallurgical silicon by horizontal zone melting”, Sol. Energ. Mat. Sol., 98 (2012), 233-239.
[2] P. Siffert, E.F. Krimmel, eds. Silicon: Evolution and future of a technology. Berlin,Springer (2004).

[3] K. Yasuda, T.H. Okabe, “Solar-grade silicon production by metallothermic reduction”, JOM,62 (12) (2010), 94-101.
[4] Siemens & Halske: BRD Patents 1.102.117 and 1.140.1594 filed 1954, issued 1956
[5] G.Z. Chen, D. J. Fray, T. W. Farthing, “Direct Electrochemical Reduction of Titanium Dioxide to Titanium in Molten Calcium Chloride”, Nature, 407 (2000), 361-364.
[6] E. Ergül, İ. Karakaya, M. Erdoğan, “Electrochemical decomposition of SiO2 pellets to form silicon in molten salts” Journal of Alloys and Compounds, 509 (2011), 899-903.
Simulation of Transport Properties in Gas Diffusion Layer of PEMFC Using Lattice Boltzmann Method
Authors: Kim Jongsung , Lee Sungho , Yim Chulho , Hwang Inchul 
Published: February 2020

Gas diffusion layer (GDL) in fuel cell plays an important role of passage for reactant transport and water removal between the bipolar plate and the electrode. In the present work, effective transport physical properties of gas diffusion layer in proton exchange membrane fuel cells (PEMFC) are deduced using lattice Boltzmann simulation, which is applicable for both GDL substrate with a pore size of 10~100 micrometer and MPL with 10~100 nanometer pore size. We also use GDL microstructure scanned using high resolution X-ray computed tomography and compressed under realistic levels with virtual material design tool. Liquid water saturation in the GDL is considered in the simulation because the blockage of pores by water has a strong influence on its effective gas transport properties. The deduced properties can be applied to fuel cell performance program and its influence on cell performance be measured.
A Combined Aging and Abuse Study of Li-Ion Cells
Authors: Juarez Robles Daniel , Chen Chien-Fan , Jeevarajan Judith A. , Mukherjee Partha P. 
Published: February 2020

Lithium-ion batteries have been powering a wide range of electrical and electronic devices, from consumer products and medical equipment to automotive systems and space applications. Some highly publicized failures of products powered by lithium ion cells, such as laptops, cellphones and electronic toys, have been reported recently. A portion of these failures has been linked to overheating of the battery resulting in fire and explosion. Overall, these incidents have catalyzed a great deal of research and design activities aimed at trying to understand the causes of such failures and help guide safer cell designs.
In this work, the degradation mechanisms in commercial 18650 lithium ion cells, due to long term cycling under nominal-use charge discharge cycling as well as under electric vehicle drive cycling, are studied. In addition, studies were carried out after subjecting the cells to overcharge and external short circuit testing on fresh as well as cycled cells. During the external short test, the cells were subjected to a low resistance load (50 mΩ). Actual results indicate that for a very short time the cell experiences a very high current causing a rise in the cell temperature (>70 oC). In the overcharge test, the cell is charged up at a constant C-rate until the test is stopped due to either an abnormal event or the cell protection activation. Preliminary results have shown lithium metal deposition, as expected, in the negative electrode once that the intercalation rate has been overcome by the diffusion rate. Also, cell temperature has shown a significant increment during the overcharge process. Finally, the electrodes and electrolyte from the cycled cells were subjected to a similar analysis to understand the degradation mechanisms in long term use as well as to understand their behavior under abuse conditions after long term use. Understanding what causes this temperature rise and its effect on the electrodes could provide some information about how to prevent thermal runaway in cells and batteries used in various applications for long periods.
The cells under these tests have been characterized by conducting a Destructive Physical Analysis (DPA). The study is being accomplished through charge/discharge cycling, internal resistance measurement, capacity fading, and impedance spectroscopy. Cell temperatures are monitored in all the experiments. The morphological changes are studied by extracting the electrodes from the abused cells and analyzing them by microscopy and spectroscopy techniques. This analysis will help to obtain the changes in the electrochemical properties of the cell as well as its morphology.
Solid Electrolyte Interphase Formation and Failure Mechanisms in Lithium Ion Batteries: In Situ and in Operado AFM Imaging
Authors: Kumar Ravi , Tokranov Anton , Huang Zhuangqun , Li Chunzeng , Xiao Xingcheng , Mueller Thomas , Sheldon Brian W. 
Published: February 2020

The lifetime and performance of lithium-ion batteries depend significantly on the formation and evolution of the solid electrolyte interphase (SEI) layer. A stable SEI is necessary for utilization of high specific capacity anode materials such as Si which goes through huge volume changes (upto ~400%) during cycling. In this study we report in situ atomic force microscopy (AFM) investigation on the formation and failure mechanisms of SEI layer using patterned Si island structures. Due to the shear lag effect [1], these patterned Si islands go through lateral expansion and contraction. This puts the SEI layer on the top of the island in tension and compression during lithiation and delithiation, respectively. We performed the studies in a glovebox at the environment with < 1 ppm O2 and H2O. In addition, the unique PeakForce tapping mode was used to image the extremely fragile SEI layer, which is very challenging for conventional AFM modes in organic solvent. Our in situ studies show for the first time the in operando cracking of SEI layer and its evolution during cycling. To understand the mechanics of the SEI layer, the critical strain at which this cracking starts to evolve was derived from a progression of the AFM images. This observation will be complemented with coin cell data on comparison of irreversible capacities of continuous film and patterned island samples which differ in their mode of deformation. We are also using Scanning electrochemical microscopy (SECM) to detect local electrochemical differences at stable and unstable SEI sites. Our comprehensive studies not only provide a new in-depth understanding of the in
operando SEI formation, evolution and its mechanical response, but also offer guidance to tailor passivation layers for optimal battery performance.
Reference:
[1] Tokranov et. al. ACS Appl. Mater. Interfaces, 2014, 6, 6672
Investigation of Nano Carbon Materials with Incorporation of Catalyst As Air-Cathode Materials for Sodium-Air Batteries
Authors: Wu James J. , Peng Zhenmeng 
Published: February 2020

NASA’s future missions demand high energy density batteries. Current state-of-the-art lithium-ion batteries (LIBs) reach the specific energy capacity limits (<250 Wh/kg), thus new electrochemical storage technologies are needed to meet NASA’s future mission requirement of >400 Wh/kg. Battery chemistries with higher theoretical energy densities in particular, Li-metal based battery chemistries such as Li-air, are being actively pursued, but there remains a number of issues to be solved. The development of a new system based on sodium (Na)-air battery chemistry, with theoretical energy of 1600 Wh/kg and an equilibrium discharge potential of 2.3V, is an attractive and promising new system that has potential to achieve a rechargeable battery that meets NASA’s needs. Being rich abundance on earth but having similar electrochemical properties as lithium, sodium has the potential to be a low cost replacement for lithium in electrochemical storage technologies.
Development of novel and optimized air cathodes will be crucial for improving capacity retention and cycle life of Na-air battery. The microstructure of carbon substrates and the catalytic oxygen reduction of the air-cathode play critical roles in the electrochemical performance in metal-air batteries. With the development and proper selection of air cathodes, the energy efficiency and energy density can be enhanced significantly. In this presentation, the results of air cathodes with nano carbon materials and incorporation with catalysts on oxygen reduction reactions will be presented, and the performance of these air-cathodes in the Na-air cells will be discussed as well.
Returning to Zinc to Meet the Challenges for Next-Generation Energy Storage
Authors: Parker Joseph F. , Chervin Christopher N. , Long Jeffrey W. , Nelson Eric S. , Rolison Debra R. 
Published: February 2020

The number of battery chemistries that check the boxes of high specific energy (>100 W h kg–1), rechargeability, power performance, inherent safety, low cost, and worldwide abundance is a short list. While lithium-based batteries continue to permeate the energy-storage landscape, many safety and supply concerns remain. Aqueous-electrolyte batteries meet many of the requirements for next-generation energy storage devices, but depending on the chemistry (Pb acid, Ni–MH, Ni–Zn, Zn–Air) often fail when it comes to safety, specific energy, and/or rechargeability. The radar chart below reveals the advantages and disadvantages of several battery technologies and especially highlights that improvements to rechargeable Zn-based batteries will propel them to the forefront of the energy landscape. The historical hindrance to broader use of Zn-based batteries is the poor rechargeability of the Zn electrode, especially when formulated as a powder-bed electrode that is too prone to launch dendrites upon cycling, which then short-circuit battery operation. The U.S. Naval Research Laboratory has redesigned the Zn electrode into a monolithic, metallically interconnected three-dimensional sponge form factor that supports a more uniform current distribution, thereby allowing nearly complete utilization of the Zn active material (>90%; projecting to ~450 W h kg–1) and avoiding the local critical current density required to spawn dendrites upon cycling. We established the reversibility of our 3D Zn sponge electrodes by cycling in Ni–3D Zn coin cells with particular emphasis on suitability in next-generation electric and start–stop vehicles. The lessons derived from studying Ni–3D Zn deep cycling allow us to demonstrate preliminary cycling performance of 3D Zn–air cells and offer prescriptions on appropriate electrolytes, current collectors, cell-fabrication particulars, and the future of Zn-based batteries.

Figure 1
(Invited) Unveiling the Mechanism of Magnesium Battery Cathode
Authors: Ling Chen 
Published: February 2020

Li-ion battery plays a dominant role in portable electronic devices. Yet in large scale applications the requirement remains to find new chemistry with improved performances such as energy density and power density as well as lower cost. Magnesium battery is one of such candidates,[1] as the bivalency of Mg2+ ion provides good potential to exceed the energy density of current Li-ion technology. Metal Mg has a volumetric capacity of 3833 mAh/cc, nearly twice that of Li. However, the great hurdle to realize a practical Mg battery lies in the lack of appropriate cathode that can marry metal Mg anode with good capacity, cyclability and rate capability.
In this talk, we will discuss the mechanism of magnesiation for several Mg battery cathodes. In comparison with Li-ion battery, we demonstrated that the chemistry of Mg battery cathode is more complicated. Even for classical intercalation-type Li-ion battery cathodes, the magnesiation can deviate from the intercalation reaction and follow the conversion pathway.[2-8] Hence the intercalation of Mg is not only challenged by the sluggish mobility of bivalent Mg2+ ions. Necessary consideration about the stronger structural deformation and side reactions is also essential for the discovery of cathode candidates. The effect of conversion reaction will be carefully examined and discussed in details. Finally, we conclude our talk by suggesting several methods to avoid the challenges brought by intercalation with given examples.[9-11]
Reference:
[1]. D. Aurbach, Nature, 2001, 407, 73
[2]. R. Zhang, et al. Electrochem. Commun., 2012, 23, 110
[3]. T. S. Arthur, et al. ACS Appl. Mater. Interfaces, 2014, 6, 7004
[4]. C. Ling, et al. Chem. Mater., 2012, 24, 3943
[5]. R. Zhang, et al. J. Power Sources, 2015, 282, 630
[6]. C. Ling, Chem. Mater., 2015, 27, 5799
[7]. C. Ling, et al. in preparation
[8]. C. Ling, et al. submitted
[9]. C. Ling, et al. Chem. Mater., 2013, 25, 3062
[10]. R. Zhang, Chem. Commun., 2015, 51, 1108
[11]. R. Zhang, Chem. Commun., 2015, 51, 1457
A Rocking-Chair-Type Magnesium Hybrid Supercapacitor
Authors: Yoo Hyun Deog , Han Sang-Don , Bayliss Ryan D , Gewirth Andrew A. , Genorio Bostjan , Burrell Anthony K. , Cabana Jordi 
Published: February 2020

Supercapacitors can provide high rate capability and long-term cycleability, profited by their simple mechanism based on the adsorption and desorption of ions on the surface of electrodes. It is possible to charge or discharge supercapacitor cells in a minute for 10,000 cycles without notable degradation. Based on the high power characteristics, supercapacitors can augment the batteries or fuel cells for electric vehicles or heavy equipment. So far, most of supercapacitors have symmetric configuration with activated carbon electrodes as the positive and negative electrodes (Fig. 1a). And they follow Daniell-type mechanism, where the electrolyte is depleted of and replenished with ions upon charging and discharging, respectively (Fig. 1b). In this mechanism, electrolyte serves as an ionic reservoir, from which cations and anions are separated to negative and positive electrodes, respectively. As a result, sufficient volume of electrolyte is indispensable for the operation of supercapacitors. This leads to a limitation in energy density and an increase in the internal resistance as the starvation of the concentration of salts in the electrolyte decreases during operation.
Herein, we introduce a hybrid supercapacitor that follows ‘rocking-chair’-type mechanism for the first time. This hybrid supercapacitor is composed of magnesium metal and activated carbon as the negative and positive electrodes, respectively (Fig. 1c). Mg2+ ions are replenished at the negative electrode while they are adsorbed into the pores of the positive electrode upon the discharging of the cell (Fig. 1d). On the other hand, Mg2+ ions are released from the positive electrode while Mg metal is deposited on the negative electrode upon the charging of the cell. As a result, only a minimum amount of electrolyte is needed to operate the cell since the electrolyte serves as a medium of Mg2+ ions. The use of Mg metal electrode can increase the energy density of the cell significantly by virtue of the large volumetric capacity of 3832 mAh/cc and the low redox potential of -2.2 V vs activated carbon’s open circuit potential. Therefore, the ‘rocking-chair’-type magnesium hybrid supercapacitor can double the energy density of a supercapacitor, and the internal resistance can be kept constant during the operation of the cell. The electrochemical results show highly reversible reactions at the positive and negative electrodes thanks to newly-developed Mg2+ electrolytes. Charge-discharge cycles at rates up to 5 mA/cm2 were possible, whereas cycling tests showed 64% retention of the capacity after 400 cycles. Detailed studies of the mechanisms of degradation and evidence of the ‘rocking-chair’-type mechanism will be presented.

Figure 1
Development of Stable Organic Redox Shuttles for Applications in Lithium Ion Batteries
Authors: Guarr Thomas F. , Mortimer Nicholas , Prins Amber J. , Polik Robert 
Published: February 2020

The inclusion of a “redox shuttle” in a battery electrolyte can provide passive cell balancing as well as overcharge protection by functioning as a molecular shunt when the desired maximum charge voltage is reached. There are many requirements for effective shuttle operation; chief among these are: 1) compatibility with other electrolyte components; 2) high oxidation potential (generally > 4.0 V vs Li/Li+); and 3) high stability in both reduced and oxidized forms (leading to long cycle life).
The most common traditional strategy for designing organic compounds that possess such high oxidation potentials involves the incorporation of electron withdrawing substituents; however, the resultant lack of electron density in the ring system often leads to undesirable side reactions and/or decomposition. We have developed an alternative approach that exploits the change in molecular geometry that often accompanies the oxidation of heterocyclic compounds. Specifically, by introducing bulky groups to sterically impede this reorganization, computer models suggest that oxidation potentials can be shifted to more positive values without sacrificing stability. Preliminary results employing this strategy on various substituted carbazoles and phenothiazines will be presented.
New Iron-Based Polyanion Compounds As Low-Cost Cathode Materials for Rechargeable Alkali-Ion Batteries
Authors: Choudhury Amitava , Yaghoobnejad Asl Hooman 
Published: February 2020

Polyanion compounds (Phosphates, sulfates, borates, and silicates) of transition metals are receiving an ever increasing attention as potential positive electrode in the secondary alkali ion batteries. They possess certain advantages over the traditional transition metal oxides due to their higher inherent safety and structural stability granted by the covalent bonding in the polyanion. In this context iron compounds are especially attractive, thanks to the natural abundance of iron resources and its environmental friendliness. Most importantly polyanion-based compounds of iron get big boost in Li-ion insertion voltage compared to pure oxide because of the inductive effect of the polyanions. Thus far the search for polyanion compound of iron yielded promising results, among which the Olivine LiFePO4 (3.45 V) and Triplite LiFeSO4F (3.9 V) are currently being considered for replacing the existing transition metal oxides. The vast possibilities of creating diverse 2D layered and 3D framework crystal structures through the incorporation of different secondary anion/polyanion into the primary polyanion compounds and subsequent tuning of the cell voltage has not been explored much.
In this paper we are presenting scalable fabrication of new mixed polyanionic compounds of iron and will demonstrate their ability to function as the cathode materials for low-cost alkali-ion batteries with good current capabilities and cycle-life. This work will introduce three recently discovered iron polyanion compounds containing mixed anions: Li3Fe(HPO3)3Cl, LixFe(H2O)2B(PO4)2∙H2O, and LiFePO4NO3; a report on their electrochemical activities with respect to Li- and Na-ion cells. The last compound, LiFePO4NO3, is a newly discovered family of mixed polyanionic compounds akin to Lix
MPO4CO3 (where M = Fe and Mn) where it allows the study of the effect of variation of ligand groups on the cell voltage and performance. Moreover for the same compound reversible Na+ intercalation proved to be effective which makes it a possible candidate for Na-ion battery cathode material. The presentation will cover the crystal structure of the respective compounds as solved through single-crystal or synchrotron powder X-ray diffraction as well as chemical, compositional and electrochemical studies including Mӧssbauer spectroscopy and galvanostatic charge/discharge tests.