bluuebunny/crossref_metadata_2025 huggingface dataset:
Exploration of Flash Sintering Mechanisms and Increase Mechanical Strength of YSZ for Dental Application
Authors: Chan Ho-Wei , Chen Hsun-Yi
Published: February 2020

Flash sintering is a rapid ceramics sintering method with an external electric field assistance. Compared to conventional sintering by which YSZ should be heated to 1200~1400OC and hold for 2~4 hours to be sintered, flash sintering can lower the sintering temperature and shorten the sintering time markedly. In addition, the grain size of YSZ observed after flash sintering is often smaller than those sintered by conventional sintering approach. However, it is still not well understood how ceramics could be sintered in a few seconds and accompanied by a sudden increase of electric conductivity of the ceramic material. One proposed explanation of the electric field effect during flash sintering is the Joule heat generation within the sample, leading to significantly higher local temperature that in turn enhances mass transfer. However, the in-situ observed temperature of flash-sintered samples in literatures suggests a diffusion rate based on Arrhenius equation insufficient to meet the required mass transfer rate for rapid densification.

Flash sintering process is commonly divided into three stages. Stage I is considered an incubation time while a constant voltage is applied. Stage II is the period during which the flash event occurred, accompanied by a sharp increase of current. Stage III is the constant-current period after flash sintering when the pre-set limiting power is reached. In order to understand how electric field affects the sintering exactly, we performed flash sintering on 3YSZ compact and investigated the sample at the end of each aforementioned stages: case A, before the flash event; case B, at flash event and cut off the electric field instantly; case C, constant current mode for 300 s, as illustrated in figure (d). All of the samples are flash sintered at 850OC with an applied field of 150 V/cm and a current limit of 0.5 A.

SEM images are shown in figure (a), (b), and (c), which correspond to case A, B, and C, respectively. As shown in figure (a) and (b), very little grain growth is observed under constant voltage, and then grain growth accelerated after the flash event. If we extend the holding time of constant current period, as demonstrated in figure (c), the grain boundaries merging is more obvious and larger grain sizes are observed. However, too large a grain size of YSZ could lead to phase transformation from tetragonal to monoclinic structure and in turn reduce its mechanical strength. In this work, we focus on enlarging current limit and shorten holding time to sinter YSZ of smaller grain sizes and elevate uniformity of grain distribution by improving the electric contact. The goal is to raising the hardness of sintered YSZ to 1200 HV in Vickers hardness and density to 6 g/cm3 while controlling the proportion of phase transformation to be less than 5%. We aim to flash sinter YSZ of smaller grain size and higher mechanical strength for the dental application while reducing energy consumption during its manufacture.

Figure 1
Micropatterning of Metals by Tip Electrode Dissolution and Imaging of Oxygen Reduction Reaction Using Scanning Electrochemical Microscopy
Authors: Jo Ara , Lee Youngmi , Park Hyun S. , Lee Chongmok
Published: February 2020

Surface patterning on substrate has been applied to various nano-devices, microfluidics, cell biology, microelectrochemical systems, and electronics. Most strategies have been based on lithography, but despite the many advantages of conventional lithography, its complex procedures, facilities and high cost arouse desire for the alternative technique. The major complexity in lithography is due to the indirect patterning which uses mask as a template and results in multi-step process. Meanwhile, electrochemical patternings have been also carried out for patterning of metals, and especially maskless patternings are possible using scanning electrochemical microscopy (SECM). We have electrodeposited palladium and gold micropatternings using SECM with the metal precursor ions generated via anodic dissolution of the ultramicroelectrode (UME) tip itself. Simultaneously, in‐situ reduction of the metal ions occurred at the substrate electrode. Contrary to general electrodeposition methods where metal precursor ions exist in the entire solution, in case of local deposition, the metal ions were supplied only from the anodic dissolution of the tip electrode composed of the identical metal which was positioned in a close proximity to the substrate. Therefore, the ions generated from the tip can be reduced only on nearby substrate, not on the entire conductive surface. Especially, this is the first study on the local deposition of Pd using direct Pd dissolution. The catalytic activities of oxygen reduction on the Pd or Au patterns were investigated simultaneously but separately with tip generation‐substrate collection mode of SECM and the activities of each metal deposit varied with potentials applied on substrate. This local deposition technique using SECM could be also applied to other metals if the metal dissolution is possible in proper electrolyte solution within water-stable potential window.

Figure 1
Revealing the Dynamics of Single-Molecule Reactions in a Single-Molecule Nanoreactor
Authors: Qiu Kaipei , Yuan Bo , Zhang Wei-Wei , Wang Pei-Yao , Long Yi-Tao
Published: February 2020

The dynamics of bond breaking and formation at the single-molecule level are of both fundamental importance and practical significance. Tremendous efforts have been made over the last decade toward the visualization of such transient phenomenon, with quite a few amazing single-molecule techniques being designed and developed [1-3]. However, it remains a major challenge to realize the truly single-molecule (cascade) reactions largely due to the stochastic nature of, e.g. molecular motions. Inspired by the enzymatic biosynthesis, the authors consider that a nanoscale confined space, or nanoreactor, must be essential to the highly ordered single-molecule reactions. Moreover, an ideal nanoreactor also needs to possess a well defined structure that is of comparable size to the individual reactant molecules. Hence, the rationally-mutated biological nanopores may be applied as a new brand of single-molecule nanoreactors, where the entry of reactants and exit of products are voltage-driven.

Herein, a mutant areolysin was adopted to study the unique confinement induced selectivity of nanopore reactor. In addition to regio- or stereo-selectivity, it is hypothesized that the mismatch between the bond formation kinetics of reactant molecules and their translocation speeds can offer an extra level of control on reaction selectivity. To prove this concept, the reaction dynamics of three constitutional isomers, 2-, 3-, and 4-mercaptobenzoic acid, at seven identical reaction sites (i.e. at the same position on each monomer) were examined in this work. Surprisingly, those tiny structural variations of three isomers could be easily distinguished by not only the different current blockades caused by each tethered molecule, but also the most frequent and prolonged current levels as well. This observation shed light on the transient dynamics of single-molecule reactions within a single-molecule nanoreactor, providing a crucial first step to the ultimate objective of 100% yield of targeted product at ambient conditions.

Scheme 1 Illustration of the single-molecule nanoreactor presented in this work, the mutant aerolysin nanopore.

Keywords: Single-Molecule Reactions, Single-Molecule Nanoreactor, Mutant Aerolysin Nanopore, Confinement Induced Selectivity, Electroanalytical Chemistry

References:

[1] D.G. de Oteyza, P. Gorman, Y.C. Chen, S. Wickenburg, A. Riss, D.J. Mowbray, G. Etkin, Z. Pedramrazi, H.-Z. Tsai, A. Rubio, M.F. Crommie and F.R. Fischer, Science 340 (2013): 1434.

[2] N.V. Voigt, T. Tørring, A. Rotaru, M.F. Jacobsen, J.B. Ravnsbæk, R. Subramani, W. Mamdouh, J. Kjems, A. Mokhir, F. Besenbacher and K.V. Gothelf, Nat. Nanotech. 5 (2010): 200.

[3] W. Xu, J.S. Kong, Y.-T.E. Yeh and P. Chen, Nat. Mater. 7 (2008): 992.

Figure 1
Operando Atomic Force Microscopy Reveals Mechanics of Structural Water Driven Battery-to-Pseudocapacitor Transition
Authors: Wang Ruocun , Mitchell James Brooks , Gao Qiang , Tsai Wan-Yu , Boyd Shelby , Pharr Matt , Balke Nina , Augustyn Veronica
Published: February 2020

The presence of structural water leads to a transition of energy storage mechanism in tungsten oxide from battery-type intercalation (bulk diffusion limited) to pseudocapacitance (interface kinetics limited). In this study, we demonstrate that the energy storage mechanisms are linked to the material’s mechanical response to the intercalation process and present a method to study local electrochemical intercalation through mechanical coupling. We employed operando atomic force microscopy dilatometry (operando AFM dilatometry) to monitor the real-time mechanical response of WO3 and WO3·2H2O thin film electrodes during cyclic voltammetry in a 0.5 M H2SO4 electrolyte at sweep rates from 10 to 200 mV s-1 (80- to 4-second charge/discharge). This technique reveals that the deformation of WO3·2H2O is more facile and more gradual than that of WO3 during intercalation. We attribute the transition of energy storage mechanism to the more facile mechanical deformation of WO3·2H2O as compared to WO3. In addition, a mapping technique was developed to correlate local mechanical response from electrochemistry to the electrode nanostructure.
Electrochemical Bridging-Impact Method for Characterizing the NCA@Carbon Core–Shell Cathode
Authors: Krittayavathananon Atiweena , Duangdangchote Salatan , Sawangphruk Montree
Published: February 2020

Carbon-based core–shell (CBCS) materials have received considerable and could be the next generation of cathode materials for high energy density lithium-ion batteries (LIBs). The carbon shell provides a large interfacial area between active-material core and electrolyte for charge transport and shortened diffusion path for intercalation/de-intercalation of active species. In order to achieve high performance of CBCS cathode, tuning diffusion path is required via varying the shell-thickness. Herein, Li-Ni-Co-Al Oxide/Carbon (NCA/C) core-shell is prepared with varying shell thickness within the range of ca. 0.1 to 0.5 µm. In order to study the electrical properties of CBCS, we use the “Electrochemical Bridging-Impact”1
,
2 methodology along with a molecular dynamics (MD) simulation to investigate the ion communication between the solid-liquid interface. The bridging-impact is used to determine the contact resistance across the individual particle contact via measuring the current magnitude resulting from the arrival particle contacting with the supporting electrode can be investigated fundamental electrical properties, i.e., contact resistance and zero charge potential of the materials. Ion diffusion (Li+) between solid (inner-core NCA towards porous carbon shell) and liquid interface can be simulated via MD. The result depends on the thickness of the carbon layer, which should be tuned the electrical contact and ion communication between the solid-liquid junction. This study should be a guide rational design of practical core-shell materials.
High-Performance Ionic Liquid Gel Polymer Electrolytes for Solid-State Lithium Metal Batteries
Authors: Pan Xiaona , Yang Peixia , Lin Feng
Published: February 2020

Lithium metal is considered as a “Holy Grail” anode material for secondary batteries because of its extremely high theoretical specific capacity (3860 mA h g−1), low electrochemical potential (-3.04 V vs. SHE), and low density (0.59 g cm-3). Ionically conductive polymer electrolytes represent a class of environmental-friendly and inflammable electrolytes for solid-state batteries that can enable the use of lithium metal. In our study, we fabricated lithium metal batteries based on transparent self-standing ionic liquid gel polymer electrolytes (ILGPEs) and LiFePO4cathodes. We evaluated the properties of ILGPEs by engineering the compositional space between the constituting components: poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide (PP13TFSI), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The ionic conductivity of ILGPE increases with the increase of PP13TFSI and LiTFSI, and a maxima conductivity was obtained when the mass ratio of PP13TFSI, PVDF-HFP, and LiTFSI was 3:1:1, and the value was 1.3 mS cm-1at 22 ºC, and then increased to 5.82 mS cm-1at 80 °C. The optimized ILGPE showed excellent compatibility with lithium metal, determined by the interfacial resistance stability with the elapsed time. The solid-state LiFePO4cells delivered a practical capacity approaching 89.5% of the theoretical capacity and a capacity retention of 95.1% after 200 cycles with a current density of C/5 at 22 ºC. The solid-state lithium metal batteries using various cathodes materials, such as NMC, Co-free layered oxides, disordered rocksalt were also evaluated.
Graphene and Carbon Supported Manganese(IV)-Cobalt(II/III) Oxides Nanoparticles As High-Performance Electrochemical Supercapacitors
Authors: Jablonskiene Jolita , Vaičiūnienė Jūratė , Pakštas Vidas , Stalnionis Giedrius , Drabavičius Audrius , Jasulaitienė Vitalija , Tamašauskaitė-Tamašiūnaitė Loreta , Norkus Eugenijus
Published: February 2020

The search for cleaner energy sources is required to shift focus to the generation of energy from electrochemical systems, batteries, fuel cells, solar cells, and super capacitors, among others. In this study we report a simple approach for preparation of the graphene (GR) and carbon (C) supported manganese(IV) and cobalt(II/III) oxides using microwave-assisted synthesis. The X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) methods were used for the characterization of morphology, structure and composition of the prepared the graphene and carbon supported MnO2-Co3O4 nanocomposites. Electrochemical performance of the MnO2-Co3O4/GR and MnO2-Co3O4/C nanocomposites was evaluated using long life cyclic voltammetry (CV) and galvanostatic charge-discharge.

The MnO2-Co3O4/GR and MnO2-Co3O4/C nanocomposites which have different morphologies, have been prepared by microwave synthesis. It was found that the graphene supported MnO2-Co3O4 nanoparticles has significant influence on the electrochemical performance of composites electrodes compared with that of the carbon supported MnO2-Co3O4 nanoparticles. The maximum specific capacitance was achieved at the MnO2-Co3O4/GR electrode in the 1 M Na2SO4 aqueous solution at the scan rate of 10 mV s-1. After 1000 charge/discharge cycles at the scan rate 100 mV s-1 the capacitance of all the materials synthesized in this study remains over 94 %, suggesting great potential for supercapacitors.
The Effect of Embedded Dye Molecules with Conducting Polymer to Enhance the Photo-Generated Charges at the Working Electrode Toward the Performance of Solar-Capacitor Device
Authors: Aljafari Belqasem
Published: February 2020

The nature of solar radiation is not steady, therefore having a solar-capacitor device that can simultaneously capture, convert and store solar energy is a considerable device. A self-charging capacitor is designed and fabricated as a functional solar energy storage device, which is accomplished in situ self-assembled storage technique. The solar-capacitor device is assembled on a multilayered photoelectrode combining different concentration of cationic dye (i.e. methylene blue, MB) and conducting polymer (i.e. polyaniline, PANI) in contact with H2SO4-Polyvinyl alcohol (PVA) gel electrolyte. The mechanism of storage the photo-generated charges takes place at the changing of redox oxidation states. Due to the high porosity of the multi-walled carbon nanotube (MWCNT) based counter electrode and PANI at the working electrode the device is working as photocapacitor. But, because of the presence of MB molecules that embed in the PANI can absorb the light and excite the electron from the highest occupied molecular orbital (HOMO) level to the lowest unoccupied molecular orbital (LUMO) level. Therefore, the supercapacitor can be charged when the working electrode is illuminated. In this study, a photo-electrochemical device based on two-terminals that combines H2SO4-PVA, MWCNT, and fluorine doped tin oxide conductive substrate (FTO) as working electrode is successfully designed and fabricated. This device can work independently as solar cell, supercapacitor, or a solar-capacitor device. Different concentrations of the cationic dye, MB, composite with PANI have been used as a thin film coated electrochemically on the surface of the FTO. The experiments are carried out in the dark at the beginning and then repeated when the working electrode is under the effect of solar irradiation. After illumination, the experiments repeat in dark again to see the effect of the light on the performance of the device. When the device is exposed to the light, the redox oxidation peaks of PANI/MB change. This clearly shows the photo-electrochemical reaction of the PANI/MB. The open circuit voltage across the cell in the dark is 0.92 mV. Then, the cell voltage is increased gradually from 0.92 mV to 4.9 mV in 400 s of illumination. After turning off the light, the voltage is dropped to the dark value immediately. The results of electrochemical and electrical characterization techniques such as Cyclic Voltammetery (CV), Electrochemical Impedance Spectroscopy (EIS), Open Circuit Voltage (OSV), and Short Circuit Current (SCC) on the solar-capacitor device have been addressed in this study. The results are encouraging for application of PANI/dye composite film for solar-capacitor devices to harvest solar energy and store charges in a single device with two-terminals.

Figure 1
(Invited) Graphene for Bioapplications: Toxicological Studies and Integration in 3D-Scaffolds
Authors: Vazquez Ester
Published: February 2020

The biological applications of graphene materials are strongly conditioned by the need to handle these nanostructures under physiological conditions, essentially complex aqueous media. While the water stabilization of Graphene Oxide (GO) can be easily achieved, this material do not possess the electrical properties of graphene. On the other hand, the mechanical exfoliation of graphite has led to the efficient separation and stabilization of graphene sheets in water when water-soluble dispersant species are used in the exfoliation process. However, many surfactants may cause toxicity problems if they are not thoroughly removed.

Our group has developed a facile and inexpensive ball milling process to exfoliate graphite and to prepare graphene dispersions in water. These aqueous suspensions can be freeze-dried, resulting in a soft powder that can be easily re-suspended in aqueous media, including cell culture media, at the desired concentration. We have also made sure that the redispersed solid retains the original properties of graphene.

During this talk, we will discuss (i) studies of interaction of so-prepared solutions with cells; (ii) the use of graphene in hybrid hydrogels for drug delivery purposes and for 3D cell culture media.
Oxygen-Doped Carbon Nanotubes for Near-Infrared Imaging Probes
Authors: Okazaki Toshiya
Published: February 2020

Optical imaging is one of the most important techniques in biomedical studies. Recently, usage of near-infrared light has been extensively tried because of the higher transparency in biomaterials than the visible light. Single-walled carbon nanotubes (SWCNTs) are nanocarbon materials that show optical absorption and fluorescence in the near infrared (NIR) wavelength region. Especially, due to the bright fluorescence in NIR, SWCNTs have been expected as imaging probes.

In this talk, we show our recent results about the bio-application of oxygen-doped SWCNTs [1,2]. Interestingly, covalent doping of the nanotube surface with a low concentration of oxygen atoms can create a new optically allowed defect state [3]. Consequently, nanotube fluorescence is red-shifted and can be over 10 times brighter. Fluorescence vascular angiography and observation of the intestinal contractile activity of mice are demonstrated by using the produced oxygen-doped SWCNTs as infrared fluorescent labels and imaging agents [1]. Further, the biodistribution analysis after the administration of the oxygen-doped SWCNTs in mice is also discussed by the resonance Raman spectroscopy and NIR fluorescence microscopy [2].

[1] Y. Iizumi, M. Yudasaka, J. Kim, H. Sakakita, T. Takeuchi, T. Okazaki, Sci. Rep., 8, 6272 (2018).

[2] T. Takeuchi, Y. Iizumi, M. Yudasaka, S. Kondoh, T. Okazaki, in preparation.

[3] S. Ghosh, S. M. Bachilo, R. A. Simonette, K. M. Beckingham, R. B. Weisman, Science 330, 1656-1659 (2010).
(Invited) Progress in Carbon Nanotube Terahertz Photodetectors
Authors: Léonard François
Published: February 2020

Terahertz photodetectors based on carbon nanotubes have shown promising performance and could lead to new detection modalities due to the ability to fabricate the detectors on non-planar flexible substrates using inkjet printing. To realize this promise, a number of materials and device challenges must be overcome. In this presentation, I will discuss our recent work to understand the inner workings of these devices, and to improve their performance based on this knowledge. In particular, I will show how managing the materials and thermal properties of the system can lead to more sensitive and faster performance while enabling ultraflexible devices.
Towards Bottom-up Engineered Electrode Microstructures for Redox Flow Batteries
Authors: Forner-Cuenca Antoni , Wan Charles Tai-Chieh , Jacquemond Remy , Weijers Cees , Tenny Kevin , Greco Katharine Virginia , Brushett Fikile R.
Published: February 2020

Redox flow batteries (RFBs) are promising rechargeable electrochemical devices for grid-scale energy storage, but further cost reductions are needed for widespread implementation. While research efforts have primarily focused on molecular discovery, there has been significantly less attention paid to the engineering aspects (i.e. transport, reactor design) of the battery. Of particular importance are the porous electrodes used in the electrochemical stack. Today’s electrodes largely draw from the fuel cell material set, but, within a RFB, the porous electrode must perform a number of different roles including providing active surfaces for electrochemical reactions, facilitating uniform liquid electrolyte distribution, and supporting low pressure drops. Accordingly, before purpose-built electrodes can be developed for RFB applications, performance-limiting factors for the present materials set must be quantified. Unambiguous analysis is challenging in an operating RFB due to the complex coupling of transport and reactions, which vary as a function of state of charge during cell cycling. Deconvoluting the role of electrode properties on flow battery performance requires the development of diagnostic techniques that enable electrode characterization under well-controlled but application-relevant conditions.

To this end, we systematically evaluate the performance of several different carbon paper, felt, and cloth electrodes using the single-electrolyte cell configuration [1] and a model organic redox couple (TEMPO/TEMPO+) [2]. Using polarization and electrochemical impedance spectroscopy, we quantify the impact of electrode microstructure on battery performance. To further understand the role of electrode microstructure on the performance, we use tomography, and numerical simulation in tandem with the aforementioned electrochemical diagnostics. We find that woven electrodes, which feature a bimodal pore size distribution, provide an outstanding electrochemical performance and low pressure drop [3]. Inspired on these learnings, our most recent work focuses on developing bottom-up synthetic methods to fabricate porous electrodes with engineered microstructures, with a particular interest in bimodal pore size distributions and porosity gradients across the electrode thickness. In this talk, I will discuss our most recent experimental strategies to engineer electrodes with highly-controlled microstructures tailored for specific RFB chemistries.

Darling et al., J. Electrochem. Soc., 161, A1381 (2014).

D. Milshtein et al., J. Power Sources, 327, 151 (2016).

Forner-Cuenca et al., Under Review at Electrochem. Soc.

Acknowledgments

We gratefully acknowledge the financial support of the Swiss National Science Foundation (P2EZP2_172183) and the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by the United States Department of Energy.
Petroleum Coke As Active Material of Negative Electrode for Lithium-Sulfur Batteries
Authors: Kuzmina Elena , Chudova Nadezhda , Dmitrieva Liana , Ivanov Alexey , Karaseva Elena , Kolosnitsyn Vladimir
Published: February 2020

We studied the possibility of using graphite and petroleum coke as active materials of negative electrodes for lithium-sulfur batteries.

Petroleum coke was previously subjected to thermochemical activation in its own vapor in an air atmosphere for 10 hours at 800 °C.

Positive sulfur electrodes were made by casting a slurry on aluminum foil. The composition of the electrode layer was 70% wt. sulfur, 10% wt. carbon (Ketjenblack EC-600JD), and 20% wt. binder (poly(ethylene) oxide, MW 4x106).

The separator was 1 layer of microporous polypropylene Celgard®3501. The electrolyte was 1M LiClO4 in sulfolane.

Negative electrodes based on graphite and activated petroleum coke were prepared by slurry casting onto copper foil. The composition of the electrode layer was 94% wt. of the active material (petroleum coke or graphite), 1% wt. of the carbon black (Super P), and 5% wt. of the binder (LA-132).

Negative electrodes based on carbon materials were pre-lithiated. For this purpose, cells with a lithium electrode and carbon electrode were assembled and subjected to 5 molding cycles. Figure (a) shows the typical charge-discharge voltage profiles of the semi-cells of Li - Carbon electrode. After 5 molding cycles, the cells were transferred to the glove box and lithiated carbon electrodes were removed from them. Lithium sulfur cells were assembled with these lithiated carbon electrodes.

It was shown that regardless of the negative electrodes used, there are two plateau on the discharge voltage profiles of lithium-sulfur cells, corresponding to electrochemical reduction (Figure b):

(1) sulfur and high ordered lithium polysulfides through a series of intermediate stages to lithium tetrasulfide:

S8 + 4Li+ + 4e- → 2Li2S4

(2) Lithium tetrasulfide to lithium disulfide and lithium sulfide:

Li2S4 + 4Li+ + 4e- → 2Li2S + Li2S2.

It should be noted that the discharge voltage of lithium-sulfur cells with carbon electrodes is decreased by the magnitude of the voltage of lithium-carbon semi-cells (Figure (a) and (b)).

At the initial stages, the rate of decrease in the discharge capacity of lithium-sulfur cells weakly depends on the composition of the negative electrode. Cycling efficiency is 91-92%.

Based on the obtained results, it can be concluded that activated petroleum coke can be used as the active material of the negative electrode for lithium-sulfur batteries.

This work was performed as part of a Government Order to Ufa Institute of Chemistry of the Russian Academy of Sciences by the Ministry of Science and Higher Education of the Russian Federation (Theme No. AAAA-A17-117011910031-7) Russia and was also financially supported by the Russian Science Foundation (project No 17-73-20115).

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Low and High Voltage Li-Ion Batteries Using Dinitrile Based Electrolytes
Authors: Ghamouss Fouad , Farhat Douaa , Lemordant Daniel
Published: February 2020

Due to their low vapor pressure as well as their electrochemical (5~6 V) and thermal stability, dinitriles N≡C-(CH2)n-C≡N are proposed as alternative electrolyte solvents to alkyl carbonates commonly used in Li- ion batteries. The objective of this communication is to study the physico-chemical behavior of these alternative electrolytes (viscosity, ionic conductivity, thermal behavior, volumetric properties, etc.) and their use in Li-ion batteries. Two battery systems are studied using a lamellar oxide (LiNi1/3Mn1/3Co1/3O2) as positive electrode associated with graphite or Li4Ti5O12 as negative electrodes. The cyclability of electrodes in half-cell and full-cell is studied according to the electrolyte composition and the nature of the dinitrile used. Characterization techniques like: electrochemical impedance spectroscopy, electron microscopy and X-Ray photoelectrons spectroscopy, are used to study the passivation of the negative electrode and the stability of the positive electrode. Furthermore, the effect of adding specific solid electrolyte interphase (SEI) builders is investigated and their efficiency is demonstrated.
Enhanced Performance of Cobalt Vanadium Oxide upon Doping with Sulfur for Hybrid Supercapacitor Application in Aqueous and Non-Aqueous Medium
Authors: Sharma Gyan Prakash , Gupta Prashant Kumar , Pala Raj Ganesh , Sivakumar Sri
Published: February 2020

Cobalt Vanadate is one of the electroactive material for charge storage application due to earth abundant and environment friendly nature of cobalt. Further, vanadate system renders the material with multiple stable oxidation states, high electrical and ionic conductivity and high rate capability. However, the electrochemical performance of cobalt vanadate is limited either by high resistance of binder material or by the introduction of dead weight during electrode fabrication. This limitation can be circumvented by in-situ synthesis of cabalt vanadate onto current collector. Further, the doping of Sulfur in cobalt vanadate matrix significantly improves the electrochemical performance by improving the electrical conductivity. Herein, we report binder-free synthesis of Sulfur doped cobalt vanadate (S-Co3V2O8) nanosheet arrays on Ni foam using hydrothermal approach. The hydrothermally synthesized S-Co3V2O8 achieves nanosheet morphology with height and thickness of ~200 nm and ~10 nm, respectively wherein the size remains unchanged before and after the doping of sulfur in Co3V2O8. Further, the increased duration of hydrothermal reaction increases the thickness of synthesized nanosheet. We found that the electrochemical performance of Sulfur doped Co3V2O8 is ~25% more as compared to its undoped Co3V2O8 counterpart. In 6M KOH aqueous electrolyte, S-Co3V2O8 nanosheet array shows a specific capacity of 1476 C/g (3690 F/g) at 2 A/g. Further, the material exhibits enhanced rate capability and excellent capacity retention of 94.2% at 5 A/g specific current after 4000 cycles. The introduction of sulfur into vanadate matrix improves the electrochemical performance due to low electronegativity and large size of sulfur as compared to oxygen, which improves the charge transport properties, charge storage capacity with highly robust structure. An asymmetric supercapacitor device fabricated using S-Co3V2O8 as cathode and active carbon (AC) as anode shows specific capacity (or capacitance) of 174.5 C/g (or 116.33 F/g), energy density (36.4 Wh/kg) and power density (740 W/kg) at 2 A/g with 98.4% capacity retention after 4000 cycles. Further, the electrochemical performance of S-Co3V2O8 has been checked in 1M LiPF6 in non-aqueous electrolyte as Li-ion hybrid capacitor. The capacitor fabricated in a CR2032 coin cell exhibits specific capacity of 994 mAh/g with energy density of 695 W/kg at specific current of 1 A/g with good rate capability and 46.5% capacity retention after 100 cycles which makes it a potential candidate for robust high electrochemical energy storage system.
Recent Advances in Low-Cost, Highly Efficient Bi-Functional Oxygen Electrocatalysts for High-Performance Zinc-Air Batteries
Authors: Nam Gyutae , Cho Jaephil , Liu Meilin
Published: February 2020

Zn-air batteries (ZABs) have attracted much attention for possible applications in portable electronics and electric vehicles because of several advantages such as low cost, excellent safety, and high energy density (ca. 1,084 Wh kg–1) in alkaline media. However, the development of ZABs has been hampered by low working voltage due to the sluggish rate of oxygen reduction reaction (ORR) and short lifespan under deep discharge conditions (over 30%) due to poor durability of the air electrode associated with limited stability of ORR and oxygen evolution reaction (OER) electrocatalysts. Thus, platinum group metals (e.g., Pt and Ir-based alloys) have been widely used for ORR and OER electrocatalysts, respectively. However, these materials not only are expensive but also show poor durability in practical ZABs. In this presentation, we will report some latest advances in the development of low-cost, highly efficient bi-functional oxygen electrocatalysts for ZABs. In particular, we will highlight a composite catalyst consisting of Ni46Co40Fe14 nanoparticles (with a size distribution of 30~60 nm) dispersed in a carbon matrix (denoted as C@NCF-900), produced via supercritical reaction and subsequent heat treatment at 900 °C. Among all the transition metal-based electrocatalysts, the C@NCF-900 exhibits the highest ORR performance in terms of half-wave potential (0.93 V) in 0.1 M KOH. Furthermore, C@NCF-900 exhibits negligible activity decay after 10,000 voltage cycles with minor reduction of half-wave potential (0.006 V). When evaluated in ZABs, the C@NCF-900 outperforms the mixture of 20 wt% Pt/C and IrO2, cycled over 100 h under 58 % depth of discharge condition. Furthermore, a plausible ORR/OER mechanism of C@NCF-900 is elucidated by density functional theory calculations and confirmed by operando X-ray absorption spectroscopy.
A Reversible Electrochemical Side Reaction of Li Electrodeposition / Dissolution Using N(SO2)X(SO2)Y Anion-Containing Molten Salt (X, Y = F, CF3)
Authors: Sano Hikaru , Kubota Keigo , Siroma Zyun , Kuwabata Susumu , Matsumoto Hajime
Published: February 2020

LiTFSA (Lithium Bis(trifluoromethanesulfonyl)imide) and LiFSA (Lithium bis(fluorosulfonyl)imide) are well-known as a salt of an electrolyte of a Li-based secondary battery, and also used as a salt of an electrolyte of a secondary battery using metal Li as a negative electrode. In many cases, when using these electrolytes to electrodeposit metal Li, side reactions occur at about 1.8 V vs Li+/Li.1,2 Recently, we have discovered that this side reaction is reversible and appears prominently at temperatures as high as 150 ° C.

The electrolyte was prepared by dissolving 1 M of Li [TFSA] in Pyr13 [TFSA] (N-Propyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide). A Ni (Nickel) substrate was immersed in this electrolytic solution to form a working electrode. A metal Li was used as a counter electrode to form a two-electrode cell. A current was flowed to the reduction side at a current density of 0.2 and 1 mA cm-2, and a current was flowed to the oxidation side when it reached 0.1 V. The voltage-time profiles are shown in Figure (a)(b). At the time of reduction, it has a plateau at a voltage of 1.5 V, indicating that some electrochemical reaction has occurred. The oxidation has a plateau near 1.9 V, suggesting that this reaction is electrochemically reversible.

The result of performing cyclic voltammetry measurement for the cells of the same configuration is shown in Figure (c). Reversible reduction and oxidation waves can be confirmed at the potential (ca. 1.5 V and 1.9 V) corresponding to the plateau potential in constant current measurement. Also, it was seen that the peak increases with each cycle.

At the meeting site, we will also describe the results of using LiFTA (lithium (fluorosulfonyl)(trifluoromethylsulfonyl)amide), which is a molten Li single salt, and discuss the origin of side reactions.

Acknowledgments

This work was performed as a cross-appointment project between Osaka University and the National Institute of Advanced Industrial Science and Technology (AIST).

References

1. D.Aurbach, M. Daroux, P. Faguy, E. Yeager, J. Electroanal. Chem. Interfacial Electrochem., 297, 225 (1991).

2. T. Shiga, Y. Kato, M. Inoue, N. Takahashi, Y. Hase, J. Phys. Chem. C, 119, 3488 (2015).

Figure 1
Corrosion of Candidate Alloys in Molten LiCl-Li2O-Li for Pyroprocessing of Used Nuclear Fuel
Authors: Moon Jeremy , Phillips William , Chidambaram Dev
Published: February 2020

Pyrochemical reprocessing of used nuclear fuel (UNF) requires large structural process vessels and functional components fabricated from stainless steel 316L (SS316L) or another high-temperature molten salt-compatible material like Inconel 625 (I625). The unique chemistry of the molten salt electrolyte during processing of UNF leads to complex interactions between container materials and the electrolyte that have been well documented by our group.

In the head-end process to incorporate oxide UNF into the pyrochemical reprocessing scheme, LiCl with 1-2 wt. % Li2O is utilized as an electrolyte to facilitate the electrolytic reduction of UO2 via the Fray-Farthing-Chem (FFC) process. The Li+ reduction potential is quite close to the UO2 reduction potential and it is generally recognized that lithium metal will be produced at the cathode during the reduction process. While much of the metallic lithium further facilitates the reduction of UO2 via a metallothermic pathway, forming Li2O, a fraction of the metallic lithium dissolves or otherwise disperses into the molten salt. The metallic lithium then diffuses throughout the salt and reacts with process vessels and other components.

To further understand corrosion in these conditions, SS316L and I625 coupons were exposed to LiCl-1 wt. % Li2O-Li and LiCl-2 wt. % Li­2O-Li with lithium metal concentrations of 0, 0.3, 0.6 or 1.0 wt. %. These samples were then studied using focused ion beam (FIB) milling, scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and energy dispersive spectroscopy (EDS). Results from these studies will be discussed.

Acknowledgements: The authors thank Zachary Karmiol, research scientist at Materials Characterization Nevada, for technical input. One of the authors, JM, acknowledges the Graduate Research Fellowship from the US National Science Foundation. This work was supported by the United States Department of Energy (DOE) under contracts, DE-NE0008262, DE-NE0008236, and DE-NE0008572, and the United States Nuclear Regulatory Commission (NRC) under Contract NRC-HQ-13-G-38-0027. Dr. Kenny Osborne and Ms. Nancy Hebron-Israel serve as the DOE and NRC award program managers, respectively. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-1447692.
Application of a Reaction-Transport Model with Cation Complexation and Variable Diffusivity to Galvele’s Criteria for Pitting Corrosion
Authors: Nguyen Van Anh T. , Newman Roger C.
Published: February 2020

A reaction-transport model in a one-dimensional pit geometry is constructed to study the effects of cation complexation, hydrolysis and multiple aggressive anions on the mass transport of ions, and the IR drop, within a pit at the anodic limiting current density. In particular, the study focuses on the B value in Galvele’s pit model, which states the dependence of pitting potential (Epit
) on chloride concentration ([Cl-])

Epit = A- B log[Cl-]

where the B value is predicted to be 60 mV from Galvele’s model [1]. However, this value is found to vary up to around 100 mV in practice for stainless steels, indicating that the IR drop inside the developing pit is not explainable by a simple model [1-4]. The present model is constructed at steady state and with a limiting anodic current density (fixed dissolved metal concentration at the bottom of the pit), which is carried by metal-containing species. When there is no cation complexation or hydrolysis, the B value remains at 60 mV in NaCl and 30 mV in Na2SO4, even when the ionic diffusivities are functions of chloride concentration. However, the B value is found to vary between 30 mV and 60 mV at different ratios of anionic bulk concentration in the mixed solution of singly and doubly charged anions (such as chloride-thiosulfate systems). Due to the charge difference between these anions, the bulk ratio between the anionic concentrations is not preserved inside the pit, which results in an enrichment of the doubly charged anions at the bottom of the pit. For a one metal system, the effect of hydrolysis on the B value is negligible compared with that of cation complexation, which is very significant and could potentially explain a lot of practical observations. For an Fe-17Cr alloy, the B value increases up to 100 mV, in agreement with experiments, assuming dissolved chromium can make cationic chloro-complexes. The obtained results can be rationalized via the change of potential gradient and ionic fluxes near the top of the pit at different bulk NaCl concentration, to maintain the critical chemistry for pit stability and the complexation reaction inside the pit.

References:

J. R. Galvele, Transport Processes and the Mechanism of Pitting of Metals, J. Electrochem. Soc., 123, 464 (1976).

N. J. Laycock, R.C. Newman, Localised Dissolution Kinetics, Salt Films and Pitting Potentials. Corros. Sci., 39, 1771 (1997).

R. C. Newman, Pitting Corrosion of Metals, The Electrochemical Society Interface, 19, 33 (2010).

W. Zhang, A. G. Carcea, R. C. Newman, Pitting of Steam-generator Tubing Alloys in Solutions Containing Thiosulfate and Sulfate or Chloride, Faraday Discussions, 180, 233 (2015).
Visualization of pH and Cl− Distributions inside Crevice of Type 430 Stainless Steel
Authors: Matsumura Kengo , Muto Izumi , Sugawara Yu
Published: February 2020

The decrease in pH caused by the hydrolysis of metal ions inside crevice is widely accepted to be the predominant factor affecting the initiation of crevice corrosion for stainless steels. The accumulation of chloride ions inside crevice is also thought to be of great importance for the initiation of crevice corrosion. 1, 2 In this study, a simultaneous measurement technique for pH and Cl− concentration was applied to the visualization of pH and Cl− distributions inside crevice in the initial stage of crevice corrosion of Type 430 stainless steel.

A sensing layer with fluorescent dyes was made on one side of a SiO2 plate using the sol-gel SiO2 coating technique. Quinine sulfate (fluorescent dye) was used to measure Cl− concentration. The excitation wavelength was 350 nm. The emitted light was filtered through a 420-nm long-pass filter, since quinine sulfate has a peak wavelength of 451 nm (blue fluorescence). 1 Tb3+-DPA (dipicolinic acid) complex was used as the fluorescent dye for pH measurements. 2 The excitation wavelength of this dye was 270 nm, and the emitted light was filtered through a 510–550-nm band-pass filter. In this case, green fluorescence was observed.

The crevice specimens were prepared from Type 430 stainless steel (Fe-16.5Cr). A crevice (3 mm × 3 mm) was made between the stainless steel and the sensing plate. 1,2 Crevice corrosion tests were carried out in a naturally aerated 0.01 M NaCl at pH 3.0, and the specimen was polarized at 0.0 V (vs. Ag/AgCl, 3.33 M KCl). Before the initiation of crevice corrosion, pH inside the crevice gradually decreased with time. And also, Cl− concentration increased with time. At pH 1.8 and ca. 0.1 M Cl−, crevice corrosion initiated, and a large pH drop and a large Cl− increase were observed.

References:

T. Kaji, T. Sekiai, I. Muto, Y. Sugawara, N. Hara, J. Electrochem. Soc., 159, C289-C297 (2012).

M. Nishimoto, J. Ogawa, I. Muto, Y. Sugawara, N. Hara, Corros. Sci., 106, 298-302 (2016).
Pit Initiation Behavior at Sulfide Particles in Sintered Stainless Steels
Authors: Nishimoto Masashi , Muto Izumi , Sugawara Yu , Hara Nobuyoshi
Published: February 2020

The pit initiation sites for commercial stainless steels have been attributed to sulfide inclusions such as MnS. The chemical composition of the inclusions affects the pitting corrosion resistance of stainless steels. Systematic investigation on the relationship between the chemical composition of the inclusions and the pitting corrosion resistance is required. However, it is difficult to prepare a series of the steel specimens of which the chemical composition of the inclusions is precisely controlled. In this study, spark plasma sintering was used to fabricate stainless steel specimens containing sulfide particles, and a microelectrochemical technique was applied to analyze the effect of the chemical composition of the sulfides on the pitting corrosion resistance of stainless steels.

A type 304 stainless steel powder was mixed with a MnS powder to prepare the sintered specimen containing 0.03 mass% S. The particle sizes of the stainless steel and the MnS powder were –100 mesh and –325 mesh, respectively. The mixed powders were loaded into a cylindrical graphite die and were compressed using a hydraulic press. The pressed compact was spark plasma sintered in vacuum, under uniaxial pressure at 30 MPa. The sintered specimen was ground with SiC papers and then was polished with an 1 µm diamond paste. Potentiodynamic polarization was conducted in naturally aerated 0.1 M NaCl (pH 5.5) at 298 K. The specimen surface was masked to make an electrode area of ca. 100 µm × 100 µm containing a sulfide particle. All the potentials reported in this study refer to the Ag/AgCl (3.33 M KCl) electrode (0.206 V vs. standard hydrogen electrode at 298 K). The potential scan rate was 3.8 × 10-4 V/s.

The anodic polarization curve was measured in 0.1 M NaCl to characterize the pit initiation behavior at the MnS particle in the sintered stainless steel. Polarization was started at –0.2 V and was stopped after the large increase in the current density was measured. The electrode area was observed using an optical microscope after polarization. The MnS particle partly dissolved, and the pit was found at the boundary between the particle and the steel matrix. This suggests that the large current increase was attributed to the pit initiation at the particle. It is expected that the sintered specimen can be used to investigate the pit initiation behavior at the sulfides in stainless steels.
Corrosion Behavior of High Entropy Alloys Made By Directed Energy Deposition Additive Manufacturing
Authors: Melia Michael Anthony , Carroll Jay , Argibay Nicolas , Kustas Andrew , Schindelholz Eric John
Published: February 2020

Additive manufacturing (AM) is an attractive process for fabricating high entropy alloys (HEAs) with the ability to leverage high cooling rates for the single phase formation of complex alloys. This study investigates the corrosion behavior of the equi-atomic CoCrFeMnNi HEA made by directed energy deposition in the as-built and homogenized condition (1100oC for 1 hr). The as-built microstructure exhibited dendritic chemical segregation with interdendrite areas enriched with Mn and Ni compared to the chemically uniform microstructure after annealing. Corrosion behavior of the CoCrFeMnNi HEAs was investigated using potentiodynamic polarization measurements in 0.6 M NaCl solutions to determine each materials open circuit and breakdown potential, on average -0.25 VSCE and ~0.40VSCE, respectively for both conditions. Comparison in pit propagation was also explored with the as-built microstructure showing preferential corrosion of the Mn/Ni enriched interdendrite areas while the annealed materials pits were similar to those observed on 304L stainless steel.

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc. for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.