bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Molecular Dynamics Study of Concentrated Aqueous Solutions of Lithium Salts at Charged Electrodes
Authors: Vatamanu Jenel , Borodin Oleg 
Published: February 2020

Li-ion batteries (LiBs) are widely used in very diverse set of applications from portable electronics, to electric vehicle transportation. Hence, improving LiBs’ power and energy while not compromising safety, remains a hot research topic. Organic solvents permit higher operating voltages; however, they have the disadvantage of being volatile and flammable. Aqueous solvents, on the other hand, are inexpensive and non-flammable but they are typically stable only at low voltages (<1V) resulting in relatively low energy density (<100Wh/kg). Recently, an intriguing paradigm shift regarding the extending electrochemical stability window of aqueous electrolytes was reported for the aqueous electrolytes.(1-4) Specifically, highly concentrated aqueous solutions of electrolytes (i.e. “water in salt”) were shown to have electrochemical stability window above 3V, despite the presence of water in the system.
In this presentation we explore an intriguing supposition that the electrochemical stability of these systems can be correlated with the electrolyte structure near surface. Using classical molecular dynamics simulations we investigate the electrolyte partition near the electrode, as a function of the applied potential. The studied system consisted of a highly concentrated solution of two salts LiTFSI and LiCF3SO3in water that was recently shown to have one wide electrochemical stability.(2) The electrolyte structuring near the electrode was found to be strongly dependent on the applied potential. Specifically, at the positively charged electrode water is displaced from the surface by the voluminous anions, while at the negatively charged electrode a large accumulation of water is observed in the interfacial layer. Interestingly, the water is displaced rapidly from the negative surface as the potential increases from -2V to 0V, and surprisingly elevated densities of F groups were found next to surface at -1V.
In such concentrated electrolytes, the Li ions are only partly coordinated with water (2-2.6 water molecules per Li). The partly desolvated Li+ can drag the TFSI anion near the negative electrode. In agreement with this observation, our simulations confirmed the presence of F groups in the proximity of the interfacial Li+ at the negative electrode. The presence of Li+and F next to the negative charged surface can trigger electrochemical reactions that kinetically passivate the negative electrode surface.

References

1. L. Suo, O. Borodin, T. Gao, M. Olguin, J. Ho, X. Fan, C. Luo, C. Wang and K. Xu, Science, 350, 938 (2015).
2. L. Suo, O. Borodin, W. Sun, X. Fan, C. Yang, F. Wang, T. Gao, Z. Ma, M. Schroeder, A. von Cresce, S. M. Russell, M. Armand, A. Angell, K. Xu and C. Wang, Angew. Chem. Int. Ed, 55, 7136 (2016).
3. F. Wang, Y. Lin, L. Suo, X. Fan, T. Gao, C. Yang, F. Han, Y. Qi, K. Xu and C. Wang, Energy Environ. Sci.,, 9, 3666 (2016).
4. Y. Yamada, K. Usui, K. Sodeyama, S. Ko, Y. Tateyama and A. Yamada, Nature Energy, 1, 16129 (2016).

Figure 1
Investigating the Electrode-Electrolyte Behaviour of Carbon Materials in Various Non-Aqueous Electrolytes
Authors: Cameron Amanda , Donne Scott W 
Published: February 2020

Charge storage in electrochemical capacitors has been shown to be via charge separation at the electrode-electrolyte interface (so called electrical double layer charge storage) and via pseudo-capacitance, which is often described as fast redox reactions through the same interface. Charge storage via both of these mechanisms depends heavily on the interaction between the electrode morphology (electrochemically active surface area, pore size distribution, etc.) and the solvated ion in the electrolyte. In this work the interaction between a series of carbon-based substrates and various electrolyte species has been investigated.
Electrolytes examined include tetraethylammonium bis(trifluoromethane)sulfonimide (Et4NTFSI), 1-butyl-1-methylpyrrolidinium tetrafluoroborate (PYR14BF4), 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14TFSI), and tetraethylammonium tetrafluoroborate (Et4NBF4) in acetonitrile. The interaction between these electrolytes and various carbon-based substrates was examined using a combination of cyclic voltammetry (CV) and step potential electrochemical spectroscopy (SPECS). These techniques have enabled differentiation of the charge storage mechanisms based on ion size, solvated ion size and charge density, as well as substrate surface area and porosity.
Low-Temperature Performance of Symmetric MnOx-Carbon Nanofoam-Based Ecs with Mild-pH Aqueous Electrolytes
Authors: Sassin Megan B. , Wallace Jean , Ko Jesse , Long Jeffrey W. 
Published: February 2020

Electrochemical capacitors, ECs, should provide high performance over the broadest range of operating temperatures which is primarily determined by the properties of the electrolyte (freezing and boiling points, ionic conductivity and salt solubility as a function of temperature, flash point for flammable solvents). In the case of mild-pH aqueous electrolytes, where flammability is a non-issue, the sub-ambient temperature performance is the most critical factor. En route to demonstrating the performance of aqueous-electrolyte ECs at low temperature, we have characterized both the bulk thermal properties of single and multi-component electrolytes and their behavior when used in EC pouch cells. The ionic conductivities of bulk electrolytes with a fixed cation concentration of 5 M for single-component (e.g. Li2SO4, NaNO3) and multi-component electrolytes (e.g. Li2SO4 + NaNO3) ranged from 63 to 136 mS cm-1 at 20oC. The freezing points of these electrolytes were measured with differential scanning calorimetry. It was found that the anion dominates the freezing-point behavior, with sulfate-based electrolytes supporting freezing points down to –45oC and nitrate-based electrolytes down to –35oC. To assess the impact of temperature on performance as a function of electrolyte composition, we fabricated symmetric pouch cells comprising MnOx-carbon nanofoam electrodes and tested them over the temperature range of 25oC to –45oC in an environmental chamber. All ECs exhibited a gradual decrease in capacitance as the temperature decreased; however, upon re-warming to 25°C, the capacitance was recovered, indicating that freezing does not cause significant degradation to electrode or separator components. Aqueous electrolytes comprising mixtures of Li2SO4 and NaNO3 yielded the best combination of depressed freezing point and ionic conductivity among the compositions evaluated in EC pouch cells.
Printed Planar Supercapacitors (SCs) Having High Energy Density
Authors: Hsieh Bing R 
Published: February 2020

Although SCs (Fig. 1a) are known for their very high power density, very long cycle life, and being relatively innocuous, their energy densities are about 10 - 25X lower as compared to lithium ion batteries (LIBs). Despite this shortcoming, replacement of traction LIBs with SCs in hybrid electric vehicles is now commonplace but the opposite is not. However, SCs have rather long road ahead. For example, the specific energy of the recently launched Maxwell 2.85V DuraBlue SC cell is only 7.7 Wh/kg which is one fourth of that for the lead acid batteries (35 Wh/kg), the capacity target for the next generation of SCs. Recently, graphene or activated carbon based microsupercapacitors having planar interdigitated electrodes and current collectors (Fig. 1b) showed high energy densities rivaling or surpassing those of thin film LIBs and lead acid batteries were reported by several groups [1]. These results gave us a glimpse of the possibility of competing with LIBs in both consumer electronics and EVs in the future and inspired us to invent new planar SC designs in order to achieve even higher energy density.
The first question we asked was "Is the MSC design shown in Fig. 1b scalable?" And our initial response was “unlikely” because the driving force for ion movement between the positive and negative carbon electrodes is limited to the relatively weak fringe electric field (shown as the yellow dash lines in Fig. 1b) which cannot effectively drive the ion movement through the entire thickness of the carbon electrode (t2) as it increases into the micron range.
In order to overcome the lack of driving force for facile ion movement, we came up with several new designs in a recent patent application [2]. One of them is shown in Fig. 2 as an example, wherein the current collectors are coated on the sidewalls of the carbon electrodes and gives raise to the direct electric field, as indicated by the purple arrow. In this presentation we will discuss other planar designs, their corresponding pack designs, as well as low cost fabrication methods involving printing processes.
1. (a) D. Pech et al., Nature Nanotech. 2010, 5, 651; (b) W. Gao et al. ibid., 2011, 6, 496; (c) M. F. El-Kady et al., Science, 2012, 335, 1326; (d) M. F. El-Kady; R. B. Kaner, Nature Comm. 2013, 4, 1475; (e) Z.-S. Wu et al., ibid., 2013, 4, 2487; (f) T. Lin et al., Science, 2015, 350, 1508.
2. B. R. Hsieh, US patent application US20160133396A1 (2016).

Figure 1
Simultaneous Analysis of Thin-Film MnO2 Deposits Using Cyclic Voltammetry (CV), Step Potential Electrochemical Spectroscopy (SPECS), Electrochemical Quartz Crystal Microbalance (EQCM) and Electrochemical Impedance Spectroscopy (EIS)
Authors: Cameron Hayden , Donne Scott W 
Published: February 2020

As a population the reliance on portable electronics and rapid development in electric vehicles in order to combat global warming has caused researchers to search for materials that exhibit excellent energy storage properties. Thin film manganese dioxide deposits have been observed to exhibit excellent behaviour and have become a popular research material for electrochemical capacitors and batteries.
In this project a method was developed in which the mass change for a thin film of manganese dioxide during electrochemical experiments could be observed. Manganese dioxide was electrodeposited onto a platinum EQCM electrode allowing for the mass change throughout the deposition process to be recorded providing a better understanding of the electrodeposition mechanism. Once the manganese dioxide was prepared the EQCM was used as a working electrode throughout further electrochemical testing which included cyclic voltammetry (CV), step potential electrochemical spectroscopy (SPECS), and electrochemical impedance spectroscopy (EIS) while recording the mass change throughout each test.
Cyclic voltammetry was conducted with a 25 mV/s sweep in 0.5 M K2SO4 from 0-0.8V vs SCE for 250 cycles. By doing this the capacitive performance of the material was determined, and by recording the mass change throughout the experiment it was possible to determine if there were faradaic, non-faradaic process occurring on the surface of the electrode affecting the charge storage mechanism and to observe sample stability throughout cycling.
SPECS and EIS immediately followed the cycling which allowed for the observation of the maximum charge storage capability of the material and the mechanism in which the material stores charge. The impedance data allows for the analysis of the charge transfer mechanism and the various interfacial resistance and capacitance at the electrode-electrolyte interface.
This combination of techniques has allowed for significantly greater understanding of the processes that the electrode materials are undergoing throughout the experiments and can be used as a powerful tool in various aspects of electrochemical analysis.
Supercapacitor Electrode from Electrospray of Polymeric Sol As Carbon Precursor on Current Collector
Authors: Chavhan Madhav Prabhakar , Ganguly Somenath 
Published: February 2020

This presentation describes a process, involving electrospray of carbonaceous polymer sol on a current collector-substrate, followed by in situ curing, drying and carbonization. The electrospray process splits the precursor sol into fine droplets by Coulombic fission, prior to the deposition on the substrate. The pyrolysis of cured and dried gel film provides the active layer with enhanced internal surface area for the double layer capacitance, and lower resistance to charge transport. The choices of different methods and parameters e.g., sol composition, electrospray voltage, drying method, pyrolysis and pore activation protocols make possible the tuning of pore structure.
The carbonaceous precursor sol, considered in this work is resorcinol formaldehyde (RF). The sol-gel transition involves addition and polycondensation reactions respectively, where the latter step contributes to crosslinks. Upon pyrolysis, the crosslinks develop into micropores. RF gel can be prepared in either aqueous or organic solvent, and the choice of solvent may affect the morphology of the deposited film. Further, the method of solvent removal for the drying of cured RF gel film contributes to the mesopore formation in the carbon film. In particular, the simultaneous evaporation of organic solvent at the time of curing vis-à-vis the lyophilization of aqueous gel film can lead to distinctly different pore structure. The hierarchical structure with connected mesopores enables better access to the micropores. The presentation addresses these aspects using experimental measurements. The nitrogen adsorption-desorption experiment on bulk carbon powder showed the pore size distribution and specific surface area. The carbon powder is also analyzed here using XRD, FTIR, and Raman spectroscopy.
Carbon paper is used in this work as the current collector. Sufficient adhesion between the deposited film and the carbon paper enabled handling of the composite through curing, solvent removal, and carbonization steps without peel. The morphology of the film is studied under SEM, and the pore size is calculated using the image analysis software. The electrochemical performance of the electrode is studied in a symmetric cell using KCl and KOH respectively as electrolytes. The cyclic voltammetry, chronopotentiometry, and impedance spectroscopy are performed to estimate specific capacitance, electrolyte resistance at different extents of ion penetration into the pore. The retention of capacitance and coulombic efficiency after several charge-discharge cycles are reported here.
Transformation of Plant Biomass Waste into Resourceful Activated Carbon Materials for Mixed-Assembly Type Electrochemical Capacitors
Authors: Momodu Damilola , Okafor Chimaka , Manyala Ncholu , Bello Abdulhakeem , Zebaze-Kana Martiale Gaetan , Ntsoenzok Esidor 
Published: February 2020

Activated carbon (AC) was obtained from three different plant biomass wastes sources (coconut shell, pine cones and rice husk) via hydrothermal treatment followed by carbonization at 800 °C. The morphological and structural characteristics of the transformed carbon material revealed a porous network suitable for energy storage application. The asymmetric cells fabricated exhibited EDLC behaviour in all material sample combinations using all three transformed activated carbons. The mixed assembly device worked comfortably in a voltage window of 1.5 V in a neutral electrolyte. A specific capacitance (C
S) of ∼110 F g-1 was obtained with a corresponding energy density of 8.5 W h kg-1 and power density of 380 W kg-1 at a current density of 0.5 A g-1. An excellent stability was exhibited with a coulombic efficiency of a 99.7% and capacitance retention of 80% after 10000 continuous cycling at 5.0 A g-1. Furthermore, subjecting the device to a floating test for ∼48 h (2 days) at the optimum voltage (1.5 V) revealed a drop in the initial capacitance value but still without any recorded device failure. Remarkably, the asymmetric design showed a potential for adopting EDLC materials of different carbon sources in order to capture the entire properties for efficient and stable energy storage devices.
Keywords: Plant waste; Energy storage materials; Activated carbon; Mixed-assembly; Supercapacitors

Figure 1
Iron Sulfides Electroactivity in Environments in the Presence of Strong Acid, Carbonic Acid and Aqueous Hydrogen Sulfide
Authors: Navabzadeh Esmaeely Saba , Nesic Srdjan 
Published: February 2020

Iron sulfides, particularly the two most stable polymorphs: pyrite and pyrrhotite, have captured the attention of scholars due to their semi-conductive properties. Their semi-conductive nature allows for the corrosive species to be reduced at their surface while electrons are transported from the steel surface via their network. Thus, as a corrosion product layer, pyrite or pyrrhotite do not offer sufficient protection to the steel underneath in the form of a mass transfer barrier for corrosive species. In addition, these layers could accelerate the corrosion rate via an enhancement of reduction of corrosive species rate on their surface. The electrochemistry of iron sulfide layers as it is related to the field of corrosion is unclear and the reported data in the literature has not reached a conclusion. Most of the available literature about electrochemistry of iron sulfides reports on their anodic, rather than cathodic behavior. However, it is noteworthy that in the mechanism related to a mild steel corrosion under such layers, the mild steel is the anode, and the iron sulfide layers are the cathode. A much higher cathodic surface area emerges due to the porous nature of these layers, which results in a higher corrosion currents of the mild steel. Therefore, in order to understand their main role on mild steel corrosion, it is important to study the rate of reduction of corrosive species such as: hydrogen (H+), carbonic acid (H2CO3) and hydrogen sulfide (H2S) on their surface to investigate their electroactivity. This would extend the current understanding of galvanic corrosion of a mild steel under iron sulfide layers.
In the current study, pyrite and pyrrhotite electrodes made from geological specimens were polarized negatively and the results were compared with the data obtained from a mild steel electrode. The experiments were conducted in deaerated aqueous solutions with and without H2S at different pH at a room temperature.
The experimental results revealed the significance of electroactivity of pyrite and pyrrhotite related to H+, H2CO3 and H2S reduction rates. A comparison of their polarization data with a bare mild steel data showed a similar level of electroactivity.
The measured data were compared with the calculated data from an electrochemical model developed and validated for a mild steel electrode exposed to aqueous environments with and without H2S.
The experimental results from the pyrrhotite electrode showed an extra wave on the polarization curves with a distinct limiting current, it remains unclear what this wave represents. The nature of this wave is still under investigation.

Figure 1
Sulfide Scaling and Corrosion of Carbon Steel in a Sour Medium
Authors: Al-Qahtani Noora , Qi Jiahui , Abdullah Aboubakr Moustafa , Laycock Nick , Ryan Mary P 
Published: February 2020

The damage caused by the building up of scale inside wellbores and pipelines costs millions of pounds each year. A better understanding of scale formation and the kinetic nature of the process is essential, for asset management in general and the development of new protection approaches. Surface scale formation is one of the important factors related to the corrosion rate. The internal corrosion of carbon steel in the presence of hydrogen sulfide represents a significant problem for both oil refineries and gas treatment facilities/pipelines. Many studies have revealed that the system is complex since more than one iron sulfide compound may form. However, the kinetics of scale formation, such as the nucleation and growth processes of the scale are not at all well-understood and how corrosion inhibitors interact with scales. The kinetics of the scale formation will be investigated by using a variety of methods, some more successful than others. The methods employed include SEM, TEM, EDX, and Raman analysis, and this was done with the aim of obtaining the physical structure, the chemical composition and the crystal structure of the iron sulfide scale formed at different time scales.
Overview of U.S. Department of Energy Office of Fossil Energy’s Solid Oxide Fuel Cell Program
Authors: Vora Shailesh D , Lundberg Wayne L. , Pierre Joseph F. 
Published: February 2020

The primary mission of the U.S. Department of Energy’s Office of Fossil Energy (FE) is to ensure the nation can continue to rely on its indigenous fossil fuel resources for clean, secure, and affordable energy. A component of that effort is the Solid Oxide Fuel Cell (SOFC) Program, administered by FE’s National Energy Technology Laboratory (NETL). The SOFC Program is committed to: developing efficient, low-cost electricity from natural gas or coal with intrinsic carbon capture capabilities for distributed generation and central power generation applications; maintaining cell development and core technology research to increase the reliability, robustness, and durability of cell, stack, and system technology; and providing the technology base to permit cost-competitive distributed generation applications. The program recently initiated two focused efforts: addressing cell and system reliability and an Innovative Concepts initiative.
Based on feedback from several program participants, chromium contamination of cathode was identified as a major contributor to performance degradation and reduced system reliability. NETL has launched an initiative to address the issue of chromium contamination. The SOFC Program portfolio presently has 13 projects addressing this critical issue.
The SOFC Program is also funding an Innovative Concepts initiative that supports the research, development, and demonstration (RD&D) of SOFC technology that has the potential to surpass current anode supported planar SOFC technology in terms of cost and reliability. Program participants are developing novel cell and stack architectures and/or material sets. This next-generation SOFC technology development in the near-term includes nominally 5-10 kWe-scale stack tests using cells envisioned in the developer’s future commercial systems.
The status of these strategically oriented research programs, along with the status of the program’s integrated systems tests and the roadmap to deploy a MWe-class natural gas-fueled distributed generation system, will be presented.