Polysulfide Mitigation at the Electrode-Electrolyte Interface: Experiments in Rechargeable Lithium Sulfur Batteries

In the field of energy storage technology, the lithium sulfur battery is intensely studied in interest of its great theoretical gravimetric capacity (1672 Ah kg–1) and gravimetric density (2600 Wh kg–1). The theoretical performance values satisfy viability thresholds for petroleum–free electric vehicles and other emerging technologies. However, this elusive technology remains in the research sector due to a wealth of challenges resulting from its complex chalcogenide electrochemistry. The most infamous challenge remains the polysulfide redox shuttle, a phenomenon in which lithium polysulfide intermediates are produced as elemental sulfur S8 is reduced to lithium sulfide Li2S during the discharge cycle. Because the higher order polysulfides are soluble in organic electrolyte, battery cycling can result in dissolution of the cathode, dendrite formation upon the lithium metal anode, and passivation of electrode surfaces. These problems can ultimately cause rapid capacity fade and unstable Coulombic efficiency. As lithium sulfur battery research enters its 3rd decade, it is becoming increasingly clear that solutions will be holistic or synergistic; that is, addressing the aforementioned issues by suppressing their source in the polysulfide redox shuttle rather than isolated symptoms of the underlying mechanism. This thesis serves as a summary of research performed to study polysulfide suppression and mitigation through electrode material synthesis, electrolyte design, and in situ characterization. Synthesis techniques include solid state pyrolysis, autogenic synthesis, and ultrasound sonochemistry. Material characterization techniques include isothermal nitrogen sorption; scanning, transmission, and scanning transmission electron microscopy; thermogravimetric analysis; energy dispersive X–ray spectroscopy; organic elemental analysis; X– ray diffraction; and Raman spectroscopy. Electrochemical characterization includes galvanostatic battery cycling, differential potentiometric analysis, and electrochemical impedance spectroscopy. Altogether, this research demonstrates the challenges of polysulfide degradation are not sufficiently addressed by symptomatic approaches. Synthesis pathways for carbon sulfur cathodes that encourage homogeneous sulfur distribution (i.e., autogenic or sonochemical synthesis) improve specific capacity across extended cycling, but show excessive polysulfide production at slow cycling rates. In combination with fluorinated electrolyte, carbon sulfur cathode morphology improves Coulombic efficiency at cycling rates between C/20 — 2 C but at the cost of gravimetric capacity. Synchrotron tomography characterization, developed for Advanced Photon Source Beamline 6–BM–A, evidences that fluorinated electrolytes may also effectively suppress dendrite formation on lithium metal anodes. This suggests more holistic and optimized techniques, or their combinations, may lead to effective polysulfide suppression and successful commercialization of the lithium sulfur battery. Supplementary research explores broader impact of synthesized carbon applications in lithium sulfur batteries. Pyrolysis synthesis processes are evaluated for health and environment impacts using optical by–product sizing and life cycle analysis, respectively. In the context of pyrolytic synthesis of carbon microsheets, micro and nano-sized carbonaceous particulate by–products released during synthesis must be collected to minimize health exposure risks. The environmental impact of this synthesis process is a function of mode of oxygen deficiency, that is, whether pyrolytic atmosphere is facilitated by vacuum or inert gas stream. Finally, submicron carbon spheres, a carbon morphology produced by pyrolysis of sonochemically-synthesized polymer spheres, demonstrate gravimetric capacity which is a strong function of microstructure (i.e., pore distribution, crystallite size, structural disorder). In turn, microstructural properties are determined by synthesis temperature, a dimension of synthesis pathway

Photoelectrochemical ion concentration polarization : a microfluidic ion filtration system using light-driven electrochemical reactions

We report an ion separation or filtration method used in microchannel called photoelectrochemical ion concentration polarization (pICP). As a variant of faradaic ion concentration polarization (fICP), pICP utilizes TiO₂ photoelectrochemistry to form an ion depletion zone (IDZ) with light. A microfluidic device with TiO₂ photoanode and Pt cathode generated IDZ near the cathode by generating a corresponding electrochemical reaction. Local electric field near the cathode was amplified with TiO₂ irradiation. Furthermore, on-chip solution conductivity measurement confirmed decrease in ion concentration as a consequence of pICP ion filtration.Chemistr

Book of abstracts of the 15th International Symposium of Croatian Metallurgical Society - SHMD \u272022, Materials and metallurgy

Book of abstracts of the 15th International Symposium of Croatian Metallurgical Society - SHMD \u272022, Materials and metallurgy, Zagreb, Croatia, March 22-23, 2022. Abstracts are organized in four sections: Materials - section A; Process metallurgy - Section B; Plastic processing - Section C and Metallurgy and related topics - Section D

Book of abstracts of the 15th International Symposium of Croatian Metallurgical Society - SHMD \u272022, Materials and metallurgy

Book of abstracts of the 15th International Symposium of Croatian Metallurgical Society - SHMD \u272022, Materials and metallurgy, Zagreb, Croatia, March 22-23, 2022. Abstracts are organized in four sections: Materials - section A; Process metallurgy - Section B; Plastic processing - Section C and Metallurgy and related topics - Section D

NASA SBIR abstracts of 1991 phase 1 projects

The objectives of 301 projects placed under contract by the Small Business Innovation Research (SBIR) program of the National Aeronautics and Space Administration (NASA) are described. These projects were selected competitively from among proposals submitted to NASA in response to the 1991 SBIR Program Solicitation. The basic document consists of edited, non-proprietary abstracts of the winning proposals submitted by small businesses. The abstracts are presented under the 15 technical topics within which Phase 1 proposals were solicited. Each project was assigned a sequential identifying number from 001 to 301, in order of its appearance in the body of the report. Appendixes to provide additional information about the SBIR program and permit cross-reference of the 1991 Phase 1 projects by company name, location by state, principal investigator, NASA Field Center responsible for management of each project, and NASA contract number are included

Arc-discharge In Solution: A Novel Synthesis Method For Carbon Nanotubes And In Situ Decoration Of Carbon Nanotubes With Nanoparticles

Nanotechnology has reached the status of the 21st century\u27s leading science and technology based on fundamental and applied research during the last two decades. An important feature of nanotechnology is to bridge the crucial dimensional gap between the atomic and molecular fundamental sciences and microstructural scale of engineering. Accordingly, it is very important to have an in-depth understanding of the synthesis of nanomaterials for the use of state-of-the-art high technological devices with enhanced properties. Recently, the \u27bottom-up\u27 approach for the fabrication of nanomaterials has received a great deal of attention for its simplicity and cost effectiveness. Tailoring the various parameters during synthesis of selected nanoparticles can be used to fabricate technologically important components. During the last decade, carbon nanotubes (CNTs) have been envisioned for a host of different new applications. Although carbon nanotubes can be synthesized using a variety of techniques, large-scale synthesis is still a great challenge to the researchers. Three methods are commonly used for commercial and bulk productions of carbon nanotubes: arc-discharge, chemical vapor deposition and laser ablation. However, low-cost, large-scale production of high-quality carbon nanotubes is yet to be reported. One of the objectives of the present research is to develop a simplified synthesis method for the production of large-scale, low-cost carbon nanotubes with functionality. Herein, a unique, simple, inexpensive and one-step synthesis route of CNTs and CNTs decorated with nanoparticles is reported. The method is simple arc-discharge in solution (ADS). For this new method, a full-fledged optoelectronically controlled instrumen is reported here to achieve high efficiency and continuous bulk production of CNTs. In this system, a constant gap between the two electrodes is maintained using a photosensor which allows a continuous synthesis of the carbon nanostructures. The system operates in a feedback loop consisting of an electrode-gap detector and an analogue electronic unit, as controller. This computerized feed system was also used in single process step to produce in situ-decorated CNTs with a variety of industrially important nanoparticles. To name a few, we have successfully synthesized CNTs decorated with 3-4 nm ceria, silica and palladium nanoparticles for many industrially relevant applications. This process can be extended to synthesize decorated CNTs with other oxide and metallic nanoparticles. Sixty experimental runs were carried out for parametric analysis varying process parameters including voltage, current and precursors. The amount of yield with time, rate of erosion of the anode, and rate of deposition of carbonaceous materials on the cathode electrode were investigated. Normalized kinetic parameters were evaluated for different amperes from the sets of runs. The production rate of pristine CNT at 75 A is as high as 5.89 ± 0.28 g.min-1. In this study, major emphasis was given on the characterizations of CNTs with and without nanoparticles using various techniques for surface and bulk analysis of the nanostructures. The nanostructures were characterized using transmission electron microscopy, high resolution transmission electron microscopy, scanning transmission electron microscopy, energy dispersive spectroscopy and scanning electron microscopy, x-ray photo electron spectroscopy, x-ray diffraction studies, and surface area analysis. Electron microscopy investigations show that the CNTs, collected from the water and solutions, are highly pure except the presence of some amorphous carbon. Thermogravimetric analysis and chemical oxidation data of CNTs show the good agreement with electron microscopy analysis. The surface area analysis depicts very high surface area. For pristine multi-walled carbon nanotubes, the BET surface area is approximately 80 m2.g-1. X-ray diffraction studies on carbon nanotubes shows that the products are clean. Nano-sized palladium decorated carbon nanotubes are supposed to be very efficient for hydrogen storage. The synthesis for in-situ decoration of palladium nanoparticles on carbon nanotubes using the arc discharge in solution process has been extensively carried out for possible hydrogen storage applications and electronic device fabrication. Palladium nanoparticles were found to form during the reduction of palladium tetra-chloro-square planar complex. The formation of such a complex was investigated using ultraviolet-visible spectroscopic method. Pd-nanoparticles were simultaneously decorated on carbon nanotubes during the rolling of graphene sheets in the arc-discharge process. Zero-loss energy filtered transmission electron microscopy and scanning transmission electron microscopy confirm the presence of 3 nm palladium nanoparticles. The deconvoluted X-ray photoelectron spectroscopy envelope shows the presence of palladium. Surface area measurements using BET method show a surface area of 28 m2.g-1. The discrepancy with pristine CNTs can be explained considering the density of palladium (12023 kg.m-3). Energy dispersive spectroscopy suggests no functionalization of chlorine to the sidewall of carbon nanotubes. The presence of dislodged graphene sheets with wavy morphology as observed with high-resolution transmission electron microscopy supports the formation of CNTs through the \u27scroll mechanism\u27

Reactor R&D: Synthesis and Optimization of Metallic Nitride Fullerenes and the Introduction of Two New Classes of Endohedral Metallofullerenes, Metallic Nitride Azafullerenes and Oxo-metallic Fullerenes

Metallic nitride fullerenes (MNFs) were discovered in 1999. This class of endohedral fullerenes show promise in a new diverse range of useful applications. Since then, focus has shifted to the selective synthesis of these molecules with yields that would accommodate adequate sample distribution. Using the electric arc method, the traditional yield of these molecules has been very low (i.e. \u3c 5 mg), and only a small percentage of the fullerene products (i.e. \u3c 5%). This dissertation introduces the novel CAPTEAR (Chemically Adjusting Plasma Temperature, Energy, And Reactivity) method that allows the targeted synthesis of MNFs in high purity and yield. This method utilizes a nontraditional oxidizing method for fullerene synthesis that has not only provided optimization of MNFs, but also resulted in the discovery of two new classes of fullerenes: metallic nitride azafullerenes (MNAFs) and oxo-metallic fullerenes (OMFs). Evidence suggests that the nitrogen of the MNAF cage provides stability for the trimetallic nitride clusters, while the OMFs are the first fullerenes to encapsulate oxygen and incorporate a seven atom cluster inside a Cgo cage. Other efforts to increase yields resulted from scaling up production of fullerenes by using larger quantities of starting materials. These larger quantities required energy (electrical current) beyond the capacity of the traditional electric arc generator. Therefore, a new electric arc generator was designed and fabricated to accommodate these demands. This scale-up process resulted in yield increases by an average of 400%. However, to reduce the waste of scaling up as well as costs, our lab developed a recycling method for the expensive metal oxide starting materials. This method has greatly improved cost effectiveness and waste reduction

Development of ion-conducting ceramics for reversible Solid Oxide Cells

El consumo excesivo de las reservas de combustible fósil y las graves consecuencias que el calentamiento global ha causado y sigue causando han hecho que el desarrollo de nuevas fuentes de energía alternativas se haya vuelto una tarea imperativa. Uruguay no se ha quedado atrás, implementando nuevas Políticas estatales que revolucionaron la matriz energética nacional a través del uso de fuentes de energía renovables tradicionales y la búsqueda de otras modernas. El surgimiento del hidrógeno como fuente de energía del futuro, ha provocado la necesidad de nuevas tecnologías de generación y almacenamiento del mismo (y otros combustibles en general). Las Celdas de Óxido Sólido, funcionando tanto en modo celda de combustible como en modo electrolizador (operación reversa), han atraído mucho interés en las últimas décadas gracias a su alta eficiencia y flexibilidad. Uno de los grandes desafíos que presentan estos dispositivos, es el desarrollo de nuevos materiales que permitan bajar la temperatura de funcionamiento hasta el rango de 600-800 ºC, lo que implica la búsqueda de electrodos que presenten alta actividad electrocatalítica pero no se degraden en las condiciones de operación. La presente tesis se encuentra dedicada al diseño, preparación y caracterización de nuevos materiales cerámicos micro y nanoestructurados para su uso como electrodo de oxígeno en celdas de óxido sólido reversibles. Para esto, se propuso el uso del método de auto-combustión de gel para la obtención de compositos que pudieran exhibir mejor performance electroquímica que los electrodos tradicionales, y luego, junto al uso de electrolitos y electrodos de combustible convencionales, el armado de una celda de óxido sólido completa.La metodología aplicada permitió la obtención, caracterización y testeo de tres materiales (un cerámico ya reportado y dos compositos del mismo con CeO2) con potencial aplicación como electrodos de oxígeno en celdas de óxido sólido reversibles. Los mismos exhibieron valores de potencia similares a los reportados en literatura al testearse en celdas completas usando YSZ como xvii electrolito y Ni-YSZ como electrodo de combustible. Estas medidas representan los primeros resultados de caracterización de dispositivos de óxido sólido reversibles obtenidos por el grupo

Index to 1984 NASA Tech Briefs, volume 9, numbers 1-4

Short announcements of new technology derived from the R&D activities of NASA are presented. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This index for 1984 Tech B Briefs contains abstracts and four indexes: subject, personal author, originating center, and Tech Brief Number. The following areas are covered: electronic components and circuits, electronic systems, physical sciences, materials, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences

NASA SBIR abstracts of 1990 phase 1 projects

The research objectives of the 280 projects placed under contract in the National Aeronautics and Space Administration (NASA) 1990 Small Business Innovation Research (SBIR) Phase 1 program are described. The basic document consists of edited, non-proprietary abstracts of the winning proposals submitted by small businesses in response to NASA's 1990 SBIR Phase 1 Program Solicitation. The abstracts are presented under the 15 technical topics within which Phase 1 proposals were solicited. Each project was assigned a sequential identifying number from 001 to 280, in order of its appearance in the body of the report. The document also includes Appendixes to provide additional information about the SBIR program and permit cross-reference in the 1990 Phase 1 projects by company name, location by state, principal investigator, NASA field center responsible for management of each project, and NASA contract number