Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “organic electrode materials”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Understanding the limits of Li-NMC811 half-cells

As we push the boundaries of state-of-the-art lithium-ion intercalation materials, such as nickel-rich chemistries, the ability to isolate and understand specific degradation and performance limitations is becoming increasingly important. Half-cells, wherein lithium metal is employed as a dual counter and reference electrode, are commonly used in industry and academia for this purpose. However, the high reactivity of lithium metal drives premature electrolyte degradation and limits cell lifetime, bringing into question the reliability and validity of this cell configuration. Here we explore the limitations of half-cell studies of LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) electrodes with commercially relevant loading. We identify the failure mechanism of this cell configuration through a combination of electrochemical, chemical, and spectroscopic techniques and show that the Li has a direct detrimental impact on the NMC811 chemistry. Our measurements show that vinylene carbonate is critical for these half-cell studies and underpins the cycle limits. Furthermore, we demonstrate the use of Li 4 Ti 5 O 12 (LTO) as an alternative counter electrode for understanding the performance of NMC positive electrode materials, due to its high coulombic efficiency and low reactivity with the organic carbonates routinely employed in lithium-ion battery cell chemistries. These data confirm that NMC811 electrodes can tolerate high voltages (stressed) conditions and that cell failure is mainly a result of crossover effects.

25 ENERGY STORAGE↗
DOE OSTI2021

Fundamental Investigations of Mechanical and Chemical Degradation Mechanisms in Lithium Ion Battery Materials (Final Technical Report)

The objective of our effort under the DOE EPSCoR Implementation grant is to establish a comprehensive and internationally recognized research program at Brown University and University of Rhode Island in understanding degradation mechanisms and to improve the cycle and calendar life of lithium ion battery (LIB) materials. A series of basic investigations are undertaken to characterize the mechanical and chemical degradation mechanisms, which can help enable new higher capacity and longer lasting electrode designs. Controlling mechanical and chemical degradation is the primary challenge in developing the next generation of higher energy density batteries. The development of failure resistant battery microstructures will require a fundamental understanding of the evolution of stress, deformation, damage, and electrochemistry in battery materials during cyclic charging and discharging. In addition, controlling the reactions at the electrode/electrolyte interface is critical for the formation of a stable SEI layer. We address these issues through a combination of controlled experiments on model battery materials and practical composite electrodes, together with multi-scale computations. Our effort is organized into three focus areas that encompass many critical challenges in Lithium Ion Battery Technologies: (i) Mechanical properties, fracture and damage in electrode materials; (ii) Chemistry and Mechanics of Solid Electrolyte Interphase (SEI); (iii) Mechanical and Chemical Integrity of Solid-Solid Interfaces in Practical Electrodes.

25 ENERGY STORAGE↗
NASA NTRS1992

Symposium on High Power, Ambient Temperature Lithium Batteries, 180th Meeting of the Electrochemical Society, Phoenix, AZ, Oct. 13-17, 1991, Proceedings

Papers presented in these proceedings are on the state of the art in high-power lithium batteries, a design analysis of high-power Li-TiS2 battery, the performance and safety features of spiral wound lithium/thionyl chloride cells, the feasibility of a superhigh energy density battery of the Li/BrF3 electrochemical system, and an enhanced redox process of disulfide compounds and their application in high energy storage. Attention is also given to the structure and charge-discharge characteristics of mesophase-pitch based carbons, a study of carbons and graphites as anodes for lithium rechargeable cells, Li metal-free rechargeable Li(1+x)Mn2O4/carbon cells, and rechargeable lithium batteries using V6O13/V5O5 as the positive electrode material. Other papers discuss the electrochemical stability of organic electrolytes in contact with solid inorganic cathode materials, the electrochemical behavior of methyl formate solutions, and the interface between a solid polymer electrolyte and lithium anode.

Clark, W. D. K.↗
DOE OSTI2020

Macroscale and Nanoscale Photoelectrochemical Behavior of p-Type Si(111) Covered by a Single Layer of Graphene or Hexagonal Boron Nitride

Two-dimensional (2D) materials may enable a general approach to the introduction of a dipole at a semiconductor surface as well as control over other properties of the double layer at a semiconductor/liquid interface. Vastly different properties can be found in the 2D materials currently studied due in part to the range of the distribution of density-of-states. In this work, the open-circuit voltage (V oc ) of p-Si–H, p-Si/Gr (graphene), and p-Si/h-BN (hexagonal boron nitride) in contact with a series of one-electron outer-sphere redox couples was investigated by macroscale measurements as well as by scanning electrochemical cell microscopy (SECCM). The band gaps of Gr and h-BN (0–5.97 eV) encompass the wide range of band gaps for 2D materials, so these interfaces (p-Si/Gr and p-Si/h-BN) serve as useful references to understand the behavior of 2D materials more generally. The value of Voc shifted with respect to the effective potential of the contacting solution, with slopes (ΔV oc /ΔE Eff ) of -0.27 and -0.38 for p-Si/Gr and p-Si/h-BN, respectively, indicating that band bending at the p-Si/h-BN and p-Si/Gr interfaces responds at least partially to changes in the electrochemical potential of the contacting liquid electrolyte. Additionally, SECCM is shown to be an effective method to interrogate the nanoscale photoelectrochemical behavior of an interface, showing little spatial variance over scales exceeding the grain size of the CVD-grown 2D materials in this work. The measurements demonstrated that the polycrystalline nature of the 2D materials had little effect on the results and confirmed that the macroscale measurements reflected the junction behavior at the nanoscale.

2D material↗
DOE OSTI2020

Nanotechnology for catalysis and solar energy conversion

This roadmap on Nanotechnology for Catalysis and Solar Energy Conversion focuses on the application of nanotechnology in addressing the current challenges of energy conversion: 'high efficiency, stability, safety, and the potential for low-cost/scalable manufacturing' to quote from the contributed article by Nathan Lewis. This roadmap focuses on solar-to-fuel conversion, solar water splitting, solar photovoltaics and bio-catalysis. It includes dye-sensitized solar cells (DSSCs), perovskite solar cells, and organic photovoltaics. Smart engineering of colloidal quantum materials and nanostructured electrodes will improve solar-to-fuel conversion efficiency, as described in the articles by Waiskopf and Banin and Meyer. Semiconductor nanoparticles will also improve solar energy conversion efficiency, as discussed by Boschloo et al in their article on DSSCs. Perovskite solar cells have advanced rapidly in recent years, including new ideas on 2D and 3D hybrid halide perovskites, as described by Spanopoulos et al 'Next generation' solar cells using multiple exciton generation (MEG) from hot carriers, described in the article by Nozik and Beard, could lead to remarkable improvement in photovoltaic efficiency by using quantization effects in semiconductor nanostructures (quantum dots, wires or wells). These challenges will not be met without simultaneous improvement in nanoscale characterization methods. Terahertz spectroscopy, discussed in the article by Milot et al is one example of a method that is overcoming the difficulties associated with nanoscale materials characterization by avoiding electrical contacts to nanoparticles, allowing characterization during device operation, and enabling characterization of a single nanoparticle. Besides experimental advances, computational science is also meeting the challenges of nanomaterials synthesis. The article by Kohlstedt and Schatz discusses the computational frameworks being used to predict structure–property relationships in materials and devices, including machine learning methods, with an emphasis on organic photovoltaics. The contribution by Megarity and Armstrong presents the 'electrochemical leaf' for improvements in electrochemistry and beyond. In addition, biohybrid approaches can take advantage of efficient and specific enzyme catalysts. These articles present the nanoscience and technology at the forefront of renewable energy development that will have significant benefits to society.

14 SOLAR ENERGY↗
DOE OSTI2021

Nanoarchitectonics of Metal–Organic Frameworks for Capacitive Deionization via Controlled Pyrolyzed Approaches

Abstract Next‐generation desalination technologies are needed to meet the increasing demand for clean water. Capacitive deionization (CDI) is a thermodynamically efficient technique to treat non‐potable water with relatively low salinity. The salt removal capacity and rate of CDI are highly dependent on the electrode materials, which are preferentially porous to store ions through electrosorption and/or redox reactions. Metal–organic frameworks (MOFs) with “infinite” combinations of transition metals and organic linkers simplify the production of carbonaceous materials often with redox‐active components after pyrolysis. MOFs‐derived materials show great tunability in both compositions and structures but require further refinement to improve CDI performance. This review article summarizes recent progress in derivatives of MOFs and MOF‐like materials used as CDI electrodes, focusing on the structural and compositional material considerations as well as the processing parameters and electrode architectures of the device. Furthermore, the challenges and opportunities associated with this research area are also discussed.

Wang, Hao↗
NASA NTRS1989

Electrochemical incineration of wastes

A low temperature electrolysis process has been developed for the treatment of solid waste material and urine. Experiments are described in which organic materials are oxidized directly at the surface of an electrode. Also, hypochlorite is generated electrochemically from chloride component of urine. Hypochlorite can act as a strong oxidizing agent in solution. The oxidation takes place at 30-60 C and the gaseous products from the anodic reaction are carbon dioxide, nitrogen, oxygen. Hydrogen is formed at the cathode. Carbon monoxide, and nitrogen oxides and methane were not detected in the off gases. Chlorine was evolved at the anode in relatively low amounts.

Kaba, L.↗
DOE OSTI2021

Toward the Development of a High-Voltage Mg Cathode Using a Chromium Sulfide Host

Development of Mg-ion batteries as advanced electrochemical energy storage systems relies on the design and discovery of high-voltage positive electrode (cathode) materials. To date, a variety of sulfide cathodes have been reported (e.g., Mg x Mo 6 S 8 , Mg x Ti 2 S4, etc.), but the voltages of these materials are too low to prepare a high energy density Mg cell. Theoretical computations predicted that Mg x Cr 2 S 4 operating with the high-voltage Cr 3+/4+ redox couple would serve as a suitable cathode candidate, but experimental attempts to extract Mg 2+ from the lattice have been largely unsuccessful. Here, we show that reversible electrochemical activity within a thiospinel framework (AB 2 S 4 ) relies on a redox-active transition metal present in the B site; otherwise, anionic redox activity triggers decomposition of the spinel structure. Since Cr and S states are highly coupled in MgCr 2 S 4 , the Cr 3+/4+ redox couple is inaccessible so that reversible (de)intercalation of Mg 2+ cannot occur and charging leads to dissolution of the active material. These findings point to an insufficiency in the screening criteria previously used to identify MgCr 2 S 4 as a promising Mg cathode. Thus, a computable descriptor based on the electronic structure of the discharged material is proposed to predict the prevalence of cation vs anion redox and improve future surveys of potential candidates. It is unlikely that the high-voltage Cr redox couple will be accessible to oxidation in the presence of sulfur within the restrictions of a spinel framework; however, it is possible that a suitable layered Mg x CrS 2 structure could serve as a reversible high-voltage Mg cathode.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Role of Fluorine in Chemomechanics of Cation-Disordered Rocksalt Cathodes

The role of nanoscale chemomechanical behavior in the macroscopic performance of functional materials is well recognized. For lithium-ion battery cathodes, tremendous effort has been devoted to the development of new chemistry and structure, yet fundamental understanding of the correlation between redox processes and mechanical properties of the novel materials lags behind. In the present study, we prepare large discrete single grains of Li-excess cation-disordered rocksalts (DRX) and investigate their chemomechanical behavior at the particle level, using nanoresolution X-ray and electron-based spectro-imaging and chemical mapping techniques. While irregular cracking upon lithium extraction leads to the eventual breakdown of the baseline DRX oxide (Li 1.2 Ti 0.4 Mn 0.4 O 2 ) particles at a high delithiation state, the fluorinated-DRX (Li 1.3 Ti 0.3 Mn 0.4 O 1.7 F 0.3 ) clearly displays aligned cracking along the <001> direction. The resulting periodicity in the cracking pattern enables the particles to retain their integrity and, consequently, improved electrochemical stability. Density functional theory (DFT) calculations showed that fluorination leads to increased concentration of Li+ on the (001) planes and preferential Li movements along the <001>-family directions, revealing the underlying mechanism for directional cracking. Overall, our study demonstrates the unique role of fluorine in modulating nanoscale chemomechanics, which in turn influences the evolution of charge and strain heterogeneity at the particle level. These insights provide important design guidelines in further improving DRX cathode materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Significance of a Solid Electrolyte Interphase on Separation of Anode and Cathode Materials from Spent Li-Ion Batteries by Froth Flotation

The separation of electrode active materials from spent Li-ion batteries (LIBs) by froth flotation is challenging due to the changes in surface properties of electrode active materials from cycling as well as the presence of organic binders. In this work, the froth flotation separation of aged anode and cathode composite materials from spent LIBs was systematically investigated after the materials were heat treated. The results show that aged anode and cathode materials from spent LIBs can be well separated from each other after a heating process in air at 400 degrees C and at which some of the PVDF binder remains intact. The underlying mechanism was investigated by X-ray photoelectron spectroscopy (XPS), contact angle measurements, and scanning transmission electron microscopy (STEM) coupled with energy-dispersive X-ray spectroscopy (EDX). The results from the XPS and contact angle measurements show that there is a hydrophilic and oxygen-rich layer on the surface of aged anode materials. This hydrophilic surface, associated with the solid electrolyte interface (SEI) layer, impacts the froth flotation process significantly. The results also show that both the SEI layers and PVDF binder residues on the surface are removed at 400 degrees C for an hour, restoring the hydrophobicity of the anode materials, which, in turn, benefits the separation of anode and cathode materials. The STEM/EDX elemental analysis data confirms that there are 20 nm-thick oxygen-rich SEI layers on the surfaces, which can be removed after a heating process. The present result illustrates the significance of the SEI layers in flotation separation of electrode materials and sheds new lights into the future development of the recycling processes for the separation of anode and cathode composite materials from spent Li-ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2021

The Surge of Metal–Organic-Framework (MOFs)-Based Electrodes as Key Elements in Electrochemically Driven Processes for the Environment

Metal–organic-frameworks (MOFs) are emerging materials used in the environmental electrochemistry community for Faradaic and non-Faradaic water remediation technologies. It has been concluded that MOF-based materials show improvement in performance compared to traditional (non-)faradaic materials. In particular, this review outlines MOF synthesis and their application in the fields of electron- and photoelectron-Fenton degradation reactions, photoelectrocatalytic degradations, and capacitive deionization physical separations. This work overviews the main electrode materials used for the different environmental remediation processes, discusses the main performance enhancements achieved via the utilization of MOFs compared to traditional materials, and provides perspective and insights for the further development of the utilization of MOF-derived materials in electrified water treatment.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Probing Mg Intercalation in the Tetragonal Tungsten Bronze Framework V 4 Nb 18 O 55

While commercial Li-ion batteries offer the highest energy densities of current rechargeable battery technologies, their energy storage limit has almost been achieved. Therefore, there is considerable interest in Mg batteries, which could offer increased energy densities in comparison to Li-ion batteries if a high-voltage electrode material, such as a transition-metal oxide, can be developed. However, there are currently very few oxide materials which have demonstrated reversible and efficient Mg 2+ insertion and extraction at high voltages; this is thought to be due to poor Mg 2+ diffusion kinetics within the oxide structural framework. Here, in this paper, the authors provide conclusive evidence of electrochemical insertion of Mg 2+ into the tetragonal tungsten bronze V 4 Nb 18 O 55 , with a maximum reversible electrochemical capacity of 75 mA h g –1 , which corresponds to a magnesiated composition of Mg 4 V 4 Nb 18 O 55 . Experimental electrochemical magnesiation/demagnesiation revealed a large voltage hysteresis with charge/discharge (1.12 V vs Mg/Mg 2+ ); when magnesiation is limited to a composition of Mg 2 V 4 Nb 18 O 55 , this hysteresis can be reduced to only 0.5 V. Hybrid-exchange density functional theory (DFT) calculations suggest that a limited number of Mg sites are accessible via low-energy diffusion pathways, but that larger kinetic barriers need to be overcome to access the entire structure. The reversible Mg 2+ intercalation involved concurrent V and Nb redox activity and changes in crystal structure, as confirmed by an array of complementary methods, including powder X-ray diffraction, X-ray absorption spectroscopy, and energy-dispersive X-ray spectroscopy. Consequently, it can be concluded that the tetragonal tungsten bronzes show promise as intercalation electrode materials for Mg batteries.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Non-planar platinum group metal-free fuel cell cathodes for enhanced oxygen transport and water rejection

Proton exchange membrane fuel cells (PEMFC) with cathodes using platinum group metal-free (PGM-free) catalysts could significantly reduce costs, but the lower volumetric oxygen reduction reaction (ORR) activity requires thick electrodes that suffer from liquid water flooding and increased oxygen transport resistance. To address these challenges, we developed a 3D gas diffusion electrode (GDE) architecture to enhance liquid water removal through the diffusion media and reduce cathode saturation. The cathode features a uniform catalyst layer adjacent to the membrane for high ORR activity and then pillars of the hydrophilic catalyst layer that pass through the microporous layer (MPL), providing a low capillary pressure barrier pathway to the carbon fiber paper layer and channel. The non-planar cathode also increases the interfacial area between the catalyst layer and hydrophobic MPL for a greater fraction of the cathode with high O 2 concentration. Our studies included parametric experimental study of the pillar density to identify the optimum pitch between pillars. Our measurements show significant improvements in the mass transport region of the polarization curve with 3D structured electrodes leading to an 8% increase in maximum current density, 19% increase in maximum power density, and 16% increase in current density at 0.67 V with air.

25 ENERGY STORAGE↗
DOE OSTI2025

One-Step Transfer of Symmetric and Asymmetric Contacts for Large-Scale 2D Electronics and Optoelectronics

Two-dimensional (2D) semiconductors are highly promising candidates for thin-film transistor applications due to their scalability, transferability, atomic thickness, and relatively high carrier mobility. However, a substantial performance gap remains between individual devices based on single-crystalline 2D films and wafer-scale integrated circuits, primarily due to defects introduced during conventional fabrication processes. Here, we report a diamond-assisted electrode transfer technique for the van der Waals integration of wafer-scale prefabricated electrode arrays onto 2D materials, enabling scalable electronics and optoelectronics. Implemented on metal–organic chemical vapor deposition-grown monolayer molybdenum disulfide, this method forms ultraclean metal–semiconductor interfaces, yielding field-effect transistors with excellent ohmic contacts, a low contact resistance of 400 Ω·μm, and a Schottky barrier height of only 9 meV. Furthermore, we demonstrate a scalable transistor array on monolayer molybdenum disulfide with excellent device performance uniformity, achieving an average field-effect mobility of 30 cm 2 V –1 s –1 and an on/off current ratio exceeding 105. Additionally, high photocurrent and responsivity were demonstrated in the array devices, showing their potential for excellent image detection. We further demonstrate the versatility of this technique by fabricating a Schottky diode array through a single-step transfer of asymmetric electrodes─low work function aluminum and high work function gold─onto monolayer tungsten diselenide. This approach provides a clean, effective solution for contact engineering in 2D materials, offering a viable pathway toward wafer-scale, high-performance 2D electronics, optoelectronics, and integrated circuits.

2D electronics↗
NASA NTRS1995

Nafion(TM) Coats For Electrodes In Liquid-Feed Fuel Cells

Coating or impregnation with commercially available material enables oxidation of organic liquid fuels. Nafion(TM) investigated for use in application because of known combination of desirable characteristics: It is perfluorinated, hydrophilic, proton-conducting ion-exchange polymer exhibiting relatively high thermal and electrochemical stability and not detrimental to kinetics of electrochemical processes. Available in solubilized form and used to apply stable coats to surfaces of electrodes.

Narayanan, Sekharipuram R.↗
NASA NTRS1975

Long-distance recording of the humidity over the sea

A procedure is developed for long distance recording of humidity over the sea that uses humidity detectors of the sorption type, whose electrical properties depend on the relative humidity of the air. The moisture sensitive material of the hygristor is the organic polymer polyacrylonitryl, deposited on silver electrodes and thermally treated. In the measurements of the relative humidity from 60% to 95%, the resistance of the hygristor varies from several hundred kiloohms to a few kiloohms, and is an essentially nonlinear function of the humidity.

Buklanov, V. V.↗