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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.

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At least 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
NASA NTRS2001

The Marshall Magnetic Mirror Beam-Plasma Experiment

Plasma propulsion is an advanced propulsion concept with the potential to realize very high specific impulse. Present designs for plasma propulsion devices share a common feature, the incorporation of a magnetic mirror. A magnetic mirror is a plasma confinement scheme whereby charged particles are trapped (or reflected) between two regions of high magnetic field strength. A cylindrical geometry is most often employed to create a magnetic mirror, which is a natural geometry for propulsion devices. To utilize the magnetic mirror configuration in a plasma propulsion device, however, will require efficient coupling of power into the system. With the development of compact and efficient electron sources, such as hollow cathode sources, coupling power into a magnetic mirror using electron beams may be an attractive approach. A system, the Marshall Magnetic Mirror (M3), has been constructed to study the coupling of an electron beam into a magnetic mirror. A description of the M3 device will be provided as well as data from initial beam-plasma coupling experiments.

Schneider, Todd A.↗
NASA NTRS2004

Discharge Chamber Performance of the NEXIS Ion Thruster

The Nuclear-Electric Xenon Ion System (NEXIS) thruster was designed to produce greater than or equal to 70% efficiency at ISPs in excess of 6500 sec and total power levels in excess of 15 kW. In order to achieve this performance, the thruster requires a large area plasma generator capable of high propellant utilimtion efficiency and low discharge loss while producing a very flat, uniform beam profile. Fortunately, larger thrusters can be made more uniform and efficient due to the higher volume to surface ratio, provided that the magnetic cusp confinement is designed properly and the thruster length to diameter ratio is adequate. This paper describes the discharge chamber performance of the NEXIS Laboratory Model (LM) thruster. The LM discharge chamber is 65 cm in diameter at the grid plane and uses 6 ring-cusps to provide magnetic confinement of the plasma. The thruster was tested with flat carbon-carbon composite grids with the hole pattern masked to 57 cm in diameter and a conventional Type-B "1/2" diameter hollow cathode. During the preliminary "discharge only" tests, the LM thruster demonstrated profile factors of 0.84 and a discharge loss of about 160 eV/ion at 25 V discharge voltage and over 90% propellant utilization efficiency in simulated beam extraction experiments at 3.9 A of beam current. Analysis of the data from these tests used the discharge-only model developed by Brophy. Subsequent beam extraction experiments validated the key variables used in the model to predict the performance from the discharge-only data, and demonstrated 3.9 A of beam current at over 90% propellant utilization efficiency with a flatness parameter of better than 0.8 and a discharge loss of about 185 eV/ion. The slightly higher discharge loss measured during beam extractions was found to be due to a lower screen transparency in the as-manufactured LM grid set. Plasma measurements with a scanning probe internal to the thruster near the screen grid showed plasma densities over l x 10(exp 11) per cubic centimeter and electron temperatures of 3.5 to 5.5 eV depending on the operation parameters. The performance of the NEXIS discharge chamber contributed to the over 78% thruster efficiency measured during beam extraction at 7500 sec ISP and 25 kW of power, and over 81% thruster efficiency measured at 8500 sec ISP.

plasma generation↗
DOE OSTI2019

Cost-effective solid state reactive sintering method for protonic ceramic fuel cells

The present invention relates to a protonic ceramic fuel cell and a method of making the same. More specifically, the method relates to a cost-effective route which utilizes a single moderate-temperature (less than or equal to about 1400° C.) sintering step to achieve the sandwich structure of a PCFC single cell (dense electrolyte, porous anode, and porous cathode bone). The PCFC layers are stably connected together by the intergrowth of proton conducting ceramic phases. The resulted PCFC single cell exhibits excellent performance (about 450 mW/cm2 at about 500° C.) and stability (greater than about 50 days) at intermediate temperatures (less than or equal to about 600° C.). The present invention also relates to a two step method for forming a PCFC, and the resulting PCFC.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2019

Electrolyte Concentration Effect on Sulfur Utilization of Li-S Batteries

Electrolyte is the critical component of the Li-S battery. Past studies have shed light on the behavior of the Li-S cells when the electrolyte salt concentration is increased to the solvent-in-salt regime and demonstrated tremendously improved cycle life. However, there is no systematic study on the Li-S cell when the electrolyte salt concentration is reduced from the standard 1.0M condition. This work investigates the lower salt concentration regime by doing a systematic study with the standard LiTFSI in DME:DOL combination, using sulfur electrodes with relatively high loading (> 6 mg cm -2 ). Although reducing the electrolyte salt concentration lowers the ionic conductivity, it is found that the sulfur utilization and rate capability of the Li-S cells benefits from this process. Similar observations are also found when LiTFSI is replaced with LiI and LiBr, which form less conductive electrolytes than LiTFSI at the same concentration levels. Data correlation indicates a stronger correlation between the Li-S cell’s rate-capability and the electrolyte conductivity than electrolyte viscosity. It is proposed in this work that free Li + concentration, which is proportional to the electrolyte conductivity, is the real rate-capability determining parameter. Reducing the electrolyte salt concentration and replacing LiTFSI with less dissociable salts (LiI, LiBr) both will reduce the free Li + in the electrolyte, which will allow a higher saturation point of Li 2 S 2 /Li 2 S. This probably will delay the insulating layer build-up on the cathode conductive network and improve the dissolved Li-polysulfide to Li 2 S 2 /Li 2 S conversion efficiency. Both impedance and cathode morphology support this theorem.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2022

The Role of Electrolyte Composition in Enabling Li Metal‐Iron Fluoride Full‐Cell Batteries

Abstract FeF 3 conversion cathodes, paired with Li metal, are promising for use in next‐generation secondary batteries and offer a remarkable theoretical energy density of 1947 Wh kg −1 compared to 690 Wh kg −1 for LiNi 0.5 Mn 1.5 O 4 ; however, many successful studies on FeF 3 cathodes are performed in cells with a large (>90‐fold) excess of Li that disguises the effects of tested variables on the anode and decreases the practical energy density of the battery. Herein, it is demonstrated that for full‐cell compatibility, the electrolyte must produce both a protective solid‐electrolyte interphase and cathode‐electrolyte interphase and that an electrolyte composed of 1:1.3:3 (m/m) LiFSI, 1,2‐dimethoxyethane, and 1,1,2,2‐tetrafluoroethyl‐2,2,3,3‐tetrafluoropropyl ether fulfills both these requirements. This work demonstrates the importance of verifying electrode level solutions on the full‐cell level when developing new battery chemistries and represents the first full cell demonstration of a Li/FeF 3 cell, with both limited Li and high capacity FeF 3 utilization.

25 ENERGY STORAGE↗
DOE OSTI2020

Revealing the working mechanism of a multi-functional block copolymer binder for lithium-sulfur batteries

The lithium-sulfur (Li-S) battery is one of the most promising substitutes for current energy storage systems because of its low cost, high theoretical capacity, and high energy density. However, the high solubility of intermediate products (i.e., lithium polysulfides) and the resultant shuttle effect lead to rapidly fading capacity and a low coulombic efficiency, which hinder the practical application of Li-S batteries. In this study, block copolymers are constructed with both an ethylene oxide unit and a styrene unit and then used as binders for Li-S batteries. Electrochemical performance improvements are attributed to the synergistic effects contributed by the different units of the block copolymer. Here, the ethylene oxide unit traps polysulfide, which bonds strongly with the intermediate lithium polysulfide, and enhances the transport of lithium ions to reach high capacity. Meanwhile, the styrene unit maintains cathode integrity by improving the mechanical properties and elasticity of the constructed block copolymer to accommodate the large volume changes. By enabling multiple functions via different units in the polymer chain, high sulfur utilization is achieved, polysulfide diffusion is confined, and the shuttle effect is suppressed during the cycle life of Li-S batteries, as revealed by operando ultraviolet–visible spectroscopy and S K-edge X-ray absorption spectroscopy.

25 ENERGY STORAGE↗
DOE OSTI2018

Understanding trends in lithium binding at two-dimensional materials

Layered structure and peculiar electronic properties of two-dimensional (2D) materials foster the concept of utilizing them as main components of lithium-ion batteries. Understanding basic physical mechanisms governing the interaction of Li with 2D crystals is of key importance to succeeding in a rational design of cathode and anode materials with superior functionalities. In this study density functional theory was applied to reveal the microscopic picture of Li interaction with 15 2D crystals, including several transition metal oxides and dichalcogenides, carbides of Group XIV elements, functionalized graphene, silicene, and germanene, as well as black phosphorus and Ti2C MXene. We found that the general trend in Li binding can be estimated from positions of conduction band minima of 2D materials, since the energy of the lowest empty electronic states shows a nice correlation with the strength of Li adsorption. At variance to the majority of studied surfaces where the electron transferred from Li is spread across the substrate, in monolayers of carbides of Group XIV elements the interaction with Li and the charge transfer are well localized. This gives rise to their capability to accommodate Li structures with a nearly constant binding energy of alkaline atoms over Li coverages ranging from well-separated adatoms to a full monolayer. © 2018 American Physical Society.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

To Pave the Way for Large-Scale Electrode Processing of Moisture-Sensitive Ni-Rich Cathodes

High-capacity Ni-rich cathode such as LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) has a great potential to enable high energy lithium-ion batteries (LIBs) for long-range electrical vehicles. However, the utilization of NMC 811 in large-scale application is still challenging. While many published papers on NMC811 focus on materials modification, the moisture sensitivity of NMC811 and its implications in storage and large-scale electrode coating are not well explored, not to mention how to overcome those challenges for industry application. This work discusses the key parameters impacting the rheological properties of NMC811 slurries and their correlations to the properties of dried electrodes. Effective solutions are proposed to address the gelation issue of NMC811 slurry during large-scale coating to hopefully inspire more effective and practical approaches to tackle the grand challenges in electrochemical energy storage.

25 ENERGY STORAGE↗
DOE OSTI2018

Unveiling the Structural Evolution of Ag 1.2 Mn 8 O 16 under Coulombically Controlled (De)Lithiation

MnO 2 materials are considered promising cathode materials for rechargeable lithium, sodium, and magnesium batteries due to their earth abundance and environmental friendliness. One polymorph of MnO 2 , α-MnO 2 , has 2 × 2 tunnels (4.6 Å × 4.6 Å) in its structural framework, which provide facile diffusion pathways for guest ions. In this work, a silver-ion-containing α-MnO 2 (Ag 1.2 Mn 8 O 16 ) is examined as a candidate cathode material for Li based batteries. Electrochemical stability of Ag 1.2 Mn 8 O 16 is investigated through Coulombically controlled reduction under 2 or 4 molar electron equivalents (e.e.). Terminal discharge voltage remains almost constant under 2 e.e. of cycling, whereas it continuously decreases under repetitive reduction by 4 e.e. Thus, detailed structural analyses were utilized to investigate the structural evolution upon lithiation. Significant increases in lattice a (17.7%) and atomic distances (~4.8%) are observed when x in Li x Ag 1.2 Mn 8 O 16 is >4. Ag metal forms at this level of lithiation concomitant with a large structural distortion to the Mn–O framework. In contrast, lattice a only expands by 2.2% and Mn–O/Mn-Mn distances show minor changes (~1.4%) at x < 2. The structural deformation (tunnel breakage) at x > 4 inhibits the recovery of the original structure, leading to poor cycle stability at high lithiation levels. This report establishes the correlation among local structure changes, amorphization processes, formation of Ag 0 , and long-term cycle stability for this silver-containing α-MnO 2 type material at both low and high lithiation levels.

36 MATERIALS SCIENCE↗
DOE OSTI2019

H 3 PO 4 treatment to enhance the electrochemical properties of Li(Ni 1/3 Mn 1/3 Co 1/3 )O 2 and Li(Ni 0.5 Mn 0.3 Co 0.2 )O 2 cathodes

In this paper, Li(Ni 1/3 Mn 1/3 Co 1/3 )O 2 (NMC333) and Li(Ni 0.5 Mn 0.3 Co 0.2 )O 2 (NMC532) have been subjected to a phosphoric acid (H 3 PO 4 ) solution treatment to form a thin Li 3 PO 4 coating on their surfaces. The Li 3 PO 4 coating formed is found to be very potent in enhancing the specific capacity of the first discharge as well as the rate capability and capacity retention in the subsequent charge/discharge cycles for both NMC333 and NMC532. The specific capacity of the first discharge for NMC532 has been increased drastically from ~160 mA h g –1 for pristine NMC532 to ~250 mA h g –1 for Li 3 PO 4 -coated counterpart at 0.1C and such a large capacity enhancement is retained throughout the subsequent cycles at 1C. The final specific capacity of Li 3 PO 4 -coated NMC532 is 187 mA h g –1 after 100 cycles at 1C, whereas the corresponding value of pristine NMC532 is only 50 mA h g –1 . The rate capability has also been improved significantly with Li 3 PO 4 -coated NMC532 exhibiting ~150 mA h g –1 capacity at 6C while pristine NMC532 showing zero capacity. Similar improvements have also been achieved with NMC333. These results demonstrate that the H 3 PO 4 treatment is a facile and general method to improve the electrochemical properties of NMCs with different compositions and can be utilized for practical applications.

25 ENERGY STORAGE↗
DOE OSTI2024

Origin of deactivation of aqueous Na–CO 2 battery and mitigation for long-duration energy storage

Here, the development of long-duration energy storage technology is crucial to facilitate the efficient utilization of renewable energy sources while mitigating carbon dioxide production. In this study, we investigate the deactivation and reactivation mechanisms of the aqueous Na–CO 2 battery during extended cycling. We have designed the cathode to include non-precious intermetallic catalysts. As the cell undergoes repeated cycles, the voltage polarization during discharge progressively rises, eventually leading to the cell's deactivation and formation of decomposition products clogging the electrode surface. Results obtained from comprehensive characterization techniques, including conductive atomic force microscopy (cAFM), Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and inductively coupled plasma-mass spectrometry provide insight into the decomposition products. We also showcase an electrochemical approach for regeneration of these aqueous cells. Our findings, along with the insights we have gained, provide a path toward creating long-duration systems with self-healing properties.

25 ENERGY STORAGE↗
DOE OSTI2026

Controlled Acidity Gradients Enable CO 2 Reduction to Formic Acid (Not Formate) by Molecular Electrocatalysts

Neutral or basic conditions are commonly required for the selective electrochemical reduction of CO 2 , leading to the accumulation of carbonate salts and the generation of formate rather than formic acid. A generalizable strategy for obtaining formic acid (not formate) in the electroreduction of CO 2 with molecular catalysts is introduced, based on controlling acidity gradients using a dual-electrolyte cell with a proton-exchange membrane. This approach uses anodic water oxidation as the source of protons and electrons for CO 2 reduction to formic acid, while mitigating H 2 evolution near the cathode and avoiding carbonate formation. Mechanistic studies, including systems modeling, provide insight into the origin of the formic acid selectivity and guide the broader implementation of this strategy in molecular electrocatalysis for CO 2 utilization.

Alcohols↗
NASA NTRS1980

Preliminary evaluation of time and distance spacing cues using a cockpit displayed target

A simulator evaluation was conducted to compare time and distance selfspacing cues wherein a pilot establishes and maintains separation from a cockpit displayed target. Langley's terminal configured vehicle simulator which represents an advanced aircraft employing cathode ray tubes for primary flight displays and highly augmented flight control modes was used. Three tasks, two in trail rendezvous tasks (target straight and level and target turning) and one merge task were utilized. Three pilots flew each task twice, once with a time predictor cue and once with a distance predictor. Both time and distance spacing methods are operationally acceptable to the pilots. A slight preference was indicated by the pilots for the distance based predictor in performing rendezvous and merging tasks. Analysis of the recorded data showed the spacing performance with both predictors was essentially the same.

Kelly, J. R.↗
DOE OSTI2019

Charge Distribution on S and Intercluster Bond Evolution in Mo 6 S 8 during the Electrochemical Insertion of Small Cations Studied by X-ray Absorption Spectroscopy

Mo 6 S 8 is regarded as a promising cathode material in rechargeable Mg batteries. Despite extensive studies, some fundamental questions are still unclarified, including the origination of the chemical stability, key factors inducing the structural evolution, and the factors determining the electrochemical reversibility. In this work, Mo L 2,3 and S K-edge X-ray absorption spectroscopy are utilized to uncover the underlying mechanism. Two kinds of S with different effective charge are found, indicating the nonuniform charge distribution. With one cation inserted, the charge distribution becomes homogeneous, relevant to the chemical stability and electrochemical reversibility. The structural evolution is attributed to the change of bond length induced by the delocalization of inserted cations. Moreover, the evolution of intercluster Mo-Mo bond length can be revealed by the drastic change of the S K pre-edge and is closely related to the electrochemical reversibility. This study can shed light on the aforementioned questions and guide the development of Mg cathode material.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Fundamental Understanding of Water‐Induced Mechanisms in Li–O 2 Batteries: Recent Developments and Perspectives

Abstract Modern sustainability challenges in recent years have warranted the development of new energy storage technologies. Practical realization of the lithium–O 2 battery holds great promise for revolutionizing energy storage as it holds the highest theoretical specific energy of any rechargeable battery yet discovered. However, the complete realization of Li–O 2 batteries necessitates ambient air operations, which presents quite a few challenges, as carbon dioxide (CO 2 ) and water (H 2 O) contaminants introduce unwanted byproducts from side reactions that greatly affect battery performance. Although current research has thoroughly explored the beneficial incorporation of CO 2 , much mystery remains over the inconsistent effects of H 2 O. The presence of water in both the cathode and electrolyte has been observed to alter reaction mechanisms differently, resulting in a diverse range of effects on voltage, capacity, and cyclability. Moreover, recent preliminary research with catalysts and redox mediators has attempted to utilize the presence of water to the battery's benefit. Here, the key mechanism discrepancies of water‐afflicted Li–O 2 batteries are presented, concluding with a perspective on future research directions for nonaqueous Li–O 2 batteries.

Dai, Alvin↗
DOE OSTI2019

PdMo bimetallene for oxygen reduction catalysis

The efficient interconversion of chemicals and electricity through electrocatalytic processes is central to many renewable-energy initiatives. The sluggish kinetics of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) has long posed one of the biggest challenges in this field, and electrocatalysts based on expensive platinum-group metals are often required to improve the activity and durability of these reactions. The use of alloyingsurface strain and optimized coordination environments has resulted in platinum-based nanocrystals that enable very high ORR activities in acidic media; however, improving the activity of this reaction in alkaline environments remains challenging because of the difficulty in achieving optimized oxygen binding strength on platinum-group metals in the presence of hydroxide. Here we show that PdMo bimetallene—a palladium–molybdenum alloy in the form of a highly curved and sub-nanometre-thick metal nanosheet—is an efficient and stable electrocatalyst for the ORR and the OER in alkaline electrolytes, and shows promising performance as a cathode in Zn–air and Li–air batteries. The thin-sheet structure of PdMo bimetallene enables a large electrochemically active surface area (138.7 square metres per gram of palladium) as well as high atomic utilization, resulting in a mass activity towards the ORR of 16.37 amperes per milligram of palladium at 0.9 volts versus the reversible hydrogen electrode in alkaline electrolytes. This mass activity is 78 times and 327 times higher than those of commercial Pt/C and Pd/C catalysts, respectively, and shows little decay after 30,000 potential cycles. Density functional theory calculations reveal that the alloying effect, the strain effect due to the curved geometry, and the quantum size effect due to the thinness of the sheets tune the electronic structure of the system for optimized oxygen binding. Finally, given the properties and the structure–activity relationships of PdMo metallene, we suggest that other metallene materials could show great promise in energy electrocatalysis.

25 ENERGY STORAGE↗
DOE OSTI2024

Quantifying the Entropy and Enthalpy of Insertion Materials for Battery Applications Via the Multi-Species, Multi-Reaction Model

The entropy coefficient of a battery cell is the property that governs the amount of reversible heat that is generated during operation. In this work, we propose an extension of the Multi-Species, Multi-Reaction (MSMR) model to capture the entropy coefficient of a large format lithium-ion battery cell. We utilize the hybridized time-frequency domain analysis (HTFDA) method using a multi-functional calorimeter to probe the entropy coefficient of a large format pouch type lithium-ion battery with a NMC 811 cathode and a graphite anode. The measured entropy coefficient profile of the battery cell is deconvoluted into an entropy coefficient for each active material, which is then estimated using an extension of the MSMR model. Finally, we extend the entropy of a material to individual entropy for each gallery as treated by the model.

Electrochemistry↗