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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 721 records · Page 40
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Inhibiting collective cation migration in Li-rich cathode materials as a strategy to mitigate voltage hysteresis

Lithium-rich cathodes are promising energy storage materials due to their high energy densities. However, voltage hysteresis, which is generally associated with transition metal migration, limits their energy efficiency and implementation in practical devices. Here we reveal that voltage hysteresis is related to the collective migration of metal ions, and that isolating the migration events from each other by creating partial disorder can create high-capacity reversible cathode materials, even when migrating transition metal ions are present. In this study, we demonstrate this on a layered Li-rich chromium manganese oxide that in its fully ordered state displays a substantial voltage hysteresis (>2.5 V) associated with collective transition metal migration into Li layers, but can be made to achieve high capacity (>360 mAh g –1 ) and energy density (>1,100 Wh kg –1 ) when the collective migration is perturbed by partial disorder. This study demonstrates that partially cation-disordered cathode materials can accommodate a high level of transition metal migration, which broadens our options for redox couples to those of mobile cations.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Severe, short-term sleep restriction reduces gut microbiota community richness but does not alter intestinal permeability in healthy young men

Sleep restriction alters gut microbiota composition and intestinal barrier function in rodents, but whether similar effects occur in humans is unclear. This study aimed to determine the effects of severe, short-term sleep restriction on gut microbiota composition and intestinal permeability in healthy adults. Fecal microbiota composition, measured by 16S rRNA sequencing, and intestinal permeability were measured in 19 healthy men (mean ± SD; BMI 24.4 ± 2.3 kg/m 2 , 20 ± 2 years) undergoing three consecutive nights of adequate sleep (AS; 7–9 h sleep/night) and restricted sleep (SR; 2 h sleep/night) in random order with controlled diet and physical activity. α-diversity measured by amplicon sequencing variant (ASV) richness was 21% lower during SR compared to AS (P = 0.03), but α-diversity measured by Shannon and Simpson indexes did not differ between conditions. Relative abundance of a single ASV within the family Ruminococcaceae was the only differentially abundant taxon (q = 0.20). No between-condition differences in intestinal permeability or β-diversity were observed. Findings indicated that severe, short-term sleep restriction reduced richness of the gut microbiota but otherwise minimally impacted community composition and did not affect intestinal permeability in healthy young men.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2016

Modification of Ni-Rich FCG NMC and NCA Cathodes by Atomic Layer Deposition: Preventing Surface Phase Transitions for High-Voltage Lithium-Ion Batteries

The energy density of current lithium-ion batteries (LIBs) based on layered LiMO 2 cathodes (M=Ni, Mn, Co: NMC; M=Ni, Co, Al: NCA) needs to be improved significantly in order to compete with internal combustion engines and allow for widespread implementation of electric vehicles (EVs). In this report, we show that atomic layer deposition (ALD) of titania (TiO 2 ) and alumina (Al 2 O 3 ) on Ni-rich FCG NMC and NCA active material particles could substantially improve LIB performance and allow for increased upper cutoff voltage (UCV) during charging, which delivers significantly increased specific energy utilization. Our results show that Al2O3 coating improved the NMC cycling performance by 40% and the NCA cycling performance by 34% at 1C/₋1C with respectively 4.35V and 4.4V UCV in 2Ah pouch cells. High resolution TEM/SAED structural characterization revealed that Al 2 O 3 coatings prevented surface-initiated layered-to-spinel phase transitions in coated materials which were prevalent in uncoated materials. Lastly, EIS confirmed that Al 2 O 3 -coated materials had significantly lower increase in the charge transfer component of impedance during cycling. In conclusion, the ability to mitigate degradation mechanisms for Ni-rich NMC and NCA illustrated in this report provides insight into a method to enable the performance of high-voltage LIBs.

25 ENERGY STORAGE↗
DOE OSTI2017

Relating surface roughness and magnetic domain structure to giant magneto-impedance of Co-rich melt-extracted microwires

Understanding the relationship between the surface conditions and giant magneto-impedance (GMI) in Co-rich melt-extracted microwires is key to optimizing their magnetic responses for magnetic sensor applications. The surface magnetic domain structure (SMDS) parameters of ~45 μm diameter Co 69.25 Fe 4.25 Si 13 B 13.5-x Zr x (x = 0, 1, 2, 3) microwires, including the magnetic domain period (d) and surface roughness (Rq) as extracted from the magnetic force microscopy (MFM) images, have been correlated with GMI in the range 1–1000 MHz. It was found that substitution of B with 1 at. % Zr increased d of the base alloy from 729 to 740 nm while retaining Rq from ~1 nm to ~3 nm. A tremendous impact on the GMI ratio was found, increasing the ratio from ~360% to ~490% at an operating frequency of 40 MHz. Further substitution with Zr decreased the high frequency GMI ratio, which can be understood by the significant increase in surface roughness evident by force microscopy. Lastly, this study demonstrates the application of the domain period and surface roughness found by force microscopy to the interpretation of the GMI in Co-rich microwires.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Probing the initiation of voltage decay in Li-rich layered cathode materials at the atomic scale

Li-rich layered oxides hold great promise for improving the energy density of present-day Li-ion batteries. However, their application is limited by the voltage decay upon cycling, and the origin of such a phenomenon is poorly understood. A major issue is determining the voltage range over which detrimental reactions originate. In the present study, a unique yet effective approach was employed to probe this issue. Instead of studying the materials during the first cycle, electrochemical behavior and evolution of the atomic structures were compared in extensively cycled specimens under varied charge/discharge voltages. With the upper cutoff voltage lowered from 4.8 to 4.4 V, the voltage decay ceased to occur even after 60 cycles. In the meantime, the material maintained its layered structure without any spinel phase emerging at the surface, which is unambiguously shown by the atomic-resolution Z-contrast imaging and electron energy loss spectroscopy. These results have conclusively demonstrated that structural/chemical changes responsible for the voltage decay began between 4.4 and 4.8 V, where the layered-to-spinel transition was the most dramatic structural change observed. Thus, this discovery lays important groundwork for the mechanistic understanding of the voltage decay in Li-rich layered cathode materials.

25 ENERGY STORAGE↗
DOE OSTI2018

Occurrence and formation of incidental metallic Cu and CuS nanoparticles in organic-rich contaminated surface soils in Timmins, Ontario

This study investigates the fate of Cu in organic-rich soils contaminated by mining related activities at the Timmins Kidd Creek metallurgical site, Ontario, Canada. The surficial soil layers (top 5 cm) contain on average 13000 ppm Cu, predominantly in the form of Cu–Fe-sulfide particulate matter (PM) attached to organic residues. The sequestration of Cu by organic material (OM) is investigated with a combination of focused ion beam (FIB) technology and transmission electron microscopy (TEM). FIB sections are extracted from the interior of OM as well as along the interface between OM and a Cu–Fe sulfide grain. Nanoscale analyses show that Cu occurs as incidental metallic Cu and covellite (CuS) nanoparticles (NPs) within the OM. These NPs can occur along the interface towards attached Cu–Fe sulfide grains (e.g. mooihoekite Cu9Fe9S16, talnakhite Cu9?Fe,Ni)8S16), in remote pore spaces in the interior of the OM, and in association with magnetite precipitates within the OM. These occurrences indicate that Cu is sequestered by OM through various redox and precipitation mechanisms, induced by ferrous iron or humic substances. This sequestration process is thus similar to the formation of supergene Cu-ore deposits where the dissolution of primary ore minerals (e.g. chalcopyrite CuFeS2) and the subsequent precipitation of secondary sulfides (chalcocite Cu2S, covellite) result in an enrichment of Cu. Furthermore, the extraction of the colloidal (mobile) fraction of the upper 1 cm of the studied soil (through column experiments and ultra-centrifugation) indicate that Cu-bearing colloids are predominantly composed of incidental covellite NPs embedded within colloidal OM. The speciation of Cu within organic residues and colloids indicates that Cu is recycled in surficial organic-rich soil through repetition of (a) sequestration processes within OM, (b) decomposition of OM resulting in the release of Cubearing incidental NPs, and (c) re-adsorption to newly formed OM as solutes or incidental NPs.

Mantha, Haley↗
DOE OSTI2018

Insights into Li/Ni ordering and surface reconstruction during synthesis of Ni-rich layered oxides

Nickel-rich layered transition metal oxides (NMCs) have been intensively studied as promising cathode candidates for next-generation Li-ion batteries, known for low cost and high theoretical capacity. However, the practical capacity of NMCs is largely determined by cationic ordering and has yet to be well controlled during synthesis, largely due to the complexity and non-equilibrium nature of the reactions occurring in the sintering process. In this work, high-energy synchrotron X-ray diffraction is employed to investigate the kinetic and thermodynamic aspects of cationic ordering during synthesis of LiNi 0.7 Mn 0.15 Co 0.15 O 2 (NMC71515). It is found that cationic ordering in the bulk is coupled to surface reconstruction during synthesis, occurring concomitantly and both being greatly affected by Li 2 CO 3 decomposition and Li loss at the particle surface. Through tuning the sintering temperature and time, highly ordered NMC71515 with high capacity and excellent rate capability is synthesized. The developed approach may be applied broadly to the synthesis of high-performance Ni-rich NMC and other cathode materials.

25 ENERGY STORAGE↗
DOE OSTI2019

Solid-state hydrogen rich boron–nitrogen compounds for energy storage

Boron compounds have a rich history in energy storage applications, ranging from high energy fuels for advanced aircraft to hydrogen storage materials for fuel cell applications. In this paper we review some of the aspects of energy storage materials comprised of electron-poor boron materials combined with electron-rich nitrogen elements with the goal of moderate temperature release of hydrogen. The parent compounds of ammonium borohydride, ammonia borane, and diammoniate of diborane provide approaches for storing high gravimetric and volumetric densities of hydrogen. Here we provide a review with a historical perspective and current developments in the area of solid state B and N containing compounds. This review highlights developments in synthesis of ammonia borane and its derivatives over the last 80 years. Thermodynamics and kinetics of hydrogen release in the solid state are discussed. By changing either substituents on the boron and nitrogen atoms or the physical environment by embedding in mesoporous scaffolds, the thermodynamics can be modified to reduce the exothermicity of hydrogen release and minimize formation of volatile impurities. Several mechanistic studies are reviewed identifying the key distinctions between homopolar and heteropolar H 2 release. Strategies for economical and efficient regeneration of the hydrogen storage materials via chemical transformation are critically reviewed. The limited efficiency of these chemical regeneration has limited some of the potential applications.

25 ENERGY STORAGE↗
DOE OSTI2021

Enabling stable and high-rate cycling of a Ni-rich layered oxide cathode for lithium-ion batteries by modification with an artificial Li⁺-conducting cathode-electrolyte interphase

Ni-rich LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) cathodes are investigated to realize high energy density Li ion batteries for long life electric vehicle applications. However, capacity decay and thermal instability due to cathode-electrolyte interfacial degradation remain challenges that require sophisticated surface stabilization methods to address. Here, we propose a strategy, for the first time, to form an artificial Li + -conducting cathode-electrolyte interphase (ALCEI) on the NCM811 cathode surface using a nucleophilic reaction between polysulfides and vinylene carbonate (VC). Furthemore, the as-formed ALCEI layer simultaneously protects the NCM particles from electrolyte corrosion and facilitates Li + ion transport, thus enabling stable and high rate cycling of NCM811. As a result, the ALCEI-modified NCM811 cathode exhibits a high capacity (211.6 mA h g -1 at 0.1C), notable rate capability (134 mA h g -1 at 10C), and superior cycle stability (94.2% over 200 cycles at 1C). These results underscore the use of interfacial engineering in high voltage cathode material development and provide a feasible strategy for stabilizing Ni-rich cathode interfaces in practical Li ion battery applications.

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

Chemical and structural evolutions of Li–Mn-rich layered electrodes at different current densities

Although the two active redox centers in Li-rich cathodes, including the anionic and cationic contributions, can enable Li-ion batteries to achieve outstanding specific energy, their behaviors at different current densities have not been clarified. In this report we provide a comparative study of transition metals (TMs) and oxygen redox activities by directly accessing their oxidation states in Li-rich materials operated at very different current rates. Our data reveal that the oxidation of oxygen in the near-surface region is at the same level for electrodes cycled with a wide range of current rates, indicating a reaction gradient of lattice oxygen redox reactions. The oxidation process of lattice oxygen is found to be dynamically compatible with that of the TMs. Combining the results of first principles calculations and complementary experimental findings, we propose a detailed mechanism of structural distortion from octahedral Li to tetrahedral Li and the role of oxygen vacancy in Li + diffusion. It is found that fast delithiation occurring at high current densities can easily cause local structural transformation, leading to a limited Li + diffusion rate and consequently suppressing rate capability.

25 ENERGY STORAGE↗
DOE OSTI2023

An in situ formed inorganic conductive network enables high stability and rate capability of single-crystalline nickel-rich cathodes

Single-crystalline Ni-rich cathodes are promising for the next generation of high-energy-density Li-ion batteries due to their better capacity retention than their polycrystalline counterparts. However, there is still much room for improving the electrochemical performances when considering their surface degradation and severe kinetic hindrance during cycling. Herein, we report a strategy to construct an in situ formed robust Li-conductive Li 3 PO 4 layer on the surface of cathode particles. This Li-conductive layer significantly increases the Li-ion diffusion coefficients and suppresses detrimental surface phase transformation. In situ XRD reveals that the improved kinetics alleviate the local stress at high voltage. The as-prepared single-crystalline LiNi 0.83 Co 0.12 Mn 0.05 O 2 delivers good durability (96.8% after 100 cycles at 1C) and excellent rate capability (177.08 mA h g -1 at 5C). Here, this work provides a facile and efficient strategy to improve the cycling performance and boost the rate capability of single-crystalline Ni-rich cathodes.

25 ENERGY STORAGE↗
DOE OSTI2026

Novel architectures for stabilization of Mn-rich cathodes: a high-valent approach to interfaces

Lithium- and manganese-rich (LMR) layered oxides continue to generate significant interest as promising, earth-abundant cathode materials for next-generation Li-ion batteries. In spite of their attractive capacity and cost advantages, a few long-standing challenges still hamper their widespread adoption, with manganese dissolution being one of the most persistent and vexing issues. In the present study, we explore the incorporation of Sb5+ as a high-valent cation and exploit its ability to form unique lithium-rich surface and grain-boundary structures that can integrate directly with the LMR lattice. When synthesized under appropriate conditions, Sb5+ orders strongly with Li+ to form localized Li+–Sb5+ motifs, which play a key role in restructuring the surface and grain-boundary regions. These restructured regions act as protective, stabilizing entities that substantially suppress electrolyte-driven side reactions, reduce impedance growth, limit manganese dissolution, and help retain cyclable lithium during long-term electrochemical cycling. Further improvements of the electrochemical performance of Sb-treated LMR were achieved using a well-known additive to mitigate Mn dissolution and highlight the synergistic effects of combined strategies. Overall, this work showcases how high-valent elements such as Sb5+ can help tailor the surface and intergranular regions and work in synergy with other modifiers (e.g. electrolyte additives), enhancing the cycle life and practical viability of LMR cathodes for use in graphite-based full cells.

Mallick, Subhadip [Argonne National Laboratory (AN↗
DOE OSTI2021

SN 2018ijp: the explosion of a stripped-envelope star within a dense H-rich shell?

In this work, we discuss the outcomes of the follow-up campaign of SN 2018ijp, discovered as part of the Zwicky Transient Facility survey for optical transients. Its first spectrum shows similarities to broad-lined Type Ic supernovae around maximum light, whereas later spectra display strong signatures of interaction between rapidly expanding ejecta and a dense H-rich circumstellar medium, coinciding with a second peak in the photometric evolution of the transient. This evolution, along with the results of modeling of the first light-curve peak, suggests a scenario where a stripped star exploded within a dense circumstellar medium. The two main phases in the evolution of the transient could be interpreted as a first phase dominated by radioactive decays, and a later interaction-dominated phase where the ejecta collide with a pre-existing shell. We therefore discuss SN 2018jp within the context of a massive star depleted of its outer layers exploding within a dense H-rich circumstellar medium.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

Negative ion rich plasmas in continuous and pulsed wave modes in a minimum-B magnetic field

Generation of hydrogen negative ion rich plasmas is investigated in continuous wave (CW) and pulse modulated (PM) wave modes of 2.45 GHz in a minimum-B magnetic field. The waves are launched directly into the plasma device and utilize wave particle resonances for high density plasma generation. In CW operation, the chamber is divided into two sections, namely, the source and downstream region, separated by a transverse magnetic field that allows only cold electrons ({approx}1 eV) into the downstream region helpful for the generation of negative ions. The H{sup -} density is measured by the second derivative beat method and is compared with the values obtained from a steady state model and the extracted current density. In the pulsed mode, temporal filtering generates negative ion rich plasmas in the afterglow phase. The H{sup -} density in the afterglow is estimated using saturation current ratio method and the results are compared with a time dependent model using particle balance equations. The essential idea in both the filtering techniques is to assist generation of negative ions and prevent its destruction by hot electrons.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

Carbon-rich icosahedral boron carbide designed from first principles

The carbon-rich boron-carbide (B{sub 11}C)C-C has been designed from first principles within the density functional theory. With respect to the most common boron carbide at 20% carbon concentration B{sub 4}C, the structural modification consists in removing boron atoms from the chains linking (B{sub 11}C) icosahedra. With C-C instead of C-B-C chains, the formation of vacancies is shown to be hindered, leading to enhanced mechanical strength with respect to B{sub 4}C. The phonon frequencies and elastic constants turn out to prove the stability of the carbon-rich phase, and important fingerprints for its characterization have been identified.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Role of silicon excess in Er-doped silicon-rich nitride light emitting devices at 1.54 μm

Erbium-doped silicon-rich nitride electroluminescent thin-films emitting at 1.54 μm have been fabricated and integrated within a metal-oxide-semiconductor structure. By gradually varying the stoichiometry of the silicon nitride, we uncover the role of silicon excess on the optoelectronic properties of devices. While the electrical transport is mainly enabled in all cases by Poole-Frenkel conduction, power efficiency and conductivity are strongly altered by the silicon excess content. Specifically, the increase in silicon excess remarkably enhances the conductivity and decreases the charge trapping; however, it also reduces the power efficiency. The main excitation mechanism of Er{sup 3+} ions embedded in silicon-rich nitrides is discussed. The optimum Si excess that balances power efficiency, conductivity, and charge trapping density is found to be close to 16%.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Electrical transport properties of (BN)-rich hexagonal (BN)C semiconductor alloys

The layer structured hexagonal boron nitride carbon semiconductor alloys, h-(BN)C, offer the unique abilities of bandgap engineering (from 0 for graphite to ∼6.4 eV for h-BN) and electrical conductivity control (from semi-metal for graphite to insulator for undoped h-BN) through alloying and have the potential to complement III-nitride wide bandgap semiconductors and carbon based nanostructured materials. Epilayers of (BN)-rich h-(BN){sub 1-x}(C{sub 2}){sub x} alloys were synthesized by metal-organic chemical vapor deposition (MOCVD) on (0001) sapphire substrates. Hall-effect measurements revealed that homogeneous (BN)-rich h-(BN){sub 1-x}(C{sub 2}){sub x} alloys are naturally n-type. For alloys with x = 0.032, an electron mobility of about 20 cm{sup 2}/Vs at 650 °K was measured. X-ray photoelectron spectroscopy (XPS) was used to determine the chemical composition and analyze chemical bonding states. Both composition and chemical bonding analysis confirm the formation of alloys. XPS results indicate that the carbon concentration in the alloys increases almost linearly with the flow rate of the carbon precursor (propane (C{sub 3}H{sub 8})) employed during the epilayer growth. XPS chemical bonding analysis showed that these MOCVD grown alloys possess more C-N bonds than C-B bonds, which possibly renders the undoped h-(BN){sub 1-x}(C{sub 2}){sub x} alloys n-type and corroborates the Hall-effect measurement results.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Molecular switches in carbon-rich organometallic compounds: Theoretical aspects

Organometallic complexes associated with an appropriate choice of ancillary ligands reveal to have a wide range of physical properties leading to promising applications when incorporated in nano-size devices. The challenge is to design innovative multifunctional compounds based on redox active carbon-rich organometallics associated with spin carriers and/or photochromic units. A multidisciplinary approach in this area has proved to be efficient in a series a systems combining carbon-rich bridging ligands and redox metallic moieties. In this domain, the role of theoretical investigations based on quantum mechanics tools have a crucial role in rationalizing and in helping designing systems possessing target properties.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗