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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 1,045 records · Page 58
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Phosphorus-Rich Colloidal Cobalt Diphosphide (CoP 2 ) Nanocrystals for Electrochemical and Photoelectrochemical Hydrogen Evolution

Developing earth-abundant and efficient electrocatalysts for photoelectrochemical water splitting is critical to realizing a high-performance solar-to-hydrogen energy conversion process. Here in this paper, phosphorus-rich colloidal cobalt diphosphide nanocrystals (CoP 2 NCs) are synthesized via hot injection. The CoP 2 NCs show a Pt-like hydrogen evolution reaction (HER) electrocatalytic activity in acidic solution with a small overpotential of 39 mV to achieve -10 mA cm -2 and a very low Tafel slope of 32 mV dec -1 . Density functional theory (DFT) calculations reveal that the high P content both physically separates Co atoms to prevent H from over binding to multiple Co atoms, while simultaneously stabilizing H adsorbed to single Co atoms. The catalytic performance of the CoP 2 NCs is further demonstrated in a metal–insulator–semiconductor photoelectrochemical device consisting of bottom p-Si light absorber, atomic layer deposition Al–ZnO passivation layers, and the CoP 2 cocatalyst. The p-Si/AZO/TiO 2 /CoP 2 photocathode shows a photocurrent density of -16.7 mA cm -2 at 0 V versus reversible hydrogen electrode (RHE) and an output photovoltage of 0.54 V. The high performance and stability are attributed to the junction between p-Si and AZO, the corrosion-resistance of the pinhole-free TiO 2 protective layer, and the fast HER kinetics of the CoP 2 NCs.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Ultrafast Heterogeneous Nucleation Enables a Hierarchical Surface Configuration of Lithium‐Rich Layered Oxide Cathode Material for Enhanced Electrochemical Performances

Abstract Lithium‐rich layered oxides have attracted much attention for the high energy density, but they still suffer from cycling degradation and sluggish kinetic capability. In the present study, a novel modification of Li 1.143 Mn 0.544 Ni 0.136 Co 0.136 O 2 sphere cathode materials by a hierarchical surface configuration is proposed, which integrates advantages of dual oxide layers of both amorphous and nanocrystalline Al 2 O 3, as well as an inner spinel membrane. Mainly promoted by an ultrafast heterogeneous nucleation of Al(NO) 3 nanoseeds caused by huge solubility differences, it only takes several minutes for pretreatment. After common annealing at low temperature, the obtained material is capable to deliver a high discharge capacity of 296.3 mAh g −1 with initial Coulombic efficiency of 92.9% at 0.1 C rate, and maintain stable cycling at both 0.2 and 0.5 C rates. Besides, rate performances are also enhanced as a result of the superior interface gained after surface modification, which produces reduced polarization during cycling. Through comprehensive analyses, improved surface property and stability are confirmed as the key to these enhancements. This strategy is anticipated to inspire new modification designs in future high energy density cathode materials.

Guo, Haocheng↗
DOE OSTI2018

Silicon Oxide‐Rich Diamond‐Like Carbon: A Conformal, Ultrasmooth Thin Film Material with High Thermo‐Oxidative Stability

Abstract Silicon oxide‐containing diamond‐like carbon (a‐C:H:Si:O) films are a promising class of protective coatings for environmentally‐demanding applications owing to their lower residual stresses and superior thermal stability and oxidation resistance relative to undoped diamond‐like carbon. However, existing versions of a‐C:H:Si:O deposited by traditional methods such as plasma‐enhanced chemical vapor deposition (PECVD) undergo substantial degradation and oxidation at temperatures above 250 °C. This, together with the difficulty of PECVD in depositing conformal coatings on complex geometries such as high‐aspect‐ratio features, has limited the applicability of a‐C:H:Si:O. Here, the unique capabilities of plasma immersion ion implantation and deposition (PIIID) to grow silicon oxide‐rich diamond‐like carbon materials that are ultrasmooth, continuous, and conformal on high‐aspect‐ratio topographies are explored. The high concentration of silicon and oxygen in PIIID‐grown films (23 ± 5 at.% and 11 ± 4 at.%, respectively) is unrivalled for this class of materials, and drastically increases the resistance to oxidation at high temperatures, compared with PECVD‐grown films. The results open the path for using a‐C:H:Si:O in applications involving exposure of materials to extreme environments.

Mangolini, Filippo↗
DOE OSTI2026

The Influence of Mesoscale Particle Structure on the Electrode Degradation and Resultant Electrochemistry of Lithium Ion Cells With Nickel Rich Lithium Nickel Manganese Cobalt Oxide Positive Electrodes

Nickel-rich lithium nickel manganese cobalt oxide, NMC (LiNi x Mn y Co z O 2 ), materials are desirable positive electrodes in lithium ion batteries, providing high capacity and energy density. The mesoscale structure of NMC materials is commonly a polycrystalline aggregate, providing opportunity for short lithium ion transport distance of the small primary particles, yet facile material handling due to the larger secondary particles. On (de)lithiation the NMC unit cell changes volume, where the anisotropic strain can result in secondary particle fracture. This secondary particle fracture process during cycling has been associated with several degradation modes of NMC materials in LIBs. In this work, a milling process was determined whereby the secondary particles could be pre-fractured with retention of the parent primary particle crystallographic structure, crystallite size, and morphology, providing the ability to unambiguously determine the influence of NMC secondary particle size and mesostructure on resultant functional behavior. The bulk and interfacial properties and electrochemistry of as-received commercially obtained polycrystal NMC811 (LiNi 0.8 Mn 0.1 Co 0.1 O 2 , PC NMC) and its milled MPC NMC counterpart were compared. The smaller secondary particle size, higher surface area MPC NMC was found to result in 1) greater cathode tortuosity, 2) reduced surface Ni on the cycled MPC cathodes consistent with surface reconstruction, and 3) increased Ni deposition on the anodes from cathode-anode crosstalk. These factors manifested in unfavorable electrochemical behavior of MPC with lower functional capacity at both 1C and C/10 rates and higher impedance over extended moderate voltage (dis)charge cycling.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Stabilized Co-Free Li-Rich Oxide Cathode Particles with An Artificial Surface Prereconstruction

Li-rich metal oxide (LXMO) cathodes have attracted intense interest for rechargeable batteries because of their high capacity above 250 mAh g –1 . However, the side effects of hybrid anion and cation redox (HACR) reactions, such as oxygen release and phase collapse that result from global oxygen migration (GOM), have prohibited the commercialization of LXMO. GOM not only destabilizes the oxygen sublattice in cycling, aggravating the well-known voltage fading, but also intensifies electrolyte decomposition and Mn dissolution, causing severe full-cell performance degradation. In this study, an artificial surface prereconstruction (ASR) for Li 1.2 Mn 0.6 Ni 0.2 O 2 particles with a molten-molybdate leaching is conducted, which creates a crystal-dense anion-redox-free LiMn 1.5 Ni 0.5 O 4 shell that completely encloses the LXMO lattice (ASR-LXMO). Differential electrochemical mass spectroscopy and soft X-ray absorption spectroscopy analyses demonstrate that GOM is shut down in cycling, which not only stabilizes HACR in ASR-LXMO, but also mitigates the electrolyte decomposition and Mn dissolution. ASR-LXMO displays greatly stabilized cycling performance as it retains 237.4 mAh g –1 with an average discharge voltage of 3.30 V after 200 cycles. More crucially, while the pristine LXMO cycling cannot survive 90 cycles in a pouch full-cell matched with a commercial graphite anode and lean (2 g A –1 h –1 ) electrolyte, ASR-LXMO shows high capacity retention of 76% after 125 cycles in full-cell cycling.

25 ENERGY STORAGE↗
DOE OSTI2023

Effect of the Nature of Both Cation and Anion Substitution on the Structural Symmetry of Li‐Rich 3 d ‐Metal Chalcogenide Electrodes

Abstract Li‐rich layered chalcogenides have recently led to better understanding of the anionic redox process and its associated high capacity while providing ways to overcome its practical limitations of voltage fade and irreversibility. This study reports on the feasibility of triggering anionic activity in Li 2 TiS 3 , through anionic substitution (Se for S) or cationic substitution (Fe for Ti). Herein, the chalcogenide chemical space is further explored to prepare mono‐substituted Li 1.7 Ti 0.85 Mn 0.45 Ch 3 (Ch = S/Se) and doubly substituted cationic and anionic phases (Li 1.7 Ti 0.85 Fe 0.45 S 3‐z Se z ) which crystallize either in the O3‐ or O1‐type structures depending upon substituents. All series show a bell‐shape capacity variation as function of the transition metal (TM) substitution degree with values up to 240 mAh g −1 . For specific compositions, a structural O3 to O1 phase transition is observed upon Li removal, which is not reversible upon Li re‐insertion due to kinetic limitations and negatively affects long‐term cycling performance. Density functional theory (DFT) calculations confirm the O3/O1 relative stability along the different series and point subtle electronic differences in the TM‐doping, rationalizing the structural and electrochemical behaviors of these phases upon cycling. These findings provide further insights into the link between structural and electronic stability, which is of key importance for designing chalcogenide‐based anionic redox compounds.

Chemistry↗
DOE OSTI2025

Solvent‐Phobic and Ionophilic Carboxylated Polythiophene Layer for Fluoride‐Rich Cathode Electrolyte Interphase

Abstract One focal area of contemporary organic mixed ionic‐electronic conductor (OMIEC) research relates to utilization of dual‐conductive properties to enhance the ion/electron transfer kinetics for energy storage applications. Insight regarding OMIEC response toward the electrolyte anion and solvent used in lithium‐ion batteries (LIBs), however, is limited. Here, for the first time, the solvent‐phobic and ionophilic (SP‐IP) properties of the OMIEC, poly[3‐(potassium‐4‐butanoate)thiophene‐2,5‐diyl] (P3KBT), are revealed through comprehensive evaluation and characterization. The solvent‐phobic characteristics arise from the cooperation of dispersive interaction, polar interaction, and hydrogen‐bonding between P3KBT and electrolyte solvent. The ionophilic nature is driven by electrostatic interactions between P3KBT side chain carboxylate groups and LiPF 6 , and the reversible electrochemical doping/de‐doping of the polythiophene backbone with PF 6 ⁻ . The SP‐IP properties induce formation of a LiF‐ rich , Li 2 CO 3 ‐ limited cathode electrolyte interphase (CEI) layer when a P3KBT coating layer is applied to the active material surface, significantly improving half‐cell life to over 1500 cycles at 2C.

Ren, Haoze [Department of Chemical and Bimolecular↗
DOE OSTI2021

Electric Dipole Polarizability of Neutron Rich Nuclei

We report that insights into the equation of state of neutron rich matter obtained from the neutron skin thickness of 208 Pb are in sharp conflict with earlier measurements of the electric dipole polarizability. A set of accurately calibrated energy density functionals are used to highlight the tension and to articulate how a highly-intense Gamma Factory may help resolve the present dilemma.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Ligand Transformations and Efficient Proton/Water Reduction with Cobalt Catalysts Based on Pentadentate Pyridine‐Rich Environments

Abstract A series of cobalt complexes with pentadentate pyridine‐rich ligands is studied. An initial Co II amine complex 1 is prone to aerial oxidation yielding a Co III imine complex 2 that is further converted into an amide complex 4 in presence of adventitious water. Introduction of an N‐methyl protecting group to the ligand inhibits this oxidation and gives rise to the Co II species 5 . Both the Co III 4 and Co II 5 show electrocatalytic H 2 generation in weakly acidic media as well as in water. Mechanisms of catalysis seem to involve the protonation of a Co II H species generated in situ.

Basu, Debashis↗
DOE OSTI2020

An Inorganic‐Rich Solid Electrolyte Interphase for Advanced Lithium‐Metal Batteries in Carbonate Electrolytes

Abstract In carbonate electrolytes, the organic–inorganic solid electrolyte interphase (SEI) formed on the Li‐metal anode surface is strongly bonded to Li and experiences the same volume change as Li, thus it undergoes continuous cracking/reformation during plating/stripping cycles. Here, an inorganic‐rich SEI is designed on a Li‐metal surface to reduce its bonding energy with Li metal by dissolving 4 m concentrated LiNO 3 in dimethyl sulfoxide (DMSO) as an additive for a fluoroethylene‐carbonate (FEC)‐based electrolyte. Due to the aggregate structure of NO 3 − ions and their participation in the primary Li + solvation sheath, abundant Li 2 O, Li 3 N, and LiN x O y grains are formed in the resulting SEI, in addition to the uniform LiF distribution from the reduction of PF 6 − ions. The weak bonding of the SEI (high interface energy) to Li can effectively promote Li diffusion along the SEI/Li interface and prevent Li dendrite penetration into the SEI. As a result, our designed carbonate electrolyte enables a Li anode to achieve a high Li plating/stripping Coulombic efficiency of 99.55 % (1 mA cm −2 , 1.0 mAh cm −2 ) and the electrolyte also enables a Li||LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NMC811) full cell (2.5 mAh cm −2 ) to retain 75 % of its initial capacity after 200 cycles with an outstanding CE of 99.83 %.

Liu, Sufu↗
DOE OSTI2013

Lithium Polysulfidophosphates: A Family of Lithium-Conducting Sulfur-Rich Compounds for Lithium-Sulfur Batteries

Given the great potential for improving the energy density of state-of-the-art lithium-ion batteries by a factor of 5, a breakthrough in lithium-sulfur (Li-S) batteries will have a dramatic impact in a broad scope of energy related fields. Conventional Li-S batteries that use liquid electrolytes are intrinsically short-lived with low energy efficiency. The challenges stem from the poor electronic and ionic conductivities of elemental sulfur and its discharge products. We report herein lithium polysulfidophosphates (LPSP), a family of sulfur-rich compounds, as the enabler of long-lasting and energy-efficient Li-S batteries. LPSP have ionic conductivities of 3.0 10-5 S cm-1 at 25 oC, which is 8 orders of magnitude higher than that of Li2S (~10-13 S cm-1). The high Li-ion conductivity of LPSP is the salient characteristic of these compounds that impart the excellent cycling performance to Li-S batteries. In addition, the batteries are configured in an all-solid state that promises the safe cycling of high-energy batteries with metallic lithium anodes.

batteries↗
DOE OSTI2017

Enhanced Carbon Dioxide Electroreduction to Carbon Monoxide over Defect-Rich Plasma-Activated Silver Catalysts

Efficient, stable catalysts with high selectivity for a single product are essential if electroreduction of CO 2 is to become a viable route to the synthesis of industrial feedstocks and fuels. A plasma oxidation pre-treatment of silver foil enhances the number of low-coordinated catalytically active sites, which dramatically lowers the overpotential and increases the activity of CO 2 electroreduction to CO. At -0.6 V versus RHE more than 90 % Faradaic efficiency towards CO was achieved on a pre-oxidized silver foil. While transmission electron microscopy (TEM) and operando X-ray absorption spectroscopy showed that oxygen species can survive in the bulk of the catalyst during the reaction, quasi in situ X-ray photoelectron spectroscopy showed that the surface is metallic under reaction conditions. Finally, DFT calculations reveal that the defect-rich surface of the plasma-oxidized silver foils in the presence of local electric fields drastically decrease the overpotential of CO 2 electroreduction.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Vacancy-Rich Monolayer BiO 2- x as a Highly Efficient UV, Visible, and Near-Infrared Responsive Photocatalyst

Here in this paper, a full-spectrum responsive vacancy-rich monolayer BiO 2-x has been synthesized. The increased density of states at the conduction band (CB) minimum in the monolayer BiO 2-x is responsible for the enhanced photon response and photo-absorption, which were confirmed by UV/Vis-NIR diffuse reflectance spectra (DRS) and photocurrent measurements. Compared to bulk BiO 2-x , monolayer BiO 2-x has exhibited enhanced photocatalytic performance for rhodamine B and phenol removal under UV, visible, and near-infrared light (NIR) irradiation, which can be attributed to the vacancy VBi-O"' as confirmed by the positron annihilation spectra. The presence of V Bi-O "' defects in monolayer BiO 2-x promoted the separation of electrons and holes. This finding provides an atomic level understanding for developing highly efficient UV, visible, and NIR light responsive photocatalysts.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Nitrogen–Rich Conjugated Macrocycles: Synthesis, Conductivity, and Application in Electrochemical CO 2 Capture

Here we report a series of nitrogen-rich conjugated macrocycles that mimic the structure and function of semiconducting 2D metal–organic and covalent organic frameworks while providing greater solution processability and surface tunability. Using a new tetraaminotriphenylene building block that is compatible with both coordination chemistry and dynamic covalent chemistry reactions, we have synthesized two distinct macrocyclic cores containing Ni–N and phenazine-based linkages, respectively. The fully conjugated macrocycle cores support strong interlayer stacking and accessible nanochannels. For the metal–organic macrocycles, good out-of-plane charge transport is preserved, with pressed pellet conductivities of 10 –3 S/cm for the nickel variants. Lastly, using electrochemically mediated CO2 capture as an example, we illustrate how colloidal phenazine-based organic macrocycles improve electrical contact and active site electrochemical accessibility relative to bulk covalent organic framework powders. Together, these results highlight how simple macrocycles can enable new synthetic directions as well as new applications by combining the properties of crystalline porous frameworks, the processability of nanomaterials, and the precision of molecular synthesis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Surface Vacancy Engineering Re-Routes First-Cycle Redox for Stabilized Li-Rich Layered Cathodes

We demonstrate that atomic-scale surface disorder can control the first-cycle redox sequence of Li-rich layered oxides, eliminating the detrimental process of oxygen release and lattice collapse that degrades performance. In Li1.14Ni0.32Mn0.54O2 (LNMO), a simple chemical treatment introduces oxygen and transition metal (TM) vacancies confined to the particle surface while preserving the bulk layered framework. Multi-modal synchrotron analyses reveal that these vacancies trigger an early oxygen oxidation below 4.4 V, delay nickel oxidation to higher potential, and suppress the formation of covalent Ni4+─O states. This modified pathway prevents irreversible oxygen release, suppresses manganese dissolution, and maintains metal-oxygen coordination at high voltages. Consequently, the treated cathode delivers higher first-cycle Coulombic efficiency (CE), mitigated voltage fade, and superior capacity retention. By directly linking engineered surface disorder to redox reactions and associated structural transformations, this work establishes a general design principle for durable, high-energy-density cathodes.

Kang, Seongkoo↗
DOE OSTI2015

Eliminating Voltage Decay of Lithium-Rich Li 1.14 Mn 0.54 Ni 0.14 Co 0.14 O 2 Cathodes by Controlling the Electrochemical Process

Lithium-rich material owns a particularly high capacity owing to the activation of electrochemical inactive Li 2 MnO 3 phase. But at the same time, MnO 2 phase formed after Li 2 MnO 3 activation confronts a severe problem of converting to spinel phase, and resulting in voltage decay. To our knowledge, this phenomenon is inherent property of layered manganese oxide materials and can hardly be overcome. Based on this, unlike previous reports, herein we design a method for the first time to accelerate the phase transformation by tuning the charge upper-limit voltage at a high value, so the phase transformation process can be finished in a few cycles. Then material structure remains stable while cycling at a low upper-limit voltage. By this novel method voltage decay is eliminated significantly.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Effects of Sugars, Furans, and their Derivatives on Hydrodeoxygenation of Biorefinery Lignin-Rich Wastes to Hydrocarbons

Hydrodeoxygenation of biorefinery lignin–rich wastes to jet fuel hydrocarbons offers a significant opportunity for enhancing the overall operational efficiency, carbon conversion efficiency, economic viability, and sustainability of biofuels production. However, these wastes usually mainly contain lignin with sugars, furans, and their derivatives as “impurities”. Although several factors, including reactant structure, solvents, or the decreased ratio of catalyst to reactant, could be responsible for the jet fuel hydrocarbons yield loss, we found evidence that glucose, xylose, and 5–hydroxymethylfurfural dramatically decreased conversion yields. For example, xylose and glucose lowered the final hydrocarbon yield by 78 and 63 %, respectively. The results revealed that these compounds could suppress metal catalysts and inhibit lignin depolymerization and hydrodeoxygenation (HDO) reactions thus decrease yields of jet fuel range hydrocarbons from biomass–derived lignin. As a result, the first–principles calculations and TGA results from spent catalysts validated these findings.

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

Supercapacitive properties of micropore- and mesopore-rich activated carbon in ionic liquid electrolytes with various constituent ions

Ionic-liquid (IL) electrolytes, characterized by large potential windows, intrinsic ionic conductivity, low environmental hazard, and high safety, are used for micropore- and mesopore-rich activated-carbon (AC micro and AC meso ) supercapacitors. IL electrolytes consisting of various cations [1-ethyl-3-methylimidazolium (EMI + ), N-propyl-N-methylpyrrolidinium (PMP + ), and N-butyl-N-methylpyrrolidinium (BMP + )] and various anions [bis(trifluoromethylsulfonyl)imide (TFSI - ), BF 4 - , and bis(fluorosulfonyl)imide (FSI-)] are investigated. The electrolyte conductivity, viscosity, and ion transport properties at the AC micro and ACmeso electrodes are studied. In addition, the capacitance, rate capability, and cycling stability of the two types of AC electrodes are systematically examined and post-mortem material analyses are conducted. The effects of IL composition on the charge–discharge capacitances of the AC micro electrodes are more pronounced than those for the AC meso electrodes. The FSI-based IL electrolytes, for which electrochemical properties are cation dependent, are found to be promising. Incorporating EMI + with FSI - results in a low electrolyte viscosity and a fast ion transport, giving rise to optimized electrode capacitance and rate capability. Replacing EMI + with PMP + increases the cell voltage (to 3.5 V) and maximum energy density (to 42-Wh kg -1 ) of the AC micro cell at the cost of cycling stability.

36 MATERIALS SCIENCE↗