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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Oxygen redox chemistry in P2-Na 0.6 Li 0.11 Fe 0.27 Mn 0.62 O 2 cathode for high-energy Na-ion batteries

Owing to the abundance of raw material reserves and low cost, Na-ion batteries (NIBs) have successfully gained widespread attention from academic and industrial communities in the past few decades. However, the insufficient cathode energy density is still one of the critical bottlenecks restricting the development of NIBs. Following a strategy of introducing Li+ into the transition-metal (TM) layer to enhance the oxygen redox reaction, a novel layered cathode material P2-Na 0.6 Li 0.11 Fe 0.27 Mn 0.62 O 2 (NLFMO) was designed and successfully synthesized. This NLFMO cathode not only delivers a large initial reversible capacity of 207.3 mA h g -1 , but also shows a good cycling performance (104.2 mA h g -1 after 80 cycles) and rate capability (126.2 mA h g -1 at 1C). The ultrahigh capacity is contributed by both cationic (Fe 3+ /Fe 4+ and Mn 3+ /Mn 4+ ) and partially reversible anionic redox (O 2- /O n- ) reactions, revealed by in situ X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) techniques. Moreover, no detrimental P2–O2 phase transition was observed in ex situ X-ray diffraction (XRD) patterns, confirming the high structural stability during Na + deintercalation/intercalation processes. These results provide valuable information about the high-energy density layered cathode materials based on anionic redox reactions for NIBs.

25 ENERGY STORAGE↗
DOE OSTI2020

Na-FeCl2 Batteries: A Low-Cost Durable Na-FeCl2 Battery with Ultrahigh Rate Capability (Adv. Energy Mater. 10/2020)

In article 1903472, Guosheng Li and co-workers report an advanced high-rate Na-FeCl2 battery using low cost NaCl and crust-rich Fe as cathode materials. The fast-charging capability of the Na-FeCl2 battery, rooted in a fast Fe/Fe2+ redox reaction, rapid NaCl-Na6FeCl8-FeCl2 phase transitions, and quick Fe2+ lattice diffusion within FeCl2, revamps the understanding of Na-metal halide batteries.

Zhan, Xiaowen↗
DOE OSTI2023

Topology driven and soft phonon mode enabled Na-ion diffusion in quaternary chalcogenides, Na 3 ZnGaX 4 (X = S, and Se)

The compounds Na 3 ZnGaX 4 (X = S, Se) are potential solid electrolyte materials in sodium-based batteries, which have certain advantages over oxide materials and have shown significant ionic conductivity at ambient temperature. In this paper, we bring out atomic-level features of the diffusion process in these new materials using the microscopic techniques of inelastic neutron scattering (INS), quasielastic neutron scattering (QENS), and ab initio molecular dynamics (AIMD) simulations. The insights obtained from these techniques are unique and not available from other macroscopic experiments. Neutron scattering experiments have been performed at temperatures from 100 to 700 K. The simulations have been carried out up to 900 K. We have calculated the phonon spectra and the space–time correlation functions and found good agreement with the results of the neutron scattering experiments. The simulations enable detailed analysis of the atomic-site dependent dynamical information. We observe low-energy phonon modes of ~6 meV involving the vibrations of certain Na atoms in the lattice. This reveals that the Na at 32g Wyckoff sites (Na2) has sufficiently shallow potential among the two available crystallographic sites. This shallow potential facilitates diffusion. Furthermore, the specific structural topology of the network of interconnected zig-zag chains of the Na2 atomic sites provides the low-barrier energy pathways for diffusion. A small fraction of vacancy defects appears essential for diffusion. We further observe that the Na2 atoms undergo jump-like diffusion to the vacant next or the 2nd next neighbour sites at ~4 Å. While the QENS experiments reveal the jump-like diffusion and its time scale, detailed analysis of the AIMD simulations shows that the jumps appear mostly along zig-zag chains of the Na2 sites in the tetragonal ab-plane, as well as between the chains along the c-axis. In conclusion, the net diffusion is essentially 3-dimensional, with little anisotropy despite the anisotropy of the tetragonal crystal structure.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Bobfinchite, Na[(UO2)8O3(OH)11]·10H2O, a new Na-bearing member of the schoepite family

Abstract The new mineral bobfinchite (IMA2020-082), Na[(UO2)8O3(OH)11]·10H2O, was found in the Burro mine, Slick Rock district, San Miguel County, Colorado, U.S.A., where it occurs as an oxidation product of uraninite on asphaltite matrix in intimate association with gypsum, natrozippeite, metaschoepite, and uranopilite. Bobfinchite crystals are transparent to translucent, yellow, lozenge-shaped disks up to 0.3 mm wide. Crystals are flattened on [100] and exhibit the forms {100}, {011}, {021}, {021}, and {011}. Bobfinchite has a pale-yellow streak and emits very dim yellow fluorescence under 365 nm ultraviolet illumination. The crystals are brittle with very good {100} cleavage and irregular, stepped fracture. The Mohs hardness is ca. 2 based on scratch tests. The calculated density is 5.044 g/cm3 based on the empirical formula and 5.036 g/cm3 for the ideal formula. Bobfinchite is optically biaxial (–), with α = 1.690(5), β = 1.7205(5), and γ = 1.730(5) (white light). The measured 2V, estimated from the interference figure, is 55(5)° and the calculated value is 59.1°. Dispersion is moderate, r > v; orientation: X = a, Y = b, Z = c; pleochroism: X nearly colorless, Y yellow, Z yellow; X < Y ≈Z. Electron microprobe analysis provided the empirical formula (Na0.99Pb0.02)[(UO2)7.99O3(OH)11]·10H2O. The five strongest X-ray powder diffraction lines are [dobs in Å(I)(hkl)]: 7.34(100)(200), 3.59(50)(024), 3.23(60)(224), 3.18(36)(240), and 2.01(23)(624,551,208,640,346). Bobfinchite is orthorhombic, Pbcn, a = 14.6249(9), b = 14.0389(10), c = 16.6923(10) Å, V = 3427.2(4) Å3, and Z = 4. The structure of bobfinchite (R1 = 0.0330 for 3770 I > 4σI) is built from uranyl oxide-hydroxide sheets that adopt the fourmarierite topology, with interlayer Na+ and H2O groups. Both the sheet and interlayer topology mimic those observed in natural and synthetic Na-metaschoepites studied previously, and as seen in other uranyl oxide hydrate minerals, charge balance is achieved at specific sites in the sheet through the substitution O2– ↔ (OH)–.

Geochemistry & Geophysics↗
DOE OSTI2020

Goldilocks and the three glymes: How Na+ solvation controls Na–O 2 battery cycling

In this work we report a framework to understand the role of solvent-salt interactions and how they mediate the performance of sodium-air/O 2 batteries. The utilization of suitable electrolyte materials remains a point of major concern within the research community, as their stability and decomposition pathways during cycling are intimately connected with capacity and cycle life. Glyme based solvents have been widely utilized in Na–O 2 batteries, however, to date no clear correlation between solvent/electrolyte properties and battery performance has been given. Herein, we have examined the effect of glyme chain length (ethylene glycol dimethyl ether DME; diethylene glycol dimethyl ether, DEGDME; and tetraethylene glycol dimethyl ether, TEGME) on the cycling behaviour of Na–O 2 batteries and conclude that overall cell performance is highly dependent on solvent selection, salt concentration and rate of discharge/charge. We demonstrate how solvent selection helps define cell chemistry and performance by linking salt-solvent interactions to enthalpy of dissolution - and subsequently to sodium battery electrolyte properties - through the combination of both experimental and theoretical methodologies. The approaches detailed in this study could be used to predictively prepare electrolytes for Li-air batteries, other glyme-based electrochemical systems and low temperature applications.

25 ENERGY STORAGE↗
DOE OSTI2020

Identification of a Na + -Binding Site near the Oxygen-Evolving Complex of Spinach Photosystem II

The oxygen-evolving complex (OEC) of photosystem II (PSII) is an oxomanganese cluster composed of four redox-active Mn ions, and one redox-inactive Ca 2+ ion, with two nearby bound Cl – ions. Sodium is a common counter-ion of both chloride and hydroxide anions, and a sodium-specific binding site has not been identified near the OEC. Furthermore, we find that the oxygen-evolution activity of spinach PSII increases with [Na + ], particularly at high pH. A Na + -specific binding site next to the OEC, upon deprotonation of the D1-H337 amino-acid residue, is suggested by the analysis of two recently published PSII cryo-EM maps in combination with quantum mechanical calculations and molecular dynamics simulations.

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

Ab initio free energies of liquid metal alloys: Application to the phase diagrams of Li-Na and K-Na

Comparison of free energies between different phases and different compositions underlies the prediction of alloy phase diagrams. To allow direct comparison, consistent reference points for the energies or enthalpies are required, and the entropy must be placed on an absolute scale, yielding absolute free energies. Here we derive absolute free energies of liquids from ab-initio molecular dynamics (AIMD) by combining the directly simulated enthalpies with an entropy derived from simulated densities and pair correlation functions. Additionally, as an example of the power of this method we calculate the phase diagrams of two binary alkali metal alloys, Li-Na and K-Na, revealing a critical point and liquid-liquid phase separation in the former case, and a deep eutectic in the latter. Good agreement with experimental data demonstrates the power of this simple method.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Na + -gated water-conducting nanochannels for boosting CO 2 conversion to liquid fuels

Robust, gas-impeding water-conduction nanochannels that can sieve water from small gas molecules such as hydrogen (H 2 ), particularly at high temperature and pressure, are desirable for boosting many important reactions severely restricted by water (the major by-product) both thermodynamically and kinetically. Identifying and constructing such nanochannels into large-area separation membranes without introducing extra defects is challenging. We found that sodium ion (Na + )–gated water-conduction nanochannels could be created by assembling NaA zeolite crystals into a continuous, defect-free separation membrane through a rationally designed method. Highly efficient in situ water removal through water-conduction nanochannels led to a substantial increase in carbon dioxide (CO 2 ) conversion and methanol yield in CO 2 hydrogenation for methanol production.

Science & Technology - Other Topics↗
DOE OSTI2021

Ab initio Molecular Dynamics Assessment of Thermodynamic and Transport Properties in (K,Li)Cl and (K, Na)Cl Molten Salt Mixtures

Molten salt mixtures are integral part of highly important technological applications such as nuclear reactors. However, due to inherent difficulties associated with experiment at high temperatures and the intrinsic complexity of liquid-phase multi-component systems, understanding their properties at a molecular level remains a challenge. Here, we report on an ab initio molecular dynamics investigation on structural, electronic, transport, and thermal properties of two common molten salt mixtures, (K, Li)Cl and (K,Na)Cl, at five different compositions and three temperatures. Most of the properties were found to depend on both composition and temperature. While properties, like atomic charges, show additive behaviors, other properties, such as electrical conductivity, show considerable deviations from additivity. We shall show that the mixing of the molten salt mixtures is mainly driven by entropy, and that the KCl and LiCl mix better than KCl and NaCl. Our computational results are in general consistent with available experimental data. Comparison with available theoretical data is also provided.

Nguyen, Manh Thuong↗
DOE OSTI2020

Salt Effects on Li-Ion Exchange Kinetics of Na 2 Mg 2 P 3 O 9 N: Systematic In Situ Synchrotron Diffraction Studies

The kinetics and thermodynamics of solid-state ion exchange of Li+ into Na2Mg2P3O9N were investigated using in situ synchrotron X-ray diffraction methods for a series of Li-containing salts, allowing systematic trends with general applicability to ion exchange reactions to be elucidated. The collection of data for a wide range of reaction conditions was enabled through the use of a novel multiwell sample environment which leverages the ability of the synchrotron beamline to rapidly (similar to 1 s) collect high-quality data suitable for monitoring reaction progress. From these data, it was possible to resolve the influence of salt choice and salt concentration on the ion exchange reaction kinetics. Furthermore, by carrying out experiments at different temperatures, initial estimates of activation energies were obtained. It was generally found that the ion exchange reaction kinetics strongly depended on the salt chosen as the ion source rather than being primarily determined by the ion mobility of the ceramic.

Cosby, Monty R.↗
DOE OSTI2020

Soft elastic constants from phonon spectroscopy in hole-doped Ba 1-x (K,Na) x Fe 2 As 2 and Sr 1-x Na x Fe 2 As 2

We report inelastic x-ray scattering measurements of the in-plane polarized transverse acoustic phonon mode propagating along q ∥ [ 100 ] in various hole-doped compounds belonging to the 122 family of iron-based superconductors. Additionally, the slope of the dispersion of this phonon mode is proportional to the square root of the shear modulus C 66 in the q → 0 limit and, hence, sensitive to the tetragonal to orthorhombic structural phase transition occurring in these compounds. In contrast to a recent report for Ba ( Fe 0.94 Co 0.06 ) 2 As 2 [Weber et al. , Phys. Rev. B 98 , 014516 (2018) ], we find qualitative agreement between values of C 66 deduced from our experiments and those derived from measurements of the Young modulus in Ba 1 - x ( K , Na ) x Fe 2 As 2 at optimal doping. These results provide an upper limit of about 50 Å for the nematic correlation length for the investigated optimally hole-doped compounds. Furthermore, we also studied compounds at lower doping levels exhibiting the orthorhombic magnetic phase, where C 66 is not accessible by volume probes, as well as the C 4 tetragonal magnetic phase.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗