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15 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Optimization of the compositions of polyanionic sodium-ion battery cathode NaFe 2-x V x (PO 4 )(SO 4 ) 2

Sodium (Na) super ionic conductor (NASICON) polyanionic compounds have recently attracted much attention from the battery community because of their electroactive properties and reasonably high ionic conductivities, leading to their use as a cathode in sodium-ion batteries. This article describes the compositional optimizations, crystallographic evaluations, and electrochemical behavior of a new mixed NASICON polyanionic compound, NaFe 2-x V x (PO 4 )(SO 4 ) 2 . By doping the characteristic Fe 3+ sites of the FeO 6 octahedrons with varying amounts of V 3+ , the electrochemical stability and charge transport in NaFe 2 (PO 4 )(SO 4 ) 2 were enhanced. The resulting best composition, with crystal structure NaFe 1.4 V 0.6 (PO 4 )(SO 4 ) 2 resolved through the Rietveld method, exhibited a stable capacity compared with the other synthesized compositions. In situ powder x-ray diffraction measurements, a single-phase intercalation/deintercalation mechanism of the NASICON structure in the measured sodium concentration window was observed with no impurity phase formation. Further electrochemical assessments revealed the interfacial charge transfer kinetics to be the rate-limiting step in the sodium concentration window. Also, the measured sodium-ion diffusivity values in the range of 6 × 10 -11 to 7 × 10 -11 cm 2 /s in the measured sodium concentration range. The results reported here highlight the potential of compositionally and morphologically optimized NaFe 1.4 V 0.6 (PO 4 )(SO 4 ) 2 with higher particle surface areas as a cathode material for high-performance sodium-ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2020

Materials Data on NaFe(SO)2 by Materials Project

NaFe(SO)2 crystallizes in the monoclinic C2/c space group. The structure is two-dimensional and consists of two NaFe(SO)2 sheets oriented in the (0, 1, 0) direction. Na1+ is bonded in a see-saw-like geometry to four equivalent O2- atoms. All Na–O bond lengths are 2.34 Å. Fe3+ is bonded to four equivalent S atoms to form edge-sharing FeS4 tetrahedra. There are two shorter (2.35 Å) and two longer (2.38 Å) Fe–S bond lengths. S is bonded in a 3-coordinate geometry to two equivalent Fe3+ and one O2- atom. The S–O bond length is 1.56 Å. O2- is bonded in a distorted trigonal planar geometry to two equivalent Na1+ and one S atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaFe(SO)2 by Materials Project

NaFe(SO)2 crystallizes in the monoclinic C2/c space group. The structure is two-dimensional and consists of two NaFe(SO)2 sheets oriented in the (0, 1, 0) direction. Na1+ is bonded in a see-saw-like geometry to four equivalent O2- atoms. There are two shorter (2.34 Å) and two longer (2.36 Å) Na–O bond lengths. Fe3+ is bonded in a distorted rectangular see-saw-like geometry to four equivalent S atoms. There are two shorter (2.33 Å) and two longer (2.36 Å) Fe–S bond lengths. S is bonded in a distorted trigonal non-coplanar geometry to two equivalent Fe3+ and one O2- atom. The S–O bond length is 1.56 Å. O2- is bonded in a distorted trigonal planar geometry to two equivalent Na1+ and one S atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaFe(SO4)2 by Materials Project

NaFe(SO4)2 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Na1+ is bonded in a distorted hexagonal planar geometry to six O2- atoms. There are two shorter (2.45 Å) and four longer (2.66 Å) Na–O bond lengths. Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six equivalent SO4 tetrahedra. There are two shorter (1.99 Å) and four longer (2.04 Å) Fe–O bond lengths. S6+ is bonded to four O2- atoms to form SO4 tetrahedra that share corners with three equivalent FeO6 octahedra. The corner-sharing octahedra tilt angles range from 36–45°. There are a spread of S–O bond distances ranging from 1.45–1.51 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to one Fe3+ and one S6+ atom. In the second O2- site, O2- is bonded in a 2-coordinate geometry to one Na1+ and one S6+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Fe3+, and one S6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaFe(MoO4)2 by Materials Project

NaFe(MoO4)2 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Na1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Na–O bond distances ranging from 2.45–2.77 Å. Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with three equivalent FeO6 octahedra. The corner-sharing octahedra tilt angles range from 22–52°. There are a spread of Mo–O bond distances ranging from 1.75–1.83 Å. Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six equivalent MoO4 tetrahedra. There are two shorter (2.00 Å) and four longer (2.03 Å) Fe–O bond lengths. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to one Mo6+ and one Fe3+ atom. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Na1+, one Mo6+, and one Fe3+ atom. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to one Na1+, one Mo6+, and one Fe3+ atom. In the fourth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Na1+ and one Mo6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaFe(SeO3)2 by Materials Project

NaFe(SeO3)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Na1+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Na–O bond distances ranging from 2.53–2.86 Å. Fe3+ is bonded in an octahedral geometry to six O2- atoms. There are a spread of Fe–O bond distances ranging from 1.99–2.06 Å. There are two inequivalent Se4+ sites. In the first Se4+ site, Se4+ is bonded in a trigonal non-coplanar geometry to three O2- atoms. There is one shorter (1.72 Å) and two longer (1.73 Å) Se–O bond length. In the second Se4+ site, Se4+ is bonded in a distorted trigonal non-coplanar geometry to three O2- atoms. All Se–O bond lengths are 1.73 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two equivalent Na1+, one Fe3+, and one Se4+ atom. In the second O2- site, O2- is bonded to two equivalent Na1+, one Fe3+, and one Se4+ atom to form a mixture of distorted corner and edge-sharing ONa2FeSe tetrahedra. In the third O2- site, O2- is bonded in a bent 120 degrees geometry to one Fe3+ and one Se4+ atom. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Fe3+, and one Se4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaFe(TeO3)2 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaFe(SiO3)2 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaFe(WO4)2 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaFe(GeO3)2 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaFe(SeO4)2 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2025

Impurity-induced moment freezing in NaFe x⁢ Ru 1–x O 2

We report the impact of magnetic impurity substitution on the quantum disordered magnetic ground state of NaRuO 2 . Local S = 5/2 moments are introduced into the frustrated triangular lattice of J eff = 1/2 Ru moments via Fe substitution in NaFe x⁢ Ru 1–x O 2 , and the evolution of the magnetic ground state is reported. Local spin freezing associated with conventional spin-glass behavior is observed upon Fe substitution, marking an impurity-induced freezing of the primarily dynamic magnetic ground state in NaRuO 2 . Furthermore, local Fe moments induce a Curie-Weiss magnetic behavior in the uniform magnetic susceptibility, and the local moment magnitude is best described by dynamic Ru moments polarized about impurity sites. Furthermore, our results establish an impurity-doping phenomenology consistent with inherently dynamic moments in NaRuO 2 that are pinned by local magnetic impurities, similar to “swiss cheese” models of impurity-substituted copper oxides.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Spin dynamics in NaFeAs and NaFe 0.53 Cu 0.47 As probed by resonant inelastic x-ray scattering

The parent compounds of iron-based superconductors are magnetically ordered bad metals, with superconductivity appearing near a putative magnetic quantum critical point. The presence of both Hubbard repulsion and Hund’s coupling leads to rich physics in these multiorbital systems, and motivated descriptions of magnetism in terms of itinerant electrons or localized spins. The NaFe 1–x Cu x As series consists of magnetically ordered bad metal (x = 0), superconducting (x ≈ 0.02) and magnetically ordered semiconducing/insulating (x ≈ 0.5) phases, providing a platform to investigate the connection between superconductivity, magnetism and electronic correlations. Here we use x-ray absorption spectroscopy and resonant inelastic x-ray scattering to study the valence state of Fe and spin dynamics in two NaFe 1–x Cu x As compounds (x = 0 and 0.47). We find that magnetism in both compounds arises from Fe 2+ atoms, and exhibits underdamped dispersive spin waves in their respective ordered states. The dispersion of spin excitations in NaFe 0.53 Cu 0.47 As is consistent with being quasi-one-dimensional. Compared to NaFeAs, the band top of spin waves in NaFe 0.53 Cu 0.47 As is slightly softened with significantly more spectral weight of the spin excitations. Here, our results indicate the spin dynamics in NaFe 0.53 Cu 0.47 As arise from localized magnetic moments and suggest the iron-based superconductors are proximate to a correlated insulating state with localized iron moments.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Fluctuating magnetism of Co- and Cu-doped NaFeAs

We report an x-ray emission spectroscopy study of the local fluctuating magnetic moment (μbare) in NaFe 1-x Co x As and NaFe 1-x Cu x As. In NaFeAs, the reduced height of the As ions induces a local magnetic moment higher than BaFe 2 As 2 despite lower TN and ordered magnetic moment. As NaFeAs is doped with Co, μbare is slightly reduced, whereas Cu doping leaves it unaffected, indicating a different doping mechanism: based on electron counting for Co, whereas impurity scattering dominates in the case of Cu. Finally, we observe an increase in μbare with temperature in all samples as observed in electron- and hole-doped BaFe 2 As 2 . Since both Co and Cu doping display superconductivity, our findings demonstrate that the formation of Cooper pairs is not connected with the complete loss of fluctuating paramagnetic moments.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Expanding the Ambient-Pressure Phase Space of CaFe 2 O 4 -Type Sodium Postspinel Host–Guest Compounds

CaFe 2 O 4 -type sodium postspinels (Na-CFs), with Na + occupying tunnel sites, are of interest as prospective battery electrodes. While many compounds of this structure type require high-pressure synthesis, several compounds are known to form at ambient pressure. Here we report a large expansion of the known Na-CF phase space at ambient pressure, having successfully synthesized NaCrTiO 4 , NaRhTiO 4 , NaCrSnO 4 , NaInSnO 4 , NaMg 0.5 Ti 1.5 O 4 , NaFe 0.5 Ti 1.5 O 4 , NaMg 0.5 Sn 1.5 O 4 , NaMn 0.5 Sn 1.5 O 4 , NaFe 0.5 Sn 1.5 O 4 , NaCo 0.5 Sn 1.5 O 4 , NaNi 0.5 Sn 1.5 O 4 , NaCu 0.5 Sn 1.5 O 4 , NaZn 0.5 Sn 1.5 O 4 , NaCd 0.5 Sn 1.5 O 4 , NaSc 1.5 Sb 0.5 O 4 , Na 1.16 In 1.18 Sb 0.66 O 4 , and several solid solutions. In contrast to earlier reports, even cations that are strongly Jahn–Teller active (e.g., Mn 3+ and Cu 2+ ) can form Na-CFs at ambient pressure when combined with Sn 4+ rather than with the smaller Ti 4+ . Order and disorder are probed at the average and local length-scales with synchrotron powder X-ray diffraction and solid-state NMR spectroscopy. Strong ordering of framework cations between the two framework sites is not observed, except in the case of Na 1.16 In 1.18 Sb 0.66 O 4 . This compound is the first example of an Na-CF that contains Na + in both the tunnel and framework sites, reminiscent of Li-rich spinels. Trends in the thermodynamic stability of the new compounds are explained on the basis of crystal-chemistry and density functional theory (DFT). Further DFT calculations examine the relative stability of the CF versus spinel structures at various degrees of sodium extraction in the context of electrochemical battery reactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗