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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Dual-site catalysts featuring platinum-group-metal atoms on copper shapes boost hydrocarbon formations in electrocatalytic CO2 reduction

Abstract Copper-based catalyst is uniquely positioned to catalyze the hydrocarbon formations through electrochemical CO 2 reduction. The catalyst design freedom is limited for alloying copper with H-affinitive elements represented by platinum group metals because the latter would easily drive the hydrogen evolution reaction to override CO 2 reduction. We report an adept design of anchoring atomically dispersed platinum group metal species on both polycrystalline and shape-controlled Cu catalysts, which now promote targeted CO 2 reduction reaction while frustrating the undesired hydrogen evolution reaction. Notably, alloys with similar metal formulations but comprising small platinum or palladium clusters would fail this objective. With an appreciable amount of CO-Pd 1 moieties on copper surfaces, facile CO * hydrogenation to CHO * or CO-CHO * coupling is now viable as one of the main pathways on Cu(111) or Cu(100) to selectively produce CH 4 or C 2 H 4 through Pd-Cu dual-site pathways. The work broadens copper alloying choices for CO 2 reduction in aqueous phases.

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

Binding, Release and Functionalization of Intact Pnictogen Tetrahedra Coordinated to Dicopper Complexes

The bridging MeCN ligand in the dicopper(I) complexes [(DPFN)Cu 2 (μ,η 1 : η 1 -MeCN)][X] 2 (X=weakly coordinating anion, NTf 2 (1 a), FAl[OC 6 F 10 (C 6 F 5 )] 3 (1 b), Al[OC(CF 3 ) 3 ] 4 (1 c)) was replaced by white phosphorus (P 4 ) or yellow arsenic (As 4 ) to yield [(DPFN)Cu 2 (μ,η 2 : η 2 -E 4 )][X] 2 (E=P (2 a-c), As (3 a-c)). The molecular structures in the solid state reveal novel coordination modes for E 4 tetrahedra bonded to coinage metal ions. Experimental data and quantum chemical computations provide information concerning perturbations to the bonding in coordinated E 4 tetrahedra. Reactions with N-heterocyclic carbenes (NHCs) led to replacement of the E 4 tetrahedra with release of P 4 or As 4 and formation of [(DPFN)Cu 2 (μ,η 1 : η 1 - Me NHC)][X] 2 (4 a,b) or to an opening of one E-E bond leading to an unusual E 4 butterfly structural motif in [(DPFN)Cu 2 (μ,η 1 : η 1 -E 4 Dipp NHC)][X] 2 (E=P (5 a,b), E=As (6)). With a cyclic alkyl amino carbene ( Et CAAC), cleavage of two As-As bonds was observed to give two isomers of [(DPFN)Cu 2 (μ,η 2 : η 2 -As 4 Et CAAC)][X] 2 (7 a,b) with an unusual As 4 -triangle+1 unit.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1990

Electronic state and superconductivity of YBa2Cu3-xO7-y (M=Al,Zn and Sn) systems

A series of YBa2Cu(3-x)MxO(7-y) (M=Al,Zn and Sn) single phase samples were prepared, and the measurements of the crystal structure, oxygen content, electric resistivity, thermoelectric power, Mossbauer spectrum, XPS and superconductivity were performed. The experimental results of X ray powder diffraction, Mossbauer spectrum and oxygen content show that the Zn(2+) and the Al(3+) occupy the Cu(2) site in Cu-O planes and the Cu(1) site in Cu-O chains respectively, but the Sn(4+) occupies both the Cu(1) sites. As regards the properties in superconducting state, both the Zn(2+) and the Al(3+) depress T(sub c) strongly, but the Sn(4+) does not. As for the electronic transport properties in normal state, the system doped by Al(3+) displays a rapid increase of resistivity and some electron localization-like effects, and the thermoelectric power enhances obviously; the series contained Zn(2+) almost shows no changes of electric resistivity but the sign of the thermoelectric power is reversed. Other results are given and briefly discussed.

Zhao, Y.↗
DOE OSTI2020

Materials Data on Al4Cu9 by Materials Project

Al4Cu9 is gamma-brass-like structured and crystallizes in the cubic P-43m space group. The structure is three-dimensional. there are six inequivalent Cu sites. In the first Cu site, Cu is bonded in a 12-coordinate geometry to six Cu and six Al atoms. There are three shorter (2.51 Å) and three longer (2.64 Å) Cu–Cu bond lengths. There are three shorter (2.59 Å) and three longer (2.60 Å) Cu–Al bond lengths. In the second Cu site, Cu is bonded in a 12-coordinate geometry to nine Cu and three equivalent Al atoms. There are a spread of Cu–Cu bond distances ranging from 2.53–2.61 Å. All Cu–Al bond lengths are 2.58 Å. In the third Cu site, Cu is bonded in a distorted trigonal planar geometry to nine Cu and three equivalent Al atoms. There are three shorter (2.57 Å) and three longer (2.66 Å) Cu–Cu bond lengths. All Cu–Al bond lengths are 2.46 Å. In the fourth Cu site, Cu is bonded in a 4-coordinate geometry to seven Cu and six Al atoms. There are one shorter (2.51 Å) and four longer (2.79 Å) Cu–Cu bond lengths. There are four shorter (2.53 Å) and two longer (2.81 Å) Cu–Al bond lengths. In the fifth Cu site, Cu is bonded in a 9-coordinate geometry to nine Cu and four equivalent Al atoms. There are a spread of Cu–Cu bond distances ranging from 2.47–2.73 Å. All Cu–Al bond lengths are 2.74 Å. In the sixth Cu site, Cu is bonded in a 5-coordinate geometry to six Cu and five Al atoms. There are a spread of Cu–Al bond distances ranging from 2.53–2.60 Å. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 9-coordinate geometry to nine Cu atoms. In the second Al site, Al is bonded in a 11-coordinate geometry to eleven Cu atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on In4Cu9 by Materials Project

Cu9In4 is gamma-brass-like structured and crystallizes in the cubic P-43m space group. The structure is three-dimensional. there are six inequivalent Cu sites. In the first Cu site, Cu is bonded in a 11-coordinate geometry to six Cu and five In atoms. There are a spread of Cu–Cu bond distances ranging from 2.54–2.98 Å. There are a spread of Cu–In bond distances ranging from 2.67–2.73 Å. In the second Cu site, Cu is bonded in a 4-coordinate geometry to seven Cu and six In atoms. There are one shorter (2.60 Å) and two longer (2.80 Å) Cu–Cu bond lengths. There are a spread of Cu–In bond distances ranging from 2.67–2.98 Å. In the third Cu site, Cu is bonded in a 2-coordinate geometry to nine Cu and four equivalent In atoms. There are a spread of Cu–Cu bond distances ranging from 2.63–2.80 Å. All Cu–In bond lengths are 2.89 Å. In the fourth Cu site, Cu is bonded in a 3-coordinate geometry to nine Cu and four In atoms. All Cu–Cu bond lengths are 2.63 Å. There are three shorter (2.61 Å) and one longer (3.24 Å) Cu–In bond lengths. In the fifth Cu site, Cu is bonded in a distorted q6 geometry to nine Cu and three equivalent In atoms. All Cu–Cu bond lengths are 2.55 Å. All Cu–In bond lengths are 2.79 Å. In the sixth Cu site, Cu is bonded to six Cu and six In atoms to form distorted face-sharing CuIn6Cu6 cuboctahedra. There are three shorter (2.73 Å) and three longer (2.77 Å) Cu–In bond lengths. There are two inequivalent In sites. In the first In site, In is bonded in a 11-coordinate geometry to eleven Cu atoms. In the second In site, In is bonded in a 9-coordinate geometry to ten Cu atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ga4Cu9 by Materials Project

Cu9Ga4 is gamma-brass-like structured and crystallizes in the cubic P-43m space group. The structure is three-dimensional. there are six inequivalent Cu sites. In the first Cu site, Cu is bonded in a 9-coordinate geometry to nine Cu and four equivalent Ga atoms. There are a spread of Cu–Cu bond distances ranging from 2.49–2.76 Å. All Cu–Ga bond lengths are 2.75 Å. In the second Cu site, Cu is bonded in a 11-coordinate geometry to six Cu and five Ga atoms. There are a spread of Cu–Cu bond distances ranging from 2.52–2.79 Å. There are a spread of Cu–Ga bond distances ranging from 2.53–2.61 Å. In the third Cu site, Cu is bonded in a 12-coordinate geometry to six Cu and six Ga atoms. All Cu–Cu bond lengths are 2.67 Å. There are three shorter (2.57 Å) and three longer (2.62 Å) Cu–Ga bond lengths. In the fourth Cu site, Cu is bonded in a 12-coordinate geometry to nine Cu and three equivalent Ga atoms. There are three shorter (2.58 Å) and three longer (2.60 Å) Cu–Cu bond lengths. All Cu–Ga bond lengths are 2.59 Å. In the fifth Cu site, Cu is bonded in a 3-coordinate geometry to nine Cu and three equivalent Ga atoms. All Cu–Ga bond lengths are 2.48 Å. In the sixth Cu site, Cu is bonded in a 4-coordinate geometry to seven Cu and six Ga atoms. The Cu–Cu bond length is 2.51 Å. There are four shorter (2.54 Å) and two longer (2.83 Å) Cu–Ga bond lengths. There are two inequivalent Ga sites. In the first Ga site, Ga is bonded in a 9-coordinate geometry to nine Cu atoms. In the second Ga site, Ga is bonded in a 11-coordinate geometry to eleven Cu atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cu5Ge2 by Materials Project

Cu5Ge2 crystallizes in the trigonal R3m space group. The structure is three-dimensional. there are five inequivalent Cu sites. In the first Cu site, Cu is bonded in a 11-coordinate geometry to five Cu and six Ge atoms. There are a spread of Cu–Cu bond distances ranging from 2.44–2.58 Å. There are three shorter (2.78 Å) and three longer (2.85 Å) Cu–Ge bond lengths. In the second Cu site, Cu is bonded in a 10-coordinate geometry to seven Cu and three equivalent Ge atoms. There are a spread of Cu–Cu bond distances ranging from 2.44–2.58 Å. All Cu–Ge bond lengths are 2.84 Å. In the third Cu site, Cu is bonded in a 8-coordinate geometry to four Cu and four Ge atoms. There are one shorter (2.56 Å) and three longer (2.57 Å) Cu–Ge bond lengths. In the fourth Cu site, Cu is bonded in a 4-coordinate geometry to four Cu and four Ge atoms. There are three shorter (2.45 Å) and one longer (2.46 Å) Cu–Ge bond lengths. In the fifth Cu site, Cu is bonded in a distorted body-centered cubic geometry to four Cu and four Ge atoms. There are one shorter (2.56 Å) and three longer (2.57 Å) Cu–Ge bond lengths. There are two inequivalent Ge sites. In the first Ge site, Ge is bonded in a 11-coordinate geometry to eleven Cu atoms. In the second Ge site, Ge is bonded in a 10-coordinate geometry to ten Cu atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Facet‐Selective Deposition of Ultrathin Al 2 O 3 on Copper Nanocrystals for Highly Stable CO 2 Electroreduction to Ethylene

Abstract Catalysts based on Cu nanocrystals (NCs) for electrochemical CO 2 ‐to‐C 2+ conversion with high activity have been a subject of considerable interest, but poor stability and low selectivity for a single C 2+ product remain obstacles for realizing sustainable carbon‐neutral cycles. Here, we used the facet‐selective atomic layer deposition (FS‐ALD) technique to selectively cover the (111) surface of Cu NCs with ultrathin Al 2 O 3 to increase the exposed facet ratio of (100)/(111), resulting in a faradaic efficiency ratio of C 2 H 4 /CH 4 for overcoated Cu NCs 22 times higher than that for pure Cu NCs. Peak performance of the overcoated catalyst (Cu NCs/Al 2 O 3 ‐10C) reaches a C 2 H 4 faradaic efficiency of 60.4 % at a current density of 300 mA cm −2 in 5 M KOH electrolyte, when using a gas diffusion electrode flow cell. Moreover, the Al 2 O 3 overcoating effectively suppresses the dynamic mobility and the aggregation of Cu NCs, which explains the negligible activity loss and selectivity degradations of Cu NCs/Al 2 O 3 ‐10C shown in stability tests.

Li, Hui↗
DOE OSTI2021

Facet-Selective Deposition of Ultrathin Al 2 O 3 on Copper Nanocrystals for Highly Stable CO 2 Electroreduction to Ethylene.

Catalysts based on Cu nanocrystals (NCs) for electrochemical CO 2 -to- 2+ conversion with high activity have been a subject of considerable interest, but poor stability and low selectivity for a single C 2+ product remain obstacles for realizing sustainable carbon-neutral cycles. In this study, we used the facet-selective atomic layer deposition (FS-ALD) technique to selectively cover the (111) surface of Cu NCs with ultrathin Al 2 O 3 to increase the exposed facet ratio of (100)/(111), resulting in a faradaic efficiency ratio of C 2 H 4 /CH 4 for overcoated Cu NCs 22 times higher than that for pure Cu NCs. Peak performance of the overcoated catalyst (Cu NCs/Al 2 O 3 -10C) reaches a C 2 H 4 faradaic efficiency of 60.4 % at a current density of 300 mA cm -2 in 5 M KOH electrolyte, when using a gas diffusion electrode flow cell. Moreover, the Al 2 O 3 overcoating effectively suppresses the dynamic mobility and the aggregation of Cu NCs, which explains the negligible activity loss and selectivity degradations of Cu NCs/Al 2 O 3 -10C shown in stability tests.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

N-induced soil acidification triggers metal stimulation of soil methane oxidation in a temperate steppe ecosystem

Methane (CH 4 ) is a potent greenhouse gas, and it is well established that low nitrogen (N) stimulates- and high N suppresses CH 4 oxidation in grassland ecosystems. Here, in this study, we examined the response of CH 4 uptake to long-term (>10 years) multi-level N additions in a temperate steppe of northern China. The N impacts on CH 4 uptake transitioned from positive to negative at the N addition rate of 4 g N m -2 y -1 . However, the high-N suppression on CH 4 uptake was partially relieved when the continuous (>10 years) high N inputs (16 g N m -2 y -1 to 64 g N m -2 y -1 ) caused soil pH drop to < 5.7. Further experiments revealed that continuous high-N inputs acidified soil to pH < 5.7 that released metal ions to stimulate monooxygenase enzyme activity; therefore, the CH 4 oxidation suppression was partially relieved under continuous N loading. Structural equation model results confirmed that metal ions, such as Iron (Fe 3+ ), Manganese (Mn 4+ ), and Copper (Cu) desorbed by soil particles, were negatively correlated with soil pH while positively correlated with CH 4 oxidation under high N inputs. These analyses suggested that continuous high N inputs-induced soil acidification can release previously bounded metal elements that partially alleviated the N suppression on CH 4 uptake. The N-induced soil acidification impacts on CH 4 uptake might play a critical role in global CH 4 cycling and deserve further investigation as external N inputs continue climbing.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1994

Trans-Bis(acetato-0)bis(4-methylpyridine-N)copper(II)

The structure of trans-bis(acetato-O)bis (4-methylpyridine-N)copper(II), (Cu(C2H3O2)2(C6H7N)2), reported herein, represents a monomeric parent acetate complex with a distorted square-planar arrangement of acetate and 4-methylpyridine ligands around the Cu atom with the following distances and angles: Cu-N = 2.027(4) and Cu-O(1) = 1.950 (3) A; O(1)-Cu-N = 89.1 (2) and O(1)-Cu-N' = 90.0(2)deg. The Cu atom resides on a center of inversion. the most important dihedral angles are the angle between the 4-methylpyridine plane and the acetate plane (O(1), O(2), C(21), and C(22)), 78.2 deg, and the angle between the 4-methylpyridine ring and the coordination plane (Cu, N, O(1)), 31.6 deg.

Jedrzejas, Marek J.↗
DOE OSTI2021

Post-growth annealing effects on charge and spin excitations in ND 2-x Ce x CuO 4

We report a Cu K- and L 3 -edge resonant inelastic x-ray scattering study of charge and spin excitations of bulk Nd 2-x Ce x CuO 4 , with focus on post-growth annealing effects. For the parent compound Nd 2 CuO 4 (x = 0), a clear charge-transfer gap is observed in the as-grown state, whereas the charge excitation spectra indicate that electrons are doped in the annealed state. This is consistent with the observation that annealed thin-film and polycrystalline samples of RE 2 CuO 4 (RE = rare earth) can become metallic and superconducting at sufficiently high electron concentrations without Ce doping. For x = 0.16, a Ce concentration for which it is known that oxygen reduction destroys long-range antiferromagnetic order and induces superconductivity, we find that the high-energy spin excitations of non-superconducting as-grown and superconducting annealed crystals are nearly identical. This finding is in stark contrast to the significant changes in the low-energy spin excitations previously observed via neutron scattering

36 MATERIALS SCIENCE↗
DOE OSTI2020

STRUCTURE AND PROPERTIES STUDY ON ENERGY MATERIALS: THERMOELECTRIC MATERIAL TETRAHEDRITE AND LITHIUM ION CONDUCTOR

Development of efficient energy materials is critical in order to ease the energy demand and reduce our dependence of fossil fuel. Thermoelectric materials are promising due to their capability of generating electrical power by recovering waste heat. The performance of thermoelectric materials is quantified by a dimensionless figure of merit zT, which depends on their properties such as electrical conductivity, Seebeck coefficient and thermal conductivity. Tetrahedrites, a copper antimony sulfosalt mineral, typified by Cu 12-x MxSb 4 S 13 , where M is a transition metal element such as Ni, Zn, Fe or Mn, have great potential for thermoelectric application due to their relatively high zT (close to 1 at 700 K), earth-abundance, environmental friendliness, favorable electrical properties, and most importantly intrinsic low lattice thermal conductivity (less than 1 W m -1 K -1 ) in wide temperature. In addition to energy recovery, reliable energy storage devices are also emerging to relieve the energy demand and improve the efficiency of consuming energy resources. Lithium-ion batteries are known to be reliable and successful electrochemical energy storage devices and appliable in various aspects, including laptops, smartphones and electrical vehicles. Lithium phosphorous oxynitride (LiPON) are widely used as thin-film solid-state electrolytes in Li-ion battery, which is the only demonstrated solid-state electrolyte that is quite stable in direct contact with Li metal at potentials from 0-5 V. However, the structure of LiPON, the effects of N doping, and the origin of its good electrochemical stability remains inconclusive. In this thesis, reliable modeling techniques accompanied with experimental tools, are applied to study the thermoelectric material tetrahedrite and the ionic conductor LiPON, in order to study their structural and dynamical properties. Accurate and efficient density-functional theory (DFT) and density-functional tight-binding (DFTB) methods, combined with molecular dynamics (MD) simulations are utilized in order to investigate the structures and properties of these energy materials. The incoherent and coherent atomic dynamics study of tetrahedrite Cu 10.5 NiZn 0.5 Sb 4 S 13 provides the origin of softening upon cooling by investigate the motion of Cu12e at different temperatures. The dynamic structure factors in the longitudinal and transverse direction will also be discussed. The Cu movement of Cu-rich tetrahedrite Cu 14 Sb 4 S 13 is revealed by Cu self-diffusivity, nuclear density map and “nudged elastic band” (NEB). Moreover, we investigate the effect of simulation cell size and basis sets on the DFT-based MD simulation results using tetrahedrite Cu1 0 Zn 2 Sb 4 S 13 thermoelectric as a model material, showing the advantage of larger cell by accessing smaller Q range. In addition, the low-temperature structural properties of Cu 12 Sb 4 S 13 is measured by neutron diffraction, which indicates that no cubic to tetragonal transition occurs at metal-semiconductor transition (MST) temperature. Thermoelectric properties such as Seebeck coefficient, electrical resistivity and electrical thermal conductivity will also be investigated. DFTB method is implemented to study the structure and transport properties of Li 3 PO 4 and LiPON, while the exploration of N doping effect is included. Lastly, the LiPON/Li interphase will be revealed in order to study the origin of electrochemical stability.

Li, Junchao↗
NASA NTRS1995

Creep Testing of High-Temperature Cu-8 Cr-4 Nb Alloy Completed

A Cu-8 at.% Cr-4 at.% Nb (Cu-8 Cr-4 Nb) alloy is under development for high-temperature, high heatflux applications, such as actively cooled, hypersonic vehicle heat exchangers and rocket engine combustion chambers. Cu-8 Cr-4 Nb offers a superior combination of strength and conductivity. It has also shown exceptional low-cycle fatigue properties. Following preliminary testing to determine the best processing route, a more detailed testing program was initiated to determine the creep lives and creep rates of Cu-8 Cr-4 Nb alloy specimens produced by extrusion. Testing was conducted at the NASA Lewis Research Center with constant-load vacuum creep units. Considering expected operating temperatures and mission lives, we developed a test matrix to accurately determine the creep properties of Cu-8 Cr-4 Nb between 500 and 800 C. Six bars of Cu-8 Cr-4 Nb were extruded. From these bars, 54 creep samples were machined and tested. The figure on the left shows the steady-state, or second-stage, creep rates for the samples. Comparison data for NARloy-Z (Cu-3 wt % Ag-0.5 wt % Zr), the alloy currently used in combustion chamber liners, were not unavailable. Therefore the steady-state creep rates for Cu at similar temperatures are presented. As expected, in comparison to pure Cu, the creep rates for Cu-8 Cr-4 Nb are much lower. The lives of the samples are presented in the figure on the right. As shown, Cu-8 Cr-4 Nb at 800 C is comparable to NARloy-Z at 648 C. At equivalent temperatures, Cu-8 Cr-4 Nb enjoys a 20 to 50 percent advantage in stress for a given life and 1 to 3 orders of magnitude greater life at a given stress. The improved properties allow for design tradeoffs and improvements in new and existing heat exchangers such as the next generation of combustion chamber liners. Average creep rates for Cu-8 Cr-4 Nb and pure Cu are shown. Average creep lives for Cu-8 Cr- 4 Nb and NARloy-Z are also shown. Currently, two companies are interested in the commercial usage of the Cu-8 Cr-4 Nb alloy. The Rocketdyne Division of Rockwell International is conducting independent testing to analyze the properties for their projected needs in advanced rocket engine applications. Metallamics, a company based in Traverse City, Michigan, is entering into a Space Act Agreement to evaluate and test Cu-Cr-Nb alloys as materials for welding electrodes that are used in robotic welding operations. Creep rate is one of the alloy properties that determines the degree to which a welding electrode will mushroom or expand at the tip. A material with a low creep rate will resist mushrooming and give the electrode a longer life, minimizing downtime. This application holds the potential for large-scale usage of the alloy in the automotive and other industries. Success here would dramatically decrease the cost of the alloy and increase availability for aerospace applications.

Source record↗
DOE OSTI2020

Materials Data on CuPd by Materials Project

PdCu crystallizes in the orthorhombic Cmmm space group. The structure is two-dimensional and consists of two PdCu sheets oriented in the (0, 1, 0) direction. Pd is bonded in a 4-coordinate geometry to four equivalent Cu atoms. All Pd–Cu bond lengths are 2.59 Å. Cu is bonded in a 4-coordinate geometry to four equivalent Pd atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Gd(CuGe)2 by Materials Project

GdCu2Ge2 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Gd is bonded in a 4-coordinate geometry to eight equivalent Cu and eight equivalent Ge atoms. There are a spread of Gd–Cu bond distances ranging from 3.23–3.36 Å. There are four shorter (3.12 Å) and four longer (3.20 Å) Gd–Ge bond lengths. Cu is bonded in a 4-coordinate geometry to four equivalent Gd and four equivalent Ge atoms. There are three shorter (2.45 Å) and one longer (2.46 Å) Cu–Ge bond lengths. Ge is bonded in a 9-coordinate geometry to four equivalent Gd, four equivalent Cu, and one Ge atom. The Ge–Ge bond length is 2.49 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Coupling Redox Compensation and Interfacial Stabilization in Low-Ni O3-Type Sodium Layered Oxide Cathodes

Low-Ni O3-type sodium layered oxides are attractive cathodes for cost-robust sodium-ion batteries, yet high-voltage cycling is often limited by Fe-driven degradation, including cation migration/dissolution, irreversible slab gliding with large strain, particle cracking, and accelerated interfacial parasitic reactions. Here, in this study, we introduce a redox-interface codesign strategy using stoichiometric, charge-balanced Cu 2+ /Ti 4+ cosubstitution while preserving full Na stoichiometry, transitioning from NaNi 1/4 Fe 1/2 Mn 1/4 O 2 to NaNi 1/4 Fe 1/5 Mn 1/4 Cu 3/20 Ti 3/20 O 2 . With the cosubstitution, Cu and Ti suppress Fe migration and dissolution and facilitate sustained Fe oxidation at high voltage. Meanwhile, Cu is also shown to be redox-active, providing reversible cationic charge compensation that mitigates the capacity penalty typically associated with reducing Fe participation. Operando diffraction and spectroscopy collectively indicate a more reversible high-voltage structural evolution with suppressed Fe-related irreversibility. Particularly, spontaneous Ti enrichment at surface/grain-boundary regions stabilizes the cathode−electrolyte interface and promotes a more NaF-rich interphase signature. This work establishes a generalizable route to reconcile stability and capacity in low-Ni, Fe-containing O3 sodium layered oxide cathodes via compositionally encoded bulk-interfacial coupling.

25 ENERGY STORAGE↗