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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Demonstration of MgCr 2– x Mn x O 4 Spinel Oxide Cathodes in High-Voltage Mg Batteries

Solid-solution oxide spinels with high redox voltages and facile Mg 2+ mobility have been identified as promising candidates for practical, high-voltage cathodes in Mg batteries. In this work, we discuss the development of MgCr 2-x Mn x O 4 [x = 0.5, 1, 1.2] solid-solution spinel oxides as a cathode material and their electrochemical performance paired with an Mg anode in a full cell. This work presents the first demonstration of full cells with these materials. Mg-Cr-Mn spinel oxides with varying Cr and Mn contents were synthesized using alternative synthetic routes for optimal electrochemical performance. High-resolution synchrotron powder X-ray diffraction (PXRD), solid-state nuclear magnetic resonance (NMR) spectroscopy, and electron microscopy showed that these different synthetic routes resulted in changes in structures and particle morphologies, which in turn affect the electrochemical performance. Particularly, the urea coprecipitation synthetic route resulted in high-surface-area particles that enabled lower overpotentials and increased discharge capacity. The high surface area also resulted in expedited structural degradation caused by the irreversible migration of Mg 2+ into normally vacant 16c sites in the spinel lattice. This structural degradation was lessened by using a hydrosauna-urea synthesis method, which decreased the Mg/Mn inversion ratio while retaining high-surface-area particles with good cycling performance. Furthermore, our findings highlight the necessity for high surface area or nanostructured spinel oxide cathodes with minimized Mg-Mn inversion to enable spinel oxide cathodes in Mg full cells.

Mg anode↗
DOE OSTI2025

Hund’s flat band in a frustrated spinel oxide

Electronic flat bands associated with quenched kinetic energy and heavy electron mass have attracted great interest for promoting strong electronic correlations and emergent phenomena such as high-temperature charge fractionalization and superconductivity. Intense experimental and theoretical research has been devoted to establishing the rich nontrivial metallic and heavy fermion phases intertwined with such localized electronic states. Here, in this study, we investigate the transition metal oxide spinel LiV 2 O 4 , an enigmatic heavy fermion compound lacking localized f orbital states. We use angle-resolved photoemission spectroscopy and dynamical mean-field theory to reveal a kind of correlation-induced flat band with suppressed interatomic electron hopping arising from intra-atomic Hund’s coupling. The appearance of heavy quasiparticles is ascribed to a proximate orbital-selective Mott state characterized by fluctuating local moments as evidenced by complementary magnetotransport measurements. The spectroscopic fingerprints of long-lived quasiparticles and their disappearance with increasing temperature further support the emergence of a high-temperature “bad” metal state observed in transport data. This work resolves a long-standing puzzle on the origin of heavy fermion behavior and unconventional transport in LiV 2 O 4 . Simultaneously, it opens a path to achieving flat bands through electronic interactions in d-orbital systems with geometrical frustration, potentially enabling the realization of exotic phases of matter such as the fractionalized Fermi liquids.

36 MATERIALS SCIENCE↗
DOE OSTI2024

High-temperature thermochemical energy storage materials using doped magnesium-transition metal spinel oxides

High-temperature thermochemical energy storage materials using doped magnesium-transition metal spinel oxides are provided. —transition metal spinel oxides, such as magnesium manganese oxide (MgMn) 3 O 4 , are promising candidates for high-temperature thermochemical energy storage applications. However, the use of these materials has been constrained by the limited extent of their endothermic reaction. Embodiments described herein provide for doping magnesium-transition metal spinel oxides to produce a material of low material costs and with high energy densities, creating an avenue for plausibly sized modules with high energy storing capacities.

Muhich, Christopher↗
DOE OSTI2024

Morphology‐controlled synthesis of multi‐metal‐based spinel oxide nanocatalysts and their performance for oxygen reduction

Abstract We present a one‐pot colloidal synthesis method for producing monodisperse multi‐metal (Co, Mn, and Fe) spinel nanocrystals (NCs), including nanocubes, nano‐octahedra, and concave nanocubes. This study explores the mechanism of morphology control, showcasing the pivotal roles of metal precursors and capping ligands in determining the exposed crystal planes on the NC surface. The cubic spinel NCs, terminated with exclusive {100}‐facets, demonstrate superior electrocatalytic activity for the oxygen reduction reaction (ORR) in alkaline media compared to their octahedral and concave cubic counterparts. Specifically, at 0.85 V, (CoMn)Fe 2 O 4 spinel oxide nanocubes achieve a high mass activity of 23.9 A/g and exhibit excellent stability, highlighting the promising ORR performance associated with {100}‐facets of multi‐metal spinel oxides over other low‐index and high‐index facets. Motivated by exploring the correlation between ORR performance and surface atom arrangement (active sites), surface element composition, as well as other factors, this study introduces a prospective approach for shape‐controlled synthesis of advanced spinel oxide NCs. It underscores the significance of catalyst shape control and suggests potential applications as nonprecious metal ORR electrocatalysts.

Li, Can↗
DOE OSTI2023

Manganese-cobalt spinel oxide nanowire arrays

Manganese-cobalt (Mn—Co) spinel oxide nanowire arrays are synthesized at low pressure and low temperature by a hydrothermal method. The method can include contacting a substrate with a solvent, such as water, that includes Mn04- and Co2 ions at a temperature from about 60° C. to about 120° C. The method preferably includes dissolving potassium permanganate (KMn04) in the solvent to yield the Mn04- ions. the substrate is The nanoarrays are useful for reducing a concentration of an impurity, such as a hydrocarbon, in a gas, such as an emission source. The resulting material with high surface area and high materials utilization efficiency can be directly used for environment and energy applications including emission control systems, air/water purifying systems and lithium-ion batteries.

Gao, Pu-Xian↗
DOE OSTI2024

Zero-strain high entropy spinel oxide (FeNiCuCrMn) 3 O 4 @rGO as high-performance anode for sodium ion battery

High entropy spinel oxides (HEOs), as a new type of anode material with at least five transition metal elements and high theoretical specific capacity, have enormous promise in sodium ion batteries (SIBs). However, the influence of different transition metal elements on the structure and electrochemical performances of HEOs is not clear. Here, in this study, the addition of Mn to HEO can increase the surface oxygen vacancy (O v ) concentration, shorten the band gap, and enhance the electrochemical performance of (FeNiCuCrMn) 3 O 4 @rGO. XPS results show (FeNiCuCrMn)3O4@rGO has the highest surface O v concentration. Ab initio calculations demonstrate that the indirect band gap of (FeNiCuCrMn)3O4@rGO is 0.068 eV. In situ X-ray diffraction and synchrotron X-ray absorption spectroscopy reveal that (FeNiCuCrMn) 3 O 4 @rGO exhibits a zero-strain characteristic with an inconsequential unit cell volume change of 0.2 %. Specifically, (FeNiCuCrMn) 3 O 4 @rGO as anode materials for SIBs show good cyclic stability (with a capacity retention of 84 % at 500 mA g −1 after 3000 cycles). Overall, this work provides a new direction for optimizing transition metal elements in HEOs.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Low Thermal Conductivity and Diffusivity at High Temperatures Using Stable High–Entropy Spinel Oxide Nanoparticles

The realization of low thermal conductivity at high temperatures (0.11 W m –1 K –1 800 °C) in ambient air in a porous solid thermal insulation material, using stable packed nanoparticles of high-entropy spinel oxide with 8 cations (HESO-8 NPs) with a relatively high packing density of ≈50%, is reported. The high-density HESO-8 NP pellets possess around 1000-fold lower thermal diffusivity than that of air, resulting in much slower heat propagation when subjected to a transient heat flux. The low thermal conductivity and diffusivity are realized by suppressing all three modes of heat transfer, namely solid conduction, gas conduction, and thermal radiation, via stable nanoconstriction and infrared-absorbing nature of the HESO-8 NPs, which are enabled by remarkable microstructural stability against coarsening at high temperatures due to the high entropy. Furthermore, this work can elucidate the design of the next-generation high-temperature thermal insulation materials using high-entropy ceramic nanostructures.

thermal insulation↗
DOE OSTI2023

Studies on the structure and the magnetic properties of high-entropy spinel oxide (MgMnFeCoNi)Al 2 O 4

The study of high-entropy materials has attracted enormous interest since they could show new functional properties that are not observed in their related parent phases. Here, we report single crystal growth, structure, thermal transport, and magnetic property studies on a novel high-entropy oxide with the spinel structure (MgMnFeCoNi)Al 2 O 4 . We have successfully grown high-quality single crystals of this high-entropy oxide using the optical floating zone growth technique for the first time. The sample was confirmed to be a phase pure high-entropy oxide using x-ray diffraction and energy-dispersive spectroscopy. Through magnetization measurements, we found (MgMnFeCoNi)Al 2 O 4 exhibits a cluster spin glass state, though the parent phases show either antiferromagnetic ordering or spin glass states. Furthermore, we also found that (MgMnFeCoNi)Al 2 O 4 has much greater thermal expansion than its CoAl 2 O 4 parent compound using high resolution neutron Larmor diffraction. We further investigated the structure of this high-entropy material via Raman spectroscopy and extended x-ray absorption fine structure spectroscopy (EXAFS) measurements. From Raman spectroscopy measurements, we observed (MgMnFeCoNi)Al 2 O 4 to display a combination of the active Raman modes in its parent compounds with the modes shifted and significantly broadened. This result, together with the varying bond lengths probed by EXAFS, reveals severe local lattice distortions in this high-entropy phase. Additionally, we found a substantial decrease in thermal conductivity and suppression of the low temperature thermal conductivity peak in (MgMnFeCoNi)Al 2 O 4 , consistent with the increased lattice defects and strain. These findings advance the understanding of the dependence of thermal expansion and transport on the lattice distortions in high-entropy materials.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Local structural distortions drive magnetic molecular field in compositionally complex spinel oxide

Understanding how local distortions determine the functional properties of high entropy materials, containing five or more elements at the same crystallographic site, is an open challenge. We address this for a compositionally complex spinel oxide (Mn 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 )Cr 2 O 4 (A 5 Cr 2 O 4 ). By comparatively examining extended X-ray absorption fine structure on A 5 Cr 2 O 4 and its parent counterparts, ACr 2 O 4 , along with density functional theory calculations for multiple configurations, we find that the element-specific distortions go beyond the first neighbor. Specifically, the strong Jahn-Teller distortion present in CuCr 2 O 4 is found to be completely suppressed in A 5 Cr 2 O 4 even locally. Instead, there is a broad distribution of Cu-O and Cu-Cr bond distances, while other A-O distances acquire certain specific values. This study demonstrates the additional flexibility of a cationic sublattice in maintaining a uniform long-range structure, in contrast to previous reports showing only the accommodative anionic sublattice. The mean-field magnetic interactions of A 5 Cr 2 O 4 exhibit a striking resemblance to those of NiCr 2 O 4 , despite the presence of multiple magnetic ions and variable bond lengths. This originates from the comparability of bond lengths around Cr in both materials. Our study paves the way for a deeper understanding of the impact of local structural distortions on the physical properties of compositionally complex quantum materials.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Defect-Engineered High-Entropy Spinel Oxide@Onion-Like Carbon Catalysts for High-Areal-Energy Rechargeable Zinc–Air Batteries

Rechargeable zinc-air batteries (ReZAB) have emerged as the next-generation batteries with several advantages over the conventional lithium-ion battery. In this work, single nanocrystals of inverse-type high-entropy spinel oxides (HESOx, particle size of 10−12 nm) confined in highly curved defective onion-like carbons (HESOx/OLC AT ) as efficient electrocatalysts for oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and ReZAB, have been synthesized. The HESOx materials were thoroughly characterized using several analytical techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning transmission electron microscopy (STEM), Raman, and electron paramagnetic resonance (EPR). HESOx/OLC AT catalyst was tested for ReZAB using literature-recommended parameters that would allow for real technological application. These parameters include a current loading of 10 mA cm −2 and a discharge areal energy density of 35 mWh cm geometric −2 , which maps a Li-ion battery pack-level specific energy of 120 Wh kg pack −1 . HESOx/OLC AT electrocatalysts allowed for continuous discharging and charging at a current loading of 10 mA cm −2 with discharge areal energy densities between 37 and 74 mWh cm geometric −2 , thus outperforming the recommended threshold of 35 mWh cm geometric −2 . Considering that most studies (>90%) hardly meet the recommended threshold for technological application of ReZAB, the present work represents one of the top-performing electrocatalysts for ReZAB. The excellent electrocatalytic properties of defect-rich HESOx/OLC AT toward ORR/OER and ReZAB are governed by the strong electronic modulation arising from d-π hybridization, the availability of multiple catalytic sites for intermediates, and weakened d-band centers of the rate-determining intermediates (i.e., *O adsorption for ORR and *OOH formation for OER) compared to the pristine HESOx. This work introduces an effective approach for the design and synthesis of single nanocrystals of high-entropy electrocatalysts for the development of low-cost, robust, and technologically relevant rechargeable zinc−air batteries.

25 ENERGY STORAGE↗
DOE OSTI2026

(CrMnCoNiTi) 3 O 4 high-entropy spinel oxide as a high-performance electrode for supercapacitors

In this study, spinel-structured (CrMnCoNiTi)₃O₄ high-entropy oxides (HEOs) have been successfully synthesized using the solution combustion method, and their performance as supercapacitor electrode materials was investigated. These HEOs exhibit excellent performance, stemming from the unique high-entropy effect and lattice distortion. This structure effectively buffers volumetric strain during cycling, conferring the material with extremely high structural stability and specific capacity. The material demonstrates a high specific capacity of 491.5 C∙g⁻¹ at a current density of 0.5 A∙g⁻¹. Furthermore, it shows extraordinary cycling stability: after 10,000 charge/discharge cycles at 5 A∙g⁻¹, the capacity retention rate is 99%, and the Coulombic efficiency consistently remains close to 100%. Ex-situ structural characterizations further reveal that this excellent cycling durability originates from a cooperative multination valence reconstruction mechanism within an entropy-stabilized spinel framework. Additionally, a symmetric supercapacitor assembled using this material and 1 M KOH electrolyte successfully extended the working voltage to 1.2 V. This research highlights the great potential of high-entropy oxides in synergizing high energy density and ultra-long cycling life, laying a solid foundation for the development of next-generation high-performance supercapacitor electrode materials.

High entropy oxides↗
DOE OSTI2024

Non-Stoichiometric High Entropy Spinel Oxides as Regenerable Catalysts for Methane Dry Reforming

In this work, novel high entropy oxides were developed and applied as catalysts in the methane dry reforming reaction. Catalytic results show high activity and regenerable structure of the high entropy oxides but degradation of simple nickel aluminate spinels commonly applied to this reaction. A proof-of-concept experiment demonstrated heating of the high entropy oxide catalyst to reaction relevant temperatures using concentrating solar power equipment.

Riva, Andrew↗
DOE OSTI2025

Compositionally Complex Spinel Oxides as Conversion Anodes for Lithium-Ion Batteries

Four different compositionally complex multicomponent M 3 O 4 spinels containing 5–8 distinct metals were prepared by a rapid combustion synthesis method or solvothermal synthesis. High resolution synchrotron X-ray diffraction patterns show that the materials consist primarily of spinel phases with small amounts of rock salt impurities, and, in several samples, a minor amount of contracted spinel phase. Materials were investigated as conversion anodes in lithium half-cells and delivered significantly higher capacities than two-component MgFe 2 O 4 made by combustion synthesis. X-ray absorption near-edge structure (XANES) was used to estimate the oxidation states of the metals in the pristine, lithiated (discharged) and delithiated (charged) materials to better understand the redox processes in half cells that led to the improvement. Co, Ni, and Zn are reduced to low oxidation states during lithiation (cell discharge) but are only partially oxidized. The presence of a conductive metallic network that forms after lithiation is thought to account for the improved electrochemical characteristics. Interestingly, in most of the samples, iron is not fully reduced during initial lithiation unlike what happens with a set of related high entropy spinel ferrites studied previously. Finally, the improved electrochemical properties of these materials illustrates both the advantages of complexity and the difficulties in predicting their behavior.

25 ENERGY STORAGE↗
DOE OSTI2023

Synergistic effects of mixing and strain in high entropy spinel oxides for oxygen evolution reaction

Developing stable and efficient electrocatalysts is vital for boosting oxygen evolution reaction (OER) rates in sustainable hydrogen production. High-entropy oxides (HEOs) consist of five or more metal cations, providing opportunities to tune their catalytic properties toward high OER efficiency. This work combines theoretical and experimental studies to scrutinize the OER activity and stability for spinel-type HEOs. Density functional theory confirms that randomly mixed metal sites show thermodynamic stability, with intermediate adsorption energies displaying wider distributions due to mixing-induced equatorial strain in active metal-oxygen bonds. The rapid sol-flame method is employed to synthesize HEO, comprising five 3d-transition metal cations, which exhibits superior OER activity and durability under alkaline conditions, outperforming lower-entropy oxides, even with partial surface oxidations. The study highlights that the enhanced activity of HEO is primarily attributed to the mixing of multiple elements, leading to strain effects near the active site, as well as surface composition and coverage.

08 HYDROGEN↗
DOE OSTI2026

Cobalt-free and high-rate stable 5V lithium nickel manganese oxide spinel cathodes enabled via surface oxygen vacancies

Spinel LiNi 0.5 Mn 1.5 O 4 offers both the high-rate, low-cost and safety advantages of LiFePO 4 and the high energy density of LiNiₓMnᵧCo₁₋ₓ₋ᵧO₂ and LiNiₓCoᵧAlzO₂ cathodes. However, the large operating voltage of these materials induces electrolyte oxidation, which degrades the interface and drives Mn dissolution. These reactions are further exacerbated at high rates due to temperature rise. In this study, we discover that ammoniacal treatment followed by annealing introduces a high density of oxygen vacancies in the “near-surface region” of LiNi 0.5 Mn 1.5 O 4 particles. These vacancies release electrons changing the oxidation state of Mn and suppressing its tendency to oxidize the electrolyte. Further, these vacancies enhance the electrode’s electronic conductivity (by ∼3-fold) and Li + diffusivity (by ∼2-fold) greatly improving charge transport, especially when operated at high rates. This results in an across-the-board improvement in self-discharge, specific capacity, energy density, rate capability, coulombic efficiency and cycling stability. When cycled at ∼200 mA g −1 , the capacity fade averaged over 3000 cycles for the surface vacancy-enriched material is ∼0.0167% per cycle compared to an order of magnitude higher fade rate for the baseline material. In conclusion, these findings reveal the potential of targeted surface oxygen vacancy doping to develop cobalt-free and high energy density cathodes that tolerate fast charging and deliver improved cycle life.

Cobalt-free cathodes↗
DOE OSTI2023

Design Strategies of Spinel Oxide Frameworks Enabling Reversible Mg-Ion Intercalation

In this study, reversible Mg 2+ intercalation in metal oxides frameworks is a key enabler for an operational Mg ion battery with high energy density needed for the next generation of energy storage technologies. While functional Mg-ion batteries have been achieved in structures with soft anions (e.g., S 2- and Se 2- ), they do not meet energy density requirements to compete with the current rechargeable lithium-ion batteries due to their low insertion potentials, emphasizing the necessity of finding an oxide-based cathode that operates at high potentials. A leading hypothesis to explain the limited availability of oxide Mg-ion cathodes is the belief that Mg 2+ has sluggish diffusion kinetics in oxides due to strong electrostatic interactions between the Mg 2+ ions and oxide anions in the lattice. From this assessment, it can be hypothesized that such rate limiting kinetic shortcomings can be mitigated by tailoring an oxide framework through creating less stable Mg 2+ - O 2- coordination.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗