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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Lithium-Ion Mobility in Layered Oxide Li 2 (La 0.75 Li 0.25 )(Ta 1.5 Ti 0.5 )O 7 Containing Lithium on both Intra and Inter‐Stack Positions

With the aid of neutron diffraction and electrochemical impedance spectroscopy, we have demonstrated the effect of the increase in lithium concentration and distribution on Li-ion conductivity. This has been done through the synthesis of a layered oxide Li 2 (La 0.75 Li 0.25 )(Ta 1.5 Ti 0.5 )O 7 , with the so-called Ruddlesden-Popper type structure, where bilayer stacks of (Ta/Ti)O 6 octahedra are separated by lithium ions, located in inter-stack spaces. There are also intra-stack spaces that are occupied by a mixture of La and Li, as confirmed by neutron diffraction. The distribution of lithium over both inter- and intra-stack positions leads to the enhancement of Li-ion conductivity in Li 2 (La 0.75 Li 0.25 )(Ta 1.5 Ti 0.5 )O 7 compared to Li 2 La(TaTi)O 7 , which has a lower concentration of lithium ions, located only in inter-stack spaces. Furthermore, the analyses of real and imaginary components of electrochemical impedance data confirm the enhanced mobility of ions in Li 2 (La 0.75 Li 0.25 )(Ta 1.5 Ti 0.5 )O 7 . While the Li-ion conductivity needs further improvement for practical applications, the success of the strategy implemented in this work offers a useful methodology for the design of layered ionic conductors.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Influence of Clay size on corrosion protection by Clay nanocomposite thin films

In this work, the influence of clay platelet size on the corrosion barrier performance of highly-aligned polymer clay nanocomposite (PCN) thin films was examined. Layer-by-layer (LbL) deposition of alternating branched polyethylenimine (PEI) and either laponite (LAP), montromorillonite (MMT) or vermiculite (VMT) clay platelets were assembled on mild steel plates to obtain 20 bilayer (BL) films and cross-linked using glutaraldehyde after deposition. The clay platelets were chosen based on their aspect ratio, approximately 30:1, 400:1, and 2000:1, respectively. Electrochemical impedance spectroscopy of the coated steel plates during immersion showed corrosion rates and coating permeability followed LAP > MMT > VMT for up to 7 days of exposure in 0.6 M NaCl. The PEI/VMT films, ~250 nm thick, slowed corrosion by a factor of >1000 compared to bare steel. The results support the premise that high aspect ratio clay platelets can improve the corrosion barrier efficacy of LbL PCN films by decreasing film permeability and provide exceptional protection to steel in saline environments compared to other thin multilayer coatings and pretreatments.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Damage of prismatic lithium‐ion cells subject to bending: Test, model, and detection

Abstract The mechanically induced internal short circuit (ISC) is one of the major safety concerns of lithium‐ion batteries. Mechanical abuse tests are often performed to evaluate the integrity and safety of lithium‐ion batteries under mechanical loadings. Except for the widely explored compression‐dominated indentation tests, bending is another typical real‐world loading condition that is tension‐dominated. To investigate the mechanical damage and ISC behavior of batteries under bending, we carried out controlled three‐point bending tests in four progressive steps on prismatic battery cells with maximum deflections ranging from 38% to 76% of the cell thickness. None of the tested cells experienced an ISC. We then conducted 3D X‐ray computed tomography (CT) scanning on the bent cells after unloading. X‐ray CT images showed three out of the four tested cells have extensive cracking in the electrode layers at the bottom side (opposite to the loading head). This indicates that cracking does not necessarily lead to an ISC under bending. Electrochemical impedance spectroscopy was also measured on the bent cells and substantial changes were observed. Both the bulk resistance and charge‐transfer resistance increased significantly after bending, which could influence the battery performance and lifespan. We then developed a detailed finite (FE) element model to further investigate the mechanical deformation and failure mechanisms. The FE model successfully predicts the load–displacement response and reproduces the deformation patterns. The findings and the FE model developed in the present study provide useful insights and tools for the battery structure and crash safety design. image

25 ENERGY STORAGE↗
DOE OSTI2025

Metal ion dopant-induced famatinite to chalcostibite phase transformation of copper antimony sulphide colloidal nanostructures: effect on photophysical and pseudocapacitance properties

Here, the strategic doping of transition metal ions into copper antimony sulphide (CAS) semiconducting nanostructures can significantly influence their photophysical and pseudocapacitive properties, for which there are few reports and therefore is the focus of this study. Accordingly, highly crystalline metal ion (Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ and Zn 2+ ) doped off-stoichiometric copper rich/poor, antimony-rich/poor, and sulphur-poor CAS nanostructures (10–23 nm) were grown via colloidal (hot-injection) synthesis using metal diethyldithiocarbamate precursors. Importantly, metal ion doping significantly influences the structure and composition of the off-stoichiometric CAS nanostructures. Data from powder X-ray diffraction, Raman spectroscopy, high-resolution scanning/transmission electron microscopy, and energy dispersive X-ray spectroscopy confirm that the heavier metal ion dopants induce a novel phase transformation from famatinite (fCAS) to chalcostibite (cCAS) nanostructures. The influence of the metal ion dopants is also observed in the optical properties of as-synthesized nanostructures. This involves blue-shifted ultraviolet-visible absorption, reduced Urbach tailing, and tunable bandgaps between 2.17 and 2.38 eV. Also, the doped nanostructures display broad visible-near infrared photoluminescence via a triple radiative pathway with relatively short decay lifetimes between 0.2 and 6.1 ns. This is mediated by electronic transitions involving intrinsic (copper/antimony/sulphur interstitial) and extrinsic (metal ion interstitial) defect states. Additionally, electrodes prepared from Mn 2+ -doped fCAS nanostructures show enhanced pseudocapacitance via Na+ surface adsorption and intercalation relative to undoped fCAS electrodes, while Zn 2+ -doped cCAS electrodes exhibit pseudocapacitance via a combination of Na+ surface adsorption, intercalation, and redox reactions. These electrodes exhibit reduced charge transfer resistance, improved electronic conductivity and notably enhanced specific capacitance (∼222 F g −1 ), and charge transport, as measured in 1 M Na 2 SO 4 electrolyte via cyclic voltammetry and electrochemical impedance spectroscopy. To this end, the discovery of the metal ion-induced phase transformation presents a new avenue for optimizing the functional properties of fCAS and cCAS nanostructures, highlighting the critical role of metal ion-related defects in controlling the optical and electrochemical properties, towards potential solar absorption and energy storage applications.

25 ENERGY STORAGE↗
DOE OSTI2026

Advancing the Performance of Anion Exchange Membrane Electrolysis by Employing a Powder-Based Ionomer during Anode Catalyst Layer Fabrication

The performance of anion exchange membrane water electrolysis (AEMWE) can be significantly improved by utilizing powdered ionomers during the fabrication of the anode catalyst layer (CL) to modify the CL properties. When comparing powdered ionomers to dispersed ionomers across various catalysts including cobalt oxide (Co 3 O 4 ), nickel−iron oxide (NiFe 2 O 4 ), and iridium oxide (IrO 2 ) the anode fabricated with powdered ionomers demonstrates improved performance in polarization curves, enhanced charge transfer kinetics, and reduced ohmic and transport losses, as evidenced by voltage breakdown and electrochemical impedance spectroscopy analyses. Optimal performance is achieved using a Co 3 O 4 catalyst with a 10 wt % powdered ionomer via the catalystcoated substrate method. Microscopy analyses reveal that electrodes formed with powdered ionomers during fabrication exhibit a more uniform catalyst and ionomer distribution, increased porosity with smaller pore areas, improved electronic conduction with less catalyst agglomeration isolated by a nonconductive ionomer, and enhanced interfacial contact with the membrane and transport layer. These findings highlight that ionomers in a powdered form can promote beneficial properties and are a promising approach to improving AEMWE efficiency.

08 HYDROGEN↗
DOE OSTI2020

Ultrathin Amorphous Silica Membrane Enhances Proton Transfer across Solid-to-Solid Interfaces of Stacked Metal Oxide Nanolayers while Blocking Oxygen

A large jump of proton transfer rates across solid-to-solid interfaces by inserting an ultrathin amorphous silica layer into stacked metal oxide nanolayers is discovered using electrochemical impedance spectroscopy and Fourier-transform infrared reflection absorption spectroscopy (FT-IRRAS). The triple stacked nanolayers of Co 3 O 4 , SiO 2 , and TiO 2 prepared by atomic layer deposition (ALD) enable a proton flux of 2400 ± 60 s -1 nm -2 (pH 4, room temperature), while a single TiO 2 (5 nm) layer exhibits a threefold lower flux of 830 s -1 nm -2 . Based on FT-IRRAS measurements, this remarkable enhancement is proposed to originate from the sandwiched silica layer forming interfacial SiOTi and SiOCo linkages to TiO 2 and Co 3 O 4 nanolayers, respectively, with the O bridges providing fast H + hopping pathways across the solid-to-solid interfaces. Finally, together with the complete O 2 impermeability of a 2 nm ALD-grown SiO 2 layer, the high flux for proton transport across multi-stack metal oxide layers opens up the integration of incompatible catalytic environments to form functional nanoscale assemblies such as artificial photosystems for CO 2 reduction by H 2 O.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Insight into the Solid Electrolyte Interphase Formation in Bis(fluorosulfonyl)Imide Based Ionic Liquid Electrolytes

The formation of the solid electrolyte interphase (SEI) in an ionic liquid electrolyte of 0.5 m lithium bis(fluorosulfonyl)imide (LiFSI) in 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide at high cell voltages (1.7–1.9 V) is investigated in ordered mesoporous carbon (OMC) based Li metal cells using an operando small-angle neutron scattering (SANS) technique coupled with electrochemical impedance spectroscopy and ex situ X-ray photoelectron spectroscopy (XPS). It is demonstrated that discharging the OMC Li metal cells to ≈2 V and holding the cell voltage constant induces a rapid current increase with time, confirming extensive reduction and SEI formation. XPS analysis reveals that LiF is formed at open cell voltage (OCV), which is attributed to the carbenes generated at the lithium negative electrode because of its reaction with EMIm cation diffusing to and initiating the reaction with FSI - anions at the carbon positive electrode. It is confirmed that the chemical reaction at OCV and electrochemical reduction at high cell voltage of the FSI - anion plays a protective role against EMIm cation co-intercalation into the carbon positive electrode during the initial discharge. Operando SANS studies also suggest that slight differences occur in the surface composition and reaction mechanism as a function of cell voltage.

1-ethyl-3- methylimidazolium bis(fluorosulfonyl)im↗
DOE OSTI2021

Engineering the Interlayer Spacing by Pre-Intercalation for High Performance Supercapacitor MXene Electrodes in Room Temperature Ionic Liquid

MXenes exhibit excellent capacitance at high scan rates in sulfuric acid aqueous electrolytes, but the narrow potential window of aqueous electrolytes limits the energy density. Organic electrolytes and room-temperature ionic liquids (RTILs) can provide higher potential windows, leading to higher energy density. The large cation size of RTIL hinders its intercalation in-between the layers of MXene limiting the specific capacitance in comparison to aqueous electrolytes. In this work, different chain lengths alkylammonium (AA) cations are intercalated into Ti 3 C 2 T x , producing variation of MXene interlayer spacings (d-spacing). AA-cation-intercalated Ti 3 C 2 T x (AA-Ti 3 C 2 ), exhibits higher specific capacitances, and cycling stabilities than pristine Ti 3 C 2 T x in 1 m 1-ethly-3-methylimidazolium bis-(trifluoromethylsulfonyl)-imide (EMIMTFSI) in acetonitrile and neat EMIMTFSI RTIL electrolytes. Pre-intercalated MXene with an interlayer spacing of ≈2.2 nm, can deliver a large specific capacitance of 257 F g –1 (1428 mF cm –2 and 492 F cm –3 ) in neat EMIMTFSI electrolyte leading to high energy density. Quasi elastic neutron scattering and electrochemical impedance spectroscopy are used to study the dynamics of confined RTIL in pre-intercalated MXene. Furthermore, molecular dynamics simulations suggest significant differences in the structures of RTIL ions and AA cations inside the Ti 3 C 2 T x interlayer, providing insights into the differences in the observed electrochemical behavior.

36 MATERIALS SCIENCE↗
DOE OSTI2024

In Situ Cyclized Polyacrylonitrile Coating: Key to Stabilizing Porous High-Entropy Oxide Anodes for High-Performance Lithium-Ion Batteries

High-entropy oxides (HEOs) composed of multiple metal elements have attracted great attention as anode materials for lithium-ion batteries (LIBs) due to the synergistic effects of various metal species. However, the practical applications of HEOs are still plagued by poor conductivity, unstable solid electrolyte interphase (SEI) and poor cycling stability. In this work, nanosized (FeCoNiCrMn) 3 O 4 HEO (NHEO) is prepared successfully by the NaCl-assisted mechanical ball-milling strategy. Novelly, polyacrylonitrile (PAN) is used as the binder and then in situ thermochemically cyclized to construct a cyclized PAN (cPAN) outer layer onto NHEO (NHEO-cPAN). The in situ formed cPAN coating not only improves the electrical conductivity, but also reinforces the structural and interfacial stability, and thereby, the resulted NHEO-cPAN electrode exhibits significantly enhanced rate and cyclic performance. Specifically, NHEO-PAN500 electrode delivers a high reversible capacity of 560 mAh g –1 at 5 A g –1 and a high-capacity retention of 83% over 800 cycles at 3 A g –1 . Furthermore, the structural evolution and electrochemical behavior of NHEO-PAN electrode during discharge/charge is systematically investigated by operando X-ray diffraction, in situ impedance spectroscopy and ex situ high-resolution transmission electron microscopy. Therefore, this work provides new insights into the engineering of electrode and interphase for high-performance HEO electrode materials, potentially enlightening the practical applications of HEO-based LIBs.

25 ENERGY STORAGE↗
DOE OSTI2026

Powder‐to‐Film Conversion of Nickel Single‐Atom Catalysts into Binder‐Free and Resistant Electrodes

Although a few binder-free and self-supported single-atom electrodes have been reported, achieving mechanically robust, defect-engineered, and reproducible films that preserve atomic dispersion under electrochemical operation remains challenging. This work addresses this limitation by presenting a versatile and generalizable strategy to transform powders into standalone, defect-engineered thin films hosting atomically dispersed Ni centers within conductive 2D frameworks. The physicochemical and electronic properties of these materials are thoroughly characterized using a comprehensive set of spectroscopic and microscopic techniques and confirmed the homogeneous dispersion and monoatomic nature of the Ni centers (0.94 wt.%) on the electrode films. Electrochemical testing via cyclic voltammetry and electrochemical impedance spectroscopy under a range of experimental conditions revealed that integration of Ni single atoms markedly enhanced performance and stability compared to carbon nanotube-only electrodes, maintaining integrity after 15 h of continuous operation. This improvement is accompanied by a notable reduction in charge transfer resistance (30.50 Ω) and an increase in double-layer capacitance (295.45 µF). Post-electrochemical analyses corroborated the structural integrity and robustness of the electrodes. Overall, this work bridges atomically precise catalysis and device-level electrochemistry, opening a route toward reproducible and scalable single-atom electrodes for sensing and energy conversion.

36 MATERIALS SCIENCE↗
DOE OSTI2026

All‐Solid‐State Batteries With Mechanically Stable Interfaces Consisting of a Zero‐Strain Cation‐Disordered Rocksalt Cathode

Interface stabilization is critical to the development of working all‐solid‐state batteries. Rigid cathode/solid electrolyte interfaces often disintegrate due to anisotropic volume change of cathode‐active materials, resulting in irreversible capacity loss. Herein, we demonstrate that Li 1.211 Mo 0.467 Cr 0.3 O 2 (LMCO), a pioneering cation‐disordered rocksalt oxide (DRX) cathode that has intrinsically small volume change upon lithium intercalation, can be integrated with a thiophosphate‐based solid electrolyte for all‐solid‐state batteries. Interface stability of the all‐solid LMCO cell was investigated by electrochemical impedance spectroscopy, X‐ray micro‐computed tomography, and electron microscopy. Since LMCO was initially synthesized as a layered phase exhibiting a large volume change, interface disintegration can be observable in the early cycles. As layered LMCO phase‐transformed into DRX LMCO in subsequent cycles, reintegration of the interfaces occurs within a pressurized cell as a result of its zero‐stain behavior. Consequently, the DRX LMCO cathode maintains interface integrity, and thus electrical wiring, over an extended number of cycles, leading to improved capacity retention with small internal cell resistance.

DRX↗
DOE OSTI2023

Beneficial Effects of La 0.5 Sr 0.5 CoO 3 Coatings on Thin‐Film LiMn 2 O 4 Cathodes for Lithium Ion Batteries

Abstract The severe capacity loss of spinel LiMn 2 O 4 (LMO) limits the utility of this otherwise promising lithium ion battery cathode material. One of the strategies to mitigate capacity fade is applying a coating on LMO particle surfaces. While this approach yields promising results, there is limited understanding of mechanisms whereby coatings improve LMO capacity retention. Herein, the effects of a new protective coating material, La 0.5 Sr 0.5 CoO 3 (LSCO), in a thin‐film battery geometry that is amenable to fundamental studies of electrode processes, are reported. RF sputtering deposition is used to produce high quality 25–100 nm LMO cathodes on Al 2 O 3 substrates with an intervening Pt/Ti back‐side contact layer. Cycling of the un‐coated cathodes results in capacity loss of 18% over 300 cycles. Adding a 2 nm LSCO layer reduces the capacity loss to 3%. While this may be due in part to reduced Mn dissolution, scanning transmission electron microscopy results indicate that the coating helps to preserve crystallinity and reduce lattice structure distortion due to inhibited formation of defect tetragonal spinel. Three‐electrode electrochemical impedance spectroscopy results reveal that the LSCO coating increases charge transfer and ohmic resistances, but the increases are generally too small to significantly impact cell performance even at high C‐rates.

25 ENERGY STORAGE↗
DOE OSTI2021

Local Multimodal Electro-Chemical-Structural Characterization of Solid-Electrolyte Grain Boundaries

Typical models of polycrystalline ionic materials treat the grain boundary properties as single valued, without consideration of the full range of values that define the macroscopically measured average. Here a unique experimental platform suitable for local multimodal characterization of individual grain boundaries in bicrystal fibers is reported. A variation of three orders of magnitude in the grain boundary conductivity of ceria is observed, as measured across six individual bicrystals by both alternating current impedance spectroscopy and direct current (D.C.) linear sweep voltammetry. Nonlinear behavior of the D.C. measurements is consistent with resistance due to a space charge effect. Time-of-flight secondary ion beam spectroscopy reveals a correlation between grain boundary resistance and the concentration of impurities Si, Al, and Ca segregated at the grain boundaries, although the bulk concentrations of these impurities are negligible. Electron backscatter diffraction analysis of the crystal orientations suggests a correlation between the misorientation across the grain boundaries and grain boundary resistance. These correlations point towards a grain boundary resistance that arises from impurity-generated space charge effects and variations in impurity concentration and hence resistivity driven by the energetics of impurity segregation to grain boundaries of differing surface energies.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Contact Resistance of Carbon–Li x (Ni,Mn,Co)O 2 Interfaces

Abstract Electronic resistance in lithium‐ion battery positive electrodes is typically attributed to the bulk resistance of the active material and the network resistance of the carbon additive. Expected overpotentials from these bulk components are minimal relative to that from charge‐transfer resistance. However, literature reports show that cell overpotentials are often much more sensitive to conductive additives than the expected level from bulk or percolating‐network transport. This discrepancy motivated a detailed examination of the contact resistance between the active material and conductive additive. The contact and bulk resistances are simultaneously measured using dense bar samples of lithium‐layered oxides (Li x Ni 1 /3 Mn 1/3 Co 1/3 O 2 and Li x Ni 0.5 Mn 0.3 Co 0.2 O 2 ) in contact with carbon black. It is found that the contact resistance dominates the overall electronic resistance when the length scale is smaller than millimeters; after correcting for contact effects, bulk conductivity of layered oxides is determined to be orders‐of‐magnitude higher than previously reported. In porous electrodes, it is found from three‐electrode electrochemical impedance spectroscopy that the carbon content most heavily influences the low‐frequency regime (≈0.01 Hz), as opposed to the high frequency (>10 3 Hz) regime expected from electronic percolating properties. Constriction effects within the layered oxide are identified as the dominant mechanism for contact resistance and its implication is investigated for porous electrodes.

Kuo, Jimmy Jiahong↗
DOE OSTI2022

Double Paddle‐Wheel Enhanced Sodium Ion Conduction in an Antiperovskite Solid Electrolyte

Abstract Antiperovskite structure compounds (X 3 AB, where X is an alkali cation and A and B are anions) have the potential for highly correlated motion between the cation and a cluster anion on the A or B site. This so‐called “paddle‐wheel” mechanism may be the basis for enhanced cation mobility in solid electrolytes. Through combined experiments and modeling, the first instance of a double paddle‐wheel mechanism, leading to fast sodium ion conduction in the antiperovskite Na 3− x O 1− x (NH 2 ) x (BH 4 ), is shown. As the concentration of amide (NH 2 − ) cluster anions is increased, large positive deviations in ionic conductivity above that predicted from a vacancy diffusion model are observed. Using electrochemical impedance spectroscopy, powder X‐ray diffraction, synchrotron X‐ray diffraction, neutron diffraction, ab initio molecular dynamics simulations, and NMR, the cluster anion rotational dynamics are characterized and it is found that cation mobility is influenced by the rotation of both NH 2 − and BH 4 − species, resulting in sodium ion conductivity a factor of 10 2 higher at x = 1 than expected for the vacancy mechanism alone. Generalization of this phenomenon to other compounds could accelerate fast ion conductor exploration and design.

25 ENERGY STORAGE↗
DOE OSTI2024

Battery Electrolyte Design for Electric Vertical Takeoff and Landing (eVTOL) Platforms

Here, the development of robust and high-performance battery systems is crucial for the advancement of Electric Vertical Takeoff and Landing (eVTOL) vehicles for urban air mobility. This study evaluates the performance of different lithium-ion battery chemistries under Electric Vertical Takeoff and Landing (eVTOL) load profiles. The actual flight data coupled with physical models is used to create discharge profiles for testing on developed lithium-ion cells for eVTOLs. The performance of a standard liquid electrolyte (1.2 M LiPF 6 in EC:EMC), labeled Gen-2, is benchmarked and compared with a fast-charging electrolyte (1.2 M LiFSI in EC:EMC), labeled XFC. Cell analysis involves the use of various techniques, such as impedance spectroscopy, polarization curves, and capacity retention measurements. Capacity retention is stable for both systems over 500 cycles, but unique discharge capacity trends are observed for different mission segments. During the initial takeoff hover stages, Gen-2 electrolytes experience substantial voltage fade, while XFC electrolytes maintain consistent behavior. In general, the Gen-2 electrolyte demonstrated lower discharge overpotentials and higher decay during cycling compared to the XFC electrolyte. This work highlights the complexity of eVTOL battery behavior and provides insights into battery system design, contributing to the advancement of battery energy storage solutions for urban air mobility.

25 ENERGY STORAGE↗