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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Investigation of Low-Energy Lattice Dynamics and Their Role in Superionic Na Diffusion and Ultralow Thermal Conductivity of Na 3 PSe 4 as a Solid-State Electrolyte

The atomic dynamics of Na 3 PSe 4 were investigated using a combination of neutron scattering experiments and ab initio and machine-learned molecular dynamics simulations to probe the interplay of fast ionic diffusion with atomic vibrations (phonons) of the host lattice. Our results reveal the existence of low-energy vibrational modes, simultaneously involving motions of Na + ions and framework polyanion subunits, and show that these modes become strongly overdamped in the superionic regime as they couple with the Na + hopping process. In particular, the Na+ migration energy landscape is strongly impacted by low-energy phonons derived from a soft acoustic branch of the host lattice, which modulates the diameter of the Na + diffusion channel at the bottleneck. We find that an additional factor for the enhanced Na + conductivity in Na 3 PSe 4 is the presence of Na-vacancies, which also affect the low-frequency dynamics and thermal vibration amplitudes, pointing to an interplay between Na + vacancies and host dynamics, jointly enhancing ionic diffusivity. Finally, we investigate the origin of ultralow thermal conductivities in Na 3 PSe 4 and Na 3 PS 4 using Green–Kubo simulations and find that low-energy acoustic phonon modes of the overall crystal framework provide a dominant contribution to the thermal conductivity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Anharmonic lattice dynamics and superionic transition in AgCrSe 2

Intrinsically low lattice thermal conductivity ( κ l a t ) in superionic conductors is of great interest for energy conversion applications in thermoelectrics. Yet, the complex atomic dynamics leading to superionicity and ultralow thermal conductivity remain poorly understood. Here, we report a comprehensive study of the lattice dynamics and superionic diffusion in A g C r S e 2 from energy- and momentum-resolved neutron and X-ray scattering techniques, combined with first-principles calculations. Our results settle unresolved questions about the lattice dynamics and thermal conduction mechanism in A g C r S e 2 . We find that the heat-carrying long-wavelength transverse acoustic (TA) phonons coexist with the ultrafast diffusion of Ag ions in the superionic phase, while the short-wavelength nondispersive TA phonons break down. Strong scattering of phonon quasiparticles by anharmonicity and Ag disorder are the origin of intrinsically low κ l a t . The breakdown of short-wavelength TA phonons is directly related to the Ag diffusion, with the vibrational spectral weight associated to Ag oscillations evolving into stochastic decaying fluctuations. Furthermore, the origin of fast ionic diffusion is shown to arise from extended flat basins in the energy landscape and collective hopping behavior facilitated by strong repulsion between Ag ions. These results provide fundamental insights into the complex atomic dynamics of superionic conductors.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Lithium Oxide Superionic Conductors Inspired by Garnet and NASICON Structures

Abstract The key component in lithium solid‐state batteries (SSBs) is the solid electrolyte composed of lithium superionic conductors (SICs). Lithium oxide SICs offer improved electrochemical and chemical stability compared with sulfides, and their recent advancements have largely been achieved using materials in the garnet‐ and NASICON (sodium superionic conductor)‐ structured families. In this work, using the ion‐conduction mechanisms in garnet and NASICON as inspiration, a common pattern of an “activated diffusion network” and three structural features that are beneficial for superionic conduction: a 3D percolation Li diffusion network, short distances between occupied Li sites, and the “homogeneity” of the transport path are identified. A high‐throughput computational screening is performed to search for new lithium oxide SICs that share these features. From this search, seven candidates are proposed exhibiting high room‐temperature ionic conductivity evaluated using ab initio molecular dynamics simulations. Their structural frameworks including spinel, oxy‐argyrodite, sodalite, and LiM(SeO 3 ) 2 present new opportunities for enriching the structural families of lithium oxide SICs.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Mechanistic insights into superionic thioarsenate argyrodite solid electrolytes via machine learning interatomic potentials

The lithium argyrodite sulfide solid electrolyte Li 6 PS 5 Cl has attracted considerable interest for all-solid-state batteries owing to its high ionic conductivity, which can be further enhanced through ionic substitution. Although a variety of substitutions have been investigated, thioarsenate argyrodites remain comparatively underexplored. Here, we systematically investigate the phase stability and Li-ion conduction mechanisms in superionic Br-incorporated thioarsenate argyrodites using first-principles calculations and molecular dynamics simulations based on machine learning interatomic potentials (MLIPs). Systematic variation of S/Br site inversion reveals that an optimal degree of anion disorder significantly enhances inter-cage connectivity and facilitates long-range Li-ion diffusion. Configurational entropy serves as an effective quantitative descriptor of anion disorder, exhibiting a strong correlation with ionic conductivity. While greater anion disorder induced by site inversion and higher Br content enhances ionic conductivity up to 50 mS cm −1 , it simultaneously reduces structural stability. This trade-off results in an optimal window in which a moderate level of disorder yields conductivities exceeding 20 mS cm −1 while maintaining synthetic feasibility. In conclusion, this work highlights the reliability and efficiency of MLIPs for elucidating ion-transport mechanisms and accelerating the design of novel superionic argyrodites.

Jang, Myeongcho [Korea Institute of Science and Te↗
DOE OSTI2018

A New Version of the Lithium Ion Conducting Plastic Crystal Solid Electrolyte

Abstract Portable electronic devices are predominantly powered by lithium ion batteries in which the electrolyte is a liquid or gel of lithium salts dissolved in molecular solvents. There have been many attempts to replace the flammable liquid component of the electrolyte by alternative alkali metal transporting media, such as superionic crystals, alkali‐conducting glassy solids, ionic liquids, salt‐in‐molecular plastic crystal solvent, and salt‐in‐ionic plastic crystal solvents. Except for the first two of the above, which have their own problems, all the above have the disadvantage that the alkali cation is the least mobile of the ionic species due to its high charge/radius ratio. Here, some new, silylsulfate‐based are introduced. Members of the class of lithium ion conductor in which the alkali ion is the only cationic species present, and the salt itself is a plastic crystal, a solid in which the anion centers of mass are ordered, but the anion orientations are disordered and dynamic (best example NaCB 9 H 10 , see text). It is shown that depending on the nature of the anion, the conductivity may be within a factor of two of the standard liquid carbonate electrolyte. The soft, spreadable electrolyte, impregnated in Celgard separators, supports truly reversible Li insertion into the LiCoO 2 cathode.

Klein, Iolanda S.↗
DOE OSTI2018

Characteristics of the Li{sup +}-Ion Conductivity of Li{sub 3}R{sub 2}(PO{sub 4}){sub 3} Crystals (R = Fe, Sc) in the Superionic State

The characteristics of Li+-ion conductivity σdc of structural γ modifications of Li{sub 3}R{sub 2}(PO{sub 4}){sub 3} compounds (R = Fe, Sc) existing in the superionic state have been investigated by impedance spectroscopy. The type of structural framework [R{sub 2}P{sub 3}O{sub 12}]{sub ∞}{sup 3-} affects the σdc value and the σdc activation enthalpy in these compounds. The ion transport activation enthalpy in γ-Li{sub 3}R{sub 2}(PO{sub 4}){sub 3} (ΔH{sub σ} = 0.31 ± 0.03 eV) is lower than in γ-Li{sub 3}Fe{sub 2}(PO{sub 4}){sub 3} (ΔH{sub σ} = 0.36 ± 0.03 eV). The conductivity of γ-Li{sub 3}Fe{sub 2}(PO{sub 4}){sub 3} (σ{sub dc} = 0.02 S/cm at 573 K) is twice as high as that of γ-Li{sub 3}R{sub 2}(PO{sub 4}){sub 3}. A decrease in temperature causes a structural transformation of Li{sub 3}R{sub 2}(PO{sub 4}){sub 3} from the superionic γ modification (space group Pcan) through the intermediate metastable β modification (space group P2{sub 1}/n) into the “dielectric” α modification (space group P2{sub 1}/n). Upon cooling, σdc for both phosphates decreases by a factor of about 100 at the superionic TSIC transition. In Li{sub 3}Fe{sub 2}(PO{sub 4}){sub 3} σdc gradually decreases in the temperature range T{sub SIC} = 430–540 K, whereas in Li{sub 3}R{sub 2}(PO{sub 4}){sub 3} σdc undergoes a jump at T{sub SIC} = 540 ± 25 K. Possible crystallochemical factors responsible for the difference in the σdc and ΔH{sub σ} values and the thermodynamics and kinetics of the superionic transition for Li{sub 3}R{sub 2}(PO{sub 4}){sub 3} are discussed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Using Data-Science Approaches to Unravel Insights for Enhanced Transport of Lithium Ions in Single-Ion Conducting Polymer Electrolytes

Solid polymer electrolytes have yet to achieve the desired ionic conductivity (>1 mS/cm) near room temperature required for many applications. This target implies the need to reduce the effective energy barriers for ion transport in polymer electrolytes to around 20 kJ/mol. In this work, we combine information extracted from existing experimental results with theoretical calculations to provide insights into ion transport in single-ion conductors (SICs) with a focus on lithium ion SICs. Through the analysis of temperature-dependent ionic conductivity data obtained from the literature, we evaluate different methods of extracting energy barriers for lithium transport. The traditional Arrhenius fit to the temperature-dependent ionic conductivity data indicates that the Meyer–Neldel rule holds for SICs. However, the values of the fitting parameters remain unphysical. Our modified approach based on recent work (Macromolecules 2023, 56, 15, 6051), which incorporates a fixed pre-exponential factor, reveals that the energy barriers exhibit temperature dependence over a wide range of temperatures. Using this approach, we identify anions leading to the energy barriers <30 kJ/mol, which include trifluoromethane sulfonimide (TFSI), fluoromethane sulfonimide (FSI), and boron-based organic anions. In our efforts to design the next generation of anions, which can exhibit the energy barriers <20 kJ/mol, we have performed density functional theory (DFT) based calculations to connect the chemical structures of boron-based anions via the binding energy of cation (lithium)-anion pairs with the experimentally derived effective energy barriers for ion hopping. Not only have we identified a correlation between the binding energy and the energy barriers, but we also propose a strategy to design new boron-based anions by using the correlation. This combined approach involving experiments and theoretical calculations is capable of facilitating the identification of promising new anions, which can exhibit ionic conductivity >1 mS/cm near room temperature, thereby expediting the development of novel superionic single-ion conducting polymer electrolytes.

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

Using data-science approaches to unravel insights for enhanced transport of lithium ions in single-ion conducting polymer electrolyte

Solid polymer electrolytes have yet to achieve the an ionic conductivity > 1 mS/cm at room temperature for realistic applications. This target implies the need to reduce the effective energy barriers of ion transport in polymer electrolytes to around 20 kJ/mol. In this work, we combine information extracted from existing experimental results with theoretical calculations to provide insights into ion transport in single-ion conductors (SICs) with a focus on lithium ion SICs. Through the analysis of temperature-dependent ionic conductivity data obtained from the literature, we evaluate different methods of extracting energy barriers for lithium transport. The traditional Arrhenius fit to the temperature-dependent ionic conductivity data indicates that the Meyer-Neldel rule holds for SICs. However, the values of the fitting parameters remain unphysical. Our modified approach based on recent work (Macromolecules, 56, 15, 6051(2023)), which incorporates a fixed pre-exponential factor, reveals that the energy barriers exhibit temperature dependence over a wide range of temperatures. Using this approach, we identify a series of anions leading to the energy barriers less than 30 kJ/mol, which include trifluoromethane sulfonimide (TFSI), fluoromethane sulfonimide (FSI), and boron-based organic anions. In our efforts to design the next generation of anions, which can exhibit the energy barriers less than 20 kJ/mol, we focused on boron-containing SICs, and performed density functional theory (DFT) based calculations to connect the chemical structures via the binding energy of cation (lithium)-anion pairs with the experimentally derived effective energy barriers for ion transport. Not only have we identified a correlation between the binding energy and the energy barriers, but we also propose a strategy to design new boron-based anions by using the correlation. This combined approach involving experiments and theoretical calculations is capable of facilitating the identification of promising new anions, which can exhibit ionic conductivity $> 1$ mS/cm near room temperature, thereby expediting the development of novel superionic single-ion conducting polymer electrolytes. The published datasets include all the temperature-dependent ionic conductivity collected from the literature with literature DOIs, DFT calculated binding energies, and python scripts to analyze data, construct statistical models, and generate plots.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Increase in the Fluorine-Ion Conductivity of Single Crystals of Tysonite-type CeF{sub 3} Superionic Conductor by Substituting Polarized Cd{sup 2+} Ions for Ce{sup 3+} Ions

The fluorine-ion conductivity of single crystals with a tysonite (LaF{sub 3}) structure with heterovalent isomorphic substitutions of highly polarizable Cd{sup 2+} cations with a 18-electron shell for rare earth ions Ce{sup 3+} have been studied for the first time. Ce{sub 0.995}Cd{sub 0.005}F{sub 2.995} single crystals have been grown from melt by the Bridgman technique in a fluorinating atmosphere. The fluorine-ion conductivity of single crystal is measured by impedance spectroscopy in the temperature range from 153 to 1073 K, where it increases by a factor of 10{sup 9}, approaching the value σ{sub dc} = 5 × 10{sup –2} S/cm at 1073 K. At T{sub 0} = 450 ± 20 K, the dependence σ{sub dc}(T) is split into two portions with the ion-transport activation enthalpy ΔH{sub σ} = 0.39 ± 0.01 eV (T < T{sub 0}) and ΔH{sub σ} = 0.23 ± 0.02 eV (T > T0). It is found that at T = 293 K the conductivity σ{sub dc} = 3 × 10{sup –5} S/cm of Ce{sub 0.995}Cd{sub 0.005}F{sub 2.995} crystal is higher by a factor of 10 than the conductivity of the tysonite matrix CeF{sub 3} and close to the σ{sub dc} value for Ce{sub 0.995}Sr{sub 0.005}F{sub 2.995} crystal. This finding indicates a significant effect of the substitutions of Cd{sup 2+} ions for Ce{sup 3+} on the σdc value and the advantage of Cd{sup 2+} ions over Ca{sup 2+} and Ba{sup 2+} from the viewpoint of increasing σ{sub dc}.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Selective breakdown of phonon quasiparticles across superionic transition in CuCrSe 2

Superionic crystals exhibit ionic mobilities comparable to liquids while maintaining a periodic crystalline lattice. The atomic dynamics leading to large ionic mobility have long been debated. A central question is whether phonon quasiparticles—which conduct heat in regular solids—survive in the superionic state, where a large fraction of the system exhibits liquid-like behaviour. Here we present the results of energy- and momentum-resolved scattering studies combined with first-principles calculations and show that in the superionic phase of CuCrSe 2 , long-wavelength acoustic phonons capable of heat conduction remain largely intact, whereas specific phonon quasiparticles dominated by the Cu ions break down as a result of anharmonicity and disorder. The weak bonding and large anharmonicity of the Cu sublattice are present already in the normal ordered state, resulting in low thermal conductivity even below the superionic transition. Furthermore, these results demonstrate that anharmonic phonon dynamics are at the origin of low thermal conductivity and superionicity in this class of materials.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2018

Sodium Superionic Conductors Based on Clusters

Owing to the high abundance and low cost of sodium (Na), Na-based rechargeable batteries hold great potential for large-scale applications in the future energy industry. However, as key component of the battery electrolyte, only a few Na-based superionic conductors can reach the ionic conductivity comparable to that of liquid or gel electrolytes. Here, we provide a guideline for the development of cluster-based Na-rich antiperovskite superionic conductors using computational studies. With a selected cluster ion BCl 4 – , we are able to achieve high-room-temperature Na-ionic conductivity over 10 –3 S/cm and low activation energies below 0.2 eV in the antiperovskite crystals Na 3 S(BCl 4 ) and Na 3 S(BCl 4 ) 0.5 I 0.5 . In addition, these materials have large bandgaps and favorable mechanical properties. Here, a comprehensive study of the stability and formation energy of these materials further illustrates possible routes for their synthesis. New insights into the conduction mechanism of these cluster-based superionic conductors are provided, including the cooperative motion of Na ions and the significant reduction of the migration barrier due to the changing orientation of the cluster ion.

25 ENERGY STORAGE↗
DOE OSTI2024

Critical Role of Framework Flexibility and Disorder in Driving High Ionic Conductivity in LiNbOCl 4

Understanding Li-ion transport is key for the rational design of superionic solid electrolytes with exceptional ionic conductivities. LiNbOCl 4 is reported to be one of the most highly conducting materials in the recently realized new class of soft oxyhalide solid electrolytes, exhibiting an ionic conductivity of ~11 mS·cm -1 . Here, we apply X-ray/neutron diffraction and pair distribution function analysis - coupled with density functional theory/ab-initio molecular dynamics - to determine a structural model that provides a rationale for the high conductivity that we observe experimentally in this nanocrystalline solid. We show that it arises from unusually high framework flexibility at room temperature. This owes to isolated 1-D [NbOCl 4 ] - anionic chains which exhibit energetically favorable orientational disorder that is - in turn - correlated to multiple, disordered and equi-energetic Li + sites in the lattice. As the Li-ions sample the 3-D energy landscape with a fast predicted diffusion coefficient of 5.1 x 10 -7 cm 2 /s at room temperature (σ i calc = 17.4 mS·cm -1 ), the inorganic polymer chains can reorient or vice versa. The activation energy barrier for Li migration through the frustrated energy landscape is especially reduced by the elastic nature of the NbO 2 Cl 4 octahedra evident from very widely dispersed Cl-Nb-Cl bond angles in AIMD snapshots at 300 K. The phonon spectra are predominantly influenced by Cl vibrations in the low energy range, and there is strong overlap between the framework (Cl, Nb) and Li partial pDOS in the region between 1.2 - 4.0 THz. The framework flexibility is also reflected in a relatively low bulk modulus of 22 GPa. In conclusion, our findings pave the way for investigation of future “flex-ion” inorganic solids and open up a new direction for the design of high conductivity, soft solid electrolytes for all-solid-state batteries.

AIMD↗
DOE OSTI2018

Practical Challenges and Future Perspectives of All-Solid-State Lithium-Metal Batteries

The fundamental understandings and technological innovations in lithium-ion batteries are essential for delivering high energy density, stable cyclability, and cost-effective energy storages with the growing demands in the applications of electrical vehicles and smart grid. Solid-state electrolytes (SSEs) are more promising than organic liquid electrolyte in terms of excellent safety in developing lithium-metal anode as well as other high-capacity cathode chemistries, such as sulfur and oxygen. Considerable efforts have been made to give birth to the superionic conductors with ionic conductivities higher than 10 –3 S cm –1 at room temperature. Furthermore, the high interfacial impedances from the poor compatibility of SSEs with electrodes limit their practical applications, which are discussed in this review. Furthermore, the recent advances and critical challenges for all-solid-state lithium-metal batteries based on the cathode materials of lithium-intercalation compounds, sulfur, and oxygen are overviewed, and their future developments are also prospected.

25 ENERGY STORAGE↗
DOE OSTI2025

Synthetic Accessibility and Sodium Ion Conductivity of the Na8–x A x P2O9 (NAP) High-Temperature Sodium Superionic Conductor Framework

Advancement of solid-state electrolytes (SSEs) for all solid-state batteries typically focuses on modification of a known structural framework to improve conductivity, e.g., cation substitution for an immobile ion or varying the concentration of the mobile ions. Novel frameworks can be disruptive by enabling fast ion conduction aided by different structure and diffusion mechanisms, thereby unlocking optimal conductors with different properties. Herein, we perform a high-throughput survey of a structural framework for sodium ion conduction, Na8–x A x P2O9 (NAP), to understand the family’s thermodynamic stability, synthesizability, and ionic conduction. We show that the parent phase Na4TiP2O9 (NTP) undergoes a structural distortion (with accompanying conductivity transition) due to unstable phonons arising from pseudo-Jahn–Teller mode in the 1D titanium chains. Screening compounds in which Ti is substituted by other metals computationally reveal a number of candidates that are predicted to be low in formation energy and have high predicted ionic conductivities. High-throughput experimental and subsequent methodology optimization trials deliver one new compound, Na4SnP2O9 (NSP). X-ray diffraction (XRD), microscopy, and spectroscopy characterization indicate that the room-temperature structure of NSP is similar to the high-temperature, orthorhombic NTP phase but with some small unresolved structural differences. These uncharacterized structural details are speculated to limit the ion conductivity. Temperature-dependent XRD and electrochemical impedance spectroscopy indicate multiple coupled conductivity–structure transitions at a high temperature. We demonstrate the challenges with synthesis development and a priori identification of promising SSE phases as a major bottleneck in new (energy) materials development.

Chemical reactions↗
DOE OSTI2022

Argyrodite-type advanced lithium conductors and transport mechanisms beyond paddle-wheel effect

Abstract Development of next-generation solid-state Li-ion batteries requires not only electrolytes with high room-temperature (RT) ionic conductivities but also a fundamental understanding of the ionic transport in solids. In spite of considerable work, only a few lithium conductors are known with the highest RT ionic conductivities ~ 0.01 S/cm and the lowest activation energies ~0.2 eV. New design strategy and novel ionic conduction mechanism are needed to expand the pool of high-performance lithium conductors as well as achieve even higher RT ionic conductivities. Here, we theoretically show that lithium conductors with RT ionic conductivity over 0.1 S/cm and low activation energies ~ 0.1 eV can be achieved by incorporating cluster-dynamics into an argyrodite structure. The extraordinary superionic metrics are supported by conduction mechanism characterized as a relay between local and long-range ionic diffusions, as well as correlational dynamics beyond the paddle-wheel effect.

25 ENERGY STORAGE↗
DOE OSTI2019

Chemistry Design Towards a Stable Sulfide-Based Superionic Conductor Li 4 Cu 8 Ge 3 S 12

Sulfide-based superionic conductors with high ionic conductivity have been explored as candidates for solid-state Li batteries. However, moisture hypersensitivity has made their manufacture complicated and costly and also impeded applications in batteries. Now, a sulfide-based superionic conductor Li 4 Cu 8 Ge 3 S 12 with superior stability was developed based on the hard/soft acid–base theory. The compound is stable in both moist air and aqueous LiOH aqueous solution. The electrochemical stability window was up to 1.5 V. An ionic conductivity of 0.9×10 -4 S cm with low activation energy of 0.33 eV was achieved without any optimization. The material features a rigid Cu-Ge-S open framework that increases its stability. Meanwhile, the weak bonding between Li + and the framework promotes ionic conductivity. This work provides a structural configuration in which weak Li bonding in the rigid framework promotes an environment for highly conductive and stable solid-state electrolytes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗