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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

A Crystal-Physical Model of Electrotransfer in the Superionic Conductor Pb{sub 1–} {sub x}Sc{sub x}F{sub 2+} {sub x} (x = 0.1)

The frequency (ν = 10{sup –1}–107 Hz) dependences of electrical conductivity σ(ν) of single crystals of superionic conductor Pb{sub 0.9}Sc{sub 0.1}F{sub 2.1} (10 mol % ScF{sub 3}) with fluorite type structure (CaF{sub 2}) in the temperature range 153–410 K have been investigated. The static bulk conductivity σ{sub dc} =1.5 × 10{sup –4} S/cm and average hopping frequency ν{sub h} = 1.5 × 10{sup 7} Hz of charge carriers (mobile ions F{sup −}) at room temperature (293 K) have been defined from the σ{sub dc}(ν) experimental curves. Enthalpies of thermoactivated processes of ionic conductivity σ{sub dc}(T) (ΔH{sub σ} = 0.393 ± 0.005 eV) and dielectric relaxation ν{sub h}(T) (ΔH{sub h} = 0.37 ± 0.03 eV) coincide within their errors. A crystal-physical model of fluorine-ion transport in a Pb{sub 0.9}Sc{sub 0.1}F{sub 2.1} crystal lattice has been proposed. The characteristic parameters of charge carriers have been calculated: concentration n{sub mob} = 2.0 × 10{sup 21} cm{sup −3}, the distance of the hopping d ≈ 0.5 nm and mobility μ{sub mob} = 4.5 × 10{sup −7} cm{sup 2}/s V (293 K).

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

String-Like Transport in Superionic Conductors

Superionic or fast-ion conductors are multicomponent solid-state systems in which one sublattice becomes mobile and exhibits extraordinarily high ionic conductivity before the melting within the solid state. Uranium dioxide (UO{sub 2}) - the fuel material of choice in most nuclear reactors - shows superionic behavior, although the mechanism of fast ion transport of the mobile oxygen ions, and its implication, is not well-understood. UO{sub 2} belongs to the category of Type II superionics wherein the conductivity rises gradually with increasing temperature, without an attendant phase change. In a recent work, using atomistic simulations and available neutron and x-ray scattering data, we have shown that all Type II superionic conductors exhibit a well-defined onset of dynamic disorder at a characteristic temperature T{sub α} = (∼2000 K for UO{sub 2}). Unlike the familiar superionic or Bredig transition temperature T{sub α} (∼2650 K for UO{sub 2}) that is associated with a second-order thermodynamic phase transition, T{sub α} represents an order-disorder (O-D) transition that marks a structural and kinetic crossover from a crystalline state to a semi-ordered state. In the temperature range between T{sub α} and T{sub λ}, the oxygen ions in UO{sub 2} exhibit jammed dynamics even though the mobile oxygen ions favor collective hopping from one native crystalline site to another. This cooperative dynamics manifests as dynamical heterogeneity (DH) - the tendency of highly mobile oxygen ions to form dynamic clusters, and dynamical facilitation (DF) - the mode of system relaxation facilitated solely through the kinetic ions transferring their mobility to neighboring ions. The jammed dynamics portrayed by the oxygen ions is similar to that observed in supercooled liquids and glassy materials, and other disordered systems such as granular media and polymers. In the current work, we probe the ionic dynamics in UO{sub 2} for the presence of another ubiquitous signature of glassy and jammed systems, namely, the one-dimensional string-like motion of the mobile species. Unlike the uncorrelated vacancy exchanges and interstitial migration in defected crystalline states, the string motion is a collective mechanism among the mobile species wherein each member of the string induces the next member to move in a correlated, sequential fashion. Using atomistic simulations, we demonstrate that oxygen ions in UO{sub 2} are transported through a string-like mechanism in the temperature range between T{sub α} and T{sub λ}, and the probability distribution of occurrence of the strings varies exponentially with string length. The discovery of string-like motion of the oxygen ions is somewhat surprising given the crystalline underpinning of the mobile species and the dynamic tendency of the oxygen ions to hop between lattice sites. In addition to dynamical heterogeneity and dynamical facilitation, our work has added one more entry, namely the occurrence of string-like transport, to the list of phenomenological similarities between superionic conductors and jammed systems. Using atomistic simulations, we have established the occurrence of string-like ionic motion among the oxygen ions in UO{sub 2} between temperatures T{sub α} - the order-disorder (O-D) transition temperature, and T{sub λ} - the Bredig transition temperature. As observed in other jammed systems, the length of the strings is observed to have an exponential distribution implying that the probability of occurrence of a smaller string is much higher than that of a longer string. Interestingly, using Temperature-Accelerated Dynamics (TAD) we have also established that string-like hopping takes place at temperatures lower than T{sub α}; these results will be published elsewhere. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2025

Mechanism of Contrasting Ionic Conductivities in Li 2 ZrCl 6 via I and Br Substitution

Understanding the complex structural and chemical factors that influence ionic conduction mechanisms is paramount for developing advanced inorganic superionic conductors in all‐solid‐state batteries, particularly halide solid electrolytes with excellent electrochemical oxidative stability and mechanical sinterability. Herein, contrasting ionic conduction behaviors in I − and Br − substituted Li 2 ZrCl 6 are revealed by combining experimental structural analyses and theoretical calculations. The inter‐slab distance along the c ‐axis, which varies with the anion substitution and M2‐M3 site disorder, is a key factor for opening the ab ‐plane conduction and facilitating the overall Li + conduction. Increased M3 site occupancy generally leads to contracted inter‐slab distance. The substantial increase in Li + conductivity upon I substitution (from 0.40 to 0.91 mS cm −1 ) originates from a sufficiently expanded lattice volume owing to its large ionic radii (I − = 2.20 Å), particularly inter‐slab distance that facilitates the ab intra‐plane Li + conduction, which also benefits from decreased M2‐M3 disorder. In contrast, Br (Br − = 1.96 Å) substitution results in insufficiently expanded Li + channels, which, exacerbated by increased M2‐M3 disorder, leads to degradation in Li + conductivity. Implementing I − substituted Li 2 ZrCl 6 resulted in superior electrochemical performance in LiCoO 2 ||Li‐In cells compared to those with an unsubstituted catholyte.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Superionic iron oxide–hydroxide in Earth’s deep mantle

Water ice becomes a superionic phase under the high pressure and temperature conditions of deep planetary interiors of ice planets such as Neptune and Uranus, which affects interior structures and generates magnetic fields. The solid Earth, however, contains only hydrous minerals with a negligible amount of ice. Here we combine high pressure and temperature electrical conductivity experiments, Raman spectroscopy and first-principles simulations to investigate the state of hydrogen in the pyrite-type FeO 2 H x (x ≤ 1), which is a potential H-bearing phase near the core–mantle boundary. We find that when the pressure increases beyond 73 GPa at room temperature, symmetric hydroxyl bonds are softened and the H + (or proton) becomes diffusive within the vicinity of its crystallographic site. Increasing temperature under pressure, the diffusivity of hydrogen is extended beyond the individual unit cell to cover the entire solid, and the electrical conductivity soars, indicating a transition to the superionic state, which is characterized by freely moving protons and a solid FeO 2 lattice. Furthermore, the highly diffusive hydrogen provides fresh transport mechanisms for charge and mass, which dictate the geophysical behaviours of electrical conductivity and magnetism, as well as geochemical processes of redox, hydrogen circulation and hydrogen isotopic mixing in Earth’s deep mantle.

58 GEOSCIENCES↗
DOE OSTI2015

Effect of cation ordering on oxygen vacancy diffusion pathways in double perovskites

Perovskite structured oxides (ABO 3 ) are attractive for a number of technological applications, including as superionics because of the high oxygen conductivities they exhibit. Double perovskites (AA’BB’O 6 ) provide even more flexibility for tailoring properties. Using accelerated molecular dynamics, we examine the role of cation ordering on oxygen vacancy mobility in one model double perovskite SrLaTiAlO 6 . We find that the mobility of the vacancy is very sensitive to the cation ordering, with a migration energy that varies from 0.6 to 2.7 eV. In the extreme cases, the mobility is both higher and lower than either of the two end member single perovskites. Further, the nature of oxygen vacancy diffusion, whether one-dimensional, two-dimensional, or three-dimensional, also varies with cation ordering. We correlate the dependence of oxygen mobility on cation structure to the distribution of Ti 4+ cations, which provide unfavorable environments for the positively charged oxygen vacancy. The results demonstrate the potential of using tailored double perovskite structures to precisely control the behavior of oxygen vacancies in these materials.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Revealing the Structural Stability and Na-Ion Mobility of 3D Superionic Conductor Na 3 SbS 4 at Extremely Low Temperatures

All-solid-state batteries that employ superionic solid conductor potentially enable the broadening of battery operation in harsh environments, such as under subzero temperatures and even lower. The solid electrolyte as the key component requires structural stability, high-efficiency of ion transportation channels, and low activation energy to maintain the fast-ionic conduction against temperature drop. Herein, we use 3D superionic conductor Na 3 SbS 4 as a model to investigate the structure and conductive mechanism at extremely low temperature. Cryogenic in situ neutron and X-ray diffractions reveal that Na 3 SbS 4 maintains a stable tetragonal crystal structure and the anisotropic lattice contraction upon cooling. The dimensions of the S-gate (represented by the S–S pair length) that Na ions hop through in the 3D transportation network is found to maintain open sizes in the xy -plane, contributing to the low activation energy and impressive ionic conductivity. The Na-ion transportation network is demonstrated to be directionally accessible at the extremely low temperature, which reveals the ion conductive mechanism at broadened temperature range in the view of structure. Furthermore, these findings provide valuable guidance in the search for materials as promising solid electrolyte in solid-state batteries to fulfill harsh environmental needs.

36 MATERIALS SCIENCE↗
DOE OSTI2015

The phase diagram of high-pressure superionic ice

Superionic ice is a special group of ice phases at high temperature and pressure, which may exist in ice-rich planets and exoplanets. In superionic ice liquid hydrogen coexists with a crystalline oxygen sublattice. At high pressures, the properties of superionic ice are largely unknown. Here we report evidence that from 280 GPa to 1.3 TPa, there are several competing phases within the close-packed oxygen sublattice. At even higher pressure, the close-packed structure of the oxygen sublattice becomes unstable to a new unusual superionic phase in which the oxygen sublattice takes the P2 1 /c symmetry. We also discover that higher pressure phases have lower transition temperatures. The diffusive hydrogen in the P2 1 /c superionic phase shows strong anisotropic behaviour and forms a quasi-two-dimensional liquid. The ionic conductivity changes abruptly in the solid to close-packed superionic phase transition, but continuously in the solid to P2 1 /c superionic phase transition.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

Chemical Bond Covalency in Superionic Halide Solid‐State Electrolytes

Abstract Halide solid‐state electrolytes (SSEs) are promising superionic conductors with high oxidative stability and ionic conductivity, making them attractive for all‐solid‐state lithium‐ion batteries. However, most studies have focused on ion‐stacking structures, overlooking the role of bond characteristics in ionic transport. Here, we investigate bond dynamics and the superionic transition (SIT) in bromide electrolyte, Li 3 InBr 6 , using synchrotron X‐ray techniques and ab initio molecular dynamics (AIMD) simulations. We demonstrate that the SIT in halide SSEs is driven by a thermally induced transition in bonding character (ionic to covalent) rather than a change in crystal phase. AIMD simulations further reveal enhanced Li⁺ diffusion and collective anion motion at elevated temperatures. Expanding our study to Li 3 LnBr 6 (Ln = Gd, Tb, Ho, Tm, and Lu), we confirm the widespread occurrence of SIT in this material class, with Li 3 GdBr 6 exhibiting the highest ionic conductivity (5.2 mS cm −1 at 298 K). More importantly, the ionic‐covalent transition is highly tunable through electrolyte modifications, such as cation/anion substitution and synthesis methods. Our findings provide a new perspective on ionic transport, highlighting the critical role of chemical bond characteristics in halide SSEs.

Chemistry↗
DOE OSTI2026

Aliovalent Anion Incorporation in Halide Na-ion Conductors for Enhanced Ionic Conductivity

Halide-based solid electrolytes (SEs), particularly zirconium (Zr)-centered halides, are attractive from a material cost perspective. Nevertheless, Zr-centered halide SEs are hindered by their low ionic conductivity. Here, in this study, we report on the cubic Na 3 ZrCl 5 S superionic conductor through strategic sulfur anion incorporation, achieving 10 times higher ionic conductivity than that of Na 2 ZrCl 6 . With the optimal composition, the highest ionic conductivity of 0.753 mS cm –1 is obtained for the 0.6Na 2 S–1.4NaCl–ZrCl 4 compound. When paired with a NaCrO 2 cathode, the assembled all-solid-state batteries (ASSBs) achieve a specific discharge capacity of 110 mA h g –1 at 0.1C and exhibit long-term cycling stability at 0.3C at room temperature over 1000 cycles (with 83% capacity retention). Moreover, in situ electrochemical impedance spectroscopy combined with distribution of relaxation times analysis reveal the dynamically interfacial stability between Na halide with electrodes. In conclusion, this work highlights the design and synthesis of advanced halide electrolytes through anion incorporation, paving the way for the development of next-generation ASSBs.

Guo, Xiaolin [Univ. of Louisville, KY (United Stat↗
DOE OSTI2024

LaCl 3 -based sodium halide solid electrolytes with high ionic conductivity for all-solid-state batteries

To enable high performance of all solid-state batteries, a catholyte should demonstrate high ionic conductivity, good compressibility and oxidative stability. Here, a LaCl 3 -based Na + superionic conductor (Na 1–x Zr x La 1–x Cl 4 ) with high ionic conductivity of 2.9 × 10 –4 S cm –1 (30 °C), good compressibility and high oxidative potential (3.80 V vs. Na 2 Sn) is prepared via solid state reaction combining mechanochemical method. X-ray diffraction reveals a hexagonal structure (P6 3 /m) of Na 1–x Zr x La 1–x Cl 4 , with Na + ions forming a one-dimensional diffusion channel along the c-axis. First-principle calculations combining with X-ray absorption fine structure characterization etc. reveal that the ionic conductivity of Na 1–x Zr x La 1–x Cl 4 is mainly determined by the size of Na + -channels and the Na + /La 3+ mixing in the one-dimensional diffusion channels. When applied as a catholyte, the NaCrO 2 ||Na 0.7 Zr 0.3 La 0.7 Cl 4 ||Na 3 PS 4 ||Na 2 Sn all-solid-state batteries demonstrate an initial capacity of 114 mA h g –1 and 88% retention after 70 cycles at 0.3 C. In addition, a high capacity of 94 mA h g –1 can be maintained at 1 C current density.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Rigidity‐Driven Structural Isomers in the NaCl–Ga 2 S 3 System: Implications for Energy Storage

Alternative energy sources require the search for innovative materials with promising functionalities. Systems with unusual chemical properties represent an insufficiently explored domain, concealing unexpected features. Using diffraction and Raman spectroscopy over a wide temperature range, supported by first‐principles simulations, a rare phenomenon is unveiled: phase‐dependent chemical interactions between binary components in the NaCl–Ga 2 S 3 system. In this unique occurrence, previously intact binary crystalline species transform upon melting into mixed liquid structural isomers, forming bonds with new partners. The chemical combinatorics appears to be fully reversible for stable crystals and liquids. Despite this, rapidly frozen glasses out of thermodynamic equilibrium remain in a metastable isomeric state, offering remarkable properties, particularly a high room‐temperature Na + conductivity, comparable to the best sodium halide superionic conductors and therefore encouraging for sodium solid‐state batteries and energy applications. A rigidity paradigm is responsible for the observed phenomenon, as the extremely constrained Ga 2 S 3 crystal lattice does not survive viscous flow, breaking up at a short‐range level. The removal of rigidity constraints and dense packing leads to a significant increase in empty space, which is the origin of high sodium diffusivity. Broadly, the rigidity‐driven structural isomerism opens up an inspiring path to the discovery of atypical materials.

25 ENERGY STORAGE↗
DOE OSTI2021

Deep potential generation scheme and simulation protocol for the Li 10 GeP 2 S 12 -type superionic conductors

We report solid-state electrolyte materials with superior lithium ionic conductivities are vital to the next-generation Li-ion batteries. Molecular dynamics could provide atomic scale information to understand the diffusion process of Li-ion in these superionic conductor materials. Here, we implement the deep potential generator to set up an efficient protocol to automatically generate interatomic potentials for Li 10 GeP 2 S 12 -type solid-state electrolyte materials (Li 10 GeP 2 S 12 , Li 10 SiP 2 S 12 , and Li 10 SnP 2 S 12 ). The reliability and accuracy of the fast interatomic potentials are validated. With the potentials, we extend the simulation of the diffusion process to a wide temperature range (300 K–1000 K) and systems with large size (~1000 atoms). Important technical aspects such as the statistical error and size effect are carefully investigated, and benchmark tests including the effect of density functional, thermal expansion, and configurational disorder are performed. The computed data that consider these factors agree well with the experimental results, and we find that the three structures show different behaviors with respect to configurational disorder. Our work paves the way for further research on computation screening of solid-state electrolyte materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Structural and Na-ion conduction characteristics of Na 3 PS x Se 4–x

The recent discovery of the isostructrual cubic Na 3 PS 4 and Na 3 PSe 4 as fast Na-ion conductors provided a general structural framework for the exploration of new sodium superionic conductors. In this work, we systematically investigated the structures and ionic conduction characteristics of a series of compounds with the general chemical formula of Na 3 PS x Se 4–x . Synthesis of Na 3 PS 4 under different conditions (e.g., temperature, reaction vessel, mass of the precursors) reveals the reactivity of the precursors with the reaction tubes, producing different polymorphs. X-ray diffraction studies on the solid solution phases Na 3 PS x Se 4–x identified a tetragonal-to-cubic phase transition with increasing Se concentration. This observation is consistent with the computed stability of the tetragonal and cubic polymorphs, where the energy difference between the two polymorphs becomes very close to zero in Se-rich compositions. Furthermore, ab initio molecular dynamic simulations suggest that the fast Na-ion conduction in Na 3 PS x Se 4–x may not be causally related with the symmetry or the composition of these phases. The formation of defects, instead, enables fast Na-ion conduction in this class of materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Anharmonic Cation–Anion Coupling Dynamics Assisted Lithium‐Ion Diffusion in Sulfide Solid Electrolytes

Abstract Sulfide‐based lithium superionic conductors often show higher Li‐ion conductivity than other types of electrolyte materials. This work unveils a unique Li‐ion conductive behavior in these materials through the perspective of anharmonic coupling assisted Li‐ion diffusion. Li hopping events can happen simultaneously with various types of lattice dynamics, while only a statistically important synchronization of motions may indicate coupling. This method enables a direct evaluation of the coupling strength between these motions, which more fundamentally decides if a specific type of lattice motion is really anharmonically coupled to the Li hopping event and whether the coupling can facilitate the Li diffusion. By a new ab initio computational approach, this work unveils a unique phenomenon in prototype sulfide electrolytes in comparison with typical halide ones, that Li‐ion conduction can be boosted by the anharmonic coupling of low‐frequency Li phonon modes with high‐frequency anion stretching or flexing phonon modes, rather than the low‐frequency rotational modes. The coupling pushes Li ions toward the diffusion channels for reduced diffusion barriers. The result from the lower temperature range (≈0–300 K) of simulation can also be more relevant to the application of solid‐state batteries.

Chemistry↗
DOE OSTI2023

Molten Sodium Penetration in NaSICON Electrolytes at 0.1 A cm –2

High-conductivity solid electrolytes, such as the Na superionic conductor, NaSICON, are poised to play an increasingly important role in safe, reliable battery-based energy storage, enabling advanced sodium-based batteries. Coupled demands of increased current density (≥0.1 A cm –2 ) and low-temperature (<200 °C) operation, combined with increased discharge times for long-duration storage (>12 h), challenge the limitations of solid electrolytes. Here, we explore the penetration of molten sodium into NaSICON at high current densities. Previous studies of β"-alumina proposed that Poiseuille pressure-driven cracking (mode I) and recombination of ions and electrons within the solid electrolyte (mode II) are the two main mechanisms for Na penetration, but a comprehensive study of Na penetration in NaSICON is necessary, particularly at high current density. To further understand these modes, this work employs unidirectional galvanostatic testing of Na|NaSICON|Na symmetric cells at 0.1 A cm –2 over 23 h at 110 °C. Further, while galvanostatic testing shows a relatively constant yet increasingly noisy voltage profile, electrochemical impedance spectroscopy (EIS) reveals a significant decrease in cell impedance correlated with significant sodium penetration, as observed in scanning electron microscopy (SEM). Further SEM analysis of sodium accumulation within NaSICON suggests that mode II failure may be far more prevalent than previously considered. Further, these findings suggest that total (dis)charge density (mAh cm –2 ), as opposed to current density (mA cm –2 ), may be a more critical parameter when examining solid electrolyte failure, highlighting the challenge of achieving long discharge times in batteries using solid electrolytes. Together, these results provide a better understanding of the limitations of NaSICON solid electrolytes under high current and emphasize the need for improved electrode–electrolyte interfaces.

25 ENERGY STORAGE↗
DOE OSTI2024

Coherent-Precipitation-Stabilized Phase Formation in Over-Stoichiometric Rocksalt-Type Li Superionic Conductors

Rationalizing synthetic pathways is crucial for material design and property optimization, especially for polymorphic and metastable phases. Over-stoichiometric rocksalt (ORX) compounds, characterized by their face-sharing configurations, are a promising group of materials with unique properties; however, their development is significantly hindered by challenges in synthesizability. Here, taking the recently identified Li superionic conductor, over-stoichiometric rocksalt Li–In–Sn–O (o-LISO) material as a prototypical ORX compound, the mechanisms of phase formation are systematically investigated. It is revealed that the spinel-like phase with unconventional stoichiometry forms as coherent precipitate from the high-temperature-stabilized cation-disordered rocksalt phase upon fast cooling. This process prevents direct phase decomposition and kinetically locks the system in a metastable state with the desired face-sharing Li configurations. This insight enables us to enhance the ionic conductivity of o-LISO to be >1 mS cm -1 at room temperature through low-temperature post-annealing. This work offers insights into the synthesis of ORX materials and highlights important opportunities in this new class of materials.

36 MATERIALS SCIENCE↗
DOE OSTI2017

High Electron Mobility and Disorder Induced by Silver Ion Migration Lead to Good Thermoelectric Performance in the Argyrodite Ag 8 SiSe 6

Superionic chalcopyrites have recently attracted interest in their use as potential thermoelectric materials because of extraordinary low thermal conductivities. To overcome long-term stability issues in thermoelectric generators using superionic materials at evaluated temperatures, materials need to be found that show good thermoelectric performance at moderate temperatures. Here, we present the structural and thermoelectric properties of the argyrodite Ag 8 SiSe 6 , which exhibits promising thermoelectric performance close to room temperature.

36 MATERIALS SCIENCE↗