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Results for “ionic conductivities”

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 1,063 records · Page 59
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Solid-state rigid-rod polymer composite electrolytes with nanocrystalline lithium ion pathways

A critical challenge for next-generation lithium-based batteries lies in development of electrolytes that enable thermal safety along with use of high-energy-density electrodes. We describe molecular ionic composite (MIC) electrolytes based on an aligned liquid crystalline polymer combined with ionic liquids and concentrated Li salt. This high strength (200 MPa) and non-flammable solid electrolyte possesses outstanding Li + conductivity (1 mS cm -1 at 25 °C) and electrochemical stability (5.6 V vs Li|Li + ) while suppressing dendrite growth and exhibiting low interfacial resistance (32 Ω cm 2 ) and overpotentials (≤ 120 mV @ 1 mA cm -2 ) during Li symmetric cell cycling. A heterogeneous salt doping process modifies a locally ordered polymer-ion assembly to incorporate an inter-grain network filled with defective LiFSI & LiBF 4 nanocrystals, strongly enhancing Li + conduction. Furthermore, this modular material fabrication platform shows promise for safe and high-energy-density energy storage and conversion applications, incorporating the fast transport of ceramic-like conductors with the superior flexibility of polymer electrolytes.

25 ENERGY STORAGE↗
DOE OSTI2020

Boron phosphide as a p-type transparent conductor: Optical absorption and transport through electron-phonon coupling

Boron phosphide has recently been identified as a potential high-hole-mobility transparent conducting material. This promise arises from its low hole effective masses. However, boron phosphide has a relatively small, 2 eV, indirect bandgap which will affect its transparency. In this study, we computationally study both optical absorption across the indirect gap and phonon-limited electronic transport to quantify the potential of boron phosphide as a p-type transparent conductor. We find that phonon-mediated indirect optical absorption is weak in the visible spectrum and that the phonon-limited hole mobility is very high (around 900 cm 2 /Vs) at room temperature. This exceptional mobility comes from the combination of a low hole effective mass and very weak scattering by polar phonon modes. We rationalize the weak scattering by the less ionic bonding in boron phosphide compared to oxides. We suggest that this could be a general advantage of nonoxides for p-type transparent conducting applications. Using our computed properties, we assess the transparent conductor figure of merit of boron phosphide and show that it exceeds by one order of magnitude that of established p-type transparent conductors, confirming the potential of this material.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Interference of electrical double layers: Confinement effects on structure, dynamics, and screening of ionic liquids

Ionic liquids are widely used as electrolytes in electronic devices in which they are subject to nanoconfinement within nanopores or nanofilms. Because the intrinsic width of an electrical double layer is on the order of several nanometers, nanoconfinement is expected to fundamentally alter the double layer properties. Furthermore, in confined systems, a large portion of the ions are interfacial, e.g., at the electrode interface, leading to significant deviations of electrostatic screening and ion dynamics as compared to bulk properties. In this article, we systematically investigate the interference between electrical double layers for nanoconfined ionic liquids and the resulting influence on the structure, dynamics, and screening behavior. We perform molecular dynamics simulations for the ionic liquids [BMIm + ][BF$^-_4$] and [BMIm + ][PF$^-_6$] confined between two flat electrodes at systematic separation distances between 1.5 nm and 4.5 nm for both conducting and insulating boundary conditions. We find that while ion dynamics is expectedly slower than in the bulk (by ~2 orders of magnitude), there is an unexpected non-linear trend with the confinement length that leads to a local maximum in dynamic rates at ~3.5–4.5 nm confinement. We show that this nonlinear trend is due to the ion correlation that arises from the interference between opposite double layers. We further evaluate confinement effects on the ion structure and capacitance and investigate the influence of electronic polarization of the ionic liquid on the resulting properties. This systematic evaluation of the connection between electrostatic screening and structure and dynamics of ionic liquids in confined systems is important for the fundamental understanding of electrochemical supercapacitors.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Quantum Ornstein-Zernike theory for two-temperature two-component plasmas

Laboratory plasma production almost always preferentially heats either the ions or electrons, leading to a two-temperature state. In this state, density functional theory molecular dynamic simulation is the state of the art for modeling bulk material properties. We construct a statistical mechanics model for the two temperature limit that is theoretically consistent with the molecular dynamics method. We proceed to derive the electron-ion multi-temperature quantum Ornstein-Zernike equations for the first time. This allows the construction of a two-temperature two-component plasma model using the average atom from which we can compute bulk material properties at a fraction of the computation time of the two-temperature density functional theory simulation. The accuracy of the model is benchmarked against ion pair correlation and self-diffusion results from ab initio simulation. Here, we proceed to compute the viscosity and ion thermal conductivity as a function of both ion and electron temperature.

Ab initio molecular dynamics↗
DOE OSTI2026

Additive-Induced Morphology Change of Polymer Film Enables Enhanced Charge Mobility and Faster Organic Electrochemical Transistor Switching

Conjugated polymers (CPs) play an important role in organic electrochemical transistors (OECTs) for bioelectronics and related applications, where they serve as channel materials. Currently, most successful polymers for CPs are re-engineered from traditional CPs by replacing hydrophobic alkyl side chains with hydrophilic ethylene glycol or ionic groups. Frustratingly, the enhanced ion transport often compromises the charge mobility of the original CP. In this work, we present an additive-mediated method to construct a modified poly(3-hexylthiophene) (P3HT) film to enable efficient ion migration. The additive is designed with a cleavable diazo group that releases nitrogen and 2-methoxyethanol, a volatile compound, to alter the P3HT film morphology. OECTs based on the film exhibit improved response times. Interestingly, the process also enhances the crystallinity of P3HT, leading to higher hole mobility compared with pristine P3HT. This study proposes an in situ strategy to achieve the functionality of the OMIEC via morphological regulation, offering a promising route to simultaneously enhance both ion accessibility and charge mobility.

Organic polymers↗
DOE OSTI2021

The Influence of Water Vapor on the Electrochemical Shift of an Ionic Liquid Measured by Ambient Pressure X-ray Photoelectron Spectroscopy

Ionic liquids (ILs) are considered to be one of the steppingstones to fabricate next generation electrochemical devices given their unique physical and chemical properties. The addition of water to ILs significantly impact electrochemical related properties including viscosity, density, conductivity, and electrochemical window. Here, we utilize ambient pressure X-ray photoelectron spectroscopy (APXPS) to examine the impact of water on values of the electrochemical shift (S), which is determined by measuring changes in binding energy shifts as a function of an external bias. APXPS spectra of C 1s, O 1s and N 1s regions are examined for the IL 1-butyl-3-methylimidazolium acetate, [C 4 mim][OAc], at the IL/gas interface as a function of both water vapor pressure and external bias. Results reveal that in the absence of water vapor there is an IL ohmic drop between the working electrode and quasi reference electrode, giving rise to chemical specific S values of less than one. Upon introducing water vapor, S values approach one as a function of increasing water vapor pressure, indicating a decrease in the IL ohmic drop as the IL/water mixture becomes more conductive and the potential drop is driven by the electric double layer at the electrode/IL interface.

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

Model for the electrical conductivity in dense plasma mixtures

A new density functional theory, average atom based model for the electrical conductivity of dense plasmas with a mixture of ion species, containing no adjustable parameters, is presented herein. The model takes the temperature, mass density and relative abundances of the species as input. It takes into account partial ionization, ionic structure, and core-valence orthogonality, and uses quantum mechanical calculations of cross sections. Comparison to an existing high fidelity but computationally expensive method reveals good agreement. The new model is computationally efficient and can reach high temperatures. A new mixing rule is also presented that gives reasonably accurate conductivities for high temperature plasma mixtures.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

Superior photodynamic effect of single-walled carbon nanotubes in aprotic media: a kinetic study

It has been confirmed that single-walled carbon nanotubes (SWCNTs) could generate reactive oxygen species in aprotic media by utilizing photon energy. However, the impact of photon irradiation on SWCNTs and the kinetics of the generation process in aprotic media are still unclear, which significantly limits the yield performance. In this work, the kinetics for photodynamic effects has been investigated by performing characterizations on ultraviolet-treated SWCNTs using Raman spectroscopy, conductive atomic force microscope (in-situ), kelvin probe force microscope, and X-ray photoelectron spectroscopy. It is found that ultraviolet-treated SWCNTs are observed to have more defects, lower conductivity, and less surface charge after energy conversion. Starting from the fundamental intrinsic properties of SWCNTs, the kinetics and formation of these changes are thoroughly discussed. It turns out that the dispersion, chirality, and structural integrity of SWCNTs are important for achieving high-performance photodynamic effects, which are validated using several different SWCNTs as well as other carbon nanomaterials. A type of (6,5) s-SWCNTs exhibited the highest energy efficiency among a variety of other carbon nanomaterials. The yield rate is 2.15 mM/h, and the energy consumption is determined to be 2.79 W∙h/mM. This work is expected to help dramatically boost the energy efficiency of the photodynamic effect in aprotic media and pave the way for designing high-performance carbon nanomaterial-based photoinduced devices.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Solid-state thermometry via ionic–electronic coupling in two-dimensional heterostructures

The coupling of ionic and electronic transport in solid-state systems offers new opportunities for realizing compact, energy-efficient sensing technologies, yet practical implementations remain limited. In this article, we introduce a two-dimensional iontronic platform based on field-effect transistors that integrate monolayer MoS 2 channels with van der Waals bimetallic thiophosphates ( AB P 2 X 6 , A = Li, Cu, Ag and so on; B = In, Sc and so on; and X = S and Se) as ionic gate dielectrics to realize on-chip thermometry. Specifically, we exploit thermally activated ion migration within the gate dielectric leading to conductance modulation in the MoS 2 channel for temperature sensing. We achieve ~1–2 °C resolution, fast electronic readout and subpicojoule energy consumption in an ultracompact footprint (~1 µm 2 ). Beyond thermometry, these results establish bimetallic thiophosphates as a versatile platform for solid-state iontronics and broaden the functional design space of van der Waals heterostructures for sensing, actuation and adaptive electronics.

42 ENGINEERING↗
DOE OSTI2025

Water-mediated ion transport in an anion exchange membrane

Water is a critical component in polyelectrolyte anion exchange membranes (AEMs). It plays a central role in ion transport in electrochemical systems. Gaining a better understanding of molecular transport and conductivity in AEMs has been challenged by the lack of a general methodology capable of capturing and connecting water dynamics, water structure, and ionic transport over time and length scales ranging from those associated with individual bond vibrations and molecular reorientations to those pertaining to macroscopic AEM performance. In this work, we use two-dimensional infrared spectroscopy and semiclassical simulations to examine how water molecules are arranged into successive solvation shells, and we explain how that structure influences the dynamics of bromide ion transport processes in polynorbornene-based materials. We find that the transition to the faster transport mechanism occurs when the reorientation of water molecules in the second solvation shell is fast, allowing a robust hydrogen bond network to form. Our findings provide molecular-level insights into AEMs with inherent transport of halide ions, and help pave the way towards a comprehensive understanding of hydroxide ion transport in AEMs.

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

Semiconducting High-Entropy Chalcogenide Alloys with Ambi-ionic Entropy Stabilization and Ambipolar Doping

Entropy stabilization is a novel materials-design paradigm to realize new compounds with widely tunable properties. However, almost all entropy-stabilized materials so far are either conducting metals or insulating ceramics, with a clear dearth in the semiconducting regime. Here, a new class of the multi-cationic and -anionic entropy-stabilized chalcogenide alloys based on the (Ge,Sn,Pb)(S,Se,Te) formula are synthesized and characterized experimentally. The con-figurational entropy from the disorder of both the anion and the cation sublattices reaches a record value of ~2.2 R mol -1 for the equimolar composition and stabilizes the single-phase solid solution. Theoretical calculations and experiments both show that the synthesized alloys are thermodynamically stable at the growth temperature and kinetically metastable at room temperature, segregating by spinodal decomposition at moderate temperatures. In conclusion, doping and electronic transport measurements verify that the synthesized materials are ambipolarly dopable semiconductors, which paves the way for the wider adoption of entropy-stabilized chalcogenide alloys in functional applications.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Synthetic Nuances to Maximize n-Type Organic Electrochemical Transistor and Thermoelectric Performance in Fused Lactam Polymers

A series of fully fused n-type mixed conduction lactam polymers p(g 7 NC n N), systematically increasing the alkyl side chain content, are synthesized via an inexpensive, nontoxic, precious-metal-free aldol polycondensation. Employing these polymers as channel materials in organic electrochemical transistors (OECTs) affords state-of-the-art n-type performance with p(g 7 NC 10 N) recording an OECT electron mobility of 1.20 x 10 -2 cm 2 V -1 s -1 and a μC* figure of merit of 1.83 F cm -1 V -1 s -1. In parallel to high OECT performance, upon solution doping with (4-(1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl)phenyl)dimethylamine (N-DMBI), the highest thermoelectric performance is observed for p(g 7 NC 4 N), with a maximum electrical conductivity of 7.67 S cm -1 and a power factor of 10.4 μWm -1 K -2 . These results are among the highest reported for n-type polymers. Importantly, while this series of fused polylactam organic mixed ionic-electronic conductors (OMIECs) highlights that synthetic molecular design strategies to bolster OECT performance can be translated to also achieve high organic thermoelectric (OTE) performance, a nuanced synthetic approach must be used to optimize performance. Herein, we outline the performance metrics and provide new insights into the molecular design guidelines for the next generation of high-performance n-type materials for mixed conduction applications, presenting for the first time the results of a single polymer series within both OECT and OTE applications.

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

Examination of Solvent- Room Temperature Ionic Liquid Interactions using 2D NMR and Computational Chemistry

Rare earth metals (REMs) are the key functioning material found in microelectronics, advanced batteries, and high-efficiency electrical motors. Current methods for producing REMs require high temperatures (i.e. energy intensive) and produce an abundance of hazardous fluoride waste. Room temperature ionic liquids (RTILs) are an ideal alternative electrolyte because they allow for a low-temperature, energy-efficient electrochemical process. RTIL properties such as viscosity and conductivity determine how effective they can be in this process. Since viscosity is directly related to both intra and intermolecular forces, this study sets out to investigate two RTILs-Trihexyltetradecylphosphonium dicyanamide (Cyphos 105) and Trihexyltetradecylphosphonium bistrifimide (Cyphos 109) and their interactions. Results from 2-dimensional nuclear magnetic resonance (2D NMR) spectroscopy show that there is an interaction between the tetradecyl tail and the phosphorus atom of the Cyphos RTIL. In order to establish whether this is an intra or an inter-molecular interaction, DFT-based computational calculations were performed to determine the optimized geometry. Calculations were done both in the gas phase and with propylene carbonate as an augmenting solvent. Preliminary results show that there is minimal intramolecular interaction between the tetradecyl tail and the phosphorus atom of the RTILs, and that the interaction seen in the 2D NMR experiment is likely of an intermolecular nature instead.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

A theoretical study of the bonding properties of R 4 Sb 3 compounds

Here, this study investigates the electronic structure and bonding properties of rare-earth antimonide compounds, specifically Yb 4 Sb 3 and La 4 Sb 3 , utilizing density functional theory calculations. The analysis reveals that Yb 4 Sb 3 exhibits a predominantly ionic character whereas La 4 Sb 3 displays a greater degree of covalent bonding. Moreover, the presence of divalent ytterbium leads to p-type conduction at high temperatures in Yb 4 Sb 3 . Conversely, La 4 Sb 3 displays n-type conduction because of a larger electronic transfer from the rare-earth metal towards antimony. These findings provide valuable insights into the structural and electronic properties that govern the performance of R 4 Sb 3 compounds, contributing to the development of advanced materials for thermoelectric energy conversion.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Computational Insights into the Salt-Induced Modulation of Electron Transporting Conjugated Polyelectrolytes

The morphological and electronic properties of conjugated polyelectrolytes (CPEs) are highly sensitive to their ionic environment and remain poorly understood. To elucidate structure–property relationships in CPEs, we investigate the role of salt concentration on CPE morphology and hole conductivity using a quantum mechanically informed coarse-grained (CG) model coupled with semiclassical rate theory. Under good solvent conditions, high salt concentration induces torsional disorder along the conjugated backbone, decreasing hole delocalization. In contrast, under poor solvent conditions, high salt concentration promotes CPE aggregation, leading to thicker fibers and increased hole mobilities. Collectively, this work characterizes the competing interactions governing CPE assembly and hole transport as a function of salt concentration, highlighting ion engineering as a powerful strategy for tailoring the properties of mixed-conducting polymers.

diseases↗
DOE OSTI2020

Thermal Properties of Sodium Borosilicate Glasses as a Function of Sulfur Content

SO3 additions, up to 3.0 wt%, were systematically investigated for effects on the physical properties of sodium borosilicate glass melted in air, with a sulfur-free composition of 50SiO2-10Al2O3-12B2O3-21Na2O-7CaO (wt%). Solubility measurements, using electron microscopy chemical analysis, determined the maximum loading to be ~1.5 wt% SO3. It was found that sulfur (here as sulfate) in this glass increased the glass transition temperature, thermal diffusivity, heat capacity, and thermal conductivity, and decreased the mass density. Structural analysis, performed with Raman spectroscopy, indicated that the borosilicate network polymerized with sulfur additions, presumably due to Na2O being required to charge compensate the ionic SO42- additions, thus becoming unavailable to form non-bridging oxygen in the silicate network. It is postulated that this increased crosslinking of the borosilicate backbone lead to a structure with higher dimensionality and average bond energy. This increased the mean free paths and vibration frequency of the phonons, which resulted in the observed increase in thermal properties.

Thermal properties, Borosilicate glass, Sulfur sol↗
DOE OSTI2021

High-Speed Ionic Synaptic Memory Based on 2D Titanium Carbide MXene

Synaptic devices with linear high-speed switching can accelerate learning in artificial neural networks (ANNs) embodied in hardware. Conventional resistive memories however suffer from high write noise and asymmetric conductance tuning, preventing parallel programming of ANN arrays. Electrochemical random-access memories (ECRAMs), where resistive switching occurs by ion insertion into a redox-active channel, aim to address these challenges due to their linear switching and low noise. ECRAMs using 2D materials and metal oxides however suffer from slow ion kinetics, whereas organic ECRAMs enable high-speed operation but face challenges toward on-chip integration due to poor temperature stability of polymers. Here, ECRAMs using 2D titanium carbide (Ti 3 C 2 T x ) MXene that combine the high speed of organics and the integration compatibility of inorganic materials in a single high-performance device are demonstrated. These ECRAMs combine the speed, linearity, write noise, switching energy, and endurance metrics essential for parallel acceleration of ANNs, and importantly, they are stable after heat treatment needed for back-end-of-line integration with Si electronics. The high speed and performance of these ECRAMs introduces MXenes, a large family of 2D carbides and nitrides with more than 30 stoichiometric compositions synthesized to date, as promising candidates for devices operating at the nexus of electrochemistry and electronics.

2D materials↗