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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS2014

Investigation of Structure and Transport in Li-Doped Ionic Liquid Electrolytes: [pyr14][TFSI], [pyr13][FSI], [EMIM][BF4]

Ionic liquid electrolytes have been proposed as a means of improving the safety and cycling behavior of advanced lithium batteries; however, the properties of these electrolytes under high lithium doping are poorly understood. Here, we employ both polarizable molecular dynamics simulation and experiment to investigate the structure, thermodynamics and transport of three potential electrolytes, N-methyl-N-butylpyrrolidinium bis(trifluoromethylsufonyl)imide ([pyr14][TFSI]), N- methyl-N-propylpyrrolidinium bis(fluorosufonyl)imide ([pyr13][FSI]), and 1-ethyl-3-- methylimidazolium boron tetrafluoride ([EMIM][BF4]), as a function of Li (-) salt concentration and temperature. Structurally, Li(+) is shown to be solvated by three anion neighbors in [pyr14][TFSI] and four anion neighbors in both [pyr13][FSI] and [EMIM][BF4], and at all levels of xLi we find the presence of lithium aggregates. Furthermore, the computed density, diffusion, viscosity, and ionic conductivity show excellent agreement with experimental data. While the diffusion and viscosity exhibit a systematic decrease and increase, respectively, with increasing xLi, the contribution of Li(+) to ionic conductivity increases until reaching a saturation doping level of xLi 0.10. Comparatively, the Li(+) conductivity of [pyr14][TFSI] is an order of magnitude lower than that of the other liquids, which range between 0.1-0.3 mScm. The differences in Li(+) transport are reflected in the residence times of Li(+) with the anions, which are revealed to be much larger for [pyr14][TFSI] (up to 100 ns at the highest doping levels) than in either [EMIM][BF4] or [pyr13][FSI]. Finally, we comment on the relative kinetics of Li(+) transport in each liquid and we present strong evidence for transport through anion exchange (hopping) as opposed to the net motion of Li(+) with its solvation shell (vehicular).

ionic liquids↗
NASA NTRS2014

Investigation of Structure and Transport in Li-Doped Ionic Liquid Electrolytes: [pyr14][TFSI], [pyr13][FSI], [EMIM][BF4]

Ionic liquid electrolytes have been proposed as a means of improving the safety and cycling behavior of advanced lithium batteries; however, the properties of these electrolytes under high lithium doping are poorly understood. Here, we employ both polarizable molecular dynamics simulation and experiment to investigate the structure, thermodynamics and transport of three potential electrolytes, N-methyl-N-butylpyrrolidinium bis(trifluoromethylsufonyl)imide ([pyr14][TFSI]), N- methyl-N-propylpyrrolidinium bis(fluorosufonyl)imide ([pyr13][FSI]), and 1-ethyl-3-- methylimidazolium boron tetrafluoride ([EMIM][BF4]), as a function of Li (-) salt concentration and temperature. Structurally, Li(+) is shown to be solvated by three anion neighbors in [pyr14][TFSI] and four anion neighbors in both [pyr13][FSI] and [EMIM][BF4], and at all levels of xLi we find the presence of lithium aggregates. Furthermore, the computed density, diffusion, viscosity, and ionic conductivity show excellent agreement with experimental data. While the diffusion and viscosity exhibit a systematic decrease and increase, respectively, with increasing xLi, the contribution of Li(+) to ionic conductivity increases until reaching a saturation doping level of xLi 0.10. Comparatively, the Li(+) conductivity of [pyr14][TFSI] is an order of magnitude lower than that of the other liquids, which range between 0.1-0.3 mScm. The differences in Li(+) transport are reflected in the residence times of Li(+) with the anions, which are revealed to be much larger for [pyr14][TFSI] (up to 100 ns at the highest doping levels) than in either [EMIM][BF4] or [pyr13][FSI]. Finally, we comment on the relative kinetics of Li(+) transport in each liquid and we present strong evidence for transport through anion exchange (hopping) as opposed to the net motion of Li(+) with its solvation shell (vehicular).

molecular dynamics↗
NASA NTRS2017

Novel Polyimide Battery Separator Imbibed with Room-Temperature Ionic Liquids

The journey to Mars will require advancements in many existing technologies, including space power and energy storage systems. According to the 2015 NASA Technology Roadmaps, energy storage is a critical technology area to develop for both terrestrial as well as future long-term space missions. Currently, batteries represent one of the major areas in need of advancement, both in terms of energy density as well as safety. Recently, concerns regarding the fire safety of commercial lithium-ion batteries have prompted efforts to produce nonflammable battery components, namely the electrolyte and separator. Commercial lithium-ion batteries utilize polyolefin separators imbibed with a lithium salt dissolved in cyclic carbonates. This separator/electrolyte combination imparts good ionic conductivities in the range of 10(exp -2) to 10(exp -3) S/cm. However, the cyclic carbonates and polyolefin separator are inherently flammable. Room-temperature ionic liquids (RTILs) appear to be a safer alternative to cyclic carbonates. They offer good ionic conductivities, similar to those observed in cyclic carbonates, but are inherently nonvolatile and nonflammable giving them a safety advantage. Many promising RTILs for battery electrolytes are not compatible with commercial polyolefin separator materials. Polyimide aerogels possess an open-porous, fibrillar network architecture which offers a high degree of porosity (typically greater than 85 porous), required for lithium ion conduction, as well as good mechanical properties. Furthermore, these materials are compatible with all tested RTILs. By creating a polyimide gel and imbibing the gel with a RTIL containing a lithium salt instead of super critically drying them to form aerogels, a nonflammable separator/electrolyte system with conductivities in the range of 1x10(exp -3) S/cm has been demonstrated.

Polyimide↗
NASA NTRS2016

Simulations of Li+ in Ionic Liquids: Structure, Transport, and Electrochemical Windows

Ionic liquids have been proposed as candidate electrolytes for a number of electrochemical applications. The Li+ solvation structure in these liquids is of central importance to electrolyte properties, like ionic conductivity and electrochemical stability. To this point, we employ simulations at three different size scales to better understand various aspects of the interplay between Li+ solvation structure and dynamics. The smallest systems are Li(Anion)n clusters that are treated with high-accuracy density functional theory (DFT) techniques to provide insight into solvation shell structure through energetics and comparisons to experimental IRRaman spectra. Mid-range sized liquid-phase systems (12-24 ion pairs) are treated with DFT molecular dynamics (MD) to provide temperature-dependent insight into Li+ solvation structure, diffusion, and electrochemical window. The largest systems (144-216 ion pairs) are treated with polarizable MD simulations to evaluate the influence of Li-networks on structure and provide size independent values of transport properties. We perform this procedure on three technologically important ionic liquids and comment on property correlations with solvation structure.

batteries↗
NASA NTRS2016

Influence of Molecular Simulation Model Accuracy on the Interfacial Properties of an Ionic Liquid: Overview of Recommended Practices

Increasing the energy storage capability of ionic liquid supercapacitors will require better understanding of ion-electrode interactions. We have probed the influence of these interactions on the structure and differential capacitance of of an ionic liquid ([EMIM][BF4]) at an ideal graphite interface as a function of model accuracy. Of note, differential capacitance is determined through newly derived and validated fluctuation formulas. In terms of model accuracy, we test electrostatic techniques, electrode charging techniques, and electrolyte interatomic potentials. For electrostatic summations, we employ high cost, high fidelity techniques as well as less expensive, approximate techniques for summation in slab geometry. For electrode charging, uniform, constant-charge and environmentally responsive, constant-potential conditions are employed. For the ionic liquid, constant charge and atomically polarizable models are employed. We comment on the role of model accuracy on the structure and energetics of the electric double layer as well as on the magnitude and shape of differential capacitance.

simulations↗
NASA NTRS2021

Investigation of Ionic Liquids Isolated Iron for Ductile Iron Castings

As research continues for missions beyond low-Earth orbit, in-situ resource utilization (ISRU) methods are critical. For Lunar and Martian colonization, the ability to manufacture mechanical and structural components with local resources is essential. Ionic liquids (IL) are being studied at NASA Marshall Space Flight Center (MSFC) to harvest elemental metals from meteorites and regolith oxides. In this investigation, the viability of casting ductile iron using ionic liquids sourced iron and nickel was explored given ductile iron’s range of applications and performance as an as-cast alloy. Ingots were produced using commercial elements to simulate the use of IL iron with carbon sourced from the by-products of a life support system currently tested at MSFC. Samples were cast and compared to commercial ductile iron with phase transformation diagrams,microstructures, and hardness. Results showed ionic liquids sourced elements are a viable source of elemental alloying materials for a range of ductile iron alloys.

Ionic Liquids↗
DOE OSTI2026

Molecular-Level Insights into the Influence of Ionic Liquids on the Structure and Dynamics of Neutral and Charged Polyimides

We use all-atom molecular dynamics simulations to investigate how increasing ionic functionalization influences polyimide (PI) behavior in ionic liquid (IL) solvation environments. Here, we examine three polymer systems with varying charge densities: a neutral polyimide [N−PI] containing imidazole rings and progressively introduce charge through quaternization to create singly [C−PI] + and doubly charged [C−2PI] 2+ variants across a wide range of IL concentration (0−90 wt %). Through comprehensive structural, mechanical, and electrostatic analyses, we reveal that polymer charge density plays a central role in shaping IL organization and interaction with the polymer matrix. At low IL content, charged systems exhibit strong electrostatic complexation, leading to chain compaction, localized ESP environments, and elevated dielectric constants. As IL concentration increases, the effect of the different polymer charge states becomes less significant. Notably, an intermediate composition regime at approximately 50 wt % IL is associated with changes in IL-rich domain connectivity and overall system behavior across all three PI systems.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Nonuniform Ionic and Electronic Transport of Ceramic and Polymer/Ceramic Hybrid Electrolyte by Nanometer-Scale Operando Imaging for Solid-State Battery

Replacing the liquid electrolyte in lithium batteries with solid-state ion conductor is promising for next-generation energy storage that is safe and has high energy density. In this work, nanometer-resolution ionic and electronic transport imaging of Li 3 PS 4 (LPS), a solid-state electrolyte (SSE), is reported. This nm resolution is achieved by using a logarithm-scale current amplifier that enhances the current sensitivity to the fA range. Large fluctuations of ion current—one to two orders of magnitude on the LPS and on the LPS region of a polymer/LPS bulk hybrid SSE—that must be mitigated to eliminate Li dendrite formation and growth, are found. This ion current fluctuation is understood in terms of highly anisotropic transport kinetic barriers along the different crystalline axes due to different grain orientations in the polycrystalline and glass ceramic materials. The results on the bulk hybrid SSE show a sharp transition of ionic and electronic transport at the LPS/polymer boundary and decreases in average ionic current with decreasing polyimine particle size and with extensive cycling. The results elucidate the mechanism of polyimine extension into interparticles to prevent Li dendrite growth. This work opens up novel characterization of charge transport, which relates to Li plating and stripping for solid-state-batteries.

Li3PS4↗
DOE OSTI2020

Correlating Macro and Atomic Structure with Elastic Properties and Ionic Transport of Glassy Li 2 S‐P 2 S 5 (LPS) Solid Electrolyte for Solid‐State Li Metal Batteries

Abstract A combination of high ionic conductivity and facile processing suggest that sulfide‐based materials are promising solid electrolytes that have the potential to enable Li metal batteries. Although the Li 2 S‐P 2 S 5 (LPS) family of compounds exhibit desirable characteristics, it is known that Li metal preferentially propagates through microstructural defects, such as particle boundaries and/or pores. Herein, it is demonstrated that a near theoretical density (98% relative density) LPS 75‐25 glassy electrolyte exhibiting high ionic conductivity can be achieved by optimizing the molding pressure and temperature. The optimal molding pressure reduces porosity and particle boundaries while preserving the preferred amorphous structure. Moreover, molecular rearrangements and favorable Li coordination environments for conduction are attained. Consequently, the Young's Modulus approximately doubles (30 GPa) and the ionic conductivity increases by a factor of five (1.1 mS cm −1 ) compared to conventional room temperature molding conditions. It is believed that this study can provide mechanistic insight into processing‐structure‐property relationships that can be used as a guide to tune microstructural defects/properties that have been identified to have an effect on the maximum charging current that a solid electrolyte can withstand during cycling without short‐circuiting.

Garcia‐Mendez, Regina↗
DOE OSTI2021

Increasing Ionic Conductivity of Poly(ethylene oxide) by Reaction with Metallic Li

Poly(ethylene oxide) (PEO) was the first lithium-ion conducting polymer developed 50 years ago and is still the most popular electrolyte matrix for solid-state lithium metal batteries. While many studies focus on increasing PEO ionic conductivity through doping with Li salts, little work has addressed using PEO and Li directly to generate Li + -conducting species in situ. Reaction between PEO and Li leads to ionic conductivity largely from Li + , in contrast to the case of added salts where the anion contribution dominates. Herein, electrochemical impedance spectroscopy shows the ionic conductivity of PEO thin films increases up to three orders of magnitude (from 10 –7 to 10 –4 S cm –1 ) when contacted with Li at elevated temperature. This is due to the reduction of ether bonds, which produces lithium alkoxides that are responsible for Li + transport. Density functional theory analysis confirms this mechanism as thermodynamically favorable. X-ray photoelectron spectroscopy also shows the presence of organolithium species and Li 2 O, which are responsible for propagating reactions with PEO and forming an electronically insulating layer at the PEO–Li interface that halts further reaction, respectively. The underlying mechanisms of Li–polymer electrolyte reactions is clarified and new pathways for in situ Li + doping of polymer electrolytes is presented.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Direct Insertion Polymerization of Ionic Monomers: Rapid Production of Anion Exchange Membranes

Abstract The limited number of methods to directly polymerize ionic monomers currently hinders rapid diversification and production of ionic polymeric materials, namely anion exchange membranes (AEMs) which are essential components in emerging alkaline fuel cell and electrolyzer technologies. Herein, we report a direct coordination‐insertion polymerization of cationic monomers, providing the first direct synthesis of aliphatic polymers with high ion incorporations and allowing facile access to a broad range of materials. We demonstrate the utility of this method by rapidly generating a library of solution processable ionic polymers for use as AEMs. We investigate these materials to study the influence of cation identity on hydroxide conductivity and stability. We found that AEMs with piperidinium cations exhibited the highest performance, with high alkaline stability, hydroxide conductivity of 87 mS cm −1 at 80 °C, and a peak power density of 730 mW cm −2 when integrated into a fuel cell device.

Hsu, Jesse H.↗
DOE OSTI2025

Electrical Energy Storage by Poly(ionic Liquids)

Abstract Manipulating van der Waals (vdW) and ionic interactions in polymers enable energy storage and formations of active or passive components of electrical circuits. The energy storage is achieved by electrically activating ion pairs containing polymers, which create ergotropically favorable non‐equilibrium gradient states. Molecular‐level events responsible for this behavior involve concurrent ion pairs' polarization‐depolarization gradients and conformational changes of aliphatic tails that collectively contribute to lowering local disorder states. Manipulating ionic and vdW interactions stabilizes polarized anion‐cation pairs, thus maintaining electrical energy storage for extended periods. These transparent and easily moldable materials require no multilayered assemblies, and their functional features depend upon polarization conditions and ionic‐vdW interactions, making them applicable in energy storage and other devices transcending classical time intricacy limits.

Liu, Jiahui [Department of Materials Science and E↗
DOE OSTI2023

Direct Insertion Polymerization of Ionic Monomers: Rapid Production of Anion Exchange Membranes

The limited number of methods to directly polymerize ionic monomers currently hinders rapid diversification and production of ionic polymeric materials, namely anion exchange membranes (AEMs) which are essential components in emerging alkaline fuel cell and electrolyzer technologies. Herein, we report a direct coordination-insertion polymerization of cationic monomers, providing the first direct synthesis of aliphatic polymers with high ion incorporations and allowing facile access to a broad range of materials. We demonstrate the utility of this method by rapidly generating a library of solution processable ionic polymers for use as AEMs. We investigate these materials to study the influence of cation identity on hydroxide conductivity and stability. Furthermore, we found that AEMs with piperidinium cations exhibited the highest performance, with high alkaline stability, hydroxide conductivity of 87 mS cm –1 at 80 °C, and a peak power density of 730 mW cm –2 when integrated into a fuel cell device.

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

Electrical Energy Storage by Poly(ionic Liquids)

Abstract Manipulating van der Waals (vdW) and ionic interactions in polymers enable energy storage and formations of active or passive components of electrical circuits. The energy storage is achieved by electrically activating ion pairs containing polymers, which create ergotropically favorable non‐equilibrium gradient states. Molecular‐level events responsible for this behavior involve concurrent ion pairs' polarization‐depolarization gradients and conformational changes of aliphatic tails that collectively contribute to lowering local disorder states. Manipulating ionic and vdW interactions stabilizes polarized anion‐cation pairs, thus maintaining electrical energy storage for extended periods. These transparent and easily moldable materials require no multilayered assemblies, and their functional features depend upon polarization conditions and ionic‐vdW interactions, making them applicable in energy storage and other devices transcending classical time intricacy limits.

Liu, Jiahui [Department of Materials Science and E↗
DOE OSTI2025

Self‐Healable Poly(ionic liquid) Copolymers Driven by Polar and Dipolar Forces

Abstract Commodity aliphatic and aromatic acrylic‐based copolymers self‐heal due to ubiquitouskey‐and‐lock,ring‐and‐lock, andfluorophilic‐σ‐lockvan der Waals (vdW) interactions. However, the role of these interactions in the presence of covalently copolymerized ionic liquid (IL) is not known. This study is driven by the hypothesis that covalently incorporated cation–anion pairs to form poly(ionic liquid) copolymers (PILCs) can perturb inter‐ or intra‐chain vdW interactions reflected in mechanical and electrical responses. To test this hypothesis, we synthesized a series of PILCs comprising of pentafluorostyrene (PFS) and imidazolium‐based IL monomers with variable‐length aliphatic tails (methyl and butyl). Using a combination of 2D 1 H‐ 1 H and 19 F ‐ 19 F NOESY NMR and FTIR measurements supplemented by molecular dynamic (MD) simulations, these studies demonstrate that preferentially alternating/random PILCs topologies facilitate self‐healing. The introduction of cation–anion moieties modifies thefluorophilic‐σ‐lockinteractions and, along with longer aliphatic tails ─(CH 2 ) 3 CH 3 covalently attached to the imidazolium cation, enhances cation‐anion mobility, thus faster recovery from mechanical damage occurs. These findings underline how precise control over dipolar and ionic interactions through copolymer composition enables self‐healing in PILCs. These insights may open pathways for designing sustainable, mechanically resilient materials for applications in energy storage and energy harvesting.

Chemistry↗
DOE OSTI2024

Chemical and Electrochemical Characterization of Hot–Pressed Li 6 PS 5 Cl Solid State Electrolyte: Operating Pressure–Invariant High Ionic Conductivity

Sulfide solid state electrolytes (SSE) are among the most promising materials in the effort to replace liquid electrolytes, largely due to their comparable ionic conductivities. Among the sulfide SSEs, Argyrodites (Li 6 PS 5 X, X=Cl, Br, I) further stand out due to their high theoretical ionic conductivity (~1×10 –2 S cm –1 ) and interfacial stability against reactive metal anodes such as lithium. Generally, solid state electrolyte pellets are pressed from powder feedstock at room temperature, however, pellets fabricated by cold pressing consistently result in low bulk density and high porosity, facilitating interfacial degradation reactions and allowing dendrites to propagate through the pores and grain boundaries. Here, we demonstrate the mechanical and electrochemical implications of hot-pressing standalone LPSCl SSE pellets with near-theoretical ionic conductivity, superior cycling performance, and enhanced mechanical stability. X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and x-ray diffraction spectroscopy (XRD) analysis reveal no chemical changes to the Argyrodite surface after hot pressing up to 250°C. Furthermore, we use electrochemical impedance spectroscopy (EIS) to understand mechanical stability of Argyrodite SSE pellets as a function of externally applied pressure, demonstrating for the first time pressed standalone Argyrodite pellets with near-theoretical conductivities at external pressures below 14 MPa.

25 ENERGY STORAGE↗
DOE OSTI2022

Ionic Conductive and Highly-Stable Interface for Alkali Metal Anodes

Alkali metals are regarded as the most promising candidates for advanced anode for the next-generation batteries due to their high specific capacity, low electrochemical potential, and lightweight. However, critical problems of the alkali metal anodes, especially dendrite formation and interface stabilization, remain challenging to overcome. The solid electrolyte interphase (SEI) is a key factor affecting Li and Na deposition behavior and electrochemical performances. Herein, a facile and universal approach is successfully developed to fabricate ionic conductive interfaces for Li and Na metal anodes by modified atomic layer deposition (ALD). In this process, the Li metal (or Na metal) plays the role of Li (or Na) source without any additional Li (or Na) precursor during ALD. Moreover, the key questions about the influence of ALD deposition temperature on the compositions and structure of the coatings are addressed. The optimized ionic conductive coatings have significantly improved the electrochemical performances. In addition, the electrochemical phase-field model is performed to prove that the ionic conductive coating is very effective in promoting uniform electrodeposition. Further, this approach is universal and can be potentially applied to other different metal anodes. At the same time, it can be extended to other types of coatings or other deposition techniques.

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