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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 OSTI2025

Understanding the structure and mechanism of Na + diffusion in NASICON solid-state electrolytes and the effect of Sc- and Al/Y-substitution

NASICON (sodium superionic conductor) based ceramics are one of the most promising classes of solid-state electrolytes for all-solid-state batteries. However, the mechanism of sodium ion diffusion is not understood in great detail since there is still a discrepancy between reported average structure models, local structures, and the number and position of sodium sites. To close this gap, we investigate the underlying diffusion mechanism and structural changes governing the Na + transport in Na 3.4 Zr 2 Si 2.4 P 0.6 O 12 using quasielastic neutron scattering (QENS) and powder X-ray diffraction (XRD). In the temperature range from 298 K to 640 K, the correlations between structural changes of a monoclinic C2/c to rhombohedral R $\bar{3}$c phase transition and the result of ion diffusion are investigated. The analysis of the quasielastic neutron scattering data reveals two quasielastic components corresponding to the Chudley-Elliott jump-diffusion model. It clearly shows two different Na + diffusion processes, local and long-range, on two different time and length scales and allows calculations of their corresponding activation energies. Additionally, the effects of Sc 3+ and Al 3+ /Y 3+ aliovalent substitution of Zr 4+ ions on the crystal structure and Na + diffusion are also studied. We can distinguish a local, chain, and cross-chain diffusion mechanism based on correlated QENS and XRD comparison of relevant nearest crystallographic Na–Na distances. The results reveal that the Na + diffusion in these NASICONs is three-dimensional and can provide guidelines on how dopants and changes in the crystal structure can affect the Na + conductivity.

25 ENERGY STORAGE↗
DOE OSTI2021

Effects of fluorinated solvents on electrolyte solvation structures and electrode/electrolyte interphases for lithium metal batteries

Electrolyte is very critical to the performance of the high-voltage lithium (Li) metal battery (LMB), which is one of the most attractive candidates for the next generation high-density energy storage systems. Electrolyte formulation and structure determine the physical properties of the electrolytes and their interfacial chemistries on the electrode surfaces. Localized high-concentration electrolytes (LHCEs) outperform state-of-the-art carbonate electrolytes in many aspects in LMBs due to their unique solvation structure. Types of fluorinated co-solvents used in LHCEs are investigated here in searching for the most suitable diluent for high concentration electrolytes (HCEs). Non-solvating solvents (including fluorinated ethers, fluorinated borate and fluorinated orthoformate) added in HCEs enable the formation of LHCEs with high-concentration solvation structures. However, low solvating fluorinated carbonate will coordinate with Li+ ions and form a second solvation shell or a pseudo-LHCE which diminishes the benefits of LHCE. In addition, it is evident that the diluent has significant influence on the electrode/electrolyte interphases (EEIs) beyond retaining the high-concentration solvation structures. Diluent molecules surrounding the high-concentration clusters could accelerate or decelerate the anion decomposition through co-participation of diluent decomposition in the EEI formation. The varied interphase features lead to significantly different battery-performance. This study points out the importance of diluents and their synergetic effects with the conductive salt and the solvating solvent in designing LHCEs. These systematic comparisons and fundamental insights into LHCEs using different types of fluorinated solvents can guide further development of advanced electrolytes for high-voltage LMBs.

Cao, Xia↗
DOE OSTI2022

Importance of Nuclear Quantum Effects on Aqueous Electrolyte Transport under Confinement in Ti 3 C 2 MXenes

Protons display a high chemical activity and strongly affect the charge storage capability in confined interlayer spaces of two-dimensional (2D) materials. As such, an accurate representation of proton dynamics under confinement is important for understanding and predicting charge storage dynamics in these materials. While often ignored in atomistic-scale simulations, nuclear quantum effects (NQEs), e.g., tunneling, can be significant under confinement even at room temperature. Here, using the thermostatted ring polymer molecular dynamics implementation of path integral molecular dynamics (PIMD) in conjunction with the ReaxFF force field, density functional tight binding (DFTB), and NequIP neural network potential simulations, we investigate the role of NQEs on proton and water transport in bulk water and aqueous electrolytes under confinement in Ti 3 C 2 MXenes. Although overall NQEs are relatively small, especially in bulk, we find that they can alter both quantitative values and qualitative trends on both proton transport and water self-diffusion under confinement relative to classical MD predictions. Therefore, our results suggest the need for NQEs to be considered to simulate aqueous systems under confinement for both qualitative and quantitative accuracy.

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

Electrolyte–Electrocatalyst Interfacial Effects of Polymeric Materials for Tandem CO 2 Capture and Conversion Elucidated Using In Situ Electrochemical AFM

Integrating CO 2 capture and electrochemical conversion has been proposed as a strategy to reduce the net energy required for CO 2 regeneration in traditional CO 2 capture and conversion schemes and can be coupled with carbon-free renewable electricity. Polyethylenimine (PEI)-based materials have been previously studied as CO 2 capture materials and can be integrated in these reactive capture processes. PEI-based electrolytes have been found to significantly increase the CO 2 loading, and impact selectivity and rate of product formation when compared to the conventional aqueous electrolytes. However, the influence of these materials at the catalyst–electrode interface is currently not well understood. In this study, PEI-based electrolytes were prepared and their impact on the morphology of a silver electrode performing electrochemical CO 2 reduction (CO 2 R) was studied using in situ electrochemical atomic force microscopy (EC-AFM). The presence of PEI on the electrode surface could be distinguished based on nanomechanical properties (DMT modulus), and changes were observed as negative polarization was applied, revealing a reorganization of the PEI chains due to electrostatic interactions. These changes were impacted by the electrolyte composition, including the addition of supporting electrolyte KHCO 3 salt, as well as CO 2 captured by the PEI-based electrolyte, which minimized the change in surface mechanical properties and degree of PEI alignment on the electrode surface. The changes in surface mechanical properties were also dependent on the PEI polymer length, with higher molecular weight PEI showing different reconfiguration than the shorter polymer brushes. The study highlights that the choice of polymer material, the electrolyte composition, and CO 2 captured impact the nearelectrode environment, which has implications for CO 2 R, and presents EC-AFM as a new tool that can be used to probe the dynamic behavior of these interfaces during electrocatalysis.

36 MATERIALS SCIENCE↗
DOE OSTI2021

New Cost-Effective Halide Solid Electrolytes for All-Solid-State Batteries: Mechanochemically Prepared Fe 3+ -Substituted Li 2 ZrCl 6

Owing to the combined advantages of sulfide and oxide solid electrolytes (SEs), that is, mechanical sinterability and excellent (electro)chemical stability, recently emerging halide SEs such as Li 3 YCl 6 are considered to be a game changer for the development of all-solid-state batteries. However, the use of expensive central metals hinders their practical applicability. In this study, a new halide superionic conductors are reported that are free of rare-earth metals: hexagonal close-packed (hcp) Li 2 ZrCl 6 and Fe 3+ -substituted Li 2 ZrCl 6 , derived via a mechanochemical method. Conventional heat treatment yields cubic close-packed monoclinic Li 2 ZrCl 6 with a low Li + conductivity of 5.7 × 10 –6 S cm –1 at 30 °C. In contrast, hcp Li 2 ZrCl 6 with a high Li + conductivity of 4.0 × 10 –4 S cm –1 is derived via ball-milling. More importantly, the aliovalent substitution of Li 2 ZrCl 6 with Fe 3+ , which is probed by complementary analyses using X-ray diffraction, pair distribution function, X-ray absorption spectroscopy, and Raman spectroscopy measurements, drastically enhances the Li + conductivity up to ≈1 mS cm –1 for Li 2.25 Zr 0.75 Fe 0.25 Cl 6 . The superior interfacial stability when using Li 2+ x Zr 1– x Fe x Cl 6 , as compared to that when using conventional Li 6 PS 5 Cl, is proved. Furthermore, an excellent electrochemical performance of the all-solid-state batteries is achieved via the combination of Li 2 ZrCl 6 and single-crystalline LiNi 0.88 Co 0.11 Al 0.01 O 2 .

25 ENERGY STORAGE↗
DOE OSTI2020

Effect of Liquid Electrolyte Soaking on the Interfacial Resistance of Li 7 La 3 Zr 2 O 1 2 for All-Solid-State Lithium Batteries

In this work, the impact of liquid electrolyte soaking on the interfacial resistance between the garnet-structured Li 7 La 3 Zr 2 O 12 (LLZO) solid electrolyte and metallic lithium has been studied. Lithium carbonate (Li 2 CO 3 ) formed by inadvertent exposure of LLZO to ambient conditions is generally known to increase interfacial impedance and decrease lithium wettability. Soaking LLZO powders and pellets in the electrolyte containing lithium tetrafluoroborate (LiBF 4 ) shows a significantly reduced interfacial resistance and improved contact between lithium and LLZO. Raman spectroscopy, X-ray diffraction, and soft X-ray absorption spectroscopy reveal how Li 2 CO 3 is continuously removed with increasing soaking time. On-line mass spectrometry and free energy calculations show how LiBF 4 reacts with surface carbonate to form carbon dioxide. Using a very simple and scalable process that does not involve heat-treatment and expensive coating techniques, we show that the Li–LLZO interfacial resistance can be reduced by an order of magnitude.

25 ENERGY STORAGE↗
DOE OSTI2021

Essential effect of the electrolyte on the mechanical and chemical degradation of LiNi 0.8 Co 0.15 Al 0.05 O 2 cathodes upon long-term cycling

Capacity fading during long-term cycling (>1500×) is still a critical challenge for Li-ion batteries that use Ni-rich layered oxides, e.g. LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA), as the cathode. Microcracks have been previously recognized as one of the primary reasons for the observed capacity fade. Although there exists a generally developed mechanical understanding of microcracks, the role of the electrolyte has not been clearly understood, especially after extended cycling and at the atomic scale. Here, we unveil the microstructural evolution of spherical NCA secondary particles after long-term cycling using scanning transmission electron microscopy accompanied with electron energy loss spectroscopy. In this work, we found that the microcracks initiated and grew through grain boundaries, which then serve as the pathway for electrolyte penetration into secondary NCA particles. Additionally, the rock-salt phase reconstruction is prone to occur at the (003) surfaces of the primary particles or the crack surfaces, largely due to electrolyte (LiPF 6 EC/EMC) corrosion. Crack propagation within the NCA grains is primarily a joint consequence from electrolyte corrosion and mechanical strain during lithiation/delithiation. During extended cycling, due to the distinctive surface facets, the primary grains located in the center of the secondary particles experience more intensive electrolyte corrosion, leading to a reduced contact with nearby particles, impairing the overall capacity. These results establish the initiation and growth mechanism of microcracks and voids in NCA-based cathodes during cycling and point out the role of the electrolyte in affecting the degradation of NCA-based cathodes.

25 ENERGY STORAGE↗
DOE OSTI2020

Incorporating the Nanoscale Encapsulation Concept from Liquid Electrolytes into Solid-State Lithium–Sulfur Batteries

Solid-state Li–S batteries are attractive due to their high energy density and safety. However, it is unclear whether the concepts from liquid electrolytes are applicable in the solid state to improve battery performance. Here, we demonstrate that the nanoscale encapsulation concept based on Li 2 S@TiS 2 core–shell particles, originally developed in liquid electrolytes, is effective in solid polymer electrolytes. Using in situ optical cell and sulfur K-edge X-ray absorption, we find that polysulfides form and are well-trapped inside individual particles by the nanoscale TiS 2 encapsulation. We see that this TiS 2 encapsulation layer also functions to catalyze the oxidation reaction of Li 2 S to sulfur, even in solid-state electrolytes, proven by both experiments and density functional theory calculations. A high cell-level specific energy of 427 W·h·kg –1 is achieved by integrating the Li 2 S@TiS 2 cathode with a poly(ethylene oxide)-based electrolyte and a lithium metal anode. This study points to the fruitful direction of borrowing concepts from liquid electrolytes into solid-state batteries.

25 ENERGY STORAGE↗
DOE OSTI2024

HTO and selenate diffusion through compacted Na-, Na–Ca-, and Ca-montmorillonite

Radionuclide transport in smectite clay barrier systems used for nuclear waste disposal is controlled by diffusion, with adsorption significantly retarding transport rates. While a relatively minor component of spent nuclear fuel, 79 Se is a major driver of the safety case for spent fuel disposal due to its long half-life (3.3×10 5 yr) and its low adsorption to clay (K D < 10 L/kg), thus a thorough understanding of Se diffusion through clay is critical for understanding the long-term safety of spent fuel disposal systems. Through-diffusion experiments with tritiated water (HTO, conservative tracer) and Se(VI) were conducted with a well-characterized, purified montmorillonite source clay (SWy-2) under a constant ionic strength (0.1 M) and three different electrolyte compositions: Na + , Ca 2+ , and a Na + -Ca 2+ mixture at pH 6.5 in order to probe the effects of electrolyte composition and interlayer cation composition on clay microstructure, Se(VI) aqueous speciation, and ultimately diffusion. Further, the results were modeled using a reactive transport modeling approach to determine values of porosity (ε), D e (effective diffusion coefficient), and K D (distribution coefficient for adsorption). HTO diffusive flux was higher in Ca-montmorillonite (D e =1.68×10 -10 m 2 s -1 ) compared to Na-montmorillonite (De=7.83×10 -11 m 2 s -1 ). This increase in flux is likely due to a greater degree of clay layer stacking in the presence of Ca 2+ compared to Na + , which leads to larger inter-particle pores. Overall, the Se(VI) flux was much lower than the HTO flux due to anion exclusion, with Se(VI) flux following the order Ca (D e = 1.03×10 -11 m 2 s -1 ) > Na–Ca (D e = 2.12×10 -12 m 2 s -1 ) > Na (D e = 1.28×10 -12 m 2 s -1 ). These differences in Se(VI) flux are due to a combination of factors, including (1) larger accessible porosity in Ca-montmorillonite due to clay layer stacking and smaller electrostatic effects compared to Na-montmorillonite, (2) larger accessible porosity for neutral-charge CaSeO4 species which makes up 32% of aqueous Se(VI) in the pure Ca system, and (3) possibly higher Se(VI) adsorption for Ca-montmorillonite. Through a combination of experimental and modeling work, this study highlights the compounding effects that electrolyte and counterion compositions can have on radionuclide transport through clay. Diffusion models that neglect these effects are not transferable from laboratory experimental conditions to in situ repository conditions.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2026

Unraveling interphase-driven failure pathways in LiMn0.6Fe0.4PO4/graphite pouch cells

LiMnxFe1−xPO4 (LMFP) is a promising high-voltage, thermally stable, and earth-abundant cathode material, yet its practical application is limited by interphase instability and Mn dissolution. In this work, we systematically evaluate LiMn0.6Fe0.4PO4/graphite pouch cells using three electrolyte formulations including control carbonate electrolyte, control + 2 wt% vinylene carbonate (VC), and control + 2 wt% VC + 1 wt% 1,3,2-dioxathiolane 2,2-dioxide (DTD), to establish how electrolyte composition governs interphase chemistry and long-term degradation. Electrochemical testing shows that both additives are preferentially reduced prior to ethylene carbonate (EC) during cell formation, generating robust cathode-electrolyte interphase (CEI) and solid-electrolyte interphase (SEI) layers that suppress gas evolution and raise the first-cycle coulombic efficiency to 89.3%. Additionally, the dual-additive electrolyte delivers the most stable performance, retaining over 85% capacity after 600 cycles while minimizing impedance growth under long-term cycling at C/3 and 40 °C. Soft X-ray absorption spectroscopy confirms that VC + DTD effectively suppresses electrolyte oxidation at the cathode surface, and micro-X-ray fluorescence shows substantially reduced Mn dissolution and deposition on the graphite anode. Density functional theory simulations further provided insights into the structural and energetic influences of alkoxide species on the cathode surface, proposing a Mn2+ extraction mechanism. The combined experimental and computational findings establish a mechanistic link between electrolyte composition and interphase evolution, highlighting the effectiveness of electrolyte engineering for extending the operational lifetime of LMFP-based lithium-ion batteries.

Chak, Chanmonirath Michael↗
DOE OSTI2023

Dissolution of the Solid Electrolyte Interphase and Its Effects on Lithium Metal Anode Cyclability

At >95% Coulombic efficiencies, most of the capacity loss for Li metal anodes (LMAs) is through the formation and growth of the solid electrolyte interphase (SEI). However, the mechanism through which this happens remains unclear. One property of the SEI that directly affects its formation and growth is the SEI’s solubility in the electrolyte. Here, in this work, we systematically quantify and compare the solubility of SEIs derived from ether-based electrolytes optimized for LMAs using in-operando electrochemical quartz crystal microbalance (EQCM). A correlation among solubility, passivity, and cyclability established in this work reveals that SEI dissolution is a major contributor to the differences in passivity and electrochemical performance among battery electrolytes. Together with our EQCM, X-ray photoelectron spectroscopy (XPS), and nuclear magnetic resonance (NMR) spectroscopy results, we show that solubility depends on not only the SEI’s composition but also the properties of the electrolyte. This provides a crucial piece of information that could help minimize capacity loss due to SEI formation and growth during battery cycling and aging.

25 ENERGY STORAGE↗
DOE OSTI2021

Evaluating temperature dependent degradation mechanisms of silicon-graphite electrodes and the effect of fluoroethylene carbonate electrolyte additive

Understanding and overcoming the relatively high rate of degradation observed with silicon (Si)-based anodes in lithium (Li)-ion batteries (LiBs) is crucial for developing cells with increased energy density. The capacity fade of Si-graphite (Gr) electrodes in electrolytes with and without 10 wt% fluoroethylene carbonate (FEC) is explored during cycling at temperatures of 25, 45, and 70 °C, focusing on the complex degradation modes arising from loss of active material, loss of Li inventory, and cell resistance growth. We first show the common half-cell testing cannot be used at elevated temperatures as the performance of Li metal overshadows the behavior of Si-Gr electrode. Symmetric cell configuration successfully eliminates the effect of foreign materials, and reveals that while the presence of FEC provides better passivation of Si, it also results in greater parasitic reactions at 70 °C and faster capacity fade. The electrolyte without FEC, on the other hand, shows higher capacity retention at 70 °C. Finally, we propose a multi-step test protocol which can successfully deconvolute the information on loss of Li inventory and of active material. By combining half-cell and symmetric cell test methods, we demonstrate that loss of active material is reduced at higher temperatures and the dominant mechanisms of capacity loss for Si-Gr electrodes at elevated temperatures is loss of Li inventory.

25 ENERGY STORAGE↗
DOE OSTI2024

A weakly ion pairing electrolyte designed for high voltage magnesium batteries

High-voltage rechargeable magnesium batteries (RMBs) are potential alternatives to lithium-ion batteries owing to the low cost and high abundance of magnesium. However, the parasitic reactions of the latter with many electrolytes greatly hinders the stability and kinetics of Mg plating/stripping. Here we report a new and easily accessible solvent-designed electrolyte, which effectively solves the difficulty of ion pair dissociation and facilitates fast nanoscale Mg nucleation/growth using simple Mg(TFSI)2 as the salt, enabling a facile interfacial charge transfer process. Dendrite-free Mg plating/stripping is maintained for over 7000 hours (∼10 months) at a practical areal capacity of 2 mA h cm−2. The high-voltage stability of these electrolytes is demonstrated by benchmarking with polyaniline||Mg full cells with an operating voltage up to 3.5 V that exhibit stable cycling at a 2C rate with 99% coulombic efficiency after 400 cycles. This work opens up new frontiers in coupling low-cost electrolytes with next-generation high-voltage cathode materials for fast-charging RMBs with long life and high energy densities.

Li, Chang↗
DOE OSTI2023

Suppressing the Shuttle Effects with FeCo/SPAN Cathodes and High-Concentration Electrolytes for High-Performance Lithium–Sulfur Batteries

The shuttle effects and the sluggish redox kinetics are two of the main challenges in lithium–sulfur (Li–S) batteries, which significantly reduce the capacity of the batteries and restrict their commercialization. Herein, FeCo/sulfurized polyacrylonitrile (SPAN) is synthesized as a cathode material via the electrospinning technique and a further heat treatment. Synchrotron X-ray absorption spectroscopy confirmed the existence of Fe–S/Fe and Co–S bonds in FeCo/SPAN, which benefit the adsorptive and catalytic activities toward lithium polysulfides (LiPSs). Here, we further investigated the effect of electrolyte concentration in inhibiting the shuttle of LiPSs in Li–S batteries. Small-angle X-ray scattering (SAXS) reveals that more contact ion pairs are formed and fewer free solvent molecules exist with the increase of the electrolyte concentration, which can inhibit the dissolution and shuttle of LiPSs. Finally, the batteries assembled with high-concentration electrolytes (3 M LiTFSI in DOL/DME) exhibit a higher specific capacity retention compared to those assembled with low-concentration electrolytes. This work enriches the route to prepare Li–S batteries with the rational design of cathode materials and electrolytes.

25 ENERGY STORAGE↗
DOE OSTI2020

Low-temperature paddlewheel effect in glassy solid electrolytes

Glasses are promising electrolytes for use in solid-state batteries. Nevertheless, due to their amorphous structure, the mechanisms that underlie their ionic conductivity remain poorly understood. Here, ab initio molecular dynamics is used to characterize migration processes in the prototype glass, 75Li2S–25P2S5. Lithium migration occurs via a mechanism that combines concerted motion of lithium ions with large, quasi-permanent reorientations of PS4 3- anions. This latter effect, known as the ‘paddlewheel’ mechanism, is typically observed in high temperature crystalline polymorphs. In contrast to the behavior of crystalline materials, in the glass paddlewheel dynamics contribute to Lithium-ion mobility at room temperature. Paddlewheel contributions are confirmed by characterizing spatial, temporal, vibrational, and energetic correlations with Lithium motion. Furthermore, the dynamics in the glass differ from those in the stable crystalline analogue, γ-Li3PS4, where anion reorientations are negligible and ion mobility is reduced. These data imply that glasses containing complex anions, and in which covalent network formation is minimized, may exhibit paddlewheel dynamics at low temperature. Consequently, these systems may be fertile ground in the search for new solid electrolytes.

36 MATERIALS SCIENCE↗