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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 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Life cycle assessment of coir fiber-reinforced composites for automotive applications

Past decades have seen an increasing prevalence of natural fiber-reinforced composites (NFRCs) due to growing conscientiousness around sustainability and a push towards vehicle lightweighting. The environmentally friendly and sustainable claims of NFRCs need to be validated due to their large variability and variety, particularly where material substitutions are concerned, such as in substituting glass fiber with natural fiber. Additionally, the objective of this work is to determine the cumulative energy demand (CED) and greenhouse gas emissions (GHG) associated with an automotive part (of volume 0.001 m3) made from 40 wt% coir fiber-reinforced polypropylene (PP) and compared with a similar part made from 40 wt% glass fiber reinforced PP. SimaPro v. 9.0.0.49 was used for the analysis, whereas inventory data were collected from databases, such as Ecoinvent 3, Transportation Energy Databook, Greet model 2022, and published papers. The results showed that CED and GHG associated with the coir fiber-reinforced composite part were lower than the glass fiber-reinforced composite part for both cradle-to-gate (~34–40%) and cradle-to-grave (excluding end-of-life) (~24%) analysis.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Extending wire-arc directed energy deposition using non-gravity aligned (NGA) torch methods

For standard Additive Manufacturing (AM) processes, traditional path planning typically relies on a 2.5-dimensional approach. In wire-arc directed energy deposition (DED), commonly referred to as wire-arc additive manufacturing (WAAM), this 2.5D approach inherently limits final near net shape due to the stair-step effect and restricts the maximum overhang angle achievable without part degradation. To achieve better near net shape and part quality, a 3D planning approach that modulates the tool tip position and angle without process changes is demonstrated in components containing up to 105° of unsupported overhang. The experimental methods are validated with half and fully enclosed cylinder sections containing 90° of overhang. The non-gravity aligned methods are then applied to a commercial WAAM system for a composite tool mold demonstrator part. As a result, the methods developed in this paper enable expansion of WAAM system capabilities to parts containing large overhangs without compromising the net shape or material structure of the resulting parts and without the need for a part positioner.

Additive manufacturing↗
DOE OSTI2025

Investigation of UO 2 doped with Fe 2 O 3 sintered under a reducing atmosphere

Nuclear fuel produced with trace amounts of transition metal additives is of potential interest for introducing intentional signatures for accelerating nuclear forensics. In this work, we investigate the effects on microstructure, grain size, crystal structure, and stoichiometry when trace amounts of Fe in the form of Fe 2 O 3 are added to UO 2 . Sintering of compacts with different concentrations, from 250 to 3000 ppmw, was performed under a reducing atmosphere at 1773 K. The persistence of the taggant during the fuel fabrication process as well as its impact on grain size, crystal lattice, and first-neighbor chemistry was evaluated using inductively coupled plasma–optical emission spectroscopy, powder X-ray diffraction (pXRD), Raman spectroscopy, scanning electron microscopy–backscatter electron spectroscopy, energy dispersive spectroscopy, and thermogravimetric analysis. We observed that a negligible amount of Fe was lost during sintering. Our results indicate that the feedstock, Fe 2 O 3 transforms into Fe and FeO under the test sintering conditions. For all compositions, metallic Fe precipitate was found in grain boundaries as a secondary phase. In conclusion, the potential incorporation of ionic Fe into the UO 2 unit cell was determined by pXRD and Raman spectra.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2025

Microstructure, stored energy, and stability of H/He-filled nanocavities in low temperature irradiated Inconel 718

The microstructure, trapped transmutation gases, stored energy, and mechanical behavior of samples from an irradiated Inconel 718 proton beam window were characterized using transmission electron microcopy, thermal desorption spectrometry (TDS), differential scanning calorimetry (DSC), and tensile testing. In the as-irradiated condition the microstructure contained a high number density of 1–3 nm gas-filled nanocavities. Emissions of trapped gases, H and He, during TDS correlated with peaks of the energy release curves from DSC examinations, which suggest these gases were likely stored in highly stable defect traps. The stored energy from radiation damage saturated at doses of a few dpa and did not increase with increasing radiation dose, but the amount of stored H and He increased with increasing dose. Effects of post-irradiation annealing were studied as well. After exposure to 700 °C, the nanocavities grew only slightly to 2–4 nm in diameter, but after exposure to 900 °C, the cavities grew to 10–20 nm in diameter and electron energy-loss spectroscopy showed these cavities contained a core of He surrounded by a shell of H. Further, this study demonstrated that the irradiation defect structures containing H and He were remarkably stable during irradiation and after exposure up to 700 °C. The effect of the irradiation temperature, defect mobility, and interaction of H, He, and irradiation defects on mechanical behavior provides insight into the processes responsible for the unusual recovery in ductility with increasing radiation dose observed in Inconel 718 after high energy proton and spallation neutron irradiation.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Optimizing processing conditions for additively reinforced thermoforming (ART) in convergent manufacturing

This study utilized additively reinforced thermoforming (ART) to enhance the thermomechanical properties of polyethylene terephthalate glycol (PETG) sheet. ART materials were produced by overprinting PETG/carbon fiber filament (PETG/CF) on neat PETG sheets at varying conditions. The mechanical properties of the PETG sheet, PETG/CF, and ART materials were assessed, showing that ART exhibited superior tensile strength and modulus of elasticity. The tensile strength and modulus in the x-direction for ART at 265°C were 57.32 ± 2.9 MPa and 3.41 ± 0.4 GPa, respectively, compared to 49.1 ± 0.5 MPa and 1.92 ± 0.09 GPa for neat PETG. Microstructural analysis revealed strong interfacial adhesion between layers, while thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and heat deflection temperature analysis provided insights into the ART material's thermoforming behavior, aiding design optimization for enhanced stiffness, reduced necking, and improved customization. In conclusion, this information can be used to design for the thermoforming operation.

Additive reinforcement↗
DOE OSTI2025

Extrusion compression molded critical rare earth free bonded permanent magnets

Samarium iron nitride (Sm-Fe-N) bonded magnets have emerged as promising candidates for various industrial applications due to their exceptional magnetic properties. Compounds with magnetic material 95 wt fraction (wt.%) (∼74 vol%) and 97 wt.% (∼81 vol%) of SmFeN in a polyamide (PA12) polymer binder are manufactured using a batch mixer followed by compression molding. A maximum energy product ( BH ) max of 186.21 kJ.m -3 (23.4 MGOe) is achieved in the 95 wt.% bonded magnets; 97 wt.% magnets had a ( BH ) max of 165.52 kJ.m -3 (20.8 MGOe). It is found that the degree of alignment (DoA) of 99 % is achieved in the 95 wt.% magnets, whereas the 97 wt.% magnets are limited to a DoA of 90 % respectively. The high DoA can be attributed to low particle-particle interaction during the post-magnetic field alignment process. Finally, this research provides a useful insight of binder-particle interactions at very high magnet weight fractions and their effect on magnetic strength and performance.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Post-build stress-relief optimization for laser powder bed fusion 316H stainless steel

Nuclear energy remains a critical component of a diversified and efficient energy portfolio, offering reliable, high-capacity, and low-carbon power. However, in the U.S., aging infrastructure and the slow qualification and deployment of advanced materials and manufacturing techniques hinder progress in next-generation reactor technologies. This study explores the application of laser powder bed fusion (LPBF) additive manufacturing for stainless steel 316H, with a focus on optimizing post-build heat treatments to enhance material properties for high-temperature nuclear applications. The research targets the optimization of stress-relief temperatures to alleviate postbuild residual stresses, ensuring improvements in the microstructural corelated properties. A series of microstructural and mechanical evaluations were performed on LPBF-printed SS-316H samples which were subjected to annealing at temperatures varying between 650 °C and 850 °C. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy analyses revealed that increasing the heattreatment temperature accelerated dislocation recovery. Vickers microhardness measurements showed an initial reduction in values, followed by stabilization over extended durations at all the temperatures. While higher temperatures facilitated faster recovery, they also promoted carbide precipitation along grain and solidification cell boundaries, narrowing the safe processing window. In contrast, heat treatment at 650°C preserved the cellular substructure and enabled controlled carbide precipitation over time. In conclusion, these findings highlight the importance of time–temperature optimization and suggest that 650°C for up to 2 h provides the most favorable balance between recovery and carbide control for a stress-relief treatment.

316 stainless steel↗
DOE OSTI2026

ROADRUNNER uranium nitride MiniFuel: Experimental design, fabrication and pre-irradiation baseline characterization for accelerated burnup testing

Uranium nitride (UN) is a promising fuel candidate for advanced reactor systems owing to its high uranium density and thermal conductivity; however, its qualification remains constrained by the scarcity of well-controlled irradiation performance data. Here, to address this limitation, the ROADRUNNER (Research On ADvancing the peRformance of UraNium Nitrides in Extreme enviRonments) campaign employs the MiniFuel platform in the High Flux Isotope Reactor (HFIR) to enable accelerated burnup irradiation testing under tightly controlled and largely isothermal conditions. This paper presents the experimental design, fuel fabrication, and pre-irradiation baseline characterization of the ROADRUNNER UN MiniFuel campaign. Thirty-six UN minidisc specimens were fabricated with systematically varied as-fabricated density (86–96% of theoretical density), carbon impurity content (961–5240 ppm), oxygen content (≤ ∼2000 ppm), and grain size (2.5–24 μm). The irradiation matrix spans nominal fuel temperatures of 873 K, 1173 K, and 1473 K and target burnups of 3.75%, 6.0%, and 7.5% fissions per initial metal atom (FIMA). Neutronic and thermal analyses were performed to define specimen-specific burnup accumulation and temperature histories, establishing the boundary conditions for subsequent in-pile behavior. Comprehensive pre-irradiation characterization—including dimensional metrology, density verification, impurity analysis, X-ray diffraction, Raman spectroscopy, scanning electron microscopy, X-ray computed tomography, and confocal profilometry—provides a detailed baseline for post-irradiation examination. Pre-irradiation data were further used to generate predictive estimates of fission gas release and swelling using existing empirical correlations. This quantitative comparison reveals substantial inter-model divergence at intermediate and elevated temperatures that exceeds propagated input uncertainties, highlighting structural gaps in the historical irradiation database. The ROADRUNNER irradiation campaign is currently underway in HFIR, with initial firs cycle completed in late 2025 and remaining targets scheduled through 2027. The experimental design and baseline dataset presented here establish the framework needed to interpret forthcoming post-irradiation measurements and to provide discriminating data for the validation and refinement of physics-based UN fuel performance models.

Lopes, Denise Adorno [Oak Ridge National Laborator↗
DOE OSTI2025

U-Pu and Ba-Cs isotopic measurements on Trinitite by laser ablation sampling on the Neoma MC-ICP-MS

In this study we present the results of combined U-Pu and Ba-Cs isotope measurements obtained by laser ablation (LA) sampling of two glassy debris fragments (‘Trinitite’) from the world's first atomic bomb detonation conducted in New Mexico on July 16, 1945. Our primary goal in conducting these measurements was to understand whether examination of the U-Pu and Ba-Cs systematics by direct sampling (e.g. without any chemical separation or purification prior to isotope ratio measurement) could yield meaningful information that would differentiate the Trinitite fragments from glassy material lacking a nuclear fission signature. These measurements were conducted on a ThermoFisher Scientific Neoma multi collector – inductively coupled plasma – mass spectrometer (MC-ICP-MS), which is a relatively new MC-ICP-MS platform, so we also examine the behavior of these isotope systems in standards sampled in solution and via LA. Unsurprisingly, the measurements made on purified solutions of the U, Pu, and Ba isotopic standards produce high precision isotope ratios. Furthermore, this extends to the U-Pu measurements made by LA sampling, with the expected degradation in precision and accuracy related to matrix effects and signal intensity fluctuation. However, the Ba-Cs data acquired by LA is of low precision across all of the matrices examined and bears evidence of complex mass fractionation that will require further investigation to resolve. In total, our results indicate that the observed U-Pu isotope data are of sufficient quality to accurately constrain the U and Pu isotopic composition of glass containing sub-ppm levels of these elements which in turn could be used to differentiate glass containing anthropogenic fission products from natural glass whereas the Ba-Cs LA data cannot be used for this purpose until further methodological refinement is performed.

Ba-Cs↗
DOE OSTI2024

Analysis of biokinetic parameters reveals patterns in mercury accumulation across aquatic species

Mercury (Hg) is a potent neurotoxicant and poses a risk to human health through the ingestion of Hg-contaminated fish. Mercury, especially in its organic form methylmercury (MeHg), biomagnifies up food chains such that even small aqueous concentrations of Hg can result in significant concentrations of total Hg in fish. Understanding the ecological and human health risks associated with Hg and MeHg exposure requires an understanding of the factors that affect its bioaccumulation in aquatic species. We compiled estimates of three biokinetic parameters: uptake rate (k u ), assimilation efficiency (AE), and efflux rate (k e ). These parameters describe contaminant uptake from aqueous (k u ) and dietary (AE) exposure and the rate of excretion (k e ). We found parameter values for 38 and 34 different species of fish and aquatic invertebrates, respectively, and collected 502 parameter values in total. Here, we used a machine learning technique to establish the relationships between experimental and physiological variables and these parameter values. We found differences in which variables were associated with biokinetic parameter values for fish and aquatic invertebrates. The form of Hg was the most impactful variable, influencing values of all parameters except k u for invertebrates, for which aqueous exposure time was the only significant predicator variable. The parameter k e were the only values significantly influenced by more than one variable, with water type (freshwater, brackish, or marine), organism weight, and form of Hg significantly impacting parameter values for fish and/or invertebrates. To our knowledge, this study represents the most extensive review of biokinetic parameters of Hg and MeHg accumulation in aquatic organisms. Environmental parameters found to significantly impact Hg and MeHg bioaccumulation in past studies were not identified as important in our analyses across aquatic ecosystems and species. Our dataset and analysis reveal novel patterns that may help us better understand and manage Hg bioaccumulation.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Lattice Structure and Dynamics of Sparse Molecular Crystals: OsO 4 and RuO 4

OsO 4 and RuO 4 are molecular oxides with unique tetrameric structures and rare +8 oxidation states. Accurately modeling their properties remains challenging for density functional theory (DFT) due to weak intertetramer interactions, which standard functionals fail to capture. Here, in this work, we show that the van der Waals (vdW)-corrected density functional (vdW-DF-optB86b) provides structural parameters that are much closer to experimental values than the standard generalized gradient approximation, with volume predictions that fall within the experimentally observed range. Phonon band structure analysis shows that the inclusion of vdW interactions stabilizes soft phonon modes, highlighting the importance of dispersion corrections for accurate predictions of lattice dynamics. Experimental measurements of the phonon density of states for OsO 4 , obtained via inelastic neutron scattering, demonstrate good agreement with our vdW-DF-optB86b calculations. These results validate OsO 4 and RuO 4 as valuable benchmarks for structural and vibrational calculations via vdW-corrected DFT methods and offer insights for studying the broader class of sparse molecular materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Protein Adhesion on Semi-Fluorinated Polystyrene Surfaces in Static and Dynamic Measurements

Reducing protein adhesion is a critical strategy in fouling-resistant material innovation, with broad applications spanning biomedical and healthcare devices, biosensors, industrial and environmental systems, and other important technological domains. Here, in this study, we elucidated protein adhesion behavior on polystyrene-based thin films by neutron reflectometry (NR) and quartz crystal microbalance with dissipation (QCM-D), using both lysozyme and bovine serum albumin (BSA) as model proteins. To this end, semifluorinated polystyrene thin films with gradient wettability and surface energy were fabricated through dry processing using plasma oxidation and gas-phase deposition. Although it is believed that a fully fluorinated alkyl chain offers extremely low surface energy, thus rejecting foulants, and has been used in many fouling-resistant surface designs, enhanced protein–surface interactions were observed consistently in NR and QCM-D results, due to the combined effects of surface morphology and chemistry. On the contrary, depositing shorter fluorinated silane onto a hydrophilic PS surface contributed to a more homogeneous nanoscale fluorine coating, resulting in less initial protein adsorption and improved surface recovery. Comparative analysis of proteins with different sizes on the nanopatterned semifluorinated surface revealed the influence of molecular characteristics on surface interactions. Lysozyme, being smaller and more compact, showed faster adsorption kinetics and higher surface coverage but largely reversible binding, whereas BSA, with its larger and more flexible structure, formed broader and more stable interfacial layers. This study fills the gap in understanding protein adhesion within the range of hydrophobicity (water contact angle ∼90°), as current strategies often associate with extreme hydrophilic and superhydrophobic surfaces due to hydration or low-surface-energy rejection mechanisms, respectively. It also provides in-depth insights into current combinatorial fouling-resistant surface design.

Yuan, Yue [Oak Ridge National Laboratory (ORNL), O↗
DOE OSTI2025

Scalable Bottom-Up Synthesis of Nanoporous Hexagonal Boron Nitride ( h -BN) for Large-Area Atomically Thin Ceramic Membranes

Nanopores embedded within monolayer hexagonal boron nitride (h-BN) offer possibilities of creating atomically thin ceramic membranes with unique combinations of high permeance (atomic thinness), high selectivity (via molecular sieving), increased thermal stability, and superior chemical resistance. However, fabricating size-selective nanopores in monolayer h-BN via scalable top-down processes remains nontrivial due to its chemical inertness, and characterizing nanopore size distribution over a large area remains extremely challenging. Here, we demonstrate a facile and scalable approach of exploiting the chemical vapor deposition (CVD) process temperature to enable direct incorporation of subnanometer/nanoscale pores into the monolayer h-BN lattice, in combination with manufacturing compatible polymer casting to fabricate centimeter-scale nanoporous atomically thin ceramic membranes. We leverage diffusive transport of analytes including size-selective Ficoll sieving to characterize subnanometer-scale and nanoscale defects that manifest as pores in centimeter-scale h-BN membranes, overcoming previous limitations in large-area characterization of nanoscale defects in h-BN. Our approach opens a new frontier to advance atomically thin membranes to 2D ceramic materials, such as h-BN via facile and direct formation of nanopores, for size-selective separations.

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

Enhanced Neutron and γ-Ray Detection via 6 Li Substitution in Undoped and Tl-Doped Zero-Dimensional Perovskite Cs 3 Cu 2 I 5 Scintillators

Radiation detectors are crucial in a wide variety of research and commercial applications, such as oil and gas exploration, medical imaging, nuclear nonproliferation, and homeland security. Neutron and gamma-ray detectors are fundamental components in portal monitors at ports and border crossings, bolstering national security against radiological threats. This study presents a dual-mode scintillator, undoped and Tl-doped 6 Li-Cs 3 Cu 2 I 5 , and demonstrates its potential as a promising material for simultaneous thermal neutron and gamma-ray detection. We explore the Bridgman growth of both undoped and thallium doped Li → Cu and Li → Cs substitutional systems with various Li doping levels and assess their impact on scintillation properties. Under 662 keV gamma-ray excitation, the undoped crystals had light yields up to 35,900 ph/MeV, with energy resolutions down to 4.5%. The Tl-doped crystals performed better than the undoped crystals with light yields peaking at 65,900 ph/MeV and energy resolutions as low as 3.5%. When exposed to a moderated 252 Cf excitation source, our crystals had light yields between 102,900 and 167,200 photons per thermal neutron capture, with a full energy thermal neutron peak reaching 3 MeV in gamma equivalent energy. Pulse shape discrimination studies reveal well-separated gamma and neutron events, resulting in Figure-Of-Merit (FOM) as high as 3.7. Furthermore, these findings highlight the potential of Li-doped Cs 3 Cu 2 I 5 as a viable candidate for next-generation dual-mode scintillators.

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

Pathway to High Rate Capability in Interconnected Composite Electrolytes: A Case Study with a Single-Ion-Conducting Polymer

In a three-dimensional interconnected polymer/ceramic composite electrolyte (3D composite), both the polymer and ceramic electrolyte phases are individually connected with a polymer-rich surface layer to provide conformal contact with the electrodes. This work investigates how the transference number of the polymer phase affects the electrochemical properties of the 3D composite. Here, we fabricate a 3D composite using a “single-ion” conducting polymer electrolyte (PE), Li 1+x+y Al x Ti 2–x Si y P 3–y O 12 (LICGC) ceramic, and compare its electrochemical properties with the neat polymer, and with a 3D composite made with a dual-ion-conducting PE (we reported previously). Our results reveal that changing the polymer phase from a dual-ion-conducting PE to a single-ion-conducting PE results in a 9-fold increase in the limiting current density, although the interfacial impedance between the polymer and LICGC ceramic remains high (and contributes significantly to the total impedance of the 3D composite). Further, the limiting current density of the 3D composite is dictated by the PE and minimally affected by the ceramic scaffold. The ceramic scaffold, however, helps to ease the concentration gradient buildup within the PE and moderately improves the overall transference number. The LICGC scaffold does not provide any additional Li dendrite resistance due to its high reactivity with Li.

25 ENERGY STORAGE↗
DOE OSTI2025

Design and Fabrication of Polyisocyanurate Foams toward Significantly Enhanced Thermal Resistivity

Developing high-performance thermal insulation is vital for addressing the ongoing global demand for reduced energy costs. Polyisocyanurate (PIR) foams are commonly used in residential and commercial buildings and in various industrial applications owing to their relatively high thermal insulation properties and fire resistivity. Here, this study aims to further improve the thermal resistivity of PIR foams by (1) incorporating low thermal conductivity blowing agents; (2) tailoring the anisotropy of their cells; (3) tuning polymeric isocyanate quantities; and (4) incorporating a facer barrier, while using steps that easily integrate into current manufacturing processes for PIR foams. The resulting PIR foams exhibit a significant enhancement in thermal resistivity, achieving initial values as high as 8.3 h·ft 2 ·°F/Btu/in., commonly abbreviated as R-8.3/in., which is a 20% improvement compared with that of commercially used PIR foams that achieve approximately R-7/in. The detailed analysis of thermal conductivity measurements, mechanical testing, and morphological characterization elucidates the structure–property relationships. The developed high-performance PIR foams provide a critical pillar for next-generation high-performance insulation, offering promising thermal insulation for buildings and many other applications that have a significant effect on global energy costs.

Anisotropic pores↗
DOE OSTI2025

Understanding the Dissolution and Passivation of an Aluminum Electrode during Electrocoagulation of Groundwater Using Neutron and X-ray Reflectometry

An aluminum (Al)-based electrocoagulation (EC) system can effectively remove dissolved silica and hardness in groundwater. The effectiveness of Al-EC in terms of pollutant removal, Faradaic efficiency, and energy consumption depends on the interfacial electrolysis or passivation of the electrode in water. Thus, understanding the electrolysis reaction at the liquid/electrode interface during operation is important for sustainable EC deployment. Here, a continuous flow-through Al-EC system was tested with various groundwater simulants, i.e., chloride (Cl – )-based, sulfate (SO 4 2– )-based, and mixed solutions. High pollutant removal with low energy consumption was observed in Cl – -based groundwater treatment, while low pollutant removal with high energy consumption was observed in SO 4 2– -based groundwater. For example, the required energy per unit mass of Al dosing in SO 4 2– -based groundwater is three times higher than that in Cl – -based groundwater at 10 mA/cm 2 . However, increasing the Cl – concentration significantly reduces this energy demand. In SO 4 2– -based groundwater, the silicate removal efficiency drops from 85.1% to 24.0% compared to that for Cl – -based groundwater, while Mg 2+ and Ca 2+ removal efficiencies decrease to 0.6% from 15.8% and 5.7% from 44.8%, respectively. To better understand this EC performance, we used in situ neutron reflectometry (NR) to examine the interfacial dynamics of Al dissolution and passivation at a 100 nm scale occurring on the surface of the sacrificial Al electrodes during EC. Ex situ X-ray reflectometry (XRR) was also used to support the in situ NR results. Both NR and XRR results revealed that Al dissolution is influenced by the presence of Cl – in the simulants, while a passivating layer forms on the electrode in a SO 4 2– -based solution. In the Cl – -based solution, anodic Al dissolution occurred locally and inhomogeneously across the surface of the Al anode film, resulting in a localized thickness reduction over time. In the SO 4 2– -based solution, no apparent dissolution of the Al anode was identified. Instead, Al underwent oxidation, forming an amorphous Al 2 O 3 surface layer within the Al electrode film that increased in thickness over time. In the mixed solution, both anodic Al dissolution and surface Al 2 O 3 layer formation occurred, indicating that Al dissolution and surface Al 2 O 3 layer formation are attributable to the Cl – and SO 4 2– ions, respectively.

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

Surprising Relationship between Silicon Anode Calendar Aging and Electrolyte Components in a Localized High-Concentration Electrolyte System

Although localized high-concentration electrolytes (LHCEs) have been shown to improve the calendar lifetime of silicon anodes, the roles of the electrolyte constituents in calendar aging are not well understood. Here, in this work, we utilize a voltage hold protocol and an LHCE with varying molar ratios of lithium bis(fluorosulfonyl)imide (LiFSI), tetramethylene sulfone (TMS), and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) to probe the component roles during aging. Interestingly, the estimated calendar lifetime and irreversible lithium losses from the V-hold experiments are independent of the electrolyte formulations. Contrarily, the solid electrolyte interphase (SEI) composition depends on the electrolyte formulation. X-ray photoelectron spectroscopy shows that TMS-coordinated species decompose to form insoluble alkanes and lithium hydroxide (LiOH), while lithium fluoride (LiF) originates from the anion-coordination complex. The SEI composition does not appear to play a significant role in the silicon anode passivity, as measured by parasitic current, suggesting that the SEI-electrolyte interactions dictate the calendar aging mechanisms.

Si anode↗