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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

A Novel High‐Performance Electrolyte for Extreme Fast Charging in Pilot Scale Lithium‐Ion Pouch Cells

Realizing extreme fast charging (XFC) in lithium-ion batteries for electric vehicles is still challenging due to the insufficient lithium-ion transport kinetics, especially in the electrolyte. Herein, a novel high-performance electrolyte (HPE) consisting of lithium bis(fluorosulfonyl)imide (LiFSI), lithium hexafluorophosphate (LiPF 6 ) and carbonates is proposed and tested in pilot-scale, 2-Ah pouch cells. Moreover, the origin of improved electrochemical performance is comprehensively studied via various characterizations, suggesting that the proposed HPE exhibits high ionic conductivity and excellent electrochemical stability at high charging rate of 6-C. Furthermore, the HPE-based pouch cells deliver improved discharge specific capacity and excellent long-term cyclability up to 1500 cycles under XFC conditions, which is superior to the conventional state-of-the-art baseline electrolyte.

25 ENERGY STORAGE↗
DOE OSTI2024

Lithium ion cells with high performance electrolyte and silicon oxide active materials achieving very long cycle life performance

Improved negative electrodes can comprise a silicon based active material blended with graphite to provide more stable cycling at high energy densities. In some embodiments, the negative electrodes comprise a blend of polyimide binder mixed with a more elastic polymer binder with a nanoscale carbon conductive additive. Electrolytes have been formulated that provide for extended cycling of cells incorporating a mixture of a silicon-oxide based active material with graphite active material in negative electrodes that can be matched with positive electrodes comprising nickel rich lithium nickel manganese cobalt oxides to cells with unprecedented cycling properties for large capacity cell based on a silicon negative electrode active material.

Dong, Yingnan↗
NASA NTRS1990

The improvement of rechargeable lithium battery electrolyte performance with additives

The deliberate introduction of additives like 2-methylfuran (2-MeF) is known to improve Li cycleability in cyclic ether electrolytes. The authors found that the proclivity of 2-MeF to polymerize in the bulk electrolyte or on a TiS2 cathode was inhibited by the addition of reduced oxygen species, such as O2- and OH-. Additionally, the polymerization of tetrahydrofuran and dioxolane and the destructive processes initiated by AsF6- decomposition to AsF5 and AsF3 were inhibited by the introduction of reduced oxygen species, particularly OH- at the 10-ppm to 100-ppm level.

Dominey, L. A.↗
DOE OSTI2024

Random Copolymerization of Substituted Dioxolanes: Rational Design of High-Performance Polymer Electrolytes

Polymer electrolytes enhance the safety of lithium-ion battery systems, but current state-of-the-art poly­(ethylene oxide)-based polymer electrolytes fail to achieve the electrochemical properties necessary for practical applications. We probed the impact of substituent density on the electrolyte performance by introducing methyl substituents into the backbone of a series of poly­(1,3-dioxolane) (PDXL)-based copolymers. The polymerization of 1,3-dioxolane (DXL) and 4-methyl-1,3-dioxolane (MeDXL) yielded a series of random copolymers that were amorphous above 10% MeDXL incorporation. The copolymers with 10 and 20% MeDXL incorporation exhibited higher efficacies than those of either PDXL or poly­(ethylene oxide) (PEO), highlighting the use of methyl substituents to control the electrochemical properties of polymer electrolytes.

Rugh, Haley J↗
DOE OSTI2023

Impact of the fluorination degree of ether-based electrolyte solvents on Li-metal battery performance

Electrolytes using fluorinated solvents have proven effective in improving the cycling life of Li-metal batteries, by forming a robust solid–electrolyte interphase through decomposition of anion and fluorinated solvent molecules. Herein, we modulated the fluorination degree of ether-based electrolyte solvents to investigate their performance in Li-metal batteries. Here, we tuned the fluorination degree by installing a monofluoro substituent on one ethoxy group of 1,2-diethoxyethane (DEE) and varying the fluorination degree on the other one, providing three fluorinated DEE solvent molecules (i.e., F1F0, F1F1 and F1F2) with a relatively low fluorination degree. All three electrolytes showed improved solvation strength and ionic conductivities compared with previous highly fluorinated DEE electrolytes while retaining good oxidative stability. A full cell test using the Li-metal anode and nickel-rich cathode revealed that a higher degree of fluorination is beneficial to the cycling performance, and the cycling stability follows F1F0 < F1F1 < F1F2. Specifically, F1F0 exhibited poor cycling stability due to its instability against both the anode and cathode. While F1F1 and F1F2 both showed good stability against the Li metal anode, their relative long-term oxidative stability was responsible for the distinct performance, in which the cycle numbers at 80% capacity retention for F1F1 and F1F2 were ~20 and ~80, respectively. Finally, we demonstrated that F1F2 was able to achieve 90 cycles before reaching 80% capacity retention in practical lithium iron phosphate (LFP) pouch cells. This work shows the importance of modulating the fluorination degree of electrolyte solvents, and this approach is suitable for various cathode materials.

25 ENERGY STORAGE↗
DOE OSTI2020

Boosting solid oxide fuel cell performance via electrolyte thickness reduction and cathode infiltration

Increasing the power density and reducing the operating temperature of solid oxide fuel cells (SOFCs) is important for improving commercial viability. Here we discuss two strategies for achieving such improvements in Ni–YSZ supported SOFCs – electrolyte thickness reduction and cathode infiltration. Microstructural and electrochemical results are presented showing the effect of reducing YSZ/GDC electrolyte thickness from 8 to 2.5 μm, and the effect of PrO x infiltration into the LSCF–GDC cathode. Both of these measures are effective, particularly at lower temperatures, leading to an increase in the maximum power density at 650 °C from 0.4 to 0.95 W cm –2 , for example. Electrochemical impedance spectroscopy utilizing subtractive analysis shows that PrO x enhances the cathode charge transfer process. Reducing the electrolyte thickness reduces not only the cell ohmic resistance but also the electrode polarization resistance. Furthermore, the latter effect appears to be an artifact associated with a slight increase in the steam partial pressure at the anode due to minor gas leakage across the thinner electrolyte.

25 ENERGY STORAGE↗
DOE OSTI2022

Rational solvent molecule tuning for high-performance lithium metal battery electrolytes

Electrolyte engineering improved cycling of Li metal batteries and anode-free cells at low current densities; however, high-rate capability and tuning of ionic conduction in electrolytes are desirable yet less-studied. In this study, we design and synthesize a family of fluorinated-1,2-diethoxyethanes as electrolyte solvents. The position and amount of F atoms functionalized on 1,2-diethoxyethane were found to greatly affect electrolyte performance. Partially fluorinated, locally polar –CHF 2 is identified as the optimal group rather than fully fluorinated –CF 3 in common designs. Paired with 1.2 M lithium bis(fluorosulfonyl)imide, these developed single-salt-single-solvent electrolytes simultaneously enable high conductivity, low and stable overpotential, >99.5% Li||Cu half-cell efficiency (up to 99.9%, ±0.1% fluctuation) and fast activation (Li efficiency >99.3% within two cycles). Combined with high-voltage stability, these electrolytes achieve roughly 270 cycles in 50-μm-thin Li||high-loading-NMC811 full batteries and >140 cycles in fast-cycling Cu||microparticle-LiFePO 4 industrial pouch cells under realistic testing conditions. The correlation of Li + –solvent coordination, solvation environments and battery performance is investigated to understand structure–property relationships.

25 ENERGY STORAGE↗
DOE OSTI2025

Critical Insights into Solvent Choice for High-Voltage Organosulfur Electrolytes

Organosulfur electrolytes are promising candidates for enabling high-voltage cathodes due to their superior oxidative stability compared to conventional carbonate-based systems. However, their viscous nature and inability to passivate the anode necessitate the use of passivating agents and diluents to achieve meaningful charge/discharge rates. In this study, we investigate the use of cyclic fluorinated carbonates (CFCs) to form passivating interphases on electrode surfaces, aiming to optimize electrolyte performance in high-voltage systems. Electrolyte formulations containing 1.2 M LiPF 6 in a CFC:sulfone:1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropylether (TTE) mixture (2/5/3 V/V/V) were assessed in full-cell configurations with a LiNi 0.8 Mn 0.1 Co 0.1 O 2 (FCG-NMC) cathode and a 4.5 V upper cutoff potential. The results reveal that 3-3-3-trifluoropropylene carbonate (TFPC) combined with ethyl methyl sulfone (EMS) optimizes electrolyte performance, resulting in lower resistance buildup and reduced capacity loss compared to commercial electrolytes. We also explore the failure mechanisms of several carbonate/sulfone mixtures and identify key considerations for electrolyte compatibility in high-voltage systems. TFPC enhances cycling stability and lowers overall cell resistance, while fluoroethylene carbonate (FEC) formulations, despite higher ionic conductivity, fail to form adequate passivation layers, leading to rapid capacity loss. Additionally, EMS provides superior physical properties that avoid common failure modes seen with other sulfone solvents like methyl isopropyl sulfone and tetramethylene sulfone. Furthermore, this study underscores the importance of carefully selecting passivating carbonates and sulfone solvents to improve electrolyte performance and expand the viability of high-voltage electrolyte systems.

LiNi0.8Mn0.1Co0.1O2 cathode↗
DOE OSTI2021

Effects of Ink Formulation on Construction of Catalyst Layers for High-Performance Polymer Electrolyte Membrane Fuel Cells

Rational design of catalyst layers in a membrane electrode assembly (MEA) is crucial for achieving high-performance polymer electrolyte membrane fuel cells. Establishing a clear understanding of the property (catalyst ink)–structure (catalyst layer)–performance (MEA) relationship lays the foundation for this rational design. Here, a synergistic approach was taken to correlate the ink formulation, the microstructure of catalyst layers, and the resulting MEA performance to establish such a property–structure–performance relationship. The solvent composition (n-PA/H 2 O mixtures) demonstrated a strong influence on the performance of the MEA fabricated with an 830-EW (Aquivion) ionomer, especially polarization losses of cell activation and mass transport. The performance differences were studied in terms of how the solvent composition affects the catalyst/ionomer interface, ionomer network, and pore structure of the resulting catalyst layers. The ionomer aggregates mainly covered the surface of catalyst aggregates acting as oxygen reduction reaction active sites, and the aggregate sizes of the ionomer and catalyst (revealed by ultrasmall angle X-ray scattering and cryo-transmission electron microscopy) were dictated by tuning the solvent composition, which in turn determined the catalyst/ionomer interface (available active sites). In n-PA/H 2 O mixtures with 50~90 wt % H 2 O, the catalyst agglomerates could be effectively broken up into small aggregates, leading to enhanced kinetic activities. The boiling point of the mixed solvents determined the pore structure of ultimate catalyst layers, as evidenced by mercury porosimetry and scanning electron microscopy. For mixed solvents with a higher boiling point, the catalyst–ionomer aggregates in the ink tend to agglomerate during the solvent evaporation process and finally form larger catalyst–ionomer aggregates in the ultimate catalyst layer, resulting in more secondary pores and thus lower mass transport resistance. Both the enlarged catalyst/ionomer interface and appropriate pore structure were achieved with the catalyst layer fabricated from an n-PA/H 2 O mixture with 90 wt % H 2 O, leading to the best MEA performance.

25 ENERGY STORAGE↗
DOE OSTI2025

Reversible self-assembly of small molecules for recyclable solid-state battery electrolytes

Performance often overshadows recyclability in contemporary battery designs, leading to sustainability challenges. Preemptive strategies integrating recyclable chemistry from the outset are thus increasingly critical for addressing the complexities in conventional recycling. Here we harness bio-inspired molecular self-assembly to create inherently recyclable battery materials. We use aramid amphiphiles that self-assemble in water through strong, collective hydrogen bonding and π–π stacking, forming air-stable, high-aspect-ratio nanoribbons with gigapascal-level stiffness. When processed into bulk solid-state electrolytes, these nanoribbons retain their ordered molecular arrangement and exhibit total conductivities of 1.6 × 10 −4 S cm −1 at 50 °C, Young’s moduli of 70 MPa and toughness values of 1 MJ m −3 , despite being stabilized solely by reversible non-covalent bonds. We further demonstrate clean separation of battery components by exposing used cells to an organic solvent, which disrupts the non-covalent cohesion and reverts all battery components to their original forms. Furthermore, this study underscores the potential of molecular self-assembly for specialized recyclable designs in energy storage applications.

Batteries↗
DOE OSTI2024

Electrochemical formation of bis(fluorosulfonyl)imide-derived solid-electrolyte interphase at Li-metal potential

Lithium bis(fluorosulfonyl)imide-based liquid electrolytes are promising for realizing high Coulombic efficiency and long cycle life for next-generation Li-metal batteries. However, the role of anions in the formation of solid-electrolyte interphase remains unclear. Herein, we combine electrochemical analyses and X-ray photoelectron spectroscopy measurements both with and without sample washing, together with computational simulations, to propose the reaction pathways of electrolyte decomposition and correlate the interphase component solubility with the efficacy of passivation. Additionally, we discovered that not all the products derived from interphase-forming reactions were incorporated into the resulting passivation layer, with a notable portion present in the liquid electrolyte. Further, we found that the high-performance electrolytes can afford a sufficiently passivating interphase with minimized electrolyte decomposition, by incorporating more anion-decomposition products. Overall, this work presents a systematic approach of coupling electrochemical and surface analyses to paint a comprehensive picture of solid-electrolyte interphase formation, while identifying key attributes of high-performance electrolytes for guiding future designs.

Yu, Weilai [Stanford University, CA (United States↗
DOE OSTI2022

Design, Processing, and Integration of Pouch-Format Cell for High-Energy Lithium-Sulfur Batteries

This project objective was to develop and demonstrate a lithium-sulfur (Li-S) battery in a pouch-format cell capable of achieving an energy density ≥ 500 Wh/kg while achieving a 1,000 cycle life. The research focused on cell optimization and fabrication addressing different technical barriers and challenges including: 1) thin lithium anode optimization; 2) current collector and tab attachment design; 3) cathode porosity control; 4) electrolyte to sulfur ratio control; 5) cell design; and 6) cell fabrication. The project developed and demonstrated various technologies to address these technical barriers and challenges. The project demonstrated a thin lithium anode by vapor deposition, a collector design and validation of laser welding of tab attachment method, a cathode porosity control strategy by binder optimization, a calendaring process control and surface/interface treatment, and an electrolyte to sulfur ratio control with influence on cell energy density. The sulfur cathode was optimized by tuning the formulation, optimizing the calendaring process, and introducing a novel electrode fabrication process. To address the electrolyte performance issue, the electrolyte optimization was achieved with additive and formulation tuning and the introduction of a dual-phase electrolyte system. In addition to the demonstration of the optimized electrode with a novel fast-curing coating process and dual-phase electrolyte, a coating separator was further developed to address the polysulfide shuttling issue. The resulting new cell design with these optimized cell components was demonstrated in the 1 Ah pouch cell with medium sulfur loading and moderate porosity (~ 4.5 mAh cm-2, 65% porosity) and showed an energy density of > 400 Wh/kg (with E/S ratio of 2.8). The Li-SPAN cell configuration was also evaluated in combination with a new dual-phase electrolyte system. Initial coin cell performance demonstrated cycle stability of >300 cycles with an estimated energy density of 300 Wh/kg at the pouch format level. The corresponding 1 Ah pouch format SPAN cells with the new polymer electrolyte were developed which has shown a stable capacity at 800-900 mAh for ~40 cycles so far.

25 ENERGY STORAGE↗
DOE OSTI2023

Recent advancements in high performance polymer electrolyte fuel cell electrode fabrication – Novel materials and manufacturing processes

The global effort to introduce polymer electrolyte fuel cells for clean and renewable energy to the market is increasing the demand for high performance, robust and affordable membrane electrode assemblies (MEAs). There is not yet a standard method for large scale production of MEAs, or the methods employed are generally unsatisfactory in terms of quality and performance. A large number of published data of newly developed catalyst and electrolyte materials, claim to improve the state of the art, but are often not fully comparable due to different experimental studies and experimental designs. This article summarizes the trends in material developments and emerging MEA-manufacturing techniques. The materials and techniques are systematically compared in terms of cell performance and scalability. Current and future scientific challenges are identified and analysed based on published findings over the past five years. Finally, the results of the cited papers have been quantitatively compared to each other and to the internal benchmarks used in each cited work to provide a complete picture of the state of the art in PEFC MEA manufacturing.

25 ENERGY STORAGE↗
DOE OSTI2022

Facile Dual-Protection Layer and Advanced Electrolyte Enhancing Performances of Cobalt-free/Nickel-rich Cathodes in Lithium-Ion Batteries

Despite cobalt (Co)-free/nickel (Ni)-rich layered oxides being considered as one of the promising cathode materials due to their high specific capacity, their highly reactive surface is one of the shortcomings that still hinder their practical usages in high-energy-density batteries. Herein, a polyimide/polyvinylpyrrolidone (PI/PVP, denoted as PP) coating layer is demonstrated as dual-protection for LiNi 0.96 Mg 0.02 Ti 0.02 O 2 (NMT) cathode material to suppress surface contamination against moisty air and to prevent unwanted side reactions between cathode and electrolyte during electrochemical cycling. The optimal PP-coated NMT (PP@NMT) preserves a clean surface without generation of lithium (Li) residues, structural degradation, and gas evolution after exposure to air with ~30% humidity for 2 weeks. Contrarily, the exposed bare NMT shows severe contamination, structural shrinkage due to Li loss, and increased gas release during charging. In addition, the exposed PP@NMT significantly enhances the electrochemical performance of graphite (Gr)||NMT cells by decreasing byproducts and maintaining structural stability. Moreover, the exposed PP@NMT achieves a high capacity retention of 86.7% after 500 cycles in Gr||NMT cells using an advanced localized high-concentration electrolyte. Furthermore, this work demonstrates a promising facile approach to the protection of Co-free/Ni-rich layered cathodes for their practical applications even after exposure to moisty air.

25 ENERGY STORAGE↗
NASA NTRS1982

Basic investigation into the electrical performance of solid electrolyte membranes

The electrical performance of solid electrolyte membranes was investigated analytically and the results were compared with experimental data. It is concluded that in devices that are used for pumping oxygen the major power losses have to be attributed to the thin film electrodes. Relations were developed by which the effectiveness of tubular solid electrolyte membranes can be determined and the optimum length evaluated. The observed failure of solid electrolyte tube membranes in very localized areas is explained by the highly non-uniform current distribution in the membranes. The analysis points to a possible contact resistance between the electrodes and the solid electrolyte material. This possible contact resistance remains to be investigated experimentally. It is concluded that film electrodes are not appropriate for devices which operate with current flow, i.e., pumps though they can be employed without reservation in devices that measure oxygen pressures if a limited increase in the response time can be tolerated.

Richter, R.↗
DOE OSTI2021

Ion‐Conducting, Electron‐Blocking Layer for High‐Performance Solid Electrolytes

Lithium metal batteries bring greater promise for energy density, often relying on solid‐state electrolytes to meet critical benchmarks. However, Li dendrite formation is a prevailing problem that limits the cycle life and Coulombic efficiency of solid‐state Li metal batteries. For the first time, a thin (<100 nm) layer of electronically insulating, ionically conducting lithium phosphorus oxynitride (LiPON) is applied using atomic layer deposition between a Li anode and garnet Li 7 La 3 Zr 2 O 12 (LLZO). The performance of a conformal LiPON layer as an electron barrier in symmetric Li‐LLZO cells is observed through potential step chronoamperometry, galvanostatic cycling, electron microscopy, and various spectroscopic techniques. The LiPON‐coated LLZO achieves 100 times lower electronic conductance than LLZO alone. Cycling carried out at 0.1 mA cm −2 for 100 cycles demonstrates that suppression of electron pathways into the bulk solid electrolyte improves the cycle life of a lithium metal cell. These findings suggest an electronic conductivity effect in solid‐state electrolytes. A strategy is demonstrated to design thin‐film (LiPON)‐modulated bulk solid‐state electrolytes (LLZO) capable of maintaining high ionic conductivity and electrochemical stability while reducing the effective electronic conductivity, which results in significantly decreased dendrite formation, improved cycle life, and greater interfacial integrity between the electrolyte and a Li anode.

Hitz, Emily M.↗