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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Insights into the Enhanced Reversibility of Graphite Anode Upon Fast Charging Through Li Reservoir

Increasing the charging rate and reducing the charging time for Li-ion batteries are crucial to realize the mainstream of electric vehicles. However, it is formidable to avoid the Li plating on graphite anode upon fast charging. Despite the tremendous progress in Li detection techniques, the fundamental mechanism of Li plating and its chemical/electrochemical responses upon cycling still remains elusive. Herein, we present a comprehensive electrochemical method to investigate the fast charging behavior of graphite electrode. A detailed analysis is directed toward understanding the changes in phase, composition, and morphology of the fast-charged graphite. By applying a resting process, we scrutinize the further reactions of the plated Li, which readily transforms into irreversible (dead) Li. We further develop a modified graphite electrode with a thin Ag coating as the Li reservoir. The plated Li can be "absorbed" by the Ag layer to form the Li-Ag solid solution that suppresses the formation of dead Li and provides structural stability, thus promoting the further lithiation of graphite and enhancing the reversibility. Here this work not only provides additional insights into the fast charging behavior of graphite electrode but also demonstrates a potential strategy to improve the fast charging performance of graphite anode.

25 ENERGY STORAGE↗
DOE OSTI2022

Co-intercalation-free ether electrolytes for graphitic anodes in lithium-ion batteries

Carbonate-based electrolytes are widely used in Li-ion batteries but are limited by a small operating temperature window and poor cycling with silicon-containing graphitic anodes. The lack of non-carbonate electrolyte alternatives such as ether-based electrolytes is due to undesired solvent co-intercalation that occurs with graphitic anodes. Here, we show that fluoroethers are the first class of ether solvents to intrinsically support reversible lithium-ion intercalation into graphite without solvent co-intercalation at conventional salt concentrations. In full cells using a graphite anode, they enable 10-fold higher energy densities compared to conventional ethers, and better thermal stability over carbonate electrolytes (operation up to 60 °C) by producing a robust solvent-derived solid electrolyte interphase (SEI). As single-solvent–single-salt electrolytes, they remarkably outperform carbonate electrolytes with fluoroethylene carbonate (FEC) and vinylene carbonate (VC) additives when cycled with graphite–silicon composite anodes. In conclusion, our molecular design strategy opens a new class of electrolytes that can enable next generation Li-ion batteries with higher energy density and a wider working temperature window.

25 ENERGY STORAGE↗
DOE OSTI2023

Electrospun Si and Si/C Fiber Anodes for Li-Ion Batteries

Due to structural changes in silicon during lithiation/delithiation, most Li-ion battery anodes containing silicon show rapid gravimetric capacity fade upon charge/discharge cycling. Herein, we report on a new Si powder anode in the form of electrospun fibers with only poly(acrylic acid) (PAA) binder and no electrically conductive carbon. The performance of this anode was contrasted to a fiber mat composed of Si powder, PAA binder, and a small amount of carbon powder. Fiber mat electrodes were evaluated in half-cells with a Li metal counter/reference electrode. Without the addition of conductive carbon, a stable capacity of about 1500 mAh/g (normalized to the total weight of the anode) was obtained at 1C for 50 charge/discharge cycles when the areal loading of silicon was 0.30 mgSi/cm2, whereas a capacity of 800 mAh/g was obtained when the Si loading was increased to ~1.0 mgSi/cm2. On a Si weight basis, these capacities correspond to >3500 mAh/gSi. The capacities were significantly higher than those found with a slurry-cast powdered Si anode with PAA binder. There was no change in fiber anode performance (gravimetric capacity and constant capacity with cycling) when a small amount of electrically conductive carbon was added to the electrospun fiber anodes when the Si loading was ≤1.0 mgSi/cm2.

Mondal, Abhishek N.↗
DOE OSTI2025

Mechanically Robust Bismuth-Embedded Carbon Microspheres for Ultrafast Charging and Ultrastable Sodium-Ion Batteries

Advancements in the development of fast-charging and long-lasting microstructured alloying anodes with high volumetric capacities are essential for enhancing the operational efficiency of sodium-ion batteries (SIBs). These anodes, however, face challenges such as declined cyclability and rate capability, primarily due to mechanical degradation reduced by significant volumetric changes (over 252%) and slow kinetics of sodium-ion storage. Herein, we introduce a novel anode design featuring densely packed bismuth (Bi) embedded within highly conductive carbon microspheres to overcome the aforementioned challenges. Remarkably, the high loading Bi anode within carbon microspheres with a high tap density of 2.59 g cm -3 possesses significant mechanical strength exceeding 590 MPa and limits volume swelling of only 10.9% post-sodiation. This anode demonstrates a high volumetric capacity (908.3 mAh cm -3 ), ultrafast chargeability (200 A g -1 , full charge/discharge in just 5.5 s), and outstanding cyclability over 12,000 cycles and maintains exceptional cycling stability even at -30 °C. The full cell paired with a Na 3 V 2 (PO 4 ) 3 cathode retains over 80% capacity after 600 cycles at 36 C, demonstrating a remarkable rate capability of 126 C (full charge/discharge in 28.6 s). Our comprehensive experimental evaluations and chemo-mechanical simulations shed light on the mechanisms underpinning the anode's superior performance. In conclusion, this development marks a significant advancement in the design of durable and fast-charging anodes for high-performance SIBs.

25 ENERGY STORAGE↗
DOE OSTI2022

Alloy based electrochemical catalyst for conversion of carbon dioxide to hydrocarbons

An electrocatalyst comprising (i) carbon nanospikes and (ii) copper alloy nanoparticles containing copper and at least one noble metal and residing on and/or between the carbon nanospikes. Also disclosed herein is a method of producing the electrocatalyst. Also described herein is a method for converting carbon dioxide into hydrocarbons by use of the above-described electrocatalyst. The method for producing hydrocarbons more specifically involves contacting the electrocatalyst with an aqueous solution of a bicarbonate salt while the aqueous solution is in contact with a source of carbon dioxide, and electrically powering the electrocatalyst as a cathode at negative potential condition while the cathode is in electrical communication with a counter electrode electrically powered as an anode, to convert the carbon dioxide into hydrocarbons containing at least four carbon atoms and composed of only carbon and hydrogen.

Rondinone, Adam J.↗
DOE OSTI2021

System and method for removing water and hydrogen from anode exhaust

A fuel cell system includes an anode configured to output an anode exhaust stream comprising hydrogen, carbon dioxide, and water; and a membrane dryer configured to receive the anode exhaust stream, remove water from the anode exhaust stream, and output a membrane dryer outlet stream. The membrane dryer includes a first chamber configured to receive the anode exhaust stream; a second chamber configured to receive a purge gas; and a semi-permeable membrane separating the first chamber and the second chamber. The semi-permeable membrane is configured to allow water to diffuse therethrough, thereby removing water from the anode exhaust stream. The membrane dryer may further be configured to remove hydrogen from the anode exhaust stream.

Jolly, Stephen↗
DOE OSTI2022

Stable all-solid-state sodium-sulfur batteries for low-temperature operation enabled by sodium alloy anode and confined sulfur cathode

All-solid-state sodium-sulfur (Na-S) batteries are promising for stationary energy storage devices because of their low operating temperatures (less than 100 °C), improved safety, and low-cost fabrication. Using Na alloy instead of Na metal as an anode in Na-S batteries can prevent dendrite growth and improve interfacial stability between the anode and solid electrolytes to achieve long-cycling stability. A high-sulfur content cathode possessing high sulfur utilization is also important to enable an energy-dense Na-S battery. In this work, we studied Na-Sb and Na- Sn alloy anodes and demonstrated the superiority of Na 3 Sb alloy undergoing a stable Na alloying/dealloying process at 0.04 mA cm -2 for over 500 hours. Combining the optimized Na3Sb alloy anode with sulfur-carbon composites prepared by the vapor deposition approach, the full cell shows a high sulfur specific capacity and improved rate performance. Moreover, the all-solid-state Na alloy-S battery can deliver a high initial discharge specific capacity of 1377 mAh g -1 and maintain good capacity retention of 70 % after 180 cycles at 60 °C. Further, post-cycle characterizations show that both the anode and cathode perform a reversible discharge/charge process after the 1st cycle, and the cathode undergoes significantly rearranged distributions of carbon and solid-state electrolytes after 180 cycles due to severe volume change induced by repeated sodiation/desodiation process.

25 ENERGY STORAGE↗
DOE OSTI2024

Strain-Induced Shifts in Defective Graphite Phonon Modes Predicted by Density Functional Theory

Carbon fiber composites have gained attention as a structural material because of their high strength-to-weight ratio, and understanding the effect of defects on reactivity and mechanical properties is important for the longevity and safety of the composite. Although it is known that strain causes the underlying graphitic vibrational modes to redshift, it is not clear how strain may alter reactivity and defect-induced vibrational changes. To investigate the strain-induced phonon changes of defective carbon fiber composites, density functional theory calculations of graphite are used, including intercalated hydrogen and fluorine defects. By comparing changes in the bond lengths, formation energies, and phonon density of states for uniaxially and biaxially strained graphite, strain was found to generally make defect formation more favorable and the specific behavior changes are dependent on the strain direction and defect identity. Specifically, intercalated fluorine phonons are more sensitive to strain than hydrogen intercalation phonons, and strain applied along the zigzag direction alters the calculated properties more than strain along the armchair direction. Finally, these results highlight the importance of understanding the microstructural effect of deviations from the ideal material because small changes in strain or defect type can significantly alter the behavior of the carbon fiber composite core.

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

Consequences of 131 I Transmutation in Gas Phase Radioiodine Molecules and Adsorbed on Graphite Surface

In the case of nuclear power plant accidents, several radionuclides are being dispersed into the environment. In particular, the release of radioiodine 131 I represents a major health concern because of its absorption by the thyroid gland. To reduce the release of 131 I into the environment, capture materials, such as activated carbon, provide a mean to efficiently retain radioiodine-bound molecular species. Here, we use ab initio molecular dynamic calculations to investigate the effects of 131 I radioactive decay on the molecular stability of I 2 , acid iodine (HI, HIO, HIO 2 , and HIO 3 ), and methyl-iodine species in both gas phase and adsorbed on graphite. In gas phase, we found that I 2 is the least resistant to 131 I transmutation, followed by the HIO x family of molecules, then HI and CH 3 I which are the most resistant. However, the graphite surface is found to greatly favorize the fragmentation of adsorbed molecular species. While the identification of gas phase fragments can offer new chemical route to consider in chemical kinetics models, the formation reactive fragment products at the graphite surface can favorize their reaction with surface carbon atoms which overtime could reduce the number of adsorption sites of capture materials available, and hence, impacting their capture capability.

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

3D Carbon Coating Enabled High‐capacity and Stable Micro‐sized Silicon Suboxide‐graphite Blended Anodes for Practical Lithium‐ion Batteries

Abstract Silicon oxide (SiO x ) is a promising anode candidate of lithium‐ion batteries (LIBs) owing to its extremely high specific capacity. However, the low initial Coulombic efficiency (ICE) and rapid capacity degradation of SiO x , triggered by the enormous volume variation upon repeated (de)lithiation, gravely hinder its practical use. Herein, two mass‐produced micro‐sized SiO x @C composites with obviously different morphologies for commercial LIBs are reported. Particularly, the SiO x ‐graphite blended anode (SiO x @3D‐G‐Gr) based on SiO x wrapped by three‐dimensional (3D) carbon layers (SiO x @3D‐G) exhibits a capacity of 519 mAh g −1 , an ICE of 90.0 % and a capacity retention of 83.4 % at 0.2 C over 100 cycles. which is far exceeding its counterpart SiO x @C‐H‐Gr (65.7 %). The obtained impressive properties of SiO x @3D‐G originate from the critical contribution of 3D carbon layers, which serves as the effective stress buffer and protective layer as well as the strong networks for electron/Li + transport. Accordingly, the full‐cell based on SiO x @3D‐G‐Gr anode and commercial LiCoO 2 cathode delivers a capacity of 803 mAh and an excellent capacity retention of 95.6 % (616 mAh, 96.6 % for graphite, respectively) at 1 C over 100 cycles with a stabilized CE of nearly 100 %. The micro‐sized SiO x @3D‐G showing a promising prospect in the commercial‐grade anodes in LIBs.

Electrochemistry↗
DOE OSTI2024

Nanoporous Carbon Coatings Direct Li Electrodeposition Morphology and Performance in Li Metal Anode Batteries

Li metal anodes could significantly improve battery energy density. However, Li generally electrodeposits in poorly controlled morphology, leading to safety and performance problems. One factor that controls Li anode performance and electrodeposition morphology is the nature of the electrolyte–current collector interface. Herein, we modify the Cu current collector interface by depositing precisely controlled nanoporous carbon (NPC) coatings using pulsed laser deposition to develop an understanding of how NPC coating density and thickness impact Li electrodeposition. We find that NPC density and thickness guide Li morphological evolution differently and dictate whether Li deposits at the NPC-Cu or NPC-electrolyte interface. NPC coatings generally lower overpotential for Li electrodeposition, though thicker NPC coatings limit kinetics when cycling at a high rate. Lower-density NPC enables the highest Coulombic efficiency (CE) during calendar aging tests, and higher-density NPC enables the highest CE during cycling tests.

25 ENERGY STORAGE↗
DOE OSTI2020

Nonflammable Lithium Metal Full Cells with Ultra-high Energy Density Based on Coordinated Carbonate Electrolytes

Coupling thin Li metal anodes with high-capacity/high-voltage cathodes such as LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) is a promising way to increase lithium battery energy density. Yet, the realization of high-performance full cells remains a formidable challenge. Here, we demonstrate a new class of highly coordinated, nonflammable carbonate electrolytes based on lithium bis(fluorosulfonyl)imide (LiFSI) in propylene carbonate/fluoroethylene carbonate mixtures. Utilizing an optimal salt concentration (4 M LiFSI) of the electrolyte results in a unique coordination structure of Li + -FSI - -solvent cluster, which is critical for enabling the formation of stable interfaces on both the thin Li metal anode and high-voltage NCM811 cathode. Under highly demanding cell configuration and operating conditions (Li metal anode = 35 μm, areal capacity/charge voltage of NCM811 cathode = 4.8 mAh cm -2 /4.6 V, and anode excess capacity [relative to the cathode] = 0.83), the Li metal-based full cell provides exceptional electrochemical performance (energy densities = 679 Wh kg cell -1 /1,024 Wh L cell -1 ) coupled with nonflammability.

25 ENERGY STORAGE↗
DOE OSTI2023

Carbon Corrosion in CO2 Electrolysis Systems

Driven by concerns over climate change, interest in CO2 conversion technologies has dramatically increased in recent years. By viewing CO2 as a readily available feedstock, many pathways for the production of carbon-neutral fuels and chemicals become available. In converting CO2, low carbon emitting energy sources must be used to ensure a low carbon footprint of the fuel and chemical products. The low-temperature electrochemical conversion of CO2 is a promising technology and allows for direct integration with renewable electricity sources. The development of low-temperature CO2 electrolysis technologies is informed by both PEM fuel cells and water electrolyzers, both of which are at a higher stage of development. However, CO2 electrolysis operates at a much higher cell voltage (-3V) than other low-temperature electrochemical processes, which can have implications for materials compatibility in the electrolyzer device. Carbon corrosion is of particular concern for the anode of CO2 electrolyzers, as a large driving force for corrosion exists due to the high required cell potentials. In this presentation, recent observations will be shared on carbon corrosion of the anode gas diffusion electrode (GDE) in low-temperature alkaline exchange membrane CO2 electrolysis. Results from ex-situ tests designed to isolate the carbon corrosion process for anode GDEs will be shared. These results will provide guidance on materials selection for CO2 utilization MEAs, which need to have a lifetime of several years to ensure industrial viability.

BIOMASS FUELS↗
DOE OSTI2022

High-Accuracy Semiempirical Quantum Models Based on a Minimal Training Set

A great need exists for computationally efficient quantum simulation approaches that can achieve an accuracy similar to high-level theories at a fraction of the computational cost. In this regard, we have leveraged a machine-learned interaction potential based on Chebyshev polynomials to improve density functional tight binding (DFTB) models for organic materials. The benefit of our approach is two-fold: (1) many-body interactions can be corrected for in a systematic and rapidly tunable process, and (2) high-level quantum accuracy for a broad range of compounds can be achieved with ~0.3% of data required for one advanced deep learning potential. Our model exhibits both transferability and extensibility through comparison to quantum chemical results for organic clusters, solid carbon phases, and molecular crystal phase stability rankings. Overall, our efforts thus allow for high-throughput physical and chemical predictions with up to coupled-cluster accuracy for systems that are computationally intractable with standard approaches.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Enhanced Electrochemical Performance of Disordered Rocksalt Cathodes Enabled by a Graphite Conductive Additive

Cobalt-free cation-disordered rocksalt (DRX) cathodes are a promising class of materials for next-generation Li-ion batteries. Although they have high theoretical specific capacities (>300 mA h/g) and moderate operating voltages (~3.5 V vs Li/Li + ), DRX cathodes typically require a high carbon content (up to 30 wt %) to fully utilize the active material which has a detrimental impact on cell-level energy density. To assess pathways to reduce the electrode’s carbon content, the present study investigates how the carbon’s microstructure and loading (10–20 wt %) influence the performance of DRX cathodes with the nominal composition Li 1.2 Mn 0.5 Ti 0.3 O 1.9 F 0.1 . While electrodes prepared with conventional disordered carbon additives (C65 and ketjenblack) exhibit rapid capacity fade due to an unstable cathode/electrolyte interface, DRX cathodes containing 10 wt % graphite show superior cycling performance (e.g., reversible capacities ~260 mA h/g with 85% capacity retention after 50 cycles) and rate capability (~135 mA h/g at 1000 mA/g). Furthermore, a suite of characterization tools was employed to evaluate the performance differences among these composite electrodes. Overall, these results indicate that the superior performance of the graphite-based cathodes is largely attributed to the: (i) formation of a uniform graphitic coating on DRX particles which protects the surface from parasitic reactions at high states of charge and (ii) homogeneous dispersion of the active material and carbon throughout the composite cathode which provides a robust electronically conductive network that can withstand repeated charge–discharge cycles. Overall, this study provides key scientific insights on how the carbon microstructure and electrode processing influence the performance of DRX cathodes. Based on these results, exploration of alternative routes to apply graphitic coatings is recommended to further optimize the material performance.

25 ENERGY STORAGE↗