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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 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Incorporating Solvate and Solid Electrolytes for All‐Solid‐State Li 2 S Batteries with High Capacity and Long Cycle Life

Abstract The development of all‐solid‐state lithium–sulfur batteries is hindered by the poor interfacial properties at solid electrolyte (SE)/electrode interfaces. The interface is modified by employing the highly concentrated solvate electrolyte, (MeCN) 2 −LiTFSI:TTE, as an interlayer material at the electrolyte/electrode interfaces. The incorporation of an interlayer significantly improves the cycling performance of solid‐state Li 2 S batteries compared to the bare counterpart, exhibiting a specific capacity of 760 mAh g −1 at cycle 100 (330 mAh g −1 for the bare cell). Electrochemical impedance spectroscopy shows that the interfacial resistance of the interlayer‐modified cell gradually decreases as a function of cycle number, while the impedance of the bare cell remains almost constant. Cross‐section scanning electron microscopy (SEM)/ energy dispersive X‐ray spectroscopy (EDS) measurements on the interlayer‐modified cell confirm the permeation of solvate into the cathode and the SE with electrochemical cycling, which is related to the decrease in cell impedance. In order to mimic the full permeation of the solvate across the entire cell, the solvate is directly mixed with the SE to form a “solvSEM” electrolyte. The hybrid Li 2 S cell using a solvSEM electrolyte exhibits superior cycling performance compared to the solid‐state cells, in terms of Li 2 S loading, Li 2 S utilization, and cycling stability. The improved performance is due to the favorable ionic contact at the battery interfaces.

Shin, Minjeong↗
DOE OSTI2019

Filamentation and Self-Focusing of Electron Beams in Vacuum and Gas Diodes

In this paper, we experimentally studied pulsed electron beams with a high local density. The conditions in which the energy density cumulation is observed during the interaction of electrons with the anode are shown to develop in vacuum and gas diodes at nanosecond and subnanosecond durations of a beam current pulse and a decrease in the interelectrode gap. The average electron energy in filamentation and self-focusing of an electron beam in a vacuum diode of an accelerator at a current of ~2 kA and a no-load voltage of ~400 kV was established to be 50–100 keV while the energy density was 10{sup 9}–10{sup 10} J/cm{sup 3}. It is confirmed that the beam current density in a gas diode can exceed 1 kA/cm{sup 2}. It is hypothesized that superdense electron beams in vacuum and gas diodes are formed as a result of avalanche multiplication of runaway electrons in the cathode–anode gap plasma.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Interdigitated power connector

An electrical connector carries large amounts of electrical current between two circuit boards with low resistance and low self-inductance by means of an interdigitated anode and cathode, thereby providing low dynamic voltage loss. The connector also may include, near where power will be consumed, an interposer board with on-board capacitance to provide even lower dynamic voltage loss. The connector has application to delivering low-voltage, high-current power from a power supply on a first board to electronics on a second board: the low resistance provides low voltage drop for a load current that is constant, while the low inductance and the capacitors provide low voltage fluctuation for a load current that changes. These issues are of great importance, for example, in designing high-performance computers.

Coteus, Paul W.↗
DOE OSTI2011

Optimization of mesoporous carbon structures for lithium–sulfur battery applications

Mesoporous carbon (MC) with tunable pore sizes (22nm, 12nm, 7nm, and 3nm) and pore volumes (from 1.3 to 4.8 cc/g) containing sulfur inside the pores were systematically studied as mesoporous carbon-sulfur (MCS) composite electrodes for Li-S batteries. Investigation on these MCS composites reveals that the pore structure has no influence on the battery performance at full sulfur loading conditions (the pore volume is fully filled by sulfur) but the maximum sulfur loading capability is higher for MC with larger pore volume. MC with large pore volumes, partial sulfur filling (part of the pore volume left unfilled), and surface modification, can have reasonably high sulfur loading, improved electrical and ionic contacts of sulfur with MC and with electrolytes, which subsequently promotes the battery performance. An initial capacity of ~1250 mAh/g (based on sulfur) and 650 mAh/g capacity retention over 100 cycles were obtained with 50 wt% sulfur loading in the MC with 22nm pore size (4.8 cc/g). When the surface of MCS was coated with Clevios P to reduce the dissolve of polysulfide anions in electrolytes, it exhibits a high initial discharge capacity of ~1390 mAh/g and improved cycling stability with capacity retention of ~840 mAh/g over 100 cycles. The reported correlation among the structure, sulfur filling, surface modification and the electrochemical performance of the MCS composite cathodes provides guidance in designing new electrodes for lithium-sulfur batteries

25 ENERGY STORAGE↗
DOE OSTI2018

A rejuvenation process to enhance the durability of low Pt loaded polymer electrolyte membrane fuel cells

Here, an effective method to enhance the durability of polymer electrolyte membrane fuel cells (PEMFCs) is reported. PEMFC performance loss is mitigated by exposing the electrodes of fuel cells to dry nitrogen gas periodically at high temperature. This method extends the lifetime of fuel cells significantly compared to their non-treated counterparts. The impact of treatment temperature and exposure time on PEMFC durability is reported, using potential cycling accelerated stress tests. The enhanced durability is attributed to the suppression of “ionomer relaxation” that occurs under the nearly water saturated operating conditions of a PEMFC cathode.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2016

Resolving Electrode Morphology’s Impact on Platinum Group Metal-Free Cathode Performance Using Nano-CT of 3D Hierarchical Pore and Ionomer Distribution

This paper reports on the characterization of polymer electrolyte fuel cell (PEFC) cathodes featuring a platinum group metal-free (PGM-free) catalyst using nano-scale resolution X-ray computed tomography (nano-CT) and morphological analysis. PGM-free PEFC cathodes have gained significant interest in the past decade since they have the potential to dramatically reduce PEFC costs by eliminating the large platinum (Pt) raw material cost. However, several challenges remain before they are commercially viable. Since these catalysts have lower volumetric activity, the PGM-free cathodes are thicker and are subject to increased gas and proton transport resistances that reduce the performance. To better understand the efficacy of the catalyst and improve electrode performance, a detailed understanding the correlation between electrode fabrication, morphology, and performance is crucial. In this work, the pore/solid structure and the ionomer distribution was resolved in three dimensions (3D) using nano-CT for three PGM-free electrodes of varying Nafion® loading. The associated transport properties were evaluated from pore/particlescale simulations within the nano-CT imaged structure. These characterizations are then used to elucidate the microstructural origins of the dramatic changes in fuel cell performance with varying Nafion® ionomer loading. We show that this is primarily a result of distinct changes in ionomer’s spatial distribution. The significant impact of electrode morphology on performance highlights the importance of PGM-free electrode development in concert with efforts to improve catalyst activity and durability.

42 ENGINEERING↗
DOE OSTI2022

High-Platinum-Content Catalysts on Atomically Dispersed and Nitrogen Coordinated Single Manganese Site Carbons for Heavy-Duty Fuel Cells

Fuel cells for heavy-duty vehicles (HDVs) have attracted considerable attention because of their unique scalability, better fuel economy, the less demand for hydrogen refilling infrastructure. However, the potential application requires more stringent fuel cell durability up to 25,000 h. Membrane electrode assemblies (MEAs) made from platinum group metal (PGM) catalyst with relatively high loading 0.3 mgPt cm –2 play a crucial role in ensuring high-power and long-term durability. Integrating fine PGM nanoparticles and robust carbon support with strengthened interactions is critical for improving MEA performance and durability. Herein, a unique atomically dispersed and nitrogen coordinated single Mn site-rich carbon (M–N–C) support was developed for high content (40 wt%) platinum catalysts for the oxygen reduction reaction (ORR) cathode with reduced thickness. Compared with two controls studied in this work (e.g., a porous graphitic carbon-supported Pt and a commercial TKK Pt/C catalysts), the Pt (40 wt%)/Mn–N–C catalyst exhibited much enhanced catalytic activity and stability for the ORR in both aqueous acidic electrolyte and polymer electrolyte-based MEA. Here, we carefully elucidated the—role of the Mn–N–C support in promoting Pt catalyst concerning its high surface area, partially graphitic structure, and nitrogen dopants, providing better Pt nanoparticle dispersion, and strengthened interactions between Pt and carbon. Consequently, the MEA from the Pt (40 wt%)/Mn–N–C catalyst generated a 1.61 A cm –2 at 0.7 V based on HDV conditions (0.2 mgPt cm –2 and 250 kPa air). More importantly, the MEA is highly durable and can retain 1.31 A cm –2 at 0.7 V after 30,000 voltage cycles (~19% loss), surpassing the commercial Pt/C catalyst (loss of ~56%). Therefore, the Mn–N–C carbon-supported Pt catalyst holds a great promise to meet the challenging DOE target (1.07 A cm –2 at 0.7 V after 150,000 cycles) for HDVs.

25 ENERGY STORAGE↗
DOE OSTI2023

Designing Low Tortuosity Electrodes through Pattern Optimization for Fast-Charging

The development of fast-charging technologies is crucial for expediting the progress and promotion of electric vehicles. In addition to innovative material exploration, reduction in the tortuosity of electrodes is a favored strategy to enhance the fast-charging capability of lithium-ion batteries by optimizing the ion-transfer kinetics. To realize the industrialization of low-tortuosity electrodes, a facile, cost-effective, highly controlled, and high-output continuous additive manufacturing roll-to-roll screen printing technology is proposed to render customized vertical channels within electrodes. Extremely precise vertical channels are fabricated by applying the as-developed inks, using LiNi 0.6 Mn 0.2 Co 0.2 O 2 as the cathode material. Additionally, the relationship between the electrochemical properties and architecture of the channels, including the pattern, channel diameter, and edge distance between channels, is revealed. The optimized screen-printed electrode exhibited a seven-fold higher charge capacity (72 mAh g -1 ) at a current rate of 6 C and superior stability compared with that of the conventional bar-coated electrode (10 mAh g -1 , 6 C) at a mass loading of 10 mg cm -2 . Finally, this roll-to-roll additive manufacturing can potentially be applied to various active materials printing to reduce electrode tortuosity and enable fast charging in battery manufacturing.

42 ENGINEERING↗
DOE OSTI2018

Laser Sintering of Printed Anodes for Al-Air Batteries

We report on a 3D printed Al anode for Al-air battery combined with laser sintering method. We verified that laser sintering contributed to effective removal of the organic solvent in the slurry and increased the conductivity of the printed anode. By application of infrared laser sintering, we significantly improved electrical contacts of Al nanoparticles and electrochemical performance of Al-air cells. A Pt/C coated hydrophobic carbon paper was used for air cathode to provide a good electrical contact, an oxygen flow ability, and the water sealing. Gel-style KOH was introduced as the electrolyte and waterways also utilized in the chemical reaction. The laser sintered Al-air battery could provide 239 mAh/g discharge capacity and a 0.95 V operation voltage. Also, a 3D structured anode was fabricated by 3D printing the active material on current collectors to achieve a high mass-loading with active material thickness of 360 μm, 560 μm and 680 μm for 1, 2 and 3 layers 3D printed electrodes. The battery cells provide areal discharge capacities of 1.5 mAh/cm 2 , 2.8mAh/cm 2 , and 3.23 mAh/cm 2 , respectively for 1, 2 and 3 layers-electrodes.

25 ENERGY STORAGE↗
DOE OSTI2024

PILBCP-IL Composite Ionomers for High Current Density Performance

Wide-spread commercialization of fuel cell electric vehicles using proton exchange membrane fuel cell (PEMFC) power sources requires that several existing limitations be addressed. These include: (1) a reduction in platinum (Pt) loading in the catalytic electrodes, (2) improvements in reactant and electronic mobility throughout the catalytic electrodes, (3) reduction in the reliance on materials derived from polluting “forever chemicals”, and (4) a significant improvement in the operational longevity of catalytic electrode components. In this project, a team of two universities, Drexel University and Texas A&M University, one national lab, National Renewable Energy Laboratory, and one company, General Motors, collaborated to develop a new cathode ionomer chemistry that would address these limitations and result in an improvement in performance over existing ionomer materials. The key technology developed through this collaborative project was a composite cathode ionomer encompassing an ionic liquid interlayer between Pt catalysts and a sulfonated polymerized ionic liquid block co-polymer (S-PILBCP) that possess the orthogonal properties of protonic conductivity and ionic liquid enhanced kinetics and durability (see schematic in Figure 1). The composite S-PILBCP ionomer eliminates many of the existing issues with perfluorosulfonic acid-based ionomers including active site blocking by sulfonate specific adsorption, restricted O 2 transport through ionomer films, limited humidity tolerance and active area loss for carbon pore confined catalyst particles, and use of polluting “forever chemicals”. Following successful integration of the developed composite ionic liquid into a PEMFC cathode catalyst layer, we demonstrate enhanced performance over Nafion containing cathodes with Pt/C and PtCo/C at both low and high current density. The performance with our composite S-PILBCP ionomer meets the Department of Energy (DOE) targets for light duty vehicle applications

08 HYDROGEN↗
DOE OSTI2017

Metallic Nanocomposites as Next-Generation Thermal Interface Materials

Thermal interface materials (TIMs) are an integral and important part of thermal management in electronic devices. The electronic devices are becoming more compact and powerful. This increase in power processed or passing through the devices leads to higher heat fluxes and makes it a challenge to maintain temperatures at the optimal level during operation. Herein, we report a free standing nanocomposite TIM in which boron nitride nanosheets (BNNS) are uniformly dispersed in copper matrices via an organic linker, thiosemicarbazide. Integration of these metal-organic-inorganic nanocomposites was made possible by a novel electrodeposition technique where the functionalized BNNS (f-BNNS) experience the Brownian motion and reach the cathode through diffusion, while the nucleation and growth of the copper on the cathode occurs via the electrochemical reduction. Once the f-BNNS bearing carbonothioyl/thiol groups on the terminal edges come into the contact with copper crystals, the chemisorption reaction takes place. We performed thermal, mechanical, and structural characterization of these nanocomposites using scanning electron microcopy (SEM), diffusive laser flash (DLF) analysis, phase-sensitive transient thermoreflectence (PSTTR), and nanoindentation. The nanocomposites exhibited a thermal conductivity ranging from 211 W/mK to 277 W/mK at a filler mass loading of 0-12 wt.percent. The nanocomposites also have about 4 times lower hardness as compared to copper, with values ranging from 0.27 GPa to 0.41 GPa. The structural characterization studies showed that most of the BNNS are localized at grain boundaries - which enable efficient thermal transport while making the material soft. PSTTR measurements revealed that the synergistic combinations of these properties yielded contact resistances on the order of 0.10 to 0.13 mm2K/W, and the total thermal resistance of 0.38 to 0.56 mm2K/W at bondline thicknesses of 30-50 um. The coefficient of thermal expansion (CTE) of the nanocomposite is 11 ppm/K, which lies between the CTEs of aluminum (22 ppm/K) and silicon (3 ppm/K), which are common heat sink and heat source materials, respectively. The nanocomposite can also be deposited directly on to heat sink which will simplify the packaging processes by removing one possible element to assemble. These unique properties and ease of assembly makes the nanocomposite a promising next-generation TIM.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Metallic Nanocomposites as Next-Generation Thermal Interface Materials: Preprint

Thermal interface materials (TIMs) are an integral and important part of thermal management in electronic devices. The electronic devices are becoming more compact and powerful. This increase in power processed or passing through the devices leads to higher heat fluxes and makes it a challenge to maintain temperatures at the optimal level during operation. Herein, we report a free standing nanocomposite TIM in which boron nitride nanosheets (BNNS) are uniformly dispersed in copper matrices via an organic linker, thiosemicarbazide. Integration of these metal-organic-inorganic nanocomposites was made possible by a novel electrodeposition technique where the functionalized BNNS (f-BNNS) experience the Brownian motion and reach the cathode through diffusion, while the nucleation and growth of the copper on the cathode occurs via the electrochemical reduction. Once the f-BNNS bearing carbonothioyl/thiol groups on the terminal edges come into the contact with copper crystals, the chemisorption reaction takes place. We performed thermal, mechanical, and structural characterization of these nanocomposites using scanning electron microcopy (SEM), diffusive laser flash (DLF) analysis, phase-sensitive transient thermoreflectence (PSTTR), and nanoindentation. The nanocomposites exhibited a thermal conductivity ranging from 211 W/mK to 277 W/mK at a filler mass loading of 0-12 wt.percent. The nanocomposites also have about 4 times lower hardness as compared to copper, with values ranging from 0.27 GPa to 0.41 GPa. The structural characterization studies showed that most of the BNNS are localized at grain boundaries - which enable efficient thermal transport while making the material soft. PSTTR measurements revealed that the synergistic combinations of these properties yielded contact resistances on the order of 0.10 to 0.13 mm2K/W, and the total thermal resistance of 0.38 to 0.56 mm2K/W at bondline thicknesses of 30-50 um. The coefficient of thermal expansion (CTE) of the nanocomposite is 11 ppm/K, which lies between the CTEs of aluminum (22 ppm/K) and silicon (3 ppm/K), which are common heat sink and heat source materials, respectively. The nanocomposite can also be deposited directly on to heat sink which will simplify the packaging processes by removing one possible element to assemble. These unique properties and ease of assembly makes the nanocomposite a promising next-generation TIM.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Effect of Catalyst and Catalyst Layer Composition on Catalyst Support Durability

Polymer electrolyte membrane fuel cells (PEMFCs) are efficient, zero-emission engines for the automotive sector. However, cost and durability are major barriers for the commercialization of PEMFCs. Degradation of the carbon support in the cathode catalyst layer due to high potential excursions caused by unmitigated events like H 2 starvation, or start-up/shutdown are still a major durability issue in PEMFCs. Catalyst support durability was studied by accelerated stress tests (ASTs) that included repeated potential cycling from 1.0 to 1.5 V. The effect of catalyst layer composition on carbon corrosion was studied using membrane electrode assemblies with different catalysts (Pt, PtCo), catalyst composition (catalyst wt.%, supports), ionomer composition (loading, and equivalent weights). The corrosion of the carbon support is similar between Pt and PtCo catalysts. However, the performance degradation rate is higher for the alloy catalysts due to differences in catalyst particle size and the transition metal’s leaching accelerating the performance degradation. The carbon loss is lower for catalysts with lower initial carbon loading (or higher catalyst wt.%), which is better for durability. However, the cumulative loss of carbon is identical for electrodes with the same catalyst support irrespective of catalyst and ionomer composition in the catalyst layer.

25 ENERGY STORAGE↗
DOE OSTI2021

Characterization of the Redesigned Extended MITL for HERMES III

Modeling and simulation of the legacy HERMES III Magnetically Insulated Transmission Line (MITL) has been performed using EMPHASIS, an unstructured time-domain electromagnetic (UTDEM) particle-in-cell (PIC) simulation software. This design when used lost roughly half of its current before the pulse reached the load. The cause of the current loss in the MITL was found to be the vacuum impedance changes along the MITL. The MITL was then redesigned to maintain constant impedance and simulated in EMPHASIS once again. Following predicting simulation results, the new MITL was then built, installed, and tested, showing minimal current loss and good agreement with simulation and theoretical results, all of which are reported here. Additionally, an analysis of experimental voltage calculation techniques using cathode and anode currents is performed and compared to simulation results.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2019

Enhancing Chemical Interaction of Polysulfide and Carbon through Synergetic Nitrogen and Phosphorus Doping

The shuttling effect of the polysulfide (PS) is the most detrimental factor that causes capacity fading of Li–S batteries. By substituting carbon atoms with heteroatoms, the host materials can provide a chemical interaction with PS to trap it within the electrochemically active range of the cathode. In this study, first-principles-based calculations identify the most stable nitrogen (N) and phosphorus (P) codoped atomic structures and their corresponding adsorption energy toward different PS species. Based on the simulated predictions, we introduce a glucosamine-derived carbon nanotube aerogel (CNA) with a secondary dopant of P during the synergetic polymerization and carbonization process. The N–P codoped CNA and S composite (NPCNA-S) renders a highly stable performance even at a sulfur loading of 3.5 mg cm –2 . In conclusion, the specific capacity is >900 mAh g –1 and the stabilized capacity retention is >70% over 450 cycles at 0.2 C rate (1 C = 1675 mA g –1 ).

25 ENERGY STORAGE↗
DOE OSTI2013

How to Obtain Reproducible Results for Lithium Sulfur Batteries

The basic requirements for getting reliable Li-S battery data have been discussed in this work. Unlike Li-ion batteries, electrolyte-rich environment significantly affects the cycling stability of Li-S batteries prepared and tested under the same conditions. The reason has been assigned to the different concentrations of polysulfide-containing electrolytes in the cells, which have profound influences on both sulfur cathode and lithium anode. At optimized S/E ratio of 50 g L-1, a good balance among electrolyte viscosity, wetting ability, diffusion rate dissolved polysulfide and nucleation/growth of short-chain Li2S/Li2S2 has been built along with largely reduced contamination on the lithium anode side. Accordingly, good cyclability, high reversible capacity and Coulombic efficiency are achieved in Li-S cell with controlled S/E ratio without any additive. Other factors such as sulfur content in the composite and sulfur loading on the electrode also need careful concern in Li-S system in order to generate reproducible results and gauge the various methods used to improve Li-S battery technology.

Cycling stability↗
DOE OSTI2019

Systems and methods of preparing lithium sulfur electrode using sacrificial template

Embodiments described herein relate generally to lithium sulfur batteries and methods of producing the same. As described herein, preventing coarsening of sulfur during the well-known melt-diffusion processing of cathodes allows a high areal capacity of 10.7 mAh/cm2 at current density of 3.4 mA/cm2 (C-rate of 1/5 h−1). The addition of a lithium salt, such as LiTFSI, prior to melt-diffusion can prevent coarsening of molten sulfur and allows creation of a sulfur electrode with a high concentration of triple-phase junctions for electrochemical reaction. In some embodiments, approximately 60-70% utilization of the theoretical capacity of sulfur is reached at a high loading (e.g., greater than 7.5 mg S/cm2). The electrodes are prepared in lean-electrolyte environment of 3 mlelectrolyte/gsulfur (˜70 vol % of electrolyte in the electrode) for high areal capacity in Li—S batteries.

Chen, Xinwei↗