Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “cathode loading”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Improving Cost and Efficiency of the Scalable Solid Oxide Fuel Cells Power System

The objective of this project was to design and develop a 20kW range small-scale solid oxide fuel cells (SOFC) power system for applications such as data centers and commercial buildings. The original plan included a 5,000 hours demonstration and a Techno-Economic Analysis (TEA) which were dropped as part of project termination. The original project plan was to use a stack with a cross-flow cell design which had previously been tested for 500 hours at a community college in Malta, NY. However, it was decided to move to the advanced R-SOFC co-flow cell developed under Department of Energy Award DE-FE0031971. The advanced cell design has the advantage of a larger active area for the same manufacturing footprint which results in fewer required cells for the same stack power, hence a higher volumetric power density (kW/L) and lower cost per kW than the original cross-flow cell design. A full SOFC system Simulink model was developed and calibrated with testing data from a fuel cell stack and BOP (balance of plant) components. The simulation results from the calibrated model showed an acceptable match with the experimental data. A structural analysis conducted for various load scenarios indicated no high stress areas for all spatial directions. Major electrical system components were acquired, built and successfully tested. System sensors were verified and validated against controls. Safety checks, a diagnostic check, PID tuning, and control software commissioning tasks were also conducted. The power electronics prototype was delivered and trial testing completed. Balance of Plant component testing and simulation work was conducted to characterize Reformer-Heat Exchanger heat transfer and backpressure and reformer catalyst methane conversion and product selectivity. Simulations were conducted to design the Anode and Cathode fluid passages and size the air-air and fuel-fuel heat exchangers. A Burner operation map was created from test data and the Anode Gas Recirculation blower was tested to evaluate its durability. The SOFC system used a horizontal style design where components sit directly on a casting with a direct connection to the skid. This design has efficient packaging and a small footprint with approximate dimensions of 750 mm x 700 mm x 1700 mm. An SOFC system was built and successfully tested at the Malta, NY facility The system for over 500 hours under load of which over 300 hours was at full load of 20 kW.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2023

3D–Integrated, Multi–Functional Carbon Fibers for Stable, High–Areal–Capacity Batteries

Increasing lithium-ion batteries' (LIBs) electrode areal capacity can boost energy density and lower manufacturing costs, but faces challenges in manufacturing, rate performance, and cycling stability. A conductive framework made of commercial micro-sized carbon fibers (Cfs) is presented that serves as a host for both the LiNi 0.5 Mn 0.3 Co 0.2 O 2 (NMC 532) cathode and Cfs anode. The Cf framework has multiple functions that offer high electronic conductivity (270 mS cm –1 ), low tortuosity (1.7), low Li + diffusion resistance (22 Ω), and high thermal conductivity (200 W mK –1 ). Additionally, the Cf-integrated electrodes can have an extremely high mass loading of NMC 532 (70 mg cm –2 ) with a theoretical capacity of 14 mAh cm –2 . Thus, the practical full cells assembled with the Cfs-enabled electrodes exhibit an initial areal capacity of 4.1 mAh cm –2 and capacity retention of 90.4% at 500 cycles at a cycling rate of C/3, 1.5 mA cm –2 . Data collected from the operando isothermal microcalorimetry suggest that full cells utilizing the Cf anode experience less heat release from side reactions compared to cells utilizing a conventional graphite anode. Finally, this present approach is scalable and cost-effective and can fabricate practical LIBs that boast high areal capacity, rate performance, and a lengthy cycling lifetime.

25 ENERGY STORAGE↗
DOE OSTI2021

Cost-effective, Thin-film SOFCs for Reliable Power Generation (Final Report)

The project was aimed at developing and demonstrating an advanced solid-oxide fuel cell (SOFC) technology to cost-effectively and reliably generate electricity directly from hydrocarbon fuels (e.g., natural gas and coal-derived syngas) for distributed and central generation applications. The studied technology was built on a planar, porous metal-supported SOFC (MS-SOFC) with a unique thin-film structure having its anode intimately supported on a metal substrate. The porous metal support with graded porosity was fabricated from a low-cost scalable phase-inversion tape casting method. Anode, thin-film electrolyte, and cathode were sequentially deposited on the porous metal substrate using atmospheric plasma spray (APS). In this study, it was shown that the composition of the casting slurry could significantly influence the morphology of the metal support fabricated using the phase-inversion tape-casting method. Increasing the solid loading in the slurry favored the formation and growth of finger-like pores to a point, but the presence of excessive solid loading increased the viscosity of the casting slurry, restraining the growth of finger-like pores. With the increase in the amount of the binder polyethersulfone (PESf) in the slurry, well grown finger-like pores and a thin sponge-like layer were formed. Since the parameters of the APS process have a significant effect on the microstructure of coatings, which in turn affects or determines the SOFC cell performance, a series of metal-supported solid oxide fuel cells with a four-layer cell configuration of 430L/Ni-ScSZ/ScSZ/LSCF have been fabricated by a combination of phase inversion tape casting and APS techniques. Electrochemical testing of the cells fabricated from different deposition APS conditions revealed significant differences in cell performance.

30 DIRECT ENERGY CONVERSION↗
NASA NTRS1984

Electrodynamic Tethers. 1: Power Generator in LEO. 2: Thrust for Propulsion and Power Storage

An electrodynamic tether consists of a long insulated wire in space whose orbital motion cuts across lines of magnetic flux to produce an induce voltage that in typical low orbits averages about 200 v/km. Such a system should be capable of generating substantial electrical power, at the expense of IXB drag acting on its orbital energy. If a reverse current is driven against the induced voltage, the system should act as a motor producing IXB thrust. A reference system was designed, capable of generating 20 KW of power into an electrical load located anywhere along the wire at the expense of 2.6N (20,000 J/sec) drag on the wire. In an ideal system, the conversion between mechanical and electrical energy would reach 100% efficiency. In the actual system part of the 20 KW is lost to internal resistance of the wire, plasma and ionosphere, while the drag force is increased by residual air drag. The 20 KW PMG system as designed is estimated to provide 18.7 KW net power to the load at total drag loss of 20.4 KJ/sec, or an overall efficiency of 92%. Similar systems using heavier wire appear capable of producing power levels in excess of 1 Megawatt at voltages of 2-4 KV, with conversion efficiency between mechanical and electrical power better than 95%. The hollow cathode based system should be readily reversible from generator to motor operation by driving a reverse current using onboard power.

Mccoy, J. E.↗
DOE OSTI2018

The Improved Thermal Conductivity of a Potting Material for High-Power Fast Warm-Up Cathodes

With higher power, frequency and longer life of microwave tubes, cathode heater assembly is being modified to enhance the warm-up performance and reliability, which are governed by ceramics thermal conductivity, electrical resistivity and shrinkage. In present work, a potting material with a high thermal conductivity of 22.14 W/(m K) and low linear shrinkage of 5.5% was prepared using two kinds of alumina powders with different size and morphology. Aqueous slurries were produced for centrifugal casting. The highest solid loading slurries with 70 vol.% were obtained. Green body with relative density above 70% was easily made from slurries using centrifugal casting. Relative sintered density reached 86.75% maximum without any sintering aids. Rheological behavior of slurries, potting microstructure, sintering shrinkage and thermal conductivity were analyzed. Continuous particle distribution, series and parallel models were used to guide the powders proportion and explain the thermal conductivity. The potting material thermal conductivity experimental data agreed with the series and parallel models when the weight parameter ξ was between 0.3 and 0.5.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Advanced Pt-Based Core–Shell Electrocatalysts for Fuel Cell Cathodes

Proton-exchange membrane fuel cells (PEMFCs) are highly efficient energy storage and conversion devices. Thus, the platinum group metal (PGM)-based catalysts which are the dominant choice for the PEMFCs have received extensive interest during the past couple of decades. However, the drawbacks in the existing PGM-based catalysts (i.e., high cost, slow kinetics, poor stability, etc.) still limit their applications in fuel cells. The Pt-based core–shell catalysts potentially alleviate these issues through the low Pt loading with the associated low cost and the high corrosion resistance and further improve the oxygen reduction reaction’s (ORR’s) activity and stability. This Account focuses on the synthetic strategies, catalytic mechanisms, factors influencing enhanced ORR performance, and applications in PEMFCs for the Pt-based core–shell catalysts. We first highlight the synthetic strategies for Pt-based core–shell catalysts including the galvanic displacement of an underpotentially deposited non-noble metal monolayer, thermal annealing, and dealloying methods, which can be scaled-up to meet the requirements of fuel cell operations. Subsequently, catalytic mechanisms such as the self-healing mechanism in the Pt monolayer on Pd core catalysts, the pinning effect of nitrogen (N) dopants in N-doped PtNi core–shell catalysts, and the ligand effect of the ordered intermetallic structure in L10-Pt/CoPt core–shell catalysts and their synergistic effects in N-doped L10-PtNi catalysts are described in detail. Additionally, the core–shell structure in the Pt-based catalysts have two main effects for enhanced ORR performance: (i) the interaction between Pt shells and core substrates can tune the electronic state of the surface Pt, thus boosting the ORR activity and stability, and (ii) the outer Pt shell with modest thickness can enhance the oxidation and dissolution resistance of the core, resulting in improved durability. We then review the recent attempts to optimize the ORR performance of the Pt-based core–shell catalysts by considering the shape, composition, surface orientation, and shell thickness. The factors influencing the ORR performance can be grouped into two categories: the effect of the core and the effect of the shell. In the former, PtM core–shell catalysts which use different non-PGM element cores (M) are summarized, and in the latter, Pt-based core–shell catalysts with different shell structures and compositions are described. The modifications of the core and/or shell structure can not only optimize the intermediate-binding energetics on the Pt surface through tuning the strain of the surface Pt, which increases the intrinsic activity and stability, but also offer a significantly decreased catalyst cost. Finally, we discuss the membrane electrode assembly performance of Pt-based core–shell catalysts in fuel cell cathodes and evaluate their potential in real PEMFCs for light-duty and heavy-duty vehicle applications. Even though some challenges to the activity and lifetime in the fuel cells remain, the Pt-based core–shell catalysts are expected to be promising for many practical PEMFC applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1972

Development of a multikilowatt ion thruster power processor

A feasibility study was made of the application of silicon-controlled, rectifier series, resonant inverter, power conditioning technology to electric propulsion power processing operating from a 200 to 400 Vdc solar array bus. A power system block diagram was generated to meet the electrical requirements of a 20 CM hollow cathode, mercury bombardment, ion engine. The SCR series resonant inverter was developed as a primary means of power switching and conversion, and the analog signal-to-discrete-time-interval converter control system was applied to achieve good regulation. A complete breadboard was designed, fabricated, and tested with a resistive load bank, and critical power processor areas relating to efficiency, weight, and part count were identified.

Schoenfeld, A. D.↗
DOE OSTI2023

Conducting Polymers Meet Lithium–Sulfur Batteries: Progress, Challenges, and Perspectives

Lithium–sulfur (Li–S) batteries have attracted increased interest because of the high theoretical energy density, low cost, and environmental friendliness. Conducting polymers (CPs), as one of the most promising materials used in Li–S batteries, can not only facilitate electron transfer and buffer the large volumetric change of sulfur benefiting from their porous structure and excellent flexibility, but also enable stronger physical/chemical adsorption capacity toward polysulfides (LiPSs) when doped with abundant heteroatoms to promote the sulfur redox kinetics and achieve the high sulfur loading. This review firstly introduces the properties of various CPs including structural CPs (polypyrrole (PPy), polyaniline (PANi), polyethylene dioxothiophene [PEDOT]) and compound CPs (polyethylene oxide (PEO), polyvinyl alcohol (PVA) and poly(acrylic acid) [PAA]), and their application potential in Li–S batteries. Furthermore, the research progress of various CPs in different components (cathode, separator, and interlayer) of Li–S batteries is systematically summarized. Finally, the application perspective of the CPs in Li–S batteries as a potential guidance is comprehensively discussed.

Chen, Xin↗
NASA NTRS1990

Billion shot flashlamp for spaceborne lasers

A billion-shot flashlamp developed under a NASA contract for spaceborne laser missions is presented. Lifetime-limiting mechanisms are identified and addressed. Two energy loadings of 15 and 44 Joules were selected for the initial accelerated life testing. A fluorescence-efficiency test station was used for measuring the useful-light output degradation of the lamps. The design characteristics meeting NASA specifications are outlined. Attention is focused on the physical properties of tungsten-matrix cathodes, the chemistry of dispenser cathodes, and anode degradation. It is reported that out of the total 83 lamps tested in the program, 4 lamps reached a billion shots and one lamp is beyond 1.7 billion shots, while at 44 Joules, 4 lamps went beyond 100 million shots and one lamp reached 500 million shots.

Richter, Linda↗
DOE OSTI2020

Application of electrospinning for the fabrication of proton-exchange membrane fuel cell electrodes

We report electrospun materials have been gaining great interest in the energy sector. Their tunability and robustness make them highly attractive, particularly for proton-exchange membrane fuel cell (PEMFC) electrodes. Conventional PEMFC electrodes, prepared by either spraying, painting, or slot-die coating, have not yet met the needs of large-scale PEMFC use. Electrospinning of fibrous materials has already shown great promise as an alternative methodology for electrode fabrication. Electrospinning has been used in fuel cell electrodes through two primary means: (1) segmented carbon or inorganic fibers to serve as precious metal catalyst support, and (2) high aspect ratio polymer/particle fibers to serve directly as the electrode. The use of electrospun fibrous electrodes has led to improved PEMFC durability and increased power output at low catalyst loadings, both of which are of paramount importance to large-scale commercialization of PEMFC electric vehicles.

36 MATERIALS SCIENCE↗
NASA NTRS2021

Low and High Temperature Non-Thermonuclear Fusion Approaches to Energy Production

We are responding to the RFI points A1, A2 and A3. We appreciate the need for a high density, high power, environmentally-benign and carbon-neutral power system. Although fusion has been considered for over 70 years, the nearly intractable means of maintaining a hydrogen plasma at temperatures exceeding the center of the Sun increasingly delays not only commercialization but even the scientific breakeven point. As a recent JASON report notes, the world-wide energy grid is moving towards decentralization which is counter to the large tokamak fusion de-vices necessary given their underdense plasmas. NASA has spent several years understanding and developing Lattice Confinement Fusion as an alternative to thermonuclear fusion by exploring many means of loading and triggering fusion reactions in deuterated metal lattices. Triggering has run the gamut from bremsstrahlung-initiated photo-neutrons to the role of electron screening in assisting these reactions. Electron screening may be responsible for both nuclear effects in deuterium pumped metals as well as fast neutrons observed from electrolytically driven cathodes. Electron screened fusion rate enhancement has been observed by others, including the Lawrence Berkeley National Laboratory. NASA’s need for deep space power drove this research with a goal of a ten-year lifetime for a multi-kWe power system. Previous NASA studies have explored the use of fusion systems for nuclear thermal propulsion for manned spaceflight to the outer planets. Despite these designated uses, small-scale terrestrial power applications as well as medical isotope production are possible once scaling is achieved. ARPA-E can contribute to the Nation’s Green Energy mandates by funding research in this field that builds on condensed matter nuclear science findings by the US Navy and NASA.

L. P. Forsley↗
DOE OSTI2021

Sulfurized Polyacrylonitrile (SPAN): Changes in Mechanical Properties during Electrochemical Lithiation

Sulfurized polyacrylonitrile (SPAN) is a promising material for stable lithium-sulfur (Li-S) batteries that can potentially satisfy the demand for high-density energy storage devices for electric vehicles (EVs). However, important physical and chemical properties of the SPAN cathode material are not yet well understood. For example, the SPAN mechanical behavior that depends on the structure and chemistry of the material generated during synthesis, and the mechanical response evolution during battery discharge have been scarcely investigated. This work addresses the effects of electrochemical lithiation on the SPAN mechanical integrity via uniaxial tensile loading tests using molecular dynamics with the ReaxFF potential. Here, we evaluate the volume expansion, Young’s modulus, yield strength, and ultimate tensile strength with increasing lithium contents. Our results show how the degree of graphitization of the carbonized skeleton impacts the SPAN ability to withstand the volume expansion-induced structural stresses upon lithiation. We describe the fracture mechanisms and find out a ductility loss with increasing lithium contents

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

From Fundamental Interfacial Reaction Kinetics to Macroscopic Current–Voltage Characteristics: Case Study of Solid Acid Fuel Cell Limitations and Possibilities

The unique properties of solid acid electrolytes, in particular CsH 2 PO 4 , are in many ways ideal for fuel cell operation. However, the technology is constrained by high cathode overpotentials. Here a simplified cathode geometry is employed to obtain the fundamental electrochemical parameters (exchange current density and charge transfer coefficient) describing the oxygen reduction reaction (ORR) at the CsH 2 PO 4 -Pt-gas interface. The parameters are incorporated into a 1D model of the voltage–current characteristics of realistic SAFC cathodes, which reproduced the measured polarization behavior of such cathodes without recourse to fitting adjustable parameters. Following this validation, the model is utilized to evaluate the impact of changes to cathode properties, microstructure, and operating conditions. Of these, the charge transfer coefficient, measured to have a value of ≈0.6 for ORR on Pt in the SAFC cathode environment, is found to have the greatest impact on power output. Nevertheless, even without material modifications, a combination of microstructural and operational modifications are identified with projected performance metrics meeting Department of Energy targets (0.8 V at 300 mA cm –2 , and peak power density of 1 W cm –2 ), albeit at high Pt loadings. However, the analysis indicates that truly meaningful advances will likely necessitate the discovery of alternative ORR catalysts.

36 MATERIALS SCIENCE↗
DOE OSTI2022

High Energy Aqueous Lithium-Ion Batteries (Final Report)

Lithium-ion batteries (LIBs) are a widely used energy storage device. For decades, researchers have been studying aqueous electrolytes due to their non-flammability and environmental friendless. However, the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) of water greatly limit the voltage window of the aqueous electrolyte. The recent concept of ‘solvent-in-salt’ electrolytes, namely ‘water-in-salt’ electrolytes (WISE) for aqueous batteries and ‘super-concentrated’ electrolytes for non-aqueous batteries, greatly expands the electrochemical window of these battery systems and consequently their energy density. This expansion occurs because the large number of salt aggregates in ‘solvent-in-salt’ electrolytes enables preferential salt decomposition over solvent decomposition to form robust interphase layers on electrodes, thus enhancing their stability in a wide range of operating voltages. However, even when the salt concentration reached 63m, regardless of cost, the cathodic potential of the WISE expanded only to 1.75V with an overall electrochemical stability window of <3.25V. To design the next generation of high energy aqueous LIBs, electrolytes that possess a wider electrochemical stability window and lower cost but still maintain the merit of non-flammability are much needed. In this project, we designed the aqueous LIBs with widened voltage window. We reported a cheap and non-flammable ternary eutectic electrolyte that can form a robust solid electrolyte interface (SEI)so that the cathodic limiting potential can be decreased to <1.5 V for Li 4 Ti 5 O 12 anodes, while maintaining both a high ionic conductivity of >10 -3 S cm –1 and a low viscosity. We demonstrated the super-stable2.5V LiMn 2 O 4 ||Li 4 Ti 5 O 12 pouch cell with mass loading of 2.5 mAh/cm. Further, LiCl-LiBr-Graphite/Li full cells were designed with high energy density. Finally, we use a bi-layer design to enlarge the voltage window of aqueous electrolyte, which can endow the stable cycling of aqueous Lithium metal batteries.

25 ENERGY STORAGE↗
NASA NTRS1993

A High Performance H2-Cl2 Fuel Cell for Space Power Applications

NASA has numerous airborne/spaceborne applications for which high power and energy density power sources are needed. The proton exchange membrane fuel cell (PEMFC) is an attractive candidate for such a power source. PEMFC's offer many advantages for airborne/spaceborne applications. They have high power and energy densities, convert fuel to electrical power with high efficiency at both part and full load, and can rapidly startup and shutdown. In addition, PEMFC's are lightweight and operate silently. A significant impediment to the attainment of very high power and energy densities by PEMFC's is their current exclusive reliance on oxygen as the oxidant. Conventional PEMFC's oxidize hydrogen at the anode and reduce oxygen at the cathode. The electrode kinetics of oxygen reduction are known to be highly irreversible, incurring large overpotential losses. In addition, the modest open circuit potential of 1.2V for the H2-O2 fuel cell is unattainable due to mixed potential effects at the oxygen electrode. Because of the high overpotential losses, cells using H2 and O2 are capable of achieving high current densities only at very low cell voltages, greatly curtailing their power output. Based on experimental work on chlorine reduction in a gas diffusion electrode, we believe significant increases in both the energy and power densities of PEMFC systems can be achieved by employing chlorine as an alternative oxidant.

Anderson, Everett B.↗
DOE OSTI2022

Co-Free Cathode Materials and Their Novel Architectures

To enable cobalt-free LiNi 0.5 Mn 1.5 O 4 (LNMO) electrode and novel electrolyte formulation for use in next-generation Li-ion batteries (LIB) capable of high energy density, long cycle life and low cost, several methods were developed throughout this project. To enhance the performance of LNMO, Fe-doping on LNMO, laser treatment and atomic layer deposition (ALD) were adopted. Moreover, dry electrode method has successfully helped to fabricate ultra-high loading LNMO with stable performance. The improvement at anode side includes ALD-coating as well as pre-lithiation of graphite anode. In the novel electrolyte development, it was found that all-fluorinated electrolyte with appropriate additives can effectively extend both cycle and calendar life of LNMO full cells at practical loadings. Additional diagnosis of LNMO full cells showed that different types of carbon and porosity of separator play a critical role in the success of LNMO’s high voltage operation. The combined effort throughout the project pushed forward the understanding and commercialization of LNMO at practical level.

25 ENERGY STORAGE↗
DOE OSTI2022

Sodium-ion Battery

Room temperature rechargeable sodium-ion batteries (NIBs) are one of the most promising candidates for large-scale energy storage and load leveling of renewable energy sources due to the abundance, low cost of Na resources, and their relatively high energy density. NIBs are primarily based on intercalation chemistry and are similar to Lithium-ion batteries (LIB). The rich knowledge gained in LIBs for the past 4 decades have accelerated the discovery and development of high energy density NIBs cathode and anode materials. The use of sustainable Na, Al current collector, and Mn and Fe based cathode materials is expected to stabilize the cost and demand for Li, Co, Ni and Cu.

Omenya, Fredrick O.↗
DOE OSTI2020

Hierarchical porous silicon structures with extraordinary mechanical strength as high-performance lithium-ion battery anodes

Abstract Porous structured silicon has been regarded as a promising candidate to overcome pulverization of silicon-based anodes. However, poor mechanical strength of these porous particles has limited their volumetric energy density towards practical applications. Here we design and synthesize hierarchical carbon-nanotube@silicon@carbon microspheres with both high porosity and extraordinary mechanical strength (>200 MPa) and a low apparent particle expansion of ~40% upon full lithiation. The composite electrodes of carbon-nanotube@silicon@carbon-graphite with a practical loading (3 mAh cm −2 ) deliver ~750 mAh g −1 specific capacity, <20% initial swelling at 100% state-of-charge, and ~92% capacity retention over 500 cycles. Calendered electrodes achieve ~980 mAh cm −3 volumetric capacity density and <50% end-of-life swell after 120 cycles. Full cells with LiNi 1/3 Mn 1/3 Co 1/3 O 2 cathodes demonstrate >92% capacity retention over 500 cycles. This work is a leap in silicon anode development and provides insights into the design of electrode materials for other batteries.

25 ENERGY STORAGE↗