Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Cathode”

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 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Lifetime experimental study of graphite cathode for relativistic backward wave oscillator

Graphite cathodes are widely used due to their good emission properties, especially their long lifetime. Some previous papers have researched their lifetime under certain conditions and uncovered some important phenomena. This paper is dedicated to research the lifetime of the graphite cathode under higher power. In the lifetime test, the voltage and current amplitudes are about 970 kV and 9.7 kA, respectively. The repetition rate is 20 Hz. An X-band relativistic backward wave oscillator is used to generate high power microwave by utilizing the electron beam energy. The experimental results demonstrate that the emission property of the graphite cathode remains quite stable during 10{sup 5} pulses, despite some slight deteriorations regarding the beam and microwave parameters. The macroscopic morphology change of the cathode blade due to material evaporation is observed by a laser microscope. The mass loss of the graphite cathode is about 60 μg/C. Meanwhile, the observation by a scanning electron microscope uncovers that the original numerous flaky micro-structures are totally replaced by a relatively smooth surface at the mid region of the cathode blade and a large number of new micro-protrusions at the blade edges during the lifetime test.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Space-charge-limited currents for cathodes with electric field enhanced geometry

This paper presents the approximate analytic solutions of current density for annulus and circle cathodes. The current densities of annulus and circle cathodes are derived approximately from first principles, which are in agreement with simulation results. The large scaling laws can predict current densities of high current vacuum diodes including annulus and circle cathodes in practical applications. In order to discuss the relationship between current density and electric field on cathode surface, the existing analytical solutions of currents for concentric cylinder and sphere diodes are fitted from existing solutions relating with electric field enhancement factors. It is found that the space-charge-limited current density for the cathode with electric-field enhanced geometry can be written in a general form of J = g(β{sub E}){sup 2}J{sub 0}, where J{sub 0} is the classical (1D) Child-Langmuir current density, β{sub E} is the electric field enhancement factor, and g is the geometrical correction factor depending on the cathode geometry.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Enhancing nitrogen fixation efficiency in glow-like discharge by reducing cathode-fall voltage

In plasma nitrogen fixation devices, discharge electrodes are crucial yet susceptible to oxidation and corrosion due to plasma’s high temperatures and oxygen content, which could alter discharge modes. This research evaluates the impact of different electrode materials, including iron, chromium, nickel, copper, and 304 stainless steel, on nitrogen fixation efficiency in glow-like discharges driven by high-voltage DC power. Notably, iron and 304 stainless steel cathodes undergo a mode transition at increased currents, evident from plasma color shifts and significant voltage reductions. Fourier transform infrared spectroscopy analyses reveal that such mode changes minimally affect nitrogen oxide production rates, leading to a notable decrease in energy consumption for nitrogen fixation by up to 40%. OES and SEM-EDS measurements suggest that iron oxide, with its higher secondary electron emission, replaces metal as the cathode material, facilitating mode transitions and maintaining discharge current at lower voltages. Further, this voltage change is largely attributed to the cathode voltage drop, highlighting the minimal role of the cathode fall region in NO x synthesis. These findings underscore the potential for improving plasma nitrogen fixation energy efficiency by choosing suitable cathode materials to lower the cathode-fall voltage.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

In-situ visualization of the transition metal dissolution in layered cathodes

Transition metal dissolution in layered cathodes is one of the most intractable issues that deteriorates the battery performance and lifetime. It not only aggravates the structure degradation in cathode, but also damages the solid electrolyte interphase in anode and even induce the formation of lithium dendrites. In this work, we investigate the dissolution behaviors of polycrystalline and single-crystalline layered cathode via operando X-ray imaging techniques. The described cathode particle morphology appears to have a significant impact on the evolution of the dissolution dynamics. As a mitigation strategy, we reveal that doping with trace amount of Zr in the layered cathode could improve its robustness against the transition metal dissolution. Our finding provides valuable insights for designing the next-generation highly-stable layered battery cathodes.

25 ENERGY STORAGE↗
DOE OSTI2019

Physical Operating Principles of Palladium–Barium Cathodes of Microwave Devices

High-resolution X-ray diffraction method (XRD) is used to determine sizes and crystallographic orientation of the nanocrystallites of the Pd and Pd{sub 5}Ba phases in palladium–barium cathode. Electron spectroscopy for chemical analysis (ESCA) is used to study Ba and Pd chemical states in cathode material and determine the phase composition including dissolved microimpurities in the phases. The comparison of the XRD and ESCA data makes it possible to reveal effects related to the formation of the BaO crystallites in the cathode material, which are responsible for the emission properties. Electron-energy loss spectroscopy is used to determine the concentration of oxygen vacancies in the BaO crystallites that are formed in the cathode material due to activation. An original crystallite model of the working palladium–barium cathodes that is based on the results of this work may serve as an alternative to the known film model and makes it possible to optimize technology of cathode fabrication and activation.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Dual Protective Mechanism of AlPO 4 Coating on High-Nickel Cathode Material for High Energy Density and Long Cycle Life Lithium-Ion Batteries

Cathode material with high nickel content is a promising candidate for the future generation of Li-ion batteries (LIBs). However, severe structural degradation during cycling limits its practical use, especially for electric vehicles. Herein, AlPO 4 nanoparticles were synthesized and then coated onto the surface of a high-nickel layer-structured cathode via a dry coating method. The AlPO 4 nanoparticles coating significantly improved the cycling stability from 69.2% to over 80% capacity retention after 140 cycles. Furthermore, the structure and chemical composition of the AlPO 4 -coated cathode was investigated by XRD, SEM, XPS, and STEM. Compared with the non-coated cathode, we revealed a dual protective mechanism for enhanced cycling stability, where Al doping and Li 3 PO 4 coating play synergistic roles in protecting cathode material through long-term cycling. This work demonstrates a facile and environmentally friendly approach toward improving the performance of high-nickel LIB cathodes, which can be easily scaled up for industrial applications.

25 ENERGY STORAGE↗
DOE OSTI2018

In-Operando Evaluation of Solid Oxide Fuel Cell (SOFC) Cathodes for Enhanced Oxygen Reduction Reaction (ORR) Activity and Durability

Through this project we developed a new in-operando 18 O-isotope exchange technique, and determined the oxygen reduction reaction (ORR) kinetics and mechanisms in various solid oxide fuel cell (SOFC) cathodes under real operating conditions of applied voltage. We were able to measure and determine oxygen surface exchange coefficients of labeled oxygen with La 0.8 Sr 0.2 MnO 3 (LSM), La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 (LSCF) and other cathode material samples with varying compositions. We related the cell polarization conditions to the surface exchange process and surface exchange coefficient, and suggested a model to describe this relation. Our findings imply that LSCF keeps its higher exchange rate performance over LSM under real operating conditions. Changing the A-site cation ratio in LSM can enhance its performance, especially under cathodic polarizations larger than -400mV. Cathode powder composites of LSM and LSCF with YSZ and GDC show lower exchange coefficient values under applied polarization compared to the single constituent powder samples, probably due to limited contact between the powder particles. Using our model and basic electrochemical properties of the cathode materials we are able to successfully predict the exchange kinetic properties of SOFC cathode material under real operating conditions of applied voltage / current from surface exchange coefficients obtained in the absence of an applied bias.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Lithium halide cathodes for Li metal batteries

Lithium halides cathodes potentially offer a high energy density at a low cost for rechargeable batteries. However, these cathodes suffer from quick capacity decay in organic electrolytes and the failiure mechanism remains elusive. Here, we report that liquefying the halogen or interhalogen compounds is a prerequisite for achieving high reversibility for the lithium halides cathodes. The gas or solid halogen can be liquefied by using interhalogen compounds with different electronegativity or changing the temperature. As a proof of concept, reversible LiCl conversion-intercalation chemistry in organic electrolyte is demonstrated by using either redox coupling with less electronegative I/Br to form liquid ICl/BrCl or reducing the temperature to -30oC. Further, the LiCl-LiBr-graphite cathodes in 1.6M lithium difluoro(oxalato)borate/1.6M lithium triflate in diglyme electrolytes achieve a high reversible specific capacity of 250 mAh/g at 3.7 V with an energy density being comparable to or higher than transition metal oxide cathodes at a much lower cost.

25 ENERGY STORAGE↗
DOE OSTI2025

Operando Neutron Imaging of Lithium Flux and Gradient Cathode Design for Enhanced Kinetics in High‐Loading All‐Solid‐State Li─S Batteries

All-solid-state Li–sulfur batteries (ASSLSBs) are considered promising candidates for next-generation energy storage owing to their inherent safety, high energy density, and abundant sulfur resources. However, slow redox kinetics greatly limit sulfur utilization during solid-solid sulfur reactions, leading to significant challenges to achieve efficient performance in high-mass-loading ASSLSBs. Here, operando neutron image is employed to directly visualize, for the first time, that sluggish Li + transport kinetics and the uneven distribution of Li + during cathodic reactions are critical factors limiting sulfur conversion. To address this issue, gradient cathode architectures comprising three and five layers are designed, in which catholyte concentrations are strategically varied to optimize Li-ion flux and enhance ionic conductivity of the whole composite cathode electrode. Operando neutron imaging distinctly visualizes and confirms that three-layer gradient approach significantly enhances Li-ion mobility, resulting in more uniform redox reactions and greatly improved sulfur utilization compared to traditional non-gradient structures. Consequently, the three-layer gradient cathode achieves superior rate performance and reduced electrode polarization at high sulfur mass loadings of 4.5 and 6.0 mg cm −2 . Furthermore, the applicability and scalability of this design are demonstrated in a five-layer gradient cathode architecture, achieving an impressive discharge specific capacity increase from 656 mAh g −1 (three-layer gradient) to 1232 mAh g −1 at 1/20 C for ultra-high sulfur loading of 7.5 mg cm −2 . In conclusion, this innovative gradient cathode design offers substantial advancements in understanding and overcoming Li-ion transport limitations, paving the way toward practical, high-energy-density ASSLSBs.

25 ENERGY STORAGE↗
DOE OSTI2024

Factors Influencing Gas Evolution from High‐Nickel Layered Oxide Cathodes in Lithium‐Based Batteries

Abstract Gas evolution from high‐nickel layered oxide cathodes (>90% Ni) remains a major issue for their practical application. Gaseous species, such as CO 2 , O 2 , and CO, that are evolved at high states of charge (SOC) worsen the overall safety of batteries, as pressure build‐up within the cell may lead to cell rupture. Since these gasses are produced during cathode degradation, tracking the formation of gasses is also important in diagnosing cathode failure. Online electrochemical mass spectrometry (OEMS) is a powerful in situ technique to study gas evolution from the cathode during high‐voltage charge. However, the differences in the OEMS experimental setups between different groups make it challenging to compare results between groups. In this perspective, the various factors that influence gas evolution based on the OEMS results collected in this group are presented. The focus is on the conditions that lead to gas release, with a particular emphasis on reactive oxygen formation and subsequent chemical reactions with the electrolyte. Promising strategies, such as electrolytes, compositional tuning, and surface coatings that are effective at suppressing gas evolution from the cathode are highlighted. Critical insights into mitigating cathode degradation and gas evolution are provided to guide the development of safer, high‐energy batteries.

Chemistry↗
DOE OSTI2023

Suppressing Universal Cathode Crossover in High‐Energy Lithium Metal Batteries via a Versatile Interlayer Design**

Abstract The universal cathode crossover such as chemical and oxygen has been significantly overlooked in lithium metal batteries using high‐energy cathodes which leads to severe capacity degradation and raises serious safety concerns. Herein, a versatile and thin (≈25 μm) interlayer composed of multifunctional active sites was developed to simultaneously regulate the Li deposition process and suppress the cathode crossover. The as‐induced dual‐gradient solid‐electrolyte interphase combined with abundant lithiophilic sites enable stable Li stripping/plating process even under high current density of 10 mA cm −2 . Moreover, X‐ray photoelectron spectroscopy and synchrotron X‐ray experiments revealed that N‐rich framework and CoZn dual active sites can effectively mitigate the undesired cathode crossover, hence significantly minimizing Li corrosion. Therefore, assembled lithium metal cells using various high‐energy cathode materials including LiNi 0.7 Mn 0.2 Co 0.1 O 2 , Li 1.2 Co 0.1 Mn 0.55 Ni 0.15 O 2 , and sulfur demonstrate significantly improved cycling stability with high cathode loading.

Xie, Chuyi↗
DOE OSTI2023

Suppressing Universal Cathode Crossover in High‐Energy Lithium Metal Batteries via a Versatile Interlayer Design**

Abstract The universal cathode crossover such as chemical and oxygen has been significantly overlooked in lithium metal batteries using high‐energy cathodes which leads to severe capacity degradation and raises serious safety concerns. Herein, a versatile and thin (≈25 μm) interlayer composed of multifunctional active sites was developed to simultaneously regulate the Li deposition process and suppress the cathode crossover. The as‐induced dual‐gradient solid‐electrolyte interphase combined with abundant lithiophilic sites enable stable Li stripping/plating process even under high current density of 10 mA cm −2 . Moreover, X‐ray photoelectron spectroscopy and synchrotron X‐ray experiments revealed that N‐rich framework and CoZn dual active sites can effectively mitigate the undesired cathode crossover, hence significantly minimizing Li corrosion. Therefore, assembled lithium metal cells using various high‐energy cathode materials including LiNi 0.7 Mn 0.2 Co 0.1 O 2 , Li 1.2 Co 0.1 Mn 0.55 Ni 0.15 O 2 , and sulfur demonstrate significantly improved cycling stability with high cathode loading.

25 ENERGY STORAGE↗
DOE OSTI2025

Characterizing Disorders Within Cathode Materials of Lithium‐Ion Batteries

The demand for developing high-energy density cathode materials has been increasing. The energy densities of cathode materials have been improved by adapting structural deviation from the ideal fully ordered α-NaFeO2 type, but that led to limitations in terms of structural stability and safety. Although disorders in cathode materials are closely related to their electrochemical properties, unfortunately, characterizing the disorder itself in cathode materials has been challenging due to its complex parasitic reaction and strong correlation with other disorders occurring during charge/discharge. In this review, we categorize various disorders by their scales of ordering from short-range to long-range. We addressed the principles of various characterization tools to figure out how they can help to identify the structural disorder in cathode materials. Specifically, we focused on the underlying principles of each characterization technique to correlate different disorder-driven phenomena through several case studies. It underscores the substantial importance of disorder-property relationships and the corresponding characterization methods, which can provide novel research strategies for developing high-energy density cathode materials with decent structural stability.

Lee, Hakwoo↗
DOE OSTI2021

2D Ni 0.25 Mn 0.75 O 2 : A high-performance cathode for multivalent ion batteries

Although Li-ion batteries have driven portable energy storage in recent decades, there is increasing concern about their safety, cost, and abundance of constituents. Multivalent ion batteries (MVIBs) have the potential to remedy these issues, but they are limited by the currently known MVIB cathodes, which fail to deliver unanimously favorable voltage, energy density, and diffusion kinetics. Here we used density functional theory (DFT) to model the performance of Li, Na, Mg, Ca, and Al ions when paired with 2D Ni 0.25 Mn 0.75 O 2 , a novel cathode that uses increased layer separation to improve on the kinetics of its 3D analog. Our calculations yielded maximum voltages of 3.38 V for Na and 2.7 V for Ca, outperforming 2D Na x MnO 2 and Na x NiO 2 . Diffusion barriers for Li, Na, and Ca are below 300 meV, comparable to existing battery technology and the endpoint 2D cathodes; meanwhile, Mg and Al have prohibitively high diffusion barriers, implying their incompatibility with this cathode. Lastly, density of states calculations and Bader charge analysis show that the cathode becomes conducting following ion adsorption, which is necessary for high-rate performance. 2D Ni 0.25 Mn 0.75 O 2 maintains performance seen with other 2D transition metal oxides while increasing cathode conductivity, indicating that it is a promising candidate for experimental investigation with Li, Na, and Ca ions.

25 ENERGY STORAGE↗
DOE OSTI2022

Half-cell electrode assessments of a crossover-tolerant direct methanol fuel cell with a platinum group metal-free cathode

In this work, a platinum group metal- free (PGM-free) Fe-N-C oxygen reduction reaction (ORR) catalyst derived from metal organic framework precursors (Fe-MOF) is evaluated at the cathode side of a direct methanol fuel cell (DMFC). A wide range of methanol concentrations were used, and the performance of the DMFC using air was evaluated and compared to a commercial Pt/C cathode. We conducted our tests with a custom, integrated H 2 reference electrode that separately provided the anode and cathode overpotentials. This allowed us to perform a Tafel analysis on both electrodes and understand the dominant polarizations involved at the PGM-free cathode and the PtRu/C anode. Overall, we achieved a high cell performance using a Fe-N-C based catalyst under liquid methanol and air operation with a peak power density of 111 mW/cm 2 , where the cathode presented a markedly larger contribution to the voltage loss versus the anode. Additionally, we used nanoscale X-ray computed tomography (nano-CT) to image the Fe-N-C cathode and investigate the ionomer and pore size distributions allowing us to identify areas of improvement for catalyst layer fabrication.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2021

Surface enhanced performance of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ cathodes by infiltration Pr-Ni-Mn-O progress

Herein the present study reports the enhancement of electrochemical oxygen reduction activity of porous La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3–δ (LSCF) cathodes by coating a thin film of Pr-Ni-Mn oxide (PNM5) using a multi-step infiltration process. XRD examination reveals that PNM5 mainly contains a multiphase mixture of Pr 6 O 11 , PrNiO 3 , MnO and NiO. SEM morphology shows a thin PNM5 film and small particles are formed on the surface of LSCF backbone particles. Impedance spectrum analysis indicates that PNM5 infiltrated LSCF exhibits dramatically reduced polarization resistance (R p ), reaching R p of 0.244 Ω cm 2 at 973 K, which is one-half of the baseline LSCF cathode. The activation energy of LSCF cathodes infiltrated with PNM5 is 1.45 eV, slightly lower than the baseline LSCF cathode (1.77 eV). Distribution of relaxation time (DRT) function analysis shows PNM5 infiltration layer significantly promotes the oxygen reduction reaction (ORR) of cathode surface. With the increase in firing temperature, the total resistance increases and R p changes from ion transport to oxygen reduction reaction. Degradation rate of the PNM5-infiltrated LSCF is also lower, 0.02168% vs 0.07093% for the baseline LSCF over a 200-h period. A single cell testing indicated that the peak power density of the PNM5-infiltrated cell was increased by 140.66%. Overall, PNM5 could be a potential catalyst for boosting the performance of a commercial LSCF cathode for solid oxide fuel cells (SOFC).

36 MATERIALS SCIENCE↗
DOE OSTI2017

Full cell simulation and the evaluation of the buffer system on air-cathode microbial fuel cell

This paper presents a computational model of a single chamber, air-cathode MFC. The model considers losses due to mass transport, as well as biological and electrochemical reactions, in both the anode and cathode half-cells. Computational fluid dynamics and Monod-Nernst analysis are incorporated into the reactions for the anode biofilm and cathode Pt catalyst and biofilm. The integrated model provides a macro-perspective of the interrelation between the anode and cathode during power production, while incorporating microscale contributions of mass transport within the anode and cathode layers. Model considerations include the effects of pH (H + /OH – transport) and electric field-driven migration on concentration overpotential, effects of various buffers and various amounts of buffer on the pH in the whole reactor, and overall impacts on the power output of the MFC. The simulation results fit the experimental polarization and power density curves well. Further, this model provides insight regarding mass transport at varying current density regimes and quantitative delineation of overpotentials at the anode and cathode. Altogether, this comprehensive simulation is designed to accurately predict MFC performance based on fundamental fluid and kinetic relations and guide optimization of the MFC system.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2020

Potassium Prussian blue-coated Li-rich cathode with enhanced lithium ion storage property

With high specific capacity, the layered Li-rich Mn-based oxide (LRMO) is a promising candidate cathode material for Li-ion batteries. However, the irreversible release of Li-ions during the first charging process, instability of LRMO/electrolyte interface and relatively low ion conductivity of LRMO result in low initial Coulombic efficiency (ICE), poor cycle stability and rate performance, which prohibit its further application. Furthermore, interface engineering via additive coating is expected to effectively address these issues. Herein, we rely on potassium Prussian blue (KPB), a Li + acceptor with good ion conductivity, as a new coating material on LRMO particles. The KPB coating not only forms a protective layer on the surface of LRMO against electrolyte corrosion, but also functions as a host for Li + transport and accommodation, leading to enhanced ion conductivity and ICE of LRMO cathode. Consequently, 2 wt% KPB coated LRMO cathode achieved an initial discharge capacity of up to 281.7 mA h g -1 with an ICE of 85.69% compared to an ICE of 79.52% for the LRMO cathode without coating. The cycling and rate performance are also greatly improved as evidenced by the well maintained capacity of up to 176.8 mA h g -1 after 100 cycles at a current density of 0.5 C, compared to the limited capacity of only 135.3 mA h g -1 for the LRMO cathode without coating. Overall, this work pioneers the use of potassium Prussian blue as additive coating material to enhance performance of LRMO cathode, and we expect it to inspire the battery community with new strategies of material engineering/design toward practical application in high-energy lithium-ion batteries.

25 ENERGY STORAGE↗