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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 1,081 records · Page 60
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Nickel/silicon core/shell nanosheet arrays as electrode materials for lithium ion batteries

Highlights: • Ni nanosheet arrays is the core and Si layer is the shell. • Ni nanosheet arrays act as a three-dimensional current collector to support Si. • Ni nanosheet arrays can improve the conductivity and stability of the electrode. • Ni/Si nanosheet arrays exhibit excellent cyclic and rate performance. - Abstract: Ni/Si core/shell nanosheet arrays are proposed to enhance the electrochemical lithium-storage properties of silicon. The arrays are characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The arrays are micro-sized in height, which are constructed by interconnected Ni nanosheet as the core and Si coating layer as the shell. The electrochemical properties as anode materials of lithium ion batteries are investigated by cyclic voltammetry (CV) and galvanostatic charge-discharge tests. The arrays can achieve high reversible capacity, good cycle stability and high rate capability. It is believed that the enhanced electrochemical performance is attributed to the electrode structure, because the interconnected Ni nanosheet can act as a three-dimensional current collector, and it has the ability of improving the electrode conductivity, enlarging the electrochemical reaction interface, and suppressing the electrode pulverization.

36 MATERIALS SCIENCE↗
DOE OSTI2017

A stable graphite electrode in superconcentrated LiTFSI-DME/DOL electrolyte and its application in lithium-sulfur full battery

Graphical abstract: In superconcentrated ether-based solutions, the formed SEI film inhibits electrolyte decomposition and graphite exfoliation caused by co-intercalation of solvents. Thus, reversible lithium intercalation and de-intercalation at a graphite electrode has been realized. - Highlights: • Prelithiated graphite anodes are coupled with sulfur composite cathodes to form a Li–S full cell in superconcentrated LiTFSI-DME/DO electrolyte. • The introduced superconcentrated ether-based electrolyte permits reversible lithium intercalation and de-intercalation at a graphite electrode. • The assembled Li–S full battery exhibits better cycle performance and coulombic efficiencies. - Abstract: Herein, prelithiated graphite anodes are coupled with sulfur composite cathodes to form a Li–S full cell in superconcentrated ether electrolyte. This novel system is effective in avoiding sever corrosion of Li-metal anode and significantly improving the safety of present Li–S cell, owing to the replacement of Li-metal anode with graphite. The introduced superconcentrated ether electrolyte has a unique networking structure of Li cations and TFSI anions with Li{sup +}-solvating DME/DOL solvents, which is conducive to form a stable TFSI-derived surface film on the graphite electrode. The stable and dense TFSI-derived film inhibits further electrolyte decomposition and graphite exfoliation caused by co-intercalation of solvents, allowing reversible lithium intercalation and de-intercalation at a graphite electrode. Besides, the severe polysulfides shuttle is also suppressed by the concentrated ether-based solutions. Consequently, the assembled graphite-sulfur full battery retains outstanding capacity of 686 mAh g{sup −1}{sub sulfur} at 0.1C rate after 105 cycles, along with high Coulombic efficiency.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Highly transparent metal electrodes via direct printing processes

Highlights: • Pt(NO{sub 3}){sub 2}(ACN){sub 2} as a new molecular platinum complex has been introduced. • The complex shows excellent printability in nanoimprint lithography. • Pt line and grid pattern with linewidths as small as 40 nm could be printed. • The printed electrodes show resistance below 100 Ω and transmittance up to 90%. - Abstract: Transparent platinum electrodes are prepared using nanoimprint lithography of a newly developed molecular platinum complex. Thermal decomposition at moderate temperature of this complex gives rise to elemental platinum line and grid pattern with linewidths down to 40 nm. These electrodes exhibit transmittances of 90% and resistances below 100 Ω. Thus, for the first time, highly transparent electrodes are prepared by a direct soft lithographical printing process.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Triphase electrode performance adjustment for rechargeable ion batteries

Rechargeable batteries electrodes are mainly classical oxides with single structure, but their performance is insufficient to meet the growing energy storage needs of modern-society. Recently, composite-structure materials with great improvements in electrochemical performance have been developed. However, little research has been conducted on these materials with regard to adjusting their structures and further controlling their electrochemical performance. Herein, composite-structure Na 2/3 Ni 1/3–x Fe x Ti 2/3 O 2 (0 ≤ x ≤ 1/3) electrodes for sodium-ion batteries were designed on the basis of results from in-situ high-temperature X-ray diffraction. Triphase compositions of P2-Na 2/3 Ni 1/3 Ti 2/3 O 2 , tunnel-Na 2.65 Ti 3.35 Fe 0.65 O 9 , and tunnel-NaFeTiO 4 were prepared, and Na + insertion/extraction in different structures was observed using in-situ electrochemical X-ray diffraction. An optimum electrode with 46% P2-structure presented the best comprehensive performance: 105 mAh g –1 initial reversible capacity along with 86.5% capacity-retention after 1500 cycles. As a result, this work opens a new field for designing and adjusting composite electrodes for better electrochemical performance, not limited for sodium-ion batteries but also for other advanced battery-systems.

25 ENERGY STORAGE↗
DOE OSTI2016

Molybdenum polysulfide chalcogels as high-capacity, anion-redox-driven electrode materials for Li-ion batteries

Sulfur cathodes in conversion reaction batteries offer high gravimetric capacity but suffer from parasitic polysulfide shuttling. We demonstrate here that transition metal chalcogels of approximate formula MoS 3.4 achieve a high gravimetric capacity close to 600 mAh g –1 (close to 1000 mAh g –1 on a sulfur basis) as electrode materials for lithium-ion batteries. Transition metal chalcogels are amorphous and comprise polysulfide chains connected by inorganic linkers. The linkers appear to act as a “glue” in the electrode to prevent polysulfide shuttling. The Mo chalcogels function as electrodes in carbonate- and ether-based electrolytes, which further provides evidence of polysulfide solubility not being a limiting issue. We employ X-ray spectroscopy and operando pair distribution function techniques to elucidate the structural evolution of the electrode. Raman and X-ray photoelectron spectroscopy track the chemical moieties that arise during the anion-redox-driven processes. As a result, we find the redox state of Mo remains unchanged across the electrochemical cycling and, correspondingly, the redox is anion-driven.

25 ENERGY STORAGE↗
DOE OSTI2023

Development and Characterization of Electrodes for Surface-Specific Attenuated Total Reflection Two-Dimensional Infrared Spectroelectrochemistry

Electrochemical interfaces still have remaining mysteries surrounding the interfacial region of the electrical double layer, despite being prevalent throughout the energy and water remediation industries. The electrical double layer is where many important dynamic processes such as catalysis and electron transfer occur. The goal of this work is to study the electrical double layer with two-dimensional infrared (2D IR) spectroscopy to experimentally access the details of the structural dynamics of this complex environment. However, there are several experimental challenges to applying 2D IR spectroscopy to this application, such as assuring the surface specificity of the spectrum, optimizing the signal strength while minimizing spectral distortions from dispersion and Fano line shapes, and selecting electrode materials that are both sufficiently IR compatible and conductive. Here we will discuss various considerations when designing 2D IR experiments of electrode interfaces utilizing several substrates and experimental configurations and demonstrate a robust method for 2D IR experiments of electrode interfaces under applied potential that combines nonconducting Si ATR wafers with conductive ITO and thin nanostructured films of plasmonically active Au functionalized with 3-mercapto-2-butanone (MCB). We show that layered electrodes on thin Si ATR wafers with MCB are sensitive to applied potential and that the distortions in the linear and 2D IR spectra are heavily dependent on the morphology of the Au surface.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Direct Experimental Probe of the Ni(II)/Ni(III)/Ni(IV) Redox Evolution in LiNi 0.5 Mn 1.5 O 4 Electrodes

The LiNi 0.5 Mn 1.5 O 4 spinel is an appealing cathode material for next generation rechargeable Li-ion batteries due to its high operating voltage of ~4.7 V (vs Li/Li + ). Although it is widely believed that the full range of electrochemical cycling involves the redox of Ni(II)/(IV), it has not been experimentally clarified whether Ni(III) exists as the intermediate state or a double-electron transfer takes place. Here, combined with theoretical calculations, we show unambiguous spectroscopic evidence of the Ni(III) state when the LiNi 0.5 Mn 1.5 O 4 electrode is half charged. This provides a direct verification of single-electron-transfer reactions in LiNi 0.5 Mn 1.5 O 4 upon cycling, namely, from Ni(II) to Ni(III), then to Ni(IV). Additionally, by virtue of its surface sensitivity, soft X-ray absorption spectroscopy also reveals the electrochemically inactive Ni 2+ and Mn 2+ phases on the electrode surface. Our work provides the long-awaited clarification of the single-electron transfer mechanism in LiNi 0.5 Mn 1.5 O 4 electrodes. Furthermore, the experimental results serve as a benchmark for further spectroscopic characterizations of Ni-based battery electrodes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

A Convenient and Versatile Method To Control the Electrode Microstructure toward High-Energy Lithium-Ion Batteries

Control over porous electrode microstructure is critical for the continued improvement of electrochemical performance of lithium ion batteries. This paper describes a convenient and economical method for controlling electrode porosity, thereby enhancing material loading and stabilizing the cycling performance. Sacrificial NaCl is added to a Si-based electrode, which demonstrates an areal capacity of ~4 mAh/cm 2 at a C/10 rate (0.51 mA/cm 2 ) and an areal capacity of 3 mAh/cm 2 at a C/3 rate (1.7 mA/cm 2 ), one of the highest material loadings reported for a Si-based anode at such a high cycling rate. X-ray microtomography confirmed the improved porous architecture of the SiO electrode with NaCl. The method developed here is expected to be compatible with the state-of-the-art lithium ion battery industrial fabrication processes and therefore holds great promise as a practical technique for boosting the electrochemical performance of lithium ion batteries without changing material systems.

25 ENERGY STORAGE↗
DOE OSTI2018

Tracking the Chemical and Structural Evolution of the TiS 2 Electrode in the Lithium-Ion Cell Using Operando X-ray Absorption Spectroscopy

As the lightest and cheapest transition metal dichalcogenide, TiS 2 possesses great potential as an electrode material for lithium batteries due to the advantages of high energy density storage capability, fast ion diffusion rate, and low volume expansion. Despite the extensive investigation of its electrochemical properties, the fundamental discharge-charge reaction mechanism of the TiS 2 electrode is still elusive. In this paper, by a combination of ex situ and operando X-ray absorption spectroscopy with density functional theory calculations, we have clearly elucidated the evolution of the structural and chemical properties of TiS 2 during the discharge-charge processes. The lithium intercalation reaction is highly reversible and both Ti and sulfur are involved in the redox reaction during the discharge and charge processes. In contrast, the conversion reaction of TiS 2 is partially reversible in the first cycle. However, Ti–O related compounds are developed during electrochemical cycling over extended cycles, which results in the decrease of the conversion reaction reversibility and the rapid capacity fading. In addition, the solid electrolyte interphase formed on the electrode surface is found to be highly dynamic in the initial cycles and then gradually becomes more stable upon further cycling. Finally, such understanding is important for the future design and optimization of TiS 2 based electrodes for lithium batteries.

25 ENERGY STORAGE↗
DOE OSTI2023

Cation-Driven Assembly of Bilayered Vanadium Oxide and Graphene Oxide Nanoflakes to Form Two-Dimensional Heterostructure Electrodes for Li-Ion Batteries

Lithium preintercalated bilayered vanadium oxide (LVO or δ-Li x V 2 O 5 ·nH 2 O) and graphene oxide (GO) nanoflakes were assembled using a concentrated lithium chloride solution and annealed under vacuum at 200 °C to form two-dimensional (2D) δ-Li x V 2 O 5 ·nH 2 O and reduced GO (rGO) heterostructures. Here we found that the Li + ions from LiCl enhanced the oxide/carbon heterointerface formation and served as stabilizing ions to improve structural and electrochemical stability. The graphitic content of the heterostructure could be easily controlled by changing the initial GO concentration prior to assembly. We found that increasing the GO content in our heterostructure composition helped inhibit the electrochemical degradation of LVO during cycling and improved the rate capability of the heterostructure. A combination of scanning electron microscopy and X-ray diffraction was used to help confirm that a 2D heterointerface formed between LVO and GO, and the final phase composition was determined using energy-dispersive X-ray spectroscopy and thermogravimetric analysis. Scanning transmission electron microscopy and electron energy-loss spectroscopy were additionally used to examine the heterostructures at high resolution, mapping the orientations of rGO and LVO layers and locally imaging their interlayer spacings. Further, electrochemical cycling of the cation-assembled LVO/rGO heterostructures in Li-ion cells with a non-aqueous electrolyte revealed that increasing the rGO content led to improved cycling stability and rate performance, despite slightly decreased charge storage capacity. The heterostructures with 0, 10, 20, and 35 wt % rGO exhibited capacities of 237, 216, 174, and 150 mAh g –1 , respectively. Moreover, the LVO/rGO-35 wt % and LVO/rGO-20 wt % heterostructures retained 75% (110 mAh g–1) and 67% (120 mAh g –1 ) of their initial capacities after increasing the specific current from 20 to 200 mA g –1 , while the LVO/rGO-10 wt % sample retained only 48% (107 mAh g –1 ) of its initial capacity under the same cycling conditions. In addition, the cation-assembled LVO/rGO electrodes exhibited enhanced electrochemical stability compared to electrodes prepared through physical mixing of LVO and GO nanoflakes in the same ratios as the heterostructure electrodes, further revealing the stabilizing effect of a 2D heterointerface. The cation-driven assembly approach, explored in this work using Li + cations, was found to induce and stabilize the formation of stacked 2D layers of rGO and exfoliated LVO. The reported assembly methodology can be applied for a variety of systems utilizing 2D materials with complementary properties for applications as electrodes in energy storage devices.

25 ENERGY STORAGE↗
DOE OSTI2017

Enhanced Cycling Stability of Sulfur Electrodes through Effective Binding of Pyridine-Functionalized Polymer

Porous carbons have previously been widely used as host materials for sulfur (S) electrodes because of their high conductivity and high surface area. However, they generally lack strong chemical affinity to stabilize polysulfide species. Therefore, conducting polymers have been employed to stabilize S electrodes. Integrating conducting polymers with high-surface-area carbons can create a new materials platform and synergize their functions. However, the previously used conducting polymers were often insoluble, and coating them uniformly from solution onto a nonpolar carbon substrate is a challenge. Here, we report that solution-processable isoindigo-based polymers incorporating polar substituents provide critical features: the conjugated backbone provides good conductivity; functional pyridine groups provide high affinity to polysulfide species; and they possess high solubility in organic solvents. Here, these lead to effective coating on various carbonaceous substrates to provide highly stable sulfur electrodes. Importantly, the electrodes exhibit good capacity retention (80% over 300 cycles) at sulfur mass loading of 3.2 mg/cm 2 , which significantly surpasses the performance of others reported in polymer-enabled sulfur cathodes.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Nonplanar Electrode Architectures for Ultrahigh Areal Capacity Batteries

Here, we report on the design of a battery electrode architecture in which ion and electronic transport pathways are continuous, and span the entire volume of a thick, non-planar electrode. It is shown that for a range of active materials conductivities, the length scale for electronic transport in such an architecture can be tuned by simple manipulations of the electrode design to enable good access to the active material. The benefits of such electrodes for basic science research and practical lithium metal batteries are demonstrated in low-N:P ratio cells in which a conventional (300- 800 μm) Li foil is successfully cycled with LiCoO 2 cathodes with high areal capacities (10- 28 mAh/cm 2 ).

25 ENERGY STORAGE↗
DOE OSTI2024

Interpenetrating 3D Electrodes for High-Rate Alkaline Water Splitting

Mass transfer is critical for the reaction kinetics and efficiency of alkaline water splitting (AWS). For AWS to operate at high current densities (hundreds of mA/cm 2 ), the device architecture must ensure a large catalytic surface area, rapid ion diffusion, and minimal solution and charge transfer resistances. Effective electrodes should also facilitate gas bubble detachment and release. 3D-printed electrodes have shown promise, but stacking them increases the ion diffusion length and solution resistance. Here we demonstrate a new device architecture with interpenetrating gyroid electrodes, providing a large ion-accessible surface area and gas diffusion channels. This design significantly reduces the interelectrode distance, lowering ion diffusion length and solution resistance. Simulations show faster ion diffusion and higher current density in the interpenetrating configuration compared with separate electrodes. This improved performance, especially at low temperatures and high current densities, highlights a promising strategy for enhancing AWS and other electrochemical systems limited by slow ion diffusion.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Phase Boundary Propagation in Li-Alloying Battery Electrodes Revealed by Liquid-Cell Transmission Electron Microscopy

Battery cycle life is directly influenced by the microstructural changes occurring in the electrodes during charge and discharge cycles. In this study, we image in situ the nanoscale phase evolution in negative electrode materials for Li-ion batteries using a fully enclosed liquid cell in a transmission electron microscope (TEM) to reveal early degradation that is not evident in the charge–discharge curves. To compare the electrochemical phase transformation behavior between three model materials, thin films of amorphous Si, crystalline Al, and crystalline Au were lithiated and delithiated at controlled rates while immersed in a commercial liquid electrolyte. This method allowed for the direct observation of lithiation mechanisms in nanoscale negative electrodes, revealing that a simplistic model of a surface-to-interior lithiation front is insufficient. For the crystalline films, a lithiation front spread laterally from a few initial nucleation points, with continued grain nucleation along the growing interface. The intermediate lithiated phases were identified using electron diffraction, and high-resolution postmortem imaging revealed the details of the final microstructure. Lastly, our results show that electrochemically induced solid–solid phase transformations can lead to highly concentrated stresses at the laterally propagating phase boundary which should be considered for future designs of nanostructured electrodes for Li-ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2025

Interface Evolutionand Long-Term Performance of NegativeCarbon Fiber Structural Electrodes

Abstract Laminated structural batteries present a transformative solution to reducing weight constraints in electric vehicles. These structural batteries are based on a multifunctional material that incorporates an energy storage function within a carbon fiber-reinforced polymer. Despite the potential of this technology, the intricate morphology of fiber–matrix or electrode–electrolyte interfaces and the impact of long-term cycling at low current rates (C-rates) on these interfaces remain insufficiently understood. This study addresses these critical knowledge gaps by examining the influence of matrix composition on the long-term electrochemical performance of structural battery electrodes and exploring advanced techniques to investigate carbon fiber–matrix interfaces. Localized imaging and X-ray scattering techniques were used to characterize morphological changes at the electrode–electrolyte interfaces by analyzing negative structural electrodes. The findings revealed that the matrix composition influences long-term electrochemical behavior and fiber–matrix interface formation. While the intrinsic properties of carbon fibers largely remain unaffected by long-term cycling, cycling promotes debonding at fiber–matrix interfaces. Nonetheless, residual regions of adhesion persist, underscoring the potential for preserving multifunctionality even under prolonged cycling conditions. These insights advance the understanding of interface dynamics, which is critical for optimizing structural battery technologies.

Chemistry↗
DOE OSTI2017

Mechanisms of Furfural Reduction on Metal Electrodes: Distinguishing Pathways for Selective Hydrogenation of Bioderived Oxygenates

Electrochemical reduction of biomass-derived platform molecules is an emerging route for the sustainable production of fuels and chemicals. Understanding gaps between reaction conditions, underlying mechanisms, and product selectivity have limited the rational design of active, stable, and selective catalyst systems. Here, the mechanisms of electrochemical reduction of furfural, an important biobased platform molecule and model for aldehyde reduction, are explored through a combination of voltammetry, preparative electrolysis, thiol-electrode modifications, and kinetic isotope studies. It is demonstrated that two distinct mechanisms are operable on metallic Cu electrodes in acidic electrolytes: (i) electrocatalytic hydrogenation (ECH) and (ii) direct electroreduction. The contributions of each mechanism to the observed product distribution are clarified by evaluating the requirement for direct chemical interactions with the electrode surface and the role of adsorbed hydrogen. Further analysis reveals that hydrogenation and hydrogenolysis products are generated by parallel ECH pathways. By understanding the underlying mechanisms it enables the manipulation of furfural reduction by rationally tuning the electrode potential, electrolyte pH, and furfural concentration to promote selective formation of important biobased polymer precursors and fuels.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Phase evolution of conversion-type electrode for lithium ion batteries

Batteries with conversion-type electrodes exhibit higher energy storage density but suffer much severer capacity fading than those with the intercalation-type electrodes. The capacity fading has been considered as the result of contact failure between the active material and the current collector, or the breakdown of solid electrolyte interphase layer. Here, using a combination of synchrotron X-ray absorption spectroscopy and in situ transmission electron microscopy, we investigate the capacity fading issue of conversion-type materials by studying phase evolution of iron oxide composited structure during later-stage cycles, which is found completely different from its initial lithiation. The accumulative internal passivation phase and the surface layer over cycling enforce a rate-limiting diffusion barrier for the electron transport, which is responsible for the capacity degradation and poor rate capability. This work directly links the performance with the microscopic phase evolution in cycled electrode materials and provides insights into designing conversion-type electrode materials for applications.

25 ENERGY STORAGE↗
DOE OSTI2021

Deep learning-based segmentation of lithium-ion battery microstructures enhanced by artificially generated electrodes

Accurate 3D representations of lithium-ion battery electrodes, in which the active particles, binder and pore phases are distinguished and labeled, can assist in understanding and ultimately improving battery performance. Here, we demonstrate a methodology for using deep-learning tools to achieve reliable segmentations of volumetric images of electrodes on which standard segmentation approaches fail due to insufficient contrast. We implement the 3D U-Net architecture for segmentation, and, to overcome the limitations of training data obtained experimentally through imaging, we show how synthetic learning data, consisting of realistic artificial electrode structures and their tomographic reconstructions, can be generated and used to enhance network performance. We apply our method to segment x-ray tomographic microscopy images of graphite-silicon composite electrodes and show it is accurate across standard metrics. We then apply it to obtain a statistically meaningful analysis of the microstructural evolution of the carbon-black and binder domain during battery operation.

25 ENERGY STORAGE↗