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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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Electrochemical behavior of tungsten bronzes, formation mechanism of zinc dendrite, and organic compounds for secondary batteries
The influence of metallic impurities on solar cell characteristics has been examined to establish the cost sensitive purity versus performance trade-offs. Solar cells were fabricated on 2 to 4 ohm-cm p-type substrates obtained by Czochralski and dendritic web growth processes. Controlled amounts of metallic impurities were introduced into the melt during growth and included Fe, Cr, Mn, Ni, Cu, Ti, V, Zr, Mg, Zn, and Al. Impurity concentrations in the crystals were determined using emission and mass spectrographic techniques and in some cases by neutron activation analysis. The solar cells were characterized by means of a computer program to curve-fit measured voltage-current data. The principal effect of the added impurities is a degradation of lifetime and diffusion length.
Sodium–sulfur (Na–S) batteries with durable Na-metal stability, shuttle-free cyclability, and long lifespan are promising to large-scale energy storages. However, meeting these stringent requirements poses huge challenges with the existing electrolytes. Herein, a localized saturated electrolyte (LSE) is proposed with 2-methyltetrahydrofuran (MeTHF) as an inner sheath solvent, which represents a new category of electrolyte for Na–S system. Unlike the traditional high concentration electrolytes, the LSE is realized with a low salt-to-solvent ratio and low diluent-to-solvent ratio, which pushes the limit of localized high concentration electrolyte (LHCE). The appropriate molecular structure and solvation ability of MeTHF regulate a saturated inner sheath, which features a reinforced coordination of Na + to anions, enlarged Na + -solvent distance, and weakened anion-diluent interaction. Such electrolyte configuration is found to be the key to build a sustainable interphase and a quasi-solid–solid sulfur redox process, making a dendrite-inhibited and shuttle-free Na–S battery possible. With this electrolyte, pouch cells with decent cycling performance under rather demanding conditions are demonstrated.
Interfacial stability is one of the critical challenges in all-solid-state Li metal batteries. Multiple processes such as solid electrolyte (SE) decomposition and lithium dendrite growth take place at the solid interfaces during cycling, leading to the overall cell failure. To deconvolute these complex processes, in situ characterization is of paramount importance to elucidate the interfacial evolution on the SE upon Li plating/stripping. Herein, an all-solid-state asymmetric in situ cell is developed that allows the direct visualization of the highly localized Li plating/stripping processes under the optical microscope. Moreover, this cell configuration enables reliable post-mortem chemical and morphological analysis of the intact SE/Li interface. Using combined scanning electron microscopy and energy-dispersive X-ray spectroscopy, the study reveals that the evolution of the Li argyrodite interface is strongly influenced by the current density, particularly in terms of chemical distribution and Li plating morphology. More specifically, the solid interface is LiCl-rich with the formation of Li cubes at low current densities, while high currents result in more uniform elemental distribution and filament morphology. These findings elucidate the dynamic evolution mechanism at solid interfaces and offer valuable guidance for developing stable solid interfaces in all-solid-state Li metal batteries.
Traditional polyolefin separators used in lithium-ion batteries (LIBs) are seriously limited by the issues of inferior security and poor electrolyte wettability. Most of the very promising candidate separators based on heat-resistant polymers are, however, inherently difficult to process. Herein, a unique sulfonated aromatic heterocyclic polymer, lithiated poly(diphenyl ether oxadiazole) sulfonate (Li-SPEOD), was synthesized through a simple one-pot method and further electrospun to act as a novel separator (es-Li-SPEOD) for LIBs. In this work, the prepared Li-SPEOD possesses a high degree of sulfonation with a high molecular weight (M w = 4.31 × 10 5 ). The es-Li-SPEOD separator exhibits excellent mechanical and fire-resistance properties and is able to maintain dimensional stability at a temperature of even up to 400 °C in air. The ionic conductivity (3.57 mS cm –1 ) and lithium-ion transference number (0.37) of the es-Li-SPEOD with an electrochemical stability window of 4.5 V vs Li + /Li can be improved by 382.4 and 32.1%, respectively, compared to those of Celgard-2500 in the LiPF 6 electrolyte. The enhanced rate capability and cycle performance of the LiFePO 4 –Li half-cell are therefore obtained. Moreover, the es-Li-SPEOD displays an outstanding dendrite-suppressing effect for the lithium metal anode. This research proves that the Li-SPEOD-based separator has a broad application perspective in next-generation lithium batteries.
Traditional Li-ion intercalation chemistry into graphite anode exclusively utilizes the co-intercalation-free or co-intercalation mechanism. The latter mechanism is based on ternary graphite intercalation compounds (t-GICs), where glyme solvents were explored and proved to deliver unsatisfied cyclability in LIBs. Herein, we report a novel intercalation mechanism, that is, in-situ synthesis of t-THF-GICs in the tetrahydrofuran (THF) electrolyte via a spontaneous, controllable reaction between binary-GICs and free THF molecules during initial graphite lithiation. The spontaneous transformation from b-GIC to t-GIC, which is different from conventional co-intercalation chemistry, is characterized and quantified via operando synchrotron X-ray and electrochemical analyses. The resulting t-GIC chemistry obviates the necessity for complete Li-ion desolvation, facilitating rapid kinetics and synchronous charge/discharge of graphite particles even under high current densities. Consequently, the graphite anode demonstrates unprecedented fast charging (1 min), dendrite-free low-temperature performance, and ultralong lifetimes exceeding 10,000 cycles. Full cells coupled with layered cathode, display remarkable cycling stability upon a 15-min charging and excellent rate capability even at -40 °C. Furthermore, our chemical strategies are shown to extend beyond Li-ion batteries to encompass Na-ion and K-ion batteries, underscoring their broad applicability. Our work contributes to the advancement of graphite intercalation chemistry and presents a low-cost, adaptable approach to achieving fast-charging and low-temperature batteries.
Controlling solid electrolyte interphase (SEI) in batteries is crucial for their efficient cycling. Herein, we demonstrate an approach to enable robust battery performance that does not rely on high fractions of fluorinated species in electrolytes, thus substantially decreasing the environmental footprint and cost of high-energy batteries. In this approach, we use very low fractions of readily reducible fluorinated cations in electrolyte (~0.1 wt%) and employ electrostatic attraction to generate a substantial population of these cations at the anode surface. As a result, we can form a robust fluorine-rich SEI that allows for dendrite-free deposition of dense Li and stable cycling of Li-metal full cells with high-voltage cathodes. Our approach represents a general strategy for delivering desired chemical species to battery anodes through electrostatic attraction while using minute amounts of additive.
Numerical analysis of solvent reorganization energy and method for prevention of dendritic crystal growth and zinc electrode surface area decrease in silver batteries
Technical readiness for the production of photovoltaic modules using single crystal silicon dendritic web sheet material is demonstrated by: (1) selection, design and implementation of solar cell and photovoltaic module process sequence in a Module Experimental Process System Development Unit; (2) demonstration runs; (3) passing of acceptance and qualification tests; and (4) achievement of a cost effective module.
The Marr and Albus theories of the cerebellum are compared and contrasted. They are shown to be similar in their analysis of the function of the mossy fibers, granule cells, Golgi cells, and Purkinje cells. They both predict motor learning in the parallel fiber synapses on the Purkinje dendrites mediated by concurrent climbing fiber input. This prediction has been confirmed by experimental evidence. In contrast, Marr predicts these synapses would be facilitated by learning, while Albus predicts they would be weakened. Experimental evidence confirms synaptic weakening.
A comprehensive understanding of the effects of spaceflight and altered gravity on human physiology is necessary for continued human space exploration and long-term space habitation. Spaceflight includes multiple factors such as microgravity, hypergravity, ionizing radiation, physiological stress, and disrupted circadian rhythms and these have been shown to contribute to pathophysiological responses that target immunity, bone and muscle integrity, cardiovascular and nervous systems. In terrestrial conditions, some of these factors can lead to cancer and neuroimmunological disorders. In this study, we used a well-established spaceflight model organism, Drosophila melanogaster, to assess spaceflight-associated changes in the nervous system. We hypothesize that exposure to altered gravity triggers the oxidative stress response, leading to impairments in the nervous system. To test this hypothesis, we used two experimental paradigms: 1) hypergravity, using the ground-based chronic acceleration model, and 2) spaceflight conditions, which includes exposure to microgravity and in-flight space 1g controls. In our ground studies, acute hypergravity resulted in an induction of oxidative stress-related genes with an increase in reactive oxygen species (ROS) in fly brains. Additionally, we observed a depressed locomotor phenotype in these flies (p<0.05). These flies also show a decreased dopaminergic neuron counts in the fly brain upon exposure to acute hypergravity (p<0.05). Thus, the data suggest that altered gravity has a profound effect on the fly nervous system. Similarly, we observe behavioral impairments (p<0.001) and synaptic deficits, including decreased synaptic connections (p<0.05), in 3rd instar larvae which were developed in space. Furthermore, space-grown adults show a decrease in neuronal (p<0.05) and dendritic field (p<0.01) in adult brains coupled with an increased number of apoptotic cells (p<0.001), suggesting increased neuronal loss under spaceflight conditions. In summary, we observe that altered gravity leads to gross neurological deficits. To better understand the long-term effects of spaceflight on the nervous system, longitudinal and multigenerational changes were also identified. This study will help elucidate the different approaches to prevent nervous system dysfunction in astronauts during spaceflight, while also contributing to a better understanding of the pathways that are related to some CNS disorders on Earth.
Research on human acclimation to spaceflight, including the recent NASA's Twin Study, reports complex effects of the spaceflight environment on health, with both acute and prolonged changes in multiple tissues. Spaceflight includes multiple factors such as microgravity, ionizing radiation, physiological stress, and disrupted circadian rhythms, that have been shown to contribute to pathophysiological responses that target immunity, bone and muscle integrity, cardiovascular and nervous systems. In this study, we used a well-established spaceflight model organism, Drosophila melanogaster, to assess spaceflight-associated changes on the nervous system. With 75% disease gene orthology to humans, short generation time, large sample size and ease of genetic, neuronal and behavioral studies, Drosophila is an excellent model to study nervous system dysfunction. Here, we present results from MVP-Fly-01 spaceflight mission that was launched on SpaceX CRS-14. The MVP hardware (developed by Techshot) used in this mission enabled us to have an in-flight 1g centrifuge, to distinguish the changes resulting from gravity versus those induced by other environmental factors associated with spaceflight. We observe behavioral impairments (p<0.001) and synaptic deficits, including decreased synaptic connections (p<0.05), in 3rd instar larvae which were developed in space. Furthermore, space-grown microgravity adults show a decrease in neuronal (p<0.05) and dendritic field (p<0.01) in adult brains coupled with an increased number of apoptotic cells (p<0.001) compared to in-flight 1g controls, suggesting increased neuronal loss under spaceflight conditions. In summary, we observe that altered gravity leads to gross neurological deficits. To better understand the long-term effects of spaceflight on the nervous system, longitudinal and multigenerational changes were also identified. This study will help elucidate the different approaches to prevent nervous system dysfunction in astronauts during spaceflight, while also contributing to a better understanding of the pathways that are related to some CNS disorders on Earth.
Significant progress is reported in fabricating a 4 sq cm cell having a 10.1 percent conversion efficiency and a 10 sq cm cell having a 9.2 percent conversion efficiency. The continuous (SCIM) coater succeeded in producing a 16 sq cm coating exhibiting unidirectional solidification and large grain size. A layer was grown at 0.2 cm/sec in the experimental coater which was partially dendritic but also contained a large smooth area approximately 100 micron m thick. The dark characteristic measurements of a typical SCC solar cell yield shunt resistance values of 10K ohms and series resistance values and 0.4 ohm. The production dip-coater is operating at over 50 percent yield in terms of good cell quality material. The most recent run yielded 13 good substrates out of 15.
The technical and economic feasibility of producing solar cell quality sheet silicon was investigated. It was hoped this could be done by coating one surface of carbonized ceramic substrates with a thin layer of large-grain polycrystalline silicon from the melt. Work was directed towards the solution of unique cell processing/design problems encountered with the silicon-ceramic (SOC) material due to its intimate contact with the ceramic substrate. Significant progress was demonstrated in the following areas; (1) the continuous coater succeeded in producing small-area coatings exhibiting unidirectional solidification and substatial grain size; (2) dip coater succeeded in producing thick (more than 500 micron) dendritic layers at coating speeds of 0.2-0.3 cm/sec; and (3) a standard for producing total area SOC solar cells using slotted ceramic substrates was developed.
In this study, lithium-sulfur (Li-S) batteries are promising for automotive applications due to their high theoretical energy density (2600 Wh/kg). In addition, the natural abundance of sulfur could mitigate the global raw material supply chain challenge of commercial lithium-ion batteries that use critical elements, such as nickel and cobalt. However, due to persistent polysulfide shuttling and uncontrolled lithium dendrite growth, Li-S batteries using nonencapsulated sulfur cathodes and conventional ether-based electrolytes suffer from rapid cell degradation upon cycling. Despite significant improvements in recent decades, there is still a big gap between lab research and commercialization of the technology. To date, the reported cell energy densities and cycling life of practical Li-S pouch cells remain largely unsatisfactory. Traditional approaches to improving Li-S performance are primarily focused on confining polysulfides using electronically conductive hosts. However, these micro- and mesoporous hosts suffer from limited pore volume to accommodate high sulfur loading and the associated volume change during cycling. Moreover, they fail to balance adsorption-conversion of polysulfides during charge-discharge, leading to the formation of massive dead sulfur. Such hosts are themselves electrochemically inactive, which decreases the practical energy density. In contrast, a series of nontraditional approaches, paired with advances in multiscale mechanistic understanding, have recently demonstrated exciting performance outcomes not only in conventional coin cells but also in practical pouch cells. In this Account, we first introduce our novel cathode design strategies to overcome polysulfide shuttling and sluggish redox kinetics in thick S cathodes via selenium-sulfur chemistry and cathode host engineering. Next, we gain a mechanistic understanding of Li-S batteries in various types of electrolytes via a series of spectroscopic, nuclear magnetic resonance, and electrochemical methods. Meanwhile, a novel cathode solid electrolyte interphase encapsulation strategy via nonviscous highly fluorinated ether-based electrolyte is introduced. The established selection rule by investigating how solvating power retards the shuttle effect and induces robust cathode/solid-electrolyte interphase formation is also included. We then discuss how the synergistic interactions between rational cathode structures and electrolytes can be exploited to tailor the reaction pathways and kinetics of S cathodes under high mass loading and lean electrolyte conditions. In addition, a novel interlayer design to simultaneously overcome degradation processes (polysulfide shuttling and lithium dendrite formation) and accelerate redox reaction kinetics is presented. Finally, this Account concludes with an overview of the challenges and strategies to develop Li-S pouch cells with high practical energy density, long cycle life, and fast-charging capability.
Sodium solid-state batteries (Na-SSB) have gained interest recently due to the abundance of Na over Li, but they still tend to fail due to dendrites under practical current densities and cycling capacities. To overcome this, Na-SSBs are frequently tested with impractically high applied pressure. In this work, a porous carbon interfacial layer is utilized in conjunction with Na-ß”-Al2O3 solid electrolytes to enable Na-cycling at milder cell pressures. This sodium/porous carbon layer enables improved solid-state Na cycling in symmetric cells, up to a current density of 10 mA cm-2 at 25 °C. Cycling up to 1 mAh cm-2 is challenging with low pressure, but 1 mAh cm-2 capacity can be reliably cycled at 1 mA cm-2 at an elevated temperature of 60 °C in symmetric cells. Finally, the evolution of the interface and sodium/carbon anode is evaluated with cryogenic ion-milling and cross-sectional imaging revealing that, depending on testing temperature, pressure, current density, and capacity, void formation, Na-extraction from porous carbon, delamination of the porous carbon matrix, or a combination of these occurs at the interface between Na-metal and BASE. Despite this, excellent dendrite resistance is achieved, and a full-cell design utilizing a Na-transition metal oxide cathode is still able to achieve an areal capacity of ~ 2.7 mAh cm-2 at 0.125 mA cm-2. This work demonstrates an alternative pathway toward a Na-metal anode for Na-SSBs without the requirement of excessive stack pressure.
It is crucial to suppress lithium dendrite formation in lithium metal batteries. Formation of a good solid–electrolyte interphase (SEI) has been considered to be effective in limiting lithium dendrite growth. However, how the SEI may be modified during lithium deposition is hard to resolve due to challenges in in situ investigation of the SEI with fine details. Here, we report an in situ study that uncovers the lithium dendrite suppression mechanism arising from SEI modification by a poly(diallyldimethylammonium chloride) (PDDA) cationic polymer film, using electrochemical liquid cell transmission electron microscopy (TEM). Lithium nanogranules are obtained in the presence of the polymer film. Chemical mapping of the deposits provides remarkable details of the SEI on individual nanogranules. It shows that lithium fluorides are uniformly distributed within the inner SEI layer of individual lithium nanogranules, arising from the instantaneous reaction of the deposited lithium with PF 6 – ions accumulated by the cationic polymer film, and thus the dendritic growth of lithium is prohibited. The ability to directly measure SEI chemistry at the nanoscale down to the individual nanograins in situ and unveil its correlation with the lithium deposition behavior opens future opportunities to explore unsolved mechanisms in batteries.
Abstract Solid‐state polymer electrolytes provide better flexibility and electrode contact than their ceramic counterparts, making them a worthwhile pursuit for all‐solid‐state lithium‐metal batteries. However, their large Li/solid state electrolyte interfacial resistance, small critical current density, and rapid lithium dendrite growth during cycling still limit their viability. Owing to these restrictions, all‐solid‐state cells with solid polymer electrolytes must be cycled above room‐temperature and with a small current density. These problems can be mitigated with an in situ formed artificial solid electrolyte interphase that rapidly conducts Li + ions. Herein, a Li 3 P layer formed in situ at the Li‐metal/solid polymer electrolyte interphase is reported that significantly reduces the electrode/electrolyte interfacial resistance. Additionally, this layer increases the wettability of the solid polymer by the metallic lithium anode, allowing for the critical current density of lithium symmetric cells to be doubled by homogenizing the current density at the interface. All‐solid‐state Li/Li symmetric cells and Li/LiFePO 4 cells with the Li 3 P layer show improved cycling performance with a high current density.