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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Exceptionally High Ionic Conductivity in Na 3 P 0.62 As 0.38 S 4 with Improved Moisture Stability for Solid-State Sodium-Ion Batteries

A Na-ion solid-state electrolyte, Na 3 P 0.62 As 0.38 S 4 , is developed with an exceptionally high conductivity of 1.46 mS cm -1 at 25 degrees C and enhanced moisture stability. Dual effects of alloying element As (lattice expansion and a weaker As. S bond strength) are responsible for the superior conductivity. Improved moisture stability is regulated by shifting low-energy moisture reactions to high-energy ones due to As.

Yu, Zhaoxin↗
DOE OSTI2024

Enhancing the Conductivity and Thermoelectric Performance of Semicrystalline Conducting Polymers through Controlled Tie Chain Incorporation

Abstract Conjugated polymers are promising materials for thermoelectric applications, however, at present few effective and well‐understood strategies exist to further advance their thermoelectric performance. Here a new model system is reported for a better understanding of the key factors governing their thermoelectric properties: aligned, ribbon‐phase poly[2,5‐bis(3‐dodecylthiophen‐2‐yl)thieno[3,2‐b]thiophene] (PBTTT) doped by ion‐exchange doping. Using a range of microstructural and spectroscopic methods, the effect of controlled incorporation of tie‐chains between the crystalline domains is studied through blending of high and low molecular weight chains. The tie chains provide efficient transport pathways between crystalline domains and lead to significantly enhanced electrical conductivity of 4810 S cm −1 , which is not accompanied by a reduction in Seebeck coefficient or a large increase in thermal conductivity. Respectable power factors of 173 µW m −1 K −2 are demonstrated in this model system. The approach is generally applicable to a wide range of semicrystalline conjugated polymers and could provide an effective pathway for further enhancing their thermoelectric properties and overcome traditional trade‐offs in optimization of thermoelectric performance.

Chemistry↗
DOE OSTI2018

MXene-Conducting Polymer Asymmetric Pseudocapacitors

Conducting polymers (CPs) are attractive pseudocapacitive materials which show the highest capacitance under positive potentials in aqueous protic electrolytes. One way to expand their voltage window (thus energy density) in aqueous electrolytes is to manufacture asymmetric supercapacitors using distinctly different anodes. However, CPs lack matching pseudocapacitive anode materials that can perform well in protic electrolytes (e.g., sulfuric acid). 2D titanium carbide (Ti 3 C 2 T x ), MXene, as a universal pseudocapacitive anode material for a range of CPs, such as polyaniline, polypyrrole, and poly(3,4-ethylenedioxythiophene) deposited on reduced graphene oxide (rGO) sheets, is reported here. All-pseudocapacitive organic–inorganic asymmetric devices with MXene cathodes and rGO–polymer anodes can operate in voltage windows up to 1.45 V in 3 m H 2 SO 4 . Most importantly, these devices show outstanding cycling performance, outperforming many reported asymmetric pseudocapacitors.

catalysis (heterogeneous)↗
DOE OSTI2016

Efficient three-dimensional Poisson solvers in open rectangular conducting pipe

Three-dimensional (3D) Poisson solver plays an important role in the study of space-charge effects on charged particle beam dynamics in particle accelerators. In this paper, we propose three new 3D Poisson solvers for a charged particle beam in an open rectangular conducting pipe. These three solvers include a spectral integrated Green function (IGF) solver, a 3D spectral solver, and a 3D integrated Green function solver. These solvers effectively handle the longitudinal open boundary condition using a finite computational domain that contains the beam itself. This saves the computational cost of using an extra larger longitudinal domain in order to set up an appropriate finite boundary condition. Using an integrated Green function also avoids the need to resolve rapid variation of the Green function inside the beam. The numerical operational cost of the spectral IGF solver and the 3D IGF solver scales as , where is the number of grid points. The cost of the 3D spectral solver scales as , where is the maximum longitudinal mode number. We compare these three solvers using several numerical examples and discuss the advantageous regime of each solver in the physical application.

Computer Science↗
DOE OSTI2018

Three-dimensional conductive network formed by carbon nanotubes in aqueous processed NMC electrode [Three-dimensional conductive network formed by carbon nanotubes in aqueous processed NMC532 electrode]

Aqueous processing of lithium nickel manganese cobalt oxide (LiNi 0.5 Mn 0.3 Co 0.2 O 2 , NMC 532) cathodes was investigated by incorporating carbon nanotubes (CNTs) as the conductive additive. Morphology observation showed CNTs evenly disperse across the electrode, uniformly covering each primary particle, and form three-dimensional electronic pathways. A resistance measurement indicated the CNTs can improve the electronic conductivity of the composite electrode by an order of magnitude compared to carbon black. CNTs based electrodes showed higher rate performance, lower hysteresis, and better cycling performance with 99.4% capacity retention after 200 cycles in full pouch cells compared to 94.6% for carbon black based electrode. Meanwhile, the content of active materials in the electrode was increased from 90 wt% to 96 wt% and the energy density was increased by 11.7%. Furthermore, this research demonstrates an effective combined approach for achieving aqueous processed cathodes with enhanced durability while simultaneously achieving higher energy density by reducing the content of inactive components.

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

Superionic Conduction and Interfacial Properties of the Low Temperature Phase Li7P2S8Br0.5I0.5

Sulfide-based solid electrolytes are pursued for their application in bulk-type all-solid-state lithium batteries. Although the usefulness of Li10GeP2S12-type materials have been demonstrated in all-solid-state cathodes, a suitable material with both high ionic conductivity and good interfacial properties with common anode materials is still lacking. In this work, we explore the phase and transport properties of mechanically-milled Li7P2S8Br0.5I0.5, with emphasis on the favorable kinetics at Li metal anode. The low temperature crystalline phase Li7P2S8Br0.5I0.5 (LT-LPSBI) has exceptionally high ionic conductivity of 4.7 mS/cm at room temperature. Moreover, the LT-LPSBI supports long-term Li cycling at 0.5 mA cm-2 with low and stable interfacial resistance (5 O cm2). Transport phenomenon of Li/LT-LPSBI interface and cycling behavior of Li symmetric cells are studied and discussed in detail.

Wang, Yuxing↗
DOE OSTI2021

Conducting thermal energy to the membrane/water interface for the enhanced desalination of hypersaline brines using membrane distillation

Membrane distillation (MD) is a membrane-based thermal desalination process capable of treating hypersaline brines. Standard MD systems rely on preheating the feed to drive the desalination process. However, relying on the feed to carry thermal energy is limited by a decline of the thermal driving force as the water moves across the membrane, and temperature polarization. In contrast, supplying heat directly into the feed channel, either through the membrane or other channel surfaces, has the potential of minimizing temperature polarization, increasing single-pass water recoveries, and decreasing the number of heat exchangers in the system. When solar thermal energy can be utilized, particularly if the solar heat is optimally delivered to enhance water evaporation and process performance, MD processes can potentially be improved in terms of energy efficiency, environmental sustainability, or operating costs. Here we describe an MD process using layered composite membranes that include a high-thermal-conductivity layer for supplying heat directly to the membrane-water interface and the flow channel. Here, the MD system showed stable performance with water flux up to 9 L/m 2 /hr, and salt rejection >99.9% over hours of desalinating hypersaline feed (100 g/L NaCl). In addition to bench-scale system, we developed a computational fluid dynamics model that successfully described the transport phenomena in the system.

42 ENGINEERING↗
DOE OSTI2016

Structure and Conductivity of Semiconducting Polymer Hydrogels

Poly(fluorene-alt-thiophene) (PFT) is a conjugated polyelectrolyte that self-assembles into rod-like micelles in water, with the conjugated polymer backbone running along the length of the micelle. At modest concentrations (-10 mg/mL in aqueous solutions), PFT forms hydrogels, and this work focuses on understanding the structure and intermolecular interactions in those gel networks. The network structure can be directly visualized using cryo electron microscopy. Oscillatory rheology studies further tell us about connectivity within the gel network, and the data are consistent with a picture where polymer chains bridge between micelles to hold the network together. Addition of tetrahydrofuran (THF) to the gels breaks those connections, but once the THF is removed, the gel becomes stronger than it was before, presumably due to the creation of a more interconnected nanoscale architecture. Small polymer oligomers can also passivate the bridging polymer chains, breaking connections between micelles and dramatically weakening the hydrogel network. Fits to solution-phase small-angle X-ray scattering data using a Dammin bead model support the hypothesis of a bridging connection between PFT micelles, even in dilute aqueous solutions. Finally, time-resolved microwave conductivity measurements on dried samples show an increase in carrier mobility after THF annealing of the PFT gel, likely due to increased connectivity within the polymer network.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Wide Band Gap CuGa(S,Se) 2 Thin Films on Transparent Conductive Fluorinated Tin Oxide Substrates as Photocathode Candidates for Tandem Water Splitting Devices

Theaim of this report was to explore the potential of CuGa(S,Se)2 thin films as wide-E G top cell absorbers for photoelectrochemical (PEC) water splitting. A synthesis was developed on fluorinated tin oxide (FTO) photocathodes by converting copper-rich co-evaporated CuGaSe2 into CuGa(S,Se)2 via a post-deposition annealing. We found it necessary to first anneal CuGaSe2 at low-temperature in sulfur then at high-temperature in nitrogen to preserve the transparency and conductivity of the FTO. Using this two-step synthesis, we fabricated a 1.72eV CuGa(S,Se) 2 photocathode with a saturation current density and photocurrent onset potential of 10mA/cm 2 and -0.20V vs. RHE, respectively. Yet we found that the PEC performance and sub-E G transmittance, worsened with increasing copper content. Using flatband potential measurements and the Gerischer model, we show that divergences in PEC performance of CuGa(S,Se) 2 photocathodes can be explained by differences in conduction band minimums and Fermi levels. We also explain that sub-E G transmittance is likely hampered by a defect band 100-400 meV below E C . Additional external quantum efficiency measurements of a high-efficiency 1.1 eV Cu(In,Ga)Se 2 photovoltaic driver, while shaded by the CuGa(S,Se) 2 photocathode, yielded a short-circuit current density of 4.14 mA/cm 2 revealing that CuGa(S,Se) 2 reflects promise as a top cell for PEC water splitting.

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

High-Pressure Behavior of C 2 I 2 and Polymerization to a Conductive Polymer

Crystalline diiodoacetylene (C 2 I 2 ) was synthesized and then examined under high-pressure conditions using synchrotron X-ray diffraction, Raman/infrared spectroscopies, and first-principles calculations. At ~0.3 GPa, the starting tetragonal (P$_{4_{2}}$/n) phase, which is stabilized by donor-acceptor interactions, changes into a new orthorhombic structure (Cmca) that is more densely packed and analogous to the low-temperature phase of acetylene. Above approximately 4 GPa, compressed C 2 I 2 molecules in the Cmca structure begin to polymerize to form a predominantly sp 2 amorphous carbon network that maintains a significant fraction of C-I bonds. Transport measurements demonstrate that the polymeric material is electrically conducting. The magnitude of the electrical conductivity is similar to Br-doped polyacetylene and undoped trans-polyacetylene at 8 GPa and 1 atm, respectively. Elemental analyses performed on recovered samples show that the iodine concentration varies with specific processing conditions. Optimization of the pressure-induced polymerization pathway could allow for enhanced electrical properties to be realized, in addition to postpolymerization functionalization using the weak C-I bonds.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗