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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 1,027 records · Page 57
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Non-Conductive Polymers Enable Higher Ionic Conductivities and Suppress Reactivity in Hybrid Sulfide-Polymer Solid State Electrolytes

Hybrid ceramic-polymer solid state electrolytes are promising candidates to enable energy-dense lithium metal batteries by leveraging inorganic high ionic conductivity and flexible polymer mechanical properties. However, studies of hybrid electrolytes using sulfide-type inorganics such as Li3PS4 (LPS) have largely focused on combining the inorganic with commercial poly(ethylene oxide) (PEO). PEO has proven to be insufficient for use in hybrid systems because it reacts with LPS and provides a competing pathway for ion transport, therefore producing a hybrid with low conductivity. Our work shows that using nonconductive, nonpolar polyethylene (PE) in a hybrid electrolyte with LPS eliminates both polymer and inorganic degradation and remarkably exhibit higher conductivities than those containing PEO at different polymer and salt concentrations. Using tracer-exchange NMR, we observe that the nonconductive nature of PE allows for iontransport through the inorganic whereas PEO provides a separate, competing pathway for lithium transport. Furthermore, compared to pure LPS, these hybrids enable longer term lithium cycling at 60°C. Our work shows that the path to enabling conductive and stable sulfide hybrids for solid state lithium metal batteries may be through the use of nonconductive, nonreactive polymers.

batteries↗
DOE OSTI2023

Suppressing the Shuttle Effects with FeCo/SPAN Cathodes and High-Concentration Electrolytes for High-Performance Lithium–Sulfur Batteries

The shuttle effects and the sluggish redox kinetics are two of the main challenges in lithium–sulfur (Li–S) batteries, which significantly reduce the capacity of the batteries and restrict their commercialization. Herein, FeCo/sulfurized polyacrylonitrile (SPAN) is synthesized as a cathode material via the electrospinning technique and a further heat treatment. Synchrotron X-ray absorption spectroscopy confirmed the existence of Fe–S/Fe and Co–S bonds in FeCo/SPAN, which benefit the adsorptive and catalytic activities toward lithium polysulfides (LiPSs). Here, we further investigated the effect of electrolyte concentration in inhibiting the shuttle of LiPSs in Li–S batteries. Small-angle X-ray scattering (SAXS) reveals that more contact ion pairs are formed and fewer free solvent molecules exist with the increase of the electrolyte concentration, which can inhibit the dissolution and shuttle of LiPSs. Finally, the batteries assembled with high-concentration electrolytes (3 M LiTFSI in DOL/DME) exhibit a higher specific capacity retention compared to those assembled with low-concentration electrolytes. This work enriches the route to prepare Li–S batteries with the rational design of cathode materials and electrolytes.

25 ENERGY STORAGE↗
DOE OSTI2021

Effects of a Layered Morphology on Drip Suppression in Burning Polymers

Fire safety in polymers is critically important with products such as textiles and consumer goods, as well as materials used in construction, aerospace, transportation, and furniture. Additives used as anti-dripping and flame-retardant agents impose acute human health issues and have negative environmental impacts. With a focus on developing additive-free solutions, here we used multilayer coextrusion to fabricate layered polyethylene/polypropylene (PE/PP) films and investigated the effect of a layered morphology on dripping and burning rates. The experimental results for multilayered PE/PP samples were compared to control groups of melt blended PE/PP samples. The multilayer configuration provides two significant advantages: 154% delay in the time to the first drip and up to 87% reduction in the number of drips compared to the value for the melt blended samples with no additives. PE/PP blends with up to 2 wt % polytetrafluoroethylene, a commonly used anti-dripping agent in the industry, showed only 85% delay in the time to the first drip and about 60% reduction in the number of drips. We discovered a linear relationship between film thickness and burning rate, which allows for the use of the volumetric burning rate to normalize the effect of film thickness. No benefit in the burning rate was observed when comparing multilayered structures and conventional melt blended architectures or blends with PTFE. Annealing studies and transmission electron microscopy at areas close to the combustion zones confirmed that higher extensional viscosities induced by the layered structures and morphological changes due to the layer breakup play an important role in reducing dripping. By combining the first drip time and overall drip numbers, a parameter, “dripping index”, was defined to establish a fire safety map to simplify material comparisons. This study demonstrates that a multilayer film geometry can provide an additive-free solution to yield control over fire safety parameters in polymers.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Quantification of Shallow Defect Suppression in Aminosilane-Passivated Lead Halide Perovskites via Optical and Electrochemical Methods

We combine fluence-dependent photoluminescence (PL) and electrochemical characterization to estimate defect-dependent trapping rates, energetic distributions, and densities of defects, in lead halide perovskite films Cs 0.1 FA 0.9 PbI 3 and Cs 0.17 FA 0.83 Pb­(I 0.75 Br 0.25 ) 3 , before and after trap passivation with vapor-deposited (3-aminopropyl)­trimethoxysilane (APTMS). For both compositions, the PL studies show that energetically shallow subgap near-valence defect densities lead to bimolecular nonradiative recombination which is reduced by 92% after APTMS treatment. Electrochemical characterization of these same active layers shows for the first time that APTMS passivation impacts mainly on near-valence (mobile anionic) defects that decrease in density by 4 orders of magnitude, from 10 18 cm –3 to 10 14 cm –3 , as a result of silane modification. Here, the combination of PL and electrochemical characterization promises a unique approach to speciation and quantification of a broader distribution of trap states in perovskites and provides straightforward assessments of the efficacy of defect mitigation strategies.

Defects↗