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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Designing electrolytes with high solubility of sulfides/disulfides for high-energy-density and low-cost K-Na/S batteries

Alkaline metal sulfur (AMS) batteries offer a promising solution for grid-level energy storage due to their low cost and long cycle life. However, the formation of solid compounds such as M 2 S 2 and M 2 S (M = Na, K) during cycling limits their performance. Here we unveil intermediate-temperature K-Na/S batteries utilizing advanced electrolytes that dissolve all polysulfides and sulfides (K 2 S x , x = 1–8), significantly enhancing reaction kinetics, specific capacity, and energy density. These batteries achieve near-theoretical capacity (1655 mAh g -1 sulfur) at 75 °C with a 1 M sulfur concentration. At a 4 M sulfur concentration, they deliver 830 mAh g -1 at 2 mA cm -2 , retaining 71% capacity after 1000 cycles. This new K-Na/S battery with specific energy of 150-250 Wh kg -1 only employs earth-abundant elements, making it attractive for long-duration energy storage.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Ab initio free energies of liquid metal alloys: Application to the phase diagrams of Li-Na and K-Na

Comparison of free energies between different phases and different compositions underlies the prediction of alloy phase diagrams. To allow direct comparison, consistent reference points for the energies or enthalpies are required, and the entropy must be placed on an absolute scale, yielding absolute free energies. Here we derive absolute free energies of liquids from ab-initio molecular dynamics (AIMD) by combining the directly simulated enthalpies with an entropy derived from simulated densities and pair correlation functions. Additionally, as an example of the power of this method we calculate the phase diagrams of two binary alkali metal alloys, Li-Na and K-Na, revealing a critical point and liquid-liquid phase separation in the former case, and a deep eutectic in the latter. Good agreement with experimental data demonstrates the power of this simple method.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KNa2 by Materials Project

KNa2 is Hexagonal Laves structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. K is bonded in a 12-coordinate geometry to four equivalent K and twelve Na atoms. There are three shorter (4.56 Å) and one longer (4.58 Å) K–K bond lengths. There are nine shorter (4.37 Å) and three longer (4.38 Å) K–Na bond lengths. There are two inequivalent Na sites. In the first Na site, Na is bonded to six equivalent K and six equivalent Na atoms to form a mixture of corner, edge, and face-sharing NaK6Na6 cuboctahedra. All Na–Na bond lengths are 3.74 Å. In the second Na site, Na is bonded to six equivalent K and six Na atoms to form a mixture of corner, edge, and face-sharing NaK6Na6 cuboctahedra. There are two shorter (3.71 Å) and two longer (3.73 Å) Na–Na bond lengths.

36 MATERIALS SCIENCE↗