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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 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Effect of overcharge on Li(Ni 0.5 Mn 0.3 Co 0.2 )O 2 /Graphite lithium ion cells with poly(vinylidene fluoride) binder. I - Microstructural changes in the anode

Cells based on NMC/graphite, containing poly(vinylidene difluoride) (PVDF) binders in the positive and negative electrodes, were systematically overcharged to 100, 120, 140, 160, 180, and 250% state-of-charge (SOC). At 250% SOC the cell vented. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) of the anodes showed several state-of-overcharge-dependent trends. Starting at 120% SOC, dendrites appeared and increased in concentration as the SOC increased. Dendrite morphology appeared to be dependent on whether the active material was on the “dull” or “shiny” side of the copper collector. Significantly more delamination of the active material from the collector was seen on the “shiny” side of the collector particularly at 180 and 250% SOC. Transition metals were detected at 120% SOC and increased in concentration as the SOC increased. Finally, there was considerable spatial heterogeneity in the microstructures across each laminate with several regions displaying complex layered structures.

25 ENERGY STORAGE↗
DOE OSTI2015

Poly(vinylidene fluoride)/ CaCu{sub 3}Ti{sub 4}O{sub 12} and La doped CaCu{sub 3}Ti{sub 4}O{sub 12} composites with improved dielectric and mechanical properties

Highlights: • High ϵ′ PVDF/CCTO and La doped CCTO composites prepared by Extrusion. • With addition of ceramic, there is substantial increase in the ϵ′ of matrix PVDF. • Composites exhibit double relaxation behavior. - Abstract: Melt extrusion process has been used to prepare high relative permittivity, ϵ' PVDF–CCTO and PVDF–LaCCTO composites. Phase composition has been studied using powder X-ray diffraction (XRD). Microstructural, dielectric and mechanical properties have also been studied. Young's modulus of PVDF increases with the ceramic reinforcement. Dielectric measurements are made in the frequency range 10{sup −2}–10{sup 6} Hz using two probe Novocontrol impedance analyser (ZG4) from room temp to 120 °C to study the dielectric relaxation. There is a substantial increase in ϵ' of the matrix PVDF on addition of LaCCTO.

36 MATERIALS SCIENCE↗
DOE OSTI2018

A superior composite gel polymer electrolyte of Li7La3Zr2O12- poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) for rechargeable solid-state lithium ion batteries

Highlights: • Solid electrolyte LLZO dispersed in PVDF-HFP matrix is studied. • Garnet inorganic fillers enhance the transport number of Li{sup +}. • Composite polymer electrolytes show superior electrochemical performance. • Coin cells (Li/PVDF-HFP: LLZO/LiFePO{sub 4}) show good cycling performance. - Abstract: High-quality solid electrolyte is essential for the growing need of lithium ion batteries. Herein, we report a novel organic-inorganic composite electrolyte based on Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12} ceramic powder incorporated into PVDF-HFP through a simple combined method. At room temperature, the composite polymer electrolyte (CPE) possesses a good ionic transmission improvement of 3.71 × 10{sup −4} S cm{sup −1}. The CPE behaves a fine lithium ion transference number of 0.58 and an electrochemical window of up to 4.65 V. CPEs display meliorative electrochemical stability compared to pure PVDF-HFP electrolyte. The cathode presents an excellent initial discharge capacity of 163.1 mAh g{sup −1} at 0.2 C in Li/CPE/LiFePO{sub 4} cell. The cell with CPE displays much better capacity retention than that with pure PVDF-HFP electrolyte. The Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12} modified PVDF-HFP is a promising electrolyte for lithium ion batteries.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Thermodynamic modeling of CsF with LiF-NaF-KF for molten fluoride-fueled reactors

Gibbs energy models were developed to describe the thermochemical behavior of CsF in molten FLiNaK (46.5LiF-11.5NaF-42KF mol%), a proposed molten salt reactor (MSR) fuel solvent and coolant, as cesium is of concern due to its high radiotoxicity and volatility. Initially, it was necessary to obtain a more accurate Gibbs energy function for CsF which required fitting parameters to reported vapor pressures over condensed phase CsF. The pseudo-binary systems CsF-LiF, CsF-NaF and CsF-KF were then evaluated utilizing phase equilibria and enthalpy of mixing (Δ mix H) values, together with original differential scanning calorimetry (DSC) measurements performed for the CsF-LiF and CsF-KF systems. The CsF-LiF-NaF, CsF-LiF-KF and CsF-NaF-KF pseudo-ternary system representations were obtained by interpolation of the constituent pseudo-binary systems, with DSC measurements performed for the CsF-LiF-NaF system to corroborate the calculated liquidus temperature. Ultimately, the pseudo-ternary systems were interpolated to obtain Gibbs energy models for the pseudo-quaternary CsF-LiF-NaF-KF system, supported by DSC measurements at low CsF compositions (1–10 mol%), yielding computed equilibria and cesium-containing vapor pressures that compare favorably with reported values. In conclusion, the Molten Salt Thermal Properties Database – Thermochemical (MSTDB-TC) was subsequently expanded to include these Gibbs energy models allowing description of the thermochemical behavior of the CsF-LiF-NaF-KF system.

11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗