Ionic conductivity of solid barium fluoride
Ionic conductivity of solid barium fluoride
IONIC CONDUCTION↗
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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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Ionic conductivity and dielectric permittivity of PEO-LiClO{sub 4} solid polymer electrolyte plasticized with propylene carbonate
We have studied ionic conductivity and dielectric permittivity of PEO-LiClO{sub 4} solid polymer electrolyte plasticized with propylene carbonate. Differential scanning calorimetry and X-ray diffraction studies confirm minimum volume fraction of crystalline phase for the polymer electrolyte with 40 wt. % propylene carbonate. The ionic conductivity exhibits a maximum for the same composition. The temperature dependence of the ionic conductivity has been well interpreted using Vogel-Tamman-Fulcher equation. Ion-ion interactions in the polymer electrolytes have been studied using Raman spectra and the concentrations of free ions, ion-pairs and ion-aggregates have been determined. The ionic conductivity increases due to the increase of free ions with the increase of propylene carbonate content. But for higher content of propylene carbonate, the ionic conductivity decreases due to the increase of concentrations of ion-pairs and ion-aggregates. To get further insights into the ion dynamics, the experimental data for the complex dielectric permittivity have been studied using Havriliak–Negami function. The variation of relaxation time with temperature obtained from this formalism follows Vogel-Tamman-Fulcher equation similar to the ionic conductivity.
36 MATERIALS SCIENCE↗
Ionic conductivity of solid mixtures
Ionic conductivities of solid mixtures of lithium fluoride-lithium chloride, lithium chloride- potassium chloride, lithium fluoride-sodium chloride, and sodium chloride-potassium chloride
Fielder, W. L.↗
Simultaneously Boosting the Ionic Conductivity and Mechanical Strength of Polymer Gel Electrolyte Membranes by Confining Ionic Liquids into Hollow Silica Nanocavities
A central problem of solid polymer electrolytes is their inability to achieve robust mechanical strength with fast ionic conductivities required for commercialization of lithium metal batteries (LMBs). At present, state-of-the-art offers superiority of one at the expense of the other. Here, this dilemma has been solved by fabricating mechanically robust solid composite polymer electrolytes (SCPEs) with superior ionic conductivity (0.5 mS cm -1 at 20 °C) by confining ionic liquids (ILs) in the hollow scaffold offered by hollow silica (HS) nanospheres with unique architecture. Mechanical robustness was verified by the performance of a Li| |Li symmetric cell cycling for extended hours without short-circuiting. In addition, SCPEs with HS have higher thermal and electrochemical stabilities than those without HS, due to strong interaction and coordination of HS nanoparticles with polymer and ionic liquids. Electrode compatibility and flexibility of the membrane could advance the LMBs technology.
25 ENERGY STORAGE↗
Self-Assembly Behavior of an Oligothiophene-Based Conjugated Liquid Crystal and Its Implication for Ionic Conductivity Characteristics
Here, a joint experimental and computational study on the synthesis, selfassembly and ionic conduction characteristics of a new conjugated liquid crystal quaterthiophene/poly(ethylene oxide) (PEO4) consisting of terminal tetraethyleneglycol monomethyl ether groups on both ends of a quaterthiophene core. In agreement with molecular dynamic simulations, temperature-dependent grazing-incidence wide angle X-ray scattering and X-ray diffraction indicate that the molecule spontaneously forms a smectic phase at ambient temperature as characterized both in bulk and thin film configurations. Significantly, this smectic phase is maintained upon blending with bis(trifluoro-methanesulfonyl)imide (LiTFSI) as ion source at a concentration ratio up to r = [Li + ]/[EO] = 0.05. Nanosegregation between oligothiophene and PEO moieties and π-π stacking of thiophene rings led to the formation of efficient 2D pathways for ion transport, resulting in thin film in-plane ionic conductivity as high as 5.2 x 10 -4 S/cm -1 at 70°C and r = 0.05 as measured by electrochemical impedance spectroscopy (EIS). Upon heating the samples above a transition temperature around 95 °C, a less ordered phase forms associated with a pronounced drop in ionic conductivity. Finally, upon cooling, partial and local reordering of the conducting smectic domains leads to an ionic conductivity decrease compared to the as-cast state.
36 MATERIALS SCIENCE↗
Effect of Polymer Topology on Microstructure, Segmental Dynamics, and Ionic Conductivity in PEO/PMMA-Based Solid Polymer Electrolytes
We report Poly(ethylene oxide) (PEO)-based solid polymer electrolytes (SPEs) have attracted much interest due to their high ionic conductivity resulting from inherently fast segmental dynamics and high salt solubility, yet they lack mechanical stability in their neat form. Blending PEO with another rigid, or high glass transition temperature, polymer is a versatile way to improve the mechanical stability; however, the ionic conductivity is strongly reduced due to slower segmental dynamics of highly interpenetrating linear polymer chains. In this work, we used model PEO/PMMA blend systems prepared with various well-defined PEO architectures (linear, stars, hyperbranched, and bottlebrushes) doped with lithium bis(trifluoromethane-sulfonyl)-imide (LiTFSI) and investigated, for the first time, the role of macromolecular architecture of PEO on crystallization, segmental dynamics, and ionic conductivity in the blends and electrolytes. The results suggest that room-temperature miscibility of these polymers can be dramatically extended by using nonlinear PEO in the blends instead of linear chains, which crystallize above 35 wt %. The broadband dielectric spectroscopy results revealed enhanced decoupling of PMMA and PEO segmental dynamics in compact branched architectures, which helps to achieve faster segmental motion of star PEO in glassy PMMA. This manifests as nearly three-fold higher ionic conductivity in these nonlinear blends compared to the conventional linear PEO/PMMA system. Regardless of the PEO architectures, the temperature dependence of ionic conductivity blends with PMMA and LiTFSI is well defined using the Vogel–Fulcher–Tammann mechanism, suggesting that ion transport is mainly affected by the segmental motion. The activation energy values decrease with the increasing ionic conductivity. Overall, our results show that macromolecular architecture can be a tool to decouple segmental dynamics and ion mobility to rationally design SPEs with improved performance.
36 MATERIALS SCIENCE↗
Interpreting Ionic Conductivity for Polymer Electrolyte Fuel Cell Catalyst Layers with Electrochemical Impedance Spectroscopy and Transmission Line Modeling
A cathode catalyst layer containing optimally distributed ionomer is critical to reduce the platinum loading and increase its utilization in polymer electrolyte fuel cells. Here, electrochemical impedance spectroscopy (EIS) was used to measure effective ionic conductivity of pseudo catalyst layers (PCLs) at a relative humidity (RH) range of 50%-120%. These results are compared to previous work using the hydrogen pump (HP) method. EIS effective ionic conductivity results reported here are higher than those from the HP because in the HP set-up ionic pathways must be effectively connected through the PCL to be counted, whereas in the EIS measurement, ionomer segments that are in contact with the membrane but are not effectively connected all the way through the PCL can be detected. Double layer capacitances and effective ionic conductivities of Pt/C catalyst layers with various supports and ionomer to carbon (I/C) ratios were studied. High surface area carbon support resulted in a lower effective ionic conductivity compared to the graphitized carbon support due to worse ionomer dispersion. Effective ionic conductivities of Pt/C layers were compared to that of PCLs. On average, effective ionic conductivities of Pt/C layers were higher than PCLs because of possible carbon agglomeratio n within the PCLs.
25 ENERGY STORAGE↗
Effects of Mechanical Strain on Ionic Conductivity in the Interface between LiPON and Ni-Mn Spinel
We present first-principles calculations to understand ionic conductivity in the interface between lithium phosphorous oxynitride (LiPON) and Ni-Mn spinel (LNM), with emphasis on the effect of mechanical strain. Two LiPON/LNM interfaces, one with and the other without BaTiO3 (BTO) additive, are modeled as abrupt interfaces to minimize the effects of the space-charge layer formation. It is observed that the interface with BTO additive has higher ionic conductivity than the other. Comparison of structural geometry indicates that the LiPON part of the LiPON/LNM interface is contracted but it recovers with BTO additive, which suggests the relevance of mechanical strain to ionic conductivity in these interfaces and the role of BTO in controlling the mechanical strain. The activation energy barriers of Li-hopping in a bulk LiPON, calculated at different levels of mechanical strain, exhibit a significant increase with compressive strain, supporting the suggested effect of mechanical strain in the interfaces. Lastly, this result implies that ionic conductivity in the interface between LiPON and cathode can be enhanced by modifying the interface but with appropriate size and distribution of additives.
25 ENERGY STORAGE↗
SECTION C, PHYSICAL SCIENCES. ROCKET-BORNE INSTRUMENTATION EQUIPMENT FOR IONIC CONDUCTIVITY STUDIES IN THE UPPER ATMOSPHERE
Ionic conductivity studies in upper atmosphere - instrumentation - aerobee rocket payload design
AEROBEE ROCKET↗
Ionic conductivity of calcium and strontium fluorides
Ionic conductivity of single crystals of calcium and strontium fluorides
IONIC CONDUCTION↗
Vertically Aligned and Continuous Nanoscale Ceramic–Polymer Interfaces in Composite Solid Polymer Electrolytes for Enhanced Ionic Conductivity
Among all solid electrolytes, composite solid polymer electrolytes, comprised of polymer matrix and ceramic fillers, garner great interest due to the enhancement of ionic conductivity and mechanical properties derived from ceramic–polymer interactions. Here, we report a composite electrolyte with densely packed, vertically aligned, and continuous nanoscale ceramic–polymer interfaces, using surface-modified anodized aluminum oxide as the ceramic scaffold and poly(ethylene oxide) as the polymer matrix. The fast Li + transport along the ceramic–polymer interfaces was proven experimentally for the first time, and an interfacial ionic conductivity higher than 10 –3 S/cm at 0 °C was predicted. The presented composite solid electrolyte achieved an ionic conductivity as high as 5.82 × 10 –4 S/cm at the electrode level. In conclusion, the vertically aligned interfacial structure in the composite electrolytes enables the viable application of the composite solid electrolyte with superior ionic conductivity and high hardness, allowing Li–Li cells to be cycled at a small polarization without Li dendrite penetration.
36 MATERIALS SCIENCE↗
Influence of temperature and frequency on ionic conductivity of Li{sub 3}PO{sub 4}–Pb{sub 3}(PO{sub 4}){sub 2}–BiPO{sub 4} phosphate glasses
Highlights: • Results of ionic conductivities of Li{sub 3}PO{sub 4}–Pb{sub 3}(PO{sub 4}){sub 2}–BiPO{sub 4} phosphate glasses. • Determination of glass transition temperature using DSC method. • Study of temperature and frequency on ionic conductivity of Li{sub 3}PO{sub 4}–Pb{sub 3}(PO{sub 4}){sub 2}–BiPO{sub 4} phosphate glasses. - Abstract: Lithium–Lead–Bismuth phosphates glasses having, a composition 30Li{sub 3}PO{sub 4}–(70 − x)Pb{sub 3}(PO{sub 4}){sub 2}–xBiPO{sub 4} (45 ≤ x ≤ 60 mol%) were prepared by using the melt quenching method 1000 °C. The thermal stability of theses glasses increases with the substitution of Bi{sub 2}O{sub 3} with PbO. The ionic conductivity of all compositions have been measured over a wide temperature (200–500 °C) and frequency range (1–106 Hz). The ionic conductivity data below and above T{sub g} follows Arrhenius and Vogel–Tamman–Fulcher (VTF) relationship, respectively. The activation energies are estimated and discussed. The dependence in frequency of AC conductivity is found to obey Jonscher’s relation.
36 MATERIALS SCIENCE↗
Microstructural impacts on ionic conductivity of oxide solid electrolytes from a combined atomistic-mesoscale approach
Abstract Although multiple oxide-based solid electrolyte materials with intrinsically high ionic conductivities have emerged, practical processing and synthesis routes introduce grain boundaries and other interfaces that can perturb primary conduction channels. To directly probe these effects, we demonstrate an efficient and general mesoscopic computational method capable of predicting effective ionic conductivity through a complex polycrystalline oxide-based solid electrolyte microstructure without relying on simplified equivalent circuit description. We parameterize the framework for Li 7- x La 3 Zr 2 O 12 (LLZO) garnet solid electrolyte by combining synthetic microstructures from phase-field simulations with diffusivities from molecular dynamics simulations of ordered and disordered systems. Systematically designed simulations reveal an interdependence between atomistic and mesoscopic microstructural impacts on the effective ionic conductivity of polycrystalline LLZO, quantified by newly defined metrics that characterize the complex ionic transport mechanism. Our results provide fundamental understanding of the physical origins of the reported variability in ionic conductivities based on an extensive analysis of literature data, while simultaneously outlining practical design guidance for achieving desired ionic transport properties based on conditions for which sensitivity to microstructural features is highest. Additional implications of our results are discussed, including a possible connection between ion conduction behavior and dendrite formation.
25 ENERGY STORAGE↗
Unveiling the critical role of interfacial ionic conductivity in all-solid-state lithium batteries
Advancement of all-solid-state lithium-ion (Li + ) batteries (ASSLIBs) has been hindered by the large interfacial resistance mainly originating from interfacial reactions between oxide cathodes and solid-state sulfide electrolytes (SEs). To suppress the interfacial reactions, an interfacial coating layer between cathodes and SEs is indispensable. However, the kinetics of interfacial Li + transport across the coating layer has not been well understood yet. Herein, we tune the interfacial ionic conductivity of the coating layer LiNb 0.5 Ta 0.5 O 3 (LNTO) by manipulating post-annealing temperature. It is found that the interfacial ionic conductivity determines interfacial Li + transport kinetics and enhancing the interfacial ionic conductivity can significantly boost the electrochemical performance of SE-based ASSLIBs. A representative cathode LiNi 0.5 Mn 0.3 Co 0.2 O 2 coated by LNTO with the highest interfacial ionic conductivity exhibits a high initial capacity of 152 mAh.g -1 at 0.1 C and 107.5 mAh.g -1 at 1C. This work highlights the importance of increasing interfacial ionic conductivity for high-performance SE-based ASSLIBs.
25 ENERGY STORAGE↗
Ionic Conductivity Enhancement of Polymer Electrolytes by Directed Crystallization
Here, we report that hot stretching of poly(ethylene oxide) (PEO)-based solid polymer electrolytes (SPEs) can lead to a preferred orientation of PEO crystalline lamellae, thereby reducing the tortuosity of the ion-conduction pathway along the thickness direction of the SPE film, causing improved ionic conductivity. The hot stretching method is implemented by stretching SPE films above the melting point of PEO in an inert environment followed by crystallization at room temperature while maintaining the applied strain. The effect of hot stretching on the crystalline orientation, crystallinity, morphology, and ion transport in PEO with two types of salts, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium triflate (LiCF3SO3), is investigated in detail. Wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS) show that the orientation of PEO crystalline lamellae induces the formation of a short ion-conduction pathway along the through-plane direction of the SPE films, leading to 1.4- to 3.5-fold enhancement in the through-plane ionic conductivity.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Designing Optimal Perovskite Structure for High Ionic Conduction
Solid-oxide fuel/electrolyzer cells are limited by a dearth of electrolyte materials with low ohmic loss and an incomplete understanding of the structure-property relationships that would enable the rational design of better materials. In this work, using epitaxial thin-film growth, synchrotron radiation, impedance spectroscopy, and density-functional theory, the impact of structural parameters (i.e., unit-cell volume and octahedral rotations) on ionic conductivity is delineated in La 0.9 Sr 0.1 Ga 0.95 Mg 0.05 O 3-σ . As compared to the zero-strain state, compressive strain reduces the unit-cell volume while maintaining large octahedral rotations, resulting in a strong reduction of ionic conductivity, while tensile strain increases the unit-cell volume while quenching octahedral rotations, resulting in a negligible effect on the ionic conductivity. Calculations reveal that larger unit-cell volumes and octahedral rotations decrease migration barriers and create low-energy migration pathways, respectively. The desired combination of large unit-cell volume and octahedral rotations is normally contraindicated, but through the creation of superlattice structures both expanded unit-cell volume and large octahedral rotations are experimentally realized, which result in an enhancement of the ionic conductivity. All told, the potential to tune ionic conductivity with structure alone by a factor of ≈ 2.5 at around 600 degrees C is observed, which sheds new light on the rational design of ion-conducting perovskite electrolytes.
36 MATERIALS SCIENCE↗
Structure and Ionic Conductivity of Polystyrene-block-poly(ethylene oxide) Electrolytes in the High Salt Concentration Limit
We explore the relationship between the morphology and ionic conductivity of block copolymer electrolytes over a wide range of salt concentrations for the system polystyrene-block-poly(ethylene oxide) (PS-b-PEO, SEO) mixed with lithium bis-(trifluoromethanesulfonyl)imide salt (LiTFSI). Two SEO polymers were studied, SEO(16-16) and SEO(4.9-5.5), over the salt concentration range r = 0.03-0.55. The numbers x and y in SEO(x-y) are the molecular weights of the blocks in kg mol -1 , and the r value is the molar ratio of salt to ethylene oxide moieties. Small-angle X-ray scattering was used to characterize morphology and grain size at 120 °C, differential scanning calorimetry was used to study the crystallinity and the glass transition temperature of the PEO-rich microphase, and ac impedance spectroscopy was used to measure ionic conductivity as a function of temperature. The most surprising observation of our study is that ionic conductivity in the concentration regime 0.11 ≤ r ≤ 0.21 increases in SEO electrolytes but decreases in PEO electrolytes. The maximum in ionic conductivity with salt concentration occurs at about twice the salt concentration in SEO (r = 0.21) as in PEO (r = 0.11). Here, we propose that these observations are due to the effect of salt concentration on the grain structure in SEO electrolytes.
36 MATERIALS SCIENCE↗
Microtube-Membrane Methodology for Electrochemical Synthesis and Study of Electroactive and Ionically Conductive Materials, and the Conductivity of MnO 2
A membrane-based methodology for electrochemical synthesis and study of electroactive and ionically conductive materials is described. The Li + -intercalation material MnO 2 was used to demonstrate this methodology. The membrane was a polymeric support containing monodisperse gold microtubes (diameter 600 nm) that span the thickness of the membrane. Bipolar electrochemical synthesis of MnO 2 , from Mn 2+ solutions, was conducted across this membrane, resulting in deposition of monodisperse, hemispherical MnO 2 particles at the open ends of the tubes on one face of the membrane. The resulting microtube/MnO 2 composite membrane makes a convenient construct for investigating the transport properties of the MnO 2 particles. This was accomplished by mounting the membrane in a U-tube cell, placing electrolyte solutions on either side, and driving an ionic current through the membrane. The ionic conductivity of MnO 2 was measured in this way, and found to be 40±10 μS cm -1 when LiCl or LiClO 4 solutions were used as the electrolyte. Finally, the mechanism of ionic conductivity through these MnO 2 particles is discussed.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗