Showing papers on "Ionic conductivity published in 1999"
TL;DR: In this paper, the specific ionic conductivity, dynamic viscosity, and electrochemical stability of several imidazolium salts are reported as neationic liquids and their solutions in several organic solvents.
Abstract: The specific ionic conductivity, dynamic viscosity, and electrochemical stability of several imidazolium salts are reported as neationic liquids and their solutions in several organic solvents. The temperature dependence of conductivity and viscosity are analyzed for 1‐ethyl‐3‐methylimidazolium and 1,2‐dimethyl‐3‐n‐propylimidazolium salts, and the influence of theanions bis(trifluoromethylsulfonyl)imide , bis(perfluoroethylsulfonyl)imide , hexafluoroarsenate , hexafluorophosphate , and tetrafluoroborate on these properties are discussed. These imidazolium salts make possible electrolytes with high concentration (>3 M), high room temperature conductivity (up to 60 mS/cm), and a wide window of stability . Differential scanning calorimetric results confirm a large glass phase for the ionic liquids, with substantial (>80°C) supercooling. Thermal gravimetric results indicate the imidazolium salts with and anions to be thermally more stable than the lithium salt analogs. The Vogel‐Tammann‐Fulcher interpretation accurately describes the conductivity temperature dependence. © 1999 The Electrochemical Society. All rights reserved.
810 citations
TL;DR: In this article, the authors comprehensively review the structures, thermal expansion, phase transitions, electrical conductivity and stability of bismuth oxide and doped Bismuth Oxide systems and show that they exhibit a complex array of structures and properties depending upon the dopant concentration, temperature and atmosphere.
Abstract: Bismuth oxide systems exhibit high oxide ion conductivity and have been proposed as good electrolyte materials for applications such as solid oxide fuel cells and oxygen sensors. However, due to their instability under conditions of low oxygen partial pressures there has been difficulty in developing these materials as alternative electrolyte materials compared to the state-of-the-art cubic stabilised zirconia electrolyte. Bismuth oxide and doped bismuth oxide systems exhibit a complex array of structures and properties depending upon the dopant concentration, temperature and atmosphere. In this paper we comprehensively review the structures, thermal expansion, phase transitions, electrical conductivity and stability of bismuth oxide and doped bismuth oxide systems. ©
614 citations
TL;DR: In this paper, the authors describe a class of materials, prepared by doping lithium ions into a plastic crystalline matrix, that exhibit fast lithium ion motion due to rotational disorder and the existence of vacancies in the lattice.
Abstract: Rechargeable lithium batteries have long been considered an attractive alternative power source for a wide variety of applications. Safety and stability1 concerns associated with solvent-based electrolytes has necessitated the use of lithium intercalation materials (rather than lithium metal) as anodes, which decreases the energy storage capacity per unit mass. The use of solid lithium ion conductors—based on glasses, ceramics or polymers—as the electrolyte would potentially improve the stability of a lithium-metal anode while alleviating the safety concerns. Glasses and ceramics conduct via a fast ion mechanism, in which the lithium ions move within an essentially static framework. In contrast, the motion of ions in polymer systems is similar to that in solvent-based electrolytes—motion is mediated by the dynamics of the host polymer, thereby restricting the conductivity to relatively low values. Moreover, in the polymer systems, the motion of the lithium ions provides only a small fraction of the overall conductivity2, which results in severe concentration gradients during cell operation, causing premature failure3. Here we describe a class of materials, prepared by doping lithium ions into a plastic crystalline matrix, that exhibit fast lithium ion motion due to rotational disorder and the existence of vacancies in the lattice. The combination of possible structural variations of the plastic crystal matrix and conductivities as high as 2 × 10-4 S cm-1 at 60 °C make these materials very attractive for secondary battery applications.
556 citations
TL;DR: The physical and chemical properties of a new class of lithium conducting polymer electrolytes formed by dispersing ceramic powders at the nanoscale particle size into a poly(ethylenoxide) (PEO)− lithium salt, LiX complexes, are reported and discussed in this paper.
Abstract: The physical and chemical properties of a new class of lithium conducting polymer electrolytes formed by dispersing ceramic powders at the nanoscale particle size into a poly(ethylenoxide) (PEO)− lithium salt, LiX complexes, are reported and discussed. These true solid-state PEO−LiX nanocomposite polymer electrolytes have in the 30−80 °C range an excellent mechanical stability (due to the network of the ceramic fillers into the polymer bulk) and high ionic conductivity (promoted by the high surface area of the dispersed fillers). These important and unique properties are accompanied by a wide electrochemical stability and by a good compatibility with the lithium electrode (assured by the absence of any liquids and by the interfacial stabilizing action of the dispersed filler), all this making these nanocomposite electrolytes of definite interest for the development of advanced rechargeable lithium batteries.
490 citations
TL;DR: The relationship between the ionic conductivity and the sum of the diffusion coefficients of the lithium ion and the anion gives the degree of ion-pair formation and permits the roles of the solvents in the electrolytes to be clearly explained.
Abstract: The self-diffusion coefficients of the lithium ion, the anion, and the solvent in lithium bis(trifluromethanesulfonyl)imide (LiTFSI, LiN(SO2CF3)2) solvent systems were measured using the pulse-gradient spin-echo (PGSE) NMR method. Fourteen different organic solvents that are commonly used as organic solution electrolytes in lithium batteries were studied. The self-diffusion coefficients of the corresponding pure solvents were also measured. Since a good correlation between the self-diffusion coefficients of the pure solvents and the inverse of the viscosity was obtained, the results are discussed in terms of the Stokes-Einstein equation. Comparisons of the self-diffusion coefficients of the solvent, the lithium ion, and the anion (TFSI ion) illustrate the solvation behavior for each solvent. The relationship between the ionic conductivity and the sum of the diffusion coefficients of the lithium ion and the anion gives the degree of ion-pair formation and permits the roles of the solvents in the electrolytes to be clearly explained.
314 citations
TL;DR: In this article, the authors proposed a scaling approach, requiring no arbitrary parameters, for the analysis of the ac conductivity resulting from ionic motion in glasses, but this approach cannot be applied to alkali germanate glasses whose alkali content varies by more than a decade.
Abstract: In a recent Letter, Roling et al. [Phys. Rev. Lett. 78, 2160 (1997)] proposed a novel scaling approach, requiring no arbitrary parameters, for the analysis of the ac conductivity resulting from ionic motion in glasses. However, this approach cannot be applied to alkali germanate glasses whose alkali content varies by more than a decade, since changes which occur in the ion hopping length that accompany the changing alkali content are not incorporated. Here, I show that these changes can be incorporated into a universally valid approach which successfully scales the ac conductivity of sodium germanate glasses as well as two additional ionic systems without the introduction of arbitrary parameters.
252 citations
245 citations
TL;DR: In this article, a composite electrolyte based on poly(ethylene oxide) (PEO) has been prepared by using LiClO4 and LiN(CF3SO2)2 as doping salts, and nanoscale SiO2 as the filler.
240 citations
TL;DR: In this paper, it was shown that the dielectric response of many materials exhibits universal behavior in the form of a power law frequency dependence of the ac conductivity, which is seen in all types of structures both crystalline and amorphous.
Abstract: The dielectric response of many materials exhibits universal behavior in the form of a power law frequency dependence of the ac conductivity. This response is seen in all types of structures both crystalline and amorphous and for all types of polarizing species including dipoles and ions. Here I demonstrate that for ionic materials the power law exponent decreases with decreasing dimensionality of the ion conduction pathways. Although percolation concepts such as random walks on a self-similar fractal lattice provide a qualitative explanation, experimental findings instead indicate that the dispersion is the result of localized ion motion occurring on an atomic length scale. {copyright} {ital 1999} {ital The American Physical Society }
231 citations
TL;DR: Bunde et al. as discussed by the authors showed that the percolation theory leads to the consistent description of most puzzling conduction effects for both direct current (dc) and alternating current (ac) conductivity.
Abstract: Conduction mechanism in ionic glasses is still considered one of the great challenges in physics and chemistry of glasses [A. Bunde, K. Funke, and M. Ingram, Solid State Ionics 105, 1 (1998)]. We show that consequent application of the routine percolation theory leads to the consistent description of most puzzling conduction effects for both direct current (dc) and alternating current (ac) conductivity. Moreover, comparison of the theoretical results with experimental data reveals the well-known random-energy model suggested a few decades ago for ionic transport in glasses as a very plausible model. The results provide a general basis for the study of transport phenomena in ionic glasses.
226 citations
TL;DR: In this article, the authors measured the thermal expansion coefficients of the ceramic materials, calculated from dilatometric data, are in the range (10.5-13.2) × 10============ −6============ -1======
Abstract: The solid solutions La
2
Ni
1–x
Fe
x
O
4+δ
(x = 0.02 and 0.10), La
1.9
Sr
0.1
Ni
1 – x
Fe
x
O
4 + δ
(x = 0.02 and 0.10) and La
2
Ni
0.88
Fe
0.02
Cu
0.10
O
4+δ
with the tetragonal K
2
NiF
4
-type structure were prepared by a standard ceramic technique. The thermal expansion coefficients of the ceramic materials, calculated from dilatometric data, are in the range (10.5–13.2) × 10
–6
K
–1
at 300–1100 K. Oxygen permeation fluxes through dense La
2
NiO
4 + δ
-based membranes at 970–1170 K were found to be limited by both surface exchange and bulk ionic transport, whereas the limiting effect of the oxygen interphase exchange increases with decreasing oxygen pressure at the membrane permeate side and with decreasing temperature. Applying porous cermet layers of dispersed platinum and praseodymium oxide onto the membrane surface results in enhanced permeation fluxes. The maximum oxygen permeability was found for the La
2
Ni
0.98
Fe
0.02
O
4+δ
and La
2
Ni
0.88
Fe
0.02
Cu
0.10
O
4+δ
solid solutions; oxygen permeability data demonstrated that a vacancy diffusion mechanism and oxygen interstitial migration make significant contributions to the total ionic conductivity.
TL;DR: In this article, the authors examined the correlation between the electrical conductivity of perovskite-type oxides and the structurally related parameters, such as tolerance factor, specific free volume and oxygen deficiency.
TL;DR: In this paper, a network polymer electrolyte with hyperbranched ether side chains was synthesized, and a monosubstituted epoxide monomer, 2-(...
Abstract: To achieve solvent-free polymer electrolytes with high ionic conductivity, network polymer electrolytes with hyperbranched ether side chains were synthesized. A monosubstituted epoxide monomer, 2-(...
TL;DR: In this paper, the crystal structure, electrical conductivity and thermal expansion of oxides were studied using X-ray diffraction, four-point DC and dilatometry, respectively.
TL;DR: In this paper, the ion-conduction properties of a polyethylene oxide (PEO)-based composite polymer electrolyte comprised of PEO, LiClO{sub 4, and the ferroelectric material BaTiO(sub 3) were studied.
Abstract: The ion-conduction properties of a polyethylene oxide (PEO)-based composite polymer electrolyte comprised of PEO, LiClO{sub 4}, and the ferroelectric material BaTiO{sub 3} were studied. The addition of BaTiO{sub 3} resulted in an increase in conductivity over the temperature range 25--115 C. The optimum amount of BaTiO{sub 3} (purity 99.9%, particle size 0.6--1.2 {micro}m) was 1.4 wt %, which is very low in comparison with previously reported composite polymer electrolytes. The ionic conductivity of a composite polymer electrolyte containing 1.4 wt % BaTiO{sub 3} was 1 {times} 10{sup {minus}5} S/cm at 25 C, which is at least one order of magnitude higher than that of the pristine polymer electrolyte (4 {times} 10{sup {minus}7} S/cm). The transport number of the lithium ion in this composite polymer electrolyte was higher than that of the pristine polymer electrolyte. The increase in the conductivity and the lithium-ion transport number is explained on the basis of the spontaneous polarization of the ferroelectric material due to its particular crystal structure. The addition of BaTiO{sub 3} powder greatly enhanced the lithium/electrolyte interface stability.
TL;DR: Using N-carbobenzyloxy-l-isoleucylaminooctadecane as a low molecular weight gelator for polar solvents, organogel electrolytes were prepared from supporting electrolyte and a polar solvent such as DMF, DMSO, and PC by physical gelation as mentioned in this paper.
Abstract: Using N-carbobenzyloxy-l-isoleucylaminooctadecane as a low molecular weight gelator for polar solvents, organogel electrolytes were prepared from supporting electrolyte and a polar solvent such as DMF, DMSO, and PC by physical gelation. The ionic conductivity of the prepared organogel electrolytes decreased very slightly with increasing concentration of gelator, while the gel strength drastically increased with increasing concentration. The organogel prepared from DMF exhibited relatively high ionic conductivity, interpreted due to the high mobility of carrier ions in the low-viscosity DMF. Arrhenius plots of ionic conductivities of organogel electrolytes indicate that the behavior of supporting electrolytes in the organogels is essentially similar to that in the isotropic solution, and the ionic mobility of supporting electrolytes is scarcely affected by the gelator molecules. The optimal concentration of supporting electrolytes in organogel electrolytes to achieve both high conductivity and high gel str...
TL;DR: In this paper, the feasibility of a monolithic, fully inorganic solid state lithium battery is investigated and the reproducibility of the high reported ionic conductivity of Li13Al03Ti17(PO4)3 and the lithium-rich and lithiumpoor stability limits have been investigated.
TL;DR: In this paper, a single crystal of hexagonal apatite type Nd 9·33 (SiO 4 ) 6 O 2 which is an oxide ionic conductor was prepared by the FZ method and an anisotropy of its conductivity was investigated.
Abstract: Single crystal of hexagonal apatite type Nd 9·33 (SiO 4 ) 6 O 2 which is an oxide ionic conductor was prepared by the FZ method and an anisotropy of its conductivity was investigated. The conductivity of a parallel component to a c-axis (2·1×10 −8 S cm −1 at 30°C) was higher about one order of magnitude, compared with that of perpendicular component.
TL;DR: In this paper, the structural and electrical properties of NASICON-type compounds in the system Li1+xAlxA2−xIV(PO4)3 (AIV=Ti or Ge) are described.
Abstract: Preparations and physico-chemical characterizations of NASICON-type compounds in the system Li1+xAlxA2−xIV(PO4)3 (AIV=Ti or Ge) are described. Ceramics have been fabricated by sol-gel and co-grinding processes for use as ionosensitive membrane for Li+ selective electrodes. The structural and electrical characteristics of the pellets have been examined. Solid solutions are obtained with Al/Ti and Al/Ge substitutions in the range 0≤x≤0·6. A minimum of the rhombohedral c parameter appears for x about 0·1 for both solutions. The grain ionic conductivity has been characterized only in the case of Ge-based compounds. It is related to the carrier concentration and the structural properties of the NASICON covalent skeleton. The results confirm that the Ti-based framework is more calibrated to Li+ migration than the Ge-based one. A grain conductivity of 10−3 S cm−1 is obtained at 25°C in the case of Li1·3Al0·3Ti1·7(PO4)3. A total conductivity of about 6×10−5 S cm−1 is measured on sintered pellets because of grain boundary effects. The use of such ceramics in ISE devices has shown that the most confined unit cell (i.e. in Ge-based materials) is more appropriate for selectivity effect, although it is less conductive.©
TL;DR: In this paper, the authors describe ionic conductivities in the 7 × 10-5 to 7× 10-10 Ω-1 cm-1 range, which permit microelectrode voltammetry in the undiluted materials, examples of which are presented.
Abstract: Interesting ionic materials can be transformed into room temperature molten salts by combining them with polyether-tailed counterions such as polyether-tailed 2-sulfobenzoate (MePEG-BzSO3-) and polyether-tailed triethylammonium (MePEG-Et3N+). Melts containing ruthenium hexamine, metal trisbipyridines, metal trisphenanthrolines, and ionic forms of aluminum quinolate, anthraquinone, phthalocyanine, and porphyrins are described. These melts exhibit ionic conductivities in the 7 × 10-5 to 7 × 10-10 Ω-1 cm-1 range, which permit microelectrode voltammetry in the undiluted materials, examples of which are presented.
TL;DR: In this article, the structure, thermal expansion coefficients and ionic and electronic conductivities of Ce1−xPrxO2−δ (x=0.50) solid solutions, prepared hydrothermally for the first time, were investigated.
TL;DR: In this article, an exhaustive collection of dielectric relaxation data of glassy, crystalline, and molten ionic conductors are analyzed to obtain the magnitudes of their constant losses and the dependencies on temperature, ion density, ion mass, dc conductivity activation energy, dcconductivity level, the nonexponential conductivity relaxation parameter β, the mixed alkali effect, and the decoupling index Rτ.
Abstract: A frequency independent or nearly frequency independent contribution to the dielectric loss is present in all ionic conductors independent of the chemical and physical structures. An exhaustive collection of dielectric relaxation data of glassy, crystalline, and molten ionic conductors are analyzed to obtain the magnitudes of their constant losses and the dependencies on temperature, ion density, ion mass, dc conductivity activation energy, dc conductivity level, the nonexponential conductivity relaxation parameter β, the mixed alkali effect, and the decoupling index Rτ. Trends of changes in the constant loss when modifying the structure of the glassy matrix or mixing two different alkali ions are also found. In a glass-forming molten salt, 0.4Ca(NO3)2⋅0.6KNO3, the constant loss turns out to have approximately the same temperature dependence as the mean square displacement of the ions obtained by elastic neutron scattering measurement. All dependencies and properties found indicate that the physical origin of the constant loss may be traced to the displacement of the ions in their local librational or vibrational motion, but anharmonicity is not a necessary ingredient.
Patent•
02 Sep 1999
TL;DR: A wide range of solid polymer electrolytes characterized by high ionic conductivity at room temperature, and below, are disclosed in this article, which are suitable for use in electrochemical cells and batteries.
Abstract: A wide range of solid polymer electrolytes characterized by high ionic conductivity at room temperature, and below, are disclosed. These all-solid-state polymer electrolytes are suitable for use in electrochemical cells and batteries. A preferred polymer electrolyte is a cationic conductor which is flexible, dry, non-tacky, and lends itself to economical manufacture in very thin film form. Solid polymer electrolyte compositions which exhibit a conductivity of at least approximately 10?-3 - 10-4? S/cm at 25°C comprise a base polymer or polymer blend containing an electrically conductive polymer, a metal salt, a finely divided inorganic filler material, and a finely divided ion conductor. The new solid polymer electrolytes are combinable with various negative electrodes such as an alkali metal, alkaline earth metal, transition metal, ion-insertion polymers, ion-insertion inorganic electrodes, carbon insertion electrodes, tin oxide electrode, among others, and various positive electrodes such as ion-insertion polymers and ion-insertion inorganic electrodes to provide batteries and supercapacitors having high specific energy (Wh/kg) (gravimetric) and energy density (Wh/l) (volumetric), high cycle life, low self-discharge and providing improved safety.
TL;DR: The role of the ceramic phase is to depress the melting temperature and retard the kinetics of crystallization of PEO, which results in a conductivity relaxation below a melting temperature.
TL;DR: In this paper, the authors investigated the variation of the ionic conductivity as a function of the composition x is investigated in the temperature range 150-600 K. They showed that the variations of ionic motion process in the bulk of the material can be explained by structural considerations, and that the mobility of the Na+ ions in these materials seems to be mostly influenced by the size of the bottlenecks through which the ions have to pass.
TL;DR: In this paper, the electrical properties of Agx(GeSe3)1−x (0≤x≤0.571) glasses were investigated by impedance spectra and EMF measurements.
TL;DR: The waterborne polyurethane (WPU) dispersions synthesized from poly(ethylene glycol) (PEG), dimethylol propionic acid (DMPA), and isophorone diisocyanate (IPDI) with various DMPA contents were prepared from a modified acetone process.
TL;DR: In this article, the effects of doping Co for the Ga site on the oxide ion conductivity of La{sub 0.8}Sr{sr 0.115}Co{srs 0.085}O{sub 3} (A) were investigated in detail.
Abstract: The effects of doping Co for the Ga site on the oxide ion conductivity of La{sub 0.8}Sr{sub 0.2}Ga{sub 0.8}Mg{sub 0.2}O{sub 3} have been investigated in detail. It was found that doping Co is effective for enhancing the oxide ion conductivity. In particular, a significant increase in conductivity in the low-temperature range was observed. The electrical conductivity was monotonically increased; however, the transport number for the oxide ion decreased with an increasing amount of Co. Considering the transport number and ion transport number, an optimized amount for the Co doping seems to exist at 8.5 mol % for Ga site. The theoretical electromotive forces were exhibited on a H{sub 2}-O{sub 2} gas cell utilizing optimized composition of La{sub 0.8}Sr{sub 0.2}Ga{sub 0.8}Mg{sub 0.115}Co{sub 0.085}O{sub 3} (A). The diffusion characteristics of the oxide ion in A was also investigated by using the {sup 18}O tracer method. Since the diffusion coefficient measured by the {sup 18}O tracer method was similar to that estimated by the electrical conductivity, the conduction of A is concluded to be almost ionic. On the other hand, an oxygen permeation measurement suggests that the oxide ion conductivity increased linearly with an increasing amount of Co. Therefore, specimens with Co contentmore » higher than 10 mol% can be considered as a superior mixed oxide ion and hole conductor. The UV-vis spectra suggests that the valence number of doped Co was changed from +3 to +2 with decreasing oxygen partial pressure; the origin of hole conduction can thus be assigned to the formation of Co{sup 3+}. Since the amount of dopant in the Ga site was compensated with Mg{sup 2+}, the amount of oxygen deficiency was decreased by doping Co. Therefore, it is likely that the improved oxide ion conductivity observed by doping with Co is brought about by the enhanced mobility of oxide ion.« less
TL;DR: In this article, a cubic perovskite-type material was obtained and the dopant concentration y = 0.1 was used to obtain a hexagonal lattice structure.