Showing papers on "Ionic conductivity published in 2001"
TL;DR: In this paper, thermal properties, density, self-diffusion coefficient of the anions and cations, viscosity, and ionic conductivity were measured for these ionic liquids in wide temperature ranges.
Abstract: Room-temperature ionic liquids, 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMITFSI), 1-butylpyridinium tetrafluoroborate (BPBF4), and 1-butylpyridinium bis(trifluoromethylsulfonyl)imide (BPTFSI), were prepared and characterized The thermal property, density, self-diffusion coefficient of the anions and cations, viscosity, and ionic conductivity were measured for these ionic liquids in wide temperature ranges A pulsed-gradient spin−echo NMR method was used to independently measure self-diffusion coefficients of the anions (19F NMR) and the cations (1H NMR) The results indicate that the cations diffuse almost equally to the anion in EMIBF4 and BPBF4, whereas they diffuse faster than the anion in EMITFSI and BPTFSI The summation of the cationic and anionic diffusion coefficients for each ionic liquid follows the order EMITFSI > EMIBF4 > BPTFSI > BPBF4, under an isothermal condition The order of the magnitude of the diffusion coe
935 citations
TL;DR: It is demonstrated that ion transport in crystalline polymer electrolytes can be dominated by the cations, whereas both ions are generally mobile in the amorphous phase.
Abstract: Polymer electrolytes are the subject of intensive study, in part because of their potential use as the electrolyte in all-solid-state rechargeable lithium batteries. These materials are formed by dissolving a salt (for example LiI) in a solid host polymer such as poly(ethylene oxide) (refs 2, 3, 4, 5, 6), and may be prepared as both crystalline and amorphous phases. Conductivity in polymer electrolytes has long been viewed as confined to the amorphous phase above the glass transition temperature, Tg, where polymer chain motion creates a dynamic, disordered environment that plays a critical role in facilitating ion transport. Here we show that, in contrast to this prevailing view, ionic conductivity in the static, ordered environment of the crystalline phase can be greater than that in the equivalent amorphous material above Tg. Moreover, we demonstrate that ion transport in crystalline polymer electrolytes can be dominated by the cations, whereas both ions are generally mobile in the amorphous phase. Restriction of mobility to the lithium cation is advantageous for battery applications. The realization that order can promote ion transport in polymers is interesting in the context of electronically conducting polymers, where crystallinity favours electron transport.
838 citations
TL;DR: The lithium superionic conductor (thio-LISICON) was found in the Li 2 S-GeS 2 -P 2 S 5 system as mentioned in this paper, which has the highest conductivity of 2.2 x 10 -3 S cm -1 at 25°C of any sintered ceramic together with negligible electronic conductivity, high electrochemical stability, no reaction with lithium metal, and no phase transition up to 500°C.
Abstract: The new crystalline material family, lithium superionic conductor (thio-LISICON), was found in the Li 2 S-GeS 2 -P 2 S 5 system. The solid solution member x x 0.75 in Li 4-x Ge 1-x P x S 4 shows the highest conductivity of 2.2 x 10 -3 S cm -1 at 25°C of any sintered ceramic together with negligible electronic conductivity, high electrochemical stability, no reaction with lithium metal, and no phase transition up to 500°C. Its material design concepts of changing constituent ions with various ionic radii, valence, and polarizability are described.
814 citations
TL;DR: In this paper, a series of imidazolium cations containing covalently-bound sites, such as sulfonate or sulfonamide groups, were synthesized and polymerized.
Abstract: We synthesized a series of imidazolium cations containing covalently-bound
anionic sites, such as sulfonate or sulfonamide groups. These zwitterionic
imidazolium salts were found to form molten salts just like ordinary imidazolium
salts. However, regardless of the high ion density, these ions cannot migrate
along potential gradients induced in the bulk. This is a new and unique characteristic
in molten salts. When other salts were added to this, the ions generated from
the newly added salts were able to behave as carrier ions. The ionic conductivity
of a pure molten salt was 10−9 S cm−1
at 25°C, but jumped to 10−5 S cm−1
by adding an equimolar amount of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)
at 50°C. The zwitterionic salt having a sulfonamide group instead
of sulfonate had an ionic conductivity of 10−4 S cm−1
at 50°C after adding an equimolar amount of LiTFSI. These zwitterionic
imidazolium salts having vinyl groups were synthesized and polymerized. In
spite of their rubber-like properties they showed excellent ionic conductivities
of around 10−5 S cm−1 at 50°C
following the addition of an equimolar amount of LiTFSI to the imidazolium
cation unit.
325 citations
TL;DR: In this paper, a series of molecular dynamics simulations of aqueous NaCl and KCl solutions at different concentrations, ranging from 0 M to 4.5 M, were performed to investigate the effects of ion concentration on the single-particle, pair, and collective dynamical properties of an electrolyte solution.
Abstract: We have performed a series of molecular dynamics simulations of aqueous NaCl and KCl solutions at different concentrations, ranging from 0 M to 4.5 M, to investigate the effects of ion concentration on the single-particle, pair, and collective dynamical properties of aqueous electrolyte solutions. The SPC/E model is used for water and the ions are modeled as charged Lennard-Jones particles. The single-particle dynamics is investigated by calculating the self-diffusion coefficients of ions and water molecules and also the orientational relaxation times. The pair dynamics is studied by evaluating the ion–water residence and water–water hydrogen bond time correlation functions. The relaxation of relative velocity autocorrelation function and the cross velocity correlation function of two hydrogen bonded water molecules are also investigated at varying ion concentration. Finally, we explore the collective dynamical properties by calculating the frequency dependent dielectric function and conductivity. It is found that the self and relative diffusion coeffcients decrease and the orientational relaxation times increase with ion concentration. The residence times of water molecules near ions and also the structural relaxation time of water–water hydrogen bonds show an increasing trend as the ion concentration is increased. The dielectric relaxation time is found to decrease with ion concentration for the solutions investigated here. The static conductivity of concentrated solutions shows significant departure from the Nernst–Einstein behavior due to formation of ion pairs. With an increase of frequency, the conductivity first increases substantially and then decreases at very high frequency. The initial increase of conductivity is attributed to the disruption of ion pairs on application of high frequency electric fields.
301 citations
TL;DR: In this paper, the effect of nanoparticles inorganic oxides to poly(ethylene oxide) (PEO) complexed with LiClO 4 on cation transport properties has been explored by electrochemical and 7 Li nuclear magnetic resonance (NMR) methods.
271 citations
TL;DR: In this article, the relationship between structure and conductivity for two apatite-type phases, La 9.33 Si 6 O 26 and La 8 Sr 2 Si 6O 26, was investigated.
271 citations
TL;DR: In this paper, the electrical conductivity of polycrystalline cerium oxide was investigated in the nanometer and micrometer size range and the effect of a variation in temperature or oxygen partial pressure revealed the rather different nature of the electrical transport properties in the nano- and micro-crystaline materials.
255 citations
TL;DR: The ionic conductivity studies have been conducted for polyvinyl chloride polymer electrolytes (PVC:LiCF 3 SO 3 :LiBF 4 :PC:EC) over a wide frequency regime as discussed by the authors.
Abstract: The ionic conductivity studies have been conducted for poly (vinyl chloride) polymer electrolytes (PVC:LiCF 3 SO 3 :LiBF 4 :PC:EC) over a wide frequency regime. It was found that the addition of plasticizers significantly improved the ionic conductivity. The dielectric data were analyzed using complex impedance Z *, complex admittance A *, complex permittivity e * and complex electric modulus M * of the sample with the highest ionic conductivity at various temperatures. The conductivity–temperature data obeys the classical Arrhenius relationship.
237 citations
TL;DR: In this paper, the effect of space charges along grain boundaries on the electrical conductivity of polycrystalline mixed ionic/electronic conductors (MIECs) was investigated.
227 citations
TL;DR: In this article, the authors investigated the role of oxygen interstitial migration in the rock-salt-type layers of the K2NiF4-like lattice and showed that the role in oxygen vacancy diffusion in perovskite layers increases when temperature decreases.
TL;DR: In this paper, the apatite-type lanthanum silicates, La 10 (SiO 4 ) 6 O 3 and La 9.33 6 O 2, were synthesized via a sol-gel process.
TL;DR: In this article, the ionic conductivity of the polymers improved by a factor of 100 when a hydrocarbon chain was used instead of oligo(ethylene oxide) to minimize the drop in conductivity.
TL;DR: In this paper, the authors report the design of new block copolymer electrolytes based on poly(methyl methacrylate), PMMA, and poly(oligo oxycthylene methacelate), POEM, which are segmentally mixed at elevated temperatures appropriate for melt processing, while exhibiting a mierophase separated morphology at ambient temperature.
Abstract: Microphase separated block copolymers consisting of an amorphous poly(ethylene oxide) (PEO)-based polymer covalently bound to a second polymer offer a highly attractive avenue to achieving both dimensional stability and high ionic conductivity in polymer electrolytes for solid-state rechargeable lithium batteries. However, due to the strong thermodynamic incompatibility typically found for most polymer pairs, the disordered, liquid state of the copolymer can rarely he achieved without the incorporation of a solyent, which complicates processing, Herein, we report the design of new block copolymer electrolytes based on poly(methyl methacrylate), PMMA, and poly(oligo oxycthylene methacrylate), POEM, which are segmentally mixed at elevated temperatures appropriate for melt processing, while exhibiting a mierophase separated (ordered) morphology at ambient temperature. Although pure PMMA-b-POEM is segmentally mixed at all temperatures, it is shown that mierophase separation in these materials can be induced in a controlled manner by the incorporation of even limited amounts of lithium trifluoromethane sulfonate (LiCF 3 SO 3 ), a salt commonly employed to render PEO ionically conductive. Such salt-induced microphase separation suggests a simple method for designing new solid polymer electrolytes combining high ionic conductivities with excellent dimensional stability and improved processing flexibility.
TL;DR: In this article, the ionic conductivity and DSC measurement of molten salt-type polymer brushes were carried out and poly(ethylene oxide) derivatives having both vinyl group and imidazolium salt structure on their ends were prepared and polymerized to analyze the effect of flexible spacer.
TL;DR: An electrochemical impedance spectroscopy (EIS) study of three members of the family of compounds LixNi1-yCoyO2 (y = 0, 0.2, and 1) has been performed by taking spectra at closely spaced bias potentials over the potential windows of utilization as cathodes in lithium-ion batteries.
Abstract: An electrochemical impedance spectroscopy (EIS) study of three members of the family of compounds LixNi1-yCoyO2 (y = 0, 0.2, and 1) has been performed by taking spectra at closely spaced bias potentials over the potential windows of utilization as cathodes in lithium-ion batteries. The spectra have been interpreted in terms of electronic and ionic transport properties. It has been found that, for x values greater than about 0.9, all the compounds show semiconductive properties with a specific resistance that increases with decreasing Ni content. For x close to about 0.9−0.8, the properties change into those of a metal-like material in which the ionic conductivity becomes the limiting factor. The transition between these two limiting conditions clearly appears in the impedance spectra.
TL;DR: In this article, conductivity measurements and thermogravimetry (TG) were used to investigate the physicochemical properties of water from a humid atmosphere on the oxide Y2O3-doped ZrO2 (YSZ).
TL;DR: In this article, the authors measured the ionic conductivity in chitosan-based polymer electrolytes using impedance spectroscopy and showed that the conductivity is due to the mobile ions from the salt.
TL;DR: In this paper, the oxide ion conductor La9.33(SiO4)6O2 was doped with al-vacancy to achieve a conductivity enhancement of 1-2 orders of magnitude for intermediate x values.
Abstract: Al can be doped into the oxide ion conductor La9.33(SiO4)6O2 according to the formula La9.33 + x/3(SiO4)6 − x(AlO4)xO2 where 0 ≤ x ≤ 2; a conductivity enhancement of 1–2 orders of magnitude is observed for intermediate x values and illustrates the important role that La vacancies have in optimising the conductivity.
TL;DR: Ionic conductivity and swelling data are measured for Nafion® perfluorinated ionomeric membranes in nonaqueous solvents and solvent mixtures and correlated with solvent physical properties as mentioned in this paper.
TL;DR: In this article, a series of proton exchange membranes based on sulfonated αββ-trifluorostyrene-co-substituted-αββ -triflurostyrenes (BAM ® ) were compared to Nafion ® 117 and ethylenetetrafluoroethylene-g -polystyrene sulfonic acid membranes.
TL;DR: The first use of ion beam irradiation-induced disordering in Gd 2Ti 2O is reported to produce a strain-free, buried, disordered defect-fluorite layer approximately 12 nm thick within an ordered pyrochlore matrix, providing a new means of creating nanoscale, mixed ionic-electronic conductors in pyroChlore ceramics.
Abstract: The ionic conductivity of isometric pyrochlore, ideally A2B2O (7), is extremely sensitive to disordering of A- and B-site cations and oxygen anion vacancies. We report the first use of ion beam irradiation-induced disordering in Gd 2Ti 2O (7) to produce a strain-free, buried, disordered defect-fluorite layer approximately 12 nm thick within an ordered pyrochlore matrix. This approach provides a new means of creating nanoscale, mixed ionic-electronic conductors in pyrochlore ceramics, such as those required for solid-state electrochemical cells.
TL;DR: In this article, the lithium ionic conductivity and electrochemical stability of perovskite La{sub 2/3-x}Li{sub 3x}TiO-sub 3} (LLTO) have been determined with AC impedance spectroscopy, cyclic voltammetry and galvanostatic cycling.
TL;DR: A number of novel organic ionic compounds based on the pyrrolidinium cation are described which have been found to be ion conductors in their solid states around room temperature.
Abstract: A number of novel organic ionic compounds based on the pyrrolidinium cation are described which have been found to be ion conductors in their solid states around room temperature. The properties of the compounds are consistent with their exhibiting plastic crystal phases. In order to understand some of the molecular origins of the plastic crystal behaviour and the ion conductivity that it promotes, a number of related compounds based on the imidazolium and ammonium cations are also described which have structural elements in common with the pyrrolidinium cation, but which do not show the plastic behaviour. It is found therefore that the nature of the cation is quite critical to the development of this behaviour. The alkyl methyl pyrrolidinium cation is found to produce plastic crystal phases when the alkyl chains are short, thereby preserving the ability of the cation to rotate with minimal steric hindrance. The ammonium and imidazolium cations of comparable size and structure are less able to produce these plastic phases, in many cases because the low temperature phase proceeds to melt rather than forming a stable rotator phase.
TL;DR: In this article, the authors investigated ionic conduction in two non-perovskite-oxides, fluorite-related-type lanthanum tungsten oxide and aragonite-structure Lanthanum borate, at elevated temperatures.
TL;DR: In this article, the potential and ac impedance spectra were measured to construct a model to describe porous Sm 1-x Sr x CoO 3 (SSC) cathodes for solid oxide fuel cells (SOFCs).
Abstract: Overpotential and ac impedance spectra were measured to construct a model to describe porous Sm 1-x Sr x CoO 3 (SSC) cathodes for solid oxide fuel cells (SOFCs). Analysis of the impedance spectra revealed that there are three processes involved in the overall electrochemical reaction; (i) the adsorption/desorption process on the surface of the electrode. (ii) the ionic conduction in the bulk SSC, and (iii) the diffusion of oxygen in the gas phase. It was found that in air atmosphere, the reaction processes (i) and (ii) were dominant, while the diffusion process of gaseous oxygen was fast enough not to limit the overall reaction rate. A reaction model for the porous SSC cathodes used in SOFCs was proposed to determine the electrode resistance hy taking processes (i) and (ii) into account. It was found that our model explained the experimental results well. These results suggested the possibility of using our model to describe the cathodes with high ionic conductivity and to design the high-performance cathode systematically. The validity of the analysis hy conventional equivalent circuit was also discussed.
TL;DR: In this article, composite gel-type polymer electrolytes have been prepared by dispersing selected ceramic powders into a matrix formed by a lithium salt solution contained in a poly(acrylonitrile) (PAN) network.
TL;DR: In this article, the ionic conductivity by a.c. impedance was calculated using four different methods, and three kinds of representations of the complex impedance spectra were adopted, based on the Nyquist impedance plot of the imaginary part (Z″) versus the real part of complex impedance, and the plots of imaginary impedance Z″ as a function of frequency (f).
Abstract: Composite polymeric electrolytes of PEO-LiClO4-Al2O3 and PEO-LiClO4-EC were prepared and the ionic conductivity by a.c. impedance was calculated using four different methods, and three kinds of representations of a.c. impedance spectra were adopted. The first is based on the Nyquist impedance plot of the imaginary part (Z″) versus the real part (Z′) of the complex impedance. The second and the third correspond to the plots of imaginary impedance Z″ as a function of frequency (f), and the absolute value (|Z|) and phase angle (θ) as a function of f, respectively. It was found that the values of the ionic conductivity calculated using the three representations of a.c. impedance spectra are basically identical.
TL;DR: In contrast to La free compositions, La containing compositions show high stability against reaction with yttria stabilised zirconia (YSZ) and a closely matching thermal expansion coefficient (∼1×10−5 K−1) as discussed by the authors.
Abstract: Both physical properties and the level of mixed conduction obtained in La and Fe doped SrTiO3 are widely influenced by composition. In contrast to La free compositions, La containing compositions show high stability against reaction with yttria stabilised zirconia (YSZ) and a closely matching thermal expansion coefficient (∼1×10−5 K−1). Faradaic efficiency measurements for Sr0.97Ti0.6Fe0.4O3–δ and La0.4Sr0.5Ti0.6Fe0.4O3–δ show ionic transference numbers in air between 5 × 10−3 to 4 × 10−2, and 2 × 10−4 to 6 × 10−4 respectively, decreasing with decreasing temperature. The substitution of La for Sr is observed to deplete the level of both ionic and total conductivity obtained in air.
TL;DR: In this paper, the authors examined the correlation between the internal structure and the ionic conductivity behavior of lipophilized smectic clay (SPN)/polymer nanocomposites having various dispersed morphology of the clay layers.