Recent Trends in Polymer Electrolytes Based on Poly(Ethylene Oxide)

Recent work on the crystallographic and morphological structure of semicrystalline PEO complexes with alkali metal salts is described. The thermal properties of the materials and the influence of solvent on complex formation is also considered. The dependence of the ionic conductivity of the complexes on their morphology, the temperature and ionic association is discussed and some current work relating to the mechanism of conduction is considered. The various strategies which have been adopted to suppress crystallinity and so to optimize ionic conductivity, including networks, “comb” structures, and linear copolymers, are reviewed. The morphological organization and mesogenic behavior of some novel crystalline complexes of PEO with organo-alkali salts, such as sodium phenolates and naphtholates, are discussed. Some PEO composite materials which have mixed electronic-ionic mechanisms of conductivity are also described.     

NMR and impedance spectroscopy data on the ionic mobility and conductivity in PbSnF4 doped with alkali metal fluoride

NMR and impedance spectroscopy are used to study the ionic mobility and conductivity in crystalline samples in PbSnF₄-MF systems (M = Li, Na, K) in a 150?C473 K temperature range. The ¹⁹F NMR spectral parameters, types of ionic motion, and ionic conductivity value in the PbSnF₄ compound doped with alkali metal fluoride is found to be determined by the temperature, nature, and concentration of an alkali cation. The specific conductivity of the crystalline samples in PbSnF₄-MF systems (M = Li, Na, K) is rather high at room temperature and hence, it seems possible to apply them in the development of functional materials with high ionic (superionic) conductivity.     

聚醚介质中的离子传导机理

以单阳离子导体作为传导模型,通过对阳离子淌度的表征,证实了碱金属盐在聚合物介质中的负温度依赖性。发现在离子传导过程中,离子淌度对其电导率温度依赖性的影响远甚于载流离子数。并运用聚合物链段松驰理论对这种反常离解行为进行了唯象学的诠释。     

Relationship between ion conductivity and morphology of complexes formed from poly(ethylene oxide) and potassium thiocyanate

Solid polymer electrolytes with different stoichiometries were prepared from molten poly(ethylene oxide) (PEO) containing various amounts of potassium thiocyanate (KSCN). X-ray diffraction and conductivity measurements revealed that both morphology and conductivity were dependent on their stoichiometries, and that the highest conductivity at ambient temperature corresponded to 3.98 × 10^?6 S cm^?1 for the amorphous complex with the composition of X = 0.15 (X = [KSCN]/[EOunit]). The temperature dependence of the conductivity showed a WLF-type behavior for the amorphous complex, whereas it showed an Arrhenius-type behavior for a crystalline complex with the composition of X = 0.2. It was also found that the ionic mobility at 60°C of the amorphous complex was approximately 2.25 times greater than that of the crystalline complex. Furthermore, results of the infrared reflection spectroscopy measurements suggested that the mobility of potassium ion (K⁺) was correlated to the degree of the interaction between K⁺ and ether oxygens.     

梳状高分子固体电解质的离子导电性研究

深入研究了交替马来酸酐共聚物多缩乙二醇酯（ＣＰ３５０）两种锂盐络合物ＣＰ３５０／ＬｉＡｓＦ＿６和ＣＰ３５０／ＬｉＰＦ＿６的离子传导性能,给出了与复阻抗谱相对应的等效电路．离子电导率随［Ｌｉ］／［ＥＯ］的变化而出现一极大值,室温下,两体系电导率极大值分别为１．３８×１０（－４）,８．３２×１０（－５）Ｓ／ｃｍ．电导率随温度升高而增加．导电行为呈非－Ａｒｒｈｅｎｉｕｓ特征．阴阳离子半径之和（ｒ＿ｃ＋ｒ＿ａ）愈大,离子电导率愈高．     

Glass structure and ion dynamics of lead-cadmium fluorgermanate glasses

Glass structure and fluorine motion dynamics are investigated in lead-cadmium fluorgermanate glasses by means of differential scanning calorimetry, Raman scattering, x-ray absorption (EXAFS), electrical conductivity (EC), and (19)F nuclear magnetic resonance (NMR) techniques. Glasses with composition 60PbGeO(3)-xPbF(2)-yCdF(2) (in mol %), with x+y=40 and x=10, 20, 30, 40, are studied. Addition of metal fluorides to the base PbGeO(3) glass leads to a decrease of the glass transition temperature (T(g)) and to an enhancement of the ionic conductivity properties. Raman and EXAFS data analysis suggest that metagermanate chains form the basic structural feature of these glasses. The NMR study leads to the conclusion that the F-F distances are similar to those found in pure crystalline phases. Experimental results suggest the existence of a heterogeneous glass structure at the molecular scale, which can be described by fluorine rich regions permeating the metagermanate chains. The temperature dependence of the NMR line shapes and relaxation times exhibits the qualitative and quantitative features associated with the high fluorine mobility in these systems.     

Semiconductivity,optical properties,and EPR spectra of phenothiazine derivatives in the solid state

The optical, EPR, and electrical properties of phenothiazine derivatives have been investigated as a function of R₂ substituents. Diffuse reflectance spectra show a charge transfer complex transition between 600 and 1100 nm. The EPR spectra show the existence of the radical cation with an unpaired electron per molecule; also there can be seen a dependence of the bandwidth on the R₂ substituents. Measurements of electrical conductivity show a semiconductor behavior in the studied temperature range; the values show as well a dependence of conductivity on R₂. The estimation of the drift mobility of charge carriers seems to indicate a hopping mechanism for the charge conduction.     

Structural and conductivity analysis on cerium fluoride nanoparticles prepared by sonication assisted method

The article deals with the effect of sonication on ionic conductivity of cerium fluoride. Cerium fluoride nanoparticles have been prepared by simple precipitation method from aqueous solution with sonication assistance. The structural and morphology of the nanoparticles prepared have been studied using X-ray Diffraction (XRD) and Field Emission Scanning Electron Microscopic (FESEM) analysis. The morphological analysis confirms the formation of nanorods. Ac impedance spectroscopy has been used to study the ion conduction and conductivity of the prepared nanoparticles. The surface area of the prepared nanoparticles has been studied by nitrogen adsorption–desorption analysis. From the impedance spectra analysis the sample prepared at 2 h sonication time is found to have high ionic conductivity. The conductance spectra show an orderly shifting which is due to the effect of sonication. The temperature dependence of conductivity follows the Arrhenius behavior.     

Superionic conductivity in lithium-rich anti-perovskites

Lithium ion batteries have shown great promise in electrical energy storage with enhanced energy density, power capacity, charge-discharge rates, and cycling lifetimes. However common fluid electrolytes consisting of lithium salts dissolved in solvents are toxic, corrosive, or flammable. Solid electrolytes with superionic conductivity can avoid those shortcomings and work with a metallic lithium anode, thereby allowing much higher energy densities. Here we present a novel class of solid electrolytes with three-dimensional conducting pathways based on lithium-rich anti-perovskites (LiRAP) with ionic conductivity of σ > 10(-3) S/cm at room temperature and activation energy of 0.2-0.3 eV. As temperature approaches the melting point, the ionic conductivity of the anti-perovskites increases to advanced superionic conductivity of σ > 10(-2) S/cm and beyond. The new crystalline materials can be readily manipulated via chemical, electronic, and structural means to boost ionic transport and serve as high-performance solid electrolytes for superionic Li(+) conduction in electrochemistry applications.     

A conductivity study and calorimetric analysis of dried poly(sodium 4-styrene sulfonate)/poly(diallyldimethylammonium chloride) polyelectrolyte complexes

Ionically cross-linked polyelectrolyte complexes (PECs) of anionic poly(sodium 4-styrene sulfonate) (PSS) and cationic poly(diallyldimethylammonium chloride) (PDADMAC), xPSS.(1-x)PDADMAC, with molar fractions x ranging from 0.30 to 0.70, were prepared and subsequently dried. The PEC samples were analyzed by differential scanning calorimetry, and the ionic conductivity sigmadc of the samples was measured as a function of temperature by means of impedance spectroscopy. The thermograms display an endothermic peak in the temperature range of 90-143 degrees C, which is attributed to a glass transition of the PEC. The glass transition temperature Tg has a symmetric x dependence with a minimum at x=0.50. The temperature dependence of sigmadcT is not affected by the glass transition. The ionic conductivity of the samples before drying is three orders of magnitude larger than sigmadc after drying; nevertheless, their activation enthalpies are identical. Arrhenius parameters obtained from the systematic study of several PEC compositions are discussed. The ionic conductivity of the PSS-rich samples is significantly higher than sigmadc of PDADMAC-rich samples. This implies a relatively high Na+ mobility as compared to Cl(-) mobility in PEC. In contrast to the symmetric x dependence of Tg, the conductivity of PEC increases and the activation enthalpy decreases with increasing x in the investigated composition range. A strong x dependence of sigmadc is observed for PSS-rich PEC, which is attributed to a significant variation in the mobility of the charge carriers.     

Ionic mobility and conductivity in PbSnF<Subscript>4</Subscript> doped with CaF<Subscript>2</Subscript> from the NMR and impedance spectroscopy data

The ionic mobility and conductivity in the crystalline phases of PbSnF_4–xCaF₂ systems (x = 2.5 mol.%, 5 mol.%, 7.5 mol.%, and 10 mol.%) in the temperature range of 150-500 K are studied by NMR and impedance spectroscopy. The parameters of ¹⁹F NMR spectra, types of ion motions, and ionic conductivity in the PbSnF₄ compound doped with calcium fluoride are found to be determined by the temperature and concentration of calcium fluoride. The specific conductivity of the crystalline phases in the PbSnF₄–CaF₂ systems is rather high at room temperature, and hence, one cannot exclude the possibility to use them for the creation of functional materials with a high ionic (superionic) conductivity.     

Experimental and theoretical study of AC electrical conduction mechanisms of semicrystalline parylene C thin films

The electrical conduction mechanisms of semicrystalline thermoplastic parylene C (-H(2)C-C(6)H(3)Cl-CH(2)-)(n) thin films were studied in large temperature and frequency regions. The alternative current (AC) electrical conduction in parylene C is governed by two processes which can be ascribed to a hopping transport mechanism: correlated barrier hopping (CBH) model at low [77-155 K] and high [473-533 K] temperature and the small polaron tunneling mechanism (SPTM) from 193 to 413 K within the framework of the universal law of dielectric response. The conduction mechanism is explained with the help of Elliot's theory, and the Elliot's parameters are determined. From frequency- and temperature-conductivity characteristics, the activation energy is found to be 1.27 eV for direct current (DC) conduction interpreted in terms of ionic conduction mechanism. The power law dependence of AC conductivity is interpreted in terms of electron hopping with a density N(E(F)) (~10(18) eV cm(-3)) over a 0.023-0.03 eV high barrier across a distance of 1.46-1.54 ?.     

Electrical transport properties of semiconducting lithium molybdate glass nanocomposites

We have reported the formation of lithium molybdate glass nanocomposites embedded with lithium molybdate nanophases from the x-ray diffraction and transmission electron microscopic studies. We have investigated the dc electrical conductivity in a wide temperature range for these glass nanocomposites, which exhibit semiconducting behavior. We have analyzed the dc electrical data in the light of polaronic conduction models of Mott and Schnakenberg. We have also studied ac electrical conductivity of these glass nanocomposites in wide temperature and frequency ranges. The experimental ac results have been analyzed with reference to various theoretical models based on quantum-mechanical tunneling and hopping over the barrier. We have observed that the temperature dependence of the dc conductivity is consistent with the polaronic hopping models, while the temperature and frequency dependence of the ac conductivity is consistent with the polaronic tunneling models.     

Influence of PEG-borate ester on thermal property and ionic conductivity of the polymer electrolyte

We have focused on the poly(ethylene glycol) (PEG)-borate ester as a new type plasticizer for solid polymer electrolyte for lithium ion secondary battery. Adding the PEG-borate ester into the electrolyte shows the increase in the ionic conductivity of the polymer electrolyte. By measuring the glass-transition temperature of the polymer electrolytes with DSC, it is found that the increase in ionic conductivity of the polymer electrolyte is due to the increase in ionic mobility. By investigating the temperature dependence of the ionic conductivity of the polymer electrolytes using William-Landel-Ferry type equation, we considered that the PEG-borate ester does not have any influence for dissociation of Li-salt. This revised version was published online in August 2006 with corrections to the Cover Date.     

Preparation and Some Properties of Lithium Vanadium Bronzes

Lithium vanadium bronzes with composition formula Li_xV₂O₅ (0.04 ≤ × ≤ 0.92) have been prepared by solid‐state reaction at 650 °C in argon atmosphere. The obtained products were characterized by X‐ray powder diffraction and IR spectroscopy. The results reveal that four phases are present in the range from x = 0.04 to 0.92, namely α, β, β′, and γ phase. The magnetic susceptibility for the investigated bronzes was measured using the conventional Gouy's method. The values of the effective magnetic moments, as calculated from experimental data, indicate the presence of V⁴⁺ ions in all bronze samples. The electrical conductivity as a function of temperature and lithium content was measured in the temperature range from room temperature to 483 K. The electrical conductivity of the bronzes is found to be affected by lithium content. The values of the electrical conductivity increase with temperature for the prepared samples and both electronic and ionic conduction are discussed.     

无定形梳状高分子固体电解质的二重玻璃化转变及典型VTF特征

研究了交替马来酸酐共聚物多缩乙二醇酯(CP350)-LiNO₃络合物的热行为及离子导电性。实验表明:CP350/LiNO₃络合物在所研究的[Li]/[EO]配比范围呈均相无定形并具有二重玻璃化转变。2个玻璃化转变温度均随盐含量的增加而上升。离子电导率随盐浓度的变化出现1个极大值,室温电导率最大可达3.72×10^-5S/cm.导电行为呈典型VTF特征。     

Simultaneous large enhancements in thermopower and electrical conductivity of bulk nanostructured half-Heusler alloys

Large reductions in the thermal conductivity of thermoelectrics using nanostructures have been widely demonstrated. Some enhancements in the thermopower through nanostructuring have also been reported. However, these improvements are generally offset by large drops in the electrical conductivity due to a drastic reduction in the mobility. Here, we show that large enhancements in the thermopower and electrical conductivity of half-Heusler (HH) phases can be achieved simultaneously at high temperatures through coherent insertion of nanometer scale full-Heusler (FH) inclusions within the matrix. The enhancements in the thermopower of the HH/FH nanocomposites arise from drastic reductions in the "effective" carrier concentration around 300 K. Surprisingly, the mobility increases drastically, which compensates for the decrease in the carrier concentration and minimizes the drop in the electrical conductivity. Interestingly, the carrier concentration in HH/FH nanocomposites increases rapidly with temperature, matching that of the HH matrix at high temperatures, whereas the temperature dependence of the mobility significantly deviates from the typical T(-α) law and slowly decreases (linearly) with rising temperature. This remarkable interplay between the temperature dependence of the carrier concentration and mobility in the nanocomposites results in large increases in the power factor at 775 K. In addition, the embedded FH nanostructures also induce moderate reductions in the thermal conductivity leading to drastic increases in the ZT of HH(1 - x)/FH(x) nanocomposites at 775 K. By combining transmission electron microscopy and charge transport data, we propose a possible charge carrier scattering mechanism at the HH/FH interfaces leading to the observed anomalous electronic transport in the synthesized HH(1 - x)/FH(x) nanocomposites.     

BaCe0.9Y0.1O3-α固体电解质的离子导电性

用交流复阴抗谱法测定了混合离子(质子+氧离子)导电性固体电解质BaCe0.9Y0.1O3-α在600～1000℃下不同气氛(干燥空气、湿润空气及湿润氢气)中的电导率;通过测定总电导率(离子电导率+电子电导率)随气氛中氧分压po2变化,求得离子电导率和离子迁移数;用氢浓差电池方法测得氢气中的质子迁移数。结果表明,BaCe0.9Y0.1O3-α固体电解质在氧分压<10Pa的气氛(如氢气)中几乎为纯离子导体,而在氧分压为10～10^5Pa的气氛(如空气)中为离子和电子空穴混合导体;样品在各气氛中的离子电导率均高于10^-2S·cm^-1。     

Gamma-irradiation effects on the electrical conductivity behaviour of some N,N&#x27;-ethylenebis (salicylideneiminato) divalent metal chelates

γ-Irradiation effects on the electrical conductivity behaviour of some newly prepared mono-, homobi- and heterobinuclear metal chelates containing divalent Co, Ni, Cu, Cd and Hg cations of N,N'-ethylenebis (salicylideneimine) H₂SED were investigated. The complexes were identified on the basis of elemental analysis, electronic and infrared spectra. X-Ray diffraction patterns showed that all complexes are well crystalline substances. The variation of the electrical conductivity with temperature was found to be characteristic of an intrinsic semiconductor with impurity centres. The rate constants of the isothermal annealing and the activation energies of the electrical conduction of the irradiated and unirradiated metal chelates were calculated and discussed. It was found that electrical conductivity increases on increasing temperature and decreasing irradiation dose. However, the rate constant of thermal annealing increases in the order mono-, homobi- and heterobinuclear chelates. Seeback effect studies showed that electrons are the majority charge carriers in all irradiated and unirradiated complexes.     

Correlation between chain segment and ion mobility in an epoxy resin system. A free volume analysis

Steady shear viscosity and ionic conductivity have been measured for nine commercial diglycidyl ether of bisphenol-A (DGEBA) epoxy resins with molecular weights ranging from 340 to 14,200. The temperature dependence of viscosity and ionic conductivity was modeled using free volume viscosity and ionic conductivity relationships, which correlate the fractional free volume required for polymer chain segment motion (B) and the fractional free volume required for ion motion (B′) with polymer structure. The fractional free volume required for polymer chain segment mobility was observed to increase systematically with the molecular weight of the resins. The fractional free volume required for ion mobility did not vary for the resin series. A stoichiometric mixture of a low molecular weight DGEBA resin and a 4,4′-diaminodiphenyl sulfone cross-linker was partially polymerized to extents of reaction ranging from 0% to 49%. The fractional free volume required for polymer segment mobility for these partially polymerized samples was consistent with results for the neat resins. © 1993 John Wiley & Sons, Inc.