New protonic solid electrolyte with tetragonal tungsten bronze structure obtained through ionic exchange

Proton exchange reactions have been performed on tetragonal tungsten bronze-like NaNbWO₆ by using nitric acid as an exchanging agent. The characterization of the exchange reaction products has been made by means of chemical analysis, X-ray diffraction, thermal analysis, and IR spectroscopy. The exchange reaction takes place topotactically and the following formula is proposed for the obtained phase of variable composition: Na_1−xH_xNbWO₆·yH₂O (0<x?0.46 and 0?y?0.12). Impedance spectroscopy on the present proton exchanged samples indicated that these samples behaved as solid electrolytes under high humidity. As an example, the compound with the composition Na_0.68H_0.32NbWO₆·0.1 H₂O exhibits ionic conductivity of 8×10⁻³ and 1×10⁻² S cm⁻¹ at 70°C and 90°C, respectively.     

Research on the electrochemistry of oxygen ion conductors in the former Soviet Union

Following previous reviews of research results on oxygen ion-conducting materials obtained in the former USSR, this article addresses the case of Bi₂O₃-based compositions. Phase formation in oxide systems with Bi₂O₃, thermal expansion, stability, bulk transport properties and oxygen exchange of bismuth oxide solid electrolytes are briefly discussed. Primary attention is focused on oxides with high ionic and mixed conductivity, including stabilized fluorite-type (δ) and sillenite (γ) phases of Bi₂O₃, γ-Bi₄V₂O₁₁ and other compounds of the aurivillius series. Another major point being addressed is on the applicability of these materials in high-temperature electrochemical cells, which is limited by numerous specific disadvantages of Bi₂O₃-based ceramics. The electrochemical properties of various electrode systems with bismuth oxide electrolytes are also briefly analyzed. Electronic Publication     

Preparation and characterization of pva based solid polymer electrolytes for electrochemical cell applications

Solid polymer electrolyte films containing poly(vinyl alcohol) (PVA) and magnesium nitrate (Mg(NO3)2) were prepared by solution casting technique and characterized by using XRD, FTIR, DSC and AC impedance spectroscopic analysis. The amorphous nature of the polymer electrolyte films has been confirmed by XRD. The complex formation between PVA and Mg salt has been confirmed by FTIR. The glass transition temperature decreases with increasing the Mg salt concentration. The AC impedance studies are performed to evaluate the ionic conductivity of the polymer electrolyte films in the range of 303 383 K, and the temperature dependence seems to obey the Arrhenius behavior. Transport number measurements show that the charge transport is mainly due to ions. Electrochemical cell of configuration Mg/(PVA + Mg(NO3)2) (70:30)/(I2 + C + electrolyte) has been fabricated. The discharge characteristics of the cell were studied for a constant load of 100 kΩ.     

Characterization on conduction properties of carboxymethyl cellulose/kappa carrageenan blend-based polymer electrolyte system

The present work deals with the development of carboxymethyl cellulose (CMC) blended with kappa carrageenan (KC) as a host-based polymer electrolyte (PE) system. The CMC/KC films were successfully prepared using solution casting method and were characterized through electrical impedance spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD) methods, respectively. The FTIR spectrum revealed that the significant region of interaction transpires at wave number 1,057, 1,326, 1,584, and 3,387?cm^?1 which correspond to the bending of C–O–C, bending of –OH, asymmetric of –COO^? as well as the stretching of –OH, respectively. It has also been demonstrated that the complexation process occurred between CMC and KC. The CMC/KC blend PE system with a ratio of 80:20 achieved an optimum conductivity of 3.91?×?10^?7?S?cm^?1 and had the lowest crystallinity percentage as suggested by the XRD analysis.     

Synthesis and electrical properties of Li1+ x M x Ti2– x (PO4)3 (where M =Sc, Al, Fe, Y; x =0.3) superionic ceramics

Compounds of the system Li_{1+ x} M _x Ti_{2– x} (PO₄)₃ (where M=Sc, Al, Fe, Y; x=0.3) were synthesized by a solid-state reaction and studied by X-ray diffraction. The ceramic samples were sintered and investigated by complex impedance spectroscopy in the frequency range 10⁶–1.2×10⁹ Hz in the temperature range 300–600 K. Two relaxation dispersions related to the fast Li⁺ ion transport in bulk and grain boundaries were found. The activation energies of the bulk conductivity and relaxation frequency were obtained from the slops of Arrhenius plots. The values of the activation energies of the bulk ionic conductivity and relaxation frequency were found to be very similar in all the materials investigated. That can be attributed to the fact that the temperature dependences of the bulk conductivity are caused only by the mobility of the fast Li⁺ ions, while the number of charge carriers remains constant with temperature. Electronic Publication     

Quasi-solid-state dye-sensitized solar cell based on a polymer gel electrolyte with in situ synthesized ionic conductors

A polymer gel electrolyte with in situ synthesized Acac-Py-I₂ ionic conductors was prepared for fabricating a quasi-solid-state dye-sensitized solar cell (QS-DSSC). The in situ synthesized Acac-Py-I₂ ionic conductors show weaker influence on the liquid electrolyte absorbency of the polymer gel electrolyte than that of Acac-Py-I₂ ionic conductors dissolved in liquid electrolyte. Owing to the higher liquid electrolyte absorbency, the polymer gel electrolyte with in situ synthesized Acac-Py-I₂ ionic conductors shows higher ionic conductivity than that of polymer gel electrolyte with Acac-Py-I₂ ionic conductors absorbed from liquid electrolyte. QS-DSSC containing the polymer gel electrolyte with in situ synthesized Acac-Py-I₂ ionic conductors shows 3.815% energy conversion efficiency, which is 21.6% higher than that of QS-DSSC containing polymer gel electrolyte with Acac-Py-I₂ ionic conductors absorbed from liquid electrolyte.     

Chitosan-based solid electrolyte composite membranes: I. Preparation and characterization

Some chitosan-based solid electrolyte composite membranes were prepared by incorporating potassium hydroxide as the functional ionic source, using glutaraldehyde as cross-linking agent. A three-layer structure with a porous intermediate layer for each composite membrane was observed using SEM. It was found that the concentration of potassium hydroxide solution used to prepare the composite membranes largely influenced the pore volume, porosity, pore size of the intermediate layer, as well as determined the content of potassium hydroxide inside the composite membranes, whereas the degree of cross-linking of composite membrane did not show notable effects. All composite membranes showed significant decreases in both their T_g and onset thermal degradation temperatures with respect to the solid cross-linked chitosan membranes without containing potassium hydroxide. Potassium hydroxide was found to be located inside the intermediate layer of composite membranes with shapes of bulky or fabric crystals. The crystalline properties of matrices of the composite membranes themselves were remarkably modified after being incorporated with potassium hydroxide and main crystalline peaks of matrices almost disappeared for all composite membranes.     

Effect of MgO nanoparticles on ionic conductivity and electrochemical properties of nanocomposite polymer electrolyte

This paper analyzes the comparison between the performances and morphologies of the PMMA gel and composite electrolyte membrane with nanosized MgO particles. These polymer electrolytes were studied in detailed using XRD, DSC, SEM and AC impedance analysis. The conductivity enhancement has been attributed to the addition of ceramic filler that yields a significant increase of surface to volume ratio related to the decrease in glass transition temperature values in the composite polymer electrolyte. Good interfacial stability at the electrode/electrolyte interface resulted on account of the improved ion dissociation by ceramic filler and a rise in the room temperature conductivity (8.14 × 10⁻³ S cm⁻¹) due to the iono-covalent or Lewis acid–base bonds to the ions and ether oxygen base groups was also observed. Further enhancement of conductivity has been observed on MgO surface, as Lewis-acidic sites interact with both PMMA and ClO₄⁻ ions. The percentage of swelling was found to increase with increasing soaking periods upto 12 h. Beyond that soaking period, it was found that there was a negligible increase in the % of swelling.     

A composite microporous gel polymer electrolyte prepared by ultra-violet cross-linking

A new type of composite microporous gel polymer electrolyte was prepared by directly coating the hydrolyzed prepolymers onto PVdF microporous membrane, and then polymerizing and cross-linking with ultra-violet (UV). Their chemical, thermal, surface microscopic configuration, swelling ability and electrochemical properties have been investigated for various prepolymer’s solution concentrations. The swelling ability and ionic conductivity of the membrane supporting hybrid gel electrolyte (MSHGE) could reach an extreme point at 0.15 g/ml of the prepolymer’s solution. It is thought that their performance can be affected by the surface microscopic configuration and the quality of coated copolymer. The Arrhenius-type relationship was observed in the temperature dependence of ionic conductivity. The ionic conductivity of MSHGE (PVdF-15) at room temperature can reach 6.18 × 10⁻³ S cm⁻¹, and its electrochemical stability window is about 4.9 V.     

Lithium transport within the solid electrolyte interphase

A LiClO₄ SEI film grown on copper was examined with time-of-flight secondary ion mass spectrometry. The SEI porosity profile and Li⁺ transport processes within the SEI were studied with isotopically labeled ⁶LiBF₄ electrolyte. An ~ 5 nm porous region, into which electrolytes can easily diffuse, was observed at the electrolyte/SEI interface. Below the porous region, a densely packed layer of Li₂O and/or Li₂CO₃ prevents electrolyte diffusion, but Li⁺ transports through this region via ion exchange.     

Novel polymer electrolytes prepared by copolymerization of ionic liquid monomers

Ionic liquid monomer couples were prepared by the neutralization of 1‐vinylimidazole with vinylsulfonic acid or 3‐sulfopropyl acrylate. These ionic liquid monomer couples were viscous liquid at room temperature and showed low glass transition temperature (Tg) at ?83 °C and ?73 °C, respectively. These monomer couples were copolymerized to prepare ion conductive polymer matrix. Thus prepared ionic liquid copolymers had no carrier ions, and they showed very low ionic conductivity of below 10^?9 S cm^?1. Equimolar amount of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to imidazolium salt unit was then added to generate carrier ions in the ionic liquid copolymers. Poly(vinylimidazolium‐co‐vinylsulfonate) containing equimolar LiTFSI showed the ionic conductivity of 4 × 10^?8 S cm^?1 at 30 °C. Advanced copolymer, poly(vinylimidazolium‐co‐3‐sulfopropyl acrylate) which has flexible spacer between the anionic charge and polymer main chain, showed the ionic conductivity of about 10^?6 S cm^?1 at 30 °C, which is 100 times higher than that of copolymer without spacer. Even an excess amount of LiTFSI was added, the ionic conductivity of the copolymer kept this conductivity. This tendency is completely different from the typical polyether systems. Copyright © 2002 John Wiley & Sons, Ltd.     

High ionic conductivity of all-solid polymer electrolytes based on polyorganophosphazenes

A series of all-solid polymer electrolytes were prepared by cross-linking new designed poly(organophosphazene) macromonomers. The ionic conductivities of these all-solid, dimensional steady polymer electrolytes were reported. The temperature dependence of ionic conductivity of the all-solid polymer electrolytes suggested that the ionic transport is correlated with the segmental motion of the polymer. The relationship between lithium salts content and ionic conductivity was discussed and investigated by Infrared spectrum. Furthermore, the polarity of the host materials was thought to be a key to the ionic conductivity of polymer electrolyte. The all-solid polymer electrolytes based on these poly(organophosphazenes) showed ionic conductivity of 10⁻⁴ S cm⁻¹ at room temperature.     

Monitoring the mechanical properties of the solid electrolyte interphase(SEI) using electrochemical quartz crystal microbalance with dissipation

Stable solid electrolyte interphase(SEI) has been well established to be critical for the reversible operation of Li(ion) batteries,yet our understanding of its mechanical properties currently remains incomplete.Here,we used an electrochemical quartz crystal microbalance combined with dissipation monitoring(EQCM-D) to investigate SEI formation.By quantitatively estimating in-situ,the change in mass,shear modulus,and viscosity of the SEI,we show that the SEI formation in propylene carbonate(PC)-and ethylene carbonate/diethyl carbonate(EC/DEC)-based electrolytes involves the growth of a rigid laye r followed by a viscoelastic layer,whereas a distinct "one-layer" rigid model is applicable to the SEI formulated in tetraethylene glycol dimethyl ether(TEGDME)-based electrolyte.With the continuous formation of the SEI,its shear modulus decreases accompanied by an increase in viscosity.In TEGDME,the lightest/thinnest SEI(mass lower than in PC by a factor of nine) yet having the greatest stiffness(more than five times that in PC) is obtained.We attribute this behavior to differences in the chemical composition of the SEIs,which have been revealed by tracking the mass-change-per-mole-of-electrontransferred using EQCM-D and further confirmed by X-ray photoelectron spectroscopy.     

Thermodynamic stability of AuSe at temperature from (400 to 700) K by a solid state galvanic cell

The numerical values on the standard thermodynamic functions of AuSe were determined by the electromotive force (EMF) method in a solid-state galvanic cell with a superionic conductor AgI as the solid electrolyte. According to the experimental data on the EMF vs. temperature, the analytical equations for Gibbs free energy, enthalpy and entropy were obtained for the single stable polymorphic form of AuSe. The temperature-dependent relationships of Gibbs free energy of formation of AuSe and the standard thermodynamic functions of compounds within the temperature range (400 to 700) K were also evaluated. No α–β transformation was identified in the gold saturation and β-form is a metastable modification of AuSe.     

以脲和硫脲为主体的高分子固体电解质的研究

研制了一种以脲和硫脲为主体的固体电解质,其室温电导率可达到6.84×10^-3S·cm^-1,分析了影响该电解质电导率的因素.初步确定该物质为一种不定型固熔体,导电机理是硫脲转化为硫氰酸铵,硫氰酸铵电离导电.     

Research on the electrochemistry of oxygen ion conductors in the former Soviet Union

This review is focused on the analysis of experimental results on oxygen ion-conducting ceramic materials based on HfO₂, CeO₂, and ThO₂, published in the former Soviet Union. In particular, the physicochemical and transport properties of fluorite-related oxides and the characteristics of electronic conduction in these solid electrolytes are briefly reviewed. Emphasis is given to electrocatalytic and electrochemical properties of cerium-containing oxides, which are promising materials for electrodes of electrochemical cells operating in reducing atmospheres, and mixed-conducting membranes. A comparative analysis of specific features of the solid-electrolyte ceramics based on hafnia, zirconia, ceria, and thoria is performed in order to reveal basic tendencies of oxygen ionic transport in fluorite-type oxides, and to identify the potential applicability of these materials in various high-temperature electrochemical devices. Received: 23 September 1999 / Accepted: 10 October 1999     

Temperature-dependences of cationic mobility and carrier generation in solid polyether media

The temperature-dependences of cationic conductivity and mobility in a macromolecular lithium salt/copolyether blend were investigated by means of complex impedance analysis and a time-of-flight technique, respectively. The transient ionic current after reversing the d.c. bias polarity exhibits two peaks, corresponding to cationic and anionic movement respectively, and verifying a cationic transfer number of 0.99 at 50°C. The comparison between conductivity and mobility makes it possible to reveal the temperature-dependence of the cation carrier number. As a result, the population of free ions was found to decrease exponentially with increasing temperature. However, this “anomalous” behavior of salt dissociation has little effect on the temperature-dependence of conductivity, since it is cation carrier mobility rather than its number which is the main factor influencing the ion transport process.     

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．     

Investigation of the anodic decomposition of the solid electrolyte RbCu4Cl3I2

The process of electrochemical decomposition of the solid electrolyte RbCu₄Cl₃I₂ at a vitreous carbon electrode has been investigated. The anodic decomposition of the electrolyte occurs in two steps. At first, the oxidizing electrode reaction of Cu⁺ ions to Cu²⁺ ions takes place at potentials higher than 0.57 V and a layer of decomposition products is formed on the electrode surface, including the divalent copper compound RbCuCl₃. Then the oxidizing reaction of I^– ions occurs at potentials higher than approximately 0.67 V, with deposition of an iodine layer onto the electrode surface. The deposition rate of the layers of decomposition products is controlled by instantaneous nucleation and two-dimensional growth of the deposit. The total thickness of the passivating layer of decomposition products on the anode is equal to ca. 1 μm. Electronic Publication