Solid State Ionics

The following sections are included:

• PERFACE

• CONTENTS

A phase equilibria diagram is a pictorial representation of the thermodynamic equilibria between phases in any given chemical system and must obey the Gibbs Phase Rule, P+F = C+2, where P = the number of phases, F = the degrees of freedom and C = the number of components. However, in practice, the experimental phase equilibria diagram is a compromise between the constraints imposed by the Phase Rule and the observed experimental data, colored by the experimentalist's prejudices. The latter of course are dependent on the type, amount and quality of the experimentalist's education and experience. Furthermore, the results are very strongly dependent on the type of experimental data accumulated, and the sophistication of the instrumentation utilized. For all these reasons, the phase equilibria diagram for a given system tends to change with time. As more and more data are accumulated by more and more workers, the diagram should become more representative of the true equilibrium conditions. However, it is very likely that no diagram is ever completely finished. Nevertheless, even crudely constructed diagrams based on very little experimental data can be of value to the industrial community. Any real information is better than none at all! The discussion of experimental techniques and problems involved in the determination of phase equilibria diagrams will be limited to temperature–composition diagrams at constant pressure. The talk includes specific examples of ceramic oxide systems chosen to illustrate problems associated with phases with possible "ions in motion".

In materials featuring high ionic conductivities, structural and dynamic disorder is the key factor. In such materials, which may be crystalline, glassy or polymeric, ionic transport cannot be described in terms of individual defects performing random walks in a static energy landscape. Instead, we are facing a challengingly complicated many-particle problem, with the mobile ions interacting with each other and with their surrounding matrix, thus creating a dynamic energy landscape. The hopping motion of the mobile ions is now highly correlated. Today, one of the central problems of solid state ionics consists in finding simple, yet relevant rules for describing the development of the complicated ion dynamics with time, from the individual hop to macroscopic transport, i.e., from less than a picosecond up to minutes and hours. Experimentally, this development is best monitored by taking spectra of the complex conductivity, covering a range of frequencies from less than 1 mHz up to more than 100 THz, i.e., of more than 17 decades. The connection between such spectra and the time-dependent ion dynamics is provided by linear response theory. It is, therefore, possible to model the dynamics in terms of simple equations ("rules") and to compare the resulting frequency-dependent conductivities and permittivities with the experimental ones. We present such rules along with state-of-the-art complex-conductivity spectra of crystalline and glassy ion conductors. The essential features of the experimental spectra are indeed well reproduced by the model. The model equations convey a physical meaning that is easy to visualise. The basic idea of our "MIGRATION concept" is contained in the acronym, standing for MIsmatch Generated Relaxation for the Accommodation and Transport of IONs.

The following sections are included:

• Introduction

• Setting the scene

• Theory of ordered solid solutions

• Chemical kinetics of the solid state

• Solid state electrochemistry

• Diversifications

• References

LaGaO₃ based perovskite oxide exhibits a high oxide ion conductivity over wide P_o2 range and the application of this new fast oxide ion conductor, LaGaO₃, to the electrolyte of intermediate temperature SOFC (IT-SOFC) is strongly expected. The high power density of the cell was achieved by using LaGaO₃ based oxide for electrolyte. The power density was further improved by doping small amount of Fe, Co, or Ni for Ga site and the maximum power density of 500 mW/cm² was achived by using 0.2mm thick LaGaO₃ based electrolyte. 1kW fuel cell stack using LaGaO₃ based oxide for electrolyte was successfully developed by Mitsubishi Materials and Kansai Electric Power Company. The operating temperature of this unit is around 1023 K and degradation rate of power density fading is less than 0.3 % per 1000h.

An intermediate temperature solid oxide fuel cell (ITSOFC) based on 8YSZ electrolyte, La_0.6Sr_0.4CoO_3-δ (LSCo) cathode, and Ni-8YSZ anode were fabricated by atmospheric plasma spraying (APS) technique. The cell components i.e. anode, electrolyte and cathode were consecutively deposited onto a porous Ni-plate substrate. The results showed that the spray parameters played an important role in controlling microstructure and performance of the cell component coating. The spray parameters were investigated by an orthogonal experiment in order to prepare a thin gas-tight 8YSZ electrolyte layer. By proper selection of the spray parameters the sprayed NiO+8YSZ layer after reducing with hydrogen showed a good electrocatalytic activity for H₂ oxidation. With the similar treatment, the deposited LSCo cathode showed a good cathode performance and chemical compatibility with 8YSZ electrolyte. Output power density of the APS fabricated cell achieved 410 mW/cm² at 850□ and 260 mW/cm² at 800□. The main factors affecting the cell performance were discussed. Electrochemical characterization indicated that IR drop of 8YSZ electrolyte, cathodic polarization, and the contact resistance at LSCo/8YSZ interface were the main factors restricting the cell performance.

For anode-supported SOFCs, concentration polarization loss in the anode can be a crucial problem because fresh fuel and electrochemical reaction products have to diffuse through a thick anode substrate in the opposite direction between the flow field (fuel distribution channel) and the anode/electrolyte interface. In order to investigate the diffusion characteristics of a fuel in the anode-substrates, limiting current density with a diluted H₂ was measured and analyzed. Diffusion parameters obtained by the analysis were verified by measurement of the limiting current density with diluted CO and voltage response for depolarization process after current-interruption.

Recent results on intermediate temperature-operating solid oxide fuel cells (IT-SOFC) are mainly focused on getting the higher performance of single cell at lower operating temperature, especially using planar type. We have started a project to develop 1 kW-class SOFC system for Residential Power Generation(RPG) application. For a 1 kW-class SOFC stack that can be operated at intermediate temperatures, we have developed anode-supported, planar type SOFC to have advantages for commercialization of SOFCs considering mass production and using cost-effective interconnects such as ferritic stainless steels. At higher temperature, performance of SOFC can be increased due to higher electrochemical activity of electrodes and lower ohmic losses, but the surface of metallic interconnects at cathode side is rapidly oxidized into resistive oxide scale. For efficient operation of SOFC at reduced temperature at, firstly we have developed alternative cathode materials of LSCF instead of LSM to get higher performance of electrodes, and secondly introduced functional-layered structure at anode side. The I-V and AC impedance characteristics of improved single cells and small stacks were evaluated at intermediate temperatures (650°C and 750°C) using hydrogen gas as a fuel.

The anode supported PEN configuration has been commonly accepted as the favorite design for the intermediate temperature SOFCs. The key to perform its promise in the commercialization is to develop proper thin film techniques to fabricate electrolyte on anode support. This article presents briefly the results on preparation of thin electrolytes on anode support by employing techniques, including tape-casting and co-firing processes, screen printing, dip-coating from particle suspensions, and the novel CVD processes, newly developed at the author's lab. The electrolytes materials involve Y₂O₃ stabilized ZrO₂, Gd₂O₃ doped CeO₂, Sm₂O₃ doped CeO₂, Y₂O₃ doped CeO₂ as well as Yb doped SrCeO₃ The morphology and thickness of these thin electrolytes deposited on anode support and the performance of SOFCs based on the thin electrolyte/anode structure are mainly reported. An evaluation on these techniques is made from viewpoint of applicability for SOFC commercialization.

We developed anode supported flat tube SOFC to improve the power density of the cylindrical tube cell and studied basic technology of key components in anode supported flat tube SOFC such as electrode, electrolyte, ceramic interconnect materials, and metallic bipolar plate materials for making the cell stack. Performance of the flat tube cell showed 300 mW/cm² (0.6V, 500 mA/cm²) at 800°C. Fe-16Cr (SUS 430) alloy as metallic bipolar plate was coated with LSM (La_0.85Sr_0.15)_0.9MnO₃) and LCC (La_0.75Ca_0.27CrO₃) and their electrical conductivity and microstructure were examined. The Fe-16Cr alloy with LSM coating layer was sustained for 2600hrs with 70mΩcm² without increasing it's value and the alloy with LCC layer showed lower resistance. These results indicated that these metallic bipolar plates could be used effectively for making anode supported flat tube cell stack. As ceramic interconnect of flat tube cell, several kinds of materials with compositions of La_1-xCa_xCrO₃ were synthesized by Pechini method and coated onto one side of the anode flat tube in the form of band by plasma spray and vacuum slurry coating method. Through these experiments, we obtained basic technology of the anode-supported flat tube cell and established the proprietary concept of the anode-supported flat tube cell stack.

An ITSOFC consisted of Ni/YSZ anode supported YSZ composite thin film and La_0.6Sr_0.4CoO₃ (LSCO) cathode combined with a Ce_0.8Sm_0.2O_1.9 (CSO) interlayer was studied. Tape cast method was applied to prepare green sheets of Ni/YSZ anode supported YSZ composite thin film. After isostatic pressing and cosintering, the YSZ film on the Ni/YSZ anode was gas-tight dense, and 15-30μm thick. The area of the composite film was over 100 cm². A CSO interlayer was sintered on to the YSZ electrolyte film to protect LSCO cathode from reaction with YSZ at high temperatures. The LSCO cathode layer was screen printed onto the CSO interlayer and sintered at 1200°C for 3h to form a single cell. The obtained single cell was operated with H₂ as fuel and O₂ as oxidant. The cell performance and impedance were measured and discussed relating with the component contributions.

A polymer composite membrane incorporated with a hygroscopic material for high temperature polymer electrolyte membrane fuel cell was prepared by hot pressing the mixture of melt fabricable perfluorosulfonylfluroride copolymer resin (Nafion resin) with fine mordenite powder. The results of current-voltage relationship at various operation temperatures showed that the composite membrane containing 10 wt.% mordenite has better performance than the others. It suggests that the improvements of fuel cell performance are not due simply to increased water content in the composite membrane, but that there is an interaction between proton mobility and structure.

The following sections are included:

• Acknowledgement

• References

Experimental results of photoelectron-based microscopic and spectroscopic studies on the kinetics of the Pt/YSZ electrode are summarized. Photoelectron Emission Microscopy (PEEM) offers information on the spatial distribution of surface species which influence the work function. Scanning Photoelectron Microscopy (SPEM) or μ-ESCA offers additional spectroscopic information on the chemical identity of surface species. We compare the oxygen and zirconium signals for conventional chemical adsorption and electrochemical pumping experiments. First evidence for different reaction paths is given.

The concept of "charge carrier maps" is briefly introduced; the maps can depict the predominant charge carrier (i.e., oxide-ion, proton, hole and electron) domains of metal oxides as functions of temperature, T, oxygen partial pressure, P(O₂), and hydrogen partial pressure, P(H₂) in a uniform format. As the concrete examples, the "charge carrier maps" of (Ce_0.8Sm_0.2)O_2-δ fluorite-type oxide, (La_0.9Sr_0.1)(Ga_0.9Mg_0.1)O_3-δ and (La_0.9Sr_0.1)ScO_3-δ perovskite-type ones are shown. These maps are useful to predict the T, P(O₂), and P(H₂) ranges where each oxide can be used as the electrolyte or electrode material of high temperature electrochemical devices such as solid oxide fuel cells, gas sensors, gas separation membranes, etc.

Powders and dense crystalline bodies were prepared for manganese-chromium-iron oxides to evaluate the oxide scales formed on the surface of alloy interconnect of solid oxide fuel cells (SOFC). MnCr₂O₄-based spinel oxides were obtained, and the lattice parameter increased with iron substitution for chromium at B-site. The iron can substitute for manganese at A-site as well as chromium. MnCr₂O₄ is stable and has low oxygen isotope diffusivity, however, the fast diffusions of both oxide ion and cations were observed for iron substituted samples (MnCr_2-yFe_yO₄). The lattice parameter expanded by the long term annealing in 1% H₂O + air at 1073 K, indicating that the iron rich phase is more stable in oxidizing conditions.

Effects of various additives to Ni anode on SOFC using La_0.9Sr_0.1Ga_0.8Mg_0.2O₃ based oxide were investigated in this study. Among the examined additives, it was found that the addition of small amount of Fe is highly effective for increasing the anodic activity. When 5 wt% Fe was added to Ni anode, the anodic overpotential was as small as 34 mV at 873 K, 0.1A/cm², which is almost half of pure Ni anode. Since the estimated activation energy for anodic reaction decreased, addition of Fe to Ni seems to be effective for increasing the activity of Ni for anodic reaction. XRD measurement after power generating property suggests that added Fe was formed alloy with Ni. Consequently, this study reveals that Ni-Fe bimetal is highly active for anodic reaction of SOFCs at decreased temperature.

Mechanical properties of creep rate and fracture strength were investigated on rare earth doped ceria. The samples were prepared by coprecipitation method, and relative density was over 90% for each composition. Creep test of yttria doped ceria (Ce_1-xY_xO_2-X/2, x = 0 ~ 0.2) was performed using 4-point bending method under a constant load at temperature range of 1050 ~ 1125°C, applied stress of 20 ~ 50 MPa and oxygen partial pressure of P(O₂) = 0.21~10^-15.2 atm. The testing conditions were decided taking into the operating conditions of SOFC. Steady state strain rate calculated from creep curve showed clear oxygen partial pressure dependence. The creep rate increased as decreasing P(O₂) and showed a peak at P(O₂) = 10^-13.6atm. The activation energy of creep was increased from 264kJmol^-1 to 333kJmol^-1 in accordance with P(O₂) decreasing. The activation energy was much higher than reported activation energy of anion diffusion in ceria. So it is concluded that creep control species is cation in air and reduction atmosphere. Since the electrical conductivity and nonstichiometry of this material show similar P(O₂) dependence, the results obtained this work suggest the coincidence between cation and anion diffusion processes in this material. It is also found that the creep mechanism of Ce_0.8Y_0.2O_1.9 changed from Nabarro-Heriing creep to grain boundary sliding in reduction atmosphere which P(O₂) was lower than 10^-14.5 atm. Fracture strength of rare earth doped ceria (Ce_1-xR_xO_2-x/2, R = Y, Sm, Gd, x = 0 ~ 0.2) was measured by small punch testing method. Test was performed in air at room temperature. Fracture strength showed significant dependence on dopant density, and had a minimum value at x = 0.05 and a maximum value at x = 0.1. The paper will discuss between the relationship between the mechanical properties and electrical properties on doped ceria.

Mesoporous Al₂O₃ was synthesized by the sol-gel method and the pore size was controlled over the range of 3-15nm. Proton conductivity of these samples was examined, which was as high as 0.004 S·cm-1 at 25°C. A systematic dependence of conductivity upon pore size was observed, in which the conductivity increased with increasing the pore size. Meanwhile the conductivity increased with increasing the humidity. Two peaks were observed in ¹H NMR spectra, assigned to a "mobile" and an "immobile" proton, respectively. It can be seen that the conductivity of mesoporous-Al₂O₃ increased with increasing the "mobile" proton concentration. From TG-DTA measurement, proton species were categorized into three groups. It is suggested the group II protons have close relation with the NMR observed "mobile" protons.

A multi-layer composite cathode material has been investigated. The cathode on YSZ electrolyte disk was fabricated by spraying the mixtures with different ratios of La_0.7Sr_0.3MnO₃ (LSM), La-Sr-Co-Fe-O (LSCF) and YSZ for different layers. The preparation process was separated into two steps, the LSM/YSZ layers were sprayed at first and the samples were sintered at 1100°C, then the layers of LSM/LSCF were sprayed and sintered at 900°C-1000°C. XRD results show that the solid reaction between YSZ and perovskite phase has been restrained. There are more pores in the topper layers with LSCF and LSM sintered at lower temperature than the layers with LSM and YSZ sintered at higher temperature. The results of resistance for each layer measured at high temperature show that the conductivity increases with the increasing of LSM and LSCF ratio. However, the thermal expansion coefficient (TEC) increases too. The results of electrochemical measurement show that the material has the better performance than that of LSM and LSCF, the polarization resistance for this sample is about 0.3Ω.cm² at 800°C. The preparing process has been optimized and the best technique condition is to sinter the cathode at 900°C for 4h.

Scandia stabilized zirconia (ScSZ) is a candidate new electrolyte for use at intermediate temperature solid oxide fuel cells (SOFC). ScSZ powders for membranes of SOFC were synthesized using Pechini or solid state reaction methods. The cubic-rhombohedral phase transformation and phase stability of ScSZ was investigated using XRD and DSC/TG. The appearance of the rhombohedral phase was inhibited by the addition of transition oxide (MnO₂). Thermal analyses and phase compositions of the precursors and synthesized powders were performed using DSC/TG and XRD.

Protonic-electronic mixed conductors are of particular interest due to their variety of possible applications. Some acceptor-doped perovskites known as high-temperature proton conductors (HTPCs) are counted as solid electrolytes because they have quite small electronic conductivities in moist reducing atmospheres. In this paper, mixed protonic-electronic conduction has been investigated for transition-metal doped perovskite-type oxides, intending to add electronic conductivity to the base HTPCs. The mixed conduction was experimentally suggested for Y-doped BaCeO₃ and SrZrO₃ when they are co-doped with ruthenium. These materials actually showed hydrogen permeability with respect to the ambipolar diffusion ensuring the ionic-electronic mixed conduction. The mixed-conducting mechanism is revealed by electrochemical and spectroscopic measurements.

Yttria-stabilized-zirconia (YSZ) can be used as an oxygen permeating membrane at elevated temperature (>1400°C). The permeation kinetics can be different in different surrounding atmosphere, e.g., the bulk-diffusion limit in high Po₂ and the surface-exchange limit in low Po₂, as shown in this study. The oxygen flux of YSZ was measured as a function of the temperature (>1400°C) and Po₂ (1 ~ 1 × 10^-3, 2 × 10^-3 ~ 2 × 10^-7 atm and 3 × 10^-12 ~ 2 × 10^-8 atm). In high and middle Po₂ region, the measured oxygen flux matches well the value estimated from the reported electrical conductivity. This observation implies that the oxygen permeation was mostly limited by the bulk diffusion, which was proved by (in high Po₂) or (in middle Po₂)-dependence of oxygen flux. However, in very low Po₂ region, the measured oxygen flux was about one order of magnitude smaller than the expected value. It means that the oxygen permeation was mostly limited by the surface oxygen-exchange kinetics in spite of very high temperature. Therefore, the modification of YSZ surface with porous coating layer was considered as one method for increasing the oxygen flux. YSZ, YSZ-GDC, and GDC (Gd-doped ceria) were coated on both sides of YSZ and the flux was measured and compared with that without coating layer. Among them, the oxygen flux of GDC-coated YSZ drastically increased. However, the increased flux was not maintained for long time due to the reaction and sintering of porous layer.

The grain-boundary conduction of 15 mol% Calcia-Stabilized Zirconia (CSZ) was improved markedly by post sintering heat-treatment (HT). The grain-boundary conductivity increased ~7 times when the specimen was heat-treated at 1300°C for >10h during cooling after sintering. From the change of the intergranular phase in crystallinity, morphology, and composition by HT, the dewetting of the intergranular phase due to its crystallization was suggested to decrease the current constriction effect near the grain boundary.

This paper describes the preparation of Pr_0.7Sr_0.3Fe_0.8Al_0.2O_3-δ membranes by means of tape-casting technique, and their oxygen permeation and methane reforming properties. Pr_0.7Sr_0.3Fe_0.8Al_0.2O_3-δ powders were prepared by a conventional solid-state reaction technique. The resultant powders were mixed with solvents, dispersants, binders, and plasticizers; the amount of additives was optimized to give an appropriate viscosity in the range of 1000 ~ 4500 mPa·s. The slurry was tape-cast by using doctor-blade-type apparatus. After tape-casting, green sheets were densified by sintering at 1400 °C for 5 h. As a result, crack-free dense membranes with thickness in the range 60 ~ 100 μm were successfully prepared. An oxygen flux density of 9.7 μmol·cm^-2·s^-1 was attained for 68 μm-thick membrane at 1000 °C under air (100 sccm) / Ar-10%CH₄ (270 sccm) gradients. The oxygen flux density increased as pure CH₄ (20 sccm) was fed to permeate side; the highest oxygen flux density of 4.6 μmol·cm^-2·s^-1 was attained for the same tape-cast membrane with CO selectivity and CH₄ conversion of 98 % and 32 %, respectively.

ScSZ(Scandia Stabilized Zirconia) powders with 8-11 mol% scandia were synthesized for the electrolyte of a solid oxide fuel cell using glycine nitrate process. The powder was compacted into a disc and sintered at 1600°C for 6 hours in air. The sintered compact was characterized using impedance analysis to estimate ionic conductivity. X-ray diffraction to identify the phases, scanning electron microscopy to study the morphology and thermomechanical analysis to estimate linear thermal expansion coefficient. The ScSZs generally showed much higher ionic conductivity than the conventional YSZ electrolyte at a relatively low temperature of 800°C, with the highest value of 0.16 S/cm for 8ScSZ(ScSZ with 8 mol% Scandia) which could be compared to 0.07 S/cm for 8YSZ. A density of 99% of the theoretical value was obtained for the sintered 8ScSZ compact which was 8 mm in diameter and 1 mm thick. 8ScSZ consist of a mixture of cubic and tetragonal phases after sintering. The phase stability of 8ScSZ in contact at 1000°C with La_0.5Sr_0.5MnO₃, one of the most frequently used cathode materials, turned out to be fairly good. Its linear thermal expansion coefficient was measured to be 11.9 × 10^-6/°C which was very close to 11.5 × 10^-6/°C for La_0.5Sr_0.5MnO₃.

Electronic conductivity of doped lanthanum gallate electrolytes were determined by using a Hebb-Wagner type polarization cell. Electronic conductivity of cobalt-doped, La_0.8Sr_0.2Ga_0.8Mg_0.15Co_0.5O_3-δ (LSGMC), and non cobalt-doped, La_0.8Sr_0.2Ga_0.8Mg_0.2O_2.8 (LSGM8282), were measured as a function of oxygen partial pressures. The electronic conductivity of LSGM8282 showed a linear dependence on p(O₂)^1/4 in the higher p(O₂) region, which is attributed to the electronic hole conductivity. The electronic conductivity of LSGMC showed a linear dependence on p(O₂)^1/6 in the higher p(O₂) region. LSGMC has higher electronic conductivity than LSGM, and the conductivity was not clearly changed with temperatures between 600 and 800 °C. In lower p(O₂) region, the electronic conductivity data have poor reproducibility and did not show any dependence on p(O₂) because of the degradation of the electrolytes in severe reducing atmospheres.

To get a stable and dense interconnect layer of anode-supported flat tubular solid oxide fuel cell stack, we have studied on the synthesis of precursors with a fine particle size and the ceramic interconnect coating technology. Coated interconnects by slurry dipping and air plasma spray processes were sintered by 2-step sintering method. Ca-doped LaCrO₃ perovskites such as La_0.75Ca_0.27CrO₃(LCC27), La_0.6Ca_0.41CrO₃(LCC41), and La_0.8Sr_0.05Ca_0.15CrO₃(LSCC), were synthesized by Pechini process and their average particle sizes were about 1 μm. LSCC layer is a functional layer to prevent Ca migration and then LCC41 layer is coated onto it. The Ca migration in the LSCC layer did not occur. The LCC41 was coated on the air plasma spray-coated LCC27 layer by slurry dip coating process and sintered at 1200°C for 20hr. Its electrical conductivity indicated about 27 S/cm at 800°C and the bubble test showed that there is no gas permeation at pressure difference of 0.4 kg_f/cm² at room temperature.

An anode-supported micro tube SOFC was developed to increase the cell power density and thermal stability by decreasing diameter of tube. Also, the decreasing diameter of tube was possible the rapid start-up of the micro tube SOFC due to rapid heating at operating temperature. In this paper, we investigate the micro tube SOFC for the rapid start-up. The micro tube SOFC consisted of an extruded Ni/YSZ anode tube with an outside diameter and thickness of approximately 6mm and 2mm, respectively. The quick starting operation of a micro tube SOFC was demonstrated. The cell reached the operating temperature and started generating electricity. It took only 20 second to starting with butane as fuel. The propeller of quick starting demonstrator was operated during 45 minute. During the propeller turning, the output current of micro tube SOFC was on the average 0.4A at 0.2V. Also, we investigate the effect of nano YSZ for the improved performance of micro tube. The good stability of the aqueous nano YSZ suspension was investigated the effect of the pH on the anionic polymer. The surface charge of nano YSZ was reduced as the addition of polyacrylic acid at pH 7.5. This surface charge behavior was well correlated with the dispersion stability of suspension.

The high temperature stability of alkaline-earth metal substituted lanthanum manganites, (La_1-xSr_x)_yMnO₃ (x = 0, 0.1, 0.2 and 0.3; y = 1.0 and 0.95), and reactivity with the yttria-stabilized zirconia(8YSZ) have been investigated in pure O₂, air, Ar and 1%H₂/99%N₂ gas atmosphere. (La_1-xSr_x)_yMnO₃ (x = 0.1, 0.2 and 0.3; y = 1.0 and 0.95) was partially decomposed to produce (La, Sr)₂MnO₄ and MnO in 1%H₂/99%N₂ atmosphere. (La_1-xSr_x)_yMnO₃ (x = 0, 0.1, 0.2 and 0.3; y = 1.0 and 0.95) reacted with 8YSZ and formed La₂Zr₂O₇ and SrZrO₃ as reaction products in 1%H₂/99%N₂ atmosphere. The reactivity of (La_1-xSr_x)_yMnO₃ were depressed with increasing of alkaline-earth metal substitution and nonstoichiometry of La site.

Although La_1-xSr_xMnO₃ (LSM) is a good cathode material on zirconia-based electrolyte, it shows high cathodic overpotential on LaGaO₃–based electrolyte. The reaction between LSM and LaGaO₃-based electrolyte was cited as a possible reason. When LSM was composited with LaGaO₃-based electrolyte and processed at low temperature, the much reduced cathodic overpotential was observed.

When composite was used as a cathode on La_0.9Sr_0.1Ga_0.8Mg_0.2O₃(LSGM) electrolyte for intermediate temperature SOFC, composite cathode showed better performance with smaller IR drop and low cathodic overpotential than LSM cathode. However, the overpotential of fuel cell employing the LSM-LSGM composite cathode was still too high in spite of the improvement.

In this study, La_0.6Sr_0.4CoO₃ (LSC) was tested as a cathode on LaGaO₃ since LSC has the higher mixed conductivity than LSM. The current interruption method was used to measure IR drop and thus to see the reaction between LSC and LaGaO₃. LSC showed much reduced cathodic overpotential than LSM. A porous LSC-LSGM composite cathode coated on a dense LSGM electrolyte exhibited similar or slightly worse performance than LSC cathode. Thus the improvement using composite cathode is minimal for LSC-LSGM system.

Fuel processing is a bridging technology for faster commercialization of fuel cell system under lack of hydrogen infrastructures. Argonne national laboratory has been developing fuel processing technologies for fuel cell based electric power. We have reported the development of novel catalysts that are active and selective for hydrocarbon reforming reactions. It has been realized, however, that with pellet or conventional honeycomb catalysts, the reforming process is mass transport limited. This paper reports the development of catalyst structures with microchannels that are able to reduce the diffusion resistance and thereby achieve the same production rate within a smaller reactor bed. These microchannel reforming catalysts were prepared and tested with natural gas and gasoline-type fuels in a microreactor (1-cm dia.) at space velocities of up to 250,000 per hour. These catalysts have also been used in engineering-scale reactors (10 kWe, 7-cm dia.) with similar product qualities. Compared to pellet catalysts, the microchannel catalysts enable a nearly 5-fold reduction in catalyst weight and volume.

As alternative bipolar plate for PEMFCs, the carbon composites bipolar plates were fabricated by machining and compression molding methods. To examine the feasibility of the compression molding method for fabrication of bipolar plate, contact resistance, flexural strength, density, gas tightness, water absorption and plate uniformity used for the carbon composite bipolar plate using compression molding method were measured and compared with those of machined graphite and carbon composite bipolar plate, which are the most commonly used bipolar plate for conventional bipolar plate. All results of them showed that the carbon composite bipolar plate using compression molding method was promising candidate for PEMFC bipolar plate material. In case of i-V characteristics of the single cell test, the single cell using carbon composite bipolar plate made by compression molding exhibited considerable initial and long-term performance compared with conventional bipolar plates.

Several noble metals were prepared as the electrocatalyst of oxygen electrode for PEM URFC system and evaluated on the URFC performance in a single cell PEM URFC system. Among the catalysts prepared in the present study, PtIr showed the best URFC performance revealing high round-trip efficiency and stability during the cycling operation of the URFC system. On the other hand, Pt/C, PtRu and PtRuOx showed serious performance loss during the cycling operation of the URFC system.

In this study, we prepared various mixed oxide catalysts by the method of coprecipitation and tested their reactivity in the selective oxidation of CO in hydrogen. Among the binary combinations of CuO-CeO₂, CuO-Fe₂O₃ CuO-ZrO₂, NiO-CeO₂, and Co₂O₃-CeO₂, the CuO-CeO₂ was found to be the best catalyst for the selective oxidation. The activity of CuO-CeO₂ catalyst increased with Cu loading up to 10 at% (Cu/(Cu+Ce)) but did not increase further with Cu loading above 10 at% to 50 at%. Addition of oxides of Mg, Ca, Mn, Zn, Al, Ni, Co, La to the 20at% CuO-CeO₂ catalyst did not affect the activity, reconfirming that the combination CuO-CeO₂ alone was highly active for the reaction. pH of the precipitation in the range of 8-12 and aging of the precipitates for 1-10 hours did not affect appreciably the BET area and the reactivity of the catalysts. Among three calcination temperatures of 300°C, 500°C and 800°C of the precipitate, calcinations at 800°C caused considerable sintering of CeO₂ and formation of bulk CuO on the surface by driving out the Cu species dispersed in CeO₂, reducing the activity and BET area. X-ray diffraction measurements of the CuO-CeO₂ catalysts revealed the presence of CuO bulk phase in the catalysts above 20 at% Cu, whereas the catalyst with Cu loading lower than 20at% only showed the characteristic fluorite structure of CeO₂, indicating that bulk CuO did not contribute to the activity of the catalysts and the finely dispersed Cu species closely interact with CeO₂ were the active sites for the reaction.

Electrochemical oxidation of thiocyanate in sulphuric acid medium at 0-2°C was studied using cyclic voltammetry. The electro oxidation produces trithiocyante, SCN₃^- as the relatively stable, reducible species. The SCN₃^- is produced only up to a limited potential range at low concentration of thiocyanate. The potential range of SCN₃^- formation increases with increase in concentration of thiocyanate and it is exclusively produced in the potential range of 0.450 - 1.40 V with 1.0M thiocyanate.

Impedance arising from ion-conducting polymer electrolyte membrane systems was examined using electrical impedance spectroscopy in this study. The Nyquist plots showed that the impedance at high frequencies included significant geometric effects of the impedance-measuring cell. The impedance measurements at low frequencies below 150 Hz described the ion-conducting polymer electrolyte membrane systems. They consisted of an ion-conducting polymer electrolyte membrane, bulk electrolyte solutions, diffusion boundary layers and/or microscopic phenomena (i.e., electrical double layers and micro-fluid flows) arising from heterogeneous transport of counter ions between the ion-conducting polymer electrolyte membrane and electrolyte solutions. Taking into account the physical and electrochemical understandings of the ion-conducting polymer electrolyte membrane system, an equivalent circuit was suggested to quantitatively analyze each component of the ion-conducting polymer electrolyte membrane system. In order to confirm the reliability of the proposed equivalent circuit, the obtained impedance data was analyzed using the equivalent circuit. As a result, it was found that the effects of the heterogeneous transport (i.e., the effects of the electrical double layers) of the counter ions caused more energy loss rather than the effect of diffusion boundary layer (i.e., the effects of the concentration polarization). Moreover, the electrical impedance spectroscopy enabled to identify that the micro-fluid flows relieved the effect of the severer concentration polarization, resulting in an increase in conductivity of the system at higher current density.

In this paper, we report the oxygen permeability of a model composite of (La_0.8Sr_0.2)_0.98MnO_3±δ and 8mol% Y₂O₃ stabilised ZrO₂. The membrane was tested successfully for a period of more than 200 hours at temperatures in the range 1073-1273K with significant contribution of phase reactions during operation being excluded. The activation enthalpy for permeation was calculated to be 155 kJ/mol. The composite was shown to have an overall significant improvement of the oxygen permeation in comparison to the individual parent materials and comparable to La_0.8Sr_0.2Fe_0.8Co_0.2O₃. This is in excellent agreement to our earlier studies showing relatively high surface exchange and diffusion coefficients for this material from isotope exchange experiments.

Mixed electronic-ionic conducting La_0.6Sr_0.4Co_0.2Fe_0.8O₃ ceramics were prepared by a citrate method and a conventional solid state method, respectively. The chemical state of oxygen on the surfaces of the ceramics made by the two different methods was characterized by X-ray photoelectron spectroscopy (XPS). It was detected that there are five different kinds of oxygen on the ceramic surfaces, including lattice oxygen (O_L), chemisorbed oxygen (O_C) in the forms of O^-2, O^-1 and , and oxygen in hydroxyl environment (O_H). The concentrations of O_C + O_H relative to total detected oxygen attain 67.11% and 64.80% for the specimens made by the citrate method and the solid state method, respectively. Compared with the specimen made by the solid state method, the specimen made by the citrate method generally exhibits relative larger electronic conductivity and ionic conductivity at an identical measuring temperature. An essential relation between the chemical states of oxygen on the surfaces and the electrical nature of the ceramics was confirmed. It was considered that the mixed electronic-ionic conducting properties are responsible for the complex chemical states of oxygen on the ceramic surfaces.

La_0.6Sr_0.4Co_0.2Fe_0.8O₃ powders were synthesized by a glycine-nitrate process (GNP). A pure perovskite structure was produced by calcining at 750°C for the powders with a mole ratio of glycine to total metal cation content (G/M) in the range of 2.0-3.0. The microstructural evolution and mixed electronic-ionic conducting properties of La_0.6Sr_0.4Co_0.2Fe_0.8O₃ ceramics made by the GNP method (G/M = 2.0) were investigated in the sintering temperature range of 1100-1250°C. The results confirm an important role of sintering temperature on the microstructure and mixed conducting properties of the ceramics. The preferred sintering temperature of La_0.6Sr_0.4Co_0.2Fe_0.8O₃ ceramics made by the GNP method (G/M = 2.0) was ascertained to be 1200°C with respect to the mixed conducting properties. La_0.6Sr_0.4Co_0.2Fe_0.8O₃ synthesized by the GNP method (G/M = 2.0) exhibits superior sinterability and mixed conducting properties than that synthesized by a conventional solid state reaction method.

For the use of hydrogen separation from reformed hydrocarbons, electrochemical hydrogen pumping using high temperature-type proton-conducting solid electrolytes has been investigated. Conventional porous Pt electrodes had quite poor activity for SrZr_0.9Y_0.1O_3-α electrolytes; the electrodes showed quite high overpotentials both as the anode and cathode. This feature was dramatically improved by employing electroless-plated Pt electrodes. High performance of the plated Pt electrode can be explained in terms of the triple phase boundary. Compatibility between SrZr_0.9Y_0.1O_3-α and Pt is discussed by comparing their pumping capacities with Pt/SrCe_0.95Yb_0.05O_3-α that is characterized by high hydrogen pumping ability.

The electrical conductivities of Ca_1-xZrO_3-δ (0 ≤ x ≤ 0.1) systems were measured as a function of Ca/Zr ratio, temperature and oxygen partial pressure (Po₂) by using impedance spectroscopy at temperatures between 550°C and 1100°C. Stoichiometric CaZrO₃ revealed poor sinterability due possibly to the free CaO observed at grain junctions. With decreasing Ca/Zr ratio, both the ionic and electronic conductivity rapidly decreased, ~ 100 times, when the Ca content decreased below 0.98. The activation energy of grain boundary resistivity also rapidly increased with decreasing Ca/Zr ratio. The total conductivity of stoichiometric CaZrO₃ was proportional to in high Po₂ region and it was Po₂ independent in low Po₂ region. The ionic transference number revealed that CaZrO₃ is a mixed ionic and electronic (hole) conductor above 10^-13 atm and it is an ionic conductor with t_ion ~ 1 below ~10^-13 atm.

Acceptor-doped LaAlO₃ shows enhanced ionic conductivity due to doping. However, its mixed conductivity value is low in reducing condition. In this study, Ti was added into acceptor-doped LaAlO₃ to enhance the mixed electronic and ionic conductivity in low Po₂. Electrical conductivities of [La_0.9Sr_0.1Al_0.9Mg_0.1O_3-δ]_1-x[La_2/3TiO₃]_x (LAT) for x = 0-0.30 were measured using 4-probe d.c. method at temperatures between 800 and 1400°C and as a function of oxygen partial pressure (1 ~ 10^-15 atm) at 1200°C. Electrical conductivities decreased with increasing Ti contents (x) for 0 < x < 0.15, and increased for 0.15 < x < 0.30 in air after showing minimum values at x = 0.15. LAT samples for 0 ≤ x ≤ 0.10 were oxygen ion conductor in low Po₂ and mixed conductor in high Po₂. But for x ≥ 0.15, n-type conductivity was shown in low Po₂. The p-type conductivity disappeared in high Po₂ for x ≥ 0.20.The mixed conductivity obtained from the fitted value of Po₂ dependence made it clear that Ti in LSAM increased the mixed conductivity in low Po₂ for x = 0.15. LAT with x = 0.30 was the best mixed conductor in low Po₂ (Po₂ < 10^-8 atm at 1200°C).

The effect of cathode particle size on cell potential was investigated using a voltage prediction method from the Coulomb potential created by the atoms of a cathode active material. LiNiO₂ was selected as a typical cathode of an ordered rock salt structure. From the calculation, it was found that the voltage changes when the size becomes less than about 10 nm. The voltage increased with decreasing in-plane size, and decreased with decreasing the number of layers.

Commercial lithium ion batteries (LIB) use layer-type compounds as the electrode materials and Li-ion conducting liquid or polymeric gel as the electrolyte. The preferred cathode and anode are LiCoO₂ and graphite respectively. Efforts to improve the performance as well as safety-in-operation of LIB led to the search for alternate electrode materials. As regards the anodes, metal-oxide systems received special attention: Tin (Sn) containing mixed oxides and various 3d- and 4d- transition metal (M) mixed oxides. The reversible capacities in these systems arise either from alloying/de-alloying, formation/decomposition of Li₂O aided by the nanosize metal (M) particles/Li-M-O bronze or Li-intercalation/de-intercalation. A brief account of the recent studies is presented.

Inorganic solid electrolytes are promising for the solution to the safety issue of lithium batteries. In spite of this advantage, solid-state lithium batteries are, in general, lower in energy density than organic electrolyte systems. One of the reasons for the lower energy densities of solid systems is that combination of carbon materials and LiCoO₂, which offers high energy density in lithium-ion batteries, have not been used. This paper presents how to construct solid-state lithium batteries with a graphite anode and a LiCoO₂ cathode from a consideration on compatibility of solid electrolytes with electrode materials. The consideration led us to a unique construction of a solid-state lithium battery employing two kinds of solid electrolytes, which enabled us to realize C / LiCoO₂ solid-state batteries with a high energy density.

Recent research efforts to improve the ambient temperature conductivity in polyethylene oxide (PEO) based solid polymer electrolytes have been directed towards the incorporation of ultra-fine nano-sized particles of ceramic fillers into the polymer electrolyte. However, the mechanism of ionic conductivity enhancement in these nano-composite polymer electrolytes is still not well understood. In this paper we report the ionic conductivity of the (PEO)₉LiCF₃SO₃ + 10 wt% SiO₂ system incorporating nano-sized silica fillers of different specific surface areas. (PEO)₉LiCF₃SO₃ + 10 wt% SiO₂ films were prepared by solvent casting technique by incorporating SiO₂ filler grains of three different specific surface areas: 225 m²/g, 338 m²/g and 390 m²/g. Results show that (i) the discontinuity in the log σ vs 1/T plots around 60 °C becomes less visible for the filler concentrations that correspond to higher conductivities, (ii) the VTF behaviour extends down to ambient temperatures (iii) the conductivity of both the amorphous phase above 60 °C and the partially crystalline phase below 60 °C have increased substantially due to the presence of the silica filler, (iv) the observed conductivity trend clearly shows that the conductivity enhancement increases with specific surface area of filler grains and the highest conductivity enhancement is obtained for the SiO₂ particle having largest specific surface area (390 m²/g).

It is suggested that for PEO based nano-composite electrolytes with silica filler grains, the conductivity enhancement at temperatures above as well as below 60 °C results from Lewis acid-base type surface interactions of ionic species with O/OH groups in the filler surface. These surface interactions are expected to create additional high conducting pathways for migrating ions. An additional contribution below 60 °C appears to come from the retention of an increased fraction of the amorphous phase due to the presence of the filler.

The fabrication and characterization of Lithium phosphorus oxynitride (Lipon) and nickel nitride thin films were reported by nitrogen plasma assisted deposition of e-beam reactive evaporated Li₃PO₄ and pulsed laser deposition methods as electrolyte and anode materials, respectively. Insight on the electrochemical reaction mechanism of transition metal nitrides with Li was provided. A preliminary all-solid-state lithium battery of Li/Lipon/0.5Ag:V₂O₅ exhibited a well electrochemical property.

Cu doped vanadium oxide nanotubes (VONT) were prepared via a rheological phase reaction followed by self-assembling process. The nanotubes were characterized by SEM, XRD, electrochemical investigation, etc. The results show that the Cu doping improves the electrochemical performance of VONTs due to the bonding of the Cu ions and the residual H₂O in the nanotubes. Cu doped VONTs exhibit a specific discharge capacity of about 210 mAh/g during the first 10 cycles, revealing a promissory material for utilization as cathode for Li-ion batteries.

An open framework type new material Li_xCo₂(MoO₄)₃ [0 ≤ x < 3] possessing NASICON structure was identified as positive electrode material for use in 3V class lithium batteries. The new material was synthesized in its non-lithiated phase employing a metal/organic precursor method using a soft-combustion approach. We report here on the structural and electrochemical Li⁺ insertion/extraction properties of the resultant product. XRD revealed a single phase Co₂(MoO₄)₃ powders and the annealed powders were found to contain ultrafine spherical grains. The redox behavior of the new material was demonstrated in lithium containing cells using the conventional wet cell configuration under Li⁺ aprotic organic electrolyte environment. The material offered a discharge capacity of ~ 110 mAh/g between 3.5V and 1.5V during the first cycle and ~ 50% of the initial capacity was retained at the end of 20^th cycle.

LiCo_0.90Mg_0.05Al_0.05O₂ bulk powders are synthesized using combustion process and made into a thin film by depositing on silicon wafer using a pulsed laser ablation technique. A comparative study by SEM (Scanning Electron Microscope) XRD (X-ray diffraction), Infrared spectroscopy and Raman Spectroscopy is performed on both bulk and PLD thin films.

Among the various ion-conducting materials, polymer salt complexes are of current interest due to their possible application as solid electrolyte as well as their physical nature in advanced high-energy electrochemical devices such as batteries, fuel cells, electrochromic display devices, photo electro-chemical solar cells^52-55 etc. The main advantages of polymeric electrolytes are their mechanical properties, ease of fabrication of thin films of desired sizes and their ability to form proper electrode-electrolyte contact. Polymer electrolyte usually consists of a polymer and a salt and is considered to be solid solutions in which the polymer functions as solvent. In the present paper the synthesis, characterization and the conductivity study of the polymer poly (vinyl 4-hydroxy-3-methoxy benzal) (PV-HMB) and its sodio salt (PV-HMB-Na) have been reported. The polymer was prepared by carrying out homogenous acetalization between the prepolymer poly vinylalcohol (PVA) and 4-hydroxy-3-methoxy benzaldehyde (vanilline). PVA was dissolved in dimethyl formamide (DMF) and lithium chloride (LiCl) system i.e., in non-aqueous medium. The sodio salt was prepared by alkalization. The polymer and its salt were characterized by IR, 1H NMR and DSC. Frequency and temperature dependence of ac conductivity has been studied to learn about the electrical conduction behaviour in this material. The electrical conductivity of the new polymeric salt was found to be in the range 10^-4 to 10^-6 Scm^-1. There is about 10³ to 10⁴ fold increase in the conductivity of the new polymer salt. Apparent activation energy of the polymer and its salt were found to be 0.139 and 0.08998 ev respectively.

Polyaniline secondary batteries in the configuration of Zn/d-PANI+electrolyte/carbon were fabricated using the powder compacting method and characterized. This system is very simple and has low cost. It can be considered as superior one Ni-Cd dry cell, which is available in the consumer market. Chemically synthesized emeraldine base form of polyaniline and other additives can be used as an active cathode material, ammonium chloride and zinc chloride were used as electrolytes. This battery uses a solid polymer electrolyte composed of polyvinyl alcohol and phosphoric acid, and it can also act as a separator. Cylindrical type of batteries have been designed and fabricated. The weight reduction from the conventional dry cell is around 25% with an open circuit voltage of 1.433V. The capacity of the cell is also comparable with that of the existing dry cell. These batteries were found usable in low power source applications at room temperature. This battery also shows very promising features such as high capacity, energy density, good cyclability and satisfactory stand life.

Layered structural Li_xMnO₂ was successfully synthesized by sol-gel and ion-exchange method in this study. The conditions of synthesis of layered Li_xMnO₂ were investigated, the phase content of layered Na_xMnO₂ precursor and layered Li_xMnO₂ were identified by X-ray diffractometer (XRD) with Cu Kα radiation. The microstructures of oxide powders were characterized by scanning electron microscope (SEM). The electrochemical properties of layered Li_xMnO₂ cathode materials were tested, The effect of Co³⁺ and Zn²⁺ doped on the electrochemical properties were studied. We found that the P2 type layered structure β-Na_0.7Mn_1-xM_xO₂ (M = Co, Zn) could be obtained by heating the sol-gel precursor in air at 750°C for 1 h, layered β-Na_0.7Mn_1-xM_xO₂ could were transited into O2 type layered Li_yMn_1-xM_xO₂(y ≈ 0.67). The electrochemical properties of the layered Li_yMn_1-xM_xO₂ are high. The capacity of cathode material was increased by Co doped, the capacity of the cathode material was decreased by Zn doped.

Electrochemical intercalation of PF₆^-, counter anion of supporting acid in electrolyte, into graphitic carbon was investigated in this study for a new concept of positive electrode for Li ion rechargeable battery. It was found that potential for PF₆^- electrochemical intercalation occurs at 4.5 - 5.0V Vs. Li/Li⁺. Therefore, graphitic carbon can be used for cathode of Li ion rechargeable battery. Capacity for PF₆^- intercalation increased with increasing the content of graphitic carbon and capacity of ca. 60 and 40 mAh/g were obtained for intercalation and de-intercalation on the carbon with graphitic carbon content of 98%. The intercalation capacity further increased by oxidation treatment and the largest capacity was achieved by oxidation at 773K for 3h. Ex-situ XRD measurement suggests that distance between (002) plane was expanded by intercalation and reduced by de-intercalation. XRF measurement suggests that intercalated species are PF₆^-, which is counter anion of Li⁺ in electrolyte. Therefore, electrochemical intercalation of PF₆^- into graphitic carbon can be used for cathodic reaction of Li ion rechargeable battery.

Effects of carbon nanotube coating on doped Si powder were studied for anode of Li ion rechargeable battery. Although the large Li intercalation capacity higher than 1500 mAh/g is exhibited on pure Si, it decreased drastically with the cycle number. Increasing the electrical conductivity by doping chromium is effective for increasing the initial capacity and the cycle stability of Si for Li intercalation, and the reversible capacity of 250mAh/g was sustained after 5 cycles of charge and discharge. Coating Cr doped Si with the carbon nanotube obtained by decomposition of CH₄ is effective for increasing the cycle stability, though the initial Li intercalation capacity decreased to ca. 1900 from 2500 mAh/g. Binder is also important factor and it was found that high capacity of 1800 mAh/g can be sustained after 10 cycles by using PVDF as conducting binder.

Lithium ion batteries have been attracting considerable interest worldwide in the past few years in the field of rechargeable batteries because they posses high energy density, long cycle life, good safety, and wide range of working temperatures. Lithium batteries based on vanadates such as LiNiVO₄, and LiCoVO₄ have gained a new interest since such material based electrodes display a large Li acceptance/removal at low voltages. A new electrode material LiBiVO₄ has been prepared using solid state reaction method. The formation of the compound has been characterized by XRD analysis. The Laser Raman Spectroscopy reveals the structural and phase analysis of LiBiVO₄. The electrical characterization has been carried out using the Impedance spectroscopy method in the frequency range of 50 Hz to 5 MHz. The bulk resistance of the material has been extracted from the impedance analysis and it is found to be 4.96 × 10^-7 Ω cm^-1 at 473 K. The modulus peak maximum shifts to higher frequency with increase in temperature and broad nature of the peaks indicate the non-debye nature of the material.

Oxide coating helps in the suppression of capacity-fading of oxide cathodes for use in lithium ion batteries. Presently we coated NiO on to Li(Ni_1/2Mn_1/2)O₂ and studied the cathodic properties. The bare compound was prepared by the mixed hydroxide method and subsequently coated with 3 and 6 wt% of Li(4%)-doped nickel oxide by solution method and characterized by X-ray diffraction and SEM. Cyclic voltammetry of bare and coated samples show clear redox process at 3.65-4.0 V corresponding to Ni^2+/4+ and at 4.25-4.4 V due to Mn^3+/4+ couples. Galvanostatic charge-discharge cycling was done at a specific current 30mA/g upto 70 cycles in the voltage range 2.5-4.3 V and 2.5-4.5 V vs Li. At the end of 10 cycles, the discharge capacities are 140 ± 3 mAh/g with 4.3 V cut-off, and are in the range 160-185 mAh/g with 4.5 V cut-off for the bare, 3% and 6% NiO-coated compounds. Capacity-fading was observed after 25-30 cycles in all the cases. But, the 6% NiO-coated compound performed better with both 4.3 and 4.5 V cut-off by way of showing stable discharge capacity upto 30 cycles and smaller capacity-fading upto 70 cycles.

Porous TiO₂ was synthesized by using bicontinuous microemulsion and colloidal crystal as templates. The porous TiO₂ from bicontinuous microemulsion have such high surface areas as 400 m²g^-1 for amorphous TiO₂ and 130 m²g^-1 for anatase TiO₂. Cyclic voltammograms indicated that electrochemical double layer capacitance of porous TiO₂ was estimated to be 5 μFcm^-2 for amorphous and 12 μFcm^-2 for anatase. The stored charge on the surface was 12 mAhg^-1 for porous TiO₂ synthesized by using bicontinuous microemulsion and calcination at 300°C. The results of galvanostatic lithium insertion/extraction to porous TiO₂ indicate that it is important to control porous structure as well as to use materials with large surface area to obtain high capacity at high current density. Bimodal porous structure that is composed of both macropores and mesopores are suggested to be one of the possible structures.

The poor cycleability of lithium, the lower energy density of graphite/carbonaceous anodes, an intense search for alternative anode materials have been made and such a search has resulted in the exploration of variety of 3d-metal oxides generally, from which different types of Co and Ni-based oxides of both commercial and synthesized category have been chosen for the present study. The study aims at the evaluation of certain novel Co and Ni based oxides, wherein newer synthesis attempts have been adopted and a systematic approach has been followed to evaluate the electrochemical performance of the candidates individually. Two types of cobalt oxides, viz., CoO and Co₃O₄ along with two types of nickel oxides (green and black type) were chosen for the present investigation, among which the compound Co₃O₄ has been synthesized at least through three different routes. A suitable correlation of the results of the physical as well as the electrochemical characterization studies were made and a comparative study upon the anodic behavior of these variety of cobalt oxides and nickel oxides has also been made with a view to understand the inherent effect of the individual oxide as well as the extent of effect of synthesis methodology in improving the electrochemical behavior of the 3d-metal oxides.

A free standing solid polymer electrolyte film based on poly (methyl methacrylate) PMMA can be obtained when blend with 10% and 20% of 50% epoxidised natural rubber, ENR 50. This modification is expected to reduce the glass transition temperature, Tg of PMMA and exhibited soft elastomeric characteristic with good elasticity and adhesion hence providing excellent contact between the electrode and the electrolytic layer in batteries. This work conducted ionic conductivity measurements on non-plasticised and plasticised PMMA / ENR 50-based polymer electrolyte systems containing lithium triflate, LiCF₃SO₃ salt. The thermal dependence of ionic conductivity of these systems is also discussed. The plots of logarithm of ionic conductivity against the reciprocal of absolute temperature for the samples are linear as predicted by Arrhenius activation equation.

Cathode materials for Li-ion battery LiMn₂O₄ and LiCo_0.1Mn_1.9O₄ were prepared by soft chemical method. Carbon, which was made by decomposing organic compounds, was used as modifying agent. Cathode material matrix was mixed with water solution that had contained organic compound such as cane sugar, soluble amylum, levulose et al. These mixture were reacted at 150 ~ 200 °C for 0.5 ~ 4 h in a Teflon-lined autoclave to get a series of homogeneously C-coated cathode materials. The new products were analyzed by X-ray diffraction (XRD) and infrared (IR). Morphology of cathode materials was characterized by scanning electron microscope (SEM) and transition electron microscope (TEM). The new homogeneously C-coated products that were used as cathode materials of lithium-ion battery had good electrochemical stability and cycle performance. This technique has free-pollution, low cost, simpleness and easiness to realize the industrialization of the cathode materials for Li-ion battery.

Doped spinel lithium cobalt manganese oxide LiCo_0.1Mn_1.9O₄ was prepared by soft chemical method involving LiOH ∙ H₂O, MnO₂ and CoCO₃ as precursor. By using the way of liquid state successive isochronical annealing, B₂O₃ was homogeneously coated on LiCo_0.1Mn_1.9O₄. B₂O₃-coated and uncoated LiCo_0.1Mn_1.9O₄ were analyzed by X-ray diffraction (XRD) and infrared (IR). Morphologies of cathode materials were characterized by scanning electron microscope (SEM). The electrochemical properties of B₂O₃-coated and uncoated products were also studied in this paper.

LiFePO₄ was synthesized by means of solid-state reaction. Two kinds of LiFePO₄/C composites were also prepared using carbon-gel and high-surface area carbon-black. Those carbon materials were added to the precursors before formation of the crystalline phase. The products were characterized by X-ray diffraction(XRD) and scanning electron microscope(SEM). TG-DSC analysis was also be used to study the processes experienced by the raw mixtures, which were prepared for the synthesizing of LiFePO₄.

In present paper DV-Xα method was employed to calculate the electronic structure of cathode materials LiMn₂O₄ and LiCo_xMn_(2-x)O_(4-y)S_y. Cluster models for the calculation on the electronic structures of those materials were chosen to get the atomic charge, bond order, and charge density in different clusters. The purpose of this study is trying to elucidate the influence of S-Co on electrical properties of cathode materials. The results shown that the introduce of S-Co could increase the stability of spinel structure for the cathode material LiCo_xMn_(2-x)O_(4-y)S_y. The Jahn-Teller effects of LiCo_xMn_(2-x)O_(4-y)S_y did not happen easily as LiMn₂O₄ The calculation results agreed with our experimental date of the electrochemical properties of LiCo_xMn_(2-x)O_(4-y)S_y.

In the present paper, the solid chemical reactions for Li-Mn-O compound as cathode materials of Li-ion batteries in electromagnetic field at millimeter wavelength were studied. The reaction could be finished in a short time comparing with conventional synthesis method. The microstructures of reaction product were detected by employed X-ray diffraction (XRD) and scanning electron microscope (SEM). The chemical reactions in electromagnetic fields were influenced by several factors including heat preservation time, pre-heating and coupled agent, and it is a simple way to obtain Li-Mn-O compounds due to the different reaction mechanism comparing with conventional reaction method.

A new type of full solid state cell has been manufactured by using gel polymer electrolyte membrane containing water (referred to as GPE) as positive electrode material. GPE consists of poly(methyl acrylic acid), poly(methyl acrylic lithium) and glycerol whose weight ratio is 3:2:3. A cell of magnesium water has been manufactured. The open circuit voltage of cell is 1.4-1.7 V, The short circuit current is 0.05-1.7mA, The discharge capacity is 6mAh/g under constant load resistance of 5.2K Ω.

LiMn_2-xCo_xO₄ spinels doped with a range (x = 0-0.1) were synthesized by microwave-template method. The structure and characteristics of the samples were studied in detail by means of SEM, XRD and electrochemical measurements. The result of SEM shows the samples have preferable morphology and relatively uniform particle size. XRD data reveals that Co-doped lithium manganese spinels have smaller lattice constant than LiMn₂O₄. The electrochemistry test shows that LiMn_2-xCo_xO₄(x = 0.01) presents higher charge and discharge efficiency and better cycling properties. The first discharge capacity of LiMn_2-xCo_xO₄(x = 0.01) is 124mAhg^-1 (3.0-4.3V).

LiFePO₄ cathode materials with dispersive nanostuctured carbon were prepared through two-step decomposing technics with middle and high temperature ranges as well as PAM template craft was employed. The materials with different amount of organogel-decomposing carbon were studied by XRD. SEM and electrochemical measurements. According to the results of XRD, all samples showed pure olivine structure and a decline of the crystalline parameter was found. SEM tests gave uniform dispersed particles with a grain size under 1μm. The electrochemical measurement showed the optimized carbon content was 5.6wt%, and it had a higher charge/discharge capacity and better cycling life than other materials. In this article the dispersive nanosturctured carbon decomposing from resin was confirmed by XRD and it is beneficial for the intrinsic conductivity according to the electrochemical performance.

A new simple way of synthesizing Li[NiMnCo]O₂ was contrived and its electrochemical characteristics were enhanced by Si doping using solution-based synthetic route. The newly synthesized Li[NiMnCo]O₂ showed capacity of 175mAh/g and good cycle life at as high cut-off voltage as 4.5V. Si-doping improved the rate capability, specific capacity, and cycle life of the material through increasing lattice parameters and lowering electrochemical impedance.

The first charge-discharge mechanism of LiCoVO₄ with spinel structure as an anode material for a Li ion battery was investigated by XRD and XAS measurements. During first charge process, three voltage plateaus were observed. In the first plateau, some side reaction such as decomposition of solvent occurred at the surface of electrode. Second plateau region was attributed to the reduction of vanadium ion and the environmental coordination of vanadium also transformed from tetrahedral symmetry to octahedral one, which was due to the phase transition from inverse spinel to atacamite-type. In the third plateau, further reduction of vanadium ion and deposition of cobalt metal occurred, and the structure of LiCoVO₄ irreversibly transformed into amorphous structure. During the followed lithium removal process, vanadium ion showed good reversibility in view of oxidation state and local environmental structure, while the oxidation state of cobalt did not revert due to poor kinetic property, which would relate to capacity fading upon several charge-discharge cycles.

Solid-state thin-film lithium-ion batteries consisting of an amorphous Li₂O-V₂O₅-SiO₂ solid electrolyte (LVSO), crystalline LiCoO₂ cathode and amorphous SnO anode were fabricated by pulsed laser deposition technique. The morphology of the films were sensitive to the preparation conditions especially the optical absorbance of the target materials. The film was characterized by X-ray diffraction, FE-SEM, AFM and ICP-AES. The ionic conductivity of the LVSO film is estimated by impedance spectroscopy to be 2.5 × 10^-7 Scm^-1 at 25°C with activation energy of 0.54eV. The thin-film battery exhibits an open circuit voltage at full charge of about 2.7V, and a good reversibility on charge-discharge cycling over 100 cycles.

Two types of solid-state electrochemical sensors using yttria-stabilized zirconia (YSZ) and oxide sensing-electrodes (SE) were fabricated and examined for NOx detection at high temperatures. The mixed-potential-type NOx sensor using ZnO-SE has shown rather high sensitivity to NOx among other single-oxides tested as an SE in the temperature range of 600-700°C. The sensing mechanism of this sensor is discussed on the basis of the catalytic activity data for the oxides examined. The complex-impedance-based NOx sensor attached with ZnCr₂O₄-SE gave good sensing characteristics to NOx at 700°C; the sensitivity to NO was almost equal to that to NO₂ from 0 ppm up to 200 ppm at 700°C, and almost linear relationship was observed between the sensitivity and NOx concentration even in the presence of 8 vol.% H₂O and 15 vol.% CO₂ at 700°C.

The electrochromic materials are the materials that change their optical properties in the presence of ionic substances and under the application of bias potential. The optical properties can recover to the original state when the bias potential was reversed. Over last two decades, much work has been devoted to study and development of electrochromic materials and devices in wide applications such as light transmission and modulation controller. Electrochromic materials can be used as a sensor to detect the presence of ionic substances in water or in other liquid media. The working principle of this sensor is based on the change of the optical properties of materials during the electrochromic reaction. This sensing system is expected to offer a high selectivity effect that is the change of the optical properties during the electrochromic process depending on the type of ionic substances involved. Some materials showed the electrochromic behavior, particularly transition metal oxides and the organic compounds. Porphyrins are amongst the possible organic materials that show the electrochromic behavior. This paper reports the use of two metalloporphyrins derivatives of; 5, 10, 15, 20-tetraphenyl 21H, 23H-porphine cobalt (II) and 5, 10, 15, 20-tetraphenyl 21H, 23H-porphine manganese (III) chloride thin films as an electrochromic materials to detect the presence of chloride in water. Although the both thin films were sensitive towards the presence of chloride, the 5, 10, 15, 20-tetraphenyl 21H, 23H-porphine manganese (III) chloride was found the most stable and repeatable material for this purpose.

In recent years rare earth compounds especially their fluorides have drawn particular attention as electrochemical gas sensors. Lanthanum and cerium fluoride based sensors have been investigated for sensing the fluorine, oxygen, and carbon monoxide because of their high chemical stability and high ionic conductivity. The fast response and good sensitivity of these sensors rely on the ion conduction properties of these thin films. In the present work Cerium Fluoride thin film has been prepared by vacuum thermal evaporation method. The electrical characterization is carried out using the Impedance spectroscopy method in the frequency range of 50 Hz to 5 MHz. The temperature dependence of ionic conductivity obeys the Arrhenius behavior and the activation energy E_a is found to be 0.3eV. The modulus and the dielectric spectra analysis reveal the non – Debye nature and the distribution of relaxation time due to the presence of grain and grain boundaries in the film. The relaxation energy E_d has been calculated from the dielectric spectra. The similar value of activation and relaxation energies suggests that the charge carriers that are responsible for bulk conductivity and relaxation process are the same. The optical measurement done in the wavelength range of 400-2500 nm confirms that the CeF₃ thin film is highly transparent and the band gap energy is found to be 3.5 eV.

The investigation of structural and electrical properties of pure α, β and γ bismuth molybdate phases is described and discussed. All phases undergo a slight structural change resulting in a decrease of conductivity due to an order-disorder change in the oxygen arrangement during the heating of samples. The changes observed in the electrical conductivities are reversible in the high-temperature regions and irreversible in the low-temperature ones. The blocking of oxygen ion transport by the bismuth lone-pair electrons results in an increase of the activation energy and a decrease of the electrical conductivity in the high-temperature region. Relatively high relative dielectric permittivities ε_r, 36 – 52, were observed depending on the investigated phase.

Thiometallic cluster continue to attract great interest not only because of their unusual catalytic activities in biological and industrial processes [1], but also their intriguing optical and electrical properties [2]. Among these physical properties, there is an interest in their optical limiting effect for potential application in protecting optical sensors from laser beams of high intensity. The design and synthesis of new materials with large optical limiting capability represents an active field in modern chemistry, physics and material science [3]. Thus, the synthetic and structural chemistry of heterometallic sulfide clusters containing d¹⁰ copper has been developed rapidly and some interesting Mo-Cu-S clusters with novel structural types have been synthesized [4]. Novel cluster compound MoS₄Cu₄(pz^Me2)₆Cl₂ was synthesized in acetone and its crystal structure has been characterized by X-ray diffraction [Fig.1], infrared, UV-Vis and ¹HNMR spectroscopy.

Interfering effects of NO and SO₂ gases on CO₂ sensing performance of the solid state galvanic cell, Pt, O₂, CO₂, Na₂CO₃-BaCO₃ | Na⁺ | Na₂Ti₆O₁₃-TiO₂, O₂, Pt was investigated in terms of interfering gas concentrations (NO: 50 ~ 150ppm, SO₂: 5 ~ 15ppm) at 673K and 773K to investigate the feasibility of CO₂/NO_x/SO_x multi gas sensor and further to quantify the degree of interference of these gases. Whereas NO gas exposure guaranteed recovery of sensor with relatively small electro motive force (EMF) deviation (dE), SO₂ gas remarkably degraded sensor performance arising from thermodynamic formation of sulfate on the sensing electrode.

Electrochromic WO₃ thin film was prepared by using tungsten metal solution in hydrogen peroxide as a starting solution and by sol-gel dip coating method. XRD pattern showed that tungsten oxide crystal phase formed at 400°C. In the view of electrochemical property, WO₃ thin film which was heat-treated at 300°C and was amorphous had better than that of the crystalline phase.

A new type of nitrogen monoxide (NO) gas sensor was fabricated by the combination of trivalent aluminum cation conducting (Al_0.2Zr_0.8)_20/19Nb(PO₄)₃ and divalent oxide anion conducting yttria stabilized zirconia (YSZ) with the lithium nitrate doped (Gd_0.9La_0.1)₂O₃ solid as the sensing auxiliary electrode and its NO sensing performance was investigated. The time to attain a 90 % response was less than two minutes in the NO concentration range of 200–2000 ppm and the theoretical linear relationship was observed between the sensor EMF output and the logarithm of the NO concentration at 250 °C. Since the present sensor shows quantitative NO gas sensing characteristics, it is greatly expected to be applicable for a smart NO gas sensor even at such a low temperature.

The piezoelectric ceramic-polymer composites were prepared by Pb(Zr_0.52Ti_0.48)O₃ (PZT)-based ceramics with high piezoelectricity and electromechanical coupling factor and the polyvinylidene fluoride (PVdF) polymer with high acoustic impedance. The composites with 0-3 connectivity type were fabricated by hot pressing and tape casting methods. Their crystallinity, microstructure, dielectric, and piezoelectric properties were systematically evaluated.

Solid-oxide electrolytes develop electrical potential when their two opposite electrodes are exposed to the different oxygen potential. When an electrolyte is exposed to the same ambient gas, a potential may develop due to the different catalytic behavior of two electrodes to ambient gas. Such a sensor is called as a non-equilibrium e.m.f.-type sensor or mixed potential sensor. In this study, to improve the sensitivity of the sensor to reducing gases (CO, H₂), transition metal oxide (T.M.O.) was added to one of two SnO₂ electrodes of the sensor. T.M.O. addition was expected to change the catalytic behavior of the electrode and to change e.m.f. values. The Co addition increased the e.m.f. of working electrode (T.M.O.-added SnO₂) in air, implying the enhanced oxygen adsorption. Fe addition showed the reverse effect. The addition of T.M.O. to SnO₂ was also effective in changing the e.m.f. values in H₂ balanced by air. Fe and Ni addition exhibited decreased e.m.f. in H₂ from that in air. Thus, Fe and Ni addition improved the catalytic activity for H₂ oxidation. On the other hand, the catalytic activity for H₂ oxidation was suppressed by Co addition. However, no appreciable change in CO sensitivity was obtained with the T.M.O. addition.

NiO is a representative electrochromic counter electrode material of which transmission of visible light could be controlled by applying a small voltage. The coating solution of NiO was synthesized by mixing nickel acetate and Dimethylethanol amine in isopropyl alcohol. NiO film was coated on ITO glass, dried at 100°C and heat-treated at 300-500°C. The electrochemical and optical properties of NiO film were characterized by using Autolab electrochemical measurement system and UV spectroscopy, respectively.

Thin films of VI-VI compound semiconducting transition meta' oxide have an excellent feature in cost effective electrochromic devices. Electrochromic devices have been extensively studied in the application of "smart windows". A material change its optical properties under the application of the external potential and return back to its original state during the potential reversal, that kind of material is referred as electrochromic material and it is the best candidate for novel electrochromic devices. In this trend thin film of tungsten oxide (WO₃) plays a vital role, because of its excellent electrochromic behaviour. This film has been prepared by one of the physical vapour depositions of electron beam evaporation technique (PVD: EBE). The electrochromic behavior of the films was tested using three electrode electrochemical cell by employing the Cyclic-Voltammetry (C-V) technique. The eletrochromic nature of the films has been analyzed by inserting H⁺ ions from the H₂SO₄ electrolyte solution. The different electrochemical parameters were estimated and discussed in detail for the suitability of electrochromic devices.

Supercapacitors were fabricated by employing nanosized carbon black (NCB) powders and studied in an aqueous electrolyte. The capacitor properties were studied by means of electrochemical techniques such as cyclic voltammetry and constant current charge/discharge. Specific capacitance of these carbon materials, power density and energy density of the supercapacitor were derived from constant current charge/discharge tests. AC impedance technique was employed to deduce the ESR (equivalent series resistance) value and the frequency dependent capacitance. A high specific capacitance of 40 F/g was achieved using the above nanosized carbons in a symmetric electrode configuration.

The ternary selenide Cr₄TiSe₈ was prepared and intercalated with Li using n-BuLi in n-hexane. In situ x-ray diffraction of Li_xCr₄TiSe₈ during intercalation revealed a phase transformation from a monoclinic to a trigonal structure which starts at x ≈ 0.4 and is induced by a modification of the electronic structure. The maximum Li content x ≈ 3 is reached after about 30 days. The intercalation of the sample is reversible. During intercalation a structural relaxation was observed which leads to a homogenization of the material.

The two universal behaviors as to ionic transport are discussed in seeking after their mechanisms: one is the conductivity ceiling observed in energetically ordered lattices, whose mechanism is explained by interactions among mobile ions, while the other is the non-Debye conductivity found in energetically disordered lattices, explained by a distribution of mode mean square displacements existing in random systems.

Spinel lithium manganates are widely studied as cathode materials in rechargeable lithium batteries. One of the significant characteristics of these compounds is the presence of numerous electronic phenomena below the room temperature. Especially, interesting ground-state magnetic properties can be expected due to the geometrical frustration of antiferromagnetically interacting spins. Our recent results on the study of such materials are reviewed.

Perovskite type oxides based on LaGaO₃ are of large technical interest because of their high oxygen-ion conductivity. Lanthanum gallate doped with Sr on A- and Mg on B-sites, La_1-xSr_xGa_1-yMg_yO_3-(x+y)/2 (LSGM), reaches higher oxygen-ion conductivities than yttria-doped zirconia (YSZ). Thus LSGM represents a promising alternative for YSZ as electrolyte in solid oxide fuel cells (SOFC). Cells using thin LSGM-layers as electrolyte are expected to operate at intermediate temperatures around 700°C for more than 30000 hours without severe degradation. A potential long term degradation effect of LSGM is kinetic demixing of the electrolyte, caused by different cation diffusion coefficients. In this paper we report on experimental studies concerning the phase diagram of LSGM and the diffusion of cations. Cation self-diffusion of ¹³⁹La, ⁸⁴Sr and ²⁵Mg and cation impurity diffusion of ¹⁴⁴Nd, ⁸⁹Y and ⁵⁶Fe in polycrystalline LSGM samples was investigated by secondary ion mass spectrometry (SIMS) for temperatures between 900°C and 1400°C. It was found that diffusion occurs by means of bulk and grain boundaries. The bulk diffusion coefficients are similar for all cations with activation energies which are strongly dependent on temperature. At high temperatures, the activation energies are about 5 eV, while at low temperatures values of about 2 eV are found. These results are explained by a frozen in defect structure at low temperatures. This means that the observed activation energy at low temperatures represents only the migration energy of the different cations while the observed activation energy at high temperatures is the sum of the defect formation energy and the migration energy. The migration energies for all cations are nearly identical, although ¹³⁹La, ⁸⁴Sr and ¹⁴⁴Nd are occupying A-sites while ²⁵Mg and ⁵⁶Fe are occupying B-sites in the perovskite-structure. To explain these experimental findings we propose a defect cluster containing cation vacancies in both the A- and the B-sublattice and anion vacancies as well.

In single ion conducting glasses, the dc conductivity and the onset frequency of the dispersion changes in characteristic fashion and leads to scaling laws. Scaling was not applied to mixed alkali glasses previously. The major objective of this paper is to study whether scaling functions applied to single alkali glasses can explain ion dynamics of mixed alkali glasses. With this purpose experimental results on the mixed alkali glasses in the system xLiF–(80-x) KF–20Al(PO₃)₃ are reported. The frequency dependent conductivity data has been recorded at 323 K ≤ T ≤ 523 K and over a frequency range 20 Hz ≤ v ≤ 1 MHz. While the individual compositions exhibit temperature independent scaling of the ac conductivity, the composition dependent ac conductivity can be explained only using two scaling functions, one each for the dominant K and Li cation regions on either side of the minimum in the ac/dc conductivity of the mixed alkali glasses.

The electronic states of silver halides and sodium halides are calculated by the DV-Xα cluster method to get more microscopic evidence for the p – d hybridization and the covalency in noble metal halides. The calculations are carried out for the A₁₃B₁₄ (A = Ag or Na ion, B = halogen ion) clusters. It is found that both components of anti-bonding and bonding exist in the diagram of overlap population (DOP) for AgX (X = halogen) and these two components are made up of the 4d band of Ag ion and the p band of halogen ion, which form the p – d hybridization. The covalency of noble metal halides is in the border between that of the fourfold coordinated compounds and that of the sixfold coordinated compounds. These calculation results on the covalency support the tendency of the Phillips's ionicity.

The bond fluctuation model of superionic conductors provides a framework to understand the characteristic features of superionic conducting materials. According to the model, the superionic behaviour is related to a change of bonding that occurs locally and fluctuates in time. In the present study, the presence of such processes is investigated by studying the time evolution of the electronic states around a mobile Cu ion in the superionic conductor CuI by the ab initio molecular dynamics simulation. It is shown that the results of ab initio simulations agree well with the prediction of the model.

In the present work, we explained the dispersive behavior of σ'(ω) and ε″(ω) with a complex relaxation function ɸ* (t) = exp (-t/τ*), where τ* =τ^g/i^(1-g). The exponent g is origin for the stretched exponential behavior and it stretches the Debye relaxation time τ to τ^g. The physical meaning for the exponent g is described in terms of energy process and the exponent g < 1 characterizes the deviation from Debye behavior and can be regarded as a direct measure of non-Debye. At the dielectric loss peak frequency ω_p = 1/τ^g, the dielectric loss tan[δ] attains a minimum and signifies the energy dissipation through exponent g. Expression for the ac conductivity is derived from dielectric response function. Further, at the dielectric loss peak frequency ω_p = 1/τ^g establishes BNN relation with dc conductivity. All the experimentally known features of the σ'(ω) and ε″(ω) are explained satisfactorily. The measured ac conductivity and permittivity data of lithium phosphate glassy system at different temperatures are analyzed using the present function and Jonscher's power law. The dc conductivity, hopping frequency, dielectric loss peak frequency and the exponents (n, g) are compared and the results are presented.

High-energy X-ray diffraction experiments were performed for glass samples with those compositions expressed as (AgI)_x(As₂Se₃)_1-x (x = 0, 0.4 and 0.6) using incident photon energy of 113.1 keV at the beamline BL04B2, SPring-8 (Kobe, Japan). Diffraction intensities were measured up to Q_max = 30 Å^-1 for all samples. The addition of AgI leads to a measurable shift in the position of a first sharp diffraction peak in the structure factors S(Q). Well-defined first peaks are found at around 2.4 and 2.8 Å in the pair distribution functions g(r) for the AgI-doped glass samples. The results of a least-squares fitting analysis for the diffraction data allow us to predict that the structure model for AgI-As₂Se₃ glasses can be proposed to be a pseudo-binary mixture of the As(Se_1/2)₃ network matrix and AgI-related conduction pathways, which would be responsible for the high mobility and diffusivity of Ag⁺ in the present glass system.

The structure of Ag₂O-B₂O₃ glasses are studied by the scale-transformed energy space sampling Monte Carlo method which is an efficient algorithm for investigating materials that have complex energy surface such as proteins and glasses. The high-energy barriers that exist between quasi-stable states can be overcome easily by logarithmically flattening the energy surfaces. The radial distribution functions obtained by our Monte Carlo method show a good agreement with the result of molecular dynamics simulations. The calculated structure factor S(Q) exhibits a peak at low wave number Q ≈ 20nm^-1, which indicates the existence of intermediate range order. The composition dependence of this peak is in agreement with the result of neutron scattering experiments.

Ordered-mesoporous-Al₂O₃ was synthesized by sol-gel method using neutral copolymer surfactants as templates. The pore size was controlled over the range of 3 ~ 22 nm by using different surfactant copolymers under different synthetic conditions. By utilizing cyclohexane as a co-solvent, mesoporous-Al₂O₃ having relatively mono-dispersed particle size was obtained. Composites composed of synthesized mesoporous-Al₂O₃ and lithium iodide (LiI) was prepared. Dc electrical conductivity of 50LiI-50(mesoporous-Al₂O₃) was 2.6 × 10^-4 S cm^-1 at room temperature, which was considerably higher than the previously reported LiI-alumina composites. A systematic dependence of conductivity upon pore size was observed, in which the conductivity increased with decreasing the pore size except for pore size=3 nm. The ⁷Li diffusion constant of the composite was investigated by quasi-elastic neutron scattering (QENS) as well as pulsed field gradient nuclear magnetic resonance (PFG-NMR). The dc conductivities showed reasonable agreement with an Einstein equation using measured diffusion constants.

Diffusion coefficients of grain boundary materials in polycrystalline semiconducting SrTiO₃ oxides, which were prepared from the powders coated with Na ions, were obtained using TEM facilities. The defect chemistry as well as the diffusion behavior of the coating materials near the grain boundary of the oxides can be estimated based on the kinetic information; electrostatic potential barriers were formed, due to the excess negative electrical charges formed by the distribution of the chemical defects near the grain boundary. The electrostatic potential barrier heights can be calculated, which indicates the possibility of using this method for better control of the electrical properties of the SrTiO₃ oxides.

Silver atomic traps in both the low temperature phase β-Ag₂Se and the high temperature one α-Ag₂Se are created by defects introduced during the growing processes in the presence of excess silver. Two types of distorted Ag₂Se were prepared as the forms of powder at the β phase and a polycrystalline ingot at the α phase. Small single crystals of α-Ag₂Se were prepared by solid/vapor reaction for a reference sample which has no Ag traps. The lattice distortion was introduced by the excess silver. The excess silver in the distorted Ag₂Se was removed before examination. The density of atomic traps was measured by a coulometric titration curve, which shows large hysteresis and hump. The hysteresis and hump in the titration curves of a distorted Ag₂Se was interpreted by the capture and emission of silver atoms at Ag atomic traps. The capturing process is analogous to a nucleation and dissolution processes of a silver metallic cluster during the titration experiment.

Nuclear magnetic resonance offers several methods that allow one to measure directly and model-free the ion diffusion coefficient in solids. This paper reviews such studies performed in solid electrolytes. The "pulsed-field gradient" technique invented by Skejskal and Tanner and the "static fringe-field" method are discussed. Several examples are presented proving the applicability and the potential of these methods. Topics are (i) the temperature and orientation dependence of the diffusion coefficient in crystals; (ii) measurements of the Haven ratio by combining the diffusion coefficient with conductivity data; (iii) diffusion in polymers dealing with the Vogel-Tammann-Fulcher behavior, the measurement of transference numbers, the question of ion-ion correlation, and the influence of the polymer neighborhood on the type of ion motion.

The importance of optical spectroscopy for studying elementary migration processes of ions in superionic conductors is being discussed, especially using the results of β-alumina as an example; namely, their Raman scattering, quasielastic light scattering, reflection, luminescence and hole burning spectroscopy. Namely, the crystallographic structure, localized structure and disordered nature have been obtained from Raman scattering, luminescence spectroscopy. The electronic structure has been studied by optical reflection spectroscopy. The attempt frequency and the activation energy for ionic conduction are obtained from analyses of Raman scattering and quasi-elastic light scattering, respectively. Ion dynamics will be discussed by the results of hole burning spectroscopy.

To realize novel proton-conducting polymer electrolytes, strategies to incorporate protic ionic liquids into polymer networks have been developed. In situ radical polymerization of vinyl monomers in ionic liquids derived from a simple combination of organic amines with bis(trifluoromethanesulfonyl)imide yields ion-gels, which exhibit high ionic conductivity and sufficient mechanical strength. Brønsted acid-base ionic liquids may also be impregnated into polymer networks to have polymer electrolytes for their potential use as anhydrous proton conductors. Preliminary results with an ion-gel containing a protic ionic liquid show that polymer electrolytes of this variety are proton conducting and show electroactivity for H₂ oxidation and O₂ reduction at a Pt/C electrode under non-humidifying conditions. The prospects of ion-gels as fuel cell electrolytes under non-humidifying conditions have finally been discussed.

Non aqueous polymer gel electrolytes are materials of current research interest due to their use in commercial lithium polymer batteries. In these gel electrolytes polymer generally provides mechanical strength by increasing the viscosity, which also results in small decrease in conductivity. However in proton conducting polymer gel electrolytes containing weak acids the addition of polymer has been found to result in an increase in conductivity. This has been explained to be due to the dissociation of undissociated acid present in these electrolytes which increases the free H⁺ ion concentration and this has been monitored by pH measurements. Similar results have also been observed for lithium ion conducting polymer gel electrolytes for the first time and increase in conductivity with polymer addition has been found to depend upon the dielectric constant of the solvent and the salt concentration in the electrolytes.

Extraordinary high trivalent ion conducting solid electrolytes of (M_xZr_1-x)_4/(4-x)Nb(PO₄)₃ (M = Al, Ce, and Pr) were successfully realized by forming the NASICON type structure, with accompanying a suitable three dimensional trivalent ion pass way. Since the M³⁺ ion conductivity of the present solid electrolytes is as high as the ion conductivity region of the well-known and commercially available oxide anion conducting solid electrolytes of stabilized zirconias such as yttria stabilized zirconia (YSZ) and calcia stabilized zirconia (CSZ), practical applications of the present M³⁺ ion conducting (M_xZr_1-x)_4/(4-x)Nb(PO₄)₃ (M = Al, Ce, and Pr) solids for various functional materials such as chemical sensors, are greatly expected.

A series of transition metal-doped ceria, Ce_1-xM_xO_2-δ (M = Mn, Fe, Ni, Co), were synthesized, and crystal phase analysis by XRD and measurements of electrical properties were performed. Solubility limits of transition metal ions, which depended on the heat-treatment temperature and the kind of doped metal ions, seemed to be less than 15 mol% even at the highest case (Mn-doping). The total conductivity (σ_total) of Ce_1-xM_xO_2-δ (M = Mn, Fe) increased with an increase in the composition (x). Judging from the oxygen partial pressure dependence of (σ_total) and emf measurements, Ce_1-xM_xO_2-δ is a single-phase mixed conductor within the composition below the solubility limit, and is MO_x/Ce_1-xM_xO_2-δ dual-phase mixed conductor when the amount of by-produced transition metal oxide (MO_x) becomes high enough to realize the interconnectivity of the MO_x phase.

The solid solution Ce_0.9RE_0.1O_2-δ(M = Pr, Nd, Sm, Gd, Dy) were prepared by glycine-nitrate process. The XRD measurement showed that the solid solution was crystallized in cubic fluorite-type structure and the cell volume of Ce_0.9RE_0.1O_2-δ decreased with the increase of atomic number of RE. The ionic conduction for Ce_0.9RE_0.1O_2-δ was measured by impedance spectroscopy and the ionic conductivity of Ce_0.9RE_0.1O_2-δ decreases with the increase of atomic number Of RE. The linear thermal expansion of Ce_0.9RE_0.1O_2-δ decreased with the increase of atomic number of RE.

We carried out the H⁺/Li⁺ ion exchange for La_0.28Li_0.16NbO₃ and investigated its conductivity. The Li ion in La_0.28Li_0.16NbO₃ was easily exchanged and the composition of ion-exchanged material is considered to be La_0.27Li_0.0021H_0.16NbO₃. Its conductivity of a bulk part is 2.1 × 10^-9 S/cm at 400 K, which is very low compared with other proton ion conductors.

Natural kaolinite has been used as a starting material for preparing the fast ion conductors of Na_1+2x+yAl_xSm_yZr_2-x-ySi_xP_3-xO₁₂ system (Al-Sm-Nasicon) by high temperature solid phase reaction. A Nasicon phase with C2/c or space group exists in a rather wide composition region of above system. The unit-cell dimensions of Al-Sm-Nasicon change with changing x and y. The maximum conductivity in the above system is 1.25 × 10^-2 S/cm at 400°C for the initial composition x = 0.5, y = 0.3, its activation energy is 37.31 KJ/mole in the temperature range 200 ~ 400°C.

A high anion conducting PbSnF₄ has been prepared through ball-milling technique from the starting materials of PbF₂ and SnF₂ in the ratio 1:1 at room temperature as well as by the precipitation route from aqueous solution of Pb(NO₃)₂ and SnF₂. X-ray diffraction method reveals the formation of α-PbSnF₄ and the differential scanning calorimetry technique shows all allotropic phase transformations of the material. The temperature and frequency dependence of electrical conductivity have been investigated by means of impedance spectroscopy. The conductivity of a ball-milled PbSnF₄ sample was around 1 × 10^-4 S/cm at 303 K and the electrical conductivity study carried out in the temperature range 303–513 K shows an activation energy of 0.23 eV. The average grain size and the strain factor were calculated from the line width of XRD patterns and their correlation with the conductivity value has been investigated. The real part of the frequency dependent conductivity exhibits a simple power law feature and the dimensionless frequency exponent n has been determined. A low frequency dispersion of the conductivity was observed due to the space charge polarisation, which resulted from the high ionic conductivity of the material. Various electrical parameters as a function of temperature have been analysed in different complex planes. The frequency dependent plots of M" and Z" show that the conductivity relaxation is non-Debye in nature. The conductivity relaxation time has been estimated from the modulus spectra and the activation energy responsible for relaxation has been evaluated.

Lithium molybdosilicate (LMS) glasses in different formers compositions, of 20% Li₂O – 80 % [x MoO₃ + (1-x) SiO₂]; where x = 0.1 to 0.5 in steps of 0.1, were synthesized through sol-gel process. Structural characterisations of LMS glasses were made using XRD, FTIR and DSC techniques. XRD pattern of LMS samples showed amorphous phase for gels heat treated to 573 K and further heat treatment above 583 K showed the formation of crystalline multiphases. FTIR spectra for dried LMS gels heated between 338 K – 443 K showed the presence of hydroxyl group on the surface of silicate and molybdoates in the matrix and on further heat treatment, the FTIR spectra revealed the formation of silicate and molybdoate linkages in LMS glassy matrix. DSC curve confirmed the presence of adsorbed water molecules in LMS glassy matrix. Impedance measurements were carried out on LMS samples of different former compositions and the data were analyzed using Boukamp equivalent circuit software. The conductivity was calculated from analyzed impedance data and it is found to be 6.36 × 10^-5 Scm^-1 for x = 0.1 composition of LMS glass.

Various modifier to former (m/f) ratios of 60%AgI - m%Ag₂O - f% (0.7TeO₂ + 0.3 P₂O₅), silver phosphotellurite [SPT] glasses were prepared by melt quench technique. The prepared samples were characterized by XRD, FTIR and DSC technique to find out respectively the glassy nature, structure and glass transition temperature (T_g). Complex impedance measurement were made for the SPT sample pellets in the frequency range from 40 Hz to 100 kHz and the impedance data were analyzed using the Boukamp equivalent circuit software. The best conductivity data is obtained from the conductivity results and its variation with m/f ratios 60%AgI - 28.57%Ag₂O - 11.43% (0.7TeO₂ + 0.3 P₂O₅) was explained using weak electrolyte model.

Theoretical relationships for the thermoelectric power of the electrons and holes in ionic crystals containing transition metal components were derived, based on the solid-state electrochemistry. Equations were found that related the thermoelectric power of the electrons and holes in these ionic crystals to the chemical potentials of the ions on which the electrons or holes were localized. In addition, the Heikes formulae could be derived using the ideal solution model. Based on our model, it was predicted that an anomalous temperature dependence should occur at the magnetic phase transition temperature. The anomalous temperature dependence was experimentally confirmed by measuring the thermoelectric power of La_0.9Sr_0.1FeO_3-δ as function of temperature.

Li₃InBr_6-xCl_x and Li_3-2xMxInBr₆ (M = Mg, Ca, Sr and Ba; x = 0 - 1.0) was synthesized, and the substitution effect was investigated by means of ⁷Li and ¹¹⁵In NMR, X-ray diffraction and AC conductivity measurements. With increasing x the lattice volume of Li₃InBr_6-xCl_x decreased and the gradient changed at x = 3. The phase transition temperature in Li₃InBr₃Cl₃ lowered than that of Li₃InBr₆ and the high ionic conduction phase is stable under the room temperature. The ionic conductivity in high temperature phase of Li₃InBr₃Cl₃ was almost equal to original Li₃InBr₆ and highest in Li₃InBr_6-xCl_x. The substitution with chloride ion improved the ionic conductivity. On the other hand, in the high temperature phase of Li_3-2xMxInBr₆ (M = Mg, Ca, and Ba), the conductivity decreased with x. In Li_3-2xSrxInBr₆(x < 0.7), the conductivity of high temperature phase also decreased with an increase of x but LiSrxInBr₆ show almost the same conductivity to Li₃InBr₆.

Temperature dependencies of infrared reflectivity spectra have been measured for a glass ionic conductor (Ag₂S)_0.3-(AgPO₃)_0.7. The long- or short-range force, estimated from the frequencies of TO and LO like vibration modes as a function of temperature with similar procedure to that of crystal, decreases or increases below and near the glass transition temperature. Binding strength for Ag ions forming frame and mobile ions exhibit different temperature dependence, it is similar to that of crystal superionic conductors.

Very few studies are available which deal with sulphide systems while a large number of different types of oxide ion conducting ceramics are described in the open literature. The research here has focused on oxide ion conducting analogues. Solid solutions of CaNd₂S₃ and Nd₂S₃ were characterized using Impedance Spectroscopy (IS), temperature programmed oxidation (TPO) and temperature programmed reduction (TPR). The materials resist oxidation up to a temperature of approximately 680°C and reduction up to 750°C. Instability of impedance arcs at elevated temperatures have been reported previously and are explained in terms of three phase boundary area (TPB). Examples include CaS using gold electrodes and Yttria-Stabilized-Zirconia (YSZ) with platinum electrodes. Only a single impedance arc is observed for the undoped CaNd₂S₄. Two arcs are observed for the doped material indicating ionic mobility. At low frequencies significant instability is observed as a function of temperature (change of decreasing real component of impedance to increasing real component at approximately 250°C for the undoped and 200°C for the doped material). This may be explained by the formation and subsequent decomposition of Au₂S forming at the interface of electrolyte and electrode.

Investigations of materials in the PbO-Bi₂O₃-V₂O₅/P₂O₅,/As₂O₅ ternary systems have led to the discovery of many new materials of complex crystal chemistry and improved anionic transport properties^1,2. PbBi₆V₂O₁₅ and SrBi₆V₂O₁₅, obtained by complete substitution of Pb with Sr, have been shown to be oxide ion conductors with conductivity of 4.70 × 10^-6 and 4.75 × 10^-5 Scm^-1 at 500°C, respectively³. These materials have transport numbers as high as 0.8 at ~600°C. Introduction of Na and Bi into Pb sites in PbBi₆V₂O₁₅ has resulted in a new material, NaBi₁₃V₄O₃₀. The similarity of its XRD pattern to that of PbBi₆V₂O₁₅ indicates that these materials could be isostructural. The XRD data could be indexed on an orthorhombic cell with a = 23.9358(5), b = 17.1663(5) and c = 11.0888(4) Å. Substitution of V with As resulted in the formation of a complete solid solution series, NaBi₁₃V_4-xAs_xO₃₀, 0 ≤ x ≤ 4. On the other hand, partial solid solutions were formed upon introduction of P, NaBi₁₃V_4-xP_xO₃₀, 0 ≤ x ≤ 1. ac impedance studies show that these materials are predominantly oxide ion conductors. Conductivity decreased in the order of NaBi₁₃V₄O₃₀ > NaBi₁₃As₄O₃₀ > NaBi₁₃V₃P₁O₃₀. The conductivity of NaBi₁₃V₄O₃₀, 1.4 × 10^-4 S cm^-1 at 500°C, is higher than that of PbBi₆V₂O₁₅ and SrBi₆V₂O₁₅. This material thus appears to be a promising oxide ion conductor.

(La,Zn)TiO₃ was synthesized by an ion exchange method using ZnCl₂ molten salt. By a powder X-ray diffraction, it was confirmed that perovskite structure was retained after ion exchange. The composition of ion exchanged sample was determined to be La_0.55(6)Li_0.064(4)Zn_0.13(1)Ti_1.0(1)O_2.97 by ICP analysis, and the homogeneous distribution of Zn in this sample was confirmed by the scanning electron microscope (SEM). The bulk and total conductivity of the sample at the room temperature was measured to be 6.9 × 10^-7 S·cm^-1, 1.7 × 10^-7 S·cm^-1, respectively. The mobile species was confirmed to be Zn²⁺ by the electrolysis at 500°C.

Fast ion conductors of Li₂O~SiO₂~V₂O₅ system have been prepared by using Li₂O, SiO₂ and V₂O₅ as starting materials. The optimal ratio of starting materials was designed by Uniform Design. The conductivities of both electric and ionic were investigated. The highest ion conductivity is 1.5 × 10^-4S/cm at ambient temperature for the above lithium fast ion conductor system, the electronic conductivity is 4 orders of magnitude lower than the ionic conductivity.

Proton conducting polymer gel electrolytes containing weak aromatic carboxylic acid (ortho-hydroxybenzoic acid with dissociation constant 105 × 10^-5) with polyvinylidenefluoride (PVdF) as the gelling polymer show high conductivity (10^-4 S/cm) at 25°C and the conductivity of gel electrolytes is higher than the corresponding liquid electrolytes. FTIR results have been used to investigate interactions between the solvent, acid and polymer and it has been observed that polymer plays an active role.

In order to obtain high ionic conductors, a new solid solution of La_2/3-xLi_3xWO₄ with a scheelite-type structure was synthesized and the lithium ionic conduction were confirmed by electrochemical measurements and neutron radiography(NR). For pure La_2/3WO₄, the conductivity was about 10^-5 S cm^-1 at 900°C. Enhanced conductivities are observed in the substituted samples. According to the oxygen gas concentration cell measurements and the electrolysis, it was found that the main charge carriers are not electrons but ions for the substituted samples. From the NR images of electrolyzed La_0.56Li_0.30WO₄ samples, furthermore, it could be obviously seen the lithium movement in the sample. From the profile of lithium, the lithium ion transport number of the oxide was known to be 0.67 at 900°C, which would mean partly oxide ion contribution to the total electrical conduction.

A new type of polycrystalline Li⁺ ion conductor, lithium and potassium nitrates co–doped (Gd_0.9La_0.1)₂O₃, was successfully developed. Since KNO₃ was doped into the interstitial open spaces in the (Gd_0.9La_0.1)₂O₃ lattice together with LiNO₃, the high ion conductivity was achieved down to 373 K. Among the single phase samples obtained, the 0.55(Gd_0.9La_0.1)₂O₃–0.18LiNO₃–0.27KNO₃ showed a highest Li⁺ ion conductivity which was comparable to those of LISICON series above 373K.

The blend polymer electrolyte membranes comprising PVAc-PVdF with various LiClO₄ concentrations have been characterized. FT-IR, XRD studies indicate the polymer-salt complex formation. The ac impedance cole-cole plot shows the high frequency semi-circle which is due to the bulk effect of the material and the depression in the semi circle shows the non-Debye nature of the material. The bulk conductivity is found to vary between 3.2 × 10^-7 to 1.3 × 10^-4 Scm^-1 at 303K with the increase of salt concentration of blend polymer electrolytes. The ionic transference number has been found by Wagner's polarization method and the results reveal that the conducting species are ions. The low frequency dispersion of the dielectric constant implies the space charge effects arising from the electrodes.

Many types of polymer electrolytes have been developed and characterized for the past few years. Recently special attention has been focused on the development of proton conducting polymer electrolytes as they may find unique applications in electrochromic and fuel cell devices. Polymer electrolyte films consisting of poly (vinyl alcohol) (PVA) with various concentrations of CH₃COONH₄ have been characterized. Ac conductivity studies, FT-IR and XRD have been used to characterize the polymeric electrolytes. Relative to the various salt concentrations of polymer electrolytes, structural changes in the films have been investigated. The polymer-salt complex formation has been confirmed by XRD and FT-IR studies. The conductivity studies are carried out in the frequency range 42Hz-5MHz over the temperature range 303-373K. The conductance spectra show the DC plateau and dispersive region suggesting the correlated hopping motion of ions. The DC conductivity value for pure PVA is 3.7 × 10^-10 Scm^-1 at room temperature and the value increases to 9 × 10^-7 Scm^-1 for 80m%PVA-20m% CH₃COONH₄ polymer complexes. The transference number measurements have been carried out by Wagner's polarization measurement and the results indicate that the conduction is mainly due to the ions.

Polypyrrole films were prepared by electro polymerization in the presence of surfactant anions, dodecyl benzene sulphonate, in pure water. The ion transfer in such films during the redox process has been investigated using a combination of cyclic voltammetry and electrochemical quartz crystal microbalance measurements by cycling the films in NaBr or NaCl aqueous electrolytes at different scan rates. As the large surfactant anions are trapped in the polymer matrix, both cations and anions present in the electrolyte take part in the redox process. Water is also inserted or expelled as molecules bound to the moving ions and as a result of the osmotic effect. While the dominant cation motion does not depend very much on the speed of cycling, the water transport strongly depends on the rate of the potential scan.

Deproteinized natural rubber having epoxy group (EDPNR) was applied to transport Li⁺ as a solid polymer electrolyte. The deproteinized natural rubber, incubated with proteolytic enzyme and surfactant, was subjected to epoxidation followed by oxidative depolymerization in latex stage. The resulting rubber was proved to be a liquid deproteinized natural rubber (LEDPNR) having polar epoxy groups, low T_g, low M_n and well-defined terminal units. Ionic conductivity of LEDPNR mixed with alkali metal salts was investigated through impedance analysis to clarify an effect of proteins present in the rubber. The ionic conductivity of the resulting LEDPNR depended on the kind of salts, their concentrations and temperature. The ionic conductivity of LEDPNR/lithium bis(trifluoromethan sulfonyl)imide (LiTFSI) was higher than that of LEDPNR/ lithium perchlorate (LiClO₄). The difference in the ionic conductivity was attributed to the solubility of the salts as results of both high-resolution solid-state ¹³C-NMR spectroscopy and measurements of spin-lattice relaxation time. The conductivity of LEDPNR/LiTFSI was also dependent upon concentrations of LiTFSI and it reached the highest value at 20 wt%, which was different from the monotonic increase in the Li⁺ conductivity of liquid epoxidized natural rubber prepared from untreated natural rubber.