Papers by Keyword: Ionic Conductivity

Abstract: In the present work, using nanosized rare earth oxide CeO₂ as filler and acetonitrile as organic solvent, a novel solid-state composite polymer electrolyte (CPE) films (PEO)₁₀LiClO₄-x wt.%CeO₂ (x=0,2,6,9,12,15) was prepared by solution-casting technique. The effect of CeO₂ filler concentration on morphology and electrical characteristics of CPE films has been investigated and analyzed. The AC impedance measurements show that the ionic conductivity of CPE can be efficiently enhanced by adding appropriate CeO₂. The highest room temperature (25^OC) ionic conductivity of 1.71×10^-5S•cm^-1 is achieved with the CeO₂ content of 9 wt.%. With the CeO₂ content continues to increase, CPE ionic conductivity begin to decline. This is because appropriate CeO₂ can disorder the chain structure and effectively inhibit the crystallization of PEO, which expands the amorphous region required for the lithium-ion transport.

Abstract: The effect of MnO₂ addition (0–2.0 mol%) on the densification, crystal structure, and ionic conductivity of Ce_0.8Sm_0.2O_1.9 (SDC) was studied. The addition of MnO₂ promotes densification, reducing sintering temperature by ~150°C. X-ray diffraction analysis showed that all the samples exhibit a fluorite structure. Impedance spectroscopy measurements indicated that SDC with appropriate ratio of MnO₂ addition has higher ionic conductivity and lower activation energy compared with that of SDC. As the addition amount of Mn increases up to 1.0 mol% [(Ce_0.8Sm_0.2O_1.9)_0.99+(MnO₂)_0.01], the sample attains the highest ionic conductivity, about 35% higher than that of SDC at 600°C. In addition, Mn addition has little effect on bulk conductivity, but a marked influence on grain boundary behavior is observed.

Abstract: Polycrystalline Li₂Ge_xSi_1-xO₃ (x = 0.0~1.0) was synthesized by solid state reaction, and its ionic conductivity was studied as a function of x in a temperature range of 500–700 K. The ionic conductivity was found to depend on x and was enhanced at x = 0.2–0.7. Furthermore, the pre-exponential factor and activation energy in the Arrhenius equation were also found to depend on x. These results suggest that lithium ionic conduction in Li₂Ge_xSi_1-xO₃ is strongly influenced by the structure of the framework.

Abstract: Ionic liquid oligomer, 1-oligo(ethyleneoxide)-3-methylimidazolium salt　(PEO(X)MIm) and Ionic liquid polymer, poly(1-oligo (ethylene glycol) methacrylate-3-methylimidazolium) salt (P(MOEMIm)) prepared by incorporating imidazolium ionic liquid with PEO oligomer and polymer were investigated as electrolytes for dye-sensitized solar cells (DSCs). Ionic liquid electrolytes were composed of LiI, I2, and PEO(X)MImCl or the mixture of 1-hexyl-3-methylidazolium iodide (HMImI), 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4) and PEO(X)MImCl. Quasi-solid-state electrolytes were prepared by employing the imidazole polymers P(MOEMImCl) to solidify the liquid electrolyte containing lithium iodide, iodine and ethylene carbonate (EC)/propylene carbonate (PC) mixed solvent. Ionic liquid based quasi-solid state electrolytes were prepared by solidifying the ionic liquid electrolytes containing HMImI or a binary mixture of HMImI and EMImBF4 with an ionic liquid polymer P(MOEMImCl), respectively. The influences of PEO molecular weight, polymer content, addition of alkyl ionic liquid and various anions of the ionic liquid oligomers and polymer on the ionic conductivity, apparent diffusion coefficient of the redox species in the electrolytes and the performance of solar cells were examined. The influences on the kinetic behaviors of dye regeneration and triiodide reduction reactions taken place at nanocrystalline TiO2 electrode and Pt counter-electrode, respectively, were also studied by cyclic-voltammetry and electrochemical impedance spectroscopy measurements. By using ternary ionic liquid electrolyte containing 1M lithium iodide and 0.5M iodine in the ionic liquid of the ionic liquid mixture of PEO(X)MImCl), HMImI and EMImBF4, quasi-solid-state electrolytes and ionic liquid based quasi-solid state electrolytes the photoelectron conversion efficiency of DSCs is 7.89%, 7.6% and 6.1%, respectively(AM 1.5, 100mWcm−2). These results show the potential application of PEO based ionic liquid in SCs.

Abstract: The present study focuses on preparation of ENR-50/PEMA-NH4CF3SO3 proton conducting polymer electrolytes by solution casting technique. Conductivity increases with NH4CF3SO3 concentration up to 40 wt.% but decreases with further increase in salt content. The temperature dependent conductivity study shows that the conductivity-temperature behaviour of ENR-50/PEMA-NH4CF3SO3 electrolytes follows the VTF rule. DSC studies show that the Tg increases with increase in salt content. This means that the increase in conductivity of ENR-50/PEMA-NH4CF3SO3 is incorrelated to the increase of the segmental motion of the host polymer chains but may be attributed to the increase in the concentration and migration rate of charge carriers.

Abstract: The compositions La0.56Li0.33TiO2.95F0.05•xLiF (x=0-025) were prepared by addition of LiF to the disordered form of the well-known Li ion conductor La0.56Li0.33TiO3. Although the total conductivities improved, there was no change in the bulk conductivity with LiF addition. No reflections due to LiF were observed in their XRD patterns, and the profiles and the chemical shifts of their 19F MAS-NMR resonances were almost the same as those of LiF. The results indicate that no substitution of F takes place, and that the added LiF acts simply as a sintering assistant agent.

Abstract: In this paper one attempted to discuss the effect of reducing the experimental duration of electrochemical impedance spectroscopy (EIS) measurements by reducing the sampling frequency without affecting the measured parameters. The experimental setup is based on a novel cell consisting of two electrodes or three electrodes cell configuration. The experimental layout allows a precise evaluation of the membrane thickness, at micrometer resolution, during the determination of the electrochemical impedance spectra.

Abstract: This work first explores high resolution transmission electron microscopy (TEM) to determine the interfacial regions and provide experimental evidences for interfaces between the SDC and carbonate constituent phases of the SD-carbonate two-phase composites to further investigate the superionic conduction mechanism in the ceria-carbonate composite systems and enhancement of conductivity. Schober first reported interfacial superionic conduction in ceria-based composites but without direct experimental proofs. Such superionic conduction mechanism remains unknown. Especially, in the nano-scale, this region is trifle to be detected.

Abstract: The anisotropy of self-diffusion of K+ ions, ionic conductivity, and static permittivity in stoichiometric disordered K5Bi1-xRx(MoO4)4 (R = Nd, Gd; x = 0, 0.92, 1) single crystals is studied. A high value of the 2-D diffusion and ionic conductivity by K+ ions is detected. The fast ionic transport is parallel to the double layers formed by MoO4 tetrahedrons.

Abstract: Poly(vinylidene fluoride)(PVDF) is photochemically stable even in the presence of TiO2 and Pt nanoparticles, and poly(methacrylate)(PMMA) has good solvent retention. The quasi-solid electrolytes based on PVDF-PMMA blend polymer were prepared in this work by soaking a porous membrane in an organic electrolyte solution containing the I−/I3− redox couple. The as-prepared electrolytes were characterized by means of Fourier Transform Infrared Spectroscopy, Scanning Electron Microscope respectively. Moreover, the conductivity and the voltage-current curves of the electrolytes were measured by electrochemical workstation. The results indicated that the optimum blend proportion of PVDF and PMMA was 6:4. The porous structure prepared with the addition of propanetriol was beneficial to ion diffusion and thus enhanced the conductivity of the electrolytes. The gel polymer electrolyte had a conductivity of 0.14 mS•cm-1 under the ambient atmosphere. Furthermore, electrolytes were assembled to fabricate DSSCs and the performance of the cells was tested. The good properties with the open-circuit voltage of 0.60V and the short-circuit current of 1.1mAcm-2 were achieved upon illumination with visible light.