Ionic conductivity

About: Ionic conductivity is a research topic. Over the lifetime, 19412 publications have been published within this topic receiving 519167 citations.

Impedance and Raman spectroscopic studies of (Na0.5Bi0.5)TiO3

Abstract: Polycrystalline powder of (Na0.5Bi0.5)TiO3 (NBT) was prepared by a high-temperature solid-state reaction route. Preliminary x-ray diffraction analysis carried out at room temperature showed the formation of a single phase compound with a rhombohedral crystal system. Scanning electron micrograph reveals the polycrystalline nature of the material with size anisotropy. Dielectric study showed an existence of diffuse phase transition around 300 °C. The ac conductivity spectrum obeyed the Jonscher power law. The temperature dependent pre-exponential factor (A) shows peak and frequency exponent (n) possesses a minimum at transition temperature. The bulk conductivity of the material indicates an Arrhenius type of thermally activated process with three different conduction mechanisms as different activation energies are observed. The hopping charge carriers dominate at low temperature, small polaron and oxygen vacancy dominates at intermediate temperature and ionic conduction at higher temperatures. Studies of impedance spectroscopy indicate that the dielectric relaxation is of non-Debye type. In situ high-temperature Raman spectroscopy shows discontinuous changes in the phonon frequencies across the rhombohedral–tetragonal transition. In addition, anomalous changes in the intensity and the linewidth of a lattice mode are found around 350 °C.

Proton Conductivity in Nafion® 117 and in a Novel Bis[(perfluoroalkyl)sulfonyl]imide Ionomer Membrane

Abstract: A study of proton conductivity in a commercial sample of Nation® 117 and a structurally similar bis[(perfluoroalkyl)sulfonyl]imide ionomer membrane under variable temperature and humidity conditions is reported. The sulfonyl imide ionomer was synthesized using a novel redox‐initiated emulsion copolymerization method, and conductivities were measured using a galvanostatic four‐point‐probe electrochemical impedance spectroscopy technique. Both materials exhibited a strong dependence of conductivity on temperature and humidity, with conductivity in both cases being strongly diminished with decreasing humidity (at constant temperature) and increasing temperature (at constant water partial pressure). The observed behavior is consistent with a "liquid‐like" mechanism of proton conductivity whereby protons are transported as hydrated hydronium ions through water‐filled pores and channels in the ionomer.

Review of PVA-based gel polymer electrolytes in flexible solid-state supercapacitors: Opportunities and challenges

Abstract: Flexible solid-state supercapacitors with high power density and rate performance, long cycle life, high safety and ease of fabrication are highly desirable. They can be used in an emerging market of flexible and wearable electronic gadgets. Gel polymer electrolytes are being considered as one of the best candidates. They typically have higher ionic conductivity than solid electrolytes without safety concerns of liquid electrolytes. This article reviews the latest achievements in the application of PVA-based gel polymer electrolytes for flexible supercapacitors and new findings on the improvement of their ionic conductivity, mechanical properties, and overall electrochemical performance. Several current kinds of research attempt to overcome these challenges with the main goal of improving ionic conductivity and electrochemical properties. There is no limitation for ionic conductivity of gel electrolyte because high ionic conductivity can lead to higher specific capacitance and also sufficient electrochemical performance. A recent study of gel electrolytes has shown the highest ionic conductivity of 82 mS.cm−1 for PVA/H2SO4/Glutaraldehyde/H2O which results in a large areal capacitance of 488 mF.cm−2 (100 reference).

The zwitterion effect in high-conductivity polyelectrolyte materials

Abstract: The future of lithium metal batteries as a widespread, safe and reliable form of high-energy-density rechargeable battery depends on a significant advancement in the electrolyte material used in these devices. Molecular solvent-based electrolytes have been superceded by polymer electrolytes in some prototype devices, primarily in a drive to overcome leakage and flammability problems, but these often exhibit low ionic conductivity and prohibitively poor lithium-ion transport. To overcome this, it is necessary to encourage dissociation of the lithium ion from the anionic polymer backbone, ideally without the introduction of competing, mobile ionic species. Here we demonstrate the effect of zwitterionic compounds, where the cationic and anionic charges are immobilized on the same molecule, as extremely effective lithium ion 'dissociation enhancers'. The zwitterion produces electrolyte materials with conductivities up to seven times larger than the pure polyelectrolyte gels, a phenomenon that appears to be common to a number of different copolymer and solvent systems.