Determination Of Ionic Conductivity Research Articles

Effect of Substrate Permeability on Scanning Ion Conductance Microscopy: Uncertainty in Tip-Substrate Separation and Determination of Ionic Conductivity.

Composite electrodes can significantly improve the performance of an electrochemical device by maximizing surface area and active material loading. Typically, additives such as carbon are used to improve conductivity and a polymer is used as a binder, leading to a heterogeneous surface film with thickness on the order of 10s of micrometers. For such composite electrodes, good ionic conduction within the film is critical to capitalize on the increased loading of active material and surface area. Ionic conductivity within a film can be tricky to measure directly, and homogenization models based on porosity are often used as a proxy. SICM has traditionally been a topography-mapping microscopy method for which we here outline a new function and demonstrate its capacity for measuring ion conductivity within a lithium-ion battery film.

Paradigms of Structural, Chemical, and Dynamical Frustration in Superionic Conductors

Rationally motivated computational discovery and optimization of solid electrolytes require the development of reliable descriptors for fast ionic conductivity. However, many of the fundamental motivations for superionic behavior in solids remain enigmatic, which has generally slowed progress in screening electrolyte candidates, as well as in tuning existing materials to maximize ionic conductivity. I will discuss our efforts using first-principles molecular dynamics simulations to unravel various mechanisms of ionic conductivity in model classes of solid electrolytes. Using computational “experiments”, our simulations systematically isolate factors such as stoichiometry, strain, composition, and crystal structure in the determination of ionic conductivity. Collectively, the results point to the importance of a frustrated energy landscape in promoting ultrafast diffusion. Different types of frustration in model superionic conductors will be discussed, arising from factors such as off-stoichiometry, competition between interstitial site occupancies, symmetry incompatibilities between local bonding character and lattice geometry, and dynamical frustration coupled to anharmonic processes. Physicochemical origins of the relevance of these factors for cation mobility will be explored, with a view towards developing design rules for engineering faster ionic conductors. Our findings suggest that the relative contributions of the different frustration paradigms depend chiefly on the fundamental nature of the lattice-forming ions, suggesting there may be no single universal descriptor for ionic conductivity, but rather classes of superionic conductors with similar underlying motivations. Specific examples will be drawn from our recent results on superionic materials based on oxides, halides, and polyatomic anions. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Determination of ionic conductivity in the Bi-Si-O and Pb-Si-O glasses

Abstract Impedance spectroscopy measurements in various gas atmospheres were carried out in order to explain the doubts about the type of carriers and the mechanism of electrical conductivity in Bi-Si-O and Pb-Si-O glasses. In bismuth silicate glass, a typical ionic conductivity with oxygen ions as charge carriers was observed. The level of electrical conductivity of the glass at 400 °C was 5 × 10-8 S·cm-1, with the activation energy of 1.3 eV and was independent of measuring atmosphere. In the case of lead silicate glasses, the conductivity changed with measuring atmosphere. Two types of charge carriers: oxygen ions and proton ions were postulated. Proton conductivity measured in wet argon at temperature 400 °C was estimated at the level of 4 × 10-8 S·cm-1 while the oxygen ions conductivity in such conditions was 78 × 10-8 S·cm-1. We suggest that both types of charge carriers are transported along the same conduction paths using oxygen defects in the glass structure.

Novel approach in determination of ionic conductivity and phase transition temperatures in gel electrolytes based on Low Molecular Weight Gelators

The performance of a method for ionic conductivity measurements in physical gels with use of thermal scanning approach is investigated. It has been shown that this new experimental protocol has several advantages over conventional conductometry with temperature stabilization of the sample. Improved sensitivity of “ongoing” changes, in situ observations of the gel phase and measurements during gelation stage showed interesting features in conductivity and temperature dependences undetectable in conventional conductometry. The comparison of the results for both methods showed very good agreement concerning global features and additional important detail accessible only by the new proposed here method. Ultimately, the method can be used for characterization of the conductivity properties of the system in the gel phase as well as during gelation process, together with detection and validation of the gel-to-sol phase transition temperatures.

Determination of Ionic Conductivity and Its Impact on Proton Diffusion Model for Nickel Hydroxide

The ionic conductivity is an important but previously ignored aspect for the nickel hydroxide used in alkaline batteries. With a specially designed device, the ionic conductivity is determined for single beads of spherical nickel hydroxide in KOH solutions. The apparent ionic conductivity is found on the order of 10(-3)-10(-2) S cm-1 in 6 M KOH and to change with the conductivity of the solution in which the bead is immersed. The ionic conductivity of the bead can be mainly attributed to the electrolyte absorbed in the bead. On the basis of these findings, the dual structure model for proton diffusion in spherical nickel hydroxide is refined by specifying nanoparticles to be the component showing a large apparent proton diffusion coefficient (on the order of 10(-7) cm2 s-1). This refined model is able to interpret the main features of the diffusion coefficients reported in the literature, including the unusually large scattering (up to 6 orders of magnitude) and inconsistency in the dependence of proton diffusion coefficient on the state of the charge. Besides, this refined model is supported by the influence of bulk KOH concentration on chronoamperometry and transmission electron microscopy observations.

New sulfonated engineering polymers via the metalation route. I. Sulfonated poly(ethersulfone) PSU Udel� via metalation-sulfination-oxidation

A new process has been developed for the sulfonation of arylene polymers which can be lithiated, like polysulfone Udel®. The sulfonation process consists of the following steps: (1) lithiation of the polymer at temperatures from −50 to −80°C under argon, (2) gassing of the lithiated polymer with SO2; (3) oxidation of the formed polymeric sulfinate with H2O2, NaOCl, or KMnO4; (4) ion-exchange of the lithium salt of the sulfonic acid in aqueous HCl. The advantages of the presented sulfonation procedure are: (1) in principle all polymers which can be lithiated can be subjected to this sulfonation process; (2) by this sulfonation procedure the sulfonic acid group is inserted into the more hydrolysis-stable part of the molecule; (3) this process is ecologically less harmful than many common sulfonation procedures. The sulfonated polymers were characterized by NMR, titration and elemental analysis, by IR spectroscopy, and by determination of ionic conductivity. Also the hydrolytic stability of the sulfonated ion-exchange polymers was investigated. Polymers with an ion-exchange capacity of 0.5 to 3.2 mequiv SO3H/g Polymer have been synthesized and characterized. The following results have been achieved: membranes made from the sulfonated polymers show good conductivity, good permselectivity (>90%), and good hydrolytic stability in 1N HCl and water at temperatures up to 80°C. © 1996 John Wiley & Sons, Inc.

New sulfonated engineering polymers via the metalation route. I. Sulfonated poly(ethersulfone) PSU Udel® via metalation‐sulfination‐oxidation

A new process has been developed for the sulfonation of arylene polymers which can be lithiated, like polysulfone Udel®. The sulfonation process consists of the following steps: (1) lithiation of the polymer at temperatures from −50 to −80°C under argon, (2) gassing of the lithiated polymer with SO2; (3) oxidation of the formed polymeric sulfinate with H2O2, NaOCl, or KMnO4; (4) ion-exchange of the lithium salt of the sulfonic acid in aqueous HCl. The advantages of the presented sulfonation procedure are: (1) in principle all polymers which can be lithiated can be subjected to this sulfonation process; (2) by this sulfonation procedure the sulfonic acid group is inserted into the more hydrolysis-stable part of the molecule; (3) this process is ecologically less harmful than many common sulfonation procedures. The sulfonated polymers were characterized by NMR, titration and elemental analysis, by IR spectroscopy, and by determination of ionic conductivity. Also the hydrolytic stability of the sulfonated ion-exchange polymers was investigated. Polymers with an ion-exchange capacity of 0.5 to 3.2 mequiv SO3H/g Polymer have been synthesized and characterized. The following results have been achieved: membranes made from the sulfonated polymers show good conductivity, good permselectivity (>90%), and good hydrolytic stability in 1N HCl and water at temperatures up to 80°C. © 1996 John Wiley & Sons, Inc.

Evaluation of 2- and 4-point conductivity measurements on oxide ion conductors

A comaprison between different ac measuring techniques has been performed and evaluation methods for the determination of ionic conductivity in oxygen ion conductors are described. 2- and 4-point impedance measurements using two different frequency response analysers (Solartron FRA-1174 and FRA-1250) are compared. The materials studied were polycrystalline cubic ceriagadolinia, tetragonal zirconia-yttria ceramics and single crystallin YSZ. Empirical rules for the determination of conductivity by geometrical methods from “overlapping” semicircies in the complex plane representation of the immittance data were established. This was supported by model calculations and non-linear least squares fitting techniques.