Ionic conductivity

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

Polar Fluorooxoborate, NaB4O6F: A Promising Material for Ionic Conduction and Nonlinear Optics

Abstract: The search of new borates with improved functional properties has attracted considerable attention. Herein, a new polar fluorooxoborate, NaB4 O6 F (NBF) was prepared by high-temperature solid-state reaction. NBF belongs to the AB4 O6 F family (A=alkali metal or ammonium), a series of compounds that undergoes significant cation-dependent structural changes. NBF is of particular interest owing to the special cation position. Temperature-dependent ionic conductivity measurements show that NBF is a solid ionic conductor, and it has the lowest active energy of 32.5 kJ mol-1 of fluorooxoborates. NBF also shows a second-harmonic generation (SHG) response of 0.9×KH2 PO4 and 0.2×β-BaB2 O4 , at 1064 and 532 nm, respectively, and it has a short UV cutoff edge below 180 nm. Based on bond valence (BV) concepts, symmetry analysis, and the first principles calculation, the unique [B4 O6 F]∞ layer can be regarded as the "multifunctional unit", which is responsible for the observed properties of NBF.

Concentrated electrolytes: decrypting electrolyte properties and reassessing Al corrosion mechanisms

Abstract: Highly concentrated electrolytes containing carbonate solvents with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) have been investigated to determine the influence of eliminating bulk solvent (i.e., uncoordinated to a Li+ cation) on electrolyte properties. The phase behavior of ethylene carbonate (EC)–LiTFSI mixtures indicates that two crystalline solvates form—(EC)3:LiTFSI and (EC)1:LiTFSI. Crystal structures for these were determined to obtain insight into the ion and solvent coordination. Between these compositions, however, a crystallinity gap exists. A Raman spectroscopic analysis of the EC solvent bands for the 3–1 and 2–1 EC–LiTFSI liquid electrolytes indicates that ∼86 and 95%, respectively, of the solvent is coordinated to the Li+ cations. This extensive coordination results in significantly improved anodic oxidation and thermal stabilities as compared with more dilute (i.e., 1 M) electrolytes. Further, while dilute EC–LiTFSI electrolytes extensively corrode the Al current collector at high potential, the concentrated electrolytes do not. A new mechanism for electrolyte corrosion of Al in Li-ion batteries is proposed to explain this. Although the ionic conductivity of concentrated EC–LiTFSI electrolytes is somewhat low relative to the current state-of-the-art electrolyte formulations used in commercial Li-ion batteries, using an EC–diethyl carbonate (DEC) mixed solvent instead of pure EC markedly improves the conductivity.

High‐Temperature Proton Conducting Membranes Based on Perfluorinated Ionomer Membrane‐Ionic Liquid Composites

Abstract: Composite membranes that exhibit fast proton transport at elevated temperatures are needed for proton‐exchange‐membrane fuel cells and other electrochemical devices operating in the 100 to 200°C range. Traditional water‐swollen proton conducting membranes such as the Nafion membrane suffer from the volatility of water in this temperature range leading to a subsequent drop in conductivity. Here we demonstrate that perfluorinated ionomer membranes such as the Nafion membrane can be swollen with ionic liquids giving composite free‐standing membranes with excellent stability and proton conductivity in this temperature range while retaining the low volatility of the ionic liquid. Ionic conductivities in excess of 0.1 S/cm at 180°C have been demonstrated using the ionic liquid 1-butyl, 3-methyl imidazolium trifluoromethane sulfonate. Comparisons between the ionic‐liquid‐swollen membrane and the neat liquid itself indicate substantial proton mobility in these composites. © 2000 The Electrochemical Society. All rights reserved.