158,126 research outputs found
Highly conductive, ionic liquid-based polymer electrolytes
In this manuscript is reported a thermal and impedance spectroscopy investigation carried out on quaternary polymer electrolytes, to be addressed as separators for lithium solid polymer batteries, containing large amount of the N-methyl-N-propylpyrrolidinium bis(fluorosulfonyl)imide ionic liquid. The target is the development of Li+ conducting membranes with enhanced ion transport even below room temperature. Polyethylene oxide and polymethyl methacrylate were selected as the polymeric hosts. A fully dry, solvent-free procedure was followed for the preparation of the polymer electrolytes, which were seen to be self-consistent and handled even upon prolonged storage periods (more than 1 year). Appealing ionic conductivities were observed especially for the PEO electrolytes, i.e., 1.6 × 10-3and 1.5 × 10-4 S cm-1 were reached at 20 and -20°C, respectively, which are ones the best, if not the best ion conduction, never detected for polymer electrolytes
The Electrostatic Screening Length in Concentrated Electrolytes Increases with Concentration
According to classical electrolyte theories interactions in dilute (low ion
density) electrolytes decay exponentially with distance, with the Debye
screening length the characteristic length-scale. This decay length decreases
monotonically with increasing ion concentration, due to effective screening of
charges over short distances. Thus within the Debye model no long-range forces
are expected in concentrated electrolytes. Here we reveal, using experimental
detection of the interaction between two planar charged surfaces across a wide
range of electrolytes, that beyond the dilute (Debye-Huuckel) regime the
screening length increases with increasing concentration. The screening lengths
for all electrolytes studied - including aqueous NaCl solutions, ionic liquids
diluted with propylene carbonate, and pure ionic liquids - collapse onto a
single curve when scaled by the dielectric constant. This non-monotonic
variation of the screening length with concentration, and its generality across
ionic liquids and aqueous salt solutions, demonstrates an important
characteristic of concentrated electrolytes of substantial relevance from
biology to energy storage.Comment: This document is the unedited authors' version of a Submitted Work
that was subsequently accepted for publication in the Journal of Physical
Chemistry Letters, copyright American Chemical Society, after peer review. To
access the final edited and published work see
http://pubsdc3.acs.org/articlesonrequest/AOR-EW6FuIC6wIh6D9qqEeH
Properties of nonaqueous electrolytes Quarterly report, 20 Dec. 1966 - 19 Mar. 1967
Properties of nonaqueous electrolytes - preparation of electrolytes, nuclear magnetic resonance structural studies, and physical property determination
Molecular Dynamics simulations of concentrated aqueous electrolyte solutions
Transport properties of concentrated electrolytes have been analyzed using
classical molecular dynamics simulations with the algorithms and parameters
typical of simulations describing complex electrokinetic phenomena. The
electrical conductivity and transport numbers of electrolytes containing
monovalent (KCl), divalent (MgCl), a mixture of both (KCl + MgCl), and
trivalent (LaCl) cations have been obtained from simulations of the
electrolytes in electric fields of different magnitude. The results obtained
for different simulation parameters have been discussed and compared with
experimental measurements of our own and from the literature. The
electroosmotic flow of water molecules induced by the ionic current in the
different cases has been calculated and interpreted with the help of the
hydration properties extracted from the simulations
The effect of isoelectric amino acids on the pH(+) of a phosphate buffer solution - A contribution in support of the "Zwitter Ion" hypothesis
The relative merits of the classical conception and of the Zwitter Ion conception of the dissociation of amphoteric electrolytes are discussed, and the following data are presented which confirm the Zwitter Ion hypothesis of Bjerrum, and which are not in accord with the classical view.
1. Amino acids in the isoelectric form resemble strong electrolytes in that they contribute to the ionic strength of the solution.
2. The dielectric constants of aqueous solutions of amino acids, like those of solutions of strong electrolytes greater than 0.02 normal, are considerably greater than that of pure water.
3. The magnitude of the dissociation constants of substituted acetic acids and of glycine, are more easily accounted for with the Zwitter Ion than with the classical conception
The Latin Leaflet, Number 29
Polymer electrolytes represent the ultimate in terms of desirable properties of energy storage/conversion devices, as they can offer an all-solid-state construction, a wide variety of shapes and sizes, light-weight, low costs, high energy density and safety.
Here we present our recent results concerning a novel strategy for preparing efficient polymer membranes which are successfully demonstrated as suitable electrolytes for several energy conversion and storage devices (i.e., Li- and Na-based batteries and DSSCs). Highly ionic conducting polymer electrolytes containing PEO-based functionalities and different components (e.g., Li/Na salts, RTILs, natural biosourced and cellulosic fillers) are successfully prepared via a rapid process and, directly or subsequently, cross-linked via UV irradiation (patent pending, PCT/IT2014/000008). All the prepared materials are thoroughly characterised in terms of their physical, chemical and morphological properties and tested for their electrochemical performances and durability. The UV-curing process on such materials led to the production of elastic and resistant amorphous macromolecular networks. Noticeably increased ionic conductivities are registered (10-3 S cm-1 at RT), along with very stable interfacial and storage stability and wide electrochemical stability windows. The different lab-scale solid-state devices show remarkable performances even at ambient temperature, at the level of those using liquid electrolytes, respect to which demonstrate much greater durability and safety.
The obtained findings demonstrate a new, easy and low cost approach to fabricate and tailor-make polymer electrolytes with highly promising prospects for the next generation of advanced flexible energy production and storage devices
A unified model for temperature dependent electrical conduction in polymer electrolytes
The observed temperature dependence of electrical conduction in polymer
electrolytes is usually fitted with two separated equations: an Arrhenius
equation at low temperatures and Vogel-Tamman-Fulcher (VTF) at high
temperatures. We report here a derivation of a single equation to explain the
variation of electrical conduction in polymer electrolytes at all temperature
ranges. Our single equation is in agreement with the experimental dataComment: 13 pages, 2 figure
- …