Ionically conductive polymeric materials

Details Ionically conductive polymeric materials Ionically conductive polymeric materials

1992-11-06

1994-09-27

Kalafut, Stephen

Chemistry: electrical current producing apparatus, product, and

Current producing cell, elements, subcombinations and...

Include electrolyte chemically specified and method

429198, 359270, H01M 1040

Patent

active

053506464

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to ionically conductive polymeric materials, to their preparation and to their use as a solid electrolyte.
2. Discussion of the Background
Metal salts MX.sub.n, in which M denotes a metal cation and X denotes a monovalent anion, form complexes with some solvating polymers, in particular those incorporating sequences of polyether type (for example poly(ethylene oxide) PEO, poly(propylene oxide) PPO, poly(bis-.omega.-methoxy-oligooxyethylene-phosphazene) ME.sub.n P) or polyamines (PEI). These materials have, in a determined range of temperature and salt concentration, an ionic conduction which can be employed for the production of electrochemical systems, in particular storage batteries (European Patent No. 13,199).
The ionic conductivity of these complexes depends on the degree of dissociation of the salt MX.sub.n and the highest values for a given species M are obtained with anions X.sup.- in which the negative charge is delocalized and which do not have any complexing character. However, the mobility of the cations M.sup.n+ in this macromolecular medium depends on the rate of exchange in the ligands incorporated in the macromolecular framework in the form of solvating units around these cations. In the case of n>1 and/or in the case of the transition elements, these kinetics are slow and generally entail low or zero values of the cation transport number in these materials. In particular it is therefore difficult to perform electrochemical reactions involving a reversible contribution of the species M.sup.n+ to the electrode (metal deposition-dissolution, insertion, etc).


SUMMARY OF THE INVENTION

The objective of the present invention is to remedy these disadvantages by providing materials of the polymer-salt type in which the transport of the species M is independent of the dissociation of the salt MX.sub.n into anions and M.sup.n+ cations.


BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 illustrate the variation of ionic conductivity as a function of temperature for Examples 1 and 2, respectively, of the present invention.


DESCRIPTION OF THE PREFERRED EMBODIMENTS

The ionically conductive materials of the present invention, comprising a solid solution of one or more salts in a polymer, are characterized in that the transport and the mobility of a metal cation M.sup.n+ which has the valency n, 1.ltoreq.n.ltoreq.5, are provided by at least one complex anion corresponding to the general formula [MZ.sub.n Y.sub.p].sup.p- formed between an anionic ligand Z.sup.-, an anionic ligand Y.sup.- and the cation M.sup.n+, with 1.ltoreq.p.ltoreq.3.
Among the ionically conductive materials of the present invention there may be mentioned the polymeric complexes denoted by the overall formula with p=1, 2 or 3 providing the solvation of a cation A. they permit the coexistence, in finite quantities, of the complex anion [MZ.sub.n Y.sub.p ].sup.p- and of a species chosen from the group consisting of the anion Z.sup.- the anion Y.sup.-, the complex anion [MZ.sub.n Y.sub.p+1 ].sup.(p+1)-, and the neutral species MZ.sub.n.
The transport of the species M.sup.n+ is therefore provided by diffusion of the anionic complex [MZ.sub.n Y.sub.p ].sup.p- to the electrode. At the electrode, the complex loses some metal M, which deposits on the electrode. In parallel, the complex anion is re-formed from MZ.sub.n or its charge is increased or the ligand Y.sup.- and/or the ligand Z.sup.- are liberated by desolvation of the complex anions. The complex anion which has an increased charge or Y.sup.- or Z.sup.- migrate towards the opposite electrode. The phenomenon reverses if the direction of the current is reversed.
The relatively high mobility of the ionic species in the solvating polymers makes it possible to ensure fast kinetics in the case of the abovementioned mechanism.
The cation A which is capable of being easily solvated by the polymer can be chosen from alkali metals, alkaline-earth metals, lanthanum, quaternary ammonium radicals, amidinium

REFERENCES:
patent: 4293623 (1981-10-01), Klemann et al.
patent: 4908284 (1990-03-01), Hooper et al.
patent: 4925752 (1990-05-01), Fauteux et al.
Chemical Abstracts, vol. 74, 1971, A. I. Falicheva, et al., "Cathode Polarization In Sulfate Electrolytes Of Various Modification Compositions", p. 418 (month unavailable).

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