Electric heating – Heating devices – With heating unit structure
Patent
1991-02-14
1994-04-12
Reynolds, Bruce A.
Electric heating
Heating devices
With heating unit structure
219209, H05B 316, H05B 100
Patent
active
053028104
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for rapid and uniform heating of a multilayer assembly comprising at least one thin layer of an ion-conducting macromolecular material, that is to say of a polymeric solid electrolyte, which is intercalated between two structures with high electronic conduction so as to be in intimate contact with the said structures.
A large class of multilayer assemblies of the abovementioned type is that of thin-layer electrochemical current generators, rechargeable or otherwise, among which there may be mentioned the electrochemical current generators which are described in reference EP-A-0,013,199 and which rely on an ion-conducting macromolecular material consisting of a solid solution of an ionisable alkali metal salt M.sup.+ X.sup.-, especially a lithium salt, within a plastic polymeric material made up, at least partially, of one or more polymers and/or copolymers of monomers containing at least one heteroatom, especially oxygen or nitrogen, capable of forming bonds of the donor-acceptor type with the cation M.sup.+.
Thin-layer electrochemical current generators make it possible to store a large quantity of energy per unit of volume and of weight. The power which they can deliver depends directly on the mobility of the ions in the ion-conducting macromolecular material, that is to say on the ion conductivity of this material.
It is known that the ion conductivity of ion-conducting macromolecular materials employed in thin-layer electrochemical current generators is relatively low at temperatures below or equal to room temperature, but that the said conductivity increases with temperature. It is therefore useful, when it is desired to make such generators operate at high instantaneous power, to be able to raise their temperature rapidly and, if possible, homogeneously.
This is particularly useful for making the best use of highly energetic, essentially primary, generators which have been stored for a long time at temperatures close to or below room temperature, which are particularly suited to a reduction or even a complete suppression of the self-discharge phenomenon. When rapidly heated, such generators can instantaneously supply extremely high powers even after several years' storage, provided that they can be heated rapidly and homogeneously just before their intensive use.
The use of an external source of heat for heating the abovementioned thin-layer current generators does not allow the required result to be obtained because operating in this way results in the appearance of a temperature gradient inside the generator, due to the poor diffusion of heat in the multilayer structure forming the generator, and this is reflected in a nonhomogeneous operation of the generator.
It has already been proposed, as described in reference GB-A-2,065,027, to perform the heating of a polymeric composition forming a thin layer and containing an ion-conducting macromolecular material consisting of a polyether coupled with an ionisable salt by relying on a heating technique using dielectric losses, which consists in subjecting the said composition to the action of electromagnetic waves of very high frequencies, namely frequencies of the order of 10.sup.6 to 10.sup.8 hertz.
Such a heating technique using dielectric losses is not suitable for heating thin-layer electrochemical current generators such as referred to above, or more generally for heating assemblies comprising at least one thin layer of an ion-conducting macromolecular material sandwiched between two structures with high electronic conduction because, apart from the difficulties linked with its implementation and the disadvantages which it entails for the environment owing to the use of electrical signals of very high frequency, this technique does not lend itself well to heating multilayer structures comprising a number of layers with high electronic conduction which are close to each other.
The subject of the invention is a method of rapid and uniform heating of a multilayer assembly comprising at least one thin layer of an ion-c
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Journal of Applied Physics, vol. 57, No. 1, Jan. 1985, American Institute of Physics, (Woodbury, N.Y., U.S.), M. Watanabe et al.: "Ionic Conductivity and Mobility in Network Polymers from Poly(propylene oxiode) Containing Lithium Perchlorate", pp. 123-128.
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Gauthier Michel
Muller Daniel
Ricoux Philippe
Hydro-Quebec
Reynolds Bruce A.
Societe Nationale Elf Aquitaine
Switzer Michael D.
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