Ionically conductive material having a block copolymer as the so

Details Ionically conductive material having a block copolymer as the so Ionically conductive material having a block copolymer as the so

1994-12-15

1996-06-04

Yoon, Tae

Chemistry: electrical current producing apparatus, product, and

Current producing cell, elements, subcombinations and...

Include electrolyte chemically specified and method

429191, 429192, 429198, 524401, 524422, 524423, 252 622, 252518, 525 88, H01M 618, C08K 300, C08L 5300

Patent

active

055231802

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to ionically conductive materials and to their uses.
Polymeric electrolytes obtained by dissolving a salt in a solvating polymer containing hetero atoms are known. Such electrolytes in which the solvent is a polyethylene oxide or an ethylene oxide copolymer are described, for example, in EP 13199 (M. Armand, M. Duclot). These polymeric electrolytes have many applications, in particular in the field of electrochemical generators, light-modulating systems (M. Armand et al., EP-87401555) or sensors, for example for selective or reference membranes (A. Hammou et al., FR-86.09602).
Polyethylene oxide is a semicrystalline polymer which forms stoichiometric complexes with salts. The conductive amorphous phases of these complexes exist only above a eutectic temperature which is in general between 40.degree. C. and 65.degree. C. depending on the nature of the complex salts. At normal temperature, good conductivities are obtained only with macromolecular systems exhibiting a low or zero crystallinity. Much work has been carried out to improve the conduction properties of these materials. It has resulted, for example, in the formation of copolymers based on ethylene oxide (M. Armand et al., FR-83.09886). Copolymerization of ethylene oxide with other epoxides such as propylene oxide or methyl glycidyl ether appreciably decreases the crystallinity of the material. However, random introduction of defects is reflected in a marked loss in the solvating and dissociating power of the polyethylene oxide uniform block. The preparation of copolymers which have high macromolecular masses, higher than 10.sup.5, and which have good mechanical properties requires reactants of high purity and reproducible control of the proportions of comonomers which are introduced is difficult because of the difference in reactivity between ethylene oxide and its homologues
Amorphous polymers which have a good conductivity but mediocre mechanical behaviour have been obtained by polycondensation of oligooxyethylene glycols (M.sub.w .apprxeq.200-1000) with dichloromethane [C. V. Nicholas, D. J. Wilson, C. Booth & R. J. M. Gilles, Brit. Polym. J., 20, 289 (1988)]. In addition, these materials do not contain reactive functional groups and cannot therefore be crosslinked. In addition, they are easily degraded in acidic medium.
The formation of networks crosslinked with isocyanates is also known (H. Cheradame et al., FR-8007135, U.S. Pat. No. 4,357,401). The introduction of urethane bridges into the electrolytes makes the latter reactive, particularly towards lithium.
The objective of the present invention is to provide ionically conductive materials comprising a solid electrolyte and at the same time exhibiting a good conductivity and a good mechanical behaviour.
To this end, the subject of the invention is an ionically conductive material comprising a salt in solution in a polymeric solid electrolyte.
Another subject of the invention is various uses of the said material.
The ionically conductive material according to the present invention comprises at least one salt dissolved in a polymeric solvent. It is characterized in that the polymeric solvent consists essentially of a block copolymer comprising at least one solvating segment A and at least one segment B which has good intrinsic mechanical properties or which has good mechanical properties after crosslinking between a number of segments B.
The block copolymer constituting the solvent of a material according to the present invention can have various forms. Mention may be made, among the preferred forms, of the diblock copolymer form AB; the triblock copolymer form BAB, in which the two segments B may be identical or different; the triblock copolymer form ABA, in which the two segments A may be identical or different; or the branched polymer form of the type (AB).sub.n R or (BA).sub.n R, R representing an organic radical having a multiple functionality n.
The segment A of the block copolymer is a solvating segment which gives the material its conductivity properties.

REFERENCES:
patent: 4752544 (1988-06-01), Gregory
patent: 5159001 (1992-10-01), Motogami et al.
patent: 5350646 (1994-09-01), Armand et al.
Derwent Publications Ltd., London, GB; AN 92-175868 & DD,A,297 281 (Technische Hochschule Schorlemmer) Jan. 2, 1992.
Derwent Publications, Ltd., AN 90-323713.
Derwent Publications, Ltd., AN 91-292874.

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