Polymeric electrolytes

Details Polymeric electrolytes Polymeric electrolytes

1986-06-20

1988-04-12

Walton, Donald L.

Chemistry: electrical current producing apparatus, product, and

Current producing cell, elements, subcombinations and...

Include electrolyte chemically specified and method

429194, H01M 618, H01M 1040

Patent

active

047374225

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to polymeric electrolytes and their use in electrolytic cells and batteries containing such cells.
The electrolytes commonly used in electrolytic cells are liquids in the form of solutions containing ionic species, which allow migration of charged ions between the anode and the cathode of the cell. However, liquid electrolytes suffer from several disadvantages in that they are often corrosive or toxic and can be spilled which presents handling difficulties and necessitates precautions ensuring the avoidance of spillage or leakage.
In order to overcome the difficulties inherent with liquid electrolytes and to obtain superior long-term storage stability there has been considerable interest recently in solid polymeric electrolyte materials in which ion mobility is possible through coordination of an electrolyte ion with suitable sites on a polymer chain, such as for example polyethylene oxide (PEO), forming a polymeric complex. However the properties of such conventional complexed polymers, although encouraging, have not proved to be as good as had been hoped. In particular PEO tends to crystallise at ambient temperature (20.degree. C.) and this adversely affects the ionic conductivity of the electrolyte.
The present invention seeks to overcome the disadvantages of known polymeric electrolytes based on PEO by providing novel polymeric electrolytes which have generally higher ambient temperature conductivities and which are based on modified PEO polymers.
According to the present invention there is provided a polymeric electrolyte comprising a solution of an ionic salt in a polymer X having a backbone of formula --A--B--, where A is an oligomeric chain and B is a chain extender group, attached to oligomer A, containing one or more linkage atoms Z selected from Si, C and P, wherein the polymer contains oxymethylene units which are present in one or more of the polymeric backbone, sidechains or crosslinks such that, where A is an oxyethylene oligomer of formula --CH.sub.2 --CH.sub.2 --O).sub.n, n is an integer from 3 to 10 and where the oxyethylene oligomer is contained in a sidechain or crosslink, attached to B, n is from 2 to 25.
The linkage atoms Z in the chain extender groups B may be single atoms. The linkage atoms Z in the chain extender groups B may each link more than two units A. for example they may each link three units A in a cross linked network.
Where side groups other than units A and other than hydrogen atoms are attached to the linkage atoms Z the side groups (labelled herein as R') may be simple, for example methyl or ethyl, although they may be independently selected from C.sub.1-20 alkyl, alkonyl or fluorine-containing alkyl or alkonyl or optionally substituted derivatives including unsaturated derivatives or (OCH.sub.2 CH.sub.2).sub.p OR.sup.2, where p is an integer preferably less than 25 and R.sup.2 is an alkyl or alkonyl or fluorine-containing alkyl or alkonyl or optionally substituted derivatives; or may comprise other oligomers or polymeric side chains or be a chain branch in the polymer.
For example, where Z is silicon, the chain extender group B may be: ##STR1## where R' is as defined above, g is an integer preferably less than 100, and L is a simple linkage group such as --O--, phenyl, alkyl, O(CH.sub.2 CH.sub.2 O).sub.k where k is less than 12, or --ORO-- where R.sup.3 is alkyl or optionally substituted alkyl, and M is a simple group such as alkyl or phenyl, and b is 0 or 1.
For example where Z is carbon the chain extender group or grouping may be C(R.sup.4 R.sup.5) or C(R.sup.4 R.sup.5)OC(R.sup.4 R.sup.5) where R.sup.4 and R.sup.5 are independently selected from H, alkyl, alkonyl or R' groups as previously defined.
Where Z is phosphorus for example, the chain extender group B may be selected from: ##STR2## and ##STR3## where R' is as defined previously, and T is --O--, O(CH.sub.2 CH.sub.2 O).sub.t where t is from 1 to 12 or --OR.sup.6 -- where R.sup.6 is alkyl or optionally substituted C.sub.1 to C.sub.10 alkyl or derivatives thereof, especially fluoro

REFERENCES:
patent: 4303748 (1981-12-01), Armand et al.
patent: 4357401 (1982-11-01), Andre et al.
patent: 4556614 (1985-12-01), Mehaute et al.
patent: 4556616 (1985-12-01), Armand et al.
patent: 4578326 (1986-03-01), Armand et al.
GTE, Molecular Crystals and Liquid Crystals, vol. 106, Nos. 3 and 4 (1984), Proceedings of the Symposium on Order in Polymeric Materials, Part B, pp. 361-369.

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