DK200101740A - Compsns. for polymeric electrolyte prodn. - comprising radiation polymerisable cpd., ionically conducting liq. and alkali metal salt - Google Patents

Abstract

Compsns. (I) for prodn. of polymeric electrolytes comprise a radiation-polymerisable liq. monomer or prepolymer (II), a radiation-inert ionically conducting liq. (III) and an ionisable alkali metal salt (IV) Also claimed is the prodn. of polymeric electrolytes by exposing (I) to actinic radiation, and the prodn. of anode and cathode half elements and solid-state electrochemical cells. - Pref. (II) is a polyethylenically unsatd. cpd. contg. at least one heteroatom, esp. a polyethylene glycol di(meth)acrylate, or a polyethylene glycol diglycidyl ether. (III) is a polar aprotic solvent esp. a polyethylene glycol dimethy ether. (IV) is of formula MX, where M=Li, Na, K or NH4 and X=I, Br, SCN, ClO4, CF3SO3, BF4, PF6, CF3COO or AsF6. The actinic radiation is UV or electron beam radiation. (I) contain at least 45 (pref.) at least 70) wt.% (III). - Anode half elements are produced by coating an anodic metal foil with (I) and irradiating. Cathode half elements are produced by coating a metal foil with a compsn. (Ia) comprising (II), (III), an active cathode material (V) and an electronic conductor, and irradiating (V) is pref. an intercalation cpd., esp. a V oxide.(0/0)

Description

A process for the preparation of a solid electrolyte suitable for use in a solid state electrochemical cell comprising forming a mixture of a crosslinkable polysiloxane, an ionic conductor liquid and an ionizable ammonium or alkali metal salt, and exposing the mixture for actinic radiation to crosslink the polysiloxane and form a solid polymer matrix constituting a network structure permeated by the ion conducting liquid formed with the ionizable salt, with continuous high conductivity paths extending in all directions through the polymer matrix. A process according to claim 1, wherein the mixture also contains a crosslinkable polyethylenically unsaturated compound. The process according to claim 1 or 2, wherein the crosslinkable polysiloxane is a polyethylene oxide grafted polysiloxane. The process of claim 2, wherein the polyethylenically unsaturated compound comprises at least one heteroatom in the molecule. The process of claim 4, wherein the polyethylenically unsaturated compound comprises a repeating unit selected from the group consisting of

where R 'is hydrogen or a lower alkyl group. A process according to claim 2, wherein the polyethylenically unsaturated compound corresponds to one of the following formulas I to III:

where n is approx. 3 to 50 and R represents hydrogen or a C (1-3) alkyl group and A represents an ethylenically unsaturated group or a glycidyl group. A process according to any one of claims 2-6, wherein the polyethylenically unsaturated compound is a polyethylene glycol modified to include terminal ethylenically unsaturated groups. The process of claim 7, wherein the polyethylenically unsaturated compound is polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, an acrylate functionalized polyurethane or polyethylene glycol diglycidyl ether. A process according to any one of the preceding claims, wherein the ionizable salt is a salt of a cation selected from the group consisting of lithium, sodium, potassium and ammonium cations, and an anion selected from the group consisting of I ", Br ~, SCN ", C104-, CFSO3-, BF4-, PFg-,

AsFg and CF3COO. The process of claim 9, wherein the ionizable salt is a lithium salt. The process of claim 10, wherein the lithium salt is LiCF3SC> 3. A process according to any one of the preceding claims, wherein the ion-conducting liquid is selected from the group consisting of polyethylene glycol dimethyl ether, propylene carbonate, gamma-butyrolactone, 1,3-dioxolane, 2-methyltetrahydrofuran, tetraglyme, hexaglime and heptaglyme. and polyethylene oxide - grafted polysiloxane. The process of claim 12, wherein the ion-conducting liquid is a polyethylene oxide-grafted polysiloxane. A process according to any one of the preceding claims, wherein the ion-conducting liquid is present in the mixture in an amount of at least 45% by weight. The method of claim 14, wherein the ion-conducting liquid is present in the mixture in an amount of at least 70% by weight. A method according to any one of the preceding claims, wherein the mixture further contains a radiation curable comonomer. The process of claim 16, wherein the radiation curable comonomer is trimethylol propane triacrylate, trimethylol propane ethoxylated triacrylate or trimethylol propane propoxy triacrylate. A process for forming a solid electrolyte comprising a polymeric network structure containing an ionic conductive liquid for use in solid state electrochemical cells, comprising a mixture of a crosslinkable, polyethylenically unsaturated compound, a crosslinkable polysiloxane, a ionic conductive liquid, polyethylene oxide-grafted-polysiloxane and LiCF3SC> 3, which polyethylenically unsaturated compound is represented by a formula

in which n is approx. 3 to 50, R is hydrogen or a C (1-3) alkyl group and A represents an ethylenically unsaturated group or a glycidyl group and subjecting the mixture to radiation to form a solid matrix through which the ionically conductive liquid polyethylene oxide grafted polysiloxane penetrates to provide continuous high-conductivity paths in all directions. The process of claim 18, wherein the polyethylene oxide grafted polysiloxane is present in the mixture in an amount of at least 45% by weight. A process according to claim 18 or 19, wherein the mixture further contains trimethylolpropane triacrylate, trimethylolpropane ethoxylated triacrylate or trimethylolpropane propoxylated triacrylate. An electrolyte material obtainable according to any one of claims 1-20. An electrochemical device comprising an electrolyte material according to claim 21 between a cathode and an anode.