Ionically conductive polymer gels

Abstract

A bulk ionically conductive polymer gel is prepared by dissolving a salt such as lithium trifluoromethanesulphonate (which would provide lithium ion conductors) in an organic compound such as N-formylpiperidine. The organic compound dissolves the salt at 20° C. but is not a solvent at 20° C. though it is at 215° C.) for polyethylene terephthalate. The last-named is a crystallizable polymer which is added in a minor amount at a high temperature to the other components and provides the required mechanical rigidity for the product at lower temperatures.

What is claimed is:  
     
       1. An ionically conductive ion-containing gel having a bulk ionic conductivity at 20° C. and 10 kHz greater than 10 31 4  Siemens/cm and a dynamic modulus at 10 Hz greater than 10 3  Pa, wherein the gel consists of a crystallizable polymer, wherein the crystallizable polymer is present up to 50% by mass, and over 50% by mass of an organic compound selected from the group consisting of amides, sulphoxides and ethers, and a lithium salt with an anion selected from the group consisting of Br, I, a pseudohalogen and a perfluorinated alkyl carboxylate or sulphonate, said salt being soluble in said organic compound at 20° C. and dissolved therein at a concentration greater than 4% by mass based on said organic compound, wherein the said crystallizable polymer does not dissolve in the said organic compound at 20° C. but does dissolve therein at some higher temperature. 
     
     
       2. A gel according to  claim 1 , wherein the crystallizable polymer forms a coherent film or fiber. 
     
     
       3. A gel according to  claim 1 , wherein the crystallizable polymer is a polyamide, polyester, polyether or substituted polyolefin. 
     
     
       4. A gel according to  claim 3 , wherein the crystallizable polymer is poly(ethylene terephthalate), poly(1,4-butylene terephthalate), poly(3-oxybutanoate), polyhydroxybutyric acid, poly(hexamethylene adipamide), poly(metaxylylene adipamide), poly(m-phenylene isophthalamide), poly (vinylidene fluoride), polyoxymethylene or polyoxyethylene. 
     
     
       5. A gel according to  claim 1 , whose dynamic modulus at 10 Hz exceeds 10 4  Pa. 
     
     
       6. A gel according to  claim 5 , whose dynamic modulus at 10 Hz exceeds 10 5  Pa. 
     
     
       7. A gel according to  claim 1 , wherein the said organic compound is a solvent for the crystallizable polymer at some temperature above 100° C. 
     
     
       8. A gel according to  claim 1 , wherein the amide is a tertiary amide. 
     
     
       9. A gel according to  claim 1 , wherein said compound is dimethyl formamide, dimethyl acetamide, N-methyl-2-pyrrolidinone, N-formyl piperidine, a dimethyl ether of diethylene glycol, triethylene glycol or tetraethylene glycol, or dimethyl sulphoxide. 
     
     
       10. A method of making a gel, said gel being as defined in  claim 1 , said method comprising the steps of: 
       forming a solution of a crystallizable polymer in an organic compound at above 20° C.;  
       incorporating a lithium salt beforehand, simultaneously or afterwards; and  
       cooling the solution.  
     
     
       11. A method according to  claim 10 , wherein said solution is formed at above 100° C. 
     
     
       12. A method according to  claim 11 , wherein said solution is formed at above 150° C. 
     
     
       13. A galvanic cell having an electrolyte wherein the electrolyte comprises a gel made by the method of  claim 10 . 
     
     
       14. A galvanic cell having an electrolyte wherein the electrolyte comprises a gel according to  claim 1 . 
     
     
       15. An ionically conductive ion- containing gel having a bulk ionic conductivity at  20 ° C. and  10  kHz greater than  10     −4    Siemens/cm and a dynamic modulus at  10  Hz greater than  10     4    Pa, wherein the gel consists of a crystallizable polymer, wherein the crystallizable polymer is present in an amount of  20  to  40   %  by mass, and over  60   %  by mass of an organic compound or mixture of organic compounds, and a lithium salt with a monovalent anion selected from the group consisting of Br, I, a pseudohalogen a perfluorinated alkyl carboxylate or sulphonate anion and a complex inorganic monovalent anion, said salt being soluble in said organic compound at  20 ° C., and dissolved therein at a concentration greater than  4   %  by mass based on said organic compound, wherein said crystallizable polymer is a crystallizable halo substituted polyolefin which does not dissolve in said organic compound or mixture of organic compounds at  20 ° C. but does dissolve therein at some higher temperature.   
     
     
       16. A gel as claimed in  claim 15  wherein the gel comprises one said organic compound. 
     
     
       17. A gel as claimed in  claim 15  wherein the crystallizable polymer is a halo substituted polyvinylidene. 
     
     
       18. A gel as claimed in  claim 15  wherein the crystallizable polymer is poly( vinylidene fluoride ) .   
     
     
       19. A gel as claimed in  claim 15  wherein the salt is lithium trifluoromethane sulphonate. 
     
     
       20. A method of making a gel as defined in  claim 15 , said method comprising the steps of: 
       
         forming a solution of crystallizable polymer in an organic compound at above  20 ° C.;  
       
       
         incorporating a lithium salt beforehand, simultaneously or afterwards; and  
       
       
         cooling the solution. 
       
     
     
       21. A method according to  claim 20 , wherein said solution is formed at above  100 ° C. 
     
     
       22. A method according to  claim 20 , wherein said solution is formed at above  150 ° C. 
     
     
       23. A galvanic cell having an electrolyte wherein the electrolyte comprises a gel made by the method of  claim 20 . 
     
     
       24. A galvanic cell having an electrolyte wherein the electrolyte comprises a gel according to  claim 15 . 
     
     
       25. A gel as claimed in  claim 15  wherein said anion is selected from the group consisting of SCN −   , ClO   4   −   , HgI   3   −   , BF   4   −   , CF   3   COO   −    and CF   3   SO   3   −   .