Multilayer electrolyte membrane

Abstract

The present invention relates to a proton-conducting multilayer electrolyte membrane with a barrier layer, a process for producing it and a fuel cell containing such a membrane.

1 . A membrane-electrode unit comprising:
 a) at least one multilayer electrolyte membrane that includes:
 i) a sheet-like material doped with one or more mineral acids, and 
 ii) at least one barrier layer which covers at least one of the two surfaces of the sheet-like material; and 
   b) two electrodes, the multilayer electrolyte membrane arranged between the two electrodes.   
     
     
         2 . The membrane-electrode unit of  claim 1 , characterized in that the barrier layer applied on a cathode side is thicker than the barrier layer located on an anode side. 
     
     
         3 . An electrode coated with a layer of a cation-exchange material, wherein the thickness of the layer is from 10 to 30 ÿm. 
     
     
         4 . The electrode of  claim 3 , characterized in that the cation-exchange material has at least one of the physical properties selected from the group consisting of a cation-exchange capacity of less than 0.9 meq/g, an area swelling in water at 80° C. of less than 20%, and a conductivity of less than 0.06 S/cm at 80° C. in a moistened state. 
     
     
         5 . An electrode coated with a layer of a cation-exchange material, wherein the thickness of the layer is less than 10 ÿm. 
     
     
         6 . The electrode of  claim 5 , characterized in that the cation-exchange material has at least one of the physical properties selected from the group consisting of a cation-exchange capacity of less than 0.9 meq/g, an area swelling in water at 80° C. of less than 20%, and a conductivity of less than 0.06 S/cm at 80° C. in a moistened state. 
     
     
         7 . A membrane-electrode unit comprising:
 a) an electrolyte membrane doped with mineral acids, and   b) at least one electrode coated with a layer of a cation-exchange material, wherein the thickness of the layer is from 10 to 30 ÿm.   
     
     
         8 . The membrane-electrode unit of  claim 7 , characterized in that the cation-exchange material has at least one of the physical properties selected from the group consisting of a cation-exchange capacity of less than 0.9 meq/g, an area swelling in water at 80° C. of less than 20%, and a conductivity of less than 0.06 S/cm at 80° C. in a moistened state. 
     
     
         9 . A membrane-electrode unit comprising:
 a) an electrolyte membrane doped with mineral acids, and   b) at least one electrode coated with a layer of a cation-exchange material, wherein the thickness of the layer is less than 10 ÿm.   
     
     
         10 . The membrane-electrode unit of  claim 9 , characterized in that the cation-exchange material has at least one of the physical properties selected from the group consisting of a cation-exchange capacity of less than 0.9 meq/g, an area swelling in water at 80° C. of less than 20%, and a conductivity of less than 0.06 S/cm at 80° C. in a moistened state. 
     
     
         11 . A fuel cell system comprising a plurality of different or similar membrane-electrode units of which at least one contains a multilayer electrolyte membrane that includes a sheet-like material doped with one or more mineral acids and at least one barrier layer which covers at least one of the two surfaces of the sheet-like material.