Electrode for an electric double layer capacitor and process for producing it

Abstract

A process for producing an electrode for an electric double layer capacitor, which comprises extruding a mixture comprising a carbonaceous material, a polytetrafluoroethylene and a processing aid by screw extrusion, and rolling the obtained extruded product by rolling rolls to form it into a sheet shape.

What is claimed is:  
     
         1 . A process for producing an electrode for an electric double layer capacitor, which comprises extruding a mixture comprising a carbonaceous material, a polytetrafluoroethylene and a processing aid by screw extrusion, and rolling the obtained extruded product by rolling rolls to form it into a sheet shape.  
     
     
         2 . The process for producing an electrode for an electric double layer capacitor according to    claim 1   , wherein the mixture contains from 1 to 50 wt % of the polytetrafluoroethylene and from 20 to 200 wt % of the processing aid, based on the carbonaceous material.  
     
     
         3 . The process for producing an electrode for an electric double layer capacitor according to    claim 1   , wherein the extrusion temperature for the screw extrusion is from 5 to 300° C.  
     
     
         4 . The process for producing an electrode for an electric double layer capacitor according to    claim 1   , wherein the extrusion pressure for the screw extrusion is from 2 to 300 kg/cm 2 .  
     
     
         5 . The process for producing an electrode for an electric double layer capacitor according to    claim 1   , wherein the compression ratio in the screw extrusion is from 1.0 to 4.0.  
     
     
         6 . The process for producing an electrode for an electric double layer capacitor according to    claim 1   , wherein the rolling temperature is from 20 to 350° C.  
     
     
         7 . The process for producing an electrode for an electric double layer capacitor according to    claim 1   , wherein after rolling the extruded product by rolling rolls to form it into a sheet shape, the formed product of sheet shape is monoaxially or multiaxially stretched from 1.01 to 5.0 times the original length and further rolled by rolling rolls.  
     
     
         8 . The process for producing an electrode for an electric double layer capacitor according to    claim 1   , wherein the carbonaceous material comprises an activated carbon having a specific surface area of from 200 to 3,500 m 2 /g and a particle size of from 0.1 to 100 μm, and a carbon black having a specific surface area of from 200 to 1,500 m 2 /g and a particle size of from 0.001 to 1 μm.  
     
     
         9 . The process for producing an electrode for an electric double layer capacitor according to    claim 1   , wherein the extruded product is rolled by rolling rolls in the same direction as the screw extrusion direction.  
     
     
         10 . The process for producing an electrode for an electric double layer capacitor according to    claim 1   , wherein as soon as the electrode is formed into a sheet shape by rolling by rolling rolls, it is continuously bonded and integrated with a current collector made of an aluminum foil.  
     
     
         11 . The process for producing an electrode for an electric double layer capacitor according to    claim 10   , wherein the electrode and the aluminum foil are bonded by means of an electroconductive adhesive, and the electrode and the aluminum foil bonded are rolled by rolling rolls.  
     
     
         12 . An electrode for an electric double layer capacitor, which is prepared by extruding a mixture comprising a carbonaceous material, a polytetrafluoroethylene and a processing aid by screw extrusion, and rolling the obtained extruded product by rolling rolls to form it into a sheet shape.  
     
     
         13 . The electrode for an electric double layer capacitor according to    claim 12   , which has a tensile strength of at least 1.5 kg/cm 2  in at least one direction.  
     
     
         14 . The electrode for an electric double layer capacitor according to    claim 12   , wherein the electrode contains from 1 to 50 wt % of the polytetrafluoroethylene, based on the carbonaceous material.  
     
     
         15 . The electrode for an electric double layer capacitor according to    claim 12   , wherein the carbonaceous material comprises an activated carbon having a specific surface area of from 200 to 3,500 m 2 /g and a particle size of from 0.1 to 100 μm, and a carbon black having a specific surface area of from 200 to 1,500 m 2 /g and a particle size of from 0.001 to 1 μm.  
     
     
         16 . An electric double layer capacitor, which has an electrode prepared by extruding a mixture comprising a carbonaceous material, a polytetrafluoroethylene and a processing aid by screw extrusion, and rolling the obtained extruded product by rolling rolls to form it into a sheet shape.  
     
     
         17 . The electric double layer capacitor according to    claim 16   , wherein the electrode has a tensile strength of at least 1.5 kg/cm 2  in at least one direction.  
     
     
         18 . The electric double layer capacitor according to    claim 16   , which has an electrode assembly having the electrode bonded with a current collector made of an aluminum foil.