JPS6125204B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing an electric double layer capacitor that improves polarizable electrodes, reduces loss value, and increases capacity. Conventional polarizable electrodes of electric double layer capacitors are made by using carbon powder as a binder, such as water-soluble polymer, dispersion or alcohol emulsion of tetrafluoroethylene or tetrafluoroethylene/propylene hexafluoride copolymer, or fluorine rubber elastomer. It was obtained by mixing and applying or press-molding the mixture onto a current collector. All of these binders are electrical insulators, and if the blending ratio to the carbon powder is low, the adhesion force to each other and to the current collector will be weak.On the other hand, if the blending ratio is high, the mutual contact of the powders will be reduced and the effective surface will also be reduced. The disadvantages were that the equivalent series resistance increased and the capacitance significantly decreased. The present inventor has also proposed a manufacturing method as disclosed in Japanese Patent Application No. 148610/1983, which involves roll-coating carbon paste directly onto the metal foil surface, drying and baking, and applying pressure during baking. Since there is no carbon layer, the density of the carbon layer is low, making it difficult to obtain a large capacity, and the equivalent series resistance is also high. The total thickness of the carbon layer on the front and back sides of the metal foil is constant, but it is difficult to make the front and back sides the same thickness, and the equivalent series resistance varies widely.
There are drawbacks such as. The present invention was made in view of the above circumstances, and involves adding a mixture of carbon powder and an aqueous polyvinyl alcohol solution to boric acid or an aqueous solution containing boric acid and an organic carboxylic acid or a salt thereof to form a gel composition. After that, a carbon sheet of a certain thickness is formed by roll pressing, and it is stacked on both sides of metal foil and baked under pressure to form polarizable electrodes.A separator is interposed between the plurality of polarizable electrodes arranged in series, and electrolysis is performed. It is an object of the present invention to provide a method for manufacturing an electric double layer capacitor with stable characteristics by impregnating the capacitor with a liquid, thereby reducing the loss value and increasing the capacity. The present invention will be explained in detail below. That is, the present invention involves adding a mixture of fine activated carbon powder or a mixed powder of fine activated carbon powder and carbon black and an aqueous polyvinyl alcohol solution to boric acid or an aqueous solution containing boric acid and an organic carboxylic acid or a salt thereof to proceed with an esterification reaction. A gel-like composition is prepared. This is dried using a roll press at a temperature of 90 to 105°C to form a carbon sheet 1 of a certain thickness, which is stacked on both sides of the metal foil 2 and pressed at a temperature of 140 to 160°C to firmly bond it to the metal foil 2. When brought into close contact, a polarizable electrode 3 with low resistance can be obtained. A plurality of polarizable electrodes 3 are arranged in series, a separator 4 is interposed between each electrode, and an electrolytic solution is impregnated to obtain an electric double layer capacitor. In this case, the polarizable electrodes 3 at both ends have one layer of carbon sheet formed only on one side,
The metal foils at both ends act as a current collector 5, 6 is an external lead terminal, and 7 is a rubber packing. Next, a table shows an example of a comparison of characteristics of electric double layer capacitors obtained according to an example of the present invention and a conventional reference example. Example 40 parts of activated carbon powder of 325 mesh or more and 60 parts of furnace black of 110 mμ are added with a 20% by weight aqueous polyvinyl alcohol solution and thoroughly mixed to form a paste. Separately, an aqueous solution containing 2% by volume of ethylene glycol, 4% by weight of orthoboric acid, and 4% by weight of maleic acid is prepared, and the aqueous solution and the paste-like material are mixed and kneaded into a rubber-like mixture. This is passed through rolls at regular intervals and formed into a sheet of constant thickness.
Dry at 100℃. This carbon sheet was stacked on both sides of a roughened stainless steel foil with a thickness of 10 μm and baked under pressure of 5 kg/cm ² using a flat plate press at a temperature of 150° C. for 60 minutes to obtain a polarizable electrode. This is cut into a certain shape and size, placed on both sides with a separator in between, impregnated with 1 mol ammonium hydrogen maleate-formamide electrolyte, and then arranged in four pieces in series using rubber packing. An electric double layer capacitor was obtained. Reference Example Add 20% by weight aqueous polyvinyl alcohol solution to 55 parts of activated carbon powder of 325 mesh or more and 45 parts of 110 mμ furnace black and mix thoroughly to form a paste. This was coated to a constant thickness on both sides of textured stainless steel foil using a roll coater, dried at a temperature of 110°C for 30 minutes, and then baked under pressure at a temperature of 150°C for 60 minutes to obtain a polarizable electrode. This was cut into a certain shape and size, placed on both ends with a separator in between, impregnated with 1 mol ammonium hydrogen maleate-formamide electrolyte, and then connected in series using rubber packing. An electric double layer capacitor was obtained by arranging four capacitors and using the stainless steel foils at both ends as current collectors.

[Table] As is clear from the above table, it can be seen that the example exhibits stable characteristics with both the equivalent series resistance and leakage current being smaller than the reference example. As detailed above, according to the present invention, a mixture of carbon powder and an aqueous polyvinyl alcohol solution is added to boric acid or an aqueous solution containing boric acid and an organic carboxylic acid or a salt thereof to form a gel-like composition, and then the mixture is formed into a gel composition by roll pressing. A carbon sheet of a certain thickness was layered on both sides of metal foil and baked under pressure to form polarizable electrodes, and a separator was interposed between the plurality of polarizable electrodes arranged in series and impregnated with electrolyte. As a result, it is possible to provide a method for manufacturing an electric double layer capacitor with stable characteristics while reducing loss value and increasing capacity.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an electric double layer capacitor according to the present invention. 1...Carbon sheet, 2...Metal foil, 3...
polarizable electrode, 4... separator, 5... current collector,
6...External lead-out terminal, 7...Rubber packing.

Claims (1)

[Claims] 1. A mixture of carbon powder and an aqueous polyvinyl alcohol solution is added to boric acid or an aqueous solution containing boric acid and an organic carboxylic acid or a salt thereof to form a gel-like composition, and then a carbon sheet of a certain thickness is formed by roll pressing, and a sheet of metal foil is formed. A method for manufacturing an electric double layer capacitor, characterized in that polarizable electrodes are formed by stacking and baking on both sides, and a separator is interposed between a plurality of the polarizable electrodes arranged in series and impregnated with an electrolyte. .