JPS5950207B2 - Manufacturing method of electric double layer capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an electric double layer capacitor, which improves the binder of inert powder such as activated carbon or carbon black that forms polarizable electrodes, thereby reducing loss value and increasing capacity.

Conventionally, polarizable electrodes for electric double layer capacitors are made by mixing carbon-based powder with a water-soluble polymer, a dispersion of tetrafluoroethylene or its copolymer, an alcohol emulsion, a fluororubber elastomer, etc., and applying or pressing the mixture onto a current collector. It was obtained by molding.

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. It has the drawbacks of increasing equal series resistance and a significant decrease in capacitance.

The present invention has been made in view of the above circumstances and has been made with great success.
After applying a mixture of carbon powder and an aqueous polyvinyl alcohol solution to a current collector, the applied body is immersed in boric acid or an aqueous solution containing boric acid and an organic carboxylic acid or a salt thereof to gel the carbon layer, or the carbon layer is previously mixed. The boric acid-based aqueous solution is mixed with the boric acid-based aqueous solution, gelled, press-molded into a current collector, and then heated to form a polarizable electrode, thereby reducing the loss value and increasing the capacity, creating an electric double layer with stable characteristics. The present invention aims to provide a method for manufacturing a capacitor.

The present invention will be explained in detail below.

That is, in the present invention, activated carbon fine powder or a mixed powder of activated carbon fine powder and carbon black is mixed with an aqueous polyvinyl alcohol solution, this mixture is applied to a current collector, and then air-dried.

When this is immersed in boric acid or an aqueous solution containing boric acid and an organic carboxylic acid or a salt thereof, an esterification reaction occurs, and the polyvinyl alcohol immediately solidifies to produce a conductive gel composition.

Next, by heating and baking at a temperature of 140 to 160° C., a low-resistance polarizable electrode that firmly adheres to the current collector is obtained.

Another method is to mix a mixture of activated carbon powder and polyvinyl alcohol with a boric acid aqueous solution in advance to proceed with the esterification reaction to form a gel, and then wash the rubber-like product with water to dissolve unreacted components and stabilize the mixture. It was pressed into a sheet with a thickness of 1 to 100°C, dried at a temperature of 90 to 105°C, then stacked on a current collector and hot press-molded at a temperature of 140 to 160°C, and it adhered firmly to the current collector in the same way. A polarizable electrode with low resistance can be obtained.

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 1 A 20% by weight aqueous polyvinyl alcohol solution is added to 60 parts of activated carbon powder of 325 mesh or more and 40 parts of furnace black of 50 mμ, and thoroughly mixed to form a paste.

This was applied to a current collector made of 200 mesh stainless steel net and left at 20° C. for 30 minutes.

This coated body was immersed for 1 minute in a solution containing 4% by weight of orthoboric acid and 5% by weight of maleic acid, pulled up, dehydrated under pressure with a roller, and then baked at a temperature of 150°C for 60 minutes to form a polarizable electrode. Obtained.

This was used as a pair of electrodes and was wound around a separator and impregnated with 1 mol of ammonium hydrogen maleate-formamide electrolyte to obtain a capacitor.

Example 2 A 20% by weight aqueous polyvinyl alcohol solution is added to 40 parts of activated carbon powder of 325 mesh or more and 60 parts of furnace black of 110 mμ, and thoroughly mixed to form a paste.

Separately, 2% by volume of ethylene glycol and 4% by weight of orthoboric acid.
Then, an aqueous solution containing 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 pressed into a sheet of constant thickness and dried at 100°C.

This carbon sheet was stacked on both sides of a current collector made of roughened stainless steel foil with a thickness of 10 mμ, and heated to 60°C at a temperature of 150°C.
Heat baking was performed for 0 minutes to obtain a polarizable electrode.

These were placed as a pair of electrodes with a separator in between, and impregnated with 1 mol of ammonium hydrogen maleate-formamide electrolyte to form a unit capacitor, which was stacked in series using a rubber backing. I obtained a capacitor.

Reference Example 3 A 20% by weight polyvinyl alcohol aqueous solution is added to 55 parts of activated carbon powder of 325 mesh or more and 45 parts of furnace black of 50 mμ and thoroughly mixed to form a paste.

This was applied to a current collector made of 200 mesh stainless steel net and dried at a temperature of 110°C for 30 minutes.
A polarizable electrode was obtained by heating and baking at a temperature of 0° C. for 60 minutes.

This was used as a pair of electrodes and was wound around a separator and impregnated with 1 mol of ammonium hydrogen maleate-formamide electrolyte to obtain a capacitor.

Reference Example 4 A 20% by weight aqueous polyvinyl alcohol solution is added to 55 parts of activated carbon powder of 325 mesh or more and 45 parts of furnace black of 110 mμ, and thoroughly mixed to form a paste.

This was applied to a current collector made of textured stainless steel foil, dried at a temperature of 110° C. for 30 minutes, and then baked at a temperature of 150° C. for 60 minutes to obtain a polarizable electrode.

These were placed as a pair of electrodes through a separator, and impregnated with 1 mol of ammonium hydrogen maleate-formamide electrolyte to form a unit capacitor, and then four of these were connected in series using a rubber backing. A capacitor was obtained by laminating the layers.

Example 1 and Reference Example 3 are wound type capacitors, and Example 2
and Reference Example 4 are multilayer capacitors, but as is clear from the table above, Examples 1 and 2 exhibit stable characteristics with lower equal series resistance and leakage current than Reference Examples 3 and 4. I understand that.

As detailed above, according to the present invention, a mixture of Nabon powder and an aqueous polyvinyl alcohol solution is applied to a current collector, and then the applied body is placed in an aqueous solution containing boric acid or boric acid and an organic carboxylic acid or a salt thereof. The loss value can be determined by immersing the carbon layer in water to gel it, or by mixing the mixture and the boric acid aqueous solution in advance to gel it, press-molding it into a current collector, and then baking it with heat to form a polarizable electrode. It is possible to provide a method for manufacturing an electric double layer capacitor with stable characteristics while reducing the capacitance and increasing the capacitance.

Claims (1)

[Claims] 1. After applying a mixture of carbon powder and polyvinyl alcohol to a current collector, the applied body is immersed in an aqueous solution containing boric acid and an organic carboxylic acid or a salt thereof to gel the carbon layer, A method for manufacturing an electric double layer capacitor, characterized in that polarizable electrodes are formed by heating and baking. 2 A mixture of carbon powder and polyvinyl alcohol and boric acid or an aqueous solution containing boric acid and an organic carboxylic acid or a salt thereof are mixed and gelled, then press-molded into a current collector, and then heated and baked to form a polarizable electrode. A method for manufacturing an electric double layer capacitor, characterized in that the electric double layer capacitor has the following characteristics: