JPH10242009A - Method of assembling electric double layer capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a capacitance value and life characteristics, by using polarizable electrodes which are not exposed to air, after electrodes are formed, and assembling a capacitor in a non-oxidizing atmosphere. SOLUTION: Polarizable electrodes 15, which are preserved in a nitrogen atmosphere without being exposed to air after baking, are accommodated in a glove box in which nitrogen gas is made to flow. In the box, a positive pole 11 is constituted of a collector electrode 13 for a positive pole which has a lead part and is rectangular, and polarizable electrodes 15 arranged on both sides of the electrode 13. A negative pole 12 is constituted of a collector electrode 14 which has a lead part and is rectangular, and polarizable electrodes 15 arranged on both sides of the electrode 14. Separators 16 are interposed between the positive poles 11 and the negative poles 12. A specified number of them are alternately stacked, and a close contact laminated body is obtained by taping 18. The laminated body is accommodated in an encapsulating case 19 made of propylene resin. After the lead parts of the positive electrodes 13 and the negative electrodes 14 are connected with terminals 20, 21, the laminated body is impregnated with an organic solution based electrolyte and tightly closed. Thereby the capacitance value and the life characteristics can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of assembling a laminated electric double layer capacitor having a polarizable electrode using activated carbon as an electrode material and a phenol resin as a binder and using an organic solution electrolyte. It is.

[0002]

2. Description of the Related Art As is well known, an electric double layer capacitor utilizes electric energy by electric charges accumulated in an electric double layer formed at an interface between a polarizable electrode mainly composed of activated carbon and an electrolyte. And can be charged like a secondary battery.

[0003] For example, electric wheelchairs, electric bicycles,
Phenol, a thermosetting resin made of activated carbon, is used as an electric double layer capacitor for large capacity and large current with a capacitance of several hundreds to several thousand F (farads) because it is used as a power source for power tools. Plural positive electrodes comprising a plate-shaped polarizable electrode using a resin as a binder and a positive electrode collector, a plate-shaped polarizable electrode using activated carbon as an electrode material and a phenolic resin as a binder, and a negative electrode collector And a plurality of negative electrodes consisting of
A so-called lamination having an electrode laminated body alternately laminated with a porous separator interposed therebetween, and containing the electrode laminated body impregnated with an organic solution electrolyte in a rectangular outer case. Type electric double layer capacitors are known. The use of the organic solution electrolyte has an advantage that the withstand voltage of the electric double layer capacitor can be increased as compared with the aqueous solution electrolyte.

[0004]

However, conventionally, a polarizable electrode used in such an electric double layer capacitor using an organic solution-based electrolytic solution has a plate-like molded body composed of powdered activated carbon and a phenol resin at 1000 ° C. No particular attention was paid to the preservation state after the production by baking at a temperature as high as possible, and the specimen was stored in a room exposed to air. Prior to assembling the electric double layer capacitor, the polarizable electrode, which has been stored in the state of being exposed to air, is subjected to vacuum drying at a temperature of 200 ° C., and thereafter, a non-oxidizing gas (inert gas). The polarizable electrode that has been subjected to low-temperature vacuum drying is housed in a glove box that has been flushed with nitrogen gas, and the withstand voltage of the capacitor decreases due to moisture entering the organic solution electrolyte impregnated in the electrode stack. In order to prevent this, an electric double layer capacitor was assembled in this glove box in which nitrogen gas was supplied.

In such a situation, the present inventors have
The resulting electrostatic double layer capacitor electrostatic capacitance is caused by the adsorption of impurities such as moisture and oxygen to the activated carbon of the polarizable electrode by exposing the polarizable electrode to air during the period from the electrode fabrication to the capacitor assembly. The capacity is small, and the integrated value (cumulative value) of the number of charge / discharge cycles since the start of using the capacitor
It has been found that there is a problem that the degree of decrease of the capacitance with the increase of the capacitance is large, that is, the life characteristics are poor.

The present invention has been made to solve such a problem, and has a polarizing electrode using activated carbon as an electrode material and a phenolic resin as a binder, and using an organic solution-based electrolyte. By using polarizable electrodes that are not exposed to air between the time of electrode fabrication and the time of capacitor assembly when assembling a type electric double layer capacitor, the capacitance value and life characteristics can be improved compared to the conventional type. An object of the present invention is to provide a method for assembling an electric double layer capacitor that can obtain an improved electric double layer capacitor.

[0007]

In order to achieve the above-mentioned object, a method of assembling an electric double layer capacitor according to the present invention comprises a plate-shaped polarizable electrode using activated carbon as an electrode material and a phenolic resin as a binder. A plurality of positive electrodes composed of a positive electrode collector and a plurality of negative electrodes composed of a plate-shaped polarizable electrode using activated carbon as an electrode material and a phenol resin as a binder and a negative electrode collector are provided with a separator between them. In the method for assembling an electric double layer capacitor comprising an electrode laminate having alternately laminated layers interposed therebetween and containing the electrode laminate impregnated with an organic solution electrolyte in an outer case, after the electrode is produced, Is characterized in that a polarizable electrode which is not exposed to air is used for assembling a capacitor, and an electric double layer capacitor is assembled in a non-oxidizing atmosphere.

In producing a polarizable electrode using activated carbon as an electrode material and a phenol resin as a binder, when the plate-like molded body is fired at a high temperature of about 1000 ° C., the phenol resin is carbonized and has conductivity. On the other hand, from the activated carbon, water and the like which had been physically adsorbed thereto were desorbed, and
Acidic functional groups such as COOH and -OH that cause a decrease in capacitance are also removed. In addition, even after the bond with the acidic functional group is broken, the surface of the activated carbon has an activity capable of binding to moisture and the like.

The electric double layer capacitor is assembled in a non-oxidizing atmosphere such as a glove box in which nitrogen gas is flown, using the polarizable electrode obtained as a result of the firing (high temperature heat treatment). The case is good, but after firing,
When the polarizable electrode is exposed to air, impurities such as moisture and oxygen are adsorbed on the activated carbon while interacting with the activated carbon, although not as strong as a chemical bond. Due to the adsorption of impurities such as moisture and oxygen to the activated carbon of the polarizable electrode due to the exposure to air, the obtained electric double layer capacitor has a small capacitance and deteriorates life characteristics. Although the reason is not clear, the adsorption of electrolyte ions by the above-mentioned impurities such as water and oxygen is inhibited, the impurities react with the electrolyte (mainly a solvent), generation of a decomposition gas, and precipitation of a polymer. It is considered that the deterioration proceeds due to the occurrence of the above. According to the method of the present invention, a polarizable electrode which is stored in a nitrogen gas atmosphere or the like so as not to be exposed to air after the electrode is manufactured is used for assembling an electric double layer capacitor. An electric double layer capacitor with improved capacitance value and life characteristics can be obtained.

[0010]

Embodiments of the present invention will be described below.

[0011]

【Example】

Example 1 First, a thin rectangular plate-shaped polarizable electrode used for an electric double layer capacitor was manufactured by the following manufacturing procedure. The polarizable electrode of this example is obtained by adding a granular or powdery phenol resin as a binder to a powdered activated carbon and a solvent for dispersing a phenol resin, mixing them to form a mixture, and granulating the mixture using the mixture as a material. Performing a granulation step to produce a granulated product, a pressure forming step of obtaining a plate-shaped product by press-forming the granulated product, and a firing process of firing the plate-shaped product in a non-oxidizing atmosphere. And, I try to get.

That is, powdered activated carbon (specific surface area: 3000)
m ² / g), a granular phenol resin which is a thermosetting resin as a binder, and ² g as a solvent for dispersing the phenol resin.
-Methoxyethanol was added and mixed to obtain a mixture for granulation. Here, the mixing ratio of powdered activated carbon / granular phenol resin is 70/30 (weight ratio), and 2-methoxyethanol is used in this example to produce a granulated product of 10 to 48 mesh. Part 2.
It was added so that the amount of the solvent became 0 times.

The mixture for granulation was used as a material and granulated with a stirring granulator. Next, after drying and removing the solvent for dispersing the phenolic resin, the obtained granulated product was put into a mold, and was pressed with a thickness of 0.5 mm and a size of 45 × 90.
mold temperature 150 ° C x pressure 30
Pressure molding was performed under the conditions of 0 kg / cm ² × time 10 minutes. Thereafter, the plate-shaped molded body is fired in an electric furnace under a nitrogen gas atmosphere at a temperature of 1100 ° C. for 2 hours, and cut into a 0.5 mm-thick and 30 × 30 mm-sized plate-shaped polarizable electrode. I got

In assembling an electric double layer capacitor for experiments, two polarizable electrodes were prepared, and a total of two positive electrode and negative electrode collector electrodes each made of an aluminum foil having a thickness of 10 μm were used. Prepare one separator made of a polypropylene porous film having a thickness of 25 μm having an insulating property, and as an organic solution electrolyte,
A propylene carbonate solution (organic solvent) having a concentration of 1 mol / liter of tetraethylammonium tetrafluoroborate (electrolyte salt: Et ₄ NBF ₄ ) was prepared.

After the firing, the polarizable electrode stored in a nitrogen gas atmosphere without being exposed to air is housed in a glove box to which a nitrogen gas has been flown. The capacitor was assembled. That is, in the glove box in which the nitrogen gas was flowed, a positive electrode composed of one of the two polarizable electrodes and the positive electrode collector, and a negative electrode composed of the other polarizable electrode and the negative electrode collector, An electrode laminate is formed by laminating the two polarizable electrodes facing each other with a separator interposed therebetween, and the above-mentioned organic solution-based electrolysis is applied to the electrode laminate housed in a rectangular outer case made of polypropylene resin. By impregnating the liquid, an experimental electric double layer capacitor was assembled.

Subsequently, a charging / discharging cycle test in which 3.5 V is applied between the two collector electrodes of the experimental electric double layer capacitor and charging / discharging is repeated at 20 mA is performed in a glove box in which a nitrogen gas is supplied. Then, changes in the capacitance per unit volume and the amount of electric power per unit volume (electric energy of the capacitor) with respect to the integrated value of the number of charge / discharge cycles from the start of use of the capacitor were examined. The initial capacitance was 10.6 F / ml. FIG. 2 shows the results of the charge / discharge cycle test. Discussion of the results will be described later.

Comparative Example 1 As Comparative Example 1, an electric double layer capacitor was assembled by a conventional method. That is, the polarizable electrode produced in the same procedure as in Example 1 was not fired in a nitrogen gas atmosphere or in a non-oxidizing atmosphere such as in a vacuum thermostat after being fired. Stored in the exposed state for about 24 hours. Prior to assembling the electric double layer capacitor, a temperature of 23 ° was applied to the polarizable electrode which had been stored in the state of being exposed to air.
Vacuum drying was performed at 0 ° C. Next, the polarizable electrode subjected to the vacuum drying was accommodated in a glove box in which a nitrogen gas was flown. In this glove box, an experimental electric double layer capacitor was assembled in the same manner as in Example 1, and the obtained electric double layer capacitor for experiment was subjected to the same charge / discharge cycle test as in Example 1. The initial capacitance was 9.5 F / ml. FIG. 3 shows the results of the charge / discharge cycle test.

FIG. 2 according to Example 1 and FIG. 3 according to Comparative Example 1.
As is clear from the above description, in the assembling method of Example 1, an electric double layer capacitor having an improved capacitance value and improved life characteristics as compared with Comparative Example 1 is obtained. (Comparing the graphs showing the amount of power in proportion to the value of the capacity can be clearly seen.) In Comparative Example 1, impurities such as moisture and oxygen adsorbed on the activated carbon of the polarizable electrode due to exposure to air were removed before the capacitor was assembled.
It remains without being removed by vacuum drying at about 00 ° C.,
It is considered that the capacitance was small and the life characteristics were deteriorated.

Example 2 A polarizable electrode 15 manufactured in the same procedure as in Example 1 except that the size is different, and stored in a nitrogen gas atmosphere without exposing to air after firing,
It was housed in a glove box through which nitrogen gas was flown, and an electric double layer capacitor having a structure schematically shown in FIG. 1 was assembled in this glove box. As shown in FIG. 1, the positive electrode 11 is composed of a rectangular positive electrode collecting electrode 13 having a narrow band-shaped lead (not shown), and polarizable electrodes 15 arranged on both sides thereof. The negative electrode 12 is a rectangular negative electrode collecting electrode 14 having a lead portion.
And polarizable electrodes 15 arranged on both sides of the polarizer. The positive electrode 11 and the negative electrode 12 are alternately stacked by a predetermined number with the separator 16 interposed therebetween. Note that the positive electrode collecting electrode 13 and the negative electrode collecting electrode 14 are stacked such that the lead portions for terminal connection are at left and right opposite positions. In this example, the polarizable electrode 15 is arranged only on one side of the collector electrode in the outermost negative electrode and positive electrode (the positive electrode is not shown).

Then, these laminated products are pressed in the laminating direction via pressing plates 17 arranged on both outermost sides in order to bring the collector electrodes and the polarizable electrodes of the electrodes 11 and 12 into close contact with each other. Then, taping and fixing are performed with the fastening tape 18 to obtain a square electrode laminate. Next, this electrode laminate is formed into a square outer case 1 made of polypropylene resin.
9 and the adjacent positive electrode 1 via a separator 16
In order to obtain a large-capacity electric double-layer capacitor by connecting the cells constituted by the anode 1 and the anode 12 in parallel, each of the positive electrode collectors 13 is fixed to the cathode terminal 20 fixed to the case upper lid 19a.
Are connected collectively by caulking or the like, and the leads of each negative electrode collecting electrode 14 are collectively connected to the negative electrode terminal 21. Thereafter, the same organic solution system as in Example 1 is added to the electrode laminate. The electric double layer capacitor was assembled by impregnating with the electrolytic solution and attaching the case upper lid 19a to the opening of the outer case 19 and sealing the case. In this example, withstand voltage 3.
The configuration is such that 20 cells are connected in parallel to make a large-capacity capacitor of 5 V and a capacity of 3000F.

As described above, the electric double layer capacitor is assembled in the glove box in which the nitrogen gas is flown by using the polarizable electrode 15 which is not exposed to air during the period from the production of the electrode to the assembly of the capacitor. Was done. In this example, the polarizable electrode 15 mainly composed of activated carbon has a thickness of 0.5 mm, a short side of 46 mm and a long side of 92 mm. The collector electrodes 13 and 14 are made of aluminum foil having a thickness of 10 μm, and the lead portions thereof have a width of 18 mm.
× length 20 to 80 mm, collector electrode part is the same size as polarizable electrode 15 and has a size of 46 mm short side × 92 mm long side. The separator 16 is made of a 25 μm-thick polypropylene porous film, and its size is almost the same as that of the polarizable electrode 15. Also in the electric double layer capacitor of this example, the capacitance value and the life characteristics are improved by using the polarizable electrode 15 which is not exposed to the air after the electrode is manufactured and before the capacitor is assembled. Make sure you have

[0022]

As described above, according to the method for assembling an electric double layer capacitor according to the present invention, a polarizable electrode having activated carbon as an electrode material and a phenol resin as a binder is provided, and an organic solution electrolyte is used. At the time of assembling the laminated electric double layer capacitor to be used, after the electrodes are manufactured, polarizable electrodes that are not exposed to air are used for capacitor assembly,
Since the electric double-layer capacitor is assembled in a non-oxidizing atmosphere such as in a glove box to which nitrogen gas has flowed, the electric capacity and the life characteristics of the electric double-layer capacitor have been improved compared to the conventional type. A multilayer capacitor can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration example of an electric double layer capacitor according to an embodiment of the present invention, with a part thereof being cut away.

FIG. 2 is a graph related to an example of the present invention, showing a result of a charge / discharge cycle test.

FIG. 3 is a diagram related to a comparative example, and is a graph showing a result of a charge / discharge cycle test.

[Explanation of symbols]

11 positive electrode 12 negative electrode 13 positive electrode collecting electrode 14
Collector electrode for negative electrode 15 ... Polarizable electrode 16 ... Separator
17 ... Pressing plate 18 ... Tightening tape 19 ... Outer case 19a ... Case upper cover 20 ... Positive electrode terminal 21 ... Negative electrode terminal

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[Procedure amendment]

[Submission date] January 19, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction contents]

The mixture for granulation was used as a material and granulated with a stirring granulator. Next, after the solvent for dispersing the phenolic resin is dried and removed, the obtained granulated product is placed in a mold, and a hot plate having a heating element embedded therein is taken at the tip.
The temperature was 150 ° C., the pressure was 300 kg / cm ^{2, and the} time was 10 hours by a press machine equipped with a hot plate equipped with a pressure punch and having a thickness of 0.5 mm and a size of 45 × 90 mm.
Pressure molding was performed under the conditions of min. Thereafter, the plate-like molded body was heated at a temperature of 1100 ° C. in an electric furnace under a nitrogen gas atmosphere.
Baking for 2 hours, this is 0.5 mm thick and 30 ×
The plate was cut out to 30 mm to obtain a plate-shaped polarizable electrode.

Claims (2)

[Claims] 1. A plurality of positive electrodes comprising a plate-shaped polarizable electrode using activated carbon as an electrode material and a phenol resin as a binder, and a positive electrode collector electrode, and activated carbon as an electrode material and a phenol resin as a binder. An electrode laminate comprising a plurality of negative electrodes each comprising a plate-shaped polarizable electrode and a negative electrode collecting electrode, which are alternately laminated with a separator interposed therebetween, and an organic solution electrolyte in an outer case. In the method for assembling an electric double layer capacitor containing the electrode laminate impregnated with a polarizable electrode which is not exposed to air after the electrode is produced, the polarizable electrode is used for assembling the capacitor. A method for assembling an electric double layer capacitor, comprising assembling a double layer capacitor. 2. The method for assembling an electric double layer capacitor according to claim 1, wherein the electric double layer capacitor is assembled in a glove box into which nitrogen gas has flowed.