JPH11251194A - Preparation of thin type gel electrolyte and electric double layer capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an inside resistance by thinning the thickness of electrolyte by pouring, holding and cooling dissolved gel electrolyte constituent material between glass plates or between silicone sheets. SOLUTION: Gel electrolyte of an electric double layer capacitor is constituted of polymer, organic solvent and electrolytic salt and polyacrylonitrile is used for polymer, propylene carbonate is used for organic solvent and tetraethyle ammonium borate tetrafluoride is used for electrolytic salt. In the preparation method, a specified amount of a constituent material of gel electrolyte is weighed and is heated and dissolved at 100 deg.C. Then, a 0.2 mm-thick Teflon spacer 2 is put on a glass plate 1a, dissolved gel electrolyte 3 is cast between the Teflon spacers 2 and furthermore, a glass plate 1b is pressed from an upper part thereof and is cooled. As a result, a 0.2 mm-thick thin type gel electrolyte is obtained. The gel electrolyte 3 of an arbitrary thickness can be prepared by changing the thickness of the Teflon spacer 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a thin gel electrolyte and an electric double layer capacitor, and more particularly to a method for backing up a memory of a computer which is required to have a small size and a large capacity.

[0002]

2. Description of the Related Art Currently used computers include:
An electric double layer capacitor is used for backing up a memory. This capacitor is characterized in that it is not only compact and has a large capacity but also has a long repetitive life. The electric double layer capacitor has a capacity per volume 300 to 1000 times higher than a case where a dielectric is provided between electrodes typified by an A1 electrolytic capacitor. This electric double layer capacitor operates on the principle of storing electricity by physically adsorbing anions and cations in the electrolyte on the positive electrode and the negative electrode surfaces, respectively, on the polarizable electrode. You. Therefore, at present, activated carbon having a specific surface area of 1000 to 3000 (m ² / g) is used as an electrode of this electric double layer capacitor. The electric double layer capacitor has a structure in which an electrolyte exists between these two electrodes.

In recent years, this type of electric double layer capacitor has
It has been widely used as a backup power source for various devices. With an increase in capacity of an application object, an increase in capacity of an electric double layer capacitor used as a backup is also desired. In a large-capacity capacitor used for such a purpose, it is desirable that the working voltage is high and the internal resistance is low, so that a large current can be supplied.

There are three types of electrolytes for electric double layer capacitors: an aqueous solution type, an organic electrolytic solution type, and a gel electrolyte type obtained by mixing a polymer with an organic electrolytic solution to form a gel. In an aqueous solution system, dilute sulfuric acid is mainly used as an electrolytic solution. Dilute sulfuric acid has high electrical conductivity, but has a low decomposition voltage of 1.2 V. on the other hand,
In the organic electrolyte solution, the decomposition voltage is higher (2.5 to 3 V) than in the aqueous solution system, but the electric conductivity is small. Thus, the aqueous solution and the organic solution have mutually contradictory properties. Further, the gel electrolyte system has properties similar to those of the organic electrolyte system, but is slightly inferior to the organic electrolyte system in terms of electric conductivity because it contains a polymer. But,
The gel electrolyte system does not require a separator, and has an advantage that a superior structure can be constructed when forming a capacitor.

[0005]

As an approach for lowering the internal resistance of the electric double layer capacitor so that a large current can be supplied, there is a method of reducing the material of the electric double layer capacitor. Specifically, the thickness of the electrode material, the thickness of the electrolyte material, and the like are reduced.

When a gel electrolyte is used as an electrolyte of an electric double layer capacitor, it is necessary to consider the function as an electrolyte and the function as a separator. It is desirable that the ionic conductivity is high, the decomposition voltage range of the electrolyte is wide, and the strength of the electrolyte is high. Reducing the thickness of the electrolyte also lowers the resistance of the electrolyte and the resistance of the capacitor itself. Therefore, it can be said that reducing the thickness of the electrolyte is an important issue when constructing an electric double layer capacitor.

In view of the above prior art, an object of the present invention is to provide a method for producing a thin gel electrolyte and an electric double layer capacitor capable of reducing the internal resistance by reducing the thickness of the electrolyte.

[0008]

The structure of the present invention that achieves the above object has the following features.

1) A method in which a polymer, an organic solvent, and an electrolyte salt are heated and dissolved, and the mixture is poured between glass plates or silicone rubber and allowed to cool.

2) A thin gel electrolyte prepared by the method described in 1) above and a set of activated carbon electrodes using activated carbon, activated carbon fibers and the like.

3) A predetermined distance between the electrodes is ensured by inserting a spacer when the polymer, the organic solvent, and the electrolyte salt are heated and dissolved, and are poured between the opposed electrodes.

4) In the electric double layer capacitor described in 3) above, a thin impregnated electrode produced by impregnating the activated carbon electrode with an electrolyte and gelling the electrolyte while applying pressure is used.

5) In the electric double layer capacitor described in 4) above, when the activated carbon electrode and the collecting electrode are joined by using a conductive adhesive, the pressing force at the time of heat curing of the conductive adhesive is set to a predetermined pressing force. A predetermined discharge capacity can be obtained by joining at

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings.

In the first embodiment of the present invention, a method for producing a gel electrolyte having a small thickness applied to an electrolyte of an electric double layer capacitor and an example of an electric double layer capacitor using the same are proposed. The gel electrolyte is a polymer,
It was composed of an organic solvent and an electrolyte salt, and was prepared using polyacrylonitrile as a polymer, propylene carbonate as an organic solvent, and tetraethylammonium tetrafluoroborate as an electrolyte salt. Specifically, it is as follows.

<Example 1> A predetermined amount of a constituent material of a gel electrolyte is weighed and dissolved by heating at 100 ° C. Next, as shown in FIG. 1, a Teflon spacer 2 having a thickness of 0.2 mm is placed on a glass plate 1a, the gel electrolyte 3 previously dissolved is cast between the Teflon spacers 2, and the glass plate is further Press 1b and allow to cool. As a result, a thin gel electrolyte having a thickness of 0.2 mm is produced. Here, by changing the thickness of the Teflon spacer 2, a gel electrolyte 3 having an arbitrary thickness can be produced.

<Example 2> As in Example 1, a predetermined amount of the constituent material of the gel electrolyte is weighed and dissolved by heating at 100 ° C. Next, as shown in FIG. 2, a Teflon sheet 4a is attached on a glass plate 1a, a Teflon spacer 2 having a thickness of 0.2 mm is placed thereon, and the gel electrolyte 3 previously dissolved between the Teflon spacers 2 is placed between the Teflon spacers 2. And a glass plate 1 on which a Teflon sheet 4b is adhered from above
Press b and allow to cool. As a result, a thin gel electrolyte having a thickness of 0.2 mm is produced. Here, by changing the thickness of the Teflon spacer 2, a gel electrolyte 3 having an arbitrary thickness can be produced. By the way, gel electrolyte 3
When the thickness of the gel electrolyte 3 was 0.2 mm, the internal resistance was 2.3 ohms, and when the thickness of the gel electrolyte 3 was 1.0 mm, the internal resistance was 6.3 ohms.

<Embodiment 3> As shown in FIG. 3, an activated carbon electrode (specific surface area 2000 m ² / g, apparent area 7.07 cm ² ) 5 made of activated carbon fiber impregnated with gel electrolyte 3
An electric double layer capacitor was produced by sandwiching the thin gel electrolyte (thickness 0.2 mm) 3 produced in Examples 1 and 2 between a and 5b. It was confirmed that the electric double layer capacitor manufactured in this manner could be repeatedly charged and discharged without deteriorating the characteristics while keeping the internal resistance (2.8Ω) low.

In another embodiment of the present invention, another example of an electric double layer capacitor in which the distance between electrodes is shortened is proposed.
The gel electrolyte of the electric double layer capacitor is a polymer,
It is composed of an organic solvent and an electrolyte salt. The polymer was prepared using polyacrylonitrile, the organic solvent was propylene carbonate, and the electrolyte salt was tetraethylammonium tetrafluoroborate. The electrode used was an aluminum plate for the collector and an activated carbon fiber cloth (made by Nippon Kainol (ACC-
561-25) (0.4 mm thick).
Specifically, it is as follows.

<Embodiment 1> In this embodiment, as shown in FIG. 4, after the active carbon electrodes 12a and 12b are impregnated with a dissolved gel electrolyte, the electrolyte is gelled while being pressurized through a Teflon spacer 13. It has a gel electrolyte 14. FIG. 4 shows a molding state of the electric double capacitor using the glass plates 15a and 15b.

In manufacturing the electric double capacitor, first, a predetermined amount of a constituent material of the gel electrolyte 14 is weighed, and
Heat and dissolve at 00 ° C. Gel electrolyte 14 dissolved by heating
Is the activated carbon electrode 12 of the electric double layer capacitor
a and 12b are impregnated. Then, the activated carbon electrode 1 on one side
A Teflon spacer 13 having a thickness of 0.2 mm is arranged on 2a. At this time, the Teflon spacer 13 is provided with a hole of φ40 mm, and the gel electrolyte 14 is made to exist in this portion. Further, the gel electrolyte 14 dissolved in the activated carbon electrodes 12a and 12b is cast, and after facing the collecting electrodes 11a and 11b from above, the cooling is performed while applying a pressure of 0.01 MPa through the glass plate 15b while cooling. . As a result, an electric double layer capacitor having a thin gel electrolyte 14 having a thickness of 0.2 mm was produced. By using this method, it is possible to prevent the counter electrodes from coming into contact with each other due to bending or warpage of the collecting electrodes 11a and 11b. According to this embodiment, an electric double layer capacitor having a distance between electrodes of 0.2 mm can be manufactured, and the internal resistance of the capacitor is 1.5Ω.
And an internal resistance of 3.5 in the case of the conventional distance between electrodes of 1 mm.
It was confirmed that it decreased compared to Ω.

<Embodiment 2> This embodiment is an electric double layer capacitor using a thin impregnated electrode produced by impregnating the activated carbon electrode 12 with the gel electrolyte 14 and then pressurizing and cooling.

In manufacturing the electric double capacitor, first, similarly to the first embodiment, a predetermined amount of a constituent material of the gel electrolyte 14 is weighed and heated and melted at 100 ° C. FIG. 5 shows an electrolyte impregnated state. As shown in the figure, the dissolved gel electrolyte 14 is cast on the activated carbon electrode 12 of the electric double layer capacitor, and a silicon sheet 16 is placed on the gel electrolyte 14 from above the gel electrolyte 14 via the glass plate 15. The mixture was allowed to cool while being pressurized at a pressure of 0.01 MPa.

To prepare a "thin impregnated electrode" impregnated with the gel electrolyte 14, the thickness of the collector electrode 11 and the activated carbon electrode 12 (thickness of the collector electrode 11 + thickness of the activated carbon electrode 12) is adjusted by the above method. It is possible to do. In this example, the collector electrode thickness was 0.5 mm and the activated carbon electrode thickness was 0.4 mm.
The conductive adhesive was cured while applying a pressure of 0.1 Mpa at the time of joining the collecting electrode 11 and the activated carbon electrode 12 using an electrode of mm. The subsequent electrode thickness (thickness of the collecting electrode 11 + thickness of the activated carbon electrode 12) was 0.7 mm. After casting the gel electrolyte 14 on this electrode, the electrolyte was gelled while applying pressure. At this time, the thickness of the collector electrode 11 + the activated carbon electrode 12 could be maintained at 0.7 mm. On the other hand, when impregnation and gelation are performed without pressurization, it is confirmed that the thickness of the collector electrode 11 + the activated carbon electrode 12 expands by about 0.1 mm to 0.2 mm due to the impregnation of the electrolyte and the gelation of the electrolyte. ing.

In the present embodiment, an electric double layer capacitor was formed in the same manner as in Embodiment 1 using the thin impregnated electrode manufactured in the above-described manner. The performance of the capacitor determined by the constant current charge / discharge test was a charge / discharge current density of 5 mA / c.
m ² , the discharge capacity was 0.34 F / cm ² , and the internal resistance was 1.
0Ω. Therefore, the gel electrolyte 14 is applied to the activated carbon electrode 12.
The electric double layer capacitor using the thin impregnated electrode gelled while being pressurized after being impregnated with, can further reduce the internal resistance of the electric double layer capacitor as compared with Example 1.

<Embodiment 3> In this embodiment, the discharge capacity of the electric double layer capacitor is secured by reducing the pressure applied when the collector electrode 11 and the activated carbon electrode 12 are joined. Example 2
In the production of the electrodes of the electric double-layer capacitor, the conductive adhesive is applied, and then the adhesive is cured while applying pressure, and the bonding is performed. An electrode joined with a smaller pressing force than that of the above was used. The pressing force in the second embodiment is 0.10 MPa, while the pressing force in the present embodiment is 0.01
The collector electrode 11 and the activated carbon electrode 12 were joined to each other while reducing the pressure to Mpa. An electric double layer capacitor was produced in the same manner as in Example 2 except that the applied pressure was changed, and the performance of the capacitor was examined from constant current charge / discharge measurement. As a result, at a charge / discharge current density of 5 mA / cm ² , the discharge capacity was 0.50 F / cm ² and the internal resistance was 1.0Ω. As described above, by adjusting the pressing force when the collector electrode is formed, an electric double layer capacitor having a high discharge capacity can be manufactured.

[0027]

According to the first aspect of the present invention, a gel electrolyte constituent material dissolved between glass plates or silicone sheets is poured, sandwiched, and allowed to cool as described above. By doing so, it is possible to produce a thin gel electrolyte. In addition, it is possible to produce a gel electrolyte having an arbitrary thickness depending on the thickness of the spacer sandwiched between the glass plates and the silicone rubber.

According to the second aspect of the invention, an electric double layer capacitor can be manufactured by sandwiching the thin gel electrolyte and the activated carbon electrode so as to face each other. Further, by reducing the thickness of the electrolyte, the internal resistance of the capacitor can be reduced.

According to the third aspect of the present invention, the spacers are arranged on the electrodes and are allowed to cool and gel while being pressurized, so that the distance between the electrodes can be made the same as that of the spacers. Can be manufactured.

According to the invention of claim 4, in the step of impregnating the activated carbon electrode with the gel electrolyte, the electrolyte is allowed to cool,
At the time of gelation, by performing gelation while applying pressure, the thickness of the electrode after impregnation can be made uniform, and an electric double layer capacitor with lower internal resistance can be manufactured.

According to the fifth aspect of the present invention, in joining the activated carbon electrode and the collector electrode, in the step of curing the conductive adhesive, an electrode obtained by curing while applying a predetermined pressure is used. This makes it possible to secure a predetermined discharge capacity of the electric double layer capacitor in addition to the effect of the fourth aspect of the invention.

[Brief description of the drawings]

FIG. 1 is a first example of the first embodiment of the present invention.
Explanatory drawing which shows notionally.

FIG. 2 is a second example according to the first embodiment of the present invention;
Explanatory drawing which shows notionally.

FIG. 3 is a third example according to the first embodiment of the present invention;
Explanatory drawing which shows notionally.

FIG. 4 is a first example according to the second embodiment of the present invention;
Explanatory drawing which shows notionally.

FIG. 5 is a second example according to the second embodiment of the present invention;
FIG. 7 is an explanatory diagram conceptually showing Example 3 and Example 3;

[Explanation of symbols]

 1a, 1b glass plate 2 Teflon spacer 3 gel electrolyte 4a, 4b Teflon sheet 5a, 5b activated carbon electrode 11, 11a, 11b collector electrode 12, 12a, 12b activated carbon electrode 13 Teflon spacer 14 gel electrolyte 15, 15a, 15b glass plate

Claims (5)

[Claims] 1. A method for producing a thin gel electrolyte, comprising heating and dissolving a polymer, an organic solvent, and an electrolyte salt, flowing the mixture between glass plates or silicone rubber, and allowing it to cool. 2. An electric double layer capacitor comprising a thin gel electrolyte produced by the method according to claim 1 and a set of activated carbon electrodes using activated carbon, activated carbon fiber or the like. 3. An electric double layer, wherein a predetermined distance between electrodes is secured by inserting a spacer when a polymer, an organic solvent, and an electrolyte salt are heated and dissolved and poured into the space between opposed electrodes. Capacitors. 4. The electric double layer capacitor according to claim 3, wherein a thin impregnated electrode produced by impregnating the activated carbon electrode with an electrolyte and gelling the electrolyte while applying pressure is used. . 5. The electric double layer capacitor according to claim 4, wherein when the activated carbon electrode and the collector electrode are joined by using a conductive adhesive, the pressure applied during heating and curing of the conductive adhesive is set to a predetermined pressure. An electric double layer capacitor characterized in that a predetermined discharge capacity can be obtained by joining the capacitors.