JPH1167601A - Electric double-layer capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the internal resistance of a capacitor by joining an collecting electrodes at a specified temperature with the aid of an activated brazing metal containing Ti at a specified weight %. SOLUTION: Electrolytic iron 12 is disposed between polarized electrodes 11a and 11b. Collecting electrodes 13 are provided outside the polarized electrodes. In this case, the polarized electrodes 11a and 11b are made of activated carbon textile. The activated carbon textile and the collecting electrodes are joined by vacuum brazing with the aid of an activated brazing metal. In this case, the brazing metal contains 2 weight % Ti and the brazing is performed at a temperature lower than the highest temperature of the melting point of the brazing metal by 20-40 deg.C. In this way, junction between the activated carbon and the collecting plate which are different materials is made possible and the internal resistance can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an electric double layer capacitor.

[0002]

2. Description of the Related Art Currently used computers include:
An electric double layer capacitor is used for memory backup. This capacitor is characterized in that it is small, has a large capacity, and has a long repeated life. The electric double layer capacitor is compared with a capacitor having a dielectric between electrodes typified by a conventional Al electrolytic capacitor.
The capacity per volume is 300 to 1000 times higher. The above-mentioned double-layer capacitor operates on the principle of storing electricity by physically adsorbing anions and cations in the electrolyte to the polarizable electrode on the positive and negative electrode surfaces, respectively, and therefore requires a large surface area of the adsorbed electrode. .

Therefore, at present, the specific surface area is 1000-1000.
3000 (m ² / g) activated carbon 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 electric double layer capacitor has been widely used as a backup power supply for various devices. With the increase in the capacity of the object to be applied, the capacity of the electric double layer capacitor used as a backup is also desired to be increased. At this time, in a capacitor with a large capacity,
It is desirable that the working voltage be high. Thus, studies on organic solution-based electrolytes have been conducted.

[0004]

[Problems to be solved by the invention]

<First problem> Here, the electrolytic solution of the electric double layer capacitor is largely classified into a water-soluble type and an organic solution type. The aqueous system is
Dilute sulfuric acid is mainly used as an electrolyte. Although the diluted sulfuric acid has high electric conductivity, it has a problem that the decomposition voltage is as low as 1.2 V. On the other hand, in the organic electrolyte system, the decomposition voltage is
Although it is as high as 2.5 to 3 V as compared with the aqueous solution system, there is a problem that the electric conductivity is small. As described above, the aqueous solution system and the organic solution system have mutually contradictory properties. here,
In order to increase the capacity, it is desirable that the working voltage of the capacitor is high. From this point, the organic solution system is effective, but the electric conductivity of the organic solution system is lower than that of the aqueous solution system.
As a result, there is a problem that the internal resistance of the capacitor is high.

[0005] When activated carbon is used as a polarizable electrode of an electric double layer capacitor, an electrode manufacturing method is currently (1)
A method of kneading powdered activated carbon with a binder and molding,
(2) A method using an activated carbon fiber cloth can be mentioned. Here, examples of the activated carbon fibers include kainol activated carbon fibers (trade name: manufactured by Gunei Chemical Industry Co., Ltd.) and the like. For the current collection from the activated carbon fiber electrode, a method of contacting with a case, a method of extracting a lead from an aluminum sprayed coating applied to one surface of activated carbon, and the like have been proposed.

However, the method of contacting the case has a problem that the contact resistance is large. Also, the method of taking out the lead from the aluminum sprayed coating is difficult to take a laminated structure for high operating voltage, it becomes complicated structure, requires advanced technology for manufacturing, and as a simple method,
A bonding method using a conductive adhesive (silver paste) is desired.

<Second Problem> Here, in order to constitute the electric double capacitor, it is necessary to join a polarizable activated carbon electrode and a metal collector electrode for inputting and outputting current. This bonding is performed because the electrical resistance at the contact interface between the activated carbon electrode and the collector electrode increases, and heat generation due to energization increases. In a conventional capacitor, a conductive adhesive sheet is used for joining an activated carbon electrode and a metal collecting electrode. The material of the metal collecting electrode is aluminum, and the aluminum surface is polished with a # 180 abrasive paper to improve the adhesion between the aluminum and the adhesive sheet. Conventional adhesive, as shown in FIG. 10, sandwiched conductive sheet 03 between the polished aluminum collector electrode 01 and the activated carbon fiber cloth electrodes 02, at 0.99 ° C. under pressure of about 0.2 kg / cm ² 4 Heating for hours.

FIG. 11 shows a single-cell structure using bonded electrodes (cross-sectional view). As shown in the figure, an electrolyte 04 is disposed between opposing activated carbon electrodes 02a and 02b, and sealed with a spacer 05 to prevent the electrolyte 04 from leaking. In addition, 06 is a lead wire. The conventional joining method has the following problems. When the electrode area is large, it is difficult to uniformly pressurize the entire joined body. If the pressure is not uniform, the adhesion is not uniform and the contact resistance increases. Since the conductive sheet is expensive, there is a problem that a capacitor having a large electrode area is not practically acceptable.

[0009]

According to a first aspect of the present invention, there is provided an electric double layer capacitor using an activated carbon fiber cloth as a polarizable electrode. The present invention is characterized in that the internal resistance of the capacitor is reduced by bonding the collector electrode using the same.

The electric double layer capacitor according to claim 2 is
Claim 1 is characterized in that the active metal brazing material contains 2% by weight of Ti.

[0011] The electric double layer capacitor according to claim 3 is:
Claim 1 or 2 is characterized in that the joining is performed at a joining temperature 20 to 40 ° C lower than the maximum temperature of the melting point of the brazing material.

The electric double layer capacitor according to claim 4 is
In an electric double layer capacitor using an activated carbon fiber cloth as a polarizing electrode, the activated carbon fiber cloths are joined to each other using an active metal brazing material, and the brazing material simultaneously forms a current collecting portion and joins the activated carbon fiber cloth. It is characterized by the following.

[0013] The electric double layer capacitor according to claim 5 is:
The electric double layer capacitor according to any one of claims 1 to 4, wherein the activated carbon fiber cloth is subjected to a vacuum heating treatment.

[0014] The electric double layer capacitor of claim 6 is:
An electric double layer capacitor using an activated carbon fiber cloth as a polarizable electrode is characterized in that an aluminum sprayed film is formed on the activated carbon fiber cloth and soldered to an aluminum collector electrode.

[0015] The electric double layer capacitor of claim 7 is:
According to a sixth aspect of the present invention, the bonding solder is a tin-zinc solder.

The electric double layer capacitor according to claim 8 is:
The electric double layer capacitor according to claim 6 or 7 is characterized in that an activated carbon fiber cloth is soldered to each other to form an intermediate electrode of a multilayer capacitor.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment showing the effects of the present invention will be described, but the present invention is not limited to this.

FIG. 1 schematically shows a model cell of an electric double layer capacitor according to this embodiment. In this embodiment, a method of collecting current of an electric double layer capacitor that reduces internal resistance is proposed. As shown in FIG. 1, in the double-layer capacitor of the present embodiment, an electrolyte 12 is arranged between opposing polarizable electrodes 11a and 11b having an inter-electrode distance of 2 mm, for example.
A collecting electrode 13 is provided outside the electrode. Here, the polarizable electrodes 11a and 11b are activated carbon fiber cloth, the activated carbon fiber cloth is kainol activated carbon fiber (trade name), the specific surface area is 2500 m ² / g, and the electrolyte 12 is a supporting electrolyte. Tetraethylammonium tetrafluoroborate (concentration: 1.2 Mol / l) was used, and the solvent was propylene carbonate.

[First Embodiment] In the electrode of this embodiment, the joining between the activated carbon fiber cloth and the collector was vacuum brazed using an active metal brazing material (hereinafter referred to as "brazing material").
The shapes of the activated carbon fiber cloth 11 and the brazing material 14 are substantially the same, and the collector 13 has a slightly larger size (60 m).
mx 60 mm). The brazing material 14 is manufactured by Tokyo Blaze Co., Ltd. “Activated Silver Brazing (Part No .: TB-629)
T)). The melting temperature of the brazing material used here was 62
0 ° C to 720 ° C. The chemical components of this brazing material are shown in Table 1 below.

[0020]

[Table 1]

Using this brazing material, a maximum melting point of 72
The temperature was held at 750 ° C., which was 30 ° C. higher than 0 ° C., for 30 minutes to join the activated carbon electrode and the collector electrode. FIG. 2 shows the surface state of the joined electrodes. In this embodiment, 2% of Ti is used as a brazing filler metal.
The use of a material containing by weight allowed the current collector to be joined to the activated carbon fiber cloth. In this example, as shown in FIG. 2, elution of the brazing material 14 was observed.

Using the electrodes joined by the method of this embodiment,
A model cell was prepared and a charge / discharge test was performed. The test results are shown in Table 2 below.

On the other hand, as a comparison, the same table shows the results of producing and charging / discharging a model cell using an electrode joined using a conventionally used silver paste. According to the present example, the internal resistance was reduced as compared with the conductive adhesive (silver paste).

According to the present embodiment, the internal resistance of the electric double layer capacitor can be reduced by joining the collector electrode 13 using the active metal brazing material 14.

[Second Embodiment] In the second embodiment, the junction temperature of the collector is 680 ° C., which is lower than that of the first embodiment.
It was carried out in the range of -700 ° C. In the present embodiment, the joining temperature is set to 20 to
The bonding is performed at a temperature lower by 40 ° C. The used electrode material, brazing material and current collector plate are the same as in the first embodiment. According to the present example, as shown in FIG. 3, there was no stain of the brazing material on the side in contact with the electrolyte. FIG. 4 is an enlarged view showing a case where the bonding is performed at a bonding temperature of 700 ° C.
As shown in FIG. 4, it can be seen that the brazing material 14 reacts and is bonded only to a part of the collecting electrode 13 and the activated carbon fiber cloth 11. According to the present example, as shown in Table 2, it can be seen that both the capacitance and the internal resistance are greatly improved as compared with the comparative example.

[0026]

[Table 2]

[Third Embodiment] In a third embodiment, a bipolar electrode is manufactured by bonding activated carbon fiber cloths. Note that the temperature conditions in this embodiment were the same as those in the above-described second embodiment. In electric double layer capacitors, it is necessary to stack single cells to increase the operating voltage,
At this time, it is effective to use a bipolar electrode.

FIG. 5 shows a cross-sectional view of the joined state. In the present embodiment, a bipolar electrode is manufactured by brazing, and as shown in FIG.
The brazing material 14 is sandwiched between the members 11b, and brazing is performed under the conditions of the second embodiment. FIG. 6 is an enlarged cross-sectional view of a portion A showing the bonding state.

According to this method, since the brazing material 14 is not completely dissolved and is in a semi-molten state, a part thereof remains as a solid, and only the contact portions with the activated carbon fiber cloths 11a and 11b slightly penetrate into the activated carbon side. Then, a brazing reaction layer 15 is formed and joined. According to this method, the brazing material 14 becomes a current collecting portion of the bipolar electrode, and the joining of the activated carbon electrode and the formation of the collecting electrode can be simultaneously performed.

[Fourth Embodiment] In a fourth embodiment, the activated carbon fiber cloth is subjected to vacuum heating and collector electrode bonding simultaneously. In any of the manufacturing steps of the first to third embodiments, the brazing atmosphere is in a vacuum.

Activated carbon has been applied to various fields because of its high adsorption capacity. Also, when used for electric double layer capacitors, they are used with good dehydration treatment or storage conditions at the time of use. Activated carbon fiber cloth can be obtained with a high discharge capacity by performing a vacuum heating treatment (600 to 1000 ° C.). Therefore, through the steps of the first to third embodiments, the electrode bonding (collector electrode bonding, bipolar electrode formation) and the vacuum heating process can be performed at the same time, and the process can be simplified.

Next, an expensive conductive sheet (silver paste)
An embodiment in which the conventional bonding according to the above is joined with solder for aluminum will be described. In this method, an activated carbon fiber cloth is coated with aluminum using a high-speed plasma spraying machine, thereby enabling the activated carbon fiber cloth to be joined with zinc-tin solder.

[Fifth Embodiment] In the case of spraying aluminum onto activated carbon fiber cloth, in a normal gas plasma spraying method, the penetration of the sprayed coating into the weave (gap) of the fiber cloth is shallow, and it is sufficient to adhere to the surface. Good adhesion cannot be obtained. The high-speed plasma sprayed coating penetrates about 0.1 mm into the cloth with a thickness of 0.8 mm for bonding, and a sufficient adhesion can be obtained. 90% tin-10% zinc solder is used for joining the activated carbon fiber with the aluminum film and the aluminum current collector plate. The melting temperature of this solder is 19
The heating is performed at a temperature of 230 to 250 ° C. as the bonding temperature.

In this embodiment, as shown in FIG. 7, an activated carbon fiber cloth electrode 22 coated with an aluminum film 21 by high-speed plasma spraying and an aluminum collector plate 23 are heated on a hot plate, and the surface of the aluminum sprayed film 21 is heated. Is coated with solder 24 and sprayed, and pressed with a metal spatula to react the coating with the solder. Next, the aluminum collector plate 23
Is also heated and hot-dip plating of the solder 24 is performed. The activated carbon fiber cloth electrode 22 that has been subjected to the solder base treatment and the aluminum current collector plate 23 are overlapped and heated to be joined.

As shown in Table 3, the bonding electrode 25 thus formed can have a smaller contact resistance as compared with a conventional bonding electrode using a conductive bonding sheet.
This is because the specific resistance of the conductive sheet is 3 Ω · cm, while the specific resistance of the solder is as small as 50 × 10 ⁻⁶ Ω · cm. In addition, since the solder flows so as to fill the gap, the unjoined portion hardly remains. Since the tin-zinc solder reacts with the aluminum without the flux, there is no fear of deterioration of the capacitor characteristics due to the residual flux.

[0036]

[Table 3]

[Sixth Embodiment] Since the aluminum sprayed coating of the activated carbon fiber cloth and the tin-zinc solder can be bonded without flux as shown in the fifth embodiment, the present invention is also applicable to electrode bonding between laminated cells. An embodiment using the joining method will be described below.

FIG. 8 shows a case where the activated carbon fiber cloth electrodes 22a and 22b coated with the aluminum
2 shows the solder joint electrode 26 joined by. In the conventional method, a conductive adhesive sheet was used for the members of the thermal spray coating and the solder layer. FIG. 9 shows an example in which a multi-stage multilayer capacitor is manufactured using the solder bonding electrodes 26. The electrodes bonded with the conductive adhesive sheet of the conventional example have low rigidity and are easily deformed, so that it is difficult to laminate large electrodes. However, as in the present embodiment, the electrodes bonded using solder are rigid. And the work at the time of lamination becomes easy. In the drawings, reference numeral 27 denotes an electrolyte, 28 denotes a holding frame, and 29 denotes a lead wire.

[0039]

As described above, according to the present invention, the following effects can be obtained. (1) By joining using an active metal brazing material containing 2% of Ti, joining of different materials such as activated carbon and a current collector plate becomes possible. (2) By joining using an active metal brazing material, an electric double layer capacitor having a low internal resistance can be manufactured. (3) By manufacturing a bipolar electrode using an active metal brazing material, a current collecting material is not required at the junction between the current collecting portion of the bipolar electrode and the activated carbon electrode, which has been conventionally required, and the bipolar electrode can be thinned. Becomes

Further, since the cloth is used as the polarizable electrode of the electric double layer capacitor in the activated carbon claim, the effect of enabling the joining with the aluminum collecting electrode and the solder joining between the activated carbon electrodes is as follows. (4) Compared to the adhesive electrode using the conventional conductive adhesive sheet,
The electric resistance at the bonding interface can be reduced by more than 30%. (5) Since the tin-zinc solder used for the bonding reacts with the aluminum without the flux, there is no fear that the residual flux may adversely affect the capacitor characteristics. (6) By soldering the electrodes between the stacked cells, the rigidity of the electrodes is increased, and the formation of a large electrode is facilitated. (7) Since an expensive conductive adhesive sheet is not used, a large-capacity capacitor can be manufactured at low cost. (8) The 90% tin-10% zinc solder used for bonding has a melting start (solid phase) temperature of 198 ° C., a temperature at which it becomes completely liquid at 10 ° C., and is in a semi-molten state at temperatures between these. When reacting with aluminum, the upper limit temperature of the temperature range in the semi-molten state increases (about 240 ° C.), so that excessive erosion of aluminum is suppressed, and an appropriate bonding state can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a structure of an electric double layer capacitor.

FIG. 2 is a state diagram of an electrode surface according to the first embodiment.

FIG. 3 is a state diagram of an electrode surface according to a second embodiment.

FIG. 4 is a sectional view of an electrode according to a second embodiment.

FIG. 5 is a sectional view of a bipolar electrode.

FIG. 6 is a sectional view of a joint according to a third embodiment.

FIG. 7 is a sectional view of an electrode according to a fifth embodiment.

FIG. 8 is a sectional view of an electrode according to a sixth embodiment.

FIG. 9 is a sectional view of a multilayer capacitor according to a sixth embodiment.

FIG. 10 is a cross-sectional view of a conventional electrode-collector electrode.

FIG. 11 is a schematic view of a conventional single cell structure.

[Explanation of symbols]

 11a, 11b Polarized electrodes 12 Electrolyte 13 Collector electrode 14 Brazing material 15 Brazing reaction layer 21 Aluminum film 22 Activated carbon fiber cloth electrode 23 Aluminum collector electrode plate 24 Solder 25 Joining electrode 26 Joining electrode 27 Electrolyte 28 Holding frame 29 Lead wire

Claims (8)

[Claims] 1. An electric double layer capacitor using an activated carbon fiber cloth as a polarizing electrode, wherein an active metal brazing material is used to join a collecting electrode,
An electric double layer capacitor characterized by reduced internal resistance of the capacitor. 2. The electric double layer capacitor according to claim 1, wherein the active metal brazing filler metal contains 2% by weight of Ti. 3. The electric double layer capacitor according to claim 1, wherein the joining is performed at a joining temperature lower by 20 to 40 ° C. than the maximum temperature of the melting point of the brazing material. 4. An electric double layer capacitor using an activated carbon fiber cloth as a polarizing electrode, wherein said activated carbon fiber cloths are joined to each other using an active metal brazing material, and the brazing material forms a current collecting portion and activates the activated carbon fiber cloth. An electric double-layer capacitor, wherein the electric double-layer capacitors are simultaneously bonded. 5. The electric double layer capacitor according to claim 1, wherein the activated carbon fiber cloth is subjected to a vacuum heating treatment. 6. An electric double-layer capacitor using an activated carbon fiber cloth as a polarizing electrode, wherein an aluminum sprayed film is formed on the activated carbon fiber cloth and soldered to an aluminum collector electrode. . 7. The electric double layer capacitor according to claim 6, wherein the joining solder is tin-zinc solder. 8. An electric double layer capacitor, wherein the electric double layer capacitor according to claim 6 or 7 is joined by soldering activated carbon fiber cloths to each other as an intermediate electrode of a multilayer capacitor.