JPH0424849B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for manufacturing a small, thin, and large-capacity wet type electric double layer capacitor. Conventional technology Conventionally, as a thin electric double layer capacitor,
For example, there is one shown in Japanese Patent Application Laid-Open No. 56-83920. That is, a conductive layer of aluminum, nickel, etc. is formed on one side of a polarizable electrode made of activated carbon fiber cloth, and is placed facing each other with a separator interposed between them, and this is applied together with an electrolytic solution to a metal case, a sealing plate, and a gasket that insulates the two. It was then sealed. Here, the activated carbon fibers used in the polarizable electrode are obtained by directly carbonizing and activating phenol-based, rayon-based, acrylic-based, and pitch-based fibers. Considering the electrical resistance, strength, activation yield, etc. of activated carbon fibers, among the above-mentioned fibers, phenolic fibers are most suitable for polarizable electrodes. Further, the metal current collector (conductive layer) can be easily formed by plasma spraying or arc spraying. A small, large-capacity capacitor having the above-mentioned structure is realized by punching out the polarizable electrode having the above-mentioned structure into a circular shape having a desired diameter. Furthermore, since this type of polarizable electrode does not use a binder, the resistance of the electrode itself can be reduced. In particular, when a conductive layer is formed by thermal spraying,
The adhesive strength between the sprayed metal layer and the activated carbon fiber layer is strong, the contact resistance can be reduced, and good capacitor characteristics can be obtained. Problems to be Solved by the Invention In conventional double-layer capacitors using activated carbon fibers, when the electrode diameter is set to about 6 mm, it is extremely difficult to reduce the capacitance to 0.1 F or less due to the manufacturing process, which is currently not acceptable. It is difficult to realize a 6mm capacitor with a large resistance and capacitance, such as 0.06F.
Therefore, if a paper-like polarizable electrode made of activated carbon fibers and a binding medium such as pulp is used, the capacity can be controlled by changing the content of activated carbon fibers. However, since this type of polarizable electrode uses a binding medium such as natural pulp, the binding medium swells during long-term use. Therefore, the charges accumulated in the electric double layer cannot be efficiently extracted as an external current during discharge. Means for Solving the Problems In order to solve the above problems, the present invention mechanically provides a large number of small holes in a paper-like polarizable electrode composed of activated carbon fibers and a bond, and a polarizable electrode having a conductive layer formed on the surface and the inner surface of the small hole;
This is a method for manufacturing an electric double layer capacitor in which a counter electrode is opposed to each other with a separator interposed therebetween. Effects The polarizable electrode according to the method for manufacturing an electric double layer capacitor of the present invention has an enhanced current collecting ability due to the above structure, and can realize a highly reliable thin and large capacity electric double layer capacitor. Embodiment FIG. 1 shows an electric double layer capacitor according to an embodiment of the present invention. 1 is a polarizable electrode, 2 is a large number of small holes provided in the polarizable electrode 1, 3 is a conductive layer as a current collector, 4 is a separator, and 5 is a counter electrode. It is sealed by a sealing plate 6 that also serves as a terminal, a case 7 that also serves as a terminal for the counter electrode 5, and a gasket 8 that insulates both. In this example, the counter electrode 5 has the same configuration as the electrode 1. Next, a method for manufacturing the polarizable electrode will be explained. Generally, to obtain activated carbon fibers, starting materials such as phenol, rayon, and PAN are used, but phenol-based materials are most suitable for polarizable electrodes in electric double layer capacitors, considering their electrical properties and strength. There is. First, TOW-like phenolic novolac resin fibers are carbonized using a catalyst or steam at a temperature of 800 to 1000°C, and the specific surface area is 1800 to 2500 m ² /g.
2 activated carbon fibers were obtained and made into paper.
It is crushed into chips of ~4 mm and made into natural pulp,
Paper is made using artificial pulp such as polyethylene or polypropylene, or a mixture of natural pulp and artificial pulp as a binding medium. After the paper is made, the paper is calendered or pressed to increase its density and create many small holes. As shown in FIG. 2, a thermal spray conductive layer 3 is formed on the polarizable electrode 1 which has a large number of small holes and has an increased density even inside the small holes 2 using a thermal spray gun 9 obliquely. Example 1 Phenolic activated carbon fibers with a specific surface area of 2200 m ² /g and kraft pulp as a binding medium were mixed at a weight ratio of 90:10, and a small amount of a dispersant was added to make paper.
A paper-like polarizable electrode with a basis weight of 60 g/m ² and a density of 0.3 was obtained.
A large number of small holes with a diameter of 1.5 mm were made in this electrode at a pitch of 1.5 mm, and a conductive layer made of a sprayed aluminum layer was formed as shown in Fig. 2. The spraying was performed obliquely to the polarizable electrode to facilitate the formation of a sprayed layer on the inner surface of the small hole. This was punched out into a disk with a diameter of 6 mm. A capacitor shown in FIG. 1 was obtained using a pair of polarizable electrodes having the above configuration. Note that the conductive layer of the electrode 15 was spot welded to the sealing plate 6 and the case 7, respectively. In addition, a polypropylene nonwoven fabric is used for the separator 4, and the electrolyte is
A propylene carbonate solution in which (C ₂ H ₅ ) ₄ NBF ₆ was dissolved at a ratio of 1 mol/mol was used. The above capacitor is designated as Comparative Example A, and a capacitor B uses a polarizable electrode having the same configuration except that it does not have a large number of small holes. The results of a reliability test by applying 2V to both in an atmosphere of 70℃ are shown in the third section.
As shown in the figure. The figure clearly shows the improvement in reliability of the capacitor of the present invention. This is considered to be because the swelling of the polarizable electrode is suppressed and the current collecting ability in the vertical direction is improved. Example 2 A capacitor similar to that of Example 1 was used, and 10% by weight of carbon fiber or graphite was added to the polarizable electrode as a conductivity improver. That is, a polarizable electrode with a ratio of activated carbon fiber, binding medium, and conductivity improver of 80:10:10 was used. As in Example 1, the results of the 2V application test at 70°C are shown in FIG. In the figure, a ₁ is the charcoal fiber additive, a ₂
is a graphite additive product. Example 3 A polarizable electrode had the following composition, had a large number of small holes with a pitch of 1.5 mm and a diameter of 1 mm, and was used as a current collector pair.
A capacitor similar to that of Example 1 was constructed using a 250 μm aluminum sprayed layer.

[Table] Figure 5 shows the results of the 2V application test at 70°C. In the diagram
A ₃ shows the capacitor of this example, and b shows a capacitor using a polarizable electrode having the same composition as that of the example and not having many small holes. It can be seen that in this example as well, the current collection property was significantly improved. Example 4 Using a paper-like polarizable electrode having the same composition as in Example 1 and having a large number of small holes of 1.5 mm pitch and 1.0 mm diameter, a roll-up type cylindrical capacitor as shown in FIG. 6 was produced. In this example, the polarizable electrode 1 on the positive side
0, both polarizable electrodes 11 on the negative electrode side are thick.
On top of this, a thermally sprayed aluminum layer 12 is formed to a thickness of 100μm, and an auxiliary current collector 13 made of aluminum etched foil is placed on the side of the thermally sprayed layer. The lead 14 was attached to the aluminum etched foil 13 by spot welding. 1
5 is a sealing packing, 16 is a case, and 17 is a separator. The size of the electrodes was 30 x 200 mm for the positive electrode and 30 x 210 mm for the negative electrode, and the same electrolyte and separator as in Example 1 were used. In this example, the thickness of the polarizable electrode is as thin as 200 μm, and the current collecting ability in the thickness direction is improved, resulting in a capacitor with excellent charging and discharging characteristics. The capacity reduction rate after charging and discharging 10,000 times at room temperature between 0 and 2.0 V was 5%. Example 5 The same electrode as in Example 1 was used as the positive polarizable electrode, and as the negative polarizable counter electrode, a wood alloy consisting of 85% Sn and 15% Cd was used, in which lithium equivalent to 10 mAh was occluded. Using this method, a flat capacitor as shown in FIG. 1 was fabricated. A propylene carbonate solution in which 1 mol/LiClC ₄ was dissolved was used as the electrolyte. The size of the above electrode is 14 mm in diameter. The following table shows the characteristics of this capacitor. The withstand voltage was as high as 3.0V, and the reliability was also good.

[Table] Effects of the Invention As described above, according to the present invention, a small, large-capacity electric double layer capacitor with good current collection performance and high reliability can be obtained.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an electric double layer capacitor in a method of manufacturing an electric double layer capacitor according to an embodiment of the present invention, FIG. 2 is a view showing how a current collector layer is formed on a polarizable electrode, and FIG. Figures 3, 4 and 5
6 is a diagram showing the reliability test results of the capacitor of the example, and FIG. 6 is a side view of the electric double layer capacitor partially cut in cross section in the method of manufacturing the electric double layer capacitor according to the example of the present invention. DESCRIPTION OF SYMBOLS 1... Polarizable electrode, 2... Small hole, 3... Conductive layer, 4... Separator, 5... Counter electrode, 6... Sealing plate, 7... Case, 8... Gasket.

Claims (1)

[Claims] 1. A paper-like polarizable electrode made of activated carbon fibers and a binding medium is mechanically provided with a large number of small holes, and a conductive layer is formed on one surface of the electrode and the inner surface of the small holes. A method for manufacturing an electric double layer capacitor in which a polarizable electrode and a counter electrode are opposed to each other with a separator interposed therebetween. 2. The method for producing an electric double layer capacitor according to claim 1, wherein the binding medium is natural pulp. 3. Claims characterized in that the inner surface of the many small holes of the polarizable electrode and the conductive layer formed on one surface of the electrode are electrically connected to a conductive case or a current collector. 2. A method for manufacturing an electric double layer capacitor according to item 1.