JP2559163B2 - Electric double layer capacitor - Google Patents

Abstract

PURPOSE:To make small intrinsic resistance value, and to improve adhesive property against a polarizable electrode by a method wherein the mixture of polyisobutylene and polyvinyl isobutyl ether is used as the resin component of the conductive filmy which constitutes current-collecting material. CONSTITUTION:Solid polalizable electrodes 3 are arranged on the upper and lower surfaces of a separator 2, a metal electrode plate 5 is made to adhere to the surface of each polalizable electrode 3 through the intermediary of a current-collecting material 4 consisting of a conductive film, and the inside part is airtightly sealed by coating. Two-component type resin consisting of polyisobutylene (PIB) and polyvinyl isobutyl ether (PIBE) is used for the resin component of a conductive film, the resin constituting the conductive film is set at 10 to 50wt.% against the total weight, and the remaining part can be used as a conductive agent. It is desirable that the mixture of acetylene black and black lead is used as the conductive agent. Also, PIB:PIBE=1:1 to 4:1 or thereabout is desirable. The conductive film of the above-mentioned composition can be formed by rolling, and its desirable thickness is 0.1 to 1mm taking into consideration of the intrinsic resistance value and the adhesive property when a hot-melting operation is conducted.

Description

Description: TECHNICAL FIELD The present invention relates to an electric double layer capacitor, and more particularly to a collector for reducing a contact resistance of an electrode plate with a polarizable electrode and obtaining a stable contact state. Regarding improvement.

<Prior art> The basic configuration of an electric double layer capacitor is that a pair of polarizable electrodes are placed inside a frame that also functions as a sealing material via a separator, and the surface of each polarizable electrode also serves as a current collector. It is a structure in which it is covered and sealed with a metal electrode plate.

However, in the case of this structure, if the polarizable electrode and the electrode plate are simply in contact with each other, a partially insufficient contact state occurs, and the internal resistance increases.

Therefore, in order to solve this kind of problem, it is necessary to bond the polarizable electrode and the metal electrode plate by using a graphite-based conductive adhesive, or as shown in JP-A-2-65114. It has also been proposed to bond the two by thermocompression bonding via a conductive film forming the body.

However, these structures have the following drawbacks.

<< Problems to be Solved by the Invention >> That is, when the former conductive adhesive is used, it shows non-uniform conductivity depending on the volatilization state of the solvent contained in the adhesive, or the solvent is partially In addition to being unevenly distributed, the conductivity of this part was significantly impaired, and the contact resistance was large, making it impossible to extract a large current.

Further, in the latter method of interposing the conductive film, since the resistance of itself is large, it was necessary to reduce the thickness in order to reduce the electric resistance. In addition, the adhesiveness to the polarizable electrode is poor, and the thickness is made thin to reduce the resistance. Therefore, there are drawbacks such as holes or breaks in the film during thermocompression bonding.

That is, the conventional conductive film is polypropylene,
Carbon black is dispersed as a conductive material in a resin such as polyethylene, polyvinyl chloride, polystyrene / polyurethane, or polyimide, and molded into a film shape, so if the resin content decreases, the moldability is affected and the film is easily broken. On the contrary, when the resin content increases, the conductivity is affected and the resistance increases.

Therefore, in the past, when the resin content was set to about 20-40 wt%, the thickness was at most 20-80μ in consideration of resistance.
It can only be made to a thickness of about m, and if it is about this thickness, it tends to tear or break due to hot pressing,
This has been a cause of lowering the product yield.

This invention relates to an electric double layer capacitor using the latter conductive film as a current collector, by devising the material and composition of the conductive film so that the specific resistance value is small and the hot An object of the present invention is to provide an electric double layer capacitor capable of preventing breakage or breakage during pressing and improving adhesiveness to a polarizable electrode.

That is, the present invention, as a resin component of the conductive film, by using a two-component resin mixture of polyisobutylene and polyvinyl isobutyl ether, the specific resistance value becomes extremely small compared to the case of using a conventional resin. It was found that a conductive film in which a sufficient amount of a conductive agent can be mixed and dispersed can be obtained, and the present invention has been completed.

<< Means for Solving the Problems >> In order to achieve the above object, the present invention provides an electric double layer capacitor in which a solid polarizable electrode is adhered to a current collector made of a conductive film, and a resin component of the conductive film. Is a two-component resin composed of polyisobutylene and polyvinyl isobutyl ether.

The composition ratio of the resin forming the conductive film may be 10 to 50 wt% with respect to the total weight, and the balance may be the conductive agent.

Further, the conductive agent dispersed in the conductive film is a mixture of acetylene black and graphite.

The polyisobutylene (PIB) has a viscosity average molecular weight of 2,1.
It is 00,000.

The polyvinyl K-butyl ether (PIBE) has an average K value (viscosity) of 100 to 130.

The composition ratio of both is preferably in the range of PIB: PIBE = 1: 1 to 4: 1.

In addition, the resin with the above composition ratio is 10 to 50 wt% of the total amount.
(Remaining conductive agent) means that when it is less than 10 wt%, the film formability is hindered, and when it exceeds 50 wt%, the content of the conductive agent is rapidly decreased, as shown in FIG. As described above, this is because the volume resistivity value is increased, and a preferable result is not given in any case.

The conductive agent used is preferably a mixture of acetylene black and graphite in terms of dispersibility and conductivity, and its particle size is preferably about 5 μm in terms of uniform dispersibility.

As a method of molding the conductive film having the above composition, the conductive film is continuously formed to have a predetermined thickness by rolling.

The thickness of the obtained conductive film is preferably 0.1 to 1 mm in consideration of the specific resistance value and the adhesiveness during hot melt.

FIG. 1 shows an electric double layer capacitor using the above conductive film.

Further, FIG. 3 shows an electric double layer capacitor having a laminated structure using an electrode plate in which only a solid polarizable electrode is adhered to a conductive film.

In the figure, 1 is a resin frame that also serves as a sealing material, 2 is a separator that is arranged inside the frame 1, and 3 is a solid polarizable electrode that is arranged on the upper and lower surfaces of the separator 2. The inside is filled with an electrolytic solution.

Further, a metal electrode plate 5 is adhered to the surface of each polarizable electrode 3 via a collector 4 made of the conductive film to cover and seal the inside.

As this bonding method, the current collector 4 is installed on the frame body 1 in which the polarizable electrode 3 is installed, and then the metal electrode plate 5 is installed on the upper surface of the current collector 4 so that the surface By heating and pressurizing the current collector to a temperature above the softening point and below the melting point, the current collector 4 is once softened, and both surfaces are fused to the surfaces of the polarizable electrode 3, the frame 1 and the metal electrode plate 5. Then, it is solidified by cooling and the respective parts are bonded together.

<< Examples >> Next, examples of the present invention will be described. However, it is not limited to the following examples.

Example A master batch in which 75 wt% of a mixture of acetylene black and graphite was mixed and dispersed in 25 wt% of a resin adjusted to PIB: PIBE = 2: 1 to obtain a conductive film having a thickness of 0.4 mm by roll rolling.

Then, this conductive film is cut into a predetermined size and the first
The electric double layer capacitor shown in FIG. 1 was assembled by using the current collector 4 shown in the figure and adhering it by heating and pressing at 140 ° C.

Comparative Example With the same specifications as the conventional example, polyethylene was used as a resin, and a masterbatch in which carbon black was mixed and dispersed at a composition ratio of 25:75 wt% was melt-extruded to form a conductive film having a thickness of 0.06 mm. Obtained and using this as a current collector, an electric double layer capacitor having the structure shown in FIG. 1 was obtained.

Next, the physical properties of the above Examples and Comparative Examples were compared and measured, and the results shown in the following table were obtained.

<< Effects of the Invention >> As is clear from the above table, in the electric double layer capacitor using the conductive film of the present invention as a current collector, the thickness is about 10 times the conventional film thickness. Even if it is present, the specific resistance value is low, the workability in hot melt is good, and the adhesiveness to the polarizable electrode is also good.

Therefore, in the electric double layer capacitor of the present invention, the contact resistance of the electrode plate with respect to the polarizable electrode can be further reduced as compared with that using the conventional conductive film, and the internal resistance at the initial stage and after the lapse of time is Can be lowered and performance can be improved.

Further, there is no breakage or breakage during hot melt bonding of the current collector, and the product yield is improved.

[Brief description of drawings]

FIG. 1 is an explanatory sectional view of an electric double layer capacitor, and FIG.
FIG. 3 is a graph showing the relationship between the resin content ratio and the volume resistivity value, and FIG. 3 is a sectional view showing another example of the electric double layer capacitor. 1 ... Frame 2 ... Separator 3 ... Solid polarizable electrode 4 ... Current collector made of conductive film 5 ... Metal electrode plate

Front page continuation (72) Nobuyuki Osawa Inventor Nobuyuki Osawa No. 8 Soil Shelf, Fujisawa City, Kanagawa Prefecture Isuzu Motors Co., Ltd. Fujisawa Plant (72) Seiichi Kito, No. 8 Soil Shelf, Fujisawa City, Kanagawa Isuzu Automobile Co., Ltd. Fujisawa Plant (72) Inventor Kohei Yamamoto 5-36-1 Shimbashi, Minato-ku, Tokyo Fujiden Ki Kagaku Co., Ltd. (72) Masanori Nakanishi 5-36-11 Shinbashi, Minato-ku, Tokyo Fuji Denki Kagaku Co., Ltd. (72) Inventor Mitsuhiro Nakamura 5 36-11 Shinbashi, Minato-ku, Tokyo Fuji Electric Chemicals Co., Ltd. (56) Reference JP 49-25456 (JP, A) JP 58-158862 (JP) , A)

Claims (4)

(57) [Claims] 1. An electric double layer capacitor in which a solid polarizable electrode is adhered to a current collector made of a conductive film: The resin component of the conductive film is a two-component resin made of polyisobutylene and polyvinyl isobutyl ether. Is an electric double layer capacitor. 2. The electric double layer capacitor according to claim 1, wherein the composition ratio of the resin constituting the conductive film is 10 to 50 wt% with respect to the total weight, and the balance is a conductive agent. 3. The electric double layer capacitor according to claim 1, wherein the conductive agent dispersed in the conductive film comprises acetylene black and graphite. 4. The electric double layer capacitor according to claim 1, wherein the composition ratio of polyisobutylene and polyvinyl isobutyl ether of the resin constituting the conductive film is 1: 1 to 4: 1.