JP2001035756A - Manufacture of polarizable electrode for capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a polarizable electrode which is homogeneous, thin and is used for a capacitor. SOLUTION: Carbon fine powder, conductive auxiliary agents, and binder added with water or organic solvent are wet-blended, which is then kneaded under a shear force. A drying processing is conducted after either the wet- blending or kneading is completed, and a lump provided after completion of both kneading and drying is crushed to provide a material 12, which is used to manufacture a mold sheet 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for manufacturing a uniform and thin polarizable electrode used for a capacitor.

[0002]

2. Description of the Related Art Capacitors have a farad-class large capacity and excellent charge / discharge cycle characteristics, so they are used as backup power supplies for electronic devices and batteries for various transport vehicles such as automobiles. From the viewpoint of effective use of energy, use in applications such as storage of nighttime power is also being considered.

[0003] In each of these applications, an important property required of the capacitor is high energy density and / or high power density. Therefore, in order to realize such characteristics, improvement of the performance of the polarizable electrode used for the capacitor and reduction of the manufacturing cost have been studied. For example, JP-A-4-67610 discloses that activated carbon powder and carbon A method is disclosed in which a material obtained by dry-kneading black and a binder (hereinafter, referred to as “activated carbon powder or the like”) is supplied from a hopper between parallel rolls to produce a polarizable electrode having a predetermined thickness. I have.

[0004]

Problems to be solved by the invention
No. 67610 discloses that when raw materials such as activated carbon powder are mixed in a wet manner, a problem arises in that carbon floats and a solvent to be added may cause an electrochemical reaction.
There is a description that the life of the capacitor is shortened, which is not preferable. Further, according to the method for kneading raw material powder disclosed in the same publication, as shown in FIG. 4 of the same publication, a material having a form in which the surface of activated carbon particles is covered with fine powder of a binder is obtained. There is a statement to the effect.

Certainly, if a slurry or paste is formed by adding a large amount of an organic solvent or the like in order to obtain a sheet molded body made of activated carbon powder or the like, there is a possibility that a problem such as floating and separation of carbon black may occur. Although not preferred, the addition and use of a predetermined amount of an organic solvent or the like for efficient kneading of activated carbon powder or the like increases the efficiency of subsequent kneading and contributes to a reduction in production cost. Conceivable.

Activated carbon powder obtained by kneading is
If the surface is covered with a binder,
It is presumed that in a sheet compact obtained by increasing the plasticity of the binder with the heated parallel rolls, the binding in the state where the activated carbon powder is covered with the binder is likely to occur. In this case, it is considered that the sheet strength is improved, but the contact area between the activated carbons is reduced, and the effect of improving the conductivity of the carbon black between the activated carbon particles is also reduced. It is presumed that the resistance of the battery becomes large, and the charge / discharge efficiency may decrease.

[0007] Japanese Patent Application Laid-Open No. 4-67610 does not disclose the thickness of a sheet to be manufactured, and how thin a sheet can be satisfactorily manufactured using the disclosed method. I'm not sure.

The present invention has been made in view of such problems of the prior art, and an object of the present invention is to provide a binder while ensuring the contact between carbon fine powders in a process of kneading carbon fine powder and the like. To provide a method for efficiently and inexpensively manufacturing a particularly thin polarizable electrode sheet having sufficient strength by efficiently forming fibers into fibers and binding the carbon fine powder to each other, and efficiently performing the fiberization. Is to do.

[0009]

That is, according to the present invention, according to the present invention, carbon fine powder, a conductive auxiliary, a binder obtained by adding water or an organic solvent to a binder are wet-mixed, and then kneaded while applying a shearing force, A drying process is performed after either the wet mixing or the kneading is completed, and a sheet molded body is obtained using a crushed mass obtained after both the kneading and the drying process are completed. And a method for manufacturing a polarizable electrode for a capacitor.

In the method for producing a polarizable electrode for a capacitor according to the present invention, it is preferable that the binder is formed into fibers during the kneading process. Further, it is preferable that the mass obtained through kneading and drying is pulverized so that the maximum particle size becomes 2 mm or less, and is subjected to molding with parallel rolls.
It is suitably used for the purpose of obtaining a sheet molded body having a size of 00 μm or less. The processing temperature during kneading is preferably 20 ° C. to 250 ° C., and / or the temperature of the parallel roll is 4 ° C.
It is preferable that the temperature is maintained in the temperature range of 0 ° C to 250 ° C.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments. The polarizable electrode for a capacitor (hereinafter, referred to as “polarizable electrode”) of the present invention includes a carbon fine powder, a conductive auxiliary, and a binder (hereinafter, referred to as “carbon fine powder”).
As a main component. Activated carbon is mainly used as the carbon fine powder, but fibrous carbon, carbon nanotubes and the like can also be used. Typically, carbon black is used as the conductive assistant. Activated carbon is a main material contributing to the development of an electric double layer, and its form is preferably in the form of powder, and its average particle size is 5 to 50 μm.
m is preferable. The form of the powder is not limited, and various forms such as a sphere, a needle, and a plate can be used.

[0012] Carbon black is amorphous carbon industrially produced by thermal decomposition or oxidative decomposition of hydrocarbons, and improves the conductivity of the polarizable electrode and contributes to a reduction in internal resistance. Also, the binder does not dissolve in the electrolytic solution,
Further, a material having excellent durability against an electrochemical reaction is used, and specifically, a fluororesin such as PTFE (polytetrafluoroethylene) is suitably used. Its morphology is generally spherical.

[0013] There are two types of PTFE, powder and dispersion.
The FE primary particles are aggregated to form secondary particles,
In the dispersion, primary particles of PTFE are dispersed in water. In the present invention, water or an organic solvent is added to activated carbon or the like when mixing activated carbon or the like.
The dispersibility of FE is improved, which is preferable.

In the present invention, water (distilled water, purified water, etc.) or an organic solvent (hereinafter referred to as
"Water etc." ) Is added and wet mixed. As the organic solvent, various alcohols, ethylene glycol, or the like can be used, and the wet mixing means is not particularly limited. The amount of water or the like to be added is determined by taking into account the specific gravity thereof,
It is preferable that the amount be from 200 parts by weight to 200 parts by weight. When a PTFE dispersion is used as a binder, the amount of water in the dispersion is included in the amount of water or the like to be added.

In the wet mixing of the present invention to which water or the like is added, a large amount of water or the like is not added until the activated carbon or the like becomes a slurry or paste, and the resulting admixture is granular or bulky. It is. Therefore, the release of carbon black does not occur, and the electrochemical reaction of the activated carbon is hardly caused by water or the like, so that the characteristics of the capacitor are not adversely affected.

The obtained mixture is kneaded while applying a shearing force under heat and pressure. A kneader such as a kneader is preferably used for kneading, but as shown in FIG. 1, the two rotary blades 2 and the kneaded mixture 3 are closed by a lid 4 so as to maintain a constant pressure. It is preferable to use a kneading machine 1 having a structure for performing a kneading process in the closed space 5.

The pressure in this space 5 is preferably 1 k
It is preferably at least gf / cm ^2, but is appropriately set in consideration of the power load of the rotary blade 2, the pressure resistance of the kneader 1, the processing time, and the like. The heating of the mixture 3 is performed using a heater attached to the kneading apparatus, and the heat generated by the kneading can be used. The heating and holding temperature is preferably in the range of 20C to 250C,
Particularly, it is preferable to keep the temperature around 100 ° C. in consideration of safety, productivity, and the like. In addition, if necessary, a cooling device may be attached to the kneader to prevent excessive heating.

In this kneading treatment, the binder contained in the admixture undergoes a shearing force and changes into a fibrous form while binding the activated carbon particles together. FIG. 2 is an SEM photograph of the obtained kneaded material, in which the fiberization of the binder is clearly observed. The process in which the binder is fiberized and a homogeneous kneaded material is obtained is a process in which mixing of carbon fine powder or the like is performed in a dry manner, or when carbon fine powder or the like is directly applied to a kneading machine, etc. It takes a long time to finish,
In addition, there are various problems that the deterioration of the kneading apparatus is apt to proceed because the heating conditions and the pressing conditions must be strict.

However, by adding an appropriate amount of water or the like in the process of mixing the carbon fine powder or the like as in the present invention, a nucleus which is a starting point of fiberization of the binder in kneading is easily formed, and as a result, heating conditions It is possible to obtain a homogeneous kneaded product in which carbon fine powder and conductive auxiliary agent are bound by the fiberized binder while reducing the kneading time while keeping the pressure and pressure conditions mild. It is thought that it was.

Incidentally, in the method for producing a polarizable electrode according to the present invention, a drying process is performed after either the wet mixing or the kneading is completed. That is, a drying treatment may be performed after mixing the carbon fine powder or the like and before kneading, or a drying treatment may be performed after performing both mixing and kneading treatments. In addition, even when the drying process is performed before the kneading after mixing, compared to the case where the carbon fine powder or the like is directly kneaded by a dry method, the kneading process time is shortened while the binder is fiberized. . Also, no difference is observed in the obtained kneaded product as compared with the case where drying is performed after kneading, and no adverse effect is observed on the molding characteristics of the parallel roll in the next step.

That is, in the present invention, water or the like added in the mixing process of the carbon fine powder or the like does not mainly play a role in facilitating kneading, but in the mixing process, the core of the fiberization of the binder in the kneading process. It is considered that this greatly contributes to the formation of the portion that becomes.

As described above, even when the drying treatment is performed after mixing or after kneading, the lump obtained after both kneading and drying are finished is subjected to pulverization treatment. And subjected to forming using parallel rolls. The pulverization of the lump is preferably performed so that the maximum particle size is 2 mm or less in forming a thin sheet having a thickness of 300 μm or less.

The pulverization here can be carried out using various crushing mills using a rotary blade, and may be obtained by successively separating pulverized particles having a size of 2 mm or less at the time of pulverization by a method such as sieving. Alternatively, the pulverization may be performed until the lump subjected to the pulverization treatment has a total thickness of 2 mm or less.

The outline of the sheet forming using the parallel rolls is as shown in FIG. From the hopper 11, a predetermined amount of the crushed particles 12 obtained by crushing the lump is supplied between the parallel rolls 13 adjusted to a predetermined gap to produce a sheet 14 having a thickness substantially equal to the roll gap.

The rotation speed of the parallel roll 13 varies depending on the thickness of the sheet 14 to be manufactured, the holding temperature of the parallel roll 13, and the roll diameter, but the linear velocity on the outer surface of the roll in the gap portion is 1 cm / sec. It is preferred to be in the range of 15 cm / sec. In addition, the parallel roll 13 is used to
For the purpose of increasing the viscosity of the binder in No. 2 and promoting the binding of the crushed particles 12, it is preferable to use the binder while maintaining the temperature in a temperature range of 40 ° C. to 250 ° C., preferably about 100 ° C.

By the way, as described above, the hopper 1
By setting the particle size of the crushed particles 12 supplied from 1 to the parallel roll 13 to 2 mm or less, the crushed particles 12 can be smoothly supplied to the roll gap. In addition, the deformation of the crushed grains 12 becomes easy, and the thickness is 300 μm.
This is preferable because a thin sheet such as the following can be formed with a uniform thickness and uniformly. Crushed grains 12
If the particle size adjustment is not performed, there is a problem that clogging occurs between roll gaps and it becomes difficult to obtain a uniform sheet, which is not preferable in a production process.

However, as described above, the adjustment of the particle size of the crushed particles 12 to 2 mm or less is not a process that must be strictly adhered to when forming a sheet thicker than 300 μm. That is, in order to form a thin sheet, it is preferable to use particles having a small particle diameter. Conversely, when forming a thick sheet, particles having a large particle diameter can be used. In the examples described later, parallel rolls are used for the purpose of continuously forming a sheet. However, a polarizable electrode can be formed from the crushed particles 12 using a uniaxial press.

The obtained sheet 14 can be used as it is or after being processed into a predetermined shape, as a polarizable electrode sheet. In addition, it is also preferable that the sheet 14 is subjected to a rolling process and further processed to be thin to a predetermined thickness. On the other hand, 30
When a polarizable electrode having a thickness of 0 μm or more is required, a plurality of thin polarizable electrode sheets formed by parallel rolls may be stacked and subjected to a rolling treatment to produce an integrated sheet.

[0029]

EXAMPLES Hereinafter, examples of the present invention will be described, but the present invention is not limited to the following examples.
15 parts by weight of carbon black and 10 parts by weight of fluororesin (PTFE) are added to 100 parts by weight of activated carbon, and 70 parts by weight of ethanol are added to the total weight of activated carbon and carbon black. I got something. After drying this mixture, kneading was performed while applying shearing force using a kneader. Kneading was performed for 15 minutes at a pressure of 1 kgf / cm ² and a temperature of 100 ° C.

The obtained kneaded product was analyzed by SEM,
The binder as shown in FIG. 2 had a microstructure in which fibers were formed and activated carbon particles were bonded. The kneaded material was pulverized by a mixer so that the particle diameter became 2 mm or less, and the pulverized particles were supplied to a gap of a parallel roll whose gap was adjusted to 200 μm. At this time, a parallel roll having a roll diameter of 300 mmφ was used and maintained at 100 ° C., and the rotation speed during molding was 2.0 rpm.

The obtained sheet has an average thickness of about 200
With a thickness of μm, there were almost no defects such as wrinkles, the uniformity of the thickness was good, and even when the sheet was broken by tension, the fracture surface was uniform.

[0032]

As described above, according to the method for manufacturing a polarizable electrode for a capacitor of the present invention, it is possible to efficiently produce a thin, uniform sheet-shaped polarizable electrode with high production efficiency, This has a remarkable effect on reducing product costs. In addition, the polarizable electrode obtained by the present invention has a characteristic of low resistance because of good contact between the carbon fine powder and the conductive auxiliary agent, and has the effect of achieving high output. Also play.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an outline of a kneading apparatus.

FIG. 2 is a photograph showing one mode of a particle structure (microstructure) of a kneaded material.

FIG. 3 is an explanatory diagram showing an outline of sheet forming.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Kneading machine, 2 ... Rotating blade, 3 ... Mixed material, 4 ... Lid, 5 ... Space, 11 ... Hopper, 12 ... Pulverized particles, 13 ... Parallel roll, 14 ... Sheet.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshihiko Nakagawa 2-56, Suda-cho, Mizuho-ku, Nagoya-shi, Aichi Japan Inside Nihon Insulators Co., Ltd. (72) Inventor Hiroyuki Katsukawa 2-56, Suda-cho, Mizuho-ku, Nagoya-shi, Aichi No. Japan Insulators Co., Ltd.

Claims (4)

[Claims] 1. A method in which water or an organic solvent is added to a carbon fine powder, a conductive auxiliary, or a binder, and the mixture is wet-mixed.
Kneading while applying a shearing force, performing a drying treatment after either the wet mixing or the kneading, and crushing the lump obtained after both the kneading and the drying treatment are completed. A method for producing a polarizable electrode for a capacitor, comprising obtaining a molded article. 2. The method for producing a polarizable electrode for a capacitor according to claim 1, wherein the binder is fiberized in the kneading. 3. The sheet formed body is obtained by a parallel roll using crushed particles obtained by crushing the lump so that the maximum particle size is 2 mm or less. Method for manufacturing a polarizable electrode for a capacitor. 4. An average thickness of the sheet molding is 300 μm.
The method for producing a polarizable electrode for a capacitor according to any one of claims 1 to 3, wherein m is equal to or less than m.