JP3793751B2 - Method for producing polarizable electrode for electric double layer capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable material to be mixed well so as to manufacture a sheet-like polarizable electrode which is stable in quality and sheet strength. <P>SOLUTION: A method of manufacturing a sheet-like polarizable electrode comprises processes of mixing and kneading the materials, granulating the kneaded materials into particles, screening the particles so as to form molding materials, molding the molding material into sheets, and rolling the sheet into the sheet-like polarizable electrode. When the materials are mixed, active carbon and carbon black are primarily mixed first, and PTFE to which IPA is previously added for swelling is added to the primary mixture to form a secondary mixture. At this point, PTFE turns easily into fibers, and the superior mixture can be obtained. IPA is added to the molding material once more in a calender molding pre-treatment just before molding the molding material into sheets. <P>COPYRIGHT: (C)2004,JPO&amp;NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a sheet-like polarizable electrode for an electric double layer capacitor.
[0002]
[Prior art]
An electric double layer capacitor (capacitor) has a large capacity and is excellent in charge / discharge cycle characteristics, and therefore, its use as various backup power sources including automobiles is being studied. When used as a backup power source for automobiles or the like, a large capacitance is required. Therefore, a polar sheet used for such an electric double layer capacitor requires a long sheet. . Therefore, various methods have been proposed as a method for manufacturing this type of sheet-like polarizable electrode.
[0003]
For example, there are the following methods. An aqueous solution obtained by mixing isopropyl alcohol with pure water was added to activated carbon, mixed using a mixer, carbon black and fluororesin were added to the mixture, and the mixture was mixed using a mixer to obtain a mixture. This mixture was kneaded using a kneader. After drying this kneaded material, it is pulverized by a mixer so as to have a particle size of 2 mm or less, and the pulverized particles are supplied between adjusted parallel rolls. The obtained sheet-like molded body has an average thickness of about 200 μm and a density of 0.70 g / cm ³ (see, for example, Patent Document 1).
[0004]
[Patent Document 1]
JP 2001-307964 A (paragraph number [0034])
[0005]
[Problems to be solved by the invention]
By the way, when manufacturing such a sheet-like polarizable electrode, activated carbon and carbon black, which are main components of raw materials, a fluororesin as a binder, and a solvent for this fluororesin (a binder aid) are mixed at a time. However, according to the method of the above-mentioned Patent Document 1, it is difficult to perform uniform mixing, and poor mixing is likely to occur. When mixing failure occurs, the action of the binder is unstable, and when it is made into a sheet, undulations, edge cracks, nests, etc. are likely to occur, the quality is not stable, and the required sheet strength can be obtained. there is a problem that no longer and combed.
[0006]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electric double layer capacitor capable of producing a sheet-like polarizable electrode in which raw materials can be mixed well and the quality and sheet strength are stable. Another object of the present invention is to provide a method for manufacturing a polarizing electrode for use.
[0007]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the invention of claim 1 is to form a molding material after mixing and kneading raw materials including carbonaceous powder, a conductive auxiliary agent and a binder, and then molding the molding material. A method of rolling a sheet-shaped polarizable electrode for an electric double layer capacitor, wherein when the raw materials are mixed, a binder auxiliary agent is added to the binder in advance to swell the binder, The carbonaceous powder and the conductive auxiliary are mixed.
[0008]
When the raw materials are mixed, a binder aid is added to the binder in advance to preferentially swell the binder, thereby facilitating fiberization of the binder. By adding and mixing this binder with respect to the carbonaceous powder and the conductive auxiliary agent, the raw materials are mixed well. For this reason, it becomes easy to carry out subsequent steps such as kneading, molding, rolling, etc., and it becomes possible to produce a good sheet electrode with increased strength and less occurrence of undulation, end cracks, nests, etc. Become.
The term “swelling” as used herein means that the binder auxiliary agent is absorbed by the binder, whereby the binder expands and softens, and the softening facilitates fiberization. The term “binder aid” is a term commonly used in this type of technical field, and refers to a material that promotes the binding function of the binder material.
[0009]
By the way, when the binder aid is added and mixed together with the carbonaceous powder, the conductive aid and the binder, the binder and the binder aid are difficult to contact and the binder is difficult to fiberize. There exists a possibility that kneading | mixing may not be performed favorably and there exists a malfunction that quality and intensity | strength are not stabilized.
[0010]
Here, among the raw materials of the polarizable electrode, activated carbon is mainly used as the carbonaceous powder, but carbon nanotubes, fibrous carbon, and the like can also be used. As the conductive auxiliary agent, carbon black is mainly used. As the binder, a fluororesin such as PTFE is preferable. Examples of the binder assistant include alcohols such as IPA (isopropyl alcohol), ethanol, and methanol, ethers, and ketones.
[0011]
In order to achieve an object similar to that of the first aspect, the invention of the second aspect is such that after forming a molding material through a process of mixing and kneading raw materials including a carbonaceous powder, a conductive auxiliary agent and a binder, this molding is performed. A method for producing a sheet-shaped polarizable electrode for an electric double layer capacitor by molding and rolling a material, wherein a binder aid is added in advance to the binder to swell the binder when the raw materials are mixed. In addition to mixing the carbonaceous powder and the conductive auxiliary agent, a binder auxiliary agent is added to the molding material and mixed immediately before molding the molding material into a sheet. It is characterized by.
[0012]
According to the above-described means, as in the first aspect of the invention, when the raw materials are mixed, a binder assistant is added to the binder in advance to preferentially swell the binder, and the swelled binder Is added to and mixed with the carbonaceous powder and the conductive auxiliary agent, whereby the binder is easily fibrillated, and the raw materials are mixed well. For this reason, subsequent steps such as kneading, forming, and rolling are facilitated, and the quality and strength of the sheet are stabilized.
[0013]
In addition, since the binder aid is added separately when mixing the raw materials and immediately before being formed into a sheet, the binder auxiliary agent is added in a large amount at a time when mixing the raw materials. In contrast, the amount added at the time of mixing the raw materials may be a small amount that can at least swell the binder, and it is not necessary to perform a drying process to remove the binder aid before molding. Furthermore, since the remaining binder auxiliary agent is added and mixed immediately before forming into a sheet, it is not necessary to consider that the binder auxiliary agent evaporates in the middle, and the binder auxiliary agent The amount is stable and the quality is stable.
[0014]
The invention of claim 3 is characterized in that the additive amount of the binder auxiliary agent added to the binder at the time of mixing the raw materials is in the range of 70 to 130% of the binder weight.
If the amount of the binder auxiliary agent added is too small at this time, the binder is difficult to be fiberized when the raw materials are mixed, and mixing and kneading cannot be performed satisfactorily. On the other hand, if the amount is too large, it is necessary to perform a drying treatment to remove the remaining binder aid before molding. For this reason, it is preferable that the additive amount of the binder auxiliary agent added to the binder at the time of mixing the raw materials is in the range of 70 to 130% of the binder weight.
[0015]
The invention of claim 4 is characterized in that the additive amount of the binder auxiliary agent when added to the molding material is in the range of 50 to 100% of the total weight of the carbonaceous powder, the conductive auxiliary agent and the binder. To do.
If the additive amount of the binder aid is less than 50% at this time, the sheet strength at the time of forming the sheet becomes weak or the nest is likely to occur in the sheet, and it exceeds 100%. However, when the sheet is formed, the sheet strength is weakened and nests are easily generated. For this reason, the addition amount of the binder auxiliary agent just before molding is preferably in the range of 50 to 100% of the total weight of the carbonaceous powder, the conductive auxiliary agent and the binder.
[0016]
The invention of claim 5 adds the contents of claims 3 and 4 to the invention of claim 2.
The invention of claim 6 is characterized in that when the binder auxiliary is added to the molding material and mixed, they are mixed in a sealed container.
By mixing the molding material and the binder aid in a sealed container, it is possible to prevent the binder aid from volatilizing and going out of the container, and these can be mixed sufficiently in the container. It becomes. As a result, the quality of the molding material is stabilized, and a sheet-like polarizable electrode can be manufactured more satisfactorily.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a manufacturing process for manufacturing an electrode sheet for an electric double layer capacitor. The raw materials used when manufacturing the polarizable electrode are activated carbon as the carbonaceous powder, carbon black as the conductive auxiliary agent, PTFE powder as the binder, and liquid IPA (isopropyl alcohol) as the auxiliary agent for the binder. The blending ratio of the raw materials is% by weight, 80% of activated carbon, 10% of carbon black, 10% of PTFE, and IPA of 10% of the same weight as PTFE.
[0018]
First, each raw material is weighed. Next, activated carbon and carbon black are put into a container of a mixer, and primary mixing is performed by mixing them with a rotating stirring blade. Thereby, activated carbon and carbon black are mixed as uniformly as possible.
Then, PTFE and IPA mixed beforehand to swell PTFE are put into the container of the mixer, and secondary mixing is performed by mixing this with the primary mixture. As a result, the activated carbon, carbon black, and PTFE are mixed, and the PTFE is fiberized to entangle the activated carbon and carbon black.
[0019]
Next, the secondarily mixed mixture is accommodated in a container of a kneader (kneader), and kneading is performed by rotating the blade while covering and pressurizing. By this kneading, the mixture is kneaded in a clay state, and PTFE is further fibrillated so that activated carbon and carbon black are entangled. At this time, the temperature of the container, lid, and blade of the kneader is controlled to be 90 ° C., for example.
Next, the kneaded material kneaded by the kneader is placed in a kneader container, and is chopped into fine particles by a rotating knurled blade. Next, the crushed grains are sieved and classified. The particle size is set to be 1.0 mm or less, for example. The grains thus obtained become a molding material.
[0020]
Next, in the calendar molding pretreatment step, the molding material is accommodated in the sealed container 2 of the mixer 1 as shown in FIG. 2 and the total weight of the raw materials (activated carbon, carbon black, and PTFE) is used. Add 70% IPA and mix them. The container 2 of the mixer 1 has a substantially cylindrical shape, is rotated in the circumferential direction by the roller 3, and is swung in the vertical direction together with the table 4. By mixing by the mixer 1, the granular molding material accommodated in the container 2 and the liquid IPA are mixed as much as possible.
[0021]
Next, in the calendar molding step, the mixture of molding materials mixed by the mixer 1 is put into a hopper of a calendar molding machine, and this mixture is passed between two rollers to be molded into a sheet shape. The formed sheet-like molded body is wound up by a winding roller. At this time, the thickness of the sheet-like molded body is set to 200 μm, for example.
[0022]
Next, in the roll rolling step, the sheet-like formed body is rolled through two rollers. By performing this roll rolling process a plurality of times, a sheet-like electrode having a predetermined thickness, for example, 160 μm is formed, and this sheet-like electrode becomes a polarizable electrode. In the final step of the roll rolling, both end portions in the width direction of the sheet electrode are cut with a cutter.
Here, the schematic diagram which expands and shows the surface of a sheet-like electrode is shown by FIG. In FIG. 3, it can be seen that activated carbon 5 and carbon black 6 smaller than this are entangled with PTFE 7 that forms a fiber.
[0023]
Next, in the laminating step, the rolled sheet-like electrode is bonded to an aluminum foil serving as a collector electrode. The bonded electrode sheet is wound around a winding roller.
Next, in the drying step, the electrode sheet wound up in a roll is fed out and passed through a drying chamber of a dryer to be dried. In the drying chamber, the remaining moisture and IPA contained in the sheet-like electrode are removed by the heating air from the heater. If necessary, vacuum drying can be performed.
[0024]
In the above-described embodiment, when the raw materials are mixed, the binder is easily fibrillated by preferentially swelling the PTFE by adding IPA as a binder aid to the PTFE serving as a binder in advance. Since the PTFE in this state is added to and mixed with the primary mixed activated carbon and carbon black, the raw materials are mixed well. For this reason, it becomes easy to perform subsequent processes such as kneading, scratching, forming and rolling, and the quality and strength of the sheet become stable.
[0025]
At this time, if the amount of IPA added is too small, PTFE is difficult to fiberize when the raw materials are mixed, and mixing and kneading cannot be performed satisfactorily. On the other hand, if the amount is too large, it is necessary to perform a drying process to remove the remaining IPA before molding. For this reason, it is preferable that the addition amount of IPA at the time of adding to PTFE at the time of mixing raw materials is 70 to 130% of the PTFE addition weight.
[0026]
In addition, since IPA is added separately when mixing raw materials and immediately before forming into a sheet (pre-calendering treatment), there is a case where IPA is added in a large amount at a time when mixing raw materials. On the other hand, the amount added at the time of mixing the raw materials may be a small amount that can at least swell PTFE, and there is no need to perform a drying process to remove IPA before molding. Furthermore, since IPA is added and mixed immediately before forming into a sheet shape, there is no need to consider that IPA evaporates in the middle, and the amount of IPA becomes stable and the quality is further improved. Stabilize.
[0027]
Here, in FIG. 4, the amount of IPA added (the ratio to the total weight of the raw material excluding IPA at the time of raw material mixing) of the second time (calender molding pretreatment) and the sheet-like molded body after the calendar molding are performed. Experimental results showing the relationship with density are shown. Note that the amount of IPA added for the first time (when the raw materials are mixed) is 10% of the same weight as PTFE. In FIG. 4, when the amount of IPA added is less than 50%, particularly 40%, the sheet density is small. Further, the sheet density is small even when the addition amount of IPA is 110%. The fact that the sheet density is low is considered to be because there is a nest (space part) inside the molded sheet-like molded body. In the case where there is a nest inside the sheet-like molded body, it tends to become a defect even after a subsequent process. In this case, the sheet density is drastically decreased when the addition amount of IPA is 100% to 110%, but it is considered that the sheet density is stable up to 100 wt%. From the result of FIG. 4, when the amount of IPA added in the calendering pretreatment is in the range of 50 to 100%, the sheet density is stable in a high state. Therefore, the amount of IPA added in the calendering pretreatment is The range of 50 to 100% is preferable.
[0028]
In addition, when IPA is added to the molding material and mixed, by mixing them in the sealed container 2 of the mixer 1, it is possible to prevent the IPA from volatilizing and going outside. Can be sufficiently mixed in the container 2, the quality of the molding material at the time of calendering can be stabilized, and a sheet-like polarizable electrode can be manufactured more satisfactorily.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a manufacturing process when manufacturing an electrode sheet for an electric double layer capacitor according to an embodiment of the present invention. FIG. 2 is a side view of a mixer. Schematic diagram of the surface [Fig. 4] Characteristic diagram showing the relationship between the amount of IPA added in the calendering pretreatment and the sheet density of the sheet-like molded product after calendering
1 is a mixer, 2 is a sealed container, 5 is activated carbon (carbonaceous powder), 6 is carbon black (conductive aid), and 7 is PTFE (binder).

Claims (6)

After creating a molding material through the process of mixing and kneading raw materials containing carbonaceous powder, conductive auxiliary agent and binder, this molding material is molded and rolled to produce a sheet-shaped polarizable electrode for an electric double layer capacitor A way to
When the raw materials are mixed, a binder auxiliary added to the binder in advance to swell the binder is mixed with the carbonaceous powder and the conductive auxiliary. Manufacturing method of polarizable electrode for electric double layer capacitor. After creating a molding material through the process of mixing and kneading raw materials containing carbonaceous powder, conductive auxiliary agent and binder, this molding material is molded and rolled to produce a sheet-shaped polarizable electrode for an electric double layer capacitor A way to
At the time of mixing the raw materials, a binder auxiliary added to the binder in advance to swell the binder is mixed with the carbonaceous powder and the conductive auxiliary, and the molding material is formed into a sheet form. A method for producing a polarizable electrode for an electric double layer capacitor, wherein a binder auxiliary is added to the molding material and mixed immediately before the molding. 3. The electric double layer according to claim 1, wherein an amount of the binder auxiliary agent added to the binder during mixing of the raw materials is in a range of 70 to 130% of the binder weight. A method for producing a polarizable electrode for a capacitor. The amount of the binder auxiliary agent added to the molding material is in the range of 50 to 100% of the total weight of the carbonaceous powder, the conductive auxiliary agent, and the binder. The manufacturing method of the polarizable electrode for electric double layer capacitors of description. The amount of the binder aid added to the binder during mixing of the raw materials is in the range of 70 to 130% of the binder weight, and further the binder aid added to the molding material. The method for producing a polarizable electrode for an electric double layer capacitor according to claim 2, wherein the addition amount is in the range of 50 to 100% of the total weight of the carbonaceous powder, the conductive auxiliary agent and the binder. The electricity according to any one of claims 2, 4 and 5, wherein the binder aid is added to and mixed with the molding material in a sealed container. Manufacturing method of polarizable electrode for double layer capacitor.

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