JP3811122B2 - Method for producing electrode sheet for electric double layer capacitor and laminating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To paste a sheet electrode on a conductive foil with a conductive adhesive agent so as to form a bonded electrode sheet which is reduced enough in contact resistance and improved enough in bonding strength. <P>SOLUTION: An aluminum foil 2 previously subjected to etching is fed from an aluminum foil feeder 1, and the conductive adhesive agent 3 is applied on the aluminum foil 2 through a gravure coater. On the other hand, material whose main component is active carbon is molded into the sheet electrode 5, and the sheet electrode 5 is fed from a sheet electrode feeder 6 pasted on the aluminum foil 2 at a pasting spot 7, and wound on a take-up 9. At this point, the gravure coater is used, so that the conductive adhesive agent 3 can be applied on the surface of the aluminum foil 2 so as to be uniform in thickness and thin enough. The state of the surface of the aluminum foil 2 where the adhesive agent is applied is continuously monitored through an application monitoring CCD camera 10, and the state of the pasted end of the sheet electrode 5 is continuously monitored by a pasting position monitoring CCD camera 11. <P>COPYRIGHT: (C)2004,JPO&amp;NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrode sheet manufacturing method for an electric double layer capacitor in which a sheet electrode is bonded to the surface of a long conductive foil via a conductive adhesive, and a laminating apparatus suitable for carrying out the manufacturing method.
[0002]
[Prior art]
An electric double layer capacitor (capacitor) has a large capacity and is excellent in charge / discharge cycle characteristics. Therefore, application to various devices such as various backup power sources including automobiles has been studied. This type of large-capacity electric double layer capacitor has a cylindrical type, which is a pair of positive and negative electrodes in which an aluminum foil (collector electrode) holds a carbonaceous sheet (polarizable electrode) mainly composed of activated carbon. A sheet wound in a coil shape with a separator in between is housed in a cylindrical case in an impregnated state with an electrolytic solution.
[0003]
In this case, in order to integrate the carbonaceous sheet (sheet-like electrode) and the aluminum foil (conductive foil), they are bonded (laminated) using a conductive adhesive (for example, patent document). 1). The reason for using the conductive adhesive is to reduce the contact resistance at the bonding interface between the sheet-like electrode and the conductive foil. When the contact resistance between the sheet-like electrode and the conductive foil is large, the internal resistance of the electric double layer capacitor is increased, leading to a decrease in performance.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-154630
[Problems to be solved by the invention]
By the way, in order to manufacture a large-capacity cylindrical electric double layer capacitor as described above, a continuous long electrode sheet is required, and the sheet-like electrode constituting the electrode sheet and the conductive foil are used. It is desirable that the contact resistance at the bonding interface be as small as possible and that sufficient bonding strength be obtained. At this time, the thickness of the conductive adhesive layer for bonding the sheet-shaped electrode and the conductive foil is thick, becomes large internal resistance, increased thickness packing density of the capacitor container is reduced as more whole End up. Moreover, when the thickness becomes non-uniform | heterogenous, adhesion will not be stabilized and sufficient joint strength will not be obtained.
[0006]
The present invention has been made in view of the above circumstances, and one object thereof is to bond a sheet-like electrode and a conductive foil with a conductive adhesive, and the contact resistance between the sheet-like electrode and the conductive foil is reduced. An object of the present invention is to provide a method for producing an electrode sheet for an electric double layer capacitor that can be made sufficiently small and that can secure a sufficient bonding strength. Another object is to provide a laminating apparatus suitable for carrying out the above manufacturing method.
[0007]
[Means for Solving the Problems]
In manufacturing a long electrode sheet for an electric double layer capacitor, the present inventors combined a research on material surface and the like with a laminating process in which a sheet-like electrode and a conductive foil are bonded with a conductive adhesive. Therefore, various trial manufactures and researches were conducted on how to reduce the contact resistance of the joint between the sheet-like electrode and the conductive foil and to secure the joint strength. As a result, an optimum laminating method using a conductive adhesive was finally developed, and the present invention was accomplished.
[0008]
That is, in the method for manufacturing an electrode sheet for an electric double layer capacitor according to claim 1 of the present invention, a laminating step of laminating a long sheet electrode to the surface of a long conductive foil via a conductive adhesive is performed. While applying the conductive adhesive to the surface of the conductive foil with a thickness of 10 μm or less using a coater, the sheet-like electrode is laminated, and in the laminating step, the conductive adhesive is The surface state of the applied conductive foil is characterized by being continuously monitored by an imaging device (the thickness of the application is measured by drying after application).
[0009]
According to this, the gravure coater has a concave portion engraved on the surface of the application roll in a mesh shape, and the conductive adhesive held on the surface is transferred to the surface of the conductive foil, and is applied. . In this case, the conductive adhesive is kept on the surface of the coating roll at a constant amount per unit area while being uniformly thin and sufficiently thin (thickness of 10 μm or less, more preferably 0.1 to 5 μm). It can be applied to the surface. In addition, the conductive particles in the conductive adhesive are transferred into the recesses of the coating roll, so that the conductive particles are applied evenly distributed on the surface of the conductive foil, and the electrical characteristics Even better.
[0010]
Therefore, according to the first aspect of the invention, the sheet-like electrode and the conductive foil are bonded together with the conductive adhesive, and the thickness of the adhesive layer can be made uniform and sufficiently thin. The contact resistance between the sheet-like electrode and the conductive foil can be sufficiently reduced, and an excellent effect that a sufficient bonding strength can be ensured can be obtained.
[0011]
At this time, aluminum foil or the like can be used as the conductive foil, but it is preferable to roughen the surface by performing an etching process or the like in advance on the bonded portion of the surface. The so-called anchor effect can further increase the bonding strength, and the conductive particles in the conductive adhesive (for example, fine particles of graphite or carbon black) can be fitted into the roughened holes. As a result, the electrical characteristics can be further improved (contact resistance can be reduced).
[0012]
Of the molding materials used for the production of the sheet-like electrode, as the carbonaceous powder, activated carbon is mainly used, but carbon nanotubes, fibrous carbon, and the like can also be used. As the conductive auxiliary agent, carbon black is mainly used, but fine particles of highly conductive metal can also be employed. As the binder, fluororesin powder such as polytetrafluoroethylene (hereinafter abbreviated as “PTFE”) can be used.
[0013]
In producing the above molding materials, it is desirable to mix and knead them in an appropriate composition, and further crush the kneaded product to granulate to have an appropriate particle size distribution. By adding and mixing the agent, it can be made suitable for preforming. As the binder aid at that time, alcohols such as isopropyl alcohol (hereinafter abbreviated as “IPA”), ethers, ketones and the like can be employed.
[0014]
In order to produce a long sheet-like electrode, a continuous plate-like sheet-like molded body is first formed from the above molding material, for example, by calendar roll molding, and then roll rolling is performed a plurality of times as necessary. A long sheet-like electrode having a desired thickness (for example, 160 μm) can be obtained. Moreover, by performing a slit process in the last process of roll rolling, the both-ends edge part of the rolled sheet-like electrode can be excised, and it can be set as predetermined width.
[0015]
By the way, in this invention, since a conductive adhesive is continuously applied very thinly to a conductive foil, there is a possibility that the conductive adhesive may be partially cut (application failure) or the like. Since pasting with an electrode is performed continuously, there is a situation where it is difficult to specify the position of application failure of the adhesive later. Therefore, in the above Symbol lamination step, the surface condition of the conductive foil conductive adhesive agent is applied, by continuously monitoring by the imaging device, for example, also partially broken of the adhesive it occurs, its location By storing, it becomes possible to perform an appropriate treatment after bonding.
[0016]
In the laminating apparatus according to claim 2 of the present invention, a long sheet-like electrode is bonded to the surface of a long conductive foil via a conductive adhesive to form an electrode sheet for an electric double layer capacitor. there are, Rutotomoni provided an adhesive applying means for applying at the surface to below 10μm thickness of the conductive foil of a conductive adhesive using gravure coater, the conductive adhesive of the surface state of the conductive foil is applied, It is characterized by providing monitoring means for continuously monitoring by the imaging device . According to this, as described above, since the thickness of the adhesive layer can be made uniform and sufficiently thin, the contact resistance between the sheet-like electrode and the conductive foil can be sufficiently reduced, Moreover, sufficient bonding strength can be ensured, which is suitable for carrying out the manufacturing method described above.
[0017]
And since the monitoring means for continuously monitoring the surface state of the conductive foil coated with the conductive adhesive by the imaging device is provided , even if the adhesive breaks partially, the position is memorized. By doing so, it becomes possible to perform an appropriate treatment after bonding.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 schematically shows the entire process of manufacturing an electrode sheet for an electric double layer capacitor in the present embodiment. In this embodiment, a long electrode sheet made of activated carbon as a main component is bonded to both sides of a long aluminum foil serving as a collecting electrode to produce a long electrode sheet, and the electrode sheet All processes are performed until the product is dried. This electrode sheet is used, for example, as a material for a large-capacity cylindrical electric double layer capacitor. In the present specification, what is a polarizable electrode of a cylindrical electric double layer capacitor is referred to as a sheet-like electrode, and what is bonded to an aluminum foil as a conductive foil is referred to as an electrode sheet for distinction.
[0019]
In order to manufacture an electrode sheet, as shown in FIG. 1, each of a metering step P1, a mixing step P2, a kneading step P3, a crushing step P4, a calendar forming step P5, a roll rolling step P6, a laminating step P7, and a drying step P8. The steps are executed in order. Hereinafter, the outline of each process will be described in order.
[0020]
First, in the measurement process P1, the raw material used for manufacturing the sheet-like electrode is measured. In the present embodiment, activated carbon as carbonaceous powder, fine powder of carbon black as a conductive auxiliary agent, and PTFE powder as a binder are used as raw materials. The blending ratio of these raw materials is% by weight, for example, 80% for activated carbon, 10% for carbon black, and 10% for PTFE. In this embodiment, IPA is used as a binder aid.
[0021]
In the mixing step P2, the activated carbon and the carbon black are mixed among the raw materials. In this mixing, the measured activated carbon and carbon black are put into the container of the mixer and rotated for a predetermined time, whereby the fine powdery carbon black is uniformly dispersed between the activated carbon particles. Further, PTFE and IPA are added and mixed by rotating. Thereby, the activated carbon and the carbon black are further uniformly mixed, and the fine powder of the carbon black is uniformly dispersed among the particles of the activated carbon particles, and the PTFE is fibrillated to entangle the activated carbon and the carbon black.
[0022]
In the kneading step P3, the mixture that has undergone the mixing step P2 is kneaded. In this step, the mixture is placed in a container of a kneader (kneader), covered with a blade, and pressed with a blade. This is done by rotating. At this time, the temperature of the container, lid and blade of the kneader is controlled so as to maintain, for example, about 90 ° C. In addition, the hardness of the kneaded product is managed. As a result, the PTFE is further fibrillated so that the activated carbon and the carbon black are entangled, and the kneaded material is like a lump of rubber.
[0023]
In the crushing step P4, the kneaded material kneaded in the kneading step P3 is chopped into fine particles (granulated powder). This step is performed by storing the kneaded material in a container of a scratching machine and rotating a scratching blade.
[0024]
In the calendar molding step P5, a sheet-shaped molded body having a long sheet shape is preformed from the molding material obtained from the granulated powder. This step is performed by putting a molding material into a hopper of a calendar molding machine, forming the molding material discharged from the outlet portion of the hopper into a continuous plate shape with two calendar rolls, and winding it with a winding roll. The thickness dimension of the sheet-like molded body obtained at this time is, for example, 200 μm.
[0025]
In the roll rolling step P6, the sheet-like formed body is continuously rolled by a roll rolling apparatus to produce a long sheet-like electrode having a predetermined thickness (for example, 160 μm). This step is performed by rolling the sheet-like molded body through two rolling rolls while feeding it from the feeding portion, and winding it at the winding portion.
[0026]
At this time, although not shown in the drawing, a tension controller is provided in the feeding portion, and the tension of the fed sheet-like molded body is controlled to a constant value, and the fed sheet-like molded body is adjusted by the edge position controller. It is supplied to the rolling roll in a state where the position in the width direction is controlled. Further, the winding unit performs winding by so-called touch winding so that the sheet-like electrode is wound at a constant speed (tension).
[0027]
This roll rolling process is repeated a plurality of times (2 to 3 times) to obtain a desired thickness dimension. In the final process, although not shown, the cutting blade is wound up. The secondary slit process of cutting off both edge portions of the sheet-like electrode so as to be pressed against the driving roll on the side is also performed, so that the sheet-like electrode has a predetermined width and the thickness is not uniform and cracks. Both edges where cracks are likely to occur are removed.
[0028]
In the next laminating step P7, the sheet-like electrode 5 is bonded to the aluminum foil 2 as the conductive foil with the conductive adhesive 3 by using the laminating apparatus according to this embodiment, and the electrode sheet 8 is attached. Forming is done. In this case, the sheet-like electrode 5 is bonded twice to each side of the aluminum foil 2. Details of the laminating step P7 and laminating apparatus will be described later.
[0029]
In the next drying step P8, the electrode sheet wound up in a roll is fed out and dried through a drying chamber of a dryer. At this time, heating air is supplied to the drying chamber by a heater, and most of the solvent contained in the conductive adhesive 3, the IPA contained in the sheet-like electrode 5, and moisture are contained. Is removed. If necessary, vacuum drying can also be performed.
[0030]
Here, the laminating process P7 and the laminating apparatus will be described with reference to FIGS.
FIG. 2 shows a schematic configuration of the laminating apparatus according to the present embodiment. The laminating apparatus includes an aluminum foil feeding unit 1 for feeding the aluminum foil 2, a gravure coater for applying the conductive adhesive 3 to the surface of the aluminum foil 2, a sheet-like electrode feeding unit 6 for feeding the sheet-like electrode 5, A laminating unit 7 for laminating the aluminum foil 2 and the sheet-like electrode 5, a winding unit 9 for winding the laminated electrode sheet 8, a CCD camera 10 for monitoring the application state as an imaging device constituting the monitoring means, the aluminum foil 2 And a bonding position monitoring CCD camera 11 for monitoring the bonding state of the sheet-like electrode 5 with respect to.
[0031]
In the aluminum foil feeding portion 1, a long aluminum foil 2 wound in a roll shape is set so as to be rotatable (in the direction of arrow A) and fed out, and is not shown in detail. However, there are provided a tension controller for adjusting the tension of the fed aluminum foil 2 to a set value, and an edge position controller for controlling the width direction position of the fed aluminum foil 2 to prevent meandering. ing.
[0032]
At this time, the aluminum foil 2 has, for example, a thickness dimension of 50 μm and a width dimension of 120 mm. In this embodiment, the surface (both sides) is pre-etched and has an infinite number of fine holes. A processing surface 2a (see FIG. 4) is formed.
[0033]
The aluminum foil 2 fed out from the aluminum foil feeding portion 1 reaches a gravure coater described later, where a conductive adhesive 3 is applied to the surface and sent to the laminating portion 7. On the other hand, the sheet-like electrode feeding portion 6 is configured such that a long sheet-like electrode 5 wound in a roll shape is set so as to be rotatable (in the direction of arrow B) and fed. A tension controller (not shown) for adjusting the tension of the sheet-like electrode 5 and an edge position controller for controlling the position in the width direction to prevent meandering are provided.
[0034]
The laminating portion 7 includes a drive roll 12 that is rotationally driven at a constant speed in the direction of arrow D in FIG. 2 and a pressure-bonding roll 13 to which a pressing force in the direction of arrow E is applied. The aluminum foil 2 coated with the conductive adhesive 3 and the sheet-like electrode 5 fed from the sheet-like electrode feeding portion 6 pass between the drive roll 12 and the pressure-bonding roll 13 in an overlapping state. And by being pinched | interposed between them and receiving compression force, it is bonded together and it is set as the electrode sheet 8. FIG.
[0035]
The gravure coater includes an application roll (gravure roll) 4 for applying the conductive adhesive 3 to the aluminum foil 2, a driving mechanism (not shown) for rotating the application roll 4 in the direction of arrow C, and the conductive A pan 14 in which the adhesive 3 is accommodated, a blade 15 for scraping off an excess of the conductive adhesive 3 held on the coating roll 4, and a space between the coating roll 4 and the coating roll 4. And a pinch roll 16 sandwiching the aluminum foil 2 and the like.
[0036]
Of these, as shown in FIG. 3, the coating roll 4 has a predetermined width region at the center as a sculpture portion 4 a in which a large number of quadrangular pyramid recesses are formed in a mesh shape. The coating roll 4 is continuously rotated at a constant speed in the direction of arrow C with its lower end immersed in the conductive adhesive 3 in the pan 14, whereby the conductive adhesive 3 is transferred to the engraving portion 4 a. The conductive adhesive 3 is transferred onto the surface of the aluminum foil 2 at a portion sandwiched between the pinch rolls 16 while being held at a constant amount per unit area, and is thus applied. The application of the conductive adhesive 3 is performed only on the etched surface 2a of the aluminum foil 2.
[0037]
And in this embodiment, immediately after application | coating of the conductive adhesive 3 (before reaching the bonding part 7), the state of the adhesive application surface of the aluminum foil 2 is continuously measured by the CCD camera 10 for application state monitoring. Filmed and monitored. Although not shown, the captured image data of the CCD camera 10 is input to an image processing apparatus (monitoring apparatus) mainly composed of a microcomputer and the like, and the presence or absence of coating failure is determined. In this case, if the ratio of the area area to which the conductive adhesive 3 is applied is equal to or less than the threshold value, it is determined that the application is defective, and the position where the application failure occurs (for example, how many meters from the tip of the aluminum foil 2) ) Or the occurrence time (the position where the defect occurs can be specified by back calculation) is stored.
[0038]
Furthermore, in this embodiment, immediately before the bonded electrode sheet 8 is wound up by the winding unit 9, the bonded end state of the sheet-like electrode 5 is continuously maintained by the bonding position monitoring CCD camera 11. Are being photographed and monitored. Thereby, the quality of the bonding position of the sheet-like electrode 5 with respect to the aluminum foil 2 is also monitored, and the position where the defect occurs is stored.
[0039]
Now, in the laminating process P7 executed using the laminating apparatus having the above configuration, the aluminum foil 2 fed from the aluminum foil feeding unit 1 is applied to its surface (etching surface 2a) by the gravure coater (coating roll 4). The conductive adhesive 3 is applied, and the sheet-like electrode 5 fed from the sheet-like electrode feeding portion 6 and the laminating portion 7 are pasted together, and the winding portion 9 continuously takes up. Thereby, the electrode sheet 8 for a long electric double layer capacitor can be obtained.
[0040]
At this time, since the conductive adhesive 3 was applied by the application roll 4 having the engraving portion 4a using a gravure coater, the conductive adhesive 3 was uniformly and sufficiently applied to the surface of the aluminum foil 2. Can be applied thinly. In this case, the conductive adhesive 3 can be uniformly applied with a predetermined value in the range of 10 μm or less (in this embodiment, for example, a thickness of 2.5 μm). In addition, the conductive fine particles in the conductive adhesive 3 are transferred into the engraving portion 4a (recessed portion) of the coating roll 4 so that the conductive fine particles are evenly distributed on the surface of the aluminum foil 2. In addition to being applied to the state and being able to make the layer of the conductive adhesive 3 thin, the electrical characteristics are also excellent.
[0041]
In addition, at this time, since the surface of the aluminum foil 2 is previously set as the etching treatment surface 2, a so-called anchor effect of the adhesive 3 is obtained, and the bonding strength between the aluminum foil 2 and the sheet-like electrode 5 is further increased. Can be increased. At the same time, the conductive fine particles (carbon black fine particles) in the conductive adhesive 3 are fitted into the holes of the etching treated surface 2a, thereby further improving the electrical characteristics (reducing contact resistance). Will be able to.
[0042]
By the way, in the gravure coater part, the conductive adhesive 3 is continuously applied to the long aluminum foil 2 very thinly, so that the conductive adhesive 3 is partially cut (application failure), etc. Since there is a risk of the occurrence of the occurrence of such a problem and the pasting with the sheet-like electrode 5 is continuously performed, there is a situation in which it is difficult to specify a position where the adhesive 3 is poorly applied later. Moreover, even if the positional deviation in the width direction of the sheet-like electrode 5 bonded to the aluminum foil 2 occurs, the electrode sheet 8 is continuously wound, so that it is difficult to specify the position later.
[0043]
However, in this embodiment, the state of the adhesive application surface of the aluminum foil 2 is continuously monitored by the CCD camera 10 for application state monitoring. Since the occurrence position is stored, it is possible to perform an appropriate treatment after bonding. Moreover, since the state of the bonding edge of the sheet-like electrode 5 is continuously monitored by the bonding position monitoring CCD camera 11, even if there is a defect in the bonding position, an appropriate measure is taken after the bonding. It becomes possible.
[0044]
Thus, according to the present embodiment, the sheet-like electrode 5 and the aluminum foil 2 are bonded together by the conductive adhesive 3 to produce a long electrode sheet 8 for an electric double layer capacitor. The excellent effect that the contact resistance between the sheet-like electrode 5 and the aluminum foil 2 can be made sufficiently small and sufficient bonding strength can be secured can be obtained. Moreover, the laminating apparatus of this embodiment becomes a thing suitable for implementing the said manufacturing method.
[0045]
In the above embodiment, both the coating state monitoring CCD camera 10 and the bonding position monitoring CCD camera 11 are provided. However, these monitoring may be performed as necessary, and only one of them is provided. You may do it. The imaging device is not limited to a CCD camera. Moreover, as a structure of a laminating apparatus, for example, a sheet-like electrode can be bonded to both sides of an aluminum foil at a time.
[0046]
In addition, as the conductive foil, various metal foils can be adopted without being limited to aluminum foil, and various types of materials, combinations and combinations thereof can be used as the molding material for the sheet-like electrode. The dimensions are just an example. Furthermore, in the above-described embodiment, each process is merely an example, and the present invention can be implemented with appropriate modifications within a range not departing from the gist, such as omission and modification. is there.
[Brief description of the drawings]
FIG. 1 shows an embodiment of the present invention, and schematically shows the entire manufacturing process of an electrode sheet. FIG. 2 is a front view schematically showing the configuration of a laminating apparatus. FIG. [Fig.4] Cross-sectional view of etched surface of aluminum foil [Explanation of symbols]
In the drawings, 1 is an aluminum foil feeding portion, 2 is an aluminum foil, 2a is an etching treatment surface, 3 is a conductive adhesive, 4 is a coating roll, 4a is an engraving portion, 5 is a sheet electrode, and 6 is a sheet electrode feed. , 7 is a bonding unit, 8 is an electrode sheet, 9 is a winding unit, 10 is a coating state monitoring CCD camera (imaging device, monitoring means), and 11 is a bonding position monitoring CCD camera.

Claims (2)

A long sheet-like electrode having a predetermined thickness is manufactured from a molding material containing carbonaceous powder, a conductive auxiliary agent and a binder, and then the sheet-like electrode is placed on the surface of the long conductive foil via a conductive adhesive. A method for producing an electrode sheet for an electric double layer capacitor, wherein a laminating step is performed by using a gravure coater to apply the conductive adhesive to a surface of the conductive foil to a thickness of 10 μm or less. While being applied, while being performed by pasting the sheet-like electrode ,
In this laminating step, the surface state of the conductive foil coated with the conductive adhesive is continuously monitored by an imaging device, and the method for producing an electrode sheet for an electric double layer capacitor is characterized in that A sheet-like electrode formed into a long sheet of a predetermined thickness from a molding material containing carbonaceous powder, a conductive auxiliary agent and a binder is bonded to the surface of a long conductive foil via a conductive adhesive. A laminating device as an electrode sheet for an electric double layer capacitor,
An adhesive application means for applying the conductive adhesive to the surface of the conductive foil with a thickness of 10 μm or less using a gravure coater;
A laminating apparatus comprising: monitoring means for continuously monitoring a surface state of the conductive foil coated with the conductive adhesive by an imaging apparatus.

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