JP2008124193A - Electric double-layer capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem wherein poor ESR and poor product dimension, which are caused by a position gap between an enveloping film and a terminal board or a laminated cell, occur usually in an assembly process, a terminal board/laminated cell/terminal board and the enveloping film are put into a state wherein they are set free from each other because the terminal board/laminated cell/terminal board is configured so as to be wrapped up with the enveloping film in a product manufacturing process, and the assembly is mounted with a position gap between the enveloping film and the terminal board/laminated cell/terminal board in an enveloping film sealing process as a post process. <P>SOLUTION: The terminal board 7a and enveloping film 8 are joined together so as to prevent a position gap from occurring among the laminated cell, terminal board 7a and enveloping film 8, and a current collector can be brought into close contact with the terminal board 7a containing a conductive layer, so that poor ESR and poor product dimensions related to the length of lead terminals and a lead pitch can be reduced, and a quality and uniform electric double-layer capacitor can be obtained. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electric double layer capacitor, in particular, a porous body for an electrode, a porous insulator for a separator, an electrode and a separator laminated without being wound, and an electric double layer capacitor using an electrolyte and It relates to the manufacturing method.

  In recent years, in portable electronic devices such as mobile phones, low current and low voltage have been achieved. However, depending on the function, a very large current may be required instantaneously. As a result of voltage fluctuations (IR drop or the like) in the power source, the electronic circuit may not operate normally, and the battery life may be shortened.

  For example, in a communication card or the like, if the operating voltage falls below the lower limit value, the communication state cannot be secured and a communication error occurs. For this reason, only when instantaneously a large current is required, power is supplied from an electric double layer capacitor capable of rapid charging and discharging of a large current to level the entire power. Furthermore, along with the downsizing and thinning of electronic devices such as portable music players equipped with digital cameras and hard disk drives (HDDs), there is a need for longer use time and smaller power supplies, which are equivalent to thicknesses of 2.0 mm or less. There is also a demand for an electric double layer capacitor having a series resistance (hereinafter referred to as ESR) of 300 mΩ or less.

  FIG. 3 is a sectional view of a unit cell of the electric double layer capacitor, and FIG. 4 is a sectional view of the electric double layer capacitor. As shown in FIG. 3, the unit cell 5 of the electric double layer capacitor has a pair of flat electrodes 1 disposed on both sides of the separator 2, and a current collector 3 disposed on the opposite side of the separator 2 of the electrode 1, A frame-like gasket 4 interposed between the electrode 1 and the separator 2 is interposed between the current collectors 3 and sealed in a state in which an electrolytic solution is contained therein. As shown in FIG. 4, the electric double layer capacitor is provided with terminal plates 7a and 7b for taking out terminals via the conductive bonding layer 6 on the upper and lower sides of the unit cells 5 stacked, and more usually, the terminal plates 7a and 7b It is sealed from the outside with an exterior film 8 such as a laminate film.

  Conventionally, in order to improve ESR, Patent Document 1 specifies the difference in hardness of the elastomer of the raw material used for the current collector and the conductive bonding layer, and the surface between the current collector and the conductive bonding layer is well blended. Proposals have been made to establish a connected state. Patent Document 2 proposes to integrate the interface between the conductive bonding layer and the gasket by thermal fusion. However, in the production process of the electric double layer capacitor according to the prior art, the terminal plate / laminated unit cell / terminal plate is sealed with an exterior film. However, the terminal plate, the laminated unit cell, the terminal plate and the exterior film Since the positioning is not performed, each of them is in a free state, and when the exterior film is sealed in the subsequent process, the cells are lifted up or misaligned, and due to the misalignment between the exterior film, the terminal board, and the laminated unit cell that occurs in the assembly process. There was a problem that ESR failure and product dimensional failure would occur. Further, as the size and thickness are reduced, the shape of the laminated cell and peripheral parts becomes smaller. Therefore, even in the electric double layer capacitor, high quality is required for assembly accuracy.

JP 2003-224040 A Japanese Patent Laid-Open No. 2004-235283

  Under such circumstances, an object of the present invention is to provide an electric double layer capacitor with high quality and less variation such as ESR failure and product dimension failure.

  In order to solve the above problems, the present invention has been found that the assembly accuracy is improved by previously joining the terminal board and the exterior film.

  The electric double layer capacitor of the present invention includes a pair of electrodes disposed opposite to each other with a separator, a pair of current collectors disposed on the opposite side of the pair of electrodes from the separator, and the current collector together with the separator. And an electric double layer capacitor in which at least one unit cell having a frame-shaped gasket for sealing the electrode around is laminated, a terminal plate is disposed on the outermost layer via a conductive bonding layer, and is sheathed with an exterior film Further, at least a part of the surface of the main body portion of the terminal board opposite to the conductive bonding layer and the exterior film are joined before joining at an outer edge portion of the exterior films.

  In the electric double layer capacitor of the present invention, it is preferable that the exterior film has an ionomer film layer, and the terminal board and the exterior film are joined by heat fusion.

  According to the present invention, by joining the exterior film and the terminal plate with an ionomer that preferably has an outermost layer of the exterior film, the unit cell, the terminal plate, and the exterior film are prevented from being displaced, Can prevent boarding and displacement of the terminal board, and can easily maintain the adhesion between the current collector and the terminal board including the conductive bonding layer, thus preventing ESR defects and product dimension defects related to lead terminal length and lead pitch. Therefore, a high-quality electric double layer capacitor can be provided.

  Next, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 3, the unit cell used in the present invention is composed of an electrode 1, a separator 2, a current collector 3, and a gasket 4. The electrode 1 ensures activated carbon represented by a coconut shell system and conductivity. Made of carbon and binder. The separator 2 is a porous film, and a polytetrafluoroethylene film or a polyolefin film is used. The outer dimension of the separator 2 is not less than the outer dimension of the electrode 1 and not more than the outer dimension of the current collector 3. The current collector 3 is made of conductive rubber. The gasket 4 is a thing for ensuring the insulation in a cell, and uses the thermoplastic resin or the rubber | gum or resin which can be adhere | attached with a thermoplastic resin. Here, the gasket is disposed on the outer periphery of the electrode 1, the separator 2, and the current collector 3.

  As shown in FIG. 4, the electric double layer capacitor of the present invention has a plurality of unit cells 5 composed of electrodes, separators, current collectors, and gaskets, which are stacked in accordance with a predetermined operating voltage, and take out electric charges inside the cells. A metal foil and a polyolefin-based material in which terminal plates 7a and 7b made of a metal such as copper are arranged on the upper and lower end surfaces through a conductive bonding layer 6 made of a conductive paste to which a conductive material such as silver or copper and a binder are added. It is configured by being sealed with an exterior film 8 made of a laminate film or the like bonded with a film. Here, in the terminal plates 7a and 7b, a lead tab portion is formed in a rectangular portion that comes into contact with the cell, and the conductive bonding layer 6 is provided in advance on one side of the rectangular portion, and the outermost layer of the exterior film 8 on the opposite side. It joins with the ionomer layer which is these by heat sealing | fusion etc. Thereafter, the current collectors of the stacked unit cells 5 and the conductive bonding layer 6 provided on the terminal plates 7a and 7b are arranged so as to overlap, and the overlapping portions of the exterior films 8 are heat-sealed, thereby the terminal plate 7a. 7b and the unit cell 5 are formed as an electric double layer capacitor. Also, polypropylene can be used as an alternative to the ionomer in the outermost layer of the exterior film 8.

  Next, the present invention will be specifically described with reference to some examples and comparative examples.

As shown in FIG. 3, two sheets were prepared by bonding the current collector 3 and the gaskets 4a and 4c by thermocompression bonding. A slurry is formed in which a powdered coconut shell activated carbon having an average particle diameter of 15 μm, non-spherical carbon having an average particle diameter of 15 μm, fibrous carbon having a fiber diameter of 10 to 20 μm, and a binder are formed at a weight ratio of 75: 10: 10: 5. The electrode 1 was formed by applying and drying this on a current collector inside the gasket. In this way, two current collectors 3 to which the electrode 1 was applied were produced, and then a gasket 4b was bonded to one of them by thermocompression bonding. Next, a 40 wt% aqueous sulfuric acid solution was added onto the electrode 1. A portion of the separator 2 other than the portion in contact with the electrode 1 was subjected to pressure pretreatment for 1 second at 25 ° C. and 5 kg / cm ² . After this separator 2 was placed on one of the sheets added with sulfuric acid, the two sheets were bonded so that the current collector was on the outside, and the gasket was melted and bonded by thermocompression bonding.

  FIG. 1 is a front view for explaining a process of joining a terminal plate on the bottom surface side of an electric double layer capacitor according to a first embodiment of the present invention. FIG. 1 (a) shows a case where the joint area ratio is 5%. ) Shows the case of 20%, and FIG. 1C shows the case of 100%.

  As shown in FIG. 4, six unit cells produced as described above were stacked to prepare a laminated cell having a size of 13.5 × 32 × 0.87 mm. Next, a 0.1 mm thick copper terminal plate 7a having a conductive bonding layer 6 made of silver paste is applied to an outer film 8 having an ionomer as an outermost layer as shown in FIG. Heat fusion was performed under the condition of a fusion pressure of 0.40 MPa. At this time, heat bonding was performed by changing the bonding area ratio to 5% (FIG. 1A), 20% (FIG. 1B), and 100% (FIG. 1C). In addition, the junction part 10 corresponds to the back surface of the terminal plate 7a on the bottom surface side in FIGS. 1 (a), 1 (b), and 1 (c). After that, the laminated cell prepared on the terminal board 7a on the bottom surface side and the terminal board on the upper surface side are arranged in a superimposed state, the exterior film 8 is folded back, the exterior films 8 are overlapped around each other, and the exterior is applied under reduced pressure. By heat-sealing the overlapping portions of the films, an outer film sealing body of the terminal plate and the laminated cell was formed. Here, a laminate film having a thickness of 0.11 mm was used as the exterior film 8. 1000 electric double layer capacitors were produced by the above method. The area of the terminal board and exterior film joined by thermal fusion is defined as follows. Bonding area ratio = (Area of terminal board bonded to exterior film) / (Total area of terminal board bottom face)

  FIG. 2 is a front view for explaining a process of joining the terminal plates on the upper surface side and the bottom surface side of Example 2 of the electric double layer capacitor of the present invention. FIG. 2 (b) shows the case of 20%, and FIG. 2 (c) shows the case of 100%.

  Six unit cells produced in the same manner as in Example 1 were stacked to prepare a stacked cell. Next, a 0.1 mm thick copper bottom terminal plate 7a and a top surface terminal plate 7b, each having a conductive bonding layer made of silver paste, are thermally fused to the exterior film 8 as shown in FIG. Bonding was performed at a bonding area ratio of 5% (FIG. 2A), 20% (FIG. 2B), and 100% (FIG. 2C). The conditions for heat sealing were the same as in Example 1. Thereafter, the exterior film 8 was folded back and the exterior films 8 were stacked around each other, and 1000 electric double layer capacitors were produced in the same manner as in Example 1.

(Comparative example)
Except for not joining the terminal plates 7a and 7b and the exterior film 8, 1000 electric double layer capacitors were produced using the same material as in Example 1.

  With respect to the electric double layer capacitors of Examples 1 and 2 and Comparative Example manufactured as described above, immediately after the sample was prepared and subjected to load for 1,000 hours at 70 ° C., 5.4 V (0.9 V per cell), to room temperature After cooling, ESR was measured. Here, ESR was obtained by applying an alternating voltage of 1 kHz, 10 mVrms and measuring the current and phase difference, and 160 mΩ or more was regarded as ESR failure. In addition, the product dimensions were measured, and a product having a dimensional tolerance of ± 0.5 mm or more was regarded as a product dimension defect, and Table 1 shows the ratio between the ESR defect and the product dimension defect.

  Comparing the ESR failure shown in Table 1 with the product dimension failure, it can be seen that Example 1 is lower than the comparative example. This is because when the laminated cell and the terminal plate in which the exterior film and the terminal plate are not fixed as in the comparative example are set at predetermined positions of the exterior film, the laminated cell tends to ride on the terminal plate. Further, when sealing the exterior film, there was a tendency that the terminal plate / laminated cell / terminal plate shifted from a predetermined position. It can be seen that climbing of the terminal board causes an ESR defect, and the positional deviation of the terminal board / laminated cell / terminal board causes a product dimension defect.

  In Example 1, by bonding the exterior film and the terminal board on the bottom side of the product, the above-described ESR failure due to the terminal board climbing and the product dimension failure due to the positional deviation of the terminal board / laminated cell / terminal board can be reduced. I was able to. It can be seen that the defective rate is further reduced by bonding the entire area of the bonding area ratio from 5% to 100%. This is because, when the bonding area ratio is low, the outer film and the terminal plate are unbonded during the operation.

  In Example 2, the terminal board and the exterior film are bonded not only to the bottom surface side but also to the top surface side of the product, so that it is possible to further reduce the rise and displacement of the terminal board on the top surface side. It turns out that it is hard to generate. Further, as in Example 1, the higher the bonding area ratio, the lower the ESR defect and the product dimension defect.

  From Examples 1 and 2, the ESR defect and the product dimension defect are set to these conditions because the conditions in which the exterior film on the product upper surface side and the product bottom surface side of Example 2 are fully bonded to the terminal board show the best results. It can be said that a greater effect can be obtained.

  The embodiment of the present invention has been described in detail with reference to the drawings. Needless to say, the specific configuration is not limited to this embodiment, and the design of the present invention is not limited to the scope of the present invention. Any changes or the like are included in the present invention.

FIG. 1A is a front view for explaining a bonding process of a terminal plate on the bottom surface side of Embodiment 1 of an electric double layer capacitor of the present invention, FIG. 1A is a case where the bonding area ratio is 5%, and FIG. FIG. 1C is a front view in the case of 100%. FIG. 2A is a front view for explaining a process of joining the terminal plates on the upper surface side and the bottom surface side of Example 2 of the electric double layer capacitor of the present invention, FIG. 2A shows a case where the joining area ratio is 5%, and FIG. In the case of 20%, FIG. 2 (c) is a front view in the case of 100%. Sectional drawing of the unit cell of an electric double layer capacitor. Sectional drawing of an electric double layer capacitor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrode 2 Separator 3 Current collector 4,4a, 4b, 4c Gasket 5 Unit cell 6 Conductive joining layer 7a (bottom side) terminal board 7b (top side) terminal board 8 exterior film 9 electric double layer capacitor 10 junction

Claims (2)

  A pair of electrodes disposed opposite to each other with a separator interposed therebetween, a pair of current collectors disposed on the opposite side of the pair of electrodes from the separator, and the separator and the electrodes are sealed together with the current collector. In an electric double layer capacitor in which at least one unit cell having a frame-shaped gasket is laminated, a terminal plate is disposed on the outermost layer via a conductive bonding layer, and is packaged with an exterior film, the body portion of the terminal plate An electric double layer capacitor, wherein at least a part of a surface opposite to the conductive bonding layer and the outer film are bonded before bonding at an outer edge portion of the outer films.   2. The electric double layer capacitor according to claim 1, wherein the exterior film has an ionomer film layer, and the terminal board and the exterior film are joined by heat fusion.

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