JP2002158146A - Electric double-layer capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric double-layer capacitor with improved productivity and reliability under high temperature conditions. SOLUTION: Each of cells 61a, 61b has a pair of polarized electrodes opposed to each other with a separator, a frame-shaped gasket for receiving the pair of polarized electrodes, and a pair of current collectors that are in contact with outside surfaces of the polarized electrodes and is bonded to both end surfaces of the gasket to seal the gasket. The cells are laminated to constitute a cell laminated body 71. The current collector 20b on the cell connection surface also serves as the collector of the cells 61a, 61b. The side edges of the current collectors 20a, 20b are received in stepped portions made inside the upper end surfaces of the gaskets 52a, 52b, and gaskets 51, 53 are bonded on both sides of the cells, to both end surfaces of the current collectors 20a, 20b and the gaskets 52a, 52b. The arrangement structure of these current collectors and gaskets improves the reliability of the electric double-layer capacitor under high temperature conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric double layer capacitor, and more particularly to a large capacity electric double layer capacitor using solid polarizable electrodes.

[0002]

2. Description of the Related Art An electric double layer capacitor according to a conventional example 1 will be described with reference to FIGS.

Referring to FIG. 7, a cell laminate 171 of an electric double layer capacitor according to Conventional Example 1 has a frame-like gasket 1.
51, a cell 161 including a pair of polarizable electrodes 110 housed therein and separated by a separator 140, and a current collector 121 adhered to the upper end of a gasket 151. . An electrolyte solution 130 is sealed inside the cell 161. Polarizing electrode 110
It is in contact with the current collector 121. The end face of the gasket 151 is flat as shown in FIG.

[0004] The polarizable electrode 110 is disclosed in Japanese Patent Laid-Open No. 4-288.
No. 361 discloses a solid activated carbon containing an activated carbon / polyacene-based material or the like as a main component. The current collector 121 is made of rubber or plastic containing conductive carbon.

In the electric double layer capacitor, since the withstand voltage is limited by the electrolysis voltage of the electrolyte solution 130, the cells 161 are connected in series according to the required withstand voltage. Further, as shown in FIG. 9, by sandwiching both sides of the cell stack 171 with the pressing plate 190, pressure is applied between the cells and between the terminal electrodes 180, and the current collector 121 and the polarizable electrode 11 are pressed.
The contact resistance with zero has been reduced.

In recent years, such an electric double layer capacitor has been increased in capacity by using an improved polarizable electrode, and has an equivalent series resistance (hereinafter referred to as ESR; eq).
New applications have been found by lowering uivalent series resistance). As an example,
There are uses of a power supply for driving an automobile start motor in combination with a lead storage battery, and uses as an auxiliary power supply in combination with a solar cell.

When an electric double layer capacitor is used for these applications, the electric double layer capacitor is likely to be installed in a high temperature environment, and the electric double layer capacitor has a high reliability under such an environment. Is required.

[0008]

However, the electric double layer capacitor of the prior art 1 has the following problems. (1) In the cell laminate 171, the electrolyte solution 130 inside the cell 161 is sealed by bonding the gasket 151 and the current collector 121, which are made of different materials. Under a high temperature, the electrolyte solution 130 thermally expands. In addition, gas is generated inside the cell by application of a large voltage or high temperature. As shown in FIG. 7, the outer peripheral side end surface of the current collector 121 has a structure exposed to the side surface of the cell stack 171. Due to such a structure, the gasket 151 and the current collector 12 are formed by thermal expansion and gas generation of the electrolyte solution inside the cell.
A gap is formed between the cell and the electrolyte solution 130, and the electrolyte solution 130 inside the cell easily leaks out from the gap. (2) In order to improve the electrical contact between the polarizable electrode 110 and the current collector 121, the cell laminate 171 is formed of a highly rigid metal plate that is hardly deformed from the outside of the outermost current collector 121 (see FIG. 9 (see the pressure plate 190). Also, among the constituent materials of the electric double layer capacitor, the polarizable electrode 110 uses a hard and rigid member such as a sintered body of activated carbon, and the gasket 151 uses a hard material such as ABS resin to improve the dimensional accuracy of the product. Materials are often used. Since the current collector 121 is made of a thin and elastic conductive rubber or the like, a displacement occurs when pressure is applied to the current collector 121. As a result, a strong force is locally applied to the current collector 121 and the current collector 1
Cracks tend to occur in 21.

A technique for solving the above problem is disclosed in Japanese Patent Application Laid-Open No. 8-7.
No. 8291 (conventional example 2), Japanese Utility Model Application Laid-Open No. 61-11723.
No. 8 (conventional 3) and Japanese Utility Model Laid-Open No. 5-46026 (conventional example 4).

In the electric double layer capacitor of the prior art 2, as shown in FIG. 10, the outer diameter of the current collector 122 inside the cell 162 of the cell stack 172 is smaller than the outer diameter of the outermost current collector 121. That is, by setting the outer diameter of the current collector 122 inside the cell to a value intermediate between the inner diameter and the outer diameter of the gasket 152,
As shown in FIG. 11, the periphery of the current collector 122 is
A concave portion 153 is provided on the inner peripheral surface of the base 52, and the current collector 122 is housed in the concave portion 153.

In the electric double layer capacitor of the prior art example 3, as shown in FIG. 12, a step 58 is provided on the inner wall side of both end faces of the gasket 154, and the current collector 123 is housed in the step 58 to constitute a cell. are doing. A plurality of these cells are stacked to form a cell stack.

Further, in the electric double layer capacitor of the conventional example 4, as shown in FIG.
A concave portion is formed over the entire periphery of the upper and lower frames of the third gasket 155. A convex portion is formed at a position of the current collector 124 corresponding to the concave portion, and the concave portion and the convex portion are fitted. FIG. 14 is a schematic view of the gasket 155, and reference numeral 156 indicates a concave portion formed over the entire circumference of the upper and lower surfaces of the gasket 155.

In the electric double layer capacitors of the above-mentioned conventional examples 2 to 4, the sealing strength between the cells is increased to prevent the electrolyte solution from leaking due to cracking or peeling.

However, the above conventional examples 2 to 4
The capacitor described above has a problem that it is difficult to improve productivity and ensure reliability as described below.

In the manufacture of the electric double layer capacitor of Conventional Example 2, the edge of the current collector 122 inside the cell is
After insertion into the second recess, the gasket 152 is compressed.
As a result, in the electric double layer capacitor of Conventional Example 2, the adhesion strength between the current collector 122 and the gasket 152 is improved, and the sealing reliability is improved as compared with the capacitor of Conventional Example 1 described above.

However, in this capacitor, the upper and lower end surfaces of the gasket 152 have a flat structure as shown in FIG. 11, and a portion of the concave portion 153 of the gasket 152 in which the side edge of the current collector 122 is housed. Then the current collector 12
2, the thickness of the concave portion 153 where the current collector 122 does not enter is thinner, and the thickness is distorted at the boundary where the current collector 122 does not enter.

In the capacitor of the second conventional example, the outermost current collector 121 has a structure in which the gasket 152 and the current collector 121 are made of different materials and is sealed. In a high-temperature environment, a pressure load is likely to be applied to the outermost
Liquid leakage is likely to occur due to separation between the gasket 152 and the current collector 121. Further, the current collector 122 inside the cell is likely to shift during assembly. Due to this displacement, the pressure becomes non-uniform, and the ESR of the cell stack may increase, and the liquid may leak from the cell stack. This may cause a decrease in the yield of the capacitor, that is, a decrease in productivity. .

In the capacitor of the conventional example 3, the gasket 1
The current collector 12 is provided on a step 58 provided on the inner wall side of both end surfaces of the current collector 54.
3, the adhesiveness of the outermost current collector of the cell stack to the gasket is improved as compared with Conventional Example 2. However, even in this capacitor, in a high temperature environment, the outermost current collector of the cell stack may peel off from the gasket and the electrolyte solution 130 may leak. Further, at a high temperature, the capacitor of Conventional Example 3 has a problem that the electrical contact reliability between cells of the cell stack is reduced.

Next, the electric double layer capacitor of the conventional example 4 will be considered. In this capacitor, the gasket 155
When pressure is applied from the outermost current collector of the cell stack due to the fitting of the unevenness between the current collector 124 and the current collector 124, displacement of the current collector 124 is less likely to occur. However, when the thickness of the convex portion of the current collector 124 is larger than the depth of the concave portion of the gasket 155, wrinkles are generated in the gasket 155 at the fitting portions of the concave and convex portions of the current collector 124 and the gasket 155. This wrinkle creates a gap between the current collector and the gasket, and makes it easy for both to peel off.

The capacitor of Conventional Example 4 is the same as that of Conventional Example 1.
The outer diameters of the current collector 124 and the gasket 155 are the same as in the structure of the capacitor described above, and the gasket 155 and the current collector 124, which are made of different materials, are bonded to each other. Separation easily occurs between the gasket 155 and the current collector 124.

Therefore, one of the objects of the present invention is to provide an electric double layer capacitor capable of improving the productivity.

Another object of the present invention is to provide an electric double layer capacitor having improved reliability even in a high temperature environment.

[0023]

According to the present invention, the following electric double layer capacitor is provided. A pair of polarizers sandwiching a porous separator in the middle are accommodated inside a frame-shaped first gasket, and a first current collector and a second current collector are respectively provided on upper and lower ends of the first gasket. Glued. Further, a second current collector is sandwiched between both ends of the first gasket so as to sandwich the first current collector and the second current collector, respectively.
Gasket and a third gasket are bonded,
The inside of the gasket is sealed.

In the electric double layer capacitor of the present invention, a step portion is provided on at least one inner inner peripheral edge portion of the gasket opposed thereto, and the side edge portion of each current collector is accommodated in the step portion. The step makes it easy to align the current collector with the gasket, and allows the current collector to be bonded to the gasket with low stress.

Further, on the peripheral surface of all the current collectors,
Since the gasket is crimped, it is possible to prevent the electrolyte solution from leaking from the inside of the cell under a high temperature environment. In particular,
In the electric double layer capacitor of the present invention, by setting the ratio of the depth of the step portion to the thickness of the current collector to 0.1 to 3.0, a highly reliable electric double layer capacitor in a high temperature environment can be obtained. .

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the electric double layer capacitor of the present invention will be described with reference to the drawings.

An electric double layer capacitor according to a first embodiment of the present invention will be described with reference to FIG.

Referring to FIG. 1, the electric double layer capacitor of the present invention has a structure in which cells 61a and 61b are vertically stacked. The cell 61a has a frame-like gasket 52a.
And the separator 40a housed in the gasket 52a.
A pair of polarizable electrodes 10a and 10b arranged in contact with the upper and lower surfaces of the polarizer electrode 10a, respectively, and a gasket 52 arranged in contact with the outer surface of the polarizable electrode 10a.
a and a current collector 20a adhered to the current collector 20a. Cell 61
b has the same structure as the cell 61a, and has a frame-like gasket 52b and a pair of polarizable electrodes 10c and 10c housed in the gasket 52b and arranged in contact with the upper and lower surfaces of the separator 40b, respectively. 10d
And a current collector 20b disposed in contact with the outer surface of the polarizable electrode 10c and bonded to the gasket 52b.

Gasket 5 is provided on the upper end of gasket 52a.
A gasket 51 having the same outer peripheral size as 2a is bonded. The gasket 51 is also adhered to the current collector 20a.

A gasket 51 having the same outer peripheral size as the current collector 20c and the gasket 52b is bonded to the lower end of the gasket 52b. The electrolyte solution 30 is housed inside the cells 61a and 61b.

As shown in FIG. 2, gaskets 52a, 52b
Steps 56a, 56b
Is provided. In addition, a step 56c is provided on the inner peripheral edge of the upper end of the gasket 53. The side edges of the current collector are housed in these steps. Each step 56a
The depth of ~ 56c is preferably set to be the same as the thickness of the current collectors 20a, 20b. The upper and lower end surfaces of the gasket 51 are flat.

The polarizable electrodes 10a to 10d are preferably formed to have the same thickness. For these polarizable electrodes, block-shaped activated carbon obtained by mixing powdered activated carbon with a binder material such as a phenol resin and firing the mixture is used. The binder material and manufacturing method of the polarizable electrode are not limited.

As the current collectors 20a to 20c, a butyl rubber sheet or a polyethylene sheet kneaded with a conductive material such as carbon powder is used.

The separator 40 is a porous member.
Any material can be used as long as it is non-conductive and ion-permeable. For example, a glass fiber separator or the like can be used.

Gaskets 51, 52a, 52b, 53
Is a frame-shaped member, and the shape is generally a rectangular frame or a tubular shape. The gasket, together with the current collectors 20a to 20c, the polarizable electrodes 10a to 10c, the separators 40a, 4
0b and an electrolyte solution 30 such as dilute sulfuric acid. As a material of the gasket,
An insulator such as rubber or plastic, for example, butyl rubber, polyethylene resin, ABS resin, or the like is used.

As described above, in the electric double layer capacitor of the present invention, a pair of polarizable electrodes separated by a porous separator are disposed in a frame-shaped gasket, and current collectors are provided on both end surfaces of the gasket. Is pressed to form a cell in which the inside of the frame-shaped gasket is sealed. The peripheral edge of the current collector is housed in a step provided inside the end face of the gasket.

The steps make it easy to dispose the current collector on the gasket, and the adhesion between the current collector and the gasket can be performed with low stress. Further, a gasket is pressure-bonded to the peripheral surface of all the current collectors, so that leakage of the electrolyte solution from inside the cell due to reduced adhesion between the current collector and the gasket in a high-temperature environment can be prevented.

Next, a method of manufacturing the electric double layer capacitor according to the present embodiment will be described with reference to FIGS. First, the current collector 20c is incorporated into the gasket 53 such that the side edge of the current collector 20c is attached to the step 56c of the gasket 53. Next, a gasket 52b having a step portion 56b inside the upper end portion is bonded thereon.

Next, the polarizable electrode 10d and the polarizable electrode 10
The separator 40b is interposed between the gasket 52c and the gasket 52c, and is housed in the frame of the gasket 52b. Next, the polarizable electrode 10
Gasket 5 containing c, 10d and separator 40b
In 2b, for example, an electrolyte solution 30 of 30 wt% diluted sulfuric acid
Inject. Next, the current collector 20b is attached to the step 56b of the gasket 52b by attaching the side edge of the current collector 20b.
0b is incorporated into the gasket 52b.

Next, a gasket 52a having a step 56a on the inner peripheral edge at the upper end is bonded thereon. Subsequently, the separator 40a is interposed between the polarizable electrode 10b and the polarizable electrode 10a, and these are accommodated in the frame of the gasket 52a. Next, after injecting the electrolyte solution 30 into the gasket 52a, the step portion 56 of the gasket 52a is formed.
The current collector 20a is incorporated into the gasket 52a such that the side edge of the current collector 20a is mounted on the gasket 52a. When further stacking the cells, the steps from bonding the gasket to assembling the current collector are repeated.

Next, the gasket 52a and the current collector 2
A gasket 51 having a flat upper and lower surface is adhered to Oa to obtain a cell laminate 71 of an electric double layer capacitor. The gasket 52a and the gasket 5
The sealing between the cells 61a and 61b can be reinforced by applying an epoxy resin-based insulating resin to the outer peripheral surface of the bonding surface of 2b. A thermosetting resin or an ultraviolet curing resin can be used as the epoxy resin-based insulating resin.

Next, as shown in FIG.
A terminal electrode 80 is interposed between a pressure plate 90 provided on the surface of the current collector on both sides of the outermost contour of the battery, and the pressure plates 90 on both sides are pressed by bolts and nuts (not shown), and the A double-layer capacitor can be completed.

Next, the gasket 52a and the current collector 2
A gasket 51 having a flat upper and lower surface is adhered to Oa to obtain a cell laminate 71 of an electric double layer capacitor. The gasket 52a and the gasket 5
The sealing between the cells 61 and 62 can be reinforced by applying an epoxy resin-based insulating resin to the outer peripheral surface of the bonding surface 2b. A thermosetting resin or an ultraviolet curing resin can be used as the epoxy resin-based insulating resin.

Table 1 shows an example of dimensions of a completed electric double layer capacitor sample (Example 1).

[0045]

[Table 1]

As shown in Table 1, the gaskets 52a, 52
There is a difference of 0.1 mm between the outer and inner thicknesses of 2b and 53. This difference indicates the depth (A) of the steps 56a to 56c, and has the same size as the thickness (t) of the current collectors 20a to 20c. The length (L) of the steps 56a to 56c is 83 mm, and the width (W) is 63 mm. The preferred value of the ratio (A / t) of the depth (A) of the steps 56a to 56c to the thickness (t) of the current collector is a value larger than 0.1 and smaller than 3. More preferably, it is 0.2 or more and 2.5 or less. The reason will be described later.
In the sample of Table 1, the value of A / t is set to 1. In this example, 18 cells were stacked in series to produce a cell stack having a withstand voltage of 15 V.

The polarizable electrodes 10a to 10d are made by mixing, pulverizing, granulating and firing the same phenolic powdered activated carbon and powdered phenolic resin at a weight ratio of 70/30.

Next, the second embodiment of the electric double layer capacitor of the present invention will be described.
The embodiment will be described with reference to FIG. 4 and FIG.

Referring to FIG. 4, it can be seen that steps for accommodating the current collector are provided at both ends of the gasket of the cell. This point is different from the above-described first embodiment of the present invention in the capacitor of the present embodiment.

Referring to the schematic diagram of the gasket of FIG.
In the electric double layer capacitor of the present embodiment, steps 57b and 57c are provided inside the upper and lower ends of the gasket 55a to accommodate the side edges of the current collectors 20a and 20b, respectively. Further, inside the upper and lower ends of the gasket 55b, step portions 57d and 57e for accommodating the side edges of the current collectors 20b and 20c, respectively, are provided.

The outermost gasket 54 of the cell stack 72
Steps 57a, 5b for accommodating the side edges of the current collectors are provided on the surfaces of the current collectors 20a, 20c which contact the current collectors 20a, 20c.
7f is provided. The depth of the steps 57a to 57f is about half the thickness of the side edge of each current collector. Each current collector is provided with a stepped portion 57a-57f of a gasket bonded vertically.
In the recess formed by These steps make it easier to dispose the current collector on the gasket, and the current collector and the gasket can be bonded with low stress.

The electric double layer capacitor of this embodiment is
As in the capacitor of the first embodiment of the present invention, a porous separator and a pair of polarizable electrodes are arranged in a frame-shaped gasket with the separator interposed therebetween. A current collector is crimped by being brought into contact with a polarizing electrode, and a cell having a structure in which the inside is sealed is provided.
Also in the electric double layer capacitor of the present embodiment, the gasket is pressed on the peripheral surface of all the current collectors, and the electrolyte from the inside of the cell due to the reduced adhesion between the current collector and the gasket under a high temperature environment. Solution leakage can be prevented.

The manufacturing conditions and the method of manufacturing the electric double layer capacitor of the present embodiment are the same as those of the first embodiment. Table 2 shows a dimension example of the completed electric double layer capacitor sample (Example 2).

Gasket 54 for accommodating side edges of current collector
Steps 57a-57 of a, 54b, 55a and 55b
The dimensions of f are 83 mm in length (L), 63 mm in width (W), and 0.05 mm in depth (B). In Table 2, the current collector 20
The sum of the depths of the steps on the stacking surfaces of the gaskets stacked vertically with respect to each thickness (t) of a, 20b, and 20c (2 × B
Is set to 1, a preferable value of this ratio is a value larger than 0.1 and smaller than 3. More preferably, it is 0.2 or more and 2.5 or less. The reason will be described later.

Next, a comparative example (prior art) of Example 1 and Example 2 of the present invention will be described.

[0056]

[Table 2]

(Comparative Example 1) As Comparative Example 1, an electric double layer capacitor having the same cell laminated body as that of FIG. The manufacturing conditions and method of the electric double layer capacitor are almost the same as those of the above-described embodiment of the present invention.

Table 3 shows an example of dimensions of a completed sample of the electric double layer capacitor of the comparative example. The materials of the electrolyte solution 130 and other members are substantially the same as those in the above-described embodiment of the present invention.

(Comparative Example 2) As Comparative Example 2, an electric double layer capacitor having a cross-sectional structure of the same cell stack as in FIG. 10 was manufactured. The manufacturing conditions and method of the electric double layer capacitor are almost the same as those of the above-described embodiment of the present invention.

The materials of the electrolyte solution 130 and other members are almost the same as those of the above-described embodiment of the present invention.

The size of the current collector 122 inside the cell was 82 mm in length (L), 62 mm in width (W), and 0.1 mm in thickness (t). The size of other components is Comparative Example 1.
Is the same as

[0062]

[Table 3]

(Comparative Example 3) As Comparative Example 3, an electric double layer capacitor having a cross-sectional structure of the same cell laminate as in FIG. 13 was manufactured. The manufacturing conditions and method of the electric double layer capacitor are almost the same as those of the above-described embodiment of the present invention.

The materials of the electrolyte solution 130 and other members are almost the same as those of the above-described embodiment of the present invention. The depth of the concave portion 156 of the gasket 155 was 1 mm.

Next, with respect to the electric double layer capacitors of Examples 1 and 2, and the electric double layer capacitors of Comparative Examples 1 to 3, the measurement results of the defect occurrence rate during the production and the relative average life in the reliability test. Is described.

The relative average life in the reliability test was 70
The time to failure (leakage of the electrolyte solution to the outside) of each sample was determined in a state where 15 V DC was applied at 15 ° C., and this was printed on Weibull probability paper, and the average life for each level obtained from the result was obtained. (MTTF) was determined. The average life of each sample was standardized with the average life of Comparative Example 1 as 1. The number of samples was 30 for each level, and the average was determined. Table 4 shows the results.

In Table 4, A / t of Example 1 is shown.
The value is the ratio of the depth of the step portion of the gasket to the thickness of the current collector, and the 2B / t value of Example 2 represents the ratio of the sum of the upper and lower step portions of the laminated gasket to the thickness of the current collector. ing.

FIG. 6 shows the ratio (A / A) of the depth of the step portion and the current collector of the gaskets of Examples 1 and 2 of the present invention shown in Table 4.
3 and 2B / t) are plotted on the horizontal axis, and the failure rate is plotted on the vertical axis.

Referring to Table 4, as compared with Comparative Example 1,
In the capacitors of Comparative Example 2 and Comparative Example 3, the process failure rates are 21% and 29%, respectively, which are 30% and 22% lower than those of Comparative Example 1, respectively. The relative life expectancy has also increased by a factor of 2.4 and 2.8, respectively.

[0070]

[Table 4]

On the other hand, in the first embodiment of the present invention, A / t
Is in the range of 0.5 to 1.5, and the process failure rate is 0 to 2%.
In addition, the relative average life is 10 times or more, which is remarkably improved as compared with Comparative Example 1 as well as Comparative Examples 2 and 3. Also, as in Example 1, the process failure rate and the relative average life of Example 2 of the present invention were 2 B / t in the range of 0.5 to 1.5. Has been improved. FIG.
Comparative Example 3 also relates to the conventional capacitor having the cell structure of No. 2.
The same defective rate and relative average life were obtained.

Referring to FIG. 6, according to the present invention, the defect rate is 2
In order to make it 0% or less (yield 80% or more), A / t
Alternatively, it is understood that the value of 2B / t needs to be larger than 0.1 and smaller than 3. In consideration of safety, it was found that it is more preferable to set the value to 0.2 or more and 2.5 or less.

Normally, the storage portion of the current collector (the steps 56a to 56a)
When the thickness of the current collector 20 is slightly thicker than the depth dimension (A or 2B) of 56c, 57a to 57f), the current collector is soft and is not broken when pressure is applied to the current collector. Since it is crushed, it also functions as a packing, and liquid leakage hardly occurs. However, when the thickness of the current collector gradually becomes larger than the depth dimension of the storage portion of the current collector, a positional shift occurs when pressure is applied to the current collector. In addition, the sealing strength is weakened similarly to the conventional structure in which gaskets of the same material do not contact each other. Conversely, if the size (A or 2B) of the current collector storage portion (steps 56a to 56c, 57a to 57f) is too large than the current collector to be inserted, positional displacement when pressure is applied hardly occurs. However, when pressure is applied to the opposite side because the current collector is in a floating state, the current collector moves in the cells, and the electrolyte solution 30 is connected between the cells to increase the voltage per unit cell. In addition, it is considered that the problem that the potential balance is lost occurs and the decrease in reliability cannot be improved.

In the electric double layer capacitor of the present invention, there are almost no defects in the process, and the relative average life is greatly improved. In particular, the effect is remarkable when the current collector housing portion (step portion) is provided on one side of the gasket. Think about this reason.

In the capacitor of Comparative Example 4 (see FIG. 13), the gasket and the current collector are provided with uneven fitting portions, but different materials have insufficient bonding strength. Due to a temperature load or the like, peeling or cracking is likely to occur on the bonding surface between the gasket and the current collector other than the fitting portion, and the cracking and peeling will also spread to the fitting portion and the electrolyte solution will leak. On the other hand, for example, if there is a portion where the materials of the same material (gaskets) are in contact with each other as in Example 1 of the present invention (see FIG. 1), the adhesive strength is increased and peeling is less likely to occur. Therefore, it is considered that even if a crack is formed in a portion where the current collector and the gasket are in contact with each other, if the crack is not formed in a portion where the gasket is in contact with the gasket, there is almost no possibility that the internal electrolyte solution leaks out. Actually, even if the A / t value of Example 1 tested this time is 0.5 to 1.5, even if a crack is formed in the portion where the current collector and the gasket are in contact with each other, the crack stops there. There were no cracks up to the point where the gaskets were attached.

[0076]

As described above, in the electric double layer capacitor of the present invention, the gasket is provided outside the outermost current collector, and the side edge of the current collector is accommodated at the end face of the gasket. The following effects can be obtained by adopting a structure having a step portion. (1) The generation of wrinkles and displacement when the current collector is bonded to the gasket can be suppressed, and the production yield of the electric double layer capacitor, that is, the productivity can be improved. (2) Since the adhesion between the gasket and the current collector can be prevented from lowering in a high temperature environment, external leakage of the electrolyte solution can be prevented, and the reliability of the electric double layer capacitor in a high temperature environment can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a cell stack in an electric double layer capacitor according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a gasket in the electric double layer capacitor according to the first embodiment of the present invention.

FIG. 3 is a side view of the electric double layer capacitor according to the first embodiment of the present invention.

FIG. 4 is a cross-sectional view of a cell stack in an electric double layer capacitor according to a second embodiment of the present invention.

FIG. 5 is a sectional view of a gasket in an electric double layer capacitor according to a second embodiment of the present invention.

FIG. 6 is a graph in which the relationship between the depth of the step portion of the gasket of Example 1 and Example 2 and the ratio of the thickness of the current collector to the defect rate in Table 4 is plotted.

FIG. 7 is a cross-sectional view of a cell stack in the electric double layer capacitor of Conventional Example 1.

FIG. 8 is a cross-sectional view of a gasket in the electric double layer capacitor of Conventional Example 1.

FIG. 9 is a side view of the electric double layer capacitor of Conventional Example 1.

FIG. 10 is a sectional view of a cell stack in the electric double layer capacitor of Conventional Example 2.

FIG. 11 is a cross-sectional view of a gasket in the electric double layer capacitor of Conventional Example 2.

FIG. 12 is a cross-sectional view of a cell in an electric double layer capacitor of Conventional Example 3.

FIG. 13 is a cross-sectional view of a cell stack in the electric double layer capacitor of Conventional Example 4.

FIG. 14 is a cross-sectional view of a gasket in an electric double layer capacitor of Conventional Example 4.

[Explanation of symbols]

10a to 10d, 110-minute polar electrodes 20a to 20c, 121, 122, 123 Current collector 30, 130 Electrolyte solution 40a, 40b, 140 Separator 51, 52a, 52b, 53, 54, 55a, 55b,
151, 152, 154, 155 Gaskets 56a to 56c, 57a to 57f, 58 Step portions 153, 156 Concave portions 61, 61a, 61b, 62a, 62b, 161, 16
2,163 cells 71,72,171,172,17
3 cell laminate 80, 180 Terminal electrode 90, 190 Pressing plate

Claims (10)

[Claims] 1. A frame-shaped first element containing a pair of polarizing electrodes sandwiching a porous separator in the middle and containing the cell element, and having a first stepped portion formed on an inner peripheral edge at an upper end. A first current collector attached to the first step and adhered to the upper surface of the first gasket; and a first current collector adhered to the upper surface of the first gasket and the first current collector A frame-shaped second gasket having the same outer peripheral dimension as the first gasket, and a second current collector adhered to a lower surface of the first gasket and having an outer peripheral dimension smaller than the first gasket. Has the same outer dimensions as the first gasket, is adhered to the lower surface of the first gasket and the second current collector, and has a side edge of the second current collector on an inner peripheral edge portion. A third gasket having a second step portion for housing the portion And an electric double-layer capacitor. 2. The depth of the first step portion is equal to the thickness of the first current collector, and the thickness of the second step portion is equal to the thickness of the second current collector. The electric double layer capacitor according to claim 1, wherein: 3. The second gasket includes a third step portion on an inner peripheral edge portion for partially accommodating the side edge portion of the first current collector, and a lower portion of a lower end of the first gasket. 2. The electric double layer capacitor according to claim 1, further comprising a fourth step portion that partially accommodates the side edge portion of the second current collector on an inner peripheral edge portion. 3. 4. The method according to claim 1, wherein said first step portion has a depth of said first step portion.
The ratio of the thickness of the current collector to the thickness of the current collector is 0.1 to 3.0,
2. The electric double layer capacitor according to claim 1, wherein a ratio of a depth of the second step to a thickness of the second current collector is 0.1 to 3.0. 3. 5. A ratio of the sum of the depths of the first step portion and the third step portion to the thickness of the first current collector is 0.1 to 3, and The ratio of the sum of the depths of the step portion and the fourth step portion to the thickness of the second current collector is 0.1 to 3.
3. The electric double layer capacitor according to claim 1. 6. The material according to claim 1, wherein the material of the first current collector and the second current collector is one of a butyl rubber sheet and a polyethylene sheet provided with conductivity. Electric double layer capacitor. 7. The electric double layer capacitor according to claim 1, wherein the material of the polarizable electrode is a block-shaped activated carbon. 8. The electric double layer according to claim 1, wherein the material of the first gasket, the second gasket and the third gasket is one selected from butyl rubber, polyethylene resin and ABS resin. Capacitors. 9. The electric double layer capacitor according to claim 1, wherein an electrolyte solution is sealed inside the first gasket. 10. A third step portion is provided between the first gasket and the third gasket at the outer peripheral edge at the upper end in the same shape as the first gasket, and the second step portion is provided inside the third gasket. A fourth gasket containing the cell element of
The electric double layer capacitor according to claim 1, wherein the third current collector mounted on the third step portion is integrally sandwiched between the third current collector and the third current collector.