JP2009289968A - Coin type cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of breaking of a gasket during manufacture while keeping the sealing property of the gasket satisfactory using a relatively inexpensive gasket material for a coin type cell. <P>SOLUTION: In the coin type cell 1, the gasket 15 is made of a raw material consisting principally of butyl rubber. The gasket 15 is sectioned in a transformed U shape, and has a cylindrical sidewall 15a, a bottom portion 15b extending inward from a lower edge of the sidewall 15a, and a folded portion 15c raised from an inner edge of the bottom portion 15b. When the coin type cell is &le;1.5 mm thick, the thickness d1 of the sidewall 15a of the gasket 15 is about 0.2 mm. The ratio (d2/d1) of the thickness d1 of the sidewall 15a of the gasket 15 to the thickness d2 of the bottom portion 15b is set to 1.2 to 3. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a coin-type cell, and particularly to a coin-type cell sealed with a gasket made of butyl rubber.

As an electrochemical element typified by an electric double layer capacitor, a coin-type cell is known.
In this coin-type cell, a power generating element formed by laminating first and second polarizable electrodes through a separator is stored together with an electrolyte in a round dish-shaped outer can, and the opening of the outer can has a negative electrode cap. It is sealed with a ring gasket provided on the outer periphery of the member, and members around the opening are caulked and internally sealed.

Hard materials such as PEEK (polyetheretherketone) and PPS (polyphenylene sulfide) are often used as the material for the annular gasket, but it is also considered to use inexpensive butyl rubber from the standpoint of cost. (Described in Patent Documents 1 to 3).
In general, cylindrical butyl rubber gaskets used for aluminum electrolytic capacitors have a wall thickness of 1 mm or more, whereas gaskets used for coin-type cells have a thin wall thickness and a coin cell having a thickness of 1.5 mm or less. In general, a gasket having a wall thickness of about 0.2 mm is used.
JP 2007-207942 A JP 2008-66407 A Japanese Patent Laid-Open No. 2007-324531

In such a coin-type cell, in order to improve the sealing property of the cell, it is necessary to select a hard material having a JIS-A hardness of 75 or more and 110 or less as a gasket material.
However, when a butyl rubber gasket having a small thickness and a high hardness is used, the gasket is likely to be cut when sealed by caulking during manufacturing.
That is, in the process of manufacturing the coin-type cell, the pressure applied to the gasket from the outer periphery of the negative electrode cap, or the cell is pushed out from the mold for sealing (the positive electrode can of the cell that has entered the mold at the time of sealing is The pressure at the time of pushing the cell out of the mold with a knock bar because it bites into the mold) causes an overload from the outer peripheral edge of the negative electrode cap to the bottom of the gasket. Here, since resin gaskets such as PEEK and PPS have high strength, even if the wall thickness is about 0.2 mm, no gasket breakage occurs due to overload, and there is a case where a butyl rubber gasket with low hardness is used. Since the rubber is sufficiently stretched, it is difficult for the gasket to break due to overload. However, when a butyl rubber gasket having a small thickness and high hardness is used, there is a problem that the gasket is likely to break due to overload.

  The present invention has been made in view of the above-described problems, and aims to suppress the occurrence of gasket breakage during manufacturing while using a relatively inexpensive gasket material and maintaining good sealing performance of the gasket. .

  In order to solve the above-described problems, the present invention provides an electrode body having a pair of electrodes arranged opposite to each other with a separator interposed between an electrolyte and an outer can, and the outer can opening has a dish-shaped outer lid. In a coin-type cell that is sealed by crimping and sealed in a state where the side wall portion of the outer lid is fitted inside the side wall portion of the outer can through an annular gasket, the gasket includes butyl rubber. The JIS-A hardness is made of a material having a hardness of 75 or more and 110 or less, a side wall portion interposed between the side wall portion of the outer lid and the side wall portion of the outer can, and an inward extension of the outer lid from the side wall portion. It is configured to have a bottom portion interposed between the edge of the side wall portion and the bottom surface portion of the outer can, and in the state before the gasket is assembled in the cell, the ratio of the thickness of the bottom portion to the thickness of the side wall portion, It was set to 1.2 or higher.

  Here, it is preferable that the ratio of the thickness of the bottom portion to the thickness of the side wall portion is set to 3 or less before the gasket is assembled in the cell.

According to the coin-type cell of the present invention, since butyl rubber is used for the gasket, it is less expensive than a gasket using PEEK or PPS.
Moreover, since the gasket has a JIS-A hardness of 75 to 110, the gasket is not softened and deformed during reflow. Therefore, the cell can be sealed well and the holding characteristics are also good.

  Further, since the ratio of the thickness of the bottom portion to the thickness of the side wall portion of the gasket is set to 1.2 or more, even if the thickness of the side wall portion of the gasket is as thin as about 0.2 mm, the thickness of the bottom portion is Relatively large (0.24 mm or more) is secured. Therefore, when sealing by caulking during cell manufacturing, even if an overload is applied from the outer peripheral edge of the negative electrode cap to the bottom of the gasket, it is difficult for the gasket to break.

This contributes to improving the yield at the time of manufacturing the cell and reducing the manufacturing cost.
Here, if the ratio of the thickness of the bottom portion to the thickness of the side wall portion of the gasket is larger than 3, the amount of the compressed and deformed gasket that protrudes into the cell increases. In that case, the internal volume of the cell decreases, so the internal pressure of the cell increases. If reflow is performed in this state, the amount of increase in cell thickness also increases. On the other hand, if the ratio is set to 3 or less, the amount of gasket protruding into the cell is suppressed, and the increase in cell thickness during reflow is also suppressed.

An electric double layer capacitor will be described as an embodiment of a coin-type cell according to the present invention. However, the present invention is not limited to this type, and may be changed as appropriate without departing from the technical scope of the invention. Good.
<Composition of coin cell>
FIG. 1 is a cross-sectional view showing the configuration of the coin-type cell 1, and FIG. 2 is a cross-sectional set view showing the configuration of the coin-type cell 1.

The coin-type cell 1 shown in FIG. 1 is an electric double layer capacitor of 414 size (diameter Φ4 mm, thickness t1.4 mm), and the electrode body 3 is housed in an outer can (positive electrode can) 20 together with the electrolytic solution 40. The opening is configured by being sealed by an exterior lid (negative electrode cap) 10 fitted with a gasket 15.
The electrode body 3 is composed of a pair of electrodes (a first polarizable electrode 32 and a second polarizable electrode 34) arranged to face each other with a separator 30 interposed therebetween. A current collector 33 is disposed in the positive electrode can 20, and a negative electrode cap 10. Is provided with a current collector 31. The first polarizable electrode 32 is in electrical contact with the current collector 31 of the negative electrode cap, and the second polarizable electrode 34 is in electrical contact with the current collector 33 of the positive electrode can 20.

The first and second polarizable electrodes 32 and 34 are both formed into a disk shape by solidifying the active material with a binder, and the size is 0.5 mm in thickness and 2.4 mm in diameter.
A material generally used for an electric double layer capacitor may be used. For example, the active material may be powdered activated carbon, and the binder may be polytetrafluoroethylene, polyvinylidene fluoride, or the like. Further, a conductive agent may be added to the active material. Examples of the conductive agent include carbon materials such as natural graphite such as flaky graphite and earthy graphite, artificial graphite, carbon black, acetylene black, ketjen black, and carbon fiber.

The current collectors 31 and 33 are films formed by applying a conductive paint obtained by mixing graphite powder and a resin to one side of the negative electrode cap 10 and the positive electrode can 20.
The separator 30 is an insulating permeable membrane (microporous membrane) having good ion flowability and moderate mechanical strength, and is made of a material such as glass fiber, PPS, PET, PA, PI, The thickness is about 10 to 250 μm, and the pore diameter is about 0.01 to 5 μm.

The positive electrode can 20 is made of a stainless steel material, and includes a circular bottom surface portion 21 and a cylindrical side wall portion 22 that rises from the outer peripheral edge of the bottom surface portion 21, and a tip edge portion of the side wall portion 22 faces inward. A curved portion 23 is formed by bending.
The negative electrode cap 10 is made of a stainless material similar to that of the positive electrode can 20 in a dish shape, and has a circular main surface portion 11 and a cylindrical side wall portion 10 a that falls from the outer peripheral edge of the main surface portion 11. ing.

As shown in FIG. 1, the edge of the side wall portion 10a of the negative electrode cap 10 is formed by being folded twice.
When the negative electrode cap 10 having such a configuration is used, the rigidity of the side wall portion 10a is relatively increased.
However, in the present invention, it is not essential to double-fold the peripheral edge of the negative electrode cap 10. Moreover, the raw material of the positive electrode can 20 and the negative electrode cap 10 is not restricted to stainless steel, What is necessary is just a metal material excellent in electrical conductivity, and raw materials, such as iron, aluminum, titanium, nickel, can also be used.

The electrolytic solution 40 is a solution in which a supporting salt is dissolved in an organic solvent. Examples of the organic solvent include cyclic esters, chain esters, cyclic ethers, chain ethers and the like, and examples of supporting salts include tetraethylammonium tetrafluoroborate (TEA-BF4), triethylmethylammonium tetrafluoroborate, and the like. Is mentioned.
(Details of gasket 15)
The gasket 15 is formed by thermoforming an insulating material in an annular shape, and the inner diameter of the gasket 15 is equal to the outer diameter of the negative electrode cap 10.

The material constituting the gasket 15 is mainly composed of butyl rubber obtained by copolymerizing isobutylene and a small amount of isoprene, and is mixed with a reinforcing material, a filler, a vulcanizing material (crosslinking material), and the like.
Carbon black as the reinforcing material, silica-based, mica-based, clay-based as the filler, resin, sulfur, etc. as the vulcanizing material, phenol-based, amine-based as the anti-aging agent, as auxiliary materials And a mixture of zinc oxide and stearic acid.

The hardness of JIS-A (3-second value) of the gasket 15 is set in the range of 75 to 110. The hardness of the gasket 15 can be adjusted by adjusting the type and mixing ratio of the reinforcing material, filler, and vulcanizing material to be used.
As shown in FIG. 2, the gasket 15 has an annular shape (cylindrical shape having a low height), and the cross section of the annular shape is a deformed U-shape. That is, the gasket 15 has a cylindrical side wall portion 15a, a bottom portion 15b extending inward from the lower edge of the side wall portion 15a, and a folded portion 15c rising from the inner edge of the bottom portion 15b. A groove 15d is formed between the folded portion 15c.

In the state where the gasket 15 is incorporated in the cell, the leading edge of the side wall portion 10a of the negative electrode cap 10 is fitted into the groove portion 15d, and the side wall portion 15a includes the side wall portion 10a of the negative electrode cap 10 and the side wall portion 22 of the outer can 20. The bottom portion 15 b is interposed between the edge of the side wall portion 10 a of the negative electrode cap 10 and the bottom surface portion 21 of the positive electrode can 20.
As shown in FIG. 1, the side wall 15 a and the bottom 15 b of the gasket 15 are compressed and deformed between the negative electrode cap 10 and the positive electrode can 20, and seal between the negative electrode cap 10 and the positive electrode can 20. ing.

About the thickness of gasket 15:
The wall thickness d1 of the side wall portion 15a of the gasket 15 is preferably set to be thin in order to increase the internal volume of the cell, but a minimum wall thickness is necessary to ensure the function as a gasket. Usually, when the thickness of the coin-type cell is 1.5 mm or less, the wall thickness d1 of the side wall 15a of the gasket 15 is about 0.2 mm.

The ratio (d2 / d1) of the thickness d2 of the bottom 15b to the thickness d1 of the side wall 15a of the gasket 15 is set to 1.2 or more and 3 or less.
The ratio (d2 / d1) here refers to the ratio in a state before the gasket 15 is assembled in the cell (a state in which no force is applied).
Although details will be described in the manufacturing process, the wall thickness d2 of the bottom portion 15b of the gasket 15 is set to 1.2 times or more than the wall thickness d1 of the side wall portion 15a as described above. In the caulking process when manufacturing, the bottom 15b of the gasket 15 is not cut.

  On the other hand, if the ratio (d2 / d1) is greater than 3, the amount of the compressed and deformed gasket will protrude into the cell. In that case, the internal volume of the cell decreases, so the internal pressure of the cell increases. If reflow is performed in this state, the amount of increase in cell thickness also increases. On the other hand, if the ratio (d2 / d1) is set to 3 or less, the amount of gasket protruding into the cell can be suppressed, and the increase in cell thickness during reflow can also be suppressed.

<Manufacturing process of coin cell>
An example of the coin cell manufacturing process will be described with reference to FIGS.
First, as shown in FIG. 3A, the first polarizable electrode 32 and the separator 30 are housed on the inner surface of the negative electrode cap 10 provided with the current collector 31, and the gasket 15 is disposed on the outer periphery of the negative electrode cap 10. Installing.

At this time, the leading edge of the side wall 10 a of the negative electrode cap 10 is fitted into the groove 15 d of the gasket 15. Then, the electrolytic solution 40 is injected, and the second polarizable electrode 34 is placed on the separator 30.
A cell 1a before caulking is assembled by covering the bottomed cylindrical member 20X on which the outer can 20 provided with the current collector 33 is placed from above the second polarizable electrode 34 (FIG. 3B). ).

In addition to the manufacturing method described above, the cell 1a before crimping is sealed by, for example, covering the electrode body 3 and the electrolytic solution 40 in the bottomed cylindrical member 20X and covering the negative electrode cap 10 with the gasket 15 attached thereto. It can also be produced by the method of
Next, a sealing step is performed by crimping the cell 1a produced using a sealing mold.

FIG. 4 is a diagram for explaining this sealing step.
An inclined pressing surface 103 is formed on the lower surface of the sealing mold 100. A knock 101 is slidably mounted on the mold 100, and the knock 101 is biased downward by a spring 102.
As shown in FIG. 4A, when the cell 1a is placed and the mold 100 is pushed down, the shoulder height is lowered. That is, the pressing surface 103 presses the distal end portion 23X of the side wall portion 22 inwardly, and as a result, the curved portion 23 is formed and sealed, thereby completing the coin-type cell 1 ((FIG. 3B). At this time, the knock 101 hits the negative electrode cap 10 and is pushed up relative to the mold 100 as the mold 100 descends.

Although the outer can 20 of the coin cell 1 is biting the mold 100, when the mold 100 is raised, the knock 10 pushes the coin cell 1 downward by the biasing force of the spring 102, so that the coin cell 1 Is separated from the mold 100 (FIG. 3C).
<Effects of coin-type cell of embodiment>
Since butyl rubber is used for the gasket, it is less expensive than PEEK or PPS.

If the gasket has a low hardness, it tends to be softened and deformed easily during reflow, so the holding characteristics are likely to deteriorate. However, in this embodiment, the gasket has a high JIS-A hardness of 75 to 110, so the holding characteristics are good.
Since the ratio (d2 / d1) of the thickness d2 of the bottom 15b to the thickness d1 of the side wall 15a of the gasket 15 is set to 1.2 or more and 3 or less, the thickness of the side wall 15a of the gasket is 0. Even if it is as thin as about 2 mm, the thickness of the bottom portion 15b is relatively large (0.24 mm or more).

  In the sealing step, when the shoulder height is lowered, the bottom 15b is pressed by the side wall 10a of the negative electrode cap 10 and the bottom 21 of the positive electrode can 20, and the bottom 15b is overloaded. Also, the bottom portion 15b is overloaded when the knock 10 pushes the coin cell 1 downward. However, as described above, since the thickness of the bottom portion 15b of the gasket is ensured to be relatively large (0.24 mm or more), the gasket bottom portion 15b is unlikely to be cut.

<Performance confirmation test>
The following samples were produced and a performance confirmation test was performed.
In each of Examples 1 to 4 and Comparative Examples 1 and 2, coin-type cells were produced using gaskets mainly composed of butyl rubber.
In either case, the cell size was 414, and the electrolyte used was 1 mol / l of TEA-BF ₄ (tetraethylammonium borofluoride) dissolved in PC (propylene carbonate). Further, the wall thickness d1 of the side wall of the gasket was uniformly set to 0.2 mm.

  In each of the examples and comparative examples, the ratio (d2 / d1) of the bottom wall thickness d2 to the wall thickness d1 of the gasket and the hardness were set to the values shown in Table 1.

試験内容：
各コイン型セルについて、１０個作製した中で封口後のガスケット切れ発生数と、リフロー試験後におけるセルの厚み上昇を測定した。その試験結果は、上記表１に示すとおりである。

contents of the test:
Among 10 coin-type cells, the number of occurrences of gasket breakage after sealing and the increase in cell thickness after the reflow test were measured. The test results are as shown in Table 1 above.

Discussion:
Based on the test result shown in Table 1, it considered as follows.
In Comparative Example 1 in which the gasket thickness ratio (d2 / d1) is 1, 2 out of 10 gaskets occurred, but the thickness ratio (d2 / d1) was 1.2 or more. In No. 4, although the hardness is 75 or more, the gasket is not cut. From this, it can be seen that if the thickness ratio (d2 / d1) of the gasket is 1.2 or more, the gasket can be prevented from being cut even if the hardness is as high as 75 or more.

In Comparative Example 2 where the hardness of the gasket was as low as 72, the gasket was not cut, but the increase in cell thickness was higher than in Examples 1 to 4 and Comparative Example 1. This indicates that when the hardness of the gasket is low, the gasket sticks out and the cell thickness is likely to increase.
Moreover, when the thickness increase of a cell is compared between Examples 2-4, it becomes large in order of Example 2,3,4. This indicates that the increase in the thickness of the cell increases as the wall thickness ratio (d2 / d1) of the gasket increases.

  When the increase in cell thickness exceeds 0.1 mm, the size is not 414 size (Φ4 mm × t1.4 mm), but another size is 4.15, but in Examples 1 to 4, the cell thickness increase is 0.1 mm. Rather low. It is known that when the gasket has a hardness of 87, the cell thickness increase does not exceed 0.1 mm if the thickness ratio (d2 / d1) is within 3.

  In Comparative Example 2 (hardness 72) where the hardness of the gasket is low, the increase in cell thickness is 0.09 mm, which is close to 0.1 mm. Therefore, in consideration of the variation in cell thickness, the increase in cell thickness is 0.1 mm. It is considered that the hardness is preferably 75 or more in order to keep it below. On the other hand, in Example 1 (hardness 91) where the gasket has a high hardness, the cell thickness increase is low (0.01 mm). The higher the hardness of the gasket, the smaller the increase in the thickness of the cell. However, if the hardness is too high, the elongation of the gasket deteriorates and the gasket is likely to break. Therefore, the hardness of the gasket should be set to 110 or less. Is preferred.

<Other matters>
In the above embodiment, the edge of the side wall portion 10a of the negative electrode cap 10 is double-folded, and this point is also considered to contribute to the effect of suppressing gasket breakage. It is not indispensable to bend the gasket 15, and even if the peripheral portion of the negative electrode cap 10 is not folded twice, the gasket 15 can be cut off by setting the gasket thickness ratio (d2 / d1) to 1.2 or more. There is an effect to suppress.

In the coin-type cell 1 of the above embodiment, the outer lid is the negative electrode and the outer can is the positive electrode, but it can also be set to have the opposite polarity.
In the present invention, the size of the coin-type cell is not limited to the 414 size, but can be applied to a certain size range. However, this is particularly effective for a coin-type cell having a thickness of 1.5 mm or less.

  In the above embodiment, the configuration of the electric double layer capacitor is exemplified as the coin-type cell that is an electrochemical element, but the present invention is not limited to this and can be applied to a coin-type battery. In this case, the electrode body can be composed of a power generation element in which a negative electrode and a positive electrode are stacked via a separator, as in a known coin-type battery. In the case of a lithium battery, manganese dioxide can be used as the positive electrode agent, metallic lithium as the negative electrode agent, and a polypropylene nonwoven fabric as the separator.

The coin-type cell of the present invention can be mounted on an electronic circuit board and used as an RTC for a small portable communication device, a memory back-up power supply for a personal computer, or the like.
Moreover, since the yield at the time of manufacture can be ensured by using a relatively inexpensive butyl rubber as the gasket material, there is an advantage that the manufacturing cost can be reduced.

It is sectional drawing which shows the structure of the coin-type cell which concerns on embodiment. It is a partial cross section assembly figure showing the structure of a coin type cell. It is a figure which shows the manufacturing process of a coin-type cell. It is a figure which shows the manufacturing process of a coin-type cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Coin type cell 3 Electrode body 10 Negative electrode cap 10a Side wall part of negative electrode cap 11 Main surface part of negative electrode cap 15 Gasket 15a Side wall part of gasket 15b Bottom part of gasket 15c Folded part of gasket 15d Groove part of gasket 20 Positive electrode can 21 Bottom surface of positive electrode can Part 22 Side wall part of positive electrode can 23X End part of side wall part 23 Curved part 30 Separator 31 Current collector 32 First polarizable electrode 33 Current collector 34 Second polarizable electrode 40 Electrolytic solution 100 Mold 101 Knock 102 Spring 103 Gold Mold pressing surface

Claims (2)

An electrode body having a pair of electrodes arranged opposite to each other via a separator is housed in an outer can together with an electrolytic solution, the opening of the outer can is sealed with a dish-shaped outer lid, and the side wall of the outer lid is a circle. A coin-type cell that is crimped and sealed in a state of being fitted inside the side wall of the outer can through an annular gasket,
The gasket is
It is composed of a material containing butyl rubber and having a JIS-A hardness of 75 or more and 110 or less,
A side wall portion interposed between the side wall portion of the outer lid and the side wall portion of the outer can, and an inward extending from the side wall portion between the edge of the side wall portion of the outer lid and the bottom surface portion of the outer can And a bottom portion interposed between
The coin-type cell, wherein a ratio of the thickness of the bottom portion to the thickness of the side wall portion is 1.2 or more in a state before the gasket is incorporated into the cell.   2. The coin-type cell according to claim 1, wherein a ratio of a thickness of the bottom portion to a thickness of the side wall portion is 3 or less before the gasket is assembled into the cell.

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