JPH01140553A - Flat electrochemical device - Google Patents

Abstract

PURPOSE:To obtain an excellent sealing property by contacting a terminal plate which consists of a metal plate or the like along the inner surface of the main plane of at least one side of two half cases closely to the main plane through an insulating resin. CONSTITUTION:A case 10 furnishes the first and the second half cases 11 and 12, which consist of a metal plate or a metal foil of such as a stainless steel, for example, and deposited to line up main planes 13 and 14 parallel. In such a way, the case 10 of a flat form as a whole can be obtained. In this case, along the inner surface of the main plane of at least one side of the half cases 11 and 12, along the inner surface of the main plane 13, for example, a terminal plate 17 which consists of a metal plate or a metal foil to be one side of the outer terminals is,disposed on condition that it is contacted closely to the main plane through an insulating resin 22. And at the main plane 13, an opening 23 where a part of the terminal plate 17 is exposed is formed. In such a way, the sealing property of the contacts at the peripheries 15 and 16 can be improved extensively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to an electrochemical device such as an electric double layer capacitor or a battery, and particularly relates to a flat electrochemical device having a case having an overall flat shape. The present invention relates to improvements in the structure of a case and external terminal means in a device.

[Conventional technology] Power supplies for IC cards that have been developed in recent years include:
Lithium batteries or electric double layer capacitors are suitable, and these electrochemical devices for power supply are of a thin shape, that is, of a flat type.

The electrolyte for lithium batteries is usually a non-aqueous electrolyte made by dissolving lithium perchlorate in an organic solvent such as propylene carbonate or γ-butyrolactone. It is desirable to use the same type of electrolytic solution because the withstand voltage can be set high.

However, when using such a non-aqueous electrolyte, if the amount of water in the system increases, the internal resistance increases, the withstand voltage decreases, and the performance deteriorates, so it is necessary to maintain a highly dehydrated state. There is.

For example, as an example of a flat battery suitable as a power source for an IC card, there is a structure shown in FIG. In FIG. 6, the structure of a so-called "paper lithium battery" is shown. Referring to FIG. 6, case 1 includes first and second case halves 2 and 3 made of metal plates or foils such as stainless steel. The respective peripheral edges of the first and second case halves 2 and 3 are joined via a sealing material 4 made of an organic material such as a thermally adhesive film, whereby the case 1 having a sealed structure is formed. Given. Inside the case 1, a positive electrode active material 5 and a negative electrode active material 6 are arranged with a separator 7 containing an electrolyte sandwiched between them.

In such a structure, the first case half 2 and the second case half 3 are electrically insulated from each other by the sealing material 4, and the first case half 2 is insulated from the positive electrode active material. 5 , the second case half 3 is in electrical contact with the negative electrode active material 6 . Therefore, the first and second case halves 2 and 3 also serve as first and second external terminal means, respectively.

[Problems to be solved by the invention] In the structure of the "paper lithium battery" shown in FIG. 6, the permeation of moisture in the first and second case halves 2 and 3 themselves can be ignored, but As mentioned above, since the sealing material 4 uses an organic substance, there is a drawback that moisture permeates or enters through the sealing material 4, and the internal electrolyte often volatilizes, resulting in poor sealing reliability. Ta.

The permeation or intrusion of moisture and the volatilization of the electrolyte occur due to the diffusion of the moisture and electrolyte in the sealing material 4. For example, in order to make the case 1 flexible, it is desirable to use a flexible organic material such as a thermoadhesive resin for the sealing material 4, but in that case, the above-mentioned diffusion occurs particularly markedly. .

When the diffusion species and resin layer are constant, the amount of diffusion can be generally considered to be proportional to [cross-sectional area/diffusion distance]. In the structure shown in FIG. 6, the sealing material 4 included therein will be explained with reference to FIG. 7, which shows a plan view. Material 4
The product of (2a+2b+8w)Xt with the thickness t is obtained, and the diffusion distance is W. Here, the length of the outermost periphery of the sealing material 4 is adopted as a factor for determining the cross-sectional area because the outer peripheral portion of the sealing material 4 is exposed to the outside. In this way, the cross-sectional area that determines the amount of diffusion is proportional to the length of the outermost periphery of the sealing material 4, but if the diffusion distance W is simply increased to reduce the amount of diffusion, the length of the outermost periphery and the cross-sectional area becomes even larger, which not only reduces the effect but also increases the external dimensions of the product and conversely reduces the internal volume of the case 1, which is undesirable from a practical standpoint.

As described above, in the structure shown in FIG. 6, the reliability of the sealing is poor, so the life of the battery is short, and the usage environment is also severely restricted.

On the other hand, electric double layer capacitors, more than the batteries mentioned above,
Since long life and high reliability are required, the structure shown in FIG. 6 was insufficient in terms of sealing reliability. Therefore, with regard to electric double layer capacitors, the current situation is that a sealing structure that provides excellent sealing properties while providing a flat shape has not yet been practically realized.

Therefore, the present invention is directed to, for example, batteries (including primary batteries and secondary batteries) equipped with functional materials such as active materials or polarizable electrodes using organic electrolytes, or electrochemical devices such as electric double layer capacitors. An object of the present invention is to provide a structure for a flat electrochemical device that can be made into a flat shape while providing excellent sealing performance.

[Means for Solving the Problems] The flat electrochemical device according to the present invention first includes first and second case halves, each of which has a main plane portion and a peripheral portion and is made of a metal plate or foil. The first and second case halves are assembled together so that the main plane parts are arranged substantially parallel to each other and form a joining part at each peripheral edge part, and the case has an overall flat shape. a case for the electrochemical device, a separator housed in the case and extending substantially parallel to the main plane, and a separator housed in the case and positioned with the separator in between. The method is based on the premise that the method includes first and second functional substances, and first and second external terminal means that electrically contact the first and second functional substances, respectively, and the above-mentioned technology In order to solve the problems of
It is characterized by having the following configuration.

That is, the peripheral edges of the first and second case halves are welded together.

Further, along the inner surface of the main plane portion of at least one of the first and second case halves, the first and second
A terminal plate made of a metal plate or a foil, which is to be one of the external terminal means, is disposed in close contact with the main plane part via an insulating resin layer, and An opening is formed to expose a portion of the terminal plate.

[Operations and Effects of the Invention] According to the present invention, the case having a flat shape as a whole is integrated by welding the peripheral edges of the first and second case halves to each other. The reliability of the sealing of the joint by such welding is high, and therefore no or negligible diffusion of moisture or electrolyte occurs in the outer peripheral portion of the case.

Further, according to the present invention, the terminal plate to be one of the first and second external terminal means is connected to the first and second external terminal means.
The terminal board is disposed along the inner surface of at least one main plane part of the case half, and the terminal board is in close contact with the main plane part via an insulating resin layer. An opening is formed in the main plane portion to expose a part of the terminal board. In such a structure, the opening is formed in order for the terminal plate to function as an external terminal means, but this opening only causes the permeation and intrusion of moisture and volatilization of the electrolyte as described above. It can be a place. However, in the structure according to the present invention, the cross-sectional area where diffusion occurs is defined by the product of the inner circumference length and thickness of the insulating resin layer, but the inner circumference length of the insulating resin layer is
The opening can be made as small as the length of the inner circumference of the opening, and the opening only needs to be large enough to allow the terminal plate to function as external terminal means. Therefore, this opening can be made much smaller than the dimensions indicated by a and b in the conventional sealing material 4 shown in FIG. 7, and as a result, the cross-sectional area in which diffusion occurs can be made extremely small. be able to.

Further, according to the present invention, the width of the insulating resin layer, that is, the dimension measured in the radial direction on the surface on which the main plane portion extends, can be made sufficiently large without increasing the external dimensions of the product. This means that the diffusion distance can be increased, and from this point of view as well, it is possible to more effectively prevent the permeation and intrusion of moisture and the volatilization of the electrolyte.

As is clear from the above description, the flat electrochemical device according to the present invention can achieve extremely high sealing performance, and therefore can further extend the life span and improve reliability of the flat electrochemical device. can be achieved.

DESCRIPTION OF THE EMBODIMENTS FIG. 1 shows a first embodiment of the invention in an end view taken along the center. The flat electrochemical device shown here is, for example, an electric double layer capacitor or a battery.

Referring to FIG. 1, case 10 includes first and second case halves 11 and 12. Case halves 11 and 12 are each made of a metal plate or foil, such as stainless steel, and have main plane parts 13 and 14 and peripheral parts 15 and 16. In particular, in this embodiment, the first case half 11 is arranged between the main plane part 13 and the peripheral edge part 15 such that the main plane part 13 and the peripheral edge part 15 are located on different planes. bent part 1
7 is formed. The first and second case halves 11 and 12 are mated together such that their respective major planes 13 and 14 are aligned substantially parallel to each other, with their respective peripheral edges 15 and 16 being welded together. joined by. In this way, the case 10 having an overall flat shape is obtained.

A separator 18 extending substantially parallel to the main plane portion 13.14 is housed within the case 10, and first and second functional substances 19 and 20 are housed sandwiching the separator 18. . The separator 18 is
Contains electrolyte.

Further, the first and second functional substances 19 and 20 are polarizable electrodes when the electrochemical device is an electric double layer capacitor, and on the other hand, when the electrochemical device is a battery, the first and second functional substances 19 and 20 are polarizable electrodes. , one is a positive electrode active material and the other is a negative electrode active material. The second functional substance 20 is in electrical contact with the second case half 12 and the first case half 11 is connected to the second case half 12 via a peripheral edge 15.16. The first and second
The case halves 11 and 12 also serve as one external terminal means.

Along the inner surface of the main plane part 13 of the first case half 11,
A terminal plate 21 made of a metal plate or foil, such as stainless steel, is arranged. This terminal plate 21 is to serve as the other external terminal means and is in electrical contact with the first functional material 19. The terminal board 21 is
It is brought into close contact with the main plane portion 13 via the insulating resin layer 22 . The insulating resin layer 22 is made of, for example, an insulating heat-adhesive film or an adhesive. An opening 23 is formed in the main plane part 13 to expose a part of the terminal board 21.

The opening 23 described above is preferably located at the center of the main plane portion 13. Further, the terminal board 21 has an insulating resin layer 2 in almost the entire area except for the area facing the opening 23.
It is preferable that it be brought into close contact with the first surface part 13 of the earthen flat through the second part 2.

FIG. 2 shows a second embodiment of the invention.

The second embodiment differs from the first embodiment described above only in the following points.

That is, in the first embodiment, the second case half 12 had a flat plate shape as a whole with the main plane part 14 and the peripheral part 16 located on the same plane. In the example, a bent portion 24 is also formed between the main plane portion 14 and the peripheral edge portion 16 in the second case half 12a. Therefore, the bend 17a formed in the first case half 11a is made shallower, and the case 10a is generally symmetrical with respect to the separator 18. The rest of the structure is the same as the first embodiment, so the same reference numbers used in FIG. 1 will be used in FIG. 2 for corresponding elements, and redundant explanation will be omitted. .

FIG. 3 shows a third embodiment of the invention.

This third example is based on case 10 in the second example.
The case 10b has a shape similar to that of the case 10b. Therefore, regarding the first and second case halves 11a and 12a constituting the case 10b, the same reference numerals as shown in FIG. 2 are used in FIG. do. Also, case 10b
The separator 18, the first and second functional materials 19 and 20, the terminal board 21, and the insulating resin layer 22 housed in the interior are the same as those in the first and second embodiments, so similar references will be made. By assigning reference numerals in FIG. 3, redundant explanation will be omitted.

The features of the third embodiment shown in FIG. 3 are as follows:
The terminal plate 25 is also arranged along the inner surface of the main plane portion 14 of the second case half 12a. The terminal plate 25 is in electrical contact with the second functional material 20 and is closely attached to the main plane portion 14 via an insulating resin layer 26 . An opening 27 is also formed in the main plane portion 14 to expose a portion of the terminal board 25.

According to the third embodiment shown in FIG.
terminal boards 21 and 25 are connected to the first and second terminal boards, respectively.
Therefore, the first and second case halves 11a and 12a do not perform any particular electrical function.

According to the first to third embodiments described above, diffusion of moisture or electrolyte occurs in the insulating resin layers 22 and 26, but the amount of such diffusion can be made extremely small. This will be explained with reference to FIG. FIG. 4 shows, for example, the first embodiment shown in FIG. 1 in a plan view. In FIG. 4, particularly the area where the insulating resin layer 22 is formed is shown with hatching. As can be seen from FIG. 4, the cross-sectional area where moisture permeates or intrudes or where the electrolyte evaporates is determined by the product of the inner circumference length of the opening 23 and the thickness of the insulating resin layer 22. Regarding the inner circumference, terminal plate 2
It is sufficient to have a size that allows 1 to function as an external terminal means, so it can be made considerably small.
As a result, the above-mentioned cross-sectional area can be made extremely small.

Further, the width of the insulating resin layer 22 can be made sufficiently wide without increasing the external dimensions of the product. These two factors both work to reduce the permeation or intrusion of moisture or the volatilization of electrolyte.
Therefore, a sealed structure with high sealing performance can be obtained.

Next, comparative evaluation results when an electric double layer capacitor is constructed with the structure shown in FIG. 1 and the structure shown in FIG. 6 will be described below.

First, in order to obtain the structure shown in FIG. 1 which is an embodiment of the present invention, a terminal plate 21 made of stainless steel foil with a thickness of 30 μm,
After applying a phenolic resin carbon paste on each predetermined surface of the second case half 12 made of stainless steel foil with a thickness of 50 μm, activated carbon containing about 5 ffi of polytetrafluoroethylene as a binder is added. Pressure/
Polarizable electrodes 19 and 20 were formed by pressure bonding.

Each dimension of these polarizable electrodes 19 and 20 is 13 mm.
The dimensions were 18 mm x 0.15 mm. The other surface of the terminal board 21 was thermocompression bonded to the first case half 11 made of stainless steel foil with a thickness of 50 μm using a modified polyethylene film with a thickness of 30 μm as the insulating resin layer 22. The opening 23 formed in the first case half 11 is 3 mm x 5 m.
Is it the size of m? Ta. Next, each polarizable electrode 19
and 20, after injecting propylene carbonate containing 1M LiClO4 as an electrolyte, these polarizable electrodes 19 and 20 were made to face each other with a separator 18 made of a 25 μm microporous polypropylene film interposed therebetween, and then, First and second case halves 11 and 12
The peripheral edges 15 and 16 of were welded using a laser.

The external dimensions of the obtained electric double layer capacitor were 19 mm.
It was 24mm x 0.50mm. Further, the water content in the electrolyte was about 30 ppm.

On the other hand, as a comparative example, in order to obtain the structure shown in FIG. 6 and separator 7, the same ones as in the above example were used. The sealing material 4 was made of the same material as the insulating resin layer 22 described above, and the width of the sealing material 4 was 3 mm. The outer dimensions of the obtained electric double layer capacitor were 23 mm x 28 mm x 0.45 mm. Further, the water content in the electrolyte was about 30 ppm.

FIG. 5 shows the results of tracking the amount of moisture increase in the system when these two samples were left in an atmosphere of 85° C. and relative humidity of 90% RH. From FIG. 5, it can be seen that the sealing performance of the embodiment according to the present invention is extremely superior to that of the comparative example.

[Brief explanation of the drawing]

FIG. 1 shows a first embodiment of the present invention in a cut-away end view taken at the center. Second
The figure corresponds to FIG. 1 and shows a second embodiment of the invention. FIG. 3 shows a third embodiment of the invention,
This is a diagram corresponding to FIG. 1. FIG. 4 is a plan view of the embodiment of FIG. 1. FIG. 5 shows the effect of this invention in comparison with the conventional example.
It is a graph showing the degree of increase in water content. Figure 6 shows an example of a conventional flat type electrochemical device.
FIG. 2 is a diagram corresponding to FIG. 1 showing a paper lithium battery. FIG. 7 is a plan view showing how the sealing material 4 shown in FIG. 6 is formed. In the figure, 10.10g, 10b are cases, 11, l
la is the first case half, 12.12a is the m2 case half, 13.14 is the main plane part, 15.16 is the peripheral part, 1
7.24 is a bent part, 18 is a separator, 19 is a first functional material, 20 is a second functional material, 21.25 is a terminal plate,
22.26 is an insulating resin layer, and 23.27 is an opening. b Figure 5

Claims (6)

[Claims] (1) First and second case halves each having a main plane part and a peripheral edge part and made of a metal plate or foil, wherein the main plane parts are arranged substantially parallel to each other and each of the peripheral edges a case having an overall flat shape, in which the first and second case halves are joined together to form a joint at a portion thereof; a separator extending substantially in parallel; first and second functional substances for the electrochemical device that are housed in the case and are positioned between the separators; and the first and second functional substances. A flat electrochemical device comprising first and second external terminal means in electrical contact with each other, wherein the first
and the peripheral edges of the second case halves are welded to each other, and the first and second external A terminal plate made of a metal plate or a foil to serve as either one of the terminal means is disposed in close contact with the main plane part via an insulating resin layer, and the main plane part includes: A flat electrochemical device, characterized in that an opening is formed to expose a part of the terminal plate. (2) The flat electrochemical device according to claim 1, wherein the opening is located at the center of the main plane portion. (3) The terminal board is in close contact with the main plane portion via the insulating resin layer in almost the entire area except the area facing the opening. flat type electrochemical device. (4) The first case half forms a bent part between the main plane part and the peripheral edge part so that the main plane part and the peripheral edge part are respectively located on planes parallel to each other. However, on the other hand, the second case half has an overall flat plate shape in which the main plane part and the peripheral edge part are located on the same plane. The flat electrochemical device according to any one of Items 1 to 3. (5) Each of the first and second case halves has a space between the main plane part and the peripheral edge part so that the main plane part and the peripheral edge part are respectively located on different planes. The flat electrochemical device according to any one of claims 1 to 3, which forms a bent portion. (6) the terminal board includes first and second terminal boards that constitute each of the first and second external terminal means;
The first terminal plate is arranged along the inner surface of the main plane part of the first case half, and the second terminal plate is arranged along the inner surface of the main plane part of the second case half. the insulating resin layer and the opening are formed in relation to each of the first and second case halves;
A flat electrochemical device according to any one of claims 1 to 5.