JPH0290457A - flat sealed battery - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a flat sealed battery.

[Conventional technology]

In recent years, with the development of electronic devices, lithium batteries with low self-discharge and long life have come into widespread use. Therefore, as memory backup power sources for CMO and SRAM, cylindrical metal-glass metal so-called hermetic seals were adopted for battery lids, and lithium-oxyhalide batteries (e.g., lithium-thionyl chloride batteries) were developed. Demand is rapidly increasing because it has a high airtightness and can be used for a long period of 10 years or more.

However, in addition to the above-mentioned cylindrical backup batteries, the market is demanding smaller and thinner memory bank backup batteries due to the need to reduce current consumption of ICs, or to reduce the size and weight of devices. It is being

On the other hand, flat-shaped lithium batteries such as lithium-manganese dioxide batteries and lithium-fluorinated graphite batteries have been commercialized for some time, but these batteries are sealed by sealing the open end of the positive electrode can and the negative electrode can. This is because it uses the so-called crimp seal method, in which a synthetic resin gasket is interposed between the positive electrode can and the outer circumference, and the opening end of the positive electrode can is sealed by tightening inward (for example, Japanese Patent Laid-Open No. 56-167274). There is a limit to the period during which the airtightness can be maintained, and the maximum usable period is 5 to 7 years, and it is impossible to withstand use for more than 10 years. Therefore, users are demanding a flat sealed battery that uses a hermetic seal and has a high degree of airtightness.However, in the case of a flat sealed battery, it is difficult to seal the electrolyte injection port after the electrolyte is injected. At present, we are unable to meet such demands.

In other words, in the case of a cylindrical battery, the shape is large, the total height of the battery is at least 25 mm, and the sealing after injecting the electrolyte is performed at the two ends of the pipe used as the electrolyte injection port (for example, (Kokai No. 62-160660), the distance from the electrolyte surface in the battery container to the sealing part is at least 5 mm.
Therefore, the heat during welding for sealing has little effect on the electrolyte, but in a flat battery with a total battery height of at most 10 mm, the distance from the electrolyte surface to the welded part is 1
Since the electrolyte will be vaporized by the heat during sealing welding, the vaporized electrolyte will come out to the welding area, interfering with welding or creating pinholes in the welding area, so it is completely impossible to remove the electrolyte. It is not possible to achieve a sealed structure.

In addition, with flat batteries, if the electrolyte inlet is provided at the terminal part of the battery lid, the welded part will be too close to the glass layer, and the glass layer will be damaged by the heat during welding.
For example, as shown in FIG. 6, the bottom of the battery container (5) (
Drill a through hole in the center of 5a) and insert the electrolyte inlet (12).
After injecting the electrolyte (at least from the time of injecting the electrolyte,
6), cover the electrolyte inlet (12) with a sealing plate θω, and cover the outer periphery of the sealing plate θω with the battery container (5). ) bottom (5a
), but as mentioned above, because the distance between the welded part and the electrolyte level is short, the electrolyte vaporizes due to the heat during welding, causing the electrolyte to leak. Vaporized substances may come out to the welding area, interfering with welding, or causing pinholes to occur in the welding area, resulting in a loss of airtightness.

[Problem to be solved by the invention]

The present invention solves the difficulty of sealing the electrolyte inlet when producing a flat sealed battery that uses a hermetic seal as described above, achieves good welding, and provides sealing that can withstand long-term use. The purpose of the present invention is to provide a flat sealed battery with high performance.

[Means to solve the problem]

The present invention has been made to achieve the above object, and will be explained with reference to FIGS. 1 to 5, particularly FIGS. 1 to 3, which correspond to embodiments thereof. ) is provided with a cylindrical or tapered cylindrical electrolyte inlet (12a) having a tip (12a) on the inside of the battery, and after injecting the electrolyte, a sealing plug (13) is provided in the electrolyte inlet (12). ) and press-fit the metal outer can θ4 so that the outer can G4 is connected to the battery container (
5), and the open end [14a] of the outer nuclear can is welded to the open end (5b) of the battery container (5).

[Effect]

Since the sealing plug 03) is press-fitted into the electrolyte injection port 0,
The repulsive stress of the cylindrical or tapered electrolyte inlet surface (sealing plug (1) as described above) is applied to the sealing plug (1) from its surroundings.
By press-fitting (3), the cylindrical or tapered cylindrical electrolyte inlet surface is pushed and expanded, so a repulsive force is applied to the electrolyte inlet (12) to return it to its original state. As the degree of closeness increases, the electrolyte inlet surface is at least connected to the open end (14a) of the outer can Oa and the battery container (5).
Until the welding with the open end (5b) is completed, it is sealed with a sealing plug 03).

As a result, when welding the open end (14a) of the outer case (14) and the open end (5a) of the battery container (5), we have ensured that there are no pinholes, such as vaporized electrolyte coming out into the welded part. Welding is possible, and the inside of the battery is completely sealed, resulting in a highly airtight flat battery.

Further, in the battery of the present invention, the positive terminal (9) is attached to the battery lid (6).
), the open end (5b) of the battery container (5)
) approaches the positive electrode (2), which is relatively stable against heat, but
It moves away from the negative electrode (1), which has low thermal stability, which is placed on the bottom (5b) side of the battery container (5), and the open end (5b) of the battery container (5) and the open end on the outer can side. Part (14
The thermal effect of the heat during welding with a) on the negative electrode (1) is less than when welding is performed at the bottom (5a) of the battery container (5), and as a result, the lithium constituting the negative electrode (1) Alkali metals with low melting points such as are less likely to melt due to heat during welding, resulting in loss of negative electrode electricity due to reaction between negative electrode constituent materials and positive electrode active material used as electrolyte solvent, or melted negative electrode structure. The material is separator (3
) and comes into contact with the positive electrode (2), which rarely causes an internal short circuit.

〔Example〕

Next, embodiments of the present invention will be described based on the drawings. However, although a lithium-thionyl chloride flat sealed battery will be described in the Examples, the present invention is not limited to that case.

FIG. 1 is a sectional view showing a first embodiment of the flat sealed battery of the present invention, and FIG. 2(a) is an enlarged sectional view showing only the main parts of the battery shown in FIG. , FIG. 2(b) is an exploded view of FIG. 2(a). However, in the cross-sectional views, to avoid complication, the outline of the portion located on the back side of the cross-section is omitted.

First, to roughly explain the structure of the battery, (1)
is a negative electrode made of lithium, (2) is a positive electrode made of a carbon porous molded body, and (3) is a separator made of glass fiber nonwoven fabric, which separates the negative electrode (1) and the positive electrode (2). (4) is an electrolytic solution, (5) is a battery container made of stainless steel, and (6) is a battery lid. This battery lid (6) is annular and is made of a stainless steel body (7) and glass. The outer periphery (7a) of the body (7) is connected to the open end (5b) of the battery container (5) from the inner periphery side. Welded in contact. 00) is a positive electrode current collector, which is made of a stainless steel mesh and is spot welded to the lower part of the positive electrode terminal (9). (11) is an insulator made of glass fiber nonwoven fabric, which insulates between the positive electrode (2) and the positive electrode current collector 0[I] and the body (7) of the battery lid (6). Q21 is an electrolyte injection port, and this electrolyte injection port (12) is provided at the center of the bottom (5a) of the battery container (5), but in this example, the electrolyte injection port (12) is provided at the tip (12a) ( (See Figure 2)
It has a cylindrical shape with an inner side of the battery. 03) is a sealing plug, and this sealing plug 03) is press-fitted into the electrolyte injection port (12) after the electrolyte is injected into the battery from the electrolyte injection port (12). . (14) is an outer can made of stainless steel, and this outer can (14 is the above-mentioned battery container (
5), and its open end (14a) is in contact with and welded to the open end (5b) of the battery container (5) from the outer peripheral side. This battery has an outer diameter of 36 mm and a total height of 6.
It is a flat battery in the shape of a five-open disk, and the negative electrode (1)
, a positive electrode (2), a separator (3), an electrolytic solution (4), and other power generating elements are housed in a space formed by a battery container (5) and a battery lid (6).

Next, to explain the main components in detail, the negative electrode (1) is a lithium sheet punched into a ring shape and pressed onto the bottom inner surface of the battery container (5), and is composed only of lithium as the negative electrode active material. The positive electrode (2) consists of a porous molded body made of a carbonaceous material mainly composed of acetylene black and to which graphite and polytetrafluoroethylene are added, a so-called carbon porous molded body. . The electrolytic solution (4) consists of a thionyl chloride solution in which 1 mol/A of lithium aluminum tetrachloride is dissolved in thionyl chloride, and thionyl chloride is not only the solvent of the electrolytic solution as described above, but also the positive electrode active material. As is clear from the fact that thionyl chloride is used as the positive electrode active material, the positive electrode (2) itself does not react, but is ionized from the positive electrode active material thionyl chloride and the negative electrode (1). This provides a site for reaction with the lithium ions that have been eluted.

The battery container (5) is made of a stainless steel plate with a thickness of 0.5 mm and is formed into a container shape with an outer diameter of 33 mm and a height of 61 mm, and the center of the bottom (5a) has an inner diameter of 2.1 mm and a tip facing inside the battery. A cylindrical electrolyte inlet (121) with a height of about 1.5 mm and a portion (12a) is provided.The cylindrical electrolyte inlet surface is the surface of the electrolyte when injecting the electrolyte. This means that the space through which it can pass is formed by a cylinder.

As mentioned above, the battery cover (6) has a stainless steel body (
7), an annular insulating layer (8) made of glass, and a positive electrode terminal (9) made of stainless steel, and the insulating layer (8) made of glass has a stainless steel body (
7), and the inner peripheral surface is fused to the outer peripheral surface of the positive electrode terminal (9) made of stainless steel, and has a so-called metal-glass-metal hermetic seal. The outer periphery of the body (7) of the battery cover (6) as shown in
7a) is welded to the open end (5b) of the battery container (5), and this battery is configured to have a so-called completely sealed structure.

In this embodiment, the sealing plug 03) is made of a polytetrafluoroethylene ball with a diameter of 2.3 mm, and the diameter of the sealing plug 03) is slightly larger than the inner diameter of the electrolyte injection port (12), as described above. It is press-fitted into the electrolyte injection port (121) after the electrolyte is injected into the electrolyte injection port (121).Therefore, the repulsive stress of the electrolyte injection port (12) is applied to this sealing plug 03 from around it, and the closeness between the two is high. The electrolyte inlet (12) is in the above-mentioned state at least until the welding of the open end (14a) of the outer case (14) and the open end (5b) of the battery container (5) is completed. Since it is sealed by the sealing plug 03),
When welding the open end (14a) of the outer case (14) and the open end (5b) of the battery container (5), the vaporized electrolyte does not come out to the welded part, and the welding can be performed smoothly. At the same time, pinholes do not occur in the welded area.

The outer can side is a stainless steel plate with a thickness of 0.3 mm and an outer diameter of 36 mm.
It is formed into a container shape (can shape) with a height of 6 mm and a height of 5 mm.
It is arranged so as to surround the battery container (5), and the base end (12) of the electrolyte injection port 0 is located at the bottom (+4b).
Cover the opening on the b) side (see Figure 2), and cover the opening end (
14a) is in contact with and welded to the open end (5b) of the battery container (5) from its outer circumferential side. And this outer can (
14) doubles as a negative electrode terminal by welding it to the battery container (5) which is in contact with the negative electrode (1).

In addition, the bottom (14b) of the outer can (141) is provided with an explosion-proof thin-walled part 05, and if the battery is exposed to high temperature heating or charged at high voltage, the battery may When the pressure inside the battery rises abnormally due to the rise in internal pressure, the thin interior 05) breaks down within the pressure range that can ensure safety, causing the battery to explode under high pressure. It is designed to prevent explosions. In this embodiment, the thickness of this thin part 05) is 0.07 m.
m, but generally the thickness of this thin part θω is 0.
．． Selected from the range of 0.05 to 0.20.

This battery is manufactured, for example, as shown below.

First, the electrolyte inlet (12) is provided in the central part of the bottom (5a) of the battery container (5) in the above-described specific manner, and the positive electrode current collector is placed under the positive electrode terminal (9) of the battery lid (6). The body (00) is spot welded, and the insulator (11) is inserted between the body (7) and the positive electrode current collector (00).

Then, a lithium sheet punched into a ring shape is crimped onto the bottom inner surface of the battery container (5) to form a negative electrode (1),
A separator (3) is placed on top of it. Next, place the positive electrode (2) on the separator (3), and then place the battery lid (
6) into the battery container (5), and connect the outer periphery (7a) of the body (7) of the battery lid (6) and the open end (
The joint with 5b) was welded using a carbon dioxide laser. The output of the carbon dioxide laser for this sealing was 700 W, and the welding speed was 60 mm/sec.

Next, turn the battery being assembled above upside down from the state shown in Figure 1, and pour the electrolyte into the electrolyte injection port (12).
) into the battery, the sealing plug 03) is press-fitted into the electrolyte injection port θ, and the whole is inserted into the outer can (14) from the bottom (5a) side of the battery container (5). , outer can Oa
The outer can (14) surrounds the battery container (5).
The open end (14a) of the outer can Q41 is tightened inward and brought into contact with the open end (5b) of the battery container (5) from its outer circumferential side, and the open end of the outer can is removed using a carbon dioxide laser. Welding the part (14a) to the open end (5b) of the battery container (5) to seal the gap between the outer can (14) and the battery container (5),
A desired battery was produced. The welding conditions at this time were a laser output of 700W and a welding speed of 60mm/see.
Met.

This welding can be performed smoothly, and when the leakage amount was measured with a helium leak detector as described later, the leakage amount was as low as 10-910-9at/see, resulting in a highly airtight battery. It was done.

FIG. 3 is a sectional view showing a second embodiment of the flat sealed battery of the present invention, and section A in FIG. 3 is an enlarged sectional view showing only the main parts of the battery shown in FIG. 3. .

The battery of the second embodiment shown in FIG. 3 has an electrolyte injection port 0.
The shape of the battery is different from that of the battery of the first embodiment shown in FIG. 1, and is tapered cylindrical, but other than that, the structure is almost the same as that of the battery of the first embodiment shown in FIG. be.

Therefore, only the electrolyte inlet (12) and related parts will be described.

The battery container (5) is made of a stainless steel plate with a thickness of 0.5 mm and is shaped like a container with an outer diameter of 33 mm and a height of 6 mm, as in the case of the battery of the first embodiment shown in FIG. 1. However, in the center of the bottom (5a), there is provided a tapered cylindrical electrolyte inlet θ2) having a tip (12a) (see section A in FIG. 3) on the inside of the battery. Note that the tapered cylindrical electrolyte injection port (12) means that a tapered tube forms a gap through which the electrolyte can pass during injection of the electrolyte.

Base end (12b) of the electrolyte injection port (12) (third
(see part A in the figure) has an inner diameter of 3 mm, and the inner diameter of the smallest inner diameter portion of the tip (12a) is 2.1 mm.

After injecting the electrolyte into the battery from this electrolyte injection port (12), the electrolyte injection port (12) has a diameter of 2 mm.
, a sealing plug 03) made of a 3 mm polytetrafluoroethylene ball is press-fitted.

In this way, also in the battery of the second embodiment shown in FIG. ), the repulsive stress of the electrolyte inlet (12) due to the press-fitting is applied to the sealing plug 03) from its periphery, and the closeness between the two becomes high, causing at least the outer can (14) Until the welding between the open end (14a) of the battery container (5) and the open end (5b) of the battery container (5) is completed, the electrolyte inlet θ is sealed by the sealing plug 03). , the battery container (5) at the open end (14a) of the outer can (14).
) When welding to the open end (5b) of the welding part, vaporized electrolyte solution does not come out to the welded part and interfere with welding or cause pinholes in the welded part. In addition, the above outer can (1
4 is made of a stainless steel plate with a thickness of 0.3 mm, as in the case of the first embodiment shown in FIG. The open end (148) is welded to the open end (5b) of the battery container (5) using a carbon dioxide laser. The welding was performed at a power output of 00 W and a welding speed of 60 mm/sec, as in the case of the battery of the first embodiment shown in FIG. 1. Also, in the battery of the second embodiment shown in FIG. 3, welding after injecting the electrolyte is performed between the open end (14a) of the outer can θ and the opening of the battery container (5), which is remote from the negative electrode (1). Since it is carried out at the end (5b), there is little effect on the lithium that constitutes the negative electrode (1), and lithium and thionyl chloride (thionyl chloride is a positive electrode active material, but is also used as an electrolyte solvent). It is possible to reduce the loss of negative electrode electricity due to this reaction, or the occurrence of internal short circuits caused by molten lithium penetrating the separator (3) and coming into contact with the positive electrode (2).

Next, the open end (1
4a) and the open end (5b) of the battery container (5), and the occurrence of welding defects when welding the open end (5b) of the battery container (5) and the outer periphery of the sealing plate 06) of the flat sealed battery that was previously attempted. Bottom (5a)
The results of the investigation into the occurrence of welding defects during welding with
Shown in the table.

In Table 1, the denominator of the numerical value in the column indicating the number of batteries with welding defects represents the total number of batteries subjected to welding, and the numerator represents the number of batteries with welding defects due to the generation of pinholes. In addition, the first example and the second example showing the types of batteries are as described above, and these have a sealing plug of 0.
3) all use polytetrafluoroethylene bulbs, and the diameter of the sealing plug (13) and the electrolyte injection port θ2)
The relationship between the minimum inner diameter portion and the inner diameter is as described above.

Further, in the third and fourth examples, a stainless steel ball was used as the sealing plug 03), and in the third example, a stainless steel ball with a diameter of 2.3 mm was used as the sealing plug 03). Otherwise, the structure is the same as that of the first embodiment, and the fourth embodiment has the same structure as the second embodiment, except that a stainless steel ball with a diameter of 2.3 mm is used as the sealing plug surface. The conditions for welding the open end (14a) of the outer can (14) and the open end (5b) of the battery container (5) using a carbon dioxide laser in these first to fourth embodiments are as follows. In the same way as exemplified in Example 1, the output of the cuff is 00 W.
, the welding speed was 60 mm/sec.

Comparative Example 1 shows a flat sealed battery that has been attempted in the past.The battery of Comparative Example 1 has the configuration shown in FIG. 2m
A through hole of m is made to serve as an electrolyte injection port (12), and after the electrolyte is injected, a sealing plate 00 made of a disc-shaped stainless steel plate with a thickness of 0.3 mm and a diameter of 5 mm is used to connect the electrolyte injection port θ2).
The outer periphery of the sealing plate 06) is welded to the bottom (5a) of the battery container (5) using a carbon dioxide laser.

However, since the welded part is close to the electrolyte surface, the output of the carbon dioxide laser should be low at 400W, and the welding speed should be set at 2.
The welding speed was set to 0 mm/sec, and milder welding conditions were selected than in the case of the previous example.

As shown in Table 1, in the batteries of Comparative Example 1, welding defects occurred in all the batteries subjected to welding, but in all the batteries of the examples of the present invention, welding defects did not occur.

In addition, all of the batteries of the first to fourth examples had a leakage amount of 10-91 measured with a helium leak detector.
It was 0-9 at/sec or less, indicating high airtightness and high airtightness.

In the above embodiment, the sealing plugs (13) were all spherical, but the sealing plug 03) was not only spherical.
For example, as shown in Fig. 4, there is a cylindrical sealing plug 03) with a spherical tip (13a), or a conical sealing with a rounded tip f138) as shown in Fig. 5. Plug 03)
It may be. In short, the sealing plug 03) has a tip whose diameter is smaller than the part with the smallest inner diameter of the electrolyte injection port (12), and a part of which is larger than the part with the smallest inner diameter of the electrolyte injection port (12). Any material having a portion that has a diameter may be used.

In addition, in the example, a material made of polytetrafluoroethylene was used as the sealing plug 03), but the material of the sealing plug 03) may be other than the above-mentioned polytetrafluoroethylene. Tetrafluoroethylene copolymer, stainless steel, metal such as nickel, etc. can be used.

Although the shape of the electrolyte inlet θ is described as cylindrical or tapered, the present invention is capable of 10 m even if the total height of the battery is high.
Since the object is a flat battery of about 1.5 mm in size, the height of the battery is about 1.5 mm, as shown in the example, and is not very tall.

Further, in the example, the insulating layer (8) was made of glass, but
The insulating layer (8) may be made of ceramic instead of glass. Furthermore, in the examples, lithium was used as the negative electrode active material and thionyl chloride was used as the positive electrode active material, and a lithium-thionyl chloride battery was described. In addition to thionyl chloride, the positive electrode active material may also be an oxyhalide that is liquid at room temperature (25 C), such as sulfuryl chloride or phosphoryl chloride. Although the present invention is intended for batteries that use oxyhalides as a positive electrode active material and a solvent for an electrolyte, the present invention is not limited to this, but can also be applied to flat sealed batteries with a hermetic seal structure that use an organic electrolyte. can.

〔Effect of the invention〕

As explained above, in the present invention, a cylindrical or tapered cylindrical electrolyte inlet (12) is provided in the center of the bottom (5a) of the battery container (5), and after the electrolyte is injected, the electrolyte inlet By press-fitting the sealing plug 03) into the inlet θ2), the open end (14a) of the outer can 0/8 is inserted into the battery container while the electrolyte inlet (12) is sealed with the sealing plug 03). Since welding was performed on the open end (5b) of (5), it was possible to provide a flat sealed battery with high airtightness and no welding defects. In addition, after the electrolyte was injected, welding was performed between the open end (14a) of the outer can (14) away from the negative electrode (1) and the battery container (5).
Since this is carried out at the open end (5b) of the negative electrode (1), the thermal effect on the lithium etc. that constitutes the negative electrode (1) is reduced, and the loss of negative electrode electricity due to the reaction between the negative electrode constituent material and the electrolyte or the melted negative electrode constituent material is reduced. penetrates the separate lake (3) and connects to the positive electrode (
2) It is possible to reduce the occurrence of internal short circuits due to contact with

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a first embodiment of the flat sealed battery of the present invention, and FIG. 2(a) is an enlarged sectional view showing only the main parts of the battery shown in FIG. Figure 2 (+)) is Figure 2 (
FIG. FIG. 3 is a sectional view showing a second embodiment of the flat sealed battery of the present invention, and section A in FIG.
FIG. 2 is an enlarged cross-sectional view showing only the essential parts of the battery shown in the figure. FIGS. 4 and 5 are cross-sectional views showing other examples of sealing plugs used in the flat sealed battery of the present invention. FIG. 6 is a sectional view showing a conventionally attempted flat sealed battery. (1)...Negative electrode, (2)...Positive electrode, (3)...
・Separator, (4)...Electrolyte, (5)...Battery container, (5a)...Bottom, (5b)...Open end, (6)...Battery lid, (7) ...Body, (7
a)...outer periphery, (8)...insulating layer, (9)...
・Positive terminal, θ2) ・Electrolyte inlet, (12a
)...Tip part, 03)...Sealing plug, 0 leak...Outer can, (14a)...Open end part Fig. 1 Fig. 1...Negative electrode 2...Positive electrode 3. Separator 4 Electrolyte 5 Battery container 5a Bottom 5b Open end 6 Battery lid 7 Body 7a Outer periphery 8 Insulating layer 9 Positive electrode Terminal 12... Electrolyte inlet 12a... Tip part 13... Sealing plug

Claims (1)

[Claims] (1) The power generation element is made of metal battery container (5) and battery lid (6).
), the battery lid (6) is made of metal and has an annular body (7).
and an annular insulating layer (8) made of glass or ceramics located on the inner circumferential side of the annular body (7), and a positive terminal (9) located in the center of the annular insulating layer (8). , the outer periphery (7a) of the body (7) of the battery cover (6)
) is welded to the open end (5b) of the battery container (5), and in the center of the bottom (5a) of the battery container (5) is a cylindrical or tapered tube having a tip (12a) on the inside of the battery. A shaped electrolyte inlet (12) is provided, and after injecting the electrolyte, a sealing plug (13) is press-fitted into the electrolyte inlet (12), and a metal outer can (14) is inserted into the outer can (14). ) is the above battery container (
5), and the open end (14a) of the outer can (14) is placed so as to surround the open end (5) of the battery container (5).
b) A flat sealed battery characterized by being formed by welding.