JP2000149902A - Secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery capable of welding a gas exhaust valve to a cover without producing defects such as pinholes and cracks. SOLUTION: This secondary battery is constituted such that a secondary battery element is housed in a battery can 1 having airtightness by fixing a cover 12 to an opening of a cylinder 11, a disk-shaped valve 4 having a valve membrane 42 to be opened when the inner pressure of the battery can 1 exceeds a specified value is fixed to the opening edge of a through hole 14 installed in the cover 12 by welding the periphery of the valve 4, and a narrowing part 51 for narrowing down the cross section of a heat path through which heat in welding is passed is formed in the surroundings of the welded part of the valve 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery element, such as a wound electrode body, housed in a battery can, and generating electric power of the secondary battery element from a pair of electrode terminals attached to the battery can. The present invention relates to a secondary battery that can be taken out.

[0002]

2. Description of the Related Art In recent years, lithium secondary batteries having a high energy density have attracted attention as power sources for portable electronic devices, electric vehicles and the like. For example, a cylindrical lithium secondary battery having a relatively large capacity used in an electric vehicle has lids (12) and (12) welded and fixed to both ends of a cylindrical body (11) as shown in FIGS. The wound electrode body (2) is housed inside a cylindrical battery can (1). Both lids (12) (12)
Has a pair of positive and negative electrode terminal mechanisms (9) and (9) attached thereto, and includes a winding electrode body (2) and a double electrode terminal mechanism (9) and (9).
Are connected to each other by a plurality of current collecting tabs (3),
The power generated by the winding electrode body (2) can be taken out from the pair of electrode terminal mechanisms (9) (9). Further, a pressure opening / closing gas discharge valve (13) is attached to the lid (12).

As shown in FIG. 13, a non-aqueous electrolyte is impregnated between a positive electrode (21) containing a lithium composite oxide and a negative electrode (23) containing a carbon material, as shown in FIG. Separator
These are configured to be spirally wound with (22) interposed. Positive electrode (21) and negative electrode (23) of winding electrode body (2)
, A plurality of current collection tabs (3) are respectively drawn out, and the tip portions (31) of the plurality of current collection tabs (3) having the same polarity are connected to one electrode terminal mechanism (9). In FIG. 13,
For convenience, only a state in which the tip of one of the current collecting tabs is connected to the electrode terminal mechanism (9) is shown, and for the other current collecting tabs, the tip is connected to the electrode terminal mechanism (9). Illustration of the state is omitted.

The electrode terminal mechanism (9) is provided with a lid (1) of the battery can (1).
The screw member (91) has a flange (92) formed at the base end of the screw member (91). An insulating packing (93) is attached to the through-hole of the lid (12), so that electrical insulation and sealing between the lid (12) and the fastening member (91) are maintained. A washer (94) is fitted into the screw member (91) from outside the cylindrical body (11), and a first nut (95) and a second nut (96) are screwed together. And the first nut (9
5) Tighten the flange (92) of the screw member (91) and the washer (9).
By pinching the insulating packing (93) by 4),
It has improved sealing performance. The tips (31) of the plurality of current collecting tabs (3) are fixed to the flange (92) of the screw member (91) by spot welding or ultrasonic welding.

As shown in FIG. 9, a pressure release type gas discharge valve (operated when the internal pressure of the battery can (1) exceeds a predetermined value) is inserted into a through hole (14) formed in the lid (12). A secondary battery equipped with 4) is known (JP-A-6-68861 [H01M2-04]). As shown in FIG. 10 (a), the gas discharge valve (4)
A disc-shaped valve membrane (42) is fixed to 1), and the outer periphery of the ring body (41) is laser-welded to the opening edge of the through hole (14) of the lid (12) as shown in FIG. (15) Then, it is fixed to the lid (12).

[0006]

However, in the case of a large secondary battery, a large lid (1) having a thickness of several mm or more is required.
When fixing the gas discharge valve (4) to 2) by laser welding,
Because the thickness of the lid (12) is very large compared to the thickness of the gas discharge valve (4), the heat dissipated during welding is remarkable, and the molten metal that is irradiated with the laser beam cools rapidly. Accordingly, there is a problem that defects such as pinholes and cracks occur in the welded portion.

An object of the present invention is to provide a valve for discharging gas without generating defects such as pinholes and cracks.
An object of the present invention is to provide a secondary battery capable of welding (4) to the lid (12).

[0008]

Means for Solving the Problems A secondary battery according to the present invention comprises:
A lid (12) is fixed to an opening of a cylindrical body (11), and a secondary battery element is housed in an airtight battery can (1). The lid (12) has a disc-shaped valve (4) provided with a valve membrane (42) that opens when the internal pressure of the battery can (1) exceeds a predetermined value.
However, the outer peripheral portion is fixed by welding to an opening edge of a through hole (14) formed in the lid (12). The lid (12) is provided with a throttle (51) around the weld of the valve (4) for narrowing the cross-sectional area of the heat flow path through which heat during welding passes.

In the above secondary battery according to the present invention, the valve
Since the squeezed portion (51) is formed around the welded portion of (4), heat during welding is first transmitted to the squeezed portion (51), then transmitted to the periphery of the squeezed portion (51) and radiated. Will be. Here, the heat capacity of the constricted portion (51) is extremely small compared to the entire lid (12), and the cross-sectional area of the heat flow path through which the heat flux passes is also small in the constricted portion (51). Because it becomes
(51) becomes the heat conduction resistance, and the dissipation of heat during welding is suppressed. As a result, the weld cools at a moderate rate and solidifies without pinholes or cracks.

Specifically, a circumferential groove (5) extending around the welded portion of the valve (4) is formed in the front surface or the back surface of the lid (12), and the valve of the circumferential groove (5) is provided. The restricting portion (51) is formed between the side surface on the side and the welded portion of the valve (4). In another specific configuration, the narrowed portion (51) is formed by a cylindrical convex portion (6) protruding from the surface of the lid (12) so as to surround the through hole (14). The valve (4) is welded and fixed to the central opening of the part (6).

The circumferential groove (5) has a groove width in a range of 1/50 to 1 of the inner diameter of the through hole (14) formed in the lid (12), and a groove depth of the lid (12). It is desirable that the thickness is not more than 2/3 of the thickness of 12). The groove width of the peripheral groove (5) is 1/5 of the inner diameter of the through hole (14)
If the value is less than 0, the effect of the diaphragm portion (51) is low.
A problem occurs in the strength of the lid (12). In addition, groove depth is lid (12)
If the thickness exceeds 2/3 of the thickness, a problem occurs in the strength of the lid (12).

The secondary battery has, for example, a battery capacity of 5 Ah or more and 200 Ah or less, and a thickness of the lid (12) of 1 to 5 m.
m. In such a large-sized secondary battery, heat is conventionally remarkably dissipated from the welded portion of the gas discharge valve, and the throttle portion (51) of the present invention exhibits an excellent effect.

[0013]

According to the secondary battery of the present invention, the cover (1)
By forming the squeezed portion (51) in (2), the dissipation of heat when welding the valve (4) to the lid (12) is suppressed, and the molten metal during welding cools down at an appropriate speed, Defects such as pinholes and cracks do not occur in the weld.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to FIGS.
Large lithium secondary battery (battery capacity 5 Ah to 20
0Ah) will be specifically described with reference to the drawings. Note that the same components as those of the secondary batteries shown in FIGS. 11 to 13 are denoted by the same reference numerals, and description thereof will be omitted.

[0015]First embodiment  In the secondary battery of this embodiment, as shown in FIG.
Opening a through hole (14) in the lid (12) that constitutes the can (1)
Then, the through hole (14) is closed, and the gas discharge valve (4) is fixed by welding.
ing. A gas exhaust valve (4) is wrapped around the surface of the lid (12).
A peripheral groove (5) is recessed so as to surround the peripheral groove (5) and the gas discharge valve.
Between (4), a narrowed portion (51) is formed.

The gas discharge valve (4) is formed by fixing a disc-shaped valve membrane (42) to an annular ring (41) as shown in FIG. 2 (a). On the other hand, a through hole (14) formed in the lid (12) is formed in a stepped groove with which the gas discharge valve (4) can be engaged. The gas discharge valve (4) is a through hole in the lid (12) as shown in FIG.
While attached to (14), cover the outer periphery of the ring body (41) with the lid
(12) is fixed by laser welding.

At this time, a gas discharge valve is provided on the surface of the lid (12).
Since an annular narrowed portion (51) is formed surrounding the welded portion (15) of (4), heat during welding is first transmitted to the narrowed portion (51), and then the narrowed portion (51) is formed. ) And is radiated. Therefore, the narrowed portion (51) has a heat conduction resistance, and the dissipation of heat during welding is suppressed. As a result, the welded portion (15) in the molten state is gradually cooled, and the gas discharge valve (4) is welded and fixed to the lid (12) without generating defects such as cracks and pinholes.

In this embodiment, the lid (12) is made of aluminum and has an outer diameter E of 60 m as shown in FIG.
m, a thickness F of 4 mm, a thickness T of 1.0 mm, an inner diameter H of the lid (12) of 7 mm, an outer diameter D of the gas discharge valve (4) of 9 mm, and an inner peripheral surface of the circumferential groove (5). Diameter A is 11 mm and outer diameter B is 13
mm, the groove width C of the circumferential groove (5) is 1 mm, and the groove depth G is 1.5 m
m.

In order to demonstrate the effects of the above-described secondary battery of the present invention, a battery can of the present invention having a throttle portion (51) in a lid (12) and a comparative example without a throttle portion (51) were used as comparative examples. Ten lids were prepared for each of the battery cans, and a leak check with nitrogen gas and an operating pressure of a gas discharge valve were checked. Table 1 shows the results. The leak check is performed by pressurizing with 3 Kg / cm ² of nitrogen gas.
The soap solution was used to check for leaks. The gas discharge valve has a working pressure specification of 8 ± 1 kg / cm as a single valve.
^Two things were adopted.

[0020]

[Table 1]

As is clear from the results in Table 1, no leak was observed in any of the lids of the present invention, and the operating pressure was within the specified value. In contrast, in the comparative example, pinholes and cracks occurred in the four lids, and a decrease in the operating pressure of the gas discharge valve was observed in the three lids. The cause of the pinholes and cracks may be that the heat dissipation during laser welding is remarkable, so that the temperature of the welded portion has rapidly decreased. Also, as a cause of the decrease in the operating pressure, the heat dissipation during laser welding is remarkable, so that the welding time becomes excessively long, and the valve membrane (42) of the gas discharge valve (4) is overheated. It is considered that the valve membrane (42) was deformed by the stress, and a thin portion was locally generated.

Further, the lid (FIG. 4A) of the present invention and the throttle (5)
With respect to the conventional lid (1) having no 1), the lid immediately after laser welding of the gas discharge valve (4) (after 5 seconds and 20 seconds).
The temperature of each part of (12) was measured by thermography.
The results are shown in Tables 2 and 3. The measurement location N in the table
o. Corresponds to the numbered positions shown in FIGS.

[0023]

[Table 2]

[Table 3]

In the conventional lid, heat dissipation during welding is remarkable, and the temperature after welding is sharply reduced. As a result, pinholes and cracks occur in the welded portion as described above. On the other hand, in the lid of the present invention, since the narrowed portion of the heat flow path is formed, the temperature drop after welding is relatively small, and as a result, pinholes and cracks are reduced as described above. Without causing
The gas discharge valve can be welded.

In the above secondary battery of the present invention, the peripheral groove
In order to examine the optimum range of the groove width of (5), a through hole (1 mm) having a diameter of 60 mm and a thickness of 4.1 mm and an inner diameter of 10 mm was used.
4) and a cover of the present invention in which a circumferential groove (5) having a depth of 1.5 mm is formed, wherein the circumferential groove (5) has a cover having various groove widths, and a gas discharge valve is formed. Temperature measurement 5 seconds after welding and 3 kg
/ Cm ² of nitrogen gas was checked for leaks. Also, only the circumferential groove (5) of the same size as each lid is recessed,
Lids without through-holes (14) were prepared, and these lids were checked for leakage with 20 kg / cm ² of nitrogen gas, and the presence or absence of deformation and distortion of the lids was checked with a level meter. Table 4 shows the results.

[0026]

[Table 4]

As is clear from the results in Table 4, when the width of the peripheral groove (5) is smaller than 1/50 of the inner diameter of the through hole (14),
The temperature drop near the weld was remarkable, which caused pinholes. Also, the width of the peripheral groove (5) is
When the inner diameter is larger than the inner diameter of 4), the strength of the lid 12 is extremely reduced, and the lid 12 cannot withstand a predetermined pressure (20 kg / cm ² ). Therefore, it can be said that the groove width of the peripheral groove (5) is desirably in the range of 1/50 to 1 of the inner diameter H of the through hole (14) of the lid (12).

In the above secondary battery of the present invention, the circumferential groove
In order to check the optimal range of the depth of (5), the circumferential groove (5) has a width of 1 m.
m, having various groove depths and lids having the same dimensions as above except for the above, and subjected to the same pressure resistance test. Table 5 shows the results.

[0029]

[Table 5]

As is clear from the results in Table 5, when the depth of the circumferential groove (5) exceeds 2/3 of the thickness F of the lid (12), the lid (12)
A problem arises in the strength of Therefore, it can be said that the depth of the peripheral groove (5) is desirably 2/3 or less of the thickness F of the lid (12).

[0031]Second embodiment  As shown in FIG. 5, the secondary battery of this embodiment has a cover (12) with a cover.
On the surface, a cylindrical convex portion (6) is projected to surround the through hole (14).
Then, a gas discharge valve (4) is fixed to the central opening of the projection (6) by welding.
It is specified. In the secondary battery, the protrusion (6) is
Becomes the constricted portion (51) and suppresses heat dissipation of the welded portion (15)
I do.

[0032]Third embodiment  As shown in FIG. 6, the secondary battery of the second embodiment
The circumferential groove (5) of the first embodiment is recessed around the protrusion (6).
It is.

[0033]Fourth embodiment  As shown in FIG. 7, the secondary battery of this embodiment is
A peripheral groove (5) similar to that of the first embodiment is recessed on the surface.
You. In the secondary battery, the bottom of the peripheral groove (5) and the lid (12)
The narrowed portion (51) is formed between the surfaces.

[0034]Fifth embodiment  As shown in FIG. 8, the secondary battery of this embodiment has a circumferential groove (5).
It is not continuous as in one embodiment, but one or more
It is provided with an intermittent circumferential groove (5) interrupted at the place. This
Numerous circular holes are arranged in a circle instead of these multiple circumferential grooves (5)
It is also possible. In any of the above second to fifth embodiments
Also, the same effects as those of the secondary battery of the first embodiment can be obtained.
Needless to say,

[Brief description of the drawings]

FIG. 1 is a sectional view showing a main part of a secondary battery according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing steps (a) and (b) of welding and fixing a gas discharge valve to a lid in the secondary battery.

FIG. 3 is a cross-sectional view illustrating dimensions of each part of a lid.

FIG. 4 is a view showing a temperature measurement place in the lid (a) of the present invention and the lid of the comparative example (b).

FIG. 5 is a sectional view of a lid according to a second embodiment.

FIG. 6 is a sectional view of a lid according to a third embodiment.

FIG. 7 is a sectional view of a lid according to a fourth embodiment.

FIG. 8 is a plan view of a plurality of circumferential grooves recessed in a lid according to a fifth embodiment.

FIG. 9 is a cross-sectional view showing a main part of a secondary battery provided with a conventional pressure release type gas discharge valve.

FIG. 10 is a cross-sectional view showing steps (a) and (b) of welding and fixing a gas discharge valve to a lid in the secondary battery.

FIG. 11 is a perspective view of a conventional cylindrical lithium secondary battery provided with a pressure opening / closing type gas discharge valve.

FIG. 12 is an exploded perspective view of the secondary battery.

FIG. 13 is a cross-sectional view illustrating a main part of the secondary battery.

[Explanation of symbols]

 (1) Battery can (11) Cylindrical body (12) Lid (14) Through hole (4) Gas exhaust valve (41) Ring body (42) Valve membrane (5) Circumferential groove (51) Restricted part (6) Convex part

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Kazuyasu Fujiwara 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Toshiyuki Noma 2 Keihanhondori, Moriguchi-shi, Osaka 5-5-5 Sanyo Electric Co., Ltd. (72) Inventor Ikuro Yonezu 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd.

Claims (5)

[Claims] An airtight battery can (1) having a lid (12) fixed to an opening of a cylindrical body (11), and a secondary battery element housed therein. In 12), a disc-shaped valve (4) having a valve membrane (42) that opens when the internal pressure of the battery can (1) exceeds a predetermined value, the outer peripheral portion of which is opened in the lid (12). Through hole
In the secondary battery welded and fixed to the opening edge of (14), the lid (12) has a heat flow path around the welded portion of the valve (4) through which heat during welding should pass. Throttle section (5
A secondary battery, wherein 1) is formed. 2. A circumferential groove (5) extending around the welded portion of the valve (4) is formed in the front or back surface of the lid (12),
The secondary battery according to claim 1, wherein the throttle portion (51) is formed between a side surface of the peripheral groove (5) on a valve side and a welded portion of the valve (4). 3. The groove width of the peripheral groove (5) is in the range of 1/50 to 1 of the inner diameter of the through hole (14) formed in the lid (12), and the groove depth is equal to the lid (12). The secondary battery according to claim 2, wherein the thickness of the secondary battery is 2/3 or less. 4. The throttle (51) has a through hole formed in the surface of the lid (12).
The valve (4) according to claim 1, wherein the valve (4) is formed by a cylindrical projection (6) protruding around the (14), and the valve (4) is fixed by welding to a central opening of the projection (6). Rechargeable battery. 5. The secondary battery according to claim 1, wherein the battery capacity is 5 Ah or more and 200 Ah or less, and the thickness of the lid (12) is 1 to 5 mm.