JP2012200768A - Welding method for container and method for manufacturing secondary battery using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a welding method for a container capable of preventing generation of pores in the container, and to provide a method for manufacturing a secondary battery using the welding method for a container.SOLUTION: A manufacturing step S1 of the secondary battery 1, which has a container 10 made of a storage section 11 having an open surface and a cover 12 for closing the open surface of the storage section 11, includes a welding step S12 where welding is carried out along the whole circumference of the sides of the airtight container 10 until a section obtained by melting a contact portion between the storage section 11 and the cover 12 reaches to the inside of the airtight container 10 while differential pressure between the inside and outside of the airtight container 10 is generated by using a decompression pump 40 so as to make the inside of the airtight container 10 become at a decompressed state against the outside.

Description

  The present invention relates to a container welding method and a battery manufacturing method using the same, and more particularly to a technique for suppressing generation of pores in a welded portion of a metal sealed container.

  Conventionally, a storage part and a lid part are joined to a metal hermetic container including a storage part whose upper surface is opened and a lid part that closes the opening surface of the storage part like a container of a secondary battery. Welding is being performed.

In welding to the container as described above, the contact portion is melted by a laser in a state where the storage portion and the lid portion are in contact with each other, and the fusion portion is solidified to join the storage portion and the lid portion. is doing.
At this time, in order to ensure the strength of the joint portion between the storage portion and the lid portion, it is necessary to set the welding depth to a predetermined value or more (for example, 0.3 mm or more). Therefore, in order to realize such a welding depth, so-called keyhole type laser welding is performed using a hole generated by a reaction force caused by evaporation of metal during welding.

  According to keyhole type laser welding, the welding depth as described above can be achieved, but high power density laser vaporizes impurities such as hydrogen contained in the molten metal (for example, aluminum alloy), and the metal As a result, the molten portion of the material solidifies and remains as a pore in the weld formed. Therefore, there arises a problem that the strength of the welded portion, that is, the joint portion between the storage portion and the lid portion cannot be made desired.

  Patent Document 1 discloses a technique for suppressing the generation of pores in a welded portion by adopting a metal with a relatively small hydrogen content as a metal to be welded.

  However, the technique described in Patent Literature 1 is disadvantageous in that hydrogen is contained in the metal to be welded in a trace amount. Moreover, it is disadvantageous in that the generation of pores formed by the vaporization of the metal to be welded cannot be suppressed.

JP 7-118783 A

  An object of the present invention is to provide a method for welding a container capable of preventing the generation of pores in a welded portion, and a method for manufacturing a secondary battery using the same.

  The container welding method of the present invention is a container welding method comprising: a storage portion having an opening surface; and a lid portion that closes the opening surface of the storage portion, wherein the inside of the sealed container is external to the outside. In such a state that a pressure difference is generated between the inside and the outside of the container, the contact portion between the storage portion and the lid portion is melted so that the molten portion is inside the container. Until reaching the contact area.

  In the container welding method of the present invention, it is preferable that keyhole laser welding is applied to the container.

  In the container welding method of the present invention, the differential pressure is preferably 22 to 70 [kPa].

  A method for manufacturing a secondary battery according to the present invention is a method for manufacturing a secondary battery including the container, wherein the container welding method according to any one of claims 1 to 3 is used. A welding process for welding the container;

According to the container welding method of the present invention, generation of pores in the welded portion can be prevented.
Moreover, according to the manufacturing method of the secondary battery which concerns on this invention, the intensity | strength of the container of a secondary battery can be improved.

The figure which shows the secondary battery which concerns on this invention. The flowchart which shows the manufacturing process of the secondary battery which concerns on this invention. The end view which shows the contact part of an accommodating part and a cover part. The figure which shows the mode of the exterior of the container in a welding process. The end elevation which shows the mode inside the container in a welding process. The end elevation which shows the mode of the welding process in case the differential pressure | voltage between the inside of a container and the exterior is comparatively large. The end elevation which shows the mode of the welding process in case the differential pressure | voltage between the inside of a container and the exterior is comparatively small. The figure which shows the relationship between the differential pressure | voltage of the inside and the exterior of a container, and the weld thickness of a welding part. The end view which shows the partition part formed in the side plate of a storage part. The end view which shows the notch formed in the side plate of a storage part. The figure which shows the partition part and notch part which were formed in the side plate of a storage part. The figure which shows the relationship between the welding position of a container, and the differential pressure | voltage between the inside of a container, and the exterior.

Below, with reference to FIG. 1, the secondary battery 1 which concerns on this invention is demonstrated.
For convenience of explanation, the vertical direction in FIG. 1 is defined as the vertical direction of the secondary battery 1.

  As shown in FIG. 1, the secondary battery 1 includes an electrode body (not shown) and a container 10 in which an electrolytic solution is stored, and terminals 20 and 20 connected to the positive electrode and the negative electrode of the electrode body.

  The container 10 is a sealed container made of an aluminum alloy and is used as an exterior of the secondary battery 1. The container 10 includes a storage part 11 and a lid part 12.

  The storage part 11 is a box-shaped member having a substantially rectangular parallelepiped shape with an upper surface opened.

  The lid portion 12 is a flat plate-like member having a shape corresponding to the outer peripheral shape of the opening surface of the storage portion 11. The lid portion 12 is brought into contact with the upper end portion of the storage portion 11 in a state where the electrode body is stored therein so as to cover the opening surface (upper surface) of the storage portion 11. In this state, a contact portion between the storage portion 11 and the lid portion 12 is melted by a laser or the like, and the weld portion 30 is formed by solidifying the melted portion, and the storage portion 11 and the lid portion 12 are joined. . That is, the storage portion 11 and the lid portion 12 are welded in a state where the upper end portion of the storage portion 11 is in contact with the lower surface of the lid portion 12.

The lid portion 12 is formed with a liquid inlet 13 which is an opening for injecting the electrolytic solution so as to communicate the inside and the outside of the container 10. After the storage portion 11 and the lid portion 12 are welded, the electrolytic solution is injected from the injection port 13, and the injection port 13 is sealed with the sealing material 14.
Further, the lid portion 12 is formed with two openings through which the terminals 20 and 20 can pass. By inserting and fixing the terminals 20 and 20 into these openings, the terminals 20 and 20 are finally fixed. -20 will be fixed in the state which protruded the exterior of the container 10. FIG.

  The terminals 20 and 20 are members made of metal such as aluminum or copper. One end portions of the terminals 20 and 20 are electrically connected to the positive electrode and the negative electrode of the electrode body, respectively, and the other end portions of the terminals 20 and 20 are disposed so as to protrude from the lid portion 12 toward the outside of the container 10. Is done.

  Below, with reference to FIGS. 2-12, manufacturing process S1 of the secondary battery 1 which is one Embodiment of the manufacturing method of the secondary battery which concerns on this invention is demonstrated.

  As shown in FIG. 2, the manufacturing process S1 includes a storage process S11, a welding process S12, and a liquid injection process S13.

The storing step S <b> 11 is a step for storing the electrode body in the container 10.
In the storing step S11, one end of each of the terminals 20 and 20 is connected to the positive electrode and the negative electrode of the electrode body, respectively, and the other end of the terminals 20 and 20 is passed through the lid portion 12 so that they are integrated, The electrode body is housed from the opening surface of the housing portion 11 to the inside.
At this time, as shown in FIG. 3, the opening surface (upper surface) of the storage portion 11 is brought into contact with the lower end portion of the contact portion 12a formed on the lid portion 12 and the upper end portion of the side plate 11a of the storage portion 11. ) Is closed by the lid 12.
The contact portion 12a is formed by cutting the outer edge portion of the lid portion 12 upward from the lower surface of the lid portion 12 over the entire circumference. That is, in the cover part 12, the thickness (vertical dimension) of the contact part 12a is smaller than the thickness of other parts. The contact portion 12a is formed from the outer edge portion of the lid portion 12 to a position slightly inward (left side in FIG. 3) from the inner peripheral surface of the side plate 11a of the storage portion 11, and the side plate 11a contacts the contact portion 12a. A predetermined clearance is formed between the inner peripheral surface of the side plate 11a and the lid portion 12 in the contact state.
In the present embodiment, it is assumed that the electrode body is manufactured before the storing step S11, and the electrode body is a known one used for a general secondary battery. The detailed description of is omitted.

As shown in FIG. 2, after the storing step S11, a welding step S12 is performed.
The welding step S12 is a step of welding the container 10, and is an embodiment of the container welding method according to the present invention.

As shown in FIG. 4, in the welding step S <b> 12, first, the storage portion 11 is brought into contact with the lid portion 12 by an actuator (not shown) such as an air cylinder with a predetermined pressing force, and the suction pipe 41 is set. Then, a vacuum pump 40 is attached to the liquid injection port 13 to seal the container 10.
The decompression pump 40 is a pump that decompresses the inside of the container 10 and functions as a means for generating a differential pressure between the inside and the outside of the container 10 so that the inside of the container 10 is in a decompressed state with respect to the outside. To do.
The suction pipe 41 is a pipe that communicates the inside of the container 10 with the decompression pump 40.

Next, the inside of the container 10 is decompressed by the decompression pump 40.
In this state, the storage portion 11 and the lid portion 12 are welded over the entire side surface of the container 10.
Specifically, as shown in FIG. 5, the contact portion between the side plate 11a of the storage portion 11 and the contact portion 12a of the lid portion 12 is melted by the laser over the entire area.
At this time, so-called keyhole type laser welding is performed using a hole generated by a reaction force due to evaporation of the aluminum alloy forming the container 10 so that the melted portion of the container 10 by the laser reaches the inside of the container 10.
Here, keyhole type laser welding is a welding method that allows deep penetration, and by increasing the laser output or reducing the laser condensing diameter, the metal to be welded is rapidly changed. This is realized by increasing the power density of the laser to such an extent that it can be evaporated.

In this way, the container 10 is melted so as to reach the inside of the container 10 while the inside of the container 10 is decompressed by the decompression pump 40, so that it is formed between the inner peripheral surface of the side plate 11 a and the lid 12. The melted portion of the container 10 is sucked from the clearance thus formed toward the inside of the container 10.
Here, the molten portion of the container 10 includes impurities such as hydrogen contained in the aluminum alloy constituting the container 10 and a gas generated by vaporization of the aluminum alloy itself. It is clear that a large amount remains in a portion of the melted portion far from the laser irradiation portion, that is, a portion close to the inside of the container 10.
Therefore, as described above, the gas is removed from the melted portion of the container 10 by performing welding while sucking the melted portion of the container 10 from the inside of the container 10 by the decompression pump 40.
Thereby, when the fusion | melting part of the container 10 solidifies and the welding part 30 is formed, it can prevent that the said gas remains in the welding part 30 as a pore C (refer FIG. 7).
Therefore, the weld thickness of the welded portion 30 (the dimension from the outer surface of the welded portion 30 to the inside of the container 10 and refer to D in FIG. 5) is a sufficient value (in this embodiment, 0.3 mm or more). And a reduction in strength of the container 10 can be prevented.
In the present embodiment, the pressure inside the container 10 is reduced by the pressure reducing pump 40, thereby providing a differential pressure between the inside and the outside of the container 10. If it can be said, the means will not be ask | required. For example, a pressure difference may be provided between the inside and the outside of the container 10 by pressurizing the outside of the container 10 in a sealed state.

Note that the internal pressure of the container 10 is reduced by the vacuum pump 40 so that the differential pressure between the inside and the outside of the container 10 becomes an appropriate value.
For example, when the differential pressure between the inside and the outside of the container 10 is larger than an appropriate value, as shown in FIG. In addition to being able to form a welded portion 30 that is excessively depressed toward the inside of the container 10 and has a sufficient weld thickness (see D in FIG. 6), the molten portion of the container 10 falls into the container 10, and the container 10 There is a possibility of adversely affecting the electrode body and the like housed in the interior of the housing.
Further, when the pressure difference between the inside and the outside of the container 10 is smaller than an appropriate value, as shown in FIG. Therefore, there is a problem that the weld thickness (see D in FIG. 7) of the welded portion 30 is reduced by the amount of the pores C formed in the welded portion 30.
Therefore, as shown in FIG. 8, it is preferable to perform decompression of the interior of the container 10 by the decompression pump 40 so that the differential pressure between the interior and the exterior of the container 10 is 22 to 70 [kPa].
FIG. 8 is a diagram showing the relationship between the pressure difference between the inside and the outside of the container 10 and the weld thickness of the welded portion 30, and the pressure difference between the inside and the outside of the container 10 is 22 to 70 [kPa]. When it is within the range, it can be confirmed that the welded portion 30 having a weld thickness of 0.3 mm or more can be formed.

Further, as shown in FIG. 9, in a state where a clearance formed between the inner peripheral surface of the side plate 11a and the lid portion 12 is secured, the clearance of the side plate 11a is prevented from communicating with the interior of the container 10. The partition wall 11b may be formed on the inner peripheral surface.
The partition wall portion 11b projects a portion located below the lower end portion of the lid portion 12 on the inner peripheral surface of the side plate 11a toward the inside of the container 10 so that the projecting portion and the lower end portion of the lid portion 12 are in contact with each other. It is formed.
If the partition wall portion 11b is formed over the entire inner peripheral surface of the side plate 11a, the clearance and the inside of the container 10 do not communicate with each other, and the decompression pump 40 cannot suck the melted portion of the container 10. Therefore, as shown in FIGS. 10 and 11, a notch portion 11c for communicating the clearance with the inside of the container 10 is formed in a part of the partition wall portion 11b.
The notch portion 11c is formed so as to cut out a contact portion with the lower end portion of the lid portion 12 in the partition wall portion 11b, and is arranged at one place on the inner peripheral surface of the side plate 11a.

Thus, by forming the partition part 11b and the notch part 11c in the side plate 11a of the storage part 11, when the melted part of the container 10 is sucked by the vacuum pump 40, a part of the melted part becomes a container. 10 can be prevented from falling into the interior.
In the present embodiment, the partition wall 11b is formed on the side plate 11a of the storage unit 11. However, a similar partition wall can be formed on the lid 12 instead.

As shown in FIG. 12, when welding is performed on a portion of the container 10 near the notch 11c, the pressure difference between the inside and the outside of the container 10 is set to be relatively small, and the welding position is set to the notch. It is preferable to gradually increase the differential pressure between the inside and the outside of the container 10 as the distance from 11c increases, and the range of the differential pressure set at this time is when the partition wall 11b and the notch 11c are not formed. Similarly, it is more preferable to set it as 22-70 [kPa].
Thereby, welding of the container 10 can be favorably performed while suppressing the molten portion of the container 10 from dropping into the container 10 from the notch 11c.
FIG. 12 is a diagram showing the relationship between the welding position of the container 10 and the differential pressure between the inside and the outside of the container 10, and welding is started from the portion where the notch 11c is located on the side surface of the container 10, Change in pressure difference between the inside and the outside of the container 10 until welding is continuously performed on the entire circumference of the side surface of the container 10 and the side surface of the container 10 is returned to the portion where the notch 11c is located again. It is shown.

As shown in FIG. 2, after the welding step S12, a liquid injection step S13 is performed.
The liquid injection step S13 is a step of injecting the electrolytic solution into the container 10 in which the electrode body is accommodated.
In the liquid injection step S <b> 13, the electrolytic solution is injected into the container 10 from the liquid injection port 13 formed in the lid portion 12 of the container 10. Thereafter, the liquid injection port 13 is sealed by fixing the sealing material 14 to the lid 12 by welding or the like in a state where the liquid injection port 13 is closed with the sealing material 14.

  After the liquid injection step S13, the secondary battery 1 is manufactured through a known predetermined step (initial charging step, aging step, etc.).

  As described above, by performing the welding step S12 in the manufacturing process S1 of the secondary battery 1, the weld thickness of the welded portion 30 formed in the container 10 can be set to a good value, and eventually two. The strength of the container 10 of the secondary battery 1 can be improved.

  In addition, the container 10 of the secondary battery 1 in the present embodiment is a so-called square container, and is configured such that the upper end portion of the storage portion 11 and the lower surface of the lid portion 12 are in contact with each other. The present invention can be similarly applied to the container or the like configured such that the outer edge portion of the lid portion or the outer peripheral portion of the lid portion contacts the inner peripheral surface of the storage portion.

DESCRIPTION OF SYMBOLS 1 Secondary battery 10 Container 11 Storage part 11a Side plate 11b Partition part 11c Notch part 12 Lid part 12a Contact part 13 Injection port 14 Sealing material 20 Terminal 30 Welding part 40 Pressure reduction pump 41 Suction pipe

Claims (4)

A storage portion having an opening surface;
A container that includes a lid that closes an opening surface of the storage unit,
In a state where a differential pressure is generated between the inside and outside of the container so that the inside of the sealed container is in a reduced pressure state with respect to the outside,
A container welding method, wherein a contact portion between the storage portion and the lid portion is melted and welding is performed over the entire contact portion until the molten portion reaches the inside of the container.   2. The container welding method according to claim 1, wherein keyhole type laser welding is applied to the container welding.   The said differential pressure shall be 22-70 [kPa], The welding method of the container of Claim 1 or Claim 2 characterized by the above-mentioned. A method for producing a secondary battery comprising the container,
A method for manufacturing a secondary battery, comprising a welding step of welding the container using the container welding method according to any one of claims 1 to 3.

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