JP2007012406A - Battery pack and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery pack capable of welding certainly a connecting body and an outer package can while preventing deterioration of battery performance due to heat at welding, and capable of reducing deterioration of battery performance while expanding the range to control welding current, and its manufacturing method. <P>SOLUTION: The battery pack is formed by connecting a plurality of unit cells 1 through a connecting body 2. The battery pack has the connecting body 2 connected by welding to the bottom part of the outer package can 3. The outer package can 3 of the unit cells 1 has a folding protrusion 7 formed by folding back the outer package can 3 along the outer periphery of the bottom face, which is protruding to the outside from the electrode housing part 6 of the outer package can 3. The battery pack has the folding protrusion 7 and the connecting body 2 welded at the laminating part by laminating the connecting body 2 at the folding protrusion 7. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an assembled battery in which a plurality of unit cells are connected via a connection body, and a method for manufacturing the same.

An assembled battery in which a plurality of unit cells are connected in series or in parallel is connected to a unit cell by spot welding the united body of a metal plate to the unit cell. The connecting body is connected in series to the outer can and sealing plate of the adjacent unit cell, or connected in parallel to the outer can and outer can of the adjacent unit cell, and the sealing plate and the sealing plate. An assembled battery in which a plurality of unit cells are connected in series via a connection body has been developed. (See Patent Document 1)
An assembled battery has also been developed in which a sealing plate and an outer can are directly welded and connected. (See Patent Documents 2 and 3)
JP 2003-229107 A JP 2000-149907 A Japanese Utility Model Publication No. 6-5111

  The assembled battery described in Patent Document 1 has unit cells connected in a straight line in series via a connection body. The connection body is provided with a peripheral wall along the cylinder of the outer can along the outer peripheral edge. The inner shape of the peripheral wall is substantially equal to the outer shape of the outer can, and the bottom of the outer can is inserted inside the peripheral wall, and the outer can and the peripheral wall are spot welded. As shown in FIG. 1, in the assembled battery in which the unit cells 21 are connected by the connection body 22, the pair of welding electrodes 15 are pressed against the surface of the peripheral wall 24 as shown in FIG. 2. The welding electrode 15 welds the connection body 22 to the outer can 23 by passing a welding current through the connection body 22 → the outer can 23 → the connection body 22. Not only the welding current but also a reactive current flows through the connection body. The reactive current is a current that is not used for welding because it does not flow between the connection body and the outer can. Such a method of energizing and welding is called a series type. When the connection body is welded to the outer can in this manner, Joule heat is generated by the welding current and the reactive current. Joule heat heats the outer can. The heated outer can damages the electrode group housed therein due to temperature. For example, the battery separator may be melted by melting a plastic separator disposed between the positive electrode plate and the negative electrode plate. The adverse effect of the deterioration of the battery characteristics can be solved by reducing the welding current. However, if the welding current is reduced, the connection body cannot be securely welded to the outer can. For this reason, the welding current is required to be controlled to a current that can reliably fix the connection body to the outer can without deteriorating the battery performance. However, the range that satisfies this condition is considerably narrow, and in reality, after the connection body is welded to the outer can, the deterioration of the battery performance is inspected.

  In the assembled batteries of Patent Documents 2 and 3, the sealing plate is directly welded to the outer can. In this structure, the sealing plate and the outer can are welded by passing a welding current to the unit cell. For this reason, it is necessary to flow a very large welding current to the unit cell. In addition, as in the series type in which the connection body is welded to the outer can, it is necessary to control the conditions for welding the connection body and the outer can within a very narrow range. This is because, like the series type, the outer can is heated by the welding current, and the built-in electrode group is thermally damaged. In particular, the welded portion is heated to a high temperature until the outer can is melted by a large local current, causing thermal damage to the electrode group. Therefore, also in this structure, if the welding current is too large, the battery performance is deteriorated due to thermal damage of the electrode group. Conversely, if the welding current is small, the sealing plate and the outer can cannot be reliably welded.

The present invention has been developed for the purpose of solving the conventional drawbacks. An important object of the present invention is to provide an assembled battery capable of reliably welding a connection body and an outer can, while preventing deterioration of battery performance due to heat during welding, and a method for manufacturing the same.
Another important object of the present invention is to provide an assembled battery and a method for manufacturing the same that can reduce the deterioration of battery performance while widening the range in which the welding current can be controlled.

  The assembled battery according to claim 1 of the present invention is an assembled battery in which a plurality of unit cells 1 are connected via a connection body 2. In the assembled battery, the connection body 2 is connected to the bottom of the outer can 3 by welding. The outer can 3 of the unit cell 1 is provided with a folding protrusion 7 formed by bending the outer can 3 along the outer periphery of the bottom surface, and the folding protrusion 7 is externally provided from the electrode housing 6 of the outer can 3. It is protruding. In the assembled battery, the connection body 2 is stacked on the folded protrusion 7, and the folded protrusion 7 and the connection body 2 are welded at the stacked section.

  In the assembled battery of the present invention, the folded protrusion 7 protrudes outward in a direction parallel to the bottom surface of the outer can 3, and the connection body 2 is laminated on the folded protrusion 7, and the folded protrusion 7 and the connection body 2 are stacked. Can be resistance welded directly.

  In the assembled battery of the present invention, the folded protrusion 7 can be projected in a direction perpendicular to the bottom surface of the outer can 3, and the connection body 2 can be laminated and welded to the folded protrusion 7.

  In the assembled battery of the present invention, the outer can 3 can be pressed to provide the folded protrusion 7.

  The assembled battery according to claim 5 of the present invention is formed by connecting a plurality of unit cells 1 via the connection body 2. In the assembled battery, the connection body 2 is connected to the bottom of the outer can 3 by welding. The outer can 3 of the unit cell 1 is provided with a folded protrusion 7 formed by bending the outer can 3 along the outer periphery of the bottom surface. In the assembled battery, the folded protrusion 7 and the connection body 2 are laser-welded.

  The assembled battery according to claim 6 of the present invention directly welds the bottom surface of the outer can 3 of the first unit cell 1 and the sealing plate 4 of the second unit cell 1 to the first unit cell 1. The second unit cell 1 is connected in series. The outer can 3 of the first unit cell 1 includes a folded protrusion 7 formed by bending the outer can 3 along the outer periphery of the bottom surface so as to protrude outward from the electrode storage portion 6. The sealing plate 4 of the second unit cell 1 is provided with a protruding welded portion 12 that is brought into contact with the folded-back protruding portion 7. The assembled battery is formed by laminating the folded protruding portion 7 and the protruding welded portion 12, and welding the folded protruding portion 7 and the projected welded portion 12 at the stacked portion, thereby the first unit cell 1 and the second unit cell 1. Are connected in series.

  In the method for manufacturing an assembled battery according to claim 7 of the present invention, the connection body 2 is welded to the outer can 3 of the plurality of unit cells 1, and the unit cell 1 is connected through the connection body 2. In the process of manufacturing the assembled battery, in the step of manufacturing the outer can 3 by pressing a metal plate, the outer projecting portion 7 is provided outside the electrode housing portion 6 along the outer periphery of the bottom portion of the outer can 3. In the method of manufacturing the assembled battery, the connection body 2 is stacked on the folded protrusion 7, the stacked folded protrusion 7 and the connection body 2 are sandwiched between the pair of welding electrodes 15, and the welding electrode 15 is energized, The folded protrusion 7 and the connection body 2 are resistance-welded in a direct manner at the laminated portion.

  The assembled battery and the manufacturing method thereof according to the present invention have a feature that a plurality of unit cells can be welded and connected while preventing deterioration in battery performance due to heat during welding. That is, the assembled battery of the present invention and the manufacturing method thereof provide a folded protrusion formed by bending the outer can along the outer periphery of the bottom surface of the outer can of the unit cell. This is because the plurality of unit cells are connected by being welded to the connection body or the sealing plate with the folded-back projection as a welded portion. In the present invention, the folded protrusion provided outside the electrode housing portion along the outer periphery of the bottom surface of the outer can is used as a welding portion. Therefore, even if Joule heat is generated by the welding current flowing through this portion, the outer sheath Damage due to the temperature applied to the electrode group housed in the electrode housing part of the can can be extremely reduced, and deterioration of the battery performance can be prevented. In general, the electrode group housed in the electrode housing portion of the unit cell is in a very close positional relationship with the bottom surface of the outer can, and thus is easily damaged by heat when the bottom surface of the outer can is heated. On the other hand, in the present invention, since the folded protrusion that becomes the welded portion is provided so as to protrude from the bottom surface of the outer can, the position away from the electrode group is heated, and the electrode group due to heat generated during welding The heat damage to can be greatly reduced. In particular, according to the present invention, the folded protrusion is provided along the outer periphery, not the center of the bottom surface of the outer can of the unit cell, so that the electrode group accommodated in the electrode accommodating portion of the outer can also by this. Can be reduced to a minimum. As described above, in the present invention, since the influence of heat due to the welding current can be reduced to a minimum, a range in which the welding current can be controlled without controlling the current when the connecting body or the sealing plate is welded to the outer can in a narrow range. While widening, the battery performance can be reduced less.

  Embodiments of the present invention will be described below with reference to the drawings. However, the example shown below illustrates the assembled battery and the manufacturing method thereof for embodying the technical idea of the present invention, and the present invention does not specify the assembled battery and the manufacturing method thereof.

  Further, in this specification, in order to facilitate understanding of the scope of claims, numbers corresponding to the members shown in the examples are indicated in the “claims” and “means for solving problems” sections. It is added to the members. However, the members shown in the claims are not limited to the members in the embodiments.

  The assembled battery of the present invention is most suitable as a power source for driving a motor for running a vehicle. This is because a plurality of unit cells can be connected in series in a low resistance state. However, the battery pack of the present invention does not specify the use for vehicles. For applications other than vehicles, for example, it can also be used for power supplies for driving bicycles, power tools, robots, and the like. A plurality of assembled batteries used for these power sources are housed in a case and connected in series or in parallel.

  In the assembled battery, a plurality of unit cells 1 are linearly connected in series via a connection body 2. 3 to 6 are cross-sectional views showing connecting portions of adjacent unit cells 1. In the assembled battery shown in these figures, the sealing plate 4 of the lower unit cell 1 and the outer can 3 of the upper unit cell 1 are connected by the connection body 2. The connection body 2 is welded to the sealing plate 4 and the outer can 3 to connect the upper and lower unit cells 1 in a straight line in series. The connection body 2 has a central portion welded to the sealing plate 4 of the lower unit cell 1 and an outer peripheral portion welded to the bottom of the outer can 3 of the upper unit cell 1.

  The unit cell 1 is folded back along the outer periphery of the bottom surface of the outer can 3 in order to reliably weld the connector 2 while preventing thermal damage to the electrode group 5 contained in the electrode housing 6 inside. Is provided. The folded-back protruding portion 7 is provided so as to protrude from the electrode housing portion 6 in order to prevent the electrode group 5 from being damaged by heat generated when the connecting body 2 is welded thereto. The outer can 3 is manufactured by pressing a metal plate such as iron, iron alloy, aluminum or aluminum alloy. The folded protrusion 7 is provided in a process that is manufactured by pressing the outer can 3.

  The folded protrusion 7 of the assembled battery in FIGS. 3 and 4 protrudes outward in a direction parallel to the bottom surface of the outer can 3. The assembled battery of FIG. 3 can be connected by direct resistance welding by laminating the connection body 2 on the folded protrusion 7 and sandwiching the laminated portion of the folded protrusion 7 and the connection body 2 with a pair of welding electrodes 15. . For this reason, the assembled battery of this structure can eliminate the damage by the heat | fever of the electrode group 5 accommodated in the exterior can 3 while welding the connection body 2 and the exterior can 3 reliably.

  The connection body 2 includes an outer can connecting portion 2A connected to the outer can 3 of the upper unit cell 1 which is one unit cell 1, and a sealing plate connecting portion 2B connected to the sealing plate 4 of the lower unit cell 1. With. The connection body 2 including the outer can connecting portion 2A and the sealing plate connecting portion 2B is manufactured by pressing one metal plate. The connecting body 2 connects the outer can connecting portion 2A and the sealing plate connecting portion 2B with a step portion 2C. The connecting body 2 is connected by a stepped portion 2C so that the outer can connecting portion 2A protrudes from the sealing plate connecting portion 2B. The outer can connecting portion 2 </ b> A is welded to the folded protrusion 7 provided at the bottom of the outer can 3. Accordingly, the outer can connecting portion 2 </ b> A has a planar ring shape along the lower surface of the folded protrusion 7. The sealing plate connecting portion 2B has a central hole 2a that penetrates the convex electrode 8 of the lower unit cell 1 at the center. The sealing plate connecting portion 2B has a stepped portion having an outer shape smaller than the inner shape of the crimping ridge 9 so as not to contact the crimping ridge 9 of the outer can 3 provided along the outer peripheral edge of the sealing plate 4. It is connected to the outer can connecting part 2A by 2C. Furthermore, the assembled battery shown in the figure covers the end portion of the lower unit cell 1 on the side of the convex electrode in order to prevent the connecting body 2 from coming into contact with the crimping ridge 9. The insulating cover 7 is formed by molding an insulating material such as plastic into a cap shape into which the end of the unit cell 1 can be inserted. The sealing plate connecting portion 2B is fixed to the sealing plate 4 by direct or series resistance welding. The outer can connecting portion 2A is fixed to the folded protrusion 7 by direct resistance welding.

  The assembled battery of FIG. 4 uses the same connection body 2 as in FIG. 3 to laser weld the folded protrusion 7 of the outer can 3 and the outer can coupling portion 2B of the connection body 2. In this assembled battery, a laser is applied to the boundary between the folded projection 7 and the outer can connecting portion 2B of the connection body 2 which are stacked on each other, and the folded projection 7 and the connection body 2 are welded by the laser. Further, although not shown in the drawing, as shown in FIG. 3, the seam welding is performed by laminating the folded protrusion and the outer can connecting portion of the connection body, and moving and laminating the laminated portion with the roller of the electrode. It is also possible to weld the folded protrusion and the connection body. In the seam welding, the same folded protrusion and the connection body as in FIG. 3 can be welded. In the seam welding, the folded protrusion and the connection body are welded in a wide area, so that the electrical resistance of the welded portion can be reduced. Also, the connection strength can be increased.

  The assembled battery of FIG. 5 is provided with the folded-back protruding portion 7 protruding in a direction perpendicular to the bottom surface of the outer can 3. The folded protrusion 7 is formed by laminating the outer can connecting portion 2A of the connection body 2 on the outside, pressing the welding electrode 15 against the surface of the connection body 2, and energizing the welding electrode 15 to fold the connection body 2 back. Weld to. In this connection body 2, the outer can connecting portion 2 </ b> A has a shape along a cylinder into which the folded protrusion 7 can be inserted. The folded protrusion 7 is inserted into the outer can connecting part 2A of the connection body 2, the welding electrode 15 is pressed and energized to the outer can connecting part 2A, and the outer can connecting part 2A is welded to the folded protruding part 7.

  In the assembled battery of FIG. 6, the folded protrusion 7 provided on the outer can 3 of the upper unit cell 1 protrudes downward in a direction perpendicular to the bottom surface of the outer can 3, and the outer can connecting portion 2 </ b> A of the connection body 2. Is a flat ring shape. In this assembled battery, the lower end of the folded projection 7 is brought into contact with the planar ring-shaped outer can connecting portion 2A, and the boundary between the connection body 2 and the folded projection 7 is welded with a laser. This structure has a feature that the damage to the electrode group 5 due to heat of welding can be extremely reduced because the tip edge of the folded protrusion 7 is laser welded. This is because the electrode group 5 can be stored in a portion where the tip edge of the folded protrusion 7 heated until it is melted by the laser is far away from the electrode storage 6 of the outer can 3 and the heat of the laser can be efficiently radiated. is there. In addition, the assembled battery having this structure also has a feature that the electric resistance of the connection portion can be reduced by laser welding the folded protrusion 7 of the outer can 3 and the outer can connecting portion 2A of the connection body 2 for a long time.

  Further, the assembled battery of FIG. 7 causes the folded-back protruding portion 7 to protrude in a direction perpendicular to the bottom surface of the outer can 3, and directly covers the sealing plate 4 of the lower unit cell 1 without using a connection body. The unit cell 1 is welded to the folded protrusion 7. The folded protrusion 7 is bent inward so as to be parallel to the bottom surface of the outer can 3. The sealing plate 4 is provided with a protruding welded portion 12 in contact with the folded-back protruding portion 7 on the inner side of the crimping ridge 9. This assembled battery is resistance-welded by passing a welding current to the protruding welded portion 12 and the folded-back protruding portion 7 via the unit cell 1, or irradiates a laser at the boundary between the protruding welded portion 12 and the folded-back protruding portion 7, The protruding welded portion 12 and the folded protruding portion 7 are welded. Since the assembled battery of this structure does not use a connection body, the unit cell 1 can be connected in a low resistance state.

  In the assembled battery shown in the above figures, the unit cell 1 is a cylindrical battery. However, the assembled battery of the present invention does not necessarily specify a unit cell as a cylindrical battery. In the unit cell 1 shown in the figure, the sealing plate 4 is caulked and fixed to the opening of the outer can 3, and the opening of the outer can 3 is hermetically closed by the sealing plate 4. However, in the assembled battery of the present invention, the unit cell is not specified as the cylindrical battery having this structure. This is because the unit cell may be a battery in which a sealing plate is welded and fixed to the opening of the outer can. The unit cell is a secondary battery such as a lithium ion secondary battery, a nickel metal hydride battery, or a nickel cadmium battery.

  In the unit cell 1, a metal outer can 3 is filled with an electrode group 5 and an electrolytic solution. The opening of the outer can 3 airtightly closes the metal plate sealing plate 4 in an insulated state. The outer can 3 is manufactured by pressing a metal plate into a cylindrical shape with a closed bottom. At this time, the folding protrusion 7 is also provided. In the cylindrical battery, a metal plate is formed into a cylindrical shape to form an outer can 3. A prismatic battery is formed as an outer can by forming a metal plate into a rectangular tube shape. The sealing plate 4 is manufactured by pressing or casting a metal plate. The outer can 3 and the sealing plate 4 are caulked in an insulated state. An insulating material 10 is sandwiched between the outer can 3 and the sealing plate 4 for insulation. The insulating material 10 hermetically closes the gap while insulating the outer can 3 and the sealing plate 4. The outer can 3 is provided with ridges 11 along the lower surface of the sealing plate 4 in order to fix the sealing plate 4 with the caulking portion. The sealing plate 4 is set on the outer can 3 provided with the ridges 11, the opening edge is caulked, and the sealing plate 4 is sandwiched and fixed between the crimping ridges 9 and the ridges 11. Thereafter, the caulking portion is pressed from above with a punch, and the overall dimension of the outer can 3 is set to a specified value.

It is a side view of the conventional assembled battery. It is sectional drawing which shows the connection part of the unit cell of the assembled battery shown in FIG. It is a partial cross section side view which shows the connection part of the unit cell of the assembled battery concerning one Example of this invention. It is a partial cross section side view which shows the connection part of the unit cell of the assembled battery concerning the other Example of this invention. It is a partial cross section side view which shows the connection part of the unit cell of the assembled battery concerning the other Example of this invention. It is a partial cross section side view which shows the connection part of the unit cell of the assembled battery concerning the other Example of this invention. It is a partial cross section side view which shows the connection part of the unit cell of the assembled battery concerning the other Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Unit cell 2 ... Connection body 2A ... Exterior can connection part
2B ... Sealing plate connector
2C ... Step part
2a ... Center hole 3 ... Exterior can 4 ... Sealing plate 5 ... Electrode group 6 ... Electrode housing part 7 ... Folded protrusion 8 ... Convex electrode 9 ... Caulking ridge 10 ... Insulating material 11 ... Convex ridge 12 ... Protruding weld 13 ... Insulation cover 15 ... Welding electrode 21 ... Unit cell 22 ... Connector 23 ... Exterior can 24 ... Surrounding wall

Claims (7)

An assembled battery in which a plurality of unit cells (1) are connected via a connection body (2), and the connection body (2) is connected by welding to the bottom of the outer can (3). The outer can (3) of (1) is provided with a folding protrusion (7) formed by bending the outer can (3) along the outer periphery of the bottom surface, and the folding protrusion (7) is provided as an outer can ( It protrudes from the electrode housing part (6) of 3) to the outside,
A battery assembly in which the connection body (2) is laminated on the folded protrusion (7), and the folded protrusion (7) and the connection body (2) are welded at the laminated section.   The folded protrusion (7) protrudes outward in a direction parallel to the bottom surface of the outer can (3), and the connecting protrusion (7) is laminated on the folded protrusion (7) to return the folded protrusion (7). The assembled battery according to claim 1, wherein the connection body (2) is resistance-welded in a direct manner.   The folded protrusion (7) protrudes in a direction perpendicular to the bottom surface of the outer can (3), and the connection body (2) is laminated and welded to the folded protrusion (7). Assembled battery.   The assembled battery according to claim 1, wherein the outer can (3) is press-worked to provide a folded protrusion (7).   An assembled battery in which a plurality of unit cells (1) are connected via a connection body (2), and the connection body (2) is connected by welding to the bottom of the outer can (3). The outer can (3) of (1) is provided with a folded protrusion (7) formed by bending the outer can (3) along the outer periphery of the bottom surface, and is connected to the folded protrusion (7). A battery pack characterized by laser welding the body (2). The bottom of the outer can (3) of the first unit cell (1) and the sealing plate (4) of the second unit cell (1) are directly welded, and the first unit cell (1) and the first unit cell (1) An assembled battery in which two unit cells (1) are connected in series,
The outer can (3) of the first unit cell (1) is folded back by bending the outer can (3) along the outer periphery of the bottom so as to protrude outside from the electrode housing (6). With protrusions (7),
The sealing plate (4) of the second unit cell (1) is provided with a protruding welded part (12) that comes into contact with the folded-back protruding part (7).
The folded projecting portion (7) and the projecting welded portion (12) are laminated, and the folded projecting portion (7) and the projecting welded portion (12) are welded at the laminated portion, so that the first unit cell (1) and the first An assembled battery formed by connecting two unit cells (1) in series. A method of manufacturing an assembled battery in which a connecting body (2) is welded to an outer can (3) of a plurality of unit cells (1), and the unit cell (1) is connected through the connecting body (2),
In the process of manufacturing the outer can (3) by pressing the metal plate, the outer protruding portion (7) is provided along the outer periphery of the bottom of the outer can (3) by protruding from the electrode housing portion (6) to the outside. ,
The connection body (2) is laminated on the folded protrusion (7), the laminated folded protrusion (7) and the connection body (2) are sandwiched between a pair of welding electrodes (15), and the welding electrode (15) A method of manufacturing an assembled battery, wherein the folded protrusion (7) and the connection body (2) are directly resistance-welded at the laminated portion by energizing the wire.

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