Manufacturing method of secondary battery

Abstract

To more preferably bond an electrode terminal part.SOLUTION: A secondary battery 1 comprises an electrode terminal part 50 formed by bonding a first metal piece 51 and a second metal piece 52 that are formed by a different material. At the time of bonding the first metal piece 51 and the second metal piece 52, those of the first metal piece 51 and the second metal piece 52 are overlapped to a thickness direction. In addition, a laser beam L is irradiated to an upper surface edge part 56 of the second metal piece 52 mounted onto the first metal piece 51. Then, a melting pool 60 of the upper surface edge part 56 to be formed by them is flown to a lower direction to melt an upper surface 51s of the first metal piece 51, and thus, both of the first metal piece 51 and the second metal piece 52 are welded.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a secondary battery.

Background Art

[0002] Conventionally, there has been a secondary battery having an electrode terminal portion formed by joining a first metal piece and a second metal piece. For example, in the secondary battery described in Patent Document 1, the electrode terminal portion is composed of a first metal piece and a second metal piece arranged overlapping each other in the thickness direction. Further, for example, Patent Documents 2 and 3 describe a method of joining such an overlapping first metal piece and second metal piece by laser welding. And Patent Document 3 describes that the influence of heat during welding can be reduced by the method of irradiating the laser light.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the electrode terminal portion of the secondary battery, it is desired that the influence of heat during welding be less. Further, the materials of the first metal piece and the second metal piece may be different. For this reason, further improvement of the above conventional technology is also desired.

Means for Solving the Problems

[0005] Each aspect of the method for manufacturing a secondary battery for solving the above problems will be described. Aspect 1 is a method for manufacturing a secondary battery having an electrode terminal portion formed by joining a first metal piece and a second metal piece made of different materials. The first metal piece and the second metal piece are arranged by overlapping them in the thickness direction, and laser light is irradiated onto the upper surface edge portion of the second metal piece placed on the first metal piece. The molten pool formed at the upper surface edge portion by the irradiation of the laser light flows downward to melt the upper surface of the first metal piece, whereby the first metal piece and the second metal piece are welded together. This is a method for manufacturing a secondary battery.

[0006] According to the above configuration, a large welded portion can be formed by irradiating relatively less laser light. As a result, while ensuring high bonding strength, the total heat input required for laser welding of the first metal piece and the second metal piece can be kept low.

[0007] Furthermore, compared with a method called "fillet welding" in which laser light is irradiated onto the boundary portion between the first metal piece and the second metal piece, it is difficult for a compound of different metals to be formed at the melted portion. As a result, an increase in resistance value and embrittlement of the bonding site caused by the formation of the intermetallic compound can be avoided.

[0008] In addition, for example, it is difficult for a failure of laser welding to occur, such as the formation of a hole portion that penetrates the first metal piece or the second metal piece, or both of them, by the irradiation of the laser light L. Furthermore, for example, there are few restrictions on the characteristics of the laser light, such as the thickness of the light beam and the light source. As a result, there is an advantage that the design of the laser welding apparatus can be easily performed.

[0009] Aspect 2 is the method for manufacturing a secondary battery according to Aspect 1, wherein the second metal piece has a hole portion penetrating the second metal piece in the thickness direction, and the laser light is irradiated with the peripheral edge portion of the hole portion as the upper surface edge portion.

[0010] According to the above configuration, at the formation position of the hole portion, the first metal piece and the second metal piece are joined. Furthermore, it becomes easier to set the irradiation pattern of the laser beam. And thereby, the laser welding can be efficiently performed.

[0011] Aspect 3 is a method for manufacturing a secondary battery according to Aspect 2, wherein the hole portion is a circular hole. According to the above configuration, the irradiation pattern of the laser beam is simplified. And thereby, the setting of the irradiation pattern is facilitated, and the laser welding can be performed more efficiently.

[0012] Aspect 4 is a method for manufacturing a secondary battery according to any one of Aspects 1 to 3, wherein the light source of the laser beam is a disk laser. According to the above configuration, laser light with a relatively thick beam can be irradiated to the upper surface edge portion of the second metal piece. And thereby, it becomes possible to quickly form a molten pool, and the total heat input required for the laser welding can be kept low.

[0013] Aspect 5 is a method for manufacturing a secondary battery according to any one of Aspects 1 to 4, wherein one of the first metal piece and the second metal piece is formed using copper, and the other of the first metal piece and the second metal piece is formed using aluminum.

[0014] That is, for example, in the case of a lithium-ion secondary battery, among the connection members used for connecting the electrode body and the electrode terminal, on the negative electrode side, copper is often used as the material, which is the same as the current collector foil on the negative electrode side constituting the electrode body. On the other hand, for the terminal member that forms the negative electrode terminal while being electrically connected to this connection member, aluminum is often used as the material. Therefore, according to the above configuration, one of the connection member and the terminal member is used as the first metal piece, and the other of the connection member and the terminal member is used as the second metal piece, and these first metal piece and second metal piece can be suitably laser welded. And thereby, the electrode terminal portion on the negative electrode side can be efficiently formed.

Advantages of the Invention

[0015] According to the present invention, the joining of the electrode terminal portion can be performed more preferably.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0017] Hereinafter, an embodiment in which the manufacturing method of the secondary battery is embodied will be described with reference to the drawings. (Lithium Ion Secondary Battery) As shown in FIG. 1, the secondary battery 1 includes an electrode body 10 in which a positive electrode 3, a negative electrode 4, and a separator 5 are integrated, and a case 20 that houses the electrode body 10. And the secondary battery 1 of this embodiment has a configuration as a lithium ion secondary battery in which the electrode body 10 in the case 20 is impregnated with a non-aqueous electrolyte (not shown).

[0018] Specifically, in the secondary battery 1 of the present embodiment, the positive electrode 3, the negative electrode 4, and the separator 5 have a sheet-like outer shape and are laminated. Then, by winding the laminate of the positive electrode 3, the negative electrode 4, and the separator 5, an electrode body 10 is formed in which the positive and negative electrodes and the separator 5 are alternately arranged in the radial direction with the separator 5 sandwiched between the positive electrode 3 and the negative electrode 4.

[0019] In addition, the case 20 of the present embodiment includes a flat substantially rectangular box-shaped case body 21 and a lid member 22 that closes the open end 21x of the case body 21. And the electrode body 10 of the present embodiment has a flat outer shape corresponding to the box shape of the case 20.

[0020] (Electrode sheet and electrode body) More specifically, as shown in FIG. 2, in the secondary battery 1 of the present embodiment, the positive electrode 3 and the negative electrode 4 each have a configuration as an electrode sheet 35 including a current collector foil 31 having a sheet-like outer shape and an electrode active material layer 32 laminated on the current collector foil 31. Specifically, the electrode sheet 35P for the positive electrode 3 is formed by laminating a positive electrode active material layer 32P containing a lithium transition metal oxide serving as a positive electrode active material on a current collector foil 31P serving as a base material made of aluminum or the like. And the electrode sheet 35N for the negative electrode 4 is formed by laminating a negative electrode active material layer 32N containing a carbon-based material serving as a negative electrode active material on a current collector foil 31N serving as a base material made of copper or the like.

[0021] Furthermore, in the secondary battery 1 of the present embodiment, these positive and negative electrode sheets 35P and 35N are each shaped into a strip. And the electrode body 10 of the present embodiment has a configuration as a wound body in which the positive and negative electrode sheets 35P and 35N laminated with the separator 5 sandwiched therebetween are wound around a winding axis 10x extending in the width direction of the strip shape (the left-right direction in FIG. 2).

[0022] Also, in FIG. 2, the separator 5 and each electrode sheet 35 are wound in such a manner that the electrode sheet 35P constituting the positive electrode 3 is wound inside. However, this figure is an example showing the structure of the electrode body 10, and in some cases, these separator 5 and each electrode sheet 35 may be wound in such a manner that the electrode sheet 35N constituting the negative electrode 4 is wound inside. And thereby, it is determined whether the electrode sheet 35 disposed on the outermost shell of the electrode body 10 is the electrode sheet 35P constituting the positive electrode 3 or the electrode sheet 35N constituting the negative electrode 4.

[0023] Also, as shown in FIGS. 1 to 3, the lid member 22 of the case 20 is provided with a positive electrode terminal 38P and a negative electrode terminal 38N that protrude outside the case 20. Further, on each electrode sheet 35, an uncoated portion 39 where the electrode active material layer 32 is not formed is formed on the current collector foil 31. And in the secondary battery 1 of the present embodiment, by using these uncoated portions 39, the electrode sheet 35P constituting the positive electrode 3 and the positive electrode terminal 38P are electrically connected, and the electrode sheet 35N constituting the negative electrode 4 and the negative electrode terminal 38N are electrically connected.

[0024] Specifically, the electrode body 10 of the present embodiment is housed in the case 20 in a state where its winding axis 10x is along the longitudinal direction (the left-right direction in FIG. 1) of the lid member 22 having a long and substantially rectangular plate shape. Further, in this state, the uncoated portion 39P of the electrode sheet 35P constituting the positive electrode 3 and the positive electrode terminal 38P are connected via a connecting member 40P. And similarly, the uncoated portion 39N of the electrode sheet 35N constituting the negative electrode 4 and the negative electrode terminal 38N are connected via a connecting member 40N.

[0025] Furthermore, an electrolytic solution 45 is injected into the case 20. That is, for the electrolytic solution 45 of the secondary battery 1 having a configuration as a lithium-ion secondary battery, a solution in which a lithium salt serving as a supporting salt is dissolved in an organic solvent is used. And the secondary battery 1 of the present embodiment is configured such that the electrode body 10 sealed in the case 20 is impregnated with the electrolytic solution 45.

[0026] (Electrode terminal part) As shown in FIGS. 3 and 4, in the secondary battery 1 of the present embodiment, the electrode terminal part 50 used for the negative electrode terminal 38N provided on the lid member 22 of the case 20 is formed by joining a first metal piece 51 and a second metal piece 52 made of different materials. Specifically, this electrode terminal part 50 has the lid side end part 53 of the connection member 40N made of copper in the same way as the current collecting foil 31 of the electrode sheet 35N constituting the negative electrode 4 of the secondary battery 1 as its first metal piece 51. Further, the secondary battery 1 of the present embodiment includes a terminal member 54 made of aluminum that forms the terminal surface 38s of the negative electrode terminal 38N facing the outer surface 22s of the lid member 22. And the electrode terminal part 50 of the present embodiment is configured such that this terminal member 54 is its second metal piece 52.

[0027] More specifically, as shown in FIG. 4, in the secondary battery 1 of the present embodiment, the connection member 40N on the negative electrode 4 side has a substantially L-shaped bent portion 40c, so that its lid side end part 53 is arranged substantially parallel to the outer surface 22s of the lid member 22 having a substantially flat outer shape. Further, the terminal member 54 on the negative electrode 4 side also has a substantially flat outer shape and is arranged substantially parallel to the outer surface 22s of the lid member 22. And the electrode terminal part 50 of the present embodiment is thus configured such that the lid side end part 53 of the connection member 40N serving as its first metal piece 51 and the terminal member 54 serving as its second metal piece 52 are joined to each other in a state of overlapping in the thickness direction.

[0028] In the secondary battery 1 of the present embodiment, aluminum is used as the material of the case body 21 and the lid member 22. Further, the lid member 22 is provided with a resin insulating member 55 that covers the periphery of the electrode terminal part 50. And the secondary battery 1 of the present embodiment is thus configured such that the electrode terminal part 50 and the lid member 22 are insulated from each other.

[0029] (Joining method of the first metal piece and the second metal piece) As shown in FIG. 5, in the secondary battery 1 of the present embodiment, laser welding by irradiation of laser light L is used for joining the first metal piece 51 and the second metal piece 52 that constitute the electrode terminal portion 50.

[0030] Specifically, when welding the first metal piece 51 and the second metal piece 52, with the second metal piece 52 placed on the first metal piece 51, these first metal piece 51 and second metal piece 52 are arranged so as to overlap in the thickness direction (the vertical direction in FIG. 5). Next, in this state, the laser light L is irradiated onto the edge portion of the upper surface 52s of the second metal piece 52 placed on the first metal piece 51, that is, onto the upper surface edge portion 56 of this second metal piece 52. In the secondary battery 1 of the present embodiment, for example, a disk laser Ld is used as the light source (not shown) of this laser light L. Further, the molten pool 60 of the upper surface edge portion 56 formed by the irradiation of this laser light L flows downward to melt the upper surface 51s of the first metal piece 51. And in the secondary battery 1 of the present embodiment, thereby, the first metal piece 51 and the second metal piece 52 that constitute the electrode terminal portion 50 are joined.

[0031] More specifically, as shown in FIGS. 5 to 7, in the secondary battery 1 of the present embodiment, the second metal piece 52 has a hole portion 70 that penetrates the second metal piece 52 in the thickness direction. Specifically, this hole portion 70 has a configuration as a circular hole 71 having a circular opening shape. And in the secondary battery 1 of the present embodiment, laser welding is performed with the peripheral edge portion 70e of this hole portion 70 as the upper surface edge portion 56 of the second metal piece 52.

[0032] That is, when welding the first metal piece 51 and the second metal piece 52, laser light L is irradiated over the entire circumference of the peripheral edge 70e of the hole 70 provided in the second metal piece 52. Specifically, the irradiation position of the laser light L is sequentially moved along the circumferential direction of the hole 70 so that the molten pool 60 formed by the irradiation of the laser light L flows down along the inner peripheral surface 70s of the hole 70 onto the upper surface 51s of the first metal piece 51. And in the secondary battery 1 of the present embodiment, an annular welding portion 75 is formed at a position corresponding to the inner circumference of the hole 70 to join the first metal piece 51 and the second metal piece 52 disposed one above the other in the thickness direction.

[0033] More specifically, in the secondary battery 1 of the present embodiment, when the molten pool 60 formed by the irradiation of the laser light L on the peripheral edge 70e of the hole 70 flows downwards, the inner peripheral surface 70s of the hole 70 is melted. Further, the flowing-down molten pool 60 melts the upper surface 51s of the first metal piece 51 together with the melted inner peripheral surface 70s of the hole 70. And the secondary battery 1 of the present embodiment is configured such that a welding portion 75 is formed that bites into the upper surface 51s of the first metal piece 51 over the entire circumference of the hole 70 in a state continuous with the second metal piece 52.

[0034] (Reference Example) On the other hand, for example, in the reference example shown in FIGS. 8 and 9, when joining the first metal piece 51 and the second metal piece 52 that constitute the electrode terminal portion 80, the laser light L is irradiated substantially perpendicularly to the upper surface 52s of the second metal piece 52 placed on the first metal piece 51. That is, by irradiating the laser light L on the upper surface 52s of the second metal piece 52, a welding portion 85 having a substantially wedge-shaped cross section that tapers downward in the thickness direction (downward in FIG. 9) is formed. And when the tip of this welding portion 85 reaches the first metal piece 51 located below the second metal piece 52, these first metal piece 51 and second metal piece 52 are welded together.

[0035] Specifically, in this reference example, for the light source (not shown) of the laser beam L, for example, a fiber laser Lf with a thin light beam is used. This is in consideration of the reflection of the laser beam L. Further, the irradiation of the laser beam L is performed by sequentially moving the irradiation position of the laser beam L with respect to the upper surface 52s of the second metal piece 52 along a predetermined annular locus. Furthermore, in this reference example, a plurality of welding portions 85 having an annular planar shape corresponding to the irradiation locus of the laser beam L are formed concentrically. And the electrode terminal portion 80 of this reference example is configured such that, with the formation positions of these respective welding portions 85 as the joint portions 90, the first metal piece 51 and the second metal piece 52 overlapping in the thickness direction are joined.

[0036] (Operation) That is, when the laser welding method of the above reference example is adopted, since the light beam of the irradiated laser beam L is thin, when forming the annular welding portion 85 as described above, the heat input per one of them becomes relatively small. However, when considering the reflection of the laser beam L, it is difficult to thicken the light beam, that is, to thicken the width of the welding portion 85 extending in an annular shape. For this reason, in order to ensure the required joint strength, there is a need to form a plurality of welding portions 85. And thereby, there is a problem that the total heat input required for laser welding of the first metal piece 51 and the second metal piece 52 becomes large.

[0037] On the other hand, in the secondary battery 1 of this embodiment, the molten pool 60 formed by the irradiation of the laser beam L on the upper surface edge portion 56 of the second metal piece 52 flows downward to melt the upper surface 51s of the first metal piece 51, thereby forming a relatively large welding portion 75. Specifically, the contact area with respect to the first metal piece 51 is larger for the welding portion 75 in the secondary battery 1 of this embodiment than for each welding portion 85 in the above reference example. For this reason, in order to ensure the required joint strength, there is little need to expand the formation region of the welding portion 75. And thereby, the total heat input required for laser welding of the first metal piece 51 and the second metal piece 52 is suppressed low.

[0038] For example, in the case of the above reference example, laser light L is irradiated along a predetermined circular trajectory for a plurality of revolutions (see FIG. 8, “5 revolutions” in the example of the figure) equal to the number of welded portions 85 formed. On the other hand, in the secondary battery 1 of the present embodiment, it is only necessary to irradiate the laser light L “once” along the peripheral edge 70e of the hole portion 70. As a result, even considering the output difference between the disk laser Ld and the fiber laser Lf serving as the light source (Ld > Lf, for example, about 1.3 to 1.5 times), based on the difference in the number of revolutions, the secondary battery 1 of the present embodiment has a lower total heat input due to the irradiation of the laser light L.

[0039] Next, the effects of the present embodiment will be described. (1) The secondary battery 1 includes an electrode terminal portion 50 formed by joining a first metal piece 51 and a second metal piece 52 made of different materials. When joining the first metal piece 51 and the second metal piece 52, these first metal piece 51 and second metal piece 52 are arranged so as to overlap in the thickness direction. Further, the upper surface edge portion 56 of the second metal piece 52 placed on the first metal piece 51 is irradiated with the laser light L. Then, the molten pool 60 of the upper surface edge portion 56 formed thereby flows downward to melt the upper surface 51s of the first metal piece 51, whereby the first metal piece 51 and the second metal piece 52 are welded.

[0040] According to the above configuration, a large welded portion 75 can be formed by irradiating the laser light L relatively less. And thereby, while ensuring a high joining strength, the total heat input required for laser welding of the first metal piece 51 and the second metal piece 52 can be kept low.

[0041] Furthermore, compared with a method called “corner welding” in which the laser light L is irradiated to the boundary portion between the first metal piece 51 and the second metal piece 52, it is difficult for a compound of different metals to be formed at the melted portion. And thereby, an increase in the resistance value and embrittlement of the joining site caused by the formation of the intermetallic compound can be avoided.

[0042] In addition, for example, due to the irradiation of the laser beam L, it is difficult for failures in laser welding to occur, such as the formation of holes penetrating through the first metal piece 51 or the second metal piece 52, or both of them. Further, for example, there are few restrictions on the characteristics of the laser beam L, such as the thickness of the light beam and the light source. And thereby, there is an advantage that the design of the laser welding apparatus can be easily performed.

[0043] (2) The second metal piece 52 has a hole portion 70 penetrating through the second metal piece 52 in the thickness direction, and the laser beam L is irradiated with the peripheral edge portion 70e of the hole portion 70 as the upper surface edge portion 56. According to the above configuration, at the formation position of the hole portion 70, the first metal piece 51 and the second metal piece 52 are joined. Further, it becomes easier to set the irradiation pattern of the laser beam L. And thereby, the laser welding can be efficiently performed.

[0044] (3) The hole portion 70 has a configuration as a circular hole 71 having a circular opening shape. According to the above configuration, the irradiation pattern of the laser beam L is simplified. And thereby, the setting of the irradiation pattern is facilitated, and the laser welding can be performed more efficiently.

[0045] (4) The light source of the laser beam L is a disk laser Ld. According to the above configuration, a laser beam L with a relatively thick light beam can be irradiated to the upper surface edge portion 56 of the second metal piece 52. And thereby, it becomes possible to quickly form the molten pool 60, and the total heat input required for the laser welding can be kept low.

[0046] (5) The first metal piece 51 is formed using copper, and the second metal piece 52 is formed using aluminum. That is, in the case of a lithium-ion secondary battery, the connection member 40N on the negative electrode 4 side is often made of copper, the same as the current collector foil 31 of the electrode sheet 35N constituting the negative electrode 4. On the other hand, for the terminal member 54 that forms the terminal surface 38s of the negative electrode terminal 38N while being electrically connected to the lid-side end portion 53 of the connection member 40N, aluminum is often used as its material. Therefore, according to the above configuration, the lid-side end portion 53 of the connection member 40N is used as the first metal piece 51, and the terminal member 54 is used as the second metal piece 52, and these first metal piece 51 and second metal piece 52 can be preferably laser-welded. And thereby, the electrode terminal portion 50 on the negative electrode 4 side can be efficiently formed.

[0047] Note that the above embodiment can be implemented with the following modifications. The above embodiment and the following modification examples can be implemented in combination with each other within a technically non-conflicting range.

[0048] · In the above embodiment, by providing the hole portion 70 having a configuration as the circular hole 71 penetrating in the thickness direction of the second metal piece 52, the peripheral edge portion 70e of the hole portion 70 is used as the upper surface edge portion 56 of the second metal piece 52, and the laser welding is to be performed. However, it is not limited to this, and the opening shape of the hole portion 70 may be arbitrarily changed. It does not necessarily have to be the circular hole 71.

[0049] · Also, the upper surface edge portion 56 of the second metal piece 52 irradiated with the laser light L does not necessarily have to be the peripheral edge portion 70e of the hole portion 70. If there is the upper surface 51s of the first metal piece 51 where the molten pool 60 formed by the irradiation of the laser light L flows downwards, the upper surface edge portion 56 irradiated with the laser light L may be arbitrarily set.

[0050] For example, in the electrode terminal portion 50B of the reference example shown in FIG. 10, the contour of the second metal piece 52B placed on the first metal piece 51B is smaller than that of the first metal piece 51B when viewed from above. In such a case, in the range where the first metal piece 51B and the second metal piece 52B overlap in the thickness direction, the outer peripheral edge portion 52x of the second metal piece 52B may be irradiated with the laser beam L as the upper surface edge portion 56 of the second metal piece 52B. That is, also in this case, the molten pool 60 of the upper surface edge portion 56 formed by the irradiation of the laser beam L flows downward to melt the upper surface 51s of the first metal piece 51. And thereby, the welding portion 75B along the outer peripheral edge portion 52x of the second metal piece 52B is formed, and the same effect as in the above embodiment can be obtained.

[0051] · In the above embodiment, the disk laser Ld is used as the light source of the laser beam L. However, for example, the light source of the laser beam L, such as a fiber laser Lf, may be arbitrarily changed. In consideration of efficiency, it is preferable that the thickness of the light beam is relatively thick.

[0052] · In the above embodiment, the first metal piece 51 is formed using copper, and the second metal piece 52 is formed using aluminum. However, the metal types of the first metal piece 51 and the second metal piece 52 may be arbitrarily changed as long as they are different materials from each other. For example, a configuration in which the first metal piece 51 is formed using aluminum and the second metal piece 52 is formed using copper may be used. For example, in the secondary battery 1 of the above embodiment, the terminal member 54 may be used as the first metal piece 51, and the lid-side end portion 53 of the connection member 40N may be used as the second metal piece 52, and laser welding may be performed thereon. And either one, or both of the first metal piece 51 and the second metal piece 52 may be made of a material different from copper and aluminum.

[0053] · Also, when used as the electrode terminal portion 50 of the secondary battery 1, the arrangement of these first metal piece 51 and second metal piece 52 is arbitrary. That is, for example, the electrode terminal portion 50 may be used in a state where the first metal piece 51 is arranged above the second metal piece 52. And the electrode terminal portion 50 may be used in a state where these first metal piece 51 and second metal piece 52 are arranged side by side in the lateral direction.

[0054] · In the above embodiment, it is embodied in the laser welding of the first metal piece 51 and the second metal piece 52 that constitute the electrode terminal portion 50 on the negative electrode terminal 38N side, but it may also be applied to the electrode terminal portion 50 on the positive electrode terminal 38P side.

[0055] · In the above embodiment, the electrode body 10 of the secondary battery 1 is configured as a wound body, but it is not necessarily required that the positive and negative electrode sheets 35P and 35N laminated with the separator 5 in between are not wound. Also, the secondary battery 1 does not necessarily have to be a lithium ion secondary battery, and it may be applied to other non-aqueous electrolyte secondary batteries. And the terminal shapes of the positive electrode terminal 38P and the negative electrode terminal 38N may also be arbitrarily changed not limited to the shapes shown in FIG. 1.

Explanation of Reference Numerals

[0056] 1…Secondary battery 50…Electrode terminal portion 51…First metal piece 51s…Upper surface 52…Second metal piece 56…Upper surface edge 60…Melting pool L…Laser beam

Claims

1. A method for manufacturing a secondary battery having an electrode terminal portion formed by joining a first metal piece and a second metal piece made of different materials, The first metal piece and the second metal piece are arranged by overlapping them in the thickness direction, Laser light is irradiated on the upper surface edge portion of the second metal piece placed on the first metal piece, The molten pool of the upper surface edge portion formed by the irradiation of the laser light flows downward to melt the upper surface of the first metal piece, whereby the first metal piece and the second metal piece are welded A method for manufacturing a secondary battery.

2. The second metal piece has a hole portion penetrating the second metal piece in the thickness direction, and Laser light is irradiated on the peripheral edge portion of the hole portion as the upper surface edge portion The method for manufacturing a secondary battery according to Claim 1.

3. The method for manufacturing a secondary battery according to Claim 2, wherein the hole portion is a circular hole.

4. The light source of the laser light is a disk laser The method for manufacturing a secondary battery according to any one of Claims 1 to 3.

5. One of the first metal piece and the second metal piece is formed using copper, and the other of the first metal piece and the second metal piece is formed using aluminum The method for manufacturing a secondary battery according to any one of Claims 1 to 3.

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