Joining method

Abstract

Provided is a joining method wherein a battery cell (1c) having a straight-shaped positive electrode tab (11) and a battery cell (1d) having a straight-shaped negative electrode tab (12) are stacked such that the positive and negative electrode tabs (11, 12) are adjacent to each other with a first distance (L1) therebetween, the gap between the positive and negative electrode tabs (11, 12) is widened, a busbar (2) having a first bent part (21) that is bent so as to face the positive electrode tab (11) and a second bent part (22) that is bent so as to face the negative electrode tab (12) is inserted between the positive and negative electrode tabs (11, 12), the positive electrode tab (11) is pressed against the first bent part (21), the negative electrode tab (12) is pressed against the second bent part (22), the positive electrode tab (11) is joined to the first bent part (21), and the negative electrode tab (12) is joined to the second bent part (22).

Description

Joining method

[0001] The present invention relates to a joining method for joining a pair of battery tabs and a bus bar.

[0002] A battery module including multiple pairs of electrode leads for multiple battery cells and a bus bar to which the electrode leads are welded is known (see Patent Document 1). In this battery module, the bent portions of the electrode leads are welded to a straight sensing bus bar.

[0003] Special Publication No. 2023-554629

[0004] To form the bent portion of the electrode lead described in Patent Document 1, a bending jig is used. However, the gap between the electrode leads is very narrow (see Patent Document 1 (Figure 12)), and there is a possibility that the electrode lead of the opposite electrode will come into contact with the bending jig, causing a short circuit. Furthermore, if the gap between the electrode leads is to be widened, the width of the bent portion must also be narrowed, which reduces the contact area between the bus bar and the bent portion. Thus, the technology described in Patent Document 1 has the problem of poor workability in joining the electrode lead and the bus bar.

[0005] An object of the present invention is to provide a joining method that can improve the workability in joining a tab and a bus bar.

[0006] The present invention solves the above problem by widening the gap between the first tab and the second tab, inserting a bus bar between the first and second tabs, the bus bar having a first bent portion bent to face the first tab and a second bent portion bent to face the second tab, pressing the first tab against the first bent portion and pressing the second tab against the second bent portion, joining the first tab and the first bent portion and joining the second tab and the second bent portion.

[0007] According to the present invention, the workability in joining the tab and the bus bar can be improved.

[0008] Fig. 1 is a first side view illustrating a joining method according to an embodiment of the present invention. Fig. 2 is a second side view and a perspective view illustrating a joining method according to an embodiment of the present invention. Fig. 3 is a perspective view illustrating an example of an expansion jig according to an embodiment of the present invention. Fig. 4 is a side view illustrating a bus bar and a fixing jig according to an embodiment of the present invention. Fig. 5 is a perspective view illustrating a modified example of a bus bar according to an embodiment of the present invention. Fig. 6 is a perspective view illustrating a modified example of a fixing jig according to an embodiment of the present invention.

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0010] Fig. 1 is a first side view illustrating the bonding method of this embodiment, and Fig. 2 is a second side view and a perspective view illustrating the bonding method of this embodiment. Figs. 1(a) to 1(f) and 2(a) to 2(d) show the flow of the bonding method of this embodiment. Fig. 2(d) is a perspective view showing the step of Fig. 2(b).

[0011] The joining method in this embodiment is a method of joining a pair of opposing electrode tabs of opposite polarities in adjacent battery cells to a bus bar that electrically connects the pair of electrode tabs of opposite polarities. Although not particularly limited, this embodiment illustrates a case in which a positive electrode tab 11 and a negative electrode tab 12 in the lowest row are connected by a bus bar 2, and then a positive electrode tab 11 and a negative electrode tab 12 in the next row are connected by a bus bar 2. The positive electrode tab 11 and the negative electrode tab 12 in this embodiment correspond to an example of a first tab and a second tab in the present invention.

[0012] In this embodiment, the positive electrode tab 11 and the negative electrode tab 12 have a straight shape. The positive electrode tab 11 and the negative electrode tab 12 extend in the X direction and do not have any bent portions (bent or curved portions).

[0013] As shown in FIG. 1(a), multiple battery cells 1a to 1g are stacked in the Z direction (stacking direction) in the figure. The battery cells 1a to 1g are, for example, all-solid-state batteries. Although not particularly limited, the all-solid-state battery contains a solid electrolyte as an electrolyte. Although not particularly limited, the battery cells 1a to 1g are charged. For example, the SOC of the battery cells 1a to 1g is 50% or more.

[0014] Each of the battery cells 1a to 1g includes a positive electrode tab 11 made of a metal material such as copper, and a negative electrode tab 12 made of a metal material such as copper. The positive and negative electrode tabs 11, 12 of the battery cells 1a to 1g, which are to be connected by the bus bar 2, are spaced apart from each other by a first distance T １ The layers are stacked adjacent to each other with a distance of 10 mm.

[0015] As shown in Fig. 1(b), an expansion jig 3 is inserted between the positive electrode tab 11 of battery cell 1c and the negative electrode tab 12 of battery cell 1d. Fig. 3 is a perspective view showing an example of the expansion jig 3 in this embodiment. As shown in Fig. 3(a), the expansion jig 3 is a rod-shaped member with an elliptical cross-sectional shape. Therefore, the outer periphery of the expansion jig 3 includes a pair of long sides 31 and a pair of short sides 32.

[0016] Figures 3(b) to 3(d) show modified examples of the expansion jig 3. As shown in Figure 3(b), the expansion jig 3 may have an elliptical cylindrical cross section. As shown in Figure 3(c), the expansion jig 3 may have a rectangular cross section. As shown in Figure 3(d), the expansion jig 3 may have a rectangular cylindrical cross section.

[0017] Next, as shown in FIG. 1(c), the expansion jig 3 is rotated around its axis to press the short side portion 32 (see FIG. 3(a)) against the positive electrode tab 11 and the negative electrode tab 12. As a result, the distance between the positive electrode tab 11 and the negative electrode tab 12 is reduced to a first distance L １ In this way, the expansion jig 3 has long side portions 31 and short side portions 32, and can control contact / non-contact with the positive and negative electrode tabs 11, 12 by rotation, so that the expansion jig 3 does not come into contact with the positive and negative electrode tabs 11, 12 when the expansion jig 3 is inserted or retracted. This improves workability in the joining process.

[0018] Next, as shown in Fig. 1(d), with the gap between the positive electrode tab 11 and the negative electrode tab 12 widened, the bus bar 2 is inserted between the positive electrode tab 11 and the negative electrode tab 12. Fig. 4 is a side view showing the bus bar 2 and the fixing jig 4 in this embodiment. As shown in Fig. 4, the bus bar 2 in this embodiment has a substantially U-shape formed by bending a plate-like metal member.

[0019] The bus bar 2 includes a first bent portion 21, a second bent portion 22, and a connecting portion 23. The first bent portion 21 is a portion bent in the X direction in the figure, and faces the negative electrode 12 when the bus bar 2 is inserted between the positive electrode tab 11 and the negative electrode tab 12, as shown in Fig. 1(d) .

[0020] 4, the second bent portion 22 is a portion bent in the X direction in the figure so as to be substantially parallel to the first bent portion 21. As shown in FIG. 1( d ), when the bus bar 2 is inserted between the positive electrode tab 11 and the negative electrode tab 12, the second bent portion 22 faces the positive electrode tab 11.

[0021] 4 , the connecting portion 23 is a portion that connects the first bent portion 21 and the second bent portion 22, and extends along the Z direction (stacking direction). The busbar 2 is fixed to the fixing jig 4 by sandwiching the fixing jig 4 between the first and second bent portions 21, 22.

[0022] The fixing jig 4 is a rod-shaped jig extending in the Y direction and has a substantially semicircular cross section. The fixing jig 4 contacts the inner wall surface 2a of the busbar 2 on multiple surfaces, including a first contact surface 41 that contacts the first bent portion 21, a second contact surface 42 that contacts the connecting portion 23, and a third contact surface 43 that contacts the second bent portion 22. This allows the fixing jig 4 to properly fix the busbar 2, making it easier to handle the busbar 2. In other words, the workability of the joining process is improved.

[0023] In this embodiment, the shape of the busbar 2 is not limited to the above-described shape. Fig. 5 is a perspective view showing a modified example of the busbar 2 in this embodiment. In the modified example shown in Fig. 5, the connecting portion 23 is not straight but has a bent portion 24. Providing such a bent portion 24 improves the elasticity of the busbar 2 in the Z direction. In particular, when the battery cells 1a to 1g are all-solid-state batteries, the expansion and contraction of the battery cells 1a to 1g is large, but such a busbar 2 can follow this expansion and contraction.

[0024] Furthermore, in this embodiment, the inner wall surface 2a of the busbar 2 faces the battery cells 1a to 1g, but the inner wall surface 2a may be located in the opposite direction from the battery cells 1a to 1g.

[0025] In this embodiment, the length of the bus bar 2 in the Z direction is a first distance L １ As shown in FIG. 5, the length L of the busbar 2 is approximately the same as, but not limited to, ２ is the first distance L １ It is preferable that L １ <L ２ ) Such a large bus bar 2 can improve the flexibility of the bus bar 2 in the Z direction.

[0026] The shape of the fixing jig 4 can be changed as appropriate to match the shape of the busbar 2. FIG. 6 is a perspective view showing a modified example of the fixing jig 4 in this embodiment. As shown in FIG. 6( a), the fixing jig 4 may have a rectangular cross-sectional shape. As shown in FIG. 6( b), the fixing jig 4 may have a rectangular cylindrical cross-sectional shape. As shown in FIG. 6( c), the fixing jig 4 may have a square cross-sectional shape. As shown in FIG. 6( d), the fixing jig 4 may have a square cylindrical cross-sectional shape.

[0027] As shown in FIG. 6( e), the fixing jig 4 may have a circular cross-sectional shape. As shown in FIG. 6( f), the fixing jig 4 may have a circular cylindrical cross-sectional shape. As shown in FIG. 6( g), the fixing jig 4 may have an elliptical cross-sectional shape. As shown in FIG. 6( h), the fixing jig 4 may have an elliptical cylindrical cross-sectional shape. As shown in FIG. 6( i), the fixing jig 4 may have a horseshoe-shaped cross-sectional shape. As shown in FIG. 6( j), the fixing jig 4 may have a horseshoe-shaped cylindrical cross-sectional shape. Even with a fixing jig 4 having such a cross-sectional shape, the busbar 2 can be easily handled.

[0028] Returning to Fig. 1(e), the expansion jig 3 is rotated to release the pressure applied by the expansion jig 3 to the positive and negative electrode tabs 11, 12. This reduces the distance between the positive and negative electrode tabs 11, 12, and the positive and negative electrode tabs 11, 12 come into contact with the bus bar 2. Next, as shown in Fig. 1(f), the expansion jig 3 is retracted from between the positive and negative electrode tabs 11, 12.

[0029] Next, as shown in Fig. 2(a), a pair of pressing jigs 5a and 5b press the positive and negative electrode tabs 11 and 12 against the bent portion of the bus bar 2 from above and below. These pressing jigs 5a and 5b are rod-shaped jigs extending in the Y direction and have a semicircular cross section. The length L of these pressing jigs 5a and 5b in the Z direction is ３ is the first distance L １ Therefore, the holding jig 5a does not come into contact with the opposing positive electrode tab 11, and the holding jig 5b does not come into contact with the opposing negative electrode tab 12. This makes it possible to prevent short circuits from occurring due to the holding jigs 5a and 5b.

[0030] The cross-sectional shape of the holding jigs 5 a and 5 b is not limited to a circle, and may be a rectangle, a rectangular cylinder, a square, a square cylinder, a circle, a circular cylinder, an ellipse, an elliptical cylinder, a horseshoe, a horseshoe-shaped cylinder, or the like, as shown in FIG.

[0031] 2(b) and 2(d), the positive and negative electrode tabs 11, 12 are joined to the bus bar 2. Although not particularly limited, the positive and negative electrode tabs 11, 12 can be joined to the bus bar 2 by laser welding or the like.

[0032] 2(c), the fixing jig 4 and the holding jigs 5a and 5b are retracted. In this manner, the positive electrode tab 11, the negative electrode tab 12, and the bus bar 2 can be joined together.

[0033] With this joining method, there is no need to bend the positive and negative electrode tabs 11, 12. Furthermore, since the bus bar 2 is inserted after the gap between the positive and negative electrode tabs 11, 12 is expanded, the bus bar 2 can be easily inserted. This improves the workability of joining.

[0034] 1a to 1g: Battery cell 11: Positive electrode tab 12: Negative electrode tab 2: Bus bar 3: Expansion jig 4: Fixing jig 5: Pressing jig

Claims

1. A joining method comprising: stacking a first battery cell having a straight-shaped first tab and a second battery cell having a straight-shaped second tab so that the first tab and the second tab are adjacent and spaced a first distance apart; widening the gap between the first tab and the second tab; inserting a bus bar having a first bent portion bent to face the first tab and a second bent portion bent to face the second tab between the first and second tabs; pressing the first tab against the first bent portion and pressing the second tab against the second bent portion; joining the first tab and the first bent portion and joining the second tab and the second bent portion.

2. The joining method according to claim 1, wherein the length of the bus bar in the stacking direction of the first and second battery cells is greater than the first distance.

3. A joining method as claimed in claim 1 or 2, wherein the distance between the first tab and the second tab is widened by an expansion tool, the cross section of which includes a pair of long sides that are longer than the first distance and a pair of short sides that are shorter than the first distance, and wherein the expansion tool is inserted between the first tab and the second tab, and then the expansion tool is rotated to press the short sides against the first and second tabs, thereby widening the distance between the first tab and the second tab.

4. A joining method according to claim 3, wherein the cross-sectional outer shape of the expansion jig is rectangular or elliptical.

5. A joining method according to any one of claims 1 to 4, wherein the bus bar is fixed to a fixing jig and inserted between the first and second tabs together with the fixing jig, the bus bar includes an inner wall surface that is not in contact with the first and second tabs, and the fixing jig includes a plurality of contact surfaces that are in contact with the inner wall surfaces.

6. A joining method according to claim 5, wherein the cross-sectional outer shape of the fixing jig is rectangular, square, circular, elliptical or horseshoe-shaped.

7. A joining method as described in claim 6, wherein the first and second tabs are pressed against the first and second bent portions, respectively, by a pressing jig, and the length of the pressing jig in the stacking direction of the first and second battery cells is shorter than the first distance.

8. A joining method according to claim 7, wherein the cross-sectional outer shape of the holding jig is rectangular, square, circular, elliptical or horseshoe-shaped.

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