JP2021068655A - Method for connecting lead tab with electrode foil, and method for manufacturing wound type power storage element - Google Patents

Abstract

To provide a connection method capable of reliably connecting a lead tab with an electrode foil even if a drilling needle and a lead tab have a small dimension.SOLUTION: A connection method according to the present invention includes the steps of: arranging an electrode foil on a pedestal part with a recess 51; and arranging a lead tab 16 on the electrode foil so as to be located directly above the recess 51. The shape of the recess 51 in plan view is an extension of the four corners of a rectangle to the outside along the diagonal of the rectangle. The tip 61 of a drilling needle has such a shape that cross-shaped notches 17, 17 that connect the centers of the opposing sides of the rectangle can be formed in the electrode foil and the lead tab 16.SELECTED DRAWING: Figure 4

Description

The present invention relates to a method of connecting a lead tab and an electrode foil by crimping, and a method of manufacturing a wound power storage element to which this method is applied.

Conventionally, when connecting the lead tabs constituting various winding type power storage elements (including lithium ion secondary batteries and electrolytic capacitors) and the electrode foil, a connection method called crimping has been used. There is.

As seen in Patent Document 1 and the like, this connection method includes a step of superimposing a lead tab (electrode lead) on an electrode foil made of a current collector having active material layers formed on both front and back surfaces, and a drilling needle from the lead tab side. It includes a step of piercing and penetrating to generate burrs on the electrode foil side, a step of pulling out the drilling needle, and a step of crushing the burrs with a press (that is, a step of crimping the electrode foil and the electrode lead). ..

Japanese Unexamined Patent Publication No. 2008-210617

However, in the above connection method, when connecting a narrow lead tab using a very thin drilling needle (in other words, when the size of the burr that can occur is small), the connection between the lead tab and the electrode foil is unstable. The problem of becoming can occur. That is, with the above connection method, it is difficult to reliably mechanically and electrically join the lead tab and the electrode foil when manufacturing a small winding type power storage element.

The present invention has been made in view of the above circumstances, and a connection method capable of reliably connecting the lead tab and the electrode foil even if the dimensions of the drilling needle and the lead tab are small, and this method are applied. An object of the present invention is to provide a method for manufacturing a winding type power storage element.

In order to solve the above problems, the connection method according to the present invention is a method of connecting a lead tab constituting a winding type power storage element and an electrode foil, and the electrode foil is arranged on a pedestal having a recess. One step, a second step of arranging the lead tab on the electrode foil so as to be located directly above the recess, and a perforation needle pierced into the lead tab and the overlapped body of the electrode foil from the lead tab side. The third step of generating burrs on the superposed body, the fourth step of pulling out the drilling needle from the superposed body, and the fifth step of pressing the superposed body from the vertical direction to crush the burrs. The shape of the concave portion when viewed in a plan view is such that the four corners of the rectangle are extended outward along the diagonal line of the rectangle, and the tip end portion of the drilling needle is the opposite side of the rectangle. It is characterized in that it has a shape in which a cross-shaped notch connecting the centers can be formed in the superposed body.

In this configuration, the shape of the concave portion when viewed in a plan view is such that the four corners of the rectangle are extended outward along the diagonal line of the rectangle. Further, in this configuration, the tip portion of the drilling needle has a shape capable of forming a cross-shaped notch connecting the centers of the opposite sides of the rectangle in the overlapping body. Therefore, according to this configuration, the four pieces of the superposition formed by the notch are greatly bent outward along the diagonal line, and as a result, the size of the burr is maximized, so that the dimensions of the drilling needle and the lead tab are increased. Even if the size is small, the lead tab and the electrode foil can be securely connected.

Even if the connection method has a configuration in which the shape of the concave portion when viewed in a plan view is a rectangle and four circles centered on each of the four vertices of the rectangle are overlapped. Good.

Further, in the connection method, the rectangle of the recess is square, the shape of the tip of the drilling needle is a regular quadrangular pyramid, and the cross section of the regular quadrangular pyramid becomes the rectangle of the recess when viewed in a plan view. It may have a configuration in which it is tilted by 45 °.

Further, in order to solve the above problems, the method for manufacturing the winding type power storage element according to the present invention is a cylindrical shape in which two electrode foils to which lead tabs are connected by any of the above connection methods are wound together with a separator. It is characterized by including a first step of forming a battery body and a second step of housing the battery body together with a sealing rubber in an outer case.

According to the present invention, there is provided a connection method capable of reliably connecting the lead tab and the electrode foil even if the dimensions of the drilling needle and the lead tab are small, and a method for manufacturing a wound power storage element to which this method is applied. be able to.

It is an exploded perspective view which shows the component | component of the winding type lithium ion secondary battery. It is a top view which shows the electrode foil and the lead tab arranged on the electrode foil. It is an end view which shows each process included in the connection method which concerns on Example of this invention. It is a top view which shows the relationship between the lead tab, the concave part of the pedestal part, and the tip part of the drilling needle in the Example of this invention. It is the figure which looked at the burr after pressing generated by the connection method which concerns on embodiment of this invention from the electrode foil side. It is a top view which shows the relationship between the lead tab, the concave part of the pedestal part, and the tip part of the drilling needle in the comparative example of this invention. It is a top view which shows the relationship between the lead tab, the concave part of a pedestal part, and the tip part of a drilling needle in the modification of this invention.

Hereinafter, a method of connecting the lead tab and the electrode foil according to the embodiment of the present invention and a method of manufacturing a wound power storage element to which this method is applied will be described with reference to the accompanying drawings. In the following, the case where the winding type power storage element is a lithium ion secondary battery will be described, but the present invention can also be applied to the case where the winding type power storage element is an electrolytic capacitor or the like.

As shown in FIG. 1, the wound lithium-ion secondary battery 1 has a battery body 10 having a positive electrode side lead 13a and a negative electrode side lead 13b, and a seal having holes 21 and 21 for passing the leads 13a and 13b. It is composed of a rubber 20, a metal outer case 30 for accommodating a battery body 10 and a sealing rubber 20. The open end of the outer case 30 is curled after accommodating the battery body 10 and the sealing rubber 20. Further, the portion of the outer case 30 that covers the sealing rubber 20 is drawn after accommodating the battery body 10 and the sealing rubber 20.

The battery body 10 is wound by superimposing the positive electrode foil 11a to which the positive electrode side lead 13a is connected, the first separator 12a, the negative electrode foil 11b to which the negative electrode side lead 13b is connected, and the second separator 12b in this order. It was done. The positive electrode foil 11a contains a lithium manganate salt as a positive electrode material, and the negative electrode foil 11b contains a lithium titanate salt as a negative electrode material. Further, the separators 12a and 12b are made of rayon.

In the following, the positive electrode foil 11a and the negative electrode foil 11b may be referred to as the electrode foil 11 without distinction. Further, in the following, the positive electrode side lead 13a and the negative electrode side lead 13b may be referred to as a lead 13 without distinguishing between them.

As shown in FIG. 2, the lead 13 includes a lead wire 14 that protrudes to the outside through a hole 21 of the sealing rubber 20, a large-diameter portion 15 that stays in the hole 21 of the sealing rubber 20, and a large-diameter portion 15. It is composed of a lead tab 16 having a thin plate shape formed by pressing. The lead 13 is electrically and mechanically connected to the electrode foil 11 by connecting the lead tab 16 and the electrode foil 11 by crimping. The large diameter portion 15 and the lead tab 16 are made of aluminum, and the lead wire 14 is made of an iron core or a copper core obtained by tin plating as an outer layer.

The method of connecting the lead tab 16 and the electrode foil 11 according to the present embodiment includes the first step of arranging the electrode foil 11 on the pedestal portion 50 having the recess 51 and the electrode foil so as to be located directly above the recess 51. A second step of arranging the lead tab 16 on the 11 is provided (see FIG. 3A). As shown in the figure, the overlapping bodies 11 and 16 of the electrode foil 11 and the lead tab 16 are sandwiched between the pressing portion 40 above the lead tab 16 and the pedestal portion 50 below the electrode foil 11.

The connection method according to the present embodiment further includes a third step of piercing the stacking bodies 11 and 16 with the drilling needle 60 from the lead tab 16 side to generate burrs 70 of the stacking bodies 11 and 16 (FIG. FIG. 3 (B)). Since the overlapping bodies 11 and 16 are sandwiched between the pressing portion 40 and the pedestal portion 50, the lead tab 16 and the electrode foil 11 do not shift in position when the drilling needle 60 is pierced. In this embodiment, the recess 51 penetrates the pedestal portion 50, but the recess 51 is a bottomed hole having a depth sufficient to receive the drilling needle 60 in the third step. You may.

In the connection method according to the present embodiment, the fourth step of pulling out the drilling needle 60 (see FIG. 3C) and the overlapping bodies 11 and 16 are moved between the upper plate and the lower plate of the press machine. Fifth step of crushing the burr 70 by pressing from the vertical direction until the distance between the upper plate and the lower plate (hereinafter referred to as "crimping thickness") becomes a predetermined distance (see FIG. 3 (D)). And further equipped.

FIG. 4 is a plan view showing the shapes of the lead tab 16, the recess 51 of the pedestal portion 50, and the tip portion 61 of the drilling needle 60 when viewed in a plan view, and the relationship between them.

The lead tab 16 has a width direction dimension of W ₁₆ .

The recess 51 is formed by superimposing a rectangle having a width direction dimension of W ₅₁ and a length direction dimension of L ₅₁ and four circles having a radius R centered on each of the four vertices of the rectangle. It has a similar shape. In other words, the recess 51 has a shape in which the four corners of the rectangle are extended outward along the diagonal line of the rectangle.

Further, the tip portion 61 of the drilling needle 60 has a quadrangular pyramid shape in which cross-shaped notches 17 and 17 connecting the centers of the opposing sides of the rectangle forming the recess 51 can be formed in the overlapping bodies 11 and 16. have.

As can be seen from FIG. 4, in this embodiment, the tip portion 61 of the drilling needle 60 has a regular quadrangular pyramid shape. The cross section (square) of this regular quadrangular pyramid is tilted by 45 ° with respect to the rectangle (square) constituting the recess 51.

According to the connection method according to the present embodiment, when the drilling needle 60 is pierced, the four pieces of the overlapping bodies 11 and 16 separated by the cross-shaped notches 17 and 17 form a rectangular shape of the recess 51. A large bend outward along the diagonal maximizes the size of the burr 70. As a result, even if the dimensions of the drilling needle 60 and the lead tab 16 are small, the lead tab 16 and the electrode foil 11 can be reliably connected.

Next, the result of the test for confirming the connection strength of the electrode foil 11 and the lead tab 16 will be described. In this test, first, a positive electrode foil 11a having a thickness of 60 [μm] containing a lithium manganate as a positive electrode material, a negative electrode foil 11b having a thickness of 45 [μm] containing a lithium titanate salt as a negative electrode material, and rayon are used. Using the separators 12a and 12b having a thickness of 20 [μm] and _{the lead tab 16 having a width (= W 16} ) of 1.0 [mm] and a thickness of 180 [μm], φ3.0 [concerning each example and each comparative example]. mm] lithium ion secondary battery 1 was produced. Then, after pulling the ESR immediately after each production (initial) and each positive electrode side lead 13a or negative electrode side lead 13b with a force of 6 [N], 8 [N], 10 [N], 12 [N]. ESR was measured and the rate of change with respect to the initial value was evaluated. The range in which the rate of change with respect to the initial value is up to +/- 20% is marked with ⊚, the range over +/- 20% and up to +/- 25% is marked with ◯, and the result exceeding +/- 25% is marked with x.

Table 1 shows the results of the positive electrode side lead 13a of the lithium ion secondary battery 1 according to the first to ninth embodiments. In the first to ninth embodiments, the connection conditions between the positive electrode foil 11a and the lead tab 16 of the positive electrode side lead 13a, more specifically, the diagonal dimension of the burr 70 after pressing (hereinafter, also referred to as “petal dimension”). The crimping thickness is different from that of the reference numeral D).

Here, the shape of the recess 51 in the first to ninth embodiments (and the tenth to eighteenth embodiments described later) is the shape shown in FIG. 4 (hereinafter, referred to as “clover shape”).

The results shown in Table 1 show that the shape of the recess 51 is a clover shape, and the crimping thickness is 240 [μm], which is the total thickness of the positive electrode foil 11a and the lead tab 16, plus 0 to 20 [μm]. This indicates that even if the positive electrode side lead 13a is pulled with a relatively large force of 12 [N], the connection state between the positive electrode foil 11a and the lead tab 16 does not deteriorate. It is particularly preferable that the crimping thickness is a dimension obtained by adding 5 to 15 [μm] to the total thickness. If the crimping thickness is smaller than the total thickness, the positive electrode foil 11a may be damaged. On the other hand, if the crimping thickness is larger than the total thickness plus 20 [μm], the crimping may be insufficient and the connection strength may be lowered.

Further, the results shown in Table 1 show that if the petal size is 0.70 to 1.10 [mm], even if the positive electrode side lead 13a is pulled with a relatively large force of 12 [N], the positive electrode foil 11a is obtained. It shows that the connection state with the lead tab 16 did not deteriorate. The petal size is particularly preferably 0.80 to 1.00 [mm].

Table 2 shows the results for the negative electrode side lead 13b of the lithium ion secondary battery 1 according to the tenth to eighteenth examples. In the tenth to eighteenth embodiments, the connection conditions between the negative electrode foil 11b and the lead tab 16 of the negative electrode side lead 13b are different.

The results shown in Table 2 show that the shape of the recess 51 is a clover shape, and the crimping thickness is 225 [μm], which is the total thickness of the negative electrode foil 11b and the lead tab 16, plus 5 to 25 [μm]. This indicates that even if the negative electrode side lead 13b is pulled with a relatively large force of 12 [N], the connection state between the negative electrode foil 11b and the lead tab 16 does not deteriorate. It is particularly preferable that the crimping thickness is a dimension obtained by adding 10 to 20 [μm] to the total thickness.

Further, the results shown in Table 2 show that if the petal size is 0.70 to 1.10 [mm], even if the negative electrode side lead 13b is pulled with a relatively large force of 12 [N], the negative electrode foil 11b is obtained. It shows that the connection state with the lead tab 16 did not deteriorate. The petal size is particularly preferably 0.80 to 1.00 [mm].

Table 3 shows the results for the positive electrode side lead 13a of the lithium ion secondary battery 1 according to the first comparative example and the results for the negative electrode side lead 13b of the lithium ion secondary battery 1 according to the second comparative example.

Here, the shape of the recess 51 in the first and second comparative examples is the shape shown in FIG. 6 (hereinafter, referred to as “H shape”). The H shape is similar to the clover shape in that it looks like a rectangle and four circles overlapped, but differs from the clover shape in that the centers of the four circles deviate from the vertices of the rectangle. ing. That is, the shape of the recess 51 in the first to second comparative examples is not a shape in which the four corners of the rectangle are extended outward along the diagonal line of the rectangle.

The results shown in Table 3 show that assuming that the shape of the recess 51 is H, the crimping thickness is 240 [μm], which is the total thickness of the positive electrode foil 11a and the lead tab 16, plus 10 [μm]. It is shown that the connection state between the positive electrode foil 11a and the lead tab 16 can be deteriorated by the force of 10 [N]. Further, the results shown in Table 3 show that even if the crimping thickness is 225 [μm], which is the total thickness of the negative electrode foil 11b and the lead tab 16, plus 15 [μm], the negative electrode is subjected to a force of 10 [N]. It shows that the connection state between the foil 11a and the lead tab 16 can be deteriorated.

As described above, when the shape of the recess 51 is a clover shape, the electrode foil 11 and the lead tab 16 can be more firmly connected than when the shape of the recess 51 is an H shape.

Further, the ESR immediately after (initial) production of 1000 lithium ion secondary batteries 1 in which the shape of the recess 51 is formed as a clover shape and 1000 lithium ion secondary batteries 1 in which the shape of the recess 51 is formed as an H shape. The standard deviation of the clover shape was 0.47, whereas the standard deviation of the H shape was 1.03, and the former had considerably less variation. This test result also shows the advantage of making the shape of the recess 51 a clover shape.

Although the examples of the present invention have been described above, the configuration of the present invention is not limited to the examples.

For example, the shape of the recess 51 when viewed in a plan view may be the shape shown in FIG. The shape shown in FIG. 4A is different from the clover shape shown in FIG. 4 in that the expanded portions of the four corners of the rectangle are angular. Further, the shapes shown in FIGS. (B) and (C) are different from the clover shape shown in FIG. 4 in that the rectangle is not a square but a rectangle. When the shapes shown in FIGS. (B) and (C) are adopted, it is preferable that the cross section of the tip portion 61 of the drilling needle 60 is also rectangular.

1 Lithium-ion battery 10 Battery body 11 Electrode foil 11a Positive electrode foil 11b Negative electrode foil 12a First separator 12b Second separator 13 Lead 13a Positive electrode side lead 13b Negative electrode side lead 14 Lead wire 15 Large diameter part 16 Lead tab 17 Notch 20 Seal rubber 21 hole 30 Exterior case 40 Pressing part 50 Pedestal part 51 Recessed part 60 Drilling needle 61 Tip part 70 Burr

Claims (4)

It is a method of connecting the lead tab and the electrode foil that constitute the winding type power storage element.
The first step of arranging the electrode foil on the pedestal having the recess, and
The second step of arranging the lead tab on the electrode foil so as to be located directly above the recess, and
A third step of piercing the lead tab and the overlapped body of the electrode foil with a drilling needle from the lead tab side to cause burrs on the laminated body.
The fourth step of pulling out the drilling needle from the stacking body, and
The fifth step of pressing the superposed body from above and below to crush the burr, and
With
The shape of the concave portion when viewed in a plan view is a rectangle in which the four corners are extended outward along the diagonal line of the rectangle.
A connection method characterized in that the tip end portion of the drilling needle has a shape capable of forming a cross-shaped notch connecting the centers of opposite sides of the rectangle in the superposed body. The connection method according to claim 1, wherein the shape of the concave portion when viewed in a plan view is a rectangle and four circles centered on each of the four vertices of the rectangle. The rectangle of the recess is a square,
The shape of the tip of the drilling needle is a regular quadrangular pyramid.
The connection method according to claim 1 or 2, wherein the cross section of the regular quadrangular pyramid is tilted by 45 ° with respect to the rectangle of the concave portion when viewed in a plan view. A first step of forming a cylindrical battery body by winding two electrode foils to which lead tabs are connected together with a separator by the connection method according to any one of claims 1 to 3.
The second step of accommodating the battery body together with the sealing rubber in the outer case, and
A method for manufacturing a winding type power storage element.

Images