JP7245146B2 - Method for connecting lead tab and electrode foil, and method for manufacturing wound storage element - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Act On July 27, 2019, Nichicon Corporation sold a lithium-ion secondary battery to Yuko Electric Co., Ltd., making it public.

TECHNICAL FIELD The present invention relates to a method for connecting lead tabs and electrode foils by crimping, and a method for manufacturing a wound energy storage device to which this method is applied.

Conventionally, a connection method called crimping has been used to connect lead tabs and electrode foils that constitute various winding-type storage devices (including lithium-ion secondary batteries and electrolytic capacitors). there is

As seen in Patent Document 1, etc., this connection method includes a step of overlapping 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 step of inserting a perforating 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 perforating needle, and a step of crushing the burrs with a press (that is, a step of crimping the electrode foil and the electrode lead). .

JP 2008-210617 A

However, the above connection method results in unstable connections between lead tabs and electrode foils when connecting narrow lead tabs using very thin piercing needles (in other words, when the possible burr size is small). There can be a problem of becoming That is, with the above-described connection method, it is difficult to reliably connect the lead tabs and the electrode foils mechanically and electrically when manufacturing a small-sized wound storage element.

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

In order to solve the above-described problems, a connection method according to the present invention is a method for connecting lead tabs and electrode foils constituting a wound storage element, wherein the electrode foils are arranged on a base portion having a concave portion. a second step of arranging a lead tab on the electrode foil so as to be positioned right above the recess; a third step of generating burrs in the superimposed body; a fourth step of pulling out the perforating needle from the superimposed body; and a fifth step of pressing the superimposed body from above and below to crush the burrs. When viewed from above, the shape of the concave portion is such that the four corners of a rectangle are expanded outward along the diagonal lines of the rectangle, and the tip of the perforation needle is located on the opposite sides of the rectangle. It is characterized in that it has a shape that can form a cross-shaped notch connecting the centers to the overlapping body.

In this configuration, the shape of the concave portion when viewed from above is such that the four corners of the rectangle are expanded outward along the diagonal lines of the rectangle. Further, in this configuration, the tip of the perforating needle is shaped so that a cross-shaped notch connecting the centers of the opposite sides of the rectangle can be formed in the overlapping body. Thus, with this configuration, the four pieces of the lap produced by the notch are bent outward along the diagonals to maximize the size of the burr, thus minimizing the dimensions of the piercing needle and lead tab. Even if the diameter is small, the lead tab and the electrode foil can be reliably connected.

The connection method may have a configuration in which the shape of the recess when viewed from the top is a rectangle and four circles centered at four vertices of the rectangle superimposed on each other. good.

Further, in the connection method, the rectangle of the recess is square, the shape of the tip of the perforation needle is a regular quadrangular pyramid, and the cross section of the regular quadrangular pyramid corresponds to the rectangle of the recess when viewed from above. 45° to each other.

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

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

1 is an exploded perspective view showing constituent elements of a wound lithium-ion secondary battery; FIG. FIG. 4 is a plan view showing an electrode foil and lead tabs arranged on the electrode foil; It is an end elevation which shows each process included in the connection method based on the Example of this invention. FIG. 4 is a plan view showing the relationship between the lead tab, the recess of the base, and the tip of the piercing needle in the embodiment of the present invention; FIG. 4 is a view of burrs after pressing caused by the connection method according to the example of the present invention, viewed from the electrode foil side; FIG. 10 is a plan view showing the relationship between the lead tab, the recessed portion of the pedestal portion, and the tip portion of the perforating needle in a comparative example of the present invention; FIG. 11 is a plan view showing the relationship between the lead tab, the recessed portion of the pedestal, and the tip portion of the piercing needle in the modified example of the present invention.

A method for connecting lead tabs and electrode foils according to an embodiment of the present invention and a method for manufacturing a wound storage device to which this method is applied will now be described with reference to the accompanying drawings. In addition, although the case where the winding type storage element is a lithium ion secondary battery will be described below, the present invention can also be applied to the case where the winding type storage element is an electrolytic capacitor or the like.

As shown in FIG. 1, a wound type lithium ion secondary battery 1 includes a battery body 10 having a positive electrode lead 13a and a negative electrode lead 13b, and a seal having holes 21 and 21 for passing the leads 13a and 13b. It consists of a rubber 20 and a metallic exterior case 30 that accommodates the battery main body 10 and the sealing rubber 20 . The open end of the exterior case 30 is curled after the battery body 10 and the sealing rubber 20 are housed therein. Further, the portion of the exterior case 30 covering the sealing rubber 20 is drawn after the battery main body 10 and the sealing rubber 20 are accommodated.

The battery main body 10 includes a positive electrode foil 11a to which a positive electrode lead 13a is connected, a first separator 12a, a negative electrode foil 11b to which a negative electrode lead 13b is connected, and a second separator 12b, which are stacked in this order and wound. It is what I did. 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. Also, the separators 12a and 12b are made of rayon.

In addition, below, the positive electrode foil 11a and the negative electrode foil 11b may be called the electrode foil 11 without distinguishing. Further, hereinafter, the positive lead 13a and the negative lead 13b may be referred to as the lead 13 without distinguishing between them.

As shown in FIG. 2, the lead 13 includes a lead wire 14 that protrudes through the 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. and 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 or copper core plated with tin as an outer layer.

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

The connection method according to the present embodiment further includes a third step of piercing the overlapping bodies 11 and 16 with the perforating needle 60 from the lead tab 16 side to generate burrs 70 in the overlapping bodies 11 and 16 (Fig. 3(B)). Since the superimposed 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 are not misaligned when the perforating needle 60 is pierced. In the present embodiment, the recess 51 penetrates the base portion 50, but the recess 51 is a bottomed hole having a depth capable of receiving the perforation needle 60 in the third step. may

The connection method according to the present embodiment comprises a fourth step (see FIG. 3C) in which the perforating needle 60 is pulled out, the overlapping bodies 11 and 16 are moved between the upper plate and the lower plate of the press machine, A fifth step of crushing the burr 70 by pressing from above and below until the distance between the upper plate and the lower plate (hereinafter referred to as "caulking thickness") reaches a predetermined distance (see FIG. 3(D)). and furthermore.

FIG. 4 is a plan view showing the shapes of the lead tab 16, the concave portion 51 of the pedestal portion 50, and the distal end portion 61 of the perforating needle 60 and their relationship when viewed from above.

The lead tab 16 has a width dimension of _W16 .

The recess 51 is formed by overlapping a rectangle whose width dimension is W ₅₁ and whose length dimension is L ₅₁ and four circles whose centers are the four vertices of the rectangle and whose radius is R. It has a shape like In other words, the concave portion 51 has a shape in which the four corners of a rectangle are expanded outward along the diagonal lines of the rectangle.

Further, the tip portion 61 of the perforating needle 60 has a quadrangular pyramid shape that can form cross-shaped notches 17, 17 connecting the centers of the opposing sides of the rectangles forming the recess 51 in the overlapped bodies 11, 16. have.

As can be understood from FIG. 4, in this embodiment, the tip portion 61 of the perforation needle 60 has a regular quadrangular pyramid shape. The cross section (square) of this regular quadrangular pyramid is inclined by 45° with respect to the rectangle (square) forming the concave portion 51 .

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

Next, the results of tests for confirming the connection strength between 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 salt 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 Using the separators 12a and 12b with a thickness of 20 [μm] and the lead tab 16 with a width (=W ₁₆ ) of 1.0 [mm] and a thickness of 180 [μm], φ3.0 [μm] according to each example and each comparative example mm] was produced. Then, the ESR immediately after fabrication (initial) and after pulling the positive electrode side lead 13a or the negative electrode side lead 13b with a force of 6 [N], 8 [N], 10 [N], and 12 [N] was measured, and the rate of change with respect to the initial value was evaluated. A range in which the rate of change from the initial value was up to +/- 20% was rated as ⊚, a range over +/- 20% to +/- 25% was rated as ◯, and a result exceeding +/- 25% was rated as x.

Table 1 shows the results for the positive lead 13a of the lithium ion secondary battery 1 according to the first to ninth examples. In the first to ninth embodiments, the conditions for connecting the positive electrode foil 11a and the lead tab 16 of the positive electrode lead 13a, more specifically, the diagonal dimension of the burr 70 after pressing (hereinafter also referred to as "petal dimension") are shown in FIG. (see symbol D)) and the crimping thickness are different.

Here, the shape of the concave portion 51 in the first to ninth embodiments (and 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 indicate that the recess 51 has a clover shape, and the crimping thickness is 240 [μm], which is the sum of the thicknesses of the positive electrode foil 11a and the lead tab 16, plus 0 to 20 [μm]. This indicates that the connection between the positive electrode foil 11a and the lead tab 16 did not deteriorate even when the positive electrode lead 13a was pulled with a relatively large force of 12 [N]. 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 made larger than the total thickness plus 20 [μm], the crimping may be insufficient and the connection strength may decrease.

Further, the results shown in Table 1 show that when 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 and This indicates 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 of the negative electrode lead 13b of the lithium ion secondary battery 1 according to the tenth to eighteenth examples. The tenth to eighteenth embodiments differ in connection conditions between the negative foil 11b and the lead tab 16 of the negative lead 13b.

The results shown in Table 2 indicate that the shape of the recess 51 is a clover shape, and the crimping thickness is a dimension obtained by adding 5 to 25 [μm] to 225 [μm], which is the sum of the thicknesses of the negative electrode foil 11b and the lead tab 16. This indicates that the connection between the negative foil 11b and the lead tab 16 did not deteriorate even when the negative lead 13b was pulled with a relatively large force of 12 [N]. 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 when the petal size is 0.70 to 1.10 [mm], even if the negative lead 13b is pulled with a relatively large force of 12 [N], the negative electrode foil 11b and This indicates 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 lead 13a of the lithium ion secondary battery 1 according to the first comparative example and the results for the negative electrode lead 13b of the lithium ion secondary battery 1 according to the second comparative example.

Here, the shape of the concave portion 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 is a shape in which a rectangle and four circles are superimposed, but differs from the clover shape in that the centers of the four circles are shifted from the vertices of the rectangle. ing. That is, the shape of the concave portion 51 in the first and second comparative examples is not a shape in which the four corners of the rectangle are expanded outward along the diagonal lines of the rectangle.

The results shown in Table 3 show that when the shape of the concave portion 51 is H-shaped, even if the caulking thickness is 240 [μm], which is the sum of the thicknesses of the positive electrode foil 11a and the lead tab 16, plus 10 [μm], It shows that the connection state between the positive electrode foil 11a and the lead tab 16 can deteriorate with a force of 10 [N]. Further, the results shown in Table 3 show that even if the crimping thickness is the sum of the thicknesses of the negative electrode foil 11b and the lead tab 16 of 225 [μm] plus 15 [μm], the negative electrode can be crimped with a force of 10 [N]. It shows that the connection between the foil 11a and the lead tab 16 can deteriorate.

As described above, if the concave portion 51 is formed in a clover shape, the electrode foil 11 and the lead tab 16 can be connected more firmly than in the case where the concave portion 51 is formed in an H shape.

In addition, the ESR immediately after production (initial) of 1,000 lithium-ion secondary batteries 1 in which the concave portions 51 were formed in a clover shape and 1,000 lithium-ion secondary batteries 1 in which the concave portions 51 were formed in an H-shape were measured. was measured, 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 superiority of making the shape of the concave portion 51 a clover shape.

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

For example, the shape of the concave portion 51 when viewed from above 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 four corners of the rectangular shape are squared. Also, the shapes shown in FIGS. 4B and 4C differ from the clover shape shown in FIG. 4 in that the rectangle is not a square but a rectangle. When adopting the shapes shown in FIGS. 11(B) and 11(C), it is preferable that the tip portion 61 of the perforation needle 60 also has a rectangular cross section.

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 lead 13b negative electrode lead 14 lead wire 15 large diameter portion 16 lead tab 17 notch 20 sealing rubber 21 hole 30 outer case 40 pressing portion 50 pedestal portion 51 recessed portion 60 perforating needle 61 tip portion 70 burr

Claims (4)

A method for connecting lead tabs and electrode foils constituting a wound storage element, comprising:
a first step of arranging the electrode foil on a base portion having a recess;
a second step of arranging a lead tab on the electrode foil so as to be positioned directly above the recess;
a third step of piercing the superimposed body of the lead tab and the electrode foil with a perforating needle from the lead tab side to generate burrs in the superimposed body;
a fourth step of pulling out the perforating needle from the overlapping body;
a fifth step of pressing the stacked body from above and below to crush the burrs;
with
The shape of the recess when viewed from above is a rectangle with the four corners extending outward along diagonal lines of the rectangle,
A connecting method, wherein the tip portion of the perforating 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. 2. The connection method according to claim 1, wherein the shape of said recess when viewed from above is a combination of a rectangle and four circles centered at four vertices of said rectangle. the rectangle of the recess is a square;
The shape of the tip of the perforation needle is a regular quadrangular pyramid,
3. The connection method according to claim 1, wherein the cross section of the regular quadrangular pyramid is inclined by 45[deg.] with respect to the rectangular shape of the recess when viewed from above. A first step of forming a cylindrical battery body by winding two sheets of electrode foil, to which lead tabs are connected by the connection method according to any one of claims 1 to 3, together with a separator;
a second step of housing the battery body together with the sealing rubber in an exterior case;
A method for manufacturing a wound storage element, comprising:

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