JP2014203659A - Method for manufacturing secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a secondary battery, capable of suppressing thermal strain caused in resistance welding of a collector foil and a collector plate, and also securing bond strength between the collector foil and the collector plate.SOLUTION: In a method for manufacturing a secondary battery, collector foils 8a, 8a... and a collector plate 6 are bonded by resistance welding. When resistance welding is performed by bringing a first welding chip 11 into contact with a surface of one side of a collector foil 8a relative to the collector foil 8a, while bringing the collector plate 6 into contact with a surface of another side of the collector foil 8a, and by bringing a second welding chip 12 into contact with the collector plate 6, a taper 11a is provided at the tip of the welding chip 11, and has an incline angle θ of 30° or above and 60° or below.

Description

  The present invention relates to a technique of a secondary battery manufacturing method, and more particularly to a resistance welding method between a current collector foil and a current collector plate constituting a secondary battery.

  Conventionally, in a secondary battery having a wound type or laminated type electrode body, electrode foils (current collector foils) are bundled in layers at each end of the positive electrode and the negative electrode, and the stacked current collector foils are collected into current collectors. The structure joined to a board by resistance welding is known, for example, the technique is disclosed by the patent document 1 shown below, and is known.

In the prior art according to Patent Document 1, a secondary battery is disclosed in which a current collector foil is sandwiched between a pair of current collectors (current collector plates) that are bent to increase rigidity, and resistance welding is performed in this state.
In the secondary battery manufactured by the manufacturing method according to Patent Document 1, the reliability of the resistance welded portion is improved by resistance-welding current collector plates made of the same material as the core exposed portion on both sides of the core exposed portion. I am trying.

JP 2009-32670 A

However, in the conventional method for manufacturing a secondary battery according to Patent Document 1, since the current collector foil is sandwiched between a pair of current collector plates and pressed uniformly, it is orthogonal to the pressing direction of the current collector foil. There was a phenomenon in which the metal constituting the current collector foil flowed in the direction.
And since such a metal flow causes thermal distortion, there is a problem that the bonding strength between the current collector foil and the current collector plate cannot be sufficiently obtained.

In addition, if such thermal distortion occurs during resistance welding, the expansion and contraction of the current collector foil and current collector plate will vary, so the periphery of the resistance weld will be different from the shape planned for the design. There was a case.
When the electrode body is housed in the case with thermal distortion occurring in the resistance welded portion, the deformed resistance welded portion may come into contact with the case and cause a problem such as a short circuit.

  The present invention has been made in view of such current problems, and suppresses thermal distortion that occurs when resistance-welding the current collector foil to the current collector plate and reduces the bonding strength between the current collector foil and the current collector plate. It aims at providing the manufacturing method of the secondary battery which can be ensured.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

  That is, in Claim 1, it is a manufacturing method of the secondary battery which joins current collection foil and current collection board by resistance welding, Comprising: On the surface of one side of the current collection foil to the current collection foil The first welding tip is brought into contact, and the current collector plate is brought into contact with the other surface of the current collector foil, and the second welding tip is brought into contact with the current collector plate, thereby resistance welding. When performing, the taper part is provided in the front-end | tip of said 1st welding tip, and the inclination-angle of the said taper part shall be 30 degrees or more and 60 degrees or less.

  According to a second aspect of the present invention, a flat portion which is a flat portion and a bent portion which is a portion where the end portion of the flat portion is bent are formed on the current collector plate.

  According to a third aspect of the present invention, the length of the flat portion is less than twice the outer diameter of the second welding tip.

  As effects of the present invention, the following effects can be obtained.

In claim 1, during resistance welding, the metal constituting the current collector foil is caused to flow along the tapered shape of the welding tip to suppress the occurrence of thermal distortion in the resistance welded portion and to enlarge the exposed area of the new surface. can do.
Thereby, the area | region which contributes to joining can be expanded in the site | part which carries out resistance welding.

  According to the second and third aspects of the present invention, it is possible to suppress the deformation of the current collector plate in the lateral direction and to remarkably cause the flow along the chip of the current collector foil.

The schematic diagram which shows the secondary battery manufactured with the manufacturing method of the secondary battery which concerns on one Embodiment of this invention, (a) Cross-sectional schematic diagram, (b) The perspective schematic diagram which shows the welding method of a collector and current collector foil . The schematic diagram which shows the resistance welding method of the electrical power collector and current collection foil in the manufacturing method of the secondary battery which concerns on one Embodiment of this invention. The expansion schematic diagram which shows the resistance welding method of the electrical power collector which concerns on this invention, and current collection foil. The figure which shows the experimental condition for confirming the effect of this invention, and its experimental result. The figure which shows the experimental result which confirmed the effect of this invention, (a) The confirmation result of the effect difference by the inclination angle of a taper part, (b) The confirmation result of the effect difference by the length of a flat part. The schematic diagram which shows the resistance welding method of the electrical power collector and current collection foil in the manufacturing method of the conventional secondary battery.

Next, embodiments of the invention will be described.
First, the configuration of a secondary battery manufactured by the method for manufacturing a secondary battery according to an embodiment of the present invention will be described with reference to FIG.
As shown in FIG. 1A, a secondary battery 1 manufactured by a method for manufacturing a secondary battery according to an embodiment of the present invention includes a wound electrode body 2 and a square case 3. The pair of negative electrode terminals 4 and positive electrode terminals 5 are projected from the case 3.
The secondary battery 1 has a configuration in which the terminals 4 and 5 and the electrode body 2 are electrically connected by current collector plates 6 and 7 inside the case 3.

The electrode body 2 is manufactured by winding a laminate having a separator interposed between a sheet-like negative electrode and a positive electrode, and further flattening the wound body in a direction perpendicular to the winding axis. It is a member. The electrode body 2 is accommodated in the case 3 in a flattened (crushed) form.
In addition, current collectors 8 and 9, which are uncoated portions of the electrode mixture, are provided at both ends of the electrode body 2 in the winding axis direction.

As shown in FIG. 1 (b), the current collector 8 on the negative electrode side is a portion formed by bundling the current collector foils 8a, 8a... For the negative electrode in a state where the negative electrode mixture is not applied. The current collector foils 8a, 8a, ... are exposed.
Although not shown, the current collector 9 on the positive electrode side is a portion formed by bundling the current collector foils 9a, 9a,... For positive electrodes, and the current collector 9 is not coated with the positive electrode mixture. The electric foils 9a, 9a... Are exposed.

As shown in FIG. 1 (a), in the secondary battery 1, the current collector 8 on the negative electrode side (that is, the current collector foils 8a, 8a,. It is set as the structure joined by welding.
As shown in FIG. 1B, resistance welding of the current collector 8 (that is, current collector foils 8a, 8a...) And the current collector plate 6 presses the welding tip 11 to the current collector 8 side. In the state where the welding tip 12 is pressed to the current collector plate 6 side, the energization is performed.

Further, as shown in FIG. 1 (a), in the secondary battery 1, the current collector 9 on the positive electrode side (that is, the current collector foils 9a, 9a,. It is set as the structure joined by welding.
In addition, although illustration is abbreviate | omitted, while pressing the welding tip 11 to the current collection part 9 side also about the resistance welding of the current collection part 9 (namely, current collection foil 9a * 9a ...) and the current collection board 7, This is performed by energizing the welding chip 12 while pressing the welding tip 12 on the current collector plate 7 side.

  And the secondary battery 1 accommodates the electrode body 2 which connected each terminal 4 * 5 via each collector plate 6 * 7 in the case 3, and seals the case 3 after injecting electrolyte solution. Thus, the secondary battery 1 is manufactured.

Here, the resistance welding method between the current collector and the current collector plate will be described in more detail with reference to FIGS.
Here, resistance welding between the current collector 8 (current collector foils 8a, 8a...) On the negative electrode side and the current collector plate 6 will be described as an example.

As shown in FIG. 1, in the method for manufacturing a secondary battery according to one embodiment of the present invention, the current collector 8 (current collector foils 8 a, 8 a. The current collector plate 6 is brought into contact only with one surface (the lower surface in the state shown in FIG. 2) of the current collector 8 that is configured to be welded and is configured by the current collector foils 8a, 8a,. It is configured.
That is, in the method for manufacturing a secondary battery according to an embodiment of the present invention, a configuration in which the current collector is sandwiched between a pair (two) of current collector plates is not employed.

  And in the manufacturing method of the secondary battery which concerns on one Embodiment of this invention, the welding tip 11 is pressed from the current collection part 8 side in the state which accumulated the current collection foil 8a * 8a ... and the current collection board 6. FIG. And it is set as the structure which performs resistance welding in the resistance welding part P in the state which pressed the welding tip 12 from the current collector plate 6 side.

  Moreover, in the manufacturing method of the secondary battery which concerns on one Embodiment of this invention, it is set as the structure which provides the taper part 11a in the front-end | tip of the welding tip 11 of the side contacted with current collection foil 8a * 8a ....

  Furthermore, in the method for manufacturing a secondary battery according to the embodiment of the present invention, the flat portion 6a is formed on the surface of the current collector plate 6 that contacts the current collector foils 8a, 8a, etc. It is set as the structure which performs resistance welding in the state which formed the bending part 6b * 6b which is the site | part bent toward the opposite side to the part 6a.

Here, the taper shape of the welding tip 11 will be described.
As shown in FIG. 3, the tip 11 of the welding tip 11 to be brought into contact with the current collector foils 8 a, 8 a.
And in the manufacturing method of the secondary battery which concerns on one Embodiment of this invention, it is set as the structure which performs resistance welding by making inclination-angle (theta) of the taper part 11a into 30 degrees <= (theta) <= 60 degrees.

  By providing the tapered portion 11a and setting the inclination angle θ to an appropriate angle in this way, the current collector foils 8a, 8a,... Flow along the tapered portion 11a during resistance welding as shown in FIG. As a result, it is possible to suppress the occurrence of thermal distortion in the resistance weld P, and to expand the generation range of a new surface that contributes to joining, and to secure the joining strength by resistance welding. .

Here, the bent shape of the current collector plate 6 will be described.
As shown in FIG. 3, in the method for manufacturing a secondary battery according to an embodiment of the present invention, resistance welding is performed on the current collector plate 6 provided with the bent portions 6b and 6b.
When the bent portions 6b and 6b are formed on the current collector plate 6, a flat portion 6a that is a flat portion is provided between the bent portions 6b and 6b.
Furthermore, in the method for manufacturing a secondary battery according to the embodiment of the present invention, the length L of the flat portion 6a is set so that L <2A with reference to the diameter A of the welding tip 12 brought into contact with the current collector plate 6. It is set to be configured to perform resistance welding.

  Thus, by providing the bent portion 6b and making the length L of the flat portion 6a not too long, the strength of the current collector plate 6 is increased, and the current collector foil 8a. It becomes possible to flow 8a ... along the taper part 11a, and it becomes possible to ensure more reliably the joint strength by resistance welding.

  That is, in the method for manufacturing a secondary battery according to an embodiment of the present invention, the taper portion 11a having an inclination angle θ of 30 ° ≦ θ ≦ 60 ° is formed on the welding tip 11 that is brought into contact with the current collector foil 8a. In addition, the current collector plate 6 having the bent portions 6b and 6b is used, and resistance welding is performed in a state where the flat portion 6a having a flat portion length L (L <2A) is formed on the current collector plate 6. Is what you do.

  In the present embodiment, the secondary battery having a wound electrode body has been described as an example. However, depending on the configuration of the electrode body to be subjected to resistance welding, the method for manufacturing a secondary battery according to the present invention is described. For example, the present invention can be applied to the manufacture of a secondary battery having a stacked electrode body.

  In the present embodiment, the resistance welding between the current collector 8 on the negative electrode side (that is, the current collector foils 8a, 8a...) And the current collector plate 6 is described as an example. In addition, the resistance welding of the current collector 9 on the positive electrode side (that is, the current collector foils 9a, 9a...) And the current collector plate 7 is similarly performed in the resistance weld Q (see FIG. 1A). The description here is omitted.

Next, the application effect of the method for manufacturing a secondary battery according to the present invention will be described with reference to FIGS.
Here, one type of secondary battery sample (hereinafter referred to as an example) manufactured by the method for manufacturing a secondary battery according to one embodiment of the present invention, and 3 manufactured by a conventional method for manufacturing a secondary battery. An experiment was conducted to compare the yield rate of samples of secondary battery types (hereinafter referred to as Comparative Examples 1, 2, and 3). Moreover, the number of samples of the secondary battery of each specification was nine.

Here, the execution conditions of the comparative experiment will be described.
As shown in FIG. 4, in this experiment, when the current collector foil and the current collector plate are resistance-welded, two elements are 1) the shape of the welding tip on the current collector foil side, and 2) the shape of the current collector plate. To see how the yield rate changes.
In addition, the shape of the welding tip on the side of the current collector plate is a common shape that does not have a tapered portion, and the diameter A of the welding tip is 5 mm.
Moreover, the non-defective product ratio adopted as an evaluation standard in this experiment was evaluated based on the tensile strength in the resistance welded portion, and a non-defective product having a tensile strength equal to or greater than the strength of the set good product standard was determined.

First, in the case of the example, 1) a taper portion was provided on the welding tip on the current collector foil side, the taper portion was inclined at an angle θ of 45 °, and 2) a bent portion was provided on the current collector plate.
Further, the diameter B of the welding tip on the current collector foil side is 5 mm, the diameter C of the tip is 2.8 mm, and the height D of the tapered portion is 1.1 mm.
Further, the length L of the flat portion of the current collector plate is 7.5 mm, and the total length M of the current collector plate is 9.1 mm.

On the other hand, in the case of Comparative Example 1, 1) the welding tip on the current collector foil side was not provided with a taper portion, and 2) the current collector plate was not provided with a bent portion.
The diameter B of the welding tip on the current collector foil side is 5 mm, and the total length M of the current collector plate is 9.1 mm.
In addition, the implementation state of the resistance welding in the case of the comparative example 1 is illustrated in FIG.

In the case of Comparative Example 2, 1) the welding tip on the current collector foil side was not provided with a taper portion, and 2) the current collector plate was provided with a bent portion.
The diameter B of the welding tip on the current collector foil side is 5 mm.
Further, the length L of the flat portion of the current collector plate is 7.5 mm, and the total length M of the current collector plate is 9.1 mm.

Further, in the case of Comparative Example 3, 1) the welding tip on the side of the current collector foil is provided with a taper portion, the inclination angle θ of the taper portion is 45 °, and 2) the current collector plate is not provided with a bent portion. did.
Further, the diameter B of the welding tip on the current collector foil side is 5 mm, the diameter C of the tip is 2.8 mm, and the height D of the tapered portion is 1.1 mm.
Furthermore, the total length M of the current collector plate is 9.1 mm.

The current collector plate was made of copper and used to have a thickness of 0.6 mm, and the current collector foil was used by stacking 60 layers of 0.01 mm thick foil to a thickness of 1.2 mm.
Furthermore, resistance welding in this experiment was performed by applying a constant current (12 kA) for 40 ms while applying a load of 4 kN by narrowing the current collector plate and the current collector foil with each welding tip.
The material of each welding tip used in this experiment was pure tungsten.

And the comparison result of the non-defective rate at the time of manufacturing on each condition is shown in FIG.
According to the experimental results shown in FIG. 4, in the case of the example (according to the manufacturing method of the secondary battery according to the embodiment of the present invention), all nine samples are determined to be non-defective products (that is, the non-defective product rate is 100%). As a result, good welding quality is obtained.

On the other hand, in the case of Comparative Example 1, all nine samples are determined to be defective products (that is, a non-defective product rate of 0%).
This experimental result shows that when the current collector foil and the current collector plate are resistance-welded, the shape of the welding tip on the current collector foil side and the shape of the current collector plate have a great influence on the welding quality.
In other words, a non-defective product rate of 100% can be realized for the first time by providing a predetermined taper portion on the welding tip on the current collector foil side and a predetermined bent portion on the current collector plate.

As shown in FIG. 6, in the condition of Comparative Example 1, the welding tip 18 on the current collector 8 side is not provided with a taper, so that the metal immediately below the welding tip 18 on the current collector 8 side (current collector foil 8 a. It is considered that only the deformed portion 8a...) Can contribute to the joining, and a sufficient joining strength cannot be obtained.
Moreover, under the conditions of Comparative Example 1, the current collector foils 8a, 8a, etc. softened by the heat generated by resistance welding (Joule heat) reduce the thickness by the load applied by the upper and lower welding tips 18, 19 while laterally However, such a lateral flow of the metal causes problems such as an internal short circuit.
Furthermore, under the conditions of Comparative Example 1, the current collector plate 16 itself is deformed because the current collector plate 16 does not have a bent portion and the strength is insufficient.

In the case of Comparative Example 2, 6 out of 9 samples are determined to be non-defective products (that is, the non-defective product rate is about 67%), and in Comparative Example 3, 3 out of 9 samples are It is determined that the product is good (that is, the good product rate is about 33%).
The results of this experiment show that, when resistance welding the current collector foil and current collector plate, the effect of the shape of the current collector plate on the weld quality is compared to the effect of the shape of the welding tip on the current collector foil side on the weld quality. Shows that it is larger.

Next, an experimental result in which the optimum value of the inclination angle of the tapered portion is confirmed will be described.
In this experiment, when resistance-welding the current collector foil and the current collector plate, 1) providing a taper portion on the welding tip on the current collector foil side, and 2) providing a bent portion on the current collector plate, We confirmed how the yield rate changed when the tilt angle was changed.

  As shown in FIG. 5A, when the inclination angle θ of the taper portion is 30 ° or more and 60 ° or less, the yield rate is 7/9 to 9/9, and a good yield rate can be maintained. .

  On the other hand, when the inclination angle θ of the taper portion is 20 °, the yield rate is 1/9, and when the inclination angle θ of the taper portion is 70 °, the yield rate is 4/9. In either case, the yield rate is extremely low.

This experimental result shows that the inclination angle θ of the taper portion in the welding tip on the current collector foil side has a great influence on the welding quality. Even if the inclination angle θ is too large or too small, the bonding strength It was understood that improvement could not be achieved.
In other words, it is not always possible to improve the bonding strength simply by providing the taper portion on the welding tip on the current collector foil side, and the inclination angle θ of the taper portion is set to a predetermined angle (30 ° or more and 60 ° or less). By setting to, a good yield rate can be maintained for the first time.

Next, an experimental result of confirming the length of the flat portion in the current collector plate will be described.
In this experiment, when the current collector foil and the current collector plate are resistance-welded, 1) a taper portion is provided on the welding tip on the current collector foil side, and 2) a current collector plate is provided with a bent portion. By changing the length of the flat portion at, it was confirmed how the yield rate changes.

  As shown in FIG. 5B, the ratio of the length L of the flat portion to the diameter A of the welding tip on the current collector plate side (ie, L / A, hereinafter referred to as the flat portion length ratio) is less than 2.0. The non-defective product rate is 9/9 (100%), and a good non-defective product rate can be maintained.

  On the other hand, it was found that when the flat part length ratio was 2.0 or more, the yield rate was 5/9, and the yield rate was extremely deteriorated.

This experimental result has shown that the length L of the flat part in the current collecting plate which has a bending part has big influence on welding quality.
In other words, it is not always possible to improve the bonding strength simply by providing a bent portion on the current collector plate, and the length L of the flat portion is set to a predetermined length (L / A <2.0). Thus, it is possible to maintain a good non-defective rate for the first time.

That is, the manufacturing method of the secondary battery 1 according to the embodiment of the present invention includes the current collector foils 8a, 8a... And the current collector plate 6 (and the current collector foils 9a, 9a... And the current collector plate 7). The first welding tip 11 is brought into contact with one surface of the current collector foil 8a with respect to the current collector foil 8a, and other than the current collector foil 8a. When the current collector plate 6 is brought into contact with the side surface and the second welding tip 12 is brought into contact with the current collector plate 6 to perform resistance welding, a tapered portion 11a is provided at the tip of the welding tip 11, In addition, the inclination angle θ of the taper portion 11a is set to 30 ° or more and 60 ° or less.
With such a configuration, during resistance welding, the metal constituting the current collector foils 8a, 8a,... Flows along the tapered shape (tapered portion 11a) of the welding tip 11 to cause thermal distortion in the resistance welding portion P. Can be suppressed, and the exposed area of the new surface can be enlarged.
Thereby, the area | region which contributes to joining can be expanded in the site | part which carries out resistance welding.

In addition, in the method for manufacturing the secondary battery 1 according to the embodiment of the present invention, the current collector plate 6 includes a flat portion 6a that is a flat portion and a bent portion 6b that is a portion where an end portion of the flat portion 6a is bent. -It forms 6b.
Furthermore, in the method for manufacturing the secondary battery 1 according to the embodiment of the present invention, the length L of the flat portion 6a is set to a length less than twice the diameter A of the welding tip 12 (that is, L <2A). Is.
With such a configuration, deformation of the current collector plate 6 in the lateral direction can be suppressed, and the flow of the current collector foils 8a, 8a,.

DESCRIPTION OF SYMBOLS 1 Secondary battery 2 Electrode body 6 Current collecting plate 6a Flat part 6b Bending part 7 Current collecting plate 8 Current collecting part 8a Current collecting foil 9 Current collecting part 9a Current collecting foil 11 Welding tip 11a Tapered part 12 Welding tip 12a Negative electrode current collecting Foil

Claims (3)

A method of manufacturing a secondary battery in which a current collector foil and a current collector plate are joined by resistance welding,
With respect to the current collector foil, the first welding tip is brought into contact with one surface of the current collector foil, and the current collector plate is brought into contact with the other surface of the current collector foil, When performing resistance welding by bringing the second welding tip into contact with the current collector plate,
Providing a tapered portion at the tip of the first welding tip; and
The inclination angle of the tapered portion is 30 ° or more and 60 ° or less.
A method for producing a secondary battery. In the current collector plate,
A flat part which is a flat part;
Forming a bent portion which is a portion where the end portion of the flat portion is bent;
The method of manufacturing a secondary battery according to claim 1. The length of the flat portion is
The length is less than twice the outer diameter of the second welding tip.
The method for manufacturing a secondary battery according to claim 2.

Images