Method for manufacturing secondary battery energization component, and secondary battery energization component

Abstract

The present invention relates to a method for manufacturing a secondary battery energization component whereby, if using a friction stir spot welding method and joining a metal foil material and a metal plate material that are layered, it is possible to efficiently join the materials to each other while ensuring the thickness of the metal plate material. This method for manufacturing a secondary battery energization component includes: a first joining step of inserting, along a thickness direction, a rotating first friction stir welding tool downward from above a layered metal foil material 11; and, after the first joining step, a second joining step of re-inserting, along the thickness direction, a rotating second friction stir welding tool 51 downward from above the metal foil material 11 positioned on the outermost surface in a state in which a plurality of metal foil materials 11-15 are stacked above the metal plate material 20. The diameter of a tip of the second friction stir welding tool is greater than the diameter of a tip of the first friction stir welding tool.

Description

Manufacturing method of current-carrying component for secondary battery and current-carrying component for secondary battery

[0001] The present invention relates to a method for manufacturing an electric current-carrying part for secondary batteries mounted mainly on automobiles, etc., and to an electric current-carrying part for secondary batteries.

[0002] Current-carrying components formed from two or more sheets or foils, particularly current-carrying components for secondary batteries in automobiles, are also called bus bars, and Patent Document 1 discloses a technique for forming current-carrying components from highly conductive materials such as aluminum alloys and copper alloys. Patent Document 2 also discloses a method for manufacturing current-carrying components using friction stir spot joining technology as one method for joining two or more laminated foils and sheets.

[0003] Patent No. 6971990 Patent No. 6516408

[0004] However, when joining a metal foil material and a metal plate material using the friction stir spot joining method, since the thicknesses of these materials are different, for example, if the metal foil material is laminated on top of a plate material and then joined, a part of the metal foil material is pressed into the metal plate material, resulting in a poor joining of the metal foil material and the metal plate material.

[0005] Furthermore, when joining laminated metal foil material and a metal plate material with a lower melting point (than the metal foil material), when a rotating friction stir joining tool is inserted from the side where the metal foil material is laminated, the metal plate material softens first due to frictional heat, and part of the metal foil material is easily pushed into the metal plate material, resulting in the problem that the laminated metal foil materials do not join together.

[0006] Furthermore, when a rotating friction stir welding tool is inserted into the metal plate material with a low melting point to avoid the above-mentioned poor joining, the thickness of the metal plate material is reduced, and there is a problem that the part with reduced thickness generates heat when a large current is passed through it.

[0007] An object of the present invention is to provide a method for manufacturing an electrical component for a secondary battery that can efficiently join metal foil material and metal plate material of different materials and thicknesses using a friction stir spot joining method while ensuring the thickness of the metal plate material, especially when the metal plate material has a lower melting point than the metal foil material.

[0008] Therefore, the method for manufacturing a current-carrying part for a secondary battery of the present invention is a method for manufacturing a current-carrying part for a secondary battery formed from a plurality of sheets of metal foil material and a metal plate material of a different material, and includes a first joining step in which a first friction stir welding tool is rotated from above to below the topmost metal foil material in a state in which the plurality of metal foil materials are stacked in the thickness direction and inserted along the thickness direction, and a second joining step in which a second friction stir welding tool is rotated from above to below the topmost metal foil material in a state in which the plurality of metal foil materials are stacked above the metal plate material in the thickness direction after the first joining step and inserted along the thickness direction, the second friction stir welding tool having a tip diameter larger than that of the first friction stir welding tool.

[0009] In this case, the deepest position into which the tip of the second friction stir welding tool is inserted in the second joining step is set above the metal foil material located in the lowest layer. The metal foil material may be made of either copper or a copper alloy, and the metal plate material may be made of either aluminum or an aluminum alloy. Furthermore, the friction stir welding tools used in the first and second joining steps may differ in specifications such as tool diameter, shape, and material. The number of metal foil materials may be five or more, and the thickness of each sheet may be 0.21 mm or less. In addition, the current-carrying component for a secondary battery of the present invention is a current-carrying component for a secondary battery formed from a plurality of sheets of metal foil material and a metal plate material of a different material from the metal foil material, wherein the melting point of the metal plate material is lower than the melting point of the metal foil material, the plurality of sheets of metal foil material are stacked above the metal plate material and the metal foil material and the metal plate material are joined together, and a layer of an intermetallic compound between the metal foil material and the metal plate material is formed at the joint between the plurality of sheets of metal foil material and the metal plate material, and the thickness of the thickest part of the intermetallic compound layer is 20% or less of the thickness of the metal plate material before processing or 0.2 mm or less, and more preferably 10% or less of the thickness of the metal plate material before processing or 0.1 mm or less.

[0010] The method for manufacturing an electrical component for a secondary battery of the present invention has the advantage that, when laminated metal foil materials are joined to the metal foil material using a friction stir spot joining method, efficient joining can be achieved while maintaining the thickness of the metal plate material, especially even when the metal plate material has a lower melting point than the metal foil material (the melting point of the metal plate material is lower than that of the metal foil material).

[0011] 1 is a schematic cross-sectional view of a current-carrying component for a secondary battery in a first joining step of the present invention; FIG. 2 is a schematic cross-sectional view of a current-carrying component for a secondary battery 1 in a second joining step of the present invention; FIG. 3 is a structural photograph observed after etching a joint cross-section of a material according to the present invention; FIG. 4 is an enlarged photograph of a boundary between a metal foil material and a metal plate material in the structural photograph shown in FIG. 3; FIG. 5 is an enlarged photograph of a boundary between a metal foil material and a metal plate material in the structural photograph shown in FIG.

[0012] 1 shows a schematic cross-sectional view of multiple metal foil materials 11-15 during a first joining step in the manufacturing method of a secondary battery current-carrying component of the present invention, and FIG. 2 shows a schematic cross-sectional view of a secondary battery current-carrying component 1 during a second joining step in the manufacturing method of a secondary battery current-carrying component of the present invention. The five metal foil materials 11-15 that form the secondary battery current-carrying component of the present invention are formed in a form in which multiple metal foil materials 10 (11, 12, 13, 14, 15) are stacked in the thickness direction, as shown in FIG. 1. A clamp (jig) 70 is used to press and fix these metal foil materials 10 (11, 12, 13, 14, 15) from above the metal foil material 11 that is the uppermost layer.

[0013] Thereafter, the rotating first friction stir welding tool 50 is inserted from above into the metal foil materials 10 (11, 12, 13, 14, 15) in the thickness direction (of the metal foil materials), and a recess 80 is formed following the trace of the tip shape of the first friction stir welding tool 50 (first joining step). At this time, these metal foil materials 10 (11, 12, 13, 14, 15) are morphologically integrated by the solid-state welded portion 30 located immediately below the recess 80, as shown in FIG.

[0014] Next, the multiple metal foil materials 10 (11, 12, 13, 14, 15) joined in the first joining step are placed above the metal plate material 20, and then a clamp (jig) 70 is used to simultaneously press and fix the metal foil materials 10 (11, 12, 13, 14, 15) and the metal plate material 20 from above the metal foil materials 10 (11, 12, 13, 14, 15) as shown in Figure 2. Thereafter, a rotating second friction stir welding tool 51 is inserted from above the metal foil materials 10 (11, 12, 13, 14, 15) into the recesses formed in the first joining step (second joining step).

[0015] In this second joining step, the metal plate 20 is made of a material different from the metal foil materials 10 (11, 12, 13, 14, 15). For example, if the metal foil material is made of copper or a copper alloy, the metal plate can be made of aluminum or an aluminum alloy.

[0016] Furthermore, the diameter D51 of the tip (probe) of the second friction stir welding tool 51 used in the second joining step is made larger than the diameter D50 of the tip (probe) of the first friction stir welding tool 50 used in the first joining step. Note that the diameter D51 of the tip of the second friction stir welding tool 51 is preferably 1.5 times or more the diameter D50 of the tip of the first friction stir welding tool 50 used in the first joining step (D51≧1.5×D50).

[0017] At this time, the deepest position into which the tip of the second friction stir welding tool 51 is inserted in the second joining step is set to be above the metal foil material 15 located in the lowest layer. Ultimately, a recess 81 of a new shape is formed in the metal foil materials 10 (11, 12, 13, 14, 15) and the metal plate material 20 as shown in Figure 2, and a new solid-state weld 31 is formed again directly below it.

[0018] The manufacturing method of this embodiment solid-state bonds (structurally and morphologically integrated) multiple sheets of metal foil material, and also solid-state bonds with a metal plate material that is different in thickness from the metal foil material and is located in the lowest layer. This makes it possible to provide an electrically conductive component for a secondary battery that can efficiently bond metal materials of different materials and thicknesses and ensure electrical conductivity (minimize electrical resistance).

[0019] If the metal foil material is aluminum or an aluminum alloy, the thickness may be 0.2 mm or less (JIS H4160, H4170), and if the metal foil material is copper or a copper alloy, the thickness may be 0.21 mm or less (JIS C6515).

[0020] As an example of the present invention, a joining test was conducted between multiple copper foils and aluminum plates, and the results of the test are described below. First, in this joining test, 40 copper foils (oxygen-free copper C1020, 40 sheets of 0.1 mm thick x 20 mm wide x 50 mm long) were stacked together as the joining materials, and one aluminum plate (pure aluminum A1050, 1 mm thick x 20 mm wide x 50 mm long) was used as the joining material, and the joining test was conducted by a friction stir spot joining method.

[0021] Two types of test pieces were prepared for this joining test: an inventive material and a comparative material, as shown below. For the inventive material, temporary joining of only the copper foil was performed as a preliminary step in the aforementioned joining process 1, and then joining of the copper foil joined in joining process 1 and an aluminum plate was performed in joining process 2. The diameter of the friction stir spot joining tool used in joining process 1 was 5 mm, the rotation speed during joining was 5,000 rpm, and the plunge depth was 3.0 mm. In joining process 2, joining was performed under the following joining conditions: the diameter of the friction stir spot joining tool was 5.8 mm, the rotation speed during joining was 5,000 rpm, and the plunge depth was 3.2 mm. The plunge depth refers to the actual depth to which the friction stir welding tool was inserted, based on the position of the copper foil installed in the top layer of the 40 laminated copper foils (the upper end position of foil material 11 in Figure 1).

[0022] In contrast, the comparative material was directly joined to a copper foil and an aluminum plate, with a friction-stir spot joining tool diameter of 5.8 mm, a rotation speed of 3000 rpm during joining, and a plunge depth of 3.0 mm. As a result of this joining test, microstructure photographs of the joined cross section of the inventive material after etching are shown in Figures 3 (magnification: 20x) and 4 (magnification: 100x), and microstructure photographs of the joined cross section of the comparative material after etching are shown in Figures 5 (magnification: 20x) and 6 (magnification: 100x). Regarding how to read Figures 3 and 5, the layer sandwiched between the arrows A is the cross section of the copper foil, and the layer sandwiched between the arrows B is the cross section of the aluminum plate. The area indicated by the arrow C in Figure 5 is the area where an intermetallic compound of copper and aluminum has formed and rises as a mass, details of which will be explained later.

[0023] As shown in Figures 3 and 4 (see Figure 4 in particular), the boundary between the copper foil laminated portions of the inventive material was not visible, and it was confirmed that the copper foil and the aluminum plate were integrated. On the other hand, as shown in Figures 5 and 6 (see Figure 6 in particular), a crimped state was observed at the boundary between the copper foil and the aluminum plate in the comparative material. This is presumably due to insufficient stirring by the friction stir spot joining tool in some areas of the copper foil. In addition, the thickness and joining area of ​​the aluminum plate at the joints of the inventive material and the comparative material were measured.

[0024] As a result, the thickness of the aluminum plate after friction stir spot welding of the inventive material was 0.668 mm and the cross-sectional area was 13.4 mm. ２ In contrast, the comparative material had a cross-sectional area of ​​0.579 mm and a cross-sectional area of ​​11.6 mm. ２ In other words, the inventive material had a larger cross-sectional area than the comparative material, and a wider bonding area could be secured.

[0025] Furthermore, in the comparative material, a wavy, raised boundary between the metal foil and the metal plate near the center of the friction stir spot welding tool can be seen in Figures 5 and 6 (see, in particular, the area indicated by arrow C in Figure 5). This is due to the formation of an intermetallic compound between the metal foil and the metal plate (copper and aluminum), which has formed a raised mass. The thickest part of this intermetallic compound mass is approximately 0.25 mm thick. In contrast, no such raised intermetallic compound is observed in Figures 3 and 4, which are photographs of the inventive material. A separate detailed analysis of the boundary between the metal foil and the metal plate of the inventive material revealed that a thin intermetallic compound layer of 0.1 mm or less was formed at the boundary between the metal foil and the metal plate corresponding to the insertion point of the friction stir spot welding tool. Here, if the intermetallic compound is formed too thick, that portion is likely to become brittle and have high electrical resistance, so it is preferable that the layer of intermetallic compound formed be as thin as possible. In these respects, the inventive material resulted in a joint with higher strength and lower electrical resistance than the comparative material. By utilizing the joining method of the present invention, the thickness of the intermetallic compound layer at its thickest portion can be reduced to 20% or less (0.2 mm or less as an actual measured thickness) of the thickness of the metal plate 20 before processing, more preferably 10% or less (0.1 mm or less as an actual measured thickness). Furthermore, the thickness of the intermetallic compound layer at the boundary between the metal foil material and the metal plate corresponding to the insertion portion of the friction stir spot joining tool can be reduced to 20% or less (0.2 mm or less as an actual measured thickness) of the thickness of the metal plate 20 before processing, more preferably 10% or less (0.1 mm or less as an actual measured thickness).

[0026] Furthermore, by setting the diameter of the friction stir spot welding tool to a small value in the joining step 1 of the joining method of the present invention, it was possible to control the pressure during friction stir spot welding and suppress deformation of the aluminum plate. This enabled the laminated copper foil to be integrated, ensuring the cross-sectional area of ​​the aluminum plate and enabling excellent friction stir spot welding. Furthermore, the inventive material generates less heat than the comparative material, allowing the production of parts with excellent electrical conductivity.

[0027] Furthermore, the joining method of the present invention is an advantageous technology for manufacturing larger-sized current-carrying components for secondary batteries. In other words, as the diameter of the friction stir spot welding tool increases, the reaction force when the friction stir spot welding tool is pressed into the workpiece increases, which can lead to problems such as overload errors in the processing machine. Even in such cases, the joining method of the present invention allows for the use of a larger-diameter friction stir spot welding tool in the second joining step, since the load on the processing machine is reduced by inserting a larger-diameter friction stir spot welding tool into the area where a small-diameter friction stir spot welding tool was used in the first joining step. This allows for the use of a larger tool in the second joining step.

[0028] REFERENCE SIGNS LIST 1 Current-carrying component for secondary battery 10 (11 to 15) Metal foil material 20 Metal plate material 30, 31 Solid-state welded portion 50 First friction stir welding tool 51 Second friction stir welding tool 70 Clamp 80, 81 Recess D50 Diameter of tip of first friction stir welding tool D51 Diameter of tip of second friction stir welding tool

Claims

1. A method for manufacturing a conductive component for a secondary battery, which is formed from multiple metal foil materials and a metal plate material of a different material from the metal foil materials, The method for manufacturing the current-carrying component for the secondary battery is as follows: A first joining step involves joining the multiple metal foil materials together by inserting a first friction agitation joining tool, which rotates from above to below the metal foil material located on the outermost surface, along the thickness direction, while the multiple metal foil materials are stacked in the thickness direction. A second joining step is performed after the first joining step, in which a second friction agitation joining tool, which rotates from the metal foil side, is inserted with multiple metal foil materials joined in the first joining step stacked on top of the metal plate material, thereby joining the metal foil materials joined in the first joining step and the metal plate material. It has, A method for manufacturing a conductive component for a secondary battery, characterized in that the diameter of the tip of the second friction agitation bonding tool is larger than the diameter of the tip of the first friction agitation bonding tool.

2. The method for manufacturing a conductive component for a secondary battery according to claim 1, characterized in that, in the second joining step, the deepest position into which the tip of the second friction agitation joining tool is inserted is above the lowest layer of the metal foil material.

3. The method for manufacturing a conductive component for a secondary battery according to claim 2, characterized in that the melting point of the metal plate is lower than the melting point of the metal foil.

4. The method for manufacturing a power-carrying component for a secondary battery according to claim 3, characterized in that the metal foil material is made of copper or a copper alloy, and the metal plate material is made of aluminum or an aluminum alloy.

5. The method for manufacturing a conductive component for a secondary battery according to claim 1, characterized in that the melting point of the metal plate is lower than the melting point of the metal foil.

6. The method for manufacturing a power-carrying component for a secondary battery according to claim 5, characterized in that the metal foil material is made of copper or a copper alloy, and the metal plate material is made of aluminum or an aluminum alloy.

7. A method for manufacturing a conductive component for a secondary battery according to any one of claims 1 to 6, characterized in that the number of metal foil materials is five or more, and the thickness of each foil is 0.21 mm or less.

8. A conductive component for a secondary battery, formed from multiple metal foil materials and a metal plate material of a different material from the said metal foil materials, The melting point of the metal plate is lower than that of the metal foil. The plurality of metal foil materials are stacked on top of the metal plate material, and the metal foil materials and the metal plate material are joined together. A conductive component for a secondary battery, characterized in that a layer of intermetallic compound formed from the metal foil and the metal plate is formed at the joint between the plurality of metal foils and the metal plate, and the thickness of the thickest part of the intermetallic compound layer is 20% or less, or 0.2 mm or less, of the thickness of the metal plate before processing.

9. The current-carrying component for a secondary battery according to claim 8, characterized in that the thickness of the intermetallic compound layer of the metal foil material and the metal plate material at the thickest part is 10% or less of the thickness of the metal plate material before processing, or 0.1 mm or less.