Battery terminal, battery, and method of manufacturing battery terminal

Abstract

To provide a battery terminal that can be manufactured without using a welding technology.SOLUTION: A negative electrode terminal 5 includes a first metal portion 6 made of a first metal, and a second metal portion 7 made of a second metal different from the first metal. The first metal portion 6 includes a body portion 61 and an engaging portion 62 extending from the body portion 61 in a first direction D1, and the second metal portion 7 includes a base portion 71 and an engaged portion 72 extending from the base portion 71 in a second direction D2, and the engaging portion 62 and the engaged portion 72 are joined by crimping.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a battery terminal, a battery, and a method for manufacturing a battery terminal. [Background technology]

[0002] Conventionally, battery packs consisting of multiple batteries have been widely used. When a high output voltage is required, such as in an electric vehicle, the multiple batteries are connected in series by electrically connecting the positive and negative terminals of adjacent batteries via a bus bar (metal plate).

[0003] Incidentally, some batteries have positive and negative electrode terminals made of dissimilar metals. For example, in a lithium-ion battery, the positive electrode terminal is made of aluminum and the negative electrode terminal is made of copper, thereby increasing the battery capacity. In a battery pack using such batteries, an aluminum bus bar is generally used. However, when an aluminum bus bar is to be connected to each electrode terminal by laser welding, welding between the bus bar and the negative electrode terminal is welding between dissimilar metals. In addition, the bus bar is not limited to being made of aluminum, and copper or brass may also be used, and dissimilar metal joining may also occur depending on the selection of the bus bar. In the case of welding between dissimilar metals, there is a problem in that an intermetallic compound that is harder and more brittle than the base material is generated, resulting in a low joint strength.

[0004] Therefore, a common method is to use bolts to connect the bus bar and the negative terminal, but the use of bolts is an obstacle to making the battery pack lighter.

[0005] In this regard, the negative electrode terminal disclosed in Patent Document 1 has an upper portion made of an aluminum alloy and a lower portion made of a copper alloy, and the aluminum alloy and the copper alloy are joined by ultrasonic welding, resistance welding, or friction stir spot welding. An aluminum alloy bus bar is joined to the upper portion (aluminum alloy) of the negative electrode terminal by laser welding. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2023-27989 A Summary of the Invention [Problem to be solved by the invention]

[0007] Meanwhile, in the field of automobiles, autonomous driving is being promoted in line with the shift to EVs, but in order to realize autonomous driving technology, various additional parts such as sensors are required, which tends to increase the weight of the vehicle. This is an obstacle to improving electric power consumption (fuel economy), and it is essential for automobile manufacturers to improve functionality and electric power consumption while also keeping prices down. To achieve this, it is necessary to reduce the number of parts, simplify joining, eliminate joining processes, and improve material yields.

[0008] The negative electrode terminal disclosed in Patent Document 1 does not require the use of bolts for connection to the bus bar, making it possible to reduce the weight of the battery pack. However, ultrasonic welding, friction stir welding, and resistance welding each have the following problems.

[0009] First, even if sufficient joint strength was achieved initially when joining dissimilar metals using ultrasonic welding, there was a risk that the joint strength would gradually decrease due to wear. Also, since the lower surface of the joint is uneven, the area through which electricity flows is not stable.

[0010] Next, as pointed out in Patent Document 1, friction stir welding creates dents on the work surface, which must be filled. In addition, the rotating tool is pressed into the work, which can cause deformation of the entire work and the generation of burrs. This requires work to correct the shape of the work and to remove burrs.

[0011] Resistance welding is a method in which workpieces are joined by applying pressure to them and using Joule heat generated when electricity is passed through them, but a considerable amount of current is required to join materials with low electrical resistance, such as aluminum or copper. For example, a current of 25,000A is required to join plates with a thickness of 1.0 mm, which places a large burden on the environment.

[0012] An object of the present invention is to provide a battery terminal that can be manufactured without using welding technology, and a battery equipped with the same.

[0013] Another object of the present invention is to provide a method for manufacturing a battery terminal without using welding technology. [Means for solving the problem]

[0014] The battery terminal of the present invention comprises a first metal portion made of a first metal and a second metal portion made of a second metal different from the first metal, wherein the first metal portion has a body portion and an engaging portion extending from the body portion in a first direction, and the second metal portion has a base portion and an engaged portion extending from the base portion in a second direction opposite to the first direction, and the engaging portion and the engaged portion are joined by crimping.

[0015] The battery of the present invention comprises an electrode body, a housing that houses the electrode body, a positive electrode terminal electrically connected to the electrode body, and a negative electrode terminal electrically connected to the electrode body, the negative electrode terminal being the above-mentioned battery terminal.

[0016] The manufacturing method for a battery terminal of the present invention is a manufacturing method for a battery terminal having a first metal portion made of a first metal and a second metal portion made of a second metal different from the first metal, and includes a joining process of joining a first part made of the first metal to a second part made of the second metal, wherein the first part has a body portion and an engaging portion extending from the body portion in a first direction, and the outer peripheral surface of the engaging portion slopes radially outward as it approaches the first direction, and the second part is cap-shaped and has a base portion and an annular engaged portion extending from the outer peripheral edge of the base, and in the joining process, the second part is placed over the engaging portion of the first part, and the engaged portion is plastically deformed radially inward to crimp and join the engaged portion to the engaging portion. Effect of the Invention

[0017] In the battery terminal according to the present invention, the engaging portion of the first metal part made of the first metal and the engaged portion of the second metal part made of the second metal are joined by crimping, so that the battery terminal can be manufactured without using welding techniques that consume a large amount of electricity, thereby reducing the environmental impact. Furthermore, since the first metal part and the second metal part are joined by crimping, sufficient strength can be obtained compared to when they are joined by welding.

[0018] The battery according to the present invention includes the above-mentioned battery terminal as a negative terminal, and therefore provides the same effects as those described above.

[0019] According to the manufacturing method of the battery terminal of the present invention, a second part made of a second metal is placed over an engaging part of a first part made of a first metal, and the engaged part of the second part is plastically deformed radially inward to crimp and join the engaged part to the engaging part, so that the battery terminal can be manufactured without using welding techniques that consume a large amount of electricity, thereby reducing the environmental load. Also, because the first metal part and the second metal part are joined by crimping, sufficient strength can be obtained compared to when they are joined by welding. [Brief description of the drawings]

[0020] [Figure 1]1 is a schematic partially exploded perspective view showing a battery pack according to an embodiment of the present invention; [Diagram 2] 2 is a cross-sectional view showing a schematic diagram of a battery included in the battery pack shown in FIG. 1. [Diagram 3] 3 is a perspective view showing a negative electrode terminal of the battery shown in FIG. 2. [Figure 4] Cross-sectional view taken along line IV-IV in Figure 3. [Diagram 5] 4 is a cross-sectional view of a first part and a second part used in manufacturing the negative electrode terminal shown in FIG. 3. [Figure 6] 6A to 6C are diagrams illustrating a molding process for the first part shown in FIG. 5. [Figure 7] 6 is a diagram for explaining a process of forming a negative electrode terminal by press-joining the first part and the second part shown in FIG. 5 . DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Referring to Fig. 1, a battery pack 1 according to this embodiment includes a plurality of batteries (battery cells) 2 and a plurality of bus bars (metal plates) 3. Each battery 2 includes a positive electrode terminal 4 and a negative electrode terminal 5, and among adjacent batteries 2, the positive electrode terminal 4 of one battery 2 and the negative electrode terminal 5 of the other battery 2 are electrically connected via the bus bar 3, and thus the plurality of batteries 3 are connected in series by the plurality of bus bars 3. The bus bar 3 in this embodiment is made of aluminum, and is placed on the positive electrode terminal 4 and the negative electrode terminal 5 and joined by laser welding.

[0022] 2, each battery 2 further includes a housing 21, a battery element 22, a positive electrode gasket 23, and a negative electrode gasket 24. The housing 21 includes a case 21a and a lid member 21b, and the lid member 21b seals an opening provided in the case 21a. The battery element 22 is housed in the housing 21 and includes an electrode body 22a and an electrolyte 22b. The electrode body 22a is formed by stacking or rolling a positive electrode, a negative electrode, and a separator. The positive electrode terminal 4 is electrically connected to the positive electrode side of the electrode body 22a by a conductive structure (not shown), and the negative electrode terminal 5 is electrically connected to the negative electrode side of the electrode body 22a by a conductive structure (not shown).

[0023] The positive electrode gasket 23 is disposed between the cover member 21b of the housing 21 and the positive electrode terminal 4, and electrically insulates the cover member 21b from the positive electrode terminal 4. Similarly, the negative electrode gasket 24 is disposed between the cover member 21b of the housing 21 and the negative electrode terminal 5, and electrically insulates the cover member 21b from the negative electrode terminal 5.

[0024] The positive electrode terminal 4 is made of, for example, aluminum, and has a large diameter portion 41 and a small diameter portion 42 coaxial with the large diameter portion 41, the large diameter portion 41 and the small diameter portion 42 being integrally formed.

[0025] The negative electrode terminal 5 has an overall external shape similar to that of the positive electrode terminal 4, and has a large diameter portion 51 and a small diameter portion 52 coaxial with the large diameter portion 51. However, as shown in Fig. 3 and Fig. 4, the negative electrode terminal 5 is composed of a first metal portion 6 made of a first metal, and a second metal portion 7 made of a second metal different from the first metal. The first metal is, for example, copper, and the second metal is the same type of metal as the bus bar 3, which is aluminum in this embodiment. The first metal portion 6 and the second metal portion 7 are joined by caulking.

[0026] More specifically, the first metal part 6 has a body part 61, an engagement part 62, and a leg part 63. The body part 61 has a first surface 61a and a second surface 61b opposite to the first surface 61a. In this embodiment, the body part 61 is disk-shaped. The engagement part 62 extends from the first surface 61a of the body part 61 toward the first direction D1, and is formed to have a smaller diameter than the body part 61. In addition, the outer peripheral surface 62a of the engagement part 62 is inclined radially outward as it approaches the first direction D1. The leg part 63 extends from the second surface 61b of the body part 61 toward the second direction D2 opposite to the first direction D1, and is formed to have a smaller diameter than the body part 61.

[0027] The second metal part 7 is cap-shaped and has a base part 71 and an annular engaged part 72 extending in the second direction D2 from the outer periphery of the base part 71. An inner circumferential surface 72a of the engaged part 72 inclines radially inward as it approaches the second direction D2, and is in surface contact with an outer circumferential surface 62a of the engaging part 62. Also, a tip end of the engaged part 72 in the second direction D2 abuts against a first surface 61a of the trunk part 61 of the first metal part 6. Furthermore, an inner surface 71b of the base part 71 and a tip surface 62b of the engaging part 62 are in surface contact with each other.

[0028] The large diameter portion 51 of the negative electrode terminal 5 is formed by the body portion 61 and engagement portion 62 of the first metal portion 6 and the second metal portion 7, and the small diameter portion 52 of the negative electrode terminal 5 is formed by the leg portion 63 of the first metal portion 6.

[0029] In this configuration, the first metal portion 6 is electrically connected to the negative electrode side of the electrode body 22, and the bus bar 3 is joined to the surface 71a of the second metal portion 7 by laser welding.

[0030] Next, a method for manufacturing such a negative electrode terminal 5 will be described. With reference to Fig. 5, a first component 16 for constituting the first metal part 6 and a second component 17 for constituting the second metal part are formed by press working (forming step). The first component 16 is press-formed, for example, as follows.

[0031] First, an intermediate part 16B (FIG. 6(b)) having a leg portion 63 and a head portion 160 is formed by upsetting a rod-shaped material 16A made of a first metal shown in FIG. 6(a). Next, an intermediate part 16B is subjected to a backward extrusion process to form an intermediate part 16C (FIG. 6(c)) in which the body portion 160 is deformed into a body portion 61 and a protrusion portion 161. Furthermore, a lateral extrusion process is performed on the intermediate part 16C using dies B1, B1 and a punch P1 to plastically deform the outer peripheral surface 161a of the protrusion portion 161 obliquely along the inclined surface B11 of the die B1 to form a recess R1. This forms an engagement portion 62, and the first part 16 (FIG. 6(d)) is completed.

[0032] The punch P1 used when performing the lateral extrusion process on the intermediate part 16C is preferably one having a conical tip, and by using the punch P1 having a conical tip in this way, processing can be performed with a smaller load than when using a punch having a flat tip. Also, by using the punch P1 in this way, a conical depression is formed on the surface of the engagement part 62.

[0033] On the other hand, the second part 17 (FIG. 5) is formed integrally with a base part 71 and an engaged part 72' by performing a backward extrusion process on a thick sheet-like material (not shown) made of a second metal. The inner surface of the base part 71 is preferably formed in a cone shape corresponding to the surface of the engaging part 62 of the first part 16.

[0034] Next, as shown in Fig. 7(a), the first part 16 is set in the die B2, the second part 17 is placed over the engaging part 62, and the tip of the engaged part 72' of the second part 17 is butted against the surface 61a of the body part 61a of the first part 16. When the two are pressed together with the punch P2 in this state, the engaged part 72' of the second part 17 is crushed between the die B2 and the punch P2, and is plastically deformed along the outer peripheral surface 62a of the engaging part 62 of the first part 16, and enters the recess R1. As a result, the first part 16 is crimped and joined to the second part 17, and the negative terminal 5 is formed as shown in Fig. 7(b) (joining process).

[0035] Here, referring to FIG. 4, the angle α1 between the first surface 61a of the body 61 and the outer peripheral surface 62a of the engaging portion 62 is preferably 45° to 70°. If it exceeds 70°, the second metal portion 7 becomes easily removed from the first metal portion 6, and if it is smaller than 45°, when the engaged portion 72′ of the second part 17 is plastically deformed in the press working shown in FIG. 7(a), the engaged portion 72′ (second metal) becomes difficult to enter the recess R1. Moreover, the height dimension L1 of the engaging portion 62 in the first direction D1 may be 1.5 mm or more. Even if the height dimension L1 of the engaging portion 62 is small in this way, the first metal portion 6 is crimped and joined to the second metal portion 7 over its entire circumference, so that sufficient joining strength can be achieved.

[0036] As such, since the negative electrode terminal 5 of this embodiment has a second metal part 7 made of aluminum, the bus bar 3, which is also made of aluminum, can be firmly joined to the second metal part 7 of the negative electrode terminal 5 by laser welding.

[0037] In addition, since the first metal portion 6 and the second metal portion 7 of the negative electrode terminal 5 are joined by a crimping structure, the amount of power required for joining can be reduced compared to when the first metal portion 6 and the second metal portion 7 are joined by welding, and the environmental load can be reduced. Furthermore, even with joining by the crimping structure, the first metal portion 6 and the second metal portion 7 can be joined with a strength greater than that of joining by welding.

[0038] Furthermore, when the first metal part 6 and the second metal part 7 are joined by friction stir welding, recesses or holes are formed in the first metal part 6 or the second metal part 7, but when the metal part is joined by pressing, such recesses or holes are not formed.

[0039] Although the embodiment of the present invention has been described above with reference to the accompanying drawings, the present invention is not limited to such an embodiment, and various modifications and alterations are possible without departing from the scope of the present invention.

[0040] For example, the small diameter portion 52 of the negative electrode terminal 5 in the above embodiment is formed in a solid cylindrical shape, but the present invention is not limited to this configuration, and for example, the small diameter portion 52 may be formed in a hollow cylindrical shape, or a screw groove may be formed on the outer circumferential surface of the small diameter portion 52, making the small diameter portion 52 a male screw portion. In addition, the external shape of the negative electrode terminal 5 is not limited to that shown in the drawings.

[0041] In the above embodiment, the battery terminal made up of the first metal part 6 and the second metal part 7 is described as the negative electrode terminal 5, but the use of the battery terminal is not limited to this.

[0042] Furthermore, in the above embodiment, the intermediate part 16B is molded from a rod-shaped material, the intermediate part 16C is molded from the intermediate part 16B, and the first part 16 is molded from the intermediate part 16C, but the method of molding the first part 16 is not limited to this.

[0043] In the above embodiment, copper is given as an example of the first metal, and aluminum is given as an example of the second metal, but the first and second metals are not limited to these metals and are appropriately selected depending on the application of the battery terminal. For example, the busbar 3 is not limited to being made of aluminum, and may be made of copper or brass. In such a case, the second metal may be copper or brass in accordance with the material of the busbar. In this way, by matching the materials of the busbar and the second metal portion 7 of the battery terminal, welding with the same type of metal is possible, and therefore the busbar and the battery terminal can be firmly joined. [Explanation of symbols]

[0044] 1 battery pack 2 batteries 3 Busbar 4 Positive terminal 5 Negative terminal (battery terminal) 6 1st metal part 7 Second metal part 16 First Part 17 Second Part 61 Torso 62 Engagement part 71 Base 72 Engaged part

Claims

1. A first metal portion made of a first metal; a second metal portion made of a second metal different from the first metal, The first metal portion has a body portion and an engagement portion extending from the body portion in a first direction, the second metal portion has a base portion and an engaged portion extending from the base portion in a second direction opposite to the first direction, The engaging portion and the engaged portion are joined by crimping.

2. an outer circumferential surface of the engagement portion is inclined radially outward as it advances in the first direction; the engaged portion is annular, and an inner circumferential surface of the engaged portion is inclined radially inward as it extends in the second direction, The battery terminal according to claim 1 , wherein the outer circumferential surface of the engaging portion is in surface contact with the inner circumferential surface of the engaged portion.

3. An electrode body; A housing that houses the electrode body; A positive electrode terminal electrically connected to the electrode body; A negative electrode terminal electrically connected to the electrode body, The negative electrode terminal is a battery terminal according to claim 1 or 2.

4. A method for manufacturing a battery terminal having a first metal part made of a first metal and a second metal part made of a second metal different from the first metal, comprising: a joining step of joining a first part made of the first metal to a second part made of the second metal; The first component has a body portion and an engagement portion extending from the body portion in a first direction, an outer circumferential surface of the engagement portion is inclined radially outward as it advances in the first direction; the second component is cap-shaped and has a base and an annular engaged portion extending from an outer periphery of the base, In the joining process, the second part is placed over the engaging portion of the first part, and the engaged portion is plastically deformed radially inward to crimp and join the engaged portion to the engaging portion.

5. further comprising a molding step of molding the first part; The molding step includes: A step of forming a first intermediate part having a head and a foot by performing an upsetting process on a rod-shaped material; a step of forming a second intermediate part in which the head portion is deformed into the body portion and the protrusion portion by performing a backward extrusion process on the first intermediate part; The method for manufacturing a battery terminal according to claim 4 , further comprising the step of: performing a lateral extrusion process on the second intermediate part to obliquely plastically deform an outer circumferential surface of the protrusion to form the engaging portion.

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