Battery terminal manufacturing method

Abstract

To provide a method capable of manufacturing a battery terminal with improved strength reliability.SOLUTION: A method for manufacturing a battery terminal NS by joining a first member 26 made of a first metallic material and a second member 31 made of a second metallic material includes a crimping step of forming two crimping portions 28, 29 by crimping to fix the first member 26 and the second member 31 together, a heating step of heating the first member 26 and the second member 31 to a predetermined heating temperature after the crimping step, and an ultrasonic bonding step of ultrasonically bonding the interface between the first member 26 and the second member 31 at one of the crimping portions 28 of the first member 26 and the second member 31 heated to the heating temperature, thereby bonding the first member 26 and the second member 31 together.SELECTED DRAWING: Figure 8

Description

[Technical field]

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

[0002] Secondary batteries used as power sources for electric vehicles, hybrid vehicles, and other electrically powered vehicles are electrically connected together to form a battery module having increased charge / discharge capacity and output power. The secondary batteries are electrically connected together, for example, via bus bars that join the positive and negative terminals of adjacent secondary batteries.

[0003] Here, when adopting a structure in which a bus bar is joined to each terminal by welding, taking into consideration the weldability of the bus bar, it is preferable that the portions where the bus bars of each terminal are connected (bus bar joints) be made of the same type of metallic material.

[0004] In view of this, there have been proposed secondary batteries in which the bus bar joints of the terminals are made of the same type of metal material, as described in Patent Document 1, for example.

[0005] In the secondary battery described in Patent Document 1, the battery terminals are composed of a current collecting member connected to a power generating body, an external terminal exposed to the outside of the case and to which a bus bar is welded and joined to a bus bar joint portion, and a connection member that connects the current collecting member and the external terminal. In this secondary battery, the upper end of the connection member is crimped and fixed to the crimp portion of the external terminal, and the lower end of the connection portion is crimped and fixed to the current collecting member. In this secondary battery, when the current collecting member, connection member, and external terminal on the positive electrode side are made of aluminum, the current collecting member and connection member on the negative electrode side are made of copper, and the bus bar is made of aluminum, for example, the negative electrode external terminal is made of a partially clad material mainly made of an aluminum base material with a copper flat plate joined to the surface of the crimp portion.

[0006] In this secondary battery, the connection member and the external terminal are integrated by crimping at the crimping portion of the external terminal on the negative electrode side, and then the connection member, both made of copper, and the copper plate are joined by welding. Therefore, in this secondary battery, electrical continuity is ensured between the members that make up the battery terminals, and both the busbar joints of the positive and negative external terminals are made of an aluminum base material. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2012-123946 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, when a secondary battery such as that described in Patent Document 1 has a battery terminal in which a plurality of members are integrated by crimping and the members are joined by welding, the following problems may occur.

[0009] That is, when multiple components are fixed with two crimping portions and the components are ultrasonically joined at least one of the two crimping portions, the vibrations caused by the ultrasonic joining affect the other crimping portion, which may cause deformation or damage to the crimping portion and reduce the strength reliability of the secondary battery.

[0010] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a method for manufacturing a battery terminal with improved strength reliability. [Means for solving the problem]

[0011] The characteristic configuration of the manufacturing method of the battery terminal according to the present invention for achieving the above object is as follows: A method for manufacturing a battery terminal by joining a first member made of a first metallic material and a second member made of a second metallic material, comprising: a crimping process for forming two crimped portions by crimping to fix the first member and the second member; a heating step of heating the first member and the second member to a predetermined heating temperature after the crimping step; The method includes an ultrasonic bonding process for ultrasonically bonding the interface between the first member and the second member at the crimped portion of one of the first member and the second member heated to the heating temperature, thereby bonding the first member and the second member.

[0012] According to the above characteristic configuration, by applying heat to the first and second members before ultrasonic bonding at one of the crimped portions, the members to be bonded reach a temperature range where plastic flow is possible quickly, making it possible to bond them in a short time. In other words, even with the same bonding time, ultrasonic bonding can be performed with a low amplitude and a low load. Therefore, the effect of vibration during ultrasonic bonding on the other crimped portion can be suppressed, and the decrease in strength of the battery terminal during manufacturing can be suppressed. Furthermore, due to the hardening effect caused by heating the first and second members, a battery terminal with improved overall strength can be manufactured. In this manner, according to the manufacturing method of the battery terminal having the above-mentioned characteristic configuration, it is possible to manufacture a battery terminal with improved strength reliability.

[0013] A further characteristic feature of the method for manufacturing a battery terminal according to the present invention is as follows: The ultrasonic bonding process involves ultrasonically bonding the interface between the first member and the second member at one of the crimped portions, and then ultrasonically bonding the interface between the first member and the second member at the other crimped portion.

[0014] According to the above-mentioned characteristic configuration, the effect of vibration during ultrasonic bonding at the other crimped portion on the bonding point at one crimped portion is suppressed, and the bonding point is less likely to be damaged. Therefore, according to the manufacturing method of the battery terminal having the above-mentioned characteristic configuration, it is possible to manufacture a battery terminal with improved strength reliability.

[0015] A further characteristic feature of the method for manufacturing a battery terminal according to the present invention is as follows: The heating temperature is 20% to 30% of the lower of the melting points of the first metallic material and the second metallic material.

[0016] According to the above-described characteristic configuration, ultrasonic bonding can be performed in a short time, in other words, ultrasonic bonding can be performed with low amplitude and low load, and deformation and deterioration of the first and second members due to overheating can be suppressed while suppressing the effect of vibrations during ultrasonic bonding on the other crimped portion.

[0017] A further characteristic feature of the method for manufacturing a battery terminal according to the present invention is as follows: The ultrasonic bonding step is characterized in that a jig for fixing the first member and the second member is used in a heated state.

[0018] According to the above-mentioned characteristic configuration, it is possible to suppress a decrease in the temperature of the first member and the second member during ultrasonic bonding, which makes it easier to achieve ultrasonic bonding in a short time (ultrasonic bonding with low amplitude and low load), and to manufacture a battery terminal with improved strength reliability.

[0019] A further characteristic feature of the method for manufacturing a battery terminal according to the present invention is as follows: the first metallic material is aluminum or an aluminum alloy; The second metallic material is copper or a copper alloy.

[0020] According to the above characteristic configuration, a suitable negative electrode terminal can be realized in which the second member made of copper or a copper alloy is joined to the electrode body, and the bus bar is joined to the first member made of aluminum or an aluminum alloy. Effect of the Invention

[0021] As described above, the method for manufacturing a battery terminal according to the present invention makes it possible to manufacture a battery terminal with improved strength reliability. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is an exploded perspective view of a secondary battery according to an embodiment. [Diagram 2]1 is a cross-sectional view showing a schematic configuration of a secondary battery according to an embodiment. [Diagram 3] FIG. 3 is a cross-sectional view taken along line III-III of FIG. 2. [Figure 4] FIG. 2 is a perspective view showing a negative electrode terminal. [Diagram 5] FIG. 5 is a cross-sectional view of part VV of FIG. [Figure 6] FIG. [Figure 7] 5A to 5C are schematic diagrams for explaining a manufacturing process of a negative electrode terminal. [Figure 8] 5A to 5C are schematic diagrams for explaining a manufacturing process of a negative electrode terminal. [Figure 9] 5A to 5C are schematic diagrams for explaining a manufacturing process of a negative electrode terminal. [Figure 10] FIG. 11 is a perspective view showing a negative electrode terminal according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, a method for manufacturing a battery terminal according to an embodiment of the present invention will be described with reference to the drawings. Note that, in the following, an embodiment in which the battery terminal is used in a lithium ion secondary battery will be described as an example. In addition, in the following, each description and each drawing will be appropriately simplified in order to clarify the description.

[0024] [Overview of secondary battery 1] 1 is an exploded perspective view of a secondary battery equipped with a battery terminal manufactured by the manufacturing method of a battery terminal according to the present embodiment. In the following description, the direction parallel to the height direction of the secondary battery 1 is defined as the Z-axis direction, the direction parallel to the longitudinal direction of the electrode body 20 is defined as the X-axis direction, and the direction parallel to the thickness direction of the electrode body 20 is defined as the Y-axis direction. The Z-axis direction is parallel to the up-down direction, and the X-axis and Y-axis directions are perpendicular to each other and parallel to the horizontal direction.

[0025] 1 and 2, the secondary battery 1 includes a battery case 10 consisting of a case body 11 and a sealing plate 12, battery terminals PS and NS consisting of metallic external terminals 25, 26 and current collecting terminals 30, 31, and an electrode body 20. The secondary battery 1 is a sealed secondary battery in which the electrode body 20, the current collecting terminals 30, 31, etc. are accommodated inside the case body 11, the opening of the case body 11 is sealed with the sealing plate 12, and an electrolyte is injected into the inside of the case body 11.

[0026] [Configuration of battery case 10] 1 and 2, the battery case 10 is composed of a case body 11 having a generally rectangular parallelepiped shape with an open top, and a sealing plate 12 that seals the opening of the case body 11. In the battery case 10 of this embodiment, the case body 11 as a housing and the sealing plate 12 as a lid are both made of aluminum, but are not limited to this. The case body 11 and the sealing plate 12 can be made of various metals and alloys.

[0027] The sealing plate 12 has a shape corresponding to the shape of the opening of the case body 11. The sealing plate 12 is made of a flat plate member having a generally rectangular shape when viewed in the Z-axis direction. The sealing plate 12 has mounting holes 12a formed at both longitudinal ends (both longitudinal ends) that penetrate the top and bottom surfaces and into which a positive electrode insulating member 36 and a negative electrode insulating member 37, which will be described later, are fitted. As will be described in detail later, the sealing plate 12 has a positive electrode terminal PS disposed at one longitudinal end (one longitudinal end) and a negative electrode terminal NS disposed at the other longitudinal end (the other longitudinal end).

[0028] [Configuration of electrode body 20] In this embodiment, the electrode body 20 is composed of a wound body in which long strip-shaped positive and negative electrode materials are laminated with a strip-shaped separator interposed therebetween, wound, and compressed into a flat shape. As shown in Figs. 1 and 2, the electrode body 20 of this embodiment is substantially rectangular when viewed in the thickness direction (Y-axis direction), and a positive electrode terminal joint 21 in which the positive electrode material is collected is formed at one end side in the longitudinal direction (X-axis direction) when viewed in the thickness direction, and a negative electrode terminal joint 22 in which the negative electrode material is collected is formed at the other end side. The structure of the electrode body 20 is not particularly limited, and various structures used in general sealed secondary batteries can be adopted. In addition, the materials used for the positive and negative electrode materials are not particularly limited, but in this embodiment, aluminum is used for the positive electrode material and copper is used for the negative electrode material.

[0029] In this embodiment, the electrode body 20 is covered with an insulating film and housed inside the case body 11 in a position in which the thickness direction and the longitudinal direction are parallel to the horizontal direction. The electrode body 20 and the case body 11 are insulated from each other by an insulating film (not shown).

[0030] [Positive and negative electrode configurations] In this embodiment, the secondary battery 1 includes a positive external terminal 25 and a negative external terminal 26 as external terminals, and a positive current collector terminal 30 and a negative current collector terminal 31 as current collector terminals. The secondary battery 1 of this embodiment also includes a positive insulating member 36 and a negative insulating member 37. In this embodiment, the positive external terminal 25 and the positive current collector terminal 30 form a positive terminal PS, and the negative external terminal 26 and the negative current collector terminal 31 form a negative terminal NS. In this embodiment, the negative terminal NS corresponds to a "battery terminal."

[0031] In this embodiment, the positive electrode side and the negative electrode side have almost the same configuration, but the materials of the external terminals and the current collector terminals are different. Specifically, in this embodiment, the same metal material is used for the positive electrode external terminal 25 and the positive electrode current collector terminal 30 constituting the positive electrode terminal PS. On the other hand, different metal materials are used for the negative electrode external terminal 26 and the negative electrode current collector terminal 31 constituting the negative electrode terminal NS.

[0032] The configuration of the negative electrode side will be described below with reference to Fig. 3 to Fig. 6. Fig. 3 is a cross-sectional view of the III-III portion of Fig. 2. Fig. 4 is a perspective view showing the negative electrode terminal NS, Fig. 5 is a cross-sectional view of the VV portion of Fig. 4, and Fig. 6 is a bottom view of the negative electrode terminal NS.

[0033] The negative electrode external terminal 26 is a terminal for external connection. The negative electrode external terminal 26 has a plate-shaped portion 27 having a generally rectangular shape as viewed in the Z-axis direction, and a first crimping portion 28 and a second crimping portion 29 extending downward from a back surface 27b of the plate-shaped portion 27. In this embodiment, the front surface 27a of the plate-shaped portion 27 functions as a bus bar joint to which an aluminum bus bar is welded. In this embodiment, the first crimping portion 28 and the second crimping portion 29 are arranged side by side along the X-axis direction, with the first crimping portion 28 being on the other side in the X-axis direction and the second crimping portion 29 being on one side in the X-axis direction. More specifically, the plate-shaped portion 27 is divided into two equal parts in the X-axis direction, and the first crimping portion 28 is formed on the other side in the X-axis direction as viewed in the Z-axis direction, and the second crimping portion 29 is provided on one side in the X-axis direction. In this embodiment, the negative electrode external terminal 26 is made of aluminum. In this embodiment, the negative electrode external terminal 26 corresponds to the "first member", the first metal material corresponds to "aluminum", the first crimped portion 28 corresponds to the "one crimped portion", and the second crimped portion 29 corresponds to the "other crimped portion".

[0034] In this embodiment, each of the crimping portions 28, 29 has a cylindrical shaft portion 28a, 29a extending downward from the rear surface 27b of the plate-shaped portion 27, and an umbrella portion 28b, 29b formed at the lower end of each of the shaft portions 28a, 29a.

[0035] The negative current collector terminal 31 is a terminal for inputting and outputting electric power from the electrode body 20. The negative current collector terminal 31 is disposed on the lower surface side of the sealing plate 12, in other words, inside the case body 11. In this embodiment, the negative current collector terminal 31 is made of copper. In this embodiment, the negative current collector terminal 31 corresponds to the "second member", and the second metallic material corresponds to "copper".

[0036] In this embodiment, the negative electrode collector terminal 31 has a plate-shaped portion 32 that is generally rectangular when viewed in the Z-axis direction, and a plate-shaped collector portion 35 that extends downward from a back surface 32b of the plate-shaped portion 32.

[0037] The plate-shaped portion 32 is formed with a first through hole 33 and a second through hole 34 penetrating from the front to the back. In this embodiment, the first through hole 33 and the second through hole 34 are formed side by side along the X-axis direction, with the first through hole 33 formed on the other side in the X-axis direction and the second through hole 34 formed on one side in the X-axis direction. In this embodiment, recesses 33a, 34a are formed on the back surface 32b of the plate-shaped portion 32, which have a larger diameter than the through holes 33, 34 as viewed in the Z-axis direction and open to the back surface 32b side so as to communicate with the through holes 33, 34. In this embodiment, the shaft portion 28a of the first crimping portion 28 is inserted into the first through hole 33, and the shaft portion 29a of the second crimping portion 29 is inserted into the second through hole 34, and the umbrella portions 28b, 29b of the crimping portions 28, 29 extend into the recesses 33a, 34a, and the umbrella portions 28b, 29b are formed to have a larger diameter than the shaft portions 28a, 29a when viewed in the Z-axis direction. In other words, the crimping portions 28, 29 are formed so that the shaft portions 28a, 29a are located inside the through holes 33, 34, and the umbrella portions 28b, 29b extend over the back surface 32b of the plate-shaped portion 32.

[0038] In this embodiment, the current collecting part 35 is composed of a base part 35a extending downward from an edge along the longitudinal direction of the back surface 32b of the plate-shaped part 32, and a main part 35b extending downward from the other side of the X-axis direction of the base part 35a and formed at a position protruding from the plate-shaped part 32 to the other side of the X-axis direction as viewed in the Z-axis direction, and is a member having a substantially L-shape as viewed in the Y-axis direction. That is, the current collecting part 35 is provided connected to the back surface 32b of the plate-shaped part 32 of the negative electrode current collecting terminal 31. In addition, the lower end of the main part 35b has an electrode connection part 35c to which the negative electrode terminal joint part 22 of the electrode body 20 is joined.

[0039] In this way, the negative electrode terminal NS, which is composed of the negative electrode external terminal 26 and the negative electrode current collector terminal 31, is a dissimilar material joint member composed of two members made of different metal materials. Although details will be described later, in the negative electrode terminal NS, the negative electrode external terminal 26 and the negative electrode current collector terminal 31 are fixed by the engagement of the crimped portions 28, 29 with the through holes 33, 34, and the interfaces between the negative electrode external terminal 26 and the negative electrode current collector terminal 31 at the crimped portions 28, 29 are joined by ultrasonic welding. This ensures electrical continuity between the negative electrode external terminal 26 and the negative electrode current collector terminal 31.

[0040] The negative electrode insulating member 37 is a member made of an insulating material. The negative electrode insulating member 37 of the present embodiment is a member for integrating the negative electrode terminal NS and the sealing plate 12 together and for insulating the negative electrode terminal NS from the sealing plate 12.

[0041] In this embodiment, with the negative terminal NS inserted into the mounting hole 12a of the sealing plate 12, the negative electrode insulating member 37 is insert-molded to integrate the negative electrode terminal NS with the sealing plate 12 via the negative electrode insulating member 37. The negative electrode terminal NS and the sealing plate 12 are insulated by the negative electrode insulating member 37, and the negative electrode insulating member 37 maintains airtightness between the negative electrode terminal NS and the mounting hole 12a of the sealing plate 12. The electrode connection portion 35c of the negative electrode current collector terminal 31 is joined to the negative electrode terminal joint portion 22 of the electrode body 20.

[0042] Regarding the positive electrode side of this embodiment, the positive electrode terminal PS is different from the negative electrode terminal NS, which is a dissimilar material joining member, and is formed by appropriately joining a positive electrode external terminal 25 and a positive electrode current collecting terminal 30, which are made of the same metal material (aluminum in this embodiment), by ultrasonic welding.

[0043] Although details are omitted, on the positive electrode side of this embodiment, with the positive electrode terminal PS inserted into the mounting hole of the sealing plate 12, a positive electrode insulating member 36 is insert-molded to integrate the positive electrode terminal PS with the sealing plate 12 via the positive electrode insulating member 36. As with the negative electrode side, on the positive electrode side, the positive electrode terminal PS and the sealing plate 12 are insulated from each other by the positive electrode insulating member 36, and the positive electrode insulating member 36 maintains airtightness between the positive electrode terminal PS and the mounting hole of the sealing plate 12. In addition, the electrode connection portion 30a of the positive electrode collector terminal 30 is joined to the positive electrode terminal joint portion 21 of the electrode body 20.

[0044] [Manufacturing method of negative terminal NS] Next, a method for manufacturing the negative electrode terminal NS, which is a dissimilar material joint member, will be described with reference to Figs. 7 to 9. Figs. 7 to 9 are schematic diagrams for explaining the manufacturing process of the negative electrode terminal NS. Specifically, Fig. 7 is a schematic diagram for explaining the crimping step, and Figs. 8 and 9 are schematic diagrams for explaining the ultrasonic joining step. Note that in Figs. 7 to 9, the current collecting portion 35 is omitted from illustration.

[0045] The method for manufacturing the negative electrode terminal NS includes a crimping step, a heating step, and an ultrasonic bonding step.

[0046] The crimping step is a step of forming two crimped portions 28, 29 by crimping to fix the negative external terminal 26 and the negative current collector terminal 31 together.

[0047] Specifically, in the crimping step of this embodiment, first, the two shaft portions 28a, 29a of the negative external terminal 26 are inserted into the two through holes 33, 34 of the negative current collector terminal 31, and the back surface 27b of the plate-shaped portion 27 and the front surface 32a of the plate-shaped portion 32 are brought into contact with each other (see FIG. 7). Next, the tips of the shaft portions 28a, 29a are deformed by press working to form the umbrella portions 28b, 29b (see also FIG. 8). In this manner, the crimping step is performed to form the two crimp portions 28, 29, thereby fixing the negative external terminal 26 and the negative current collector terminal 31. Note that the members are fixed to each other by the two crimp portions 28, 29 and the through holes 33, 34, and thus the relative rotation of the two members is prevented.

[0048] The heating step is a step of heating the negative electrode external terminal 26 and the negative electrode current collector terminal 31 to a predetermined heating temperature after the crimping step. The heating temperature is 20% to 30% of the lower of the melting point of aluminum constituting the negative electrode external terminal 26 and the melting point of copper constituting the negative electrode current collector terminal 31. In this way, by setting the heating temperature to 20% to 30% of the lower of the melting points of the respective metal materials constituting the negative electrode external terminal 26 and the negative electrode current collector terminal 31, unexpected deformation and deterioration of the negative electrode external terminal 26 and the negative electrode current collector terminal 31 due to overheating can be suppressed.

[0049] Specifically, in the heating step of this embodiment, the assembly consisting of the negative electrode external terminal 26 and the negative electrode current collector terminal 31 after the crimping step is placed in a thermostatic chamber in which the temperature inside the chamber is about 130° C. to 190° C., and left for a predetermined time to heat the negative electrode external terminal 26 and the negative electrode current collector terminal 31 to a heating temperature. In this embodiment, the horn H and anvil A described later and other jigs used during ultrasonic bonding are also placed in the thermostatic chamber and left for a predetermined time to heat them to approximately the same heating temperature as the assembly.

[0050] In the present application, the "heating temperature" refers to the temperature of the negative electrode external terminal 26 and the negative electrode current collector terminal 31 themselves. Therefore, the set temperature of the device for heating these (for example, the temperature inside the thermostatic bath) may be appropriately set to a temperature that can heat the negative electrode external terminal 26 and the negative electrode current collector terminal 31 to the heating temperature.

[0051] The ultrasonic bonding process is a process of ultrasonically bonding the interface between the negative external terminal 26 and the negative current collector terminal 31 at one crimp portion 28, 29 of the negative external terminal 26 and the negative current collector terminal 31 that have been heated to a heating temperature, thereby bonding the negative external terminal 26 and the negative current collector terminal 31. In the ultrasonic bonding process of this embodiment, after ultrasonically bonding the interface between the negative external terminal 26 and the negative current collector terminal 31 at one crimp portion 28, the interface between the negative external terminal 26 and the negative current collector terminal 31 at the other crimp portion 29 is ultrasonically bonded.

[0052] Specifically, in the ultrasonic bonding process of this embodiment, an ultrasonic bonding device equipped with a horn H and anvil A is used. Note that the horn H resonates with the ultrasonic vibrations oscillated from the oscillation unit and applies vibrations of a frequency equal to or higher than the frequency range of the ultrasonic waves to the object, and the anvil A is a base that supports the object.

[0053] In this embodiment, first, as shown in Fig. 8, an anvil A is pressed against the surface 27a of the plate-like portion 27 of the negative electrode external terminal 26, and a horn H is pressed against the umbrella portion 28b of the first crimping portion 28 of the negative electrode external terminal 26 along the vertical direction (Z-axis direction) to apply pressure. At this time, the horn H, the anvil A, and a jig for fixing the objects to be joined are heated together with the negative electrode external terminal 26 and the negative electrode current collecting terminal 31 in the heating step. In this embodiment, a horn H having a circular tip surface is used as the horn H, and the tip of the horn H is not brought into contact with a portion of the umbrella portion 28b that overlaps with the shaft portion 28a as viewed in the Z-axis direction, but the present invention is not limited to this embodiment.

[0054] Next, ultrasonic vibration is applied in a direction parallel to the surface 27a of the plate-shaped portion 27 (direction perpendicular to the pressure direction) by the horn H. This bonds the interface between the negative electrode external terminal 26 and the negative electrode current collector terminal 31 at the first crimp portion 28.

[0055] Here, in this embodiment, before the ultrasonic bonding process is performed, the negative external terminal 26 and the negative current collector terminal 31 are heated to a heating temperature. As a result, during ultrasonic bonding, the negative external terminal 26 and the negative current collector terminal 31 (more specifically, the interface between the negative external terminal 26 and the negative current collector terminal 31) reach a temperature range where plastic flow is possible early. Therefore, compared to the case where the heating process is not performed, the negative external terminal 26 and the negative current collector terminal 31 can be bonded in a short time. In other words, if the ultrasonic bonding process is performed for the same time, it is possible to perform ultrasonic bonding with a lower amplitude and a lower load than when the heating process is not performed. Therefore, by enabling ultrasonic bonding in a short time or with a low amplitude and a low load, the influence of vibration during ultrasonic bonding on the second crimping portion 29 is suppressed, and as a result, the decrease in strength of the battery terminal can be suppressed. Furthermore, the quenching effect associated with the heating of the negative external terminal 26 and the negative current collector terminal 31 can be expected to improve the strength of the entire negative terminal NS.

[0056] In the present embodiment, in the heating step, the horn H, the anvil A, other jigs, and the like are heated together with the negative electrode external terminal 26 and the negative electrode current collector terminal 31, and these are used during ultrasonic bonding. Therefore, a decrease in temperature of the negative electrode external terminal 26 and the negative electrode current collector terminal 31 during ultrasonic bonding is suppressed, making it easier to achieve ultrasonic bonding in a short time or with a low amplitude and low load.

[0057] 9, the horn H is pressed against the umbrella portion 29b of the second crimped portion 29 of the negative external terminal 26 in the vertical direction (Z-axis direction) to apply pressure and ultrasonic vibration. This bonds the interface between the negative external terminal 26 and the negative current collecting terminal 31 at the second crimped portion 29.

[0058] At this time, by heating the negative external terminal 26 and the negative current collector terminal 31 to the heating temperature prior to ultrasonic bonding as described above, ultrasonic bonding can be performed in a short time or with a low amplitude and low load. Therefore, the influence on the bonding point in the first crimping portion 28 that has been ultrasonically bonded beforehand is suppressed, and the bonding point is less likely to be damaged. Therefore, the decrease in strength of the battery terminal can be suppressed.

[0059] As described above, the manufacturing method for a battery terminal according to this embodiment can realize ultrasonic bonding in a short time or with a low amplitude and low load, and can suppress the influence of vibration during ultrasonic bonding on the crimped portions 28, 29, thereby suppressing a decrease in strength of the battery terminal. Furthermore, the hardening effect associated with heating the negative external terminal 26 and the negative current collector terminal 31 is expected to improve the strength of the entire battery terminal. In other words, the manufacturing method for a battery terminal according to this embodiment can realize the manufacture of a battery terminal with improved strength reliability.

[0060] [Another embodiment] [1] In the above embodiment, the interface between the negative external terminal 26 and the negative current collector terminal 31 is ultrasonically joined at both of the two crimping portions 28, 29, but the present invention is not limited to this. From the viewpoint of ensuring electrical continuity between the negative external terminal 26 and the negative current collector terminal 31, it is sufficient that the interface between the negative external terminal 26 and the negative current collector terminal 31 is ultrasonically joined at either of the two crimping portions 28, 29.

[0061] [2] In the above embodiment, the heating temperature is 20% to 30% of the lower of the melting points of the metal materials constituting the negative external terminal 26 and the negative current collector terminal 31. However, the present invention is not limited to this. The heating temperature may be a temperature determined independently of the melting points of the metal materials constituting the negative external terminal 26 and the negative current collector terminal 31.

[0062] [3] In the above embodiment, the ultrasonic bonding step uses the horn H, the anvil A, and other jigs that are heated to the heating temperature together with the negative electrode external terminal 26 and the negative electrode current collector terminal 31, but the present invention is not limited to this. The horn H, the anvil A, and other jigs may be unheated.

[0063] [4] In the above embodiment, the negative electrode external terminal 26 is made of aluminum, and the negative electrode current collector terminal 31 is made of copper. However, the present invention is not limited to this embodiment. The material of the negative electrode external terminal 26 may be an aluminum alloy, and the material of the negative electrode current collector terminal 31 may be a copper alloy. Alternatively, the material of the negative electrode external terminal 26 and the negative electrode current collector terminal 31 may be any of various metals or alloys having good electrical conductivity, depending on the materials of the electrode body 20 and the bus bar.

[0064] [5] In the above embodiment, the shanks 28a, 29a of the negative external terminal 26 are inserted into the through holes 33, 34 of the negative current collector terminal 31, and the tips of the shanks 28a, 29a are deformed to form the umbrella portions 28b, 29b, thereby forming the two swaged portions 28, 29 consisting of the shanks 28a, 29a and the umbrella portions 28b, 29b. However, the present invention is not limited to such an embodiment. Any type of swaging process may be used as long as it forms two swaged portions, and the shape of the swaged portions formed by the swaging process may also be any shape. Fig. 10 is a perspective view showing a negative electrode terminal according to another embodiment. For example, as shown in Fig. 10, both sides in the X-axis direction of a plate-shaped negative electrode external terminal 40 are bent along edges of a plate-shaped portion 42 of a negative electrode current collector terminal 41. As a result, crimped portions 43, 44 may be formed on both sides in the X-axis direction of the negative electrode terminal NS, and the negative electrode external terminal 40 and the negative electrode current collector terminal 41 may be fixed together by the two crimped portions 43, 44.

[0065] [6] In the above embodiment, the positive electrode terminal PS is formed by joining the positive electrode external terminal 25 and the positive electrode current collector terminal 30 by ultrasonic welding, but the present invention is not limited to this embodiment. The positive electrode terminal PS is a member in which the positive electrode external terminal 25 and the positive electrode current collector terminal 30 are made of the same metal material, in other words, they are not a dissimilar material joining member. Therefore, the positive electrode terminal PS may be formed by joining the terminals by laser welding instead of ultrasonic welding.

[0066] In addition, the configurations disclosed in the above embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, provided no contradiction arises. Furthermore, the embodiments disclosed in this specification are illustrative, and the embodiments of the present invention are not limited thereto, and can be appropriately modified within the scope that does not deviate from the purpose of the present invention. [Explanation of symbols]

[0067] 1: Secondary battery 11: Case body 12: Sealing plate 20: Electrode body 25: Positive external terminal 26: Negative electrode external terminal (first member) 28: First crimping portion (one crimping portion) 28a:Shaft part 28b: Umbrella part 29: Second crimping portion (the other crimping portion) 29a:Shaft part 29b: Umbrella part 30: Positive collector terminal 31: Negative electrode collector terminal (second member) 33: First through hole 34: Second through hole PS:Positive terminal NS: Negative terminal (battery terminal)

Claims

1. A method for manufacturing a battery terminal by joining a first member made of a first metallic material and a second member made of a second metallic material, comprising: a crimping process for forming two crimped portions by crimping to fix the first member and the second member; a heating step of heating the first member and the second member to a predetermined heating temperature after the crimping step; and an ultrasonic bonding process for ultrasonically bonding an interface between the first member and the second member at the crimping portion of one of the first member and the second member heated to the heating temperature, thereby bonding the first member and the second member.

2. 2. The method for manufacturing a battery terminal according to claim 1, wherein in the ultrasonic bonding process, an interface between the first member and the second member at one of the crimping portions is ultrasonically bonded, and then an interface between the first member and the second member at the other crimping portion is ultrasonically bonded.

3. The method for manufacturing a battery terminal according to claim 1 , wherein the heating temperature is 20% to 30% of the lower of the melting points of the first metallic material and the second metallic material.

4. The method for manufacturing a battery terminal according to claim 1 , wherein in the ultrasonic bonding step, a jig for fixing the first member and the second member is used in a heated state.

5. the first metallic material is aluminum or an aluminum alloy; The method for manufacturing a battery terminal according to any one of claims 1 to 4, wherein the second metallic material is copper or a copper alloy.

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