JP7600178B2 - Conductive member for battery and method for producing same - Google Patents

Description

The present invention relates to a conductive member for batteries and a method for manufacturing the same.

Conventionally, a joint formed by joining multiple members has been used as a conductive member for batteries. Related prior art documents include Patent Documents 1 and 2. For example, Patent Document 1 describes a method of crimping the current collector foil laminate of the electrode body and the current collector plate, followed by resistance welding.

JP 2015-5456 A Japanese Patent Application Publication No. 3-216282

However, according to the inventor's research, when resistance welding is performed after crimping as in Patent Document 1, the contact area between the current collecting foil laminate and the current collecting plate becomes large, and the current dissipates during resistance welding. This results in multiple current paths being scattered, weakening the strength of the nugget (resistance welded part). Furthermore, if a large current is passed through the nugget in an attempt to increase its strength, the nugget becomes more brittle. As a result, the nugget may be destroyed when an external force such as vibration or impact is applied from the outside during use of the battery, causing the conductive connection to become unstable or causing a connection failure. Therefore, there is a demand for a conductive member for batteries with high conductive reliability.

The present invention was made in consideration of the above circumstances, and its main objective is to provide a conductive member for batteries with excellent conduction reliability and a method for manufacturing the same.

The present invention provides a method for manufacturing a conductive member for a battery, comprising the following steps: preparing a first metal member having a plate-shaped portion and a second metal member having a plate-shaped portion, forming a projection on the plate-shaped portion of the second metal member; preparing a crimping device including a die having a recess, a punch to be pressed into the recess, and a current supply unit to pass a welding current through the die and the punch, placing the plate-shaped portion of the first metal member on the recess of the die, and overlapping the portion of the second metal member on which the projection is formed, and then pressing the punch into the recess of the die, and forming a resistance weld by passing a welding current through the die and the punch with the current supply unit while pressing the projection against the first metal member, and forming a crimped joint around the resistance weld;

In the present invention, a projection is formed on one of the metal members, and then the two metal members are crimped while a welding current is applied to them. This allows the welding current to be concentrated on the projection, and a relatively large nugget can be formed, compared to the case of performing resistance welding after crimping as in Patent Document 1, for example. Therefore, a relatively small welding current is sufficient, and a good quality resistance weld with high mechanical strength can be formed. In addition, in the present invention, a plastic deformation portion is formed around the resistance weld, so that even if stress such as vibration or impact is applied from the outside, force is not easily applied to the resistance weld. Therefore, it is easier to maintain the first metal member and the second metal member in a close contact state. With the above effects, the conductive connection between the first metal member and the second metal member can be stably maintained, and the reliability of the conductive connection can be improved.

The present invention provides a conductive member for a battery, comprising a first metal member having a plate-shaped portion, a second metal member having a plate-shaped portion, and a joint between the first metal member and the second metal member. The joint has a resistance welded portion formed by resistance welding the first metal member and the second metal member, and a crimped joint provided around the resistance welded portion and formed by plastically deforming the plate-shaped portion of the first metal member and the plate-shaped portion of the second metal member.

The conductive member for a battery according to the present invention has two types of joints that are joined using different joining methods, namely, a resistance welded portion and a crimped joint. The resistance welded portion can be a joint that has a relatively lower rigidity than the plastically deformed portion. By arranging such a resistance welded portion inside the plastically deformed portion, even if external stress such as vibration or impact is applied, force is less likely to be applied to the resistance welded portion. This makes it easier to maintain the first metal member and the second metal member in a close contact state. With this configuration, the conductive connection between the first metal member and the second metal member can be stably maintained, and the conductive reliability can be improved over a long period of time.

FIG. 1 is a perspective view showing a schematic diagram of a battery pack according to an embodiment. FIG. 2 is a vertical cross-sectional view of the battery of FIG. FIG. 3 is a perspective view that typically illustrates the bus bar of FIG. FIG. 4 is a plan view that illustrates the bus bar of FIG. FIG. 5 is a vertical cross-sectional view taken along line V-V in FIG. 6(1) and (2) are schematic diagrams for explaining the manufacturing process of the bus bar of FIG. FIG. 7(1) is a cross-sectional SEM image of the joint, and FIG. 7(2) is an enlarged cross-sectional SEM image of a main portion of (1). 8(1) and (2) are views corresponding to FIG. 6 and explaining the manufacturing process according to the modified example.

Below, preferred embodiments of the technology disclosed herein will be described with reference to the drawings. Note that matters other than those specifically mentioned in this specification that are necessary for implementing the present invention (for example, the general configuration and manufacturing process of battery packs and batteries that do not characterize the present invention) can be understood as design matters for a person skilled in the art based on the prior art in the field. The present invention can be implemented based on the contents disclosed in this specification and common technical knowledge in the field.

<Battery assembly 100>
1 is a perspective view of a battery pack 100. The battery pack 100 includes a plurality of batteries 10 and a plurality of bus bars 90 that electrically connect the plurality of batteries 10 to one another. The bus bars 90 are conductive connecting members that connect the terminals of the plurality of batteries 10. The number of bus bars 90 used in the battery pack 100 is typically (the number of batteries - 1). The bus bars 90 are an example of a "battery conductive member" disclosed herein.

In the following drawings, the same reference numerals are used for components and parts that perform the same function, and duplicated explanations may be omitted or simplified. In the following drawings, the reference numerals U, D, F, Rr, L, and R represent top, bottom, front, back, left, and right, respectively, the reference numeral X represents the extension direction along the long side of the battery 10, the reference numeral Y represents the arrangement direction of the battery 10 perpendicular to the reference numeral X, and the reference numeral Z represents the height direction of the battery 10. However, these directions are merely for the convenience of explanation, and do not limit the installation form of the battery pack 100 in any way.

The batteries 10 are all flat and rectangular, and are of the same shape here. The batteries 10 are arranged in a row along the arrangement direction Y, with a pair of flat sides (wide sides) facing each other. The batteries 10 may be held together by a restraining mechanism such as a restraining band. The batteries 10 are electrically connected in series here by a bus bar 90. However, the shape, size, number, arrangement, connection method, etc. of the batteries 10 constituting the battery pack 100 are not particularly limited and can be changed as appropriate. In addition, for example, a heat dissipation member for efficiently dissipating heat generated by the batteries 10, or a spacer as a length adjustment means, may be arranged between the batteries 10.

In this specification, the term "battery" refers to any power storage device capable of extracting electrical energy, and is a concept that includes primary batteries and secondary batteries. In addition, in this specification, the term "secondary battery" refers to any power storage device that can be repeatedly charged and discharged by the movement of charge carriers between the positive and negative electrodes via an electrolyte. The electrolyte may be any of a liquid electrolyte (electrolytic solution), a gel electrolyte, and a solid electrolyte. Secondary batteries include so-called storage batteries (chemical batteries) such as lithium-ion secondary batteries and nickel-metal hydride batteries, and capacitors (physical batteries) such as electric double-layer capacitors.

Figure 2 is a longitudinal cross-sectional view of the battery 10. The battery 10 includes an electrode body 20, a battery case 30, a positive electrode terminal 40, and a negative electrode terminal 50. Although not shown, the battery 10 further includes an electrolyte. The battery 10 is configured by housing the electrode body 20 and the electrolyte in the battery case 30. The battery 10 is typically a secondary battery, and is a lithium ion secondary battery in this case. The configuration of the battery 10 may be the same as that of a conventional battery, and is not particularly limited.

The electrode body 20 is a wound electrode body in which a strip-shaped positive electrode 21 and a strip-shaped negative electrode 22 are stacked with two strip-shaped separators 23 and 24 between them and wound in the longitudinal direction. However, the electrode body 20 may also be a laminated electrode body in which a rectangular positive electrode and a rectangular negative electrode are stacked in an insulated state.

The positive electrode 21 has a foil-shaped positive electrode collector 21a and a positive electrode mixture layer 21b fixed on the positive electrode collector 21a. The positive electrode collector 21a is made of a conductive metal such as aluminum, an aluminum alloy, nickel, or stainless steel. The positive electrode collector 21a is made of aluminum here. The positive electrode mixture layer 21b contains a positive electrode active material (e.g., lithium transition metal complex oxide) that can reversibly store and release charge carriers. In addition, a positive electrode tab portion 21c is provided on one side edge portion (the left side edge portion in FIG. 2) of the electrode body 20 in the stretching direction X, where the positive electrode mixture layer 21b is not formed and the positive electrode collector 21a is exposed.

The negative electrode 22 has a foil-shaped negative electrode collector 22a and a negative electrode mixture layer 22b fixed on the negative electrode collector 22a. The negative electrode collector 22a is made of a conductive metal such as copper, copper alloy, nickel, stainless steel, etc. The negative electrode collector 22a is made of a metal species different from that of the positive electrode collector 21a. The negative electrode collector 22a is made of copper in this example. The negative electrode mixture layer 22b contains a negative electrode active material (e.g., a carbon material such as graphite) that can reversibly absorb and release charge carriers. In addition, a negative electrode tab portion 22c is provided on the other side edge portion of the electrode body 20 in the extension direction X (the right side edge portion in FIG. 2) where the negative electrode mixture layer 22b is not formed and the negative electrode collector 22a is exposed.

The separators 23 and 24 are insulating resin sheets with multiple fine through-holes through which charge carriers can pass. The electrolyte is, for example, a non-aqueous electrolyte solution containing a non-aqueous solvent and a supporting salt such as a lithium salt. However, the electrolyte may be in a solid state (solid electrolyte) and integrated with the positive electrode 21 and the negative electrode 22. In this case, the electrode body 20 does not need to have the separators 23 and 24.

The battery case 30 is a housing that houses the electrode body 20. Here, the battery case 30 is formed in a flat, bottomed rectangular parallelepiped (rectangular) shape. However, in other embodiments, the battery case 30 may be any shape, such as a cylinder. The battery case 30 is made of a lightweight metal material with good thermal conductivity, such as aluminum, an aluminum alloy, or stainless steel. The battery case 30 includes a rectangular case body 32 having an opening on the top surface, and a plate-shaped lid body 34 that closes the opening of the case body 32. A positive electrode terminal 40 and a negative electrode terminal 50 are attached to the lid body 34. The positive electrode terminal 40 and the negative electrode terminal 50 are respectively arranged at both left and right ends of the battery 10 in the extension direction X. The battery 10 is charged and discharged via the positive electrode terminal 40 and the negative electrode terminal 50.

The positive electrode terminal 40 is electrically connected to the positive electrode 21. The positive electrode terminal 40 is made of a metal such as aluminum, an aluminum alloy, nickel, or stainless steel. The positive electrode terminal 40 may be made of the same metal type as the positive electrode current collector 21a. Here, the positive electrode terminal 40 is made of aluminum. The positive electrode terminal 40 has a positive electrode internal terminal 42 extending along the height direction Z and a plate-shaped positive electrode external terminal 44 extending along the upper surface of the lid body 34. The positive electrode internal terminal 42 has an upper end 42a that penetrates the lid body 34 and is exposed to the outside of the battery case 30, and a lower end 42b that is connected to the positive electrode 21 (specifically, the positive electrode tab portion 21c) inside the battery case 30. The positive electrode external terminal 44 is connected to the upper end 42a of the positive electrode internal terminal 42 outside the battery case 30. An insulating member 46 is disposed between the lid 34 and the positive external terminal 44 to prevent direct contact between the lid 34 and the positive external terminal 44.

The negative electrode terminal 50 is electrically connected to the negative electrode 22. The negative electrode terminal 50 is made of a metal such as copper, copper alloy, nickel, or stainless steel. The negative electrode terminal 50 may be made of the same metal type as the negative electrode current collector 22a. Here, the negative electrode terminal 50 is made of copper. The negative electrode terminal 50 has a negative electrode internal terminal 52 extending along the height direction Z and a plate-shaped negative electrode external terminal 54 extending along the upper surface of the lid body 34. The negative electrode internal terminal 52 has an upper end 52a that penetrates the lid body 34 and is exposed to the outside of the battery case 30, a lower end 52b that is connected to the negative electrode 22 (specifically, the negative electrode tab portion 22c) inside the battery case 30, and a bent portion 52c provided between the upper end 52a and the lower end 52b. The negative electrode external terminal 54 is connected to the upper end 52a of the negative electrode internal terminal 52 outside the battery case 30. An insulating member 56 is disposed between the lid 34 and the negative external terminal 54 to prevent direct contact between the lid 34 and the negative external terminal 54.

In this embodiment, the upper end portions of the positive electrode external terminal 44 and the negative electrode external terminal 54 are each formed in a rectangular flat plate shape. The positive electrode external terminal 44 and the negative electrode external terminal 54 each have a flat surface parallel to the upper surface of the lid 34. In this embodiment, the positive electrode external terminal 44 and the negative electrode external terminal 54 each have a width in the extension direction X that is longer than the width in the arrangement direction Y. However, the shape, size, arrangement, etc. of the positive electrode terminal 40 and the negative electrode terminal 50 are not particularly limited and can be changed as appropriate.

The busbar 90 is a conductive member used to electrically connect the batteries 10 together. Here, the busbar 90 electrically connects the positive terminal 40 of the first battery 10 and the negative terminal 50 of the second battery 10 adjacent to each other in the arrangement direction Y. Here, the busbar 90 is arranged so as to cover the flat surfaces of the positive terminal 40 and the negative terminal 50. The busbar 90 is joined to the flat surfaces of the positive terminal 40 and the negative terminal 50 by a conventionally known joining method such as laser welding. A joint (typically a welded joint) (not shown) is formed at the portion where the flat surfaces and the busbar 90 are connected. As a result, the busbar 90 is integrated with the positive terminal 40 and the negative terminal 50.

Figure 3 is a perspective view of busbar 90, and Figure 4 is a plan view of busbar 90. As shown in Figures 3 and 4, busbar 90 is composed of two members, a first metal member 91 and a second metal member 92. The first metal member 91 and the second metal member 92 are integrated and electrically connected to each other via a plurality of (here, two) joints 95. Each of the plurality of joints 95 has a crimp joint 93 and a resistance welded portion 94.

The first metal member 91 is a member that is electrically connected to the positive electrode terminal 40 of the battery 10. The first metal member 91 is made of a conductive metal such as aluminum, an aluminum alloy, nickel, or stainless steel. The first metal member 91 is preferably an alloy having the same metal type as the positive electrode terminal 40, or the same metal element as the first component (the component having the highest mixing ratio by mass; the same applies below). Here, the first metal member 91 is preferably composed mainly of aluminum. Here, the first metal member 91 is made of aluminum. The first metal member 91 is formed, for example, by bending a single metal plate by pressing or the like.

The first metal member 91 has a first connection portion 91a connected to the positive terminal 40, a second connection portion 91b connected to the second metal member 92, and a linking portion 91c linking the first connection portion 91a and the second connection portion 91b. The linking portion 91c extends along the arrangement direction Y. Here, the linking portion 91c is flat. However, in other embodiments, the linking portion 91c may have a portion bent into a U-shape or the like. The first connection portion 91a and the second connection portion 91b extend in the extension direction X from both ends of the linking portion 91c in the arrangement direction Y. As shown in FIG. 3, the first connection portion 91a and the second connection portion 91b have an approximately L-shaped outer shape.

The first connection portion 91a has a plate-shaped portion 91a1 that fits along the flat surface of the positive terminal 40, and an extension portion 91a2 that extends from the plate-shaped portion 91a1 to the connecting portion 91c. The plate-shaped portion 91a1 is a portion that abuts against the positive terminal 40. The outer shape of the plate-shaped portion 91a1 is generally rectangular here. In a plan view, the outer shape of the plate-shaped portion 91a1 is preferably approximately the same as or smaller than the outer shape of the flat surface of the positive terminal 40. The plate-shaped portion 91a1 has a thickness of approximately 0.01 to 5 mm, for example, about 0.1 to 1 mm. However, the shape, size, and thickness of the plate-shaped portion 91a1 are not particularly limited and can be changed as appropriate.

The plate-shaped portion 91a1 has a through hole 91h that penetrates in the height direction Z. The through hole 91h is provided in the center of the plate-shaped portion 91a1. Here, the through hole 91h is formed in a substantially quadrangular shape (e.g., a substantially rectangular shape) in a plan view. The through hole 91h serves as a guide for indicating the position where the plate-shaped portion 91a1 is welded to the flat surface of the positive electrode terminal 40. It can also function as an escape route for gas and heat generated during welding.

The second connection portion 91b has a plate-shaped portion 91b1 that fits along the flat second metal member 92, and an extension portion 91b2 that extends from the plate-shaped portion 91b1 to the connecting portion 91c. The outer shape of the plate-shaped portion 91b1 is substantially rectangular here. The outer shape of the plate-shaped portion 91b1 may be the same as that of the plate-shaped portion 91a1. In a plan view, the outer shape of the plate-shaped portion 91b1 may be substantially the same as or smaller than that of the second metal member 92. The plate-shaped portion 91b1 has a thickness of approximately 0.01 to 5 mm, for example, approximately 0.1 to 1 mm. However, the shape, size, and thickness of the plate-shaped portion 91b1 are not particularly limited and can be changed as appropriate.

The plate-shaped portion 91b1 has a window portion 91w penetrating in the height direction Z. The window portion 91w is provided in the center of the plate-shaped portion 91b1. In the extension direction X, the window portion 91w is located between a plurality of crimped joint portions 93. The window portion 91w is formed in a generally quadrangular shape (e.g., a generally rectangular shape) in a plan view. In a plan view, the second metal member 92 is exposed from the window portion 91w.

The second metal member 92 is a member that is electrically connected to the negative terminal 50 of the battery 10. The second metal member 92 is made of a conductive metal such as copper, a copper alloy, nickel, or stainless steel. The second metal member 92 may have, for example, a first component that is the same metal type as the first metal member 91, or may have a different metal type. The second metal member 92 is preferably an alloy having the same metal type as the negative terminal 50 or the same metal element as the first component. Here, the second metal member 92 is made of a metal different from the first metal member 91. Here, the second metal member 92 is preferably made mainly of copper. Here, the second metal member 92 is made of copper. The second metal member 92 may have a metal coating portion whose surface is coated with a metal such as Ni. The second metal member 92 may have a surface that is laser roughened.

The second metal member 92 is flat here. The second metal member 92 is composed of a plate-shaped portion here. One surface (upper surface in FIG. 3) of the second metal member 92 abuts against the second connection portion 91b of the first metal member 91, and the opposite surface (lower surface in FIG. 3) abuts against the negative electrode terminal 50. The outer shape of the second metal member 92 is substantially rectangular here. In a plan view, the outer shape of the second metal member 92 is preferably substantially the same as or smaller than the outer shape of the flat surface of the negative electrode terminal 50. The second metal member 92 has a thickness of approximately 0.01 to 5 mm, for example, approximately 0.1 to 1 mm. However, the shape, size, and thickness of the second metal member 92 are not particularly limited and can be changed as appropriate.

The second metal member 92 has a through hole 92h that penetrates in the height direction Z. The through hole 92h is provided in the center of the second metal member 92. Here, the through hole 92h is formed in a substantially quadrangular shape (e.g., substantially rectangular shape) in a plan view. The through hole 92h is substantially the same size as the through hole 91h of the first metal member 91. The through hole 92h serves as a guide for indicating the position where the second metal member 92 is welded to the flat surface of the negative terminal 50. It can also function as an escape route for gas and heat generated during welding.

The two joints 95 are arranged side by side in the extension direction X perpendicular to the arrangement direction Y. Specifically, the two joints 95 are arranged at both ends of the plate-shaped portion 91b1 of the first metal member 91 in the extension direction X. This increases the joint strength between the first metal member 91 and the second metal member 92, improving the electrical connection reliability. The two joints 95 are arranged outside the window portion 91w in a plan view. The two joints 95 are arranged to sandwich the window portion 91w in the extension direction X. However, in other embodiments, the number of joints 95 may be one, or three or more (e.g., four). The joints 95 may be arranged at the four corners of the plate-shaped portion 91b1, for example. FIG. 5 is a vertical cross-sectional view of the joint 95 along the line V-V in FIG. 4.

The crimp joint 93 is a joint formed by crimping the plate-shaped portion 91b1 of the first metal member 91 and the flat second metal member 92 by plastic deformation. This allows the first metal member 91 and the second metal member 92 to be suitably joined without using bolts, rivets, etc., even if the first metal member 91 and the second metal member 92 are made of different metals. In addition, the resistance of the busbar 90 can be relatively reduced compared to when a third member (e.g., bolts, rivets, etc.) is used. As shown in FIG. 5, the crimp joint 93 is provided around the resistance welded portion 94. In other words, the crimp joint 93 is provided so as to surround the resistance welded portion 94.

As shown in FIG. 3, the crimp joint 93 protrudes upward from the plate-like portion 91b1 of the first metal member 91. The crimp joint 93 has an approximately cylindrical shape in this embodiment. As shown in FIG. 4, the crimp joint 93 has an approximately circular shape in a plan view. However, the crimp joint 93 may have other shapes, such as an approximately rectangular shape, an elliptical cylindrical shape, or a gourd-like shape in which two circles or ellipses are connected. In this specification, the term "approximately rectangular shape" includes not only a perfect rectangular shape (e.g., a rectangular shape or a square shape), but also a shape in which the corners connecting the two sides are rounded or a shape with a notch in the corner. Here, there are multiple crimp joints 93 (specifically, two).

5, the crimp joint 93 has a plastic deformation portion 93a, a convex portion 93b, and a neck portion 93c. The plastic deformation portion 93a is made of a first metal member 91 and a second metal member 92. In the plastic deformation portion 93a, the first metal member 91 and the second metal member 92 abut with a sufficient line length and are interlocked. The plastic deformation portion 93a is provided along the outer periphery of the neck portion 93c. The plastic deformation portion 93a has an approximately cylindrical outer shape. The plastic deformation portion 93a is annular (here, approximately annular) in a plan view. This increases the strength of the interlock. The convex portion 93b is made of the first metal member 91. The convex portion 93b protrudes upward. The convex portion 93b is annular (here, approximately annular) in a plan view. The neck portion 93c is made of the second metal member 92. The neck portion 93c extends along the height direction Z. The neck portion 93c has a generally cylindrical outer shape. The neck portion 93c forms the inner peripheral edge of the crimp joint portion 93.

The resistance welded portion 94 is a joint formed by resistance welding the plate-shaped portion 91b1 of the first metal member 91 and the flat second metal member 92. The resistance welded portion 94 may be a joint having a relatively low rigidity (fragile) compared to the crimped joint 93. As shown in FIG. 5, the resistance welded portion 94 is provided on the inside of the crimped joint 93 (more specifically, on the inside of the annular plastic deformation portion 93a). More specifically, it is provided in the center of the annular plastic deformation portion 93a. This allows the joint 95 (particularly the resistance welded portion 94) to be stably maintained and the electrical conductivity reliability to be improved over a long period of time.

As shown in FIG. 4, the resistance welds 94 are provided on the inside of the two crimp joints 93. The number of resistance welds 94 is the same as the number of crimp joints 93. There are multiple resistance welds 94 (specifically, two). In the extension direction X, the two resistance welds 94 are provided at both ends of the plate-shaped portion 91b1 of the first metal member 91. This makes it easier to release gas and heat that may be generated when the resistance welds 94 are formed (during resistance welding), and the occurrence of poor joints (e.g. poor welding) can be suppressed.

<Method of Manufacturing Bus Bar 90>
The bus bar 90 can be manufactured by a manufacturing method including, for example, (1) a projection forming step and (2) a bonding step in this order. In the following, the first metal member 91 and the second metal member 92 before the bonding portion 95 is formed (before the bonding step) are referred to as the first metal member 91X and the second metal member 92X to distinguish them from the members after the bonding. The manufacturing method disclosed herein may further include other steps at any stage. FIG. 6 is a schematic diagram illustrating the manufacturing method of the bus bar 90.

(1) The projection formation process is a process of preparing a first metal member 91X having a plate-shaped portion and a second metal member 92X having a plate-shaped portion, and forming a projection (protrusion) 92p on the plate-shaped portion of the second metal member 92X. Note that this process is not essential, and can be omitted, for example, when the protrusion originally present on the second metal member 92X is used to perform the next process, i.e., (2) the joining process.

The method of forming the projection 92p may be the same as in the past and is not particularly limited. In one example, the plate-shaped portion of the first metal member 91 is pressed to raise a portion of the plate-shaped portion, thereby forming the projection 92p of a predetermined shape. In this case, for example, a press mold 200 as shown in FIG. 6(1) is first prepared. The mold 200 is for forming the projection 92p of a gently curved shape, that is, for performing so-called bulging molding. The mold 200 includes a die 210 having a recess 212 and a punch 220 having a protrusion 222 that is pressed into the recess 212. The punch 220 is configured to be movable in a direction approaching the die 210 and a direction away from the die 210 (height direction Z in FIG. 6(1)). The outer shape of the protrusion 222 here is a circular dome shape.

6(1), in this process, the plate-shaped portion of the second metal member 92X is placed between the die 210 and the punch 220, and the punch 220 is moved in the pressing direction P (here, vertically downward) indicated by the arrow to press the second metal member 92X. As a result, a part of the second metal member 92X is pressed against the convex portion 222 and pushed out so as to protrude toward the inside of the concave portion 212. As a result, the plate-shaped portion of the second metal member 92X is formed into a shape (here, a circular dome shape) that follows the convex portion 222, and a projection 92p is formed. Note that the second metal member 92X typically deforms while the thickness of the plate-shaped portion remains approximately constant. The projection 92p is a gently curved shape of the second metal member 92X.

(2) The joining process is a process of joining the first metal member 91X and the second metal member 92X. More specifically, it is a process of forming a crimp joint 93 (specifically, a plastic deformation portion 93a) and a resistance welded portion 94 between the first metal member 91X and the second metal member 92X substantially simultaneously. Specifically, first, a crimping device is prepared. A conventionally known crimping device can be used. In one example, a crimping device 300 as shown in FIG. 6 (2) is prepared. The crimping device 300 includes a die 310 having a recess 312, a punch 320 pressed into the recess 312, and a current supply unit 330 that supplies a welding current to the die 310 and the punch 320.

The die 310 and punch 320 are made of metal. The die 310 and punch 320 may be commercially available tools used in conventionally known TOX (trademark) crimping. The opening of the recess 312 of the die 310 is larger than the outer shape of the projection 92p of the second metal member 92X. The recess 312 is formed so as to be able to accommodate the projection 92p. The outer shape of the recess 312 is substantially cylindrical. The diameter of the recess 312 is preferably approximately three times or more, for example three times or more, four times or more, the diameter of the projection 92p. Although not particularly limited, the diameter of the recess 312 is preferably 1.5 to 5.0 mm. An annular groove 312a is formed on the lower surface of the recess 312.

The punch 320 is configured to be movable in a direction approaching the die 310 and a direction away from the die 310 (height direction Z in FIG. 6 (2)). The outer shape of the punch 320 here is cylindrical. The diameter of the punch 320 is smaller than the recess 312 of the die 310. It is preferable that the diameter of the punch 320 is approximately 0.5 mm or more, for example 1 mm or more, smaller than the recess 312 of the die 310. Although not particularly limited, it is preferable that the diameter of the punch 320 is 1.0 to 4.0 mm.

The current supply unit 330 is a mechanism for performing projection welding (specifically, embossed projection welding). The configuration of the current supply unit 330 may be the same as that of the conventional current supply unit. The current supply unit 330 may be of a capacitor type or an inverter type. Here, the current supply unit 330 includes an input terminal 332, a welding transformer 334 having a primary winding 334a and a secondary winding 334b, a pair of electrode tips 336, a first circuit 337, and a second circuit 338. The input terminal 332 is connected to a DC power source or an AC power source and is configured to supply power to the welding transformer 334. The welding transformer 334 is configured to be driven by, for example, the output of an inverter circuit and to output a welding current to the pair of electrode tips 336. The first circuit 337 is a circuit that connects one end of the secondary winding 334b of the welding transformer 334 to the die 310. The second circuit 338 is a circuit that connects the other end of the secondary winding 334b of the welding transformer 334 to the punch 320.

As shown in FIG. 6 (2), in this process, the first metal member 91X and the second metal member 92X are placed between the die 310 and the punch 320, and the punch 320 is moved in the pressing direction P (here, vertically downward) indicated by the arrow to press the punch 320 into the recess 312 of the die 310. Although not particularly limited, it is preferable that the pressure during pressing is 500 to 2500 N. This allows a crimped joint 93 with high joint strength to be stably formed.

At this time, while pressing the projection 92p against the first metal member 91X, the current supply unit 330 applies a welding current to the die 310 and punch 320, melting the projection 92p and forming a nugget N. As the punch 320 is pressed in, the nugget N spreads in an annular shape centered on the apex of the projection 92p. This forms a resistance weld 94 at the interface between the first metal member 91X and the projection 92p. Therefore, the resistance weld 94 can be formed so that, in a cross-sectional view, the thickness is greatest at the center and gradually decreases toward the outer edge.

In addition, by TOX (trademark) crimping, the first metal member 91 and the second metal member 92 are pushed into the recess 312 by the punch 320. As a result, the first metal member 91X fills the groove 312a and forms the protrusion 93b. When pressure is further applied, the second metal member 92 spreads outward inside the first metal member 91, and the first metal member 91X and the second metal member 92X are plastically deformed following the shape of the space formed by the recess 312 and the punch 320. As a result, a crimped joint 93 having an annular (here, annular) neck portion 93c and a plastically deformed portion 93a around the resistance welded portion 94 is formed. In other words, the resistance welded portion 94 is formed inside the annular plastically deformed portion 93a of the crimped joint 93, preferably in the center of the plastically deformed portion 93a.

Figure 7 (1) is a cross-sectional SEM observation image corresponding to the joint 95 in Figure 5. Figure 7 (2) is a cross-sectional SEM observation image showing a main part of (1), specifically, an enlarged image of the resistance welded part 94. As shown in Figure 7 (2), the resistance welded part 94 is formed at the interface between the first metal member 91 and the second metal member 92. In the resistance welded part 94, the metal type of the first metal member 91 and the metal type of the second metal member 92 are mixed. Note that the top-bottom orientation of Figures 7 (1) and (2) is reversed from that of Figure 5.

As described above, in this embodiment, first, a projection 92p is formed on the second metal member 92X, and then a crimping process (here, TOX (trademark) crimping) is performed while a welding current is applied. This allows the welding current to be concentrated on the projection 92p, and a large nugget can be formed centered on the projection 92p. Therefore, there is no need to apply a large current, and a high-quality resistance weld 94 with high mechanical strength can be formed.

In addition, by sandwiching and compressing the first metal member 91X and the second metal member 92X, an annular plastic deformation portion 93a is formed. Therefore, even if the first metal member 91X and the second metal member 92X are made of different metals, they can be joined appropriately. In addition, with TOX (trademark) crimping, the nickel plating applied to the surface of the second metal member 92X is not easily peeled off, and the second metal member 92 can be stably welded to the bus bar 90 during the manufacture of the battery pack 100.

Furthermore, since the resistance weld 94 is a metallurgical joint that utilizes heat (Joule heat) generated by electrical resistance, it can be a joint that is relatively weaker (more fragile) than the crimp joint 93. By disposing such a resistance weld 94 on the inner periphery of the crimp joint 93, the resistance weld 94 can be stably maintained. Therefore, even if external stress such as vibration or impact is applied, force is less likely to be applied to the resistance weld 94, making it easier to maintain the first metal member 91 and the second metal member 92 in close contact for a long period of time. As a result, the reliability of conductivity can be improved.

<Method of manufacturing battery pack 100>
The battery pack 100 can be produced, for example, by preparing a plurality of batteries 10 and a bus bar 90 as described above, and electrically connecting the positive terminal 40 of one battery 10 to the negative terminal 50 of the other battery 10 via the bus bar 90. In detail, first, the plate-shaped portion 91a1 of the bus bar 90 is placed on the flat surface of the positive terminal 40 of one battery 10, and after alignment is performed at the through hole 91h, the plate-shaped portion 91a1 of the bus bar 90 and the positive terminal 40 are laser welded together. Similarly, the plate-shaped portion 91b1 and the second metal member 92 of the bus bar 90 are placed on the flat surface of the negative terminal 50 of the other battery 10, and after alignment is performed at the through hole 92h, the second metal member 92 exposed from the window portion 91w opened in the plate-shaped portion 91b1 and the negative terminal 50 are laser welded together. When the second metal member 92 and the negative electrode terminal 50 are laser-welded to each other, the wavelength of the laser is preferably 540 nm or less, which can improve weldability.

Although the embodiment of the present invention has been described above, the above embodiment is merely an example. The present invention can be implemented in various other forms. The present invention can be implemented based on the contents disclosed in this specification and the technical common sense in the relevant field. The technology described in the claims includes various modifications and changes to the above-exemplified embodiment. For example, it is possible to replace part of the above-mentioned embodiment with other modified forms, and it is also possible to add other modified forms to the above-mentioned embodiment. Furthermore, if a technical feature is not described as essential, it can also be deleted as appropriate.

<Modification 1>
For example, in the above-described embodiment, as shown in Fig. 6 (1) and (2), in the projection forming step, one projection (protrusion) 92p is formed on the plate-like portion of the second metal member 92X, and then in the joining step, the first metal member 91X and the second metal member 92X are joined at one location. However, this is not limited to this. Fig. 8 (1) and (2) are views corresponding to Fig. 6 (1) and (2) according to a modified example. In this modified example, the joints 95 can be formed at multiple locations (two locations in this case) at approximately the same time. This modified example is particularly effective when manufacturing a conductive member for a battery having multiple joints 95, for example, as shown in Fig. 3.

(1) In the projection forming process, as shown in FIG. 8 (1), multiple (here, two) dies 200 are prepared and arranged at a predetermined interval in the extension direction X. Then, the plate-shaped portion of the second metal member 92X is pressed at multiple locations to form multiple (here, two) projections 92p approximately simultaneously. This makes it possible to shorten the time required for this process and increase work efficiency. In addition, a predetermined interval can be maintained between the multiple projections 92p, suppressing processing errors.

(2) In the joining process, as shown in FIG. 8 (2), a crimping device 400 is prepared. The crimping device 400 includes a die 410 having multiple (here, two) recesses 412, 414, multiple punches 420a, 420b that are respectively pressed into the multiple recesses 412, 414, and a current supply unit 430 that applies a welding current to the die 410 and the punches 420a, 420b. Note that, here, the two recesses 412, 414 have the same shape and size, but the shapes or sizes may be different from each other.

The current supply unit 430 includes an input terminal 432, a welding transformer 434 having a primary winding 434a and a secondary winding 434b, a pair of electrode tips 436 attached to the punches 420a and 420b, a first circuit 437 connecting one end of the secondary winding 434b to the first punch 420a, and a second circuit 438 connecting the other end of the secondary winding 434b to the second punch 420b. In this process, a welding current is applied to the multiple punches 420a and 420b by the current supply unit 430, so that a conductive path is formed through the second metal member 92X, the first metal member 91X, and the die 410, and multiple nuggets N can be formed approximately simultaneously. This reduces the time required for this process, and improves work efficiency and productivity.

<Modification 2>
For example, in the above-described embodiment, the battery conductive member was the bus bar 90. However, this is not limited thereto. The battery conductive member may be, for example, the negative electrode terminal 50 or the negative electrode internal terminal 52 constituting the battery 10 in FIG. 2. Specifically, for example, when the negative electrode internal terminal 52 and the negative electrode external terminal 54 are made of different metal materials (dissimilar metal materials), the joint portion disclosed herein, that is, the crimp joint portion and the resistance welded portion may be formed at the connection portion between the negative electrode internal terminal 52 and the negative electrode external terminal 54. In this case, for example, the negative electrode internal terminal 52 may be grasped as the second metal member, and the negative electrode external terminal 54 may be grasped as the first metal member. The negative electrode internal terminal 52 may be made of a metal material mainly made of copper, and the negative electrode external terminal 54 may be made of a metal material mainly made of aluminum.

For example, when the upper end 52a and the lower end 52b of the negative electrode internal terminal 52 are made of different metal materials (dissimilar metal materials), the joints disclosed herein, i.e., crimp joints and resistance welds, may be formed at the connection between the upper end 52a and the lower end 52b or near the bent portion 52c. In this case, for example, the upper end 52a may be regarded as the first metal member and the lower end 52b as the second metal member. The upper end 52a may be made of a metal material mainly made of aluminum, and the lower end 52b may be made of a metal material mainly made of copper.

<Uses of battery pack 100>
The battery pack 100 can be used for various purposes, but is preferably used in purposes where external forces such as vibration and impact may be applied during use, typically as a power source (driving power source) for motors mounted on various vehicles, such as passenger cars, trucks, etc. The type of vehicle is not particularly limited, but examples include plug-in hybrid electric vehicles (PHEVs), hybrid electric vehicles (HEVs), battery electric vehicles (BEVs), etc.

As described above, specific aspects of the technology disclosed herein include those described in the following sections.
Item 1: A method for manufacturing a conductive member for a battery, comprising: a projection forming step of preparing a first metal member having a plate-shaped portion and a second metal member having a plate-shaped portion, and forming a projection on the plate-shaped portion of the second metal member; and a joining step of preparing a crimping device including a die having a recess, a punch to be pressed into the recess, and a current supply unit that supplies a welding current to the die and the punch, placing the plate-shaped portion of the first metal member on the recess of the die, overlapping the portion of the second metal member on which the projection is formed, and then pressing the punch into the recess of the die, and forming a resistance weld by passing a welding current through the die and the punch with the current supply unit while pressing the projection against the first metal member, and plastically deforming the first metal member and the second metal member to form a crimp joint around the resistance weld.
Item 2: The manufacturing method according to item 1, wherein the first metal member and the second metal member are made of different metals.
Item 3: The manufacturing method according to item 1 or 2, wherein the conductive member for a battery is composed of two members, the first metal member and the second metal member.
Item 4: The manufacturing method according to any one of items 1 to 3, wherein a plurality of the resistance welds and a plurality of the crimped joints are formed at once in the joining step.
Item 5: The method according to any one of Items 1 to 4, wherein the conductive member for a battery is a bus bar.
Item 6: The method according to any one of Items 1 to 4, wherein the conductive member for a battery is a terminal of a battery.
Item 7: A conductive member for a battery comprising a first metal member having a plate-shaped portion, a second metal member having a plate-shaped portion, and a joint between the first metal member and the second metal member, the joint having a resistance welded portion formed by resistance welding the first metal member and the second metal member, and a crimped joint provided around the resistance welded portion and formed by plastically deforming the plate-shaped portion of the first metal member and the plate-shaped portion of the second metal member.
Item 8: The conductive member for a battery according to Item 7, wherein the first metal member and the second metal member are made of different metals.
Item 9: The conductive member for a battery according to item 7 or 8, wherein the conductive member for a battery is composed of two members, that is, the first metal member and the second metal member.
Item 10: The conductive member for a battery according to any one of Items 7 to 9, wherein the joints are multiple and the multiple joints are arranged side by side in a predetermined direction.
Item 11: The conductive member for a battery according to any one of Items 7 to 10, wherein the conductive member for a battery is a bus bar.
Item 12: The conductive member for a battery according to any one of Items 7 to 10, wherein the conductive member for a battery is a terminal of a battery.

REFERENCE SIGNS LIST 10 Battery 40 Positive electrode terminal 50 Negative electrode terminal 90 Bus bar 91 First metal member 91a1 Plate-shaped portion 91a2 Extension portion 91b1 Plate-shaped portion 91b2 Extension portion 91h Through hole 91w Window portion 92 Second metal member 92h Through hole 93 Crimp joint portion 93a Plastic deformation portion 94 Resistance welded portion 100 Assembled battery 200 Press die 300, 400 Crimping device 310, 410 Die 320, 420a, 420b Punch 330, 430 Current supply portion

Claims (12)

a projection forming step of preparing a first metal member having a plate-shaped portion and a second metal member having a plate-shaped portion, and forming a projection on the plate-shaped portion of the second metal member;
a joining process including: preparing a crimping device including a die having a recess, a punch to be pressed into the recess, and a current supplying unit to supply a welding current to the die and the punch; placing the plate-like portion of the first metal member on the recess of the die, and overlaying the portion of the second metal member on which the projections are formed; pressing the punch into the recess of the die; and, while pressing the projections against the first metal member, supplying a welding current to the die and the punch by the current supplying unit to form a resistance welded portion, and plastically deforming the first metal member and the second metal member to form a crimped joint around the resistance welded portion.
A method for manufacturing a conductive member for a battery. The manufacturing method according to claim 1, wherein the first metal member and the second metal member are made of different metals. The manufacturing method according to claim 1 or 2, wherein the battery conductive member is composed of two members, the first metal member and the second metal member. The manufacturing method according to claim 1 or 2, in which a plurality of the resistance welds and a plurality of the crimped joints are formed at once in the joining process. The manufacturing method according to claim 1 or 2, wherein the battery conductive member is a bus bar. The manufacturing method according to claim 1 or 2, wherein the battery conductive member is a battery terminal. A first metal member having a plate-shaped portion;
A second metal member having a plate-shaped portion;
a joint between the first metal member and the second metal member;
Equipped with
The joint is
a resistance welded portion formed by resistance welding the first metal member and the second metal member;
a crimp joint portion provided around the resistance weld portion and formed by plastically deforming the plate-shaped portion of the first metal member and the plate-shaped portion of the second metal member;
A conductive member for a battery, wherein the resistance welded portion is provided only at the interface between the first metal member and the second metal member, and is formed so that the thickness is greatest at the center and becomes thinner toward the outer edge . The conductive member for a battery according to claim 7, wherein the first metal member and the second metal member are made of different metals. The conductive member for a battery according to claim 7 or 8, wherein the conductive member for a battery is composed of two members, the first metal member and the second metal member. The conductive member for a battery according to claim 7 or 8, wherein the joints are multiple and the multiple joints are arranged side by side in a predetermined direction. The conductive member for a battery according to claim 7 or 8, wherein the conductive member for a battery is a bus bar. The conductive member for a battery according to claim 7 or 8, wherein the conductive member for a battery is a terminal of a battery.

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