JP6385426B2 - Battery positive / negative electrode terminal connection member - Google Patents

Description

  The present invention relates to a sheet-like connection member disposed between positive and negative electrode terminals for connecting a plurality of batteries in series. More specifically, the present invention relates to a thin sheet-like connection member in which different metals are joined by explosive pressure bonding.

Conventionally, a clad material in which dissimilar metals are joined by the explosive pressure-bonding clad method by joining metal dissimilarly in a metallurgical manner using the instantaneous high energy when explosives explode (hereinafter referred to as explosive pressure-bonded clad). It is also called a material.)
Hereinafter, an outline of a method for producing such an explosion-bonded clad material will be described.
First, as shown in FIG. 1, a laminated material is stacked on a base material with a gap, and a powder explosive is set on the entire surface of the laminated material. Next, as shown in FIG. 2, the explosive is detonated from one end, and due to the high energy of the explosion, the laminated material is driven at a high speed on the base material surface, and a liquefied metal (metal jet) is generated from the impact surface, The metal jet removes the base material and the oxide, nitride, adsorbed gas, etc. on the base material surface. Then, as shown in FIG. 3, the activated surface is pressed down at a high pressure, and brought close to the point where it is attracted by the interatomic force between the two metals and joined.
Explosive crimping is completed instantaneously (2500 m / sec), so there is no room for the explosion heat to be transmitted to the metal material, so it can be said to be pure cold crimping. As shown in FIG. ”.

Such explosive pressure-bonding clad materials are used for the following applications, for example.
In Patent Document 1 below, a copper thin plate of the same size is joined to the lower surface of a large aluminum plate having a desired thickness by an explosive pressure bonding (contact) method instead of brazing, and a terminal is connected from the joint plate. A method of manufacturing an aluminum terminal in which a copper plate is joined is disclosed, in which a single piece corresponding to the battledore portion is cut and one end of an aluminum compression portion having an aluminum wire insertion hole is welded to the cut single piece. Such an aluminum terminal is used for a connection part of electric equipment of a power plant or a substation, is not for a battery, has a thickness exceeding 2 mm, is large, and is not a two-layer sheet.

  Further, Patent Document 2 below discloses an aluminum bus bar that is manufactured by an explosive pressure bonding method on an aluminum bus bar and bonded with an aluminum layer of a copper-aluminum clad plate having good flatness by rolling. In the example of the same book, a copper-aluminum clad plate of (2 + 18 mm) × 1000 mm × 1000 mm was manufactured by the explosive pressure bonding method, and since there was a distortion of about 100 mm / 1000 mm, it was cut into a width of 500 mm by shearing and 1 mm / 1000 mm It describes that, in order to obtain flatness and finish to a plate thickness of 5 mm, roll rolling was performed in three steps and finished in 15 minutes. This bus bar is assumed to be used at the connection between the power generation and substation equipment and the aluminum transmission line. In addition, the clad plate produced by the explosive pressure bonding method is greatly deformed, and as the thickness of the clad plate increases, it becomes difficult to correct the distortion, and the required plate thickness cannot be secured, or the copper surface is damaged. Therefore, in order to solve the problem that a satisfactory terminal cannot be obtained, a thick-walled copper-aluminum bus bar with improved such defects is provided by rolling. As described above, the bus bar described in Patent Document 2 is not for a battery, has a thickness exceeding 2 mm, is large, and is not a sheet of two layers.

  Further, in Patent Document 3 below, a member made of copper or an alloy thereof and a member made of aluminum or an alloy thereof are subjected to a rolling cladding method, a diffusion bonding cladding method, an explosive pressure bonding cladding method, and a friction through a titanium layer. A copper-aluminum dissimilar metal joint material characterized by being joined by any one of the joining clad methods is disclosed. The invention described in the cited document 3 is a fragile metal that is likely to occur when copper and aluminum are bonded or when a dissimilar joint formed by direct bonding thereof is exposed to a high temperature (generated at a relatively low temperature of about 200 ° C.). In order to suppress the formation of inter-oxide, titanium is inserted as an intermediate material to provide a dissimilar joint having uniform and good characteristics. That is, the invention described in the cited document 3 is to provide a joint having mechanical performance, joint strength and airtightness that can maintain the performance of the joint even after the high-temperature heat treatment and can be sufficiently reliable. It is obvious that it is not a battery electrode terminal connecting material, not a two-layer sheet, and exceeds a thickness of 2 mm.

  In Patent Document 4 below, at least a plate-like portion made of a first metal and a plate-like portion made of a second metal having a melting point higher than that of the first metal are overlapped with each other, A first region where the first metal is exposed and a second region where the second metal is exposed are formed on the surface of the other surface, and the first surface is a region facing the second region on the other surface. A terminal connection body formed so that two metals are exposed and formed so that a step in a thickness method does not substantially exist at a boundary between the first region and the second region. Is disclosed. The first metal is aluminum or an alloy thereof, the second metal is copper, nickel, iron or an alloy thereof, and is composed of a plate-like portion made of the first metal and the second metal. It is described that the formed plate-like portion is a clad material bonded to each other, and that the connection body is for connecting a plurality of batteries. In the invention described in Patent Document 4, the melting point of the metal constituting the terminal connection conductor and the metal constituting the positive electrode terminal or the negative electrode terminal are different when the terminals of the battery are connected via the terminal connection conductor. It was made to solve the problem of difficult manufacturing due to welding. As shown in FIG. 5, the connection body is a battery terminal connection body including a battery outer case and a positive electrode terminal and a negative electrode terminal provided so as to protrude upward from the battery outer case. In addition, it is described that welding for connecting and fixing the terminals of a thin battery pack can be easily and compactly made. Although the thickness of the connection body is not described, it is considered that it is about 2 to 3 mm because the thickness of the assembled battery is 5 mm or less. Both the one region and the second region do not exist in the thickness direction of the connection body, but there is a boundary between the first region and the second region.

  Patent Document 5 below discloses an assembled battery in which a plurality of battery cells for power source of a motor that drives an electric vehicle are connected by a metal plate. As shown in FIG. A plurality of battery cells 1 whose electrode terminals 2 are different metals are provided, and the positive and negative electrode terminals 2 of each battery cell 1 are connected by a metal metal plate 3, and the metal plate 3 is one of the battery cells 1. A clad formed by joining a first metal plate 3A connected to one electrode terminal 2 and a second metal plate 3B connected to the other electrode terminal 2 between the connecting portions of the positive and negative electrode terminals 2 The material is disclosed. It is described that such a clad material is not simply a laminate of dissimilar metals, but dissimilar metals are in an alloy state and strongly bonded to each other at the joint surface. The electrode terminal and the metal plate are joined by laser welding or nuts. The thickness of the metal plate is not described. In addition, the metal plate described is such that dissimilar metals are joined in the length direction, not the thickness direction of the plate, and only one of the metals exists at the position of each electrode terminal. Two dissimilar metals do not exist in the thickness direction of the metal plate at arbitrary positions in the surface and the other surface.

  Patent Document 6 below describes a mode in which one negative electrode terminal and the other positive electrode terminal of two adjacent batteries are electrically connected by a strip-shaped or flat-shaped bus bar. There is no mention that it is a clad material.

  Patent Document 7 below describes a clad material in which aluminum or an aluminum alloy and copper or a copper alloy are used as an electrical connector, a conductor, or a heat conduction device, and are solid-phase bonded. And copper are butt-joined or partly overlapped and are not joined together. Further, Patent Document 7 does not describe at all the shape and joining form of the clad material used.

  Further, in Non-Patent Document 1 below, aluminum and copper are used in a wide range for electrical materials, and the joint portion connecting these materials has a large contact resistance when mechanically fastened with bolts or the like. In addition, Al / Cu explosive materials tend to generate intermetallic compounds at the bonding interface by heating, and this reduces the bending strength of the bonding strength. With this combination of metals, the thermal effect in the vicinity of the interface is not affected even during explosive welding. Inevitably, it is described that when the conditions are bad, a thick reaction layer may be formed and sufficient bonding strength may not always be obtained. As a means for solving such a problem, it is described that an explosive welding experiment is performed in a combination of a relatively thin Al plate (4 mm thickness) and a Cu plate, and the use of a Cu intermediate material is effective. Moreover, it is described that the Al / Cu clad used for the dissimilar material joint for conduction is required to have a thickness of about 20 mm for both Al and Cu in order to ensure current capacity.

  As described above, although the explosive pressure-bonding clad material is used as an electrode terminal connecting member, a sheet-like material having a small thickness has not been conventionally used.

JP-A-48-53280 JP-A 51-20744 Japanese Patent No. 3240211 International Publication No. 2010/087472 Pamphlet JP 2011-60623 A JP 2012-160339 A Special table 2013-514188 gazette

Welding Society Proceedings Vol. 12 No. 1 p. 77-81 (1994) Journal of the Japan Institute of Metals Vol. 75, No. 3 (2011) 166 ・ 172

  For example, since lithium ion secondary batteries for automobiles require large capacity, low internal resistance, and high heat dissipation performance, laminated laminate type batteries that can satisfy these requirements have been developed. The structure of this battery is shown in FIG. In this battery, positive electrodes, separators, and negative electrodes are alternately laminated, each electrode is connected to a metal electrode called a tab, placed in a container made of an aluminum laminate film, and an electrolyte is injected and sealed. With this configuration, it is possible to reduce the weight and thickness, have excellent heat dissipation, support a large current charge and discharge with a simple current collection structure, and change the size and capacity relatively easily. have. For example, when laminating a plurality of such laminate type cells and connecting the positive electrode tab and the negative electrode tab of adjacent cells in series, the positive electrode tab is made of aluminum and the negative electrode tab is made of copper. Must be securely connected.

For example, if the cell thickness is as thin as 10 mm or less, the distance between adjacent positive electrode tabs and negative electrode tabs is also 10 mm or less, and the thickness of the aluminum plate as the positive electrode tab is 0.5 mm or less, When the thickness is 0.5 mm or less and the width is 100 mm or less, it is very important in terms of quality control how to reliably perform electrical connection between both electrodes in such a narrow place.
That is, for example, when laminating a cell of a laminate type lithium ion secondary battery, the positive electrode material is an aluminum thin plate, the negative electrode material is a copper thin plate, and the materials are different. There are problems such as a large number of locations and a limited space for the joint portion for miniaturization.

  Under such circumstances, a problem to be solved by the present invention is to provide a connection member between positive and negative electrode terminals that can reliably perform high-quality connection with positive and negative electrodes by welding and can reduce the size of a battery. That is.

  As a result of intensive studies and experiments to solve the above problems, the present inventor has found that the above problems can be solved by using an explosion-bonded clad material having a thin two-layer structure, and the present invention has been completed. It is a thing.

That is, the present invention is as follows.
[1] A sheet-like connecting member disposed between positive and negative electrode terminals for connecting a plurality of batteries in series, the sheet-like connecting member comprising a metal constituting the positive electrode terminal on one surface or an alloy thereof. The first layer is composed of a second layer composed of a metal constituting the negative electrode terminal or an alloy thereof on the other surface, and has a thickness of 2 mm or less. the second layer has been engaged against and its joint surface, there are portions where there is no part intermetallic compound of intermetallic compounds, and a portion without intermetallic compound more than 10% of the total junction area, And the said member in which both this 1st layer and this 2nd layer exist in the thickness direction of this sheet-like connection member in arbitrary positions in this one surface and this other surface.
[2] The member according to [1], wherein the battery is a lithium ion secondary battery.
[3] The member according to [1] or [2], wherein the thickness of the sheet-like connecting member is 1 mm or less.
[4] The above [1] to [3], wherein the metal constituting the first layer or an alloy thereof is aluminum or an alloy thereof, and the metal constituting the second layer or an alloy thereof is copper or an alloy thereof. ] The member in any one of.
[5] an intermediate layer composed of the intermediate titanium or an alloy thereof of the first layer and the second layer, and said more To intermediate layer and the second layer is engaged against each other [1] to [4] , in which there are a portion having no intermetallic compound and a portion having an intermetallic compound, and a portion having no intermetallic compound is 10% or more of the total bonding area . The member in any one of.
[6] The member according to any one of [1] to [5], wherein the sheet-like connection member has a rectangular flat plate shape with a length of 3 to 9 mm and a width of 50 to 100 mm.
[7] The shape of the sheet-like connecting member is a shape obtained by bending a rectangular flat plate having a length of 10 to 20 mm and a width of 50 to 100 mm into a Z shape or an S shape when viewed from the side. -The member in any one of [ 5 ].
[8] A method of joining different flat plate electrodes composed of an electrode made of material 1 and an electrode made of material 2, wherein one surface is made of material 1 and the other surface is made of material 2, And the material 2 are joined together by explosive pressure bonding, and a clad plate having a thickness of 2 mm or less is bent into a Z shape or an S shape, and the same is applied between the electrode of the material 1 and the electrode of the material 2 The said method of joining the electrode of the material 1 and the electrode of the material 2 by inserting so that materials may contact | connect each other and joining the same material of this electrode and a clad board.
[9] A method for joining parallel plate dissimilar electrodes composed of an electrode made of material 1 and an electrode made of material 2, wherein the electrode made of material 1 is opposite to the surface adjacent to the electrode made of material 2 A clad plate having one surface made of material 1 and the other surface made of material 2, the material 1 and material 2 being bonded together by explosive pressure bonding and having a thickness of 2 mm or less. , said clad plate overlapped in contact is a surface made of a material 1 of joining, the cladding plate made of a material 1 formed by joining the electrode, to the side of the electrode formed of the material 2, the material 2 of the clad plate a surface consisting outward, folding, bending an electrode made of said material substance 2 to the side of the electrode formed of the material 1, stacked as a surface made of a material 2 of electrode and the cladding plate consisting of said material substance 2 contacts And joining them together The method of bonding the electrode made of the electrode and the material 2 made of a material 1.
[10] The clad plate thickness is 0.3mm or more, the method according to [9].
[11] The electrode made of material 1 and the electrode made of material 2 are a positive electrode tab of a lithium ion secondary battery and a negative electrode tab of another lithium ion secondary battery disposed adjacent to the lithium ion secondary battery. The method according to any one of [ 8 ] to [ 10 ], wherein
[12] In the dissimilar metal joint surface of the clad plate, there is no portion and a portion where there is an intermetallic compound of intermetallic compounds, a portion having no intermetallic compound is more than 10% of the total junction area, the [8 ] To [ 11 ].
[13] The clad plate and the electrode are overlapped with the same kind of materials, laser irradiation is performed from the electrode side, and the penetration depth of the laser weld after the laser irradiation reaches the dissimilar metal joint interface of the clad plate The method according to any one of [ 8 ] to [ 12 ], which is not performed.
[14] A battery pack having parallel plate dissimilar electrodes joined by the method according to any one of [ 8 ] to [ 13 ].

  According to the present invention, the positive and negative terminals of the battery can be joined with the same kind of materials by using an explosive pressure-bonding clad that is suitable for mass production, can be joined all over and has high joint strength, or a rolled product thereof, High quality bonding is possible. Further, according to the present invention, it is possible to reduce the size of the battery and its peripheral members while maintaining a sufficient bonding area between the positive and negative electrode terminals, and further, the resistance value and inductance of the electrode portion are reduced by the miniaturization and high quality bonding. It is possible to improve performance such as an increase in output current.

It is the schematic which shows the set state in the manufacturing method of an explosive pressure-bonding clad material. It is the schematic which shows the crimping | compression-bonding progress state in the manufacturing method of an explosive-bonding clad material. It is the schematic which shows the crimping completion state in the manufacturing method of a pressure-bonding clad material. 2 is a photograph of a “ripple-like” crimp interface in a pressure-bonding clad material. It is the schematic which shows the assembled battery and the connection body which were described in patent document 4 (same as FIG. 1 of patent document 4). It is the schematic which shows the metal plate for connecting the battery cell described in patent document 5 (same as FIG. 5 of patent document 5). It is drawing which shows the specific example of the structure of the laminated ion type lithium ion secondary battery for motor vehicles. It is the schematic explaining the method which arrange | positions the sheet-like connection member which concerns on this invention between the positive electrode tab of the adjacent cell of a laminate type lithium ion secondary battery, and a negative electrode tab, and connects it with welding. It is the photograph which performed the micro observation of the junction part of an explosive pressure bonding clad material (magnification SEM: imaging | photography of the part which does not have the layer of an intermetallic compound in a junction part). It is the photograph of the connection member extract | collected after cold rolling. It is a photograph of the bent connection member. It is a micro observation photograph of the section of a laser welding part. It is a photograph which shows the result of having carried out the ultrasonic flaw test of the brazing clad material of a comparative example. It is a photograph which shows the result of having performed the ultrasonic flaw test of the pressure-contact clad material of a comparative example. It is a photograph of the joining interface of the brazing clad material of a comparative example. It is a photograph of the joining interface of the pressure-welded cladding material of a comparative example.

Hereinafter, embodiments of the present invention will be described in detail.
The present embodiment is a sheet-like connection member disposed between positive and negative electrode terminals for connecting a plurality of batteries in series, and is a first composed of a metal constituting the positive electrode terminal or an alloy thereof on one surface. Each having a second layer composed of a metal constituting the negative electrode terminal or an alloy thereof on the other surface, and the first layer and the second layer are joined by explosive pressure bonding, In this member, both the first layer and the second layer are present in the thickness direction of the sheet-like connecting member at an arbitrary position in one surface and the other surface. Preferably, the thickness of the sheet-like connecting member is 2 mm or less.

The battery is preferably a lithium ion secondary battery, more preferably a laminated laminate type automotive lithium ion secondary battery.
In the laminated laminate type automotive lithium ion secondary battery, when the positive electrode tab and negative electrode tab of adjacent cells are connected in series, the positive electrode tab is usually made of aluminum and the negative electrode tab is made of copper. In order to securely connect different kinds of metals, the metal constituting the first layer composed of the metal constituting the positive electrode terminal or the alloy thereof or the alloy thereof is aluminum or an alloy thereof and constitutes the negative electrode terminal. The metal or alloy thereof constituting the second layer composed of metal or an alloy thereof can be copper or an alloy thereof. Moreover, in order to improve the heat resistance between aluminum and copper, an intermediate layer composed of titanium or an alloy thereof is provided between the first layer and the second layer, and the first layer, the intermediate layer, and the second layer are provided. May be bonded together by explosive pressure bonding.
As shown in FIGS. 1 to 3, an explosive pressure-bonding grad material consisting of two layers of copper and aluminum can be produced by using a copper plate as a base material and an aluminum plate as a mixture. A person skilled in the art can manufacture desired clad materials by appropriately setting production conditions and the like according to common technical knowledge.

  The sheet-like connecting member according to the present embodiment includes a first layer composed of a metal constituting the positive electrode terminal or an alloy thereof on one surface and a metal constituting the negative electrode terminal or an alloy thereof on the other surface. Each having a second layer, the first layer and the second layer being joined together by explosive pressure bonding, and the first layer at any position within the one surface and the other surface Both of the second layers are present in the thickness direction of the sheet-like connecting member. That is, for example, unlike a rectangular connecting member having a lower end made of copper and an upper end made of aluminum, it is a sheet-like member in which a copper layer and an aluminum layer are laminated over the entire surface.

  In another embodiment, on the joint surface between the first layer and the second layer, there are regularly a portion having no intermetallic compound and a portion having an intermetallic compound, and a portion having no intermetallic compound is entirely present. It may be 10% or more of the bonding area.

  In another embodiment, a parallel plate dissimilar electrode composed of an electrode made of material 1 and an electrode made of material 2, one surface being made of material 1 and the other surface being made of material 2. The clad plate is bent into a Z-shape or S-shape, and the same material is inserted between the electrode of the material 1 and the electrode of the material 2 so as to be in contact with each other, and the same material of the electrode and the clad plate is joined. Thus, the above-described method of joining the electrode of material 1 and the electrode of material 2 is provided.

  In another embodiment, a parallel plate dissimilar electrode composed of an electrode made of material 1 and an electrode made of material 2 is provided, and the electrode made of material 1 is adjacent to the electrode made of material 2. The clad plate made of material 1 on one side and the material 2 on the other side is overlapped with the surface opposite to the surface so that the surface made of material 1 of the clad plate is in contact with and joined, The electrode made of the material 1 to which the clad plate is bonded is bent toward the electrode made of the material 2, the electrode made of the material 2 is bent toward the electrode made of the material 1, and the electrode made of the material 2 and the clad There is also provided the above-described method of joining an electrode made of material 1 and an electrode made of material 2 by overlapping and joining so that the surfaces made of material 2 of the plate are in contact with each other.

  Preferably, the electrode made of the material 1 and the electrode made of the material 2 are a positive electrode tab of a lithium ion secondary battery and a negative electrode tab of another lithium ion secondary battery disposed adjacent to the lithium ion secondary battery. Can be. The thickness of the clad plate is preferably 0.3 mm or more. In the dissimilar metal bonding surface of the clad plate, a portion having no intermetallic compound and a portion having an intermetallic compound are regularly present, and a portion having no intermetallic compound may be 10% or more of the total bonding area.

  Laser welding can be performed in a state where the cladding plate and the electrode are overlapped and the same kind of materials do not reach the dissimilar metal bonding interface of the cladding.

  In another aspect, a battery pack having parallel plate dissimilar electrodes joined by the above method is also provided.

In a conventional rolled clad material, for example, when a rectangular connecting member having a lower end made of copper and an upper end made of aluminum is to be obtained in a shape of 15 mm long × 70 mm wide × 1 mm thick, the lower end of the rectangle is made only of copper. A rolled clad material having a thickness of 15 mm is prepared in advance so that the upper end is made of aluminum, and a slice of the rolled clad material having a thickness of 1 mm must be cut to a length of 70 mm.
On the other hand, when the explosion-bonded clad material of laminated sheet-like copper and aluminum according to the present embodiment is finally obtained in a shape of, for example, 15 mm long × 70 mm wide × 1 mm thick, the thickness exceeds 1 mm. An explosive pressure-bonding clad material is prepared in advance, and rolled to 1 mm, and then cut into a rectangular shape having a length of 70 mm × 15 mm.

  As described above, in the explosive pressure-bonding clad material, since the crimping interface exhibits a “ripple shape”, dissociation between dissimilar metals hardly occurs, and it is difficult to generate an intermetallic compound by heating because of cold crimping. High quality electrical connection between dissimilar metals can be achieved. Such characteristics are maintained even when rolled to a thickness of 2 mm or less. Aluminum is surely present on one side of the explosion-bonded clad material of copper and aluminum in the laminated sheet-like form according to this embodiment, copper is surely present on the other side, and the same metal welding with the aluminum positive electrode tab Since the same kind of metal welding with the copper negative electrode tab is possible, there is no problem of quality deterioration when joining different metals between Al and Cu by welding. For example, since high-productivity laser welding can be used for such joining, problems such as connection by bolts and nuts, enlargement, and looseness do not occur.

With reference to FIG. 8, a sheet-like connection member according to the present embodiment is disposed between the positive electrode tab and the negative electrode tab of the adjacent cell of the laminate type lithium ion secondary battery, and connected to each other by welding. explain.
In plan 1 of FIG. 8 (a), for example, a sheet-like connecting member having a thickness of 1 mm (aluminum 0.5 mm + copper 0.5 mm) × vertical 15 mm × horizontal 70 mm (one pitch is aluminum and the other is copper) (pitch 7 mm) For example), bend it into a Z-shape as viewed from the side, weld the aluminum side of the Z-shaped upper surface against the aluminum positive electrode tab, and similarly, weld the copper side of the lower surface of the Z-shaped The positive and negative tabs can be connected by contacting and welding the copper negative electrode tabs. In this plan 1, the positive and negative electrode tabs do not need to be bent.

In plan 2 of FIG. 8B, the positive and negative electrode tabs are bent, but the sheet-like connecting member is not bent. Therefore, the plan 2 may be thicker than the plan 1, for example, one side of which is aluminum and the other side is copper having a thickness of 2 mm (aluminum 1 mm + copper 1 mm) × length 6.5 mm × width 70 mm. Prepare a sheet-like connecting member (for 7 mm pitch), abut the copper surface of the sheet-like connecting member from below the copper negative electrode tab, bend it 90 ° downward and weld it, The positive and negative tabs can be connected by bending the aluminum positive electrode tab downward by 90 °, then bending the aluminum positive electrode tab downward by 90 °, abutting against the aluminum surface of the sheet-like connecting member, and welding. Compared to Alternative 1, Plan 2 can reduce the resistance value by increasing the joint area of the dissimilar metal joint, and can increase the thickness of the connecting member. I need it.
Regarding the bending of the positive and negative electrode tabs, the positive and negative electrode tabs may be bent after being welded so as not to form an intermetallic compound of Cu and Al by overlapping with the connection member in a state before being bent. In explosive pressure bonding, since an intermetallic compound is not formed, the bonding strength is high, and therefore, the positive and negative electrode tabs can be bent after welding.

  The shape of the sheet-like connecting member according to the present embodiment can be appropriately selected depending on the interval and shape of the positive electrode tab and the negative electrode tab of the adjacent cell of the laminate type lithium ion secondary battery to be applied. 2 mm or less, preferably 1 mm or less. For example, when a rectangular flat plate having a length of 3 to 9 mm × width of 50 to 100 mm, or a rectangular plate of 10 to 20 mm × width 50 to 100 mm is viewed from the side, Z It can be a shape bent into a letter shape or S shape.

  The connection member according to the present embodiment and the positive and negative electrode tabs can be connected by various types of welding such as laser welding, ultrasonic welding, brazing, and spot welding. The optimum welding method can be selected.

  In addition, the method of connecting the positive electrode tab and negative electrode tab of the adjacent cell of the laminate-type lithium ion secondary battery described above is not limited to a method using a sheet-like connection member joined by explosive pressure bonding. If one surface is a clad plate made of the same material as the positive electrode and the other surface is the same as the negative electrode, it can be used as a connecting member in the method.

  In this specification, about the intermetallic compound, the cross section of the clad was observed with an electron microscope, and the intermetallic compound was determined by component analysis. A value obtained by dividing the length of the region where no intermetallic compound is formed at the bonding interface by the length of the entire observation cross section was calculated as the region without the intermetallic compound. Moreover, also about the penetration depth at the time of welding, the cross section of the welding part was observed with the electron microscope, and the part with the largest penetration depth was made into the penetration depth.

[Example]
A clad material was produced by explosion-bonding Cu with a thickness of 4 mm and Al with a thickness of 11 mm each with a size of 1000 x 2000 mm. As a result of an ultrasonic flaw detection test of this clad material, it was found that the non-bonded portion was limited to a very small part of the outer peripheral portion, and a full-surface bond of 900 × 1900 mm or more was obtained. By using such a whole-surface joined portion as a connecting member between the positive and negative electrode terminals, a connecting member having a low electrical resistance value and a high joining strength could be obtained.
Microscopic observation of the joint of this explosive pressure-bonded clad material confirmed that the joint was rippled. At the bonding interface, an intermetallic compound was easily formed at the rippled entrained portion, but the other portion was bonded with almost no intermetallic compound, and the bonding strength was high. The region where the intermetallic compound is not formed occupies 50% or more of the total bonding area, and FIG. 9 shows an image obtained by observing the region with an enlarged SEM. From FIG. 9, it was confirmed that there was no intermetallic compound layer.
A test piece for resistance measurement having the following size was taken from this explosion-bonded clad, and the resistance value of the joint was measured by the four-terminal method. The resistance value of the joint of the explosive pressure-bonding clad was 1 μΩ or less, and it was very small because there was almost no intermetallic compound. The resistance value of the joint portion is a value obtained by subtracting the theoretical resistance value of the material portion from the value measured using the following resistance meter to calculate the resistance value of the clad joint portion.
Specimen size: (15 + 15) x 5 x 5 (15 mm thick Cu and 15 mm thick Al clad processed to 5 mm square)
Voltage measurement position: Position 10 mm away from the joint on the respective material side Resistance meter: Using Hioki RM3545 and dedicated 4-terminal lead wire

  Non-Patent Document 2 describes that when an intermetallic compound is present in a layered manner on the entire joint surface at the joint between copper and aluminum, it becomes brittle and the joint strength is reduced. Bonding strength is high because the portion bonded without intermetallic compound accounts for 50% or more. When the tensile test was actually performed, the aluminum material portion was broken without breaking at the joint surface.

Next, the obtained explosion-bonded clad material was cold-rolled to a total thickness of 1.5 mm. For the one after rolling, the thickness of Cu is about 0.4 mm, and the thickness of Al is about 1.1 mm. Even after cold rolling, there was no change in the entire surface joining range, and even if a connecting member was taken from the one after cold rolling, almost no joint failure occurred.
In FIG. 10, the micro observation result of the connection member extract | collected after cold rolling is shown. From FIG. 10, it was found that, as with the explosive pressure-bonded clad material, even in a member manufactured by cold rolling, the portion where the intermetallic compound is not formed on the joint surface occupies 50% or more of the total joint area.

  FIG. 11 shows a bent connection member according to this embodiment. Since the clad material joined by explosive pressure bonding has high joining strength, the joint part does not peel off even if it is bent on either side, so it has been found that it can sufficiently cope with bending work such as S-shape and Z-shape.

Since the plate-like connecting member obtained as described above is used as a connecting member for positive and negative electrode terminals for a battery, each of a 0.2-mm-thick Cu simulated electrode and a 0.4-mm-thick Al simulated electrode is made of the same kind of materials. Were placed so that they overlap each other, and laser welding was performed. FIG. 12 is a micro observation photograph of the cross section of the laser weld. When the connecting member is configured as described above and laser welding is performed under the following conditions, the penetration depth can be suppressed within the range of the same type of material, and the thermal effect of welding is low even at explosive pressure bonding joints. Was found to have hardly increased.
(Laser welding conditions)
Manufacturer: Amada Miyachi Device name: Fiber laser welder Model name: ML6950A
Spot diameter: φ0.15 mm
Welding speed: 200 mm / s
Laser power: CW2.3 kW

  The penetration depth into the clad material was 0.3 mm on the Cu side and 1.0 mm on the Al side. Under the above conditions, the laser welding conditions are the same on the Cu side and Al side, so welding is possible with a single laser welding machine with a constant output, the welding work is simple, and the manufacturing time can be shortened. It leads to improvement and price reduction.

  When the laser output is changed to CW1.4 kW, the penetration depth into the clad material is 0.2 mm on the Al side, and in combination with the above conditions, if the clad material thickness is about 0.6 mm, the penetration depth The height can be adjusted so as not to reach the bonding interface.

Furthermore, if the following changes and adjustments are made, the penetration depth can be controlled with higher accuracy, and if the cladding material thickness is 0.3 mm, the penetration depth is adjusted so that it does not reach the joint interface. Is possible.
-Adjust the laser output by reducing the spot diameter to, for example, 0.05 mm.
・ Use a laser welding machine that supports highly reflective materials such as Cu and Al.
・ Reduce the thickness of Cu and Al electrodes. For example, 0.1 mm.
・ Use a pulse output type laser welding machine.

[Comparative example]
For comparison, the following two types of clad materials were prepared.
・ Clad material with 12mm thick Cu and 40mm thick Al each size 280 × 300 brazed in the thickness direction ・ 70mm long Cu and 70mm long Al diameter Cladding material with a diameter of φ30 pressed in the axial direction The results of these ultrasonic flaw tests are shown in FIGS. The theoretical reflectivity of ultrasonic waves at the copper / aluminum joint surface is about 28%, and the reflection signal of the non-joint part is adjusted to 80% at the dissimilar metal joint surface, so the reflectivity is about 22%. This is a region where the portions are joined. Since both clads are unbonded in a wide range, there is a risk that defective products such as insufficient bonding force and poor conductivity may occur when connecting members are collected.

[Comparison of intermetallic compound layer thickness]
15 and 16 show the junction interface of the above two types of clads. In the brazing clad, the thickness of the brazing material is 200 μm or more, and there are many places where there is no brazing material and there are voids. The pressure clad had an intermetallic compound thickness of 20 μm or more.
If the intermetallic compound layer is thick or has voids as described above, it causes a decrease in performance such as an increase in resistance value and a decrease in allowable current value.
In addition, when a tensile test was performed on a clad having a thick layer of the two types of intermetallic compounds, the joint surface was broken.

  If the sheet-like connecting member disposed between the positive and negative electrode terminals according to the present invention is used, the positive and negative of the battery can be obtained by using an explosive pressure-bonding clad or a rolled product suitable for mass production, capable of full-surface bonding and high bonding strength. Since the electrode terminals can be joined with the same kind of materials, high-quality joining is possible. Further, according to the present invention, it is possible to reduce the size of the battery and its peripheral members while maintaining a sufficient bonding area between the positive and negative electrode terminals, and further, the resistance value and inductance of the electrode portion are reduced by the miniaturization and high quality bonding. It is possible to improve performance such as an increase in output current. Therefore, the connection member according to the present invention can be suitably used for, for example, a laminated laminate type automotive lithium ion secondary battery that requires a large capacity, low internal resistance, and high heat dissipation performance.

Claims (14)

A sheet-like connecting member disposed between positive and negative electrode terminals for connecting a plurality of batteries in series, the sheet-like connecting member being formed of a metal constituting the positive electrode terminal on one surface or an alloy thereof. Each of the first layer has a second layer made of a metal constituting the negative electrode terminal or an alloy thereof on the other surface, and has a thickness of 2 mm or less. The first layer and the second layer are engaged contact, in its joint surface, there are portions where there is no part intermetallic compound of intermetallic compounds, and a portion without intermetallic compound more than 10% of the total bond area, and the The member, wherein both the first layer and the second layer are present in the thickness direction of the sheet-like connecting member at an arbitrary position in one surface and the other surface.   The member according to claim 1, wherein the battery is a lithium ion secondary battery.   The member of Claim 1 or 2 whose thickness of the said sheet-like connection member is 1 mm or less.   The metal constituting the first layer or an alloy thereof is aluminum or an alloy thereof, and the metal constituting the second layer or an alloy thereof is copper or an alloy thereof. The member as described in. An intermediate layer composed of the intermediate titanium or an alloy thereof of the second layer and the first layer, and said more To intermediate layer and the second layer are engaged against each other, the The bonding surface includes a portion having no intermetallic compound and a portion having an intermetallic compound, and the portion having no intermetallic compound is 10% or more of the total bonding area. The member described.   The shape of the said sheet-like connection member is a member of any one of Claims 1-5 which is a rectangular flat plate shape of length 3-9mm x width 50-100mm. The shape of the sheet-like connecting member, a rectangular flat vertical 10 to 20 mm × horizontal 50 to 100 mm, a shape bent in a Z-shaped or S-shaped when viewed from the side, one of the claims 1-5 The member according to claim 1.   A method of joining parallel plate different material electrodes composed of an electrode made of material 1 and an electrode made of material 2, wherein one surface is made of material 1 and the other surface is made of material 2, and the material 1 and the material 2 is joined by explosive pressure bonding, and a clad plate having a thickness of 2 mm or less is bent into a Z-shape or S-shape, and the same material is placed between the material 1 electrode and the material 2 electrode. The method of joining the electrode of the material 1 and the electrode of the material 2 by inserting so that it may contact | connect each other and joining the same material of this electrode and a clad board. A method of joining parallel plate dissimilar electrodes composed of an electrode made of material 1 and an electrode made of material 2, wherein the electrode made of material 1 is on the surface opposite to the surface adjacent to the electrode made of material 2 A clad plate having one surface made of material 1 and the other surface made of material 2, the material 1 and the material 2 being joined by explosive pressure bonding, and having a thickness of 2 mm or less, and overlapped in contact is a surface made of a material 1 of plate, and bonding, the electrode made of a material 1 formed by joining the clad plate, to the side of the electrode formed of the material 2, made of a material 2 of the clad plate surface the outward, folding, bending an electrode made of said material substance 2 to the side of the electrode formed of the material 1, are superimposed in such a way that a surface made of a material 2 of electrode and the cladding plate consisting of said material substance 2 is in contact, By joining the materials The method of bonding the electrode made of the electrode and the material 2 consisting of 1. The clad plate thickness is 0.3mm or more, The method of claim 9. The electrode made of the material 1 and the electrode made of the material 2 are a positive electrode tab of a lithium ion secondary battery and a negative electrode tab of another lithium ion secondary battery disposed adjacent to the lithium ion secondary battery. The method according to any one of claims 8 to 10 . In the dissimilar metal bonding surface of the cladding plate, there is no portion and a portion where there is an intermetallic compound of intermetallic compounds, a portion having no intermetallic compound is more than 10% of the total junction area of claims 8-11 The method according to any one of the above. The clad plate and the electrode are overlapped with the same kind of material, laser irradiation is performed from the electrode side, and the penetration depth of the laser weld after the laser irradiation does not reach the dissimilar metal bonding interface of the clad plate a method according to any one of claims 8-12. Battery pack having a parallel plate dissimilar electrodes joined by the method according to any one of claims 8-13.