JP2020095837A - Manufacturing method for secondary cell - Google Patents

Manufacturing method for secondary cell Download PDF

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JP2020095837A
JP2020095837A JP2018232049A JP2018232049A JP2020095837A JP 2020095837 A JP2020095837 A JP 2020095837A JP 2018232049 A JP2018232049 A JP 2018232049A JP 2018232049 A JP2018232049 A JP 2018232049A JP 2020095837 A JP2020095837 A JP 2020095837A
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external terminal
terminal
negative electrode
laser welding
laser
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JP7054454B2 (en
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利生 今堀
Toshio Imahori
利生 今堀
中山　博之
Hiroyuki Nakayama
博之 中山
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Toyota Motor Corp
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

To provide a manufacturing method for a secondary cell including laser welding of a caulking portion of a collector terminal made of copper and an external terminal made of aluminum, in which deterioration of endurance and an increase of resistance can be restrained.SOLUTION: A manufacturing method for a secondary cell includes a step of inserting a collector terminal into an open hole of a sealing lid, and the open hole of an external terminal, and causing a tip of the collector terminal to project from the external terminal in an insertion direction, a step of caulking the tip of the projecting collector terminal and forming a caulking portion, and a step of laser welding the external terminal and the caulking portion formed in the collector terminal. The collector terminal is made of copper, and the external terminal is made of aluminum. In a region where the laser welding is carried out, a position of the outside surface of the external terminal is higher than a position of the outside surface of the caulking portion. In the laser welding, the outside surface of the external terminal is irradiated with laser at first.SELECTED DRAWING: Figure 2

Description

本発明は、二次電池の製造方法に関する。 The present invention relates to a method for manufacturing a secondary battery.

近年、リチウムイオン二次電池等の二次電池は、パソコン、携帯端末等のポータブル電源や、電気自動車（ＥＶ）、ハイブリッド自動車（ＨＶ）、プラグインハイブリッド自動車（ＰＨＶ）等の車両駆動用電源などに好適に用いられている。 2. Description of the Related Art In recent years, secondary batteries such as lithium-ion secondary batteries are used as portable power sources for personal computers, mobile terminals, etc., and vehicle driving power sources for electric vehicles (EV), hybrid vehicles (HV), plug-in hybrid vehicles (PHV), etc. It is preferably used for.

一般的な二次電池は、電極体と、非水電解質とが電池ケースに収容されている構成を有する。このような構成の典型例では、電池ケースは、開口部を有するケース本体と、当該開口部を塞ぐ封口蓋とから構成される。電極体には集電端子が取り付けられ、当該集電端子は、電池ケースの外側において外部端子と電気的に接続されている。
この二次電池の集電端子部分の構造について具体的には、電池ケースの封口蓋は、貫通孔を有しており、集電端子の上端がこの貫通孔を通って電池ケース外部へと突出している。そして、封口蓋との間に外部端子およびインシュレータを介在させつつ集電端子の上端部がかしめられて、端子類と封口蓋とが固定された構造を有する。 A general secondary battery has a structure in which an electrode body and a non-aqueous electrolyte are housed in a battery case. In a typical example of such a configuration, the battery case includes a case main body having an opening and a sealing lid that closes the opening. A collector terminal is attached to the electrode body, and the collector terminal is electrically connected to an external terminal outside the battery case.
Regarding the structure of the current collector terminal portion of the secondary battery, specifically, the lid of the battery case has a through hole, and the upper end of the current collector terminal projects through the through hole to the outside of the battery case. ing. Further, the upper end portion of the current collecting terminal is caulked while the external terminal and the insulator are interposed between the terminal and the sealing lid so as to be fixed to the sealing lid.

二次電池を製造する際には、集電端子の上端部がかしめられることにより形成されたかしめ部と、外部端子とがレーザ溶接により接合される（例えば、特許文献１参照）。このレーザ溶接は、集電端子のかしめ部および外部端子の上方からレーザ照射されることにより、行なわれる。従来技術においては、集電端子および外部端子の素材には、同種の素材が選択されている。 When manufacturing a secondary battery, the crimped portion formed by crimping the upper end portion of the current collector terminal and the external terminal are joined by laser welding (for example, see Patent Document 1). This laser welding is performed by irradiating the laser from above the crimped portion of the collector terminal and the external terminal. In the prior art, the same kind of material is selected as the material of the current collector terminal and the external terminal.

国際公開第２０１５／０２５３８８号International Publication No. 2015/025388

二次電池はその普及に伴い、さらなる低コスト化が求められている。低コスト化の実現の方法の一つとして、低コスト部品の使用が挙げられる。しかしながら、従来の部品を低コストの部品に置き換えることにより様々な問題が生じ得る。
一般に、正極側の集電端子および外部端子の素材には、アルミニウムが用いられ、負極側の集電端子と外部端子の素材には、銅が用いられている。本発明者らの検討では、負極側の銅製の外部端子をアルミニウム製の外部端子で置き換えた場合には、銅製の外部端子とアルミニウム製の外部端子をレーザ溶接する際に、溶接部の耐久性が低下するという問題、および溶接部の抵抗が増加するという問題が生じることを見出した。 With the spread of secondary batteries, further cost reduction is required. One of the methods for realizing the cost reduction is the use of low cost parts. However, replacing conventional components with low cost components can cause various problems.
In general, aluminum is used as the material for the positive electrode side current collecting terminal and the external terminal, and copper is used as the material for the negative electrode side current collecting terminal and the external terminal. In the study of the present inventors, when the copper external terminal on the negative electrode side is replaced with an aluminum external terminal, the durability of the welded portion when laser welding the copper external terminal and the aluminum external terminal It has been found that there is a problem that the welding resistance decreases and that the resistance of the weld increases.

そこで本発明の目的は、銅製の集電端子のかしめ部とアルミニウム製の外部端子とをレーザ溶接することを含む二次電池の製造方法において、溶接部の耐久性の低下および抵抗の増加を抑制することができる、二次電池の製造方法を提供する。 Therefore, an object of the present invention is to suppress a decrease in durability of a welded portion and an increase in resistance in a method of manufacturing a secondary battery including laser welding a crimped portion of a current collector terminal made of copper and an external terminal made of aluminum. Provided is a method of manufacturing a secondary battery that can be manufactured.

銅製の集電端子のかしめ部とアルミニウム製の外部端子とをレーザ溶接した際に耐久性の低下および抵抗の増加が起こった溶接部の分析を本発明者らが行ったところ、溶接部において、金属間化合物が生成していることを見出した。すなわち、金属間化合物の生成が、耐久性の低下と抵抗の増加の原因になっていることを見出した。
さらに、レーザ溶融した銅とレーザ溶融したアルミニウムとが混ざり合うと、金属間化合物が生成しやすく、よってレーザ溶融する銅の量を低減させることにより、金属間化合物の生成を抑制できることを見出した。
そして、本発明者らは、銅製の集電端子のかしめ部とアルミニウム製の外部端子とをレーザ溶接する際に、レーザ溶融する銅の量を低減可能な方法に想到し、本発明の完成に至った。 When the present inventors performed an analysis of the welded portion where a decrease in durability and an increase in resistance occurred when laser welding the crimped portion of the current collector terminal made of copper and the external terminal made of aluminum, in the welded portion, It was found that an intermetallic compound was formed. That is, it has been found that the formation of the intermetallic compound causes a decrease in durability and an increase in resistance.
Further, it has been found that when the laser-melted copper and the laser-melted aluminum are mixed, an intermetallic compound is easily generated, and therefore, by reducing the amount of the laser-melted copper, the generation of the intermetallic compound can be suppressed.
Then, the present inventors have come up with a method capable of reducing the amount of copper that is laser-melted when laser-welding the crimped portion of the copper current collector terminal and the aluminum external terminal, and to complete the present invention. I arrived.

すなわち、ここに開示される二次電池の製造方法は、封口蓋の貫通孔および外部端子の貫通孔に集電端子を挿入して、前記集電端子の先端部を前記外部端子から挿入方向に突出させる工程と、前記突出した集電端子の先端部をかしめて、かしめ部を形成する工程と、前記外部端子と、前記集電端子に形成されたかしめ部とをレーザ溶接する工程と、を包含する。前記集電端子は銅製であり、かつ前記外部端子はアルミニウム製である。前記レーザ溶接を行なう領域において、前記外部端子の外表面の位置が、前記かしめ部の外表面の位置よりも高くなっている。前記レーザ溶接において、最初に前記外部端子の外表面にレーザが照射される。 That is, the method of manufacturing a secondary battery disclosed herein inserts a current collecting terminal into the through hole of the sealing lid and the through hole of the external terminal, and the tip portion of the current collecting terminal is inserted in the insertion direction from the external terminal. A step of projecting, a step of crimping the tip of the projecting current collecting terminal to form a caulking portion, a step of laser welding the external terminal and a caulking portion formed on the current collecting terminal, Include. The current collecting terminal is made of copper, and the external terminal is made of aluminum. In the region where the laser welding is performed, the position of the outer surface of the external terminal is higher than the position of the outer surface of the caulked portion. In the laser welding, the outer surface of the external terminal is first irradiated with laser.

このような構成によれば、レーザ溶接を行なう部分においては、レーザを最初にアルミニウム製の外部端子に照射しやすくなっており、さらにレーザを最初にアルミニウム製の外部端子に照射することにより、レーザ溶融する銅の量を低減することができる。そのため、溶接部の耐久性の低下と抵抗の増加の原因となる金属間化合物の生成を抑制することができる。
すなわち、このような構成によれば、銅製の集電端子のかしめ部とアルミニウム製の外部端子とをレーザ溶接することを含む二次電池の製造方法において、溶接部の耐久性の低下および抵抗の増加を抑制することができる、二次電池の製造方法が提供される。 According to such a configuration, in the portion where the laser welding is performed, it is easy to irradiate the laser to the aluminum external terminal first, and by further irradiating the laser to the aluminum external terminal first, the laser The amount of molten copper can be reduced. Therefore, it is possible to suppress the generation of intermetallic compounds that cause a decrease in durability of the welded portion and an increase in resistance.
That is, according to such a configuration, in the method of manufacturing a secondary battery including laser welding the crimped portion of the copper current collector terminal and the aluminum external terminal, deterioration of durability and resistance of the welded portion Provided is a method for manufacturing a secondary battery, which can suppress the increase.

本発明の一実施形態に係る製造方法によって製造されるリチウムイオン二次電池の概略斜視図である。1 is a schematic perspective view of a lithium ion secondary battery manufactured by a manufacturing method according to an embodiment of the present invention. 図１の二次電池の負極側の端子固定構造を示す模式断面図である。It is a schematic cross section which shows the terminal fixing structure by the side of the negative electrode of the secondary battery of FIG. 従来技術の負極側の端子固定構造を示す模式断面図である。It is a schematic cross section which shows the terminal fixing structure by the side of the negative electrode of a prior art. 本発明の一実施形態に係る製造方法の変形例の負極側の端子固定構造を示す模式断面図である。It is a schematic cross section which shows the negative electrode side terminal fixing structure of the modification of the manufacturing method which concerns on one Embodiment of this invention.

以下、図面を参照しながら、本発明による実施の形態を説明する。なお、本明細書において特に言及している事項以外の事柄であって本発明の実施に必要な事柄（例えば、本発明を特徴付けない二次電池の一般的な構成および製造プロセス）は、当該分野における従来技術に基づく当業者の設計事項として把握され得る。本発明は、本明細書に開示されている内容と当該分野における技術常識とに基づいて実施することができる。また、以下の図面においては、同じ作用を奏する部材・部位には同じ符号を付して説明している。また、各図における寸法関係（長さ、幅、厚さ等）は実際の寸法関係を反映するものではない。 Hereinafter, embodiments according to the present invention will be described with reference to the drawings. It should be noted that matters other than matters particularly referred to in the present specification and necessary for carrying out the present invention (for example, a general configuration and manufacturing process of a secondary battery that does not characterize the present invention) are It can be understood as a matter of design for a person skilled in the art based on the prior art in the field. The present invention can be carried out based on the contents disclosed in this specification and the common general technical knowledge in the field. Further, in the following drawings, the same reference numerals are given to the members/sites that have the same effect. Further, the dimensional relationships (length, width, thickness, etc.) in each drawing do not reflect the actual dimensional relationships.

なお、本明細書において「二次電池」とは、リチウムイオン二次電池、金属リチウム二次電池、ナトリウム二次電池、ニッケル水素電池、ニッケルカドミウム電池等のいわゆる蓄電池（いわゆる化学電池）のほか、電気二重層キャパシタ等のキャパシタ（いわゆる物理電池）をも包含する概念である。 In the present specification, the term "secondary battery" means a so-called storage battery (so-called chemical battery) such as a lithium ion secondary battery, a metal lithium secondary battery, a sodium secondary battery, a nickel hydride battery, a nickel cadmium battery, The concept also includes capacitors such as electric double layer capacitors (so-called physical batteries).

以下、ここで開示される二次電池の製造方法の実施形態として、リチウムイオン二次電池の製造方法を例にして説明するが、本発明の適用対象をかかる二次電池に用いられるものに限定することを意図したものではない。
まず、本発明の一実施形態に係る製造方法によって製造されるリチウムイオン二次電池の構造について説明する。図１は、本発明の一実施形態に係る製造方法によって製造されるリチウムイオン二次電池の概略斜視図である。図２は、図１の二次電池の負極側の端子固定構造を示す模式断面図である。 Hereinafter, as an embodiment of the method for manufacturing a secondary battery disclosed herein, a method for manufacturing a lithium ion secondary battery will be described as an example, but the application of the present invention is limited to those used for such a secondary battery. It is not intended to be done.
First, the structure of the lithium ion secondary battery manufactured by the manufacturing method according to the embodiment of the present invention will be described. FIG. 1 is a schematic perspective view of a lithium ion secondary battery manufactured by a manufacturing method according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing a terminal fixing structure on the negative electrode side of the secondary battery of FIG.

図１に示すように、リチウムイオン二次電池２００は、電池ケース１１０に、電極体１２０と非水電解液（図示せず）とが収容された構成を有する。電池ケース１１０は、開口部を有するケース本体１１２と、当該開口部を塞ぐ封口蓋１０とから構成されている。電池ケース１１０は、金属製であっても樹脂製であってもよく、ここでは、アルミニウム製である。封口蓋１０には、電池ケース１１０の内圧が所定レベル以上に上昇した場合に該内圧を開放するように設定された薄肉の安全弁１３０が設けられている。また、封口蓋１０には、非水電解液を注入するための注液口１４０が設けられている。 As shown in FIG. 1, the lithium ion secondary battery 200 has a configuration in which a battery case 110 contains an electrode body 120 and a non-aqueous electrolyte (not shown). The battery case 110 includes a case body 112 having an opening and a sealing lid 10 that closes the opening. The battery case 110 may be made of metal or resin, and is made of aluminum here. The sealing lid 10 is provided with a thin safety valve 130 that is set to release the internal pressure of the battery case 110 when the internal pressure rises above a predetermined level. Further, the sealing lid 10 is provided with a liquid injection port 140 for injecting the non-aqueous electrolytic solution.

電極体１２０は、図示しないが、正極と、負極とが、これらの間にセパレータが介在しながら積層された構造を有する。電極体１２０は、捲回型電極体および積層型電極体のいずれであってもよく、公知の捲回型電極体の構成または公知の積層型電極体の構成を有していてよい。 Although not shown, the electrode body 120 has a structure in which a positive electrode and a negative electrode are laminated with a separator interposed therebetween. The electrode body 120 may be either a wound electrode body or a laminated electrode body, and may have a known wound electrode body structure or a known laminated electrode body structure.

次に、負極側の端子固定構造について説明する。図１に示すように、電極体１２０の負極は、負極集電端子２０および負極外部端子４０を介して、負極端子１６０と電気的に接続されている。負極集電端子２０は、銅製である。負極外部端子４０は、アルミニウム製である。
封口蓋１０は、ここでは長辺を有する方形平板状である。
図１および図２に示すように、封口蓋１０の上には、インシュレータ３０が配置されている。インシュレータ３０の上部に負極外部端子４０が配置されている。インシュレータ３０は、典型的には、絶縁性の樹脂材料から構成される。インシュレータ３０により、封口蓋１０と負極外部端子４０とが絶縁されている。負極外部端子４０は、電池ケース１１０の外側において使用される端子であり、負極Ｚ端子とも呼ばれることがある。
図２に示すように、封口蓋１０の電池ケース１１０の内側部分には、ガスケット５０が配置されている。ガスケット５０は、典型的には、絶縁性の樹脂材料から構成される。ガスケット５０により、封口蓋１０と負極集電端子２０とが絶縁されている。 Next, the terminal fixing structure on the negative electrode side will be described. As shown in FIG. 1, the negative electrode of the electrode body 120 is electrically connected to the negative electrode terminal 160 via the negative electrode collector terminal 20 and the negative electrode external terminal 40. The negative electrode current collector terminal 20 is made of copper. The negative electrode external terminal 40 is made of aluminum.
The sealing lid 10 has a rectangular flat plate shape having long sides here.
As shown in FIGS. 1 and 2, an insulator 30 is arranged on the sealing lid 10. The negative electrode external terminal 40 is arranged on the insulator 30. The insulator 30 is typically made of an insulating resin material. The insulator 30 insulates the sealing lid 10 from the negative electrode external terminal 40. The negative electrode external terminal 40 is a terminal used on the outside of the battery case 110, and is sometimes called a negative electrode Z terminal.
As shown in FIG. 2, a gasket 50 is arranged inside the battery case 110 of the sealing lid 10. The gasket 50 is typically made of an insulating resin material. The sealing lid 10 and the negative electrode current collector terminal 20 are insulated by the gasket 50.

封口蓋１０、インシュレータ３０、負極外部端子４０、およびガスケット５０は、貫通孔を有し、負極集電端子２０が当該貫通孔に挿入されている。負極集電端子２０の先端（すなわち、上端）はかしめられて、かしめ部２２が形成されている。 The sealing lid 10, the insulator 30, the negative electrode external terminal 40, and the gasket 50 have through holes, and the negative electrode current collecting terminal 20 is inserted into the through holes. The tip (that is, the upper end) of the negative electrode current collector terminal 20 is crimped to form a crimped portion 22.

かしめ部２２の周縁部において、かしめ部２２と負極外部端子４０は、レーザ溶接により接合されている。なお、図面では接合部（すなわち、溶接痕）の図示は省略してある。図２に示すように、リチウムイオン二次電池２００の通常の使用状態（すなわち、正極端子１５０および負極端子１６０が上側に配置される状態）において、負極外部端子４０の外表面４０ａの位置が、かしめ部２２の外表面２２ａの位置よりも高くなっている。なお、本明細書において、「外表面」とは、電池ケース１１０の外側方向に露出している表面のことを指す。 At the peripheral portion of the crimped portion 22, the crimped portion 22 and the negative electrode external terminal 40 are joined by laser welding. It should be noted that illustration of the joint portion (that is, welding mark) is omitted in the drawings. As shown in FIG. 2, when the lithium ion secondary battery 200 is normally used (that is, the positive electrode terminal 150 and the negative electrode terminal 160 are arranged on the upper side), the position of the outer surface 40a of the negative electrode external terminal 40 is It is higher than the position of the outer surface 22a of the caulking portion 22. In the present specification, the “outer surface” refers to the surface exposed to the outside of the battery case 110.

電極体１２０の正極は、正極集電端子および正極外部端子を介して、正極端子１５０と電気的に接続されている。正極側の端子固定構造は、上記の負極側の端子固定構造と同様であるが、正極外部端子の外表面の位置と正極集電端子のかしめ部の外表面の位置との関係については特に制限はない。従来技術と同様に、正極外部端子の外表面の位置は、正極集電端子のかしめ部の外表面の位置よりも低くてもよい。 The positive electrode of the electrode body 120 is electrically connected to the positive electrode terminal 150 via the positive electrode collector terminal and the positive electrode external terminal. The terminal fixing structure on the positive electrode side is similar to the above-mentioned terminal fixing structure on the negative electrode side, but the relationship between the position of the outer surface of the positive electrode external terminal and the position of the outer surface of the crimped portion of the positive electrode current collector terminal is not particularly limited. There is no. Similar to the conventional technique, the position of the outer surface of the positive electrode external terminal may be lower than the position of the outer surface of the caulked portion of the positive electrode current collector terminal.

次に、本実施形態に係る製造方法について詳細に説明する。本実施形態に係る製造方法は、封口蓋の貫通孔および外部端子の貫通孔に集電端子を挿入して、当該集電端子の先端部を当該外部端子から挿入方向に突出させる工程（以下、「挿入工程」ともいう）と、当該突出した集電端子の先端部をかしめて、かしめ部を形成する工程（以下、「かしめ工程」ともいう）と、当該外部端子と、当該集電端子に形成されたかしめ部とをレーザ溶接する工程（以下、「レーザ溶接工程」ともいう）と、を包含する。当該集電端子は銅製であり、かつ当該外部端子はアルミニウム製である。当該レーザ溶接を行なう領域において、当該外部端子の外表面の位置が、当該かしめ部の外表面の位置よりも高くなっている。当該レーザ溶接において、最初に外部端子の外表面にレーザが照射される。 Next, the manufacturing method according to the present embodiment will be described in detail. The manufacturing method according to the present embodiment is a step of inserting the current collecting terminal into the through hole of the sealing lid and the through hole of the external terminal, and projecting the tip portion of the current collecting terminal in the insertion direction from the external terminal (hereinafter, "Inserting step"), a step of crimping the tip of the protruding current collecting terminal to form a crimped portion (hereinafter, also referred to as "caulking step"), the external terminal, and the current collecting terminal. A step of laser welding the formed crimped portion (hereinafter, also referred to as “laser welding step”). The current collecting terminal is made of copper, and the external terminal is made of aluminum. In the region where the laser welding is performed, the position of the outer surface of the external terminal is higher than the position of the outer surface of the caulked portion. In the laser welding, the outer surface of the external terminal is first irradiated with laser.

以下、図面を参照しながら各工程について具体的に説明する。
挿入工程においてはまず、銅製の負極集電端子２０、貫通孔を有するガスケット５０、貫通孔を有する封口蓋１０、貫通孔を有するインシュレータ３０、および貫通孔を有し、アルミニウム製の負極外部端子４０を準備する。
負極集電端子２０は、リベット状であり、これらの貫通孔に挿入可能な円柱部を有する。
負極外部端子４０は、次のかしめ工程において負極集電端子２０の先端にかしめ部２２が形成された際に、負極外部端子４０の外表面４０ａの位置が、かしめ部２２の外表面２２ａの位置よりも高くなるように、所定の厚さを有し、かつかしめ部２２を収容可能な凹部を有する。この凹部の径は、かしめ部２２の周縁部と負極外部端子４０とが溶接可能なように、かしめ部２２の径よりもわずかに大きくなっている。 Hereinafter, each step will be specifically described with reference to the drawings.
In the inserting step, first, a negative electrode current collector terminal 20 made of copper, a gasket 50 having a through hole, a sealing lid 10 having a through hole, an insulator 30 having a through hole, and a negative electrode external terminal 40 made of aluminum having a through hole. To prepare.
The negative electrode current collector terminal 20 has a rivet shape and has a cylindrical portion that can be inserted into these through holes.
In the negative electrode external terminal 40, the position of the outer surface 40a of the negative electrode external terminal 40 is the position of the outer surface 22a of the caulking part 22 when the caulking part 22 is formed at the tip of the negative electrode current collector terminal 20 in the next caulking step. The recess has a predetermined thickness and is capable of accommodating the caulking portion 22 so as to be higher than the above. The diameter of this concave portion is slightly larger than the diameter of the caulking portion 22 so that the peripheral portion of the caulking portion 22 and the negative electrode external terminal 40 can be welded.

次に、負極集電端子２０の円柱部を、ガスケット５０の貫通孔、封口蓋１０の貫通孔、インシュレータ３０の貫通孔、および負極外部端子４０の貫通孔に、順番に挿入する。このとき、ガスケット５０により、封口蓋１０と負極集電端子２０とが絶縁され、かつインシュレータ３０により、封口蓋１０と負極外部端子４０とが絶縁されるような配置とする。 Next, the columnar portion of the negative electrode current collector terminal 20 is sequentially inserted into the through hole of the gasket 50, the through hole of the sealing lid 10, the through hole of the insulator 30, and the through hole of the negative electrode external terminal 40. At this time, the gasket 50 insulates the sealing lid 10 from the negative electrode current collecting terminal 20, and the insulator 30 insulates the sealing lid 10 from the negative electrode external terminal 40.

次に、かしめ工程を行う。かしめ操作は公知方法に従い、リベット状の負極集電端子２０の円柱部の先端をかしめることにより行うことができる。
かしめ工程の実施により、負極集電端子２０の先端にかしめ部２２が形成される。本実施形態においては、図２に示すように、負極外部端子４０の外表面４０ａの位置は、かしめ部２２の外表面２２ａの位置よりも高い状態となっている。そのため、次のレーザ溶接工程において、負極外部端子４０の外表面４０ａの位置は、かしめ部２２の外表面２２ａの位置よりもレーザ溶接装置に近い位置にある。 Next, a caulking process is performed. The crimping operation can be performed by crimping the tip of the cylindrical portion of the rivet-shaped negative electrode current collector terminal 20 according to a known method.
By performing the caulking step, the caulking portion 22 is formed at the tip of the negative electrode current collector terminal 20. In the present embodiment, as shown in FIG. 2, the position of the outer surface 40a of the negative electrode external terminal 40 is higher than the position of the outer surface 22a of the caulking portion 22. Therefore, in the next laser welding step, the position of the outer surface 40a of the negative electrode external terminal 40 is closer to the laser welding device than the position of the outer surface 22a of the caulking portion 22.

次に、レーザ溶接工程について説明する。
レーザ溶接には、アルミニウムと銅とを溶接可能な公知のレーザ溶接装置を用いることができる。
レーザ溶接装置により、接合すべきかしめ部２２の周縁部および負極外部端子４０の上方より、レーザを照射する。このとき、最初に負極外部端子４０の外表面４０ａにレーザが照射される。本実施形態によれば、負極外部端子４０の外表面４０ａの位置が、かしめ部２２の外表面２２ａの位置よりも高いために、最初に負極外部端子４０の外表面４０ａにレーザを照射することが容易である。これにより、まず負極外部端子４０の素材であるアルミニウムを溶融させ、次いで負極集電端子２０の素材である銅を溶融させて溶着を行う。
これにより、負極集電端子２０と負極外部端子４０との接合がなされる。このような方法により接合することにより、溶接部の耐久性の低下および抵抗の増加を抑制することができる。その理由は以下の通りである。 Next, the laser welding process will be described.
A known laser welding device capable of welding aluminum and copper can be used for the laser welding.
The laser welding device irradiates a laser from above the peripheral portion of the crimped portion 22 and the negative electrode external terminal 40 to be joined. At this time, first, the outer surface 40a of the negative electrode external terminal 40 is irradiated with laser. According to the present embodiment, since the position of the outer surface 40a of the negative electrode external terminal 40 is higher than the position of the outer surface 22a of the crimped portion 22, the outer surface 40a of the negative electrode external terminal 40 is first irradiated with laser. Is easy. As a result, first, aluminum, which is the material of the negative electrode external terminal 40, is melted, and then, copper, which is the material of the negative electrode current collector terminal 20, is melted and welded.
As a result, the negative electrode current collector terminal 20 and the negative electrode external terminal 40 are joined. By joining by such a method, it is possible to suppress a decrease in durability of the welded portion and an increase in resistance. The reason is as follows.

図３は、従来技術の負極側の端子固定構造を示す模式断面図である。なお、図３において、本実施形態と同じ構成の部材については同じ符号を付してある。
従来技術においては、図３に示すように、負極外部端子には、貫通孔のある部分を除いて厚さが一定の負極外部端子３４０が用いられている。このため、かしめ部２２の外表面２２ａの位置が、負極外部端子３４０の外表面３４０ａの位置よりも高い。
レーザ溶接は、かしめ部２２の周縁部および負極外部端子３４０の上方より（特に斜め上方より）レーザを照射することにより行なわれる。そのため、照射されたレーザは位置の高いかしめ部２２に当たり易い。よって、通常は、レーザは最初に、かしめ部２２のみか、またはかしめ部と負極外部端子３４０の両方に照射される。
従来技術においては、負極集電端子２０および負極外部端子３４０は、共に銅製である。同種の材料の溶接であるために、レーザがかしめ部２２と負極外部端子３４０のいずれかに偏って照射されても問題は起こりにくい。
しかしながら、負極外部端子３４０の素材を銅からアルミニウムに変更した場合には、レーザ溶接する際には、レーザは最初に、かしめ部２２のみか、またはかしめ部と負極外部端子３４０の両方に照射されるために、銅製の負極集電端子２０のかしめ部から銅が溶融する。引き続きレーザ照射を続けていくと、溶融した銅と溶融したアルミニウムとが混ざり合って金属間化合物が形成する。この金属間化合物は、上述のように、溶接部の耐久性の低下と抵抗の増加を招く。 FIG. 3 is a schematic cross-sectional view showing a conventional negative electrode side terminal fixing structure. In addition, in FIG. 3, members having the same configurations as those of the present embodiment are denoted by the same reference numerals.
In the conventional technique, as shown in FIG. 3, a negative electrode external terminal 340 having a constant thickness is used as the negative electrode external terminal except for a portion having a through hole. Therefore, the position of the outer surface 22a of the crimped portion 22 is higher than the position of the outer surface 340a of the negative electrode external terminal 340.
The laser welding is performed by irradiating the laser from above the peripheral portion of the crimped portion 22 and the negative electrode external terminal 340 (particularly from diagonally above). Therefore, the irradiated laser easily hits the crimped portion 22 having a high position. Therefore, normally, the laser is first irradiated to only the crimped portion 22 or both the crimped portion and the negative electrode external terminal 340.
In the prior art, both the negative electrode current collector terminal 20 and the negative electrode external terminal 340 are made of copper. Since the same kind of material is welded, even if the laser is radiated to one of the caulked portion 22 and the negative electrode external terminal 340, the problem is unlikely to occur.
However, when the material of the negative electrode external terminal 340 is changed from copper to aluminum, the laser is first irradiated to only the caulking portion 22 or both the caulking portion and the negative electrode external terminal 340 during laser welding. Therefore, copper is melted from the caulked portion of the copper negative electrode current collector terminal 20. When laser irradiation is continued, molten copper and molten aluminum are mixed with each other to form an intermetallic compound. As described above, this intermetallic compound causes a decrease in durability of the welded portion and an increase in resistance.

しかしながら、本実施形態では、図２に示すように、最初に負極外部端子４０の外表面４０ａにレーザを照射することが容易となるように、負極外部端子４０の外表面４０ａの位置が、かしめ部２２の外表面２２ａの位置よりも高くなっている。そして、本実施形態では、最初に負極外部端子４０の外表面４０ａにレーザを照射する。アルミニウムは、銅よりも融点が低く（銅の融点：１０８５℃、アルミニウムの融点：６６０．３℃）溶融し易いため、これにより、負極外部端子４０の素材であるアルミニウムを優先的に溶融させることができる。そして、レーザ溶接を行なう際に溶融する銅の量を低減することができ、これにより溶接部の耐久性の低下と抵抗の増加の原因となる金属間化合物の生成を抑制することができる。 However, in the present embodiment, as shown in FIG. 2, the position of the outer surface 40a of the negative electrode external terminal 40 is caulked so that it is easy to irradiate the laser on the outer surface 40a of the negative electrode external terminal 40 first. It is higher than the position of the outer surface 22a of the portion 22. In this embodiment, the outer surface 40a of the negative electrode external terminal 40 is first irradiated with laser. Since aluminum has a lower melting point than copper (melting point of copper: 1085° C., melting point of aluminum: 660.3° C.), it is easy to melt, so that aluminum as a material of the negative electrode external terminal 40 is preferentially melted. You can Then, it is possible to reduce the amount of copper that is melted when performing laser welding, and thus it is possible to suppress the formation of intermetallic compounds that cause a decrease in durability of the welded portion and an increase in resistance.

なお、負極外部端子４０の外表面４０ａの位置は、レーザ溶接を行なう領域において、かしめ部２２の外表面２２ａの位置よりも高くなっていればよい。
そこで、図４に、変形例の負極側の端子固定構造を示す模式断面図を示す。なお、図４において、上述の本実施形態と同じ構成の部材については同じ符号を付してある。 The position of the outer surface 40a of the negative electrode external terminal 40 may be higher than the position of the outer surface 22a of the caulked portion 22 in the region where laser welding is performed.
Therefore, FIG. 4 shows a schematic cross-sectional view showing a modified example of the terminal fixing structure on the negative electrode side. Note that, in FIG. 4, members having the same configurations as those of the above-described present embodiment are denoted by the same reference numerals.

図４に示すように、当該変形例では、負極外部端子には、かしめ部２２を囲う部分のみ厚さが大きくなるようにして形成されたアルミニウム集積部４４２を有する負極外部端子４４０が用いられている。アルミニウム集積部４４２と負極集電端子２２とのレーザ溶接が行なわれる。よって、この変形例においても、レーザ溶接を行なう領域において、負極外部端子４４０の外表面４４０ａの位置が、かしめ部２２の外表面２２ａの位置よりも高くなっており、レーザ溶接工程において最初に負極外部端子４４０の外表面４４０ａにレーザを照射することが容易である。 As shown in FIG. 4, in this modification, the negative electrode external terminal includes a negative electrode external terminal 440 having an aluminum integrated portion 442 formed so that only the portion surrounding the crimped portion 22 has a large thickness. There is. Laser welding of the aluminum integrated portion 442 and the negative electrode current collector terminal 22 is performed. Therefore, also in this modified example, the position of the outer surface 440a of the negative electrode external terminal 440 is higher than the position of the outer surface 22a of the caulking portion 22 in the region where the laser welding is performed, and the negative electrode is first used in the laser welding process. It is easy to irradiate the outer surface 440a of the external terminal 440 with a laser.

上述したレーザ溶接工程を行なうことにより、封口蓋１０に、負極集電端子２０および負極外部端子４０が固定された部材を得ることができる。
この部材を用いてリチウムイオン二次電池を組み立てる工程を行うことにより、リチウムイオン二次電池を製造することができる。リチウムイオン二次電池を組み立てる工程は、公知方法に従い行うことができる。負極集電端子２０は、上記のレーザ溶接工程を行なう前に、電極体１２０の負極と接合されていてもよい。
本実施形態に係る二次電池の製造方法によれば、負極集電端子２０の素材を、銅からアルミニウムに変更したことにより、低コスト化を図ることができる。 By performing the laser welding process described above, a member in which the negative electrode current collector terminal 20 and the negative electrode external terminal 40 are fixed to the sealing lid 10 can be obtained.
A lithium-ion secondary battery can be manufactured by performing a step of assembling a lithium-ion secondary battery using this member. The step of assembling the lithium ion secondary battery can be performed according to a known method. The negative electrode current collector terminal 20 may be bonded to the negative electrode of the electrode body 120 before performing the above laser welding process.
According to the method for manufacturing a secondary battery according to the present embodiment, cost can be reduced by changing the material of the negative electrode current collector terminal 20 from copper to aluminum.

以上、本発明の具体例を詳細に説明したが、これらは例示にすぎず、請求の範囲を限定するものではない。請求の範囲に記載の技術には、以上に例示した具体例を様々に変形、変更したものが含まれる。 Specific examples of the present invention have been described above in detail, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

１０ 封口蓋
２０ 負極集電端子
２２ かしめ部
２２ａ かしめ部外表面
３０ インシュレータ
４０ 負極外部端子
４０ａ 外表面
５０ ガスケット
１１０ 電池ケース
１１２ ケース本体
１２０ 電極体
１３０ 安全弁
１４０ 注液口
１５０ 正極端子
１６０ 負極端子
２００ リチウムイオン二次電池 10 Sealing Lid 20 Negative Electrode Current Collecting Terminal 22 Caulking Part 22a Caulking Part Outer Surface 30 Insulator 40 Negative External Terminal 40a Outer Surface 50 Gasket 110 Battery Case 112 Case Body 120 Electrode Body 130 Safety Valve 140 Injection Port 150 Positive Electrode Terminal 160 Negative Terminal 200 Lithium Ion secondary battery

Claims (1)

封口蓋の貫通孔および外部端子の貫通孔に集電端子を挿入して、前記集電端子の先端部を前記外部端子から挿入方向に突出させる工程と、
前記突出した集電端子の先端部をかしめて、かしめ部を形成する工程と、
前記外部端子と、前記集電端子に形成されたかしめ部とをレーザ溶接する工程と、
を包含する二次電池の製造方法であって、
前記集電端子は銅製であり、かつ前記外部端子はアルミニウム製であり、
前記レーザ溶接を行なう領域において、前記外部端子の外表面の位置が、前記かしめ部の外表面の位置よりも高くなっており、
前記レーザ溶接において、最初に前記外部端子の外表面にレーザが照射される、
二次電池の製造方法。 A step of inserting a current collecting terminal into the through hole of the sealing lid and the through hole of the external terminal, and projecting the tip end portion of the current collecting terminal in the insertion direction from the external terminal;
Crimping the tip of the projecting current collector terminal to form a crimped portion,
Laser-welding the external terminal and the caulking portion formed on the current collecting terminal;
A method of manufacturing a secondary battery including:
The current collecting terminal is made of copper, and the external terminal is made of aluminum,
In the region where the laser welding is performed, the position of the outer surface of the external terminal is higher than the position of the outer surface of the caulked portion,
In the laser welding, the outer surface of the external terminal is first irradiated with laser,
Manufacturing method of secondary battery.
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