JP2013051113A - Copper-coated steel foil assembly and current-carrying member - Google Patents
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Abstract
Description
本発明は、複数の銅被覆鋼箔の一部分同士を束状に重ねて導電可能な状態に接合した銅被覆鋼箔集合体、およびそれを用いた蓄電デバイスの集電体に関する。また、複数の銅被覆鋼箔の一部分同士および金属板の一部分を重ねて導電可能な状態に接合した通電部材に関する。 The present invention relates to a copper-coated steel foil assembly in which a part of a plurality of copper-coated steel foils are stacked and joined in a conductive state, and a current collector of an electricity storage device using the same. The present invention also relates to a current-carrying member in which a part of a plurality of copper-coated steel foils and a part of a metal plate are overlapped and joined in a conductive state.
リチウムイオン二次電池をはじめとする蓄電デバイスでは、各セルの同極同士を並列接続することにより所定の電池性能を確保している。正極、負極それぞれにおいて活物質を担持する各導電シートは、集電体として電流を取り出す又は取り入れるために活物質を担持していない「タブ」の部分を有する。同極のタブ同士は束状に積層した状態で接合され、並列接続が実現されている。そのタブ同士の接合には一般的に超音波溶接が適用される。 In power storage devices such as lithium ion secondary batteries, predetermined battery performance is ensured by connecting the same polarity of each cell in parallel. Each conductive sheet carrying the active material in each of the positive electrode and the negative electrode has a “tab” portion that does not carry the active material in order to take out or take in an electric current as a current collector. The tabs of the same polarity are joined together in a stacked state, and a parallel connection is realized. In general, ultrasonic welding is applied to the tabs.
近年、蓄電デバイスには蓄電容量増大の要求が強くなっている。活物質の種類または活物質層の密度若しくは塗布厚さを変更することなく、電極面積を同等程度に保ったまま蓄電容量を増大させるためには、電極の積層枚数を増やすことが必要となる。電極の積層枚数を増やと、必然的にタブの部分で接合する導電シートの枚数が増大する。しかし、タブの部分での接合枚数を大幅に増大させることは必ずしも容易ではない。 In recent years, there has been a strong demand for power storage devices to increase power storage capacity. In order to increase the storage capacity while maintaining the same electrode area without changing the type of active material or the density or coating thickness of the active material layer, it is necessary to increase the number of stacked electrodes. Increasing the number of stacked electrodes inevitably increases the number of conductive sheets joined at the tab portion. However, it is not always easy to greatly increase the number of sheets to be joined at the tab portion.
リチウムイオン二次電池を例にとると、一般的に正極ではアルミニウム箔のシート、負極では銅箔のシートがそれぞれ使用される。アルミニウム箔のシートは超音波溶接性が良好であることから枚数の増大は比較的容易であり、例えば２０μｍ厚さのアルミニウム箔で６０枚以上の接合が可能であるとされる。しかしながら銅箔のシートは超音波溶接性がアルミニウムより劣り、例えば１０μｍ厚さの銅箔では接合の安定性等を考慮すると４０枚程度が限度とされる。このため、銅箔の接合枚数を増大させることができればリチウムイオン二次電池やリチウムイオンキャパシタの蓄電容量を大幅に増大させることが可能となる。 Taking a lithium ion secondary battery as an example, a sheet of aluminum foil is generally used for the positive electrode and a sheet of copper foil is used for the negative electrode. Since the aluminum foil sheet has good ultrasonic weldability, it is relatively easy to increase the number of sheets. For example, it is possible to join more than 60 sheets of aluminum foil having a thickness of 20 μm. However, the ultrasonic weldability of the copper foil sheet is inferior to that of aluminum. For example, a copper foil having a thickness of 10 μm is limited to about 40 sheets in consideration of the stability of bonding. For this reason, if the number of bonded copper foils can be increased, the storage capacity of the lithium ion secondary battery or lithium ion capacitor can be greatly increased.
多数枚の銅箔を積層して導電可能な状態で（すなわち絶縁性の接着剤等を介さずに）接合する手法としては、超音波溶接の他に、スポット溶接やシーム溶接に代表される「抵抗溶接」が挙げられる（特許文献１）。しかしながら、銅は電気抵抗が小さいため抵抗加熱によって昇温するには多大な電流を必要とする。このため銅箔は本質的に抵抗溶接性があまりよくない。また、蓄電デバイスの集電体用途では、銅の高い熱伝導性が抵抗溶接の際に問題を引き起こす要因となりやすい。すなわち、集電体のシート表面には活物質が担持され活物質層が形成されているが、通常、タブ部分での接合は、活物質を既に担持した状態で行われる。銅箔の接合枚数を増大させるためには、抵抗溶接の入熱もそれに伴って増大させる必要があるが、その際、銅の高い熱伝導性によって活物質層の温度が過度に上昇し、活物質層を構成する各種材料（活物質、導電助剤、バインダなど）の劣化を招く恐れがある。例えば、活物質自体の変質による蓄電性能の低下や、バインダの変質に起因した活物質層の密着性低下による電池寿命の低下が生じると考えられる。 As a technique for laminating a large number of copper foils and joining them in a conductive state (that is, without using an insulating adhesive or the like), in addition to ultrasonic welding, representative techniques include spot welding and seam welding. Resistance welding "(Patent Document 1). However, since copper has a small electrical resistance, a large amount of current is required to raise the temperature by resistance heating. For this reason, copper foil is inherently not very good in resistance weldability. Moreover, in the collector use of an electrical storage device, the high thermal conductivity of copper tends to cause a problem during resistance welding. That is, the active material is supported on the surface of the current collector sheet to form an active material layer, but the joining at the tab portion is usually performed in a state where the active material is already supported. In order to increase the number of copper foils to be joined, it is necessary to increase the heat input of resistance welding accordingly. At this time, the temperature of the active material layer rises excessively due to the high thermal conductivity of copper, and active heat is applied. There is a risk of deteriorating various materials (active material, conductive assistant, binder, etc.) constituting the material layer. For example, it is considered that a decrease in power storage performance due to the deterioration of the active material itself or a decrease in battery life due to a decrease in the adhesion of the active material layer due to the deterioration of the binder occurs.
このように、超音波溶接および抵抗溶接のいずれの手段を用いた場合でも、銅箔からなる集電体の積層枚数を従来よりも大幅に増大させることは容易でない。 As described above, it is not easy to significantly increase the number of stacked current collectors made of copper foil as compared with the conventional method, regardless of whether ultrasonic welding or resistance welding is used.
金属箔同士を積層して接合する抵抗溶接法においては、局部的に十分な大きさの溶接電流を集中させるための手段として、重ねて接合する金属板（タブリード）に突起を設けたり、金属箔表面の接合箇所の近傍を絶縁体で被覆したりする手法が提案されている（特許文献２、３）。これらの手法によれば、従来一般的な抵抗溶接に比べ金属箔の積層枚数を増大させることが可能になると考えられる。しかし、これらの手法はタブリードの形状や作業手順に対する制約が大きく、必ずしも汎用的であるとはいえない。また、銅箔を使用する場合には、積層枚数を増大させた場合に特に懸念される活物質温度上昇による蓄電性能低下の問題は解消されない。 In the resistance welding method in which metal foils are laminated and joined, as a means for concentrating a sufficiently large welding current locally, protrusions are provided on metal plates (tab leads) to be joined together, metal foils There has been proposed a technique in which the vicinity of the surface joining portion is covered with an insulator (Patent Documents 2 and 3). According to these methods, it is considered that the number of laminated metal foils can be increased as compared with conventional resistance welding. However, these methods have great restrictions on the tab lead shape and work procedure, and are not necessarily general-purpose. Moreover, when using copper foil, the problem of the electrical storage performance fall by the active material temperature rise especially worried when the number of lamination | stacking is increased is not solved.
本発明は、熱伝導性が銅箔よりも低く、かつリチウムイオン二次電池やリチウムイオンキャパシタの負極活物質を担持することが可能な金属箔を用いて、金属箔の接合枚数の増大に対応できる技術を提供しようというものである。 The present invention uses a metal foil that has a lower thermal conductivity than a copper foil and can support a negative electrode active material of a lithium ion secondary battery or a lithium ion capacitor, and supports an increase in the number of bonded metal foils. It is to provide technology that can be used.
上記目的は、金属箔として銅被覆鋼箔を用い、これら抵抗加熱して接合することによって達成される。
すなわち本発明では、鋼からなる芯材の両側表面に銅被覆層をもつ複数の銅被覆鋼箔の一部分同士を積層して抵抗加熱により一体化した銅被覆鋼箔集合体であって、各銅被覆鋼箔は下記（Ａ）〜（Ｃ）の要件を満たすものであり、前記の積層した部分において隣り合う芯材が銅融着層を介して接合している銅被覆鋼箔集合体が提供される。
（Ａ）銅被覆層を含めた両表面間の平均厚さｔが３〜１００μｍ、
（Ｂ）芯材の平均厚さをｔSとするとき、ｔS／ｔ≧０.４、
（Ｃ）銅被覆層の片面当たりの平均厚さｔCuがいずれの側も０.０２μｍ以上。
The above object is achieved by using copper-coated steel foil as the metal foil and joining by heating with resistance.
That is, in the present invention, a copper-coated steel foil assembly in which a part of a plurality of copper-coated steel foils having a copper coating layer on both surfaces of a steel core is laminated and integrated by resistance heating, The coated steel foil satisfies the following requirements (A) to (C), and a copper-coated steel foil aggregate in which adjacent core members are bonded via a copper fusion layer in the laminated portion is provided. Is done.
(A) The average thickness t between both surfaces including the copper coating layer is 3 to 100 μm,
(B) When the average thickness of the core material is t S , t S /t≧0.4,
(C) The average thickness t Cu per side of the copper coating layer is 0.02 μm or more on either side.
この銅被覆鋼箔集合体は、リチウムイオン二次電池の負極集電体をはじめとする蓄電デバイスの集電体を構成することができるものである。 This copper-coated steel foil aggregate can constitute a current collector of an electricity storage device including a negative electrode current collector of a lithium ion secondary battery.
また本発明では、鋼からなる芯材の両側表面に銅被覆層をもつ複数の銅被覆鋼箔と、金属板を、それぞれの一部分同士が積層する状態として抵抗加熱により一体化した通電部材であって、各銅被覆鋼箔は前記（Ａ）〜（Ｃ）の要件を満たすものであり、前記の積層した部分において隣り合う芯材および芯材と金属板が銅融着層を介して接合している通電部材が提供される。 Further, in the present invention, there is provided a current-carrying member in which a plurality of copper-coated steel foils having a copper coating layer on both side surfaces of a steel core and a metal plate are integrated by resistance heating in a state in which a part of each is laminated. Each copper-coated steel foil satisfies the requirements (A) to (C) described above, and the adjacent core material and the core material and the metal plate are joined to each other through the copper fusion layer in the laminated portion. An energizing member is provided.
上記の通電部材は、銅被覆鋼箔の部分がリチウムイオン二次電池の負極集電体をはじめとする蓄電デバイスの集電体を構成する通電部材として適用することができる。その場合、上記金属板は負極集電体のタブと接続される「タブリード」として機能する。タブリードに適した金属板としては、銅または銅合金からなる「銅系金属板」、ステンレス鋼板、ニッケル板、ニッケルめっきを施した銅系金属板やステンレス鋼板などが挙げられる。 The current-carrying member can be applied as a current-carrying member in which a copper-coated steel foil portion constitutes a current collector of an electricity storage device including a negative electrode current collector of a lithium ion secondary battery. In this case, the metal plate functions as a “tab lead” connected to the tab of the negative electrode current collector. Examples of the metal plate suitable for the tab lead include a “copper-based metal plate” made of copper or a copper alloy, a stainless steel plate, a nickel plate, a nickel-plated copper-based metal plate or a stainless steel plate.
ここで、「銅融着層」とは、銅被覆層同士の接触部においては、抵抗加熱の入熱によって双方の銅被覆層の厚さ方向の一部または全部が溶融したのち凝固して出来た層である。銅被覆層と金属板の接触部においては、抵抗加熱の入熱によって銅被覆層と金属板の厚さ方向の一部または全部が溶融したのち凝固して出来た層である。 Here, the “copper fusion layer” is formed at the contact portion between the copper coating layers by solidifying after part or all of the thickness of both copper coating layers is melted by heat input of resistance heating. Layer. The contact portion between the copper coating layer and the metal plate is a layer formed by solidification after part or all of the copper coating layer and the metal plate in the thickness direction is melted by heat input by resistance heating.
本発明によれば、従来、超音波溶接では接合できなかった多数枚の負極集電体用金属箔を接合することができる。また、銅箔の抵抗溶接では活物質の温度上昇が問題となって積層枚数の増大に対応できなかったところ、銅被覆鋼箔を用いる本発明では活物質の過度な温度上昇を招くことなく、積層枚数の増大が図れる。したがって本発明は、銅系の集電体を並列接続することによって構築されるリチウムイオン二次電池やリチウムイオンキャパシタなどの蓄電デバイスにおいて、その蓄電容量の増大に寄与するものである。 ADVANTAGE OF THE INVENTION According to this invention, the metal foil for negative electrode collectors which was not able to be joined conventionally by ultrasonic welding can be joined. In addition, in resistance welding of copper foil, the temperature rise of the active material was a problem and could not cope with the increase in the number of laminated layers, in the present invention using the copper-coated steel foil, without causing an excessive temperature rise of the active material, The number of stacked layers can be increased. Therefore, the present invention contributes to an increase in the storage capacity of an electricity storage device such as a lithium ion secondary battery or a lithium ion capacitor constructed by connecting copper-based current collectors in parallel.
図１に、銅箔を積層してスポット溶接機により接合を試みた抵抗加熱部断面の光学顕微鏡写真を例示する。厚さ２０μｍの銅箔２０枚を重ねて、電流６ｋＡにて接合を試みた例である。（ａ）は接合部全体を含む領域の断面、（ｂ）は（ａ）の一部を拡大観察したものである。この例の条件では抵抗加熱部での発熱が不足したものと考えられ、積層した銅箔束の外層付近を構成する銅箔が十分に接合されていない。なお、この程度の積層数の銅箔束であれば、溶接電流を更に増大させて発熱量の増大を図ることによって健全なスポット溶接部を得ることは可能である。しかし、蓄電デバイスの集電体として使用する場合は前述のように活物質層への熱影響が懸念されることから、発熱量の増大は好ましくない。 FIG. 1 illustrates an optical micrograph of a cross section of a resistance heating portion in which copper foils are stacked and attempted to be joined by a spot welder. This is an example in which 20 copper foils having a thickness of 20 μm are stacked and bonding is attempted at a current of 6 kA. (A) is a cross section of the region including the entire joint, and (b) is an enlarged view of a part of (a). Under the conditions of this example, it is considered that the heat generation in the resistance heating portion is insufficient, and the copper foil constituting the vicinity of the outer layer of the laminated copper foil bundle is not sufficiently joined. If the number of laminated copper foil bundles is about this, it is possible to obtain a healthy spot welded portion by further increasing the welding current and increasing the heat generation amount. However, when used as a current collector for an electricity storage device, there is a concern about the thermal effect on the active material layer as described above, and thus an increase in the amount of heat generation is not preferable.
図２に、本発明対象の銅被覆鋼箔を積層してスポット溶接機により接合を試みた抵抗加熱部断面の光学顕微鏡写真を例示する。この銅被覆鋼箔は普通鋼冷延鋼板を芯材としてその両側表面に電気銅めっきによる銅被覆層を有するものであり、銅被覆層を含めた両表面間の平均厚さｔは２０μｍ、銅被覆層の片面当たりの平均厚さは０.１μｍである。図１の場合と同様に積層枚数２０枚、電流６ｋＡにて接合を試みた。（ａ）は接合部全体を含む領域の断面、（ｂ）は（ａ）の一部を拡大観察したものである。図１の銅箔を使用した例と比較すると、銅被覆鋼箔を使用した場合には同じ電流値でも接合部の領域が拡大している。積層した銅被覆鋼箔束を構成する全ての銅被覆鋼箔が接合され一体化している。接合部を観察すると、各芯材間には双方の銅被覆層に由来する単一の銅層が介在している。この単一の銅層は、双方の銅被覆層の厚さ方向の一部または全部が溶融したのち凝固することにより形成されたものである。すなわち、抵抗加熱によって隣り合う芯材同士が銅融着層を介して接合することにより、各銅被覆鋼箔が一体化している。 In FIG. 2, the optical microscope photograph of the resistance heating part cross section which laminated | stacked the copper covering steel foil of this invention object, and tried joining with the spot welder is illustrated. This copper clad steel foil has a copper clad layer formed by electrolytic copper plating on both surfaces of a plain steel cold-rolled steel plate as the core material. The average thickness t between both surfaces including the copper clad layer is 20 μm, copper The average thickness per one side of the coating layer is 0.1 μm. As in the case of FIG. 1, joining was attempted with 20 stacked sheets and a current of 6 kA. (A) is a cross section of the region including the entire joint, and (b) is an enlarged view of a part of (a). Compared with the example using the copper foil of FIG. 1, when the copper-coated steel foil is used, the region of the joint is enlarged even with the same current value. All the copper-coated steel foils constituting the laminated copper-coated steel foil bundle are joined and integrated. When the joint portion is observed, a single copper layer derived from both copper coating layers is interposed between the core members. This single copper layer is formed by solidifying after a part or all of the thickness direction of both copper coating layers melts. That is, each copper covering steel foil is integrated by joining adjacent core materials through a copper fusion layer by resistance heating.
〔芯材〕
銅被覆鋼箔の芯材は、従来の銅箔との対比において、（i）強度向上、（ii）電気抵抗の増大、（iii）熱伝導性の低減、を担う部材である。
（i）強度向上；
箔の強度が向上すると、活物質層を担持させる際のロールプレスで従来より高い圧下力を付与しても箔の塑性変形による形状不良（中伸びなど）が防止される。ロールプレスでの圧下力を増大させると、活物質層の密度を高めることができる。その結果、蓄電デバイスの単位体積当たりの放電容量を増大させることが可能となる。また箔の強度向上は、それを用いた蓄電デバイスの耐久性向上にも寄与する。
[Core]
The core material of the copper-coated steel foil is a member responsible for (i) improvement in strength, (ii) increase in electrical resistance, and (iii) reduction in thermal conductivity in comparison with a conventional copper foil.
(I) Strength improvement;
When the strength of the foil is improved, shape defects (such as medium elongation) due to plastic deformation of the foil are prevented even when a higher pressing force is applied by a roll press when supporting the active material layer. When the rolling force in the roll press is increased, the density of the active material layer can be increased. As a result, the discharge capacity per unit volume of the electricity storage device can be increased. Moreover, the strength improvement of foil contributes also to the durability improvement of the electrical storage device using the foil.
（ii）電気抵抗の増大；
箔の電気抵抗が増大すると、同じ電流値で抵抗加熱を行った場合に、より大きい発熱量を得ることができる。図２の銅被覆鋼箔束の方が、図１の銅箔束よりも良好な接合性を呈するのは、銅被覆鋼箔の芯材による電気抵抗の増大作用によるところが大きい。なお、蓄電デバイスの集電体として使用する際には、芯材による電気抵抗の増大は実用上の弊害となる程ではない。むしろ、活物質密度の向上（前述）や活物質構成材料の劣化防止（後述）による蓄電デバイスの性能向上効果の方がメリットが大きい。
(Ii) increased electrical resistance;
When the electrical resistance of the foil is increased, a larger amount of heat can be obtained when resistance heating is performed with the same current value. The reason why the copper-coated steel foil bundle of FIG. 2 exhibits better bondability than the copper foil bundle of FIG. 1 is largely due to the effect of increasing the electrical resistance by the core material of the copper-coated steel foil. When used as a current collector for an electricity storage device, an increase in electrical resistance due to the core material is not a practical problem. Rather, the merit of improving the performance of the electricity storage device by improving the active material density (described above) and preventing the deterioration of the active material constituent material (described later) is greater.
（iii）熱伝導性の低減；
芯材の熱伝導性が低減することにより、活物質を担持した状態で抵抗加熱による接合を行う際には活物質層に伝わる熱量を抑制することができ、活物質構成材料（活物質、導電助剤、バインダなど）の劣化を回避しやすくなる。
(Iii) reduction of thermal conductivity;
When the thermal conductivity of the core material is reduced, the amount of heat transmitted to the active material layer can be suppressed when joining by resistance heating in a state where the active material is supported, and the active material constituent material (active material, conductive material) It is easy to avoid deterioration of auxiliary agents, binders, etc.).
銅被覆鋼箔の芯材に使用する鋼としては、（１）普通鋼、（２）フェライト系ステンレス鋼、（３）オーステナイト系ステンレス鋼、などが使用できる。規格製品としては、普通鋼の場合、例えばＪＩＳ Ｇ３１４１：２００９に規定される冷延鋼板（鋼帯を含む）を素材とするものが適用できる。また、ステンレス鋼の場合、例えばＪＩＳ Ｇ４３０５：２００５に規定されるフェライト系またはオーステナイト系の化学組成を有する鋼板（鋼帯を含む）が適用できる。 As steel used for the core material of the copper-coated steel foil, (1) ordinary steel, (2) ferritic stainless steel, (3) austenitic stainless steel, and the like can be used. As a standard product, in the case of plain steel, for example, a material made of a cold-rolled steel sheet (including a steel strip) defined in JIS G3141: 2009 can be applied. In the case of stainless steel, for example, a steel plate (including a steel strip) having a ferritic or austenitic chemical composition defined in JIS G4305: 2005 can be applied.
芯材に適用できる普通鋼、フェライト系ステンレス鋼、オーステナイト系ステンレス鋼の具体的な成分組成を以下に例示する。
（１）普通鋼
質量％で、Ｃ：０.００１〜０.１５％、Ｓｉ：０.００１〜０.１％、Ｍｎ：０.００５〜０.６％、Ｐ：０.００１〜０.０５％、Ｓ：０.００１〜０.５％、Ａｌ：０.００１〜０.５％、Ｎｉ：０.００１〜１.０％、Ｃｒ：０.００１〜１.０％、Ｃｕ：０〜０.１％、Ｔｉ：０〜０.５％、Ｎｂ：０〜０.５％、Ｎ：０〜０.０５％、残部Ｆｅおよび不可避的不純物。
Specific component compositions of ordinary steel, ferritic stainless steel, and austenitic stainless steel that can be applied to the core are illustrated below.
(1) Normal steel In mass%, C: 0.001 to 0.15%, Si: 0.001 to 0.1%, Mn: 0.005 to 0.6%, P: 0.001 to 0.00. 05%, S: 0.001 to 0.5%, Al: 0.001 to 0.5%, Ni: 0.001 to 1.0%, Cr: 0.001 to 1.0%, Cu: 0 -0.1%, Ti: 0-0.5%, Nb: 0-0.5%, N: 0-0.05%, balance Fe and inevitable impurities.
（２）フェライト系ステンレス鋼
質量％で、Ｃ：０.０００１〜０.１５％、Ｓｉ：０.００１〜１.２％、Ｍｎ：０.００１〜１.２％、Ｐ：０.００１〜０.０４％、Ｓ：０.０００５〜０.０３％、Ｎｉ：０〜０.６％、Ｃｒ：１１.５〜３２.０％、Ｍｏ：０〜２.５％、Ｃｕ：０〜１.０％、Ｎｂ：０〜１.０％、Ｔｉ：０〜１.０％、Ａｌ：０〜０.２％、Ｎ：０〜０.０２５％、Ｂ：０〜０.０１％、Ｖ：０〜０.５％、Ｗ：０〜０.３％、Ｃａ、Ｍｇ、Ｙ、ＲＥＭ（希土類元素）の合計：０〜０.１％、残部Ｆｅおよび不可避的不純物。
(2) Ferritic stainless steel In mass%, C: 0.0001 to 0.15%, Si: 0.001 to 1.2%, Mn: 0.001 to 1.2%, P: 0.001 0.04%, S: 0.0005 to 0.03%, Ni: 0 to 0.6%, Cr: 11.5 to 32.0%, Mo: 0 to 2.5%, Cu: 0 to 1 0.0%, Nb: 0 to 1.0%, Ti: 0 to 1.0%, Al: 0 to 0.2%, N: 0 to 0.025%, B: 0 to 0.01%, V : 0-0.5%, W: 0-0.3%, Ca, Mg, Y, REM (rare earth elements) total: 0-0.1%, the balance Fe and inevitable impurities.
（３）オーステナイト系ステンレス鋼
質量％で、Ｃ：０.０００１〜０.１５％、Ｓｉ：０.００１〜４.０％、Ｍｎ：０.００１〜２.５％、Ｐ：０.００１〜０.０４５％、Ｓ：０.０００５〜０.０３％、Ｎｉ：６.０〜２８.０％、Ｃｒ：１５.０〜２６.０％、Ｍｏ：０〜７.０％、Ｃｕ：０〜３.５％、Ｎｂ：０〜１.０％、Ｔｉ：０〜１.０％、Ａｌ：０〜０.１％、Ｎ：０〜０.３％、Ｂ：０〜０.０１％、Ｖ：０〜０.５％、Ｗ：０〜０.３％、Ｃａ、Ｍｇ、Ｙ、ＲＥＭ（希土類元素）の合計：０〜０.１％、残部Ｆｅおよび不可避的不純物。
ここで、下限が０％である元素は任意元素である。
(3) Austenitic stainless steel in mass%, C: 0.0001 to 0.15%, Si: 0.001 to 4.0%, Mn: 0.001 to 2.5%, P: 0.001 0.045%, S: 0.0005 to 0.03%, Ni: 6.0 to 28.0%, Cr: 15.0 to 26.0%, Mo: 0 to 7.0%, Cu: 0 -3.5%, Nb: 0-1.0%, Ti: 0-1.0%, Al: 0-0.1%, N: 0-0.3%, B: 0-0.01% , V: 0 to 0.5%, W: 0 to 0.3%, Ca, Mg, Y, REM (rare earth elements) total: 0 to 0.1%, remaining Fe and inevitable impurities.
Here, the element whose lower limit is 0% is an arbitrary element.
〔銅被覆層〕
銅被覆層は、従来から蓄電デバイスの集電体に使用されている銅箔と同等の性質を有する表面を構成する役割を担う。また、銅被覆鋼箔の束を抵抗加熱により一体化させるに際し、銅融着層を形成して隣り合う箔同士を接合させる作用を担う。抵抗加熱の条件によって銅被覆層が厚さ全体にわたって溶融する場合は、鋼シートの間に挿入された銅のインサート材（ろう材）と同様の機能を発揮する。銅被覆鋼箔と金属板との接合部を有する通電部材を抵抗加熱によって製造する際には、その接合部においても銅被覆層は上記と同様の銅融着層を形成する作用を担う。
(Copper coating layer)
A copper coating layer plays the role which comprises the surface which has the property equivalent to the copper foil conventionally used for the electrical power collector of an electrical storage device. Moreover, when integrating the bundle | flux of copper covering steel foil by resistance heating, it bears the effect | action which forms a copper fusion | melting layer and joins adjacent foils. When the copper coating layer melts over the entire thickness due to the resistance heating condition, it exhibits the same function as the copper insert material (brazing material) inserted between the steel sheets. When the current-carrying member having a joint between the copper-coated steel foil and the metal plate is manufactured by resistance heating, the copper coating layer also serves to form a copper fusion layer similar to the above in the joint.
銅被覆層の形成手法としては、芯材となる鋼板の表面に電気銅めっきを施す手法が採用できる。また、鋼板と銅箔をクラッド接合することによっても銅被覆層を形成させることができる。一般的にはこれらの手法により銅被覆層を形成した鋼板を圧延することによって銅被覆鋼箔を得ることができるが、既に箔にまで圧延された鋼箔を用意し、その表面に電気銅めっきを施す手法を採用してもよい。なお、電気銅めっき法による場合は、めっき原板として、予め下地めっきを施した鋼板または鋼箔を使用してもよい。例えば芯材の鋼種がステンレス鋼である場合には、下地にＮｉストライクめっきを施した鋼板をめっき原板として使用することが銅めっき密着性を向上させる上で有利となる。 As a method for forming the copper coating layer, a method of applying electrolytic copper plating to the surface of the steel plate serving as the core material can be employed. Moreover, a copper coating layer can be formed also by clad joining a steel plate and copper foil. Generally, a copper-coated steel foil can be obtained by rolling a steel sheet with a copper coating layer formed by these methods. However, a steel foil that has already been rolled into a foil is prepared, and the surface thereof is electro-copper-plated. You may employ | adopt the method of giving. In the case of using the electrolytic copper plating method, a steel plate or steel foil that has been previously plated may be used as a plating original plate. For example, when the steel type of the core material is stainless steel, it is advantageous to improve the copper plating adhesion by using a steel plate with Ni strike plating on the base as a plating base plate.
〔銅被覆鋼箔〕
本発明で対象とする銅被覆鋼箔は、断面構造に関し下記（Ａ）〜（Ｃ）の規定を満たすことが重要である。
（Ａ）銅被覆層を含めた両表面間の平均厚さｔが３〜１００μｍ
銅被覆鋼箔の平均厚さｔが３μｍより小さくなると、芯材に強度の高い鋼種を採用したとしても、集電体としての強度を十分に確保することが難しくなる。５μｍ以上、あるいは７μｍ以上の範囲に管理してもよい。一方、ｔが１００μｍを超えると、蓄電デバイスの小型・大容量化の要求に合致しなくなる。一般的には５０μｍ以下の範囲とすることが好適であり、２５μｍ以下、あるいは１５μｍ以下に管理してもよい。
[Copper coated steel foil]
It is important that the copper-coated steel foil that is the subject of the present invention satisfies the following provisions (A) to (C) regarding the cross-sectional structure.
(A) The average thickness t between both surfaces including the copper coating layer is 3 to 100 μm.
When the average thickness t of the copper-coated steel foil is smaller than 3 μm, it is difficult to ensure sufficient strength as a current collector even if a high-strength steel type is adopted as the core material. You may manage in the range of 5 micrometers or more, or 7 micrometers or more. On the other hand, when t exceeds 100 μm, it does not meet the demand for miniaturization and large capacity of the electricity storage device. In general, the range is preferably 50 μm or less, and may be controlled to 25 μm or less, or 15 μm or less.
（Ｂ）芯材の平均厚さをｔSとするとき、ｔS／ｔ≧０.４
鋼からなる芯材は、上述のように従来の銅箔との対比において（i）強度向上、（ii）電気抵抗の増大、（iii）熱伝導性の低減、の各機能を発揮する。これらの機能を十分に発揮させるには銅被覆鋼箔の平均厚さｔに占める芯材の平均厚さｔSの割合をある程度以上確保する必要がある。種々検討の結果、ｔS／ｔ≧０.４を満たす銅被覆鋼箔を適用することにより、従来の銅箔では実現困難であった積層厚さの集電体を抵抗加熱によって効率的に実現することが可能となる。ｔS／ｔ≧０.５あるいはｔS／ｔ＞０.５に管理してもよい。さらに、ｔS／ｔ≧０.７あるいはｔS／ｔ＞０.７に管理してもよい。銅被覆鋼箔の平均厚さｔが前述（Ａ）の規定を満たし、且つ銅被覆層の平均厚さが後述（Ｃ）の規定を満たす限り、ｔS／ｔの上限は特に規定しなくてもよいが、通常、ｔS／ｔ≦０.９９８の範囲で設定することができる。
(B) When the average thickness of the core material is t S , t S /t≧0.4
As described above, the core material made of steel exhibits the functions of (i) improving strength, (ii) increasing electrical resistance, and (iii) reducing thermal conductivity in comparison with conventional copper foils. In order to sufficiently exhibit these functions, it is necessary to secure a ratio of the average thickness t S of the core material to the average thickness t of the copper-coated steel foil to a certain extent. As a result of various studies, by applying a copper-coated steel foil that satisfies t S /t≧0.4, a current collector with a laminated thickness that was difficult to achieve with conventional copper foils is efficiently realized by resistance heating. It becomes possible to do. It may be managed such that t S /t≧0.5 or t S /t>0.5. Furthermore, it may be managed such that t S /t≧0.7 or t S /t>0.7. As long as the average thickness t of the copper-coated steel foil satisfies the above-mentioned definition (A) and the average thickness of the copper-coated layer satisfies the following definition (C), the upper limit of t S / t is not particularly specified. However, it can usually be set in the range of t S /t≦0.998.
（Ｃ）銅被覆層の片面当たりの平均厚さｔCuがいずれの側も０.０２μｍ以上
銅被覆層は、上述のように銅箔と同等の性質を有する表面を構成する機能を有する。また、銅被覆鋼箔同士あるいは銅被覆銅箔と金属板を抵抗加熱により接合させるに際し銅融着層を形成する機能を担う。発明者らの検討によれば、これらの機能を十分に発揮させるためには片面当たりの銅被覆層の平均厚さｔCuを０.０２μｍ以上とする必要がある。それより薄いと銅融着層による接合性が低下しやすくなる。片面当たりの銅被覆層の平均厚さｔCuは０.０５μｍ以上とすることがより好ましく、０.１０μｍ以上に管理してもよい。上述（Ｂ）の規定を満たしていれば、ｔCuの上限は特に規定しなくてもよいが、通常、５.０μｍ以下の範囲とすることができる。
(C) The average thickness t Cu per side of the copper coating layer is 0.02 μm or more on either side. The copper coating layer has a function of constituting a surface having properties equivalent to those of the copper foil as described above. Moreover, when joining copper covering steel foils or copper covering copper foil and a metal plate by resistance heating, it bears the function to form a copper fusion | melting layer. According to the study by the inventors, in order to sufficiently exhibit these functions, the average thickness t Cu of the copper coating layer per side needs to be 0.02 μm or more. If it is thinner than that, the bondability due to the copper fusion layer tends to deteriorate. The average thickness t Cu of the copper coating layer per side is more preferably 0.05 μm or more, and may be controlled to 0.10 μm or more. The upper limit of t Cu does not need to be specified as long as it satisfies the above-mentioned provision (B), but can usually be in the range of 5.0 μm or less.
〔銅被覆鋼箔集合体〕
上記の規定を満たす複数の銅被覆鋼箔の一部分同士を積層して抵抗加熱によって一体化した銅被覆鋼箔集合体は、図２に示されるように隣り合う芯材同士が銅融着層によって接合された接合構造を有し、各芯材間の密着性は良好である。抵抗加熱に用いる装置としては、電極間に被接合材料を挟んで加圧しながら通電することができる装置が好適である。例えば、スポット溶接機やシーム溶接機を利用することができる。
[Copper-coated steel foil assembly]
The copper-coated steel foil aggregate obtained by laminating a part of a plurality of copper-coated steel foils satisfying the above requirements and integrated by resistance heating has an adjacent core material formed by a copper fusion layer as shown in FIG. It has a joined structure and has good adhesion between the core materials. As an apparatus used for resistance heating, an apparatus that can be energized while being pressed with a material to be bonded sandwiched between electrodes is suitable. For example, a spot welder or a seam welder can be used.
このように一部分で一体化した束状の銅被覆鋼箔集合体は、蓄電デバイスの集電体として活用できる。リチウムイオン二次電池の負極集電体がその代表例である。その場合、銅被覆鋼箔集合体（箔の束）を構成する各銅被覆鋼箔は、接合部近傍を除いた大部分が蓄電デバイスのセル内に配置され、電極を構成する。電極を構成する部分の銅被覆鋼箔表面には活物質が担持される。リチウムイオン二次電池の負極活物質としてはグラファイト、ハードカーボン等の炭素系物質や、Ｓｉ、Ｓｎ等を主成分に持ちＬｉと合金を形成する合金系活物質が挙げられる。 The bundle-like copper-coated steel foil aggregate integrated in part in this way can be used as a current collector of an electricity storage device. A typical example is a negative electrode current collector of a lithium ion secondary battery. In that case, most of the copper-coated steel foils constituting the copper-coated steel foil aggregate (a bundle of foils) are arranged in the cells of the electricity storage device except for the vicinity of the joints, and constitute electrodes. An active material is supported on the surface of the copper-coated steel foil constituting the electrode. Examples of the negative electrode active material of the lithium ion secondary battery include carbon-based materials such as graphite and hard carbon, and alloy-based active materials that have Si, Sn, etc. as a main component and form an alloy with Li.
活物質は通常、集電体として束状に一体化する前の段階で、素材である金属箔の表面に担持される。抵抗加熱により付与された熱は金属箔を伝わってその表面に担持されている活物質の温度を上昇させる要因となる。過度の温度上昇は活物質を劣化させ、蓄電デバイスの充放電性能に悪影響を及ぼす。従来の銅箔を使用した集電体の場合、素材の銅が高い熱伝導性を有するため、積層部分を抵抗加熱で一体化させる際に活物質を担持した部分へと熱が伝わりやすい。一方、積層枚数を増大させるためには入熱量をより増大させる必要があるが、銅箔同士の積層部分では上記の伝熱により熱が奪われやすいので、入熱量をかなり増大させないと良好な接合ができない。入熱量の大幅な増大は活物質の劣化を助長する要因となる。他方、銅箔は超音波接合性もあまり良好ではない。このようなことから、銅箔を用いた集電体では積層枚数を増大することが難しい。 The active material is usually carried on the surface of the metal foil that is a raw material before it is integrated into a bundle as a current collector. The heat imparted by resistance heating is transmitted through the metal foil and causes the temperature of the active material carried on the surface to rise. An excessive temperature rise degrades the active material and adversely affects the charge / discharge performance of the electricity storage device. In the case of a current collector using a conventional copper foil, since the raw material copper has high thermal conductivity, heat is easily transmitted to the portion carrying the active material when the laminated portion is integrated by resistance heating. On the other hand, in order to increase the number of laminated layers, it is necessary to increase the amount of heat input. However, since heat is easily lost due to the heat transfer in the laminated portions of copper foils, good bonding is required unless the amount of heat input is significantly increased. I can't. A large increase in the amount of heat input becomes a factor that promotes deterioration of the active material. On the other hand, the copper foil is not so good in ultrasonic bondability. For this reason, it is difficult to increase the number of stacked layers with a current collector using copper foil.
これに対し、本発明に従う銅被覆鋼箔を用いた集電体では、芯材である鋼の熱伝導性が銅よりも小さいことから、積層部分での発熱量が同じであれば活物質の温度上昇は銅箔を用いた従来の集電体よりも抑制される。しかも積層部分においては、芯材の鋼の電気抵抗が高いので、抵抗加熱の電流を従来より低減しても接合に必要な発熱量を確保することが容易となり、抵抗加熱を付与する積層部分のトータル厚さは０.１〜１.０ｍｍ程度とすることができる。したがって、銅被覆鋼箔を用いると従来よりも積層枚数を増大させることが可能となり、蓄電デバイスの容量増大に対応できる。 On the other hand, in the current collector using the copper-coated steel foil according to the present invention, the thermal conductivity of steel as the core material is smaller than that of copper. The temperature rise is suppressed more than a conventional current collector using a copper foil. In addition, since the electrical resistance of the core steel is high in the laminated portion, it becomes easy to secure the heat generation necessary for bonding even if the resistance heating current is reduced compared to the conventional method, and the laminated portion that imparts resistance heating. The total thickness can be about 0.1 to 1.0 mm. Therefore, when the copper-coated steel foil is used, it is possible to increase the number of laminated layers as compared with the conventional case, and it is possible to cope with an increase in the capacity of the electricity storage device.
具体的には、従来の銅箔を用いた集電体の場合、例えば厚さ１０μｍの銅箔では超音波溶接で一体化できる積層枚数は高々４０枚程度であり、抵抗加熱では活物質構成材料の熱劣化を回避するために入熱が制限されることから、やはり４０枚程度が実用的な限度と考えられる。一方、本発明に従う銅被覆鋼箔を用いた場合は、抵抗加熱によって上記と同等厚さの銅被覆鋼箔を８０枚程度、あるいはそれより多く積層させ一体化させることが可能となる。 Specifically, in the case of a current collector using a conventional copper foil, for example, in a copper foil having a thickness of 10 μm, the number of laminated layers that can be integrated by ultrasonic welding is about 40 at most. Since heat input is limited to avoid thermal degradation of the sheet, about 40 sheets are considered to be a practical limit. On the other hand, when the copper-coated steel foil according to the present invention is used, about 80 or more copper-coated steel foils having the same thickness as described above can be laminated and integrated by resistance heating.
〔通電部材〕
上記のような集電体は、蓄電デバイスと外部機器との間の通電を担うための導体（タブリード）を接合した状態で使用されることが想定される。そのような導体として金属板を使用する場合には、集電体を構成する複数の銅被覆鋼箔と金属板とを一緒に重ね合わせて積層部分を構成し、その積層部分で抵抗加熱によって一体化することにより通電部材を構築することができる。ここでいう通電部材は、複数の銅被覆鋼箔と金属板が銅融着層によって接合され一体化したものである。
[Conductive member]
The current collector as described above is assumed to be used in a state in which a conductor (tab lead) for carrying current between the power storage device and the external device is joined. When a metal plate is used as such a conductor, a plurality of copper-coated steel foils constituting the current collector and a metal plate are laminated together to form a laminated portion, and the laminated portion is integrated by resistance heating. By enlarging, it is possible to construct an energizing member. The current-carrying member here is one in which a plurality of copper-coated steel foils and a metal plate are joined and integrated by a copper fusion layer.
芯材用の鋼板として普通鋼、ＳＵＳ４３０、ＳＵＳ３０４の各冷延焼鈍鋼板を用意した。普通鋼は以下の化学組成を有するものである。
質量％で、Ｃ：０.００３％、Ａｌ：０.０３８％、Ｓｉ：０.００３％、Ｍｎ：０.１２％、Ｐ：０.０１２％、Ｓ：０.１２２％、Ｎｉ：０.０２％、Ｃｒ：０.０２％、Ｃｕ：０.０１％、Ｔｉ：０.０７３％、Ｎ：０.００２３％、残部Ｆｅおよび不可避的不純物。
ＳＵＳ４３０、ＳＵＳ３０４はいずれもＪＩＳ Ｇ４３０５：２００５相当の市販材である。
Common steel, SUS430, and SUS304 cold-rolled annealed steel sheets were prepared as steel sheets for the core material. Normal steel has the following chemical composition.
In mass%, C: 0.003%, Al: 0.038%, Si: 0.003%, Mn: 0.12%, P: 0.012%, S: 0.122%, Ni: 0.1. 02%, Cr: 0.02%, Cu: 0.01%, Ti: 0.073%, N: 0.0027%, balance Fe and inevitable impurities.
Both SUS430 and SUS304 are commercially available materials corresponding to JIS G4305: 2005.
下記のいずれかの方法で銅被覆鋼箔を製造した。
［１］上記普通鋼の鋼板を圧延により所定の板厚に調整し、その表面に銅ストライクめっき（下地めっき）を施したのち電気銅めっきを施し、さらに所定の厚さｔまで圧延して銅被覆鋼箔とする方法。
［２］上記ＳＵＳ４３０、ＳＵＳ３０４の鋼板を圧延により所定厚さの鋼箔とし、その表面にニッケルストライクめっき（下地めっき）を施したのち電気銅めっきを施して銅被覆鋼箔とする方法。
［３］上記普通鋼、ＳＵＳ４３０、ＳＵＳ３０４の鋼板を圧延により所定厚さの板厚に調整したのち両側表面を銅シートではさんで３層とし、クラッド圧延にて一体化する方法。
Copper-coated steel foil was produced by one of the following methods.
[1] The above-mentioned plain steel sheet is adjusted to a predetermined thickness by rolling, copper strike plating (primary plating) is applied to the surface, and then copper electroplating is performed, and further rolled to a predetermined thickness t to obtain copper. Method to make coated steel foil.
[2] A method in which the steel sheets of SUS430 and SUS304 are rolled into a steel foil having a predetermined thickness, and nickel strike plating (undercoat plating) is applied to the surface, followed by electrolytic copper plating to form a copper-coated steel foil.
[3] A method in which the steel sheets of the above-mentioned ordinary steel, SUS430, and SUS304 are adjusted to a predetermined thickness by rolling, and then both surfaces are made into three layers with a copper sheet and integrated by clad rolling.
ここで、電気銅めっきは、硫酸銅：２００〜２５０ｇ／Ｌ、硫酸：３０〜７５ｇ／Ｌ、液温：２０〜５０℃のめっき浴を用いて、陰極電流密度：１〜２０Ａ／ｄｍ2の条件範囲で行い、両面に同じ厚さの銅めっきを施した。
下地めっきである銅ストライクめっきは、ピロリン酸銅：６５〜１０５ｇ／Ｌ、ピロリン酸カリウム：２４０〜４５０ｇ／Ｌ、全銅イオン濃度（ｇ／Ｌ）に対する全ピロリン酸塩イオン濃度（ｇ／Ｌ）の比（Ｐ比）：８〜１０、アンモニア水：１〜６ｍＬ／Ｌ、液温：５０〜６０℃、ｐＨ：８.２〜９.２のめっき浴を用いて、陰極電流密度：１〜７Ａ／ｄｍ2の条件範囲で、両面均等に行った。
下地めっきであるニッケルストライクめっきは、塩化ニッケル：２３０〜２５０ｇ／Ｌ、塩酸：１２５ｍｌ／Ｌ、ｐＨ：１〜１.５の常温のめっき浴を用いて、陰極電流密度：１〜１０Ａ／ｄｍ2の条件範囲で両面均等に行った。
Here, the electrolytic copper plating is performed using a plating bath of copper sulfate: 200 to 250 g / L, sulfuric acid: 30 to 75 g / L, liquid temperature: 20 to 50 ° C., and cathode current density of 1 to 20 A / dm 2 . It carried out in the condition range, and copper plating of the same thickness was given to both surfaces.
Copper strike plating, which is the base plating, is copper pyrophosphate: 65-105 g / L, potassium pyrophosphate: 240-450 g / L, total pyrophosphate ion concentration (g / L) relative to total copper ion concentration (g / L) Ratio (P ratio): 8 to 10, ammonia water: 1 to 6 mL / L, liquid temperature: 50 to 60 ° C., pH: 8.2 to 9.2, cathode current density: 1 to It was carried out equally on both sides in the condition range of 7 A / dm 2 .
Nickel strike plating, which is the base plating, uses a normal temperature plating bath of nickel chloride: 230 to 250 g / L, hydrochloric acid: 125 ml / L, pH: 1 to 1.5, and cathode current density: 1 to 10 A / dm 2. Was performed evenly on both sides of the range of conditions.
クラッド圧延では、質量％で、Ｏ：０.０００３％、Ｐ：０.０００２％、残部Ｃｕおよび不可避的不純物からなる銅シートを接合した。両面とも同じ厚さの銅箔を適用した。 In the clad rolling, copper sheets composed of O: 0.0003%, P: 0.0002%, the balance Cu and inevitable impurities were joined in mass%. Copper foil of the same thickness was applied to both sides.
上記の各手法で作製した銅被覆鋼箔の平均厚さｔは以下のように表される。
・銅ストライクめっき（下地めっき）および電気銅めっき（本めっき）を施したもの；
ｔ＝ｔCu＋ｔS＋ｔCu
ここで、ｔSは芯材の平均厚さ、ｔCuは片面当たりの銅被覆層の平均厚さ（下地めっき＋本めっき）である。
・ニッケルストライクめっき（下地めっき）および電気銅めっき（本めっき）を施したもの；
ｔ＝ｔCu＋ｔNi＋ｔS＋ｔNi＋ｔCu
ここで、ｔSは芯材の平均厚さ、ｔCuは片面当たりの銅被覆層の平均厚さ、ｔNiは片面当たりのニッケルストライクめっき層の平均厚さである。
・クラッド圧延を行ったもの；
ｔ＝ｔCu＋ｔS＋ｔCu
ここで、ｔSは芯材の平均厚さ、ｔCuは片面当たりの銅被覆層（クラッドに供した銅箔由来の層）の平均厚さである。
各銅被覆鋼箔のｔ、ｔCu、ｔSの値は表１中に示してある。
The average thickness t of the copper-coated steel foil produced by the above methods is expressed as follows.
-Copper strike plating (base plating) and electrolytic copper plating (main plating);
t = t Cu + t S + t Cu
Here, t S is the average thickness of the core material, and t Cu is the average thickness of the copper coating layer per one side (base plating + main plating).
-Nickel strike plating (base plating) and electrolytic copper plating (main plating);
t = t Cu + t Ni + t S + t Ni + t Cu
Here, t S is the average thickness of the core material, t Cu is the average thickness of the copper coating layer per side, and t Ni is the average thickness of the nickel strike plating layer per side.
・ Clad rolled
t = t Cu + t S + t Cu
Here, t S is the average thickness of the core material, and t Cu is the average thickness of the copper coating layer (layer derived from the copper foil used for the clad) per one side.
The values of t, t Cu and t S for each copper clad steel foil are shown in Table 1.
上記各銅被覆鋼箔から圧延方向が長手方向となるように２０ｍｍ×７５ｍｍの短冊状シートを多数切り出し、同種の銅被覆鋼箔の短冊状シートを複数枚重ね合わせて箔積層体とした。箔積層体の厚さ（各短冊状シートの厚さｔの合計）に等しい厚さの銅板から切り出した２０ｍｍ×７５ｍｍの短冊状銅板を２枚用意し、上記箔積層体の長手方向両端部の片側表面上に長さ２０ｍｍの重ねしろを有するように２枚の短冊状銅板を箔積層体と長手方向が一致するように重ね合わせた。２箇所の重ねしろの中央部にスポット溶接機で抵抗加熱を行い、各部材の接合を試みた。各部材が接合され一体化したものを継手試験片と呼ぶ。抵抗加熱においては、スポット溶接機の電極として先端平坦部の径が６ｍｍφのものを使用し、加圧力９８０Ｎ、通電１０サイクルの条件を固定し、電流値を変化させた。 A large number of 20 mm × 75 mm strip-shaped sheets were cut out from each of the copper-coated steel foils so that the rolling direction was the longitudinal direction, and a plurality of strip-shaped sheets of the same kind of copper-coated steel foil were overlapped to form a foil laminate. Two strips of 20 mm × 75 mm strips cut from a copper plate having a thickness equal to the thickness of the foil laminate (the total thickness t of each strip sheet) are prepared, and both longitudinal ends of the foil laminate are prepared. Two strip-shaped copper plates were overlaid on the surface of one side so that the longitudinal direction coincided with the foil laminate so as to have an overlap of 20 mm in length. Resistance heating was performed with a spot welder at the center of the two overlapping margins to try to join the members. A member in which each member is joined and integrated is called a joint test piece. In resistance heating, an electrode of a spot welder having a tip flat portion with a diameter of 6 mmφ was used, the condition of a pressure of 980 N and energization of 10 cycles was fixed, and the current value was changed.
図３に、継手試験片を得るためにスポット溶接機で抵抗加熱を行う際の重ねしろ付近の断面状態を模式的に示す。
図４に、継手試験片の形状を示す。図４（ａ）は側面図、（ｂ）は平面図である。
これらの図において、箔および銅板の厚さは誇張して描いてある。
FIG. 3 schematically shows a cross-sectional state in the vicinity of the overlapping margin when resistance heating is performed with a spot welder to obtain a joint specimen.
FIG. 4 shows the shape of the joint test piece. 4A is a side view and FIG. 4B is a plan view.
In these figures, the thicknesses of the foil and the copper plate are exaggerated.
比較のために、銅被覆鋼箔の代わりに従来の銅箔を用いて、上記と同様のスポット溶接機による抵抗加熱、または超音波溶接にて上記と同様の重ねしろ部分での一体化を試みた。超音波溶接においては、アンビルサイズ３×１０ｍｍ、加圧力６０ｐｓｉ、振動数２０ｋＨｚ、振幅５０μｍ、上限時間１ｓｅｃの条件を固定し、入力エネルギーを変動させた。 For comparison, using conventional copper foil instead of copper-coated steel foil, we attempted resistance heating with a spot welder similar to the above, or integration at the same overlap area by ultrasonic welding. It was. In ultrasonic welding, the conditions of an anvil size of 3 × 10 mm, a pressure of 60 psi, a frequency of 20 kHz, an amplitude of 50 μm, and an upper limit time of 1 sec were fixed, and the input energy was varied.
上記のようにして一体化した継手試験片を用いて、その箔積層体の両端に接合した銅板部分を引張試験機に固定して引張試験を行った。ＪＩＳ Ｚ３１３６に準じて接合部分の破断形態を調べ、プラグ破断であるものを○（接合性；良好）、界面破断であるものを×（接合性；不良）と評価した。
結果を表１に示す。
Using the joint test piece integrated as described above, the copper plate portion bonded to both ends of the foil laminate was fixed to a tensile tester, and a tensile test was performed. According to JIS Z3136, the fracture form of the joint portion was examined, and the plug fracture was evaluated as “◯” (joinability; good), and the interface fracture was evaluated as “x” (bondability; poor).
The results are shown in Table 1.
表１からわかるように、金属箔として銅被覆鋼箔を用いた本発明例では箔の積層枚数が８０枚と多い箔積層体でも比較的小さい通電電流にて良好な接合性が得られた。抵抗加熱された部分の断面を観察した結果、隣り合う芯材同士および芯材と銅板が銅融着層を介して接合されていることが確認された。 As can be seen from Table 1, in the example of the present invention using copper-coated steel foil as the metal foil, good bondability was obtained with a relatively small energization current even in a foil laminate having as many as 80 foils. As a result of observing the cross section of the resistance-heated portion, it was confirmed that the adjacent core materials and the core material and the copper plate were joined via the copper fusion layer.
一方、従来の銅箔を用いた比較例Ｎｏ.５１は箔の積層枚数が２０枚の場合、上記本発明例と同程度の小さい電流値では良好な接合性が得られていない。Ｎｏ.５２では通電電流を増大させたことにより良好な接合性が確保できた。ただし、銅は熱伝導が良好であるため銅箔上の活物質を担持した部位が過度に高温となることが想定され、活物質の性能低下が懸念される。Ｎｏ.５３はＮｏ.５２と同じ電流値で積層枚数を５０枚とした場合の一体化を試みたものであるが、銅箔を使用したものにおいて抵抗加熱でそのような厚い集電体を得ることは困難であることがわかる。Ｎｏ.５４、５５は銅箔を用いて超音波溶接により一体化を試みたものである。積層枚数が２０枚の場合には良好な接合性を確保できるが、５０枚になると安定な接合体を得ることは困難である。一方、銅被覆鋼箔を用いたものであっても、Ｎｏ.７のように箔の厚さに占める鋼芯材の割合ｔS／ｔが過小だと比較的低い電流値での接合性が不十分となり、銅箔を用いた場合に対する優位性は低下した。Ｎｏ.８は銅被覆層の厚さが薄いために十分な接合性が得られなかった。 On the other hand, in Comparative Example No. 51 using a conventional copper foil, when the number of laminated foils is 20, good bondability is not obtained at a current value as small as the above-described example of the present invention. In No. 52, good joining property was secured by increasing the energization current. However, since copper has good heat conduction, it is assumed that the portion carrying the active material on the copper foil is excessively hot, and there is a concern that the performance of the active material may be reduced. No. 53 is an attempt to integrate when the number of stacked layers is 50 with the same current value as No. 52, but in the case of using a copper foil, such a thick current collector is obtained by resistance heating. It turns out to be difficult. Nos. 54 and 55 are attempts to integrate by ultrasonic welding using a copper foil. When the number of stacked layers is 20, good bondability can be secured, but when it is 50, it is difficult to obtain a stable bonded body. On the other hand, even if the copper-coated steel foil is used, if the ratio t S / t of the steel core occupying the thickness of the foil is too small as in No. 7, the bondability at a relatively low current value is obtained. It became insufficient, and the superiority over the case of using copper foil decreased. In No. 8, since the copper coating layer was thin, sufficient bondability could not be obtained.
Claims (6)
（Ａ）銅被覆層を含めた両表面間の平均厚さｔが３〜１００μｍ、
（Ｂ）芯材の平均厚さをｔSとするとき、ｔS／ｔ≧０.４、
（Ｃ）銅被覆層の片面当たりの平均厚さｔCuがいずれの側も０.０２μｍ以上。 A copper-coated steel foil assembly in which a part of a plurality of copper-coated steel foils having a copper coating layer on both surfaces of a steel core is laminated and integrated by resistance heating. A copper-coated steel foil assembly that satisfies the requirements of (A) to (C), and in which the adjacent core members are joined via a copper fusion layer in the laminated portion.
(A) The average thickness t between both surfaces including the copper coating layer is 3 to 100 μm,
(B) When the average thickness of the core material is t S , t S /t≧0.4,
(C) The average thickness t Cu per side of the copper coating layer is 0.02 μm or more on either side.
（Ａ）銅被覆層を含めた両表面間の平均厚さｔが３〜１００μｍ、
（Ｂ）芯材の平均厚さをｔSとするとき、ｔS／ｔ≧０.４、
（Ｃ）銅被覆層の片面当たりの平均厚さｔCuがいずれの側も０.０２μｍ以上。 A current-carrying member in which a plurality of copper-coated steel foils having copper coating layers on both side surfaces of a steel core and a metal plate are integrated by resistance heating in a state in which a part of each is laminated, each copper coating The steel foil satisfies the following requirements (A) to (C), and is an energizing member in which the adjacent core material and the core material and the metal plate are joined via the copper fusion layer in the laminated portion.
(A) The average thickness t between both surfaces including the copper coating layer is 3 to 100 μm,
(B) When the average thickness of the core material is t S , t S /t≧0.4,
(C) The average thickness t Cu per side of the copper coating layer is 0.02 μm or more on either side.
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| JP2019067730A (en) * | 2017-10-05 | 2019-04-25 | イビデン株式会社 | Power storage device electrode, power storage device, and method of manufacturing power storage device electrode |
| CN112825381A (en) * | 2019-11-19 | 2021-05-21 | 深圳市海鸿新能源技术有限公司 | Pole piece of secondary battery, preparation method of pole piece and secondary battery |
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