JP2004079523A - Electrolytic copper foil and electrolytic copper foil for current collector of secondary battery - Google Patents

Electrolytic copper foil and electrolytic copper foil for current collector of secondary battery Download PDF

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JP2004079523A
JP2004079523A JP2003282469A JP2003282469A JP2004079523A JP 2004079523 A JP2004079523 A JP 2004079523A JP 2003282469 A JP2003282469 A JP 2003282469A JP 2003282469 A JP2003282469 A JP 2003282469A JP 2004079523 A JP2004079523 A JP 2004079523A
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copper foil
electrolytic copper
secondary battery
current collector
room temperature
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JP4413552B2 (en
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Hideo Otsuka
大塚 英雄
Akitoshi Suzuki
鈴木 昭利
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Furukawa Circuit Foil Co Ltd
Furukawa Research Inc
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Furukawa Research Inc
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    • YGENERAL 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
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    • Y02E60/10Energy storage using batteries

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Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolytic copper foil with very smooth surface roughness on an electrolytic copper foil deposited surface, reasonable tensile strength at normal temperature in spite of very fine crystalline structure, high elongation, retaining stable strength without causing heat softening even after heat treatment, and having high elongation in high temperature atmosphere, and to provide the electrolytic copper foil for a current collector of a secondary battery having long charge-discharge cycles and preventing breakage even in overcharge. <P>SOLUTION: The electrolytic copper foil suitable for the current collector of the secondary battery has such characteristics that the surface roughness on the electrolytic copper foil deposited surface has a minimum distance between peaks of material crests of 5 μm or less in spite of fine crystals smaller than 2.5 μm when the crystalline structure at normal temperature is represented by 10 point average roughness Rz, drop in normal temperature tensile strength after heat treatment at 130 °C for 15 hours is less than 15%, and heat softening is prevented. <P>COPYRIGHT: (C)2004,JPO

Description

 本発明は電解銅箔析出面の表面粗さが非常に平滑であり、且つ結晶組織が非常に微細でありながら、常温抗張力が高すぎず、伸び率に優れ、熱処理後でも熱軟化せずに安定した強度を維持し、高温雰囲気中でも伸び率が高い電解銅箔と、この電解銅箔からなる二次電池の集電体用電解銅箔に関するものである。
 更に、充放電サイクルを長寿命化し、過充電時でも破断し難い二次電池の集電体用電解銅箔に関するものである。
In the present invention, the surface roughness of the electrolytic copper foil deposition surface is very smooth, and the crystal structure is very fine, but the room temperature tensile strength is not too high, the elongation is excellent, and it does not soften even after heat treatment. The present invention relates to an electrolytic copper foil which maintains stable strength and has a high elongation even in a high-temperature atmosphere, and an electrolytic copper foil for a current collector of a secondary battery comprising the electrolytic copper foil.
Further, the present invention relates to an electrolytic copper foil for a current collector of a secondary battery, which has a longer charge / discharge cycle life and is not easily broken even during overcharge.

 近年、携帯電話、ビデオカメラ等の電子機器の小型化に伴い、エネルギ−密度の高い二次電池が要求されている。とりわけリチウムイオン二次電池はエネルギ−密度が高く、充放電サイクル特性に優れ、且つ軽量という優れた特性を有するため、広く使われるようになってきている。リチウムイオン二次電池の負極集電体としては、一般に銅箔が使用されており、その表面にペ−スト状に加工された炭素粉等の負極活物質を塗布、乾燥した後、ロ−ル圧延等でプレス平坦化して作製される。更にセパレ−ト材と正極活物質を塗布したアルミ箔と共に巻き回されてリチウムイオン二次電池が製造されている。 Recently, with the miniaturization of electronic devices such as mobile phones and video cameras, secondary batteries with high energy density have been required. In particular, lithium ion secondary batteries have been widely used because of their high energy density, excellent charge / discharge cycle characteristics, and light weight. A copper foil is generally used as a negative electrode current collector of a lithium ion secondary battery. A negative electrode active material such as a carbon powder processed into a paste is applied to the surface of the copper foil, dried, and then rolled. It is manufactured by press flattening by rolling or the like. Further, a lithium ion secondary battery is manufactured by being wound together with an aluminum foil coated with a separator material and a positive electrode active material.

 負極集電体に使用する銅箔には圧延加工を施して箔状とした圧延銅箔と硫酸銅を主成分とする溶液を電解して、チタン或いはSUS製の回転する陰極上に銅を析出させ、これを連続的に引き剥がして製造する電解銅箔がある。 The copper foil used for the negative electrode current collector is subjected to a rolling process, and the rolled copper foil and the solution containing copper sulfate as a main component are electrolyzed to deposit copper on a titanium or SUS rotating cathode. There is an electrolytic copper foil that is manufactured by continuously peeling it off.

 これまで、リチウムイオン二次電池の負極集電体電極用銅箔には、圧延銅箔を使用する場合が多かった。しかし、リチウムイオン二次電池の負極集電体電極用電極に使用される厚みが10μm 前後の圧延銅箔は高価であり、しかも再結晶しているために、引張り強さが極端に小さくなるため炭素等の負極活物質を塗布、乾燥後ロ−ル圧延等で圧着する製造工程でのハンドリング性が悪く、シワが発生しやすく、ときには、破断するケ−スがあった。また、圧延で製造される銅箔の幅は通常60cm程度であり、製造時の能率が悪いといった欠点もあった。 Until now, rolled copper foil has often been used as the copper foil for the negative electrode current collector electrode of lithium ion secondary batteries. However, a rolled copper foil having a thickness of around 10 μm used for an electrode for a negative electrode current collector electrode of a lithium ion secondary battery is expensive and, because it is recrystallized, the tensile strength becomes extremely small. The negative electrode active material such as carbon was coated and dried, and then the roll was subjected to pressure bonding by roll rolling or the like, resulting in poor handling properties, wrinkles were likely to occur, and there were occasional cases of breakage. Further, the width of the copper foil produced by rolling is usually about 60 cm, and there is a disadvantage that the efficiency at the time of production is poor.

 これに対して、電解銅箔は、再結晶した極端に引張り強さが落ちた圧延銅箔に比べて引張り強さが大きいためハンドリング性に優れ、更に通常100cm以上の幅の銅箔を製造することが可能であり、生産性を向上できることから、圧延銅箔に比較して安価であり最近は、圧延銅箔に代えて電解銅箔を採用しようとする試みが多くなってきている。 On the other hand, the electrolytic copper foil is excellent in handleability because the tensile strength is large compared to the recrystallized rolled copper foil having extremely low tensile strength, and usually produces a copper foil having a width of 100 cm or more. Since it is possible to improve the productivity, it is inexpensive as compared with the rolled copper foil, and recently, there have been many attempts to employ an electrolytic copper foil instead of the rolled copper foil.

 しかし、従来の電解銅箔の析出面は柱状の結晶組織であり、電解銅箔析出面の表面粗さが粗いため、炭素粉等の負極活物質との接触部分が少なく、接触抵抗が大きく、充放電サイクル寿命が短いことがわかったため、結晶組織を微細化し、電解銅箔析出面の表面粗さを圧延銅箔のように小さくした電解銅箔が開発され、リチウムイオン二次電池用として採用されてきている。 However, the deposition surface of the conventional electrolytic copper foil has a columnar crystal structure and the surface roughness of the electrolytic copper foil deposition surface is rough, so there are few contact portions with the negative electrode active material such as carbon powder, and the contact resistance is large. Since the charge-discharge cycle life was found to be short, an electrolytic copper foil with a finer crystal structure and a reduced surface roughness of the electrolytic copper foil deposition surface, like a rolled copper foil, was developed and used for lithium-ion secondary batteries. Have been.

 結晶組織を微細化し、電解銅箔析出面の表面粗さを小さくした電解銅箔としては、特許文献1、特許文献2、特許文献3に開示されている。これらに開示された電解銅箔の特性は各種添加剤、電解液組成、電解液温度、電解液流速、電流密度等を制御することによって電解銅箔析出面の表面粗さを小さくしている。
特開平7−188969 特開平8−53789 特開2000−182623公報
Patent Literature 1, Patent Literature 2, and Patent Literature 3 disclose electrolytic copper foils in which the crystal structure is refined and the surface roughness of the electrolytic copper foil deposition surface is reduced. The characteristics of the electrolytic copper foil disclosed therein reduce the surface roughness of the electrolytic copper foil deposition surface by controlling various additives, the composition of the electrolytic solution, the temperature of the electrolytic solution, the flow rate of the electrolytic solution, the current density, and the like.
JP-A-7-188969 JP-A-8-53789 JP 2000-182623 A

 ところで二次電池における重要な特性の一つに充放電サイクル寿命と過充電特性があり、更なる特性向上が求められている。充放電サイクル寿命とは充放電を繰り返すと膨張収縮によるストレスなどによって集電体(銅箔)と活物質との接触が悪くなり、一部の活物質が充放電に利用できない電気伝導度になって容量の劣化を引き起こすものである。過充電特性とは、過充電が行われた際、集電体(銅箔)の経時的劣化による亀裂や破断が発生しないことを要求するものである。 By the way, one of the important characteristics of the secondary battery is the charge / discharge cycle life and overcharge characteristics, and further improvement of the characteristics is required. The charge / discharge cycle life is that when charging and discharging are repeated, contact between the current collector (copper foil) and the active material deteriorates due to stress due to expansion and contraction, and the electrical conductivity of some active materials becomes unusable for charging and discharging. This causes the capacity to deteriorate. The overcharge characteristic requires that the current collector (copper foil) does not crack or break due to deterioration over time when overcharge is performed.

 結晶組織を微細化し、表面粗さを小さくした前記特許文献1、特許文献2、特許文献3の各公報に記載の電解銅箔は、これまでの圧延銅箔より優れてはいるが、充放電サイクル寿命、過充電特性の面で市場の要求に対して十分とはいえない状況にある。 The electro-deposited copper foils described in Patent Documents 1, 2 and 3 in which the crystal structure is refined and the surface roughness is reduced are superior to the rolled copper foils up to now, but the charge / discharge In terms of cycle life and overcharge characteristics, the situation is not enough to meet market demands.

 即ち、リチウムイオン二次電池用負極電極集電体として使用される電解銅箔の条件を検討すると、
1.表面の平滑性について:前記3つの公報で開示されている電解銅箔の表面は、十点平均粗さRzは2.5μmよりも小さいものの、電子顕微鏡でその表面を観察すると平均粒径は0.数μmの微細な結晶粒子が電解銅箔析出面に均一に露出、密集しており、平滑性が十分ではない。そして、平均粒径0.数μmの結晶粒子が表面に露出、密集しているので、それを素地山とすると、そのピ−ク間距離は粒径と同じ0.数μmである。このように、凹凸のある電解銅箔の表面では、炭素粉等の負極活物質との接触が悪く、容量の劣化、充放電サイクル寿命の低下を招く。なお、十点平均粗さRzはJIS−B−0601に基づいて、表面粗さ計で測定した値である。
That is, considering the conditions of the electrolytic copper foil used as the negative electrode current collector for the lithium ion secondary battery,
1. Regarding the surface smoothness: The surface of the electrolytic copper foil disclosed in the above three publications has a ten-point average roughness Rz of less than 2.5 μm, but when the surface is observed with an electron microscope, the average particle size becomes 0. . Fine crystal particles of several μm are uniformly exposed and dense on the electrolytic copper foil deposition surface, and the smoothness is not sufficient. Since crystal grains having an average particle diameter of 0.1 μm are exposed and densely formed on the surface, if they are used as a base, the distance between peaks is 0.1 μm, which is the same as the particle diameter. As described above, on the uneven surface of the electrolytic copper foil, the contact with the negative electrode active material such as the carbon powder is poor, and the capacity is deteriorated and the charge / discharge cycle life is shortened. The ten-point average roughness Rz is a value measured by a surface roughness meter based on JIS-B-0601.

2.常温抗張力について:前記3つの公報で開示されている電解銅箔は全て50kg/mm以上であり非常に硬い。一般に結晶組織の平均粒径が0.数μmの微細結晶で、十点平均粗さRzが2.5μm以下の銅箔の場合、常温抗張力は非常に高く硬い箔になる。銅箔が硬いため、活物質塗布後に実施されるロ−ル圧延等のプレス平坦化工程で活物質表面に合うような銅箔の変形が十分に起こらず、活物質との接触が悪く、容量の劣化、充放電サイクル寿命の低下を招く結果となる。なお、一般に、抗張力と硬さは比例関係にあることは周知である。 2. Regarding room temperature tensile strength: All of the electrolytic copper foils disclosed in the above three publications are 50 kg / mm 2 or more and are very hard. Generally, the average grain size of the crystal structure is 0. In the case of a copper foil having a fine crystal of several μm and a ten-point average roughness Rz of 2.5 μm or less, the room temperature tensile strength is extremely high and the foil becomes hard. Since the copper foil is hard, deformation of the copper foil to fit the surface of the active material does not sufficiently occur in a press flattening process such as roll rolling performed after application of the active material, and the contact with the active material is poor, and the capacity is low. , And the life of the charge / discharge cycle is reduced. It is well known that tensile strength and hardness are generally in a proportional relationship.

3.常温での伸び率について:前記3つの公報で開示されている電解銅箔の伸び率は全て11%以下である。このように伸び率が低いため、活物質塗布後に実施されるロ−ル圧延等のプレス平坦化工程で銅箔にストレスがかかり、銅箔に亀裂が入り、容量の劣化、充放電サイクルの低下を招く。 3. Regarding the elongation percentage at room temperature: The elongation percentages of the electrolytic copper foils disclosed in the three publications are all 11% or less. Due to such low elongation, stress is applied to the copper foil in a press flattening step such as roll rolling performed after application of the active material, the copper foil is cracked, the capacity is deteriorated, and the charge / discharge cycle is reduced. Invite.

4.非再結晶性について:特許文献3に記載の電解銅箔は130℃くらいで再結晶する箔である。このため、圧延銅箔と同様に熱軟化により抗張力が極端に低下し、活物質塗布、加熱乾燥時の伸びシワや箔切れが発生する。また再結晶組織界面に沿って亀裂が入り、容量の低下、充放電サイクル寿命の低下を招く。 4. Regarding non-recrystallization properties: The electrolytic copper foil described in Patent Document 3 is a foil that recrystallizes at about 130 ° C. For this reason, similarly to the rolled copper foil, the tensile strength is extremely reduced due to the heat softening, and the active material is applied, and elongation wrinkles and foil breakage during heating and drying occur. In addition, cracks are formed along the recrystallized structure interface, leading to a reduction in capacity and a reduction in charge / discharge cycle life.

5.180℃高温雰囲気中の伸び率について:特許文献2の実施例2に記載の電解銅箔は180℃高温雰囲気中の伸び率が35μm厚で9.5%であり、通常の電解銅箔よりも低く、更に常温での伸び率よりも低下する傾向にある。このため、過充電特性テストにおいて、過充電時の発熱による膨張ストレスに耐えられず、銅箔に亀裂が発生する欠陥がある。一方、過充電特性テストで銅箔に亀裂が入らなかった、特許文献1および特許文献3に記載の電解銅箔は高温雰囲気中での伸び率の方が常温での伸び率より高くなる傾向にある。 5. Regarding the elongation percentage in a 180 ° C. high temperature atmosphere: The electrolytic copper foil described in Example 2 of Patent Document 2 has a 35 μm thick elongation percentage in a 180 ° C. high temperature atmosphere of 9.5%, which is a normal electrolytic copper foil. , And tends to be lower than the elongation at room temperature. For this reason, in the overcharge characteristic test, there is a defect that the copper foil cannot withstand the expansion stress due to the heat generated at the time of overcharge and cracks occur in the copper foil. On the other hand, the electrolytic copper foils described in Patent Documents 1 and 3 in which no crack was formed in the copper foil in the overcharge characteristic test tended to have a higher elongation rate in a high-temperature atmosphere than in normal temperature. is there.

 そこで本発明者らは表面粗さの小さい電解銅箔を提供することを目的として前記各公報で開示された電解銅箔の欠陥等を改良すべく鋭意検討を重ねた結果、充放電サイクル寿命および過充電特性に影響する銅箔の特性として十点平均粗さRzでは表せない表面の平滑性、常温抗張力、伸び率、非再結晶性、高温雰囲気中の伸び率が重要であることを見出し、二次電池特性において最も効果の高い銅箔を得ることに成功した。 Therefore, the present inventors have conducted intensive studies to improve the defects and the like of the electrolytic copper foil disclosed in each of the above publications in order to provide an electrolytic copper foil having a small surface roughness, and as a result, the charge and discharge cycle life and As the characteristics of the copper foil affecting the overcharge characteristics, it is found that the smoothness of the surface which cannot be expressed by the ten-point average roughness Rz, the room temperature tensile strength, the elongation, the non-recrystallization, and the elongation in a high-temperature atmosphere are important. We succeeded in obtaining the most effective copper foil in secondary battery characteristics.

 本発明請求項1に係る電解銅箔は、電解銅箔析出面の表面粗さが、常温での結晶組織が10点平均粗さRzにして、2.5μmより小さい微細結晶でありながら、素地山の最小ピ−ク間距離が5μm以上であり、常温抗張力が40kg/mm以下であり、且つ130℃、15時間熱処理後の常温抗張力の低下が15%以内であり、熱軟化しないことを特徴とするものである。 The electrodeposited copper foil according to claim 1 of the present invention has a surface roughness of an electrodeposited copper foil deposition surface having a 10-point average roughness Rz at room temperature, a fine crystal smaller than 2.5 μm, and The minimum peak-to-peak distance is not less than 5 μm, the room temperature tensile strength is 40 kg / mm 2 or less, the room temperature tensile strength after heat treatment at 130 ° C. for 15 hours is within 15%, and it is not softened. It is a feature.

 本発明請求項2に係る電解銅箔は、前記請求項1記載の電解銅箔であって、その常温の伸び率が35μm厚さにおいて14%以上であり、常温から200℃までの高温雰囲気中での伸び率が増大傾向にあることを特徴とするものである。 The electrodeposited copper foil according to claim 2 of the present invention is the electrodeposited copper foil according to claim 1, wherein the elongation at normal temperature is 14% or more at a thickness of 35 μm, and in a high-temperature atmosphere from normal temperature to 200 ° C. Is characterized by an increase in the elongation rate.

 本発明請求項3に係る電解銅箔は、前記請求項1または2記載の電解銅箔を二次電池集電体用の銅箔として用いることを特徴とするものである。 電解 The electrolytic copper foil according to claim 3 of the present invention is characterized in that the electrolytic copper foil according to claim 1 or 2 is used as a copper foil for a secondary battery current collector.

 本発明請求項4に係る電解銅箔は、前記の二次電池がリチウムイオン二次電池であることを特徴とするものである。 電解 The electrolytic copper foil according to claim 4 of the present invention is characterized in that the secondary battery is a lithium ion secondary battery.

 本発明電解銅箔は、電解銅箔析出面に平均粒径0.数μmの微細な結晶粒子が露出しておらず、非常に平滑であるため、活物質との接触が良好になり、且つ結晶組織が非常に微細でありながら常温抗張力が高すぎないため、活物質に沿って集電体が十分に変形し、活物質と集電体との接触を良好に保つことができ、常温での伸び率が高いため、活物質塗布後に実施されるロ−ル圧延等のプレス平坦化工程での銅箔の亀裂を防ぐことができ、更に、再結晶しないため、充放電サイクル寿命特性に優れると共に、高温雰囲気中での伸び率が高く、温度上昇と共に増大する。そのため、かかる電解銅箔を採用することにより過充電特性に優れた二次電池集電体用電解銅箔を提供することができる。 電解 The electrolytic copper foil of the present invention has an average particle size of 0. Since the fine crystal particles of several μm are not exposed and are very smooth, the contact with the active material is good, and the room temperature tensile strength is not too high even though the crystal structure is very fine. The current collector is sufficiently deformed along the material, the contact between the active material and the current collector can be kept good, and the elongation at room temperature is high. In addition, since the copper foil can be prevented from cracking in the press flattening step and the like, it is not recrystallized, so that it has excellent charge-discharge cycle life characteristics, has a high elongation in a high-temperature atmosphere, and increases with increasing temperature. Therefore, by using such an electrolytic copper foil, an electrolytic copper foil for a secondary battery current collector having excellent overcharge characteristics can be provided.

 本発明に係る電解銅箔はその析出面の表面粗さが10点平均粗さRzにして、2.5μmより小さいながら、他の表面粗さが小さい電解銅箔のように析出面に平均粒径0.数μmの微細な結晶粒子が露出しておらず、素地山のピ−ク間距離が5μm以上あり、非常に平滑であることから、活物質と集電体との接触性が良く、電気伝導度が大きくなって、充放電サイクル寿命に優れたものになる。 The electrodeposited copper foil according to the present invention has a surface roughness of 10 points average roughness Rz on the deposition surface, which is smaller than 2.5 μm, but has an average grain size on the deposition surface like other electrodeposited copper foils having a small surface roughness. Diameter 0. Since fine crystal grains of several μm are not exposed, the distance between peaks of the base mountain is 5 μm or more, and it is very smooth, the contact between the active material and the current collector is good, and the electric conductivity is good. This increases the degree of charge and discharge cycle life.

 十点平均粗さRzが小さくても、平均粒径0.1μm以上の結晶粒子が表面に露出して、集電体表面に凹凸がある場合には、炭素粉である活物質と集電体の接触点が少なくなり接触抵抗が大きくなる。これに充放電を繰り返すと、膨張収縮に伴うストレス等により集電体と活物質との距離が徐々に大きくなり、一部の活物質が充放電に利用できない電気伝導度になって容量の劣化が起きる。 Even when the ten-point average roughness Rz is small, crystal particles having an average particle diameter of 0.1 μm or more are exposed on the surface and the surface of the current collector has irregularities. And the contact resistance increases. When charging and discharging are repeated, the distance between the current collector and the active material gradually increases due to stress caused by expansion and contraction, and some of the active material becomes an electrical conductivity that cannot be used for charging and discharging, resulting in deterioration of capacity. Happens.

 従って、電解銅箔析出面の表面粗さが10点平均粗さRzにして2.5μmより小さいだけでなく、析出面に平均粒径0.数μmの微細な結晶粒子が露出しておらず、素地山のピ−ク間距離が5μm以上であることを要する。素地山のピ−ク間距離が5μmよりも小さいと、前述したように負極活物質との接触点が少なくなり、充分な接触抵抗を得ることができないためである。 Accordingly, not only the surface roughness of the electrodeposited copper foil deposition surface is smaller than 2.5 μm in terms of the 10-point average roughness Rz, but also the average grain size of It is necessary that fine crystal grains of several μm are not exposed and the distance between peaks of the base mountain is 5 μm or more. If the peak-to-peak distance of the green body is smaller than 5 μm, the number of contact points with the negative electrode active material is reduced as described above, and sufficient contact resistance cannot be obtained.

 また、本発明に係る電解銅箔は、結晶組織が非常に微細でありながら常温抗張力が40kg/mm以下であるため、銅箔自体が軟らかい。 Further, the electrolytic copper foil according to the present invention has a very fine crystal structure and a room-temperature tensile strength of 40 kg / mm 2 or less, so that the copper foil itself is soft.

 一般的に、平面状集電体の表面に電極構成物質層が形成されてなる電極は、活物質とバインダ−とを含有する電極構成物質層が集電体の表面に塗布され、その後ロ−ル圧延等でプレスされて作製される。このプレス工程は、電極を所定の密度に圧縮する作用と、適切な導電性を有するように活物質粒子間を接近させる作用とを有する。プレス工程を経た電極は活物質粒子間、および活物質と集電体との接触性が良くなり、電気伝導度が大きくなる。更に、十分な電池特性を得るには、活物質粒子間、および活物質と集電体の距離を小さくすると共に、集電体の形状が活物質表面の形状に合わせて変形することが重要である。活物質表面に沿って集電体が変形した場合には、活物質と集電体との接触性が更に良くなり、電気伝導度が更に大きくなり、充放電サイクル特性が向上する。 Generally, an electrode in which an electrode constituent material layer is formed on the surface of a planar current collector has an electrode constituent material layer containing an active material and a binder applied to the surface of the current collector. It is produced by pressing by rolling or the like. This pressing step has an action of compressing the electrode to a predetermined density and an action of bringing the active material particles closer to each other so as to have appropriate conductivity. The electrode after the pressing step has good contact between the active material particles and between the active material and the current collector, and has high electric conductivity. Furthermore, in order to obtain sufficient battery characteristics, it is important to reduce the distance between the active material particles and the distance between the active material and the current collector, and to deform the shape of the current collector according to the shape of the active material surface. is there. When the current collector is deformed along the active material surface, the contact between the active material and the current collector is further improved, the electric conductivity is further increased, and the charge / discharge cycle characteristics are improved.

 このためには、常温抗張力が40kg/mm以下であることが必要で、常温抗張力が40kg/mmを越えると銅箔自体の軟らかさが不足し、活物質塗布後に実施されるロ−ル圧延等のプレス平坦化処理で活物質表面に沿った銅箔の変形が十分に起こらないため、活物質との接触が悪くなり、容量の劣化、充放電サイクル寿命が低下するため好ましくない。 For this purpose, the room temperature tensile strength needs to be 40 kg / mm 2 or less, and if the room temperature tensile strength exceeds 40 kg / mm 2 , the copper foil itself becomes insufficient in softness, and the roll performed after application of the active material is applied. Since deformation of the copper foil along the surface of the active material does not sufficiently occur in the press flattening treatment such as rolling, the contact with the active material is deteriorated, the capacity is deteriorated, and the charge / discharge cycle life is unfavorably reduced.

 また本発明に係る電解銅箔は、常温の伸び率が35μm厚さにおいて14%以上であることが望ましい。 The electrolytic copper foil according to the present invention preferably has an elongation at room temperature of 14% or more at a thickness of 35 µm.

 また本発明に係る電解銅箔は130℃、15時間熱処理後の常温抗張力の低下が15%以内であり、再結晶しないため、充放電サイクル特性と生産性に優れることを特徴とする。 電解 The electrolytic copper foil according to the present invention is characterized in that the decrease in room-temperature tensile strength after heat treatment at 130 ° C for 15 hours is within 15%, and that it does not recrystallize, so that it has excellent charge-discharge cycle characteristics and productivity.

 従来、二次電池の集電体用銅箔に使用されてきた圧延銅箔や、一部の電解銅箔は100数十℃で再結晶するため、集電体にした場合、抗張力が経時的に低下し、充放電に伴う活物質の膨張収縮によって、集電体用銅箔に亀裂や破断が発生し、容量の低下、充放電サイクル寿命の低下を招き、特に再結晶組織界面に沿って亀裂が入りやすい。 Conventionally, rolled copper foil and some electrolytic copper foils, which have been used as current collector copper foil for secondary batteries, are recrystallized at a temperature of several tens of degrees Celsius. The active material expands and contracts due to charge and discharge, causing cracks and breaks in the current collector copper foil, resulting in a decrease in capacity and a decrease in charge and discharge cycle life, particularly along the recrystallized structure interface. Easy to crack.

 また、再結晶後は抗張力が極端に小さくなるため負極活物質を塗布、乾燥後圧着する製造工程でのハンドリング性が悪く、シワが発生しやすく、ときには、破断するケ−スがあり、二次電池の集電体用銅箔は再結晶しないことが要求されていた。本発明電解銅箔は再結晶しないために亀裂や破断が発生せず、充放電サイクル寿命が長期にわたり、ハンドリング性も優れている。電解銅箔の130℃、15時間熱処理後の常温抗張力の低下を15%以内と規定したのはこれらの条件を満足するためである。  Further, after recrystallization, the tensile strength becomes extremely small, so that the handling property in the manufacturing process of applying the negative electrode active material, drying and pressing is poor, wrinkles are likely to occur, and there are cases where the case breaks, It has been required that the copper foil for the current collector of the battery does not recrystallize. Since the electrolytic copper foil of the present invention does not recrystallize, it does not crack or break, has a long charge / discharge cycle life, and has excellent handling properties. The reason why the decrease in the room temperature tensile strength after the heat treatment of the electrolytic copper foil at 130 ° C. for 15 hours is specified to be within 15% is to satisfy these conditions.

 この伸び率が低いと、活物質塗布後に実施されるロ−ル圧延等のプレス平坦化工程でストレスがかかり、銅箔に亀裂が入り、容量の劣化、充放電サイクルの低下を招く。従って、電解銅箔の常温伸び率は14%以上であることが望ましい。 (4) If the elongation is low, stress is applied in a press flattening step such as roll rolling performed after application of the active material, and the copper foil is cracked, resulting in a deterioration in capacity and a decrease in charge / discharge cycle. Therefore, the room temperature elongation of the electrolytic copper foil is desirably 14% or more.

 また、本発明に係る電解銅箔は、常温から200℃までの高温雰囲気中での伸び率が増大傾向にあり、且つ180℃雰囲気中の伸び率が35μm厚さにおいて18%以上とすることにより、二次電池において過充電特性に優れたものとなり好ましい。 Further, the electrolytic copper foil according to the present invention has a tendency that the elongation in a high temperature atmosphere from room temperature to 200 ° C. tends to increase, and the elongation in an 180 ° C. atmosphere is 18% or more at a thickness of 35 μm. This is preferable because the secondary battery has excellent overcharge characteristics.

 本発明の電解銅箔は電解銅箔析出面の表面粗さが非常に平滑であり、且つ結晶組織が非常に微細でありながら、常温抗張力が高すぎず、伸び率に優れ、熱処理後でも熱軟化せずに安定した強度を維持し、高温雰囲気中でも伸び率に優れ、二次電池の集電体用銅箔として好適であり、二次電池の充放電サイクルを長寿命化し、過充電特性に優れた特性を発揮するものであり、工業的に優れた効果を有するものである。 The electrodeposited copper foil of the present invention has a very smooth surface roughness on the electrodeposited surface of the electrodeposited copper foil and a very fine crystal structure, does not have too high a room temperature tensile strength, has an excellent elongation, and has a high heat resistance even after heat treatment. Maintains stable strength without softening, has excellent elongation even in high-temperature atmosphere, is suitable as a current collector copper foil for secondary batteries, prolongs the charge / discharge cycle of secondary batteries, and improves overcharge characteristics. It exhibits excellent properties and has industrially excellent effects.

 以下に本発明の一実施形態と比較例を示す。なお、本発明はこれらの実施形態に限定されるものではない。  の 一 One embodiment of the present invention and a comparative example are shown below. Note that the present invention is not limited to these embodiments.

〔実施例1〕
 硫酸銅五水和物280g/l、硫酸100g/l、塩素イオン35ppmを含む硫酸酸性硫酸銅電解液に平均分子量3000の低分子量ゼラチン7ppm、ヒドロキシエチルセルロ−ス3ppm、3−メルカプト−1−プロパンスルホン酸ナトリウム1ppmを添加し、電解液温度55℃、流速0.3m/分、電流密度50A/dmの条件で、電解銅箔を製箔した。この時電解液は、電解槽に入る前に活性炭処理塔を通り、電解が終了して電解槽から出た電解液を沸騰させる処理をした後、銅濃度、遊離の硫酸濃度、塩素イオン濃度を希望する濃度に調整して再度電解に供するサイクルとした。これによって箔特性測定用の厚さ35μmの電解銅箔と、二次電池電極用の厚さ12μの電解銅箔を製箔した。
[Example 1]
Copper sulfate sulfate pentahydrate 280 g / l, sulfuric acid 100 g / l, sulfuric acid acidic copper sulfate electrolyte containing 35 ppm of chloride ions, 7 ppm of low molecular weight gelatin having an average molecular weight of 3000, 3 ppm of hydroxyethyl cellulose, 3-mercapto-1-propane 1 ppm of sodium sulfonate was added, and an electrolytic copper foil was formed under the conditions of an electrolyte temperature of 55 ° C., a flow rate of 0.3 m / min, and a current density of 50 A / dm 2 . At this time, the electrolytic solution passes through an activated carbon treatment tower before entering the electrolytic cell, and after the electrolysis is completed, the electrolytic solution that has exited from the electrolytic cell is boiled, and then the copper concentration, the free sulfuric acid concentration, and the chloride ion concentration are reduced. The cycle was adjusted to a desired concentration and then subjected to electrolysis again. Thus, an electrolytic copper foil having a thickness of 35 μm for measuring foil characteristics and an electrolytic copper foil having a thickness of 12 μm for a secondary battery electrode were produced.

 得られた厚さ35μmの電解銅箔を用いて箔の特性試験を表1の項目について実施した。その結果を表1に示す。表面粗さRzはJIS−B−0601に基づき、(株)小坂研究所製SE−3C型表面粗さ計で測定した。また、素地山のピ−ク間距離は電子顕微鏡で倍率2000倍にて撮影した写真から測定した。常温および180℃と200℃高温雰囲気中および、150℃で15時間熱処理後の抗張力、伸び率はIPC−TM−650に基づいて測定した。なお、常温の抗張力、伸び率は、製箔直後に測定すると、電解時の歪が残っているので高く出る傾向があるため、常温で3日放置後に測定した。
 また、12μm厚の電解銅箔の方を1g/l濃度のCrO水溶液に5秒間浸漬して、クロメ−ト処理を施し、水洗乾燥させた。なお、ここではクロメ−ト処理を行ったが、ベンゾトリアゾ−ル系処理、或いはシランカップリング剤処理を行ってもよいことは勿論である。
Using the obtained electrolytic copper foil having a thickness of 35 μm, a property test of the foil was performed for the items in Table 1. Table 1 shows the results. The surface roughness Rz was measured by Kosaka Laboratory Co., Ltd. SE-3C type surface roughness meter based on JIS-B-0601. The peak-to-peak distance of the ground was measured from a photograph taken at a magnification of 2000 with an electron microscope. Tensile strength and elongation at room temperature and in a high-temperature atmosphere of 180 ° C. and 200 ° C. and after a heat treatment at 150 ° C. for 15 hours were measured based on IPC-TM-650. The tensile strength and the elongation at room temperature were measured immediately after the foil making, since distortion during electrolysis remained and tended to increase. Therefore, the tensile strength and elongation were measured after standing at room temperature for 3 days.
The 12 μm-thick electrolytic copper foil was immersed in a 1 g / l aqueous solution of CrO 3 for 5 seconds, subjected to chromate treatment, washed and dried. Although the chromate treatment is performed here, it goes without saying that a benzotriazole-based treatment or a silane coupling agent treatment may be performed.

 このようにして得られた12μm厚の電解銅箔を用いて二次電池の負極を次のようにして作製した。負極活物質としては石油ピッチを焼成した粗粒状のピッチコ−クスを平均粒径20μmの粉末とし、不活性ガス中で1000℃にて焼成して不純物を除去して得たコ−クス材料粉末90重量部と、結着剤としてポリフッ化ビニリデンを10重量部の割合で混合して負極合剤を調整した。次いで、この負極合剤を溶剤であるN−メチル2−ピロリドンに分散させてスラリ−にし、電解銅箔の両面に塗布し、乾燥後ロ−ラ−プレス機で圧縮成形し、帯状にして負極を得た。この帯状負極は成形後の負極合剤の膜厚が両面ともに90μmで同一であり、その幅は55.6mm、長さは551.5mmに形成した。次に正極は、LiCoOを正極活物質とし、それを91重量%、導電材としてグラファイトを6重量%、結着剤としてポリフッ化ビニリデンを3重量%の割合で混合して正極合剤を作製し、これをN−メチル−2−ピロリドンに分散してスラリ−状とした。 A negative electrode of a secondary battery was produced using the thus obtained 12 μm thick electrolytic copper foil as follows. As the negative electrode active material, a coke material powder 90 obtained by baking petroleum pitch into a coarse-grained pitch coke having an average particle size of 20 μm and baking at 1000 ° C. in an inert gas to remove impurities. A negative electrode mixture was prepared by mixing 10 parts by weight of polyvinylidene fluoride as a binder with 10 parts by weight of a binder. Next, this negative electrode mixture was dispersed in N-methyl 2-pyrrolidone as a solvent to form a slurry, applied to both sides of an electrolytic copper foil, dried, compression-molded with a roller press, and formed into a belt shape. Got. This band-shaped negative electrode had the same thickness of the negative electrode mixture of 90 μm on both sides after molding, and had a width of 55.6 mm and a length of 551.5 mm. Next, a positive electrode mixture is prepared by mixing LiCoO 2 as a positive electrode active material at a ratio of 91% by weight, graphite as a conductive material at 6% by weight, and polyvinylidene fluoride as a binder at 3% by weight. This was dispersed in N-methyl-2-pyrrolidone to form a slurry.

 次にこのスラリ−を厚み20μmの帯状のアルミニウムからなる正極集電体の両面に均一に塗布し、乾燥後ロ−ラ−プレス機で圧縮成形して厚さ160μmの帯状正極を得た。この帯状正極は成形後の正極合剤の膜厚が表面ともに70μmであり、その幅は53.6mm、長さは523.5mmに形成した。このようにして作製した帯状正極と帯状負極と厚さが25μm、幅が58.1mmの微多孔性ポリプロピレンフィルムよりなるセパレ−タとを積層して積層電極体とした。この積層電極体は、その長さ方向に沿って負極を内側にして渦巻き型に多数回巻き回し、最外周セパレ−タの最終端部をテ−プで固定して渦巻き式電極体とした。 (4) The slurry was uniformly applied to both sides of a 20 μm-thick strip of a positive electrode current collector made of aluminum, dried, and compression-molded with a roller press to obtain a 160 μm-thick strip-shaped positive electrode. This band-shaped positive electrode had a positive electrode mixture having a thickness of 70 μm on both surfaces after molding, a width of 53.6 mm, and a length of 523.5 mm. The strip-shaped positive electrode and the strip-shaped negative electrode thus manufactured, and a separator made of a microporous polypropylene film having a thickness of 25 μm and a width of 58.1 mm were laminated to form a laminated electrode body. The laminated electrode body was spirally wound many times along the length direction with the negative electrode inside, and the final end of the outermost peripheral separator was fixed with a tape to form a spiral electrode body.

 この渦巻き式電極体の中空部分は、その内径を3.5mm、外形を17mmに形成した。上述のように作製した渦巻き式電極体を、その上下に絶縁板を設置した状態で、ニッケルメッキが施された鉄製の電池缶に収納し、各リ−ドを導出した後、プロピレンカ−ボネイトとジエチルカ−ボネイトとの等容量混合溶媒中にLiPFを1モル/lの割合で溶解した非水電解液5.0gを注入し、封をして円筒形リチウムイオン二次電池を作製した。このリチウムイオン二次電池について、100サイクル後の容量維持率と、直流2Aで40分間過充電後の電池を解体し、銅箔の破れの有無を調べた。その結果を表1に示す。 The hollow portion of the spiral electrode body was formed to have an inner diameter of 3.5 mm and an outer shape of 17 mm. The spirally wound electrode body manufactured as described above is housed in a nickel-plated iron battery can with insulating plates placed above and below the spirally wound electrode body, and after each lead is led out, propylene carbonate is obtained. 5.0 g of a non-aqueous electrolyte obtained by dissolving LiPF 6 at a ratio of 1 mol / l in a mixed solvent of equal volumes of dimethyl ether and diethyl carbonate was injected and sealed to produce a cylindrical lithium ion secondary battery. With respect to this lithium ion secondary battery, the capacity retention ratio after 100 cycles and the battery after overcharging at 2 A DC for 40 minutes were disassembled, and the presence or absence of tearing of the copper foil was examined. Table 1 shows the results.

〔実施例2〕
 硫酸銅五水和物280g/l、硫酸100g/l、塩素イオン50ppmを含む硫酸酸性硫酸銅電解液にヒドロキシエチルセルロ−ス10ppm、3−メルカプト−1−プロパンスルホン酸ナトリウム1ppmを添加し、電解液温度55℃、流速0.5m/分、電流密度50A/dmの条件で電解銅箔を製箔した。電解液は、電解槽に入る前に活性炭処理塔を通り、電解が終了して電解槽から出た電解液を沸騰させる処理をした後、希望する濃度に調整してまた電解に供するサイクルとした。これによって、厚さ35μmと12μmの電解銅箔を製箔し、実施例1と同じ特性試験を実施した。その結果を表1に示す。またこの厚さ12μmの銅箔を用いて実施例1と同様にリチウムイオン二次電池を製造し、実施例1と同様に100サイクル後の容量維持率と、直流2Aで40分間過充電後の電池を解体し、銅箔の破れの有無を調べた。その結果を表1に示す。
[Example 2]
To a sulfuric acid acidic copper sulfate electrolyte containing 280 g / l of copper sulfate pentahydrate, 100 g / l of sulfuric acid and 50 ppm of chloride ion, 10 ppm of hydroxyethyl cellulose and 1 ppm of sodium 3-mercapto-1-propanesulfonate were added. An electrolytic copper foil was produced under the conditions of a liquid temperature of 55 ° C., a flow rate of 0.5 m / min, and a current density of 50 A / dm 2 . The electrolytic solution was passed through an activated carbon treatment tower before entering the electrolytic cell, and after the electrolysis was completed, the electrolytic solution coming out of the electrolytic cell was subjected to boiling treatment, and then adjusted to a desired concentration and subjected to electrolysis again. . Thus, electrolytic copper foils having a thickness of 35 μm and 12 μm were produced, and the same characteristic test as in Example 1 was performed. Table 1 shows the results. Further, a lithium ion secondary battery was manufactured using the copper foil having a thickness of 12 μm in the same manner as in Example 1, and the capacity retention after 100 cycles and the charge after overcharging with DC 2A for 40 minutes as in Example 1. The battery was disassembled, and the presence or absence of tearing of the copper foil was examined. Table 1 shows the results.

〔実施例3〕
 硫酸銅五水和物280g/l、硫酸100g/l、塩素イオン50ppmを含む硫酸酸性硫酸銅電解液に、平均分子量3000の低分子量ゼラチン10ppm 、ヒドロキシエチルセルロ−ス3ppm、3−メルカプト−1−プロパンスルホン酸ナトリウム1ppmを添加し、電解液温度55℃、流速0.3m/分、電流密度50A/dmの条件で電解銅箔を製箔した。この時電解液は、電解槽に入る前に活性炭処理塔を通り、電解が終了して電解槽から出た電解液を沸騰させる処理をした後、希望する濃度に調整してまた電解に供するサイクルとした。更にこの電解銅箔の電解析出面に、硫酸銅五水和物200g/l、硫酸60g/l、塩素イオン40ppm、液温55℃の電解液に、日本シェ−リング(株)製カパラシド210のメイキャップ剤10cc/l、光沢剤(A)0.5cc/l、光沢剤(B)を随時補充し添加して、銅光沢めっきを施した。これによって、厚さ35μmと12μmの電解銅箔を製箔し、実施例1と同じ特性試験を実施した。その結果を表1に示す。またこの厚さ12μmの銅箔を用いて実施例1と同様にリチウムイオン二次電池を製造し、実施例1と同様に100サイクル後の容量維持率と、直流2Aで40分間過充電後の電池を解体し、銅箔の破れの有無を調べた。その結果を表1に示す。
[Example 3]
To a sulfuric acid acidic copper sulfate electrolyte containing 280 g / l of copper sulfate pentahydrate, 100 g / l of sulfuric acid and 50 ppm of chloride ion, 10 ppm of low molecular weight gelatin having an average molecular weight of 3000, 3 ppm of hydroxyethyl cellulose, 3-mercapto-1- 1 ppm of sodium propanesulfonate was added, and an electrolytic copper foil was formed under the conditions of an electrolyte temperature of 55 ° C., a flow rate of 0.3 m / min, and a current density of 50 A / dm 2 . At this time, the electrolytic solution passes through an activated carbon treatment tower before entering the electrolytic cell, and after the electrolysis is completed, the electrolytic solution coming out of the electrolytic cell is boiled, and then adjusted to a desired concentration and then subjected to electrolysis again. And Further, on the electrolytic deposition surface of this electrolytic copper foil, 200 g / l of copper sulfate pentahydrate, 60 g / l of sulfuric acid, 40 ppm of chloride ions, and an electrolytic solution having a liquid temperature of 55 ° C. were added with Capallaside 210 manufactured by Nippon Schering Co., Ltd. A make-up agent 10 cc / l, a brightener (A) 0.5 cc / l, and a brightener (B) were replenished and added as needed, and copper bright plating was performed. Thus, electrolytic copper foils having a thickness of 35 μm and 12 μm were produced, and the same characteristic test as in Example 1 was performed. Table 1 shows the results. Further, a lithium ion secondary battery was manufactured using the copper foil having a thickness of 12 μm in the same manner as in Example 1, and the capacity retention after 100 cycles and the charge after overcharging with DC 2A for 40 minutes as in Example 1. The battery was disassembled, and the presence or absence of tearing of the copper foil was examined. Table 1 shows the results.

〔比較例1〕
 特許文献1に記載の実施例1−Aの条件で厚さ35μmと12μmの電解銅箔を製箔し、実施例1と同じ特性試験を実施した。その結果を表1に示す。またこの厚さ12μmの銅箔を用いて実施例1と同様にリチウムイオン二次電池を製造し、実施例1と同様に100サイクル後の容量維持率と、直流2Aで40分間過充電後の電池を解体し、銅箔の破れの有無を調べた。その結果を表1に示す。
[Comparative Example 1]
Under the conditions of Example 1-A described in Patent Literature 1, electrolytic copper foils having a thickness of 35 μm and 12 μm were produced, and the same characteristic test as in Example 1 was performed. Table 1 shows the results. Further, a lithium ion secondary battery was manufactured using the copper foil having a thickness of 12 μm in the same manner as in Example 1, and the capacity retention after 100 cycles and the charge after overcharging with DC 2A for 40 minutes as in Example 1. The battery was disassembled, and the presence or absence of tearing of the copper foil was examined. Table 1 shows the results.

〔比較例2〕
 特許文献2に記載の実施例2の条件で厚さ35μmと12μmの電解銅箔を製箔し、実施例1と同じ特性試験を実施した。その結果を表1に示す。またこの厚さ12μmの銅箔を用いて実施例1と同様にリチウムイオン二次電池を製造し、実施例1と同様に100サイクル後の容量維持率と、直流2Aで40分間過充電後の電池を解体し、銅箔の破れの有無を調べた。その結果を表1に示す。
[Comparative Example 2]
An electrolytic copper foil having a thickness of 35 μm and a thickness of 12 μm was produced under the conditions of Example 2 described in Patent Document 2, and the same characteristic test as in Example 1 was performed. Table 1 shows the results. Further, a lithium ion secondary battery was manufactured using the copper foil having a thickness of 12 μm in the same manner as in Example 1, and the capacity retention after 100 cycles and the charge after overcharging with DC 2A for 40 minutes as in Example 1. The battery was disassembled, and the presence or absence of tearing of the copper foil was examined. Table 1 shows the results.

〔比較例3〕
 特許文献3に記載の実施例1の条件で厚さ35μmと12μmの電解銅箔を製箔し、実施例1と同じ特性試験を実施した。その結果を表1に示す。またこの厚さ12μmの銅箔を用いて実施例1と同様にリチウムイオン二次電池を製造し、実施例1と同様に100サイクル後の容量維持率と、直流2Aで40分間過充電後の電池を解体し、銅箔の破れの有無を調べた。その結果を表1に示す。
[Comparative Example 3]
An electrolytic copper foil having a thickness of 35 μm and a thickness of 12 μm was produced under the conditions of Example 1 described in Patent Document 3, and the same characteristic test as in Example 1 was performed. Table 1 shows the results. Further, a lithium ion secondary battery was manufactured using the copper foil having a thickness of 12 μm in the same manner as in Example 1, and the capacity retention after 100 cycles and the charge after overcharging with DC 2A for 40 minutes as in Example 1. The battery was disassembled, and the presence or absence of tearing of the copper foil was examined. Table 1 shows the results.

Figure 2004079523
Figure 2004079523

 実施例1から3において、本発明の電解銅箔は10点平均粗さRzが2.5μm以下でありながら、素地山の最小ピ−ク間距離が5μm以上であり、常温での結晶組織が微細結晶でありながら、常温抗張力が40kg/mm以下であり、常温の伸び率が35μm厚さにおいて14%以上ある。更に130℃、15時間熱処理後の常温抗張力の低下が15%以内であり、熱軟化せず、常温から200℃までの高温雰囲気中での伸び率が増大傾向にあり、且つ180℃雰囲気中の伸び率が、35μm厚さにおいて18%以上である。これらの特性によって、充放電サイクル寿命と過充電特性が満足するものとなっている。 In Examples 1 to 3, the electrodeposited copper foil of the present invention had a 10-point average roughness Rz of 2.5 μm or less, a minimum peak-to-peak distance of 5 μm or more, and a crystal structure at room temperature. Although it is a fine crystal, the room temperature tensile strength is 40 kg / mm 2 or less, and the elongation at room temperature is 14% or more at a thickness of 35 μm. Furthermore, the decrease in room-temperature tensile strength after heat treatment at 130 ° C. for 15 hours is within 15%, there is no thermal softening, the elongation percentage in a high-temperature atmosphere from room temperature to 200 ° C. tends to increase, and in a 180 ° C. atmosphere. The elongation is 18% or more at a thickness of 35 μm. These characteristics satisfy the charge / discharge cycle life and overcharge characteristics.

 一方、比較例1は10点平均粗さRzは2.0μmで平滑であり、微細結晶だが、素地山の最小ピ−ク間距離が0.8μmであるため、炭素粉である活物質との接触点が少なく接触抵抗が大きくなり、充放電サイクル時の膨張収縮に伴うストレス等により集電体と活物質との距離が徐々に大きくなり、一部の活物質が充放電に利用できない電気伝導度になって容量の劣化が起きた。また、常温抗張力が高く、非常に硬い箔であり、常温伸び率も低いため、活物質塗布後に実施されるロ−ル圧延等のプレス平坦化工程で活物質表面に沿った銅箔の変形が十分に起こらず、活物質との接触が悪く、銅箔に一部、亀裂が発生し、容量の劣化、充放電サイクル寿命の低下を招いていた。 On the other hand, in Comparative Example 1, the 10-point average roughness Rz was 2.0 μm, which was smooth and fine crystal. However, since the minimum peak-to-peak distance of the base material mountain was 0.8 μm, the active material which was carbon powder was not used. The number of contact points is small, the contact resistance increases, and the distance between the current collector and the active material gradually increases due to the stress caused by expansion and contraction during the charge / discharge cycle. Deterioration of capacity occurred at a time. In addition, since the room temperature tensile strength is high, it is a very hard foil and the room temperature elongation is low, the deformation of the copper foil along the surface of the active material during the press flattening process such as roll rolling performed after application of the active material is performed. This did not occur sufficiently, the contact with the active material was poor, and a part of the copper foil was cracked, resulting in a deterioration in capacity and a reduction in charge / discharge cycle life.

 比較例2は比較例1と同様であるが、更に高温雰囲気中の伸び率が低く、常温の値よりも低下する傾向にある。このため、過充電特性テストにおいて、過充電時の発熱による膨張ストレスに耐えられず、銅箔に破れが発生した。 Comparative Example 2 is the same as Comparative Example 1, but has a lower elongation in a high-temperature atmosphere and tends to be lower than the value at room temperature. Therefore, in the overcharge characteristic test, the copper foil could not withstand the expansion stress due to the heat generated during overcharge, and the copper foil was torn.

 比較例3は比較例1と同様であるが、130℃×15時間熱処理すると常温抗張力が23kg/mmまで低下し、再結晶した。このため充放電に伴う活物質の膨張収縮によって、集電体用銅箔に亀裂や破断が発生し、容量の低下、充放電サイクル寿命の低下を招いていた。 Comparative Example 3 was the same as Comparative Example 1, but when heat-treated at 130 ° C. for 15 hours, the room-temperature tensile strength was reduced to 23 kg / mm 2 and recrystallized. For this reason, the active material expands and contracts due to charge and discharge, which causes cracks and breaks in the copper foil for the current collector, resulting in a decrease in capacity and a decrease in charge and discharge cycle life.

 本発明電解銅箔は二次電池の集電体用箔としての用途の他に、配線用基板等の用途にも適用可能である。 (4) The electrolytic copper foil of the present invention is applicable not only to a current collector foil of a secondary battery but also to a wiring board and the like.

Claims (4)

 電解銅箔析出面の表面粗さが、常温での結晶組織が10点平均粗さRzにして、2.5μmより小さい微細結晶でありながら、素地山の最小ピ−ク間距離が5μm以上であり、常温抗張力が40kg/mm以下であり、且つ130℃、15時間熱処理後の常温抗張力の低下が15%以内であり、熱軟化しないことを特徴とする電解銅箔。 When the surface roughness of the electrodeposited copper foil surface is a fine crystal smaller than 2.5 μm with a 10-point average roughness Rz at room temperature, the minimum peak-to-peak distance of the base mountain is 5 μm or more. An electrolytic copper foil having a room temperature tensile strength of 40 kg / mm 2 or less, a decrease in room temperature tensile strength after heat treatment at 130 ° C. for 15 hours of not more than 15%, and no thermal softening.  常温の伸び率が35μm厚さにおいて14%以上であり、常温から200℃までの高温雰囲気中での伸び率が増大傾向にあることを特徴とする請求項1記載の電解銅箔。 (4) The electrolytic copper foil according to (1), wherein the elongation at room temperature is 14% or more at a thickness of 35 μm, and the elongation in a high temperature atmosphere from room temperature to 200 ° C. tends to increase.  請求項1または2記載の電解銅箔を二次電池集電体用の銅箔として用いることを特徴とする二次電池集電体用電解銅箔。 An electrolytic copper foil for a secondary battery current collector, wherein the electrolytic copper foil according to claim 1 or 2 is used as a copper foil for a secondary battery current collector.  前記の二次電池がリチウムイオン二次電池である請求項1、2または3に記載の電解銅箔。 The electrolytic copper foil according to claim 1, 2 or 3, wherein the secondary battery is a lithium ion secondary battery.
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JP2011225987A (en) * 2010-03-31 2011-11-10 Furukawa Electric Co Ltd:The Copper (alloy) foil for negative electrode collector of lithium ion secondary battery and method for producing the same, and negative electrode of lithium ion secondary battery and method for producing the negative electrode
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