JP2012129136A - Lithium ion secondary battery copper foil and manufacturing method thereof - Google Patents
Lithium ion secondary battery copper foil and manufacturing method thereof Download PDFInfo
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- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 title claims abstract description 203
- 239000011889 copper foil Substances 0.000 title claims abstract description 150
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 56
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 56
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 17
- 239000013078 crystal Substances 0.000 claims abstract description 82
- 239000010949 copper Substances 0.000 claims abstract description 55
- 229910052802 copper Inorganic materials 0.000 claims abstract description 54
- 238000010438 heat treatment Methods 0.000 claims abstract description 20
- 238000005097 cold rolling Methods 0.000 claims abstract description 18
- 238000000137 annealing Methods 0.000 claims abstract description 14
- 239000000463 material Substances 0.000 claims abstract description 14
- 238000005096 rolling process Methods 0.000 claims description 49
- 239000012299 nitrogen atmosphere Substances 0.000 claims description 13
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims description 10
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 7
- 239000011888 foil Substances 0.000 claims description 7
- 229910052799 carbon Inorganic materials 0.000 claims description 6
- 229910045601 alloy Inorganic materials 0.000 claims description 4
- 239000000956 alloy Substances 0.000 claims description 4
- 238000005266 casting Methods 0.000 claims description 4
- 238000004381 surface treatment Methods 0.000 claims description 4
- 238000007599 discharging Methods 0.000 abstract description 4
- 239000011261 inert gas Substances 0.000 abstract description 3
- 239000012298 atmosphere Substances 0.000 abstract description 2
- 238000005098 hot rolling Methods 0.000 abstract description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 abstract 2
- 229910052757 nitrogen Inorganic materials 0.000 abstract 1
- 230000003252 repetitive effect Effects 0.000 abstract 1
- 230000000052 comparative effect Effects 0.000 description 17
- 229910000881 Cu alloy Inorganic materials 0.000 description 13
- 239000010731 rolling oil Substances 0.000 description 10
- 229910052718 tin Inorganic materials 0.000 description 10
- 238000012545 processing Methods 0.000 description 9
- 238000005259 measurement Methods 0.000 description 5
- 238000000034 method Methods 0.000 description 5
- 238000001953 recrystallisation Methods 0.000 description 4
- 238000011282 treatment Methods 0.000 description 4
- 239000000654 additive Substances 0.000 description 3
- 230000000996 additive effect Effects 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 238000007747 plating Methods 0.000 description 3
- 239000011230 binding agent Substances 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 229910052726 zirconium Inorganic materials 0.000 description 2
- QPLDLSVMHZLSFG-UHFFFAOYSA-N Copper oxide Chemical compound [Cu]=O QPLDLSVMHZLSFG-UHFFFAOYSA-N 0.000 description 1
- 239000005751 Copper oxide Substances 0.000 description 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 1
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 1
- 229910020938 Sn-Ni Inorganic materials 0.000 description 1
- 229910008937 Sn—Ni Inorganic materials 0.000 description 1
- 239000011149 active material Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- QRUDEWIWKLJBPS-UHFFFAOYSA-N benzotriazole Chemical compound C1=CC=C2N[N][N]C2=C1 QRUDEWIWKLJBPS-UHFFFAOYSA-N 0.000 description 1
- 239000012964 benzotriazole Substances 0.000 description 1
- ZCDOYSPFYFSLEW-UHFFFAOYSA-N chromate(2-) Chemical compound [O-][Cr]([O-])(=O)=O ZCDOYSPFYFSLEW-UHFFFAOYSA-N 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 150000001879 copper Chemical class 0.000 description 1
- 229910000431 copper oxide Inorganic materials 0.000 description 1
- 229910000365 copper sulfate Inorganic materials 0.000 description 1
- ARUVKPQLZAKDPS-UHFFFAOYSA-L copper(II) sulfate Chemical compound [Cu+2].[O-][S+2]([O-])([O-])[O-] ARUVKPQLZAKDPS-UHFFFAOYSA-L 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000005489 elastic deformation Effects 0.000 description 1
- 239000011883 electrode binding agent Substances 0.000 description 1
- 238000000445 field-emission scanning electron microscopy Methods 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 238000010191 image analysis Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000007773 negative electrode material Substances 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 238000004881 precipitation hardening Methods 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000003908 quality control method Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229920002554 vinyl polymer Polymers 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Cell Electrode Carriers And Collectors (AREA)
Abstract
Description
本発明はリチウムイオン二次電池用銅箔及びその製造方法に係り、特にリチウムイオンニ次電池の負極に用いて充放電時に破断する恐れのないリチウムイオン二次電池用銅箔及びその製造方法に関する。 The present invention relates to a copper foil for a lithium ion secondary battery and a method for producing the same, and more particularly to a copper foil for a lithium ion secondary battery that is used for a negative electrode of a lithium ion secondary battery and that does not break at the time of charge / discharge.
近年の携帯電話やパーソナルコンピュータ等の情報機器の普及は目覚しいものがあり、小型で高容量の二次電池に対する要求が高くなっている。二次電池のうちリチウムイオンニ次電池は、軽量で高いエネルギー密度を有していることから、最近では情報機器ばかりでなく電気自動車の分野でも注目されている。 In recent years, there has been a remarkable spread of information devices such as mobile phones and personal computers, and there is an increasing demand for small and high-capacity secondary batteries. Among secondary batteries, lithium ion secondary batteries are lightweight and have a high energy density, and thus have recently attracted attention not only in information equipment but also in the field of electric vehicles.
リチウムイオンニ次電池は、例えば図3に示すようにシート状の正極1と負極2を、各々の間にセパレータ3を介在して巻き合わせる構成している。リチウムイオンニ次電池の負極2には、一般には銅箔が使用され、この種の銅箔は製造方法によって大きく二つに分けることができる。一つには、鋳造で製造した素材に圧延加工を施して製造する圧延銅箔、他の一つには、硫酸銅を主とする溶液から銅を電解析出させて製造する電解銅箔がある。
For example, as shown in FIG. 3, the lithium ion secondary battery has a configuration in which a sheet-like
リチウムイオンニ次電池に使用する銅箔は、電池の高容量化と小型化の進展に伴い、厚み10μm以下が多く使われるようになってきており、銅箔破断の発生等の製造ラインでの通板性が悪化している。特に圧延銅箔においては、加工後の強度が高くて伸びが小さいため、製造ラインで銅箔にカーボンを塗布する作業時等の際、銅箔に与える微妙な張力変動によって破断が発生し易くなっている。 Copper foils used in lithium ion secondary batteries are increasingly used with a thickness of 10 μm or less as the capacity of batteries increases and miniaturization progresses. The plate property has deteriorated. In particular, in rolled copper foil, the strength after processing is high and the elongation is small, so breakage is likely to occur due to subtle fluctuations in tension applied to the copper foil during the operation of applying carbon to the copper foil in the production line. ing.
このため、リチウムイオンニ次電池に圧延銅箔を用いる場合は、圧延後に一定の温度条件で銅箔を加熱して軟化させることにより、予め銅箔の伸びを回復させた状態にし、リチウムイオンニ次電池の負極の製造ラインに投入することが行われている。 For this reason, when using a rolled copper foil for a lithium ion secondary battery, the copper foil is heated and softened under a certain temperature condition after rolling, so that the elongation of the copper foil is recovered in advance. To the negative electrode production line.
しかし、リチウムイオンニ次電池の高容量化に伴って、この充放電時に銅箔が破断することが多く見られるようになってきている。銅箔に生ずる破断の現象は、これまでは銅箔の伸びによって支配されていると考えられてきた。 However, with the increase in capacity of lithium ion secondary batteries, it is becoming increasingly common for copper foils to break during this charge / discharge. Until now, it has been considered that the phenomenon of fracture occurring in copper foil is governed by the elongation of copper foil.
ところが、電池が高容量化するにつれて、電解銅箔及び伸びの十分に回復した圧延銅箔でも、銅箔の破断が顕著に発生するようになっている。銅箔の破断の原因を検討すると、リチウムイオンニ次電池では、充電時にはリチウムイオンが正極から負極に移動し、放電時に再びリチウムイオンが負極から正極に移動する。リチウムイオンの移動に伴って負極材が膨張収縮するから、集電体として用いられる銅箔は充放電によって繰り返しの応力変動が働くため、銅箔は疲労変形してしまい、最終的に破断に至ることが判明している。 However, as the capacity of the battery increases, breakage of the copper foil is remarkably generated even in the electrolytic copper foil and the rolled copper foil whose elongation is sufficiently recovered. Examining the cause of the copper foil breakage, in the lithium ion secondary battery, lithium ions move from the positive electrode to the negative electrode during charging, and lithium ions move again from the negative electrode to the positive electrode during discharging. Since the negative electrode material expands and contracts with the movement of lithium ions, the copper foil used as a current collector undergoes repeated stress fluctuations due to charge and discharge, so the copper foil undergoes fatigue deformation and eventually breaks. It has been found.
リチウムイオンニ次電池の負極に使用する銅箔の強度と延性を向上させるため、例えばCrが0.05〜0.4質量%、Zrが0.01〜0.25質量%を含有し、残部が銅及び不可避不純物である銅合金を、圧延方向に走査したときの最大山高さRzと板厚tとの比であるRz/tが0.2未満で、かつ長径1μm以上の介在物の個数が100個/mm2以下であり、板厚20 μm以下にする析出硬化型銅合金箔が提案されている(特許文献1参照)。 In order to improve the strength and ductility of the copper foil used for the negative electrode of the lithium ion secondary battery, for example, Cr contains 0.05 to 0.4 mass%, Zr contains 0.01 to 0.25 mass%, and the balance is The number of inclusions with Rz / t, which is the ratio of the maximum peak height Rz and the plate thickness t when scanning copper and an inevitable impurity copper alloy in the rolling direction, is less than 0.2 and whose major axis is 1 μm or more. A precipitation hardening type copper alloy foil having a thickness of 100 pieces / mm 2 or less and a thickness of 20 μm or less has been proposed (see Patent Document 1).
また、充放電サイクル寿命の優れたリチウムイオン2次電池用負極を安価な製造するため、Niが1.0質量%以上で5質量%以下、Siが0.2質量%以上で1.2質量%以下を含有し、残部が銅及び不可避不純物とした銅合金箔に、錫鍍金を施してリチウムイオン2次電池用負極とするとき、錫鍍金の皮膜中にSn−Ni平衡状態図における金属間化合物を形成することも提案されている(特許文献2参照)。 Moreover, in order to produce a negative electrode for a lithium ion secondary battery having an excellent charge / discharge cycle life at low cost, Ni is 1.0 mass% or more and 5 mass% or less, and Si is 0.2 mass% or more and 1.2 mass. % When the copper alloy foil containing copper and the remainder made of copper and inevitable impurities is subjected to tin plating to form a negative electrode for a lithium ion secondary battery, the tin-plating film contains an intermetallic metal in the Sn-Ni equilibrium diagram. It has also been proposed to form a compound (see Patent Document 2).
しかし、上記特許文献1及び2に記載されてようにいるように、銅母材中に種々の元素を添加する合金箔では、添加元素の種類が多くしかも濃度高く、銅箔の品質管理や製造コストの面で得策ではないという問題があった。
However, as described in the
本発明の目的は、充放電時の繰返し応力で破断する恐れがなくて信頼性を向上でき、容易に製造できるリチウムイオン二次電池用銅箔及びその製造方法を提供することにある。 An object of the present invention is to provide a copper foil for a lithium ion secondary battery that can be easily manufactured without fear of breaking due to repeated stress during charge and discharge, and a method for manufacturing the same.
本発明のリチウムイオン二次電池用銅箔は、正極との間にセパレータを介在させて巻回する負極となる銅箔であり、前記銅箔は(200)結晶配向から15度以内の結晶配向を持つ結晶粒が、銅箔表面から見た面積の割合で50〜100%存在していることを特徴としている。 The copper foil for a lithium ion secondary battery of the present invention is a copper foil that becomes a negative electrode that is wound with a separator interposed between the positive electrode and the copper foil having a crystal orientation within 15 degrees from the (200) crystal orientation. It is characterized in that 50 to 100% of crystal grains having a ratio of area as viewed from the copper foil surface is present.
好ましくは、前記銅箔は最終冷間圧延前の平均結晶粒径は50μm以下であることを特徴としており、また前記銅箔は少なくとも片面に表面処理を施したことを特徴としており、更に前記銅箔は7μm〜20μmの厚みを有することを特徴としており、また前記銅箔はSnを添加した合金箔であることを特徴としており、更にまた前記銅箔はこの表面に塗布したカーボンを有することを特徴としている。 Preferably, the copper foil is characterized in that an average crystal grain size before final cold rolling is 50 μm or less, the copper foil is characterized in that at least one surface is subjected to surface treatment, and the copper foil is further characterized in that The foil is characterized by having a thickness of 7 μm to 20 μm, and the copper foil is characterized by being an alloy foil to which Sn is added, and further, the copper foil has carbon applied to this surface. It is a feature.
また、本発明のリチウムイオン二次電池用銅箔の製造方法は、溶解鋳造により作成した銅鋳塊を熱間圧延して予め定めた厚みに圧延し、前記熱間圧延材を冷間圧延と歪取り焼鈍を繰り返し行って所定の厚みの銅板を形成し、前記銅板を焼鈍後に冷間圧延して銅箔を得、前記銅箔を窒素雰囲気中において加熱する熱処理を施し、圧延加工度91〜99%で、かつ(200)結晶配向から15度以内の結晶粒が表面の面積の50〜100%割合存在する銅箔を得ることを特徴としている。 The method for producing a copper foil for a lithium ion secondary battery according to the present invention includes hot rolling a copper ingot created by melt casting to a predetermined thickness, and cold rolling the hot rolled material. A copper plate having a predetermined thickness is formed by repeatedly performing strain relief annealing, and after the copper plate is annealed, it is cold-rolled to obtain a copper foil, subjected to a heat treatment in which the copper foil is heated in a nitrogen atmosphere, and a rolling degree of 91- It is characterized by obtaining a copper foil in which 99% of the crystal grains within 15 degrees from the (200) crystal orientation are present in a proportion of 50 to 100% of the surface area.
好ましくは、前記銅鋳塊はタフピッチ銅であって、圧延加工度91〜95%で圧延加工したことを特徴としており、また前記銅鋳塊は無酸素銅に0.001〜0.009質量%の錫を添加し、圧延加工度91〜99%で圧延加工したことを特徴としている。 Preferably, the copper ingot is tough pitch copper and is rolled at a rolling work degree of 91 to 95%, and the copper ingot is 0.001 to 0.009 mass% in oxygen-free copper. The tin is added and rolled at a rolling degree of 91 to 99%.
本発明のリチウムイオン二次電池用銅箔によれば、リチウムイオン二次電池の充放電時の繰返し応力で銅箔の破断の発生を大幅に減少できるから、二次電池の信頼性を一層向上させることができる。 According to the copper foil for a lithium ion secondary battery of the present invention, the occurrence of copper foil breakage can be significantly reduced by repeated stress during charging and discharging of the lithium ion secondary battery, further improving the reliability of the secondary battery. Can be made.
また、本発明のリチウムイオン二次電池用銅箔の製造方法によれば、銅箔を容易に製造できてしかも品質管理が確実に行え、リチウムイオン二次電池用銅箔の製造コストを改善できる利点がある。 Moreover, according to the manufacturing method of the copper foil for lithium ion secondary batteries of this invention, copper foil can be manufactured easily and quality control can be performed reliably, and the manufacturing cost of the copper foil for lithium ion secondary batteries can be improved. There are advantages.
以下、本発明のリチウムイオン二次電池用銅箔及びその製造方法を、図1及び図2を用いて説明する。本発明者らは、リチウムイオン二次電池用銅箔について種々検討を重ねた結果、充放電時の繰返し応力に対して十分耐え得ることを見出した。本発明者らの検討によると、リチウムイオン二次電池用銅箔は、銅の結晶粒が(200)結晶配向から15度以内の結晶配向を持ち、しかも銅箔表面からみた面積の割合として50〜100%存在させるよう制御すれば、望ましい銅箔とすることができる。 Hereinafter, the copper foil for lithium ion secondary batteries of this invention and its manufacturing method are demonstrated using FIG.1 and FIG.2. As a result of various studies on the copper foil for lithium ion secondary batteries, the present inventors have found that the copper foil can sufficiently withstand the repeated stress during charging and discharging. According to the study by the present inventors, the copper foil for a lithium ion secondary battery has a crystal orientation in which the copper crystal grains are within 15 degrees from the (200) crystal orientation, and the ratio of the area viewed from the copper foil surface is 50. If it controls so that it may exist -100%, it can be set as a desirable copper foil.
なお、本発明において、銅の結晶粒が(200)結晶配向から15度以内とは、銅の結晶格子において、(200)面の法線ベクトルが銅箔の垂直方向を向いている状態を0度とした場合、図1(a)、(b)、(c)に示すような各結晶の(200)面の法線ベクトルが成す角度が、15度以内であることを指している。ここで、(200)面、即ち、(200)面と一致するものも含まれることに注意されたい。 In the present invention, the copper crystal grains within 15 degrees from the (200) crystal orientation means that the normal vector of the (200) plane faces the vertical direction of the copper foil in the copper crystal lattice. In this case, the angle formed by the normal vector of the (200) plane of each crystal as shown in FIGS. 1A, 1B, and 1C is within 15 degrees. Here, it should be noted that the (200) plane, that is, the one matching the (200) plane is also included.
本発明のリチウムイオン二次電池用銅箔は、例えば以下のような手順によって製造する。即ち、銅箔の製造は、(200)結晶配向から15度以内の結晶粒が50〜100%にするため、まず溶解鋳造により銅鋳塊を作成し、この銅鋳塊を熱間圧延により、厚み13mmまで圧延して銅板を作成する。 The copper foil for lithium ion secondary batteries of this invention is manufactured, for example with the following procedures. That is, in the manufacture of the copper foil, since the crystal grains within 15 degrees from the (200) crystal orientation are 50 to 100%, first, a copper ingot is created by melt casting, and this copper ingot is hot-rolled. A copper plate is prepared by rolling to a thickness of 13 mm.
次に、作成した厚み13mmの銅板を、冷間圧延と歪取り焼鈍を繰り返し、厚み0.2mmの銅板とした。更に、この0.2mmの銅板を、温度800℃で30秒焼鈍し、この時の平均結晶粒径を50μm以下になるよう調整した。その後、厚み10μmまで冷間圧延した。ここまでの銅箔の製造段階で、圧延加工度は95%になる。なお、銅箔の加工度は、純銅や銅合金の如く使用する銅材料によって異なるが、圧延加工度91%〜99%の範囲である。 Next, the produced copper plate having a thickness of 13 mm was repeatedly subjected to cold rolling and strain relief annealing to obtain a copper plate having a thickness of 0.2 mm. Furthermore, this 0.2 mm copper plate was annealed at a temperature of 800 ° C. for 30 seconds, and the average crystal grain size at this time was adjusted to 50 μm or less. Then, it cold-rolled to thickness 10micrometer. At the copper foil manufacturing stage so far, the rolling degree is 95%. In addition, although the processing degree of copper foil changes with copper materials used like pure copper or a copper alloy, it is the range of 91%-99% of rolling processing.
この製造した銅箔は、(200)結晶配向を成長させるため、不活性ガスである窒素雰囲気中において、170℃で30分の加熱処理を施している。この圧延後の加熱処理の条件としては、170℃〜300℃の温度で、30分〜10時間保持する処理を、対象銅箔によって処理条件を選択して実施する。この加熱処理により、銅箔は結晶粒を(200)結晶配向から15度以内の結晶配向を持ち、かつ表面の面積の割合で50〜100%存在する所望のリチウムイオン二次電池用銅箔とすることができる。 This manufactured copper foil is subjected to a heat treatment at 170 ° C. for 30 minutes in a nitrogen atmosphere as an inert gas in order to grow (200) crystal orientation. As the conditions for the heat treatment after rolling, a treatment for holding for 30 minutes to 10 hours at a temperature of 170 ° C. to 300 ° C. is performed by selecting the treatment conditions depending on the target copper foil. By this heat treatment, the copper foil has a crystal orientation within 15 degrees from the (200) crystal orientation, and a desired copper foil for a lithium ion secondary battery having a surface area ratio of 50 to 100%. can do.
上記した如く圧延銅箔を用いる場合、(200)結晶配向を持つ結晶粒は、圧延で与えられる加工歪を駆動力として、加熱処理時に再結晶粒として発生し、成長する。このとき、与えた加工歪が少ないと、(200)結晶配向を持つ結晶粒は十分に成長することができない。逆に、与えた加工歪が過剰であると、圧延加工中に自らの歪を駆動力として再結晶を発生させてしまい、結果として加熱処理後の再結晶粒は(200)結晶配向とは異なるものになる。 When a rolled copper foil is used as described above, crystal grains having a (200) crystal orientation are generated and grown as recrystallized grains during heat treatment using the processing strain given by rolling as a driving force. At this time, if the applied processing strain is small, crystal grains having the (200) crystal orientation cannot be sufficiently grown. On the other hand, if the applied strain is excessive, recrystallization occurs during rolling by using the strain as a driving force, and as a result, the recrystallized grains after the heat treatment are different from the (200) crystal orientation. Become a thing.
与える加工歪の量は、銅箔に使用する材質や耐熱性によって、その適切な範囲は異なっており、また加工歪の量は、圧延加工時の圧延加工度によって制御される。なお、銅箔の圧延加工度は、次の式で表される。
圧延加工度(%)=(圧延前の厚み一圧延後の厚み)/(圧延前の厚み)×100
The amount of processing strain to be applied varies depending on the material used for the copper foil and the heat resistance, and the appropriate range varies. The amount of processing strain is controlled by the degree of rolling during rolling. In addition, the rolling degree of copper foil is represented by the following formula.
Rolling degree (%) = (Thickness before rolling—Thickness after rolling) / (Thickness before rolling) × 100
圧延銅箔に用いる材質として、Cu2O酸化銅の状態で酸素を0.02〜0.05%含んだ銅99.90%以上のタフピッチ銅は、電気や熱の伝導性に優れ、展延性及び絞り加工性が良好であるから、これを用いる場合、その圧延加工度は91〜95%であることが望ましい。この範囲とするのは、タフピッチ銅では圧延加工度91%未満では圧延後の加熱処理において(200)結晶配向が十分に成長せず、圧延加工度95%を超えると(200)結晶配向とは異なる配向を持つ再結晶粒が発生してしまうためである。 As the material used for the rolled copper foil, 99.90% or more tough pitch copper containing 0.02 to 0.05% oxygen in the state of Cu 2 O copper oxide is excellent in electrical and thermal conductivity, and is malleable. And, since the drawing workability is good, when this is used, the rolling work degree is desirably 91 to 95%. In this range, with tough pitch copper, if the degree of rolling is less than 91%, the (200) crystal orientation does not grow sufficiently in the heat treatment after rolling, and if the degree of rolling exceeds 95%, the (200) crystal orientation is This is because recrystallized grains having different orientations are generated.
また、圧延銅箔の材質として、無酸素銅に0.001〜0.009質量%の錫(Sn)を添加した銅合金を用いることができる。この錫添加の銅合金を用いる場合、タフピッチ銅と比べて軟化温度が10〜50℃高くなるため、より高い圧延加工度を与えても(200)結晶配向は成長することができる。このため、望ましい圧延加工度の範囲は、91〜99%である。 Moreover, the copper alloy which added 0.001-0.009 mass% tin (Sn) to oxygen-free copper can be used as a material of rolled copper foil. When this tin-added copper alloy is used, the softening temperature is 10 to 50 ° C. higher than that of tough pitch copper, so that (200) crystal orientation can grow even when a higher degree of rolling work is given. For this reason, the range of a desirable rolling work degree is 91-99%.
圧延銅箔の場合は、(200)結晶配向を持つ結晶粒の割合は、加熱処理の温度や時間によっても変化する。加熱処理の熱量が不足した場合は圧延組織が残留し、逆に加熱処理の熱量が過剰な場合は、二次的な再結晶により(200)結晶配向とは異なる結晶配向を持った結晶粒が発生する。圧延銅箔の最適な加熱処理条件は、銅箔の材質、加熱時の雰囲気、炉の加熱方法などの条件によって異なってくる。 In the case of a rolled copper foil, the proportion of crystal grains having a (200) crystal orientation also changes depending on the temperature and time of the heat treatment. When the heat amount of the heat treatment is insufficient, the rolled structure remains, and conversely, when the heat amount of the heat treatment is excessive, secondary recrystallization causes crystal grains having a crystal orientation different from (200) crystal orientation. appear. The optimum heat treatment conditions for the rolled copper foil vary depending on the conditions such as the material of the copper foil, the atmosphere during heating, and the heating method of the furnace.
本発明のリチウムイオン二次電池用銅箔の製造には、上記の圧延銅箔ばかりでなく、電解銅箔のいずれでも用いることができる。圧延銅箔を用いる場合は、前述の如く圧延加工後に(200)結晶配向を成長させるために、銅箔に対して加熱処理を実施する。 In the production of the copper foil for a lithium ion secondary battery of the present invention, not only the rolled copper foil but also any electrolytic copper foil can be used. In the case of using a rolled copper foil, the copper foil is subjected to a heat treatment in order to grow the (200) crystal orientation after the rolling process as described above.
上記した本発明のリチウムイオン二次電池用銅箔では、(200)結晶配向性を高めることによって、充放電時における銅箔の疲労特性は向上するので、銅箔は破断しにくくなるから、充放電時のサイクル特性を改善することができる。 In the above-described copper foil for a lithium ion secondary battery according to the present invention, since the fatigue characteristics of the copper foil at the time of charge / discharge are improved by increasing the (200) crystal orientation, the copper foil is difficult to break. Cycle characteristics during discharge can be improved.
更に、最終冷間圧延前における結晶粒の平均結晶粒径を50μm以下とすることが望ましい。平均結晶粒径の測定方法としては、ラインインターセプト法を用いる。試料の圧延方向の断面組織および幅方向の断面組織について測定を行い、その平均値を平均結晶粒径として用いる。最終冷間圧延前における平均結晶粒径を50μm以下とすることにより、その後の冷間圧延時に圧延集合組織を形成しやすくなり、その結果、再結晶粒の(200)結晶配向性を高めることが可能になる。 Furthermore, it is desirable that the average crystal grain size of the crystal grains before final cold rolling be 50 μm or less. A line intercept method is used as a method for measuring the average crystal grain size. The sample is measured for the cross-sectional structure in the rolling direction and the cross-sectional structure in the width direction, and the average value is used as the average crystal grain size. By setting the average grain size before the final cold rolling to 50 μm or less, it becomes easier to form a rolling texture during the subsequent cold rolling, and as a result, the (200) crystal orientation of the recrystallized grains can be improved. It becomes possible.
本発明のリチウムイオン二次電池用銅箔は、純銅(含有成分が銅及び不可避不純物)を用いて製造しても良いし、例えばAg、Sn、Ni、Co、Fe、P、Si、Zn、Cr、Zr、Al、Mnのうち1種以上が添加された合金箔を用いて製造することもできる。この場合は、添加材料及びその量によって銅箔の軟化温度が変化するため、添加材料及びその量に応じて、加熱時間や加熱温度等の熱処理条件を調整することで上述の結晶配向をもつ結晶粒を有する銅箔を得ることができる。 The copper foil for a lithium ion secondary battery of the present invention may be manufactured using pure copper (containing components are copper and inevitable impurities), for example, Ag, Sn, Ni, Co, Fe, P, Si, Zn, It can also be manufactured using an alloy foil to which one or more of Cr, Zr, Al, and Mn are added. In this case, since the softening temperature of the copper foil changes depending on the additive material and the amount thereof, the crystal having the above crystal orientation can be obtained by adjusting the heat treatment conditions such as the heating time and the heating temperature according to the additive material and the amount thereof. A copper foil having grains can be obtained.
また、本発明のリチウムイオン二次電池用銅箔は、加熱処理された銅箔に例えば下記のようにしてカーボンを塗工し、リチウムイオン二次電池を組み立てることもできる。銅箔の面へのカーボンの塗工は、グラファイト90%に対して、バインダ10%の割合としたものを用いて行い、プレスによって塗工物質の厚みを100μmにする。なお、バインダとしては、一般的なポリビニルデンフルオライド(PVdF)+N−メチルピロリドン(MNP)を用い、またカーボンの塗工時にMNPを揮発除去するため、80℃で10分間程度の乾燥を実施する。 Moreover, the copper foil for lithium ion secondary batteries of this invention can also apply | coat carbon to the heat-treated copper foil as follows, for example, and can also assemble a lithium ion secondary battery. The coating of carbon on the surface of the copper foil is performed using a ratio of 10% of binder to 90% of graphite, and the thickness of the coating substance is set to 100 μm by pressing. As the binder, typically polyvinyl Den fluoride (PVdF) + N - using methyl pyrrolidone (MNP), and in order to volatilize removing MNP when carbon coating, to implement the drying of about 10 minutes at 80 ° C. .
しかも、本発明のリチウムイオン二次電池用銅箔は、あらゆる表面処理と組み合わせても使用できる。例えば、負極括物質との密着性を向上させるために、銅箔の片面又は両面を粗化し、或いは酸化等による銅箔の表面の変質を防ぐために、Ni鍍金やクロメート処理やベンゾトリアゾール処理を施すこともできる。銅箔の表面処理の時機は、圧延銅箔の場合は圧延加工後でも、また加熱処理後のいずれでも何ら構わない。 And the copper foil for lithium ion secondary batteries of this invention can be used even if it combines with all surface treatments. For example, in order to improve the adhesion with the negative electrode binding material, one side or both sides of the copper foil are roughened, or Ni plating, chromate treatment or benzotriazole treatment is performed to prevent the copper foil surface from being altered by oxidation or the like. You can also. The timing of the surface treatment of the copper foil may be any after the rolling process or after the heat treatment in the case of the rolled copper foil.
また更に、本発明のリチウムイオン二次電池用銅箔の厚みは20μm以下であって、望ましくは18μm〜10μmである。最適な銅箔の厚みは、対象のリチウムイオン二次電池の構成によって異なっており、一般的には厚みが薄いと活物質を多く乗せられることから、電池容量的に有利にできる。 Furthermore, the thickness of the copper foil for lithium ion secondary batteries of this invention is 20 micrometers or less, Preferably it is 18 micrometers-10 micrometers. The optimal thickness of the copper foil varies depending on the configuration of the target lithium ion secondary battery. Generally, when the thickness is small, a large amount of active material can be loaded, which can be advantageous in terms of battery capacity.
次に、本発明のリチウムイオン二次電池用銅箔である実施例1から4、及び比較例1から4について順に説明する。下記の各実施例及び各比較例では、銅箔の結晶配向性は、いずれもSEM−EBSP解析法(Scanning Electron Microscope−Electron BackScatteing diffaction Pattern:走査型電子顕微鏡による背面反射電子像解析法)にて測定した。 Next, Examples 1 to 4 and Comparative Examples 1 to 4 which are copper foils for lithium ion secondary batteries of the present invention will be described in order. In each of the following Examples and Comparative Examples, the crystal orientation of the copper foil is determined by SEM-EBSP analysis (Scanning Electron Microscope-Electron Backscattering diffraction Pattern: back reflection electron image analysis using a scanning electron microscope). It was measured.
測定にあたっては、対象の銅箔を所定の大きさに切り出し、イオンスパッタで銅箔表面の酸化物を除去した後、これをFE-SEMに投入し、EBSP解析を実施した。測定時の倍率は200倍、EBSP解析範囲は視野中の400μm四方とし、測定ピッチ2μmで測定を行った。 In the measurement, the target copper foil was cut into a predetermined size, and the oxide on the surface of the copper foil was removed by ion sputtering. Then, this was put into an FE-SEM, and EBSP analysis was performed. The magnification at the time of measurement was 200 times, the EBSP analysis range was 400 μm square in the visual field, and measurement was performed at a measurement pitch of 2 μm.
測定したデータより、各結晶粒の結晶配向を解析して、結晶配向によって色分けがされたIPF(Inverse Pole Figure:逆極点図)フルカラーマップ写真を基にして図2(a)に示すIPFグレーマップ写真を作成した。このIPFグレーマップ写真は、図2(b)に示すグレースケールで結晶配向を判別できるが、対象の結晶粒及びそれ以外のものとの判別を更に容易にするため、IPFグレーマップ写真を二値化した図2(c)に示す二値化写真を活用し、黒色箇所の対象の粒を特定する。実際の結晶粒特定作業は、コンピュータを活用し、(200)結晶配向から15度以内の結晶配向を持つ結晶粒を特定し、測定面積内での面積率を求めた。これを(200)面積率とする。 From the measured data, the crystal orientation of each crystal grain is analyzed, and the IPF gray map shown in FIG. 2 (a) is based on an IPF (Inverse Pole Figure) full color map photograph that is color-coded according to the crystal orientation. Created a photo. In this IPF gray map photograph, the crystal orientation can be discriminated on the gray scale shown in FIG. 2B. However, in order to further easily discriminate the target crystal grain from the other, the IPF gray map photograph is binary. The binarized photograph shown in FIG. 2C is used to identify the target grain in the black portion. In the actual crystal grain identification work, a computer was used to identify crystal grains having a crystal orientation within 15 degrees from the (200) crystal orientation, and the area ratio within the measurement area was obtained. This is the (200) area ratio.
実施例1
タフピッチ銅(「TPC」と表記)を用いて、加熱条件800℃15秒の焼鈍によって平均結晶粒径を30μmに調整した後、冷間圧延にて圧延加工度91%で厚み10μmの銅箔を作製した。この銅箔を表面の圧延油を洗浄除去したのち、シートの状態に切り出し、所望の結晶粒を得るため不活性ガスである窒素雰囲気中において、170℃で30分間加熱した。
Example 1
After adjusting the average crystal grain size to 30 μm by annealing at 800 ° C. for 15 seconds using a tough pitch copper (indicated as “TPC”), a copper foil having a rolling work degree of 91% and a thickness of 10 μm is obtained by cold rolling. Produced. The copper foil was washed and removed from the rolling oil on the surface, then cut into a sheet state, and heated at 170 ° C. for 30 minutes in a nitrogen atmosphere as an inert gas in order to obtain desired crystal grains.
実施例2
タフピッチ銅(TPC)を用いて、加熱条件800℃15秒の焼鈍によって平均結晶粒径を30μmに調整した後、冷間圧延にて圧延加工度95%で厚み10μmの銅箔を作製した。この銅箔を表面の圧延油を洗浄除去したのち、シートの状態に切り出し、同様に窒素雰囲気中において170で℃30分間加熱した。
Example 2
After adjusting the average crystal grain size to 30 μm by annealing at 800 ° C. for 15 seconds using tough pitch copper (TPC), a copper foil having a rolling degree of 95% and a thickness of 10 μm was produced by cold rolling. This copper foil was washed and removed from the rolling oil on the surface, then cut into a sheet state and similarly heated at 170 ° C. for 30 minutes in a nitrogen atmosphere.
実施例3
タフピッチ銅(TPC)を用いて、加熱条件800℃40秒の焼鈍によって平均結晶粒径を45μmに調整した後、冷間圧延にて圧延加工度95%で厚み10μmの銅箔を作製した。この銅箔を表面の圧延油を洗浄除去したのち、シートの状態に切り出し、同様に窒素雰囲気中において170で℃30分間加熱した。
Example 3
After adjusting the average crystal grain size to 45 μm by annealing at 800 ° C. for 40 seconds using tough pitch copper (TPC), a copper foil having a rolling degree of 95% and a thickness of 10 μm was produced by cold rolling. This copper foil was washed and removed from the rolling oil on the surface, then cut into a sheet state and similarly heated at 170 ° C. for 30 minutes in a nitrogen atmosphere.
実施例4
無酸素銅に錫(Sn)を0.001〜0.009質量%添加し、鋳造した銅合金(「HXN」と表記)を用いて、加熱条件800℃35秒の焼鈍によって平均結晶粒径を30μmに調整した後、冷間圧延にて圧延加工度91%で厚み10μmの銅箔を作製した。この銅箔を表面の圧延油を洗浄除去したのち、シートの状態に切り出し、窒素雰囲気中において250℃で1時間加熱した。添加する錫は、純銅または無酸素銅を高周波溶解炉で溶解するときに必要量を加え、得られた溶湯を鋳型に流し込み、連続的に冷却することで鋳造を行い、上述したように圧延して銅合金から銅箔を製造する。
Example 4
0.001 to 0.009 mass% of tin (Sn) is added to oxygen-free copper, and a cast copper alloy (indicated as “HX N ”) is used to anneal the average crystal grain size by annealing at 800 ° C. for 35 seconds. Was adjusted to 30 μm, and then a cold-rolled copper foil having a rolling degree of 91% and a thickness of 10 μm was produced. This copper foil was washed and removed from the rolling oil on the surface, then cut into a sheet and heated at 250 ° C. for 1 hour in a nitrogen atmosphere. The tin to be added is added in a necessary amount when pure copper or oxygen-free copper is melted in a high-frequency melting furnace, the obtained molten metal is poured into a mold, continuously cooled, cast, and rolled as described above. A copper foil is manufactured from the copper alloy.
実施例5
無酸素銅に錫(Sn)を0.001〜0.009質量%添加し、鋳造した銅合金(HXN)を用いて、加熱条件800℃35秒の焼鈍によって平均結晶粒径を30μmに調整した後、冷間圧延にて圧延加工度99%で厚み1μmの銅箔を作製した。この銅箔を表面の圧延油を洗浄除去したのち、シートの状態に切り出し、同様に窒素雰囲気中において250℃で1時間加熱した。
Example 5
Add 0.001 to 0.009 mass% of tin (Sn) to oxygen-free copper, and adjust the average grain size to 30 μm by annealing at 800 ° C. for 35 seconds using a cast copper alloy (HX N ). Then, a cold-rolled copper foil having a rolling degree of 99% and a thickness of 1 μm was produced. This copper foil was washed and removed from the rolling oil on the surface, cut into a sheet, and similarly heated at 250 ° C. for 1 hour in a nitrogen atmosphere.
比較例1
タフピッチ銅(TPC)を用いて、加熱条件800℃15秒の焼鈍によって平均結晶粒径を30μmに調整した後、冷間圧延にて圧延加工度90%で厚み10μmの銅箔を作製した。この銅箔を表面の圧延油を洗浄除去したのち、シートの状態に切り出し、窒素雰囲気中において170℃で30分間加熱した。
Comparative Example 1
After adjusting the average crystal grain size to 30 μm by annealing at 800 ° C. for 15 seconds using tough pitch copper (TPC), a copper foil having a rolling degree of 90% and a thickness of 10 μm was produced by cold rolling. This copper foil was washed and removed from the rolling oil on the surface, cut into a sheet, and heated at 170 ° C. for 30 minutes in a nitrogen atmosphere.
比較例2
タフピッチ銅(TPC)を用いて、加熱条件800℃15秒の焼鈍によって平均結晶粒径を30μmに調整した後、冷間圧延にて圧延加工度96%で厚み10μmの銅箔を作製した。この銅箔を表面の圧延油を洗浄除去したのち、シートの状態に切り出し、窒素雰囲気中において170℃30分間加熱した。
Comparative Example 2
An average crystal grain size was adjusted to 30 μm by annealing at 800 ° C. for 15 seconds using tough pitch copper (TPC), and then a copper foil having a rolling degree of 96% and a thickness of 10 μm was produced by cold rolling. This copper foil was washed and removed from the rolling oil on the surface, then cut into a sheet and heated at 170 ° C. for 30 minutes in a nitrogen atmosphere.
比較例3
タフピッチ銅(TPC)を用いて、加熱条件800℃50秒の焼鈍によって平均結晶粒径を60μmに調整した後、冷間圧延にて圧延加工度95%で厚み10μmの銅箔を作製した。この銅箔を表面の圧延油を洗浄除去したのち、シートの状態に切り出し、窒素雰囲気中において170℃30分間加熱した。
Comparative Example 3
After adjusting the average crystal grain size to 60 μm by annealing at 800 ° C. for 50 seconds using tough pitch copper (TPC), a copper foil having a rolling degree of 95% and a thickness of 10 μm was produced by cold rolling. This copper foil was washed and removed from the rolling oil on the surface, then cut into a sheet and heated at 170 ° C. for 30 minutes in a nitrogen atmosphere.
比較例4
無酸素銅に錫(Sn)を0.001〜0.009質量%添加し、鋳造した銅合金(HXN)を用いて平均結晶粒径を30μmにし、圧延にて圧延加工度90%で厚み10μmの銅箔を作製した。この銅箔を表面の圧延油を洗浄除去したのち、シートの状態に切り出し、窒素雰囲気中において250℃で1時間加熱した。
Comparative Example 4
0.001 to 0.009 mass% of tin (Sn) is added to oxygen-free copper, the average crystal grain size is made 30 μm using a cast copper alloy (HX N ), and the thickness is reduced to 90% by rolling. A 10 μm copper foil was prepared. This copper foil was washed and removed from the rolling oil on the surface, then cut into a sheet and heated at 250 ° C. for 1 hour in a nitrogen atmosphere.
比較例5
無酸素銅に錫(Sn)を0.001〜0.009質量%添加し、鋳造した銅合金(HXN)を用いて、加熱条件800℃35秒の焼鈍によって平均結晶粒径を30μmに調整した後、冷間圧延にて圧延加工度99・5%で厚み10μmの銅箔を作製した。この銅箔を表面の圧延油を洗浄除去したのち、シートの状態に切り出し、窒素雰囲気中において250℃で1時間加熱した。
Comparative Example 5
Add 0.001 to 0.009 mass% of tin (Sn) to oxygen-free copper, and adjust the average grain size to 30 μm by annealing at 800 ° C. for 35 seconds using a cast copper alloy (HX N ). After that, a copper foil having a rolling degree of 99.5% and a thickness of 10 μm was produced by cold rolling. This copper foil was washed and removed from the rolling oil on the surface, then cut into a sheet and heated at 250 ° C. for 1 hour in a nitrogen atmosphere.
上記した実施例1〜5及び比較例1〜5で得られた銅箔について、それぞれ(200)面積率、及びサイクル特性を測定して、良好な銅箔を○印にし、不良の銅箔を×印にして評価した。評価結果を表1に示している。 For the copper foils obtained in Examples 1 to 5 and Comparative Examples 1 to 5 described above, the (200) area ratio and the cycle characteristics were measured, and a good copper foil was marked with a circle. The evaluation was made with crosses. The evaluation results are shown in Table 1.
実施例1と2及び比較例1〜3は、材質としてタフピッチ銅(TPC)を使用し、異なる厚みから10μmまで圧延することにより、圧延加工度を変化させたものである。表1に示しているように、比較例1は圧延加工度90%で(200)面積率が45%であったのに対し、実施例1の如く圧延加工度91%とすることで50%、実施例2の如く加工度95%で(200)面積率67%まで増加した。しかし、比較例2の如く圧延加工度を96%まで高くすると、(200)面積率は大きく減少する。これは、圧延中に再結晶が発生することで最終的に銅箔に与えられる加工歪量が減少し、(200)結晶配向を持った再結晶粒が成長しにくくなったためである。 Examples 1 and 2 and Comparative Examples 1 to 3 use tough pitch copper (TPC) as a material and change the rolling degree by rolling from different thicknesses to 10 μm. As shown in Table 1, Comparative Example 1 had a rolling degree of 90% and a (200) area ratio of 45%, whereas it was 50% by setting the rolling degree to 91% as in Example 1. As in Example 2, the degree of processing increased to 95% (200) and the area ratio to 67%. However, when the rolling degree is increased to 96% as in Comparative Example 2, the (200) area ratio is greatly reduced. This is because recrystallization occurs during rolling, which ultimately reduces the amount of processing strain imparted to the copper foil, making it difficult for recrystallized grains having a (200) crystal orientation to grow.
また、(200)面積率が50%未満であった比較例1、2は、サイクル特性においても断線が認められた。これは鋳造した銅合金を用いた実施例4、5及び比較例4、5の場合でも同様である。ただし、鋳造した銅合金(HXN)は、錫(Sn)を添加しているためにタフピッチ銅と比べて軟化温度が高い。即ち、再結晶を発生させるためのエネルギー障壁が高いことから、タフピッチ銅と比べて高い圧延加工度まで(200)面積率は維持する。 Further, in Comparative Examples 1 and 2 in which the (200) area ratio was less than 50%, disconnection was recognized also in the cycle characteristics. The same applies to Examples 4 and 5 and Comparative Examples 4 and 5 using a cast copper alloy. However, the cast copper alloy (HX N ) has a softening temperature higher than that of tough pitch copper because tin (Sn) is added. That is, since the energy barrier for generating recrystallization is high, the (200) area ratio is maintained up to a higher degree of rolling than that of tough pitch copper.
実施例2、3および比較例3は、冷間圧延前の焼鈍条件を変えることにより、冷間圧延前の平均結晶粒径を変化させたものである。実施例2は平均結晶粒径が30μmだったのに対し、実施例3では45μm、比較例3では60μmとなっている。これによって実施例3は(200)面積率が55%、比較例3では48%まで低下し、比較例3ではサイクル特性においても不良の結果となった。 In Examples 2, 3 and Comparative Example 3, the average crystal grain size before cold rolling was changed by changing the annealing conditions before cold rolling. In Example 2, the average crystal grain size was 30 μm, whereas in Example 3, it was 45 μm, and in Comparative Example 3, it was 60 μm. As a result, in Example 3, the (200) area ratio decreased to 55%, and in Comparative Example 3, it decreased to 48%. In Comparative Example 3, the cycle characteristics were poor.
リチウムイオン二次電池用銅箔は、充放電試験によって、負極括物質は膨張収縮を繰り返し、銅箔は繰り返しの変形応力を受ける。この変形は銅箔が大きく塑性変形するほどではなく、弾性変形に近い変形の繰り返し、即ち疲労変形に近いものとなる。このような変形が与えられたとき、銅箔は与えられた歪を結晶すべりによって解消しようとする。それ故、(200)結晶配向に近い配向を持つ結晶粒が多く存在すると、この結晶すべりが結晶粒界を超えて伝播しやすくなり、結晶粒界に歪が蓄積することは無くなる。そのため、本発明のリチウムイオン二次電池用銅箔のように、(200)結晶配向に近い配向を持った結晶組織を持つことで、充放電試験時に銅箔に歪が蓄積しないから、銅箔の破断も起こらなくなる。 In the copper foil for a lithium ion secondary battery, the negative electrode binder repeatedly expands and contracts, and the copper foil is subjected to repeated deformation stress by a charge / discharge test. This deformation is not so much that the copper foil is plastically deformed, but it is a repetition of deformation close to elastic deformation, that is, close to fatigue deformation. When such deformation is applied, the copper foil tries to eliminate the applied strain by crystal slip. Therefore, when there are many crystal grains having an orientation close to the (200) crystal orientation, this crystal slip is likely to propagate beyond the crystal grain boundary, and no strain is accumulated in the crystal grain boundary. Therefore, as the copper foil for lithium ion secondary batteries of the present invention has a crystal structure having an orientation close to (200) crystal orientation, strain does not accumulate in the copper foil during the charge / discharge test. No breakage occurs.
1…正極、2…負極、3…セパレータ。
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JP2012201965A (en) * | 2011-03-28 | 2012-10-22 | Jx Nippon Mining & Metals Corp | Copper foil and secondary battery using the same |
JP2013241662A (en) * | 2012-05-22 | 2013-12-05 | Furukawa Electric Co Ltd:The | Rolled copper foil for collector of secondary battery and method for producing the same |
JP2014218730A (en) * | 2013-05-10 | 2014-11-20 | 古河電気工業株式会社 | Rolled copper foil and method of producing rolled copper foil |
JP2016191091A (en) * | 2015-03-30 | 2016-11-10 | Jx金属株式会社 | Rolled copper foil for flexible printed wiring board |
WO2019160338A1 (en) * | 2018-02-13 | 2019-08-22 | 주식회사 엘지화학 | Anode current collector for lithium metal battery, secondary battery including same, and method for manufacturing anode current collector for lithium metal battery |
CN112993261A (en) * | 2019-12-12 | 2021-06-18 | 陕西铭硕新能源科技有限公司 | Method for processing conductive current collector of ultra-low temperature battery with high specific energy |
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JP2013241662A (en) * | 2012-05-22 | 2013-12-05 | Furukawa Electric Co Ltd:The | Rolled copper foil for collector of secondary battery and method for producing the same |
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