JP4462509B2 - Perforated current collector for secondary battery and manufacturing method thereof - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、二次電池、特にリチウム系二次電池に用いる集電体及びその製造方法に関するものである。
【０００２】
【従来の技術】
二次電池は、基本的には、正極，負極，正極と負極とを絶縁するセパレーター，及び正極と負極との間でイオンの移動を可能にするための電解液で構成されている。正極及び負極は、金属箔からなる集電体の表面に、各種の活物質が塗布されてなるものである。例えば、リチウム系二次電池においては、正極として、コバルト酸リチウム等を含む活物質がアルミニウム箔よりなる集電体に塗布されてなるものが用いられ、一方、負極としては、難黒鉛化カーボン等を含む活物質が銅箔よりなる集電体に塗布されてなるものが用いられている。
【０００３】
一般に、アルミニウム箔や銅箔等の各種金属箔面に、各種の活物質を塗布した場合、金属箔と活物質とが一体化しにくく、比較的、活物質が脱落しやすいということがあった。二次電池作成の際、例えば、正極及び負極の巻き上げの際に、活物質が脱落すると、所望の容量を持つ二次電池が得られないという欠点が生じる。また、二次電池を作成した後に、活物質が脱落すると、二次電池の充放電容量が徐々に低下してゆくという欠点が生じる。
【０００４】
このため、活物質中に混合するバインダーとして、金属箔との親和性に優れたものを用いることが行なわれている。また、金属箔としても、その表面が、各種バインダーとの親和性に優れたものを採用することが行なわれている。例えば、特開平７−２０１３３２号公報には、銅箔表面に、ベンゾトリアゾール等のアゾール系皮膜を形成し、活物質中のバインダーと銅箔との一体化を向上させ、活物質の脱落を防止する技術が記載されている。
【０００５】
【発明が解決しようとする課題】
本発明の課題は、活物質の金属箔からの脱落防止を、物理的手段で解決することにある。具体的には、集電体である金属箔に、特定の貫通孔を設け、集電体の表裏面に塗布される活物質とバインダーとを、この貫通孔に係止させやすくして、活物質の脱落を防止しようというものである。
【０００６】
【課題を解決するための手段】
即ち、本発明は、多数の貫通孔が設けられている金属箔からなる孔開き集電体であって、その貫通孔の内壁面が、金属箔の裏面又は表面に対して、特定の切片角度で傾斜していることを特徴とする二次電池用孔開き集電体に関するものである。このような内壁面の傾斜に、活物質及びバインダーが係止し、集電体である金属箔面から活物質が脱落しにくくなるのである。また、本発明は、このような二次電池用孔開き集電体を得るのに適した、一つの方法に関するものである。
【０００７】
本発明においては、孔開き集電体を構成する金属箔としては、アルミニウム箔，アルミニウム合金箔，銅箔又は銅合金箔等が用いられる。リチウム系二次電池の場合、正極に用いる集電体は、一般的にアルミニウム箔又はアルミニウム合金箔であり、一方、負極に用いる集電体は、一般的に銅箔又は銅合金箔である。本発明においては、また、アルミニウム箔や銅箔以外の金属箔を用いて集電体とすることもできる。二次電池においては、その他の金属箔が用いられる場合もあるからである。孔開き集電体の厚みは、一般的には、８〜３０μｍ程度である。リチウム系二次電池に用いられるアルミニウム箔製の集電体は１５〜２５μｍ程度であるのが好ましく、銅箔製の集電体は１０〜２０μｍであるのが好ましい。なお、銅箔としては、圧延銅箔（圧延法で得られる銅箔）であっても、電解銅箔（電解法で得られる銅箔）のいずれであっても良い。
【０００８】
集電体に設けられている貫通孔の形状は、一般的には円形であるが、その他、三角形や四角形等の任意の形状であって良い。また、貫通孔の大きさは、二次電池の種類や大きさ或いは用途によって、任意の大きさとすることができる。一般的には、貫通孔の面積を仮想円の面積であるとして、その仮想円の直径が０．１〜３ｍｍになる程度である。また、貫通孔は、集電体に多数設けられているのであり、例えば、貫通孔間のピッチは０．５〜１０ｍｍ程度でよく、貫通孔の密度は１〜４００個／ｃｍ2程度で良い。
【０００９】
本発明の特徴は、貫通孔の内壁面が、金属箔の裏面又は表面に対して、特定の切片角度θ1又はθ2で傾斜していることにある。ここで、切片角度とは、貫通孔の上下方向の断面において現われる金属箔の裏面又は表面の線と、金属箔の裏面側又は表面側における内壁面の線との間で形成される角度のことである。内壁面が曲線の場合には、内壁面の線とは、金属箔の裏面又は表面の線と当該曲線との交点における、当該曲線に対する接線のことを意味している。このことは、図１〜３を参照すれば、より明瞭に理解しうるものである。また、孔開き集電体の切片角度θ1及びθ2は、集電体の任意の５箇所を裁断切取し、その断面を顕微鏡で観察し、複数個の各貫通孔の切片角度θ1及びθ2を測定することにより行なう。例えば、複数個の各貫通孔のθ1が２０°〜５０°の範囲内にあり、各貫通孔のθ2が３０°〜４０°であれば、θ1は２０°〜５０°でθ2は３０°〜４０°と決定する。また、複数個の貫通孔において、θ1が９０°以上のものと９０°未満のものとがある場合には、それぞれを分けて、θ1が９０°以上の貫通孔のθ2と、θ1が９０°未満の貫通孔のθ2とを測定し、それぞれの範囲を決定し、二種の貫通孔が混在しているものとする。本発明における、この切片角度は、具体的には、以下のとおりである。なお、金属箔の裏面と表面とは、厳密な意味で用いられているのではなく、一方の面を裏面とした場合に、他方の面が表面であるという意味で用いられているにすぎない。
【００１０】
（ｉ）金属箔の裏面と、この金属箔の裏面側における貫通孔の内壁面とで形成される切片角度θ1が１０°〜８０°であり、金属箔の表面と、この金属箔の表面側における貫通孔の内壁面とで形成される切片角度θ2が９０°〜１７０°である貫通孔が設けられてなる集電体が挙げられる（図１を参照）。このような貫通孔が開いていると、集電体である金属箔の表裏面に塗布された活物質等は、表面側や裏面側から外力が負荷されても、切片角度θ1を形成している内壁面に、活物質等が係止され、金属箔から活物質等が脱落しにくくなる。
【００１１】
（ii）金属箔の裏面と、この金属箔の裏面側における該貫通孔の内壁面とで形成される切片角度θ1が１０°〜８０°であり、金属箔の表面と、この金属箔の表面側における貫通孔の内壁面とで形成される切片角度θ2が９０°〜１７０°である貫通孔と、切片角度θ1が９０°〜１７０°であり、切片角度θ2が１０°〜８０°である貫通孔とが混在している集電体が挙げられる（図示せず）。このような貫通孔が開いていると、集電体である金属箔の表裏面に塗布された活物質等は、表面側や裏面側から外力が負荷されても、切片角度θ1が１０°〜８０°を形成している内壁面、又は切片角度θ2が１０°〜８０°を形成している内壁面によって、活物質等が係止され、金属箔から活物質等が脱落しにくくなる。
【００１５】
以上の如き集電体は、エッチング法で得ることができる。本発明においては、好ましくは、以下の如きエッチング法で得るのが良い。
【００１６】
上記（ｉ）で示した集電体は、無孔金属箔の表面に、多数の貫通孔を有する孔開きレジスト膜を接合し、この無孔金属箔の裏面には、無孔レジスト膜を接合してなる三層積層体に、エッチングを施すことにより、無孔金属箔に、孔開きレジスト膜の孔に対応する多数の貫通孔を形成するという方法で得ることができる。無孔金属箔としては、孔の開いていないアルミニウム箔や銅箔等の任意の金属箔を用いることができる。ここで、孔が開いていない（無孔）という意味は、上記した０．１〜３ｍｍ程度の貫通孔が開いていないという意味であり、ピンホールが存在しないという意味ではない。従って、極めて小さな径のピンホールは存在していても良い。
【００１７】
このような無孔金属箔の表面に、多数の貫通孔を有する孔開きレジスト膜を接合する。孔開きレジスト膜は、無孔金属箔表面に紫外線硬化型感光性樹脂よりなるレジスト液を塗布し、レジスト層を形成した後、このレジスト層にポジフィルムを通して、孔を開けたい箇所だけに紫外線を照射せずに他の箇所には紫外線を照射し、他の箇所を硬化させた後、硬化していない箇所の感光性樹脂を洗浄除去することによって、容易に得ることができる。また、逆に、紫外線分解型（崩壊型）感光性樹脂よりなるレジスト液を塗布し、レジスト層を形成した後、このレジスト層にネガフィルムを通して、孔を開けたい箇所だけに紫外線を照射し、その後、紫外線を照射した箇所の分解している感光性樹脂を洗浄除去することによって、得ることもできる。一方、無孔金属箔の裏面には、無孔レジスト膜を接合する。無孔レジスト膜は、紫外線硬化型感光性樹脂よりなるレジスト液を使用した場合には、レジスト層を形成した後、紫外線を全面に照射すれば、容易に得ることができる。また、紫外線分解型感光性樹脂よりなるレジスト液を使用した場合には、レジスト層を形成した後、なるべく紫外線が照射しないようにして放置しておけば良い。なお、このレジスト膜は、エッチングに対するレジスト膜という意味で用いられていることは自明であろう。
【００１８】
以上のようにして、孔開きレジスト膜，無孔金属箔，無孔レジスト膜の順で積層された三層積層体に、エッチングを施す。エッチングは、無孔金属箔を溶解させるけれども、レジスト膜は溶解させないエッチング液（例えば、塩化第二鉄−塩酸水溶液）を用いて行なう。エッチングは、一般的に、三層積層体の孔開きレジスト膜に向けて、エッチング液を噴射することによって行なう。また、三層積層体をエッチング液中に浸漬することによって、行なうこともできる。このような方法によって、レジスト膜の孔からエッチング液が侵入し、無孔金属箔を溶解させ、図１に示すような貫通孔を多数持つ孔開き集電体が得られるのである。即ち、エッチング液が侵入する側は、金属箔の溶解量が多くなるので、その切片角度θ2は、９０°〜１７０°であり、無孔レジスト膜が接合している側は、金属箔の溶解量が少ないので、その切片角度θ1は、１０°〜８０°となるのである。
【００１９】
上記（ii）で示した集電体は、無孔金属箔の表面に、多数の貫通孔を有する孔開きレジスト膜（表面側）を接合し、この無孔金属箔の裏面には、孔開きレジスト膜（表面側）の各孔に対応合致しない多数の貫通孔を有する孔開きレジスト膜（裏面側）を接合してなる三層積層体に、エッチングを施すことにより、無孔金属箔に、孔開きレジスト膜（表面側）及び孔開きレジスト膜（裏面側）の各々の孔に対応する多数の貫通孔を形成するという方法で得ることができる。この方法は、無孔金属箔の表面に接合される孔開きレジスト膜（表面側）と、無孔金属箔の裏面に接合される孔開きレジスト膜（裏面側）との各々の孔が同期しておらず、孔開きレジスト膜（表面側）の孔に対応する箇所においては、孔開きレジスト膜（裏面側）に孔が開いておらず、また、孔開きレジスト膜（裏面側）の孔に対応する箇所においては、孔開きレジスト膜（表面側）に孔が開いていないものである。従って、このような三層積層体の表裏面に、エッチング液を噴射したり、或いは三層積層体をエッチング液に浸漬すると、図１で示すような貫通孔と、図１で示した貫通孔とは上下が逆転している貫通孔とが混在する集電体が得られる。即ち、切片角度θ2が９０°〜１７０°で、切片角度θ1が１０°〜８０°である貫通孔と、切片角度θ1が１０°〜８０°で切片角度θ2が９０°〜１７０°である貫通孔とが多数混在する集電体が得られるのである。
【００２３】
以上の如き各種方法で得られた、各種の貫通孔を多数持つ集電体は、リチウムイオン電池，金属リチウム電池，ポリマー電池等のリチウム系二次電池の集電体として好適に用いられる。また、リチウム系二次電池以外の二次電池の集電体としても、好適に用いられる。
【００２４】
【実施例】
以下、実施例によって本発明を説明するが、本発明は実施例に限定されるものではない。本発明は、集電体に設けられた多数の貫通孔の内壁面が、金属箔の裏面又は表面に対して、特定の切片角度で傾斜しているため、集電体の表裏面に塗布された活物質等が脱落しにくくなるという技術的思想に基づいて解釈されるべきである。
【００２５】
実施例１
まず、幅５０ｃｍ，長さ８０ｃｍ，厚さ１８μｍの無孔の圧延銅箔を準備した。この圧延銅箔を、１００ｇ／ｄｍ3Ｈ2ＳＯ4＋０．０１ｇ／ｄｍ3ｎ−プロパノール＋３０ｇ／ｄｍ3Ｈ2Ｏ2よりなる前処理水溶液（液温３０℃）に３０秒間浸漬し、水洗及び乾燥した。前処理を終えた圧延銅箔の両面に、レジスト液（東京応化株式会社製、ＰＭＥＲ Ｐ−ＲＦ３０Ｓ）を、約５μｍの厚さで均一に塗布し、９０℃で２０分間乾燥し、レジスト層を形成した。
【００２６】
一方、直径０．８ｍｍの円が、幅方向に３ｍｍピッチで且つ長さ方向に３ｍｍピッチで焼き付けられたポジフィルムを準備した。このポジフィルムの大きさは、圧延銅箔の大きさに合致するように、幅５０ｃｍとし、長さを８０ｃｍとした。なお、ポジフィルムの厚さは０．２ｍｍであった。
【００２７】
このポジフィルムを、無孔圧延銅箔の表面に接合されたレジスト層上に積層し、ポジフィルムから一定の距離を置いて設けた紫外線露光器から、３００ｍＪ／ｃｍ2の紫外線を照射し、レジスト層に潜像を形成した。そして、東京応化株式会社製のＰＭＥＲ用現像液を５倍に稀釈した現像液で、３０秒間現像し、水洗後１２０℃で１０分間乾燥した。この結果、無孔圧延銅箔の表面に接合されたレジスト層には、直径ほぼ０．８ｍｍの貫通孔が、幅方向に３ｍｍピッチで且つ長さ方向に３ｍｍピッチで形成された。また、無孔圧延銅箔の裏面に接合されたレジスト層には、紫外線を照射せずに、当初のままの無孔レジスト層とした。以上のようにして、孔開きレジスト層，無孔圧延銅箔，無孔レジスト層の順で積層された三層積層体を得た。
【００２８】
この三層積層体の孔開きレジスト層側に、エッチング液を噴射した。即ち、２．２ｍｏｌ／ｄｍ3ＦｅＣｌ3＋１．０ｍｏｌ／ｃｍ3ＨＣｌ水溶液（液温約５０℃）よりなるエッチング液を、６本のノズルから０．１５ＭＰａの圧力で、２５秒間、水平に保たれた孔開きレジスト層に向けて噴射して、エッチングを行なった。この後、直ちに水洗及び乾燥した。次いで、三層積層体の各レジスト層を除去すべく、アセトンに浸漬し、乾燥した。この結果、直径（銅箔表面側における直径）が約０．８ｍｍの貫通孔が、幅方向に３ｍｍピッチで且つ長さ方向に３ｍｍピッチで設けられた銅箔が得られた。この銅箔を、幅６ｃｍ，長さ７０ｃｍに切断して、孔開き集電体を得た。この集電体の任意の５箇所を裁断切取し、貫通孔の断面形状を顕微鏡で観察したところ、図１に示す如き貫通孔であって、θ1は３０°程度で、θ2は１００°程度であった。
【００２９】
この孔開き集電体の両面に、難黒鉛化カーボンよりなる活物質とフッ素系バインダーとの混合物を塗布したところ、活物質の脱落が少なく、リチウムイオン二次電池の負極として好適に用いられるものであった。
【００３３】
【作用及び発明の効果】
本発明は、多数の貫通孔が設けられている金属箔からなる二次電池用孔開き集電体であって、その貫通孔の内壁面が、金属箔の裏面又は表面に対して、特定の切片角度で傾斜している。従って、集電体の表裏面に塗布された活物質等は、貫通孔に侵入した活物質やバインダーと共に一体化する。そして、この貫通孔の内壁面は特定の切片角度で傾斜しているので、貫通孔に侵入している活物質等は、この傾斜に係止される。依って、貫通孔に侵入した活物質等と一体化している集電体の表裏面に塗布された活物質等が、脱落しにくいという効果を奏する。
【００３４】
この結果、活物質等が塗布された集電体（二次電池用正極又は負極）を巻き上げて、二次電池を作成する際にも、活物質等の脱落が少なく、所望の容量を持つ二次電池が作成しやすいという効果を奏する。また、二次電池を作成した後も、活物質等の脱落又は活物質等と集電体との離隔を防止でき、充放電容量の低下を防止でき、二次電池の寿命を長くすることができるという効果も奏する。
【００３５】
また、本発明に係る二次電池用孔開き集電体は、無孔金属箔の表裏面に特定のレジスト膜を形成した後、特定の方法でエッチングすることによって、容易に且つ合理的に得ることができる。
【図面の簡単な説明】
【図１】本発明の一例に係る孔開き集電体の拡大断面図であり、一個の貫通孔の上下方向断面を示した拡大断面図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a current collector used for a secondary battery, particularly a lithium secondary battery, and a method for producing the current collector.
[0002]
[Prior art]
The secondary battery basically includes a positive electrode, a negative electrode, a separator that insulates the positive electrode from the negative electrode, and an electrolyte solution that enables ions to move between the positive electrode and the negative electrode. The positive electrode and the negative electrode are obtained by applying various active materials to the surface of a current collector made of a metal foil. For example, in a lithium secondary battery, a positive electrode in which an active material containing lithium cobaltate or the like is applied to a current collector made of an aluminum foil is used, while a non-graphitizable carbon or the like is used as a negative electrode. A material obtained by applying an active material containing copper to a current collector made of copper foil is used.
[0003]
Generally, when various active materials are applied to various metal foil surfaces such as an aluminum foil and a copper foil, the metal foil and the active material are difficult to be integrated, and the active material is relatively easy to fall off. When the secondary battery is produced, for example, when the active material falls off during winding of the positive electrode and the negative electrode, there arises a drawback that a secondary battery having a desired capacity cannot be obtained. Further, when the active material is dropped after the secondary battery is produced, there is a disadvantage that the charge / discharge capacity of the secondary battery is gradually reduced.
[0004]
For this reason, as a binder mixed in an active material, what is excellent in affinity with metal foil is used. Moreover, as the metal foil, one having a surface excellent in affinity with various binders has been adopted. For example, in JP-A-7-201332, an azole-based film such as benzotriazole is formed on the surface of a copper foil to improve the integration of the binder and the copper foil in the active material, thereby preventing the active material from falling off. The technology to do is described.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to solve the prevention of falling off of the active material from the metal foil by physical means. Specifically, the metal foil that is the current collector is provided with a specific through hole, and the active material and the binder applied to the front and back surfaces of the current collector are easily locked into the through hole. This is to prevent the material from falling off.
[0006]
[Means for Solving the Problems]
That is, the present invention is a perforated current collector made of a metal foil provided with a large number of through-holes, and the inner wall surface of the through-holes has a specific intercept angle with respect to the back surface or the surface of the metal foil. In particular, the present invention relates to a perforated current collector for a secondary battery, which is characterized in that it is inclined at. The active material and the binder are locked to the inclination of the inner wall surface, so that the active material is less likely to drop off from the metal foil surface that is a current collector. The present invention also relates to one method suitable for obtaining such a perforated current collector for a secondary battery.
[0007]
In the present invention, an aluminum foil, an aluminum alloy foil, a copper foil, a copper alloy foil, or the like is used as the metal foil constituting the perforated current collector. In the case of a lithium secondary battery, the current collector used for the positive electrode is generally an aluminum foil or an aluminum alloy foil, while the current collector used for the negative electrode is generally a copper foil or a copper alloy foil. In the present invention, the current collector can also be formed using a metal foil other than an aluminum foil or a copper foil. This is because other metal foils may be used in the secondary battery. The thickness of the perforated current collector is generally about 8 to 30 μm. The current collector made of aluminum foil used for the lithium secondary battery is preferably about 15 to 25 μm, and the current collector made of copper foil is preferably 10 to 20 μm. The copper foil may be a rolled copper foil (a copper foil obtained by a rolling method) or an electrolytic copper foil (a copper foil obtained by an electrolytic method).
[0008]
The shape of the through hole provided in the current collector is generally circular, but may be any other shape such as a triangle or a quadrangle. In addition, the size of the through hole can be set arbitrarily according to the type, size or application of the secondary battery. Generally, assuming that the area of the through hole is the area of a virtual circle, the diameter of the virtual circle is about 0.1 to 3 mm. In addition, a large number of through holes are provided in the current collector. For example, the pitch between the through holes may be about 0.5 to 10 mm, and the density of the through holes may be about 1 to 400 holes / cm 2. .
[0009]
The feature of the present invention is that the inner wall surface of the through hole is inclined at a specific intercept angle θ 1 or θ 2 with respect to the back surface or the front surface of the metal foil. Here, the intercept angle is an angle formed between a line on the back surface or the front surface of the metal foil appearing in a vertical section of the through hole and a line on the inner wall surface on the back surface side or the surface side of the metal foil. It is. When the inner wall surface is a curve, the line of the inner wall surface means a tangent to the curve at the intersection of the back surface or the surface line of the metal foil and the curve. This can be understood more clearly with reference to FIGS. Also, sections were angle theta 1 and theta 2 of the perforated current collector, to cut cutting any five points of the current collector, and its cross section was observed under a microscope, a plurality of sections the angle theta 1 and the through-holes by measuring the theta 2. For example, when θ 1 of each of the plurality of through holes is in the range of 20 ° to 50 ° and θ 2 of each through hole is 30 ° to 40 °, θ 1 is 20 ° to 50 ° and θ 2. Is determined to be 30 ° to 40 °. In addition, when there are a plurality of through-holes having θ 1 of 90 ° or more and less than 90 °, they are divided into θ 2 and θ 2 of the through-holes having θ 1 of 90 ° or more, and θ 1 It is assumed that 1 is measured with θ 2 of a through hole of less than 90 °, each range is determined, and two kinds of through holes are mixed. The intercept angle in the present invention is specifically as follows. In addition, the back surface and the surface of the metal foil are not used in a strict sense, but when one surface is a back surface, it is only used in the sense that the other surface is the surface. .
[0010]
(I) The intercept angle θ 1 formed between the back surface of the metal foil and the inner wall surface of the through hole on the back surface side of the metal foil is 10 ° to 80 °, and the surface of the metal foil and the surface of the metal foil Examples include a current collector provided with a through hole having an intercept angle θ 2 of 90 ° to 170 ° formed by the inner wall surface of the through hole on the side (see FIG. 1). When such a through hole is opened, the active material applied to the front and back surfaces of the metal foil as a current collector forms an intercept angle θ 1 even when an external force is applied from the front side or the back side. The active material or the like is locked to the inner wall surface, and the active material or the like is less likely to drop off from the metal foil.
[0011]
(Ii) The intercept angle θ 1 formed between the back surface of the metal foil and the inner wall surface of the through hole on the back surface side of the metal foil is 10 ° to 80 °, and the surface of the metal foil and the metal foil A through hole having an intercept angle θ 2 of 90 ° to 170 ° formed by the inner wall surface of the through hole on the surface side, an intercept angle θ 1 of 90 ° to 170 °, and an intercept angle θ 2 of 10 ° to A current collector in which a through-hole of 80 ° is mixed (not shown). When such a through-hole is opened, the active material applied to the front and back surfaces of the metal foil as a current collector has an intercept angle θ 1 of 10 ° even when an external force is applied from the front side or the back side. The active material is locked by the inner wall surface forming ˜80 ° or the inner wall surface having the intercept angle θ 2 of 10 ° ˜80 °, and the active material etc. is less likely to fall off the metal foil. .
[0015]
The current collector as described above can be obtained by an etching method. In the present invention, the following etching method is preferable.
[0016]
In the current collector shown in (i) above, a perforated resist film having a large number of through holes is bonded to the surface of the non-porous metal foil, and a non-porous resist film is bonded to the back surface of the non-porous metal foil. By etching the three-layer laminate thus formed, a large number of through holes corresponding to the holes of the perforated resist film can be formed in the non-porous metal foil. As the non-porous metal foil, any metal foil such as an aluminum foil or a copper foil having no holes can be used. Here, the meaning that the hole is not opened (no hole) means that the above-described through hole of about 0.1 to 3 mm is not opened, and does not mean that there is no pinhole. Accordingly, pinholes having a very small diameter may exist.
[0017]
A perforated resist film having a large number of through holes is bonded to the surface of such a non-porous metal foil. A perforated resist film is formed by applying a resist solution made of an ultraviolet curable photosensitive resin to the surface of a non-porous metal foil, forming a resist layer, and then passing a positive film through the resist layer to irradiate ultraviolet rays only at the locations where holes are to be formed. It can obtain easily by irradiating an ultraviolet-ray to another location, without irradiating, and hardening the other location, and wash | cleaning and removing the photosensitive resin of the location which is not hardened | cured. On the contrary, after applying a resist solution made of an ultraviolet-decomposable (collapse-type) photosensitive resin and forming a resist layer, a negative film is passed through this resist layer, and ultraviolet rays are irradiated only to the portions where holes are to be opened, Then, it can also obtain by wash | cleaning and removing the photosensitive resin which has decomposed | disassembled the location irradiated with the ultraviolet-ray. On the other hand, a non-porous resist film is bonded to the back surface of the non-porous metal foil. The non-porous resist film can be easily obtained by irradiating the entire surface with ultraviolet rays after forming a resist layer when a resist solution made of an ultraviolet curable photosensitive resin is used. Further, when a resist solution made of an ultraviolet-decomposable photosensitive resin is used, it is allowed to leave the resist layer so as not to irradiate ultraviolet rays as much as possible. It is obvious that this resist film is used as a resist film for etching.
[0018]
As described above, etching is performed on the three-layer laminate in which the perforated resist film, the non-porous metal foil, and the non-porous resist film are laminated in this order. Etching is performed using an etching solution (for example, ferric chloride-hydrochloric acid aqueous solution) that dissolves the nonporous metal foil but does not dissolve the resist film. Etching is generally performed by spraying an etching solution toward the perforated resist film of the three-layer laminate. Moreover, it can also carry out by immersing a three-layer laminated body in an etching liquid. By such a method, the etching solution enters from the holes of the resist film and dissolves the non-porous metal foil, so that a perforated current collector having a large number of through holes as shown in FIG. 1 is obtained. That is, since the amount of dissolution of the metal foil is increased on the side where the etching solution enters, the intercept angle θ 2 is 90 ° to 170 °, and the side on which the non-porous resist film is bonded is that of the metal foil. Since the dissolution amount is small, the intercept angle θ 1 is 10 ° to 80 °.
[0019]
In the current collector shown in (ii) above, a perforated resist film (front side) having a large number of through-holes is bonded to the surface of the non-porous metal foil, By etching the three-layer laminate formed by bonding a perforated resist film (back side) having a large number of through-holes that do not correspond to each hole of the resist film (front side), to the non-porous metal foil, It can be obtained by a method of forming a large number of through holes corresponding to the respective holes of the perforated resist film (front surface side) and the perforated resist film (back surface side). In this method, the holes of the perforated resist film (front side) bonded to the surface of the non-porous metal foil and the perforated resist film (back side) bonded to the back of the non-porous metal foil are synchronized. In the locations corresponding to the holes in the perforated resist film (front side), there are no holes in the perforated resist film (back side), and the holes in the perforated resist film (back side) In the corresponding part, the holed resist film (surface side) has no hole. Therefore, when an etching solution is sprayed on the front and back surfaces of such a three-layer laminate, or the three-layer laminate is immersed in the etchant, the through-hole shown in FIG. 1 and the through-hole shown in FIG. Is a current collector in which through holes whose top and bottom are reversed are mixed. That is, a through hole having an intercept angle θ 2 of 90 ° to 170 ° and an intercept angle θ 1 of 10 ° to 80 °, and an intercept angle θ 2 of 10 ° to 80 ° and an intercept angle θ 2 of 90 ° to 170 Thus, a current collector in which a large number of through-holes that are ° are mixed is obtained.
[0023]
The current collector having a large number of various through-holes obtained by the various methods as described above is suitably used as a current collector for lithium secondary batteries such as lithium ion batteries, metal lithium batteries, and polymer batteries. Moreover, it is used suitably also as a collector of secondary batteries other than a lithium-type secondary battery.
[0024]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to an Example. In the present invention, the inner wall surfaces of a large number of through holes provided in the current collector are inclined at a specific intercept angle with respect to the back surface or the surface of the metal foil, and thus are applied to the front and back surfaces of the current collector. It should be interpreted based on the technical idea that active materials are less likely to fall off.
[0025]
Example 1
First, a non-porous rolled copper foil having a width of 50 cm, a length of 80 cm, and a thickness of 18 μm was prepared. This rolled copper foil was immersed in a pretreatment aqueous solution (liquid temperature 30 ° C.) consisting of 100 g / dm 3 H 2 SO 4 +0.01 g / dm 3 n-propanol + 30 g / dm 3 H 2 O 2 for 30 seconds, washed with water and Dried. A resist solution (manufactured by Tokyo Ohka Co., Ltd., PMER P-RF30S) is uniformly applied to both sides of the rolled copper foil that has been pretreated, and dried at 90 ° C. for 20 minutes to form a resist layer. Formed.
[0026]
On the other hand, a positive film was prepared in which circles having a diameter of 0.8 mm were baked at a pitch of 3 mm in the width direction and a pitch of 3 mm in the length direction. The positive film had a width of 50 cm and a length of 80 cm so as to match the size of the rolled copper foil. The thickness of the positive film was 0.2 mm.
[0027]
This positive film is laminated on a resist layer bonded to the surface of a non-porous rolled copper foil, and irradiated with 300 mJ / cm 2 of ultraviolet light from an ultraviolet exposure device provided at a certain distance from the positive film. A latent image was formed on the layer. Then, it was developed with a developer diluted 5 times by PMER developer manufactured by Tokyo Ohka Co., Ltd. for 30 seconds, washed with water and dried at 120 ° C. for 10 minutes. As a result, through-holes having a diameter of approximately 0.8 mm were formed in the resist layer bonded to the surface of the non-porous rolled copper foil at a pitch of 3 mm in the width direction and a pitch of 3 mm in the length direction. In addition, the resist layer bonded to the back surface of the non-porous rolled copper foil was not irradiated with ultraviolet rays, and was used as the original non-porous resist layer. As described above, a three-layer laminate was obtained in which a perforated resist layer, a non-porous rolled copper foil, and a non-porous resist layer were laminated in this order.
[0028]
An etching solution was sprayed on the perforated resist layer side of the three-layer laminate. That is, an etching solution made of 2.2 mol / dm 3 FeCl 3 +1.0 mol / cm 3 HCl aqueous solution (solution temperature about 50 ° C.) was kept horizontal for 25 seconds from 6 nozzles at a pressure of 0.15 MPa. Etching was performed by spraying toward the perforated resist layer. After this, it was immediately washed with water and dried. Subsequently, in order to remove each resist layer of a three-layer laminated body, it immersed in acetone and dried. As a result, a copper foil in which through-holes having a diameter (diameter on the copper foil surface side) of about 0.8 mm were provided at a pitch of 3 mm in the width direction and a pitch of 3 mm in the length direction was obtained. This copper foil was cut into a width of 6 cm and a length of 70 cm to obtain a perforated current collector. When arbitrary five places of this current collector were cut and cut, and the cross-sectional shape of the through hole was observed with a microscope, it was a through hole as shown in FIG. 1, and θ 1 was about 30 ° and θ 2 was 100 °. It was about.
[0029]
When a mixture of a non-graphitizable carbon active material and a fluorine-based binder is applied to both surfaces of this perforated current collector, the active material is less likely to fall off and can be suitably used as a negative electrode for a lithium ion secondary battery Met.
[0033]
[Operation and effect of the invention]
The present invention is a perforated current collector for a secondary battery comprising a metal foil provided with a number of through-holes, and the inner wall surface of the through-holes is specific to the back surface or the surface of the metal foil. It is inclined at the intercept angle. Therefore, the active material and the like applied to the front and back surfaces of the current collector are integrated with the active material and the binder that have entered the through holes. And since the inner wall surface of this through-hole inclines at the specific intercept angle, the active material etc. which have penetrate | invaded the through-hole are latched by this inclination. Therefore, there is an effect that the active material applied to the front and back surfaces of the current collector integrated with the active material that has penetrated into the through hole is less likely to fall off.
[0034]
As a result, even when a current collector (positive electrode or negative electrode for secondary battery) coated with an active material or the like is wound up to produce a secondary battery, the active material or the like is less likely to fall off and has a desired capacity. The secondary battery can be easily produced. In addition, even after the secondary battery is created, it is possible to prevent the active material, etc. from falling off or the active material, etc., from being separated from the current collector, to prevent a decrease in charge / discharge capacity, and to prolong the life of the secondary battery. There is also an effect that can be done.
[0035]
Further, the perforated current collector for a secondary battery according to the present invention can be easily and rationally obtained by forming a specific resist film on the front and back surfaces of the non-porous metal foil and then etching by a specific method. be able to.
[Brief description of the drawings]
FIG. 1 is an enlarged cross-sectional view of a perforated current collector according to an example of the present invention, and is an enlarged cross-sectional view showing a vertical cross section of one through hole.
Claims (4)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP23538597A JP4462509B2 (en) | 1997-08-14 | 1997-08-14 | Perforated current collector for secondary battery and manufacturing method thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP23538597A JP4462509B2 (en) | 1997-08-14 | 1997-08-14 | Perforated current collector for secondary battery and manufacturing method thereof |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH1167217A JPH1167217A (en) | 1999-03-09 |
| JP4462509B2 true JP4462509B2 (en) | 2010-05-12 |
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| Application Number | Title | Priority Date | Filing Date |
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| JP23538597A Expired - Lifetime JP4462509B2 (en) | 1997-08-14 | 1997-08-14 | Perforated current collector for secondary battery and manufacturing method thereof |
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Families Citing this family (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3321432B2 (en) * | 1998-06-26 | 2002-09-03 | 山田 和範 | Current collector for batteries |
| JP5230878B2 (en) * | 1999-05-18 | 2013-07-10 | 大日本印刷株式会社 | Method for producing metal foil sheet |
| JP4875808B2 (en) * | 2001-08-07 | 2012-02-15 | パナソニック株式会社 | Multilayer secondary battery |
| JP2009199963A (en) | 2008-02-25 | 2009-09-03 | Fuji Heavy Ind Ltd | Power storage device, electrode, manufacturing method for electrode, and management method |
| CN102471835B (en) * | 2009-07-07 | 2014-03-19 | 东洋铝株式会社 | Perforated aluminum foil |
| JP2011198765A (en) * | 2011-05-20 | 2011-10-06 | Dainippon Printing Co Ltd | Metal foil sheet |
| KR101814889B1 (en) | 2013-05-09 | 2018-01-04 | 아사히 가세이 팍스 가부시키가이샤 | Perforated film, coating film, and electricity storage device |
| JP6473294B2 (en) * | 2014-03-04 | 2019-02-20 | 旭化成パックス株式会社 | Perforated thin film, power storage device using the same, and method for manufacturing perforated thin film |
| JP5765460B2 (en) * | 2014-04-07 | 2015-08-19 | 大日本印刷株式会社 | Method for producing metal foil sheet |
| CN106795646B (en) * | 2014-10-14 | 2018-12-18 | 富士胶片株式会社 | The manufacturing method of aluminium sheet and aluminium sheet |
| KR102212884B1 (en) | 2016-09-26 | 2021-02-08 | 후지필름 가부시키가이샤 | Manufacturing method of perforated metal foil |
| KR20190076890A (en) * | 2017-12-22 | 2019-07-02 | 주식회사 엘지화학 | Anode current for lithium metal battery and lithium metal battery including the same |
| CN110462902B (en) * | 2017-12-22 | 2022-05-13 | 株式会社Lg化学 | Anode for lithium metal battery and lithium metal battery including the same |
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1997
- 1997-08-14 JP JP23538597A patent/JP4462509B2/en not_active Expired - Lifetime
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