JP2013058378A - Lithium ion secondary battery, and method for manufacturing the same - Google Patents

Lithium ion secondary battery, and method for manufacturing the same Download PDF

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JP2013058378A
JP2013058378A JP2011195792A JP2011195792A JP2013058378A JP 2013058378 A JP2013058378 A JP 2013058378A JP 2011195792 A JP2011195792 A JP 2011195792A JP 2011195792 A JP2011195792 A JP 2011195792A JP 2013058378 A JP2013058378 A JP 2013058378A
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negative electrode
current collector
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JP5686076B2 (en
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Satoshi Nakagawa
敏 中川
Masataka Nakanishi
正孝 仲西
Tomoya Sato
友哉 佐藤
Kazuhito Kawasumi
一仁 川澄
Junichi Niwa
淳一 丹羽
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Toyota Industries Corp
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract

PROBLEM TO BE SOLVED: To provide a technology to improve the production efficiency of a lithium ion secondary battery.SOLUTION: A lithium ion secondary battery comprises a battery structure 18 where a plurality of pairs of a positive electrode 6 and a negative electrode 4 disposed on opposite sides of a separator 5 is laminated. A negative electrode collector 20X of the negative electrode 4X is provided with a first through hole 30. A positive electrode collector 26 of the positive electrode 6 is provided with a second through hole 32. A negative electrode collector 20Y of the negative electrode 4Y is provided with a third through hole 34. The percentage of the opening area of the negative electrode collector 20X of the negative electrode 4X disposed at the end of the battery structure 18 in the lamination direction is higher than the percentage of the opening area of the negative electrode collector 20Y of the negative electrode 4Y and the percentage of the opening area of the positive electrode collector 26 of the positive electrode 6.

Description

本発明は、リチウムイオン二次電池とその製造方法に関する。   The present invention relates to a lithium ion secondary battery and a method for manufacturing the same.

リチウムイオン二次電池では、電池容量を向上させるために、正極電極及び負極電極で使用する材料の検討が活発に行われている。リチウム元素を含まない材料で正極電極及び負極電極を製造すると、リチウムイオン二次電池の電池容量を向上させることができることが知られている。典型的に、正極電極は正極集電体と正極活物質で構成されており、負極電極は負極集電体と負極活物質で構成されている。ここで上記知見をより正確に表現すると、正極活物質及び負極活物質で使用する材料をリチウム元素を含まない材料とすれば、リチウムイオン二次電池の電池容量を向上させることができる。   In the lithium ion secondary battery, in order to improve battery capacity, studies on materials used for the positive electrode and the negative electrode are actively conducted. It is known that the battery capacity of a lithium ion secondary battery can be improved by manufacturing a positive electrode and a negative electrode using a material that does not contain lithium element. Typically, the positive electrode is composed of a positive electrode current collector and a positive electrode active material, and the negative electrode is composed of a negative electrode current collector and a negative electrode active material. To express the above knowledge more accurately, if the material used for the positive electrode active material and the negative electrode active material is a material that does not contain lithium element, the battery capacity of the lithium ion secondary battery can be improved.

しかしながら、正極活物質及び負極活物質の双方がリチウム元素を含まない材料である場合、少なくとも正極活物質及び負極活物質の一方にリチウムイオンをドーピングすることが必要である。この場合、正極電極及び／又は負極電極とともにリチウム金属を電解液内に配置し、正極活物質及び／又は負極活物質にリチウムイオンをドーピングする。なお、以下の説明では、正極電極と負極電極に共通する特徴を説明する場合に、単に「電極」と称する場合がある。同様に、正極集電体と負極集電体を単に「集電体」と称し、正極活物質と負極活物質を単に「活物質」と称することがある。   However, when both the positive electrode active material and the negative electrode active material are materials that do not contain lithium element, it is necessary to dope lithium ions into at least one of the positive electrode active material and the negative electrode active material. In this case, lithium metal is disposed in the electrolyte together with the positive electrode and / or the negative electrode, and the positive electrode active material and / or the negative electrode active material is doped with lithium ions. In the following description, the features common to the positive electrode and the negative electrode may be simply referred to as “electrode”. Similarly, the positive electrode current collector and the negative electrode current collector may be simply referred to as “current collector”, and the positive electrode active material and the negative electrode active material may be simply referred to as “active material”.

特許文献１には、正極活物質及び負極活物質の双方がリチウム元素を含まない材料で構成されているリチウムイオン二次電池が開示されている。特許文献１では、負極活物質にリチウムイオンをドーピングする。貫通孔を有する正極集電体と貫通孔を有する負極集電体を用いて電池構造体を作製し、リチウム箔と負極電極を電気的に接続した状態で電解液に浸す。リチウム箔からリチウムイオンが放出され、リチウムイオンが、上記した貫通孔を通過して負極活物質にドーピングされる。   Patent Document 1 discloses a lithium ion secondary battery in which both a positive electrode active material and a negative electrode active material are made of a material that does not contain a lithium element. In Patent Document 1, the negative electrode active material is doped with lithium ions. A battery structure is prepared using a positive electrode current collector having a through hole and a negative electrode current collector having a through hole, and immersed in an electrolytic solution in a state where the lithium foil and the negative electrode are electrically connected. Lithium ions are released from the lithium foil, and the lithium ions pass through the above-described through holes and are doped into the negative electrode active material.

特開２０１０−４０３７０号公報JP 2010-40370 A

リチウムイオン二次電池の生産効率を向上させるためには、活物質に対するリチウムイオンのドーピング速度を速くすることが好ましい。集電体の開孔率を大きくすれば、リチウムイオンのドーピング速度を速くすることができると考えられる。しかしながら、集電体の開孔率を大きくすると、集電体の強度が低下し、電極が破損することがある。そのため、従来の技術では、集電体の開孔率を大きくすることには限界があり、生産効率を十分に向上させることができない。本明細書は、活物質に対するリチウムイオンのドーピング速度を速くすることにより、リチウムイオン二次電池の生産効率を向上させる技術を提供することを目的とする。   In order to improve the production efficiency of the lithium ion secondary battery, it is preferable to increase the doping rate of lithium ions to the active material. It is considered that the doping rate of lithium ions can be increased by increasing the aperture ratio of the current collector. However, when the aperture ratio of the current collector is increased, the strength of the current collector is reduced and the electrode may be damaged. Therefore, in the conventional technique, there is a limit to increasing the aperture ratio of the current collector, and the production efficiency cannot be sufficiently improved. This specification aims at providing the technique which improves the production efficiency of a lithium ion secondary battery by making the doping rate of the lithium ion with respect to an active material quick.

本発明者らの研究の結果、リチウムイオンのドーピング速度は、積層方向の端部に配置されている集電体の開孔率に大きく依存することが判明した。換言すると、リチウムイオンの移動速度は、積層方向の中間に配置されている集電体（積層方向の端部以外に配置されている集電体）の開孔率にはほとんど依存しないことが判明した。すなわち、積層方向の端部に配置されている集電体の開孔率のみを大きくすれば、積層方向の中間に配置されている集電体の開孔率を小さくしても、リチウムイオンのドーピング速度が速くなるという知見を得た。積層方向の中間では集電体の開孔率を大きくする必要がないので、積層方向の中間の電極の強度は維持される。その結果、電池構造体の全体としては強度を維持することができる。   As a result of the study by the present inventors, it has been found that the doping rate of lithium ions greatly depends on the aperture ratio of the current collector disposed at the end in the stacking direction. In other words, it turns out that the moving speed of lithium ions hardly depends on the hole area ratio of the current collector arranged in the middle of the stacking direction (the current collector placed other than the end in the stacking direction). did. That is, if only the aperture ratio of the current collector disposed at the end in the stacking direction is increased, the lithium ion The knowledge that the doping rate becomes faster was obtained. Since it is not necessary to increase the aperture ratio of the current collector in the middle of the stacking direction, the strength of the intermediate electrode in the stacking direction is maintained. As a result, the strength of the battery structure as a whole can be maintained.

リチウムイオンを活物質にドーピングする場合、電池構造体の外側にリチウムイオンを供給する材料（以下、リチウムイオン供給体と称する）を配置し、電極（正極電極又は負極電極）とリチウムイオン供給体の間に電圧を印加する。あるいは、リチウムイオン供給体と電池構造体の端部の電極とを直接接触（短絡）させ、活物質にリチウムイオンをドーピングする。リチウムイオンは、電池構造体の外側から内側へ向けて、集電体の貫通孔を通過しながら移動する。リチウムイオンが電池構造体の内部に向けて移動する際に、積層方向の端部に配置されている集電体は、全てのリチウムイオンを通過させることが必要である。そのため、リチウムイオンの移動抵抗を減少させるために、積層方向の端部に配置されている集電体の開孔率は、大きい程好ましい。   When doping an active material with lithium ions, a material for supplying lithium ions (hereinafter referred to as a lithium ion supplier) is disposed outside the battery structure, and an electrode (positive electrode or negative electrode) and the lithium ion supplier A voltage is applied between them. Alternatively, the lithium ion supplier and the electrode at the end of the battery structure are brought into direct contact (short circuit), and the active material is doped with lithium ions. Lithium ions move from the outside to the inside of the battery structure while passing through the through holes of the current collector. When the lithium ions move toward the inside of the battery structure, it is necessary for the current collector disposed at the end in the stacking direction to pass all the lithium ions. Therefore, in order to reduce the movement resistance of lithium ions, it is preferable that the aperture ratio of the current collector disposed at the end in the stacking direction is larger.

リチウムイオンの一部が積層方向端部の活物質に留まるので、電池構造体の内部では、集電体に到達するリチウムイオンの数が少ない。そのため、積層方向の中間に配置する集電体は、積層方向端部の集電体のように大きな貫通孔を形成しなくても、リチウムイオンの移動抵抗を増大させない。積層方向の中間に配置されている集電体は、電極の強度を維持するために、積層方向の端部に配置されている集電体よりも開孔率を小さくすることができる。   Since some of the lithium ions remain in the active material at the end in the stacking direction, the number of lithium ions that reach the current collector is small inside the battery structure. Therefore, the current collector arranged in the middle of the stacking direction does not increase the lithium ion transfer resistance even if a large through hole is not formed unlike the current collector at the end of the stacking direction. In order to maintain the strength of the electrode, the current collector disposed in the middle in the stacking direction can have a smaller opening ratio than the current collector disposed at the end in the stacking direction.

本明細書で開示する技術は、上記知見に基づいて完成したものである。本明細書で開示するリチウムイオン二次電池は、セパレータを介して正極電極と負極電極が対向している正負極の対が複数積層されている。また、正極電極の集電体及び負極電極の集電体の各々には、厚み方向に貫通する孔が形成されている。さらに、積層方向の端部に配置されている端部電極の集電体の開孔率が、端部電極の間に配置されている中間電極の集電体の開孔率よりも大きい。   The technology disclosed in this specification has been completed based on the above findings. In the lithium ion secondary battery disclosed in this specification, a plurality of positive and negative electrode pairs in which a positive electrode and a negative electrode are opposed to each other with a separator interposed therebetween are stacked. Each of the positive electrode current collector and the negative electrode current collector has a hole penetrating in the thickness direction. Furthermore, the aperture ratio of the current collector of the end electrode disposed at the end portion in the stacking direction is larger than the aperture ratio of the current collector of the intermediate electrode disposed between the end electrodes.

上記したリチウムイオン二次電池では、正極電極と負極電極を交互に積層することにより、積層型の電池構造体を形成している。上記したように、端部電極の集電体の開孔率を大きくし、中間電極の集電体の開孔率を小さくすることにより、リチウムイオンのドーピング速度を速くしつつ、電池構造体の強度を維持することができる。なお、全ての集電体が貫通孔を有しているので、電池構造体の積層方向の中間に配置されている活物質にもリチウムイオンがドーピングされている。   In the above-described lithium ion secondary battery, a stacked battery structure is formed by alternately stacking positive electrodes and negative electrodes. As described above, by increasing the aperture ratio of the current collector of the end electrode and decreasing the aperture ratio of the current collector of the intermediate electrode, the lithium ion doping rate is increased, and the battery structure The strength can be maintained. Since all the current collectors have through holes, the active material disposed in the middle in the stacking direction of the battery structure is also doped with lithium ions.

上記したように、端部電極の集電体の開孔率を大きくすると、端部電極の強度が低下する虞がある。そのため、端部電極の集電体が、他の電極の集電体よりも厚いことが好ましい。端部電極の強度の低下をも抑制することができる。   As described above, when the aperture ratio of the current collector of the end electrode is increased, the strength of the end electrode may be reduced. Therefore, it is preferable that the current collector of the end electrode is thicker than the current collectors of the other electrodes. A decrease in strength of the end electrode can also be suppressed.

上記のリチウムイオン二次電池では、リチウムイオンが正極活物質にドーピングされていても、負極活物質にドーピングされていてもよい。しかしながら、リチウムイオンは、負極活物質にドーピングされていることが好ましい。リチウムイオンが正極活物質にドーピングされているよりもリチウムイオンが負極活物質にドーピングされている方が、負極の電位が低下するので、電池容量を高くすることができる。この場合、端部電極が負極電極であれば、端部電極の活物質にリチウムイオンの一部が留まるので、中間電極におけるリチウムイオンの移動抵抗が増大することを抑制することができる。   In the above lithium ion secondary battery, lithium ions may be doped in the positive electrode active material or the negative electrode active material. However, lithium ions are preferably doped in the negative electrode active material. Since the potential of the negative electrode is lowered when the negative electrode active material is doped with lithium ions than when the positive electrode active material is doped with lithium ions, the battery capacity can be increased. In this case, if the end electrode is a negative electrode, a part of the lithium ions stays in the active material of the end electrode, so that it is possible to suppress an increase in lithium ion migration resistance in the intermediate electrode.

上記のように、本明細書で開示するリチウムイオン二次電池は、セパレータを介して正極と負極が対向している電極対が複数積層されている電池構造体を備える。本明細書では、そのリチウムイオン二次電池の製造方法をも提供する。その製造方法は、電極形成工程と、積層工程と、配置工程と、ドーピング工程を備える。電極形成工程では、厚み方向に貫通する孔が形成された集電体を用いて、正極電極と負極電極を形成する。積層工程では、正極電極と負極電極を交互に積層して電池構造体を作製する。配置工程では、容器内に電池構造体を配置し、電池構造体の積層方向の外側にリチウムイオン供給体を配置する。ドーピング工程では、リチウムイオンを、正極電極と負極電極の少なくとも一方にドーピングする。上記積層形成工程では、他の電極の集電体よりも開孔率が大きな集電体を用いて作成した電極を、電池構造体の積層方向端部に配置する。なお、リチウムイオン供給体として、単体のリチウム金属（Ｌｉ）、リチウム化合物等を利用することができる。リチウム化合物の例として、ＬｉＦｅＯ2、ＬｉＣｏＯ2、ＬｉＮｉＯ2、ＬｉＭｎ2Ｏ4、Ｌｉ5ＦｅＯ4、Ｌｉ2ＭｎＯ3、ＬｉＦｅＰＯ4、ＬｉＶ2Ｏ4等が挙げられる。 As described above, the lithium ion secondary battery disclosed in the present specification includes a battery structure in which a plurality of electrode pairs in which a positive electrode and a negative electrode are opposed to each other with a separator interposed therebetween. In this specification, the manufacturing method of the lithium ion secondary battery is also provided. The manufacturing method includes an electrode formation process, a lamination process, an arrangement process, and a doping process. In the electrode forming step, the positive electrode and the negative electrode are formed using a current collector in which holes penetrating in the thickness direction are formed. In the stacking step, a battery structure is manufactured by alternately stacking positive electrodes and negative electrodes. In the arranging step, the battery structure is arranged in the container, and the lithium ion supplier is arranged outside the battery structure in the stacking direction. In the doping step, at least one of the positive electrode and the negative electrode is doped with lithium ions. In the stack formation step, an electrode created using a current collector having a larger opening ratio than the current collectors of the other electrodes is disposed at the end of the battery structure in the stacking direction. In addition, a single lithium metal (Li), a lithium compound, etc. can be utilized as a lithium ion supply body. Examples of the lithium compound include LiFeO 2 , LiCoO 2 , LiNiO 2 , LiMn 2 O 4 , Li 5 FeO 4 , Li 2 MnO 3 , LiFePO 4 , LiV 2 O 4 and the like.

ドーピング工程では、電池構造体の端部の電極とリチウムイオン供給体を短絡させ、活物質にリチウムイオンをドーピングしてもよい。あるいは、正極電極又は負極電極と、リチウムイオン供給体の間に電圧を印加してリチウムイオンをドーピングしてもよい。リチウムイオン供給体と電極（正極電極又は負極電極）との電位差を調整することができるという観点から、後者の方法がより好ましい。リチウムイオン供給体と電極との電位差を調整することにより、ドーピング速度を調整することができる。   In the doping step, the active material may be doped with lithium ions by short-circuiting the electrode at the end of the battery structure and the lithium ion supplier. Alternatively, lithium ions may be doped by applying a voltage between the positive electrode or the negative electrode and the lithium ion supplier. From the viewpoint that the potential difference between the lithium ion supplier and the electrode (positive electrode or negative electrode) can be adjusted, the latter method is more preferable. The doping rate can be adjusted by adjusting the potential difference between the lithium ion supplier and the electrode.

上記したように、正極活物質及び負極活物質の双方がリチウム元素を含まない材料である場合、いずれかの活物質にリチウムイオンをドーピングすることが必要である。そのため、本明細書に開示する技術は、正極活物質及び負極活物質の双方がリチウム元素を含まない材料である場合に特に有用である。しかしながら、正極活物質及び負極活物質の少なくとも一方がリチウム元素を含む材料である場合でも、電池容量を向上させるために、リチウムイオンを活物質にドーピングすることがある。本明細書で開示する技術は、リチウムイオンが活物質にドーピングされたリチウムイオン二次電池であれば、正極活物質及び負極活物質の材料に限定されることなく適用することができる。   As described above, when both the positive electrode active material and the negative electrode active material are materials not containing lithium element, it is necessary to dope lithium ions into one of the active materials. Therefore, the technology disclosed in this specification is particularly useful when both the positive electrode active material and the negative electrode active material are materials that do not contain lithium element. However, even when at least one of the positive electrode active material and the negative electrode active material is a material containing lithium element, lithium ions may be doped into the active material in order to improve battery capacity. The technology disclosed in the present specification can be applied without being limited to the materials of the positive electrode active material and the negative electrode active material as long as the lithium ion secondary battery is obtained by doping lithium ions into the active material.

本明細書で開示される技術によると、リチウムイオン二次電池の生産効率を向上させることができる。   According to the technology disclosed in this specification, the production efficiency of the lithium ion secondary battery can be improved.

リチウムイオン二次電池の要部断面図を示す。The principal part sectional drawing of a lithium ion secondary battery is shown. 電池構造体の部分拡大図を示す。The elements on larger scale of a battery structure are shown. 端部電極の集電体の平面図を示す。The top view of the electrical power collector of an edge part electrode is shown. 中間電極の集電体の平面図を示す。The top view of the electrical power collector of an intermediate electrode is shown. 中間電極の集電体の変形例を示す。The modification of the collector of an intermediate electrode is shown. 端部電極の集電体の変形例を示す。The modification of the electrical power collector of an edge part electrode is shown. リチウムイオン二次電池の製造工程を説明する図を示す（１）。The figure explaining the manufacturing process of a lithium ion secondary battery is shown (1). リチウムイオン二次電池の製造工程を説明する図を示す（２）。The figure explaining the manufacturing process of a lithium ion secondary battery is shown (2). 実験に用いた電池構造体の基本構造を示す。The basic structure of the battery structure used in the experiment is shown.

図１に示すリチウムイオン二次電池１００は、積層型の電池構造体１８を備えている。電池構造体１８は、正極電極６と負極電極４が対向している電極対（正負極の対）７を複数個備える。電極対７は、正極電極６とセパレータ５と負極電極４を備えている。正極電極６と負極電極４は、セパレータ５を介して対向している。セパレータ５によって、正極電極６と負極電極４が絶縁されている。電池構造体１８では、正極電極６と負極電極４が交互に積層されている。全ての正極電極６が正極端子１２に電気的に接続されており、全ての負極電極４が負極端子２に電気的に接続されている。電池構造体１８は、電解液とともに電池ケース１６内に配置されている。電解液は、電池ケース１６内の空間１４を満たしているとともに、電池構造体１８が有する隙間も満たしている。   A lithium ion secondary battery 100 shown in FIG. 1 includes a stacked battery structure 18. The battery structure 18 includes a plurality of electrode pairs (positive and negative electrode pairs) 7 in which the positive electrode 6 and the negative electrode 4 face each other. The electrode pair 7 includes a positive electrode 6, a separator 5, and a negative electrode 4. The positive electrode 6 and the negative electrode 4 are opposed to each other with the separator 5 interposed therebetween. The positive electrode 6 and the negative electrode 4 are insulated by the separator 5. In the battery structure 18, the positive electrodes 6 and the negative electrodes 4 are alternately stacked. All the positive electrodes 6 are electrically connected to the positive terminal 12, and all the negative electrodes 4 are electrically connected to the negative terminal 2. The battery structure 18 is disposed in the battery case 16 together with the electrolytic solution. The electrolytic solution fills the space 14 in the battery case 16 and also fills the gaps of the battery structure 18.

図１では、積層方向の端部に配置されている負極電極４Ｘと、積層方向の中間部に配置さている負極電極４Ｙを区別している。負極電極４Ｙと正極電極６は、負極電極４Ｘの間に配置されている。負極電極４Ｘは、電池構造体１８の端部電極ということができる。負極電極４Ｙと正極電極６は、電池構造体１８の中間電極ということができる。   In FIG. 1, the negative electrode 4X disposed at the end in the stacking direction is distinguished from the negative electrode 4Y disposed at the intermediate in the stacking direction. The negative electrode 4Y and the positive electrode 6 are disposed between the negative electrode 4X. The negative electrode 4 </ b> X can be referred to as an end electrode of the battery structure 18. The negative electrode 4Y and the positive electrode 6 can be said to be intermediate electrodes of the battery structure 18.

図２は、電池構造体１８の部分拡大図を示す。図２に示すように、正極電極６は、正極集電体２６と正極活物質２４を備えている。正極活物質２４は、正極集電体２６の両面に設けられている。負極電極４は、負極集電体２０と負極活物質２２を備えている。積層方向端部の負極電極４Ｘでは、負極活物質２２が、負極集電体２０Ｘの片面に設けられている。積層方向中間部の負極電極４Ｙでは、負極活物質２２が、負極集電体２０Ｙの両面に設けられている。負極活物質２２には、リチウムイオンがドーピングされている。   FIG. 2 shows a partially enlarged view of the battery structure 18. As shown in FIG. 2, the positive electrode 6 includes a positive electrode current collector 26 and a positive electrode active material 24. The positive electrode active material 24 is provided on both surfaces of the positive electrode current collector 26. The negative electrode 4 includes a negative electrode current collector 20 and a negative electrode active material 22. In the negative electrode 4X at the end in the stacking direction, the negative electrode active material 22 is provided on one surface of the negative electrode current collector 20X. In the negative electrode 4Y in the intermediate portion in the stacking direction, the negative electrode active material 22 is provided on both surfaces of the negative electrode current collector 20Y. The negative electrode active material 22 is doped with lithium ions.

正極活物質２４と負極活物質２２が、セパレータ５を介して対向している。第１貫通孔３０が負極集電体２０Ｘに形成されており，第２貫通孔３２が正極集電体２６に形成されており、第３貫通孔３４が負極集電体２０Ｙに形成されている。第１貫通孔３０は、負極集電体２０Ｘを厚み方向に貫通している。第２貫通孔３２は、正極集電体２６を厚み方向に貫通している。第３貫通孔３４は、負極集電体２０Ｙを厚み方向に貫通している。詳細は後述するが、第１貫通孔３０のサイズは、第２貫通孔３２及び第３貫通孔３４のサイズよりも大きい。なお、第２貫通孔３２及び第３貫通孔３４のサイズは等しい。   The positive electrode active material 24 and the negative electrode active material 22 face each other with the separator 5 interposed therebetween. The first through hole 30 is formed in the negative electrode current collector 20X, the second through hole 32 is formed in the positive electrode current collector 26, and the third through hole 34 is formed in the negative electrode current collector 20Y. . The first through hole 30 penetrates the negative electrode current collector 20X in the thickness direction. The second through hole 32 penetrates the positive electrode current collector 26 in the thickness direction. The third through hole 34 penetrates the negative electrode current collector 20Y in the thickness direction. Although details will be described later, the size of the first through hole 30 is larger than the sizes of the second through hole 32 and the third through hole 34. The second through hole 32 and the third through hole 34 are equal in size.

負極集電体２０及び正極集電体２６について説明する。図３は負極集電体２０Ｘの平面図を示し、図４は負極集電体２０Ｙ及び正極集電体２６の平面図を示す。図３に示すように、複数の第１貫通孔３０が負極集電体２０Ｘに形成されており、並列に並んでいる。なお、ここでいう「並列に並ぶ」とは、隣接する４個の第１貫通孔３０の中心を結ぶ線が矩形４０を形成するように、第１貫通孔３０を並べることである。第２貫通孔３２及び第３貫通孔３４も並列に並んでいる（図４を参照）。   The negative electrode current collector 20 and the positive electrode current collector 26 will be described. 3 shows a plan view of the negative electrode current collector 20X, and FIG. 4 shows a plan view of the negative electrode current collector 20Y and the positive electrode current collector 26. As shown in FIG. 3, a plurality of first through holes 30 are formed in the negative electrode current collector 20X, and are arranged in parallel. Here, “aligned in parallel” means that the first through holes 30 are arranged such that a line connecting the centers of the four adjacent first through holes 30 forms a rectangle 40. The second through hole 32 and the third through hole 34 are also arranged in parallel (see FIG. 4).

図３及び図４に示すように、集電体２０Ｘ，２０Ｙ及び２６の単位面積当たりに形成されている貫通孔の数は等しい。一方、第１貫通孔３０のサイズは、第２貫通孔３２及び第３貫通孔３４のサイズよりも大きい。そのため、負極集電体２０Ｘの開孔率は、負極集電体２０Ｙ及び正極集電体２６の開孔率よりも大きい。第１貫通孔３０の径Ｒ３０は、１００〜５００μｍであることが好ましい。一方、第２貫通孔３２の径Ｒ３２及び第３貫通孔３４の径Ｒ３４は、５０〜３００μｍであることが好ましい。また、負極集電体２０Ｘの開孔率は１０〜６０％であることが好ましく、負極集電体２０Ｙ及び正極集電体２６の開孔率は１０〜６０％であることが好ましい。   As shown in FIGS. 3 and 4, the number of through holes formed per unit area of the current collectors 20X, 20Y and 26 is equal. On the other hand, the size of the first through hole 30 is larger than the sizes of the second through hole 32 and the third through hole 34. Therefore, the aperture ratio of the negative electrode current collector 20X is larger than the aperture ratios of the negative electrode current collector 20Y and the positive electrode current collector 26. The diameter R30 of the first through hole 30 is preferably 100 to 500 μm. On the other hand, the diameter R32 of the second through hole 32 and the diameter R34 of the third through hole 34 are preferably 50 to 300 μm. Further, the aperture ratio of the negative electrode current collector 20X is preferably 10 to 60%, and the aperture ratios of the negative electrode current collector 20Y and the positive electrode current collector 26 are preferably 10 to 60%.

なお、リチウムイオン二次電池１００では、負極集電体２０Ｘの開孔率が、負極集電体２０Ｙ及び正極集電体２６の開孔率よりも大きければよい。そのため、必ずしも第１貫通孔３０のサイズを、第２貫通孔３２及び第３貫通孔３４のサイズよりも大きくする必要はない。例えば、図５に示すように、負極集電体２０Ｙ及び正極集電体２６に、第２貫通孔３２ａ及び第３貫通孔３４ａを形成してもよい。第２貫通孔３２ａの径Ｒ３２ａ及び第３貫通孔３４ａの径Ｒ３４ａは、第１貫通孔３０の径Ｒ３０と等しい（図３を参照）。図５に示す負極集電体２０Ｙ及び正極集電体２６の場合、集電体２０Ｙ及び２６の単位面積当たりに形成されている貫通孔３２ａ及び３４ａの数が、負極集電体２０Ｘに形成されている第１貫通孔３０の数よりも少ない。   In the lithium ion secondary battery 100, it is sufficient that the aperture ratio of the negative electrode current collector 20X is larger than the aperture ratios of the negative electrode current collector 20Y and the positive electrode current collector 26. Therefore, the size of the first through hole 30 is not necessarily larger than the sizes of the second through hole 32 and the third through hole 34. For example, as shown in FIG. 5, the second through hole 32a and the third through hole 34a may be formed in the negative electrode current collector 20Y and the positive electrode current collector 26. The diameter R32a of the second through hole 32a and the diameter R34a of the third through hole 34a are equal to the diameter R30 of the first through hole 30 (see FIG. 3). In the case of the negative electrode current collector 20Y and the positive electrode current collector 26 shown in FIG. 5, the number of through holes 32a and 34a formed per unit area of the current collectors 20Y and 26 is formed in the negative electrode current collector 20X. The number of first through holes 30 is smaller.

なお、集電体２０Ｘ，２０Ｙ及び２６に形成する貫通孔は、必ずしも並列に並べる必要はない。例えば、図６に示すように、複数の第１貫通孔３０を、千鳥状に並べてもよい。「千鳥状に並べる」とは、隣接する４個の第１貫通孔３０の中心を結ぶ線が菱形４２を形成するように、第１貫通孔３０を並べることである。換言すると、隣接する３個の第１貫通孔３０の中心を結ぶ線が正三角形を形成するように、第１貫通孔３０を並べることである。   Note that the through holes formed in the current collectors 20X, 20Y, and 26 are not necessarily arranged in parallel. For example, as shown in FIG. 6, a plurality of first through holes 30 may be arranged in a staggered manner. “Arranging in a staggered manner” means arranging the first through holes 30 such that a line connecting the centers of the four adjacent first through holes 30 forms a rhombus 42. In other words, the first through holes 30 are arranged so that lines connecting the centers of the three adjacent first through holes 30 form an equilateral triangle.

上記したように、負極集電体２０Ｘの開孔率は、負極集電体２０Ｙ及び正極集電体２６の開孔率よりも大きい。そのため、負極集電体２０Ｘは、負極集電体２０Ｙ及び正極集電体２６よりもリチウムイオンが通過し易い。なお、リチウムイオンが集電体２０Ｘ，２０Ｙ及び２６を通過するのは、主に製造過程であり、負極集電体２０にリチウムイオンをドーピングする工程である。リチウムイオン二次電池１００が使用（充放電）されているときは、リチウムイオンは、セパレータ５を通って正極活物質２４と負極活物質２２の間を移動する。   As described above, the aperture ratio of the negative electrode current collector 20X is larger than the aperture ratios of the negative electrode current collector 20Y and the positive electrode current collector 26. Therefore, lithium ions are more easily passed through the negative electrode current collector 20X than the negative electrode current collector 20Y and the positive electrode current collector 26. The lithium ions pass through the current collectors 20X, 20Y, and 26 are mainly manufacturing processes, and are steps of doping the negative electrode current collector 20 with lithium ions. When the lithium ion secondary battery 100 is used (charge / discharge), the lithium ions move between the positive electrode active material 24 and the negative electrode active material 22 through the separator 5.

ここで、図７及び図８を参照し、リチウムイオン二次電池１００の製造方法を説明する。まず、貫通孔３０，３２，３４を有する集電体２０Ｘ，２６，２０Ｙを用いて、正極電極６と負極電極４を形成する（電極形成工程）。電極形成工程は、集電体２０Ｘ，２６，２０Ｙに貫通孔３０，３２，３４を形成する貫通孔形成工程と、集電体２０Ｘ，２６，２０Ｙに活物質２２，２４を塗布する活物質塗布工程を備える。貫通孔形成工程では、正極集電体２６に第２貫通孔３２を形成し、負極集電体２０Ｙに第２貫通孔３２と同じサイズの第３貫通孔３４を形成する。そして、負極集電体２０Ｙよりも厚みが厚い負極集電体２０Ｘに、第２貫通孔３２及び第３貫通孔３４よりも大きな第１貫通孔３０を形成する。   Here, with reference to FIG.7 and FIG.8, the manufacturing method of the lithium ion secondary battery 100 is demonstrated. First, the positive electrode 6 and the negative electrode 4 are formed using the current collectors 20X, 26, and 20Y having the through holes 30, 32, and 34 (electrode formation step). The electrode forming step includes a through hole forming step for forming the through holes 30, 32, 34 in the current collectors 20X, 26, 20Y, and an active material application for applying the active materials 22, 24 to the current collectors 20X, 26, 20Y A process is provided. In the through hole forming step, the second through hole 32 is formed in the positive electrode current collector 26, and the third through hole 34 having the same size as the second through hole 32 is formed in the negative electrode current collector 20Y. And the 1st through-hole 30 larger than the 2nd through-hole 32 and the 3rd through-hole 34 is formed in the negative electrode collector 20X thicker than the negative electrode collector 20Y.

活物質塗布工程では、負極集電体２０の表面に負極活物質２２を塗布し、正極集電体２６の表面に正極活物質２４を塗布する。活物質の塗布方法は公知なので説明を省略する。このときに、負極集電体２０Ｘに塗布する負極活物質２２の厚みを、負極集電体２０Ｙに塗布する負極活物質２２の厚みと等しくなるように調整する。なお、電極形成工程では、貫通孔を有する市販の集電体を購入し、その集電体の表面に活物質を塗布してもよい。   In the active material application step, the negative electrode active material 22 is applied to the surface of the negative electrode current collector 20, and the positive electrode active material 24 is applied to the surface of the positive electrode current collector 26. Since the application method of an active material is well-known, description is abbreviate | omitted. At this time, the thickness of the negative electrode active material 22 applied to the negative electrode current collector 20X is adjusted to be equal to the thickness of the negative electrode active material 22 applied to the negative electrode current collector 20Y. In the electrode forming step, a commercially available current collector having a through hole may be purchased and an active material may be applied to the surface of the current collector.

次に、セパレータ５を介して、正極電極６と負極電極４を交互に積層して、電池構造体１８を作製する（積層工程）。積層工程では、負極電極４Ｘを、積層方向の両端に配置する。すなわち、他の電極（正極電極６及び負極電極４Ｙ）よりも集電体の開孔率が大きい負極電極４Ｘを、積層方向の両端に配置する。正極電極６及び負極電極４Ｙは、積層方向において、負極電極４Ｘに挟まれた位置に配置する。なお、図７は、電池構造体１８の積層方向の一端だけを示している。   Next, the positive electrode 6 and the negative electrode 4 are alternately laminated via the separator 5 to produce a battery structure 18 (lamination process). In the stacking step, the negative electrode 4X is disposed at both ends in the stacking direction. That is, the negative electrode 4X having a current collector with a higher hole area ratio than the other electrodes (the positive electrode 6 and the negative electrode 4Y) is disposed at both ends in the stacking direction. The positive electrode 6 and the negative electrode 4Y are arranged at a position between the negative electrode 4X in the stacking direction. Note that FIG. 7 shows only one end of the battery structure 18 in the stacking direction.

次に、容器（図示省略）内に電池構造体１８を配置し、電池構造体１８の両端にリチウム箔３６を配置する（配置工程）。リチウム箔３６は、リチウムイオン供給体の一例である。リチウム箔３６は、セパレータ５を介して負極集電体２０Ｘに対向する位置に配置する。その後、容器内に電解液を供給する。   Next, the battery structure 18 is placed in a container (not shown), and the lithium foil 36 is placed on both ends of the battery structure 18 (placement step). The lithium foil 36 is an example of a lithium ion supplier. The lithium foil 36 is disposed at a position facing the negative electrode current collector 20X with the separator 5 interposed therebetween. Thereafter, an electrolytic solution is supplied into the container.

次に、図８に示すように、リチウム箔３６を外部電源３７の負極に接続し、負極電極４を外部電源３７の正極に接続する。その後、負極電極４とリチウム箔３６の間に電圧を印加する（ドーピング工程）。負極電極４が高電位になるので、リチウム箔３６から負極電極４（負極電極４Ｘ及び負極電極４Ｙ）に向けてリチウムイオン３８が移動する。すなわち、リチウムイオン３８が、電池構造体１８の内部に向けて移動する。これにより、リチウムイオン３８が、負極活物質２２にドーピングされる。ドーピング工程の詳細については後述する。ドーピング工程が終了した後、残存したリチウム箔３６を除去し、電池構造体１８を電解液とともに電池ケース１６内に配置する。その後、電池ケース１６を密封することにより、図１に示すリチウムイオン二次電池１００が完成する。なお、ドーピング工程は、電池ケース１６内で実施してもよいし、電池ケース１６とは別の容器内で実施してもよい。   Next, as shown in FIG. 8, the lithium foil 36 is connected to the negative electrode of the external power source 37, and the negative electrode 4 is connected to the positive electrode of the external power source 37. Thereafter, a voltage is applied between the negative electrode 4 and the lithium foil 36 (doping process). Since the negative electrode 4 has a high potential, the lithium ions 38 move from the lithium foil 36 toward the negative electrode 4 (the negative electrode 4X and the negative electrode 4Y). That is, the lithium ions 38 move toward the inside of the battery structure 18. Thereby, the lithium ions 38 are doped into the negative electrode active material 22. Details of the doping step will be described later. After the doping process is completed, the remaining lithium foil 36 is removed, and the battery structure 18 is placed in the battery case 16 together with the electrolytic solution. Thereafter, the battery case 16 is sealed to complete the lithium ion secondary battery 100 shown in FIG. The doping process may be performed in the battery case 16 or in a container different from the battery case 16.

ドーピング工程について、さらに詳細に説明する。図８に示すように、リチウム箔３６と負極集電体２０Ｘの間には、セパレータ５が介在するだけである。そのため、通電を開始すると、多くのリチウムイオン３８が、リチウム箔３６から負極集電体２０Ｘに到達する。負極集電体２０Ｘは開孔率が大きいので、リチウムイオン３８は、負極集電体２０Ｘをスムーズに通過することができる。すなわち、負極集電体２０Ｘは、多量のリチウムイオン３８を電池構造体１８の内部に通過させることができる。負極集電体２０Ｘを通過したリチウムイオン３８の一部は、負極電極４Ｘの負極活物質２２に留まる。   The doping process will be described in more detail. As shown in FIG. 8, only the separator 5 is interposed between the lithium foil 36 and the negative electrode current collector 20X. Therefore, when energization is started, many lithium ions 38 reach the negative electrode current collector 20 </ b> X from the lithium foil 36. Since the negative electrode current collector 20X has a high hole area ratio, the lithium ions 38 can smoothly pass through the negative electrode current collector 20X. That is, the negative electrode current collector 20 </ b> X can pass a large amount of lithium ions 38 into the battery structure 18. A part of the lithium ions 38 that have passed through the negative electrode current collector 20X remains in the negative electrode active material 22 of the negative electrode 4X.

負極電極４Ｘの負極活物質２２を通過し、さらに電池構造体１８の内部に移動するリチウムイオン３８も存在する。これらのリチウムイオン３８は、セパレータ５，正極活物質２４を通過して正極集電体２６に達する。正極集電体２６に達するまでに、リチウムイオン３８の移動速度は低下している。また、負極電極４Ｘの負極活物質２２に留まったリチウムイオン３８の分だけ、正極集電体２６に達するリチウムイオン３８の数は減少している。そのため、正極集電体２６の開孔率が負極集電体２０Ｘの開孔率よりも小さくても、リチウムイオン３８は、正極集電体２６をスムーズに通過することができる。同様に、負極集電体２０Ｙの開孔率が負極集電体２０Ｘの開孔率よりも小さくても、リチウムイオン３８は、負極集電体２０Ｙをスムーズに通過することができる。   There are also lithium ions 38 that pass through the negative electrode active material 22 of the negative electrode 4 </ b> X and move into the battery structure 18. These lithium ions 38 pass through the separator 5 and the positive electrode active material 24 and reach the positive electrode current collector 26. By the time the cathode current collector 26 is reached, the moving speed of the lithium ions 38 has decreased. Further, the number of lithium ions 38 reaching the positive electrode current collector 26 is reduced by the amount of lithium ions 38 remaining on the negative electrode active material 22 of the negative electrode 4X. Therefore, even if the aperture ratio of the positive electrode current collector 26 is smaller than the aperture ratio of the negative electrode current collector 20X, the lithium ions 38 can pass through the positive electrode current collector 26 smoothly. Similarly, even if the aperture ratio of the negative electrode current collector 20Y is smaller than the aperture ratio of the negative electrode current collector 20X, the lithium ions 38 can smoothly pass through the negative electrode current collector 20Y.

正極集電体２６及び負極集電体２０Ｙの開孔率を小さくすることにより、正極電極６及び負極電極４Ｙの強度が低下することを抑制することができる。なお、負極電極４Ｘは、負極集電体２０Ｘの厚みｔ２０Ｘを正極集電体２６の厚みｔ２６及び負極集電体２０Ｙの厚みｔ２０Ｙよりも厚くすることにより、強度が低下することを抑制している（図２を参照）。また、負極集電体２０Ｙ及び正極集電体２６の開孔率を小さくすると、上記した活物質塗布工程において、負極活物質２２及び正極活物質２４の表面に凹凸が生じることを抑制することができる。活物質２２，２４の表面に凹凸が存在すると、電流が電極間を偏って流れ、電池寿命が低下することがある。負極集電体２０Ｙ及び正極集電体２６の開孔率を小さくすることにより、電極間に流れる電流を均一にすることができるので、電池寿命の低下を抑制することができる。   By reducing the aperture ratio of the positive electrode current collector 26 and the negative electrode current collector 20Y, it is possible to suppress the strength of the positive electrode 6 and the negative electrode 4Y from being lowered. Note that the negative electrode 4X suppresses the strength from decreasing by making the thickness t20X of the negative electrode current collector 20X thicker than the thickness t26 of the positive electrode current collector 26 and the thickness t20Y of the negative electrode current collector 20Y. (See FIG. 2). Further, when the porosity of the negative electrode current collector 20Y and the positive electrode current collector 26 is reduced, it is possible to suppress the occurrence of irregularities on the surfaces of the negative electrode active material 22 and the positive electrode active material 24 in the active material application step described above. it can. If there are irregularities on the surfaces of the active materials 22, 24, current flows unevenly between the electrodes, and the battery life may be reduced. By reducing the open area ratio of the negative electrode current collector 20Y and the positive electrode current collector 26, the current flowing between the electrodes can be made uniform, so that a reduction in battery life can be suppressed.

上記したように、電池構造体１８の端部に配置されている負極集電体２０Ｘには、多くのリチウムイオン３８が供給される。そのため、負極集電体２０Ｘの開孔率を正極集電体２６及び負極集電体２０Ｙの開孔率と同程度にすると、負極集電体２０Ｘが抵抗となり、リチウムイオン３８が電池構造体１８内に速やかに移動することができない。その結果、電池構造体１８の中間部に配置されている負極活物質２２に対して、リチウムイオン３８が速やかにドーピングされない。電池構造体１８に対するリチウムイオン３８のドーピング速度が低下する。それにより、リチウムイオン二次電池１００の生産効率が低下する。積層方向の端部に配置する負極集電体２０Ｘの開孔率を他の集電体（正極集電体２６，負極集電体２０Ｙ）の開孔率よりも大きくすることにより、強度及び電池寿命の低下を抑制しつつ、生産効率を向上させることができる。   As described above, many lithium ions 38 are supplied to the negative electrode current collector 20 </ b> X disposed at the end of the battery structure 18. Therefore, when the hole area ratio of the negative electrode current collector 20X is set to the same degree as the hole area ratios of the positive electrode current collector 26 and the negative electrode current collector 20Y, the negative electrode current collector 20X becomes a resistance, and the lithium ions 38 become the battery structure 18. Cannot move quickly in. As a result, the lithium ion 38 is not rapidly doped into the negative electrode active material 22 disposed in the middle portion of the battery structure 18. The doping rate of the lithium ions 38 to the battery structure 18 decreases. Thereby, the production efficiency of the lithium ion secondary battery 100 decreases. By making the aperture ratio of the negative electrode current collector 20X arranged at the end in the stacking direction larger than the aperture ratios of the other current collectors (the positive electrode current collector 26 and the negative electrode current collector 20Y), the strength and the battery Production efficiency can be improved while suppressing a decrease in the service life.

上記ドーピング工程では、負極電極４とリチウム箔３６の間に電圧を印加して、リチウムイオンを負極活物質２２にドーピングする。この方法は、負極電極４とリチウム箔３６の電位差を調整できるという点で有用な方法である。しかしながら、負極集電体２０Ｘとリチウム箔３６を直接接触させ、両者を短絡させることによりリチウムイオンをドーピングする方法を採用してもよい。この方法は、外部電源３７を必要としない簡便なドーピング方法である。   In the doping step, a voltage is applied between the negative electrode 4 and the lithium foil 36 to dope the negative electrode active material 22 with lithium ions. This method is useful in that the potential difference between the negative electrode 4 and the lithium foil 36 can be adjusted. However, a method of doping lithium ions by directly contacting the negative electrode current collector 20X and the lithium foil 36 and short-circuiting them may be employed. This method is a simple doping method that does not require the external power source 37.

なお、正極集電体２６の開孔率と負極集電体２０Ｙの開孔率は異なっていてもよい。重要なことは、積層方向の端部に配置されている負極集電体２０Ｘの開孔率が、積層方向の中間部に配置されている正極集電体２６及び負極集電体２０Ｙの開孔率よりも大きいことである。また、正極集電体２６の厚みと負極集電体２０Ｙの厚みは異なっていてもよい。正極集電体２６の厚みと負極集電体２０Ｙの厚みは、リチウムイオン二次電池の特性に併せて適宜選択することができる。さらに、負極集電体２０Ｘの厚みが負極集電体２０Ｙの厚みと同じであってもよい。負極電極４Ｘの強度が負極電極４Ｙの強度よりも弱くなる可能性があるものの、負極電極４Ｙ及び正極電極６が十分な強度を有していれば、電池構造体１８の全体としては強度が維持される。   Note that the hole area ratio of the positive electrode current collector 26 and the hole area ratio of the negative electrode current collector 20Y may be different. What is important is that the aperture ratio of the negative electrode current collector 20X disposed at the end portion in the stacking direction is equal to that of the positive electrode current collector 26 and the negative electrode current collector 20Y disposed in the intermediate portion in the stack direction. Is greater than the rate. Further, the thickness of the positive electrode current collector 26 and the thickness of the negative electrode current collector 20Y may be different. The thickness of the positive electrode current collector 26 and the thickness of the negative electrode current collector 20Y can be appropriately selected according to the characteristics of the lithium ion secondary battery. Furthermore, the thickness of the negative electrode current collector 20X may be the same as the thickness of the negative electrode current collector 20Y. Although the strength of the negative electrode 4X may be weaker than that of the negative electrode 4Y, if the negative electrode 4Y and the positive electrode 6 have sufficient strength, the overall strength of the battery structure 18 is maintained. Is done.

（実験例）
複数の電池構造体６０を作製し、活物質に対するリチウムイオンのドーピング速度について実験を行った。図９は、実験で用いた電池構造体６０の基本的な構造を示す。電池構造体６０では、負極電極５４を積層方向の両端に配置した。３個の負極電極５４と２個の正極電極５６を、セパレータ５８を介して交互に積層した。負極電極５４の外側にリチウム箔５２を配置し、負極電極５４を外部電源５０の正極に接続し、リチウム箔５２を外部電源５０の負極に接続した。なお、本実験では、負極電極５４の集電体と正極電極５６の集電体の全てに、０．３ｍｍのパンチング孔（貫通孔）を形成した。 (Experimental example)
A plurality of battery structures 60 were produced, and experiments were conducted on the lithium ion doping rate for the active material. FIG. 9 shows a basic structure of the battery structure 60 used in the experiment. In the battery structure 60, the negative electrodes 54 are disposed at both ends in the stacking direction. Three negative electrodes 54 and two positive electrodes 56 were alternately stacked via separators 58. Lithium foil 52 was disposed outside negative electrode 54, negative electrode 54 was connected to the positive electrode of external power supply 50, and lithium foil 52 was connected to the negative electrode of external power supply 50. In this experiment, 0.3 mm punching holes (through holes) were formed in all of the current collector of the negative electrode 54 and the current collector of the positive electrode 56.

本実験では、負極電極５４の開孔率、正極電極５６の開孔率、負極電極５４及び正極電極５６の貫通孔の配置位置を変化させて電池構造体６０を作製した。そして、負極電極５４とリチウム箔５２の間に電圧を加え、リチウムイオンのドーピング速度を測定した。得られた結果について、リチウムイオンのドーピング速度を目的変数（基準変数）とし、負極電極５４の開孔率、正極電極５６の開孔率、負極電極５４及び正極電極５６の貫通孔の配置位置を説明変数として多変量解析を行った。なお、貫通孔の配置位置（質的変数）については、千鳥を１とし、並列を２とした。実験で用いた試料を表１に示す。   In this experiment, the battery structure 60 was manufactured by changing the hole area ratio of the negative electrode 54, the hole area ratio of the positive electrode 56, and the arrangement positions of the through holes of the negative electrode 54 and the positive electrode 56. A voltage was applied between the negative electrode 54 and the lithium foil 52, and the doping rate of lithium ions was measured. With respect to the obtained results, the doping rate of lithium ions was used as a target variable (reference variable), and the opening ratio of the negative electrode 54, the opening ratio of the positive electrode 56, and the arrangement positions of the through holes of the negative electrode 54 and the positive electrode 56 were as follows. Multivariate analysis was performed as an explanatory variable. In addition, about the arrangement | positioning position (qualitative variable) of a through-hole, staggered was set to 1 and parallel was set to 2. Table 1 shows the samples used in the experiment.

Figure 2013058378
Figure 2013058378

多変量解析の結果、下記式１に示す回帰式が得られた。下記式１に示すように、回帰式では、負極電極５４に関する説明変数のみが採用された。なお、下記回帰式の相関係数は９８％であった。下記式１より、リチウムイオンのドーピング速度は、負極電極の開孔率、及び、負極電極の貫通孔の配置位置に依存することが明らかとなった。
(ドーピング速度)=8.7×(負極の開孔率)-108×(負極の貫通孔の配置位置）・・（式１） As a result of multivariate analysis, the regression equation shown in the following equation 1 was obtained. As shown in the following formula 1, in the regression formula, only explanatory variables related to the negative electrode 54 are employed. In addition, the correlation coefficient of the following regression equation was 98%. From the following formula 1, it became clear that the doping rate of lithium ions depends on the hole area ratio of the negative electrode and the arrangement position of the through holes of the negative electrode.
(Doping rate) = 8.7 × (opening ratio of negative electrode) −108 × (positioning position of through hole of negative electrode)

上記回帰式１では、正極電極５６に関する説明変数は採用されなかった。これは、積層方向の中間部に配置されている電極（集電体）の場合、開孔率，貫通孔の配置位置を変化させても、リチウムイオンのドーピング速度に影響を与えないことを示している。また、上記回帰式１から明らかなように、負極の開孔率を大きくすれば、リチウムイオンのドーピング速度が速くなることが確認された。すなわち、端部に配置する電極（上記実験の場合は負極）の集電体の開孔率を大きくすれば、中間部に配置される集電体の開孔率に係らず、リチウムイオンのドーピング速度が速くなることが確認された。   In the regression equation 1, the explanatory variable related to the positive electrode 56 was not adopted. This indicates that, in the case of an electrode (current collector) arranged in the middle part of the stacking direction, changing the hole area ratio and the arrangement position of the through holes does not affect the doping rate of lithium ions. ing. Further, as is clear from the above regression equation 1, it was confirmed that the lithium ion doping rate was increased by increasing the porosity of the negative electrode. That is, if the aperture ratio of the collector of the electrode disposed at the end (the negative electrode in the case of the above experiment) is increased, lithium ion doping is performed regardless of the aperture ratio of the collector disposed at the intermediate section. It was confirmed that the speed increased.

上記した実施形態のリチウムイオン二次電池では、端部電極の集電体の開孔率が中間電極の集電体の開孔率よりも大きければよく、リチウムイオン二次電池を構成する部品の材料は様々なものを使用することができる。以下に、リチウムイオン二次電池の構成部品について、好ましい材料の一例を示す。   In the lithium ion secondary battery according to the above-described embodiment, it is sufficient that the aperture ratio of the current collector of the end electrode is larger than the aperture ratio of the current collector of the intermediate electrode. Various materials can be used. Below, an example of a preferable material is shown about the component of a lithium ion secondary battery.

（負極集電体）
負極集電体として、アルミニウム（Ａｌ）、ニッケル（Ｎｉ）、銅（Ｃｕ）等、又はそれらの複合材料を用いることができる。特に、銅又は銅を含む複合材料であることが好ましい。 (Negative electrode current collector)
As the negative electrode current collector, aluminum (Al), nickel (Ni), copper (Cu), or a composite material thereof can be used. In particular, copper or a composite material containing copper is preferable.

（負極活物質）
負極活物質は、リチウムイオンが侵入及び脱離可能な材料を用いる。電池容量を向上させるため、リチウム（Ｌｉ）を含まない材料であることが好ましく、例えば、天然黒鉛，メソカーボンマイクロビーズ，高配向性グラファイト，ハードカーボン，ソフトカーボン等の炭素材料，酸化ケイ素（ＳｉＯ）等を用いることができる。負極活物質は、必要に応じて導電材，結着剤等とともに負極集電体に塗布される。なお、リチウム，ナトリウム等のアルカリ金属を使用することもできる。 (Negative electrode active material)
As the negative electrode active material, a material in which lithium ions can enter and leave is used. In order to improve battery capacity, it is preferable that the material does not contain lithium (Li). For example, carbon materials such as natural graphite, mesocarbon microbeads, highly oriented graphite, hard carbon, and soft carbon, silicon oxide (SiO 2) ) Etc. can be used. A negative electrode active material is apply | coated to a negative electrode collector with a electrically conductive material, a binder, etc. as needed. Alkali metals such as lithium and sodium can also be used.

（正極集電体）
正極集電体として、アルミニウム、ニッケル、チタン等、又はそれらの複合材料を用いることができる。特に、アルミニウム又はアルミニウムを含む複合材料であることが好ましい。 (Positive electrode current collector)
As the positive electrode current collector, aluminum, nickel, titanium, or a composite material thereof can be used. In particular, aluminum or a composite material containing aluminum is preferable.

（正極活物質）
正極活物質は、リチウムイオンが侵入及び脱離可能な材料を用いる。電池容量を向上させるため、リチウム（Ｌｉ）を含まない材料であることが好ましく、例えば、天然黒鉛，メソカーボンマイクロビーズ，高配向性グラファイト，ハードカーボン，ソフトカーボン等の炭素材料，硫黄変性ポリアクリロニトリル等を用いることができる。正極活物質は、必要に応じて導電材，結着剤等とともに正極集電体に塗布される。なお、リチウム，ナトリウム等のアルカリ金属を使用することもできる。 (Positive electrode active material)
As the positive electrode active material, a material in which lithium ions can enter and leave is used. In order to improve battery capacity, it is preferable that the material does not contain lithium (Li). For example, carbon materials such as natural graphite, mesocarbon microbeads, highly oriented graphite, hard carbon, and soft carbon, sulfur-modified polyacrylonitrile Etc. can be used. The positive electrode active material is applied to the positive electrode current collector together with a conductive material, a binder and the like as necessary. Alkali metals such as lithium and sodium can also be used.

（セパレータ）
セパレータは、絶縁性を有する多孔質を用いる。セパレータとして、ポリエチレン（ＰＥ）、ポリプロピレン（ＰＰ）等のポリオレフィン系樹脂からなる多孔質フィルム、あるいは、ポリプロピレン、ポリエチレンテレフタレート（ＰＥＴ）、メチルセルロース等からなる織布または不織布を使用することができる。 (Separator)
As the separator, a porous porous material is used. As the separator, a porous film made of a polyolefin-based resin such as polyethylene (PE) or polypropylene (PP), or a woven or non-woven fabric made of polypropylene, polyethylene terephthalate (PET), methyl cellulose or the like can be used.

（電解液）
電解液は、非水系の溶媒に支持塩（電解質）を溶解させた非水電解液であることが好ましい。非水系の溶媒として、エチレンカーボネート（ＥＣ）、プロピレンカーボネート（ＰＣ）、ジメチルカーボネート（ＤＭＣ）、ジエチルカーボネート（ＤＥＣ）、エチルメチルカーボネート（ＥＭＣ）等、又はこれらの混合液を使用することができる。また、支持塩（電解質）として、例えば、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＡｓＦ６等を使用することができる。 (Electrolyte)
The electrolytic solution is preferably a nonaqueous electrolytic solution in which a supporting salt (electrolyte) is dissolved in a nonaqueous solvent. As the non-aqueous solvent, ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), or a mixture thereof can be used. Moreover, as a supporting salt (electrolyte), for example, can be used LiPF 6, LiBF 4, LiAsF 6, and the like.

以上、本発明の具体例を詳細に説明したが、これらは例示に過ぎず、特許請求の範囲を限定するものではない。特許請求の範囲に記載の技術には、以上に例示した具体例を様々に変形、変更したものが含まれる。また、本明細書または図面に説明した技術要素は、単独であるいは各種の組合せによって技術的有用性を発揮するものであり、出願時の請求項に記載の組合せに限定されるものではない。また、本明細書または図面に例示した技術は複数の目的を同時に達成し得るものであり、そのうちの一つの目的を達成すること自体で技術的有用性を持つものである。   Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. In addition, the technical elements described in the present specification or drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in the present specification or the drawings can achieve a plurality of objects at the same time, and has technical utility by achieving one of the objects.

４：負極電極
５：セパレータ
６：正極電極
７：正負極の対（電極対）
１８：電池構造体
２０：負極集電体
２６：正極集電体
１００：リチウムイオン二次電池 4: Negative electrode 5: Separator 6: Positive electrode 7: Pair of positive and negative electrodes (electrode pair)
18: Battery structure 20: Negative electrode current collector 26: Positive electrode current collector 100: Lithium ion secondary battery

Claims (5)

セパレータを介して正極電極と負極電極が対向している正負極の対が複数積層されているリチウムイオン二次電池であって、
前記正極電極の集電体及び前記負極電極の集電体の各々には厚み方向に貫通する孔が形成されており、
積層方向の端部に配置されている端部電極の集電体の開孔率が、前記端部電極の間に配置されている中間電極の集電体の開孔率よりも大きいことを特徴とするリチウムイオン二次電池。 A lithium ion secondary battery in which a plurality of positive and negative electrode pairs in which a positive electrode and a negative electrode are opposed via a separator are laminated,
Each of the current collector of the positive electrode and the current collector of the negative electrode has a hole penetrating in the thickness direction,
The aperture ratio of the current collector of the end electrode disposed at the end in the stacking direction is larger than the aperture ratio of the current collector of the intermediate electrode disposed between the end electrodes. Lithium ion secondary battery. 前記端部電極の集電体が、他の電極の集電体よりも厚いことを特徴とする請求項１に記載のリチウムイオン二次電池。   The lithium ion secondary battery according to claim 1, wherein a current collector of the end electrode is thicker than a current collector of another electrode. 前記端部電極が、前記負極電極であることを特徴とする請求項１又は２に記載のリチウムイオン二次電池。   The lithium ion secondary battery according to claim 1, wherein the end electrode is the negative electrode. セパレータを介して正極電極と負極電極が対向している正負極の対が複数積層されている電池構造体を備えるリチウムイオン二次電池の製造方法であり、
厚み方向に貫通する孔が形成された集電体を用いて前記正極電極と前記負極電極を形成する電極形成工程と、
前記正極電極と前記負極電極を交互に積層して電池構造体を作製する積層工程と、
容器内に前記電池構造体を配置し、前記電池構造体の積層方向の外側にリチウムイオン供給体を配置する配置工程と、
リチウムイオンを前記正極電極と前記負極電極の少なくとも一方にドーピングするドーピング工程と、を備え、
前記積層工程では、他の電極の集電体よりも開孔率が大きな集電体を用いて作成した電極を、前記電池構造体の積層方向端部に配置することを特徴とするリチウムイオン二次電池の製造方法。 A method for producing a lithium ion secondary battery comprising a battery structure in which a plurality of positive and negative electrode pairs in which a positive electrode and a negative electrode are opposed via a separator are laminated,
An electrode forming step of forming the positive electrode and the negative electrode using a current collector formed with a hole penetrating in the thickness direction;
A lamination step of alternately laminating the positive electrode and the negative electrode to produce a battery structure;
An arrangement step of arranging the battery structure in a container and arranging a lithium ion supplier outside the stacking direction of the battery structure;
A doping step of doping at least one of the positive electrode and the negative electrode with lithium ions,
In the laminating step, an electrode formed using a current collector having a larger porosity than the current collectors of the other electrodes is disposed at the end of the battery structure in the stacking direction. A method for manufacturing a secondary battery. 前記ドーピング工程では、前記正極電極又は前記負極電極と、前記リチウムイオン供給体との間に電圧を印加することを特徴とする請求項４に記載の製造方法。   The manufacturing method according to claim 4, wherein a voltage is applied between the positive electrode or the negative electrode and the lithium ion supplier in the doping step.
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