JP2013020821A - Lithium ion secondary battery - Google Patents

Lithium ion secondary battery Download PDF

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JP2013020821A
JP2013020821A JP2011153424A JP2011153424A JP2013020821A JP 2013020821 A JP2013020821 A JP 2013020821A JP 2011153424 A JP2011153424 A JP 2011153424A JP 2011153424 A JP2011153424 A JP 2011153424A JP 2013020821 A JP2013020821 A JP 2013020821A
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negative electrode
positive electrode
current collector
secondary battery
ion secondary
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Inventor
Koji Kitada
耕嗣 北田
Koichi Taniyama
晃一 谷山
Takuya Miyashita
拓也 宮下
Kazunori Haraguchi
和典 原口
Yoshifumi Ojima
良文 尾嶋
Kaori Nagata
香織 永田
Hiroshi Tanada
浩 棚田
Hajime Tsunekawa
肇 恒川
Yoshio Tagawa
嘉夫 田川
Keigo Atobe
啓吾 跡部
Kana Tamaru
奏 田丸
Masahiko Hibino
真彦 日比野
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Mitsubishi Motors Corp
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Mitsubishi Motors 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
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

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  • Secondary Cells (AREA)
  • Battery Electrode And Active Subsutance (AREA)
  • Cell Electrode Carriers And Collectors (AREA)

Abstract

PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery capable of restraining an active material at the curving portions of an electrode body from being peeled off therefrom, and having an advantage of securing the battery performance.SOLUTION: A lithium ion secondary battery electrode body 12 is made of band shaped positive electrodes 20 and negative electrodes 22 whose length are longer than whose width, interposing band shaped separators 24 and 26 whose length is longer than whose width, making layers by being wound a plurality of times, with the cross section of the electrode body 12 showing a flat ellipse shape. The electrode body 12 has curved portions 36 at both longitudinal ends of its ellipse shape. At the portions of the positive electrodes 20, the negative electrodes 22, and the separator 24 configuring the curved portions 36, a corrugate structure 38 is formed over the whole length of the curved portions 36. At the corrugate structure 38, salient parts and recessed parts each extending in the width direction are alternately disposed repeatedly in a plurality of times in the longitudinal direction.

Description

本発明は、リチウムイオン二次電池に関する。   The present invention relates to a lithium ion secondary battery.

モータを駆動源とした電気自動車やハイブリッド自動車においてモータに電力を供給するバッテリとして、扁平な電極体が例えば矩形板状の角型容器に収容されたリチウムイオン二次電池が多く使用されている。
電極体は、帯状の正極と、帯状の負極とが、帯状のセパレータを介して重ね合わせて巻回され断面が扁平な長円形状を呈している。
正極は、正極集電箔とその両面に形成された正極活物質とを有しており、負極は、負極集電箔とその両面に形成された負極活物質とを有している。
このように構成されたリチウムイオン二次電池は、リチウムイオンが正極から負極に移動することで充電がなされ、リチウムイオンが負極から正極に移動することで放電がなされる。 2. Description of the Related Art As a battery for supplying electric power to an electric vehicle or a hybrid vehicle using a motor as a drive source, a lithium ion secondary battery in which a flat electrode body is accommodated in, for example, a rectangular plate-shaped rectangular container is often used.
The electrode body has an oval shape in which a belt-like positive electrode and a belt-like negative electrode are wound with being overlapped via a belt-like separator and the cross section is flat.
The positive electrode has a positive electrode current collector foil and a positive electrode active material formed on both surfaces thereof, and the negative electrode has a negative electrode current collector foil and a negative electrode active material formed on both surfaces thereof.
The lithium ion secondary battery configured as described above is charged by moving lithium ions from the positive electrode to the negative electrode, and discharged by moving lithium ions from the negative electrode to the positive electrode.

特開２００４−１５２５８１号公報JP 2004-152581 A

上記従来技術では、電極体は、長円形状の長手方向の両端が湾曲部となっている。
そのため、正極、負極、セパレータの巻回時、湾曲部において引っ張り方向の応力が作用しやすく、また、充電動作および放電動作による温度上昇による膨張収縮による応力も湾曲部に作用しやすい。
このような応力の作用が顕著になると、正極活物質および負極活物質が割れて正極集電箔および負極集電箔から部分的に剥がれることがある。この結果、充電あるいは放電に寄与する正極活物質および負極活物質が減少し導電性が低下するため、電池の性能が低下してしまう。
活物質の割れや剥がれを防止する対策として、集電箔の全域に複数の貫通孔を形成し活物質と集電箔との密着力を向上させることが考えられる。しかしながら、貫通孔を形成することで集電箔の断面積が減少して強度が低下することから、電極およびセパレータを巻回する際に破れやすくなることが懸念される。
本発明は、上記事情に鑑みなされたものであり、電極体の湾曲部における活物質の剥がれを抑制でき電池性能を確保する上で有利なリチウムイオン二次電池を提供することを目的とする。 In the above prior art, the electrode body has curved portions at both ends of the ellipse in the longitudinal direction.
Therefore, when the positive electrode, the negative electrode, and the separator are wound, stress in the pulling direction is likely to act on the curved portion, and stress due to expansion and contraction due to temperature increase due to the charging operation and discharging operation is also likely to act on the curved portion.
When the action of such stress becomes remarkable, the positive electrode active material and the negative electrode active material may be cracked and partially peeled off from the positive electrode current collector foil and the negative electrode current collector foil. As a result, the positive electrode active material and the negative electrode active material contributing to charging or discharging are reduced and the conductivity is lowered, so that the performance of the battery is lowered.
As a measure for preventing the active material from cracking or peeling off, it is conceivable to form a plurality of through holes in the entire area of the current collector foil to improve the adhesion between the active material and the current collector foil. However, since the cross-sectional area of the current collector foil is reduced and the strength is reduced by forming the through hole, there is a concern that the electrode and the separator are easily broken when wound.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a lithium ion secondary battery that can suppress peeling of an active material at a curved portion of an electrode body and is advantageous in securing battery performance.

上記目的を達成するために、本発明は、帯状の正極と帯状の負極とが、帯状のセパレータを介在させて重ね合わされ複数回巻回され断面に湾曲部が形成されている電極体を有するリチウムイオン二次電池であって、前記湾曲部を構成する正極の部分、負極の部分、セパレータのいずれかに、前記帯状の幅方向に延在する凸部と凹部とが前記長さ方向に交互に繰り返して複数設けられた波形構造が形成されていることを特徴とする。   In order to achieve the above object, the present invention provides a lithium electrode having an electrode body in which a belt-like positive electrode and a belt-like negative electrode are overlapped with a belt-like separator interposed therebetween and wound a plurality of times to form a curved portion in a cross section. In the ion secondary battery, a convex portion and a concave portion extending in the band-like width direction are alternately arranged in the length direction on any one of a positive electrode portion, a negative electrode portion, and a separator constituting the curved portion. A plurality of waveform structures are formed repeatedly.

請求項１記載の発明によれば、電極部の湾曲部に形成した波形構造により、湾曲部に作用する応力を緩和できるため、活物質が割れたり、活物質が集電箔から剥がれたりすることを抑制することができ、電池性能を確保する上で有利となる。
請求項２記載の発明によれば、凸部と凹部との位相が一致することで正極と負極との距離のばらつきを抑制できることから、リチウムイオンの往来を効率よく行うことができるため、電池の性能を確保する上でより有利となる。
請求項３記載の発明によれば、湾曲部の径方向の外側に至るほど湾曲部に作用する応力が大きくなることに対応して、応力の大きさに応じた長さの波形構造を形成することができ、応力を効果的に緩和する上で有利となる。
請求項４記載の発明によれば、正極および負極のそれぞれの表裏で貫通孔を通ってリチウムイオンの往来が可能となるため、リチウムイオンのアンバランスを解消し、また、過充電時における金属リチウムの析出を抑制することができ、電池の性能を確保する上で有利となる。また、貫通孔が形成されることにより、正極集電箔と正極活物質との結着力、負極集電箔と負極活物質との結着力を向上させることができ、活物質の集電箔からの剥がれを抑制する上でより有利となる。
請求項５記載の発明によれば、貫通孔の長手方向が帯状の正極、負極の幅方向と一致するように形成されているので、湾曲部に作用する引っ張り方向の応力に対して貫通孔の部分が変形しやすく、引張方向の応力の緩和を図る上でより有利となる。 According to invention of Claim 1, since the stress which acts on a curved part can be relieve | moderated by the waveform structure formed in the curved part of an electrode part, an active material is cracked or an active material peels from current collection foil. This is advantageous in ensuring battery performance.
According to the invention described in claim 2, since the variation in the distance between the positive electrode and the negative electrode can be suppressed by matching the phase of the convex portion and the concave portion, the lithium ion can be efficiently transported. This is more advantageous in securing performance.
According to the third aspect of the invention, the corrugated structure having a length corresponding to the magnitude of the stress is formed in response to the stress acting on the bending portion becoming larger toward the outside in the radial direction of the bending portion. This is advantageous in effectively relieving stress.
According to the fourth aspect of the present invention, since lithium ions can pass through the through holes on the front and back surfaces of the positive electrode and the negative electrode, the unbalance of lithium ions is eliminated, and the metal lithium during overcharging This is advantageous in ensuring the battery performance. Moreover, by forming the through-hole, the binding force between the positive electrode current collector foil and the positive electrode active material and the binding force between the negative electrode current collector foil and the negative electrode active material can be improved. This is more advantageous in suppressing the peeling of the film.
According to the invention described in claim 5, since the longitudinal direction of the through hole is formed so as to coincide with the width direction of the belt-like positive electrode and the negative electrode, the through hole is subjected to the tensile stress acting on the curved portion. The portion is easily deformed, which is more advantageous in reducing the stress in the tensile direction.

実施の形態におけるリチウムイオン二次電池１０の構成を示す斜視図である。It is a perspective view which shows the structure of the lithium ion secondary battery 10 in embodiment. 電極体１２の一部を展開した説明図である。FIG. 3 is an explanatory diagram in which a part of an electrode body 12 is developed. 図２のＡＡ線断面図である。FIG. 3 is a sectional view taken along line AA in FIG. 2. 図２のＢ矢視図である。FIG. 3 is a view taken in the direction of arrow B in FIG. 2. 図４のＣ部拡大図である。It is the C section enlarged view of FIG. 湾曲部３６の構成を示す説明図である。4 is an explanatory diagram showing a configuration of a bending portion 36. FIG. 湾曲部３６の一部を示す断面図である。4 is a cross-sectional view showing a part of a bending portion 36. FIG. 電極体１２から正極２０、負極２２、セパレータ２４，２６の一部を展開した状態を示す説明図である。It is explanatory drawing which shows the state which expand | deployed some positive electrodes 20, the negative electrode 22, and the separators 24 and 26 from the electrode body 12. FIG.

以下、本発明の実施の形態について図面を参照して説明する。
図１に示すように、本実施の形態に係るリチウムイオン二次電池１０は、電極体１２と、電極体１２を収容する矩形板状の容器１４と、容器１４に設けられた正負の電極１６，１８とを含んで構成されている。
図２に示すように、電極体１２は、正極２０と、負極２２と、２枚のセパレータ２４、２６とで構成されている。
正極２０は、幅よりも大きな長さを有する帯状を呈している。
正極２０は、図３に示すように、３層構造であり、厚さ方向の中央に位置する正極集電箔２８と、その両面に形成された正極活物質３０とで構成されている。正極集電箔２８は不図示の接続部材を介して容器１４の正側の電極１６に接続されている。
正極集電箔２８としてはアルミニウム箔が用いられ、正極活物質３０としてはコバルト酸リチウムなどが用いられる。 Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, a lithium ion secondary battery 10 according to the present embodiment includes an electrode body 12, a rectangular plate-like container 14 that houses the electrode body 12, and positive and negative electrodes 16 provided on the container 14. , 18.
As shown in FIG. 2, the electrode body 12 includes a positive electrode 20, a negative electrode 22, and two separators 24 and 26.
The positive electrode 20 has a strip shape having a length larger than the width.
As shown in FIG. 3, the positive electrode 20 has a three-layer structure, and is composed of a positive electrode current collector foil 28 located at the center in the thickness direction and a positive electrode active material 30 formed on both surfaces thereof. The positive electrode current collector foil 28 is connected to the positive electrode 16 of the container 14 through a connection member (not shown).
An aluminum foil is used as the positive electrode current collector foil 28, and lithium cobalt oxide or the like is used as the positive electrode active material 30.

負極２２は、幅よりも大きな長さを有する帯状を呈している。
負極２２は、図３に示すように、３層構造であり、厚さ方向の中央に位置する負極集電箔３２と、その両面に形成された負極活物質３４とで構成されている。負極集電箔３２は不図示の接続部材を介して容器１４の負側の電極１８に接続されている。
負極集電箔３２としては銅箔が用いられ、負極活物質３４としては炭素材料などが用いられる。 The negative electrode 22 has a strip shape having a length larger than the width.
As shown in FIG. 3, the negative electrode 22 has a three-layer structure, and includes a negative electrode current collector foil 32 positioned in the center in the thickness direction, and negative electrode active materials 34 formed on both surfaces thereof. The negative electrode current collector foil 32 is connected to the negative electrode 18 of the container 14 through a connection member (not shown).
A copper foil is used as the negative electrode current collector foil 32, and a carbon material or the like is used as the negative electrode active material 34.

セパレータ２４、２６は、幅よりも大きな長さを有する帯状を呈し、リチウムイオンが移動できる多孔質の絶縁フィルムで構成されている。
電極体１２は、正極２０と、負極２２とが、セパレータ２４、２６を介在させて重ね合わされ複数回巻回され、断面が扁平な長円形状を呈している。
具体的には、セパレータ２４と、正極２０と、セパレータ２６と、負極２２とがこの順番で重ね合わされ、セパレータ２４を外側にし、負極２２を内側にして複数回巻回されている。
図４に示すように、電極体１２は、長円形状の長手方向の両端が湾曲部３６となっている。
図５に示すように、正極２０、負極２２、セパレータ２４、２６が巻回される際、湾曲部３６において円周距離の差により引っ張り方向の応力が集中して作用しやすく、また、充電動作および放電動作による膨張収縮による応力も湾曲部３６に作用しやすい。 The separators 24 and 26 have a strip shape having a length larger than the width, and are made of a porous insulating film capable of moving lithium ions.
The electrode body 12 has an oval shape in which a positive electrode 20 and a negative electrode 22 are overlapped and wound a plurality of times with separators 24 and 26 interposed therebetween, and the cross section is flat.
Specifically, the separator 24, the positive electrode 20, the separator 26, and the negative electrode 22 are overlapped in this order, and are wound a plurality of times with the separator 24 on the outer side and the negative electrode 22 on the inner side.
As shown in FIG. 4, the electrode body 12 has curved portions 36 at both ends of the ellipse in the longitudinal direction.
As shown in FIG. 5, when the positive electrode 20, the negative electrode 22, and the separators 24, 26 are wound, the stress in the tensile direction tends to concentrate on the curved portion 36 due to the difference in the circumferential distance, and the charging operation Also, stress due to expansion and contraction due to the discharge operation is likely to act on the bending portion 36.

そこで、本実施の形態では、図６，図７に示すように、湾曲部３６を構成する正極２０の部分、負極２２の部分、セパレータ２４の部分に、それぞれ幅方向に延在する凸部と凹部とが前記長さ方向に交互に繰り返して複数設けられた波形構造３８が湾曲部３６の全長にわたって形成されている。
このような波形構造３８によって湾曲部３６に作用する応力が緩和されるため、正極活物質３０，負極活物質３４が割れたり、正極活物質３０，負極活物質３４が正極集電箔２８，負極集電箔３２から剥がれたりすることを抑制する上で有利となる。 Therefore, in the present embodiment, as shown in FIGS. 6 and 7, the positive electrode 20 portion, the negative electrode 22 portion, and the separator 24 portion constituting the curved portion 36 are respectively provided with convex portions extending in the width direction. A corrugated structure 38 in which a plurality of concave portions are alternately provided in the length direction is provided over the entire length of the curved portion 36.
Since the stress acting on the curved portion 36 is relieved by such a corrugated structure 38, the positive electrode active material 30 and the negative electrode active material 34 are broken, or the positive electrode active material 30 and the negative electrode active material 34 are the positive electrode current collector foil 28 and the negative electrode. This is advantageous for suppressing the peeling from the current collector foil 32.

また、湾曲部３６において正極２０に形成された凸部と、負極２２に形成された凸部と、セパレータ２４、２６に形成された凸部とは、湾曲部３６の径方向において位相が一致している。
また、湾曲部３６において正極２０に形成された凹部と、負極２２に形成された凹部と、セパレータ２４、２６に形成された凹部とは、湾曲部３６の径方向において位相が一致している。
このように凸部と凹部との位相を一致させると、正極２０と負極２２との距離のばらつきを抑制できることから、リチウムイオンの往来を効率よく行うことができるため、電池の性能を確保する上で有利となる。 In addition, the convex portions formed on the positive electrode 20, the convex portions formed on the negative electrode 22, and the convex portions formed on the separators 24 and 26 in the curved portion 36 have the same phase in the radial direction of the curved portion 36. ing.
Further, the concave portion formed in the positive electrode 20 in the curved portion 36, the concave portion formed in the negative electrode 22, and the concave portions formed in the separators 24 and 26 are in phase with each other in the radial direction of the curved portion 36.
Thus, when the phase of the convex part and the concave part is matched, the variation in the distance between the positive electrode 20 and the negative electrode 22 can be suppressed, so that lithium ions can be efficiently transported, so that the performance of the battery can be ensured. Is advantageous.

また、本実施の形態では、図６，図８に示すように、帯状の正極２０、負極２２、セパレータ２４、２６の長さ方向における波形構造３８の長さは、湾曲部３６の内側から外側に至るに従って次第に長くなるように形成されている。
このようにすると、湾曲部３６の径方向の外側に至るほど湾曲部３６に作用する応力が大きくなることに対応して、応力の大きさに応じた長さの波形構造３８を形成することができ、応力を効果的に緩和する上で有利となる。 In the present embodiment, as shown in FIGS. 6 and 8, the length of the corrugated structure 38 in the longitudinal direction of the strip-like positive electrode 20, negative electrode 22, separators 24, 26 is from the inside to the outside of the curved portion 36. It is formed so as to gradually become longer as it reaches.
In this way, the corrugated structure 38 having a length corresponding to the magnitude of the stress can be formed in response to the stress acting on the bending portion 36 becoming larger toward the outside in the radial direction of the bending portion 36. This is advantageous in effectively relieving stress.

また、湾曲部３６に対応する正極集電箔２８の部分に、該正極集電箔２８の部分の両面に形成された正極活物質３０の間でリチウムイオンが移動可能な正極活物質３０で埋められた複数の貫通孔４０が形成されている。
また、湾曲部３６に対応する負極集電箔３２の部分に、該負極集電箔３２の部分の両面に形成された負極活物質３４の間でリチウムイオンが移動可能な負極活物質３４で埋められた複数の貫通孔４２が形成されている。
このような貫通孔４０，４２を形成すると、以下の効果が奏される。
図７に示すように、部品の加工精度のばらつきによって前記の凸部と凹部との位相は多少ずれる場合がある。
このような位相のずれが生じると、正極２０と負極２２との距離のばらつきが生じるため、リチウムイオンの往来に悪影響を与え、リチウムイオンの量にアンバランスが発生することが考えられる。
しかしながら、貫通孔４０，４２を形成したため、正極２０および負極２２のそれぞれの表裏でリチウムイオンの往来が可能となるため、リチウムイオンのアンバランスを解消することができる。そのため、リチウムイオンの往来を効率よく行うことができるため、電池の性能を確保する上で有利となる。 Further, the portion of the positive electrode current collector foil 28 corresponding to the curved portion 36 is filled with the positive electrode active material 30 in which lithium ions can move between the positive electrode active materials 30 formed on both surfaces of the positive electrode current collector foil 28 portion. A plurality of through holes 40 are formed.
Further, the portion of the negative electrode current collector foil 32 corresponding to the curved portion 36 is filled with a negative electrode active material 34 in which lithium ions can move between the negative electrode active materials 34 formed on both surfaces of the negative electrode current collector foil 32 portion. A plurality of through holes 42 are formed.
When such through holes 40 and 42 are formed, the following effects are produced.
As shown in FIG. 7, the phase of the said convex part and a recessed part may shift | deviate a little depending on the dispersion | variation in the processing precision of components.
When such a phase shift occurs, a variation in the distance between the positive electrode 20 and the negative electrode 22 occurs, which adversely affects the movement of lithium ions, and may cause an imbalance in the amount of lithium ions.
However, since the through holes 40 and 42 are formed, lithium ions can be transferred between the front and back surfaces of the positive electrode 20 and the negative electrode 22, so that the lithium ion imbalance can be eliminated. Therefore, it is possible to efficiently transport lithium ions, which is advantageous in securing the battery performance.

また、過充電の状態となると、正極活物質３０の構造崩壊、負極２２における金属リチウム析出の不具合が発生することが知られている。
このような不具合を防止するため、従来では、負極２２側に取り込まれるリチウムイオン量が正極２０側に取り込まれるリチウムイオン量よりも多くなるように、正極活物質３０に対する負極活物質３４の割合が多くなるように構成されている。
しかしながら、湾曲部３６においては、湾曲部３６の径方向の外側に位置する正極２０の部分の面積に対して湾曲部３６の径方向の内側に位置する負極２２の部分の面積が小さくなるため、このような位置関係にある正極活物質３０に対する負極活物質３４の割合が相対的に少なくなり、上記不具合の発生が懸念される。
本実施の形態では、貫通孔４０，４２により正極２０および負極２２のそれぞれの表裏でリチウムイオンの往来が可能となる。したがって、負極２２の部分の面積が正極２０の部分の面積よりも小さくても、負極２２の裏表の広い範囲でリチウムイオンを十分に取り込むことができるため、過充電時における金属リチウムの析出を抑制する上で有利となる。 In addition, it is known that when the battery is overcharged, the structure of the positive electrode active material 30 collapses, and the problem of metal lithium deposition on the negative electrode 22 occurs.
In order to prevent such problems, conventionally, the ratio of the negative electrode active material 34 to the positive electrode active material 30 is such that the amount of lithium ions taken into the negative electrode 22 side is larger than the amount of lithium ions taken into the positive electrode 20 side. It is configured to increase.
However, in the bending portion 36, the area of the portion of the negative electrode 22 located on the inner side in the radial direction of the bending portion 36 is smaller than the area of the portion of the positive electrode 20 located on the outer side in the radial direction of the bending portion 36. The ratio of the negative electrode active material 34 to the positive electrode active material 30 in such a positional relationship is relatively small, and there is a concern about the occurrence of the above-described problems.
In the present embodiment, through of the through holes 40 and 42, lithium ions can be transferred between the front and back surfaces of the positive electrode 20 and the negative electrode 22, respectively. Accordingly, even if the area of the negative electrode 22 is smaller than the area of the positive electrode 20, lithium ions can be sufficiently taken in a wide range on the back and front of the negative electrode 22, thereby suppressing the deposition of metallic lithium during overcharge. This is advantageous.

また、貫通孔４０，４２が形成されることにより、正極集電箔２８と正極活物質３０との結着力、負極集電箔３２と負極活物質３４との結着力を向上させることができ、活物質の集電箔からの剥がれを抑制する上で有利となる。
また、貫通孔４０，４２は、正極集電箔２８、負極集電箔３２のうち、湾曲部３６に対応する部分にのみ限定されて設けられることから、集電箔の強度低下を最小限にでき、正極２０，負極２２、セパレータ２４、２６を巻回する際の破損を抑制する上で有利となる。
また、本実施の形態では、各貫通孔４０，４２は長円状を呈し、貫通孔４０，４２はその長手方向が帯状の正極２０、負極２２の幅方向と一致するように形成されている。
このようにすると、正極２０，負極２２、セパレータ２４、２６を巻回する際に湾曲部３６に作用する引っ張り方向の応力に対して貫通孔４０，４２の部分が変形しやすく、応力の緩和を図る上で有利となる。 Moreover, by forming the through holes 40 and 42, the binding force between the positive electrode current collector foil 28 and the positive electrode active material 30, and the binding force between the negative electrode current collector foil 32 and the negative electrode active material 34 can be improved. This is advantageous in suppressing peeling of the active material from the current collector foil.
Moreover, since the through holes 40 and 42 are provided only in the portion corresponding to the curved portion 36 of the positive electrode current collector foil 28 and the negative electrode current collector foil 32, the strength reduction of the current collector foil is minimized. This is advantageous in suppressing breakage when winding the positive electrode 20, the negative electrode 22, and the separators 24 and 26.
Further, in the present embodiment, the through holes 40 and 42 have an oval shape, and the through holes 40 and 42 are formed so that the longitudinal direction thereof coincides with the width direction of the belt-like positive electrode 20 and negative electrode 22. .
In this way, when the positive electrode 20, the negative electrode 22, and the separators 24, 26 are wound, the through holes 40, 42 are easily deformed with respect to the tensile stress acting on the curved portion 36, and the stress is relieved. It is advantageous in planning.

以上説明したように本実施の形態によれば、電極体１２の湾曲部３６を構成する正極２０の部分、負極２２の部分、セパレータ２４の部分に、それぞれ幅方向に延在する凸部と凹部とが長さ方向に交互に繰り返して複数設けられた波形構造３８を形成した。したがって、波形構造３８により湾曲部３６に作用する応力を緩和することができ、活物質が割れたり、活物質が集電箔から剥がれたりすることを抑制することができ、電池性能を確保する上で有利となる。   As described above, according to the present embodiment, the positive electrode 20 portion, the negative electrode 22 portion, and the separator 24 portion constituting the curved portion 36 of the electrode body 12 are respectively provided with a convex portion and a concave portion extending in the width direction. And a plurality of waveform structures 38 are formed by alternately repeating in the length direction. Therefore, the stress acting on the curved portion 36 can be relieved by the corrugated structure 38, the active material can be prevented from cracking, and the active material can be prevented from peeling from the current collector foil, and battery performance can be ensured. Is advantageous.

なお、本実施の形態では、電極体１２の断面が扁平な長円形状を呈している場合について説明したが、電極体１２の断面形状はこれに限定されるものではなく、従来公知の様々な断面形状が採用可能である。
また、波形構造が湾曲部３６を構成する正極２０の部分、負極２２の部分、セパレータ２４の部分のそれぞれに形成されている場合について説明したが、波形構造は、湾曲部３６を構成する正極２０の部分、負極２２の部分、セパレータ２４の部分のいずれかに形成されていてもよい。このような構成であっても、実施の形態と同様に、波形構造により、湾曲部３６に作用する応力を緩和でき実施の形態と同様の効果が奏される。ただし、本実施の形態のようにすると、波形構造が湾曲部３６を構成する正極２０の部分、負極２２の部分、セパレータ２４の部分のそれぞれに形成されているので、湾曲部３６に作用する応力を緩和する上でより一層有利となる。 In the present embodiment, the case where the cross section of the electrode body 12 has a flat oval shape has been described. However, the cross section of the electrode body 12 is not limited to this, and various conventionally known various shapes can be used. A cross-sectional shape can be adopted.
In addition, the case where the corrugated structure is formed in each of the positive electrode 20 portion, the negative electrode 22 portion, and the separator 24 portion that constitute the curved portion 36 has been described. However, the corrugated structure has the positive electrode 20 that constitutes the curved portion 36. May be formed in any of the part of the negative electrode 22, the part of the negative electrode 22, and the part of the separator 24. Even in such a configuration, the stress acting on the bending portion 36 can be relieved by the corrugated structure as in the embodiment, and the same effect as in the embodiment can be obtained. However, according to the present embodiment, the corrugated structure is formed on each of the positive electrode 20 portion, the negative electrode 22 portion, and the separator 24 portion constituting the bending portion 36, so that stress acting on the bending portion 36 is obtained. It is even more advantageous in mitigating

１０……リチウムイオン二次電池、１２……電極体、１４……容器、１６，１８……電極、２０……正極、２２……負極、２４，２６……セパレータ、２８……正極集電箔、３０……正極活物質、３２……負極集電箔、３４……負極活物質、３６……湾曲部、３８……波形構造、４０，４２……貫通孔。   DESCRIPTION OF SYMBOLS 10 ... Lithium ion secondary battery, 12 ... Electrode body, 14 ... Container, 16, 18 ... Electrode, 20 ... Positive electrode, 22 ... Negative electrode, 24, 26 ... Separator, 28 ... Positive electrode current collector Foil, 30... Positive electrode active material, 32... Negative electrode current collector foil, 34... Negative electrode active material, 36.

Claims (5)

帯状の正極と帯状の負極とが、帯状のセパレータを介在させて重ね合わされ複数回巻回され断面に湾曲部が形成される電極体を有するリチウムイオン二次電池であって、
前記湾曲部を構成する正極の部分、負極の部分、セパレータのいずれかに、前記帯状の幅方向に延在する凸部と凹部とが前記長さ方向に交互に繰り返して複数設けられた波形構造が形成されている、
ことを特徴とするリチウムイオン二次電池。 A lithium ion secondary battery having an electrode body in which a belt-like positive electrode and a belt-like negative electrode are overlapped with a belt-like separator interposed and wound a plurality of times to form a curved portion in a cross section,
A corrugated structure in which a plurality of convex portions and concave portions extending in the band-like width direction are alternately and repeatedly provided in the length direction in any one of the positive electrode portion, the negative electrode portion, and the separator constituting the curved portion. Is formed,
The lithium ion secondary battery characterized by the above-mentioned. 前記湾曲部において前記凸部及び凹部が正極の部分、負極の部分、セパレータのそれぞれに設けられ、
前記正極に形成された凸部と、前記負極に形成された凸部と、前記セパレータに形成された凸部とは、前記湾曲部の径方向において位相が一致しており、かつ、前記湾曲部において前記正極に形成された凹部と、前記負極に形成された凹部と、前記セパレータに形成された凹部とは、前記湾曲部の径方向において位相が一致している、
ことを特徴とする請求項１記載のリチウムイオン二次電池。 In the curved portion, the convex portion and the concave portion are provided in each of the positive electrode portion, the negative electrode portion, and the separator,
The convex part formed on the positive electrode, the convex part formed on the negative electrode, and the convex part formed on the separator have the same phase in the radial direction of the curved part, and the curved part In, the concave portion formed in the positive electrode, the concave portion formed in the negative electrode, and the concave portion formed in the separator are in phase with each other in the radial direction of the curved portion,
The lithium ion secondary battery according to claim 1. 前記長さ方向における前記波形構造の長さは、前記湾曲部の内側から外側に至るに従って次第に長くなるように形成されている、
ことを特徴とする請求項１または２記載のリチウムイオン二次電池。 The length of the corrugated structure in the length direction is formed so as to gradually increase from the inside to the outside of the curved portion,
The lithium ion secondary battery according to claim 1 or 2, wherein 前記正極は、正極集電箔とその両面に形成された正極活物質とを有し、
前記負極は、負極集電箔とその両面に形成された負極活物質とを有し、
前記湾曲部に対応する前記正極集電箔の部分に、該正極集電箔の部分の両面に形成された正極活物質の間でリチウムイオンが移動可能な複数の貫通孔が形成され、
前記湾曲部に対応する前記負極集電箔の部分に、該負極集電箔の部分の両面に形成された負極活物質の間でリチウムイオンが移動可能な複数の貫通孔が形成されている、
ことを特徴とする請求項１乃至３に何れか１項記載のリチウムイオン二次電池。 The positive electrode has a positive electrode current collector foil and a positive electrode active material formed on both sides thereof,
The negative electrode has a negative electrode current collector foil and negative electrode active materials formed on both sides thereof.
A plurality of through holes through which lithium ions can move between the positive electrode active materials formed on both surfaces of the positive electrode current collector foil portion are formed in the positive electrode current collector foil portion corresponding to the curved portion,
A plurality of through holes in which lithium ions can move between negative electrode active materials formed on both surfaces of the negative electrode current collector foil portion are formed in the negative electrode current collector foil portion corresponding to the curved portion,
The lithium ion secondary battery according to any one of claims 1 to 3, wherein: 前記貫通孔は長円状を呈し、前記貫通孔はその長手方向が前記帯状の正極、負極の幅方向と一致するように形成されている、
ことを特徴とする請求項４記載のリチウムイオン二次電池。 The through-hole has an oval shape, and the through-hole is formed such that its longitudinal direction coincides with the width direction of the strip-shaped positive electrode and negative electrode,
The lithium ion secondary battery according to claim 4.
JP2011153424A 2011-07-12 2011-07-12 Lithium ion secondary battery Withdrawn JP2013020821A (en)

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