JP2012169071A - Lithium ion secondary battery - Google Patents

Lithium ion secondary battery Download PDF

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JP2012169071A
JP2012169071A JP2011027419A JP2011027419A JP2012169071A JP 2012169071 A JP2012169071 A JP 2012169071A JP 2011027419 A JP2011027419 A JP 2011027419A JP 2011027419 A JP2011027419 A JP 2011027419A JP 2012169071 A JP2012169071 A JP 2012169071A
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negative electrode
active material
material layer
lithium ion
electrode active
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Katsumi Kashiwagi
克巨 柏木
Taisuke Yamamoto
泰右 山本
Shige Hiraoka
樹 平岡
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Panasonic 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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    • 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
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    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
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Abstract

PROBLEM TO BE SOLVED: To enhance charging and discharging cycle characteristics of a lithium ion secondary battery having a wound electrode group, in which the negative electrode active material comprising a plurality of columnar bodies of an alloy-based active material.SOLUTION: A lithium ion secondary battery comprises: an electrode group formed by winding strip-shaped negative electrode and strip-shaped positive electrode in the long side direction of both electrodes while interposing a strip-shaped separator therebetween; and a nonaqueous electrolyte. The negative electrode includes: a strip-shaped negative electrode collector; a strip-shaped negative electrode active material layer comprising a plurality of columnar bodies of an alloy-based active material supported on the surface of the negative electrode collector; and a strip-shaped lithium ion conductive resin film formed on the surface of negative electrode active material layer by deposition. The lithium ion conductive resin film is formed in the long side direction of the negative electrode active material layer only in the central part thereof in the short side direction, and the width of the central part in the short side direction is 20-50% of the overall short side width of the negative electrode active material layer.

Description

本発明は、合金系活物質を負極活物質として含む捲回型電極群を備えたリチウムイオン二次電池に関し、詳しくは、リチウムイオン二次電池の負極活物質層の改良に関する。   The present invention relates to a lithium ion secondary battery including a wound electrode group including an alloy-based active material as a negative electrode active material, and more particularly to improvement of a negative electrode active material layer of a lithium ion secondary battery.

リチウムイオン二次電池は、高容量で、エネルギー密度が高いことから、携帯電話、携帯情報端末（ＰＤＡ）、ノート型パーソナルコンピュータ、デジタルカメラ、携帯ゲーム機などの携帯型電子機器の電源として用いられている。また、ハイブリッド自動車、電気自動車などの車載用電源、無停電電源などへの開発も進められている。   Lithium ion secondary batteries have high capacity and high energy density, so they are used as power sources for portable electronic devices such as mobile phones, personal digital assistants (PDAs), notebook personal computers, digital cameras, and portable game machines. ing. In addition, development of in-vehicle power sources such as hybrid vehicles and electric vehicles, uninterruptible power sources, etc. is also underway.

近年、リチウムイオン二次電池のさらなる高容量化を図るために、黒鉛に代わる負極活物質として、合金化および脱合金化によってリチウムを吸蔵および放出可能な合金系活物質が用いられている。合金系活物質としては、ケイ素やスズの単体、ケイ素やスズを含む酸化物および合金などが知られている。   In recent years, in order to further increase the capacity of a lithium ion secondary battery, an alloy-based active material capable of inserting and extracting lithium by alloying and dealloying has been used as a negative electrode active material replacing graphite. Known alloy-based active materials include silicon and tin alone, oxides and alloys containing silicon and tin, and the like.

合金系活物質はリチウムを吸蔵した時に顕著に膨張することから、膨張時の応力によって負極活物質層にクラックを生じさせたり、負極活物質層を負極集電体から剥離したり、負極集電体を変形させたりする傾向がある。そこで、特許文献１は、合金系活物質を負極集電体の表面から突出した柱状体として形成し、複数の柱状体を負極集電体の表面で互いに間隔をあけて配置した負極活物質層を備えたリチウムイオン二次電池を提案している。上記負極活物質層は、隣接する柱状体間に間隙を有しており、この間隙によって合金系活物質の膨張時の応力を緩和させることができる。また、特許文献１は、上述の負極活物質層の表面に、さらにイオン伝導性樹脂層を設けた構成を開示している。イオン伝導性樹脂層は、合金系活物質の膨張により負極活物質層の表面および内部にクラックが生じた場合に、それまで非水電解液と接していなかった負極活物質層の新生面と、非水電解液との接触により、充放電反応以外の副反応が生じて副生成物が析出するのを抑制する。   Since the alloy-based active material expands significantly when lithium is occluded, the negative electrode active material layer is cracked by the stress during expansion, the negative electrode active material layer is peeled off from the negative electrode current collector, the negative electrode current collector There is a tendency to deform the body. Thus, Patent Document 1 discloses a negative electrode active material layer in which an alloy-based active material is formed as a columnar body protruding from the surface of a negative electrode current collector, and a plurality of columnar bodies are arranged at intervals on the surface of the negative electrode current collector. A lithium ion secondary battery equipped with The negative electrode active material layer has a gap between adjacent columnar bodies, and this gap can relieve stress during expansion of the alloy-based active material. Patent Document 1 discloses a configuration in which an ion conductive resin layer is further provided on the surface of the negative electrode active material layer. When the surface of the negative electrode active material layer and the inside of the negative electrode active material layer are cracked due to the expansion of the alloy-based active material, the ion conductive resin layer has a newly formed surface of the negative electrode active material layer that has not been in contact with the nonaqueous electrolyte until then. By contact with the water electrolyte, side reactions other than the charge / discharge reaction are prevented, and precipitation of byproducts is suppressed.

特許文献２は、負極集電体と、負極集電体上に形成された合金系活物質からなる負極活物質層と、負極活物質層の表面に形成された樹脂層とを備えたリチウムイオン二次電池用負極を開示している。この樹脂層は、負極活物質層の表面全面を覆うのではなく、ストライプ状などのパターンからなる開口部を備えており、開口部から負極活物質層の一部が負極表面に露出している。上述の負極によれば、リチウム吸蔵時の負極活物質層の膨張を抑制して、膨張時の応力が負極活物質層に局所的に集中するのを緩和することができる。これにより、負極活物質層にクラックが生じた場合に、合金系活物質が脱落したり、負極集電体から剥離したりするのを防止できる。   Patent Document 2 discloses a lithium ion including a negative electrode current collector, a negative electrode active material layer made of an alloy-based active material formed on the negative electrode current collector, and a resin layer formed on the surface of the negative electrode active material layer. A negative electrode for a secondary battery is disclosed. This resin layer does not cover the entire surface of the negative electrode active material layer, but has an opening made of a pattern such as a stripe shape, and a part of the negative electrode active material layer is exposed to the negative electrode surface from the opening. . According to the above-described negative electrode, expansion of the negative electrode active material layer at the time of occlusion of lithium can be suppressed, and stress during expansion can be relieved from locally concentrating on the negative electrode active material layer. Thereby, when a crack arises in a negative electrode active material layer, it can prevent that an alloy type active material falls or peels from a negative electrode collector.

負極活物質として合金系活物質を用いたリチウムイオン二次電池においては、さらに、帯状の負極および正極を、両電極間にセパレータを介在させて負極および正極の各長辺方向に捲回した捲回型電極群とすることが試みられている。この場合、電極構造を省スペース化して、さらなる高容量化を実現できる。特許文献３に開示の非水電解質二次電池は、上述の捲回型電極群を備えており、負極および正極はいずれも、集電体と、活物質および結着剤ポリマーを含む活物質層とを含み、負極および正極の少なくとも一方はさらに、セパレータとの間に、フッ化ビニリデン−ヘキサフルオロプロピレン共重合体などのマトリックスポリマーからなる高分子支持体を備えている。この非水電解質二次電池において、高分子支持体を形成するマトリックスポリマーは、非水電解液に対する膨潤性が正極および負極の各活物質層における結着剤ポリマーより高く設定されている。このため、高分子支持体を設けることで、捲回型電極群からの非水電解液の漏洩を解消することができる。   In a lithium ion secondary battery using an alloy-based active material as a negative electrode active material, a belt-shaped negative electrode and a positive electrode are further wound in the long side direction of the negative electrode and the positive electrode with a separator interposed between the two electrodes. Attempts have been made to form a rotary electrode group. In this case, the electrode structure can be saved in space, and further increase in capacity can be realized. The nonaqueous electrolyte secondary battery disclosed in Patent Document 3 includes the above-described wound electrode group, and the negative electrode and the positive electrode both include a current collector, an active material, and a binder polymer. And at least one of the negative electrode and the positive electrode further includes a polymer support made of a matrix polymer such as a vinylidene fluoride-hexafluoropropylene copolymer, between the separator and the separator. In this non-aqueous electrolyte secondary battery, the matrix polymer forming the polymer support is set to have higher swellability with respect to the non-aqueous electrolyte than the binder polymer in each of the active material layers of the positive electrode and the negative electrode. For this reason, by providing the polymer support, leakage of the non-aqueous electrolyte from the wound electrode group can be eliminated.

特開２０１０−９７８４３号公報JP 2010-97843 A 特開２００９−２５２５４７号公報JP 2009-252547 A 特開２００８−４７４０２号公報JP 2008-47402 A

本発明者らは、帯状の負極と帯状の正極とが両電極間にセパレータが介在するように負極および正極の各長辺方向に沿って捲回された捲回型電極群を備え、かつ、負極表面に負極の長辺方向に沿って形成された帯状の負極活物質層を備え、負極活物質層が複数の合金系活物質の柱状体からなるリチウムイオン二次電池に対して、充放電サイクルを繰り返したときには、負極活物質層の短辺方向における中央の領域において負極活物質層の厚みが顕著に増大することに気付いた。   The present inventors have a wound electrode group wound along each long side direction of the negative electrode and the positive electrode so that a strip-shaped negative electrode and a strip-shaped positive electrode are interposed between both electrodes, and Charge and discharge with respect to a lithium ion secondary battery comprising a strip-like negative electrode active material layer formed along the long side direction of the negative electrode on the negative electrode surface, and the negative electrode active material layer comprising a plurality of columnar bodies of alloy-based active materials When the cycle was repeated, it was noticed that the thickness of the negative electrode active material layer significantly increased in the central region in the short side direction of the negative electrode active material layer.

負極活物質層の短辺方向両端部、すなわち捲回型電極群の捲回軸方向両端部は、合金系活物質が膨張して捲回型電極群が締め付けられると、負極および正極間に存在する非水電解液が捲回型電極群の外部へと押し出される傾向がある。このため、負極活物質層の短辺方向両端部は、充放電サイクルを繰り返すと非水電解液の存在量が減少して、電極反応が円滑に進まなくなる。これに対し、負極活物質層の短辺方向中央部、すなわち捲回型電極群の捲回軸方向中央部は、合金系活物質が膨張しても捲回型電極群の内部に非水電解液が残留し、その存在量が維持される。このため、充放電時において、負極活物質層の短辺方向中央部は、両端部よりも優先的に反応して、両端部に比べて充放電容量が大きくなる。さらに、充放電サイクルを繰り返した時に、負極活物質層の短辺方向中央部は、両端部に比べて非水電解液との副反応の程度が多くなるため、活物質の体積膨張が局所的に大きくなる。こうして、負極活物質層の短辺中央部で厚みが顕著に増大するという上述の現象が起こる。   Both ends in the short side direction of the negative electrode active material layer, that is, both ends in the winding axis direction of the wound electrode group are present between the negative electrode and the positive electrode when the alloy-based active material expands and the wound electrode group is tightened. There is a tendency for the non-aqueous electrolyte to be pushed out of the wound electrode group. For this reason, if the charge / discharge cycle is repeated at both ends in the short side direction of the negative electrode active material layer, the abundance of the non-aqueous electrolyte decreases, and the electrode reaction does not proceed smoothly. On the other hand, the central portion in the short side direction of the negative electrode active material layer, that is, the central portion in the winding axis direction of the wound electrode group is non-aqueous electrolysis inside the wound electrode group even when the alloy-based active material expands. The liquid remains and its abundance is maintained. For this reason, at the time of charging / discharging, the short side direction center part of a negative electrode active material layer reacts preferentially rather than both ends, and charging / discharging capacity becomes large compared with both ends. Furthermore, when the charge / discharge cycle is repeated, the central portion of the negative electrode active material layer in the short-side direction has a greater degree of side reaction with the non-aqueous electrolyte than both ends, and therefore the volume expansion of the active material is localized. Become bigger. In this way, the above-described phenomenon that the thickness is remarkably increased at the central portion of the short side of the negative electrode active material layer occurs.

また、負極活物質層の局所的な***が顕著に成長すると、負極活物質層が負極集電体から剥離して、負極集電体と合金系活物質との電気的な接続が断たれるおそれがある。このような場合には、リチウムイオン二次電池の電池容量や充放電サイクル特性が著しく低下する。   In addition, when the local bumps of the negative electrode active material layer grow significantly, the negative electrode active material layer peels off from the negative electrode current collector, and the electrical connection between the negative electrode current collector and the alloy-based active material is broken. There is a fear. In such a case, the battery capacity and charge / discharge cycle characteristics of the lithium ion secondary battery are significantly reduced.

そこで本発明は、上記課題を解決して、捲回型電極群を備え、負極活物質層が複数の合金系活物質の柱状体からなるリチウムイオン二次電池について、充放電サイクル特性を向上させることを目的とする。   Therefore, the present invention solves the above-described problems and improves charge / discharge cycle characteristics of a lithium ion secondary battery that includes a wound electrode group and the negative electrode active material layer is formed of a columnar body of a plurality of alloy-based active materials. For the purpose.

本発明の一局面は、帯状の負極、帯状の正極、および帯状のセパレータを含み、負極および正極の間にセパレータが介在するように負極および正極の各長辺方向に沿って捲回された電極群と、非水電解液と、を備え、負極は、帯状の負極集電体と、負極集電体の表面に支持された合金系活物質からなる負極活物質層と、負極活物質層の表面に被着形成されたリチウムイオン伝導性樹脂膜と、を備え、リチウムイオン伝導性樹脂膜は、負極活物質層の長辺方向に沿って帯状に形成され、かつ、負極活物質層の短辺方向中央部にのみ形成されており、短辺方向中央部の幅は、負極活物質層の短辺の全幅に対して２０〜５０％であることを特徴とするリチウムイオン二次電池である。   One aspect of the present invention includes a strip-shaped negative electrode, a strip-shaped positive electrode, and a strip-shaped separator, and an electrode wound along the long side direction of the negative electrode and the positive electrode so that the separator is interposed between the negative electrode and the positive electrode A negative electrode, a negative electrode active material layer made of an alloy active material supported on the surface of the negative electrode current collector, and a negative electrode active material layer. A lithium ion conductive resin film deposited on the surface, wherein the lithium ion conductive resin film is formed in a strip shape along the long side direction of the negative electrode active material layer and is short of the negative electrode active material layer The lithium ion secondary battery is formed only in the central portion in the side direction, and the width of the central portion in the short side direction is 20 to 50% with respect to the entire width of the short side of the negative electrode active material layer. .

上述のリチウムイオン二次電池において、リチウムイオン伝導性樹脂膜は、ヘキサフルオロプロピレン単位を３〜２０モル％の割合で含有するヘキサフルオロプロピレン−フッ化ビニリデン共重合体、およびヘキサフルオロプロピレン単位を３〜２０モル％の割合で含有するヘキサフルオロプロピレン−テトラフルオロエチレン共重合体の少なくとも１種の樹脂を含むことが好ましい。また、リチウムイオン伝導性樹脂膜は、平均膜厚が０．１〜５μｍであることが好ましい。   In the above-described lithium ion secondary battery, the lithium ion conductive resin film includes a hexafluoropropylene-vinylidene fluoride copolymer containing 3 to 20 mol% of hexafluoropropylene units, and 3 hexafluoropropylene units. It is preferable to contain at least one resin of hexafluoropropylene-tetrafluoroethylene copolymer contained at a ratio of ˜20 mol%. The lithium ion conductive resin film preferably has an average film thickness of 0.1 to 5 μm.

上述のリチウムイオン二次電池によれば、負極活物質層の短辺方向中央部にのみ被着形成された帯状のリチウムイオン伝導性樹脂膜が、電極反応に対する抵抗層となる。このため、非水電解液が残留しやすい負極活物質層の短辺方向中央部において、局所的に電極反応が過剰に進行するのを抑制することができる。その結果、負極活物質層の短辺方向中央部と両端部とで電極反応の進行が不均一になるのを抑制することができ、電池の充放電サイクル特性が向上する。   According to the above-described lithium ion secondary battery, the strip-shaped lithium ion conductive resin film deposited only on the central portion in the short side direction of the negative electrode active material layer becomes a resistance layer against electrode reaction. For this reason, it can suppress that an electrode reaction progresses locally locally in the short side direction center part of the negative electrode active material layer in which a non-aqueous electrolyte tends to remain. As a result, it is possible to suppress the progress of the electrode reaction from becoming uneven at the short-side central portion and both ends of the negative electrode active material layer, and the charge / discharge cycle characteristics of the battery are improved.

実施形態に係るリチウムイオン二次電池の捲回型電極群の概略構成を説明するための斜視図である。It is a perspective view for demonstrating schematic structure of the winding type electrode group of the lithium ion secondary battery which concerns on embodiment. 図１に示す正極の断面模式図である。It is a cross-sectional schematic diagram of the positive electrode shown in FIG. 負極集電体の表面構造の一例を示す平面模式図である。It is a plane schematic diagram which shows an example of the surface structure of a negative electrode collector. 図３に示す負極集電体と、その表面に支持された複数の柱状体からなる負極活物質層およびイオン伝導性樹脂膜とを示す断面模式図である。It is a cross-sectional schematic diagram which shows the negative electrode electrical power collector shown in FIG. 3, and the negative electrode active material layer and ion-conductive resin film which consist of several columnar body supported on the surface. 負極活物質層を形成する装置の一例を示す正面模式図である。It is a front schematic diagram which shows an example of the apparatus which forms a negative electrode active material layer. 実施形態に係るリチウムイオン二次電池の概略構成を示す縦断面図である。It is a longitudinal cross-sectional view which shows schematic structure of the lithium ion secondary battery which concerns on embodiment.

はじめに、本発明の一実施形態であるリチウムイオン電池を形成する捲回型電極群について説明する。
図１を参照して、捲回型電極群１０は、帯状の負極１１と、帯状の正極１２と、帯状のセパレータ１３（１３ａ，１３ｂ）とを含み、これらは、負極１１と正極１２との間にセパレータ１３が介在するようにして、負極１１および正極１２の各長辺方向１４に沿って捲回されている。 First, a wound electrode group forming a lithium ion battery according to an embodiment of the present invention will be described.
With reference to FIG. 1, the wound electrode group 10 includes a strip-shaped negative electrode 11, a strip-shaped positive electrode 12, and a strip-shaped separator 13 (13 a, 13 b). Winding is performed along the long side directions 14 of the negative electrode 11 and the positive electrode 12 with the separator 13 interposed therebetween.

図２を参照して、負極１１は、帯状の負極集電体１５と、負極集電体１５の表面に支持された複数の合金系活物質の柱状体１７からなる帯状の負極活物質層１６と、負極活物質層１６の表面に被着形成されたリチウムイオン伝導性樹脂膜１８と、を備える。以下、本発明の実施形態における負極活物質層として、複数の合金系活物質の柱状体からなる帯状の負極活物質層を例示して説明する。但し、負極活物質層は、負極集電体の表面に支持された合金系活物質からなるものであること以外は特に限定されず、例えば負極集電体の表面に支持された、いわゆるベタ膜状の層であってもよい。また、負極活物質層の形成方法は特に限定されず、合金系活物質からなる負極活物質層の形成方法として公知の各種方法を用いることができる。   Referring to FIG. 2, negative electrode 11 includes a strip-shaped negative electrode active material layer 16 including a strip-shaped negative electrode current collector 15 and a plurality of columnar bodies 17 of alloy-based active materials supported on the surface of negative electrode current collector 15. And a lithium ion conductive resin film 18 deposited on the surface of the negative electrode active material layer 16. Hereinafter, as a negative electrode active material layer in an embodiment of the present invention, a strip-shaped negative electrode active material layer composed of a columnar body of a plurality of alloy-based active materials will be described as an example. However, the negative electrode active material layer is not particularly limited except that the negative electrode active material layer is made of an alloy-based active material supported on the surface of the negative electrode current collector. For example, a so-called solid film supported on the surface of the negative electrode current collector It may be a layer. Moreover, the formation method of a negative electrode active material layer is not specifically limited, Various well-known methods can be used as a formation method of the negative electrode active material layer which consists of alloy type active materials.

負極集電体１５としては、リチウムイオン二次電池の負極に用い得るものであれば特に限定されない。具体的には、銅箔、銅合金箔などが挙げられ、特に電解銅箔が好ましい。銅箔には、０．２モル％以下の割合で銅以外の成分を含んでいてもよい。負極集電体１５の厚みは、５〜５０μｍの範囲で、リチウムイオン二次電池の容量、サイズなどに合わせて適宜設定することができる。   The negative electrode current collector 15 is not particularly limited as long as it can be used for the negative electrode of a lithium ion secondary battery. Specific examples include copper foil and copper alloy foil, and electrolytic copper foil is particularly preferable. The copper foil may contain components other than copper in a proportion of 0.2 mol% or less. The thickness of the negative electrode current collector 15 can be appropriately set in the range of 5 to 50 μm according to the capacity and size of the lithium ion secondary battery.

図３を参照して、負極集電体１５は、互いに間隔をあけて配置された複数の凸部１９を表面に備えることが好ましい。図３に示すような凸部１９を備えた負極集電体１５を用いて、後述する蒸着手段により合金系活物質を負極集電体１５の表面に蒸着させることにより、負極活物質層１６を負極集電体１５の表面に支持された複数の柱状体１７で構成することができる（図４参照）。   Referring to FIG. 3, negative electrode current collector 15 preferably includes a plurality of convex portions 19 arranged on the surface at intervals. The negative electrode active material layer 16 is formed by depositing an alloy-based active material on the surface of the negative electrode current collector 15 using a negative electrode current collector 15 having a convex portion 19 as shown in FIG. It can be composed of a plurality of columnar bodies 17 supported on the surface of the negative electrode current collector 15 (see FIG. 4).

合金系活物質としては、ケイ素またはスズの単体、または、ケイ素またはスズを含む化合物が挙げられ、特に、ケイ素の単体またはケイ素を含む化合物が好ましい。ケイ素を含む化合物としては、ケイ素合金、ケイ素酸化物、ケイ素窒化物などが挙げられる。ケイ素酸化物は、一般式：ＳｉＯx（０＜ｘ＜２、好ましくは０．０１≦ｘ≦１）で表されるものが好ましく、さらにＦｅ、Ａｌ、Ｃａ、Ｍｎ、Ｔｉなどの元素を含んでいてもよい。合金系活物質は、２種以上の化合物の混合物であってもよい。   Examples of the alloy-based active material include a simple substance of silicon or tin, or a compound containing silicon or tin. In particular, a simple substance of silicon or a compound containing silicon is preferable. Examples of the compound containing silicon include a silicon alloy, silicon oxide, and silicon nitride. The silicon oxide is preferably represented by the general formula: SiOx (0 <x <2, preferably 0.01 ≦ x ≦ 1), and further contains elements such as Fe, Al, Ca, Mn, and Ti. May be. The alloy-based active material may be a mixture of two or more compounds.

図４に示すような負極活物質層１６は、例えば図５に示すような蒸着装置４０を用いて、負極集電体１５の表面に合金系活物質を蒸着することにより形成される。
図５は、蒸着装置４０の構成を模式的に示す側面図である。蒸着装置４０は、耐圧容器である真空容器４１と、真空容器４１の内部に配置される、巻出しロール４２、複数の搬送ロール４３、２本の成膜ロール４４ａ、４４ｂ、巻取りロール４５、マスク４６ａ、４６ｂ、４６ｃ、２つの蒸着ソース４７ａ、４７ｂ、２本の酸素ノズル４８ａ、４８ｂ、および真空ポンプ４９と、を含む。図５においては、真空容器４１と、その内部に配置される各構成部材とを、それぞれ実線で示した。 The negative electrode active material layer 16 as shown in FIG. 4 is formed by evaporating an alloy-based active material on the surface of the negative electrode current collector 15 using, for example, a vapor deposition apparatus 40 as shown in FIG.
FIG. 5 is a side view schematically showing the configuration of the vapor deposition apparatus 40. The vapor deposition apparatus 40 includes a vacuum container 41 which is a pressure-resistant container, an unwinding roll 42, a plurality of transport rolls 43, two film forming rolls 44a and 44b, a winding roll 45, which are disposed inside the vacuum container 41. And masks 46a, 46b, 46c, two vapor deposition sources 47a, 47b, two oxygen nozzles 48a, 48b, and a vacuum pump 49. In FIG. 5, the vacuum vessel 41 and the components disposed therein are indicated by solid lines.

巻出しロール４２には、帯状の負極集電体１５が巻き付けられている。複数の搬送ロール４３は、巻出しロール４２に巻き付けられた負極集電体１５を、２本の成膜ロール４４ａ、４４ｂをそれぞれ経由して、巻取りロール４５へと搬送する。一方の成膜ロール４４ａは、一方の蒸着ソース４７ａと鉛直方向で対向するように設けられ、他方の成膜ロール４４ｂは、他方の蒸着ソース４７ｂと鉛直方向で対向するように設けられる。各成膜ロール４４ａ、４４ｂの内部には図示しない冷却装置が配置され、それぞれ成膜ロールの周面を冷却する。巻取りロール４５は、図示しない駆動手段により回転駆動可能に設けられている。巻取りロール４５は、負極１１を巻き取って保存する。巻出しロール４２から負極集電体１５の長手方向の一端を図５に示す経路に従って送り出し、巻取りロール４５の周面に固定する。   A strip-shaped negative electrode current collector 15 is wound around the unwinding roll 42. The plurality of transport rolls 43 transport the negative electrode current collector 15 wound around the unwinding roll 42 to the winding roll 45 via the two film forming rolls 44a and 44b. One film forming roll 44a is provided to face one vapor deposition source 47a in the vertical direction, and the other film forming roll 44b is provided to face the other vapor deposition source 47b in the vertical direction. A cooling device (not shown) is disposed inside each of the film forming rolls 44a and 44b, and cools the peripheral surface of each film forming roll. The winding roll 45 is provided so as to be rotationally driven by a driving means (not shown). The winding roll 45 winds and stores the negative electrode 11. One end in the longitudinal direction of the negative electrode current collector 15 is fed out from the unwinding roll 42 along the path shown in FIG. 5 and fixed to the peripheral surface of the winding roll 45.

各成膜ロール４４ａ、４４ｂの鉛直方向下方には、それぞれ３つのマスク４６ａ、４６ｂ、４６ｃが配置されている。第１のマスク４６ａは、例えば、一方の成膜ロール４４ａと一方の蒸着ソース４７ａとの間に配置されており、２つの第２のマスク４６ｂ、４６ｃは、それぞれ第１のマスク４６ａに対して成膜ロール４４ａの周方向に離れて配置されている。３つのマスク４６ａ、４６ｂ、４６ｃを図５に示すように配置することで、蒸着ソース４７ａから負極集電体１５の表面への合金系活物質の照射方向を制御することができる。具体的には、第１のマスク４６ａによって、負極集電体１５の鉛直方向上方からの合金系活物質の照射は遮蔽されており、合金系活物質は、負極集電体１５の鉛直線に対して傾斜した方向から、負極集電体１５の凸部に向けて照射される。これにより、シャドウイング（遮蔽）効果が得られ、その結果、負極集電体１５の凸部に対して確実に合金系活物質を蒸着させることができ、かつ、凸部以外の負極集電体表面に合金系活物質が蒸着するのを抑制できる。なお、ここでは一方の成膜ロール４４ａと一方の蒸着ソース４７ａとの間に配置されたマスク４６ａ、４６ｂ、４６ｃについて説明したが、他方の成膜ロール４４ｂと他方の蒸着ソース４７ｂとの間に配置されたマスク４６ａ、４６ｂ、４６ｃについても同様である。   Three masks 46a, 46b, and 46c are disposed below the film forming rolls 44a and 44b in the vertical direction, respectively. The first mask 46a is disposed, for example, between one film forming roll 44a and one vapor deposition source 47a, and the two second masks 46b and 46c are respectively in relation to the first mask 46a. The film forming rolls 44a are arranged apart from each other in the circumferential direction. By arranging the three masks 46a, 46b, 46c as shown in FIG. 5, the irradiation direction of the alloy-based active material from the vapor deposition source 47a to the surface of the negative electrode current collector 15 can be controlled. Specifically, the irradiation of the alloy-based active material from above the negative electrode current collector 15 in the vertical direction is shielded by the first mask 46 a, and the alloy-based active material is in the vertical line of the negative electrode current collector 15. Irradiation is directed toward the convex portion of the negative electrode current collector 15 from a direction inclined with respect to the negative electrode current collector 15. Thereby, a shadowing (shielding) effect is obtained. As a result, the alloy-based active material can be reliably deposited on the convex portion of the negative electrode current collector 15, and the negative electrode current collector other than the convex portion can be obtained. It can suppress that an alloy type active material vapor-deposits on the surface. Here, the masks 46a, 46b and 46c arranged between one film forming roll 44a and one vapor deposition source 47a have been described, but between the other film forming roll 44b and the other vapor deposition source 47b. The same applies to the arranged masks 46a, 46b, and 46c.

各蒸着ソース４７ａ、４７ｂには、ターゲットとしてシリコン、スズなどの合金系活物質が収容される。ターゲットを加熱することにより合金系活物質の蒸気が発生して、各成膜ロール４４ａ、４４ｂの露出面に向けて上昇する。ターゲットの加熱には、発熱体による加熱、電子ビーム照射による加熱などを利用できる。一方の酸素ノズル４８ａは、一方の成膜ロール４４ａと一方の蒸着ソース４７ａとの間に設けられ、他方の酸素ノズル４８ｂは、他方の成膜ロール４４ｂと他方の蒸着ソース４７ｂとの間に設けられる。各酸素ノズル４８ａ、４８ｂは、それぞれ蒸着ソースで発生して成膜ローラの表面へと蒸着される合金系活物質の蒸気に対して、酸素を供給する。ケイ素またはスズのみからなる負極活物質層を形成する場合は、酸素ノズルからの酸素の供給を停止する。真空ポンプ４９は、真空容器４１に接続され、真空容器４１の内部を真空状態（減圧状態）にする。   Each deposition source 47a, 47b contains an alloy-based active material such as silicon or tin as a target. By heating the target, vapor of the alloy-based active material is generated and rises toward the exposed surfaces of the film forming rolls 44a and 44b. For heating the target, heating by a heating element, heating by electron beam irradiation, or the like can be used. One oxygen nozzle 48a is provided between one film forming roll 44a and one vapor deposition source 47a, and the other oxygen nozzle 48b is provided between the other film forming roll 44b and the other vapor deposition source 47b. It is done. Each of the oxygen nozzles 48a and 48b supplies oxygen to the vapor of the alloy-based active material that is generated at the deposition source and deposited on the surface of the film forming roller. When forming a negative electrode active material layer made of only silicon or tin, supply of oxygen from the oxygen nozzle is stopped. The vacuum pump 49 is connected to the vacuum vessel 41 and puts the inside of the vacuum vessel 41 into a vacuum state (depressurized state).

図５に示す蒸着装置４０において、負極集電体１５が、マスク４６ａ、４６ｂ、４６ｃにより遮断されていない一方の成膜ロール４４ａの露出面を走行している時には、一方の蒸着ソース４７ａと対向する負極集電体１５の表面に、合金系活物質の蒸気（または合金系活物質の蒸気と酸素との混合物）が蒸着されて、負極集電体１５の凸部１９に柱状体１７が形成される（図４参照）。また、負極集電体１５が、マスク４６ａ、４６ｂ、４６ｃにより遮断されていない他方の成膜ロール４４ｂの露出面を走行している時には、他方の蒸着ソース４７ｂと対向する負極集電体１５の表面であって、一方の蒸着ソース４７ａから合金系活物質が蒸着されたのとは反対側の表面に、合金系活物質の蒸気（または合金系活物質の蒸気と酸素との混合物）が蒸着されて、負極集電体の凸部に柱状体が形成される。これにより、負極集電体１５の両面に、複数の柱状体１７を含む負極活物質層１６を備えた負極１１が得られる。   In the vapor deposition apparatus 40 shown in FIG. 5, when the negative electrode current collector 15 runs on the exposed surface of one film forming roll 44a that is not blocked by the masks 46a, 46b, and 46c, it faces one vapor deposition source 47a. The vapor of the alloy-based active material (or a mixture of the vapor of the alloy-based active material and oxygen) is deposited on the surface of the negative electrode current collector 15 to form the columnar body 17 on the convex portion 19 of the negative electrode current collector 15. (See FIG. 4). When the negative electrode current collector 15 is running on the exposed surface of the other film forming roll 44b that is not blocked by the masks 46a, 46b, 46c, the negative electrode current collector 15 facing the other vapor deposition source 47b The vapor of the alloy-based active material (or a mixture of the vapor of the alloy-based active material and oxygen) is deposited on the surface of the surface opposite to the surface where the alloy-based active material is deposited from one deposition source 47a. Thus, a columnar body is formed on the convex portion of the negative electrode current collector. As a result, the negative electrode 11 including the negative electrode active material layer 16 including the plurality of columnar bodies 17 on both surfaces of the negative electrode current collector 15 is obtained.

なお、負極活物質層には、不可逆容量に相当する量のリチウムを予め吸蔵させることが好ましい。リチウムを予め吸蔵させる方法としては、例えば、負極活物質層を形成する柱状体に対して金属リチウムを蒸着させる方法が挙げられる。柱状体への金属リチウムの蒸着は、例えば、図５に示す蒸着装置４０を用いて行うことができる。この場合、蒸着ソース４７ａ、４７ｂに収容するターゲットとして、合金系活物質に代えて金属リチウムを用いればよい。   Note that the negative electrode active material layer is preferably preliminarily occluded with an amount of lithium corresponding to the irreversible capacity. Examples of the method for preliminarily occluding lithium include a method in which metallic lithium is vapor-deposited on a columnar body that forms the negative electrode active material layer. The vapor deposition of metallic lithium on the columnar body can be performed using, for example, a vapor deposition apparatus 40 shown in FIG. In this case, metallic lithium may be used in place of the alloy-based active material as a target accommodated in the vapor deposition sources 47a and 47b.

負極集電体１５の凸部１９の形状は特に限定されないが、負極集電体１５の表面から凸部１９の頂部までの高さは、３〜２０μｍが好ましく、５〜１５μｍがさらに好ましい。また、柱状体１７の形状は特に限定されないが、凸部１９の頂部から柱状体１７の頂部までの高さは、５〜４０μｍが好ましく、１０〜３０μｍがさらに好ましい。   Although the shape of the convex part 19 of the negative electrode collector 15 is not specifically limited, 3-20 micrometers is preferable and, as for the height from the surface of the negative electrode collector 15 to the top part of the convex part 19, 5-15 micrometers is more preferable. Moreover, the shape of the columnar body 17 is not particularly limited, but the height from the top of the convex portion 19 to the top of the columnar body 17 is preferably 5 to 40 μm, and more preferably 10 to 30 μm.

負極活物質層１６の表面の一部には、後述するリチウムイオン伝導性樹脂膜１８が被着形成される。なお、負極活物質層１６の表面とは、負極活物質層１６を形成する複数の柱状体１７のそれぞれの先端部分の表面をいう。負極活物質層１６には、リチウムイオン伝導性樹脂膜１８の形成前に、合金系活物質の不可逆容量に相当する量のリチウムを付与させてもよい。不可逆容量とは、初回充放電時に負極活物質層１６に蓄えられ、その後、負極活物質層１６から放出されないリチウムの量である。リチウムの付与方法としては、特に限定されず、蒸着、スパッタなどの真空プロセスや、電気化学的ドープといった方法を採用することができる。   A lithium ion conductive resin film 18 to be described later is deposited on a part of the surface of the negative electrode active material layer 16. The surface of the negative electrode active material layer 16 refers to the surface of each tip portion of the plurality of columnar bodies 17 that form the negative electrode active material layer 16. Prior to the formation of the lithium ion conductive resin film 18, an amount of lithium corresponding to the irreversible capacity of the alloy active material may be applied to the negative electrode active material layer 16. The irreversible capacity is the amount of lithium that is stored in the negative electrode active material layer 16 at the time of the first charge / discharge and is not subsequently released from the negative electrode active material layer 16. The method for applying lithium is not particularly limited, and a vacuum process such as vapor deposition or sputtering, or a method such as electrochemical doping can be employed.

リチウムイオン伝導性樹脂膜１８は、負極活物質層１６の長辺方向１４に沿って負極活物質層１６の短辺方向２０の中央部にのみ形成されており、短辺方向２０の両端部には形成されていない。リチウムイオン伝導性樹脂膜１８の形成領域について、負極活物質層１６の短辺方向２０の中央部の幅は、負極活物質層１６の短辺方向２０の全幅に対して２０〜５０％であり、好ましくは、３０〜５０％である。リチウムイオン伝導性樹脂膜１８の形成領域の短辺方向２０における幅が、負極活物質層１６の短辺方向２０の全幅に対して２０％を下回ると、負極活物質層１６における電極反応が短辺方向２０の中央部において過剰に進行するのを抑制できなくなる。一方、リチウムイオン伝導性樹脂膜１８の形成領域の短辺方向２０における幅が、負極活物質層１６の短辺方向２０の全幅に対して５０％を上回ると、負極活物質層１６における電極反応が過剰に抑制される。その結果、負極活物質層の短辺方向の両端部における反応量が局所的に増加して、電池のサイクル特性が低下する。   The lithium ion conductive resin film 18 is formed only at the center of the short side direction 20 of the negative electrode active material layer 16 along the long side direction 14 of the negative electrode active material layer 16, and at both ends of the short side direction 20. Is not formed. In the formation region of the lithium ion conductive resin film 18, the width of the central portion in the short side direction 20 of the negative electrode active material layer 16 is 20 to 50% with respect to the entire width in the short side direction 20 of the negative electrode active material layer 16. Preferably, it is 30 to 50%. When the width in the short side direction 20 of the formation region of the lithium ion conductive resin film 18 is less than 20% with respect to the total width in the short side direction 20 of the negative electrode active material layer 16, the electrode reaction in the negative electrode active material layer 16 is short. It becomes impossible to suppress excessive progress at the center of the side direction 20. On the other hand, when the width in the short side direction 20 of the formation region of the lithium ion conductive resin film 18 exceeds 50% with respect to the total width in the short side direction 20 of the negative electrode active material layer 16, the electrode reaction in the negative electrode active material layer 16. Is excessively suppressed. As a result, the reaction amount at both ends in the short side direction of the negative electrode active material layer is locally increased, and the cycle characteristics of the battery are deteriorated.

リチウムイオン伝導性樹脂膜としては、例えば、フッ素樹脂などのハロゲン含有樹脂、ポリエチレンオキサイドなどのポリアルキレンオキサイド、ポリアクリロニトリル、ポリアクリレートなどのアクリル樹脂、これらの誘導体などが用いられ、特に、樹脂膜のリチウムイオン伝導性を高める観点から、フッ素樹脂が好ましい。   As the lithium ion conductive resin film, for example, halogen-containing resins such as fluororesins, polyalkylene oxides such as polyethylene oxide, acrylic resins such as polyacrylonitrile and polyacrylate, derivatives thereof, and the like are used. From the viewpoint of enhancing lithium ion conductivity, a fluororesin is preferable.

フッ素樹脂としては、フッ化ビニリデン（ＶｄＦ）、ヘキサフルオロプロピレン（ＨＦＰ）、テトラフルオロエチレン（ＴＦＥ）などのフッ素原子含有オレフィンの重合体や、フッ素原子含有オレフィンまたはその誘導体を構成単位として含む共重合体が挙げられる。具体的には、ポリフッ化ビニリデン、ポリヘキサフルオロプロピレン、ポリテトラフルオロエチレンなどのホモポリマーや、ＶｄＦとＨＦＰとの共重合体（Ｐ（ＶｄＦ−ＨＦＰ））、ＨＦＰとＴＦＥとの共重合体（Ｐ（ＨＦＰ−ＴＦＥ）））などの共重合体が挙げられる。共重合体はフッ素原子含有モノマー同士の共重合体に限定されず、フッ素原子含有モノマーと他の共重合可能なモノマーとの共重合体であってもよい。フッ素樹脂は、リチウムイオン伝導性樹脂膜の耐電圧や化学的安定性を高める観点より、ＶｄＦ、ＨＦＰおよびテトラフルオロエチレンの少なくとも１種をモノマー成分として含むことが好ましく、特に、Ｐ（ＶｄＦ−ＨＦＰ）やＰ（ＨＦＰ−ＴＦＥ）が好ましい。   The fluororesin includes a polymer of a fluorine atom-containing olefin such as vinylidene fluoride (VdF), hexafluoropropylene (HFP), tetrafluoroethylene (TFE), and a co-polymer containing a fluorine atom-containing olefin or a derivative thereof as a structural unit. Coalescence is mentioned. Specifically, homopolymers such as polyvinylidene fluoride, polyhexafluoropropylene, polytetrafluoroethylene, copolymers of VdF and HFP (P (VdF-HFP)), copolymers of HFP and TFE ( P (HFP-TFE))) and the like. The copolymer is not limited to a copolymer of fluorine atom-containing monomers, and may be a copolymer of a fluorine atom-containing monomer and another copolymerizable monomer. The fluororesin preferably contains at least one of VdF, HFP and tetrafluoroethylene as a monomer component from the viewpoint of increasing the withstand voltage and chemical stability of the lithium ion conductive resin film, and in particular, P (VdF-HFP ) Or P (HFP-TFE).

Ｐ（ＶｄＦ−ＨＦＰ）やＰ（ＨＦＰ−ＴＦＥ）に含まれるＨＦＰ単位の割合は、モノマーのモル量換算で、３〜２０モル％が好ましく、５〜１５モル％がさらに好ましい。ＨＦＰ単位の含有割合を３〜２０モル％に設定することにより、リチウムイオン伝導性樹脂膜のイオン伝導性を維持しつつ、活物質との密着性を改善することができる。   The proportion of HFP units contained in P (VdF-HFP) or P (HFP-TFE) is preferably 3 to 20 mol%, more preferably 5 to 15 mol%, in terms of the molar amount of the monomer. By setting the content ratio of the HFP unit to 3 to 20 mol%, it is possible to improve the adhesion with the active material while maintaining the ion conductivity of the lithium ion conductive resin film.

リチウムイオン伝導性樹脂膜は、リチウムイオン伝導性樹脂膜を形成するポリマーを適当な溶媒に溶解または分散させ、こうして得られたポリマー溶液または分散液を負極活物質層の表面に塗布して、乾燥させることにより形成できる。ポリマー溶液または分散液の塗布は、例えば、スクリーン印刷、ダイコート、コンマコート、ローラコート、バーコート、グラビアコート、カーテンコート、スプレーコート、エアーナイフコート、リバースコート、ディップスクイズコート、ディップコートなどの、公知の液状物の塗布方法により実施できる。これらの塗布方法の中でも、ディップコートが好ましい。   The lithium ion conductive resin film is prepared by dissolving or dispersing the polymer forming the lithium ion conductive resin film in an appropriate solvent, applying the polymer solution or dispersion obtained in this way to the surface of the negative electrode active material layer, and drying. Can be formed. Application of the polymer solution or dispersion is, for example, screen printing, die coating, comma coating, roller coating, bar coating, gravure coating, curtain coating, spray coating, air knife coating, reverse coating, dip squeeze coating, dip coating, etc. It can be carried out by a known liquid coating method. Among these coating methods, dip coating is preferable.

ポリマーの溶媒または分散媒としては、ジメチルホルムアミド、ジメチルアセトアミド、メチルホルムアミドなどのアミド、Ｎ−メチル−２−ピロリドンなどのピロリドン類、ジメチルアミンなどのアミン、アセトン、シクロヘキサノンなどのケトン類、ジメチルカーボネート、ジエチルカーボネートなどの炭酸エステルなどが挙げられる。   Examples of the solvent or dispersion medium for the polymer include amides such as dimethylformamide, dimethylacetamide, and methylformamide, pyrrolidones such as N-methyl-2-pyrrolidone, amines such as dimethylamine, ketones such as acetone and cyclohexanone, dimethyl carbonate, Examples include carbonate esters such as diethyl carbonate.

リチウムイオン伝導性樹脂膜は、電池の組立て後に非水電解液と接触することによって、イオン伝導性を発現する。また、上述のポリマー溶液または分散液中にリチウム塩などの支持電解質を含有させることにより、イオン伝導性樹脂膜の形成時点であらかじめイオン伝導性を発現させることができる。   The lithium ion conductive resin film develops ion conductivity by contacting with a non-aqueous electrolyte after the battery is assembled. Further, by including a supporting electrolyte such as a lithium salt in the polymer solution or dispersion described above, ion conductivity can be expressed in advance at the time of forming the ion conductive resin film.

ポリマー溶液または分散液中のポリマーの含有割合は、ポリマー溶液または分散液の全量に対し、０．１〜２０質量％が好ましく、０．５〜１５質量％がさらに好ましく、１〜１０質量％が特に好ましい。ポリマーの含有割合を０．１〜２０質量％に設定することにより、ポリマー溶液または分散液の粘度を適度に調整することができ、柱状体同士の間隙にポリマー溶液または分散液を入り込ませることができる。それゆえ、間隙に入り込んだポリマーによるアンカー効果を発揮させて、負極活物質層とイオン伝導性樹脂膜との密着性をより一層向上させることができる。また、このように負極活物質層とイオン伝導性樹脂膜との密着性が向上することから、万一、負極活物質層の短辺方向中央部で活物質の体積膨張が局所的に大きくなって、クラックが生じたとしても、活物質がばらばらになって負極集電体から剥離したりすることを抑制できる。   The content of the polymer in the polymer solution or dispersion is preferably 0.1 to 20% by mass, more preferably 0.5 to 15% by mass, and more preferably 1 to 10% by mass with respect to the total amount of the polymer solution or dispersion. Particularly preferred. By setting the content of the polymer to 0.1 to 20% by mass, the viscosity of the polymer solution or dispersion can be adjusted appropriately, and the polymer solution or dispersion can enter the gap between the columnar bodies. it can. Therefore, it is possible to further improve the adhesion between the negative electrode active material layer and the ion conductive resin film by exerting an anchor effect by the polymer that has entered the gap. In addition, since the adhesion between the negative electrode active material layer and the ion conductive resin film is improved in this way, the volume expansion of the active material locally increases at the center in the short side direction of the negative electrode active material layer. Even if cracks occur, it can be prevented that the active material is separated and peeled off from the negative electrode current collector.

リチウムイオン伝導性樹脂膜１８は、例えば図４に示すように、少なくとも柱状体１７の先端部分の表面に被着するように形成される。図４において、リチウムイオン伝導性樹脂膜１８は、柱状体１７の凸部１９側における表面とは接触していない。また、リチウムイオン伝導性樹脂膜１８と負極集電体１５との間には、空隙が形成されている。しかしながら、リチウムイオン伝導性樹脂膜１８は図４に示すような形態に限定されるものではなく、例えば、隣接する柱状体１７間の空隙を全て埋めるように形成されていてもよい。リチウムイオン伝導性樹脂膜１８と負極集電体１５との間に空隙が形成される程度は、例えば、後述するリチウムイオン伝導性樹脂膜１８の形成に用いるポリマー溶液または分散液の粘度によって調整することができる。ポリマー溶液または分散液の粘度が高いと、リチウムイオン伝導性樹脂膜１８と負極集電体１５との間の空隙が大きくなる傾向があり、ポリマー溶液または分散液の粘度が低いと、空隙が小さくなる傾向がある。   For example, as shown in FIG. 4, the lithium ion conductive resin film 18 is formed so as to adhere to at least the surface of the tip portion of the columnar body 17. In FIG. 4, the lithium ion conductive resin film 18 is not in contact with the surface of the columnar body 17 on the convex portion 19 side. In addition, a gap is formed between the lithium ion conductive resin film 18 and the negative electrode current collector 15. However, the lithium ion conductive resin film 18 is not limited to the form shown in FIG. 4, and may be formed so as to fill all the gaps between adjacent columnar bodies 17, for example. The degree to which a void is formed between the lithium ion conductive resin film 18 and the negative electrode current collector 15 is adjusted by, for example, the viscosity of the polymer solution or dispersion used for forming the lithium ion conductive resin film 18 described later. be able to. When the viscosity of the polymer solution or dispersion is high, the gap between the lithium ion conductive resin film 18 and the negative electrode current collector 15 tends to be large. When the viscosity of the polymer solution or dispersion is low, the gap is small. Tend to be.

負極活物質層は、その表面の一部にイオン伝導性樹脂膜を形成した後で、負極活物質層に対する加熱プレス処理を施してもよい。具体的には、負極集電体と負極活物質層とイオン伝導性樹脂膜との積層体を、積層方向の両側から加熱プレスすればよい。このような加熱プレスを施すことにより、合金系活物質とイオン伝導性樹脂膜との間の密着性をさらに向上させることができる。   The negative electrode active material layer may be subjected to a heat press treatment on the negative electrode active material layer after an ion conductive resin film is formed on a part of the surface thereof. Specifically, a laminate of the negative electrode current collector, the negative electrode active material layer, and the ion conductive resin film may be heated and pressed from both sides in the stacking direction. By performing such a heat press, the adhesiveness between the alloy-based active material and the ion conductive resin film can be further improved.

リチウムイオン伝導性樹脂膜の平均膜厚は特に制限されないが、０．１〜５μｍが好ましく、０．５〜３μｍがさらに好ましい。このような範囲では、イオン伝導性樹脂膜が負極との間でイオン伝導に対する抵抗層として有効に作用するため、負極活物質層の短辺方向において電極反応を均一化させることができる。さらに、リチウムイオン伝導性樹脂膜は、負極活物質層にクラックが生じた場合であっても、負極活物質層の新生面と非水電解液との接触や、これに伴って生じる副反応をより効果的に抑制する。   The average film thickness of the lithium ion conductive resin film is not particularly limited, but is preferably 0.1 to 5 μm, and more preferably 0.5 to 3 μm. In such a range, since the ion conductive resin film effectively acts as a resistance layer against ion conduction with the negative electrode, the electrode reaction can be made uniform in the short side direction of the negative electrode active material layer. Furthermore, the lithium ion conductive resin film is more susceptible to contact between the new surface of the negative electrode active material layer and the non-aqueous electrolyte and side reactions caused by this even when cracks occur in the negative electrode active material layer. Effectively suppress.

再び図１を参照して、正極１２は、帯状の正極集電体２１と、正極集電体２１の表面に支持された帯状の正極活物質層２２と、を備える。
正極集電体２１は、リチウムイオン二次電池の正極に用い得るものであれば特に限定されない。具体的には、多孔性または無孔の導電性基板が挙げられ、導電性基板の材質としては、アルミニウム、アルミニウム合金、ステンレス鋼、チタンなどが挙げられる。 Referring to FIG. 1 again, the positive electrode 12 includes a strip-shaped positive electrode current collector 21 and a strip-shaped positive electrode active material layer 22 supported on the surface of the positive electrode current collector 21.
The positive electrode current collector 21 is not particularly limited as long as it can be used for the positive electrode of a lithium ion secondary battery. Specifically, a porous or non-porous conductive substrate can be used, and examples of the material of the conductive substrate include aluminum, aluminum alloy, stainless steel, and titanium.

正極活物質層２２は、例えば、カーボンブラックなどの導電剤と、ポリフッ化ビニリデンなどの結着剤とを含む正極合剤スラリーを、アルミニウム箔などの正極集電体の表面に塗布して乾燥し、圧延することにより得られる。正極活物質としては、リチウム含有遷移金属酸化物が好ましい。リチウム含有遷移金属化合物の代表的な例としては、ＬｉＣｏＯ2、ＬｉＮｉＯ2、ＬｉＭｎ2Ｏ4、ＬｉＭｎＯ2、ＬｉＮｉ1-yＣｏyＯ2（０＜ｙ＜１）、ＬｉＮｉ1-y-zＣｏyＭｎzＯ2（０＜ｙ＋ｚ＜１）などが挙げられる。 The positive electrode active material layer 22 is, for example, coated with a positive electrode mixture slurry containing a conductive agent such as carbon black and a binder such as polyvinylidene fluoride on the surface of a positive electrode current collector such as an aluminum foil and dried. It is obtained by rolling. As the positive electrode active material, a lithium-containing transition metal oxide is preferable. Typical examples of the lithium-containing transition metal compound include LiCoO 2 , LiNiO 2 , LiMn 2 O 4 , LiMnO 2 , LiNi 1-y Co y O 2 (0 <y <1), LiNi 1-yz Co y Mn and z O 2 (0 <y + z <1).

セパレータ１３は、リチウムイオン二次電池のセパレータとして用い得るものであれば、特に限定されない。セパレータ１３としては、ポリエチレン、ポリプロピレンなどのポリオレフィンからなる微多孔性フィルムが挙げられる。セパレータ１３の厚みは、例えば１０〜３０μｍである。   The separator 13 will not be specifically limited if it can be used as a separator of a lithium ion secondary battery. Examples of the separator 13 include a microporous film made of polyolefin such as polyethylene and polypropylene. The thickness of the separator 13 is 10-30 micrometers, for example.

次に、本発明の一実施形態であるリチウムイオン電池を、図６を参照して説明する。
リチウムイオン二次電池は、円筒型、扁平型、角形など、捲回型電極群を用いる様々な形状の電池に適用可能である。捲回型電極群は、円筒型の電池ケース内に収容された場合において、活物質の体積膨張に伴って締め付けられる程度が特に強くなる。このため、負極活物質層の短辺方向中央部にのみ、長辺方向に沿った帯状のリチウムイオン伝導性樹脂膜を設ける、という本発明の構成により得られる効果は、捲回型電極群を円筒型電池に適用する場合において特に顕著に現れる。 Next, a lithium ion battery according to an embodiment of the present invention will be described with reference to FIG.
The lithium ion secondary battery can be applied to batteries having various shapes using a wound electrode group such as a cylindrical shape, a flat shape, and a square shape. When the wound electrode group is housed in a cylindrical battery case, the degree to which the wound electrode group is tightened with the volume expansion of the active material is particularly strong. For this reason, the effect obtained by the configuration of the present invention in which a strip-like lithium ion conductive resin film along the long side direction is provided only in the central part in the short side direction of the negative electrode active material layer is This is particularly noticeable when applied to a cylindrical battery.

図６に示すリチウムイオン二次電池３０は、上述の捲回型電極群１０を備えている。捲回型電極群１０は、図示を省略する非水電解液とともに、電池ケース３１内に収容されている。電池ケース３１は有底円筒型の部材であって、電池ケース３１の開口端は封口板３２によって封鎖されている。   A lithium ion secondary battery 30 shown in FIG. 6 includes the above-described wound electrode group 10. The wound electrode group 10 is accommodated in the battery case 31 together with a non-aqueous electrolyte (not shown). The battery case 31 is a bottomed cylindrical member, and the open end of the battery case 31 is sealed with a sealing plate 32.

正極１２は、捲回型電極群１０の捲回軸方向の一端側において、正極リード３３を介して、正極端子３４と電気的に接続している。一方、負極１１は、捲回型電極群１０の捲回軸方向の他端側において、負極リード３５を介して、負極端子として兼用される電池ケース３１と電気的に接続している。   The positive electrode 12 is electrically connected to the positive electrode terminal 34 via the positive electrode lead 33 on one end side in the winding axis direction of the wound electrode group 10. On the other hand, the negative electrode 11 is electrically connected to a battery case 31 also serving as a negative electrode terminal via a negative electrode lead 35 on the other end side in the winding axis direction of the wound electrode group 10.

リチウムイオン二次電池３０は、次のようにして作製される。まず、捲回型電極群１０を電池ケース３１内に収容する。このとき、捲回型電極群１０の捲回軸方向における一方の端部に正極側絶縁板３６を装着し、他方の端部に負極側絶縁板３７を装着する。また、正極１２に対して正極リード３３を電気的に接続させ、負極１１に対して負極リード３５を電気的に接続させる。次に、電池ケース３１内に非水電解液を注入する。非水電解液の量は特に限定されず、リチウムイオン二次電池の分野における技術常識の範囲で適宜設定することができる。   The lithium ion secondary battery 30 is manufactured as follows. First, the wound electrode group 10 is accommodated in the battery case 31. At this time, the positive-side insulating plate 36 is attached to one end of the wound electrode group 10 in the winding axis direction, and the negative-side insulating plate 37 is attached to the other end. Further, the positive electrode lead 33 is electrically connected to the positive electrode 12, and the negative electrode lead 35 is electrically connected to the negative electrode 11. Next, a non-aqueous electrolyte is injected into the battery case 31. The amount of the non-aqueous electrolyte is not particularly limited, and can be appropriately set within the range of technical common sense in the field of lithium ion secondary batteries.

その後、電池ケース３１の開口部近傍に、封口板３２を受けるための段部を形成し、その上に封口板３２を配置して、電池ケース３１の開口端を封口板３２の周縁部にかしめる。これにより、電池ケース３１が密封されて、円筒型のリチウムイオン二次電池３０を得ることができる。   Thereafter, a step for receiving the sealing plate 32 is formed in the vicinity of the opening of the battery case 31, the sealing plate 32 is disposed thereon, and the opening end of the battery case 31 is placed on the peripheral portion of the sealing plate 32. Close. Thereby, the battery case 31 is sealed, and the cylindrical lithium ion secondary battery 30 can be obtained.

非水電解液は、非水溶媒と、これに溶解するリチウム塩とを含む。非水溶媒としては、エチレンカーボネート、プロピレンカーボネートなどの環状カーボネート類とジメチルカーボネート、ジエチルカーボネート、エチルメチルカーボネートなどの鎖状カーボネート類との混合溶媒が挙げられる。また、γ−ブチロラクトンやジメトキシエタンなども用いられる。リチウム塩としては、無機リチウムフッ化物やリチウムイミド化合物などが挙げられる。無機リチウムフッ化物としては、ＬｉＰＦ6、ＬｉＢＦ4、ＬｉＳｂＦ6、ＬｉＡｓＦ6などが挙げられ、リチウムイミド化合物としてはＬｉＮ（ＣＦ3ＳＯ2）2などが挙げられる。これらは単独で用いてもよく、２種以上を組み合わせて用いてもよい。 The non-aqueous electrolyte contains a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent. Examples of the non-aqueous solvent include a mixed solvent of cyclic carbonates such as ethylene carbonate and propylene carbonate and chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Further, γ-butyrolactone, dimethoxyethane and the like are also used. Examples of lithium salts include inorganic lithium fluorides and lithium imide compounds. The inorganic lithium fluoride, LiPF 6, LiBF 4, LiSbF 6, such as LiAsF 6. Examples of the lithium imide compound and the like LiN (CF 3 SO 2) 2 . These may be used alone or in combination of two or more.

リチウムイオン二次電池は、角形、円筒形、扁平形など、捲回型電極群を用いる様々な形状の電池に適用可能である。電池の形状は限定されないが、特に角形や円筒形が好ましい。捲回型電極群が角型または円筒型の電池ケースに収容されている場合には、捲回型電極群が可撓性のあるケースに収容されている扁平形電池に比べて、充電時の膨張により捲回型電極群が締め付けられる程度が高い。このため、正極活物質層の長辺に沿った両端部、および負極活物質層の長辺に沿った両端部の少なくとも一方に、樹脂からなる帯状の堰部を設けるという上述の実施形態を、角形電池や円筒形電池に適用することにより、負極活物質層の中央部と両端部とで電極反応の進行が不均一になるのを抑制するという効果をより一層顕著に発揮させることができる。   The lithium ion secondary battery can be applied to batteries having various shapes using a wound electrode group such as a square, a cylinder, and a flat shape. The shape of the battery is not limited, but a square or cylindrical shape is particularly preferable. When the wound electrode group is housed in a rectangular or cylindrical battery case, the wound electrode group can be charged more easily than a flat battery housed in a flexible case. The degree to which the wound electrode group is fastened by expansion is high. For this reason, the above-described embodiment in which at least one of both end portions along the long side of the positive electrode active material layer and both end portions along the long side of the negative electrode active material layer is provided with a belt-like dam portion made of resin, By applying the present invention to a prismatic battery or a cylindrical battery, the effect of suppressing the progress of the electrode reaction at the central portion and both end portions of the negative electrode active material layer can be exhibited more remarkably.

＜リチウムイオン二次電池の製造＞
（実施例１）
（１）負極の作製
（１−１）負極集電板の作製
直径５０ｍｍの鍛鋼製ローラの表面に、レーザ加工により、直径１０μｍ、深さ８μｍの円形の凹部を形成することにより、凸部形成用ローラを作製した。凹部は、中心間距離がローラ表面に沿って３０μｍとなるように、かつ凹部の中心点が二次元三角格子状のパターンとなるように配置した。凸部形成用ローラは、同じものを２本作製して、互いのローラの軸を平行に配置することにより、一対のニップローラとした。 <Manufacture of lithium ion secondary batteries>
Example 1
(1) Production of negative electrode (1-1) Production of negative electrode current collector plate By forming a circular concave portion having a diameter of 10 μm and a depth of 8 μm by laser processing on the surface of a forged steel roller having a diameter of 50 mm, a convex portion is formed. A roller was prepared. The recesses were arranged so that the center-to-center distance was 30 μm along the roller surface, and the center point of the recesses was a two-dimensional triangular lattice pattern. Two of the same convex forming rollers were produced, and the axes of the rollers were arranged in parallel to form a pair of nip rollers.

一対のニップローラ間に、厚さ２０μｍの合金銅箔（ジルコニアを全体の０．０３質量％含有する銅合金、商品名：ＨＣＬ−０２Ｚ、日立電線（株）製）を通過させて、合金銅箔の表裏両面を加圧した。一対のニップローラ間にかかる荷重は、線圧１０００ｋｇｆ／ｃｍ（約９．８ｋＮ／ｃｍ）とした。こうして、合金銅箔の表裏両面に、高さ約６μｍ、直径約１０μｍの凸部が複数形成された負極集電体を得た。隣り合う凸部間の中心間距離は３０μｍであった。こうして得られた負極集電体を裁断して、幅１００ｍｍの帯状部材に成形した。凸部の形状は、走査型電子顕微鏡により確認した。   An alloy copper foil having a thickness of 20 μm (a copper alloy containing 0.03% by mass of zirconia, trade name: HCL-02Z, manufactured by Hitachi Cable Ltd.) is passed between a pair of nip rollers, and the alloy copper foil Both front and back surfaces were pressurized. The load applied between the pair of nip rollers was a linear pressure of 1000 kgf / cm (about 9.8 kN / cm). Thus, a negative electrode current collector was obtained in which a plurality of convex portions having a height of about 6 μm and a diameter of about 10 μm were formed on the front and back surfaces of the alloy copper foil. The center-to-center distance between adjacent convex portions was 30 μm. The negative electrode current collector thus obtained was cut and formed into a strip member having a width of 100 mm. The shape of the convex portion was confirmed by a scanning electron microscope.

（１−２）負極活物質層の形成
図５に示す蒸着装置４０を用いて、負極集電体の表面に負極活物質層を形成した。
純度９９．７％の酸素ガスを各酸素ノズル４８ａ、４８ｂから真空容器４１内へと供給しながら、スクラップシリコン（純度９９．９９９％）を蒸着源として電子ビーム蒸着を行った。電子ビーム蒸着時の真空容器４１内部は、圧力１×１０-1Ｐａ（ａｂｓ）の酸素雰囲気とした。こうして、負極集電体１５の両面に、ＳｉＯx（ｘの平均値０．４）からなる柱状体を複数形成した。 (1-2) Formation of Negative Electrode Active Material Layer A negative electrode active material layer was formed on the surface of the negative electrode current collector using the vapor deposition apparatus 40 shown in FIG.
While supplying oxygen gas having a purity of 99.7% from each of the oxygen nozzles 48a and 48b into the vacuum vessel 41, electron beam deposition was performed using scrap silicon (purity 99.999%) as a deposition source. The inside of the vacuum vessel 41 at the time of electron beam evaporation was an oxygen atmosphere having a pressure of 1 × 10 −1 Pa (abs). Thus, a plurality of columnar bodies made of SiO x (x average value 0.4) were formed on both surfaces of the negative electrode current collector 15.

さらに、図５に示す蒸着装置４０を用いて、負極集電体１５の表面に形成された負極活物質層に対してリチウムを蒸着した。リチウムの蒸着は、蒸着源として、スクラップシリコンに代えて金属リチウムを用い、ノズルから供給されるガスとして、酸素ガスに代えてアルゴンガスを用い、さらに、電子ビーム蒸着時の真空容器４１内部を１×１０-1Ｐａ（ａｂｓ）のアルゴン雰囲気とした。リチウムの蒸着量は、負極活物質層の不可逆容量に相当する量であって、金属リチウムの蒸着膜をベタ膜として形成した場合の厚みで９μｍとした。 Furthermore, lithium was vapor-deposited with respect to the negative electrode active material layer formed in the surface of the negative electrode collector 15 using the vapor deposition apparatus 40 shown in FIG. In the vapor deposition of lithium, metallic lithium is used instead of scrap silicon as a vapor deposition source, argon gas is used instead of oxygen gas as a gas supplied from the nozzle, and the inside of the vacuum vessel 41 during electron beam vapor deposition is 1 An argon atmosphere of × 10 −1 Pa (abs) was used. The amount of lithium deposited was an amount corresponding to the irreversible capacity of the negative electrode active material layer, and was 9 μm in thickness when the metal lithium deposited film was formed as a solid film.

（１−３）リチウムイオン伝導性樹脂膜の形成
ヘキサフルオロプロピレンとフッ化ビニリデンとの共重合体（Ｐ（ＨＦＰ−ＶＤＦ））をジメチルカーボネートに溶解させて、Ｐ（ＨＦＰ−ＶＤＦ）の濃度が３質量％のポリマー溶液を調製した。Ｐ（ＨＦＰ−ＶＤＦ）中のヘキサフルオロプロピレン単位の含有割合は１２モル％であった。得られたポリマー溶液を７０℃に加熱した後、負極活物質層１６の表面にディップコートにより塗布した。塗膜を５分間自然乾燥させた後、８０℃に加熱してから、１時間真空乾燥させることにより、図１に示すようなリチウムイオン伝導性樹脂膜１８を形成した。 (1-3) Formation of lithium ion conductive resin film A copolymer of hexafluoropropylene and vinylidene fluoride (P (HFP-VDF)) is dissolved in dimethyl carbonate, and the concentration of P (HFP-VDF) is A 3% by weight polymer solution was prepared. The content ratio of hexafluoropropylene units in P (HFP-VDF) was 12 mol%. The obtained polymer solution was heated to 70 ° C. and then applied to the surface of the negative electrode active material layer 16 by dip coating. The coating film was naturally dried for 5 minutes and then heated to 80 ° C. and then vacuum-dried for 1 hour to form a lithium ion conductive resin film 18 as shown in FIG.

図１に示すように、リチウムイオン伝導性樹脂膜１８は、負極活物質層１６の短辺方向中央部にのみ形成し、短辺方向両端部には形成しなかった。リチウムイオン伝導性樹脂膜１８の幅は、負極活物質層１６の短辺の全幅に対して４０％とした。リチウムイオン伝導性樹脂膜１８の平均膜厚は２μｍであった。   As shown in FIG. 1, the lithium ion conductive resin film 18 was formed only at the central portion in the short side direction of the negative electrode active material layer 16 and was not formed at both ends in the short side direction. The width of the lithium ion conductive resin film 18 was 40% with respect to the entire width of the short side of the negative electrode active material layer 16. The average film thickness of the lithium ion conductive resin film 18 was 2 μm.

こうして得られた負極を裁断して、幅３４ｍｍ、全長３００ｍｍの帯状に成形した。負極の長辺方向の一端に、負極活物質層を取り除いて負極集電体を露出させた領域を設けて、この領域に負極リードを溶接した。   The negative electrode thus obtained was cut and formed into a strip shape having a width of 34 mm and a total length of 300 mm. A region where the negative electrode active material layer was removed to expose the negative electrode current collector was provided at one end in the long side direction of the negative electrode, and a negative electrode lead was welded to this region.

（２）正極の作製
コバルト酸リチウム粉末９３質量部と、アセチレンブラック４質量部とを混合した。得られた混合粉末と、ポリフッ化ビニリデン（ＰＶＤＦ）のＮ−メチル−２−ピロリドン（ＮＭＰ）溶液（呉羽化学工業（株）製、♯１３２０）とを、混合粉末とＰＶＤＦとの質量比が１００：３となるように加えた後、さらに適量のＮＭＰを加えて、正極合剤スラリーを調製した。得られたスラリーを、厚さ１５μｍのアルミニウム箔の両面にドクターブレード法によって塗布し、８５℃で乾燥させた後、全体の厚みが１６０μｍとなるように、ローラプレス機で圧延し、幅３２ｍｍ、全長２８０ｍｍの帯状に成形した。こうして得られた正極の長辺方向の一端に、正極活物質層を取り除いてアルミニウム箔を露出させた領域を設け、この領域に正極リードを溶接した。 (2) Production of positive electrode 93 parts by mass of lithium cobaltate powder and 4 parts by mass of acetylene black were mixed. The obtained mixed powder and an N-methyl-2-pyrrolidone (NMP) solution of polyvinylidene fluoride (PVDF) (# 1320, manufactured by Kureha Chemical Industry Co., Ltd.) were mixed at a mass ratio of 100 to 100%. : After adding so that it might be set to 3, an appropriate amount of NMP was further added and the positive mix slurry was prepared. The obtained slurry was applied to both sides of an aluminum foil having a thickness of 15 μm by a doctor blade method, dried at 85 ° C., and then rolled with a roller press so that the entire thickness was 160 μm. It was formed into a belt shape having a total length of 280 mm. A region where the positive electrode active material layer was removed and the aluminum foil was exposed was provided at one end in the long side direction of the positive electrode thus obtained, and a positive electrode lead was welded to this region.

（３）捲回型電極群の作製
セパレータとして、ポリエチレン微多孔膜（厚さ２０μｍ、商品名：ハイポア、旭化成（株）製）を使用した。２枚のセパレータと、正極と、負極とを、正極と負極との間にセパレータが介在するようにして、負極および正極の各長辺方向に捲回することにより、捲回型電極群を得た。 (3) Production of wound electrode group A polyethylene microporous membrane (thickness 20 μm, trade name: Hypore, manufactured by Asahi Kasei Co., Ltd.) was used as a separator. By winding the two separators, the positive electrode, and the negative electrode in the long side directions of the negative electrode and the positive electrode so that the separator is interposed between the positive electrode and the negative electrode, a wound electrode group is obtained. It was.

（４）非水電解液の調製
エチレンカーボネートと、ジメチルカーボネートと、エチルメチルカーボネートとの体積比１：１：１の混合溶媒に、１モル／リットルの濃度でＬｉＰＦ6を溶解させることにより、非水電解液を調製した。非水電解液には、ビニレンカーボネートを３質量％の割合で含有させた。 (4) Preparation of non-aqueous electrolyte solution By dissolving LiPF 6 at a concentration of 1 mol / liter in a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate in a volume ratio of 1: 1: 1, A water electrolyte was prepared. The non-aqueous electrolyte contained vinylene carbonate at a ratio of 3% by mass.

（５）リチウムイオン二次電池の作製
上述の捲回型電極群を用いて、リチウムイオン二次電池を組み立てた。電池ケースはアルミニウム製で、厚さ約８０μｍの底部および側壁を備え、上部が開口した角型の部材であった。電池ケース内に注入した非水電解液の量は２．５ｇであった。得られたリチウムイオン二次電池は、幅３４ｍｍ、高さ５０ｍｍ、厚さ４．５ｍｍの角型であった。電池の設計容量は８５０ｍＡｈであった。 (5) Production of Lithium Ion Secondary Battery A lithium ion secondary battery was assembled using the above wound electrode group. The battery case was a square member made of aluminum, having a bottom portion and a side wall with a thickness of about 80 μm and having an open top. The amount of non-aqueous electrolyte injected into the battery case was 2.5 g. The obtained lithium ion secondary battery was a square shape having a width of 34 mm, a height of 50 mm, and a thickness of 4.5 mm. The design capacity of the battery was 850 mAh.

（実施例２および３）
樹脂膜の短辺方向中央部の幅を、負極活物質層の短辺の全幅に対して２０％とするか（実施例２）、または５０％とした（実施例３）こと以外は、実施例１と同様にして負極およびリチウムイオン二次電池を作製した。 (Examples 2 and 3)
Implementation was performed except that the width of the central portion in the short side direction of the resin film was set to 20% (Example 2) or 50% (Example 3) with respect to the entire width of the short side of the negative electrode active material layer. In the same manner as in Example 1, a negative electrode and a lithium ion secondary battery were produced.

（実施例４および５）
ポリマー溶液の塗布量を変えることにより、樹脂膜の平均膜厚を０．１μｍとするか（実施例４）、または５μｍとした（実施例５）こと以外は、実施例１と同様にして負極およびリチウムイオン二次電池を作製した。 (Examples 4 and 5)
A negative electrode was formed in the same manner as in Example 1 except that the average film thickness of the resin film was changed to 0.1 μm (Example 4) or 5 μm (Example 5) by changing the coating amount of the polymer solution. And the lithium ion secondary battery was produced.

（実施例６）
ポリマー溶液の塗布量を変えることにより、樹脂膜の平均膜厚を８μｍとした（実施例６）こと以外は、実施例１と同様にして負極およびリチウムイオン二次電池を作製した。 (Example 6)
A negative electrode and a lithium ion secondary battery were produced in the same manner as in Example 1, except that the average film thickness of the resin film was changed to 8 μm by changing the coating amount of the polymer solution (Example 6).

（比較例１）
リチウムイオン伝導性樹脂膜を形成しないこと以外は、実施例１と同様にして負極およびリチウムイオン二次電池を作製した。 (Comparative Example 1)
A negative electrode and a lithium ion secondary battery were produced in the same manner as in Example 1 except that the lithium ion conductive resin film was not formed.

（比較例２および３）
樹脂膜の短辺方向中央部の幅を、負極活物質層の短辺の全幅に対して１０％とするか（比較例２）、または８０％とした（比較例３）こと以外は、実施例１と同様にして負極およびリチウムイオン二次電池を作製した。 (Comparative Examples 2 and 3)
Implementation was performed except that the width of the central portion in the short side direction of the resin film was set to 10% (Comparative Example 2) or 80% (Comparative Example 3) with respect to the entire short side width of the negative electrode active material layer. In the same manner as in Example 1, a negative electrode and a lithium ion secondary battery were produced.

＜リチウムイオン二次電池の評価＞
実施例１〜６および比較例１〜３で得られたリチウムイオン二次電池について、サイクル特性を評価し、負極活物質層の膨れ量を測定した。 <Evaluation of lithium ion secondary battery>
About the lithium ion secondary battery obtained in Examples 1-6 and Comparative Examples 1-3, cycling characteristics were evaluated and the swelling amount of the negative electrode active material layer was measured.

（１）サイクル特性
上述のリチウムイオン二次電池について、２０℃環境下で、以下の条件で、充放電を３００サイクル繰り返した。１サイクル目の放電容量に対する３００サイクル目の放電容量の割合（容量維持率）を百分率で求めた。
サイクル試験条件
定電流充電：充電電流値５９５ｍＡ、充電終止電圧４．２Ｖ
定電圧充電：充電電圧値４．２Ｖ、充電終止電流４２．５ｍＡ
定電流放電：放電電流値８５０ｍＡ、放電終止電圧２．５Ｖ (1) Cycle characteristics About the above-mentioned lithium ion secondary battery, charging / discharging was repeated 300 cycles on the following conditions in 20 degreeC environment. The ratio (capacity maintenance ratio) of the discharge capacity at the 300th cycle to the discharge capacity at the first cycle was obtained as a percentage.
Cycle test conditions Constant current charging: Charging current value 595 mA, end-of-charge voltage 4.2 V
Constant voltage charging: Charging voltage value 4.2V, charging end current 42.5mA
Constant current discharge: discharge current value 850 mA, discharge end voltage 2.5 V

（２）電池の膨れの評価
３００サイクル目の充電を行った電池を分解して、負極活物質層の短辺方向中央部と端部の断面を走査型電子顕微鏡（ＳＥＭ）で観察した。断面のＳＥＭ画像に基づいて、リチウムイオン伝導性樹脂膜を除いた負極の厚み（負極集電体と、負極集電体の両面に形成された負極活物質層との厚みの合計）を求めた。こうして得られた負極の厚みと、負極活物質層の形成時に求めた負極の厚みとから、２０℃での充放電サイクル経過後の負極の厚みの変化（膨れ）量［ｍｍ］を求めた。
以上の結果を表１に示す。 (2) Evaluation of battery swelling The battery charged at the 300th cycle was disassembled, and the cross section of the central part and the end part in the short side direction of the negative electrode active material layer was observed with a scanning electron microscope (SEM). Based on the SEM image of the cross section, the thickness of the negative electrode excluding the lithium ion conductive resin film (the total thickness of the negative electrode current collector and the negative electrode active material layer formed on both surfaces of the negative electrode current collector) was determined. . From the thickness of the negative electrode thus obtained and the thickness of the negative electrode obtained when the negative electrode active material layer was formed, the amount of change (swell) [mm] in the thickness of the negative electrode after the charge / discharge cycle at 20 ° C. was determined.
The results are shown in Table 1.

Figure 2012169071
Figure 2012169071

負極活物質層の短辺方向中央部のみにリチウムイオン伝導性樹脂膜を形成した実施例１〜６によれば、充放電を３００サイクル繰り返しても、短辺方向の中央部における負極活物質層の厚みの増加を抑制できた。なかでも、リチウムイオン伝導性樹脂膜の厚みが０．１〜５μｍである実施例１〜５は、充放電３００サイクル経過後の容量維持率が特に良好であった。一方、比較例１のように、リチウムイオン伝導性樹脂膜を形成しない場合は、短辺方向の中央部における負極活物質層の厚みの増加を抑制できなかった。   According to Examples 1 to 6 in which the lithium ion conductive resin film was formed only in the central part in the short side direction of the negative electrode active material layer, the negative electrode active material layer in the central part in the short side direction even when charging and discharging were repeated 300 cycles It was possible to suppress the increase in thickness. Especially, Examples 1-5 whose thickness of a lithium ion conductive resin film is 0.1-5 micrometers were especially favorable in the capacity | capacitance maintenance factor after 300 cycles of charging / discharging. On the other hand, as in Comparative Example 1, when the lithium ion conductive resin film was not formed, an increase in the thickness of the negative electrode active material layer at the central portion in the short side direction could not be suppressed.

また、負極活物質層の短辺方向中央部において、リチウムイオン伝導性樹脂膜の形成領域が狭すぎる比較例２では、負極活物質層の電極反応が中央部において過剰に進行するのを十分に抑制することができなかった。このため、中央部における負極活物質層の厚みの増加を抑制できず、サイクル特性も低下した。負極活物質層の短辺方向中央部においてリチウムイオン伝導性樹脂膜の形成領域が広すぎる比較例３では、負極活物質層における電極反応が過剰に抑制されたため、両端部における電極反応が相対的に過剰に進行した。その結果、両端部において負極活物質層の厚みが増加し、サイクル特性も低下した。   Further, in Comparative Example 2 in which the formation region of the lithium ion conductive resin film is too narrow in the central portion in the short side direction of the negative electrode active material layer, it is sufficient that the electrode reaction of the negative electrode active material layer proceeds excessively in the central portion. Could not be suppressed. For this reason, the increase in the thickness of the negative electrode active material layer in the central portion could not be suppressed, and the cycle characteristics also deteriorated. In Comparative Example 3 in which the formation region of the lithium ion conductive resin film is too wide in the short side direction central portion of the negative electrode active material layer, the electrode reaction in the negative electrode active material layer was excessively suppressed, and therefore the electrode reactions at both ends were relatively Too much progress. As a result, the thickness of the negative electrode active material layer increased at both ends, and the cycle characteristics also decreased.

本発明のリチウムイオン二次電池は、例えば、携帯電話、ＰＤＡ、ノート型パーソナルコンピュータ、デジタルカメラ、携帯ゲーム機などの携帯型電子機器の電源として有用である。また、ハイブリッド自動車などの車載用電源、無停電電源などの用途にも応用することができる。   The lithium ion secondary battery of the present invention is useful as a power source for portable electronic devices such as mobile phones, PDAs, notebook personal computers, digital cameras, and portable game machines. Moreover, it is applicable also to uses, such as a vehicle-mounted power supply and uninterruptible power supplies, such as a hybrid vehicle.

１０ 捲回型電極群、 １１ 負極、 １２ 正極、 １３（１３ａ、１３ｂ） セパレータ、 １４ 長辺方向、 １５ 負極集電体、 １６ 負極活物質層、 １７ 柱状体、 １８ リチウムイオン伝導性樹脂膜、 １９ 凸部、 ２０ 短辺方向、 ２１ 正極集電体、 ２２ 正極活物質層、 ３０ リチウムイオン二次電池、 ３１ 電池ケース、 ３２ 封口板、 ３３ 正極リード、 ３４ 正極端子、 ３５ 負極リード、 ３６ 正極側絶縁板、 ３７ 負極側絶縁板、 ４０ 蒸着装置、 ４１ 真空容器、 ４２ 巻出しロール、 ４３ 搬送ロール、 ４４ａ 成膜ロール、 ４４ｂ 成膜ロール、 ４５ 巻取りロール、 ４６ａ 第１のマスク、 ４６ｂ 第２のマスク、 ４６ｃ 第２のマスク、 ４７ａ 蒸着ソース、 ４７ｂ 蒸着ソース、 ４８ａ 酸素ノズル、 ４８ｂ 酸素ノズル、 ４９ 真空ポンプ   10 wound electrode group, 11 negative electrode, 12 positive electrode, 13 (13a, 13b) separator, 14 long side direction, 15 negative electrode current collector, 16 negative electrode active material layer, 17 columnar body, 18 lithium ion conductive resin film, 19 convex part, 20 short side direction, 21 positive electrode current collector, 22 positive electrode active material layer, 30 lithium ion secondary battery, 31 battery case, 32 sealing plate, 33 positive electrode lead, 34 positive electrode terminal, 35 negative electrode lead, 36 positive electrode Side insulating plate, 37 negative electrode side insulating plate, 40 vapor deposition apparatus, 41 vacuum vessel, 42 unwinding roll, 43 transport roll, 44a film forming roll, 44b film forming roll, 45 take-up roll, 46a first mask, 46b first mask 2 mask, 46c second mask, 47a deposition source, 47b deposition source, 48a Oxygen nozzle, 48b oxygen nozzle, 49 vacuum pump

Claims (3)

帯状の負極、帯状の正極、および帯状のセパレータを含み、前記負極および前記正極の間に前記セパレータが介在するように前記負極および前記正極の各長辺方向に沿って捲回された電極群と、非水電解液と、を備え、
前記負極は、帯状の負極集電体と、前記負極集電体の表面に支持された合金系活物質からなる負極活物質層と、前記負極活物質層の表面に被着形成されたリチウムイオン伝導性樹脂膜と、を備え、
前記リチウムイオン伝導性樹脂膜は、前記負極活物質層の長辺方向に沿って帯状に形成され、かつ、前記負極活物質層の短辺方向中央部にのみ形成されており、
前記短辺方向中央部の幅は、前記負極活物質層の短辺の全幅に対して２０〜５０％であることを特徴とするリチウムイオン二次電池。 An electrode group that includes a strip-shaped negative electrode, a strip-shaped positive electrode, and a strip-shaped separator, and is wound along each long side direction of the negative electrode and the positive electrode so that the separator is interposed between the negative electrode and the positive electrode; A non-aqueous electrolyte, and
The negative electrode includes a strip-shaped negative electrode current collector, a negative electrode active material layer made of an alloy-based active material supported on the surface of the negative electrode current collector, and lithium ions deposited on the surface of the negative electrode active material layer A conductive resin film,
The lithium ion conductive resin film is formed in a strip shape along the long side direction of the negative electrode active material layer, and is formed only in the center part in the short side direction of the negative electrode active material layer,
The lithium ion secondary battery, wherein a width of the central portion in the short side direction is 20 to 50% with respect to a full width of the short side of the negative electrode active material layer. 前記リチウムイオン伝導性樹脂膜が、ヘキサフルオロプロピレン単位を３〜２０モル％の割合で含有するヘキサフルオロプロピレン−フッ化ビニリデン共重合体、およびヘキサフルオロプロピレン単位を３〜２０モル％の割合で含有するヘキサフルオロプロピレン−テトラフルオロエチレン共重合体の少なくとも１種の樹脂を含む請求項１に記載のリチウムイオン二次電池。   The lithium ion conductive resin film contains a hexafluoropropylene-vinylidene fluoride copolymer containing a hexafluoropropylene unit in a proportion of 3 to 20 mol%, and a hexafluoropropylene unit in a proportion of 3 to 20 mol%. The lithium ion secondary battery according to claim 1, comprising at least one resin of hexafluoropropylene-tetrafluoroethylene copolymer. 前記リチウムイオン伝導性樹脂膜の平均膜厚が０．１〜５μｍである請求項１または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 or 2, wherein an average film thickness of the lithium ion conductive resin film is 0.1 to 5 µm.
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