JP2005108521A - Thin film electrode, manufacturing method of the same, and lithium secondary battery using the thin film electrode - Google Patents

Thin film electrode, manufacturing method of the same, and lithium secondary battery using the thin film electrode Download PDF

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JP2005108521A
JP2005108521A JP2003337893A JP2003337893A JP2005108521A JP 2005108521 A JP2005108521 A JP 2005108521A JP 2003337893 A JP2003337893 A JP 2003337893A JP 2003337893 A JP2003337893 A JP 2003337893A JP 2005108521 A JP2005108521 A JP 2005108521A
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thin film
current collector
film electrode
lithium
electrode
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Tokuji Ueda
上田　　篤司
Shigeo Aoyama
青山　　茂夫
Hiroshi Sugiyama
拓 杉山
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Maxell Holdings Ltd
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Hitachi Maxell Ltd
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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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    • Y02E60/10—Energy storage using batteries

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium secondary battery with a large capacity and a high cycle property of which the swelling of an electrode, the wrinkling of a current collector, and the generation of a crack inside an activator thin film are restrained by restraining the influence of the volume change of the activator thin film to the minimum. <P>SOLUTION: The thin film electrode is composed of the current collector 11 made of a metal not alloyed with lithium, and the thin film 12 formed on the current collector containing an element alloyed with lithium, wherein the thin film 12 has convex parts 14 with heights H1 of 2 μm or higher and 20 μm or lower, and a recess part 15. The manufacturing method of the thin film electrode comprises a process of forming the thin film 12 containing an element alloyed with lithium on the surface of the current collector 11 made of a metal not alloyed with lithium, and a process of forming irregularity on the surface of the thin film 12 by pressing the thin film 12 by a metal mesh 13 as an indentation forming member. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

本発明は、薄膜電極とその製造方法およびその薄膜電極を用いたリチウム二次電池に関するものである。   The present invention relates to a thin film electrode, a manufacturing method thereof, and a lithium secondary battery using the thin film electrode.

近年、携帯電話、ノートパソコン、ＰＤＡなどの携帯端末機器の需要が急激に拡大しており、これらの機器の小型軽量化および高機能化に伴って、それらの電源として主として用いられるリチウム二次電池のさらなる高エネルギー密度化が要求されている。しかし、現在実用化されているリチウム二次電池に用いられる炭素系負極の電気容量は理論値に近い値にまで到達しており、より高容量なリチウム二次電池を実現するためには負極材料の新規開発が必須である。   In recent years, the demand for portable terminal devices such as mobile phones, notebook computers, PDAs and the like has increased rapidly. As these devices become smaller and lighter and have higher functionality, lithium secondary batteries mainly used as their power source Therefore, higher energy density is required. However, the electric capacity of the carbon-based negative electrode used in lithium secondary batteries currently in practical use has reached a value close to the theoretical value, and in order to realize a higher capacity lithium secondary battery, negative electrode material New development is essential.

このような中で最近では、高容量リチウム二次電池用の新たな負極材料として、Ｌｉと合金化しない材料からなる集電体上に、Ｌｉと合金化するＳｎまたはＳｎ含有合金からなる薄膜を形成し、その薄膜を負極材料として用いる薄膜電極が注目されている（例えば、特許文献１、特許文献２参照。）。特許文献１は、集電体である銅板上に、電解めっき法によりＳｎ薄膜を形成するものであり、特許文献２は、電解めっき法により、銅箔上にＳｎ、Ｚｎ、Ｓｂ、またはそれらを含有する合金を素材とする薄膜を形成するものである。   Recently, as a new negative electrode material for a high capacity lithium secondary battery, a thin film made of Sn or an alloy containing Sn alloyed with Li is formed on a current collector made of a material not alloyed with Li. A thin film electrode that is formed and uses the thin film as a negative electrode material has attracted attention (see, for example, Patent Document 1 and Patent Document 2). Patent Document 1 is to form a Sn thin film on a copper plate, which is a current collector, by electrolytic plating, and Patent Document 2 is Sn, Zn, Sb, or them on a copper foil by electrolytic plating. A thin film is formed using the contained alloy as a raw material.

Ｌｉと合金化する金属の中でも、特にＳｎは従来の黒鉛系負極材料と比較して高いエネルギー密度（９９４ｍＡｈ／ｇ）を有するため、次世代の負極材料として注目されている。しかし、実際の薄膜電極にＳｎを用いた場合は、ＬｉxＳｎの組成式でｘ＝４．４までＬｉを電気化学的に挿入すると、薄膜の体積が３〜４倍にまで膨張してしまう。かかる体積膨張はリチウム二次電池の充放電特性（サイクル特性）の低下を招くことになる。さらに、Ｓｎを単独で用いると、Ｓｎ自身が触媒能を持つために電解液を分解してしまうという問題もある。 Among metals that alloy with Li, Sn, in particular, has attracted attention as a next-generation negative electrode material because it has a higher energy density (994 mAh / g) than conventional graphite negative electrode materials. However, when Sn is used for an actual thin film electrode, when Li is electrochemically inserted up to x = 4.4 in the Li x Sn composition formula, the volume of the thin film expands to 3 to 4 times. . Such volume expansion causes a decrease in charge / discharge characteristics (cycle characteristics) of the lithium secondary battery. Further, when Sn is used alone, there is a problem that the electrolytic solution is decomposed because Sn itself has catalytic ability.

上記問題を解決するために、Ｓｎ系の合金薄膜が提案されている（例えば、非特許文献１参照。）。非特許文献１には、電解めっき法によりＣｕ箔上に形成されたＳｎ薄膜を、Ｓｎの融点付近で熱処理することで、Ｃｕ−Ｓｎ界面でＣｕ原子とＳｎ原子とが相互拡散した傾斜性構造の薄膜を得ることができると記載されている。即ち、Ｃｕ箔上にＳｎをめっきすることで形成した薄膜をＳｎの融点付近で長時間熱処理するとＣｕ−Ｓｎ界面で原子の相互拡散が起こり、最終的にＣｕ／Ｃｕ3Ｓｎ／Ｃｕ6Ｓｎ5／Ｓｎもしくはこの組成に近い結晶構造を有するＣｕ−Ｓｎ合金が形成される。このとき形成されるＣｕ6Ｓｎ5合金はＬｉを可逆的に吸蔵・脱離可能であり、体積変化もＳｎと比較して小さく、加えて触媒能を持たないため、前述のＳｎ薄膜特有の問題を解決できる負極材料として期待されている。
特開２００１−６８０９４号公報 特開２００１−２５６９６８号公報 Ｊｏｕｒｎａｌ ｏｆ Ｐｏｗｅｒ Ｓｏｕｒｃｅｓ， １０７（２００２），ｐ．４８−５５ In order to solve the above problem, an Sn-based alloy thin film has been proposed (for example, see Non-Patent Document 1). Non-Patent Document 1 discloses a graded structure in which Cu atoms and Sn atoms are interdiffused at the Cu-Sn interface by heat-treating a Sn thin film formed on a Cu foil by an electrolytic plating method in the vicinity of the melting point of Sn. It is described that a thin film can be obtained. That is, when a thin film formed by plating Sn on Cu foil is heat-treated for a long time in the vicinity of the melting point of Sn, mutual diffusion of atoms occurs at the Cu-Sn interface, and finally Cu / Cu 3 Sn / Cu 6 Sn 5 is formed. Cu-Sn alloy having a crystal structure close to / Sn or this composition is formed. The Cu 6 Sn 5 alloy formed at this time can absorb and desorb Li reversibly, and its volume change is smaller than that of Sn. In addition, it has no catalytic ability. It is expected as a negative electrode material that can solve this problem.
JP 2001-68094 A JP 2001-256968 A Journal of Power Sources, 107 (2002), p. 48-55

上記電解めっき法により薄膜電極を形成すると、集電箔（集電体）と活物質層とがより強固に一体化する。そのため、充放電に伴う活物質の微粉化などが発生しても集電箔から活物質が脱落しにくく、サイクル特性が向上するといった利点もある。   When the thin film electrode is formed by the electrolytic plating method, the current collector foil (current collector) and the active material layer are more firmly integrated. Therefore, even if the active material is pulverized due to charging / discharging, there is an advantage that the active material is not easily dropped from the current collector foil, and the cycle characteristics are improved.

しかし、集電箔と活物質との密着性が高くなると、Ｌｉの挿入・脱離に伴う活物質薄膜の体積変化の影響を電極自体が受けやすくなるため、電極の膨張、集電箔の皺寄れおよび活物質薄膜内部のクラックの発生が顕著に現れる。その結果、電極内の電子伝導性が低下するため、サイクル特性が低下することになる。   However, if the adhesion between the current collector foil and the active material is increased, the electrode itself is more susceptible to the volume change of the active material thin film due to the insertion / desorption of Li. The occurrence of cracks and cracks in the active material thin film appears remarkably. As a result, since the electron conductivity in the electrode is lowered, the cycle characteristics are lowered.

本発明は、リチウムと合金化しない金属から形成された集電体と、前記集電体の表面に形成され、リチウムと合金化する元素を含む薄膜とを備えた薄膜電極であって、前記薄膜が、凸部および凹部を備え、前記凸部の高さが、２μｍ以上２０μｍ以下であることを特徴とする薄膜電極を提供する。   The present invention is a thin film electrode comprising a current collector formed of a metal that does not alloy with lithium, and a thin film formed on the surface of the current collector and containing an element that is alloyed with lithium, the thin film electrode However, the present invention provides a thin film electrode comprising a convex portion and a concave portion, wherein the height of the convex portion is 2 μm or more and 20 μm or less.

また、本発明は、リチウムと合金化しない金属からなる集電体の表面に、リチウムと合金化する元素を含む薄膜を形成する工程と、前記薄膜を凹凸形成部材で加圧することにより、前記薄膜の表面に凹凸を形成する工程とを含むことを特徴とする薄膜電極の製造方法を提供する。   The present invention also includes a step of forming a thin film containing an element alloying with lithium on the surface of a current collector made of a metal that does not alloy with lithium, and pressurizing the thin film with a concavo-convex forming member, whereby the thin film And a process for forming irregularities on the surface of the thin film electrode.

また、本発明は、上記薄膜電極を負極として用いたことを特徴とするリチウム二次電池を提供する。   The present invention also provides a lithium secondary battery using the thin film electrode as a negative electrode.

本発明の薄膜電極は、集電体の表面に形成された活物質薄膜に凹凸を形成することにより、Ｌｉの挿入・脱離に伴う活物質薄膜の体積変化によって発生した応力を多方向に分散させることができるため、応力の集中による電極の膨張、集電体の皺寄れおよび活物質薄膜内部のクラックの発生などを抑制することができる。さらに、上記凹凸によって生まれる空隙が活物質薄膜の体積変化を吸収できるため、Ｌｉの挿入・脱離に伴う薄膜電極の厚み変化をさらに緩和することができる。   The thin film electrode of the present invention disperses the stress generated by the volume change of the active material thin film accompanying the insertion / desorption of Li in multiple directions by forming irregularities on the active material thin film formed on the surface of the current collector. Therefore, it is possible to suppress the expansion of the electrode due to the concentration of stress, the stagnation of the current collector, the generation of cracks in the active material thin film, and the like. Furthermore, since the voids created by the irregularities can absorb the volume change of the active material thin film, the thickness change of the thin film electrode accompanying the insertion / desorption of Li can be further alleviated.

また、本発明の薄膜電極の製造方法は、上記薄膜電極を簡易かつ効率的に製造できる。   Moreover, the manufacturing method of the thin film electrode of this invention can manufacture the said thin film electrode simply and efficiently.

また、本発明のリチウム二次電池は、上記薄膜電極を負極に用いることにより、電池容量およびサイクル特性の向上を図ることができる。   Moreover, the lithium secondary battery of this invention can aim at the improvement of battery capacity and cycling characteristics by using the said thin film electrode for a negative electrode.

先ず、本発明の薄膜電極の実施の形態を説明する。本発明の薄膜電極の一例は、Ｌｉと合金化しない金属から形成された集電体と、上記集電体の表面に形成され、Ｌｉと合金化する元素を含む薄膜とを備えている。また、上記薄膜は凸部および凹部を備え、上記凸部の高さは２μｍ以上２０μｍ以下であることを特徴とする。   First, an embodiment of the thin film electrode of the present invention will be described. An example of the thin film electrode of the present invention includes a current collector formed of a metal that is not alloyed with Li, and a thin film that is formed on the surface of the current collector and contains an element that is alloyed with Li. The thin film includes a convex portion and a concave portion, and the height of the convex portion is 2 μm or more and 20 μm or less.

上記薄膜の凸部の高さが２０μｍを超えると、充放電時の薄膜構造の維持が困難となり、充放電に伴い上記凸部が微粉化するおそれがある。一方、上記凸部の高さが２μｍを下回ると、活物質薄膜の体積変化によって発生した応力を吸収できなくなる。   When the height of the convex portion of the thin film exceeds 20 μm, it is difficult to maintain the thin film structure during charge / discharge, and the convex portion may be pulverized with charge / discharge. On the other hand, when the height of the convex portion is less than 2 μm, it becomes impossible to absorb the stress generated by the volume change of the active material thin film.

上記集電体の材質としては、Ｌｉと合金化しない金属から形成されていることが必要であり、例えば、Ｎｉ、Ｃｕ、ステンレス鋼、Ｎｉ合金、Ｃｕ合金などが好ましい。Ｌｉと合金化する金属であると、電池に組み込んだ場合に活物質層より先にＬｉと反応してしまい、集電体として機能しなくなるからである。なお、ＮｉおよびＣｕと合金化する元素としては、例えば、Ｓｉ、Ｆｅ、Ｃｕ、Ｎｉ、Ｓｎ、Ｚｎ、Ｉｎ、Ｓｂ、Ｚｒなどが挙げられ、集電体の特性を損なわない範囲で合金化することができる。   The material of the current collector needs to be formed from a metal that is not alloyed with Li, and is preferably Ni, Cu, stainless steel, Ni alloy, Cu alloy, or the like. This is because when the metal is alloyed with Li, it reacts with Li prior to the active material layer when incorporated in a battery and does not function as a current collector. Examples of elements that alloy with Ni and Cu include, for example, Si, Fe, Cu, Ni, Sn, Zn, In, Sb, and Zr. Alloying is performed within a range that does not impair the characteristics of the current collector. be able to.

上記Ｌｉと合金化する元素としては、Ａｌ、Ｓｉ、Ｓｎ、Ｐｂ、Ｇｅ、Ｓｂなどが使用でき、特にＳｉおよびＳｎから選ばれる少なくとも一つの元素であることが好ましい。これらは、Ｌｉの挿入・脱離における可逆性が高いからである。   As the element to be alloyed with Li, Al, Si, Sn, Pb, Ge, Sb and the like can be used, and at least one element selected from Si and Sn is particularly preferable. This is because reversibility in insertion / extraction of Li is high.

上記集電体の表面に垂直投影した上記凸部または上記凹部の投影部の形状は、円形、三角形、四角形、および六角形から選ばれる少なくとも一つの形状であることが好ましく、これらの形状を複数用いてもよい。これらの形状は、薄膜の表面方向の膨張を吸収しやすいからである。また、上記凸部および凹部は、薄膜の全面に形成することが好ましい。   Preferably, the shape of the projection or projection of the recess vertically projected onto the surface of the current collector is at least one shape selected from a circle, a triangle, a quadrangle, and a hexagon. It may be used. This is because these shapes easily absorb expansion in the surface direction of the thin film. Moreover, it is preferable that the said convex part and a recessed part are formed in the whole surface of a thin film.

上記集電体の表面に垂直投影した上記凸部の投影部の総面積は、上記薄膜が形成された上記集電体の総面積の４０％以上８０％以下であることが好ましい。この範囲内であれば、Ｌｉの挿入・脱離に伴う活物質薄膜の体積変化によって発生した応力をより多方向に分散させることができるからである。   It is preferable that the total area of the projected portion of the convex portion projected perpendicularly on the surface of the current collector is 40% to 80% of the total area of the current collector on which the thin film is formed. This is because the stress generated by the volume change of the active material thin film accompanying the insertion / desorption of Li can be dispersed in more directions within this range.

ここで、上記集電体の表面に垂直投影した上記凸部の投影部の総面積の、上記薄膜が形成された上記集電体の総面積に対する割合を、凸部の面積占有率ｘ（％）とし、凹凸加工前の薄膜の厚みをｔ（μｍ）とすると、加工できる凸部の高さＴ（μｍ）は、ｔ（１００／ｘ）以下となる。   Here, the ratio of the total area of the projections of the projection vertically projected onto the surface of the current collector to the total area of the current collector on which the thin film is formed is expressed as the area occupancy x (% ), And the thickness of the thin film before uneven processing is t (μm), the height T (μm) of the convex portion that can be processed is t (100 / x) or less.

上記集電体の厚みは、５μｍ以上３０μｍ以下であることが好ましく、１０μｍ以上２０μｍ以下がより好ましい。この範囲内であれば、上記薄膜電極を作製する上で、集電体自体の強度と柔軟性をともに確保できるからである。   The thickness of the current collector is preferably 5 μm or more and 30 μm or less, and more preferably 10 μm or more and 20 μm or less. This is because within this range, both the strength and flexibility of the current collector itself can be secured in producing the thin film electrode.

また、上記薄膜の主成分としては、Ｃｕ6Ｓｎ5、Ｃｕ2Ｓｂ、Ｂを添加させたＳｉ、Ｎｉ3Ｓｎ4、ＭｎＳｂ、Ｍｎ2Ｓｂ、ＣｏＳｂ、Ｃｏ2Ｓｂ、Ｚｎ4Ｓｂ3などを採用できるが、Ｃｕ6Ｓｎ5、Ｂを添加させたＳｉおよびＮｉ3Ｓｎ4から選ばれるいずれか一つであることが好ましい。これらは、Ｌｉを可逆的に吸蔵・脱離可能であり、体積変化もＳｎ、Ｓｉの単体に比べて小さいからである。ここで、主成分とは、薄膜全体の重量に対して５０重量％以上含まれていることをいう。 Further, as the main component of the thin film, Si, Ni 3 Sn 4 , MnSb, Mn 2 Sb, CoSb, Co 2 Sb, Zn 4 Sb 3 and the like to which Cu 6 Sn 5 , Cu 2 Sb, and B are added are adopted. Although it is possible, it is preferably any one selected from Cu 6 Sn 5 , Si to which B is added, and Ni 3 Sn 4 . This is because Li can be reversibly occluded / desorbed and the volume change is smaller than that of Sn and Si alone. Here, the main component means that it is contained by 50% by weight or more with respect to the weight of the entire thin film.

次に、本発明の薄膜電極の製造方法の実施形態を図面に基づき説明する。   Next, an embodiment of a method for producing a thin film electrode of the present invention will be described with reference to the drawings.

（実施形態１）
図１は、本発明の薄膜電極の製造方法の一例を示す工程図である。先ず、図１（ａ）に示すように、Ｌｉと合金化しない金属からなる集電体１１の表面に、Ｌｉと合金化する元素を含む薄膜１２を形成する。 (Embodiment 1)
FIG. 1 is a process diagram showing an example of a method for producing a thin film electrode of the present invention. First, as shown in FIG. 1A, a thin film 12 containing an element alloying with Li is formed on the surface of a current collector 11 made of a metal that does not alloy with Li.

薄膜１２と集電体１１とは密着して形成することが望ましく、その薄膜の形成方法としては、例えば、物理的気相成長法（ＰＶＤ法）、化学的気相成長法（ＣＶＤ法）、液相成長法などが挙げられる。物理的気相成長法としては真空蒸着法、スパッタリング法、イオンプレーティング法、分子線エピタクシー法（ＭＢＥ法）、レーザーアブレーション法など、化学的気相成長法としては熱ＣＶＤ法、有機金属ＣＶＤ法（ＭＯＣＶＤ法）、ＲＦプラズマＣＶＤ法、電子サイクロン（ＥＣＲ）プラズマＣＶＤ法、光ＣＶＤ法、レーザーＣＶＤ法、原子層エピタクシー法（ＡＬＥ法）など、液相成長法としてはめっき法（電解めっき法、無電解めっき法）、陽極酸化法、塗布法、ゾル−ゲル法などが挙げられる。これらの中でも、液相成長法は比較的簡易な設備で実施可能であるため望ましく、特に電解めっき法は集電体表面への密着性が良く、めっき薄膜表面の平滑性も高く、さらに大面積での成膜が容易かつ安価に行えるためより好ましい。なお、これらの薄膜形成方法は、単独で用いても複数を組み合わせて用いてもよい。   The thin film 12 and the current collector 11 are preferably formed in close contact with each other. Examples of the method for forming the thin film include physical vapor deposition (PVD), chemical vapor deposition (CVD), Examples include liquid phase growth. Physical vapor deposition methods include vacuum evaporation, sputtering, ion plating, molecular beam epitaxy (MBE), laser ablation, and other chemical vapor deposition methods include thermal CVD and organometallic CVD. As a liquid phase growth method, a plating method (electroplating) such as a method (MOCVD method), an RF plasma CVD method, an electron cyclone (ECR) plasma CVD method, a photo CVD method, a laser CVD method, an atomic layer epitaxy method (ALE method), etc. Method, electroless plating method), anodic oxidation method, coating method, sol-gel method and the like. Among these, the liquid phase growth method is desirable because it can be carried out with relatively simple equipment. In particular, the electrolytic plating method has good adhesion to the current collector surface, high smoothness of the plating thin film surface, and a large area. Is more preferable because it can be easily and inexpensively formed. Note that these thin film forming methods may be used alone or in combination.

次に、図１（ｂ）に示すように、薄膜１２の上部に凹凸形成部材として金属メッシュ１３を配置した後、図１（ｃ）に示すように、薄膜１２を金属メッシュ１３で加圧する。その後、図１（ｄ）に示すように、金属メッシュ１３を除去し、薄膜１２の表面に凸部１４と凹部１５とを形成する。   Next, as shown in FIG. 1B, a metal mesh 13 is disposed as an unevenness forming member on the thin film 12, and then the thin film 12 is pressed with the metal mesh 13 as shown in FIG. Thereafter, as shown in FIG. 1 (d), the metal mesh 13 is removed, and convex portions 14 and concave portions 15 are formed on the surface of the thin film 12.

ここで、凹凸形成部材としては、例えば、図１（ｂ）に示したような凸部１４に対応した開口部１３ａを有する金属メッシュ１３を使用できるが、金属メッシュ１３の材質としては、薄膜１２の材質よりも硬度が大きい金属材料を使用する必要がある。具体的には、例えば、薄膜１２の主成分がＳｎの場合には、凹凸形成部材としてはステンレス鋼製のメッシュが適している。また、金属メッシュ１３の開口部１３ａの形状、大きさを変更することにより、凸部１４の形状、大きさ、前述の面積占有率ｘなどを容易に制御することができる。   Here, as the unevenness forming member, for example, a metal mesh 13 having an opening 13a corresponding to the convex portion 14 as shown in FIG. 1B can be used. It is necessary to use a metal material having a hardness higher than that of the material. Specifically, for example, when the main component of the thin film 12 is Sn, a stainless steel mesh is suitable as the unevenness forming member. Further, by changing the shape and size of the opening 13a of the metal mesh 13, the shape and size of the convex portion 14, the above-described area occupation ratio x, and the like can be easily controlled.

その後、図１（ｅ）に示すように、薄膜１２を形成した集電体１１を、真空、不活性雰囲気、または還元性雰囲気の下で１５０〜２３０℃程度の温度で加熱する。これにより、薄膜１２と集電体１１は完全に密着し、本実施形態の薄膜電極１６が完成する。   Thereafter, as shown in FIG. 1E, the current collector 11 on which the thin film 12 has been formed is heated at a temperature of about 150 to 230 ° C. in a vacuum, an inert atmosphere, or a reducing atmosphere. As a result, the thin film 12 and the current collector 11 are completely adhered to each other, and the thin film electrode 16 of the present embodiment is completed.

なお、凸部１４の高さＨ１は、２〜２０μｍの範囲に設定されている。   In addition, height H1 of the convex part 14 is set to the range of 2-20 micrometers.

（実施形態２）
図２は、本発明の薄膜電極の製造方法の他の一例を示す工程図である。先ず、図２（ａ）に示すように、図１（ａ）と同様にしてＬｉと合金化しない金属からなる集電体２１の表面に、Ｌｉと合金化する元素を含む薄膜２２を形成する。 (Embodiment 2)
FIG. 2 is a process diagram showing another example of the method for manufacturing a thin film electrode of the present invention. First, as shown in FIG. 2 (a), a thin film 22 containing an element alloying with Li is formed on the surface of a current collector 21 made of a metal that does not alloy with Li, as in FIG. 1 (a). .

次に、図２（ｂ）に示すように、薄膜２２の上部に凹凸形成部材として、表面に突起２３ａを有する金属板２３を配置した後、図２（ｃ）に示すように、薄膜２２を金属板２３で加圧する。その後、図２（ｄ）に示すように、金属板２３を除去し、薄膜２２の表面に凸部２４と凹部２５とを形成する。   Next, as shown in FIG. 2 (b), a metal plate 23 having protrusions 23a on the surface is disposed as an unevenness forming member on the thin film 22, and then the thin film 22 is formed as shown in FIG. 2 (c). The metal plate 23 is pressurized. Thereafter, as shown in FIG. 2 (d), the metal plate 23 is removed, and convex portions 24 and concave portions 25 are formed on the surface of the thin film 22.

ここで、金属板２３の材質としては、薄膜２２の材質よりも硬度が大きい金属材料を使用する必要がある。具体的には、例えば、薄膜２２の主成分がＳｎの場合には、凹凸形成部材としてはステンレス鋼板が適している。また、金属板２３の突起２３ａの形状、大きさを変更することにより、凸部２４の形状、大きさ、前述の面積占有率ｘなどを容易に制御することができる。   Here, as the material of the metal plate 23, it is necessary to use a metal material having a hardness higher than that of the thin film 22. Specifically, for example, when the main component of the thin film 22 is Sn, a stainless steel plate is suitable as the unevenness forming member. Further, by changing the shape and size of the protrusion 23a of the metal plate 23, the shape and size of the convex portion 24, the above-described area occupation ratio x, and the like can be easily controlled.

その後、図２（ｅ）に示すように、薄膜２２を形成した集電体２１を、真空、不活性雰囲気、および還元性雰囲気の下で１５０〜２３０℃程度の温度で加熱する。これにより、薄膜２２と集電体２１は完全に密着し、本実施形態の薄膜電極２６が完成する。   Thereafter, as shown in FIG. 2E, the current collector 21 on which the thin film 22 is formed is heated at a temperature of about 150 to 230 ° C. under a vacuum, an inert atmosphere, and a reducing atmosphere. As a result, the thin film 22 and the current collector 21 are completely adhered to each other, and the thin film electrode 26 of the present embodiment is completed.

なお、凸部２４の高さＨ２は、２〜２０μｍの範囲に設定されている。   In addition, height H2 of the convex part 24 is set to the range of 2-20 micrometers.

上記実施形態１および実施形態２ではともに、上記Ｌｉと合金化する元素としては、Ａｌ、Ｓｉ、Ｓｎ、Ｐｂ、Ｇｅ、Ｓｂなどが使用でき、特にＳｎが好ましい。Ｓｎは、Ｌｉの挿入・脱離における可逆性が高いからである。また、上記薄膜の主成分としては、Ｃｕ6Ｓｎ5およびＮｉ3Ｓｎ4から選ばれるいずれか一つであることが好ましい。これらは、Ｌｉを可逆的に吸蔵・脱離可能であり、体積変化もＳｎの単体に比べて小さいからである。ここで、主成分とは、薄膜全体の重量に対して５０重量％以上含まれていることをいう。 In both Embodiment 1 and Embodiment 2, Al, Si, Sn, Pb, Ge, Sb and the like can be used as the element alloyed with Li, and Sn is particularly preferable. This is because Sn has high reversibility in Li insertion / extraction. The main component of the thin film is preferably any one selected from Cu 6 Sn 5 and Ni 3 Sn 4 . This is because Li can be reversibly occluded / desorbed and the volume change is smaller than that of Sn alone. Here, the main component means that it is contained by 50% by weight or more with respect to the weight of the entire thin film.

特に、上記実施形態１、実施形態２で、集電体１１、２１としてＣｕ箔を用い、その集電体１１、２１の表面に例えば厚み１５μｍ以下のＳｎ薄膜１２、２２を形成した場合、凸部１４、２４および凹部１５、２５を形成した後に、真空、不活性雰囲気、または還元性雰囲気の下で１５０〜２３０℃で加熱することにより、薄膜の主成分を、Ｌｉの可逆性に優れたＣｕ6Ｓｎ5合金とすることができる。 In particular, in Embodiments 1 and 2, when Cu foil is used as the current collectors 11 and 21, and the Sn thin films 12 and 22 having a thickness of, for example, 15 μm or less are formed on the surfaces of the current collectors 11 and 21, After forming the portions 14 and 24 and the recesses 15 and 25, the main component of the thin film is excellent in Li reversibility by heating at 150 to 230 ° C. in a vacuum, an inert atmosphere, or a reducing atmosphere. A Cu 6 Sn 5 alloy can be used.

なお、上記Ｃｕ6Ｓｎ5合金を効率よく形成するためには、上記Ｃｕ箔上に例えば厚さ５μｍ以下のＳｎ薄膜とＣｕ薄膜とを交互に所定層数を形成した後に、上記凹凸処理および上記加熱処理を行うことが好ましい。 In order to efficiently form the Cu 6 Sn 5 alloy, after the predetermined number of layers are alternately formed on the Cu foil, for example, a Sn thin film having a thickness of 5 μm or less and a Cu thin film are alternately formed, It is preferable to perform heat treatment.

続いて、本発明のリチウム二次電池の実施形態を説明する。本発明のリチウム二次電池の一例は、上記で説明した薄膜電極を負極として用いたリチウム二次電池である。充放電に伴う電極の膨張、集電体の皺寄れおよび活物質薄膜内部のクラックの発生などを抑制した薄膜電極を用いることにより、高容量でサイクル特性の高いリチウム二次電池を提供できる。   Subsequently, an embodiment of the lithium secondary battery of the present invention will be described. An example of the lithium secondary battery of the present invention is a lithium secondary battery using the thin film electrode described above as a negative electrode. By using a thin film electrode that suppresses expansion of the electrode, charging of the current collector, creeping of the current collector, and generation of cracks inside the active material thin film, a lithium secondary battery with high capacity and high cycle characteristics can be provided.

本実施形態のリチウム二次電池に用いる正極としては、正極活物質に導電助剤およびポリフッ化ビニリデンなどの結着剤などを適宜添加した合剤を、アルミニウム箔などの集電体を芯材として成形体に仕上げたものが用いられる。正極活物質としては、例えば、ＬｉＣｏＯ2などのリチウム・コバルト酸化物、ＬｉＭｎ2Ｏ4などのリチウム・マンガン酸化物、ＬｉＮｉＯ2などのリチウム・ニッケル酸化物、ＬｉＮｉＯ2のＮｉの一部をＣｏで置換したＬｉＮｉxＣｏ(1-x)Ｏ2、さらに、ＭｎとＮｉとを等量含んだＬｉＮｉ(1-x)/2Ｍｎ(1-x)/2ＣｏxＯ2、オリビン型ＬｉＭＰＯ4（Ｍ：Ｃｏ、Ｎｉ、Ｍｎ、Ｆｅ）を用いることができる。 As a positive electrode used in the lithium secondary battery of the present embodiment, a mixture in which a conductive additive and a binder such as polyvinylidene fluoride are appropriately added to the positive electrode active material, and a current collector such as an aluminum foil as a core material A finished product is used. As the positive electrode active material, for example, lithium cobalt oxide such as LiCoO 2, lithium-manganese oxide such as LiMn 2 O 4, lithium nickel oxides such as LiNiO 2, a part of Ni of LiNiO 2 with Co Substituted LiNi x Co (1-x) O 2 , LiNi (1-x) / 2 Mn (1-x) / 2 Co x O 2 containing equal amounts of Mn and Ni, olivine-type LiMPO 4 ( M: Co, Ni, Mn, Fe) can be used.

上記リチウム二次電池に用いる電解質の溶媒としては、例えば、１，２−ジメトキシエタン、１，２−ジエトキシエタン、プロピレンカーボネート、エチレンカーボネート、γ−ブチロラクトン、テトラヒドロフラン、１，３−ジオキソラン、ジエチルカーボネート、ジメチルカーボネート、エチルメチルカーボネートなどが挙げられ、これらは複数を同時に使用することもできる。また、この溶媒には必要に応じて他の成分を添加することも可能である。   Examples of the electrolyte solvent used in the lithium secondary battery include 1,2-dimethoxyethane, 1,2-diethoxyethane, propylene carbonate, ethylene carbonate, γ-butyrolactone, tetrahydrofuran, 1,3-dioxolane, and diethyl carbonate. , Dimethyl carbonate, ethyl methyl carbonate and the like, and a plurality of these may be used simultaneously. Moreover, it is also possible to add another component to this solvent as needed.

上記電解質の溶質としては、例えば、ＬｉＣｌＯ4、ＬｉＰＦ6、ＬｉＢＦ4、ＬｉＡｓＦ6、ＬｉＳｂＦ6、ＬｉＣＦ3ＳＯ3、ＬｉＣ4Ｆ9ＳＯ3、ＬｉＣＦ3ＣＯ2、Ｌｉ2Ｃ2Ｆ4（ＳＯ3）2、ＬｉＮ（ＣＦ3ＳＯ2）2、ＬｉＮ（ＣＦ3ＳＯ2）2、ＬｉＣnＦ2n+1ＳＯ3（ｎ≧２）、ＬｉＮ（ＲｆＯＳＯ2）2［ここで、Ｒｆはフルオロアルキル基を示す。］、ＬｉＮ（ＣＦ3ＳＯ2）（Ｃ4Ｆ9ＳＯ2）、ＬｉＮ（Ｃ2Ｆ5ＳＯ2）（Ｃ4Ｆ9ＳＯ2）、ＬｉＮ（ＣＦ3ＳＯ2）（Ｃ2Ｆ5ＳＯ2）などが挙げられる。 The solute of the electrolyte, for example, LiClO 4, LiPF 6, LiBF 4, LiAsF 6, LiSbF 6, LiCF 3 SO 3, LiC 4 F 9 SO 3, LiCF 3 CO 2, Li 2 C 2 F 4 (SO 3 ) 2 , LiN (CF 3 SO 2 ) 2 , LiN (CF 3 SO 2 ) 2 , LiC n F 2n + 1 SO 3 (n ≧ 2), LiN (RfOSO 2 ) 2 [where Rf is a fluoroalkyl group Indicates. ], LiN (CF 3 SO 2 ) (C 4 F 9 SO 2), LiN (C 2 F 5 SO 2) (C 4 F 9 SO 2), LiN (CF 3 SO 2) (C 2 F 5 SO 2 ) And the like.

さらに、上記電解質（電解液）以外にも、Ｌｉイオンの輸送体であれば制約無く用いることができ、例えば、各種ポリマーからなるゲルポリマー電解質、真性ポリマー電解質、ＬｉＰＯＮなどの無機固体電解質、Ｌｉイオン含有常温溶融塩などを用いることができる。   In addition to the above electrolyte (electrolyte), any Li ion transporter can be used without restriction. For example, gel polymer electrolytes composed of various polymers, intrinsic polymer electrolytes, inorganic solid electrolytes such as LiPON, Li ions, etc. A room temperature molten salt or the like can be used.

上記リチウム二次電池に用いるセパレータとしては、強度が充分で上記電解液を多く保持できるものが良く、この点から、厚み１０〜５０μｍ、開口率３０〜７０％のポリプロピレン製、ポリエチレン製、またはポリプロピレンとポリエチレンのコポリマー製のフィルムや不織布からなるセパレータが好ましい。   The separator used for the lithium secondary battery is preferably a separator having sufficient strength and capable of holding a large amount of the electrolytic solution. From this point, polypropylene, polyethylene, or polypropylene having a thickness of 10 to 50 μm and an aperture ratio of 30 to 70% A separator made of a copolymer film of polyethylene and polyethylene or a nonwoven fabric is preferred.

さらに、本実施形態の薄膜電極は、上記リチウム二次電池以外にも、リチウム一次電池などの電極としても使用することができる。   Furthermore, the thin film electrode of the present embodiment can be used as an electrode for a lithium primary battery, in addition to the lithium secondary battery.

次に、本発明を実施例に基づき具体的に説明する。なお、本発明は、以下の実施例に限定されるものではない。   Next, the present invention will be specifically described based on examples. The present invention is not limited to the following examples.

（実施例１）
古河サーキットフォイル社製の厚み１５μｍの電解銅箔を５０ｍｍ×３０ｍｍに切り出して本実施例の集電体とした。次に、表面の酸化被膜、油脂、汚れなどを除去するために、上記集電体を４０℃に加熱した濃度１０％の硫酸水溶液中に４分間浸漬した。その後、水酸化ナトリウム５ｇ／ｄｍ3、オルトケイ酸ナトリウム２０ｇ／ｄｍ3、炭酸ナトリウム（無水）１０ｇ／ｄｍ3、ｎ−ドデシルトリメチルアンモニウムクロリド１ｇ／ｄｍ3をそれぞれ溶解させた脱脂水溶液を準備し、この脱脂水溶液を６０℃に加熱した浴中で、上記集電体を５Ａ／ｄｍ2の電流密度で１分間の陰極電解脱脂を行った。次に、この集電体を蒸留水で水洗した後、再び濃度１０％の硫酸水溶液中に浸漬して集電体表面を中和するとともに脱脂剤を完全に除去した。 (Example 1)
A 15 μm-thick electrolytic copper foil manufactured by Furukawa Circuit Foil Co., Ltd. was cut into 50 mm × 30 mm to obtain a current collector of this example. Next, the current collector was immersed in a 10% strength sulfuric acid aqueous solution heated to 40 ° C. for 4 minutes in order to remove oxide films, oils and dirt on the surface. Then, sodium hydroxide 5 g / dm 3, sodium orthosilicate 20 g / dm 3 sodium carbonate (anhydrous) 10 g / dm 3, to prepare a degreasing aqueous solution prepared by dissolving n- dodecyl trimethyl ammonium chloride 1 g / dm 3, respectively, the The current collector was subjected to cathodic electrolytic degreasing for 1 minute at a current density of 5 A / dm 2 in a bath in which the degreasing aqueous solution was heated to 60 ° C. Next, the current collector was washed with distilled water, and then again immersed in a 10% concentration sulfuric acid aqueous solution to neutralize the current collector surface and completely remove the degreasing agent.

続いて、硫酸第一錫４０ｇ／ｄｍ3、硫酸６０ｇ／ｄｍ3、クレゾールスルホン酸４０ｇ／ｄｍ3、ゼラチン２ｇ／ｄｍ3、β−ナフトール１ｇ／ｄｍ3を溶解させた水溶液からなるＳｎめっき液を調製した。このめっき液をスターラーで攪拌しながら、めっき液中に上記集電体を浸漬して、１Ａ／ｄｍ2の電流密度で１５０分間の電解めっきを行い、集電体表面に厚み７μｍのＳｎめっき薄膜を形成し、その後水洗して薄膜電極を得た。 Subsequently, an Sn plating solution comprising an aqueous solution in which stannous sulfate 40 g / dm 3 , sulfuric acid 60 g / dm 3 , cresol sulfonic acid 40 g / dm 3 , gelatin 2 g / dm 3 , and β-naphthol 1 g / dm 3 was dissolved. Prepared. While stirring the plating solution with a stirrer, the current collector is immersed in the plating solution, and electroplating is performed at a current density of 1 A / dm 2 for 150 minutes, and a 7 μm thick Sn plating thin film is formed on the surface of the current collector. And then washed with water to obtain a thin film electrode.

次に、円形開口部を有するニッケル製のマイクロメッシュを準備した。このマイクロメッシュの円形開口部の総面積は６５００μｍ2、空孔率は６０％、厚みは１００μｍとした。このマイクロメッシュを上記薄膜電極のＳｎめっき薄膜側に配置して、ロールプレス機を用いてギャップを調節して加圧した。これにより、図１（ｄ）に示すように、Ｓｎめっき薄膜１２に凸部１４と凹部１５を形成した。 Next, a nickel micromesh having a circular opening was prepared. The total area of the circular openings of the micromesh was 6500 μm 2 , the porosity was 60%, and the thickness was 100 μm. The micromesh was placed on the Sn plating thin film side of the thin film electrode, and the gap was adjusted using a roll press machine, and the pressure was applied. Thereby, as shown in FIG.1 (d), the convex part 14 and the recessed part 15 were formed in the Sn plating thin film 12. As shown in FIG.

その後、上記薄膜電極を真空電気炉にて２２０℃で１７時間熱処理してＳｎめっき薄膜をＣｕ合金化した後、室温まで徐冷した。次に、この薄膜電極をアルゴン雰囲気中のドライボックスに移し、４１ｍｍ×２５．５ｍｍに打ち抜いて実施例１の負極とした。   Thereafter, the thin film electrode was heat-treated at 220 ° C. for 17 hours in a vacuum electric furnace to convert the Sn plating thin film into a Cu alloy, and then gradually cooled to room temperature. Next, this thin film electrode was transferred to a dry box in an argon atmosphere and punched out to 41 mm × 25.5 mm to obtain a negative electrode of Example 1.

上記負極を電子顕微鏡で観察したところ、凸部１４の高さＨ１は９μｍであった。なお、マイクロメッシュの空孔率が６０％であるので、凸部１４の面積占有率ｘは６０％となる。   When the negative electrode was observed with an electron microscope, the height H1 of the convex portion 14 was 9 μm. Note that since the porosity of the micromesh is 60%, the area occupation ratio x of the convex portions 14 is 60%.

（実施例２）
円形開口部を有するニッケル製のマイクロメッシュに代えて、六角形開口部を有するニッケル製のマイクロメッシュを用いた以外は、実施例１と同様にして実施例２の負極を作製した。このマイクロメッシュの六角形開口部の総面積は６５００μｍ2、空孔率は４０％、厚みは１５０μｍとした。 (Example 2)
A negative electrode of Example 2 was produced in the same manner as Example 1 except that a nickel micromesh having a hexagonal opening was used instead of the nickel micromesh having a circular opening. The total area of the hexagonal openings of the micromesh was 6500 μm 2 , the porosity was 40%, and the thickness was 150 μm.

実施例１と同様に上記負極を電子顕微鏡で観察したところ、凸部１４の高さＨ１は１０μｍであった。なお、マイクロメッシュの空孔率が４０％であるので、凸部１４の面積占有率ｘは４０％となる。   When the negative electrode was observed with an electron microscope in the same manner as in Example 1, the height H1 of the convex portion 14 was 10 μm. Since the porosity of the micromesh is 40%, the area occupation ratio x of the convex portion 14 is 40%.

（実施例３）
円形開口部を有するニッケル製のマイクロメッシュに代えて、六角形開口部を有するニッケル製のマイクロメッシュを用いた以外は、実施例１と同様にして実施例３の負極を作製した。このマイクロメッシュの六角形開口部の総面積は６５００μｍ2、空孔率は７０％、厚みは２００μｍとした。 (Example 3)
A negative electrode of Example 3 was produced in the same manner as Example 1 except that a nickel micromesh having a hexagonal opening was used instead of the nickel micromesh having a circular opening. The total area of the hexagonal openings of the micromesh was 6500 μm 2 , the porosity was 70%, and the thickness was 200 μm.

実施例１と同様に上記負極を電子顕微鏡で観察したところ、凸部１４の高さＨ１は８μｍであった。なお、マイクロメッシュの空孔率が７０％であるので、凸部１４の面積占有率ｘは７０％となる。   When the negative electrode was observed with an electron microscope in the same manner as in Example 1, the height H1 of the convex portion 14 was 8 μm. In addition, since the porosity of the micromesh is 70%, the area occupation ratio x of the convex portion 14 is 70%.

（実施例４）
マイクロメッシュの空孔率を２０％とした以外は、実施例１と同様にして実施例４の負極を作製した。 Example 4
A negative electrode of Example 4 was produced in the same manner as in Example 1 except that the porosity of the micromesh was 20%.

実施例１と同様に上記負極を電子顕微鏡で観察したところ、凸部１４の高さＨ１は５μｍであった。なお、マイクロメッシュの空孔率が２０％であるので、凸部１４の面積占有率ｘは２０％となる。   When the negative electrode was observed with an electron microscope in the same manner as in Example 1, the height H1 of the convex portion 14 was 5 μm. In addition, since the porosity of the micromesh is 20%, the area occupation ratio x of the convex portions 14 is 20%.

（比較例１）
Ｓｎめっき薄膜に凹凸を形成しなかった以外は、実施例１と同様にして比較例１の負極を作製した。 (Comparative Example 1)
A negative electrode of Comparative Example 1 was produced in the same manner as in Example 1 except that the unevenness was not formed on the Sn plating thin film.

（比較例２）
薄膜の凸部１４の高さＨ１を１μｍとした以外は、実施例１と同様にして比較例２の負極を作製した。 (Comparative Example 2)
A negative electrode of Comparative Example 2 was produced in the same manner as in Example 1 except that the height H1 of the convex portion 14 of the thin film was set to 1 μm.

（比較例３）
電解めっき時間を６００分、マイクロメッシュの厚みを３００μｍ、Ｓｎめっき薄膜の厚みを１０μｍとし、Ｓｎめっき薄膜の凸部１４の高さＨ１を２２μｍとした以外は、実施例１と同様にして比較例３の負極を作製した。 (Comparative Example 3)
Comparative Example as in Example 1 except that the electrolytic plating time was 600 minutes, the thickness of the micromesh was 300 μm, the thickness of the Sn plating thin film was 10 μm, and the height H1 of the convex portion 14 of the Sn plating thin film was 22 μm. 3 negative electrode was produced.

上記実施例１〜４および比較例１〜３の負極の主な構成を表１に示す。   Table 1 shows main structures of the negative electrodes of Examples 1 to 4 and Comparative Examples 1 to 3.

Figure 2005108521
次に、上記で作製した負極と組み合わせるための正極を以下のように作製した。先ず、正極活物質であるＬｉＣｏＯ2を９０重量部、導電助剤であるカーボンブラックを６重量部、バインダとしてポリフッ化ビニリデンを４重量部、溶剤としてＮ−メチルピロリドンを４０重量部、をそれぞれ均一になるように混合して正極合剤含有ペーストを調製した。続いて、集電体となる厚さ２０μｍのアルミニウム箔の片面に、上記正極合剤含有ペーストを、単位面積あたりの合剤重量が３２ｍｇ／ｃｍ2になるように塗布して乾燥した後、カレンダー処理を行って、全厚９４μｍ、電極密度３．２ｇ／ｃｍ3となるように正極合剤層の厚みを調整した。その後、４１ｍｍ×２５．５ｍｍに打ち抜いて正極とした。
Figure 2005108521
 Next, a positive electrode to be combined with the negative electrode produced above was produced as follows. First, 90 parts by weight of LiCoO 2 as a positive electrode active material, 6 parts by weight of carbon black as a conductive additive, 4 parts by weight of polyvinylidene fluoride as a binder, and 40 parts by weight of N-methylpyrrolidone as a solvent are uniform. A positive electrode mixture-containing paste was prepared by mixing. Subsequently, the positive electrode mixture-containing paste was applied to one side of an aluminum foil having a thickness of 20 μm serving as a current collector so that the mixture weight per unit area was 32 mg / cm 2 , and then dried. The treatment was performed to adjust the thickness of the positive electrode mixture layer so that the total thickness was 94 μm and the electrode density was 3.2 g / cm 3 . Then, it punched out to 41 mm x 25.5 mm, and was set as the positive electrode.

電解液としては、１ｍｏｌ／ｄｍ3のＬｉＰＦ6を、エチレンカーボネートとジエチレンカーボネートの混合溶媒（混合体積比＝１：２）に溶解したものを用いた。セパレータとしては、ヘキストセラニーズ社製のポリプロピレン製セパレータ“Ｃｅｌｇａｒｄ♯２４００”（商品名、厚さ１０μｍ）を用いた。 As an electrolytic solution, a solution obtained by dissolving 1 mol / dm 3 of LiPF 6 in a mixed solvent of ethylene carbonate and diethylene carbonate (mixing volume ratio = 1: 2) was used. As the separator, a polypropylene separator “Celgard # 2400” (trade name, thickness: 10 μm) manufactured by Hoechst Celanese was used.

上記正極と、実施例１〜４および比較例１〜３の負極とをそれぞれ組み合わせ、その正極と負極との間に上記セパレータを配置して積層した後、アルミラミネートフィルム製の外装材に挿入し、上記電解液を注入し、外装材の電解液注入口をヒートシールにより封止して、モデルセルを作製した。   The positive electrode and the negative electrodes of Examples 1 to 4 and Comparative Examples 1 to 3 were combined, and the separator was placed between the positive electrode and the negative electrode for lamination, and then inserted into an aluminum laminate film exterior material. The above electrolyte solution was injected, and the electrolyte solution injection port of the exterior material was sealed by heat sealing to produce a model cell.

このモデルセルを用いて温度２５℃にて充放電試験を行った。充電は、電流密度０．５ｍＡ／ｃｍ2の定電流で４．３Ｖまで充電後、４．３Ｖの定電圧で充電電流が０．０５ｍＡ／ｃｍ2に到達するまで充電し、放電は、電流密度０．５ｍＡ／ｃｍ2の定電流で放電終止電圧３Ｖまで放電し、初回充電容量および初回放電容量を測定して、下記式１により初回充放電効率を算出した。なお、初回充電とは第１回目の充電をいい、初回放電とは第１回目の放電をいう。 A charge / discharge test was performed at a temperature of 25 ° C. using this model cell. Charging is performed at a constant current of 0.5 mA / cm 2 at a current density of 4.3 V, and then charged at a constant voltage of 4.3 V until the charging current reaches 0.05 mA / cm 2. The battery was discharged at a constant current of 0.5 mA / cm 2 to a discharge end voltage of 3 V, and the initial charge capacity and the initial discharge capacity were measured. Note that the first charge refers to the first charge, and the first discharge refers to the first discharge.

また、この条件で充放電試験を行い、下記式２によりサイクル特性を算出した。なお、下記放電容量および充電容量は、正極合剤１ｇあたりの電気容量（ｍＡｈ／ｇ）で表される。   In addition, a charge / discharge test was performed under these conditions, and the cycle characteristics were calculated by the following formula 2. In addition, the following discharge capacity and charge capacity are represented by electric capacity (mAh / g) per 1 g of the positive electrode mixture.

（数１）
初回充放電効率（％）＝（初回放電容量／初回充電容量）×１００ （式１）
（数２）
サイクル特性（％）＝（２０サイクル後の放電容量／初回放電容量）×１００ （式２）
また、初回充電時の電池の厚み変化をすべて負極の厚み変化によるものとして、下記式３により充電時の負極の厚み変化率（％）を算出した。 (Equation 1)
Initial charge / discharge efficiency (%) = (initial discharge capacity / initial charge capacity) × 100 (Formula 1)
(Equation 2)
Cycle characteristics (%) = (discharge capacity after 20 cycles / initial discharge capacity) × 100 (Formula 2)
Further, assuming that all changes in the thickness of the battery during the initial charge were due to changes in the thickness of the negative electrode, the rate of change in thickness (%) of the negative electrode during charging was calculated according to the following formula 3.

（数３）
厚み変化率（％）＝〔（初回充電時の電池厚み）−(充電前の電池厚み）〕／(充電前の薄膜の厚み＋集電体の厚み)×１００ （式３）
電池の厚みの測定は、上記各モデルセルをミツトヨ社製のレーザホロゲージに取り付けてカウンタ装置によって厚み変化を測定した。その結果を表２に示す。 (Equation 3)
Thickness change rate (%) = [(Battery thickness at first charge) − (Battery thickness before charge)] / (Thin film thickness before charge + Current collector thickness) × 100 (Equation 3)
The thickness of the battery was measured by attaching the above model cells to a laser holo gauge manufactured by Mitutoyo Corporation and measuring the thickness change with a counter device. The results are shown in Table 2.

Figure 2005108521
表２から明らかなように、実施例１〜４は、比較例１に比べて、サイクル特性が高く、厚み変化率が低かった。これは、実施例１〜４では、活物質薄膜の体積膨張による応力を薄膜電極の凹凸が緩和し、電極の膨張、集電体の皺寄れ、および活物質薄膜内部のクラックの発生が抑制されているためと考えられる。また、薄膜の凸部の高さが２μｍを下回った比較例２では、活物質薄膜の体積膨張による応力の緩和が不十分となり、厚み変化率が高くなったため、サイクル特性も低下したもと考えられる。さらに、薄膜の凸部の高さが２０μｍを上回った比較例３では、凸部の高さが高すぎるため薄膜構造の維持が困難となり、サイクル特性が低下したものと考えられる。
Figure 2005108521
 As is clear from Table 2, Examples 1 to 4 had higher cycle characteristics and a lower thickness change rate than Comparative Example 1. In Examples 1 to 4, the unevenness of the thin film electrode relaxes the stress caused by the volume expansion of the active material thin film, and the expansion of the electrode, the current collector creeping, and the occurrence of cracks inside the active material thin film are suppressed. It is thought that it is because. Further, in Comparative Example 2 in which the height of the convex portion of the thin film was less than 2 μm, the relaxation of the stress due to the volume expansion of the active material thin film became insufficient, and the rate of change in thickness was increased, so that the cycle characteristics were also deteriorated. It is done. Furthermore, in Comparative Example 3 in which the height of the convex portion of the thin film exceeded 20 μm, it was considered that the thin film structure was difficult to maintain because the height of the convex portion was too high, and the cycle characteristics were deteriorated.

なお、初回放電容量は、活物質であるＳｎの量に依存するため、薄膜の凹凸の有無に関わりなく約６６５ｍＡｈ／ｇの容量となった。   Since the initial discharge capacity depends on the amount of Sn as the active material, the capacity was about 665 mAh / g regardless of whether the thin film was uneven.

本発明の薄膜電極は、活物質薄膜の体積変化による影響を最小限に抑えて、電極の膨張、集電体の皺寄れ、および活物質薄膜内部のクラックの発生を抑制することが可能である。このため、本発明の薄膜電極を用いることでサイクル特性などの信頼性に優れ、かつ高容量のリチウム二次電池の作製が可能となり、このリチウム二次電池を電源とする各種の携帯電子端末機器などの小型軽量化に貢献できる。   The thin film electrode of the present invention can minimize the influence of the volume change of the active material thin film and suppress the expansion of the electrode, the current collector creeping, and the occurrence of cracks inside the active material thin film. . For this reason, by using the thin film electrode of the present invention, it is possible to produce a lithium secondary battery with excellent reliability such as cycle characteristics and a high capacity, and various portable electronic terminal devices using the lithium secondary battery as a power source This can contribute to reducing the size and weight.

本発明の薄膜電極の製造方法の一例を示す工程図である。It is process drawing which shows an example of the manufacturing method of the thin film electrode of this invention. 本発明の薄膜電極の製造方法の他の一例を示す工程図である。It is process drawing which shows another example of the manufacturing method of the thin film electrode of this invention.

符号の説明Explanation of symbols

１１、２１ 集電体
１２、２２ 薄膜
１３ 金属メッシュ
１３ａ 開口部
２３ 金属板
２３ａ 突起
１４、２４ 凸部
１５、２５ 凹部
１６、２６ 薄膜電極
Ｈ１ 凸部１４の高さ
Ｈ２ 凸部２４の高さ DESCRIPTION OF SYMBOLS 11, 21 Current collector 12, 22 Thin film 13 Metal mesh 13a Opening 23 Metal plate 23a Protrusion 14, 24 Convex part 15, 25 Concave part 16, 26 Thin film electrode H1 Height of convex part H2 Height of convex part 24

Claims (10)

リチウムと合金化しない金属から形成された集電体と、前記集電体の表面に形成され、リチウムと合金化する元素を含む薄膜とを備えた薄膜電極であって、
前記薄膜が、凸部および凹部を備え、
前記凸部の高さが、２μｍ以上２０μｍ以下であることを特徴とする薄膜電極。 A thin film electrode comprising: a current collector formed of a metal that does not alloy with lithium; and a thin film that is formed on a surface of the current collector and includes an element that is alloyed with lithium,
The thin film includes a convex portion and a concave portion,
The height of the convex part is 2 μm or more and 20 μm or less. 前記集電体の表面に垂直投影した前記凸部または前記凹部の投影部の形状が、円形、三角形、四角形、および六角形から選ばれる少なくとも一つの形状である請求項１に記載の薄膜電極。   2. The thin film electrode according to claim 1, wherein a shape of the projected portion or the projected portion of the recessed portion that is vertically projected onto the surface of the current collector is at least one shape selected from a circle, a triangle, a quadrangle, and a hexagon. 前記集電体の表面に垂直投影した前記凸部の投影部の総面積が、前記薄膜が形成された前記集電体の総面積の４０％以上８０％以下である請求項１または２に記載の薄膜電極。   3. The total area of the projections of the convex portions projected perpendicularly to the surface of the current collector is 40% or more and 80% or less of the total area of the current collector on which the thin film is formed. Thin film electrode. 前記集電体の厚みが、５μｍ以上３０μｍ以下である請求項１〜３のいずれかに記載の薄膜電極。   The thin film electrode according to claim 1, wherein the current collector has a thickness of 5 μm or more and 30 μm or less. 前記リチウムと合金化する元素が、ケイ素および錫から選ばれる少なくとも一つの元素である請求項１〜４のいずれかに記載の薄膜電極。   The thin film electrode according to claim 1, wherein the element alloyed with lithium is at least one element selected from silicon and tin. 前記薄膜の主成分が、Ｃｕ6Ｓｎ5およびＮｉ3Ｓｎ4から選ばれるいずれか一つである請求項１〜５のいずれかに記載の薄膜電極。 The thin film electrode according to claim 1, wherein a main component of the thin film is any one selected from Cu 6 Sn 5 and Ni 3 Sn 4 . リチウムと合金化しない金属からなる集電体の表面に、リチウムと合金化する元素を含む薄膜を形成する工程と、
前記薄膜を凹凸形成部材で加圧することにより、前記薄膜の表面に凹凸を形成する工程と、
を含むことを特徴とする薄膜電極の製造方法。 Forming a thin film containing an element alloying with lithium on the surface of a current collector made of a metal that is not alloyed with lithium;
Forming the irregularities on the surface of the thin film by pressing the thin film with an irregularity forming member;
A method for producing a thin film electrode, comprising: 前記凹凸形成部材が、金属メッシュおよび表面に凹凸を有する金属板から選ばれるいずれかの部材である請求項７に記載の薄膜電極の製造方法。   The method for producing a thin film electrode according to claim 7, wherein the unevenness forming member is any member selected from a metal mesh and a metal plate having unevenness on the surface. 前記凹凸を形成した薄膜および前記集電体を加熱する工程をさらに含む請求項７または８に記載の薄膜電極の製造方法。   The method of manufacturing a thin film electrode according to claim 7, further comprising a step of heating the thin film having the irregularities and the current collector. 請求項１〜６のいずれかに記載の薄膜電極を負極として用いたことを特徴とするリチウム二次電池。

A lithium secondary battery using the thin film electrode according to claim 1 as a negative electrode.

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EP3624238A4 (en) * 2017-08-17 2020-07-29 LG Chem, Ltd. Method for surface patterning of lithium metal, and lithium secondary battery electrode using same
US11271199B2 (en) 2017-08-17 2022-03-08 Lg Energy Solution, Ltd. Method for patterning lithium metal surface and electrode for lithium secondary battery using the same
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