JP3440963B2 - Anode plate for lithium secondary battery - Google Patents

Anode plate for lithium secondary battery

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Publication number
JP3440963B2
JP3440963B2 JP18875695A JP18875695A JP3440963B2 JP 3440963 B2 JP3440963 B2 JP 3440963B2 JP 18875695 A JP18875695 A JP 18875695A JP 18875695 A JP18875695 A JP 18875695A JP 3440963 B2 JP3440963 B2 JP 3440963B2
Authority
JP
Japan
Prior art keywords
negative electrode
electrode material
material layer
binder
layer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
Application number
JP18875695A
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Japanese (ja)
Other versions
JPH0935707A (en
Inventor
竹規 石津
光徳 織田
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Shin Kobe Electric Machinery Co Ltd
Original Assignee
Shin Kobe Electric Machinery Co Ltd
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Application filed by Shin Kobe Electric Machinery Co Ltd filed Critical Shin Kobe Electric Machinery Co Ltd
Priority to JP18875695A priority Critical patent/JP3440963B2/en
Publication of JPH0935707A publication Critical patent/JPH0935707A/en
Application granted granted Critical
Publication of JP3440963B2 publication Critical patent/JP3440963B2/en
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Classifications

    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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

Description

【発明の詳細な説明】Detailed Description of the Invention

【０００１】[0001]

【発明の属する技術分野】本発明は、リチウム二次電池
用負極板に関するものである。TECHNICAL FIELD The present invention relates to a negative electrode plate for a lithium secondary battery.

【０００２】[0002]

【従来の技術】近年、電気機器の小形化に伴い、電池の
小形化、軽量化が望まれており、これらの要求を満たす
高エネルギー密度の電池として、負極活物質としてリチ
ウムを用いるリチウム二次電池が提案されている。リチ
ウム二次電池は、充放電を繰り返すと充電時に、樹枝状
のリチウムが負極活物質上に析出するいわゆるデンドラ
イトが発生する。デンドライトが大きくなり、正極活物
質と接触すると電池が内部短絡し、電池のサイクル寿命
が短かくなる上、電池が発熱、発火する危険がある。そ
こで、リチウムイオンの吸蔵、放出が可能な炭素材料を
負極材として用いることが提案された。この種の電池で
は、リチウムイオンが炭素材料内に吸蔵、放出されて電
池の充放電が行われるため、リチウムが負極上に析出す
ることがなく、デンドライトの発生を抑制できる。この
ように炭素材料を負極材として用いる場合は、リチウム
イオンの吸蔵、放出が可能な炭素粉末と結着剤とを有機
溶媒に溶解してスラリーを作る。そして、このスラリー
を銅箔等の負極集電体に塗布してから乾燥し、負極材層
を形成して負極板を作る。この種の負極板を用いたリチ
ウム二次電池では、エネルギー密度が高いため、負極集
電体及び負極材層の厚みを薄くできるという特徴を有し
ている。また、結着剤及び有機溶媒は、特開平４−２４
９８６０号公報に示されるように、ポリフッ化ビニリデ
ン（ＰＶＤＦ）からなる結着剤及びＮ−メチル−２−ピ
ロリドン（ＮＭＰ）からなる有機溶媒が多用されてい
る。しかしながら、ＰＶＤＦは、炭素粉末同志は強く結
着できるものの、負極集電体とは強く結着しない。そこ
で従来では、負極材層と負極集電体との剥離を防いで、
電池容量が低下するのを防ぐために、ＰＶＤＦ量を負極
材に対して５重量％以上２０重量％以下と比較的多量に
用いて負極材層を形成していた。2. Description of the Related Art In recent years, with the miniaturization of electric devices, there has been a demand for miniaturization and weight reduction of batteries. As a high energy density battery satisfying these requirements, a lithium secondary battery using lithium as a negative electrode active material. Batteries have been proposed. When a lithium secondary battery is repeatedly charged and discharged, so-called dendrite in which dendritic lithium is deposited on the negative electrode active material is generated during charging. When the dendrite becomes large and comes into contact with the positive electrode active material, the battery is internally short-circuited, the cycle life of the battery is shortened, and there is a risk of heat generation and ignition of the battery. Therefore, it has been proposed to use a carbon material capable of inserting and extracting lithium ions as the negative electrode material. In this type of battery, since lithium ions are inserted into and discharged from the carbon material to charge and discharge the battery, lithium is not deposited on the negative electrode and dendrite generation can be suppressed. When the carbon material is used as the negative electrode material in this way, a carbon powder capable of inserting and extracting lithium ions and a binder are dissolved in an organic solvent to form a slurry. Then, this slurry is applied to a negative electrode current collector such as a copper foil and then dried to form a negative electrode material layer to form a negative electrode plate. The lithium secondary battery using this type of negative electrode plate has a feature that the thickness of the negative electrode current collector and the negative electrode material layer can be reduced because of its high energy density. The binder and the organic solvent are described in JP-A-4-24.
As shown in Japanese Patent Publication No. 9860, a binder made of polyvinylidene fluoride (PVDF) and an organic solvent made of N-methyl-2-pyrrolidone (NMP) are often used. However, PVDF can strongly bind to the carbon powder, but does not strongly bind to the negative electrode current collector. Therefore, conventionally, by preventing the peeling between the negative electrode material layer and the negative electrode current collector,
In order to prevent the battery capacity from decreasing, a relatively large amount of PVDF, which is 5% by weight or more and 20% by weight or less of the negative electrode material, is used to form the negative electrode material layer.

【０００３】[0003]

【発明が解決しようとする課題】しかしながら、負極材
層中のＰＶＤＦの重量割合が多いと、負極材層中の炭素
粉末の重量割合が少なくなって、電池の容量が低下する
という問題が生じる。またＰＶＤＦは、電気抵抗が大き
いので、このように負極材中のＰＶＤＦの重量割合が多
いと、炭素粉末と集電体との導電性が低下するという問
題が生じる。However, when the weight ratio of PVDF in the negative electrode material layer is high, the weight ratio of the carbon powder in the negative electrode material layer decreases, and the capacity of the battery decreases. Further, since PVDF has a large electric resistance, when the weight ratio of PVDF in the negative electrode material is large as described above, there arises a problem that the conductivity between the carbon powder and the current collector is lowered.

【０００４】本発明の目的は、負極材層と負極集電体と
の剥離を防ぐことができ、しかも電池の容量低下や炭素
粉末と集電体との導電性低下を防げるチウム二次電池用
負極板を提供することにある。An object of the present invention is to prevent the peeling of the negative electrode material layer from the negative electrode current collector and to prevent the reduction of the battery capacity and the reduction of the electrical conductivity between the carbon powder and the current collector. It is to provide a negative electrode plate.

【０００５】[0005]

【課題を解決するための手段】本発明は、負極集電体の
上に負極材層が形成されてなり、負極材層が、リチウム
イオンの吸蔵、放出が可能な炭素粉末とポリフッ化ビニ
リデン（ＰＶＤＦ）からなる結着剤とを含有してなるリ
チウム二次電池用負極板を対象にする。本発明では、負
極集電体と負極材層との間に導電剤が混入されたアクリ
ル系共重合体をからなる結着層を形成する。なお、ここ
で言うアクリル系共重合体とは、アクリル酸及びメタク
リル酸並びにこれらの誘電体の重合体を単量体として含
む共重合体である。According to the present invention, a negative electrode material layer is formed on a negative electrode current collector, and the negative electrode material layer is a carbon powder capable of absorbing and releasing lithium ions and polyvinylidene fluoride ( A negative electrode plate for a lithium secondary battery, which contains a binder made of PVDF). In the present invention, a binder layer made of an acrylic copolymer in which a conductive agent is mixed is formed between the negative electrode current collector and the negative electrode material layer. The acrylic copolymer referred to here is a copolymer containing acrylic acid and methacrylic acid and polymers of these dielectrics as monomers.

【０００６】導電剤としては、銀粉、銅粉等を用いるこ
とができるが、リチウムイオンの吸蔵、放出が可能な炭
素粉末を用いると、結着層も負極材としての役割を果た
し、電池の容量を高めることができる。As the conductive agent, silver powder, copper powder or the like can be used. When carbon powder capable of absorbing and desorbing lithium ions is used, the binder layer also plays a role as a negative electrode material, and the capacity of the battery is increased. Can be increased.

【０００７】また、アクリル系共重合体は銅との接着性
が高いので、負極集電体が銅箔により形成された負極板
に本発明を適用すると高い効果を得ることができる。Further, since the acrylic copolymer has high adhesiveness to copper, a high effect can be obtained by applying the present invention to a negative electrode plate in which the negative electrode current collector is formed of copper foil.

【０００８】アクリル酸エステル・スチレン共重合体及
びアクリル酸エステル・メタクリル酸エステル共重合体
は接着性が高いので、アクリル系共重合体としてアクリ
ル酸エステル・スチレン共重合体及びアクリル酸エステ
ル・メタクリル酸エステル共重合体の少なくとも一つを
用いると負極集電体と負極材層との結着性を高めること
ができる。Since the acrylic acid ester / styrene copolymer and the acrylic acid ester / methacrylic acid ester copolymer have high adhesiveness, the acrylic acid ester / styrene copolymer and the acrylic acid ester / methacrylic acid are used as the acrylic copolymer. When at least one of the ester copolymers is used, the binding property between the negative electrode current collector and the negative electrode material layer can be improved.

【０００９】負極材層と結着層とを併せた重量に対する
ポリフッ化ビニリデン（ＰＶＤＦ）の重量の割合は、１
〜４重量％とし、負極材層と結着層とを併せた重量に対
するＰＶＤＦとアクリル系共重合体とを併せた重量の割
合は、２〜５重量％とするのが好ましい。ＰＶＤＦの重
量の割合が１重量％を下回ると、炭素粉末同志を十分に
結合することができない。ＰＶＤＦの重量の割合が４重
量％を上回ると、炭素粉末の重量割合が小さくなる上、
炭素粉末と集電体との導電性が低下するので、電池の容
量が低下する。ＰＶＤＦとアクリル系共重合体とを併せ
た重量の割合が２重量％を下回ると、負極材層と負極集
電体との結着性が低下する。ＰＶＤＦとアクリル系共重
合体とを併せた重量の割合が５重量％を上回ると、電池
の容量が低下する。The ratio of the weight of polyvinylidene fluoride (PVDF) to the total weight of the negative electrode material layer and the binder layer is 1
The amount of the PVDF and the acrylic copolymer combined is preferably 2 to 5% by weight with respect to the total weight of the negative electrode material layer and the binder layer. If the weight ratio of PVDF is less than 1% by weight, the carbon powders cannot be sufficiently bonded together. When the weight ratio of PVDF exceeds 4% by weight, the weight ratio of carbon powder becomes small and
Since the conductivity between the carbon powder and the current collector is reduced, the capacity of the battery is reduced. When the ratio of the weight of PVDF and the acrylic copolymer combined is less than 2% by weight, the binding property between the negative electrode material layer and the negative electrode current collector deteriorates. When the combined weight ratio of PVDF and acrylic copolymer exceeds 5% by weight, the battery capacity decreases.

【００１０】[0010]

【発明の実施の形態】DETAILED DESCRIPTION OF THE INVENTION

（実施例１〜６）各実施例のリチウム二次電池用負極板
は、次のようにして製造した。まず、ガラス転移点の範
囲が−２０℃〜０℃の下記１の式を有するアクリル酸エ
ステル・スチレン共重合体が水に溶解したエマルジョン
と平均径５μｍのリチウムイオンの吸蔵、放出が可能な
グラファイト粉末５０ｍｇとを混練して、結着層形成材
料を作った。(Examples 1 to 6) The negative electrode plate for a lithium secondary battery of each example was manufactured as follows. First, an emulsion in which an acrylic acid ester / styrene copolymer having a glass transition point range of −20 ° C. to 0 ° C. having the following formula 1 is dissolved in water and graphite capable of storing and releasing lithium ions having an average diameter of 5 μm 50 mg of powder was kneaded to prepare a binder layer forming material.

【００１１】[0011]

【化１】 そして平坦な基体の上に厚み３０mmの銅箔からなる負極
集電体を載置してから、負極集電体にブレードを用いて
結着層形成材料を塗布した。次にこれを５０〜６０℃で
加熱して乾燥して厚み約３μｍの結着層を形成した。な
おアクリル酸エステル・スチレン共重合体は、後に説明
する負極材層と結着層とを併せた重量に対して１重量％
となる量とした。[Chemical 1] Then, a negative electrode current collector made of a copper foil having a thickness of 30 mm was placed on a flat substrate, and then a binder layer forming material was applied to the negative electrode current collector using a blade. Next, this was heated at 50 to 60 ° C. and dried to form a binding layer having a thickness of about 3 μm. The acrylic acid ester / styrene copolymer is 1% by weight based on the total weight of the negative electrode material layer and the binder layer described later.
And the amount.

【００１２】次に平均径５μｍのグラファイト粉末６３
０ｍｇとポリフッ化ビニリデン（ＰＶＤＦ）とノーマル
メチル−２−ピロリドン（ＮＭＰ）とを混合して負極材
溶液をった。Next, graphite powder 63 having an average diameter of 5 μm
0 mg, polyvinylidene fluoride (PVDF) and normal methyl-2-pyrrolidone (NMP) were mixed to prepare a negative electrode material solution.

【００１３】そして、負極材溶液を結着層上に塗布した
後に、８０℃で乾燥して厚み１６０μｍの負極材層を形
成した。なおＰＶＤＦは、後に説明する負極材層と結着
層とを併せた重量に対して表１に示す量とした。負極材
層と前記結着層とを併せた厚みに対する結着層の厚みの
割合は２〜５％が好ましい。２％を下回ると負極材層と
負極集電体との結着力が低下する。５％を上回ると負極
材層と負極集電体との導電性が低下する。次に負極集電
体の裏側にも同様にして、結着層と負極材層とを形成し
てから、両面に結着層及び負極材層を形成した負極集電
体を厚み方向に圧縮成形して、各負極板を完成した。図
１は、本実施例のリチウム二次電池用負極板の部分断面
図である。本図に示すように、負極集電体１と負極材層
２，２との間にそれぞれ結着層３，３が形成されてい
る。以上に説明したように、各実施例のリチウム二次電
池用負極板は、負極材層と結着層とを併せた重量に対す
るアクリル酸エステル・スチレン共重合体との割合を１
重量％とし、負極材層と結着層とを併せた重量に対する
ＰＶＤＦの重量の割合を表１に示すように様々に変えた
ものである。Then, the negative electrode material solution was applied on the binder layer and dried at 80 ° C. to form a negative electrode material layer having a thickness of 160 μm. The PVDF was used in the amount shown in Table 1 with respect to the total weight of the negative electrode material layer and the binder layer, which will be described later. The ratio of the thickness of the binder layer to the total thickness of the negative electrode material layer and the binder layer is preferably 2 to 5%. When it is less than 2%, the binding force between the negative electrode material layer and the negative electrode current collector is reduced. If it exceeds 5%, the conductivity between the negative electrode material layer and the negative electrode current collector will decrease. Similarly, a binder layer and a negative electrode material layer are formed on the back side of the negative electrode current collector in the same manner, and then the negative electrode current collector having the binder layer and the negative electrode material layer formed on both surfaces is compression molded in the thickness direction. Then, each negative electrode plate was completed. FIG. 1 is a partial cross-sectional view of a negative electrode plate for a lithium secondary battery of this example. As shown in the figure, binding layers 3 and 3 are formed between the negative electrode current collector 1 and the negative electrode material layers 2 and 2, respectively. As described above, in the negative electrode plates for lithium secondary batteries of each example, the ratio of the acrylic ester / styrene copolymer to the total weight of the negative electrode material layer and the binder layer was 1.
%, And the ratio of the weight of PVDF to the total weight of the negative electrode material layer and the binder layer was variously changed as shown in Table 1.

【００１４】なお本実施例では、導電剤として炭素材料
を用いているので、結着層が負極材としての役割を果た
す。そのため、結着層と負極材層とを併せたものを複合
負極材層とした場合、結着層が第１の負極材分割層を構
成し、負極材層を第２の負極材分割層を構成する。In this embodiment, since the carbon material is used as the conductive agent, the binder layer serves as the negative electrode material. Therefore, when a composite negative electrode material layer is a combination of a binder layer and a negative electrode material layer, the binder layer constitutes a first negative electrode material dividing layer, and the negative electrode material layer forms a second negative electrode material dividing layer. Constitute.

【００１５】（実施例７〜９）各実施例のリチウム二次
電池用負極板は、負極材層と結着層とを併せた重量に対
するＰＶＤＦの重量の割合を３重量％とし、負極材層と
結着層とを併せた重量に対するアクリル酸エステル・ス
チレン共重合体の割合を表１に示すように様々に変えた
ものである。そして、その他については、実施例１〜６
と同様にして製造した。(Examples 7 to 9) In the negative electrode plates for lithium secondary batteries of the respective examples, the weight ratio of PVDF to the total weight of the negative electrode material layer and the binder layer was 3% by weight, and the negative electrode material layer was As shown in Table 1, the ratio of the acrylic acid ester / styrene copolymer to the total weight of the binder and the binder layer was variously changed. And about others, Examples 1-6
It was manufactured in the same manner as.

【００１６】（実施例１０〜１５）各実施例のリチウム
二次電池用負極板は、アクリル酸エステル・スチレン共
重合体の代りに下記２の式に示すアクリル酸エステル・
メタクリル酸エステル共重合体を用い、負極材層と結着
層とを併せた重量に対するアクリル酸エステル・メタク
リル酸エステル共重合体の割合及び負極材層と結着層と
を併せた重量に対するＰＶＤＦの割合を表１に示すよう
に様々に変えたものである。その他は実施例１〜６と同
様にして製造した。(Examples 10 to 15) The negative electrode plates for lithium secondary batteries of the respective examples were prepared by replacing the acrylic ester / styrene copolymer with the acrylic ester /
Using a methacrylic acid ester copolymer, the ratio of the acrylic ester / methacrylic acid ester copolymer to the combined weight of the negative electrode material layer and the binder layer and the PVDF ratio to the combined weight of the negative electrode material layer and the binder layer The ratio is variously changed as shown in Table 1. Others were manufactured similarly to Examples 1-6.

【００１７】[0017]

【化２】 （比較例１，２）各比較例のリチウム二次電池用負極板
は、結着層を形成せずに、実施例１〜６の負極板の負極
材層と結着層とを併せた厚みと同じ厚みになるように負
極材層を形成し、負極材層と結着層とを併せた重量に対
するＰＶＤＦの重量の割合を表１に示すように様々に変
えた負極板である。その他は実施例１〜６と同様にして
製造した。[Chemical 2] (Comparative Examples 1 and 2) The negative electrode plate for a lithium secondary battery of each comparative example has a combined thickness of the negative electrode material layer and the binding layer of the negative electrode plates of Examples 1 to 6 without forming a binding layer. It is a negative electrode plate in which the negative electrode material layer is formed so as to have the same thickness as that of, and the ratio of the weight of PVDF to the total weight of the negative electrode material layer and the binder layer is changed as shown in Table 1. Others were manufactured similarly to Examples 1-6.

【００１８】次に上記各負極板を用いて試験を行った。
まず、円筒形のローラを回転可能な状態で支柱に固定
し、そのローラ上に各負極板を載置し、各負極板の両端
に５０ｇのおもりを吊した。そして、負極板がローラか
ら落下しないようにローラを回転させ、負極集電体と負
極材層との剥離状態を調べた。表１にその測定結果（剥
離の有無）を示す。Next, a test was conducted using each of the above negative electrode plates.
First, a cylindrical roller was rotatably fixed to a supporting column, each negative electrode plate was placed on the roller, and a 50 g weight was hung on both ends of each negative electrode plate. Then, the roller was rotated so that the negative electrode plate did not drop from the roller, and the state of separation between the negative electrode current collector and the negative electrode material layer was examined. Table 1 shows the measurement results (presence or absence of peeling).

【００１９】また各負極板を電解質層を介して金属リチ
ウムと積層して試験用コイン電池を作った。なお電解質
層は、体積比１：１のエチレンカーボネートとジエチル
カーボネートとの混合溶媒に１ＭのＬｉＰＦ6 を添加し
た電解液をポリプロピレンからなるセパレータに含浸さ
せて作った。そして、各電池を０．１Ｃで充放電したと
きの１サイクル目の放電容量を初期容量として測定し
た。表１にその測定結果を示す。Further, each negative electrode plate was laminated with metallic lithium through an electrolyte layer to prepare a coin battery for test. The electrolyte layer was made by impregnating a separator made of polypropylene with an electrolytic solution prepared by adding 1 M LiPF 6 to a mixed solvent of ethylene carbonate and diethyl carbonate at a volume ratio of 1: 1. Then, the discharge capacity at the first cycle when each battery was charged and discharged at 0.1 C was measured as the initial capacity. Table 1 shows the measurement results.

【００２０】[0020]

【表１】 本表より、実施例の負極板を用いると、剥離が生じにく
くなるのが分る。また剥離が生じても、初期容量を高く
できるのが分る。負極材層と結着層とを併せた重量に対
するＰＶＤＦとアクリル系共重合体とを合わせた重量
（結着剤総量）を２重量％以上にすると、負極集電体と
負極材層との剥離を防げるのが分る。比較例１の負極板
と結着剤総量が等しい実施例３，１２の負極板は、結着
層の作用により剥離を防止できるのが分る。また実施例
３，１２の負極板は、ＰＶＤＦの量が少ないため、ＰＶ
ＤＦのみを結着剤として用いた比較例２の負極板を用い
た電池よりも初期容量が高いのが分る。また実施例５，
１４の負極板を用いた電池は、比較例２の負極板を用い
た電池と結着剤総量が等しいにもかかわらず、比較例２
の負極板を用いた電池よりも初期容量が高いのが分る。
これらより、負極材層と結着層とを併せた重量に対する
ＰＶＤＦの重量の割合を１〜４重量％とし、負極材層と
結着層とを併せた重量に対する結着剤総量の重量の割合
は、２〜５重量％とするのが好ましいのが分る。[Table 1] From this table, it can be seen that peeling is less likely to occur when the negative electrode plate of the example is used. Further, it can be seen that the initial capacity can be increased even if peeling occurs. When the total weight of PVDF and acrylic copolymer (total amount of binder) is 2% by weight or more based on the total weight of the negative electrode material layer and the binder layer, the negative electrode current collector and the negative electrode material layer are separated from each other. You can see that you can prevent It can be seen that the negative electrode plates of Examples 3 and 12 having the same total amount of binder as the negative electrode plate of Comparative Example 1 can prevent peeling due to the action of the binder layer. Moreover, since the negative electrode plates of Examples 3 and 12 have a small amount of PVDF,
It can be seen that the initial capacity is higher than that of the battery using the negative electrode plate of Comparative Example 2 using only DF as the binder. Example 5,
The battery using the negative electrode plate of No. 14 has the same total amount of the binder as that of the battery using the negative electrode plate of Comparative Example 2, but Comparative Example 2
It can be seen that the initial capacity is higher than that of the battery using the negative electrode plate.
From these, the ratio of the weight of PVDF to the total weight of the negative electrode material layer and the binder layer is 1 to 4% by weight, and the ratio of the total weight of the binder to the total weight of the negative electrode material layer and the binder layer. It can be seen that is preferably 2 to 5% by weight.

【００２１】以下、明細書に記載した複数の発明の中で
いくつかの発明についてその構成を示す。The constitution of some of the inventions described in the specification will be shown below.

【００２２】（１） 銅箔からなる負極集電体の上に負
極材層が形成されてなり、前記負極材層が、グラファイ
ト粉末とポリフッ化ビニリデンからなる結着剤とを含有
してなるリチウム二次電池用負極板において、前記負極
集電体と前記負極材層との間に、グラファイト粉末が混
入されたアクリル系共重合体を主成分とする結着層が形
成され、前記アクリル系共重合体が、ガラス転移点が−
２０℃〜０℃のアクリル酸エステル・スチレン共重合体
及びアクリル酸エステル・メタクリル酸エステル共重合
体の少なくとも一つからなるリチウム二次電池用負極
板。(1) Lithium in which a negative electrode material layer is formed on a negative electrode current collector made of copper foil, and the negative electrode material layer contains graphite powder and a binder made of polyvinylidene fluoride. In a negative electrode plate for a secondary battery, a binder layer containing an acrylic copolymer mixed with graphite powder as a main component is formed between the negative electrode current collector and the negative electrode material layer. The polymer has a glass transition point of −
A negative electrode plate for a lithium secondary battery, comprising at least one of an acrylic acid ester / styrene copolymer and an acrylic acid ester / methacrylic acid ester copolymer at 20 ° C to 0 ° C.

【００２３】（２） 前記負極材層と前記結着層とを併
せた重量に対する前記ポリフッ化ビニリデンの重量の割
合は、１〜４重量％であり、前記負極材層と前記結着層
とを併せた重量に対する前記ポリフッ化ビニリデンと前
記アクリル系共重合体とを併せた重量の割合は、２〜５
重量％であることを特徴とする上記（１）に記載のリチ
ウム二次電池用負極板。(2) The weight ratio of the polyvinylidene fluoride to the total weight of the negative electrode material layer and the binder layer is 1 to 4% by weight, and the negative electrode material layer and the binder layer are combined. The ratio of the combined weight of the polyvinylidene fluoride and the acrylic copolymer to the combined weight is 2 to 5
The negative electrode plate for a lithium secondary battery according to (1) above, wherein the negative electrode plate is contained in a weight percentage.

【００２４】（３） 前記負極材層と前記結着層とを併
せた厚みに対する前記結着層の厚みの割合が２〜５％で
あることを特徴とする上記（２）に記載のリチウム二次
電池用負極板。(3) The lithium battery according to (2) above, wherein the ratio of the thickness of the binder layer to the total thickness of the negative electrode material layer and the binder layer is 2 to 5%. Negative electrode plate for secondary battery.

【００２５】（４） 前記ポリフッ化ビニリデンは、Ｎ
−メチル−２−ピロリドンからなる溶媒に溶解された状
態で、前記負極材層に添加されてなることを特徴とする
上記（２）または（３）に記載のリチウム二次電池用負
極板。(4) The polyvinylidene fluoride is N
The negative electrode plate for a lithium secondary battery according to (2) or (3) above, which is added to the negative electrode material layer in a state of being dissolved in a solvent composed of -methyl-2-pyrrolidone.

【００２６】[0026]

【発明の効果】アクリル系共重合体は、ＰＶＤＦ及び負
極集電体との結着力が強いので、本発明によれば、負極
集電体と負極材層との間に導電剤が混入されたアクリル
系共重合体を主成分とする結着層を形成するので、負極
集電体と負極材層との結着性を高めることができる。そ
のため、従来のように多量のＰＶＤＦを用いる必要がな
く、負極材層中における炭素粉末の重量割合を増やせ
る。その結果、電池容量の低下を抑制することができ
る。またＰＶＤＦの重量割合が少なくなることにより、
炭素粉末と集電体との導電性の低下も抑制できる。Since the acrylic copolymer has a strong binding force with PVDF and the negative electrode current collector, according to the present invention, a conductive agent is mixed between the negative electrode current collector and the negative electrode material layer. Since the binder layer containing an acrylic copolymer as the main component is formed, the bondability between the negative electrode current collector and the negative electrode material layer can be improved. Therefore, it is not necessary to use a large amount of PVDF as in the conventional case, and the weight ratio of the carbon powder in the negative electrode material layer can be increased. As a result, a decrease in battery capacity can be suppressed. In addition, because the weight ratio of PVDF decreases,
A decrease in conductivity between the carbon powder and the current collector can also be suppressed.

【図面の簡単な説明】[Brief description of drawings]

【図１】 本実施例のリチウム二次電池用負極板の部分
断面図である。FIG. 1 is a partial cross-sectional view of a negative electrode plate for a lithium secondary battery of this example.

【符号の説明】[Explanation of symbols]

１ 負極集電体 ２ 負極材層 ３ 結着層 1 Negative electrode current collector 2 Negative electrode material layer 3 tie layers

───────────────────────────────────────────────────── フロントページの続き (58)調査した分野(Int.Cl.7，ＤＢ名) H01M 4/00 - 4/62 H01M 4/66 H01M 10/36 - 10/40 ─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. 7 , DB name) H01M 4/00-4/62 H01M 4/66 H01M 10/36-10/40

Claims (5)

(57)【特許請求の範囲】(57) [Claims] 【請求項１】 負極集電体の上に負極材層が形成されて
なり、 前記負極材層が、リチウムイオンの吸蔵、放出が可能な
炭素粉末とポリフッ化ビニリデンからなる結着剤とを含
有してなるリチウム二次電池用負極板において、 前記負極集電体と前記負極材層との間に導電剤が混入さ
れたアクリル系共重合体からなる結着層が形成されてな
るリチウム二次電池用負極板。1. A negative electrode material layer is formed on a negative electrode current collector, and the negative electrode material layer contains carbon powder capable of inserting and extracting lithium ions and a binder made of polyvinylidene fluoride. In the negative electrode plate for a lithium secondary battery, the lithium secondary having a binder layer made of an acrylic copolymer mixed with a conductive agent is formed between the negative electrode current collector and the negative electrode material layer. Negative electrode plate for batteries. 【請求項２】 前記導電剤としてリチウムイオンの吸
蔵、放出が可能な炭素粉末を用いることを特徴とする請
求項１に記載のリチウム二次電池用負極板。2. The negative electrode plate for a lithium secondary battery according to claim 1, wherein carbon powder capable of inserting and extracting lithium ions is used as the conductive agent. 【請求項３】 前記負極集電体が銅箔により形成されて
なる請求項１または２に記載のリチウム二次電池用負極
板。3. The negative electrode plate for a lithium secondary battery according to claim 1, wherein the negative electrode current collector is made of a copper foil. 【請求項４】 前記アクリル系共重合体は、アクリル酸
エステル・スチレン共重合体及びアクリル酸エステル・
メタクリル酸エステル共重合体の少なくとも一つからな
り、 前記負極材層と前記結着層とを併せた重量に対する前記
ポリフッ化ビニリデンの重量の割合は、１〜４重量％で
あり、 前記負極材層と前記結着層とを併せた重量に対する前記
ポリフッ化ビニリデンと前記アクリル系共重合体とを併
せた重量の割合は、２〜５重量％であることを特徴とす
る請求項３に記載のリチウム二次電池用負極板。4. The acrylic copolymer is an acrylic ester / styrene copolymer and an acrylic ester.
The negative electrode material layer is made of at least one methacrylate ester copolymer, and the weight ratio of the polyvinylidene fluoride to the total weight of the negative electrode material layer and the binder layer is 1 to 4% by weight. 4. The lithium according to claim 3, wherein a ratio of a weight of the polyvinylidene fluoride and the acrylic copolymer combined with respect to a weight of the binder layer and the binder layer is 2 to 5% by weight. Negative electrode plate for secondary battery. 【請求項５】 負極集電体の上に複合負極材層が形成さ
れてなり、 前記複合負極材層が、リチウムイオンの吸蔵、放出が可
能な炭素粉末と結着剤とを含有してなるリチウム二次電
池用負極板において、 前記複合負極材層は、前記負極集電体上に形成され、結
着剤としてアクリル系共重合体を用いる第１の負極材分
割層と、前記第１の負極材分割層上に形成され結着剤と
してポリフッ化ビニリデンを用いる第２の負極材分割層
とからなることを特徴とするリチウム二次電池用負極
板。5. A composite negative electrode material layer is formed on a negative electrode current collector, and the composite negative electrode material layer contains carbon powder capable of absorbing and releasing lithium ions and a binder. In the negative electrode plate for a lithium secondary battery, the composite negative electrode material layer is formed on the negative electrode current collector, and a first negative electrode material dividing layer using an acrylic copolymer as a binder, A negative electrode plate for a lithium secondary battery, comprising a second negative electrode material dividing layer formed on the negative electrode material dividing layer and using polyvinylidene fluoride as a binder.
JP18875695A 1995-07-25 1995-07-25 Anode plate for lithium secondary battery Expired - Fee Related JP3440963B2 (en)

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JP3440963B2 true JP3440963B2 (en) 2003-08-25

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JP4461498B2 (en) 1997-12-16 2010-05-12 パナソニック株式会社 Nonaqueous electrolyte secondary battery and negative electrode thereof
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