JP4830180B2 - Method for producing electrode plate for non-aqueous electrolyte secondary battery - Google Patents
Method for producing electrode plate for non-aqueous electrolyte secondary battery Download PDFInfo
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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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Description
【０００１】
【発明の属する技術分野】
本発明は、非水電解質二次電池の、とくにその極板に用いる結着剤の結着力向上に関するものである。
【０００２】
【従来の技術】
現在、非水電解質二次電池の負極活物質には炭素材料が用いられている。この炭素材料の特性として充放電時において炭素がリチウムイオンを吸蔵し活物質粒子が膨張し、放電時にはリチウムイオンを放出することで活物質粒子が収縮する。この充放電に伴う膨張収縮により極板内に存在する電子伝導のネットワークが切断され、電池容量や充放電レート特性が劣化するという問題を有している。特に、充放電サイクルの繰り返しに伴い極板の劣化が蓄積され、電池のサイクル寿命特性を低下させる原因となっている。
【０００３】
活物質粒子の膨張収縮に伴い極板内の電子伝導ネットワークが切断されていく原因としては、極板を所定の合剤密度にまで圧延する工程において合剤層中の結着剤が切断され、十分に結着力を発揮していないことが原因と考えられる。従って、圧延工程を行わなければ上記問題を解決することができるが、極板体積当たりの容量が低下し電池の高エネルギー密度化が達成できなくなる。また、圧延後も強度な結着力を保持できるように結着剤を過剰に投入する方法があるが、活物質粒子の表面を過度に被覆することになり電池の充放電における高レート特性を低下させることになる。
【０００４】
これらを解決する手段として特開平８−２０３５００号公報では、極板の圧延を所定の温度において行うことで結着剤の塑形変形を起こし圧延時の結着剤の損傷を最小限にとどめ、これにより充放電サイクルに伴う結着剤の劣化を防ぐ方法が提案されている。しかし、この方法においても、黒鉛粒子のような滑り易い粒子では、通常行われるロール圧延時に粒子の移動が大きく結着剤の塑形変形だけでは対応できない。その結果、結着力が不充分となり充放電における電子伝導ネットワークの破壊が生じることになる。
【０００５】
【発明が解決しようとする課題】
本発明は、上記課題を解決するものであり、充放電のサイクルに伴う合剤中の結着剤が劣化し電子ネットワークが破壊されることを抑制し、電池のサイクル寿命特性を向上させることを目的とするものである。
【０００６】
【課題を解決するための手段】
上記の課題を解決すべく、本発明の非水電解質二次電池用極板の製造方法は、
（１）活物質としての炭素材料と及び結着剤を含む合剤をペースト化し導電性の支持体に塗布して合剤層を設けた後乾燥し極板を作製する工程と、前記極板を加圧成形する工程と、前記加圧成形後の極板の合剤層に結着剤を溶解又は分散保持可能な溶媒を含ませる工程と、前記溶媒を除去する工程を経ることとするもの、
（２）活物質としての炭素材料と及び結着剤を含む合剤をペースト化し導電性の支持体に塗布して合剤層を設けた後乾燥し極板を作製する工程と、前記極板に結着剤を溶解又は分散保持可能な溶媒を含ませる工程と、前記溶媒を含んだ極板を結着剤のガラス転移点以上の温度で加圧成形する工程とを経ることとするもの、
（３）活物質としての炭素材料と及び結着剤を含む合剤をペースト化し導電性の支持体に塗布して合剤層を設けた後乾燥し極板を作製する工程と、前記極板を加圧成形する工程と、前記加圧成形後の合剤層に結着剤を再度含ませる工程を経るもので、前記合剤層に結着剤を再度含ませる工程が、結着剤を溶解又は分散保持した溶媒を合剤層に含ませ、その後極板を乾燥させるものとするもの、である。
【０００７】
（１）の製造方法においては、加圧成形後の合剤層に結着剤を溶解又は分散保持可能な溶媒を含ませることにより、溶媒が結着剤を溶解し、加圧圧延工程で切断された粒子と結着剤とを再度接合し、投入した結着剤の効果を最大限に発揮させることができる。
【０００８】
（２）の製造方法は、加圧成形を行う前に結着剤の柔軟性を持たせるために次の２つの工程を行うものである。１つは、結着剤を溶解又は分散保持可能な溶媒を合剤層に含ませることで、結着剤に溶剤を含ませて柔軟な状態にするものである。もう１つは、使用する結着剤のガラス転移点以上の温度で加圧成形を行うものである。これにより、結着剤の柔軟性を向上することにより接合が切断されることなく加圧圧延後においても十分な結着力
を保持することができる。
【０００９】
（３）の製造方法は、加圧成形後に結着剤を再度導入するものである。すなわち、合剤ペースト中に混合する初期の結着剤は活物質を最低限つなげておけるだけの量だけにしておく。粒子と初期の結着剤との接合は加圧成形により切断される。そこで、再度結着剤を導入することで粒子と結着剤の接合を再生することができる。このときには、粒子と結着剤の接合が充放電サイクルに耐えうる量の結着剤を含ませることが必要である。加圧成形後に必要な結着剤を入れていることから、結着剤の変形も行われないため、上記（１）〜（２）の製造方法よりも強固な極板が得られる製造方法である。
【００１０】
以上のいずれかの製造方法により極板を作製することにより、合剤の加圧成形後においても結着剤の効力を保持し、充放電のサイクルに伴う結着剤の劣化を最小限にとどめ、サイクル寿命特性の向上を図ることができる。
【００１１】
さらに、前記炭素材料には、ＸＲＤ測定による（００２）面の面間隔が０．３３７ｎｍ以下の高結晶性の黒鉛を用いると好ましい。
【００１２】
【発明の実施の形態】
以下、本発明の実施の形態を、図１の円筒型電池の縦断面図を参照しながら説明する。
【００１３】
負極板は、先述した本発明の製造方法のいずれかにより作製する。結着剤としては、例えば、ポリエチレン、ポリプロピレン、ポリテトラフルオロエチレン、ポリフッ化ビニリデン、スチレンブタジエンゴム、テトラフルオロエチレン−ヘキサフルオロエチレン共重合体、テトラフルオロエチレン−ヘキサフルオロプロピレン共重合体、テトラフルオロエチレン−パーフルオロアルキルビニルエーテル共重合体、フッ化ビニリデン−クロロトリフルオロエチレン共重合体、エチレン−テトラフルオロエチレン共重合体、ポリクロロトリフルオロエチレン、フッ化ビニリデン−ペンタフルオロプロピレン共重合体、プロピレン−テトラフルオロエチレン共重合体、エチレン−クロロトリフルオロエチレン共重合体、フッ化ビニリデン−ヘキサフルオロエチレン−テトラフルオロエチレン共重合体、フッ化ビニリデン−パーフルオロメチルビニルエーテル−テトラフルオロエチレン共重合体、エチレン−アクリル酸共重合体または前記材料のＮａイオン架橋体、エチレン−メタクリル酸共重合体または前記材料のＮａイオン架橋体、エチレン−アクリル酸メチル共重合体または前記材料のＮａイオン架橋体、エチレン−メタクリル酸メチル共重合体または前記材料のＮａイオン架橋体を挙げることがであきる。特に好ましい材料はポリフッ化ビニリデンである。集電体としては、銅やアルミニウム等が挙げられる。活物質として、特に好ましいのは、本発明の効果が顕著に現れる炭素材料である。特にＸＲＤ測定による（００２）面の面間隔が０．３３７ｎｍ以下の高結晶性の黒鉛が望ましい。また、この黒鉛を活物質の全質量に対して０．１〜１の割合で含ませ、他の活物質粒子と混合して用いてもよい。
【００１４】
正極板は、通常の極板の製造方法により得ることができる。正極活物質に導電剤、結着剤を混合し、さらに溶媒を用いてスラリーを作製し集電体上に塗布し、乾燥後圧延して作製する。
【００１５】
作製した正極板と負極板をセパレータを介して複数回渦巻状に巻回して極板群４を形成し、電池ケース１内に収容する。尚、正極板からは正極リード５が引き出されて封口板２に、負極板からは負極リード６が引き出されて電池ケース１の底部に接続されている。また、極板群４の上下には絶縁リング７をそれぞれ設けている。電解液を注入後、封口板２を用いて電池を封口し円筒型電池を作製する。
【００１６】
【実施例】
以下、本発明の実施例について、具体的に説明する。
【００１７】
（参考例１）
負極板は次のように作製した。黒鉛９７重量％と結着剤のポリフッ化ビニリデン樹脂３重量％を混合し、これらをカルボキシメチルセルロースの１％水溶液に分散させてスラリーを作製し、銅箔からなる負極集電体上に塗布し合剤層を設け、乾燥した。このように作製した負極板を平板で挟持し、ポリフッ化ビニリデンのガラス転移点である１２０℃の温度下においてプレスによる極板の加圧成形を行った。尚、黒鉛はティムカル製の黒鉛ＳＦＧ４４（ＸＲＤ測定による（００２）面の面間隔が０．３３７ｎｍ以下）を使用し、これをターボミルによる粉砕と粒度調整を行うことで、比表面積が２．４ｍ2／ｇ、湿式レーザ粒度計による粒径が１５〜２２μｍの範囲内の黒鉛粉末サンプルを用いた。なお、活物質密度については１．３ｇ／ｃｍ3以上となるように加圧成形を行った。
【００１８】
一方、正極板はコバルト酸リチウム粉末８５重量％に対し、導電剤の炭素粉末１０重量％と結着剤のポリフッ化ビニリデン樹脂５重量％を混合し、これらをカルボキシメチルセルロースの１％水溶液に分散させてスラリーを作製し、アルミニウム箔からなる正極集電体上に塗布し、乾燥後、圧延して作製した。尚、コバルト酸リチウムは比表面積が０．４ｍ2／ｇの材料を用いた。
【００１９】
また、有機電解液には、エチレンカーボネートとエチルメチルカーボネートの体積比１：１の混合溶媒にＬｉＰＦ6を１．５モル／リットル溶解したものを使用した。
【００２０】
以上のようにして作製した極板を用い、直径１８ｍｍ、高さ６５ｍｍの図１に示すような円筒型非水電解質二次電池を構成した。
【００２１】
（実施例１）
負極板を次のように作製した。黒鉛９７重量％と結着剤のポリフッ化ビニリデン樹脂３重量％を混合し、これらをカルボキシメチルセルロースの１％水溶液に分散させてスラリーを作製し、銅箔からなる負極集電体上に塗布し合剤層を設け乾燥した。このように作製した負極板を合剤層が一定の密度になるように加圧成形を行った。次に、ポリフッ化ビニリデン樹脂を水溶液中に分散保持しうる界面活性剤を０．１重量％投入した水溶液を極板の合剤層に含ませた後、極板を乾燥させた。なお、水溶液中にポリフッ化ビニリデン樹脂は含まれていない。
【００２２】
負極板の作製工程を変更した以外は参考例１と同様に円筒型非水電解質二次電池を構成した。
【００２３】
（実施例２）
負極板を次のように作製した。黒鉛９７重量％と結着剤のポリフッ化ビニリデン樹脂３重量％を混合し、これらをカルボキシメチルセルロースの１％水溶液に分散させてスラリーを作製し、銅箔からなる負極集電体上に塗布し合剤層を設け乾燥した。次に、ポリフッ化ビニリデン樹脂を水溶液中に分散保持しうる界面活性剤を０．１重量％投入した水溶液を極板の合剤層に含ませた。なお、水溶液中にポリフッ化ビニリデンは含まれていない。その後、この極板を合剤層が一定の密度になるように１２０℃の温度下において加圧成形を行った。
【００２４】
負極板の作製工程を変更した以外は参考例１と同様に円筒型非水電解質二次電池を構成した。
【００２５】
（実施例３）
負極板を次のように作製した。黒鉛９７重量％と結着剤のポリフッ化ビニリデン樹脂１重量％を混合し、これらをカルボキシメチルセルロースの１％水溶液に分散させてスラリーを作製し、銅箔からなる負極集電体上に塗布し合剤層を設け乾燥した。このように作製した負極板を合剤層が一定の密度になるように加圧成形を行った。次に、ポリフッ化ビニリデン樹脂２０重量％を含み、これを水溶液中に分散保持しうる界面活性剤も０．１重量％含む水溶液を極板の合剤層に含ませた。このとき黒鉛９７重量％に対し、結着剤のポリフッ化ビニリデン樹脂が先にスラリーに混合したものと合わせて３重量％となるようにして合剤層へ水溶液を含ませた。その後極板を乾燥した。
【００２６】
負極板の作製工程を変更した以外は参考例１と同様に円筒型非水電解質二次電池を構成した。
【００２７】
（比較例１）
負極板を次のように作製した。黒鉛９７重量％と結着剤のポリフッ化ビニリデン樹脂３重量％を混合し、これらをカルボキシメチルセルロースの１％水溶液に分散させてスラリーを作製し、銅箔からなる負極集電体上に塗布し合剤層を設け乾燥した。このように作製した負極板を合剤が一定の密度になるように加圧成形を行った。
【００２８】
負極板の作製工程を変更した以外は参考例１と同様に円筒型非水電解質二次電池を構成した。
【００２９】
（評価）
上記参考例および実施例１〜３と比較例１の電池について充放電サイクル試験を行った。電池電圧の上限が４．２ＶのＣＶＣＣ充電を行い最大制限電流を１Ａとし、電流が１００ｍＡになった時点で充電終了とした。放電は１４００ｍＡの定電流で３．０Ｖになるまで放電し、充放電切り替え時の休止時間は２０分とした。尚、充放電は２０℃の恒温槽の中で行った。
【００３０】
尚、１サイクル目の放電容量を１００％としたときの電池の放電容量が５０％まで減少したときのサイクル数を電池のサイクル寿命としてサイクル特性の評価の指標とした。また、１サイクル目と１００サイクル目において放電状態の電池を分解し、負極板の厚みを計測し合剤の密度を計算した。（サイクルに伴う合剤の密度変化率）＝（（１００サイクル目の合剤密度）−（１サイクル目の合剤密度））／（１サイクル目の合剤密度）としてサイクルに伴う合剤の密度変化の指標とした。（表１）にこの結果を示す。
【００３１】
【表１】
【００３２】
本発明の参考例および実施例１〜３の電池においては、負極板の膨れが小さくサイクル特性がよくなっていることが確認できる。これに対しこれに対し比較の電池は極板の膨れ
が大きくこれに伴う合剤内の電子ネットワークが切断され、サイクル特性が低下したものと考えられる。
【００３３】
なお、本実施例では、結着剤を分散保持可能な溶媒として水の例を示したが、この他にエタノールなどの有機溶媒であってもよい。
【００３４】
【発明の効果】
以上のように、本発明の製造方法により極板を作製することで、電池の充放電サイクルに伴う結着剤の劣化を最小限にとどめ、合剤内の電子ネットワークを良好に保つことによりサイクル寿命特性に優れた非水電解質二次電池が得られる。
【図面の簡単な説明】
【図１】 本発明の実施の形態における円筒型非水電解質二次電池の縦断面図
【符号の説明】
１ 電池ケース
２ 封口板
３ 絶縁パッキング
４ 極板群
５ 正極リード
６ 負極リード
７ 絶縁リング[0001]
BACKGROUND OF THE INVENTION
The present invention relates to the improvement of the binding force of a binder used for a nonaqueous electrolyte secondary battery, particularly for its electrode plate.
[0002]
[Prior art]
Currently, a carbon material is used as a negative electrode active material of a non-aqueous electrolyte secondary battery. As a characteristic of the carbon material, carbon absorbs lithium ions during charge / discharge and the active material particles expand, and during discharge, the active material particles contract by releasing lithium ions. Due to the expansion and contraction associated with this charge / discharge, the network of electron conduction existing in the electrode plate is cut, and the battery capacity and charge / discharge rate characteristics deteriorate. In particular, the deterioration of the electrode plate accumulates as the charge / discharge cycle is repeated, causing the cycle life characteristics of the battery to deteriorate.
[0003]
As a cause of the electron conduction network in the electrode plate being cut along with the expansion and contraction of the active material particles, the binder in the mixture layer is cut in the step of rolling the electrode plate to a predetermined mixture density, It is thought that the cause is that the binding power is not sufficiently exhibited. Therefore, the above problem can be solved if the rolling process is not performed, but the capacity per electrode plate volume is lowered, and the high energy density of the battery cannot be achieved. In addition, there is a method of adding an excessive amount of binder so that a strong binding force can be maintained even after rolling, but the surface of the active material particles is excessively covered, and the high rate characteristics in charge / discharge of the battery are reduced. I will let you.
[0004]
As a means for solving these problems, JP-A-8-203500 discloses that the electrode plate is rolled at a predetermined temperature to cause plastic deformation of the binder, thereby minimizing the damage to the binder during rolling. Thus, a method for preventing the deterioration of the binder accompanying the charge / discharge cycle has been proposed. However, even in this method, with slippery particles such as graphite particles, the movement of the particles is large at the time of usual roll rolling, and it cannot be handled only by plastic deformation of the binder. As a result, the binding force is insufficient and the electron conduction network is destroyed during charging and discharging.
[0005]
[Problems to be solved by the invention]
This invention solves the said subject, suppresses that the binder in the mixture accompanying the cycle of charging / discharging deteriorates and destroys an electronic network, and improves the cycle life characteristic of a battery. It is the purpose.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the method for producing the electrode plate for a non-aqueous electrolyte secondary battery of the present invention is as follows.
(1) A step of preparing an electrode plate by pasting a mixture containing a carbon material as an active material and a binder, applying the mixture onto a conductive support, providing a mixture layer, and drying the electrode plate; The step of pressure-molding, the step of including a solvent capable of dissolving or dispersing the binder in the mixture layer of the electrode plate after pressure molding, and the step of removing the solvent ,
(2) Pasting a carbon material as an active material and a binder containing a binder, applying the mixture onto a conductive support, providing a mixture layer, and drying to prepare an electrode plate; A step of including a solvent capable of dissolving or dispersing and holding the binder, and a step of pressure-molding the electrode plate containing the solvent at a temperature equal to or higher than the glass transition point of the binder,
(3) Pasting a carbon material as an active material and a binder containing a binder into a conductive support and providing a mixture layer, followed by drying to produce an electrode plate; And the step of re-adding the binder into the mixture layer after the pressure molding, and the step of re-adding the binder into the mixture layer comprises the step of: A solvent dissolved or dispersed and held is included in the mixture layer, and then the electrode plate is dried .
[0007]
In the production method of ( 1 ), by adding a solvent capable of dissolving or dispersing and holding the binder in the mixture layer after pressure molding, the solvent dissolves the binder and cuts in the pressure rolling step. The formed particles and the binder can be joined again to maximize the effect of the input binder.
[0008]
In the production method ( 2 ), the following two steps are performed in order to give the binder flexibility before performing pressure molding. One is to include a solvent that can dissolve or disperse the binder in the mixture layer so that the binder is included in a flexible state. The other is pressure molding at a temperature equal to or higher than the glass transition point of the binder used. Thereby, it is possible to maintain a sufficient binding force even after the pressure rolling without cutting the joint by improving the flexibility of the binder.
[0009]
In the production method ( 3 ), the binder is introduced again after the pressure molding. That is, the initial binder mixed in the mixture paste is kept in an amount sufficient to connect the active material at a minimum. The bonding between the particles and the initial binder is cut by pressure molding. Therefore, the bonding between the particles and the binder can be regenerated by introducing the binder again. At this time, it is necessary to include an amount of the binder capable of withstanding the charge / discharge cycle in the bonding between the particles and the binder. Since a necessary binder is added after pressure molding, since the binder is not deformed, the production method can obtain a stronger electrode plate than the production methods (1) to ( 2 ) above. Oh Ru.
[0010]
By producing an electrode plate by any of the above manufacturing methods, the effectiveness of the binder is maintained even after the mixture is pressure-molded, and the deterioration of the binder accompanying the charge / discharge cycle is minimized. The cycle life characteristics can be improved.
[0011]
Further, it is preferable to use highly crystalline graphite having a (002) plane spacing of 0.337 nm or less as measured by XRD.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to a longitudinal sectional view of the cylindrical battery in FIG.
[0013]
The negative electrode plate is produced by any of the production methods of the present invention described above. Examples of the binder include polyethylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, styrene butadiene rubber, tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene. -Perfluoroalkyl vinyl ether copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer, polychlorotrifluoroethylene, vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetra Fluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, vinylidene fluoride-hexafluoroethylene-tetrafluoroethylene copolymer, vinylidene fluoride -Perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, ethylene-acrylic acid copolymer, or Na ion crosslinked body of the material, ethylene-methacrylic acid copolymer or Na ion crosslinked body of the material, ethylene-acrylic acid Mention may be made of methyl copolymers or Na ion crosslinked bodies of the above materials, ethylene-methyl methacrylate copolymers or Na ion crosslinked bodies of the above materials. A particularly preferred material is polyvinylidene fluoride. Examples of the current collector include copper and aluminum. Particularly preferable as the active material is a carbon material in which the effects of the present invention are remarkably exhibited. In particular, highly crystalline graphite having a (002) plane spacing of 0.337 nm or less by XRD measurement is desirable. Moreover, this graphite may be included in a ratio of 0.1 to 1 with respect to the total mass of the active material, and may be used by mixing with other active material particles.
[0014]
The positive electrode plate can be obtained by an ordinary electrode plate manufacturing method. A positive electrode active material is mixed with a conductive agent and a binder, a slurry is further prepared using a solvent, applied onto a current collector, dried and rolled.
[0015]
The produced positive electrode plate and negative electrode plate are spirally wound a plurality of times through a separator to form the electrode plate group 4 and accommodated in the battery case 1. A positive electrode lead 5 is drawn from the positive electrode plate to the sealing plate 2, and a negative electrode lead 6 is drawn from the negative electrode plate to be connected to the bottom of the battery case 1. Insulating rings 7 are provided above and below the electrode plate group 4, respectively. After injecting the electrolyte, the battery is sealed using the sealing plate 2 to produce a cylindrical battery.
[0016]
【Example】
Examples of the present invention will be specifically described below.
[0017]
( Reference Example 1)
The negative electrode plate was produced as follows. A mixture of 97% by weight of graphite and 3% by weight of a polyvinylidene fluoride resin as a binder was dispersed in a 1% aqueous solution of carboxymethylcellulose to prepare a slurry, which was applied onto a negative electrode current collector made of copper foil. An agent layer was provided and dried. The negative electrode plate thus produced was sandwiched between flat plates, and pressure forming of the electrode plate was performed by pressing at a temperature of 120 ° C., which is the glass transition point of polyvinylidene fluoride. The graphite used is Timcal graphite SFG44 (the (002) plane spacing by XRD measurement is 0.337 nm or less), and this is pulverized by a turbo mill and the particle size is adjusted to have a specific surface area of 2.4 m 2. / G, a graphite powder sample having a particle size measured by a wet laser particle size meter in the range of 15 to 22 μm was used. In addition, it pressure-molded so that it might become 1.3 g / cm < 3 > or more about an active material density.
[0018]
On the other hand, for the positive electrode plate, 85% by weight of lithium cobaltate powder is mixed with 10% by weight of carbon powder as a conductive agent and 5% by weight of polyvinylidene fluoride resin as a binder, and these are dispersed in a 1% aqueous solution of carboxymethyl cellulose. A slurry was prepared, applied on a positive electrode current collector made of aluminum foil, dried and rolled. In addition, lithium cobaltate used the material whose specific surface area is 0.4 m < 2 > / g.
[0019]
As the organic electrolyte, a solution obtained by dissolving 1.5 mol / liter of LiPF 6 in a mixed solvent of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 1: 1 was used.
[0020]
A cylindrical nonaqueous electrolyte secondary battery as shown in FIG. 1 having a diameter of 18 mm and a height of 65 mm was constructed using the electrode plate produced as described above.
[0021]
(Example 1 )
A negative electrode plate was produced as follows. A mixture of 97% by weight of graphite and 3% by weight of a polyvinylidene fluoride resin as a binder was dispersed in a 1% aqueous solution of carboxymethylcellulose to prepare a slurry, which was applied onto a negative electrode current collector made of copper foil. The agent layer was provided and dried. The negative electrode plate thus produced was subjected to pressure molding so that the mixture layer had a constant density. Next, the electrode plate was dried after an aqueous solution containing 0.1% by weight of a surfactant capable of dispersing and retaining the polyvinylidene fluoride resin in the aqueous solution was contained in the mixture layer of the electrode plate. In addition, the polyvinylidene fluoride resin is not contained in the aqueous solution.
[0022]
A cylindrical nonaqueous electrolyte secondary battery was constructed in the same manner as in Reference Example 1 except that the production process of the negative electrode plate was changed.
[0023]
(Example 2 )
A negative electrode plate was produced as follows. A mixture of 97% by weight of graphite and 3% by weight of a polyvinylidene fluoride resin as a binder was dispersed in a 1% aqueous solution of carboxymethylcellulose to prepare a slurry, which was applied onto a negative electrode current collector made of copper foil. The agent layer was provided and dried. Next, an aqueous solution containing 0.1% by weight of a surfactant capable of dispersing and holding the polyvinylidene fluoride resin in the aqueous solution was included in the mixture layer of the electrode plate. The aqueous solution does not contain polyvinylidene fluoride. Thereafter, this electrode plate was subjected to pressure molding at a temperature of 120 ° C. so that the mixture layer had a constant density.
[0024]
A cylindrical nonaqueous electrolyte secondary battery was constructed in the same manner as in Reference Example 1 except that the production process of the negative electrode plate was changed.
[0025]
(Example 3 )
A negative electrode plate was produced as follows. A mixture of 97% by weight of graphite and 1% by weight of a polyvinylidene fluoride resin as a binder was dispersed in a 1% aqueous solution of carboxymethyl cellulose to prepare a slurry, which was applied onto a negative electrode current collector made of copper foil. The agent layer was provided and dried. The negative electrode plate thus produced was subjected to pressure molding so that the mixture layer had a constant density. Next, an aqueous solution containing 20% by weight of a polyvinylidene fluoride resin and 0.1% by weight of a surfactant capable of dispersing and retaining the resin in the aqueous solution was included in the mixture layer of the electrode plate. At this time, the aqueous solution was included in the mixture layer so that the amount of the polyvinylidene fluoride resin as a binder was 3% by weight with respect to 97% by weight of graphite, together with the mixture of the resin previously mixed in the slurry. Thereafter, the electrode plate was dried.
[0026]
A cylindrical nonaqueous electrolyte secondary battery was constructed in the same manner as in Reference Example 1 except that the production process of the negative electrode plate was changed.
[0027]
(Comparative Example 1)
A negative electrode plate was produced as follows. A mixture of 97% by weight of graphite and 3% by weight of a polyvinylidene fluoride resin as a binder was dispersed in a 1% aqueous solution of carboxymethylcellulose to prepare a slurry, which was applied onto a negative electrode current collector made of copper foil. The agent layer was provided and dried. The negative electrode plate thus produced was subjected to pressure molding so that the mixture had a constant density.
[0028]
A cylindrical nonaqueous electrolyte secondary battery was constructed in the same manner as in Reference Example 1 except that the production process of the negative electrode plate was changed.
[0029]
(Evaluation)
A charge / discharge cycle test was performed on the batteries of the reference example and Examples 1 to 3 and Comparative Example 1. CVCC charging with an upper limit of the battery voltage of 4.2 V was performed, the maximum limiting current was set to 1 A, and charging was terminated when the current reached 100 mA. The discharge was performed at a constant current of 1400 mA until 3.0 V, and the resting time when switching between charge and discharge was 20 minutes. In addition, charging / discharging was performed in a 20 degreeC thermostat.
[0030]
The number of cycles when the discharge capacity of the battery was reduced to 50% when the discharge capacity at the first cycle was 100% was used as an index for evaluating the cycle characteristics as the cycle life of the battery. In the first cycle and the 100th cycle, the discharged battery was disassembled, the thickness of the negative electrode plate was measured, and the density of the mixture was calculated. (Density change rate of mixture with cycle) = ((mixture density at 100th cycle) − (mixture density at first cycle)) / (mixture density at first cycle) It was used as an index of density change. Table 1 shows the results.
[0031]
[Table 1]
[0032]
In the batteries of Reference Examples and Examples 1 to 3 of the present invention, it can be confirmed that the negative electrode plate is small and the cycle characteristics are good. On the other hand, in the comparative battery, the electrode plate is greatly swollen, and the electronic network in the mixture is cut off, and the cycle characteristics are considered to be deteriorated.
[0033]
In the present embodiment, water is shown as an example of a solvent capable of dispersing and holding the binder, but an organic solvent such as ethanol may also be used.
[0034]
【The invention's effect】
As described above, the electrode plate is produced by the manufacturing method of the present invention, thereby minimizing the deterioration of the binder accompanying the charge / discharge cycle of the battery and keeping the electronic network in the mixture well. A non-aqueous electrolyte secondary battery having excellent life characteristics can be obtained.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a cylindrical nonaqueous electrolyte secondary battery according to an embodiment of the present invention.
DESCRIPTION OF SYMBOLS 1 Battery case 2 Sealing plate 3 Insulation packing 4 Electrode plate group 5 Positive electrode lead 6 Negative electrode lead 7 Insulation ring
Claims (4)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| JP2000200666A JP4830180B2 (en) | 2000-07-03 | 2000-07-03 | Method for producing electrode plate for non-aqueous electrolyte secondary battery |
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| JP2000200666A JP4830180B2 (en) | 2000-07-03 | 2000-07-03 | Method for producing electrode plate for non-aqueous electrolyte secondary battery |
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| JP2002025540A JP2002025540A (en) | 2002-01-25 |
| JP4830180B2 true JP4830180B2 (en) | 2011-12-07 |
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| JP4725163B2 (en) * | 2005-03-31 | 2011-07-13 | パナソニック株式会社 | Nonaqueous electrolyte secondary battery |
| CN101536217B (en) * | 2006-09-11 | 2012-07-18 | 日本瑞翁株式会社 | Electrode for nonaqueous electrolyte secondary battery and nonaqueous electrolyte secondary battery using the same |
| US8927156B2 (en) | 2009-02-19 | 2015-01-06 | Semiconductor Energy Laboratory Co., Ltd. | Power storage device |
| JP2010239122A (en) | 2009-03-09 | 2010-10-21 | Semiconductor Energy Lab Co Ltd | Power storage device |
| JP5509644B2 (en) * | 2009-03-24 | 2014-06-04 | ダイキン工業株式会社 | Slurry for electrode mixture of lithium secondary battery, electrode, method for producing the same, and lithium secondary battery |
| JPWO2010146832A1 (en) * | 2009-06-16 | 2012-11-29 | パナソニック株式会社 | Method for producing negative electrode for nonaqueous electrolyte secondary battery, negative electrode, and nonaqueous electrolyte secondary battery using the same |
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| JP3278666B2 (en) * | 1995-01-20 | 2002-04-30 | 日本電池株式会社 | Method for producing electrode plate for non-aqueous electrolyte battery |
| JP4441933B2 (en) * | 1997-02-18 | 2010-03-31 | 住友化学株式会社 | Positive electrode for lithium secondary battery and lithium secondary battery |
| JPH11204145A (en) * | 1998-01-20 | 1999-07-30 | Yuasa Corp | Lithium secondary battery |
| JP3956478B2 (en) * | 1998-03-31 | 2007-08-08 | トヨタ自動車株式会社 | Method for manufacturing lithium ion secondary battery |
| JP2000067856A (en) * | 1998-08-18 | 2000-03-03 | Matsushita Battery Industrial Co Ltd | Manufacture of electrode for lithium secondary battery |
| JP2000067851A (en) * | 1998-08-27 | 2000-03-03 | Mitsubishi Chemicals Corp | Manufacture of lithium secondary battery and lithium secondary battery |
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