JP4124694B2 - Coin type non-aqueous secondary battery - Google Patents
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- JP4124694B2 JP4124694B2 JP2003126822A JP2003126822A JP4124694B2 JP 4124694 B2 JP4124694 B2 JP 4124694B2 JP 2003126822 A JP2003126822 A JP 2003126822A JP 2003126822 A JP2003126822 A JP 2003126822A JP 4124694 B2 JP4124694 B2 JP 4124694B2
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Description
【０００１】
【発明の属する技術分野】
本発明は、コイン形非水二次電池に関し、さらに詳しくは、正極の機械的強度が高く、サイクル特性および貯蔵特性が優れたコイン形非水二次電池に関する。
【０００２】
【従来の技術】
現在、携帯電話やノート型パソコンなどの携帯用電子機器の電源としては主としてリチウムイオン二次電池が用いられている。その理由としてはニッケル−カドミウム二次電池や金属水素化二次電池などに代表される従来の二次電池に比べて、軽量化が可能になったことと高電圧化が可能になったことが挙げられる。
【０００３】
現在使用されているリチウムイオン二次電池では、ＬｉＣｏＯ2 などの金属酸化物を正極に用い、黒鉛を負極に用いていて、市販されている円筒形や角形のリチウムイオン二次電池では、その電極として金属箔に活物質を含む合剤塗膜を形成した塗布型電極が一般的に用いられている。このリチウムイオン二次電池の負荷特性を考えると、主として正極の負荷特性が律速になっており、また、導電助剤の選定も負荷特性に重要な影響を与えていて、その導電助剤としては、これまで、人造黒鉛、カーボンブラック、アセチレンブラック、ケッチェンブラックなどが用いられ、また、合剤層と集電体との間に前記導電性物質からなる層を形成し、導電性を確保することも提案されている（例えば、特許文献１〜２参照）。
【０００４】
【特許文献１】
特開平９−９７６２５号公報（第１頁）
【特許文献２】
特開平１１−３１２５１６号公報（第１頁）
【０００５】
しかしながら、正極合剤のペレット状成形体を正極に用いる場合は、その成形体の厚みが通常の塗布型電極で採用されている厚み（通常、１００μｍ程度）よりもかなり厚く、厚みが数百μｍまたはそれ以上になる場合が多いため、厚み方向の導電性は前記のような方法では充分に向上させることができなかった。
【０００６】
そこで、導電助剤の添加量を通常の塗布型電極で採用されている以上に増加させることによって、厚み方向の導電性を向上させることが提案されている（例えば、特許文献３参照）。
【０００７】
【特許文献３】
特開２００３−０１７１３３号公報（第１頁）
【０００８】
しかしながら、上記のように導電助剤の添加量を増加させると、それに伴って、活物質の充填比率が低下し、容量密度が低下するという問題が生じると共に、比表面積の大きい導電助剤を用いた場合には、バインダーを多くしないと正極の機械的強度が低下するため、バインダーを多くせざるを得ず、そうすることによって、負荷特性の低下を引き起こすことになる。また、それらの成形体を正極に用いて電池を作製する際に、正極に電解液を浸潤させると膨潤が生じて負荷特性をさらに低下させる。これまで、正極のバインダーとしてはポリフッ化ビニリデンが最も一般的に用いられており、またフッ素ゴムなども用いられているが、これらをバインダーとして用いた場合、電解液の浸潤によって成形体が膨潤しやすく、そのため、機械的強度の低下が生じて、負荷特性が低下し、それによって、サイクル特性および貯蔵特性が低下するという問題があった。
【０００９】
【発明が解決しようとする課題】
本発明は、前記のような正極合剤のペレット形成形体を正極に用いるコイン形非水二次電池における問題点を解決し、正極の機械的強度を高めて、サイクル特性および負荷特性が優れたコイン形非水二次電池を提供することを目的とする。
【００１０】
【課題を解決するための手段】
本発明は、正極と、負極と、前記正極と負極との間に介在するセパレータと、非水系の電解液とを、正極缶と負極缶と環状の絶縁性ガスケットとで形成される密閉空間内に収容してなるコイン形非水二次電池において、前記正極を、少なくとも活物質と導電助剤とバインダーとを含む正極合剤の、厚みが０．２ｍｍ以上のペレット状成形体で構成し、かつ前記バインダーとしてポリフッ化ビニリデンとポリアミドイミドとの混合物であって、かつポリアミドイミドの比率が５〜４０質量％の混合物を用いることによって、前記課題を解決したものである。
【００１１】
【発明の実施の形態】
本発明が上記構成を採用することにより、正極の機械的強度を高めて、サイクル特性および負荷特性が優れたコイン形非水二次電池を提供することができる理由を、以下に本発明の実施の形態とともに説明する。
【００１２】
前記のように、正極のバインダーとしてポリフッ化ビニリデンを用いた場合には、電解液の浸潤によって成形体が膨潤しやすく、負荷特性が低下する上に、正極の膨張により、作製後の電池の厚みが規格値より大きくなり、また、成形体の面方向への膨張により面積がセパレータよりも大きくなることによって負極との短絡が生じることになる。これに対して、ポリアミドイミドを正極のバインダーとして用いた場合は、分子量によっても異なるが、ポリフッ化ビニリデンに比べて一般的に正極が硬くなり、強固な正極が形成できるが、その反面、負荷特性がポリフッ化ビニリデンを用いた場合に比べて低下する傾向がある。
【００１３】
そこで、本発明においては、それらのポリフッ化ビニリデンとポリアミドイミドとを混合し、その混合物をバインダーとして用いることによって、導電助剤の比率を増加させても、バインダーの比率を増加させずに、機械的強度が優れた正極を得ることができ、それによって、負荷特性が優れ、サイクル特性および貯蔵特性が優れたコイン形非水二次電池が得られることを見出したのである。
【００１４】
本発明において、上記のような目的で用いるポリフッ化ビニリデンとしては、例えば、商品名で例示すると、呉羽化学社製の♯１１２０などを用いることが好ましく、ポリアミドイミドとしては、例えば、東洋紡績社製のバイロマックスＮ−１００を用いることが好ましく、これらを用いた場合、その混合比率によってそれぞれの中間的な物性が得られる。
【００１５】
本発明において、上記ポリフッ化ビニリデンとポリアミドイミドとの混合物中において、ポリアミドイミドの比率は５〜４０質量％にすることが好ましい。すなわち、ポリアミドイミドの比率が５質量％より少ない場合は、正極の機械的強度を充分に高めることができず、また、ポリアミドイミドの比率が４０質量％多くなると、負荷特性が低下して、かえってサイクル特性や貯蔵特性が低下するおそれがある。本発明においては、ポリフッ化ビニリデンとポリアミドイミドとの混合物でバインダーを構成するとしているが、正極合剤の調製にあたって、ポリフッ化ビニリデンとポリアミドイミドはあらかじめ混合しておくことは必要とされず、正極合剤中や正極合剤のペレット状成形体で構成される正極中においてポリフッ化ビニリデンとポリアミドイミドが混在した状態で存在すればよい。
【００１６】
本発明において、正極の活物質としては、特に限定されることはないが、例えば、ＬｉＣｏＯ2 、ＬｉＮｉＯ2 、ＬｉＮｉx Ｃｏ1-x Ｏ2 、ＬｉＭｎＯ2 、ＬｉＭｎ2 Ｏ4 などのリチウムイオンの挿入・脱離が可能なリチウム含有複合酸化物が好ましい。
【００１７】
正極の導電助剤としては、特に限定されることはないが、例えば、カーボンブラック、黒鉛、ケッチェンブラック、アセチレンブラック、カーボンナノチューブ、フラーレン、気相成長炭素繊維などの炭素質材料、Ａｌ、Ｐｔなどの金属粉などが好ましい。
【００１８】
正極の作製にあたっては、上記正極活物質、導電助剤、バインダーなどを混合して、正極合剤を調製し、それを金型に充填して加圧成形することによって、正極を構成する正極合剤のペレット状成形体が作製される。そして、その正極を構成する正極合剤のペレット状成形体は、通常、０．２ｍｍ以上の厚さに作製される。また、上記正極合剤の調製にあたって、正極活物質、導電助剤、バインダーを溶剤の存在下で混合し、それを乾燥して、粉砕すると、各成分がより均一に分散した正極合剤が得られる。本発明においてバインダーとして用いるポリフッ化ビニリデンとポリアミドイミドとの混合物は、通常、正極合剤中に３〜２０質量％含有されるようにすることが好ましく、また、上記ポリフッ化ビニリデンとポリアミドイミドとの混合物からなるバインダーが正極合剤中に上記の程度含有されていれば、他のバインダーを併用してもよい。
【００１９】
本発明において、負極は、負極活物質を含む負極合剤のペレット状成形体で構成してもよいし、また、金属リチウムやリチウム合金のみで構成してもよい。負極を負極合剤のペレット状成形体で構成する場合、その負極の活物質としては、リチウムイオンが挿入・脱離できるものであれば特に限定されることはないが、例えば、黒鉛、カーボンナノチューブ、気相成長炭素繊維、低結晶カーボンなどの炭素質材料、Ｓｉ、Ｓｎなどの金属の酸化物などが好ましい。
【００２０】
また、負極を負極合剤のペレット状成形体で構成する場合、その作製にあたって、上記負極活物質以外にバインダーが必要であり、そのバインダーとしては、特に限定されることはないが、例えば、ポリフッ化ビニリデン、スチレンブタジエンゴムとカルボキシメチルセルロースとの混合物、ポリアミドイミドなどが好ましい。また、この負極のバインダーとして、前記正極のバインダーと同様のものを用いることもできる。
【００２１】
本発明において、非水系の電解液、正極缶、負極缶、セパレータ、環状の絶縁性ガスケットなどは、特に限定されることなく、従来構成のものも用いることができ、また、電解液は液状のまま用いる場合ばかりでなく、ゲル化剤でゲル化してゲル状で用いてもよい。
【００２２】
【実施例】
つぎに、実施例を挙げて本発明をより具体的に説明する。ただし、本発明はそれらの実施例のみに限定されるものではない。
【００２３】
実施例１
正極活物質として平均粒径５μｍのＬｉＣｏＯ2 を用い、導電助剤としてカーボンブラックを用い、バインダーを構成するポリフッ化ビニリデンとして呉羽化学社製♯１１２０（商品名）を用い、ポリアミドイミドとして東洋紡績社製バイロマックスＮ−１００（商品名）を用い、まず、前記ＬｉＣｏＯ2 ８７質量部とカーボンブラック５質量部とを混合し、得られた混合物９２質量部とあらかじめ前記ポリフッ化ビニリデンをＮ−メチル−２−ピロリドン中に５質量部溶解させて調製しておいたポリフッ化ビニリデンのＮ−メチル−２−ピロリドン溶液と前記ポリアミドイミドをＮ−メチル−２−ピロリドン中に３質量部溶解させて調製しておいたポリアミドイミドのＮ−メチル−２−ピロリドン溶液とを混合、攪拌することによって、合剤含有塗料を調製した。この塗料を一旦乾燥して、溶剤としてのＮ−メチル−２−ピロリドンを除去した後、粉砕し、得られた正極合剤粉末を金型に充填して加圧成形することにより直径１６ｍｍ、厚さ０．９ｍｍのペレット状成形体を作製し、これを正極とした。バインダーを構成するポリフッ化ビニリデンとポリアミドイミドの全正極合剤中での比率は５質量％で、ポリアミドイミドの全正極合剤中での比率は３質量％であり、それらのバインダーを構成するポリフッ化ビニリデンとポリアミドイミドとの合計中のポリアミドイミドの比率は３７．５質量％であった。
【００２４】
負極活物質として平均粒径３μｍのメソカーボンマイクロビーズを黒鉛化処理したものを用い、このメソカーボンマイクロビーズを黒鉛化処理したもの９０質量部とあらかじめバインダーとしてのポリフッ化ビニリデンをＮ−メチル−２−ピロリドン中に１０質量部溶解させて調製しておいたバインダー溶液とを混合、攪拌することによって合剤含有塗料を作製した。この塗料を一旦乾燥して、溶剤を除去した後、粉砕し、得られた負極合剤粉末を金型に充填して加圧成形することにより直径１６．５ｍｍ、厚さ０．７ｍｍのペレット状成形体を作製して、これを負極とした。
【００２５】
電解液としては、エチレンカーボネートとメチルエチルカーボネートとの体積比１：３の混合溶媒にＬｉＰＦ6 を１モル／リットル溶解させて調製した非水系電解液を用い、セパレータとしては微孔性ポリプロピレンフィルムを用い、正極缶としてはステンレス鋼製のものを用い、負極缶としてはステンレス鋼製のものを用い、環状の絶縁性ガスケットとしてはポリプロピレン製のものを用い、これらと前記正極および負極とで図１に示すようなコイン形非水二次電池を作製した。
【００２６】
ここで、図１に示すコイン形非水二次電池について説明すると、１は前記の正極で、２は前記の負極であり、これらの正極１と負極２との間にはセパレータ３が介在し、これらの正極１と負極２とセパレータ３と前記電解液とは正極缶４と負極缶５と環状の絶縁性ガスケット６とで形成される密閉空間内に収容されている。
【００２７】
これを詳細に説明すると、正極１は正極缶４に収容され、その正極１上にセパレータ３を載置し、電解液を注入し、負極２を載置し、その上から周辺部に絶縁性ガスケット６を取り付けた負極缶５をかぶせ、正極缶４の開口端部を内方に締めつけて絶縁性ガスケット６を負極缶５の周辺部と正極缶４の開口端部の内面に圧接することによって正極缶４と負極缶５との間隙を密閉することによってコイン形非水二次電池が組み立てられている。
【００２８】
実施例２
ポリアミドイミドとして実施例１で用いた東洋紡績社製のバイロマックスＮ−１００（商品名）の分子量を小さくすることによって硬さを増したものを用い、ポリフッ化ビニリデンの全正極合剤中の比率を７．５質量％、ポリアミドイミドの全正極合剤中の比率を０．５質量％とした以外は、実施例１と同様にコイン形非水二次電池を作製した。
【００２９】
比較例１
正極合剤の調製にあたってポリアミドイミドを用いず、バインダーをポリフッ化ビニリデンのみで構成して、全正極合剤中のポリフッ化ビニリデンの比率を８質量％とした以外は、実施例１と同様にコイン形非水二次電池を作製した。
【００３０】
比較例２
正極合剤の調製にあたって、ポリフッ化ビニリデンを用いず、バインダーをポリアミドイミドのみで構成して、全正極合剤中のポリアミドイミドの比率を８質量％とした以外は、実施例１と同様にコイン形非水二次電池を作製した。
【００３１】
上記実施例１〜２および比較例１〜２の電池について、充電終止電圧を４．２Ｖ、放電終止電圧を３．０Ｖ、充電電流密度１ｍＡ／ｃｍ2 に固定し、その充電電流密度１ｍＡ／ｃｍ2 で４．２Ｖまで充電し、放電電流密度１ｍＡ／ｃｍ2 、１０ｍＡ／ｃｍ2 で、それぞれ３．０Ｖまで放電して初回放電容量を測定し、その１０ｍＡ／ｃｍ2 での初回放電容量の１ｍＡ／ｃｍ2 での初回放電容量に対する比率を負荷特性とし、また、充電電流密度１ｍＡ／ｃｍ2 、放電電流密度１ｍＡ／ｃｍ2 で充放電を１００回繰り返して放電容量を測定し、１００サイクル後の放電容量の初回放電容量に対する比率をサイクル特性とし、また、６０℃で３０日間充電状態で貯蔵して放電電流密度１ｍＡ／ｃｍ2 での放電容量を測定し、その貯蔵後の放電容量の貯蔵前の放電容量に対する比率を貯蔵特性とし、それぞれ、百分率（％）表示で表１に示した。
【００３２】
【表１】
表１から示す結果から明らかなように、実施例１〜２の電池は、比較例１〜２の電池に比べて、サイクル特性および貯蔵特性が優れていた。これは、実施例１〜２の電池では、比較例１〜２の電池に比べて、正極の機械的強度が高くなったことに基づくものと考えられる。
【００３４】
以上説明したように、本発明によれば、正極の機械的強度を高めて、サイクル特性および負荷特性が優れたコイン形非水二次電池を提供することができる。
【図面の簡単な説明】
【図１】本発明に係るコイン形非水二次電池の一例を模式的に示す断面図である。
【符号の説明】
１ 正極
２ 負極
３ セパレータ
４ 正極缶
５ 負極缶
６ 環状の絶縁性ガスケット[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a coin-type non-aqueous secondary battery, and more particularly to a coin-type non-aqueous secondary battery having a high positive electrode mechanical strength and excellent cycle characteristics and storage characteristics.
[0002]
[Prior art]
Currently, lithium ion secondary batteries are mainly used as power sources for portable electronic devices such as mobile phones and notebook computers. The reason for this is that it has become possible to reduce the weight and increase the voltage compared to conventional secondary batteries such as nickel-cadmium secondary batteries and metal hydride secondary batteries. Can be mentioned.
[0003]
Currently used lithium ion secondary batteries use a metal oxide such as LiCoO 2 as the positive electrode and graphite as the negative electrode. In commercially available cylindrical or prismatic lithium ion secondary batteries, the electrodes In general, a coating electrode in which a mixture coating film containing an active material is formed on a metal foil is used. Considering the load characteristics of this lithium ion secondary battery, the load characteristics of the positive electrode are mainly rate-limiting, and the selection of the conductive aid has an important influence on the load characteristics. Up to now, artificial graphite, carbon black, acetylene black, ketjen black, etc. have been used, and a layer made of the conductive material is formed between the mixture layer and the current collector to ensure conductivity. This has also been proposed (see, for example,
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 9-97625 (first page)
[Patent Document 2]
Japanese Patent Laid-Open No. 11-31516 (first page)
[0005]
However, when a pellet-shaped molded body of a positive electrode mixture is used for the positive electrode, the thickness of the molded body is considerably thicker than the thickness (usually about 100 μm) employed in ordinary coating-type electrodes, and the thickness is several hundred μm. In many cases, the electrical conductivity in the thickness direction cannot be sufficiently improved by the above method.
[0006]
In view of this, it has been proposed to increase the conductivity in the thickness direction by increasing the amount of addition of the conductive auxiliary agent more than that used in ordinary coating-type electrodes (see, for example, Patent Document 3).
[0007]
[Patent Document 3]
Japanese Patent Laying-Open No. 2003-171133 (first page)
[0008]
However, when the additive amount of the conductive auxiliary agent is increased as described above, a problem arises in that the filling ratio of the active material decreases and the capacity density decreases, and a conductive auxiliary agent having a large specific surface area is used. In such a case, if the binder is not increased, the mechanical strength of the positive electrode is lowered, so that the binder must be increased. This causes a decrease in load characteristics. Further, when a battery is produced using these molded bodies for the positive electrode, if the electrolyte is infiltrated into the positive electrode, swelling occurs and load characteristics are further reduced. Up to now, polyvinylidene fluoride has been most commonly used as a positive electrode binder, and fluororubber is also used. However, when these are used as a binder, the molded body swells due to infiltration of the electrolyte. Therefore, there is a problem that the mechanical strength is lowered and the load characteristic is lowered, thereby reducing the cycle characteristic and the storage characteristic.
[0009]
[Problems to be solved by the invention]
The present invention solves the problems in the coin-type non-aqueous secondary battery using the positive electrode mixture pellet-forming body as the positive electrode as described above, improves the mechanical strength of the positive electrode, and has excellent cycle characteristics and load characteristics. An object is to provide a coin-type non-aqueous secondary battery.
[0010]
[Means for Solving the Problems]
The present invention provides a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte solution in a sealed space formed by the positive electrode can, the negative electrode can, and an annular insulating gasket. In the coin-type non-aqueous secondary battery housed in, the positive electrode comprises a pellet-shaped molded body having a thickness of 0.2 mm or more of a positive electrode mixture containing at least an active material, a conductive additive and a binder, And the said subject is solved by using the mixture of a polyvinylidene fluoride and a polyamideimide as said binder, and the ratio of a polyamideimide is 5-40 mass%.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
The reason why the present invention can provide a coin-type non-aqueous secondary battery with improved cycle characteristics and load characteristics by increasing the mechanical strength of the positive electrode by adopting the above-described configuration will be described below. This will be described together with the form.
[0012]
As described above, when polyvinylidene fluoride is used as the binder for the positive electrode, the molded body easily swells due to the infiltration of the electrolytic solution, and the load characteristics are deteriorated. Becomes larger than the standard value, and the area becomes larger than the separator due to expansion in the surface direction of the molded body, thereby causing a short circuit with the negative electrode. On the other hand, when polyamideimide is used as the binder for the positive electrode, although it varies depending on the molecular weight, the positive electrode is generally harder than polyvinylidene fluoride and a strong positive electrode can be formed. Tends to be lower than when polyvinylidene fluoride is used.
[0013]
Therefore, in the present invention, the polyvinylidene fluoride and polyamideimide are mixed, and the mixture is used as a binder, thereby increasing the ratio of the conductive auxiliary agent without increasing the binder ratio. The present inventors have found that a positive electrode with excellent mechanical strength can be obtained, thereby obtaining a coin-type non-aqueous secondary battery with excellent load characteristics and excellent cycle characteristics and storage characteristics.
[0014]
In the present invention, as the polyvinylidene fluoride used for the purpose as described above, for example, it is preferable to use # 1120 manufactured by Kureha Chemical Co., Ltd., and as the polyamideimide, for example, manufactured by Toyobo Co., Ltd. It is preferable to use Viromax N-100, and when these are used, intermediate physical properties can be obtained depending on the mixing ratio.
[0015]
In the present invention, the ratio of polyamideimide is preferably 5 to 40% by mass in the mixture of polyvinylidene fluoride and polyamideimide. That is, when the ratio of polyamideimide is less than 5% by mass, the mechanical strength of the positive electrode cannot be sufficiently increased, and when the ratio of polyamideimide is increased by 40% by mass, load characteristics are lowered. Cycle characteristics and storage characteristics may be deteriorated. In the present invention, the binder is composed of a mixture of polyvinylidene fluoride and polyamideimide. However, in preparing the positive electrode mixture, it is not necessary to mix polyvinylidene fluoride and polyamideimide in advance. It is sufficient that polyvinylidene fluoride and polyamideimide are present in a mixed state in the mixture or in the positive electrode composed of the pellet-shaped molded body of the positive electrode mixture.
[0016]
In the present invention, the positive electrode active material is not particularly limited. For example, insertion of lithium ions such as LiCoO 2 , LiNiO 2 , LiNi x Co 1-x O 2 , LiMnO 2 , and LiMn 2 O 4 can be used. -Lithium-containing composite oxide capable of desorption is preferred.
[0017]
The conductive additive for the positive electrode is not particularly limited, and examples thereof include carbonaceous materials such as carbon black, graphite, ketjen black, acetylene black, carbon nanotubes, fullerene, vapor grown carbon fiber, Al, Pt. Metal powders such as are preferable.
[0018]
In the production of the positive electrode, the positive electrode active material, the conductive auxiliary agent, the binder, etc. are mixed to prepare a positive electrode mixture, which is filled into a mold and subjected to pressure molding, thereby forming the positive electrode composition constituting the positive electrode. A pellet-shaped molded body of the agent is produced. And the pellet-shaped molded object of the positive mix which comprises the positive electrode is normally produced by the thickness of 0.2 mm or more. In preparing the positive electrode mixture, a positive electrode active material, a conductive additive, and a binder are mixed in the presence of a solvent, dried, and pulverized to obtain a positive electrode mixture in which each component is more uniformly dispersed. It is done. In general, the mixture of polyvinylidene fluoride and polyamideimide used as a binder in the present invention is preferably contained in an amount of 3 to 20% by mass in the positive electrode mixture. Also, the polyvinylidene fluoride and polyamideimide are mixed with each other. If the binder consisting of a mixture is contained in the positive electrode mixture to the extent described above, another binder may be used in combination.
[0019]
In the present invention, the negative electrode may be composed of a pellet-shaped molded body of a negative electrode mixture containing a negative electrode active material, or may be composed of only metallic lithium or a lithium alloy. When the negative electrode is composed of a negative electrode mixture pellet-shaped molded body, the active material of the negative electrode is not particularly limited as long as lithium ions can be inserted and desorbed. For example, graphite, carbon nanotube Carbonaceous materials such as vapor grown carbon fiber and low crystalline carbon, and metal oxides such as Si and Sn are preferable.
[0020]
In addition, when the negative electrode is composed of a negative electrode mixture pellet-like molded body, a binder is required in addition to the negative electrode active material in the production, and the binder is not particularly limited. Vinylidene chloride, a mixture of styrene butadiene rubber and carboxymethyl cellulose, polyamideimide and the like are preferable. Further, as the binder for the negative electrode, the same binder as that for the positive electrode can be used.
[0021]
In the present invention, the non-aqueous electrolyte solution, the positive electrode can, the negative electrode can, the separator, the annular insulating gasket and the like are not particularly limited, and those having a conventional configuration can be used, and the electrolyte solution is liquid. Not only the case of using it as it is, but it may be gelled with a gelling agent and used.
[0022]
【Example】
Next, the present invention will be described more specifically with reference to examples. However, this invention is not limited only to those Examples.
[0023]
Example 1
LiCoO 2 having an average particle diameter of 5 μm is used as the positive electrode active material, carbon black is used as the conductive auxiliary agent, # 1120 (trade name) manufactured by Kureha Chemical Co., Ltd. is used as the polyvinylidene fluoride constituting the binder, and Toyobo Co., Ltd. is used as the polyamideimide. First, 87 parts by mass of LiCoO 2 and 5 parts by mass of carbon black were mixed using Viromax N-100 (trade name), and 92 parts by mass of the obtained mixture and N-methyl-polyvinylidene fluoride in advance were mixed. Prepared by dissolving 5 parts by mass of 2-pyrrolidone in a solution of polyvinylidene fluoride in N-methyl-2-pyrrolidone and 3 parts by mass of the polyamideimide in N-methyl-2-pyrrolidone. The mixture was prepared by mixing and stirring the N-methyl-2-pyrrolidone solution of the polyamideimide A containing paint was prepared. This paint was once dried to remove N-methyl-2-pyrrolidone as a solvent, and then pulverized. The obtained positive electrode mixture powder was filled in a mold and pressure-molded to obtain a diameter of 16 mm and a thickness of A 0.9 mm thick pellet-shaped molded body was produced and used as a positive electrode. The ratio of polyvinylidene fluoride and polyamideimide constituting the binder in the total positive electrode mixture is 5% by mass, and the ratio of polyamideimide in the total positive electrode mixture is 3% by mass. The ratio of polyamideimide in the total of vinylidene chloride and polyamideimide was 37.5% by mass.
[0024]
A negative electrode active material obtained by graphitizing mesocarbon microbeads having an average particle diameter of 3 μm was graphitized, and 90 parts by mass of the mesocarbon microbeads graphitized and polyvinylidene fluoride as a binder in advance by N-methyl-2 -A mixture-containing coating material was prepared by mixing and stirring a binder solution prepared by dissolving 10 parts by mass in pyrrolidone. The paint is dried once, the solvent is removed, and pulverized. The obtained negative electrode mixture powder is filled in a mold and pressure-molded to form a pellet having a diameter of 16.5 mm and a thickness of 0.7 mm. A molded body was prepared and used as a negative electrode.
[0025]
As the electrolytic solution, a non-aqueous electrolytic solution prepared by dissolving 1 mol / liter of LiPF 6 in a mixed solvent of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 1: 3 was used, and a microporous polypropylene film was used as the separator. The stainless steel can be used as the positive electrode can, the stainless steel can be used as the negative can, and the polypropylene can be used as the annular insulating gasket. A coin-type non-aqueous secondary battery as shown in FIG.
[0026]
Here, the coin-type non-aqueous secondary battery shown in FIG. 1 will be described. 1 is the positive electrode and 2 is the negative electrode. A
[0027]
This will be described in detail. The
[0028]
Example 2
The ratio of polyvinylidene fluoride in the total positive electrode mixture is obtained by increasing the hardness by reducing the molecular weight of Viromax N-100 (trade name) manufactured by Toyobo Co., Ltd. used in Example 1 as the polyamideimide. Was formed in the same manner as in Example 1, except that the ratio of the polyamideimide in the total positive electrode mixture of polyamideimide was 0.5 mass%.
[0029]
Comparative Example 1
In the preparation of the positive electrode mixture, a polyamide imide was not used, the binder was composed only of polyvinylidene fluoride, and the proportion of polyvinylidene fluoride in the total positive electrode mixture was changed to 8% by mass. A non-aqueous secondary battery was produced.
[0030]
Comparative Example 2
In the preparation of the positive electrode mixture, a coin was formed in the same manner as in Example 1 except that polyvinylidene fluoride was not used, the binder was composed only of polyamideimide, and the ratio of polyamideimide in the total positive electrode mixture was 8 mass%. A non-aqueous secondary battery was produced.
[0031]
For the batteries of Examples 1-2 and Comparative Examples 1-2, the charge end voltage was fixed at 4.2 V, the discharge end voltage was fixed at 3.0 V, and the charge current density was 1 mA / cm 2 , and the charge current density was 1 mA / cm. 2 to 4.2 V, discharge current density of 1 mA / cm 2 and 10 mA / cm 2 to 3.0 V, respectively, and the initial discharge capacity is measured. The initial discharge capacity at 10 mA / cm 2 is 1 mA. The ratio to the initial discharge capacity at / cm 2 is the load characteristic, and the discharge capacity is measured by repeating charge and discharge 100 times at a charge current density of 1 mA / cm 2 and a discharge current density of 1 mA / cm 2 . the ratio of initial discharge capacity of the discharge capacity and cycle characteristics, and storage for 30 days charged state at 60 ° C. to measure the discharge capacity at a discharge current density of 1 mA / cm 2, savings of the discharge capacity after the storage The ratio of discharge capacity before the storage properties are shown in Table 1, respectively, the percentage (%) display.
[0032]
[Table 1]
As is clear from the results shown in Table 1, the batteries of Examples 1 and 2 were superior in cycle characteristics and storage characteristics as compared with the batteries of Comparative Examples 1 and 2. This is considered to be based on the fact that the batteries of Examples 1 and 2 have higher mechanical strength of the positive electrode than the batteries of Comparative Examples 1 and 2.
[0034]
As described above, according to the present invention, it is possible to provide a coin-type non-aqueous secondary battery with improved cycle characteristics and load characteristics by increasing the mechanical strength of the positive electrode.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing an example of a coin-type non-aqueous secondary battery according to the present invention.
[Explanation of symbols]
DESCRIPTION OF
Claims (4)
前記正極が少なくとも活物質と導電助剤とバインダーを含む正極合剤のペレット状成形体からなり、前記正極合剤のペレット状成形体の厚みが０．２ｍｍ以上であり、
前記バインダーが、ポリフッ化ビニリデンとポリアミドイミドとの混合物からなり、かつ前記混合物におけるポリアミドイミドの比率が５〜４０質量％であることを特徴とするコイン形非水二次電池。A positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte solution are accommodated in a sealed space formed by a positive electrode can, a negative electrode can, and an annular insulating gasket. A coin-type non-aqueous secondary battery,
The positive electrode comprises a pellet-shaped molded body of a positive electrode mixture containing at least an active material, a conductive additive and a binder, and the thickness of the pellet-shaped molded body of the positive electrode mixture is 0.2 mm or more,
Before SL binder, Ri Do from a mixture of polyvinylidene fluoride and polyamide-imide, and coin-type nonaqueous secondary battery the ratio of the polyamide-imide in the mixture and wherein the 5 to 40% by mass Rukoto.
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| KR101665656B1 (en) | 2015-04-28 | 2016-10-12 | 충남대학교산학협력단 | Cathode Material for secondary battery, and Lithium secondary battery manufactured therefrom |
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| DE102008049371A1 (en) * | 2008-03-06 | 2009-09-10 | Mühlbauer Ag | Device with an RFID transponder in an electrically conductive object and manufacturing method thereof |
| JP6098522B2 (en) * | 2011-12-16 | 2017-03-22 | 日本電気株式会社 | Negative electrode for secondary battery, method for producing the same, and secondary battery |
| JP6009343B2 (en) | 2011-12-26 | 2016-10-19 | 株式会社半導体エネルギー研究所 | Secondary battery positive electrode and method for producing secondary battery positive electrode |
| WO2021001315A1 (en) * | 2019-07-01 | 2021-01-07 | Solvay Specialty Polymers Italy S.P.A. | Composition for secondary battery electrodes |
| CN114050260B (en) * | 2021-10-22 | 2023-06-16 | 深圳市研一新材料有限责任公司 | Positive electrode film layer additive composition, positive electrode film layer additive, positive electrode plate and secondary battery |
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| KR101665656B1 (en) | 2015-04-28 | 2016-10-12 | 충남대학교산학협력단 | Cathode Material for secondary battery, and Lithium secondary battery manufactured therefrom |
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