JP6645040B2 - Conductive material dispersion for electrochemical element, slurry for positive electrode of electrochemical element, positive electrode for electrochemical element, and electrochemical element - Google Patents
Conductive material dispersion for electrochemical element, slurry for positive electrode of electrochemical element, positive electrode for electrochemical element, and electrochemical element Download PDFInfo
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- JP6645040B2 JP6645040B2 JP2015123149A JP2015123149A JP6645040B2 JP 6645040 B2 JP6645040 B2 JP 6645040B2 JP 2015123149 A JP2015123149 A JP 2015123149A JP 2015123149 A JP2015123149 A JP 2015123149A JP 6645040 B2 JP6645040 B2 JP 6645040B2
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- conductive material
- positive electrode
- polymer
- slurry
- mass
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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
- Y02E60/13—Energy storage using capacitors
Description
本発明は、電気化学素子用導電材分散液、電気化学素子正極用スラリー、電気化学素子用正極および電気化学素子に関するものである。 The present invention relates to a conductive material dispersion for an electrochemical device, a slurry for a positive electrode of an electrochemical device, a positive electrode for an electrochemical device, and an electrochemical device.
リチウムイオン二次電池、リチウムイオンキャパシタおよび電気二重層キャパシタなどの電気化学素子は、小型で軽量、且つ、エネルギー密度が高く、更に繰り返し充放電が可能という特性があり、幅広い用途に使用されている。ここで、例えばリチウムイオン二次電池用の電極は、通常、集電体と、集電体上に形成された電極合材層とを備えている。そして、電極合材層、例えば正極合材層は、通常、正極活物質に加え、導電性を向上させるための導電材、これらの成分を結着するための結着材を分散媒中に含んでなる正極用スラリーを集電体上に塗布し、乾燥させることにより形成されている。 Electrochemical elements such as lithium ion secondary batteries, lithium ion capacitors, and electric double layer capacitors are used in a wide range of applications because of their small size, light weight, high energy density, and the ability to be repeatedly charged and discharged. . Here, for example, an electrode for a lithium ion secondary battery usually includes a current collector and an electrode mixture layer formed on the current collector. The electrode mixture layer, for example, the positive electrode mixture layer usually contains, in addition to the positive electrode active material, a conductive material for improving conductivity and a binder for binding these components in the dispersion medium. Is formed by applying a positive electrode slurry on a current collector and drying the slurry.
ここで、電気化学素子の性能向上を達成すべく、従来から正極用スラリー等の電極用スラリーを改良する試みがなされている。具体的には、凝集し易いカーボンブラックなどの導電材の分散性を改良して電気化学素子の性能を向上させるべく、導電材、分散剤、および分散媒を予混合してなる導電材分散液と、電極活物質とを併せて電極用スラリーとし、当該電極用スラリーを用いて電極を形成する技術が提案されている。 Here, in order to achieve an improvement in the performance of the electrochemical element, attempts have been made to improve electrode slurries such as positive electrode slurries. Specifically, in order to improve the performance of an electrochemical element by improving the dispersibility of a conductive material such as carbon black, which is easy to aggregate, a conductive material dispersion liquid obtained by premixing a conductive material, a dispersant, and a dispersion medium. And an electrode active material are combined to form an electrode slurry, and a technique for forming an electrode using the electrode slurry has been proposed.
例えば、特許文献１では、導電材としてのカーボンブラックと、分散剤としての特定の性状を有するポリビニルアルコール樹脂と、分散媒としてのＮ−メチル−２−ピロリドン（ＮＭＰ）を含む導電材分散液をリチウムイオン二次電池の電極合材層の形成に用いることが提案されている。そして、特許文献１では、この導電材分散液はカーボンブラックの分散性と貯蔵安定性に優れ、かつ、当該分散液に電極活物質を加えた電極用スラリーを用いて均質な塗膜を塗布可能であり、当該電極用スラリーから表面抵抗の低い電極合材層を形成することができると報告されている。 For example, in Patent Document 1, a conductive material dispersion liquid containing carbon black as a conductive material, a polyvinyl alcohol resin having a specific property as a dispersant, and N-methyl-2-pyrrolidone (NMP) as a dispersion medium is disclosed. It has been proposed to use it for forming an electrode mixture layer of a lithium ion secondary battery. According to Patent Document 1, this conductive material dispersion is excellent in dispersibility and storage stability of carbon black, and a uniform coating film can be applied using an electrode slurry obtained by adding an electrode active material to the dispersion. It is reported that an electrode mixture layer having a low surface resistance can be formed from the electrode slurry.
また例えば、特許文献２では、導電材としてのカーボンブラックと、分散剤としてのポリビニルアセタール樹脂と、分散媒としてのＮＭＰと含む導電材分散液をリチウムイオン二次電池の電極合材層の形成に用いることが提案されている。そして、特許文献２では、この導電材分散液はカーボンブラックの分散性と貯蔵安定性に優れ、当該分散液に電極活物質を加えた電極用スラリーを用いることで、内部抵抗の低減が可能な電極合材層を形成することができると報告されている。 Further, for example, in Patent Document 2, a conductive material dispersion containing carbon black as a conductive material, a polyvinyl acetal resin as a dispersant, and NMP as a dispersion medium is used for forming an electrode mixture layer of a lithium ion secondary battery. It has been proposed to use. In Patent Document 2, this conductive material dispersion liquid has excellent dispersibility and storage stability of carbon black, and the internal resistance can be reduced by using an electrode slurry obtained by adding an electrode active material to the dispersion liquid. It is reported that an electrode mixture layer can be formed.
しかしながら、上記従来の技術では、導電材分散液および電極用スラリー中において、分散剤の導電材分散能が十分に発揮されない場合があり、経時による粘度変化により導電材の分散性が損なわれる虞、即ち、保存安定性が低下する虞があった。また、導電材分散液を含む電極用スラリーを集電体上に塗布して塗膜を形成する際に、当該塗膜の厚みを十分に均一に出来ない場合があった。そして、このような導電材分散液および電極用スラリーを用いて形成される電極合材層は、厚みが一様となり難く、また、当該電極合材層中で好適な導電材ネットワークが形成され難い場合があり、電気化学素子に十分な出力特性を発揮させることができなかった。
したがって、上記従来の技術には、導電材分散液の保存安定性を確保しつつ、当該導電材分散液を含む正極用スラリーの塗工性を改良し、そして電気化学素子の出力特性を向上させるという点において未だ改善の余地があった。
However, in the above-described conventional technique, in the conductive material dispersion and the electrode slurry, the conductive material dispersibility of the dispersant may not be sufficiently exhibited, and the dispersibility of the conductive material may be impaired due to a change in viscosity over time. That is, the storage stability may be reduced. In addition, when an electrode slurry containing a conductive material dispersion is applied on a current collector to form a coating film, the thickness of the coating film may not be sufficiently uniform. The thickness of the electrode mixture layer formed using the conductive material dispersion liquid and the electrode slurry is difficult to be uniform, and a suitable conductive material network is not easily formed in the electrode mixture layer. In some cases, sufficient output characteristics could not be exhibited in the electrochemical device.
Therefore, the above-described conventional techniques improve the coating property of the slurry for the positive electrode containing the conductive material dispersion liquid while securing the storage stability of the conductive material dispersion liquid, and improve the output characteristics of the electrochemical element. There was still room for improvement in this respect.
そこで、本発明は、保存安定性に優れ、電気化学素子電極用スラリーに良好な塗工性を付与しつつ、電気化学素子に優れた出力特性を発揮させることが可能な電気化学素子用導電材分散液を提供することを目的とする。
また、本発明は、保存安定性および塗工性に優れ、電気化学素子に優れた出力特性を発揮させることが可能な電気化学素子正極用スラリーを提供することを目的とする。
更に、本発明は、電気化学素子に優れた出力特性を発揮させることが可能な電気化学素子用正極、および出力特性に優れる電気化学素子を提供することを目的とする。
Therefore, the present invention provides a conductive material for an electrochemical element that has excellent storage stability and can exhibit excellent output characteristics to an electrochemical element while imparting good coatability to the slurry for an electrochemical element electrode. It is intended to provide a dispersion.
Another object of the present invention is to provide a slurry for a positive electrode of an electrochemical device, which is excellent in storage stability and coatability and can exhibit excellent output characteristics to the electrochemical device.
Still another object of the present invention is to provide a positive electrode for an electrochemical device capable of exhibiting excellent output characteristics to an electrochemical device, and an electrochemical device having excellent output characteristics.
本発明者らは、上記課題を解決することを目的として鋭意検討を行った。そして、本発明者らは、分散媒としてピロリドン系溶媒を使用した導電材分散液において、分散剤としてニトリル基含有単量体単位およびアルキレン構造単位を含み、そしてヨウ素価が特定の範囲内である重合体を特定量用い、かつ導電材分散液を特定の粘度以下の低粘度とすることで、導電材の保存安定性を優れたものとしつつ、この導電材分散液を含んでなる電極用スラリーの塗工性を向上させ、さらには、当該電極用スラリーを用いて形成される電極を備える電気化学素子の出力特性を高めることができることを見出し、本発明を完成させるに至った。 The present inventors have conducted intensive studies for the purpose of solving the above problems. And the present inventors include a nitrile group-containing monomer unit and an alkylene structural unit as a dispersant in a conductive material dispersion using a pyrrolidone-based solvent as a dispersion medium, and the iodine value is within a specific range. By using a specific amount of the polymer and making the conductive material dispersion a low viscosity of a specific viscosity or less, the storage stability of the conductive material is improved, and the electrode slurry containing the conductive material dispersion is obtained. It has been found that it is possible to improve the coatability of the electrode, and to further enhance the output characteristics of an electrochemical element having an electrode formed by using the electrode slurry, thereby completing the present invention.
即ち、この発明は、上記課題を有利に解決することを目的とするものであり、本発明の電気化学素子用導電材分散液は、導電材、重合体Ｘ、およびピロリドン系溶媒を含む電気化学素子用導電材分散液であって、前記重合体Ｘは、ニトリル基含有単量体単位およびアルキレン構造単位を含み、ヨウ素価が２０ｍｇ/１００ｍｇ以下であり、前記導電材１００質量部当たり、前記重合体Ｘを２質量部以上３０質量部以下含み、そして、粘度が８００ｍＰａ・ｓ以下であることを特徴とする。このように、分散媒としてピロリドン系溶媒を使用した導電材分散液において上述した重合体Ｘを特定量使用し、さらに当該導電材分散液の粘度を特定の範囲内とすれば、導電材分散液の保存安定性を高めつつ、電気化学素子電極用スラリーに良好な塗工性を付与することができ、さらには、電気化学素子に優れた出力特性を発揮させることができる。
なお、本発明において重合体Ｘのヨウ素価は、重合体Ｘの水分散液または溶液１００ｇを、メタノール１リットルで凝固した後、６０℃で１２時間真空乾燥して得られる乾燥した重合体Ｘのヨウ素価を、ＪＩＳ Ｋ６２３５（２００６）に従って測定することで得ることができる。
また、本発明において導電材分散液の粘度は、Ｂ型粘度計を用いて、温度２５℃、回転速度６０ｒｐｍ、回転時間６０秒の条件で測定することができる。
That is, an object of the present invention is to solve the above-described problem advantageously, and an electroconductive material dispersion for an electrochemical device of the present invention is an electroconductive material containing an electroconductive material, a polymer X, and a pyrrolidone-based solvent. A conductive material dispersion for an element, wherein the polymer X contains a nitrile group-containing monomer unit and an alkylene structural unit, has an iodine value of 20 mg / 100 mg or less, and has a weight per 100 parts by mass of the conductive material. It is characterized by comprising 2 parts by mass or more and 30 parts by mass or less of the combined X and having a viscosity of 800 mPa · s or less. As described above, when a specific amount of the above-described polymer X is used in a conductive material dispersion using a pyrrolidone-based solvent as a dispersion medium, and the viscosity of the conductive material dispersion is set within a specific range, the conductive material dispersion Of the slurry for an electrochemical device electrode can be imparted with good coating properties while improving the storage stability of the device, and further, the electrochemical device can exhibit excellent output characteristics.
In the present invention, the iodine value of the polymer X is the same as that of the dried polymer X obtained by coagulating 100 g of an aqueous dispersion or solution of the polymer X with 1 liter of methanol and then vacuum drying at 60 ° C. for 12 hours. The iodine value can be obtained by measuring according to JIS K6235 (2006).
In the present invention, the viscosity of the conductive material dispersion can be measured using a B-type viscometer at a temperature of 25 ° C., a rotation speed of 60 rpm, and a rotation time of 60 seconds.
ここで、本発明の電気化学素子用導電材分散液は、前記重合体Ｘが、ニトリル基含有単量体単位を１５質量％以上５０質量％以下含み、アルキレン構造単位を５０質量％以上８５質量％以下含むことが好ましい。ニトリル基含有単量体単位とアルキレン構造単位を上述の範囲内で含む重合体Ｘは、導電材分散能とピロリドン系溶媒への溶解性をバランスよく備え、当該重合体Ｘを含む導電材分散液の保存安定性を更に向上させることができるからである。 Here, in the conductive material dispersion for an electrochemical element of the present invention, the polymer X contains a nitrile group-containing monomer unit in an amount of 15% by mass to 50% by mass, and an alkylene structural unit in an amount of 50% by mass to 85% by mass. % Or less. The polymer X containing the nitrile group-containing monomer unit and the alkylene structural unit within the above range is provided with a well-balanced conductive material dispersibility and solubility in a pyrrolidone solvent, and a conductive material dispersion containing the polymer X This is because the storage stability can be further improved.
そして、本発明の電気化学素子用導電材分散液は、さらにフッ素樹脂Ｙを含むことが好ましい。フッ素樹脂Ｙを使用することで、導電材分散液から形成される電極合材層と集電体の密着性が確保され、電気化学素子の出力特性などの電気的特性を更に向上させることができるからである。 And it is preferable that the conductive material dispersion liquid for an electrochemical element of the present invention further contains a fluororesin Y. By using the fluororesin Y, the adhesion between the electrode mixture layer formed from the conductive material dispersion and the current collector is secured, and the electrical characteristics such as the output characteristics of the electrochemical element can be further improved. Because.
また、本発明の電気化学素子正極用スラリーは、上述の何れかの電気化学素子用導電材分散液および正極活物質を含むことを特徴とする。上述したいずれかの導電材分散液を用いて調製された正極用スラリーは、保存安定性および塗工性に優れる。また、当該正極用スラリーを用いて調製した正極を使用すれば、電気化学素子に優れた出力特性を発揮させることができる。 Further, a slurry for a positive electrode of an electrochemical device of the present invention is characterized by containing any one of the above-described conductive material dispersions for an electrochemical device and a positive electrode active material. The positive electrode slurry prepared using any of the above-described conductive material dispersions has excellent storage stability and coatability. In addition, if a positive electrode prepared using the positive electrode slurry is used, an excellent output characteristic of the electrochemical device can be exhibited.
また、本発明の電気化学素子用正極は、上述の電気化学素子正極用スラリーを用いて調製した正極合材層を、集電体上に備えることを特徴とする。上述の正極用スラリーから形成された正極合材層を備える正極は、電気化学素子に優れた出力特性を発揮させることができる。 Further, a positive electrode for an electrochemical device of the present invention is characterized in that a positive electrode mixture layer prepared using the above slurry for a positive electrode for an electrochemical device is provided on a current collector. The positive electrode including the positive electrode mixture layer formed from the positive electrode slurry described above can exhibit excellent output characteristics for an electrochemical device.
また、本発明の電気化学素子は、上述の電気化学素子用正極を備えることを特徴とする。上述の電気化学素子用正極を備える電気化学素子は、優れた出力特性を発揮する。 In addition, an electrochemical device of the present invention includes the above-described positive electrode for an electrochemical device. An electrochemical device including the above-described positive electrode for an electrochemical device exhibits excellent output characteristics.
本発明によれば、保存安定性に優れ、電気化学素子電極用スラリーに良好な塗工性を付与しつつ、電気化学素子に優れた出力特性を発揮させることが可能な電気化学素子用導電材分散液を提供することができる。
本発明によれば、保存安定性および塗工性に優れ、電気化学素子に優れた出力特性を発揮させることが可能な電気化学素子正極用スラリーを提供することができる。
更に、本発明によれば、電気化学素子に優れた出力特性を発揮させることが可能な電気化学素子用正極、および出力特性に優れる電気化学素子を提供することができる。
Advantageous Effects of Invention According to the present invention, a conductive material for an electrochemical element capable of exhibiting excellent output characteristics to an electrochemical element while imparting excellent coatability to a slurry for an electrochemical element electrode, having excellent storage stability. A dispersion can be provided.
ADVANTAGE OF THE INVENTION According to this invention, it is excellent in storage stability and coating property, and can provide the slurry for electrochemical element positive electrodes which can exhibit the outstanding output characteristics to an electrochemical element.
Furthermore, according to the present invention, it is possible to provide a positive electrode for an electrochemical device capable of exhibiting excellent output characteristics to an electrochemical device, and an electrochemical device having excellent output characteristics.
以下、本発明の実施形態について詳細に説明する。
ここで、本発明の電気化学素子用導電材分散液は、電気化学素子電極用スラリー、好ましくは電気化学素子正極用スラリーを製造する際の材料として用いられる。そして、本発明の電気化学素子正極用スラリーは、本発明の電気化学素子用導電材分散液を用いて形成される。加えて、本発明の電気化学素子用正極は、本発明の電気化学素子正極用スラリーを用いて形成された正極合材層を備えることを特徴とする。また、本発明の電気化学素子は、本発明の電気化学素子用正極を備えることを特徴とする。
Hereinafter, embodiments of the present invention will be described in detail.
Here, the conductive material dispersion liquid for an electrochemical device of the present invention is used as a material for producing a slurry for an electrochemical device electrode, preferably a slurry for an electrochemical device positive electrode. The slurry for a positive electrode of an electrochemical device of the present invention is formed using the conductive material dispersion liquid for an electrochemical device of the present invention. In addition, the positive electrode for an electrochemical device of the present invention includes a positive electrode mixture layer formed using the slurry for a positive electrode of an electrochemical device of the present invention. Further, an electrochemical device of the present invention includes the positive electrode for an electrochemical device of the present invention.
（電気化学素子用導電材分散液）
本発明の電気化学素子用導電材分散液は、ピロリドン系溶媒中に、導電材に加え、ニトリル基含有単量体単位およびアルキレン構造単位を含み、ヨウ素価が２０ｍｇ/１００ｍｇ以下である重合体Ｘを含み、任意にフッ素樹脂Ｙを更に含有する。そして、本発明の電気化学素子用導電材分散液は、重合体Ｘの配合量が、導電材１００質量部当たり、２〜３０質量部であり、そして、粘度が８００ｍＰａ・ｓ以下であることを特徴とする。
このように、上述した重合体Ｘを特定の割合で含み、粘度が８００ｍＰａ・ｓ以下である導電材分散液は、保存安定性に優れる上、当該導電材分散液を含む電極用スラリーの塗工性を向上させ、集電体上に均一な塗膜を形成することができる。そして、当該塗膜を乾燥等して形成された電極合材層を備える電極は、電気化学素子に優れた出力特性を発揮させることができる。
なお、本発明において「単量体単位を含む」とは、「その単量体を用いて得た重合体中に単量体由来の繰り返し単位が含まれている」ことを意味する。
また、本発明において「アルキレン構造単位を含む」とは、「重合体中に一般式−ＣｎＨ２ｎ−［但し、ｎは２以上の整数］で表わされるアルキレン構造のみで構成される繰り返し単位が含まれている」ことを意味する。
(Conductive material dispersion for electrochemical element)
The conductive material dispersion for an electrochemical device of the present invention is a polymer X containing a nitrile group-containing monomer unit and an alkylene structural unit in addition to a conductive material in a pyrrolidone-based solvent, and having an iodine value of 20 mg / 100 mg or less. And optionally further contains a fluororesin Y. And the conductive material dispersion liquid for an electrochemical element of the present invention is such that the compounding amount of the polymer X is 2 to 30 parts by mass per 100 parts by mass of the conductive material, and the viscosity is 800 mPa · s or less. Features.
As described above, the conductive material dispersion containing the polymer X in a specific ratio and having a viscosity of 800 mPa · s or less has excellent storage stability and is capable of coating the electrode slurry containing the conductive material dispersion. Properties can be improved and a uniform coating film can be formed on the current collector. An electrode including an electrode mixture layer formed by drying the coating film or the like can exhibit excellent output characteristics for an electrochemical element.
In the present invention, “including a monomer unit” means that “a polymer obtained by using the monomer contains a repeating unit derived from the monomer”.
In the present invention, “including an alkylene structural unit” refers to “a repeating unit composed of only an alkylene structure represented by a general formula —C n H 2n — [where n is an integer of 2 or more] in a polymer”. Is included. "
＜導電材＞
導電材は、電極合材層中で電極活物質同士の電気的接触を確保するためのものである。そして、本発明の導電材分散液に用いる導電材としては、特に限定されることなく、カーボンブラック（例えば、アセチレンブラック、ケッチェンブラック（登録商標）、ファーネスブラックなど）、単層または多層カーボンナノチューブ（多層カーボンナノチューブにはカップスタック型が含まれる）、カーボンナノホーン、気相成長炭素繊維、ポリマー繊維を焼成後に破砕して得られるミルドカーボン繊維、単層または多層グラフェン、ポリマー繊維からなる不織布を焼成して得られるカーボン不織布シートなどの導電性炭素材料、並びに各種金属のファイバー又は箔などを用いることができる。これらは一種単独で、または、二種以上を組み合わせて用いることができる。これらの中でも、化学的安定性に優れるという点で、導電性炭素材料が好ましい。また、近接する導電性炭素材料同士の接触頻度を高め、安定した導電パスを形成しつつ高効率での電子授受を達成して、優れた導電性を発現させる観点からは、カーボンブラックや、繊維状又はシート状である導電性炭素材料がより好ましい。
ここで、本発明において導電性炭素材料が「繊維状」であるとは、透過型電子顕微鏡（ＴＥＭ）で測定した導電性炭素材料のアスペクト比が１０以上であることをいい、繊維状導電性炭素材料としては、例えば、上述した単層または多層カーボンナノチューブ、カーボンナノホーン、気相成長炭素繊維、ミルドカーボン繊維などが挙げられる。
また、本発明において導電性炭素材料が「シート状」であるとは、導電性炭素材料が平面状に広がる構造を有することをいい、シート状導電性炭素材料としては、例えば、上述した単層または多層グラフェン、カーボン不織布シートなどが挙げられる。なお、平面状に広がる構造を有するシート状導電性炭素材料には、繊維状導電性炭素材料は含まれないものとする。
<Conductive material>
The conductive material is for ensuring electrical contact between the electrode active materials in the electrode mixture layer. The conductive material used in the conductive material dispersion of the present invention is not particularly limited, and may be carbon black (eg, acetylene black, Ketjen black (registered trademark), furnace black, etc.), single-walled or multi-walled carbon nanotubes. (Multi-walled carbon nanotubes include cup-stacked type), carbon nanohorn, vapor grown carbon fiber, milled carbon fiber obtained by crushing after sintering polymer fiber, single-layer or multi-layer graphene, firing non-woven fabric consisting of polymer fiber Conductive carbon materials such as a carbon nonwoven fabric sheet obtained as a result, and various metal fibers or foils. These can be used alone or in combination of two or more. Among these, a conductive carbon material is preferable because of its excellent chemical stability. In addition, from the viewpoint of increasing the frequency of contact between adjacent conductive carbon materials, achieving highly efficient electron transfer while forming a stable conductive path, and developing excellent conductivity, carbon black and fiber A conductive carbon material in the shape of a sheet or a sheet is more preferable.
Here, in the present invention, that the conductive carbon material is "fibrous" means that the aspect ratio of the conductive carbon material measured by a transmission electron microscope (TEM) is 10 or more, Examples of the carbon material include the above-described single-walled or multi-walled carbon nanotubes, carbon nanohorns, vapor-grown carbon fibers, and milled carbon fibers.
Further, in the present invention, that the conductive carbon material is “sheet-shaped” means that the conductive carbon material has a structure that spreads in a planar shape. Examples of the sheet-shaped conductive carbon material include, for example, the above-described single layer. Or, a multi-layer graphene, a carbon nonwoven fabric sheet, or the like can be given. Note that a fibrous conductive carbon material is not included in the sheet-shaped conductive carbon material having a structure that spreads in a plane.
カーボンブラックの平均粒子径は、好ましくは１０ｎｍ以上、より好ましくは１５ｎｍ以上、更に好ましくは２０ｎｍ以上であり、好ましくは１００ｎｍ以下、より好ましくは７０ｎｍ以下、更に好ましくは５０ｎｍ以下である。カーボンブラックの平均粒子径が上述の範囲内であれば、導電材であるカーボンブラックの分散性を確保しつつ電極合材層中において良好な導電パスを形成することができるため、導電材分散液の保存安定性、電極用スラリーの塗工性および電気化学素子の出力特性を更に向上させることができる。
なお、本発明において「カーボンブラックの平均粒子径」は、ＴＥＭを用いて無作為に選択されたカーボンブラック粒子１００個の粒子径（個々の粒子の外縁上の２点を結ぶ線分の長さのうち、最大の長さ）を測定して求めることができる。
The average particle size of the carbon black is preferably at least 10 nm, more preferably at least 15 nm, further preferably at least 20 nm, preferably at most 100 nm, more preferably at most 70 nm, further preferably at most 50 nm. If the average particle diameter of the carbon black is within the above range, a good conductive path can be formed in the electrode mixture layer while ensuring the dispersibility of the conductive carbon black. Storage stability, coatability of the electrode slurry and output characteristics of the electrochemical element can be further improved.
In the present invention, the “average particle diameter of carbon black” refers to the particle diameter of 100 carbon black particles randomly selected using a TEM (length of a line connecting two points on the outer edge of each particle). Out of them).
導電材の比表面積は、好ましくは２０ｍ２／ｇ以上、より好ましくは３５ｍ２／ｇ以上であり、好ましくは１０００ｍ２／ｇ以下、より好ましくは８００ｍ２／ｇ以下、更に好ましくは５００ｍ２／ｇ以下、特に好ましくは１００ｍ２／ｇ以下、最も好ましくは６０ｍ２／ｇ以下である。導電材の比表面積が上述の範囲内であれば、導電材の分散性を確保しつつ電極合材層中において良好な導電パスを形成することができるため、導電材分散液の保存安定性、電極用スラリーの塗工性および電気化学素子の出力特性を更に向上させることができる。特に導電材の比表面積が６０ｍ２／ｇ以下である場合は、保存安定性に優れた導電材分散液を容易に得ることができる。
なお、本発明において「導電材の比表面積」とは、窒素吸着法によるＢＥＴ比表面積のことであり、ＡＳＴＭ Ｄ３０３７−８１に準拠して測定することができる。
The specific surface area of the conductive material is preferably 20 m 2 / g or more, more preferably 35 m 2 / g or more, preferably 1000 m 2 / g or less, more preferably 800 m 2 / g or less, and further preferably 500 m 2 / g. Or less, particularly preferably 100 m 2 / g or less, most preferably 60 m 2 / g or less. If the specific surface area of the conductive material is within the above range, it is possible to form a good conductive path in the electrode mixture layer while securing the dispersibility of the conductive material, so that the storage stability of the conductive material dispersion liquid, The coatability of the electrode slurry and the output characteristics of the electrochemical element can be further improved. In particular, when the specific surface area of the conductive material is 60 m 2 / g or less, a conductive material dispersion having excellent storage stability can be easily obtained.
In the present invention, the “specific surface area of the conductive material” refers to a BET specific surface area measured by a nitrogen adsorption method, and can be measured according to ASTM D3037-81.
導電材の密度は、好ましくは０．０１ｇ／ｃｍ３以上、より好ましくは０．０２ｇ／ｃｍ３以上であり、好ましくは０．５ｇ／ｃｍ３以下、より好ましくは０．３ｇ／ｃｍ３以下、更に好ましくは０．２ｇ／ｃｍ３以下である。導電材の密度が上述の範囲内であれば、導電材分散液調製時における導電材の飛散が抑制され、作業性を確保することができる。また分散性を確保しつつ電極合材層中において良好な導電パスを形成することができるため、導電材分散液の保存安定性、電極用スラリーの塗工性および電気化学素子の出力特性を更に向上させることができる。
なお、本発明において「導電材の密度」とは、かさ密度のことであり、ＪＩＳ Ｚ ８９０１に準拠して測定することができる。
The density of the conductive material is preferably 0.01 g / cm 3 or more, more preferably 0.02 g / cm 3 or more, preferably 0.5 g / cm 3 or less, more preferably 0.3 g / cm 3 or less. More preferably, it is 0.2 g / cm 3 or less. When the density of the conductive material is within the above range, scattering of the conductive material during preparation of the conductive material dispersion is suppressed, and workability can be ensured. In addition, since a good conductive path can be formed in the electrode mixture layer while ensuring the dispersibility, the storage stability of the conductive material dispersion, the coating property of the electrode slurry, and the output characteristics of the electrochemical element are further improved. Can be improved.
In the present invention, the “density of the conductive material” means a bulk density, which can be measured according to JIS Z8901.
＜重合体Ｘ＞
重合体Ｘは、ニトリル基含有単量体単位およびアルキレン構造単位を含む共重合体であり、任意に、ニトリル基含有単量体単位およびアルキレン構造単位以外のその他の単量体単位（繰り返し単位）を含んでいてもよい。そして重合体Ｘは、本発明の導電材分散液において、導電材を分散させる分散剤として機能しうる。
<Polymer X>
The polymer X is a copolymer containing a nitrile group-containing monomer unit and an alkylene structural unit, and optionally, other monomer units (repeating units) other than the nitrile group-containing monomer unit and the alkylene structural unit. May be included. The polymer X can function as a dispersant for dispersing the conductive material in the conductive material dispersion of the present invention.
このように、重合体Ｘがニトリル基含有単量体単位およびアルキレン構造単位を含むことで、重合体Ｘの導電材分散能およびピロリドン系溶媒に対する溶解性が確保されるため、導電材分散液中で導電材を良好に分散させることができ、しかも経時による導電材の凝集が抑制されて導電材分散液の保存安定性を向上させることができる。加えて、重合体Ｘの寄与により、本発明の導電材分散液は導電材の凝集などによる高粘度化が抑制されるため、導電材分散液を適度に低粘度とすることができる。このような低粘度の導電材分散液からは、電極用スラリーを容易に調製することができ、当該電極用スラリーも適度に低粘度とすることができる。そのような低粘度の電極用スラリーは、集電体上に均一に塗布することが可能となり、塗布むらが抑制される。そして、このような導電材分散液を用いて形成される電極合材層は、導電性に優れしかも均一な厚みを有し、電気化学素子に優れた出力特性などの電気的特性を発揮させることができる。
以下、重合体Ｘに含まれるニトリル基含有単量体単位、アルキレン構造単位、および任意のその他の単量体単位について詳述する。
As described above, since the polymer X contains the nitrile group-containing monomer unit and the alkylene structural unit, the conductive material dispersibility of the polymer X and the solubility in a pyrrolidone-based solvent are ensured. Thus, the conductive material can be satisfactorily dispersed, and the aggregation of the conductive material over time can be suppressed, and the storage stability of the conductive material dispersion can be improved. In addition, due to the contribution of the polymer X, the conductive material dispersion of the present invention is prevented from becoming highly viscous due to aggregation of the conductive material and the like, so that the conductive material dispersion can have a moderately low viscosity. From such a low-viscosity conductive material dispersion, an electrode slurry can be easily prepared, and the electrode slurry can also have a moderately low viscosity. Such a low-viscosity electrode slurry can be uniformly applied on the current collector, and application unevenness is suppressed. The electrode mixture layer formed using such a conductive material dispersion liquid has excellent conductivity and a uniform thickness, and can exhibit excellent electrical characteristics such as output characteristics to the electrochemical element. Can be.
Hereinafter, the nitrile group-containing monomer unit, the alkylene structural unit, and any other monomer units contained in the polymer X will be described in detail.
［ニトリル基含有単量体単位］
ニトリル基含有単量体単位を形成しうるニトリル基含有単量体としては、α，β−エチレン性不飽和ニトリル単量体が挙げられる。そして、α，β−エチレン性不飽和ニトリル単量体としては、ニトリル基を有するα，β−エチレン性不飽和化合物であれば特に限定されないが、例えば、アクリロニトリル；α−クロロアクリロニトリル、α−ブロモアクリロニトリルなどのα−ハロゲノアクリロニトリル；メタクリロニトリル、α−エチルアクリロニトリルなどのα−アルキルアクリロニトリル；などが挙げられる。なかでも、重合体Ｘのピロリドン系溶媒への溶解性を高める観点からは、ニトリル基含有単量体としては、アクリロニトリルおよびメタクリロニトリルが好ましく、アクリロニトリルがより好ましい。
これらは一種単独で、または、２種以上を組み合わせて用いることができる。
[Nitrile group-containing monomer unit]
Examples of the nitrile group-containing monomer capable of forming the nitrile group-containing monomer unit include α, β-ethylenically unsaturated nitrile monomers. The α, β-ethylenically unsaturated nitrile monomer is not particularly limited as long as it is an α, β-ethylenically unsaturated compound having a nitrile group. For example, acrylonitrile; α-chloroacrylonitrile, α-bromo Α-halogenoacrylonitrile such as acrylonitrile; α-alkylacrylonitrile such as methacrylonitrile and α-ethylacrylonitrile; and the like. Among them, acrylonitrile and methacrylonitrile are preferred as the nitrile group-containing monomer, and acrylonitrile is more preferred, from the viewpoint of increasing the solubility of the polymer X in the pyrrolidone-based solvent.
These can be used alone or in combination of two or more.
そして、上記重合体Ｘ中でのニトリル基含有単量体単位の含有割合は、重合体Ｘ中の全繰り返し単位を１００質量％とした場合に、１５質量％以上が好ましく、２５質量％以上がより好ましく、３０質量％以上が特に好ましく、５０質量％以下が好ましく、４０質量％以下がより好ましい。重合体Ｘ中のニトリル基含有単量体単位の含有割合を１５質量％以上とすることで、重合体Ｘのピロリドン系溶媒への溶解性を向上させることができ、５０質量％以下とすることで、重合体Ｘの導電材分散能を向上させることができる。従って、重合体Ｘ中のニトリル基含有単量体単位の含有割合を上述の範囲内とすることで、導電材分散液の保存安定性を更に向上させることができる。そして、導電材分散液を用いて形成される電極合材層中で導電材を良好に分散させて、導電性を向上させる（即ち、内部抵抗を低減する）ことができ、本発明の導電材分散液を用いて製造された電極を備える電気化学素子の出力特性などの電気的特性を更に向上させることができる。 The content ratio of the nitrile group-containing monomer unit in the polymer X is preferably 15% by mass or more, and more preferably 25% by mass or more when all the repeating units in the polymer X are 100% by mass. It is more preferably at least 30% by mass, particularly preferably at most 50% by mass, more preferably at most 40% by mass. By setting the content ratio of the nitrile group-containing monomer unit in the polymer X to 15% by mass or more, the solubility of the polymer X in a pyrrolidone-based solvent can be improved, and to 50% by mass or less. Thus, the conductive material dispersing ability of the polymer X can be improved. Therefore, by setting the content ratio of the nitrile group-containing monomer unit in the polymer X within the above range, the storage stability of the conductive material dispersion can be further improved. The conductive material can be satisfactorily dispersed in the electrode mixture layer formed using the conductive material dispersion to improve the conductivity (ie, reduce the internal resistance). Electrical characteristics such as output characteristics of an electrochemical element having an electrode manufactured using the dispersion can be further improved.
［アルキレン構造単位］
アルキレン構造単位は、直鎖状であっても分岐状であってもよいが、導電材分散液の保存安定性を向上させる観点からは、アルキレン構造単位は直鎖状、すなわち直鎖アルキレン構造単位であることが好ましい。
そして、重合体Ｘへのアルキレン構造単位の導入方法は、特に限定はされないが、例えば以下の（１）、（２）の方法：
（１）共役ジエン単量体を含む単量体組成物から重合体を調製し、当該重合体に水素添加することで、共役ジエン単量体単位をアルキレン構造単位に変換する方法
（２）１−オレフィン単量体を含む単量体組成物から重合体を調製する方法
が挙げられる。これらの中でも、（１）の方法が重合体Ｘの製造が容易であり好ましい。
[Alkylene structural unit]
The alkylene structural unit may be linear or branched, but from the viewpoint of improving the storage stability of the conductive material dispersion, the alkylene structural unit is linear, that is, a linear alkylene structural unit. It is preferred that
The method of introducing the alkylene structural unit into the polymer X is not particularly limited. For example, the following methods (1) and (2):
(1) Method of converting a conjugated diene monomer unit into an alkylene structural unit by preparing a polymer from a monomer composition containing a conjugated diene monomer and hydrogenating the polymer (2) 1 -A method of preparing a polymer from a monomer composition containing an olefin monomer. Among them, the method (1) is preferable because the production of the polymer X is easy.
ここで、共役ジエン単量体としては、たとえば、１，３−ブタジエン、イソプレン、２，３−ジメチル−１，３−ブタジエン、１，３−ペンタジエンなどの炭素数４以上の共役ジエン化合物が挙げられる。中でも、１，３−ブタジエンが好ましい。すなわち、アルキレン構造単位は、共役ジエン単量体単位を水素化して得られる構造単位（共役ジエン水素化物単位）であることが好ましく、１,３−ブタジエン単量体単位を水素化して得られる構造単位（１,３−ブタジエン水素化物単位）であることがより好ましい。
また、１−オレフィン単量体としては、例えば、エチレン、プロピレン、１−ブテンなどが挙げられる。
これらの共役ジエン単量体や１−オレフィン単量体は、一種単独で、または、２種以上を組み合わせて用いることができる
Here, examples of the conjugated diene monomer include conjugated diene compounds having 4 or more carbon atoms, such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, and 1,3-pentadiene. Can be Among them, 1,3-butadiene is preferred. That is, the alkylene structural unit is preferably a structural unit obtained by hydrogenating a conjugated diene monomer unit (conjugated diene hydride unit), and is preferably a structural unit obtained by hydrogenating a 1,3-butadiene monomer unit. It is more preferably a unit (1,3-butadiene hydride unit).
Examples of the 1-olefin monomer include ethylene, propylene, 1-butene, and the like.
These conjugated diene monomers and 1-olefin monomers can be used alone or in combination of two or more.
そして、上記重合体Ｘ中でのアルキレン構造単位の含有割合は、重合体Ｘ中の全繰り返し単位（単量体単位と構造単位との合計）を１００質量％とした場合に、５０質量％以上が好ましく、６０質量％以上がより好ましく、８５質量％以下が好ましく、７５質量％以下がより好ましく、７０質量％以下が特に好ましい。重合体Ｘ中でのアルキレン構造単位の含有割合を５０質量％以上とすることで、重合体Ｘの導電材分散能を向上させることができ、８５質量％以下とすることで、重合体Ｘのピロリドン系溶媒への溶解性を向上させることができる。従って、重合体Ｘ中のアルキレン構造単位の含有割合を上述の範囲内とすることで、導電材分散液の保存安定性を更に向上させることができる。そして、導電材分散液を用いて形成される電極合材層中で導電材を良好に分散させて、導電性を向上させる（即ち、内部抵抗を低減する）ことができ、本発明の導電材分散液を用いて製造された電極を備える電気化学素子の出力特性などの電気的特性を更に向上させることができる。 The content ratio of the alkylene structural unit in the polymer X is 50% by mass or more when all the repeating units (the total of the monomer unit and the structural unit) in the polymer X are 100% by mass. Is preferably 60% by mass or more, more preferably 85% by mass or less, more preferably 75% by mass or less, and particularly preferably 70% by mass or less. By setting the content ratio of the alkylene structural unit in the polymer X to 50% by mass or more, the conductive material dispersibility of the polymer X can be improved. The solubility in a pyrrolidone-based solvent can be improved. Therefore, by setting the content ratio of the alkylene structural unit in the polymer X within the above range, the storage stability of the conductive material dispersion can be further improved. The conductive material can be satisfactorily dispersed in the electrode mixture layer formed using the conductive material dispersion to improve the conductivity (ie, reduce the internal resistance). Electrical characteristics such as output characteristics of an electrochemical device having an electrode manufactured using the dispersion can be further improved.
［その他の単量体単位］
重合体Ｘは、上述したニトリル基含有単量体単位、アルキレン構造単位以外に、その他の単量体単位を含んでいてもよい。そのようなその他の単量体単位としては、（メタ）アクリル酸エステル単量体単位、親水性基含有単量体単位などが挙げられる。
なお本発明において「（メタ）アクリル」とは、アクリルおよび／またはメタクリルを意味する。
[Other monomer units]
The polymer X may contain other monomer units in addition to the above-mentioned nitrile group-containing monomer units and alkylene structural units. Examples of such other monomer units include (meth) acrylate monomer units, hydrophilic group-containing monomer units, and the like.
In the present invention, “(meth) acryl” means acryl and / or methacryl.
［［（メタ）アクリル酸エステル単量体単位］］
（メタ）アクリル酸エステル単量体単位を形成しうる（メタ）アクリル酸エステル単量体としては、アクリル酸アルキルエステル、メタクリル酸アルキルエステルを用いることができる。
これらの単量体の具体例としては、国際公開第２０１３／０８０９８９号に記載のものが挙げられる。
[[(Meth) acrylate monomer unit]]
As the (meth) acrylate monomer capable of forming the (meth) acrylate monomer unit, an alkyl acrylate or an alkyl methacrylate can be used.
Specific examples of these monomers include those described in WO 2013/080989.
ここで、特にブチルアクリレート等の（メタ）アクリル酸エステル単量体は、重合体Ｘの柔軟性に寄与し得る一方、導電材分散能には寄与し難いため、本発明の導電材分散液を用いて製造した電気化学素子の出力特性が損なわれる場合がある。したがって、重合体Ｘ中での（メタ）アクリル酸エステル単量体単位の含有割合は、アルキレン構造単位の含有割合を十分に確保し、導電材分散能を向上させる観点から、重合体Ｘ中の全繰り返し単位を１００質量％とした場合に、３５質量％以下が好ましく、１０質量％以下がより好ましく、０．０５質量％未満（実質的に含まない）が更に好ましく、０質量％が特に好ましい。 Here, in particular, a (meth) acrylate monomer such as butyl acrylate can contribute to the flexibility of the polymer X, but hardly contributes to the dispersibility of the conductive material. In some cases, the output characteristics of the electrochemical device manufactured using the same are impaired. Therefore, the content ratio of the (meth) acrylate monomer unit in the polymer X is preferably from the viewpoint of sufficiently securing the content ratio of the alkylene structural unit and improving the conductive material dispersing ability. When all the repeating units are 100% by mass, the amount is preferably 35% by mass or less, more preferably 10% by mass or less, further preferably less than 0.05% by mass (substantially not contained), and particularly preferably 0% by mass. .
［［親水性基含有単量体単位］］
親水性基含有単量体単位を形成しうる親水性基含有単量体としては、カルボン酸基を有する単量体、スルホン酸基を有する単量体、リン酸基を有する単量体および水酸基を有する単量体を用いることができる。
これらの単量体の具体例としては、国際公開第２０１３／０８０９８９号に記載のものが挙げられる。
なお本発明において、上述した（メタ）アクリル酸エステル単量体、ニトリル基含有単量体には、カルボン酸基、スルホン酸基、リン酸基および水酸基は含まれないものとする。
[[Hydrophilic group-containing monomer unit]]
Examples of the hydrophilic group-containing monomer capable of forming the hydrophilic group-containing monomer unit include a carboxylic acid group-containing monomer, a sulfonic acid group-containing monomer, a phosphate group-containing monomer, and a hydroxyl group. Can be used.
Specific examples of these monomers include those described in WO 2013/080989.
In the present invention, the above-mentioned (meth) acrylic acid ester monomer and nitrile group-containing monomer do not include a carboxylic acid group, a sulfonic acid group, a phosphoric acid group and a hydroxyl group.
ここで、特にカルボン酸基を有する単量体などの親水性基含有単量体は、重合体Ｘの製造安定性の向上に寄与し得る一方、親水性基含有単量体単位を重合体Ｘに含めると、重合体Ｘが有する導電材分散能が損なわれる虞がある。したがって、導電材分散液の保存安定性を確保する観点から、重合体Ｘ中での親水性基含有単量体単位の含有割合は、重合体Ｘ中の全繰り返し単位を１００質量％とした場合に、０．０５質量％未満（実質的に含まない）が好ましく、０質量％がより好ましい。 Here, particularly, a hydrophilic group-containing monomer such as a monomer having a carboxylic acid group can contribute to the improvement of the production stability of the polymer X, while the hydrophilic group-containing monomer unit is a polymer X , The dispersibility of the conductive material of the polymer X may be impaired. Therefore, from the viewpoint of ensuring the storage stability of the conductive material dispersion, the content ratio of the hydrophilic group-containing monomer unit in the polymer X is defined assuming that all the repeating units in the polymer X are 100% by mass. Is preferably less than 0.05% by mass (substantially not contained), and more preferably 0% by mass.
［重合体Ｘの調製方法］
重合体Ｘの製造方法は特に限定されないが、例えば、上述した単量体を含む単量体組成物を重合して重合体を得て、任意に、得られた重合体を水素添加することで調製することができる。
ここで、本発明において単量体組成物中の各単量体の含有割合は、重合体Ｘおける各単量体単位および構造単位（繰り返し単位）の含有割合に準じて定めることができる。
重合様式は、特に制限なく、溶液重合法、懸濁重合法、塊状重合法、乳化重合法などのいずれの方法も用いることができる。各重合法において、必要に応じて既知の乳化剤や重合開始剤を使用することができる。
水素添加の方法は、特に制限なく、触媒を用いる一般的な方法（例えば、国際公開第２０１２／１６５１２０号、国際公開第２０１３／０８０９８９号および特開２０１３−８４８５号公報参照）を使用することができる。
[Method for Preparing Polymer X]
The method for producing the polymer X is not particularly limited. For example, a polymer is obtained by polymerizing a monomer composition containing the above-mentioned monomer, and optionally, the obtained polymer is hydrogenated. Can be prepared.
Here, in the present invention, the content ratio of each monomer in the monomer composition can be determined according to the content ratio of each monomer unit and structural unit (repeating unit) in the polymer X.
The polymerization method is not particularly limited, and any method such as a solution polymerization method, a suspension polymerization method, a bulk polymerization method, and an emulsion polymerization method can be used. In each polymerization method, a known emulsifier or polymerization initiator can be used as necessary.
The method of hydrogenation is not particularly limited, and a general method using a catalyst (for example, see WO2012 / 165120, WO2013 / 080989, and JP-A-2013-8485) can be used. it can.
［重合体Ｘのヨウ素価］
なお、重合体Ｘのヨウ素価は２０ｍｇ／１００ｍｇ以下である必要があり、１８ｍｇ／１００ｍｇ以下であることが好ましく、１０ｍｇ／１００ｍｇ以下であることが更に好ましく、一方、５ｍｇ／１００ｍｇ以上であることが好ましい。重合体Ｘのヨウ素価が２０ｍｇ／１００ｍｇ超であると、導電材分散液の保存安定性が確保できず、電気化学素子の出力特性が低下してしまう。一方、５ｍｇ／１００ｍｇ以上であることで、重合体Ｘのピロリドン系溶媒への溶解性が向上する。そして、重合体Ｘのヨウ素価を上述の範囲内とすることで、導電材の分散性が確保され、電気化学素子の出力特性を向上させることができる。
[Iodine value of polymer X]
The iodine value of the polymer X needs to be 20 mg / 100 mg or less, preferably 18 mg / 100 mg or less, more preferably 10 mg / 100 mg or less, and on the other hand, 5 mg / 100 mg or more. preferable. If the iodine value of the polymer X is more than 20 mg / 100 mg, the storage stability of the conductive material dispersion cannot be secured, and the output characteristics of the electrochemical element will be reduced. On the other hand, when the content is 5 mg / 100 mg or more, the solubility of the polymer X in a pyrrolidone-based solvent is improved. By setting the iodine value of the polymer X within the above range, the dispersibility of the conductive material is ensured, and the output characteristics of the electrochemical element can be improved.
［好適な重合体Ｘの構造］
そして、重合体Ｘとしては、導電材分散液を用いて形成される電極合材層中で導電材を良好に分散させて、電極合材層の導電性を向上させる観点から、単量体として、ニトリル基含有単量体としてのアクリロニトリルと、共役ジエン単量体としての１，３−ブタジエンを含む単量体組成物を重合してなる重合体に、さらに水素添加することで得られる重合体が好ましい。くわえて、重合体Ｘとしては、上述と同様の観点から、単量体として、ニトリル基含有単量体としてのアクリロニトリルと、共役ジエン単量体としての１，３−ブタジエンのみを含む単量体組成物を重合してなる重合体に、さらに水素添加することで得られる重合体がより好ましい。
[Suitable structure of polymer X]
Then, as the polymer X, from the viewpoint of dispersing the conductive material well in the electrode mixture layer formed using the conductive material dispersion and improving the conductivity of the electrode mixture layer, the polymer X A polymer obtained by further hydrogenating a polymer obtained by polymerizing a monomer composition containing acrylonitrile as a nitrile group-containing monomer and 1,3-butadiene as a conjugated diene monomer Is preferred. In addition, as the polymer X, from the same viewpoint as described above, a monomer containing only acrylonitrile as a nitrile group-containing monomer and a monomer containing only 1,3-butadiene as a conjugated diene monomer are used as monomers. A polymer obtained by further hydrogenating a polymer obtained by polymerizing the composition is more preferable.
［重合体Ｘの配合量］
導電材分散液中における重合体Ｘの配合量は、導電材１００質量部当たり、２質量部以上３０質量部以下であることが必要であり、好ましくは５質量部以上であり、より好ましくは６質量部以上であり、好ましくは２５質量部以下である。導電材分散液中の重合体Ｘの配合量が２質量部未満であると、導電材分散液中の導電材の分散性を十分に確保することができない。一方、導電材分散液中の重合体Ｘの配合量が３０質量部超であると、導電材の分散液の粘度が増加することで電極用スラリーの良好な塗工性が確保できず、また、重合体Ｘの配合量の増加に見合う分散性の向上効果が得られなくなると共に、導電材分散液から形成された電極合材層を備える電極を有する電気化学素子において、内部抵抗が上昇し、出力特性などの電気的特性が低下する。
よって、重合体Ｘの配合量を、導電材１００質量部当たり、２質量部以上３０質量部以下とすることで、電極用スラリーの良好な塗工性および電極合材層中の導電材の分散性が確保され、電気化学素子の出力特性を向上させることができる。
[Blending amount of polymer X]
The compounding amount of the polymer X in the conductive material dispersion is required to be 2 parts by mass or more and 30 parts by mass or less, preferably 5 parts by mass or more, more preferably 6 parts by mass or more per 100 parts by mass of the conductive material. It is at least 25 parts by mass, preferably at most 25 parts by mass. If the amount of the polymer X in the conductive material dispersion is less than 2 parts by mass, the dispersibility of the conductive material in the conductive material dispersion cannot be sufficiently ensured. On the other hand, if the blending amount of the polymer X in the conductive material dispersion is more than 30 parts by mass, the viscosity of the conductive material dispersion increases, so that good coating properties of the electrode slurry cannot be secured, and In addition, the effect of improving the dispersibility corresponding to the increase in the amount of the polymer X cannot be obtained, and the internal resistance of the electrochemical element having the electrode including the electrode mixture layer formed from the conductive material dispersion increases, Electrical characteristics such as output characteristics are degraded.
Therefore, by setting the compounding amount of the polymer X to 2 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the conductive material, good coating properties of the electrode slurry and dispersion of the conductive material in the electrode mixture layer are obtained. Properties can be ensured, and the output characteristics of the electrochemical element can be improved.
＜フッ素樹脂Ｙ＞
本発明の導電材分散液は、任意に、結着材として機能しうるフッ素樹脂Ｙを含有してもよい。結着材として機能しうるフッ素樹脂Ｙを使用することで、当該導電材分散液から形成される電極合材層と集電体の密着性が確保され、出力特性などの電気化学素子の電気的特性を向上させることができる。
なお、上記重合体Ｘも結着性を発揮するが、上述した通り、導電材の分散性、電極用スラリーの塗工性、および電気化学素子の電気的特性の全てを確保する観点からは、重合体Ｘの配合量には限界がある。そこで、本発明の導電材分散液では、重合体Ｘ以外に結着材として機能しうるフッ素樹脂Ｙを使用することで、電極合材層と集電体の密着性を確保することが好ましい。
<Fluorine resin Y>
The conductive material dispersion of the present invention may optionally contain a fluororesin Y that can function as a binder. By using the fluororesin Y which can function as a binder, the adhesion between the electrode mixture layer formed from the conductive material dispersion and the current collector is ensured, and the electrical characteristics of the electrochemical element such as output characteristics are secured. The characteristics can be improved.
Although the polymer X also exhibits binding properties, as described above, from the viewpoint of securing all of the dispersibility of the conductive material, the coating properties of the electrode slurry, and the electrical characteristics of the electrochemical element, The amount of the polymer X is limited. Therefore, in the conductive material dispersion liquid of the present invention, it is preferable to secure the adhesion between the electrode mixture layer and the current collector by using a fluororesin Y that can function as a binder in addition to the polymer X.
フッ素樹脂Ｙは、フッ素含有単量体単位を含む重合体である。具体的には、フッ素樹脂Ｙとしては、１種類以上のフッ素含有単量体の単独重合体または共重合体や、１種類以上のフッ素含有単量体とフッ素を含有しない単量体（以下、「フッ素非含有単量体」と称する。）との共重合体が挙げられる。
なお、フッ素樹脂Ｙにおけるフッ素含有単量体単位の割合は、通常７０質量％以上、好ましくは８０質量％以上である。また、フッ素樹脂Ｙにおけるフッ素非含有単量体単位の割合は、通常３０質量％以下、好ましくは２０質量％以下である。
The fluororesin Y is a polymer containing a fluorine-containing monomer unit. Specifically, as the fluororesin Y, a homopolymer or a copolymer of one or more fluorine-containing monomers, or a monomer containing no fluorine and one or more fluorine-containing monomers (hereinafter, referred to as a fluorine-containing monomer) And a “fluorine-free monomer”).
The proportion of the fluorine-containing monomer unit in the fluororesin Y is usually 70% by mass or more, preferably 80% by mass or more. The proportion of the fluorine-free monomer unit in the fluororesin Y is usually 30% by mass or less, preferably 20% by mass or less.
ここで、フッ素含有単量体単位を形成し得るフッ素含有単量体としては、フッ化ビニリデン、テトラフルオロエチレン、ヘキサフルオロプロピレン、三フッ化塩化ビニル、フッ化ビニル、パーフルオロアルキルビニルエーテルなどが挙げられる。これらの中でも、フッ素含有単量体としては、フッ化ビニリデンが好ましい。 Here, examples of the fluorine-containing monomer capable of forming a fluorine-containing monomer unit include vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, vinyl trifluoride chloride, vinyl fluoride, and perfluoroalkyl vinyl ether. Can be Among these, vinylidene fluoride is preferred as the fluorine-containing monomer.
また、フッ素非含有単量体単位を形成し得るフッ素非含有単量体としては、フッ素含有単量体と共重合可能なフッ素を含まない単量体、例えば、エチレン、プロピレン、１−ブテンなどの１−オレフィン；スチレン、α−メチルスチレン、ｐ−ｔ−ブチルスチレン、ビニルトルエン、クロロスチレンなどの芳香族ビニル化合物；（メタ）アクリロニトリルなどの不飽和ニトリル化合物；（メタ）アクリル酸メチル、（メタ）アクリル酸ブチル、（メタ）アクリル酸２−エチルヘキシルなどの（メタ）アクリル酸エステル化合物；（メタ）アクリルアミド、Ｎ−メチロール（メタ）アクリルアミド、Ｎ−ブトキシメチル（メタ）アクリルアミドなどの（メタ）アクリルアミド化合物；（メタ）アクリル酸、イタコン酸、フマル酸、クロトン酸、マレイン酸などのカルボキシル基を含有するビニル化合物；アリルグリシジルエーテル、（メタ）アクリル酸グリシジルなどのエポキシ基含有不飽和化合物；（メタ）アクリル酸ジメチルアミノエチル、（メタ）アクリル酸ジエチルアミノエチルなどのアミノ基含有不飽和化合物；スチレンスルホン酸、ビニルスルホン酸、（メタ）アリルスルホン酸などのスルホン酸基含有不飽和化合物；３−アリロキシ−２−ヒドロキシプロパン硫酸などの硫酸基含有不飽和化合物；（メタ）アクリル酸−３−クロロ−２−リン酸プロピル、３−アリロキシ−２−ヒドロキシプロパンリン酸などのリン酸基含有不飽和化合物などが挙げられる。 Further, as a fluorine-free monomer capable of forming a fluorine-free monomer unit, a fluorine-free monomer copolymerizable with a fluorine-containing monomer, for example, ethylene, propylene, 1-butene and the like 1-olefins; aromatic vinyl compounds such as styrene, α-methylstyrene, pt-butylstyrene, vinyltoluene, and chlorostyrene; unsaturated nitrile compounds such as (meth) acrylonitrile; methyl (meth) acrylate; (Meth) acrylic ester compounds such as (meth) butyl acrylate and 2-ethylhexyl (meth) acrylate; (meth) acrylic esters such as (meth) acrylamide, N-methylol (meth) acrylamide, and N-butoxymethyl (meth) acrylamide Acrylamide compounds; (meth) acrylic acid, itaconic acid, fumaric acid, crotonic acid, Vinyl compounds containing a carboxyl group such as maleic acid; unsaturated compounds containing an epoxy group such as allyl glycidyl ether and glycidyl (meth) acrylate; amino acids such as dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate Unsaturated compounds having a sulfonic acid group such as styrenesulfonic acid, vinylsulfonic acid, and (meth) allylsulfonic acid; unsaturated compounds having a sulfuric acid group such as 3-allyloxy-2-hydroxypropane sulfate; ) Unsaturated compounds containing a phosphate group, such as acrylate-3-chloro-2-propyl phosphate and 3-allyloxy-2-hydroxypropane phosphate.
そして、フッ素樹脂Ｙとしては、フッ素含有単量体としてフッ化ビニリデンを用いた重合体およびフッ素含有単量体としてフッ化ビニルを用いた重合体が好ましく、フッ素含有単量体としてフッ化ビニリデンを用いた重合体がより好ましい。
具体的には、フッ素樹脂Ｙとしては、フッ化ビニリデンの単独重合体（ポリフッ化ビニリデン）、フッ化ビニリデンとヘキサフルオロプロピレンとの共重合体およびポリフッ化ビニルが好ましく、ポリフッ化ビニリデン（ＰＶＤＦ）がより好ましい。
なお、上述したフッ素樹脂Ｙは、単独で使用してもよいし、２種以上を併用してもよい。
As the fluororesin Y, a polymer using vinylidene fluoride as a fluorine-containing monomer and a polymer using vinyl fluoride as a fluorine-containing monomer are preferable, and vinylidene fluoride is used as a fluorine-containing monomer. The polymer used is more preferred.
Specifically, as the fluororesin Y, a homopolymer of vinylidene fluoride (polyvinylidene fluoride), a copolymer of vinylidene fluoride and hexafluoropropylene, and polyvinyl fluoride are preferable, and polyvinylidene fluoride (PVDF) is preferred. More preferred.
The above-mentioned fluororesin Y may be used alone or in combination of two or more.
ここで、フッ素樹脂Ｙが１２質量％の濃度でＮＭＰに溶解した溶液の粘度は、好ましくは１０ｍＰａ・ｓ以上、より好ましくは１００ｍＰａ・ｓ以上であり、好ましくは１８００ｍＰａ・ｓ以下、より好ましくは１３００ｍＰａ・ｓ以下、更に好ましくは６００ｍＰａ・ｓ以下である。フッ素樹脂Ｙの１２質量％ＮＭＰ溶液の粘度が１０ｍＰａ・ｓ以上であることで、導電材分散液から形成される電極合材層と集電体との密着性を向上させることができ、１８００ｍＰａ・ｓ以下であることで、導電材分散液の粘度が過剰に上昇することにより導電材の分散性が損なわれることもない。そして、フッ素樹脂Ｙの１２質量％ＮＭＰ溶液の粘度が上述の範囲内であることにより、当該フッ素樹脂Ｙを用いた導電材分散液から形成された電極合材層を備える電極を有する電気化学素子の、出力特性などの電気的特性を向上させることができる。
なお、フッ素樹脂Ｙの１２質量％ＮＭＰ溶液の粘度は、Ｂ型粘度計を用いて、温度２５℃、回転速度６０ｒｐｍ、回転時間６０秒の条件で測定することができる。
Here, the viscosity of the solution in which the fluororesin Y is dissolved in NMP at a concentration of 12% by mass is preferably 10 mPa · s or more, more preferably 100 mPa · s or more, preferably 1800 mPa · s or less, more preferably 1300 mPa · s or less. S or less, more preferably 600 mPa · s or less. When the viscosity of the 12% by mass NMP solution of the fluororesin Y is 10 mPa · s or more, the adhesion between the electrode mixture layer formed from the conductive material dispersion and the current collector can be improved, and 1800 mPa · s Since the viscosity is not more than s, the dispersibility of the conductive material is not impaired due to an excessive increase in the viscosity of the conductive material dispersion. When the viscosity of the 12% by mass NMP solution of the fluororesin Y is within the above range, the electrochemical element having the electrode including the electrode mixture layer formed from the conductive material dispersion using the fluororesin Y In addition, electrical characteristics such as output characteristics can be improved.
The viscosity of the 12% by mass NMP solution of the fluororesin Y can be measured using a B-type viscometer at a temperature of 25 ° C., a rotation speed of 60 rpm, and a rotation time of 60 seconds.
ここで、上述したフッ素樹脂Ｙの製造方法は特に限定はされず、例えば、溶液重合法、懸濁重合法、塊状重合法、乳化重合法などのいずれの方法も用いることができる。
また、重合方法としては、イオン重合、ラジカル重合、リビングラジカル重合などの付加重合を用いることができる。また、重合開始剤としては、既知の重合開始剤を用いることができる。
Here, the method for producing the above-described fluororesin Y is not particularly limited, and for example, any method such as a solution polymerization method, a suspension polymerization method, a bulk polymerization method, and an emulsion polymerization method can be used.
As the polymerization method, addition polymerization such as ionic polymerization, radical polymerization, and living radical polymerization can be used. In addition, as the polymerization initiator, a known polymerization initiator can be used.
そして、フッ素樹脂Ｙは、分散媒に分散された分散液または溶解された溶液の状態で導電材分散液の調製に使用される。導電材分散液の調製に使用するフッ素樹脂Ｙの分散媒としては、フッ素樹脂Ｙを均一に分散または溶解し得るものであれば、特に制限されず、水や有機溶媒を用いることができ、有機溶媒を用いることが好ましい。なお、有機溶媒としては、特に限定されることなく、本発明の導電材分散液の分散媒として用いるピロリドン系溶媒を用いることができる。 Then, the fluororesin Y is used in the preparation of the conductive material dispersion in the state of a dispersion or a solution dissolved in a dispersion medium. The dispersion medium of the fluororesin Y used for preparing the conductive material dispersion is not particularly limited as long as the fluororesin Y can be uniformly dispersed or dissolved, and water or an organic solvent can be used. It is preferable to use a solvent. The organic solvent is not particularly limited, and a pyrrolidone-based solvent used as a dispersion medium for the conductive material dispersion of the present invention can be used.
そして、本発明の導電材分散液は、導電材１００質量部当たり、フッ素樹脂Ｙを好ましくは１０質量部以上含み、好ましくは２００質量部以下、より好ましくは１００質量部以下、更に好ましくは５０質量部以下含む。フッ素樹脂Ｙの配合量が導電材１００質量部当たり１０質量部以上であることで、導電材分散液から形成される電極合材層と集電体との密着性を向上させることができる。一方、フッ素樹脂Ｙの配合量が導電材１００質量部当たり２００質量部以下であることで、当該導電材分散液から形成された電極合材層を備える電極を有する電気化学素子において、フッ素樹脂Ｙの量が過剰となることに起因する内部抵抗の上昇が抑制され、出力特性などの電気的特性を確保することができる。加えて、導電材分散液の粘度が過剰に高粘度とならず、電極用スラリーの調製が容易であり、また、電極用スラリーの集電体上への塗工性が向上する。さらに、導電材分散液中での導電材の分散性を確保することができる。
なお、本発明の導電材分散液は、重合体Ｘの量とフッ素樹脂Ｙの量の合計中、フッ素樹脂Ｙの量が占める割合は、好ましくは６０質量％以上、より好ましくは６５質量％以上であり、好ましくは９０質量％以下、より好ましくは８７質量％以下である。重合体Ｘとフッ素樹脂Ｙの合計量中のフッ素樹脂Ｙの割合が上述の範囲内であることで、重合体Ｘおよびフッ素樹脂Ｙにより得られる結着能と、重合体Ｘにより得られる導電材分散能のバランスが良好となり、導電材分散液の保存安定性、そして当該導電材分散液から形成された電極合材層を備える電極を有する電気化学素子の、出力特性などの電気的特性を更に向上させることができる。加えて、重合体Ｘとフッ素樹脂Ｙの合計量中のフッ素樹脂Ｙの割合が上述の範囲内であることで、電極用スラリーの集電体上への塗工性を更に向上させることができる。
The conductive material dispersion liquid of the present invention preferably contains the fluororesin Y in an amount of 10 parts by mass or more, preferably 200 parts by mass or less, more preferably 100 parts by mass or less, and still more preferably 50 parts by mass, per 100 parts by mass of the conductive material. Part or less. When the compounding amount of the fluororesin Y is at least 10 parts by mass per 100 parts by mass of the conductive material, the adhesion between the electrode mixture layer formed from the conductive material dispersion and the current collector can be improved. On the other hand, when the compounding amount of the fluororesin Y is 200 parts by mass or less per 100 parts by mass of the conductive material, the electrochemical device having the electrode including the electrode mixture layer formed from the conductive material dispersion liquid has the fluorine resin Y Increase in the internal resistance due to an excessive amount of Pb is suppressed, and electrical characteristics such as output characteristics can be secured. In addition, the viscosity of the conductive material dispersion does not become excessively high, the preparation of the electrode slurry is easy, and the coating property of the electrode slurry on the current collector is improved. Further, the dispersibility of the conductive material in the conductive material dispersion can be ensured.
In the conductive material dispersion of the present invention, the proportion of the amount of the fluororesin Y in the total amount of the polymer X and the amount of the fluororesin Y is preferably 60% by mass or more, more preferably 65% by mass or more. , Preferably 90% by mass or less, more preferably 87% by mass or less. When the ratio of the fluororesin Y in the total amount of the polymer X and the fluororesin Y is within the above range, the binding ability obtained by the polymer X and the fluororesin Y and the conductive material obtained by the polymer X The balance of the dispersibility is improved, the storage stability of the conductive material dispersion, and the electrical characteristics such as the output characteristics of the electrochemical element having an electrode having an electrode mixture layer formed from the conductive material dispersion are further improved. Can be improved. In addition, since the ratio of the fluororesin Y in the total amount of the polymer X and the fluororesin Y is within the above range, the coating property of the electrode slurry on the current collector can be further improved. .
＜ピロリドン系溶媒＞
本発明の導電材分散液において、分散媒としてピロリドン系溶媒を用いる。ピロリドン系溶媒は、重合体Ｘの溶解度が高いため、重合体Ｘの導電材分散能を十分に発揮させることができるからである。具体的なピロリドン系溶媒としては、Ｎ−メチル−２−ピロリドン（ＮＭＰ）、Ｎ−エチル−２−ピロリドン（ＮＥＰ）が挙げられる。これらの中でも、フッ素樹脂Ｙの溶解性の観点からＮＭＰが好ましい。
なお、これらのピロリドン系溶媒は、単独で使用してもよいし、２種以上を混合して使用してもよい。
<Pyrrolidone solvent>
In the conductive material dispersion of the present invention, a pyrrolidone-based solvent is used as a dispersion medium. This is because the pyrrolidone-based solvent has a high solubility of the polymer X, and can sufficiently exhibit the conductive material dispersing ability of the polymer X. Specific examples of the pyrrolidone-based solvent include N-methyl-2-pyrrolidone (NMP) and N-ethyl-2-pyrrolidone (NEP). Among these, NMP is preferable from the viewpoint of solubility of the fluororesin Y.
These pyrrolidone solvents may be used alone or in combination of two or more.
＜導電材分散液の調製方法＞
上述の導電材、重合体Ｘ、任意のフッ素樹脂Ｙ、およびピロリドン系溶媒を混合して導電材分散液を得るにあたり、混合方法には特に制限は無く、例えば、ディスパー、ミル、ニーダーなどの一般的な混合装置を用いることができる。例えば、ディスパーを使用する場合には、１０００ｒｐｍ以上５０００ｒｐｍ以下で、５分以上６０分以下攪拌することが好ましい。
また、導電材分散液を得るにあたり、混合手順も特に制限はなく、例えば、（Ａ）ピロリドン系溶媒に重合体Ｘを溶解後、導電材を添加し、上述の混合装置および混合条件で混合してもよいし、（Ｂ）導電材、重合体Ｘおよびピロリドン系溶媒を上述の混合装置および混合条件で一括混合してもよい。これらの中でも、（Ａ）の混合手順が好ましい。
更に、フッ素樹脂Ｙを導電材分散液に添加する場合は、導電材分散液の保存安定性を一層向上させる観点から、導電材、重合体Ｘおよびピロリドン系溶媒を例えば上述の混合装置および混合条件で予混合した後に、フッ素樹脂Ｙを添加することが好ましい。そして、フッ素樹脂Ｙを添加後、例えば上述の混合装置および混合条件でさらに混合することが好ましい。フッ素樹脂Ｙの添加に先んじて、導電材、重合体Ｘおよびピロリドン系溶媒を混合することで、分散剤としての重合体Ｘを優先して導電材に吸着させることができ、重合体Ｘの導電材分散能を十分に発揮させることができるからである。なお、フッ素樹脂Ｙは、電気化学素子正極用スラリーの調製段階で添加してもよい。
<Method of preparing conductive material dispersion>
In mixing the above-described conductive material, polymer X, optional fluororesin Y, and a pyrrolidone-based solvent to obtain a conductive material dispersion, there is no particular limitation on a mixing method, and for example, a general method such as disperser, mill, and kneader can be used. A typical mixing device can be used. For example, when using a disper, it is preferable to stir at 1000 rpm or more and 5000 rpm or less for 5 minutes to 60 minutes.
In addition, in obtaining the conductive material dispersion, the mixing procedure is not particularly limited. For example, (A) After dissolving the polymer X in a pyrrolidone-based solvent, the conductive material is added, and the mixture is mixed by the above-described mixing apparatus and mixing conditions. Alternatively, (B) the conductive material, the polymer X, and the pyrrolidone-based solvent may be mixed at once using the above-described mixing apparatus and mixing conditions. Among these, the mixing procedure (A) is preferred.
Further, when the fluororesin Y is added to the conductive material dispersion, from the viewpoint of further improving the storage stability of the conductive material dispersion, the conductive material, the polymer X and the pyrrolidone-based solvent are mixed, for example, with the above-described mixing apparatus and mixing conditions. It is preferable to add the fluororesin Y after pre-mixing in the above. After the addition of the fluororesin Y, it is preferable to further mix it, for example, with the above-described mixing apparatus and mixing conditions. By mixing the conductive material, the polymer X and the pyrrolidone-based solvent prior to the addition of the fluororesin Y, the polymer X as a dispersant can be preferentially adsorbed to the conductive material, and the conductivity of the polymer X can be reduced. This is because the material dispersing ability can be sufficiently exhibited. The fluororesin Y may be added at the stage of preparing the slurry for the positive electrode of an electrochemical device.
そして、得られる導電材分散液の粘度は、８００ｍＰａ・ｓ以下である必要があり、７５０ｍＰａ・ｓ以下であることが好ましく、７００ｍＰａ・ｓ以下であることがより好ましく、３００ｍＰａ・ｓ以上であることが好ましい。導電材分散液の粘度が８００ｍＰａ・ｓ超であると、当該導電材分散液を含む電極用スラリーの塗工性が損なわれ、集電体上に塗布した際にむらが生じ、電気化学素子の出力特性などの電気的特性が低下する。一方、導電材分散液の粘度が３００ｍＰａ・ｓ以上であれば、電極用スラリーの塗布の際に生じるハジキを抑制することができる。
また、得られる導電材分散液のＴＩ値（チクソトロピックインデックス値）は、０．８０以上であることが好ましく、０．９５以上であることがより好ましく、３．５０以下であることが好ましく、２．０以下であることがより好ましい。ＴＩ値が上述の範囲内であれば、電極用スラリーの塗工性が向上し、電気化学素子の出力特性などの電気的特性を一層高めることができる。
ここで、ＴＩ値は、Ｂ型粘度計を用いて、温度２５℃、回転速度６０ｒｐｍ、回転時間６０秒の条件で測定される導電材分散液の粘度η６０に対する、回転速度を６ｒｐｍとした以外はη６０と同様にして測定される導電材分散液の粘度η６の比（η６／η６０）として求めることができる。
The viscosity of the obtained conductive material dispersion liquid needs to be 800 mPa · s or less, preferably 750 mPa · s or less, more preferably 700 mPa · s or less, and more preferably 300 mPa · s or more. Is preferred. When the viscosity of the conductive material dispersion is more than 800 mPa · s, the coating property of the electrode slurry containing the conductive material dispersion is impaired, and unevenness occurs when the slurry is applied on the current collector. Electrical characteristics such as output characteristics are degraded. On the other hand, if the viscosity of the conductive material dispersion liquid is 300 mPa · s or more, repelling generated when the electrode slurry is applied can be suppressed.
Further, the TI value (thixotropic index value) of the obtained conductive material dispersion liquid is preferably 0.80 or more, more preferably 0.95 or more, and preferably 3.50 or less, More preferably, it is 2.0 or less. When the TI value is within the above range, the coatability of the electrode slurry is improved, and the electrical characteristics such as the output characteristics of the electrochemical device can be further improved.
Here, the TI value was measured using a B-type viscometer at a temperature of 25 ° C., a rotation speed of 60 rpm, and a rotation time of 60 seconds, except that the rotation speed was 6 rpm with respect to the viscosity η60 of the conductive material dispersion. It can be obtained as the ratio (η6 / η60) of the viscosity η6 of the conductive material dispersion measured in the same manner as η60.
（電気化学素子正極用スラリー）
本発明の電気化学素子正極用スラリーは、上述した電気化学素子用導電材分散液および正極活物質を含む。即ち、導電材と、重合体Ｘと、正極活物質と、ピロリドン系溶媒と、任意にフッ素樹脂Ｙとを含む。
このように、上述した電気化学素子用導電材分散液を含む電気化学素子正極用スラリーは、本発明の導電材分散液を用いて調製されているため、保存安定性および塗工性に優れる。したがって、そのような正極用スラリーから形成される正極合材層は、その中で導電材が良好に分散しかつ均一な厚みを有し、そして電気化学素子に優れた出力特性を発揮させることができる。
(Slurry for positive electrode of electrochemical element)
The slurry for a positive electrode of an electrochemical element of the present invention contains the above-described conductive material dispersion for an electrochemical element and a positive electrode active material. That is, it contains a conductive material, a polymer X, a positive electrode active material, a pyrrolidone-based solvent, and optionally a fluororesin Y.
As described above, since the slurry for the positive electrode of an electrochemical element containing the above-described conductive material dispersion for an electrochemical element is prepared using the conductive material dispersion of the present invention, it is excellent in storage stability and coatability. Therefore, the positive electrode mixture layer formed from such a positive electrode slurry has a conductive material dispersed therein and has a uniform thickness, and can exhibit excellent output characteristics to the electrochemical element. it can.
＜正極活物質＞
電気化学素子正極用スラリーに配合する正極活物質としては、特に限定されることなく、既知の正極活物質を用いることができる。
例えばリチウムイオン二次電池に用いられる正極活物質としては、特に限定されることなく、リチウム含有コバルト酸化物（ＬｉＣｏＯ２）、マンガン酸リチウム（ＬｉＭｎ２Ｏ４）、リチウム含有ニッケル酸化物（ＬｉＮｉＯ２）、Ｃｏ−Ｎｉ−Ｍｎのリチウム含有複合酸化物、Ｎｉ−Ｍｎ−Ａｌのリチウム含有複合酸化物、Ｎｉ−Ｃｏ−Ａｌのリチウム含有複合酸化物、オリビン型リン酸鉄リチウム（ＬｉＦｅＰＯ４）、オリビン型リン酸マンガンリチウム（ＬｉＭｎＰＯ４）、Ｌｉ１＋ｘＭｎ２−ｘＯ４（０＜Ｘ＜２）で表されるリチウム過剰のスピネル化合物、Ｌｉ［Ｎｉ０．１７Ｌｉ０．２Ｃｏ０．０７Ｍｎ０．５６］Ｏ２、ＬｉＮｉ０．５Ｍｎ１．５Ｏ４等が挙げられる。
また例えばリチウムイオンキャパシタや電気二重層キャパシタに用いられる正極活物質としては、特に限定されることなく、炭素の同素体が挙げられる。炭素の同素体の具体例としては、活性炭、ポリアセン、カーボンウィスカ及びグラファイト等が挙げられ、これらの粉末または繊維を使用することができる。
<Positive electrode active material>
The positive electrode active material to be added to the electrochemical element positive electrode slurry is not particularly limited, and a known positive electrode active material can be used.
For example, the positive electrode active material used for the lithium ion secondary battery is not particularly limited, and lithium-containing cobalt oxide (LiCoO 2 ), lithium manganate (LiMn 2 O 4 ), and lithium-containing nickel oxide (LiNiO 2) ), lithium-containing composite oxide of Co-Ni-Mn, Ni- Mn-Al lithium-containing composite oxide, Ni-Co-Al lithium-containing composite oxide, olivine-type lithium iron phosphate (LiFePO 4), olivine type lithium manganese phosphate (LiMnPO 4), Li 1 + x Mn 2-x O 4 lithium-rich spinel compound represented by (0 <X <2), Li [Ni 0.17 Li 0.2 Co 0.07 Mn 0.56 ] O 2 , LiNi 0.5 Mn 1.5 O 4 and the like.
Further, for example, a positive electrode active material used for a lithium ion capacitor or an electric double layer capacitor is not particularly limited, and includes an allotrope of carbon. Specific examples of allotropes of carbon include activated carbon, polyacene, carbon whiskers, graphite, and the like, and powders or fibers thereof can be used.
上述した中でも、リチウムイオン二次電池において電池容量などを向上させる観点からは、正極活物質としてリチウム含有コバルト酸化物（ＬｉＣｏＯ２）、リチウム含有ニッケル酸化物（ＬｉＮｉＯ２）、Ｃｏ−Ｎｉ−Ｍｎのリチウム含有複合酸化物、Ｎｉ−Ｃｏ−Ａｌのリチウム含有複合酸化物、Ｌｉ［Ｎｉ０．１７Ｌｉ０．２Ｃｏ０．０７Ｍｎ０．５６］Ｏ２またはＬｉＮｉ０．５Ｍｎ１．５Ｏ４を用いることが好ましい。
なお、正極活物質の粒径は、特に限定されることなく、従来使用されている正極活物質と同様とすることができる。
そして、本発明の電気化学素子正極用スラリーは、導電材１００質量部当たり、正極活物質を好ましくは１０００質量部以上、より好ましくは２０００質量部以上含み、好ましくは１００００質量部以下、より好ましくは５０００質量部以下含む。上述の範囲内で正極活物質を含むことで、導電材の分散性を向上させつつ正極用スラリーを用いて形成される正極合材層の導電性を優れたものとすることができる。
Among the above, from the viewpoint of improving the battery capacity and the like in a lithium ion secondary battery, lithium-containing cobalt oxide (LiCoO 2 ), lithium-containing nickel oxide (LiNiO 2 ), and Co-Ni-Mn lithium-containing composite oxide, lithium-containing composite oxide of Ni-Co-Al, Li [ Ni 0.17 Li 0.2 Co 0.07 Mn 0.56] O 2 , or LiNi 0.5 Mn 1.5 O 4 It is preferable to use
The particle size of the positive electrode active material is not particularly limited, and can be the same as that of a conventionally used positive electrode active material.
And the slurry for the positive electrode of an electrochemical element of the present invention preferably contains at least 1,000 parts by mass, more preferably at least 2,000 parts by mass, preferably at most 10,000 parts by mass, more preferably at most 10,000 parts by mass, per 100 parts by mass of the conductive material. 5000 parts by mass or less. When the positive electrode active material is contained within the above range, the conductivity of the positive electrode mixture layer formed using the positive electrode slurry can be improved while improving the dispersibility of the conductive material.
＜その他の成分＞
電気化学素子正極用スラリーには、上記成分の他に、例えば、フッ素樹脂Ｙ以外の結着材、粘度調整剤、補強材、酸化防止剤、電解液の分解を抑制する機能を有する電解液添加剤などの成分を混合してもよい。これらの他の成分は、公知のものを使用することができる。また、これらの他の成分は、上述した本発明の電気化学素子用導電材分散液に配合してもよい。
<Other ingredients>
In addition to the above components, for example, a binder other than fluororesin Y, a viscosity modifier, a reinforcing material, an antioxidant, and an electrolytic solution having a function of suppressing decomposition of the electrolytic solution are added to the slurry for an electrochemical element positive electrode. Components such as agents may be mixed. As these other components, known components can be used. Further, these other components may be blended in the above-described conductive material dispersion for an electrochemical device of the present invention.
＜電気化学素子正極用スラリーの調製方法＞
導電材分散液に対して、上述の正極活物質と、任意に、その他の成分および追加のピロリドン系溶媒とを混合して電気化学素子正極用スラリーを得るにあたり、混合方法には特に制限は無く、例えば、ディスパー、ミル、ニーダーなどの一般的な混合装置を用いることができる。例えば、ディスパーを使用する場合には、２０００ｒｐｍ以上５０００ｒｐｍ以下で、５分以上１２０分以下攪拌することが好ましい。
<Method of preparing slurry for positive electrode of electrochemical element>
For the conductive material dispersion, the above-described positive electrode active material and, optionally, other components and an additional pyrrolidone-based solvent are mixed to obtain a slurry for an electrochemical element positive electrode, the mixing method is not particularly limited. For example, a general mixing device such as a disper, a mill, and a kneader can be used. For example, when using a disper, it is preferable to stir at 2,000 to 5,000 rpm for 5 to 120 minutes.
（電気化学素子用正極）
本発明の電気化学素子用正極は、本発明の電気化学素子正極用スラリーを使用して製造することができる。
そして、本発明の電気化学素子用正極は、集電体と、集電体上に形成された正極合材層とを備え、正極合材層には、少なくとも、正極活物質と、導電材と、重合体Ｘとが含まれ、任意にフッ素樹脂Ｙが含まれている。なお、正極合材層中に含まれている正極活物質、導電材および重合体Ｘは、本発明の電気化学素子用導電材分散液および電気化学素子正極用スラリー中に含まれていたものであり、それら各成分の好適な存在比は、本発明の電気化学素子用導電材分散液および電気化学素子正極用スラリー中の各成分の好適な存在比と同じである。
(Positive electrode for electrochemical device)
The positive electrode for an electrochemical device of the present invention can be produced using the slurry for a positive electrode of an electrochemical device of the present invention.
The positive electrode for an electrochemical device of the present invention includes a current collector and a positive electrode mixture layer formed on the current collector, and the positive electrode mixture layer includes at least a positive electrode active material, a conductive material, , A polymer X, and optionally a fluororesin Y. The positive electrode active material, the conductive material, and the polymer X contained in the positive electrode mixture layer were those contained in the conductive material dispersion for an electrochemical element and the slurry for an electrochemical element positive electrode of the present invention. The preferable abundance ratio of each component is the same as the preferable abundance ratio of each component in the conductive material dispersion for an electrochemical device and the slurry for a positive electrode of an electrochemical device of the present invention.
そして、上述した電気化学素子正極用スラリーから形成される正極合材層は、導電材が良好に分散し内部抵抗の上昇が抑制されているとともに、均一な厚みを有する。従って、そのような正極合材層を備える本発明の電気化学素子用正極を有する電気化学素子は、出力特性などの電気的特性に優れる。 The positive electrode mixture layer formed from the above-described slurry for a positive electrode of an electrochemical element has a uniform thickness, in which the conductive material is well dispersed and the rise in internal resistance is suppressed. Therefore, an electrochemical device having the positive electrode for an electrochemical device of the present invention including such a positive electrode mixture layer is excellent in electrical characteristics such as output characteristics.
＜電気化学素子用正極の製造方法＞
本発明の電気化学素子用正極の製造方法は、本発明の電気化学素子正極用スラリーを、集電体の少なくとも一方の面に塗布し、乾燥して正極合材層を形成する工程を含む。より詳細には、当該製造方法は、電気化学素子正極用スラリーを集電体の少なくとも一方の面に塗布する工程（塗布工程）と、集電体の少なくとも一方の面に塗布された電気化学素子正極用スラリーを乾燥して集電体上に正極合材層を形成する工程（乾燥工程）とを含む。
<Method of manufacturing positive electrode for electrochemical device>
The method for producing a positive electrode for an electrochemical device of the present invention includes a step of applying the slurry for a positive electrode of an electrochemical device of the present invention to at least one surface of a current collector and drying to form a positive electrode mixture layer. More specifically, the manufacturing method includes a step of applying the electrochemical element positive electrode slurry to at least one surface of the current collector (application step), and a step of applying the electrochemical element positive electrode slurry to at least one surface of the current collector. Drying the positive electrode slurry to form a positive electrode mixture layer on the current collector (drying step).
［塗布工程］
上記電気化学素子正極用スラリーを集電体上に塗布する方法としては、特に限定されず公知の方法を用いることができる。具体的には、塗布方法としては、ドクターブレード法、ディップ法、リバースロール法、ダイレクトロール法、グラビア法、エクストルージョン法、ハケ塗り法などを用いることができる。この際、電気化学素子正極用スラリーを集電体の片面だけに塗布してもよいし、両面に塗布してもよい。塗布後乾燥前の集電体上のスラリー膜の厚みは、乾燥して得られる正極合材層の厚みに応じて適宜に設定しうる。
[Coating process]
The method for applying the slurry for a positive electrode of an electrochemical element on a current collector is not particularly limited, and a known method can be used. Specifically, as a coating method, a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, a brush coating method, or the like can be used. At this time, the electrochemical element positive electrode slurry may be applied to only one surface of the current collector, or may be applied to both surfaces. The thickness of the slurry film on the current collector after coating and before drying can be appropriately set according to the thickness of the positive electrode mixture layer obtained by drying.
ここで、電気化学素子正極用スラリーを塗布する集電体としては、電気導電性を有し、かつ、電気化学的に耐久性のある材料が用いられる。具体的には、集電体としては、アルミニウムまたはアルミニウム合金からなる集電体を用い得る。この際、アルミニウムとアルミニウム合金とを組み合わせて用いてもよく、種類が異なるアルミニウム合金を組み合わせて用いてもよい。アルミニウムおよびアルミニウム合金は耐熱性を有し、電気化学的に安定であるため、優れた集電体材料である。 Here, as the current collector to which the slurry for the electrochemical element positive electrode is applied, a material having electrical conductivity and being electrochemically durable is used. Specifically, a current collector made of aluminum or an aluminum alloy can be used as the current collector. At this time, aluminum and an aluminum alloy may be used in combination, or different types of aluminum alloys may be used in combination. Aluminum and aluminum alloys are excellent current collector materials because they have heat resistance and are electrochemically stable.
［乾燥工程］
集電体上の電気化学素子正極用スラリーを乾燥する方法としては、特に限定されず公知の方法を用いることができ、例えば温風、熱風、低湿風による乾燥、真空乾燥、赤外線や電子線などの照射による乾燥法が挙げられる。このように集電体上の電気化学素子正極用スラリーを乾燥することで、集電体上に正極合材層を形成し、集電体と正極合材層とを備える電気化学素子用正極を得ることができる。
[Drying process]
The method for drying the slurry for the positive electrode of the electrochemical element on the current collector is not particularly limited, and a known method can be used. For example, warm air, hot air, drying with low humidity air, vacuum drying, infrared rays, electron beams, etc. Drying method. By drying the slurry for the electrochemical element positive electrode on the current collector in this way, a positive electrode mixture layer is formed on the current collector, and the positive electrode for an electrochemical element including the current collector and the positive electrode mixture layer is formed. Obtainable.
なお、乾燥工程の後、金型プレスまたはロールプレスなどを用い、正極合材層に加圧処理を施してもよい。加圧処理により、正極合材層と集電体との密着性を向上させることができる。
さらに、正極合材層が硬化性の重合体を含む場合は、正極合材層の形成後に前記重合体を硬化させることが好ましい。
After the drying step, the positive electrode mixture layer may be subjected to a pressure treatment using a mold press or a roll press. The pressure treatment can improve the adhesion between the positive electrode mixture layer and the current collector.
Further, when the positive electrode mixture layer contains a curable polymer, it is preferable to cure the polymer after forming the positive electrode mixture layer.
（電気化学素子）
本発明の電気化学素子は、特に限定されることなく、リチウムイオン二次電池、リチウムイオンキャパシタや電気二重層キャパシタであり、好ましくはリチウムイオン二次電池である。そして、本発明の電気化学素子は、本発明の電気化学素子用正極を備えることを特徴とする。このような電気化学素子は、出力特性などの電気的特性に優れる。
(Electrochemical element)
The electrochemical device of the present invention is not particularly limited, and is a lithium ion secondary battery, a lithium ion capacitor or an electric double layer capacitor, preferably a lithium ion secondary battery. The electrochemical device of the present invention includes the positive electrode for an electrochemical device of the present invention. Such an electrochemical device has excellent electrical characteristics such as output characteristics.
ここで、以下では、本発明の電気化学素子の一例としてのリチウムイオン二次電池の構成について説明する。このリチウムイオン二次電池は、通常、上記本発明の電気化学素子用正極に加え、負極、電解液、セパレーターを備える。以下、上記各構成について説明する。 Here, a configuration of a lithium ion secondary battery as an example of the electrochemical device of the present invention will be described below. This lithium ion secondary battery generally includes a negative electrode, an electrolytic solution, and a separator in addition to the positive electrode for an electrochemical device of the present invention. Hereinafter, each of the above configurations will be described.
＜負極＞
リチウムイオン二次電池の負極としては、リチウムイオン二次電池用負極として用いられる既知の負極を用いることができる。具体的には、負極としては、例えば、金属リチウムの薄板よりなる負極や、負極合材層を集電体上に形成してなる負極を用いることができる。
なお、集電体としては、鉄、銅、アルミニウム、ニッケル、ステンレス鋼、チタン、タンタル、金、白金等の金属材料からなるものを用いることができる。また、負極合材層としては、負極活物質と結着材とを含む層を用いることができる。更に、結着材としては、特に限定されず、任意の既知の材料を用いうる。
<Negative electrode>
As the negative electrode of the lithium ion secondary battery, a known negative electrode used as a negative electrode for a lithium ion secondary battery can be used. Specifically, as the negative electrode, for example, a negative electrode formed of a thin sheet of metallic lithium or a negative electrode obtained by forming a negative electrode mixture layer on a current collector can be used.
Note that a current collector made of a metal material such as iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, or platinum can be used. As the negative electrode mixture layer, a layer containing a negative electrode active material and a binder can be used. Further, the binder is not particularly limited, and any known material can be used.
＜電解液＞
電解液としては、通常、有機溶媒に支持電解質を溶解した有機電解液が用いられる。支持電解質としては、例えば、リチウム塩が用いられる。リチウム塩としては、例えば、ＬｉＰＦ６、ＬｉＡｓＦ６、ＬｉＢＦ４、ＬｉＳｂＦ６、ＬｉＡｌＣｌ４、ＬｉＣｌＯ４、ＣＦ３ＳＯ３Ｌｉ、Ｃ４Ｆ９ＳＯ３Ｌｉ、ＣＦ３ＣＯＯＬｉ、（ＣＦ３ＣＯ）２ＮＬｉ、（ＣＦ３ＳＯ２）２ＮＬｉ、（Ｃ２Ｆ５ＳＯ２）ＮＬｉなどが挙げられる。なかでも、溶媒に溶けやすく高い解離度を示すので、ＬｉＰＦ６、ＬｉＣｌＯ４、ＣＦ３ＳＯ３Ｌｉが好ましく、ＬｉＰＦ６が特に好ましい。なお、電解質は１種類を単独で用いてもよく、２種類以上を任意の比率で組み合わせて用いてもよい。通常は、解離度の高い支持電解質を用いるほどリチウムイオン伝導度が高くなる傾向があるので、支持電解質の種類によりリチウムイオン伝導度を調節することができる。
<Electrolyte>
As the electrolyte, an organic electrolyte obtained by dissolving a supporting electrolyte in an organic solvent is usually used. As the supporting electrolyte, for example, a lithium salt is used. Examples of the lithium salt include LiPF 6 , LiAsF 6 , LiBF 4 , LiSbF 6 , LiAlCl 4 , LiClO 4 , CF 3 SO 3 Li, C 4 F 9 SO 3 Li, CF 3 COOLi, and (CF 3 CO) 2 NLi. , (CF 3 SO 2 ) 2 NLi, (C 2 F 5 SO 2 ) NLi, and the like. Among them, LiPF 6 , LiClO 4 , and CF 3 SO 3 Li are preferable, and LiPF 6 is particularly preferable because they are easily soluble in a solvent and show a high degree of dissociation. One type of electrolyte may be used alone, or two or more types may be used in combination at an arbitrary ratio. In general, the higher the dissociation degree of the supporting electrolyte, the higher the lithium ion conductivity tends to be. Therefore, the lithium ion conductivity can be adjusted depending on the type of the supporting electrolyte.
電解液に使用する有機溶媒としては、支持電解質を溶解できるものであれば特に限定されないが、例えば、ジメチルカーボネート（ＤＭＣ）、エチレンカーボネート（ＥＣ）、ジエチルカーボネート（ＤＥＣ）、プロピレンカーボネート（ＰＣ）、ブチレンカーボネート（ＢＣ）、メチルエチルカーボネート（ＥＭＣ）等のカーボネート類；γ−ブチロラクトン、ギ酸メチル等のエステル類；１，２−ジメトキシエタン、テトラヒドロフラン等のエーテル類；スルホラン、ジメチルスルホキシド等の含硫黄化合物類；などが好適に用いられる。またこれらの溶媒の混合液を用いてもよい。中でも、誘電率が高く、安定な電位領域が広いのでカーボネート類を用いることが好ましく、エチレンカーボネートとエチルメチルカーボネートとの混合物を用いることが更に好ましい。
なお、電解液中の電解質の濃度は適宜調整することができ、例えば０．５〜１５質量％することが好ましく、２〜１３質量％とすることがより好ましく、５〜１０質量％とすることが更に好ましい。また、電解液には、既知の添加剤、例えばフルオロエチレンカーボネートやエチルメチルスルホンなどを添加してもよい。
The organic solvent used for the electrolytic solution is not particularly limited as long as it can dissolve the supporting electrolyte. For example, dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), Carbonates such as butylene carbonate (BC) and methyl ethyl carbonate (EMC); esters such as γ-butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; and sulfur-containing compounds such as sulfolane and dimethyl sulfoxide. And the like are preferably used. Further, a mixture of these solvents may be used. Among them, carbonates are preferably used because they have a high dielectric constant and a wide stable potential region, and more preferably a mixture of ethylene carbonate and ethyl methyl carbonate is used.
In addition, the concentration of the electrolyte in the electrolytic solution can be appropriately adjusted, for example, preferably 0.5 to 15% by mass, more preferably 2 to 13% by mass, and more preferably 5 to 10% by mass. Is more preferred. Further, a known additive such as fluoroethylene carbonate and ethyl methyl sulfone may be added to the electrolyte.
＜セパレーター＞
セパレーターとしては、特に限定されることなく、例えば特開２０１２−２０４３０３号公報に記載のものを用いることができる。これらの中でも、セパレーター全体の膜厚を薄くすることができ、これにより、リチウムイオン二次電池内の電極活物質の比率を高くして体積あたりの容量を高くすることができるという点より、ポリオレフィン系（ポリエチレン、ポリプロピレン、ポリブテン、ポリ塩化ビニル）の樹脂からなる微多孔膜が好ましい。
<Separator>
The separator is not particularly limited, and for example, those described in JP-A-2012-204303 can be used. Among these, polyolefins can be reduced in that the thickness of the entire separator can be reduced, and thereby the capacity per volume can be increased by increasing the ratio of the electrode active material in the lithium ion secondary battery. A microporous membrane made of a resin of a series (polyethylene, polypropylene, polybutene, polyvinyl chloride) is preferred.
＜リチウムイオン二次電池の製造方法＞
本発明に従うリチウムイオン二次電池は、例えば、正極と、負極とを、セパレーターを介して重ね合わせ、これを必要に応じて電池形状に応じて巻く、折るなどして電池容器に入れ、電池容器に電解液を注入して封口することにより製造することができる。二次電池の内部の圧力上昇、過充放電等の発生を防止するために、必要に応じて、ヒューズ、ＰＴＣ素子等の過電流防止素子、エキスパンドメタル、リード板などを設けてもよい。二次電池の形状は、例えば、コイン型、ボタン型、シート型、円筒型、角形、扁平型など、何れであってもよい。
<Production method of lithium ion secondary battery>
The lithium ion secondary battery according to the present invention is, for example, a positive electrode and a negative electrode are overlapped via a separator, and if necessary, wound according to the shape of the battery, folded or the like, and placed in a battery container. It can be manufactured by injecting an electrolyte into the container and sealing the container. If necessary, a fuse, an overcurrent prevention element such as a PTC element, an expanded metal, a lead plate, or the like may be provided in order to prevent an increase in the pressure inside the secondary battery and the occurrence of overcharge and overdischarge. The shape of the secondary battery may be, for example, any of a coin type, a button type, a sheet type, a cylindrical type, a square type, a flat type, and the like.
以下、本発明について実施例に基づき具体的に説明するが、本発明はこれら実施例に限定されるものではない。なお、以下の説明において、量を表す「％」及び「部」は、特に断らない限り、質量基準である。
実施例および比較例において、導電材分散液の保存安定性、正極用スラリーの塗工性およびリチウムイオン二次電池の出力特性は、それぞれ以下の方法を使用して評価した。
Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. In the following description, “%” and “parts” representing amounts are based on mass unless otherwise specified.
In Examples and Comparative Examples, the storage stability of the conductive material dispersion, the coating property of the slurry for the positive electrode, and the output characteristics of the lithium ion secondary battery were evaluated using the following methods.
＜導電材分散液の保存安定性＞
調製直後の導電材分散液の粘度η１を、Ｂ型粘度計（東機産業社製、ＲＢ―８０Ｌ）を用いて、温度２５℃、回転速度６０ｒｐｍ、回転時間６０秒で測定した。その後、導電材分散液を、２５℃環境下で３０日間保管後、そのまま上述のη１と同様にして、粘度η２を測定し、粘度変化Δη（％）＝（｜η１−η２｜／η１）×１００を求めた。そして下記基準で導電材分散液の保存安定性を評価した。粘度変化Δηが小さいほど、導電材分散液の粘度が安定であり、導電材の分散状態を良好に維持することができることを示す。
Ａ：粘度変化Δηが５％未満である。
Ｂ：粘度変化Δηが５％以上１０％未満である。
Ｃ：粘度変化Δηが１０％以上３０％未満である。
Ｄ：粘度変化Δηが３０％以上である。
＜正極用スラリーの塗工性＞
正極用スラリーを集電体としてのアルミニウム箔上に塗工し、乾燥して得られた正極を切り出して、大きさ０．５ｍ２の試験片を１０枚準備した。そして、試験片の正極合材層の表面を目視により観察し、ピンホール、ハジキが存在する試験片の枚数をカウントし、以下の指標で塗工性を評価した。ピンホール、ハジキが少ないほど、正極用スラリーの塗工性が優れることを示す。
Ａ：１０枚中、全てにピンホールおよびハジキの双方がみられない。
Ｂ：１０枚中、１〜２枚に、ピンホールおよび／またはハジキがみられる。
Ｃ：１０枚中、３〜４枚に、ピンホールおよび／またはハジキがみられる。
Ｄ：１０枚中、５枚以上に、ピンホールおよび／またはハジキがみられる。
＜リチウムイオン二次電池の出力特性＞
作製したラミネート型リチウムイオン二次電池を、２５℃環境下、電流１４０ｍＡで電圧が４．２Ｖになるまで定電流充電し、電圧４．２Ｖで充電電流が１４ｍＡになるまで定電圧充電を行った。続いて、電流１４０ｍＡで電池電圧が３Ｖになるまで定電流放電を行い、初期容量とした。
初期容量を測定したラミネート型リチウムイオン二次電池を、２５℃環境下、０．２Ｃで電池電圧が４．２Ｖになるまで定電流充電し、電圧４．２Ｖで充電電流が０．０２Ｃになるまで定電圧充電を行った。続いて、電流２Ｃで電池電圧が３．０Ｖになるまで定電流放電を行い、２Ｃ容量とした。｛（２Ｃ容量）／（初期容量）｝×１００（％）の値を出力特性とし、下記基準で評価を行った。この値が高いほど、初期出力特性に優れ、すなわち内部抵抗が小さいことを意味する。
Ａ：出力特性が９０％以上である。
Ｂ：出力特性が８７％以上９０％未満である。
Ｃ：出力特性が８４％以上８７％未満である。
Ｄ：出力特性が８０％以上８４％未満である。
Ｅ：出力特性が８０％未満である。
<Storage stability of conductive material dispersion>
The viscosity η1 of the conductive material dispersion immediately after the preparation was measured using a B-type viscometer (RB-80L, manufactured by Toki Sangyo Co., Ltd.) at a temperature of 25 ° C., a rotation speed of 60 rpm, and a rotation time of 60 seconds. Thereafter, the conductive material dispersion is stored in an environment of 25 ° C. for 30 days, and then the viscosity η2 is measured in the same manner as in the above η1, and the viscosity change Δη (%) = (| η1−η2 | / η1) × 100 was sought. The storage stability of the conductive material dispersion was evaluated according to the following criteria. It shows that the smaller the viscosity change Δη, the more stable the viscosity of the conductive material dispersion and the better the state of dispersion of the conductive material can be maintained.
A: The viscosity change Δη is less than 5%.
B: The viscosity change Δη is 5% or more and less than 10%.
C: The viscosity change Δη is 10% or more and less than 30%.
D: The viscosity change Δη is 30% or more.
<Coatability of slurry for positive electrode>
The positive electrode slurry was applied on an aluminum foil as a current collector, dried, and the obtained positive electrode was cut out to prepare ten test pieces having a size of 0.5 m 2 . Then, the surface of the positive electrode mixture layer of the test piece was visually observed, the number of test pieces having pinholes and cissing was counted, and coatability was evaluated by the following index. The smaller the number of pinholes and cissing, the more excellent the coating property of the positive electrode slurry.
A: No pinholes and cissing were observed in all of the 10 sheets.
B: Pinholes and / or cissing were observed in 1 or 2 sheets out of 10 sheets.
C: Pinholes and / or cissing are observed in 3 to 4 out of 10 sheets.
D: Pinholes and / or cissing were observed in 5 or more of the 10 sheets.
<Output characteristics of lithium ion secondary battery>
The produced laminated lithium ion secondary battery was charged at a constant current of 140 mA under a 25 ° C. environment until the voltage became 4.2 V, and was charged at a constant voltage of 4.2 V until the charging current became 14 mA. . Subsequently, a constant current discharge was performed at a current of 140 mA until the battery voltage became 3 V, thereby setting the initial capacity.
The laminated lithium ion secondary battery whose initial capacity was measured was charged at a constant current at 25 ° C. at 0.2 C until the battery voltage became 4.2 V, and the charging current became 0.02 C at a voltage of 4.2 V. Charged to constant voltage until Subsequently, constant-current discharge was performed at a current of 2 C until the battery voltage reached 3.0 V to obtain a 2 C capacity. The value of {(2C capacity) / (initial capacity)} × 100 (%) was used as an output characteristic, and evaluation was performed according to the following criteria. The higher the value, the better the initial output characteristics, that is, the lower the internal resistance.
A: The output characteristic is 90% or more.
B: Output characteristics are 87% or more and less than 90%.
C: Output characteristics are 84% or more and less than 87%.
D: Output characteristics are 80% or more and less than 84%.
E: Output characteristics are less than 80%.
（実施例１）
＜重合体Ｘの調製＞
撹拌機付きのオートクレーブに、イオン交換水２４０部、乳化剤としてアルキルベンゼンスルホン酸ナトリウム２．５部、ニトリル基含有単量体としてアクリロニトリル（ＡＮ）３６部をこの順で入れ、ボトル内を窒素で置換した後、共役ジエン単量体として１，３−ブタジエン（ＢＤ）６４部（単量体としてＡＮ，ＢＤのみを含む単量体組成物を構成）を圧入し、重合開始剤として過硫酸アンモニウム０．２５部を添加して反応温度４０℃で重合反応させ、共役ジエン単量体単位およびニトリル基含有単量体単位を含んでなる重合体を得た。重合転化率は８５％であった。
(Example 1)
<Preparation of polymer X>
In an autoclave equipped with a stirrer, 240 parts of ion-exchanged water, 2.5 parts of sodium alkylbenzenesulfonate as an emulsifier, and 36 parts of acrylonitrile (AN) as a nitrile group-containing monomer were placed in this order, and the inside of the bottle was replaced with nitrogen. Thereafter, 64 parts of 1,3-butadiene (BD) as a conjugated diene monomer (constituting a monomer composition containing only AN and BD as a monomer) was injected, and 0.25% of ammonium persulfate was used as a polymerization initiator. The polymerization reaction was carried out at a reaction temperature of 40 ° C. to obtain a polymer comprising a conjugated diene monomer unit and a nitrile group-containing monomer unit. The polymerization conversion was 85%.
得られた重合体に対してイオン交換水を添加して全固形分濃度を１２質量％に調整した４００ミリリットル（全固形分４８グラム）の溶液を、撹拌機付きの１リットルオートクレーブに投入し、窒素ガスを１０分間流して溶液中の溶存酸素を除去した後、水素添加反応触媒として、酢酸パラジウム７５ｍｇを、パラジウム（Ｐｄ）に対して４倍モルの硝酸を添加したイオン交換水１８０ｍＬに溶解して、添加した。系内を水素ガスで２回置換した後、３ＭＰａまで水素ガスで加圧した状態でオートクレーブの内容物を５０℃に加温し、６時間水素添加反応（第一段階の水素添加反応）させた。 Ion-exchanged water was added to the obtained polymer to adjust the total solids concentration to 12% by mass, and 400 ml (48 g of the total solids) of the solution was charged into a 1-liter autoclave equipped with a stirrer. After removing the dissolved oxygen in the solution by flowing nitrogen gas for 10 minutes, 75 mg of palladium acetate as a hydrogenation reaction catalyst was dissolved in 180 mL of ion-exchanged water to which nitric acid was added in an amount four times the molar amount of palladium (Pd). And added. After the inside of the system was replaced with hydrogen gas twice, the contents of the autoclave were heated to 50 ° C. while pressurized with hydrogen gas to 3 MPa, and subjected to a hydrogenation reaction (first-stage hydrogenation reaction) for 6 hours. .
次いで、オートクレーブを大気圧にまで戻し、更に水素添加反応触媒として、酢酸パラジウム２５ｍｇを、Ｐｄに対して４倍モルの硝酸を添加したイオン交換水６０ｍＬに溶解して、添加した。系内を水素ガスで２回置換した後、３ＭＰａまで水素ガスで加圧した状態でオートクレーブの内容物を５０℃に加温し、６時間水素添加反応（第二段階の水素添加反応）させた。 Next, the autoclave was returned to atmospheric pressure, and 25 mg of palladium acetate was dissolved as a hydrogenation reaction catalyst in 60 mL of ion-exchanged water to which nitric acid was added in an amount four times the molar amount of Pd, and added. After the inside of the system was replaced with hydrogen gas twice, the contents of the autoclave were heated to 50 ° C. while being pressurized with hydrogen gas to 3 MPa, and subjected to a hydrogenation reaction (second stage hydrogenation reaction) for 6 hours. .
その後、内容物を常温に戻し、系内を窒素雰囲気とした後、エバポレータを用いて、固形分濃度が４０％となるまで濃縮して重合体Ｘの水分散液を得た。また、この重合体Ｘの水分散液１００部にＮＭＰ３２０部を加え、減圧下に水を蒸発させて、ニトリル基含有単量体単位およびアルキレン構造単位を含み、ヨウ素価が６ｍｇ／１００ｍｇである重合体ＸのＮＭＰ溶液を得た。 Thereafter, the content was returned to room temperature, and the system was set to a nitrogen atmosphere, and then concentrated using an evaporator until the solid content concentration became 40% to obtain an aqueous dispersion of the polymer X. Further, 320 parts of NMP was added to 100 parts of the aqueous dispersion of the polymer X, and water was evaporated under reduced pressure to obtain a polymer containing a nitrile group-containing monomer unit and an alkylene structural unit and having an iodine value of 6 mg / 100 mg. An NMP solution of the combined X was obtained.
＜導電材分散液の製造＞
導電材としてのカーボンブラックα（電気化学工業（株）製、ＨＳ−１００、アセチレンブラック、平均粒子径：４８ｎｍ、比表面積：３９ｍ２／ｇ、密度：０．１５ｇ／ｃｍ３）１００部と、上述のようにして得た重合体ＸのＮＭＰ溶液を固形分相当量で１０部と、適量のＮＭＰとをディスパーにて攪拌（２０００ｒｐｍ、６０分）した。その後、固形分濃度が１０質量％になるように適量のＮＭＰを入れてディスパーで撹拌（２０００ｒｐｍ、１０分）し、さらにフッ素樹脂ＹとしてのＰＶＤＦ１（クレハ(株)製 Ｌ＃１１２０ １２％ＮＭＰ溶液の粘度：５５０ｍＰａ・ｓ）２０部を添加し、ディスパーで撹拌することにより、導電材分散液を製造した。調製直後の導電材分散液の粘度を測定し、またこの導電材分散液の保存安定性を評価した。結果を表１に示す。
<Production of conductive material dispersion>
100 parts of carbon black α (HS-100, acetylene black, average particle diameter: 48 nm, specific surface area: 39 m 2 / g, density: 0.15 g / cm 3 , manufactured by Denki Kagaku Kogyo KK) as a conductive material; 10 parts of the NMP solution of the polymer X obtained as described above in a solid content equivalent amount and an appropriate amount of NMP were stirred with a disper (2000 rpm, 60 minutes). Thereafter, an appropriate amount of NMP is added so that the solid content concentration becomes 10% by mass, and the mixture is stirred with a disper (2000 rpm, 10 minutes), and PVDF1 as a fluororesin Y (Kureha Corporation L # 1120 12% NMP solution) (Viscosity of 550 mPa · s) was added, and the mixture was stirred with a disper to prepare a conductive material dispersion. The viscosity of the conductive material dispersion immediately after preparation was measured, and the storage stability of the conductive material dispersion was evaluated. Table 1 shows the results.
＜正極用スラリーおよび正極の製造＞
得られた導電材分散液に正極活物質としてのＬｉＣｏＯ２２０００部を添加し、ディスパーを用いて２５００ｒｐｍで３０分間攪拌撹拌することで正極用スラリーを得た。この正極用スラリーの粘度は１５００ｍＰａ・sであった。
この正極用スラリーを、コンマコーターで、集電体である厚さ１８μｍのアルミニウム箔の上に塗布量が２０ｍｇ／ｃｍ２となるように塗布した。その後、正極用スラリーが塗布されたアルミ箔を、雰囲気温度１２０℃で３０分乾燥して、正極原反を得た。得られた正極原反をロールプレス機にて密度が３．８ｇ／ｃｍ３となるようにプレスし、正極（正極合材層の厚みが５３μｍ）を得た。この正極を用いて、正極用スラリーの塗工性を評価した。結果を表１に示す。
<Production of slurry for positive electrode and positive electrode>
2,000 parts of LiCoO 2 as a positive electrode active material was added to the obtained conductive material dispersion, and the mixture was stirred and stirred at 2500 rpm for 30 minutes using a disper to obtain a positive electrode slurry. The viscosity of the positive electrode slurry was 1500 mPa · s.
The slurry for a positive electrode was applied by a comma coater on an aluminum foil having a thickness of 18 μm as a current collector so that the application amount was 20 mg / cm 2 . Thereafter, the aluminum foil coated with the positive electrode slurry was dried at an ambient temperature of 120 ° C. for 30 minutes to obtain a positive electrode raw material. The obtained positive electrode raw material was pressed with a roll press so that the density became 3.8 g / cm 3 , to obtain a positive electrode (the thickness of the positive electrode mixture layer was 53 μm). Using this positive electrode, the coatability of the positive electrode slurry was evaluated. Table 1 shows the results.
＜負極用スラリーおよび負極の製造＞
負極活物質として人造黒鉛（平均粒子径：２４．５μｍ、黒鉛層間距離（Ｘ線回折法による（００２）面の面間隔（ｄ値）：０．３５４ｎｍ）９６部と、粘度調整剤としてのカルボキシメチルセルロースの１．５％水溶液（日本製紙社製、「ＭＡＣ３５０」）を固形分相で１．０部とをディスパーで混合し、さらにイオン交換水を固形分濃度が４５％となるように加え、混合分散した。次に結着材としてのスチレン−ブタジエン共重合体（日本ゼオン（株）製、ＢＭ−４００Ｂ）をさらに固形分相当で３．０部混合して最終固形分濃度が４０％の負極用スラリーを得た。
この負極用スラリーを、コンマコーターで、集電体である厚さ１８μｍの銅箔の上に塗布量が９ｍｇ／ｃｍ２となるように塗布した。その後、負極用スラリーが塗布された銅箔を、雰囲気温１２０℃で３０分間乾燥して、負極原反を得た。得られた負極原反をロールプレス機にて密度が１．６ｇ／ｃｍ３となるようにプレスし、負極（負極合材層の厚みが５６μｍ）を得た。
<Production of slurry for negative electrode and negative electrode>
96 parts of artificial graphite (average particle diameter: 24.5 μm, graphite interlayer distance (distance between (002) planes (d value) by X-ray diffraction method: 0.354 nm): 0.354 nm) as a negative electrode active material, and carboxy as a viscosity modifier A 1.5% aqueous solution of methylcellulose (manufactured by Nippon Paper Industries Co., Ltd., “MAC350”) was mixed in a solid phase with 1.0 part by a disper, and ion-exchanged water was further added so that the solid content concentration became 45%. Then, 3.0 parts of a styrene-butadiene copolymer (BM-400B, manufactured by Nippon Zeon Co., Ltd.) as a binder was further mixed at a solid content equivalent to 3.0 parts to give a final solid concentration of 40%. A slurry for a negative electrode was obtained.
This negative electrode slurry was applied on a 18 μm-thick copper foil as a current collector using a comma coater so that the application amount was 9 mg / cm 2 . Thereafter, the copper foil coated with the negative electrode slurry was dried at an ambient temperature of 120 ° C. for 30 minutes to obtain a negative electrode raw material. The obtained negative electrode raw material was pressed with a roll press so that the density became 1.6 g / cm 3 , to obtain a negative electrode (the thickness of the negative electrode mixture layer was 56 μm).
＜セパレーターの用意＞
単層のポリプロピレン製セパレーター（幅６５ｍｍ、長さ５００ｍｍ、厚さ２５μｍ、乾式法により製造、気孔率５５％）を、５ｃｍ×５ｃｍの正方形に切り抜いた。
<Preparation of separator>
A single-layer polypropylene separator (width 65 mm, length 500 mm, thickness 25 μm, manufactured by a dry method, porosity 55%) was cut into a square of 5 cm × 5 cm.
＜リチウムイオン二次電池の製造＞
電池の外装として、アルミ包材外装を用意した。上記で得られた正極を、４ｃｍ×４ｃｍの正方形に切り出し、集電体側の表面がアルミ包材外装に接するように配置した。正極の正極合材層の面上に、上記で得られた正方形のセパレーターを配置した。さらに、上記で得られた負極を、４．２ｃｍ×４．２ｃｍの正方形に切り出し、これをセパレーター上に、負極合材層側の表面がセパレーターに向かい合うように配置した。更に、ビニレンカーボネートを２．０％含有する、濃度１．０ＭのＬｉＰＦ６溶液を充填した。このＬｉＰＦ６溶液の溶媒はエチレンカーボネート（ＥＣ）とエチルメチルカーボネート（ＥＭＣ）との混合溶媒（ＥＣ／ＥＭＣ＝３／７（体積比））である。さらに、アルミニウム包材の開口を密封するために、１５０℃でヒートシールをしてアルミニウム外装を閉口し、ラミネート型のリチウムイオン二次電池を製造した。得られたリチウムイオン二次電池について出力特性を評価した。結果を表１に示す。
<Manufacture of lithium ion secondary batteries>
An aluminum packaging exterior was prepared as the exterior of the battery. The positive electrode obtained as described above was cut into a square of 4 cm × 4 cm, and arranged so that the surface on the side of the current collector was in contact with the exterior of the aluminum packaging material. The square separator obtained above was disposed on the surface of the positive electrode mixture layer of the positive electrode. Further, the negative electrode obtained above was cut into a 4.2 cm × 4.2 cm square, and this was disposed on a separator such that the surface of the negative electrode mixture layer side faced the separator. Furthermore, a 1.0 M concentration of LiPF 6 solution containing 2.0% of vinylene carbonate was filled. The solvent of this LiPF 6 solution is a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (EC / EMC = 3/7 (volume ratio)). Furthermore, in order to seal the opening of the aluminum packaging material, heat sealing was performed at 150 ° C. to close the aluminum exterior, and a laminated lithium ion secondary battery was manufactured. The output characteristics of the obtained lithium ion secondary battery were evaluated. Table 1 shows the results.
（実施例２、３、１０）
重合体Ｘの製造時に、表１の単量体を表１の量で含む単量体組成物を使用し、ヨウ素価が実施例１と同様となるよう水素添加条件を適宜変更した以外は、実施例１と同様にして、導電材分散液、正極用スラリー、負極用スラリー、正極、負極およびリチウムイオン二次電池を製造した。そして、実施例１と同様にして各種評価を行った。結果を表１に示す。
(Examples 2, 3, and 10)
During the production of the polymer X, a monomer composition containing the monomers in Table 1 in the amounts shown in Table 1 was used, and hydrogenation conditions were appropriately changed so that the iodine value was the same as in Example 1. In the same manner as in Example 1, a conductive material dispersion, a slurry for a positive electrode, a slurry for a negative electrode, a positive electrode, a negative electrode, and a lithium ion secondary battery were manufactured. Various evaluations were performed in the same manner as in Example 1. Table 1 shows the results.
（実施例４）
導電材分散液の製造時に、重合体Ｘの配合量を表１のように変更した以外は、実施例１と同様にして、導電材分散液、正極用スラリー、負極用スラリー、正極、負極およびリチウムイオン二次電池を製造した。そして、実施例１と同様にして各種評価を行った。結果を表１に示す。
(Example 4)
During the production of the conductive material dispersion, the conductive material dispersion, the slurry for the positive electrode, the slurry for the negative electrode, the positive electrode, and the negative electrode were prepared in the same manner as in Example 1 except that the amount of the polymer X was changed as shown in Table 1. A lithium ion secondary battery was manufactured. Various evaluations were performed in the same manner as in Example 1. Table 1 shows the results.
（実施例５）
重合体Ｘの製造時に、表１の単量体を表１の量で含む単量体組成物を使用（（メタ）アクリル酸エステル単量体としてブチルアクリレート（ＢＡ）を使用）し、さらに、導電材分散液の製造時に重合体Ｘの配合量を表１のように変更した以外は、実施例１と同様にして、導電材分散液、正極用スラリー、負極用スラリー、正極、負極およびリチウムイオン二次電池を製造した。そして、実施例１と同様にして各種評価を行った。結果を表１に示す。
(Example 5)
During the production of the polymer X, a monomer composition containing the monomers of Table 1 in the amounts shown in Table 1 was used (butyl acrylate (BA) was used as the (meth) acrylate monomer). Except that the compounding amount of the polymer X was changed as shown in Table 1 during the production of the conductive material dispersion, the conductive material dispersion, the slurry for the positive electrode, the slurry for the negative electrode, the positive electrode, the negative electrode, and the lithium were prepared in the same manner as in Example 1. An ion secondary battery was manufactured. Various evaluations were performed in the same manner as in Example 1. Table 1 shows the results.
（実施例６〜８）
導電材分散液の製造時に、ＰＶＤＦ１（フッ素樹脂Ｙ）の配合量を表１のように変更した以外は、実施例１と同様にして、導電材分散液、正極用スラリー、負極用スラリー、正極、負極およびリチウムイオン二次電池を製造した。そして、実施例１と同様にして各種評価を行った。結果を表１に示す。
(Examples 6 to 8)
Except that the compounding amount of PVDF1 (fluororesin Y) was changed as shown in Table 1 during the production of the conductive material dispersion, the conductive material dispersion, the slurry for the positive electrode, the slurry for the negative electrode, , A negative electrode and a lithium ion secondary battery. Various evaluations were performed in the same manner as in Example 1. Table 1 shows the results.
（実施例９）
導電材分散液の製造時に、ＰＶＤＦ１に替えてＰＶＤＦ２（クレハ(株)製 Ｌ＃１３２０ １２％ＮＭＰ溶液の粘度：１１５０ｍＰａ・ｓ）を使用した以外は、実施例１と同様にして、導電材分散液、正極用スラリー、負極用スラリー、正極、負極およびリチウムイオン二次電池を製造した。そして、実施例１と同様にして各種評価を行った。結果を表１に示す。
(Example 9)
Except for using PVDF2 (viscosity of L # 1320 12% NMP solution manufactured by Kureha Corporation: 1150 mPa · s) instead of PVDF1 in the production of the conductive material dispersion, the conductive material dispersion was performed in the same manner as in Example 1. A liquid, a slurry for a positive electrode, a slurry for a negative electrode, a positive electrode, a negative electrode, and a lithium ion secondary battery were produced. Various evaluations were performed in the same manner as in Example 1. Table 1 shows the results.
（実施例１１）
ピロリドン系溶媒としてのＮＭＰに替えて、ＮＥＰを使用した以外は、実施例１と同様にして、導電材分散液、正極用スラリー、負極用スラリー、正極、負極およびリチウムイオン二次電池を製造した。そして、実施例１と同様にして各種評価を行った。結果を表１に示す。
(Example 11)
A conductive material dispersion, a slurry for a positive electrode, a slurry for a negative electrode, a positive electrode, a negative electrode, and a lithium ion secondary battery were manufactured in the same manner as in Example 1 except that NEP was used instead of NMP as a pyrrolidone-based solvent. . Various evaluations were performed in the same manner as in Example 1. Table 1 shows the results.
(実施例１２)
導電材分散液の製造時に、重合体Ｘの配合量およびフッ素樹脂Ｙの配合量を表１のように変更した以外は、実施例１と同様にして、導電材分散液、正極用スラリー、負極用スラリー、正極、負極およびリチウムイオン二次電池を製造した。そして、実施例１と同様にして各種評価を行った。結果を表１に示す。
(Example 12)
Except that the compounding amount of the polymer X and the compounding amount of the fluororesin Y were changed as shown in Table 1 during production of the conductive material dispersion, the conductive material dispersion, the positive electrode slurry, and the negative electrode were prepared in the same manner as in Example 1. Slurry, a positive electrode, a negative electrode, and a lithium ion secondary battery were manufactured. Various evaluations were performed in the same manner as in Example 1. Table 1 shows the results.
（実施例１３）
導電材としてのカーボンブラックαに替えて、カーボンブラックβ（電気化学工業（株）製、デンカブラック、粉状品、平均粒子径：３５ｎｍ、比表面積：６８ｍ２／ｇ、密度０．０４ｇ／ｃｍ３）を使用した以外は、実施例１と同様にして、導電材分散液、正極用スラリー、負極用スラリー、正極、負極およびリチウムイオン二次電池を製造した。そして、実施例１と同様にして各種評価を行った。結果を表１に示す。
(Example 13)
Instead of carbon black α as a conductive material, carbon black β (manufactured by Denki Kagaku Kogyo KK, Denka Black, powdery product, average particle diameter: 35 nm, specific surface area: 68 m 2 / g, density 0.04 g / cm) Except for using 3 ), a conductive material dispersion, a slurry for a positive electrode, a slurry for a negative electrode, a positive electrode, a negative electrode, and a lithium ion secondary battery were produced in the same manner as in Example 1. Various evaluations were performed in the same manner as in Example 1. Table 1 shows the results.
（比較例１）
重合体Ｘの製造時に、水素添加を行わずＮＭＰに溶媒置換し、共役ジエン単量体単位およびニトリル基含有単量体単位を含む重合体を重合体Ｘとして使用した以外は、実施例１と同様にして、導電材分散液、正極用スラリー、負極用スラリー、正極、負極およびリチウムイオン二次電池を製造した。そして、実施例１と同様にして各種評価を行った。結果を表１に示す。
(Comparative Example 1)
Example 1 was repeated except that, during the production of the polymer X, the solvent was replaced with NMP without hydrogenation, and a polymer containing a conjugated diene monomer unit and a nitrile group-containing monomer unit was used as the polymer X. Similarly, a conductive material dispersion, a slurry for a positive electrode, a slurry for a negative electrode, a positive electrode, a negative electrode, and a lithium ion secondary battery were manufactured. Various evaluations were performed in the same manner as in Example 1. Table 1 shows the results.
（比較例２）
導電材分散液の製造時に、重合体Ｘの配合量を表１のように変更した以外は、実施例１と同様にして、導電材分散液、正極用スラリー、負極用スラリー、正極、負極およびリチウムイオン二次電池を製造した。そして、実施例１と同様にして各種評価を行った。結果を表１に示す。
(Comparative Example 2)
During the production of the conductive material dispersion, the conductive material dispersion, the slurry for the positive electrode, the slurry for the negative electrode, the positive electrode, and the negative electrode were prepared in the same manner as in Example 1 except that the amount of the polymer X was changed as shown in Table 1. A lithium ion secondary battery was manufactured. Various evaluations were performed in the same manner as in Example 1. Table 1 shows the results.
表１より、実施例１〜１３および比較例１、２より、実施例１〜１３では、保存安定性に優れた導電材分散液が得られ、正極用スラリーの塗工性も良好であり、そして、リチウムイオン二次電池に優れた出力特性を発揮させることができることがわかる。
また、表１の実施例１〜５、１０より、重合体Ｘの組成、配合量を変更することで、導電材分散液の保存安定性、正極用スラリーの塗工性およびリチウムイオン二次電池の出力特性をより向上させ得ることがわかる。
さらに、表１の実施例１、６〜９より、フッ素樹脂Ｙの配合量、１２質量％ＮＭＰ溶液の粘度を変更することで、正極用スラリーの塗工性およびリチウムイオン二次電池の出力特性をより向上させ得ることがわかる。
加えて、表１の実施例１、１１より、ピロリドン系溶媒としてＮＥＰを用いた場合でも、保存安定性に優れた導電材分散液が得られ、正極用スラリーの塗工性を良好とすることができ、そして、リチウムイオン二次電池に優れた出力特性を発揮させることができることがわかる。
そして、表１の実施例１、１２より、重合体Ｘの配合量およびフッ素樹脂Ｙの配合量を変更することで、正極用スラリーの塗工性およびリチウムイオン二次電池の出力特性をより向上させ得ることがわかる。
また、表１の実施例１、１３より、導電材の種類を変更することで、導電材分散液の保存安定性をより向上させ得ることがわかる。
From Table 1, from Examples 1 to 13 and Comparative Examples 1 and 2, from Examples 1 to 13, conductive material dispersions having excellent storage stability were obtained, and the coating properties of the positive electrode slurry were also good, Further, it is understood that excellent output characteristics can be exhibited in the lithium ion secondary battery.
Further, from Examples 1 to 5 and 10 in Table 1, by changing the composition and the amount of the polymer X, the storage stability of the conductive material dispersion, the coating property of the slurry for the positive electrode, and the lithium ion secondary battery were changed. It can be seen that the output characteristics of the above can be further improved.
Further, from Examples 1 and 6 to 9 in Table 1, the coating amount of the positive electrode slurry and the output characteristics of the lithium ion secondary battery were changed by changing the blending amount of the fluororesin Y and the viscosity of the 12% by mass NMP solution. Can be further improved.
In addition, from Examples 1 and 11 in Table 1, even when NEP is used as a pyrrolidone-based solvent, a conductive material dispersion having excellent storage stability is obtained, and the coating property of the positive electrode slurry is improved. It can be seen that the lithium ion secondary battery can exhibit excellent output characteristics.
From Examples 1 and 12 in Table 1, by changing the compounding amount of the polymer X and the compounding amount of the fluororesin Y, the coatability of the slurry for the positive electrode and the output characteristics of the lithium ion secondary battery were further improved. It can be seen that it can be done.
Further, from Examples 1 and 13 in Table 1, it is found that the storage stability of the conductive material dispersion can be further improved by changing the type of the conductive material.
本発明によれば、保存安定性に優れ、電気化学素子電極用スラリーに良好な塗工性を付与しつつ、電気化学素子に優れた出力特性を発揮させることが可能な電気化学素子用導電材分散液を提供することができる。
本発明によれば、保存安定性および塗工性に優れ、電気化学素子に優れた出力特性を発揮させることが可能な電気化学素子正極用スラリーを提供することができる。
更に、本発明によれば、電気化学素子に優れた出力特性を発揮させることが可能な電気化学素子用正極、および出力特性に優れる電気化学素子を提供することができる。
Advantageous Effects of Invention According to the present invention, a conductive material for an electrochemical element capable of exhibiting excellent output characteristics to an electrochemical element while imparting excellent coatability to a slurry for an electrochemical element electrode, having excellent storage stability. A dispersion can be provided.
ADVANTAGE OF THE INVENTION According to this invention, it is excellent in storage stability and coating property, and can provide the slurry for electrochemical element positive electrodes which can exhibit the outstanding output characteristics to an electrochemical element.
Furthermore, according to the present invention, it is possible to provide a positive electrode for an electrochemical device capable of exhibiting excellent output characteristics to an electrochemical device, and an electrochemical device having excellent output characteristics.
Claims (5)
前記重合体Ｘは、ニトリル基含有単量体単位およびアルキレン構造単位を含み、ヨウ素価が２０ｍｇ/１００ｍｇ以下であり、
前記導電材１００質量部当たり、前記重合体Ｘを２質量部以上３０質量部以下含み、
前記導電材１００質量部当たり、前記フッ素樹脂Ｙを２０質量部以上含み、
そして、粘度が８００ｍＰａ・ｓ以下である、電気化学素子用導電材分散液。 A conductive material dispersion for an electrochemical element comprising a conductive material, a polymer X, a fluororesin Y and a pyrrolidone-based solvent,
The polymer X contains a nitrile group-containing monomer unit and an alkylene structural unit, and has an iodine value of 20 mg / 100 mg or less,
Per 100 parts by mass of the conductive material, the polymer X contains 2 parts by mass or more and 30 parts by mass or less,
Per 100 parts by mass of the conductive material, the fluororesin Y contains at least 20 parts by mass,
A conductive material dispersion for an electrochemical element having a viscosity of 800 mPa · s or less.
An electrochemical device comprising the positive electrode for an electrochemical device according to claim 4 .
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