JP2007141649A - Manufacturing method of positive mix paste for nonaqueous electrolyte secondary battery, and the nonaqueous electrolyte secondary battery using the positive mix paste - Google Patents
Manufacturing method of positive mix paste for nonaqueous electrolyte secondary battery, and the nonaqueous electrolyte secondary battery using the positive mix paste Download PDFInfo
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Abstract
Description
本発明は、非水電解液二次電池用正極合剤ペーストの製造方法、特に正極合剤ペーストの保管に関する。 The present invention relates to a method for producing a positive electrode mixture paste for a non-aqueous electrolyte secondary battery, and particularly to storage of the positive electrode mixture paste.
近年、ＡＶ機器やパソコン等、電子機器のコードレス化やポータブル化に伴って、非水電解液を備える高エネルギー密度の非水電解液二次電池の代表であるリチウムイオン二次電池が採用されている。 In recent years, with the cordless and portable electronic devices such as AV equipment and personal computers, lithium ion secondary batteries, which are representative of high energy density non-aqueous electrolyte secondary batteries with non-aqueous electrolyte, have been adopted. Yes.
リチウムイオン二次電池の正極活物質は、充放電でリチウムイオンが挿入・脱離を可逆的に繰り返すことができる。一般的な正極板の製造工程は、正極活物質、導電材、および結着材を、分散溶媒中で混合、攪拌して、正極合剤ペーストを得る練合工程、正極合剤ペーストを集電体に塗工して正極活物質層を形成する塗工工程、正極活物質層を所定の厚みに調整する圧延工程、そして、正極板を所定の寸法に裁断するスリット工程からなっている。特に、練合工程で得られた正極合剤ペーストの状態の良否が正極板の出来上がりに大きく影響する。正極合剤ペーストは、集電体表面に塗工するまでの間、放置されることがある。そのため、正極合剤ペーストは、経時変化が小さく、安定性に優れていることが要求される。時間が経っても正極合剤ペーストの固形分が沈降することなく、粘度変化が小さく、適度なチキソトロピーを有し、かつ塗工し易いことが望まれる。ここで、チキソトロピーとは、静置しておけばゲル状に固まっているものの、揺り動かすと、動いている間だけ流動性が現れるという現象のことである。 The positive electrode active material of a lithium ion secondary battery can reversibly repeat insertion and removal of lithium ions during charge and discharge. A general process for producing a positive electrode plate includes a kneading process in which a positive electrode active material, a conductive material, and a binder are mixed and stirred in a dispersion solvent to obtain a positive electrode mixture paste, and the positive electrode mixture paste is collected. It comprises a coating process for coating a body to form a positive electrode active material layer, a rolling process for adjusting the positive electrode active material layer to a predetermined thickness, and a slit process for cutting the positive electrode plate to a predetermined dimension. In particular, the quality of the positive electrode mixture paste obtained in the kneading step greatly affects the completion of the positive electrode plate. The positive electrode mixture paste may be left until it is applied to the current collector surface. Therefore, the positive electrode mixture paste is required to have little change with time and excellent stability. It is desired that the solid content of the positive electrode mixture paste does not settle over time, the viscosity change is small, it has an appropriate thixotropy, and is easy to apply. Here, thixotropy is a phenomenon in which fluidity appears only while moving, although it solidifies in a gel state if left standing.
上述したような条件を満たす正極合剤ペーストを得るために、練合工程の改良技術が提案されており、練合工程での温度を管理することで、安定な正極合剤ペーストを提供できることが提案されている（例えば、特許文献１参照）。
しかしながら、従来、錬合工程で作製した正極合剤ペーストは次工程の塗工工程で使用するまでの間、常温で保管しているのが一般的であった。保管時間が長いと正極活物質が沈降し、塗工工程で使う前にミキサー等で再度撹拌してから使っていた。このように正極合剤ペーストを作り置きしておくことができず、生産性が良くなかった。 However, conventionally, the positive electrode mixture paste produced in the refining process is generally stored at room temperature until it is used in the next coating process. When the storage time was long, the positive electrode active material settled, and it was used after being stirred again with a mixer or the like before being used in the coating process. Thus, the positive electrode mixture paste could not be made and set, and the productivity was not good.
本発明はこのような従来の課題を解決するものであり、練合工程で得られた正極合剤ペーストを次工程である塗工工程へ安定に供給でき、生産性を向上させることを目的とする。 The present invention is to solve such a conventional problem, the positive electrode mixture paste obtained in the kneading step can be stably supplied to the coating step which is the next step, and the purpose is to improve productivity. To do.
本発明の非水電解液二次電池用正極合剤ペーストの製造方法は、
正極活物質、導電材、結着剤、および有機溶媒を混合して正極合剤ペーストを作製した後、前記正極合剤ペーストを０℃以下の温度で保管する非水電解液二次電池用正極合剤ペーストの製造方法である。
The method for producing a positive electrode mixture paste for a non-aqueous electrolyte secondary battery of the present invention is as follows.
A positive electrode for a non-aqueous electrolyte secondary battery in which a positive electrode mixture paste is prepared by mixing a positive electrode active material, a conductive material, a binder, and an organic solvent, and then the positive electrode mixture paste is stored at a temperature of 0 ° C. or lower. This is a method for producing a mixture paste.
本発明の製造方法を用いることにより、安定な正極合剤ペーストを供給することが可能となり、生産性を向上させることができる。 By using the production method of the present invention, a stable positive electrode mixture paste can be supplied, and productivity can be improved.
本発明によれば、安定性に優れた塗工性の良好な正極合剤ペーストを製造することができ、非水電解液二次電池に用いられる正極板の生産性を向上させることができる。 ADVANTAGE OF THE INVENTION According to this invention, the positive electrode mixture paste excellent in the coating property excellent in stability can be manufactured, and the productivity of the positive electrode plate used for a nonaqueous electrolyte secondary battery can be improved.
本発明の非水電解液二次電池用正極合剤ペーストの製造方法は、
正極活物質、導電材、結着剤、および有機溶媒を混合、攪拌して正極合剤ペーストを作製する練合工程と、
その正極合剤ペーストを集電体表面に塗布する塗工工程からなる。
錬合工程を経て得られた正極合剤ペーストを、次工程の塗工工程で使用するまでの間、０℃以下の温度で保管する。０℃以下の温度で保管すると正極合剤ペーストの粘度が増大し、重力による正極活物質粒子の沈降が抑制される。それに対して、常温より高い温度で保管した場合、正極活物質が沈降してしまう。
The method for producing a positive electrode mixture paste for a non-aqueous electrolyte secondary battery of the present invention is as follows.
A kneading step in which a positive electrode active material, a conductive material, a binder, and an organic solvent are mixed and stirred to produce a positive electrode mixture paste;
It consists of the coating process which apply | coats the positive mix paste on the collector surface.
The positive electrode mixture paste obtained through the refining process is stored at a temperature of 0 ° C. or lower until it is used in the subsequent coating process. When stored at a temperature of 0 ° C. or lower, the viscosity of the positive electrode mixture paste increases, and sedimentation of the positive electrode active material particles due to gravity is suppressed. On the other hand, when it is stored at a temperature higher than room temperature, the positive electrode active material is precipitated.
本発明の好ましい実施の形態における非水電解液二次電池用正極合剤ペーストの製造方法は、−２０〜０℃の温度で保管するのが好ましい。非常に低い温度でも本発明の効果が得られるが、正極合剤ペースト中の有機溶剤の凍結温度以下で有機溶剤が凍結する温度では、ペースト中の固形分の沈降が停止するため、凍結温度以下に低下させても効果はほとんど変わらない。しかし、正極合剤ペーストが凍結すると、塗工する前に解凍する時間を要するため生産性が悪くなり好ましくない。有機溶剤としてＮ−メチル−２−ピロリドン（以下、ＮＭＰと略す）が用いられることが多いが、ＮＭＰの融点が−２３℃であるため、保管温度範囲は−２０℃〜０℃とするのが好ましい。 In the preferred embodiment of the present invention, the method for producing a positive electrode mixture paste for a non-aqueous electrolyte secondary battery is preferably stored at a temperature of -20 to 0 ° C. The effect of the present invention can be obtained even at a very low temperature, but at a temperature at which the organic solvent freezes at a temperature below the freezing temperature of the organic solvent in the positive electrode mixture paste, the settling of solids in the paste stops, so the freezing temperature or below. The effect is almost the same even if it is lowered. However, if the positive electrode mixture paste is frozen, it takes time to thaw before coating, which is not preferable because the productivity deteriorates. N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP) is often used as the organic solvent, but since the melting point of NMP is −23 ° C., the storage temperature range is −20 ° C. to 0 ° C. preferable.
本発明の好ましい実施の形態における非水電解液二次電池用正極合剤ペーストの製造方法は、保管時間を２４〜１６８時間とするのが好ましい。これは、保管時間が２４時間以内であれば、正極活物質粒子の沈降が進まず本発明の効果が得られない。また、１６８時間を越える保管時間では本発明を用いても正極活物質粒子の沈降が進むため、顕著な効果が得られなくなる。よって、保管時間は２４〜１６８時間とするのが好ましい。 In the method for producing a positive electrode mixture paste for a non-aqueous electrolyte secondary battery in a preferred embodiment of the present invention, the storage time is preferably 24 to 168 hours. If the storage time is within 24 hours, the positive electrode active material particles will not settle and the effect of the present invention cannot be obtained. In addition, if the storage time exceeds 168 hours, the positive electrode active material particles settle down even if the present invention is used, and thus a remarkable effect cannot be obtained. Therefore, the storage time is preferably 24 to 168 hours.
本発明の好ましい実施の形態における非水電解液二次電池用正極合剤ペーストの製造方法は、導電材には、天然黒鉛、人造黒鉛、カーボンブラック、炭素繊維、および金属繊維よりなる群から選ばれた少なくとも１種を用いることが好ましい。これは、正極活物質としてコバルト酸リチウム（以下、ＬｉＣｏＯ2と略す）やＬｉXＭＯ2（ＭはＣｏ、Ｎｉ、Ｍｎ、Ｍｇ、Ａｌ、Ｖ、Ｆｅ、Ｓｒ、Ｔｉ、Ｌａ、Ｂ、Ｓｎ、Ｎｂ、Ｓｉ、Ｃａ、Ｃｕ、Ｐ、Ｉｎ、Ｍｏ、Ｙ、およびＢｉのうち１種類または１種類より多い金属を表し、０．０５＜ｘ＜１．１０）で表される含リチウム複合酸化物を用いる場合、活物質自体の導電性が低いため、導電性を補助する物質を添加することが望ましいためであり、さらに、電極内で分解されにくい性質が要求される。よって、導電材には、天然黒鉛、人造黒鉛、カーボンブラック、炭素繊維、および金属繊維よりなる群から選ばれた少なくとも１種を用いることが好ましい。 In the preferred embodiment of the present invention, the method for producing a positive electrode mixture paste for a non-aqueous electrolyte secondary battery is selected from the group consisting of natural graphite, artificial graphite, carbon black, carbon fiber, and metal fiber as the conductive material. It is preferable to use at least one selected from the above. This is because lithium cobalt oxide (hereinafter abbreviated as LiCoO 2 ) or Li x MO 2 (M is Co, Ni, Mn, Mg, Al, V, Fe, Sr, Ti, La, B, Sn, A lithium-containing composite oxide that represents one or more than one of Nb, Si, Ca, Cu, P, In, Mo, Y, and Bi, and is represented by 0.05 <x <1.10. This is because the conductivity of the active material itself is low, so it is desirable to add a substance that assists the conductivity, and further, it is required to have a property that it is difficult to be decomposed in the electrode. Therefore, it is preferable to use at least one selected from the group consisting of natural graphite, artificial graphite, carbon black, carbon fiber, and metal fiber as the conductive material.
本発明の好ましい実施の形態における非水電解液二次電池用正極合剤ペーストの製造方法は、結着剤には、フッ素原子含有高分子材料を用いることが好ましい。さらに好ましいフッ素原子含有高分子材料は、フッ化ビニリデン（以下、ＰＶｄＦと略す）、ヘキサフルオロプロピレン（ＨＦＰ）、クロロトリフルオロエチレン（ＣＴＦＥ） およびテトラフルオロエチレン（ＰＴＦＥ）よりなる群から選ばれた少なくとも１種のモノマー単位を含有する高分子材料が好ましい。これは、正極での結着剤であるため、酸化雰囲気下におかれるので、酸化抑制のためフッ素原子を含有する高分子材料であることが好ましく、さらに結着力が良好であるＰＶｄＦ、ＨＦＰ、ＣＴＦＥ、およびＰＴＦＥよりなる群から選ば
れた少なくとも１種のモノマー単位を含有することが好ましい。
In the method for producing a positive electrode mixture paste for a non-aqueous electrolyte secondary battery in a preferred embodiment of the present invention, a fluorine atom-containing polymer material is preferably used as the binder. Further preferred fluorine atom-containing polymer material is at least selected from the group consisting of vinylidene fluoride (hereinafter abbreviated as PVdF), hexafluoropropylene (HFP), chlorotrifluoroethylene (CTFE) and tetrafluoroethylene (PTFE). Polymer materials containing one monomer unit are preferred. Since this is a binder at the positive electrode and is placed in an oxidizing atmosphere, it is preferably a polymer material containing a fluorine atom to suppress oxidation, and PVdF, HFP, It is preferable to contain at least one monomer unit selected from the group consisting of CTFE and PTFE.
本発明のさらに好ましい実施の形態における非水電解液二次電池用正極合剤ペーストの製造方法は、正極活物質の平均粒径は８μｍ以上が好ましい。一般に、粒子径が小さいほど流体中の粒子の沈降速度は小さい。このことから、平均粒子径が８μｍ未満の正極活物質では、活物質粒子の沈降が顕著でないため本発明の効果が得られ難い。よって、正極活物質の平均粒径は８μｍ以上が好ましい。平均粒子径が１５μｍを超える粒子径では、沈降速度が大きくなり本発明の効果が得られ難くなる。よって、正極活物質の平均粒径は８μｍ以上１５μｍ以下が好ましい。 In the method for producing a positive electrode mixture paste for a non-aqueous electrolyte secondary battery in a further preferred embodiment of the present invention, the average particle diameter of the positive electrode active material is preferably 8 μm or more. In general, the smaller the particle size, the smaller the sedimentation rate of the particles in the fluid. For this reason, in the positive electrode active material having an average particle diameter of less than 8 μm, it is difficult to obtain the effect of the present invention because the sedimentation of the active material particles is not remarkable. Therefore, the average particle diameter of the positive electrode active material is preferably 8 μm or more. When the average particle size exceeds 15 μm, the sedimentation rate increases and it becomes difficult to obtain the effects of the present invention. Therefore, the average particle diameter of the positive electrode active material is preferably 8 μm or more and 15 μm or less.
さらに、不定形の粒子もまた沈降が起こり難く本発明の効果が得られ難い。このため、粒子形状は球状が好ましい。 Furthermore, sedimentation of amorphous particles also hardly occurs, and the effects of the present invention are difficult to obtain. For this reason, the particle shape is preferably spherical.
以下に、非水電解液二次電池の一例として円筒形リチウムイオン二次電池の作り方について述べる。耐非水電解液性のステンレス鋼板を加工した円筒形外装缶は、絶縁パッキングを介して、安全弁を設けた封口板でカシメにより封口されている。正極板および負極板が、隔離膜を介して、渦巻き状に捲回されて極板群が形成されている。正極板に溶接された正極リードは封口板にレーザー溶接より接続されている。負極板に溶接された負極リードは円筒形外装缶の底部に抵抗溶接により接続されている。 The following describes how to make a cylindrical lithium ion secondary battery as an example of a non-aqueous electrolyte secondary battery. A cylindrical outer can made from a non-aqueous electrolyte-resistant stainless steel plate is sealed by caulking with a sealing plate provided with a safety valve via an insulating packing. The positive electrode plate and the negative electrode plate are wound in a spiral shape with the separator interposed therebetween to form an electrode plate group. The positive electrode lead welded to the positive electrode plate is connected to the sealing plate by laser welding. The negative electrode lead welded to the negative electrode plate is connected to the bottom of the cylindrical outer can by resistance welding.
なお、正極活物質はコバルト酸リチウム（以下、ＬｉＣｏＯ2と略す）や、ＬｉXＭＯ2（ＭはＣｏ、Ｎｉ、Ｍｎ、Ｍｇ、Ａｌ、Ｖ、Ｆｅ、Ｓｒ、Ｔｉ、Ｌａ、Ｂ、Ｓｎ、Ｎｂ、Ｓｉ、Ｃａ、Ｃｕ、Ｐ、Ｉｎ、Ｍｏ、Ｙ、およびＢｉのうち１種類または１種類より多い金属を表し、０．０５＜ｘ＜１．１０）で表される含リチウム複合酸化物を用いてもよい。 The positive electrode active material is lithium cobalt oxide (hereinafter abbreviated as LiCoO 2 ) or Li x MO 2 (M is Co, Ni, Mn, Mg, Al, V, Fe, Sr, Ti, La, B, Sn, A lithium-containing composite oxide that represents one or more than one of Nb, Si, Ca, Cu, P, In, Mo, Y, and Bi, and is represented by 0.05 <x <1.10. May be used.
負極活物質は、黒鉛系、非晶質系等の炭素材料あるいはその混合体、合金や金属化合物などが挙げられ、これらを単独もしくは２種以上を混合して用いることができる。合金は、ケイ素、スズ、アルミニウム、亜鉛、マグネシウム、チタン、およびニッケルよりなる群から選択される少なくとも一種の元素からなるのが好ましい。また、金属化合物はケイ素、スズ、アルミニウム、亜鉛、マグネシウム、チタン、およびニッケルの酸化物や炭化物よりなる群から選択される少なくとも一種である。負極活物質の平均粒径は特に限定されないが、１〜３０μｍが好ましい。 Examples of the negative electrode active material include carbon materials such as graphite and amorphous materials, mixtures thereof, alloys, metal compounds, and the like, and these can be used alone or in admixture of two or more. The alloy preferably comprises at least one element selected from the group consisting of silicon, tin, aluminum, zinc, magnesium, titanium, and nickel. The metal compound is at least one selected from the group consisting of silicon, tin, aluminum, zinc, magnesium, titanium, and nickel oxides and carbides. Although the average particle diameter of a negative electrode active material is not specifically limited, 1-30 micrometers is preferable.
導電材は電子伝導性材料であれば何でもよい。例えば、天然黒鉛（鱗片状黒鉛など）、人造黒鉛、および膨張黒鉛などのグラファイト類や、アセチレンブラック（以下、ＡＢと略す）、チャンネルブラック、ファーネスブラック、およびサーマルブラック等のカ−ボンブラック類や、炭素繊維、金属繊維などの導電性繊維類や、銅、ニッケル等の金属粉末類や、およびポリフェニレン誘導体などの有機導電性材料などを単独又はこれらの混合物として含ませることができる。これらの導電材の中で、人造黒鉛、アセチレンブラック、および炭素繊維が特に好ましい。導電材の添加量は特に限定されないが、負極活物質に対して１〜３０重量％が好ましく、さらには１〜１０重量％が好ましい。 The conductive material may be anything as long as it is an electron conductive material. For example, graphites such as natural graphite (such as flake graphite), artificial graphite, and expanded graphite, carbon blacks such as acetylene black (hereinafter abbreviated as AB), channel black, furnace black, and thermal black, In addition, conductive fibers such as carbon fibers and metal fibers, metal powders such as copper and nickel, and organic conductive materials such as polyphenylene derivatives can be contained alone or as a mixture thereof. Among these conductive materials, artificial graphite, acetylene black, and carbon fiber are particularly preferable. The addition amount of the conductive material is not particularly limited, but is preferably 1 to 30% by weight, and more preferably 1 to 10% by weight with respect to the negative electrode active material.
負極板の結着剤は、熱可塑性樹脂、熱硬化性樹脂のいずれであっても良く、好ましい結着剤として、スチレン−ブタジエンゴム（ＳＢＲ）、ポリフッ化ビニリデン（ＰＶＤＦ）、エチレン−アクリル酸共重合体または前記材料の（Ｎａ+）イオン架橋体、エチレン−メタクリル酸共重合体または前記材料の（Ｎａ+）イオン架橋体、エチレン−アクリル酸メチル共重合体または前記材料の（Ｎａ+）イオン架橋体、およびエチレン−メタクリル酸メチル共重合体または前記材料の（Ｎａ+）イオン架橋体の単独又は混合物を挙げることができる。 The binder for the negative electrode plate may be either a thermoplastic resin or a thermosetting resin. Preferred binders include styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), and ethylene-acrylic acid. Polymer or (Na + ) ion cross-linked product of the material, ethylene-methacrylic acid copolymer or (Na + ) ion cross-linked product of the material, ethylene-methyl acrylate copolymer or (Na + ) ion of the material Mention may be made of cross-linked bodies and ethylene-methyl methacrylate copolymers or (Na + ) ion cross-linked bodies of the above materials alone or as a mixture.
負極板の集電体は電気化学的に安定な電子伝導体であれば何でも良く、銅、チタンなどを用いることができる。厚みは特に限定されないが、５〜２５μｍが好ましい。 The current collector of the negative electrode plate may be anything as long as it is an electrochemically stable electron conductor, and copper, titanium, or the like can be used. Although thickness is not specifically limited, 5-25 micrometers is preferable.
隔離膜は、ポリプロピレン、ポリプロピレンなどの有機微多孔膜あるいは、無機微多孔膜を用いてもよい。有機微多孔膜の厚さは１０〜４０μｍが好ましい。無機微多孔膜は、例えば、アルミナやシリカなどの無機フィラーと、無機フィラーを結着させるための有機系バインダーを結着剤として混合した膜である。無機微多孔膜は正極と負極との間に介在していればよい。正極と負極との間に無機微多孔膜を介在させる方法として、正極の表面に無機微多孔膜を形成させたり、負極の表面に無機微多孔膜を形成させてもよく、両極の表面に無機微多孔膜を形成させてもよい。無機微多孔膜の厚さは１〜２０μｍが好ましい。また、無機微多孔膜と有機微多孔膜との両方を用いてもよい。無機微多孔膜と有機微多孔膜の両方を用いた場合の無機微多孔膜の厚みは１〜１０μｍが好ましい。 The separator may be an organic microporous film such as polypropylene or polypropylene, or an inorganic microporous film. The thickness of the organic microporous film is preferably 10 to 40 μm. The inorganic microporous film is a film in which an inorganic filler such as alumina or silica and an organic binder for binding the inorganic filler are mixed as a binder. The inorganic microporous film may be interposed between the positive electrode and the negative electrode. As a method of interposing an inorganic microporous film between the positive electrode and the negative electrode, an inorganic microporous film may be formed on the surface of the positive electrode, or an inorganic microporous film may be formed on the surface of the negative electrode. A microporous film may be formed. The thickness of the inorganic microporous film is preferably 1 to 20 μm. Moreover, you may use both an inorganic microporous film and an organic microporous film. The thickness of the inorganic microporous film when both the inorganic microporous film and the organic microporous film are used is preferably 1 to 10 μm.
非水電解液二次電池の形状は、円筒形、角形、およびラミネートタイプなど電池形状が異なってもよい。 The shape of the nonaqueous electrolyte secondary battery may be different from the battery shape such as a cylindrical shape, a square shape, and a laminate type.
電解質はとして六フッ化リン酸リチウム（ＬｉＰＦ6）、過塩素酸リチウム（ＬｉＣｌＯ4）、および四フッ化ホウ酸リチウム（ＬｉＢＦ4）等でもよい。これらは単独で用いてもよく、２種以上を組合せて用いてもよい。また、電解質の塩濃度を０．５〜２．０ｍｏｌ／Ｌのものを用いてもよい。 The electrolyte may be lithium hexafluorophosphate (LiPF 6 ), lithium perchlorate (LiClO 4 ), lithium tetrafluoroborate (LiBF 4 ), or the like. These may be used alone or in combination of two or more. Alternatively, an electrolyte having a salt concentration of 0.5 to 2.0 mol / L may be used.
非水溶媒は、プロピレンカーボネート（ＰＣ）やエチレンカーボネート（ＥＣ）などの環状エステル、ジエチルカーボネート（ＤＥＣ）やテトラヒドロフラン（ＴＨＦ）などの環状エーテル、ジメトキシエタン（ＤＭＥ）などの鎖状エーテル、プロピオン酸メチル（ＭＰ）などの鎖状エステルなどの非水溶媒や、また、これら多元系混合溶媒を用いてもよい。 Non-aqueous solvents include cyclic esters such as propylene carbonate (PC) and ethylene carbonate (EC), cyclic ethers such as diethyl carbonate (DEC) and tetrahydrofuran (THF), chain ethers such as dimethoxyethane (DME), and methyl propionate. A non-aqueous solvent such as a chain ester such as (MP) or a multicomponent mixed solvent may be used.
非水電解液は特にこれらに限定されず、従来から非水電解液二次電池に用いられている非水電解液を用いてもよい。また、非水電解液には、耐過充電性を向上させる添加剤を含ませてもよい。添加剤には、フェニル基およびそれに隣接する環状化合物基からなるベンゼン誘導体を用いることが好ましい。このようなベンゼン誘導体として、ビフェニル、シクロヘキシルベンゼン、ジフェニルエーテル、およびフェニルラクトンなどが挙げられる。 The non-aqueous electrolyte is not particularly limited to these, and a non-aqueous electrolyte conventionally used in non-aqueous electrolyte secondary batteries may be used. Moreover, you may include the additive which improves overcharge resistance in a non-aqueous electrolyte. As the additive, a benzene derivative composed of a phenyl group and a cyclic compound group adjacent thereto is preferably used. Examples of such benzene derivatives include biphenyl, cyclohexyl benzene, diphenyl ether, and phenyl lactone.
また、非水電解液二次電池として、リチウムイオン二次電池に限らず、マグネシウム二次電池などの非水電解液二次電池においても、本発明の効果が得られるものである。 The effects of the present invention can be obtained not only in lithium ion secondary batteries but also in nonaqueous electrolyte secondary batteries such as magnesium secondary batteries as nonaqueous electrolyte secondary batteries.
以下に、本発明の一実施の形態である正極合剤ペーストの製造方法について詳述する。 Below, the manufacturing method of the positive mix paste which is one embodiment of this invention is explained in full detail.
以下の実施例では、現在工業的に実用化され、もしくは実用化に近い複合酸化物を活物質として用いる場合について詳細に説明する。 In the following examples, the case where a composite oxide that is currently industrially practical or close to practical use is used as an active material will be described in detail.
（実施例１）
正極活物質として平均粒径１１μｍのＬｉＣｏＯ2、導電材としてＡＢ、結着剤として重量平均分子量が８０万であるＰＶｄＦ、有機溶媒としてＮＭＰを用いた。ＰＶｄＦは、予めＮＭＰに溶解して、ＰＶｄＦ溶液とし、そのＰＶｄＦ溶液に正極活物質と導電材とを投入し、混合、攪拌して、正極合剤ペーストを製造した。正極合剤ペーストに含まれるＬｉＣｏＯ2１００重量部当りのＡＢの量は２．５重量部とし、正極活物質１００重量部当
りのＰＶｄＦの量は２重量部とした。
Example 1
LiCoO 2 having an average particle diameter of 11 μm was used as the positive electrode active material, AB was used as the conductive material, PVdF having a weight average molecular weight of 800,000 was used as the binder, and NMP was used as the organic solvent. PVdF was previously dissolved in NMP to form a PVdF solution, and a positive electrode active material and a conductive material were added to the PVdF solution, mixed and stirred to produce a positive electrode mixture paste. The amount of AB per 100 parts by weight of LiCoO 2 contained in the positive electrode mixture paste was 2.5 parts by weight, and the amount of PVdF per 100 parts by weight of the positive electrode active material was 2 parts by weight.
ＬｉＣｏＯ2、ＡＢ、ＰＶｄＦ、およびＮＭＰからなる混合物の錬合には、プラネタリーミキサー（特殊機化工業（株）製、内容積５Ｌ）を用いた。混合は３段階に分けて行った。１段階目は、ＬｉＣｏＯ2１００重量部に、予め調整しておいたＰＶｄＦ溶液（ＮＭＰ９２重量部にＰＶｄＦ８重量部が溶解した溶液）５重量部、ＮＭＰ６重量部を投入し、２０分間錬合した。２段階目は、ＬｉＣｏＯ2１００重量部当りＡＢ２．５重量部を投入し、ＰＶｄＦ溶液５重量部を追加して３０分間錬合した。３段階目は、ＰＶｄＦ溶液１１重量部、ＮＭＰ８．５重量部を投入し、１５分間錬合し正極合剤ペースト中間体を作製した。次に、正極合剤ペースト中間体から気泡を除去するために、プラネタリーミキサー内の減圧し、１５分間錬合した。こうして作製した正極合剤ペーストをステンレス製の保管容器に移し、０℃で２４時間保管した。 A planetary mixer (made by Tokushu Kika Kogyo Co., Ltd., internal volume 5 L) was used for refining the mixture composed of LiCoO 2 , AB, PVdF, and NMP. Mixing was performed in three stages. In the first stage, 5 parts by weight of a previously prepared PVdF solution (a solution in which 8 parts by weight of PVdF was dissolved in 92 parts by weight of NMP) and 6 parts by weight of NMP were added to 100 parts by weight of LiCoO 2 , and kneaded for 20 minutes. In the second stage, 2.5 parts by weight of AB per 100 parts by weight of LiCoO 2 was added, and 5 parts by weight of PVdF solution was added and smelted for 30 minutes. In the third stage, 11 parts by weight of PVdF solution and 8.5 parts by weight of NMP were added, and kneaded for 15 minutes to produce a positive electrode mixture paste intermediate. Next, in order to remove air bubbles from the positive electrode mixture paste intermediate, the pressure in the planetary mixer was reduced and the mixture was kneaded for 15 minutes. The positive electrode mixture paste thus prepared was transferred to a stainless steel storage container and stored at 0 ° C. for 24 hours.
（実施例２）
保管温度を−２０℃にした以外は実施例１と同じ条件とした。
(Example 2)
The conditions were the same as in Example 1 except that the storage temperature was −20 ° C.
（実施例３）
保管温度を−１０℃にした以外は実施例１と同じ条件とした。
(Example 3)
The conditions were the same as in Example 1 except that the storage temperature was −10 ° C.
（実施例４）
保管温度を−２５℃にした以外は実施例１と同じ条件とした。
Example 4
The conditions were the same as in Example 1 except that the storage temperature was −25 ° C.
（実施例５）
保管時間を１２時間にした以外は実施例１と同じ条件とした。
(Example 5)
The conditions were the same as in Example 1 except that the storage time was 12 hours.
（実施例６）
保管時間を１８時間にした以外は実施例１と同じ条件とした。
(Example 6)
The conditions were the same as in Example 1 except that the storage time was 18 hours.
（実施例７）
保管時間を７２時間にした以外は実施例１と同じ条件とした。
(Example 7)
The conditions were the same as in Example 1 except that the storage time was 72 hours.
（実施例８）
保管時間を１６８時間にした以外は実施例１と同じ条件とした。
(Example 8)
The conditions were the same as in Example 1 except that the storage time was 168 hours.
（実施例９）
保管時間を１９２時間にした以外は実施例１と同じ条件とした。
Example 9
The conditions were the same as in Example 1 except that the storage time was 192 hours.
（実施例１０）
平均粒径１１μｍのＬｉＣｏＯ2を用い、導電材として天然黒鉛と人造黒鉛の混合物を用い、結着剤としてＨＦＰとＣＴＦＥの混合物を用いた。それ以外は実施例１と同じ条件とした。
(Example 10)
LiCoO 2 having an average particle diameter of 11 μm was used, a mixture of natural graphite and artificial graphite was used as the conductive material, and a mixture of HFP and CTFE was used as the binder. The other conditions were the same as in Example 1.
（実施例１１）
平均粒径６μｍのＬｉＣｏＯ2を用いた以外は実施例１０と同じ条件とした。
(Example 11)
The conditions were the same as in Example 10 except that LiCoO 2 having an average particle diameter of 6 μm was used.
（実施例１２）
平均粒径８μｍのＬｉＣｏＯ2を用いた以外は実施例１０と同じ条件とした。
(Example 12)
The conditions were the same as in Example 10 except that LiCoO 2 having an average particle diameter of 8 μm was used.
（実施例１３）
平均粒径１５μｍのＬｉＣｏＯ2を用いた以外は実施例１０と同じ条件とした。
(Example 13)
The conditions were the same as in Example 10 except that LiCoO 2 having an average particle diameter of 15 μm was used.
（実施例１４）
平均粒径２０μｍのＬｉＣｏＯ2を用いた以外は実施例１０と同じ条件とした。
(Example 14)
The conditions were the same as in Example 10 except that LiCoO 2 having an average particle diameter of 20 μm was used.
（比較例１）
保管温度を５℃にした以外は実施例１と同じ条件とした。
＜評価＞
実施例１〜１４および比較例１それぞれの正極合剤ペーストの粘度を測定し、安定性の評価を行った。
(Comparative Example 1)
The conditions were the same as in Example 1 except that the storage temperature was 5 ° C.
<Evaluation>
The viscosities of the positive electrode mixture pastes of Examples 1 to 14 and Comparative Example 1 were measured, and the stability was evaluated.
正極合剤ペーストの粘度は次の方法で測定した。ＪＩＳ（Ｚ８８０３「液体の粘度−測定方法」）に定義されるＢ型粘度計の６番ローターを用い、回転速度２０ｒｐｍで測定した。 The viscosity of the positive electrode mixture paste was measured by the following method. The measurement was performed at a rotational speed of 20 rpm using a No. 6 rotor of a B-type viscometer defined in JIS (Z8803 “Liquid viscosity—Measurement method”).
正極合剤ペーストの安定性は次の方法で確認した。保管前の粘度と７２時間保管後に常温に戻した時の粘度を測定した。保管後の粘度の値を保管前の粘度の値で除した。この算出した値が１に近いほど、ペーストの安定性は高いと言える。 The stability of the positive electrode mixture paste was confirmed by the following method. The viscosity before storage and the viscosity when returned to room temperature after 72 hours of storage were measured. The viscosity value after storage was divided by the viscosity value before storage. It can be said that the closer the calculated value is to 1, the higher the stability of the paste.
正極合剤ペーストの粘度を測定し、安定性の評価の結果を表１に示す。 The viscosity of the positive electrode mixture paste was measured, and the results of stability evaluation are shown in Table 1.
また、発明者らの今日までの研究開発により、正極合剤ペーストの安定性の目安として、０．７以上が好ましい範囲であることがわかっている。実施例１〜１４の正極合剤ペーストは全てこの範囲に入っており、良好な塗工性が得られた。これに対し、比較例１の正極合剤ペーストの安定性は０．７０未満であった。比較例１は、保管時の温度を５℃と０℃よりも高くしたため、正極活物質の沈降が抑えられなかったためと考えられる。 Further, according to the research and development by the inventors to date, it has been found that 0.7 or more is a preferable range as a measure of the stability of the positive electrode mixture paste. The positive electrode mixture pastes of Examples 1 to 14 all fall within this range, and good coatability was obtained. On the other hand, the stability of the positive electrode mixture paste of Comparative Example 1 was less than 0.70. It is considered that Comparative Example 1 was because the temperature during storage was higher than 5 ° C. and 0 ° C., so that precipitation of the positive electrode active material could not be suppressed.
また、実施例４は、保管温度を―２５℃としたため、正極合剤ペースト中のＮＭＰの凍
結温度以下となってしまい、正極合剤ペーストの一部が凍結した。そのため、塗工する前に解凍する必要があったため生産性が悪かった。このことから、保管温度は−２０〜０℃が好ましいと言える。
In Example 4, the storage temperature was −25 ° C., so that the temperature was below the freezing temperature of NMP in the positive electrode mixture paste, and a part of the positive electrode mixture paste was frozen. Therefore, productivity was poor because it was necessary to thaw before coating. From this, it can be said that the storage temperature is preferably -20 to 0 ° C.
実施例１と実施例５〜９は、保管温度を０℃と固定し、保管時間を２４〜１９２時間まで変えて作製した。実施例９にように保管時間を１９２時間にしても本発明の効果が得られることがわかる。しかし、正極合剤ペーストの安定性は０．７以上が好ましい範囲であることから、保管時間が１９２時間の場合の安定性は０．７０であるのに対して、保管時間が１６８時間の場合の安定性は０．７１であることから、生産性の安全目を考慮すれば、保管時間は１６８時間以内が好ましいと言える。
また、実施例５と６においては、保管時間が１２時間、および１８時間であり、良好な安定性（０．８５以上）が得られている。また、ペーストの温度が均一になるには２４時間程度必要であるため、保管時間は２４時間以上が好ましい。以上より、保管時間は２４〜１６８時間が好ましい。
Examples 1 and 5 to 9 were prepared by fixing the storage temperature at 0 ° C. and changing the storage time from 24 to 192 hours. It can be seen that the effect of the present invention can be obtained even when the storage time is 192 hours as in Example 9. However, since the stability of the positive electrode mixture paste is preferably 0.7 or more, the stability when the storage time is 192 hours is 0.70, while the storage time is 168 hours. Therefore, it can be said that the storage time is preferably within 168 hours in consideration of productivity safety.
In Examples 5 and 6, the storage time was 12 hours and 18 hours, and good stability (0.85 or more) was obtained. Moreover, since it takes about 24 hours for the paste temperature to become uniform, the storage time is preferably 24 hours or more. From the above, the storage time is preferably 24 to 168 hours.
実施例１０〜１４は、導電材として天然黒鉛と人造黒鉛を用い、かつ結着剤としてＨＦＰとＣＴＦＥを用い、正極活物質の平均粒子径を６〜２０μｍまで変化させた。正極活物質の平均粒子径が６μｍである実施例１１は安定性が０．９０であり、非常に良好な結果となった。これは、正極活物質の粒子径が小さいため、沈降し難いことを示しており、本発明を用いずとも安定性が高い。このため、本発明を効果的に使用するには、平均粒径を８μｍ以上とすることが好ましい。平均粒子径２０μｍの正極活物質を用いた実施例１４は、活物質平均粒子径１５μｍを用いた実施例１３に比べて、安定性が極端に低下した。このことから、正極活物質の平均粒子径は８〜１５μｍが好ましい。 In Examples 10 to 14, natural graphite and artificial graphite were used as the conductive material, and HFP and CTFE were used as the binder, and the average particle size of the positive electrode active material was changed to 6 to 20 μm. Example 11 in which the average particle diameter of the positive electrode active material was 6 μm had a stability of 0.90, which was a very good result. This indicates that since the particle size of the positive electrode active material is small, it is difficult to settle, and the stability is high without using the present invention. For this reason, in order to use this invention effectively, it is preferable that an average particle diameter shall be 8 micrometers or more. The stability of Example 14 using a positive electrode active material having an average particle diameter of 20 μm was extremely reduced compared to Example 13 using an active material average particle diameter of 15 μm. For this reason, the average particle diameter of the positive electrode active material is preferably 8 to 15 μm.
実施例１０と実施例１では導電材と結着剤が異なるが、正極合剤ペーストの粘度、安定性がほぼ同等であった。このことから、導電材に、ＡＢのようなカーボンブラック、天然黒鉛、および人造黒鉛を用いても、結着剤に、ＰＶｄＦ、ＨＦＰ、およびＣＴＦＥを用いても同様の効果が得られると言える。 In Example 10 and Example 1, the conductive material and the binder were different, but the viscosity and stability of the positive electrode mixture paste were almost the same. From this, it can be said that the same effect can be obtained even when carbon black such as AB, natural graphite, and artificial graphite is used as the conductive material, and PVdF, HFP, and CTFE are used as the binder.
以上のことから、塗工性、および安定性に優れた正極合剤ペーストを得るためには、練合後の正極合剤ペーストの保管温度が重要であることがわかった。 From the above, it was found that the storage temperature of the positive electrode mixture paste after kneading is important in order to obtain a positive electrode mixture paste excellent in coatability and stability.
なお、実施例では、正極活物質にＬｉＣｏＯ2、導電材にＡＢ、天然黒鉛、および人造黒鉛を用いた場合を説明したが、これに制約を受けるものではない。 In the embodiment, LiCoO 2 as the positive electrode active material, AB in conductive material, a case has been described using natural graphite, and artificial graphite, do not restricted thereto.
実施例では、結着剤にＰＶｄＦ、ＨＦＰ、およびＣＴＦＥを用いたが、これに制約を受けるものではない。ＰＶｄＦ以外のフッ素原子含有高分子材料、例えば、テトラフルオロエチレンなどのフッ素原子含有高分子材料を用いた場合にも実施例と同様の結果が得られる。また、ＰＶｄＦは、ＰＶｄＦ単独から構成されている場合に限らず、分子鎖にクロロトリフルオロエチレン等からなる側鎖を有する場合にも実施例と同様の結果が得られる。また、分子鎖の末端にアルキル基などの官能基が存在する場合にも、実施例と同様の結果が得られる。 In the examples, PVdF, HFP, and CTFE were used as the binder, but this is not a limitation. Even when a fluorine atom-containing polymer material other than PVdF, for example, a fluorine atom-containing polymer material such as tetrafluoroethylene is used, the same results as in the examples can be obtained. PVdF is not limited to being composed of PVdF alone, and the same results as in the examples can be obtained when the molecular chain has a side chain composed of chlorotrifluoroethylene or the like. Further, when a functional group such as an alkyl group is present at the end of the molecular chain, the same result as in the example can be obtained.
本発明の製造方法は、安定性に優れた実用性の高い非水電解液二次電池用正極合剤ペーストを製造することができる。本発明の製造方法を用いた非水電解液二次電池は、携帯電話やノート型パソコン等の民生用モバイルツールの主電源、電動ドライバー等のパワーツールの主電源、およびＥＶ自動車等の産業用主電源の用途に適している。
The production method of the present invention can produce a highly practical positive electrode mixture paste for a non-aqueous electrolyte secondary battery excellent in stability. The non-aqueous electrolyte secondary battery using the manufacturing method of the present invention is a main power source for consumer mobile tools such as mobile phones and laptop computers, a main power source for power tools such as an electric screwdriver, and an industrial vehicle such as an EV car. Suitable for main power supply applications.
Claims (8)
正極活物質、導電材、結着剤、および有機溶媒を混合して正極合剤ペーストを作製した後、前記正極合剤ペーストを０℃以下の温度で保管する非水電解液二次電池用正極合剤ペーストの製造方法。 A method for producing a positive electrode mixture paste for a non-aqueous electrolyte secondary battery, comprising:
A positive electrode for a non-aqueous electrolyte secondary battery in which a positive electrode mixture paste is prepared by mixing a positive electrode active material, a conductive material, a binder, and an organic solvent, and then the positive electrode mixture paste is stored at a temperature of 0 ° C. or lower. A method for producing a mixture paste.
The nonaqueous electrolyte secondary battery produced by the manufacturing method of the positive mix paste for nonaqueous electrolyte secondary batteries in any one of Claims 1-7.
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| WO2011105574A1 (en) * | 2010-02-26 | 2011-09-01 | 日本ゼオン株式会社 | All solid state secondary battery and method for manufacturing all solid state secondary battery |
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| WO2011105574A1 (en) * | 2010-02-26 | 2011-09-01 | 日本ゼオン株式会社 | All solid state secondary battery and method for manufacturing all solid state secondary battery |
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