JP2014165037A - Electrode material for nonaqueous electrolyte secondary battery and nonaqueous electrolyte secondary battery using the same - Google Patents
Electrode material for nonaqueous electrolyte secondary battery and nonaqueous electrolyte secondary battery using the same Download PDFInfo
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Abstract
Description
本発明は、非水電解質二次電池用電極材料とそれを用いた非水電解質二次電池に関するものである。 The present invention relates to a nonaqueous electrolyte secondary battery electrode material and a nonaqueous electrolyte secondary battery using the same.
従来から、たとえば、リチウムイオン二次電池等の非水電解質二次電池の電極を製造するために用いられる電極材料としての電極スラリーは、電極活物質、導電剤、結着剤、および、分散媒等を混合して攪拌することにより、作製される。しかしながら、従来の結着剤では、結着強度（固着強度）が不十分であるという問題がある。 Conventionally, for example, an electrode slurry as an electrode material used for manufacturing an electrode of a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery is an electrode active material, a conductive agent, a binder, and a dispersion medium. Etc. are mixed and stirred. However, the conventional binder has a problem that the binding strength (adhesion strength) is insufficient.
このような問題を解消するために、たとえば、特開２００７‐１３１７８４号公報（以下、特許文献１という）には、数平均分子量が５×１０4〜１×１０6であり、分散度（Ｍｗ／Ｍｎ：Ｍｗは重量平均分子量、Ｍｎは数平均分子量である）が１．０１〜１．５０であるスターポリマー（樹脂）を含む電極作製用結着剤が提案されている。 In order to solve such a problem, for example, Japanese Patent Application Laid-Open No. 2007-131784 (hereinafter referred to as Patent Document 1) has a number average molecular weight of 5 × 10 4 to 1 × 10 6 and a dispersity (Mw / Mn: Mw is a weight average molecular weight, Mn is a number average molecular weight) A binder for electrode preparation containing a star polymer (resin) having a ratio of 1.01-1.50 has been proposed.
分散度が低いほど、樹脂の分布が均一になり、樹脂が電極活物質等の粒子の表面に吸着し、粒子の安定化に寄与するため、電極材料の分散性が向上する。ある程度の値までは樹脂の分散度が低いほど、電極活物質等の粒子を解砕する効果が高くなるので、電極材料の分散性が向上するにつれて電池の性能が向上する。 The lower the degree of dispersion, the more uniform the resin distribution, and the resin is adsorbed on the surface of the particles such as the electrode active material and contributes to the stabilization of the particles, thereby improving the dispersibility of the electrode material. The lower the degree of dispersion of the resin up to a certain value, the higher the effect of crushing particles such as the electrode active material, so that the performance of the battery improves as the dispersibility of the electrode material improves.
しかしながら、特許文献１に記載された樹脂のように分散度が過度に低いと、樹脂が電極活物質等の粒子の表面を過剰に被覆するので、電極の内部抵抗が増加し、電池の性能が低下するという問題がある。 However, if the degree of dispersion is excessively low as in the resin described in Patent Document 1, the resin excessively covers the surface of the particles such as the electrode active material, so that the internal resistance of the electrode increases and the performance of the battery increases. There is a problem of lowering.
そこで、本発明の目的は、所定の固着強度を確保することができるとともに電池の性能を向上させることが可能な非水電解質二次電池用電極材料とそれを用いた非水電解質二次電池を提供することである。 Accordingly, an object of the present invention is to provide an electrode material for a non-aqueous electrolyte secondary battery that can ensure a predetermined fixing strength and improve battery performance, and a non-aqueous electrolyte secondary battery using the same. Is to provide.
本発明に従った非水電解質二次電池用電極材料は、重量平均分子量が６．５×１０5以上１．２×１０6未満であり、分散度（Ｍｗ／Ｍｎ：Ｍｗは重量平均分子量、Ｍｎは数平均分子量である）が１．６以上３．０未満である樹脂を結着剤として含む。 The electrode material for a nonaqueous electrolyte secondary battery according to the present invention has a weight average molecular weight of 6.5 × 10 5 or more and less than 1.2 × 10 6 , and a dispersity (Mw / Mn: Mw is a weight average molecular weight, Mn is a number average molecular weight) and includes a resin having a value of 1.6 or more and less than 3.0 as a binder.
本発明の非水電解質二次電池用電極材料において、樹脂の重量平均分子量は７．５×１０5以上１．０×１０6未満であり、分散度は１．８以上２．８未満であることが好ましい。 In the electrode material for a non-aqueous electrolyte secondary battery of the present invention, the weight average molecular weight of the resin is 7.5 × 10 5 or more and less than 1.0 × 10 6 , and the dispersity is 1.8 or more and less than 2.8. It is preferable.
また、本発明の非水電解質二次電池用電極材料において、樹脂はポリフッ化ビニリデンを含むことが好ましい。 In the electrode material for a nonaqueous electrolyte secondary battery according to the present invention, the resin preferably contains polyvinylidene fluoride.
さらに、本発明の非水電解質二次電池用電極材料は、負極材料であることが好ましい。 Furthermore, the electrode material for a nonaqueous electrolyte secondary battery of the present invention is preferably a negative electrode material.
この場合、本発明の非水電解質二次電池用電極材料は、グラファイト、ソフトカーボン、および、チタン酸リチウムからなる群より選ばれた少なくとも一種の材料を負極活物質として含むことが好ましい。 In this case, the electrode material for a non-aqueous electrolyte secondary battery of the present invention preferably contains at least one material selected from the group consisting of graphite, soft carbon, and lithium titanate as a negative electrode active material.
本発明に従った非水電解質二次電池は、上述した非水電解質二次電池用電極材料を用いて製造される。 The nonaqueous electrolyte secondary battery according to the present invention is manufactured using the electrode material for a nonaqueous electrolyte secondary battery described above.
本発明の非水電解質二次電池用電極材料を用いることにより、塗工性が良好で所定の固着強度を確保することができるとともに、電極の内部抵抗を低下させることができ、電池の性能を向上させることが可能になる。 By using the electrode material for a non-aqueous electrolyte secondary battery of the present invention, the coating property is good and a predetermined fixing strength can be ensured, and the internal resistance of the electrode can be reduced, and the performance of the battery can be reduced. It becomes possible to improve.
以下、本発明の実施の形態について説明する。 Embodiments of the present invention will be described below.
本発明の非水電解質二次電池用電極材料の一つの実施形態としての電極スラリーは、電極活物質と、必要に応じて導電剤と、分散媒に分散した結着剤とを含み、これらの材料を混合して攪拌することによって作製される。結着剤としての樹脂の重量平均分子量が６．５×１０5以上１．２×１０6未満であり、分散度（Ｍｗ／Ｍｎ：Ｍｗは重量平均分子量、Ｍｎは数平均分子量である）が１．６以上３．０未満である。 An electrode slurry as one embodiment of the electrode material for a non-aqueous electrolyte secondary battery of the present invention includes an electrode active material, a conductive agent as necessary, and a binder dispersed in a dispersion medium. Made by mixing and stirring the materials. The resin as the binder has a weight average molecular weight of 6.5 × 10 5 or more and less than 1.2 × 10 6 and a dispersity (Mw / Mn: Mw is a weight average molecular weight, and Mn is a number average molecular weight). 1.6 or more and less than 3.0.
結着剤として重量平均分子量が６．５×１０5以上の樹脂を用いることによって、少量の結着剤で電極を安定して作製するために必要な固着強度を確保することができる。また、結着剤として分散度が３．０未満のような分子鎖が均一な樹脂を用いることによって、電極スラリーの分散性を高めることができ、集電体等への塗工性を向上させることができる。しかし、樹脂の重量平均分子量が１．２×１０6以上である場合、分子鎖が長すぎるため、分散度を低くしても集電体等への塗工性を改善することができない。 By using a resin having a weight average molecular weight of 6.5 × 10 5 or more as the binder, it is possible to secure the fixing strength necessary for stably producing the electrode with a small amount of the binder. In addition, by using a resin having a uniform molecular chain with a dispersity of less than 3.0 as the binder, the dispersibility of the electrode slurry can be increased, and the coating property to the current collector and the like is improved. be able to. However, when the weight average molecular weight of the resin is 1.2 × 10 6 or more, the molecular chain is too long, so that the coating property to the current collector cannot be improved even if the dispersity is lowered.
また、樹脂の分散度が低いと、電極材料中の電極活物質等の粒子が微粒化され、粒子内の拡散距離が短縮されることによって電池の性能が向上する。しかし、樹脂の分散度が低くなりすぎると、電極スラリー中の電極活物質等の粒子は過度に樹脂で覆われることになる。樹脂は電気抵抗体であるため、樹脂が粒子を過剰に被覆すると、リチウムイオンの拡散抵抗が増加し、電極の内部抵抗は増加する。このため、樹脂の分散度を１．６以上３．０未満とすることによって、電極活物質等の粒子を解砕する効果を高め、かつ、樹脂による粒子の過剰被覆を抑制することができるので、電極の内部抵抗を低下させることができる。 Further, when the degree of dispersion of the resin is low, particles such as an electrode active material in the electrode material are atomized, and the diffusion distance in the particles is shortened, thereby improving the performance of the battery. However, if the degree of dispersion of the resin is too low, particles such as electrode active material in the electrode slurry are excessively covered with the resin. Since the resin is an electrical resistor, if the resin covers the particles excessively, the diffusion resistance of lithium ions increases and the internal resistance of the electrode increases. For this reason, by setting the degree of dispersion of the resin to 1.6 or more and less than 3.0, it is possible to increase the effect of crushing the particles such as the electrode active material and to suppress excessive coating of the particles with the resin. The internal resistance of the electrode can be reduced.
以上のようにして、本発明の非水電解質二次電池用電極材料を用いることにより、塗工性が良好で所定の固着強度を確保することができるとともに、電極の内部抵抗を低下させることができ、電池の性能を向上させることが可能になる。 As described above, by using the electrode material for a non-aqueous electrolyte secondary battery of the present invention, the coating property is good and a predetermined fixing strength can be secured, and the internal resistance of the electrode can be reduced. And the battery performance can be improved.
樹脂の重量平均分子量は７．５×１０5以上１．０×１０6未満であり、分散度は１．８以上２．８未満であることが好ましい。結着剤として重量平均分子量が７．５×１０5以上の樹脂を用いることによって、より少量の結着剤で電極を安定して作製するために必要な固着強度を確保することができる。また、結着剤として重量平均分子量が１．０×１０6未満、かつ、分散度が２．８未満の樹脂を用いることによって、電極スラリーの分散性をより高めることができ、集電体等への塗工性を向上させることができる。さらに、結着剤として分散度が１．８以上２．８未満の樹脂を用いることによって、電極の内部抵抗をより低下させることができる。 The weight average molecular weight of the resin is preferably 7.5 × 10 5 or more and less than 1.0 × 10 6 , and the dispersity is preferably 1.8 or more and less than 2.8. By using a resin having a weight average molecular weight of 7.5 × 10 5 or more as the binder, it is possible to secure the fixing strength necessary for stably producing the electrode with a smaller amount of the binder. Further, by using a resin having a weight average molecular weight of less than 1.0 × 10 6 and a dispersity of less than 2.8 as a binder, the dispersibility of the electrode slurry can be further improved, and a current collector or the like The coating property can be improved. Furthermore, by using a resin having a dispersity of 1.8 or more and less than 2.8 as the binder, the internal resistance of the electrode can be further reduced.
また、結着剤として用いる樹脂はポリフッ化ビニリデンを含むことが好ましい。ポリフッ化ビニリデンは、高いせん断力が加えられた場合に凝集が発生しやすく、塗工性を悪化させやすい。しかし、上述したような重量平均分子量と分散度の物性値を有するポリフッ化ビニリデンを用いることによって、良好な塗工性を得ることができる。 The resin used as the binder preferably contains polyvinylidene fluoride. Polyvinylidene fluoride is prone to agglomeration when a high shear force is applied, and the coating properties are likely to deteriorate. However, good coating properties can be obtained by using polyvinylidene fluoride having physical properties such as the weight average molecular weight and the dispersity as described above.
さらに、本発明の非水電解質二次電池用電極材料は、負極材料であることが好ましい。この場合、本発明の非水電解質二次電池用電極材料は、グラファイト、ソフトカーボン、および、チタン酸リチウムからなる群より選ばれた少なくとも一種の材料を負極活物質として含むことが好ましい。高出力用途の電池を作製する際、電極の抵抗を低減させるために負極材料の塗工重量を極力小さくすることがある。塗工重量の小さい負極を作製するためには、より効果的に解砕された負極活物質等の粒子を含むスラリーを作製する必要がある。このような場合に本発明の電極材料を採用すると、スラリーの塗工性をさらに改善することができる。なお、本発明の非水電解質二次電池用電極材料は、正極材料に適用することを除外するものではない。 Furthermore, the electrode material for a nonaqueous electrolyte secondary battery of the present invention is preferably a negative electrode material. In this case, the electrode material for a non-aqueous electrolyte secondary battery of the present invention preferably contains at least one material selected from the group consisting of graphite, soft carbon, and lithium titanate as a negative electrode active material. When manufacturing a battery for high output use, the coating weight of the negative electrode material may be reduced as much as possible in order to reduce the resistance of the electrode. In order to produce a negative electrode with a small coating weight, it is necessary to produce a slurry containing particles such as a negative electrode active material that has been crushed more effectively. In such a case, when the electrode material of the present invention is employed, the coatability of the slurry can be further improved. In addition, the electrode material for nonaqueous electrolyte secondary batteries of this invention does not exclude applying to a positive electrode material.
本発明の一つの実施の形態では、非水電解質二次電池は、上述した非水電解質二次電池用電極材料を用いて製造される。非水電解質二次電池の正極と負極とは、セパレータを介して交互に積層されて配置されている。電池要素の構造は、複数の短冊状の正極、複数の短冊状のセパレータおよび複数の短冊状の負極の積層体、いわゆる枚葉構造の積層体から構成されてもよく、長尺状のセパレータを九十九折りして、短冊状の正極と短冊状の負極とを交互に介在させることによって構成してもよい。また、電池要素の構造として、長尺状の正極、長尺状のセパレータおよび長尺状の負極を巻回してなる巻回型構造を採用してもよい。 In one embodiment of the present invention, the nonaqueous electrolyte secondary battery is manufactured using the electrode material for a nonaqueous electrolyte secondary battery described above. The positive electrode and the negative electrode of the non-aqueous electrolyte secondary battery are alternately stacked with a separator interposed therebetween. The structure of the battery element may be composed of a stack of a plurality of strip-shaped positive electrodes, a plurality of strip-shaped separators and a plurality of strip-shaped negative electrodes, a stack of so-called single-wafer structures. It may be configured by folding and interposing a strip-shaped positive electrode and a strip-shaped negative electrode alternately. Moreover, as a structure of the battery element, a winding type structure in which a long positive electrode, a long separator, and a long negative electrode are wound may be employed.
正極は、正極集電体の両面に正極活物質と導電剤と結着剤とを含む正極合材層が形成されている。一例として、正極集電体はアルミニウムまたは銅からなる。正極の導電剤としては、アセチレンブラック等の炭素材料が用いられる。正極活物質は、特に限定されるものではないが、コバルト酸リチウム（ＬｉＣｏＯ2）等のリチウム遷移金属複合酸化物、マンガン酸リチウム（ＬｉＭｎ2Ｏ4）等のスピネル型構造のリチウム金属複合酸化物、リン酸鉄リチウム（ＬｉＦｅＰＯ4）等のオリビン型構造のリチウム含有リン酸化合物、等を用いることができる。正極活物質と導電剤を結着させるための結着剤としては、ポリフッ化ビニリデン（ＰＶＤＦ）、ポリアミドイミド（ＰＡＩ）、ポリアクリロニトリル（ＰＡＮ）等が用いられる。 In the positive electrode, a positive electrode mixture layer including a positive electrode active material, a conductive agent, and a binder is formed on both surfaces of the positive electrode current collector. As an example, the positive electrode current collector is made of aluminum or copper. A carbon material such as acetylene black is used as the conductive agent for the positive electrode. Although the positive electrode active material is not particularly limited, a lithium transition metal composite oxide such as lithium cobaltate (LiCoO 2 ) or a spinel-type lithium metal composite oxide such as lithium manganate (LiMn 2 O 4 ) Lithium-containing phosphate compounds having an olivine structure such as lithium iron phosphate (LiFePO 4 ) can be used. As a binder for binding the positive electrode active material and the conductive agent, polyvinylidene fluoride (PVDF), polyamideimide (PAI), polyacrylonitrile (PAN), or the like is used.
一方、負極は、負極集電体の両面に負極活物質と結着剤とを含む負極合材層が形成されている。一例として、負極集電体はアルミニウムまたは銅からなる。負極活物質は特に限定されるものではないが、炭素材料であるグラファイト、ソフトカーボン、ハードカーボン等を用いることができ、これらの混合物からなる炭素材料を用いてもよい。また、負極活物質として、リチウムチタン複合酸化物、たとえば、スピネル型構造のチタン酸リチウム（Ｌｉ4Ｔｉ5Ｏ12等）等を使用することができる。この場合、負極は、導電剤として作用するアセチレンブラック等の炭素材料を含んでもよい。負極活物質を結着させるための結着剤としては、ポリフッ化ビニリデン、ポリアミドイミド、ポリアクリロニトリル等が用いられる。 On the other hand, in the negative electrode, a negative electrode mixture layer including a negative electrode active material and a binder is formed on both surfaces of a negative electrode current collector. As an example, the negative electrode current collector is made of aluminum or copper. Although the negative electrode active material is not particularly limited, graphite, soft carbon, hard carbon, or the like, which is a carbon material, can be used, and a carbon material made of a mixture thereof may be used. Further, as the negative electrode active material, a lithium titanium composite oxide, for example, lithium titanate having a spinel structure (Li 4 Ti 5 O 12 or the like) can be used. In this case, the negative electrode may include a carbon material such as acetylene black that acts as a conductive agent. As a binder for binding the negative electrode active material, polyvinylidene fluoride, polyamideimide, polyacrylonitrile, or the like is used.
非水電解液は、支持電解質を非水溶媒に溶解して調製される。支持電解質としては、たとえば、非水溶媒中にＬｉＰＦ6を１．０ｍｏｌ／Ｌの濃度で溶解したものが使用される。ＬｉＰＦ6以外の支持電解質としては、ＬｉＢＦ4、ＬｉＡｓＦ6、ＬｉＣｌＯ4、ＬｉＣＦ3ＳＯ3、ＬｉＮ（ＳＯ2ＣＦ3）2、ＬｉＣ（ＳＯ2ＣＦ3）3、ＬｉＡｌＣｌ4、ＬｉＳｉＦ6等のリチウム塩を挙げることができる。これらの中でも、支持電解質として特にＬｉＰＦ6、ＬｉＢＦ4を用いることが酸化安定性の点から望ましい。このような支持電解質は、非水溶媒中に、０．１ｍｏｌ／Ｌ〜３．０ｍｏｌ／Ｌの濃度で溶解されて用いられることが好ましく、０．５ｍｏｌ／Ｌ〜２．０ｍｏｌ／Ｌの濃度で溶解されて用いられることがさらに好ましい。上記の非水溶媒としては、エチレンカーボネート（ＥＣ）、プロピレンカーボネート（ＰＣ）等の環状炭酸エステルに、低粘性溶媒であるジメチルカーボネート（ＤＭＣ）、エチルメチルカーボネート（ＥＭＣ）、ジエチルカーボネート（ＤＥＣ）等の低級鎖状炭酸エステルを加えたものが用いられる。 The nonaqueous electrolytic solution is prepared by dissolving the supporting electrolyte in a nonaqueous solvent. As the supporting electrolyte, for example, a solution obtained by dissolving LiPF 6 at a concentration of 1.0 mol / L in a non-aqueous solvent is used. Examples of supporting electrolytes other than LiPF 6 include lithium salts such as LiBF 4 , LiAsF 6 , LiClO 4 , LiCF 3 SO 3 , LiN (SO 2 CF 3 ) 2 , LiC (SO 2 CF 3 ) 3 , LiAlCl 4 , and LiSiF 6. Can be mentioned. Among these, LiPF 6 and LiBF 4 are particularly preferably used as the supporting electrolyte from the viewpoint of oxidation stability. Such a supporting electrolyte is preferably used by being dissolved in a non-aqueous solvent at a concentration of 0.1 mol / L to 3.0 mol / L, and at a concentration of 0.5 mol / L to 2.0 mol / L. More preferably, it is used after being dissolved. Examples of the non-aqueous solvent include cyclic carbonates such as ethylene carbonate (EC) and propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), which are low viscosity solvents. And a lower chain carbonate of the above are used.
セパレータとしては、特に限定されるべきものではなく、従来から公知のものを用いることができる。なお、本発明においては、セパレータは、その名称によって限定されるべきものではなく、セパレータの代わりにセパレータとしての機能（役割）を有するような固体電解質またはゲル状電解質を用いてもよい。また、アルミナ、ジルコニア等の無機材料を含有させたセパレータを用いてもよい。たとえば、セパレータは、ポリプロピレンおよび／またはポリエチレンを含む多孔質フィルムを用いる。 The separator is not particularly limited, and conventionally known separators can be used. In the present invention, the separator is not limited by its name, and a solid electrolyte or gel electrolyte having a function (role) as a separator may be used instead of the separator. Alternatively, a separator containing an inorganic material such as alumina or zirconia may be used. For example, the separator uses a porous film containing polypropylene and / or polyethylene.
次に、本発明の実施例を具体的に説明する。なお、以下に示す実施例は一例であり、本発明は下記の実施例に限定されるものではない。 Next, examples of the present invention will be specifically described. In addition, the Example shown below is an example and this invention is not limited to the following Example.
非水電解質二次電池用電極材料の実施例１〜８と比較例１〜７として負極スラリーを以下のようにして作製した。 As Examples 1 to 8 and Comparative Examples 1 to 7 of electrode materials for nonaqueous electrolyte secondary batteries, negative electrode slurries were prepared as follows.
以下の表１に示す数平均分子量（Ｍｎ）、重量平均分子量（Ｍｗ）および分散度（Ｍｗ／Ｍｎ）を有するポリフッ化ビニリデンを結着剤として用いて、分散媒としてのＮ‐メチル‐２‐ピロリドンにポリフッ化ビニリデンを分散させた溶液５５．５２重量部と、シュウ酸０．０３重量部とをホモジナイザーで５分間攪拌した後、負極活物質として平均粒径が１０μｍのグラファイトを３７．９５重量部、平均粒径が１４μｍのソフトカーボンを６．７０重量部加えて６０分間攪拌した（一次攪拌工程）。なお、数平均分子量と重量平均分子量は、ポリフッ化ビニリデンをＮ‐メチル‐２‐ピロリドンに溶解させ、高速液体クロマトグラフィー（ＨＰＬＣ）（測定モード：ＳＥＣ）で測定した。 Polyvinylidene fluoride having number average molecular weight (Mn), weight average molecular weight (Mw) and dispersity (Mw / Mn) shown in Table 1 below is used as a binder, and N-methyl-2- 55.52 parts by weight of a solution in which polyvinylidene fluoride was dispersed in pyrrolidone and 0.03 part by weight of oxalic acid were stirred for 5 minutes with a homogenizer, and then 37.95% by weight of graphite having an average particle size of 10 μm as a negative electrode active material. 6.70 parts by weight of soft carbon having an average particle size of 14 μm was added and stirred for 60 minutes (primary stirring step). The number average molecular weight and the weight average molecular weight were measured by dissolving high-performance liquid chromatography (HPLC) (measurement mode: SEC) after dissolving polyvinylidene fluoride in N-methyl-2-pyrrolidone.
その後、一次攪拌工程で得られた混合物を分散機としてのプライミクス社製のＴ.Ｋ.フィルミックス（８０−５０型）の容器内に入れて、高速で高いせん断力で処理することにより、攪拌を行った（二次攪拌工程）。 Thereafter, the mixture obtained in the primary stirring step is placed in a container of TK Fillmix (80-50 type) manufactured by Primix Co., Ltd. as a disperser, and the mixture is processed at high speed with high shearing force. (Secondary stirring step).
（固着強度の評価）
実施例１〜８と比較例１〜７のそれぞれの負極スラリーにおいて、負極スラリー中のポリフッ化ビニリデンの重量比率を変化させて、複数種類の負極スラリーを作製した。得られた各負極スラリーを集電体としての厚みが１０μｍの銅箔の片面上に、塗工装置としてダイコーターを用いて、１０ｍ／ｍｉｎの塗工速度で塗工し、乾燥させた後、圧延ローラーにより圧延して、銅箔の片面上に負極合材層を形成することにより、負極板を作製した。このときの単位面積あたりの負極合材の目付け量を５．６ｍｇ／ｃｍ2とした。
(Evaluation of fixing strength)
In each of the negative electrode slurries of Examples 1 to 8 and Comparative Examples 1 to 7, a plurality of types of negative electrode slurries were prepared by changing the weight ratio of polyvinylidene fluoride in the negative electrode slurry. Each negative electrode slurry obtained was applied on one side of a copper foil having a thickness of 10 μm as a current collector, using a die coater as a coating device, and dried at a coating speed of 10 m / min. A negative electrode plate was produced by rolling with a rolling roller to form a negative electrode mixture layer on one side of the copper foil. The basis weight of the negative electrode mixture per unit area at this time was 5.6 mg / cm 2 .
得られた各負極板を３ｃｍ×６ｃｍの大きさに切断した。得られた各負極板の試料において負極合材層が形成されている片面に両面テープの一方端部を貼り付け、両面テープの他方端部を治具に貼り付けた。そして、株式会社島津製作所製のオートグラフを用いて、両面テープの他方端部を５００ｍｍ／ｍｉｎの速度で引っ張り、負極合材層が銅箔から剥離するときの強度を測定した。得られた強度を固着強度とした。 Each obtained negative electrode plate was cut into a size of 3 cm × 6 cm. In each of the obtained negative electrode plate samples, one end of a double-sided tape was attached to one side where the negative electrode mixture layer was formed, and the other end of the double-sided tape was attached to a jig. And the other end part of a double-sided tape was pulled at a speed | rate of 500 mm / min using the Shimadzu Corporation autograph, and the intensity | strength when a negative electrode compound-material layer peeled from copper foil was measured. The obtained strength was defined as the fixing strength.
実施例１〜８と比較例１〜７のそれぞれの負極スラリーに対して、測定された固着強度を次のようにして評価した。ポリフッ化ビニリデンの重量比率が３重量部以上６重量部未満で６．０Ｎ／ｃｍ以上の固着強度が得られたものを最良（◎）、ポリフッ化ビニリデンの重量比率が６重量部以上８重量部未満で６．０Ｎ／ｃｍ以上の固着強度が得られたものを良（○）、ポリフッ化ビニリデンの重量比率が８重量部以上で６．０Ｎ／ｃｍ以上の固着強度が得られたものを不可（×）と評価した。その評価結果を表１に示す。 For each of the negative electrode slurries of Examples 1-8 and Comparative Examples 1-7, the measured adhesion strength was evaluated as follows. It is best that the fixing ratio of 6.0 N / cm or more is obtained when the weight ratio of polyvinylidene fluoride is 3 parts by weight or more and less than 6 parts by weight, and the weight ratio of polyvinylidene fluoride is 6 parts by weight or more and 8 parts by weight. Less than that with a fixing strength of 6.0 N / cm or more being less than (Good), and those with a weight ratio of polyvinylidene fluoride of 8 parts by weight or more and having a fixing strength of 6.0 N / cm or more are impossible (×) was evaluated. The evaluation results are shown in Table 1.
（塗工性の評価）
ポリフッ化ビニリデンの重量比率を５重量部として実施例１〜８と比較例１〜７の負極スラリーを作製した。得られた実施例１〜８と比較例１〜７のそれぞれの負極スラリーを、集電体としての厚みが１０μｍの銅箔の片面上に、塗工装置としてダイコーターを用いて、１０ｍ／ｍｉｎの塗工速度で塗工し、乾燥させた。このとき、実施例１〜８と比較例１〜７のそれぞれの負極スラリーにおいて、単位面積あたりの負極合材の目付け量を変化させた。
(Evaluation of coatability)
Negative electrode slurries of Examples 1 to 8 and Comparative Examples 1 to 7 were prepared by setting the weight ratio of polyvinylidene fluoride to 5 parts by weight. The obtained negative electrode slurries of Examples 1 to 8 and Comparative Examples 1 to 7 were each 10 m / min using a die coater as a coating device on one side of a copper foil having a thickness of 10 μm as a current collector. The coating was performed at a coating speed of and dried. At this time, in the respective negative electrode slurries of Examples 1 to 8 and Comparative Examples 1 to 7, the basis weight of the negative electrode mixture per unit area was changed.
実施例１〜８と比較例１〜７のそれぞれの負極スラリーに対して、銅箔の片面上に塗工された負極合材層の表面を目視して、ピンホールまたはスジの発生の有無で塗工性を次のようにして評価した。単位面積あたりの負極合材の目付け量が６．０ｍｇ／ｃｍ2未満でもピンホールまたはスジが発生しなければ、塗工性を最良（◎）、単位面積あたりの負極合材の目付け量が６．０ｍｇ／ｃｍ2未満でピンホールまたはスジが発生するが、６．０ｍｇ／ｃｍ2以上９．０ｍｇ／ｃｍ2未満でピンホールまたはスジが発生しなければ、塗工性を良（○）、単位面積あたりの負極合材の目付け量が６．０ｍｇ／ｃｍ2以上９．０ｍｇ／ｃｍ2未満でもピンホールまたはスジが発生すれば、塗工性を不可（×）と評価した。その評価結果を表１に示す。 For each of the negative electrode slurries of Examples 1 to 8 and Comparative Examples 1 to 7, the surface of the negative electrode mixture layer coated on one side of the copper foil was visually observed to determine whether or not pinholes or streaks were generated. The coatability was evaluated as follows. Even if the basis weight of the negative electrode mixture per unit area is less than 6.0 mg / cm 2 , if pinholes or streaks do not occur, the coatability is the best (）), and the negative electrode composite weight per unit area is 6 .0mg / cm but pinholes or streaks in less than 2 is generated, if pinholes or streaks occurs in less than 6.0 mg / cm 2 or more 9.0 mg / cm 2, the coating property good (○), If pinholes or streaks were generated even when the basis weight of the negative electrode mixture per unit area was 6.0 mg / cm 2 or more and less than 9.0 mg / cm 2 , the coating property was evaluated as impossible (×). The evaluation results are shown in Table 1.
（電池性能の評価）
＜負極の作製＞
ポリフッ化ビニリデンの重量比率を５重量部として実施例１〜８と比較例１〜７の負極スラリーを作製した。得られた実施例１〜８と比較例１〜７のそれぞれの負極スラリーを、集電体としての厚みが１０μｍの銅箔の片面上に、塗工装置としてダイコーターを用いて、１０ｍ／ｍｉｎの塗工速度で塗工し、乾燥させた後、圧延ローラーにより圧延して、銅箔の片面上に負極合材層を形成することにより、負極板を作製した。このときの単位面積あたりの負極合材の目付け量を５．６ｍｇ／ｃｍ2とした。
(Evaluation of battery performance)
<Production of negative electrode>
Negative electrode slurries of Examples 1 to 8 and Comparative Examples 1 to 7 were prepared by setting the weight ratio of polyvinylidene fluoride to 5 parts by weight. The obtained negative electrode slurries of Examples 1 to 8 and Comparative Examples 1 to 7 were each 10 m / min using a die coater as a coating device on one side of a copper foil having a thickness of 10 μm as a current collector. After coating and drying at a coating speed of 1, a negative electrode plate was produced by rolling with a rolling roller to form a negative electrode mixture layer on one side of the copper foil. The basis weight of the negative electrode mixture per unit area at this time was 5.6 mg / cm 2 .
＜正極の作製＞
厚みが２４０μｍの金属リチウム箔を正極板として用いた。
<Preparation of positive electrode>
A metal lithium foil having a thickness of 240 μm was used as the positive electrode plate.
＜非水電解液の作製＞
非水溶媒として、環状カーボネートであるエチレンカーボネートと、鎖状カーボネートであるジエチルカーボネートを３：７の体積比率で混合した混合溶媒を用い、この混合溶媒に支持電解質としてのＬｉＰＦ6を１ｍｏｌ／Ｌの濃度になるように溶解させて、非水電解液を作製した。
<Preparation of non-aqueous electrolyte>
As a non-aqueous solvent, a mixed solvent in which ethylene carbonate as a cyclic carbonate and diethyl carbonate as a chain carbonate were mixed at a volume ratio of 3: 7 was used, and LiPF 6 as a supporting electrolyte was added to this mixed solvent at a concentration of 1 mol / L. It was made to melt | dissolve so that it might become a density | concentration, and the nonaqueous electrolyte solution was produced.
＜電池の作製＞
上記で作製した負極板にニッケル製のリードタブを設け、上記で準備した正極板にアルミニウム製のリードタブを設けた。負極板と正極板の間に、セルガード株式会社製のセパレータ（製品番号２３２５）を介在させて、電池要素を作製した。この電池要素を、大日本印刷株式会社製のラミネートフィルム（製品番号Ｄ‐ＥＬ‐４０８（３））からなる外包材の内部に収納した。その後、上記で作製した非水電解液を外包材の内部に注入した後、外包材の開口部を封止することにより、非水電解質二次電池を作製した。
<Production of battery>
The negative electrode plate produced above was provided with a nickel lead tab, and the positive electrode plate prepared above was provided with an aluminum lead tab. A battery element was produced by interposing a separator (product number 2325) manufactured by Celguard Co., Ltd. between the negative electrode plate and the positive electrode plate. This battery element was housed in an outer packaging material made of a laminate film (product number D-EL-408 (3)) manufactured by Dai Nippon Printing Co., Ltd. Then, after injecting the non-aqueous electrolyte prepared above into the outer packaging material, the non-aqueous electrolyte secondary battery was fabricated by sealing the opening of the outer packaging material.
＜放電容量の測定＞
株式会社ＩＥＭ製の電池充放電試験装置を用いて、得られた実施例１〜８と比較例１〜７のそれぞれの電池の放電容量を次のようにして測定した。１Ｃの条件で電圧が４．３Ｖになるまで定電流定電圧の充電を行った後、５Ｃの条件で電圧が２．５Ｖになるまで直流放電を行ったときの５Ｃ放電容量を測定した。その測定結果を表１に示す。
<Measurement of discharge capacity>
Using the battery charge / discharge test apparatus manufactured by IEM Co., Ltd., the discharge capacities of the obtained batteries of Examples 1 to 8 and Comparative Examples 1 to 7 were measured as follows. After charging at a constant current and a constant voltage until the voltage became 4.3V under the condition of 1C, the 5C discharge capacity was measured when DC discharge was performed until the voltage became 2.5V under the condition of 5C. The measurement results are shown in Table 1.
表１から、実施例１〜８の負極スラリーを用いると、固着強度と塗工性が最良または良であり、５Ｃ放電容量が２９０ｍＡｈ／ｇ以上であるので、塗工性が良好で所定の固着強度を確保することができるとともに、電極の内部抵抗を低下させることができ、電池の性能を向上させることが可能になることがわかる。さらに、実施例２〜４の負極スラリーを用いると、固着強度と塗工性が最良であり、５Ｃ放電容量が３００ｍＡｈ／ｇ以上であるので、塗工性が良好で所定の固着強度を確保することができるとともに、電極の内部抵抗をさらに低下させることができ、電池の性能をさらに向上させることが可能になることがわかる。 From Table 1, when the negative electrode slurries of Examples 1 to 8 are used, the fixing strength and the coating property are the best or good, and the 5C discharge capacity is 290 mAh / g or more. It can be seen that the strength can be ensured and the internal resistance of the electrode can be reduced, and the performance of the battery can be improved. Further, when the negative electrode slurries of Examples 2 to 4 are used, the fixing strength and the coating property are the best, and the 5C discharge capacity is 300 mAh / g or more, so that the coating property is good and the predetermined fixing strength is ensured. It can be seen that the internal resistance of the electrode can be further reduced, and the battery performance can be further improved.
今回開示された実施の形態と実施例はすべての点で例示であって制限的なものではないと考慮されるべきである。本発明の範囲は以上の実施の形態と実施例ではなく、特許請求の範囲によって示され、特許請求の範囲と均等の意味および範囲内でのすべての修正と変形を含むものであることが意図される。 It should be considered that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is shown not by the above embodiments and examples but by the scope of claims, and is intended to include all modifications and variations within the meaning and scope equivalent to the scope of claims. .
本発明によれば、塗工性が良好で所定の固着強度を確保することができるとともに、電極の内部抵抗を低下させることができるので、本発明は、非水電解質二次電池の性能向上に寄与することができる。
According to the present invention, the coating property is good, a predetermined fixing strength can be ensured, and the internal resistance of the electrode can be reduced. Therefore, the present invention improves the performance of the nonaqueous electrolyte secondary battery. Can contribute.
Claims (6)
The nonaqueous electrolyte secondary battery manufactured using the electrode material for nonaqueous electrolyte secondary batteries of any one of Claim 1- Claim 5.
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Cited By (3)
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| WO2020059802A1 (en) * | 2018-09-19 | 2020-03-26 | 株式会社村田製作所 | Secondary battery |
| KR20200141019A (en) * | 2019-06-03 | 2020-12-17 | 닝더 엠프렉스 테크놀로지 리미티드 | Electrochemical device |
| KR20210069011A (en) * | 2019-11-29 | 2021-06-10 | 닝더 엠프렉스 테크놀로지 리미티드 | Electrolytes and electrochemical devices |
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| JP2000344838A (en) * | 1999-06-01 | 2000-12-12 | Hitachi Chem Co Ltd | Acrylic resin, non-aqueous solvent-based binder composition, manufacture of electrode, electrode, and non-aqueous solvent-based secondary cell |
| WO2013176093A1 (en) * | 2012-05-21 | 2013-11-28 | ダイキン工業株式会社 | Electrode mixture |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| WO2020059802A1 (en) * | 2018-09-19 | 2020-03-26 | 株式会社村田製作所 | Secondary battery |
| KR20200141019A (en) * | 2019-06-03 | 2020-12-17 | 닝더 엠프렉스 테크놀로지 리미티드 | Electrochemical device |
| CN112234208A (en) * | 2019-06-03 | 2021-01-15 | 宁德新能源科技有限公司 | Electrochemical device |
| KR102351040B1 (en) * | 2019-06-03 | 2022-01-12 | 닝더 엠프렉스 테크놀로지 리미티드 | electrochemical device |
| US11349124B2 (en) | 2019-06-03 | 2022-05-31 | Ningde Amperex Technology Limited | Electrochemical device |
| KR20210069011A (en) * | 2019-11-29 | 2021-06-10 | 닝더 엠프렉스 테크놀로지 리미티드 | Electrolytes and electrochemical devices |
| US11621437B2 (en) | 2019-11-29 | 2023-04-04 | Ningde Amperex Technology Limited | Electrolyte and electrochemical device |
| KR102563343B1 (en) * | 2019-11-29 | 2023-08-02 | 닝더 엠프렉스 테크놀로지 리미티드 | Electrolytes and electrochemical devices |
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