JP2018041619A - Method for manufacturing electrode - Google Patents

Method for manufacturing electrode Download PDF

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JP2018041619A
JP2018041619A JP2016174767A JP2016174767A JP2018041619A JP 2018041619 A JP2018041619 A JP 2018041619A JP 2016174767 A JP2016174767 A JP 2016174767A JP 2016174767 A JP2016174767 A JP 2016174767A JP 2018041619 A JP2018041619 A JP 2018041619A
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conductive material
electrode
active material
active substance
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直久 秋山
Naohisa Akiyama
直久 秋山
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Toyota Motor Corp
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an electrode in which the increase in electric resistance in an electrode active substance layer of a manufactured electrode is suppressed by preparing a wet granulated material in which electrode materials such as an active substance and a conductive material are mixed uniformly.SOLUTION: A method for manufacturing an electrode comprises: a granulated material preparation step of mixing at least an active substance, a conductive material 1 and a solvent to prepare a wet granulated material; and a rolling step of shaping an electrode active substance layer by rolling the wet granulated material, and attaching the electrode active substance layer to a current collector in a form of foil. A compound including at least a metal element developing hydrophilicity is used as the active substance. The method further comprises a hydrophilization step of processing the conductive material 1 by plasma under an oxygen atmosphere before the granulated material preparation step to produce hydrophilic groups on a surface of the conductive material 1 and to make an amount of functional groups on the surface of the conductive material 1 0.10-0.65 mmol/g.SELECTED DRAWING: Figure 3

Description

本発明は、電極の製造方法、詳しくは非水電解液二次電池に用いられる電極を製造する電極の製造方法に関する。   The present invention relates to an electrode manufacturing method, and more particularly to an electrode manufacturing method for manufacturing an electrode used in a non-aqueous electrolyte secondary battery.

非水電解液二次電池は、水を含まない電解液を使用し、当該電解液中のイオンが電気伝導を担う二次電池であり、例えば、リチウムイオン二次電池、ニッケル水素電池等が挙げられる。これらの非水電解液二次電池は、近年、パソコンや携帯端末等のいわゆるポータブル電源や車両駆動用電源として広く用いられている。特に、軽量で高エネルギー密度が得られるリチウムイオン二次電池は、電気自動車、ハイブリッド自動車等の車両駆動用電源として重要性が高まっている。   Non-aqueous electrolyte secondary batteries are secondary batteries that use an electrolyte solution that does not contain water, and ions in the electrolyte solution are responsible for electrical conduction, such as lithium ion secondary batteries and nickel metal hydride batteries. It is done. These non-aqueous electrolyte secondary batteries have been widely used in recent years as so-called portable power sources such as personal computers and portable terminals and vehicle driving power sources. In particular, a lithium ion secondary battery that is lightweight and has a high energy density is gaining importance as a power source for driving a vehicle such as an electric vehicle or a hybrid vehicle.

このリチウムイオン二次電池の電極は、シート状の集電体と、当該集電体の表面に設けられた電極活物質層とによって形成される。電極活物質層には、活物質やバインダ（結着剤）や導電材などの電極材料が含まれており、これらの各種の電極材料を溶媒に分散させたスラリーを調製し、当該スラリーを集電体の表面に塗布した後に乾燥させることによって作製される。   The electrode of the lithium ion secondary battery is formed by a sheet-like current collector and an electrode active material layer provided on the surface of the current collector. The electrode active material layer includes electrode materials such as an active material, a binder (binder), and a conductive material. A slurry in which these various electrode materials are dispersed in a solvent is prepared, and the slurry is collected. It is produced by drying after applying to the surface of the electric body.

また、近年では、環境への影響や生産効率の向上などを考慮して溶媒の使用量を従来よりも少なくすることができる電極の製造方法が検討されている。例えば、特許文献１には、上記した各種の電極材料を少量の溶媒とともに撹拌して湿潤造粒体を作製し、当該湿潤造粒体をロールによって圧延して電極材料層（電極活物質層）を成形し、当該電極材料層を集電体上に成膜することによってシート状の電極を作製する製造方法が記載されている。   In recent years, an electrode manufacturing method capable of reducing the amount of solvent used compared to the conventional one has been studied in consideration of the influence on the environment and improvement of production efficiency. For example, Patent Document 1 stirs various electrode materials described above with a small amount of solvent to produce a wet granulated body, and rolls the wet granulated body with a roll to form an electrode material layer (electrode active material layer). And manufacturing a sheet-like electrode by forming the electrode material layer on a current collector.

特開２０１６−１３１０９２号公報JP 2006-131092 A

上記した湿潤造粒体を圧延して電極を製造する製造方法では、湿潤造粒体を作製するに際して、活物質や導電材などの電極材料を均一に混合することが電池性能上重要な課題として検討されている。
例えば、上記した電極材料の内、活物質の嵩密度（例えば２．３ｇ／ｃｃ）と導電材の嵩密度（例えば０．０５ｇ／ｃｃ）との間には大きな差があるため、これらの材料を混合して湿潤造粒体を作製するに際して、相対的に軽い導電材が混合容器の上方に偏在し、活物質が下方に偏在して均一に混合されない傾向がある。
このように導電材と活物質とが均一に混合されていない湿潤造粒体を用いてシート状の電極を製造すると、製造後の電極の電極活物質層において、電子の通り道となる導電材が偏在して電気抵抗が増大するため電池性能が低下する原因となる。 In the above-described production method for producing an electrode by rolling a wet granulated body, it is an important issue in terms of battery performance to uniformly mix an electrode material such as an active material or a conductive material when producing a wet granulated body. It is being considered.
For example, among the electrode materials described above, there is a large difference between the bulk density of the active material (for example, 2.3 g / cc) and the bulk density of the conductive material (for example, 0.05 g / cc). When a wet granulated body is produced by mixing the above, a relatively light conductive material tends to be unevenly distributed above the mixing container, and the active material is unevenly distributed downward to be not uniformly mixed.
Thus, when a sheet-like electrode is manufactured using a wet granulated material in which the conductive material and the active material are not uniformly mixed, in the electrode active material layer of the manufactured electrode, the conductive material that becomes a path for electrons is formed. It is unevenly distributed and the electrical resistance increases, which causes a decrease in battery performance.

本発明は、かかる点に鑑みてなされたものであり、その主な目的は、活物質や導電材などの電極材料が均一に混合された湿潤造粒体を作製することによって、製造後の電極の電極活物質層における電気抵抗の増大が抑制された電極を製造することができる電極の製造方法を提供することである。   The present invention has been made in view of the above points, and its main purpose is to produce a wet granulated body in which electrode materials such as an active material and a conductive material are uniformly mixed, thereby producing an electrode after production. It is providing the manufacturing method of the electrode which can manufacture the electrode by which the increase in the electrical resistance in this electrode active material layer was suppressed.

上記目的を実現するべく、本発明によって以下の構成の電極の製造方法が提供される。   In order to achieve the above object, the present invention provides a method for manufacturing an electrode having the following structure.

ここで開示される電極の製造方法は、少なくとも活物質と導電材と溶媒とを混合することによって湿潤造粒体を作製する造粒体作製工程と、湿潤造粒体を圧延することによって電極活物質層を成形し、当該電極活物質層を箔状の集電体上に付着させる圧延工程とを備えている。
そして、ここで開示される電極の製造方法では、活物質として、親水性を発現する金属元素を少なくとも含む化合物が用いられており、造粒体作製工程の前に、導電材に酸素雰囲気下でプラズマ処理を施すことによって導電材の表面に親水基を生成し、導電材の表面の官能基量を０．１０ｍｍｏｌ／ｇ〜０．６５ｍｍｏｌ／ｇにする親水化工程を備えている。 The electrode manufacturing method disclosed herein includes a granule preparation step for preparing a wet granulation by mixing at least an active material, a conductive material, and a solvent, and an electrode active by rolling the wet granulation. A rolling step of forming a material layer and depositing the electrode active material layer on a foil-like current collector.
In the electrode manufacturing method disclosed herein, a compound containing at least a metal element that exhibits hydrophilicity is used as the active material, and the conductive material is subjected to an oxygen atmosphere before the granule preparation step. A hydrophilic group is generated on the surface of the conductive material by performing plasma treatment, and the amount of functional groups on the surface of the conductive material is 0.10 mmol / g to 0.65 mmol / g.

ここで開示される電極の製造方法では、各々の電極材料を混合する造粒体作製工程を行う前に、導電材に酸素雰囲気下でプラズマ処理を施す親水化工程を実施することによって、導電材の表面に酸素を導入して親水基を生成する。これによって、造粒体作製工程において活物質と導電材とを混合する際に、親水性を発現する金属元素を含む活物質に導電材が吸着しやすくなるため、活物質と導電材とが偏在することを防止して、均一に混合された湿潤造粒体を作製することができる。そして、かかる湿潤造粒体を用いることによって、電極活物質層における電池抵抗の増大が抑制された電極を製造することができる。   In the electrode manufacturing method disclosed herein, the conductive material is subjected to a hydrophilization step in which plasma treatment is performed on the conductive material in an oxygen atmosphere before performing the granule preparation step of mixing each electrode material. Oxygen is introduced into the surface of the substrate to generate a hydrophilic group. As a result, when the active material and the conductive material are mixed in the granule preparation process, the active material and the conductive material are easily adsorbed to the active material containing the metal element that exhibits hydrophilicity, so that the active material and the conductive material are unevenly distributed. It is possible to produce a wet granulation that is uniformly mixed. And the electrode by which the increase in the battery resistance in an electrode active material layer was suppressed by using this wet granulation body can be manufactured.

なお、上記した親水化工程において導電材の表面に生成された親水基が多すぎると、活物質と導電材とが互いに反発して各材料を均一に混合することが却って困難になる恐れがある。本発明者は、この知見に基づいて種々の実験を行った結果、親水化工程において、導電材の表面官能基量が０．１０ｍｍｏｌ／ｇ〜０．６５ｍｍｏｌ／ｇになるように、プラズマ処理の条件を調整する必要があることを見出した。   In addition, when there are too many hydrophilic groups produced | generated on the surface of the electrically conductive material in the above-mentioned hydrophilization process, there exists a possibility that an active material and a electrically conductive material may repel each other and it may become difficult on the contrary to mix each material uniformly . As a result of conducting various experiments based on this knowledge, the present inventor conducted plasma treatment so that the surface functional group amount of the conductive material was 0.10 mmol / g to 0.65 mmol / g in the hydrophilization step. We found that the conditions need to be adjusted.

本発明の一実施形態に係る電極の製造方法の各工程を示すフローチャートである。It is a flowchart which shows each process of the manufacturing method of the electrode which concerns on one Embodiment of this invention. 本発明の一実施形態に係る電極の製造方法において、親水化工程を実施する前の導電材を模式的に示した図である。In the manufacturing method of the electrode which concerns on one Embodiment of this invention, it is the figure which showed typically the electrically conductive material before implementing a hydrophilization process. 本発明の一実施形態に係る電極の製造方法において、親水化工程を実施した後の導電材を模式的に示した図である。In the manufacturing method of the electrode which concerns on one Embodiment of this invention, it is the figure which showed typically the electrically conductive material after implementing a hydrophilization process. 本発明の一実施形態に係る電極の製造方法における混合工程で用いられる撹拌造粒機を模式的に示した断面図である。It is sectional drawing which showed typically the stirring granulator used at the mixing process in the manufacturing method of the electrode which concerns on one Embodiment of this invention. 本発明の一実施形態に係る電極の製造方法における圧延工程を説明する側面図である。It is a side view explaining the rolling process in the manufacturing method of the electrode concerning one embodiment of the present invention. 試験例において用いた粉体抵抗測定器を模式的に示す断面図である。It is sectional drawing which shows typically the powder resistance measuring device used in the test example. 試験例１〜試験例８の導電材の表面官能基量と粉体抵抗との関係を示したグラフである。It is the graph which showed the relationship between the surface functional group amount of the electrically conductive material of Test Example 1-Test Example 8, and powder resistance.

以下、本発明の一実施形態について図面を参照しながら説明する。以下の実施形態では、ここで開示される電極の製造方法が適用される好適な一例として、リチウムイオン二次電池の正極の製造方法を例に挙げて説明するが、本発明の範囲を限定する意図ではない。詳しくは後述するが、ここで開示される電極の製造方法は、リチウムイオン二次電池以外の非水電解液二次電池（例えばニッケル水素電池）の電極の製造に適用することもできる。
なお、本明細書において「リチウムイオン二次電池」とは、電解質イオンとしてリチウムイオンを利用し、正負極間におけるリチウムイオンに伴う電荷の移動により充放電が実現される非水電解液二次電池をいう。また、本明細書において「活物質」とは、正極側又は負極側において充放電に関与する物質（化合物）をいう。 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following embodiments, a method for producing a positive electrode of a lithium ion secondary battery will be described as a suitable example to which the method for producing an electrode disclosed herein is applied, but the scope of the present invention is limited. Not intended. Although described in detail later, the electrode manufacturing method disclosed herein can also be applied to manufacturing an electrode of a non-aqueous electrolyte secondary battery (for example, a nickel metal hydride battery) other than a lithium ion secondary battery.
In the present specification, the term “lithium ion secondary battery” refers to a non-aqueous electrolyte secondary battery that uses lithium ions as electrolyte ions and is charged / discharged by movement of charges associated with lithium ions between the positive and negative electrodes. Say. In the present specification, the “active material” refers to a substance (compound) involved in charge / discharge on the positive electrode side or the negative electrode side.

［電極の製造方法]
図１は本実施形態に係る電極の製造方法の各工程を示すフローチャートである。図１に示すように、本実施形態に係る電極の製造方法は、親水化工程Ｓ１０と造粒体作製工程Ｓ２０と圧延工程Ｓ３０とを備えている。以下、各工程について具体的に説明する。 [Electrode manufacturing method]
FIG. 1 is a flowchart showing each step of the electrode manufacturing method according to the present embodiment. As shown in FIG. 1, the manufacturing method of the electrode which concerns on this embodiment is equipped with hydrophilization process S10, granule preparation process S20, and rolling process S30. Hereinafter, each step will be specifically described.

（１）親水化工程
親水化工程Ｓ１０は、導電材に酸素雰囲気下でプラズマ処理を施すことによって導電材の表面に親水基を生成する工程である。
ここで使用される導電材としては、製造後の電極の電極活物質層において電子の通り道となり得る導電性の微粒子、例えば、カーボンブラック（アセチレンブラック、ファーネスブラック、ケッチェンブラック等）、コークス、黒鉛（天然黒鉛およびその改質体、人造黒鉛）等の炭素材料を用いることができる。なお、かかる導電材の嵩密度は、０．０１ｇ／ｃｃ〜０．１ｇ／ｃｃである。 (1) Hydrophilization process Hydrophilization process S10 is a process of producing | generating a hydrophilic group on the surface of a electrically conductive material by performing a plasma process to an electrically conductive material in oxygen atmosphere.
Examples of the conductive material used here include conductive fine particles that can serve as electron paths in the electrode active material layer of the electrode after manufacture, such as carbon black (acetylene black, furnace black, ketjen black, etc.), coke, graphite. Carbon materials such as (natural graphite and its modified products, artificial graphite) can be used. The bulk density of the conductive material is 0.01 g / cc to 0.1 g / cc.

親水化工程Ｓ１０では、上記した通り、導電材に酸素雰囲気下（例えば、大気中）でプラズマ処理を施す。これによって、導電材の表面に酸素原子が導入されて親水基が生成されるため、導電材に親水性を付与することができる。
具体的には、図２に示すように、親水化工程Ｓ１０を実施する前の導電材１の表面には、メチル基（−ＣＨ３）や水素原子（−Ｈ）などが存在している。かかる導電材１に対して酸素雰囲気下でプラズマ処理を施すと、メチル基に酸素原子（Ｏ）が導入されることによって、親水基のカルボキシル基（−ＣＯＯＨ）が導電材１の表面に生成される（図３参照）。また、水素原子（−Ｈ）に酸素が導入されることによって、親水基のヒドロキシル基（−ＯＨ）が生成される。 In the hydrophilization step S10, as described above, the conductive material is subjected to plasma treatment in an oxygen atmosphere (for example, in the air). Thereby, oxygen atoms are introduced into the surface of the conductive material to generate a hydrophilic group, so that hydrophilicity can be imparted to the conductive material.
Specifically, as shown in FIG. 2, methyl groups (—CH 3 ), hydrogen atoms (—H), and the like exist on the surface of the conductive material 1 before the hydrophilization step S10 is performed. When plasma treatment is performed on the conductive material 1 in an oxygen atmosphere, a hydrophilic carboxyl group (—COOH) is generated on the surface of the conductive material 1 by introducing oxygen atoms (O) into methyl groups. (See FIG. 3). Further, when oxygen is introduced into a hydrogen atom (—H), a hydroxyl group (—OH) of a hydrophilic group is generated.

なお、本実施形態における親水化工程Ｓ１０では、プラズマ処理後の導電材の表面官能基量が０．１０ｍｍｏｌ／ｇ〜０．６５ｍｍｏｌ／ｇの範囲内になるように、プラズマ処理の条件が適宜調整される。
プラズマ処理後の導電材の表面官能基量が０．１０ｍｍｏｌ／ｇを下回ると、後述の造粒体作製工程において、導電材と活物質とを適切に吸着させることができず、作製後の湿潤造粒体で導電材が偏在しやすくなる。また、プラズマ処理後の表面官能基量が０．６５ｍｍｏｌ／ｇを超えると、造粒体作製工程において導電材と活物質とが反発しやすくなるため、この場合も作製後の湿潤造粒体で導電材が偏在しやすくなる。
なお、本明細書における「表面官能基量」とは、１ｇの導電材の表面に存在するカルボキシル基（−ＣＯＯＨ）とヒドロキシル基（−ＯＨ）の合計モル数を示すものであり、かかる表面官能基量は、水酸化ナトリウムおよび炭酸水素ナトリウムを用いた酸塩基滴定法によって測定される。 In the hydrophilization step S10 in the present embodiment, the conditions for the plasma treatment are appropriately adjusted so that the surface functional group amount of the conductive material after the plasma treatment is within the range of 0.10 mmol / g to 0.65 mmol / g. Is done.
When the surface functional group amount of the conductive material after the plasma treatment is less than 0.10 mmol / g, the conductive material and the active material cannot be appropriately adsorbed in the granule preparation step described later, and the wet after the preparation. The conductive material tends to be unevenly distributed in the granulated body. In addition, when the surface functional group amount after plasma treatment exceeds 0.65 mmol / g, the conductive material and the active material are likely to repel in the granule preparation step. The conductive material is likely to be unevenly distributed.
The “surface functional group amount” in the present specification indicates the total number of moles of carboxyl groups (—COOH) and hydroxyl groups (—OH) present on the surface of 1 g of the conductive material. The base amount is measured by an acid-base titration method using sodium hydroxide and sodium hydrogen carbonate.

表面官能基量が上記した数値範囲内にある導電材は、例えば、プラズマ処理時のＲＦパワーや処理時間などを所定の条件に設定することによって得ることができる。
例えば、プラズマ処理時のＲＦパワーは、１００Ｗ〜３００Ｗに設定することが好ましく、１５０Ｗ〜２５０Ｗに設定することがより好ましい。ＲＦパワーが大きすぎると、導電材の表面に過剰に酸素が導入されて表面官能基量が０．６５ｍｍｏｌ／ｇを超える恐れがある。一方、ＲＦパワーが小さすぎると、十分な量の親水基が生成されず、表面官能基量が０．１０ｍｍｏｌ／ｇを下回る恐れがある。
また、プラズマ処理の処理時間は１分〜３分に設定することが適当である。処理時間が短すぎる場合も、十分な量の親水基が生成されず、表面官能基量が０．１０ｍｍｏｌ／ｇを下回る恐れがある。また、処理時間が長すぎると、表面官能基量が０．６５ｍｍｏｌ／ｇを超える恐れがある。 A conductive material having a surface functional group amount within the above-described numerical range can be obtained, for example, by setting RF power, processing time, and the like during plasma processing to predetermined conditions.
For example, the RF power during plasma processing is preferably set to 100 W to 300 W, and more preferably set to 150 W to 250 W. If the RF power is too high, oxygen may be introduced excessively on the surface of the conductive material, and the amount of surface functional groups may exceed 0.65 mmol / g. On the other hand, if the RF power is too small, a sufficient amount of hydrophilic groups is not generated, and the amount of surface functional groups may be less than 0.10 mmol / g.
Moreover, it is appropriate to set the processing time of the plasma processing to 1 minute to 3 minutes. When the treatment time is too short, a sufficient amount of hydrophilic groups is not generated, and the amount of surface functional groups may be less than 0.10 mmol / g. Moreover, when processing time is too long, there exists a possibility that the amount of surface functional groups may exceed 0.65 mmol / g.

（２）造粒体作製工程
本実施形態における造粒体作製工程Ｓ２０は、上記した酸素雰囲気下でのプラズマ処理が施された導電材と、活物質と溶媒とを混合して湿潤造粒体を作製する。 (2) Granule body preparation process Granule body preparation process S20 in this embodiment mixes the electrically conductive material by which the above-mentioned plasma processing was performed in oxygen atmosphere, an active material, and a solvent, and wet granulation body. Is made.

本実施形態において用いられる活物質には、正極側又は負極側において充放電に関与し、かつ、親水性を発現する金属元素を少なくとも含む化合物が用いられる。親水性を発現する金属元素としては、例えば、Ｌｉ、Ｎｉ、Ｍｎなどが挙げられる。リチウムイオン二次電池の正極活物質の場合には、かかる親水性を発現する金属元素を含む活物質として、例えば、リチウムと一種または二種以上の遷移金属元素を含んだリチウム遷移金属複合酸化物が用いられる。このリチウム遷移金属複合酸化物の好適例としては、リチウムニッケル複合酸化物（ＬｉＮｉＯ２）、リチウムマンガン複合酸化物（ＬｉＭｎＯ２）、リチウムニッケルマンガン複合酸化物（ＬｉＮｉＭｎＯ２）、リチウムニッケルコバルトマンガン複合酸化物（ＬｉＮｉＣｏＭｎＯ２）などが挙げられる。かかる活物質の嵩密度は、１．５ｇ／ｃｃ〜３．０ｇ／ｃｃである。 As the active material used in the present embodiment, a compound that includes at least a metal element that is involved in charge / discharge on the positive electrode side or the negative electrode side and that exhibits hydrophilicity is used. Examples of the metal element that exhibits hydrophilicity include Li, Ni, Mn, and the like. In the case of a positive electrode active material of a lithium ion secondary battery, as an active material containing such a metal element that exhibits hydrophilicity, for example, a lithium transition metal composite oxide containing lithium and one or more transition metal elements Is used. Preferred examples of the lithium transition metal composite oxide include lithium nickel composite oxide (LiNiO 2 ), lithium manganese composite oxide (LiMnO 2 ), lithium nickel manganese composite oxide (LiNiMnO 2 ), and lithium nickel cobalt manganese composite oxide. (LiNiCoMnO 2 ) and the like. The bulk density of such an active material is 1.5 g / cc to 3.0 g / cc.

なお、上記ではリチウムイオン二次電池の正極を製造する場合の活物質の例を説明したが、ニッケル水素電池の正極を製造する場合には、正極側において充放電に関与し、かつ、親水性を発現する金属元素であるＮｉを含む化合物、例えば、ニッケル酸化物やニッケル水酸化物などを活物質として用いることができる。このように、正極側又は負極側において充放電に関与し、かつ、親水性を発現する金属元素を少なくとも含む化合物を活物質として用いる限り、ここで開示される電極の製造方法は、リチウムイオン二次電池の正極以外の電極の製造に適用することができる。   In addition, although the example of the active material in the case of manufacturing the positive electrode of a lithium ion secondary battery was demonstrated above, when manufacturing the positive electrode of a nickel metal hydride battery, it is related to charging / discharging in the positive electrode side, and is hydrophilic. A compound containing Ni, which is a metal element that expresses, for example, nickel oxide or nickel hydroxide can be used as the active material. As described above, as long as a compound that includes at least a metal element that participates in charge / discharge on the positive electrode side or the negative electrode side and exhibits hydrophilicity is used as an active material, It can be applied to the production of electrodes other than the positive electrode of the secondary battery.

また、溶媒としては、湿潤造粒体の作製に用いられる一般的な溶媒を使用することができる。かかる溶媒としては、例えば、水やＮ−メチル−２−ピロリドン（ＮＭＰ）等が挙げられる。また、かかる溶媒の添加量は、例えば、湿潤造粒体の固形分が７０％以上になるように調整することが好ましい。   Moreover, as a solvent, the general solvent used for preparation of a wet granulation body can be used. Examples of such a solvent include water and N-methyl-2-pyrrolidone (NMP). Moreover, it is preferable to adjust the addition amount of this solvent so that solid content of a wet granulation body may be 70% or more, for example.

なお、湿潤造粒体を作製するに際しては、上記した活物質、導電材、溶媒以外に、必要に応じて添加物を適宜加えてもよい。かかる添加物としては、バインダや分散剤などの一般的な非水電解液二次電池の電極活物質層に含まれる添加物が挙げられる。バインダとしては、例えば、ポリフッ化ビニリデン（ＰＶＤＦ）、ポリ塩化ビニリデン（ＰＶＤＣ）などのポリマーを好ましく採用することができる。あるいは、スチレンブタジエンゴム（ＳＢＲ）、ポリテトラフルオロエチレン（ＰＴＦＥ）、ポリエチレン（ＰＥ）、ポリアクリル酸（ＰＡＡ）等の各種のポリマー材料が用いられる。また、分散剤としては、カルボキシメチルセルロース（ＣＭＣ）等が用いられる。   In addition, when producing a wet granulated body, you may add an additive suitably as needed other than the above-mentioned active material, electrically conductive material, and a solvent. Examples of such additives include additives contained in an electrode active material layer of a general nonaqueous electrolyte secondary battery, such as a binder and a dispersant. As the binder, for example, polymers such as polyvinylidene fluoride (PVDF) and polyvinylidene chloride (PVDC) can be preferably used. Alternatively, various polymer materials such as styrene butadiene rubber (SBR), polytetrafluoroethylene (PTFE), polyethylene (PE), and polyacrylic acid (PAA) are used. Moreover, carboxymethylcellulose (CMC) etc. are used as a dispersing agent.

そして、造粒体作製工程Ｓ２０においては、例えば、図４に示すような撹拌造粒機１０を用い、上記した各材料を混合することによって湿潤造粒体を作製する。
この撹拌造粒機１０は、円筒形の混合容器１２と、混合容器１２の内部に収容される混合羽１４と、支軸１６を介して混合羽１４に接続されたモータ１８とを備えている。造粒体作製工程Ｓ２０では、かかる撹拌造粒機１０の混合容器１２内に、上記した各材料を投入して溶媒を添加した後に、モータ１８を駆動させて混合羽１４を回転させる。これによって、各々の電池材料が混合されて湿潤造粒体が作製される。 And in granule preparation process S20, a wet granulation object is produced by mixing each above-mentioned material, for example using stirring granulator 10 as shown in FIG.
The stirring granulator 10 includes a cylindrical mixing container 12, a mixing blade 14 accommodated in the mixing container 12, and a motor 18 connected to the mixing blade 14 via a support shaft 16. . In the granule preparation step S <b> 20, the above-described materials are added to the mixing container 12 of the stirring granulator 10 and the solvent is added, and then the motor 18 is driven to rotate the mixing blade 14. Thereby, each battery material is mixed and a wet granulation body is produced.

このとき、本実施形態においては、導電材と活物質の両方の表面が親水性を有しているため、導電材と活物質とを混合する際に活物質の表面に導電材が吸着する。これによって、活物質と導電材の嵩密度に差がある場合であっても、従来の技術のように導電材が混合容器１２の上方に偏在し、活物質が下方に偏在するようなことがなく、各々の電極材料を均一に混合することができる。   At this time, in this embodiment, since the surfaces of both the conductive material and the active material have hydrophilicity, the conductive material is adsorbed on the surface of the active material when the conductive material and the active material are mixed. As a result, even when there is a difference in bulk density between the active material and the conductive material, the conductive material is unevenly distributed above the mixing container 12 and the active material is unevenly distributed downward as in the prior art. In addition, each electrode material can be mixed uniformly.

（３）圧延工程
圧延工程Ｓ３０では、湿潤造粒体を圧延することによって電極活物質層を成形し、当該電極活物質層を箔状の集電体上に付着させる。図５は本実施形態に係る電極の製造方法における圧延工程を説明する側面図である。なお、図５中の集電体Ｓとしては、導電性の良い金属を主体に構成された箔状の部材が使用される。かかる集電体Ｓに使用される金属としては、例えば、アルミニウム、ニッケル、チタン、ステンレス鋼等が挙げられる。 (3) Rolling process In rolling process S30, an electrode active material layer is shape | molded by rolling a wet granulation body, and the said electrode active material layer is made to adhere on a foil-shaped collector. FIG. 5 is a side view illustrating a rolling process in the electrode manufacturing method according to the present embodiment. In addition, as the current collector S in FIG. 5, a foil-shaped member mainly composed of a metal having good conductivity is used. Examples of the metal used for the current collector S include aluminum, nickel, titanium, and stainless steel.

図５に示すように、本実施形態における圧延工程Ｓ３０では、３本のローラー２１〜２３を備えた圧延装置２０が用いられる。
具体的には、先ず、造粒体作製工程Ｓ２０で作製した湿潤造粒体Ｐを、第１のローラー２１と第２のローラー２２との間に供給する。そして、第１のローラー２１と第２のローラー２２とを回転させることによって、湿潤造粒体Ｐを圧延して電極活物質層Ｐ１を成形する。成形された電極活物質層Ｐ１は、第２のローラー２２の表面に付着した状態で、第３のローラー２３と第２のローラー２２との間に送られる。そして、第３のローラー２３と第２のローラー２２との間で、集電体Ｓと電極活物質層Ｐ１とを圧着させることによって電極を製造する。 As shown in FIG. 5, in the rolling step S30 in this embodiment, a rolling device 20 including three rollers 21 to 23 is used.
Specifically, first, the wet granulation P produced in the granule production step S <b> 20 is supplied between the first roller 21 and the second roller 22. And by rotating the 1st roller 21 and the 2nd roller 22, the wet granulation body P is rolled and the electrode active material layer P1 is shape | molded. The molded electrode active material layer P <b> 1 is sent between the third roller 23 and the second roller 22 in a state of being attached to the surface of the second roller 22. And an electrode is manufactured by crimping | bonding the electrical power collector S and the electrode active material layer P1 between the 3rd roller 23 and the 2nd roller 22. FIG.

このとき、本実施形態においては、造粒体作製工程において、導電材と活物質とが均一に混合された湿潤造粒体Ｐが作製されているため、導電材が均一に混合された電極活物質層Ｐ１を有する電極を製造することができる。かかる電極は、電極活物質層における電気抵抗が低く、高い電池性能を発揮することができる。   At this time, in the present embodiment, since the wet granulation P in which the conductive material and the active material are uniformly mixed is prepared in the granule preparation step, the electrode active in which the conductive material is uniformly mixed is prepared. An electrode having the material layer P1 can be manufactured. Such an electrode has low electric resistance in the electrode active material layer and can exhibit high battery performance.

［試験例］
本試験例では、導電材の表面にプラズマ処理を施した際の影響を調べるために以下の試験を行った。以下、本発明に関する試験例を説明するが、かかる説明は本発明を限定することを意図したものではない。 [Test example]
In this test example, the following test was performed in order to investigate the influence of the plasma treatment on the surface of the conductive material. Hereinafter, although the test example regarding this invention is demonstrated, this description is not intending limiting this invention.

１．試験例
（１）試験例１〜試験例８
試験例１〜試験例８の各々で異なる導電材を用い、導電材と正極活物質と結着剤とを９４．５：４：１．５の割合で混合して湿潤造粒体を作製した。
本試験例においては、導電材としてアセチレンブラックを使用した。また、正極活物質としてＬｉＮｉＣｏＭｎＯ２（Ｎｉ：Ｃｏ：Ｍｎ＝０．３８：０．３２：０．３０）で表されるリチウムニッケルコバルトマンガン複合酸化物を使用し、結着剤としてＰＶＤＦを用いた。
なお、各々の電極材料を混合して湿潤造粒体を作製する際には、図４に示す撹拌造粒機（容量１Ｌ）を用い、モータの回転数を４５００ｒｐｍ、混合時間を２０秒間に設定した。 1. Test Example (1) Test Example 1 to Test Example 8
A different conductive material was used in each of Test Example 1 to Test Example 8, and the conductive material, the positive electrode active material, and the binder were mixed at a ratio of 94.5: 4: 1.5 to prepare a wet granulated body. .
In this test example, acetylene black was used as the conductive material. Further, a lithium nickel cobalt manganese composite oxide represented by LiNiCoMnO 2 (Ni: Co: Mn = 0.38: 0.32: 0.30) was used as the positive electrode active material, and PVDF was used as the binder. .
In addition, when mixing each electrode material and producing a wet granulation body, the rotation speed of a motor is set to 4500 rpm and mixing time is set to 20 seconds using the stirring granulator (capacity 1L) shown in FIG. did.

そして、試験例１〜試験例８の各々の内、試験例１では、酸素雰囲気下でのプラズマ処理を行わなかった。また、試験例２〜試験例８では、表１に示すように、出力（ＲＦパワー）と処理時間（ｍｉｎ）を異ならせて、大気中でプラズマ処理を行い、導電材に親水性を付与した。   In each of Test Examples 1 to 8, in Test Example 1, plasma treatment was not performed in an oxygen atmosphere. Moreover, in Test Example 2 to Test Example 8, as shown in Table 1, plasma treatment was performed in the atmosphere with different output (RF power) and treatment time (min) to impart hydrophilicity to the conductive material. .

２．評価試験
試験例１〜試験例８の各々について、表面官能基量と粉体抵抗の測定を行った。 2. Evaluation Test For each of Test Examples 1 to 8, the surface functional group amount and the powder resistance were measured.

（１）表面官能基量の測定
各試験例で使用した導電材を中性の分散媒に分散させた後、かかる分散液に水酸化ナトリウムと炭酸水素ナトリウムを用いた酸塩基滴定法を実施することによって、各試験例の導電材の表面官能基量を測定した。なお、本試験例における「表面官能基量」は、導電材表面に存在するカルボキシル基（−ＣＯＯＨ）とヒドロキシル基（−ＯＨ）の合計量を示す。 (1) Measurement of the amount of surface functional groups After dispersing the conductive material used in each test example in a neutral dispersion medium, an acid-base titration method using sodium hydroxide and sodium hydrogen carbonate is performed on the dispersion. Thus, the surface functional group amount of the conductive material of each test example was measured. The “surface functional group amount” in this test example indicates the total amount of carboxyl groups (—COOH) and hydroxyl groups (—OH) present on the surface of the conductive material.

（２）粉体抵抗の測定
本試験例においては、作製した湿潤造粒体において導電材が均一に混合されているかを評価する指標として湿潤造粒体の粉体抵抗を測定した。湿潤造粒体において導電材が偏在している場合には粉体抵抗が大きくなり、均一に混合されている場合には粉体抵抗が小さくなる。
そして、本試験例では、かかる粉体抵抗の測定に、図６に示す粉体抵抗測定器（三菱化学アナリテック社製、ＭＣＰ−ＰＤ５１型）１００を用いた。この粉体抵抗測定器１００は、測定対象である湿潤造粒体Ｐを収納する筒状容器１１０と、筒状容器１１０の底面を封止する封止部材１２０と、筒状容器１１０内の湿潤造粒体Ｐを上方から押圧する押圧部材１３０とを備えている。そして、封止部材１２０には、上方に向けて探針（図示省略）が突出した検知部１２２が４個設けられている。
そして、本試験例では、２ｇの湿潤造粒体Ｐを筒状容器１１０内に収納して、押圧部材１３０で加圧（圧力：１２ｋＮ）しながら、４探針法で湿潤造粒体Ｐの粉体抵抗（Ω・ｃｍ）を測定した。 (2) Measurement of powder resistance In this test example, the powder resistance of the wet granulation was measured as an index for evaluating whether the conductive material was uniformly mixed in the produced wet granulation. When the conductive material is unevenly distributed in the wet granulated body, the powder resistance increases, and when it is uniformly mixed, the powder resistance decreases.
And in this test example, the powder resistance measuring device (MCP-PD51 type | mold by Mitsubishi Chemical Analytech Co., Ltd.) 100 shown in FIG. 6 was used for the measurement of this powder resistance. The powder resistance measuring device 100 includes a cylindrical container 110 that stores a wet granulated body P that is a measurement target, a sealing member 120 that seals the bottom surface of the cylindrical container 110, and a wetness in the cylindrical container 110. And a pressing member 130 that presses the granulated body P from above. The sealing member 120 is provided with four detection parts 122 from which a probe (not shown) protrudes upward.
In this test example, 2 g of wet granulated material P is stored in the cylindrical container 110 and pressed by the pressing member 130 (pressure: 12 kN). Powder resistance (Ω · cm) was measured.

３．評価結果
上記した評価試験の結果を表１および図７に示す。図７は試験例１〜試験例８の導電材の表面官能基量と粉体抵抗との関係を示したグラフであり、横軸が表面官能基量（ｍｍｏｌ／ｇ）を示し、縦軸が圧力１２ｋＮにおける粉体抵抗（Ω・ｃｍ）を示す。 3. Evaluation results The results of the evaluation tests described above are shown in Table 1 and FIG. FIG. 7 is a graph showing the relationship between the amount of surface functional groups and the powder resistance of the conductive materials of Test Examples 1 to 8, the horizontal axis represents the amount of surface functional groups (mmol / g), and the vertical axis represents The powder resistance (Ω · cm) at a pressure of 12 kN is shown.

Figure 2018041619
Figure 2018041619

表１および図７に示されるように、試験例２〜試験例６は、他の試験例と比べて粉体抵抗が大幅に低下していた。このことから、導電材の表面官能基量が０．１０ｍｍｏｌ／ｇ〜０．６５ｍｍｏｌ／ｇの範囲内になるように、酸素雰囲気下でプラズマ処理を行うことによって、活物質や導電材などの電極材料が均一に混合された湿潤造粒体を作製できることが確認できた。
なお、試験例７、８については、導電材にプラズマ処理を行って表面官能基量を増加させているにも関わらず、プラズマ処理を行っていない試験例１よりも粉体抵抗が高くなった。これは、導電材の表面官能基量が多くなりすぎると、活物質と導電材とが反発し合って偏在しやすくなるためと解される。 As shown in Table 1 and FIG. 7, in Test Examples 2 to 6, the powder resistance was significantly reduced as compared with the other test examples. Therefore, an electrode such as an active material or a conductive material is obtained by performing plasma treatment in an oxygen atmosphere so that the surface functional group amount of the conductive material is in the range of 0.10 mmol / g to 0.65 mmol / g. It was confirmed that a wet granulated material in which the materials were uniformly mixed could be produced.
In Test Examples 7 and 8, although the conductive material was subjected to plasma treatment to increase the amount of surface functional groups, the powder resistance was higher than that in Test Example 1 in which plasma treatment was not performed. . This is understood to be because the active material and the conductive material repel each other and become unevenly distributed when the surface functional group amount of the conductive material increases too much.

以上、本発明を詳細に説明したが、上記実施形態は例示にすぎず、ここで開示される発明には上述の具体例を様々に変形、変更したものが含まれる。   As mentioned above, although this invention was demonstrated in detail, the said embodiment is only an illustration and what changed and modified the above-mentioned specific example is included in the invention disclosed here.

１ 導電材
１０ 撹拌造粒機
１２ 混合容器
１４ 混合羽
１６ 支軸
１８ モータ
２０ 圧延装置
２１ 第１ローラー
２２ 第２ローラー
２３ 第３ローラー
１００ 粉体抵抗測定器
１１０ 筒状容器
１２０ 封止部材
１２２ 検知部
１３０ 押圧部材
Ｐ 湿潤造粒体
Ｐ１ 電極活物質層
Ｓ 集電体
Ｓ１０ 親水化工程
Ｓ２０ 造粒体作製工程
Ｓ３０ 圧延工程
DESCRIPTION OF SYMBOLS 1 Conductive material 10 Agitation granulator 12 Mixing container 14 Mixing blade 16 Spindle 18 Motor 20 Rolling device 21 1st roller 22 2nd roller 23 3rd roller 100 Powder resistance measuring device 110 Cylindrical container 120 Sealing member 122 Detection Part 130 Press member P Wet granulation P1 Electrode active material layer S Current collector S10 Hydrophilization step S20 Granule preparation step S30 Rolling step

Claims (1)

少なくとも活物質と導電材と溶媒とを混合することによって湿潤造粒体を作製する造粒体作製工程と、
前記湿潤造粒体を圧延することによって電極活物質層を成形し、当該電極活物質層を箔状の集電体上に付着させる圧延工程と
を備えた電極の製造方法であって、
前記活物質として、親水性を発現する金属元素を少なくとも含む化合物が用いられており、
前記造粒体作製工程の前に、前記導電材に酸素雰囲気下でプラズマ処理を施すことによって前記導電材の表面に親水基を生成し、前記導電材の表面の官能基量を０．１０ｍｍｏｌ／ｇ〜０．６５ｍｍｏｌ／ｇにする親水化工程を備えている、電極の製造方法。
A granule preparation step of preparing a wet granule by mixing at least an active material, a conductive material, and a solvent;
Forming an electrode active material layer by rolling the wet granulated body, and a rolling step of attaching the electrode active material layer on a foil-like current collector,
As the active material, a compound containing at least a metal element that exhibits hydrophilicity is used,
Before the granule preparation step, the conductive material is subjected to plasma treatment in an oxygen atmosphere to generate a hydrophilic group on the surface of the conductive material, and the functional group amount on the surface of the conductive material is set to 0.10 mmol / The manufacturing method of an electrode provided with the hydrophilization process made to g-0.65 mmol / g.
JP2016174767A 2016-09-07 2016-09-07 Method for manufacturing electrode Pending JP2018041619A (en)

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JP2019053832A (en) * 2017-09-12 2019-04-04 トヨタ自動車株式会社 Method for manufacturing electrode
JP2019169416A (en) * 2018-03-26 2019-10-03 トヨタ自動車株式会社 Manufacturing method of lithium ion secondary battery positive electrode
WO2021085344A1 (en) * 2019-10-31 2021-05-06 日本ゼオン株式会社 Paste for secondary batteries, slurry for secondary battery positive electrodes, positive electrode for secondary batteries, secondary battery and method for producing paste for secondary batteries
WO2021085343A1 (en) * 2019-10-31 2021-05-06 日本ゼオン株式会社 Paste for secondary batteries, slurry for secondary battery positive electrodes, positive electrode for secondary batteries, secondary battery, and method for producing paste for secondary batteries

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2019053832A (en) * 2017-09-12 2019-04-04 トヨタ自動車株式会社 Method for manufacturing electrode
JP2019169416A (en) * 2018-03-26 2019-10-03 トヨタ自動車株式会社 Manufacturing method of lithium ion secondary battery positive electrode
WO2021085344A1 (en) * 2019-10-31 2021-05-06 日本ゼオン株式会社 Paste for secondary batteries, slurry for secondary battery positive electrodes, positive electrode for secondary batteries, secondary battery and method for producing paste for secondary batteries
WO2021085343A1 (en) * 2019-10-31 2021-05-06 日本ゼオン株式会社 Paste for secondary batteries, slurry for secondary battery positive electrodes, positive electrode for secondary batteries, secondary battery, and method for producing paste for secondary batteries
CN114599721A (en) * 2019-10-31 2022-06-07 日本瑞翁株式会社 Paste for secondary battery, slurry for secondary battery positive electrode, secondary battery, and method for producing paste for secondary battery

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