JP2019061734A - Lithium ion secondary battery - Google Patents

Lithium ion secondary battery Download PDF

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JP2019061734A
JP2019061734A JP2015252802A JP2015252802A JP2019061734A JP 2019061734 A JP2019061734 A JP 2019061734A JP 2015252802 A JP2015252802 A JP 2015252802A JP 2015252802 A JP2015252802 A JP 2015252802A JP 2019061734 A JP2019061734 A JP 2019061734A
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positive electrode
active material
mixture layer
average particle
mixture
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繁貴 坪内
Shigetaka Tsubouchi
繁貴 坪内
野家　明彦
Akihiko Noie
明彦 野家
千恵子 荒木
Chieko Araki
千恵子 荒木
西村　悦子
Etsuko Nishimura
悦子 西村
鈴木　修一
Shuichi Suzuki
修一 鈴木
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Hitachi Ltd
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Hitachi Ltd
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Priority to PCT/JP2016/087467 priority patent/WO2017110661A1/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

To provide a positive electrode mixture which enables the achievement of a low resistance in a positive electrode mixture arranged in the form of a thin film.SOLUTION: A lithium ion secondary battery comprises: a positive electrode current collector; and a positive electrode mixture layer provided on the positive electrode current collector. The positive electrode mixture layer has: a positive electrode active material; a particulate conducting agent; and carbon nanotube. The relation b/a of an average particle diameter "a" of the positive electrode active material and an average particle diameter "b" of the particulate conducting agent is in a range of b/a≤0.04. The relation L/a of the average particle diameter "a" and a thickness "L" of the positive electrode mixture layer is in a range of 3≤L/a≤10. The relation A/CNT of a weight proportion (CNT) of the carbon nanotube in the positive electrode mixture layer, and a weight proportion (A) of the particulate conducting agent in the positive electrode mixture layer is in a range of 20≤A/CNT≤100.SELECTED DRAWING: Figure 5

Description

本発明は、リチウムイオン二次電池用電解質液それを用いたリチウムイオン二次電池に関する。   The present invention relates to a lithium ion secondary battery using the electrolyte solution for a lithium ion secondary battery.

ハイブリッド自動車へのリチウムイオン二次電池の適用に向けて、電池の高出力化が求められており、そのためには、電池の抵抗を低減する必要がある。電池設計の観点において、電池缶内に収容される電極面積を広げる事により、低抵抗化が可能である。電極の薄膜化によって、電極面積の拡張を実現できる。   For the application of lithium ion secondary batteries to hybrid vehicles, it is required to increase the output of the batteries, and for that purpose, it is necessary to reduce the battery resistance. From the viewpoint of battery design, resistance can be reduced by expanding the electrode area accommodated in the battery can. By thinning the electrode, the electrode area can be expanded.

従来、一般的な正極合剤には、ニッケル、コバルト、マンガン等を含むリチウム正極活物質と、アセチレンブラック等の導電材、バインダ等が用いられている。   Conventionally, a lithium positive electrode active material containing nickel, cobalt, manganese or the like, a conductive material such as acetylene black, a binder or the like is used for a general positive electrode mixture.

特許文献１、特許文献２には、正極活物質と導電助剤を含む正極合剤を集電体に塗布する技術が開示されている。導電性助剤としてカーボンナノチューブや導電材を用いる技術が開示されている。   Patent Document 1 and Patent Document 2 disclose a technique of applying a positive electrode mixture containing a positive electrode active material and a conductive additive to a current collector. A technique using carbon nanotubes or a conductive material as a conductive aid is disclosed.

ＷＯ２０１３／０７３５６２WO 2013/073562 ＷＯ１４／１５７０６１WO14 / 157061

従来の、正極合剤を薄膜化するには、箔上に塗布された合剤量を減らすか、合剤製造時の合剤層へのプレス圧を上げることにより、電極密度を更に上げる必要がある。前者の場合、薄膜化が可能であるが、実際には活物質量が低下し、反応面積が低下するため電極の抵抗は上昇し、期待する電池の高出力化が図れない。   In order to thin the conventional positive electrode mixture, it is necessary to further increase the electrode density by reducing the amount of the mixture applied on the foil or increasing the pressing pressure on the mixture layer at the time of preparation of the mixture. is there. In the former case, although thin film formation is possible, in reality the amount of active material is reduced and the reaction area is reduced, so that the resistance of the electrode is increased, and the expected high output of the battery can not be achieved.

後者の場合、導電材としてアセチレンブラック等を用いた場合、これら導電材は嵩高いためプレス圧を上げても薄膜化に限界がある。   In the latter case, when acetylene black or the like is used as the conductive material, since these conductive materials are bulky, there is a limit to thinning even if the press pressure is increased.

この問題を解決するために、導電材を小粒子化する案があるが、導電材を小粒子化することで活物質同士の導電パスの経路が減り抵抗が上昇する。   In order to solve this problem, there is a proposal to reduce the particle size of the conductive material, but by reducing the particle size of the conductive material, the path of the conductive path between the active materials is reduced and the resistance is increased.

特許文献１、２では、導電材にカーボンナノチューブや導電材を用いる技術が開示されているが、上記のように正極合剤層の密度が高く、膜厚が薄い場合において、抵抗を下げる検討についてはなされていない。   Patent Documents 1 and 2 disclose techniques using carbon nanotubes or a conductive material as the conductive material. However, as described above, in the case where the density of the positive electrode mixture layer is high and the film thickness is thin It has not been done.

本発明では、薄膜化した正極合剤において、低抵抗な正極合剤を提供することである。   The present invention is to provide a low-resistance positive electrode mixture in a thin-filmed positive electrode mixture.

上記課題を解決する手段は、例えば次の通りである。   The means for solving the above problems are, for example, as follows.

正極集電体と、前記正極集電体に設けられた正極合剤層を有し、前記正極合剤層は、正極活物質と、粒子状の導電剤と、カーボンナノチューブを有し、前記正極活物質の平均粒径ａと、前記粒子状の導電剤の平均粒径ｂの関係ｂ／ａは、ｂ／ａ≦０．０４の範囲であり、前記ａと、前記正極合剤層の厚さＬの関係Ｌ／ａは、３≦Ｌ／ａ≦１０の範囲であり、前記正極合剤層における前記カーボンナノチューブの重量割合（ＣＮＴ）と、前記正極合剤層における前記粒子状の導電剤との重量割合（Ａ）の関係Ａ／ＣＮＴは、２０≦Ａ／ＣＮＴ≦１００の範囲であるリチウムイオン二次電池。   A positive electrode current collector and a positive electrode mixture layer provided on the positive electrode current collector, the positive electrode mixture layer having a positive electrode active material, a particulate conductive agent, and carbon nanotubes, the positive electrode The relationship b / a of the average particle diameter a of the active material and the average particle diameter b of the particulate conductive agent is in the range of b / a ≦ 0.04, and the thickness of the a and the positive electrode mixture layer is The relationship L / a of the length L is in the range of 3 ≦ L / a ≦ 10, and the weight ratio (CNT) of the carbon nanotube in the positive electrode mixture layer and the particulate conductive agent in the positive electrode mixture layer A lithium ion secondary battery in which the relationship of weight ratio (A) with A / CNT is in the range of 20 ≦ A / CNT ≦ 100.

本発明により、薄膜化した正極合剤において、低抵抗な正極合剤を提供することができる。   According to the present invention, it is possible to provide a low resistance positive electrode mixture in a thinned positive electrode mixture.

リチウムイオン二次電池１０１の内部構造を示す図A diagram showing an internal structure of a lithium ion secondary battery 101 正極合剤が薄い場合（１４μｍ）において正極活物質粒径ａが抵抗に与える影響を調べた結果When the positive electrode mixture is thin (14 μm), the influence of the particle diameter a of the positive electrode active material on the resistance was investigated. 活物質粒子径ａに対する正極合剤層の膜厚（Ｌ／ａ）と抵抗値の関係Relationship between the film thickness (L / a) of the positive electrode mixture layer and the resistance value to the particle diameter a of the active material 正極活物質の粒径ａと粒子状の導電剤Ａの粒径ｂとの比率（b／a）と抵抗の関係The relationship between the ratio (b / a) of the particle size a of the positive electrode active material to the particle size b of the particulate conductive agent A and the resistance 正極合剤中のカーボンナノチューブに対する粒子状の導電材Ａの重量割合と抵抗の関係The relationship between the weight ratio of the particulate conductive material A to the carbon nanotubes in the positive electrode mixture and the resistance

以下、図面等を用いて、本発明の実施形態について説明する。以下の説明は本発明の内容の具体例を示すものであり、本発明がこれらの説明に限定されるものではなく、本明細書に開示される技術的思想の範囲内において当業者による様々な変更および修正が可能である。また、本発明を説明するための全図において、同一の機能を有するものは、同一の符号を付け、その繰り返しの説明は省略する場合がある。   Hereinafter, embodiments of the present invention will be described using the drawings and the like. The following description shows specific examples of the content of the present invention, and the present invention is not limited to these descriptions, and various modifications by those skilled in the art can be made within the scope of the technical idea disclosed herein. Changes and modifications are possible. Moreover, in all the drawings for explaining the present invention, what has the same function may attach the same numerals, and may omit explanation of the repetition.

＜リチウムイオン二次電池＞
図１は、リチウムイオン二次電池１０１の内部構造を模式的に示している。リチウムイオン二次電池１０１とは、非水電解質中における電極へのイオンの吸蔵・放出により、電気エネルギーを貯蔵・利用可能とする電気化学デバイスの総称である。本実施例では、リチウムイオン二次電池を代表例として説明する。 <Lithium ion secondary battery>
FIG. 1 schematically shows the internal structure of a lithium ion secondary battery 101. The lithium ion secondary battery 101 is a general term for an electrochemical device capable of storing and utilizing electric energy by absorption and desorption of ions to and from an electrode in a non-aqueous electrolyte. In this embodiment, a lithium ion secondary battery is described as a representative example.

図１のリチウムイオン二次電池１０１において、正極１０７、負極１０８、および両電極の間に挿入されたセパレータ１０９からなる電極群を、電池容器１０２に密閉状態にて収納されている。電池容器１０２の上部に蓋１０３があり、その蓋１０３に正極外部端子１０４、負極外部端子１０５、注液口１０６を有する。電池容器１０２に電極群を収納した後に、蓋１０３を電池容器１０２に被せ、蓋１０３の外周を溶接して電池容器１０２と一体になっている。   In the lithium ion secondary battery 101 of FIG. 1, an electrode group including a positive electrode 107, a negative electrode 108, and a separator 109 inserted between both electrodes is housed in a battery case 102 in a sealed state. A lid 103 is provided at the top of the battery container 102, and the lid 103 has a positive electrode external terminal 104, a negative electrode external terminal 105, and a liquid injection port 106. After the electrode group is housed in the battery case 102, the cover 103 is put on the battery case 102, and the outer periphery of the cover 103 is welded to be integrated with the battery case 102.

正極１０７または負極１０８の少なくとも一個以上を交互に重ね合わせて、正極１０７と負極１０８の間にセパレータ１０９を挿入し、正極１０７と負極１０８の短絡を防止する。正極１０７、負極１０８、セパレータ１０９で電極群が構成される。ポリエチレン、ポリプロピレンなどからなるポリオレフィン系高分子シート、あるいはポリオレフィン系高分子と４フッ化ポリエチレンを代表とするフッ素系高分子シートを溶着させた多層構造のセパレータ１０９などを使用することが可能である。電池温度が高くなったときにセパレータ１０９が収縮しないように、セパレータ１０９の表面にセラミックスとバインダの混合物を薄層状に形成しても良い。これらのセパレータ１０９は、リチウムイオン二次電池１０１の充放電時にリチウムイオンを透過させる必要があるため、一般に細孔径が０．０１〜１０μｍ、気孔率が４０％以上であれば、リチウムイオン二次電池１０１に使用可能である。   At least one or more of the positive electrode 107 or the negative electrode 108 is alternately stacked, and the separator 109 is inserted between the positive electrode 107 and the negative electrode 108 to prevent a short circuit between the positive electrode 107 and the negative electrode 108. The positive electrode 107, the negative electrode 108, and the separator 109 constitute an electrode group. It is possible to use a polyolefin polymer sheet made of polyethylene, polypropylene or the like, or a separator 109 having a multilayer structure in which a polyolefin polymer and a fluorine polymer sheet represented by polyethylene tetrafluoride are welded. The mixture of the ceramic and the binder may be formed in a thin layer on the surface of the separator 109 so that the separator 109 does not shrink when the battery temperature rises. Since these separators 109 need to transmit lithium ions at the time of charge and discharge of the lithium ion secondary battery 101, generally, if the pore diameter is 0.01 to 10 μm and the porosity is 40% or more, the secondary lithium ion It can be used for the battery 101.

セパレータ１０９は、電極群の末端に配置されている電極と電池容器１０２の間にも挿入し、正極１０７と負極１０８が電池容器１０２を通じて短絡しないようにしている。セパレータ１０９と正極１０７、負極１０８の表面および細孔内部に、電解液１１３が保持されている。   The separator 109 is also inserted between the electrode arranged at the end of the electrode group and the battery case 102 so that the positive electrode 107 and the negative electrode 108 do not short circuit through the battery case 102. An electrolytic solution 113 is held on the surface of the separator 109 and the positive electrode 107 and on the surface of the negative electrode 108 and inside the pores.

電極群の上部には、リード線を介して外部端子に電気的に接続されている。正極１０７は正極リード線１１０を介して正極外部端子１０４に接続されている。負極１０８は負極リード線１１１を介して負極外部端子１０５に接続されている。なお、正極リード線１１０と負極リード線１１１は、ワイヤ状、板状などの任意の形状を採ることができる。電流を流したときにオーム損失を小さくすることのできる構造であり、かつ電解液１１３と反応しない材質であれば、正極リード線１１０、負極リード線１１１の形状、材質は任意である。   The upper part of the electrode group is electrically connected to an external terminal through a lead wire. The positive electrode 107 is connected to the positive electrode external terminal 104 via the positive electrode lead wire 110. The negative electrode 108 is connected to the negative electrode external terminal 105 via the negative electrode lead wire 111. The positive electrode lead wire 110 and the negative electrode lead wire 111 can have any shape such as a wire shape or a plate shape. The shape and material of the positive electrode lead wire 110 and the negative electrode lead wire 111 are arbitrary as long as the material has a structure capable of reducing ohmic loss when current flows and does not react with the electrolyte solution 113.

正極外部端子１０４または負極外部端子１０５と、電池容器１０２の間には絶縁性シール材料１１２を挿入し、両端子が短絡しないようにしている。絶縁性シール材料１１２にはフッ素樹脂、熱硬化性樹脂、ガラスハーメチックシールなどから選択することができ、電解液１１３と反応せず、かつ気密性に優れた任意の材質を使用することができる。   An insulating sealing material 112 is inserted between the positive electrode external terminal 104 or the negative electrode external terminal 105 and the battery container 102 so as to prevent shorting of both terminals. The insulating sealing material 112 can be selected from a fluorine resin, a thermosetting resin, a glass hermetic seal, and the like, and any material that does not react with the electrolytic solution 113 and has excellent airtightness can be used.

正極リード線１１０または負極リード線１１１の途中、あるいは正極リード線１１０と正極外部端子１０４の接続部、または負極リード線１１１と負極外部端子１０５の接続部に、正温度係数（ＰＴＣ；ＰｏＳｉｔｉｖｅ ｔｅｍｐｅｒａｔｕｒｅ ｃｏｅｆｆｉｃｉｅｎｔ）抵抗素子を利用した電流遮断機構を設けると、電池内部の温度が高くなったときに、リチウムイオン二次電池１０１の充放電を停止させ、電池を保護することが可能となる。なお、正極リード線１１０、負極リード線１１１は箔状、板状など、任意の形状にすることができる。   A positive temperature coefficient (PTC; PoSitive temperature coefficient) in the middle of the positive electrode lead wire 110 or the negative electrode lead wire 111 or at the connection portion between the positive electrode lead wire 110 and the positive electrode external terminal 104 or at the connection portion between the negative electrode lead wire 111 and the negative electrode external terminal 105 If a current interrupting mechanism using a resistance element is provided, charging and discharging of the lithium ion secondary battery 101 can be stopped to protect the battery when the temperature inside the battery rises. In addition, the positive electrode lead wire 110 and the negative electrode lead wire 111 can be made into arbitrary shapes, such as foil shape and plate shape.

電極群の構造は、図１に示した短冊状電極の積層したもの、あるいは円筒状、扁平状などの任意の形状に捲回したものなど、種々の形状にすることができる。電池容器の形状は、電極群の形状に合わせ、円筒型、偏平長円形状、角型などの形状を選択してもよい。   The structure of the electrode group can be made into various shapes, such as a lamination of strip-like electrodes shown in FIG. 1 or a structure obtained by winding it into an arbitrary shape such as a cylindrical or flat shape. The shape of the battery case may be a cylindrical shape, a flat oval shape, a square shape, or the like in accordance with the shape of the electrode group.

電池容器１０２の材質は、アルミニウム、ステンレス鋼、ニッケルメッキ鋼製など、非水電解質に対し耐食性のある材料から選択される。また、電池容器１０２を正極リード線１１０または負極リード線１１１に電気的に接続する場合は、非水電解質と接触している部分において、電池容器の腐食やリチウムイオンとの合金化による材料の変質が起こらないように、リード線の材料を選定する。   The material of the battery case 102 is selected from materials having corrosion resistance to the non-aqueous electrolyte, such as aluminum, stainless steel, nickel plated steel, and the like. When the battery case 102 is electrically connected to the positive electrode lead wire 110 or the negative electrode lead wire 111, deterioration of the material due to corrosion of the battery case or alloying with lithium ions in the portion in contact with the non-aqueous electrolyte Select the material of lead wire so as not to occur.

その後、蓋１０３を電池容器１０２に密着させ、電池全体を密閉する。電池を密閉する方法には、溶接、かしめなど公知の技術がある。   Thereafter, the lid 103 is brought into close contact with the battery case 102 to seal the entire battery. There are known techniques such as welding and caulking as a method of sealing the battery.

＜正極＞
正極１０７は、正極合剤層、正極集電体から構成される。正極合剤層は、正極活物質、導電剤、必要に応じてバインダから構成される。その正極活物質の種類を例示すると、ＬｉＣｏＯ２、ＬｉＮｉＯ２、ＬｉＭｎ２Ｏ４が代表例である。他に、ＬｉＭｎＯ３、ＬｉＭｎ２Ｏ３、ＬｉＭｎＯ２、Ｌｉ４Ｍｎ５Ｏ１２、ＬｉＭｎ２−ｘＭｘＯ２（ただし、Ｍ＝Ｃｏ、Ｎｉ、Ｆｅ、Ｃｒ、Ｚｎ、Ｔａであって、ｘ＝０．０１〜０．２）、Ｌｉ２Ｍｎ３ＭＯ８（ただし、Ｍ＝Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｚｎ）、Ｌｉ１−ｘＡｘＭｎ２Ｏ４（ただし、Ａ＝Ｍｇ、Ｂａ、Ｂ、Ａｌ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｒ、Ｚｎ、Ｃａであって、ｘ＝０．０１〜０．１）、ＬｉＮｉ１−ｘＭｘＯ２（ただし、Ｍ＝Ｃｏ、Ｆｅ、Ｇａ、ｘ＝０．０１〜０．２）、ＬｉＦｅＯ２、Ｆｅ２（ＳＯ４）３、ＬｉＣｏ１−ｘＭｘＯ２（ただし、Ｍ＝Ｎｉ、Ｆｅ、Ｍｎであって、ｘ＝０．０１〜０．２）、ＬｉＮｉ１−ｘＭｘＯ２（ただし、Ｍ＝Ｍｎ、Ｆｅ、Ｃｏ、Ａｌ、Ｇａ、Ｃａ、Ｍｇであって、ｘ＝０．０１〜０．２）、Ｆｅ（ＭｏＯ４）３、ＦｅＦ３、ＬｉＦｅＰＯ４、ＬｉＭｎＰＯ４などを列挙することができる。正極活物質としては、上記いずれの正極活物質も任意に用いることができる。 <Positive electrode>
The positive electrode 107 is composed of a positive electrode mixture layer and a positive electrode current collector. The positive electrode mixture layer is composed of a positive electrode active material, a conductive agent, and, if necessary, a binder. When the kind of the positive electrode active material is illustrated, LiCoO 2 , LiNiO 2 and LiMn 2 O 4 are representative examples. Besides, LiMnO 3 , LiMn 2 O 3 , LiMnO 2 , Li 4 Mn 5 O 12 , LiMn 2-x M x O 2 (where M = Co, Ni, Fe, Cr, Zn, Ta, and x) = 0.01 to 0.2), Li 2 Mn 3 MO 8 (where M = Fe, Co, Ni, Cu, Zn), Li 1-x Ax Mn 2 O 4 (where A = Mg, Ba, B) , Al, Fe, Co, Ni, Cr, Zn, Ca, where x = 0.01 to 0.1), LiNi 1-x M x O 2 (where M = Co, Fe, Ga, x = 0). 01 to 0.2), LiFeO 2 , Fe 2 (SO 4 ) 3 , LiCo 1-x M x O 2 (where M = Ni, Fe, Mn, x = 0.01 to 0.2) , LiNi 1-x M x O 2 ( however, M = Mn, Fe, Co , Al, Ga Ca, a Mg, x = 0.01~0.2), Fe (MoO 4) 3, FeF 3, it is possible to enumerate LiFePO 4, LiMnPO 4, and the like. As the positive electrode active material, any of the above positive electrode active materials can be used arbitrarily.

正極合剤層は、上記の正極活物質、導電材、バインダを液体に混合させて、これを集電体に塗布し、プレス、乾燥させることにより作製することができる。正極合剤層は、薄くすることにより、集電体から正極合剤の表面までの距離（正極合剤層の厚さ）を小さくすることができ、抵抗が低いリチウムイオン二次電池とすることができる。この観点から正極合剤層の厚さは、４０μｍ以下、特に２５μｍ以下、されには１２〜１４μｍ以下が好ましく、また、正極合剤層の密度は、２．５〜３．５ｇｃｍ−３が好ましい。しかし、正極合剤に含まれる正極活物質の粒径との関係から、正極活物質粒径に対して正極合剤が薄すぎる場合逆に抵抗が上がる可能性もある。したがって、正極合剤層の厚みＬは、電極の膜厚方向の電子伝導パスを確保するために、活物質粒子径ａに対してＬ／ａが０＜Ｌ／ａ≦１０である必要がある。好ましくは、３＜Ｌ／ａ≦１０、より好ましくは、３≦Ｌ／ａ≦６である。 The positive electrode mixture layer can be produced by mixing the above-described positive electrode active material, conductive material, and binder in a liquid, applying the mixture to a current collector, and pressing and drying. By thinning the positive electrode mixture layer, the distance from the current collector to the surface of the positive electrode mixture (the thickness of the positive electrode mixture layer) can be reduced, and a lithium ion secondary battery with low resistance can be obtained. Can. From this viewpoint, the thickness of the positive electrode mixture layer is 40 μm or less, particularly 25 μm or less, preferably 12 to 14 μm or less, and the density of the positive electrode mixture layer is preferably 2.5 to 3.5 g cm −3 . However, due to the relationship with the particle diameter of the positive electrode active material contained in the positive electrode mixture, there is also a possibility that the resistance may increase when the positive electrode mixture is too thin relative to the particle diameter of the positive electrode active material. Therefore, in order to secure the electron conduction path in the film thickness direction of the electrode, the thickness L of the positive electrode mixture layer needs to satisfy L / a 0 <L / a ≦ 10 with respect to the active material particle diameter a. . Preferably, 3 <L / a ≦ 10, more preferably 3 ≦ L / a ≦ 6.

具体的には、正極合剤層の膜厚は１２〜２５μｍ、正極活物質の粒径ａは、０＜ａ≦５μｍの範囲が好ましい。ここで、粒径は、平均粒径を示し、光散乱測定から得られる、粒度分布から算出したメディアン径Ｄ５０の値とする。   Specifically, the film thickness of the positive electrode mixture layer is preferably 12 to 25 μm, and the particle diameter a of the positive electrode active material is preferably in the range of 0 <a ≦ 5 μm. Here, the particle size indicates an average particle size, and is a value of a median diameter D50 calculated from a particle size distribution obtained from light scattering measurement.

上記のように、正極合剤層は薄くすることにより抵抗を下げることができるが、導電材としてアセチレンブラック等を用いた場合、これら導電材は嵩高いためプレス圧を上げても薄膜化に限界がある。この問題を解決するために、導電材を小粒子化する案があるが、導電材を小粒子化することで活物質同士の導電パスの経路が減り抵抗が上昇する。   As described above, the resistance can be reduced by thinning the positive electrode mixture layer, but when acetylene black or the like is used as the conductive material, these conductive materials are bulky, so the film thickness is limited even if the press pressure is increased. There is. In order to solve this problem, there is a proposal to reduce the particle size of the conductive material, but by reducing the particle size of the conductive material, the path of the conductive path between the active materials is reduced and the resistance is increased.

したがって、導電材としては、粒子状の導電材Ａと、カーボンナノチューブ（ＣＮＴ）を併用することが好ましい。導電材Ａを小粒子化し、繊維状の導電材Ｂを用いることで、導電材Ａの小粒子化による導電パス経路の低減を補うことができる。   Therefore, as the conductive material, it is preferable to use a particulate conductive material A and carbon nanotubes (CNTs) in combination. By reducing the particle size of the conductive material A and using the fibrous conductive material B, it is possible to compensate for the reduction in the conductive path path due to the particle size reduction of the conductive material A.

本発明において、粒子状の導電材Ａとしては、黒鉛、非晶質炭素、易黒鉛化炭素、デンカブラックなどのカーボンブラック、活性炭、アセチレンブラックなどの公知の導電性の材料を用いることができる。本発明の効果を出す、活物質と導電材Ａの構成は、電子伝導パスの最適形成の点で、活物質の粒子径ａに対する、導電材Ａの粒子径ｂの値で表わされるｂ／ａが、０＜ｂ／ａ≦０．０４が望ましい。より望ましくは０＜ｂ／ａ≦０．０１５である。   In the present invention, as the particulate conductive material A, known conductive materials such as graphite, amorphous carbon, graphitizable carbon, carbon black such as denka black, activated carbon and acetylene black can be used. The constitutions of the active material and the conductive material A which produce the effects of the present invention are b / a represented by the value of the particle diameter b of the conductive material A with respect to the particle diameter a of the active material in terms of optimum formation of the electron conduction path. However, it is desirable that 0 <b / a ≦ 0.04. More desirably, 0 <b / a ≦ 0.015.

逆にｂ／ａは、０．００５以上が好ましく、ｂ／ａが小さすぎる（活物質が大きすぎる、もしくは導電材Ａが小さすぎる）場合、活物質への電子導電パスの形成が難しくなる可能性がある。粒子状の導電剤のアスペクト比は１〜２０、好ましくは１〜５の物を用いることができる。   On the other hand, b / a is preferably 0.005 or more, and when b / a is too small (the active material is too large or the conductive material A is too small), it may be difficult to form an electron conduction path to the active material There is sex. The particulate conductive agent may have an aspect ratio of 1 to 20, preferably 1 to 5.

粒子状の導電材Ａと併用するカーボンナノチューブ（ＣＮＴ）は、気相成長炭素、またはピッチ（石油、石炭、コールタールなどの副生成物）を原料に高温で炭化して製造した繊維、アクリル繊維（Ｐｏｌｙａｃｒｙｌｏｎｉｔｒｉｌｅ）から製造した炭素繊維などを用いることができる。製造方法としては、その他溶融法、化学気相成長法など既存の製法を利用することができる。ＣＮＴの平均直径ｄは、好ましくは５＜ｄ≦２０ｎｍである。ＣＮＴの平均長さは１μ以上が望ましい。特に、活物質間の電子伝導パスを確保するために、ＣＮＴの平均長さは２ａ以上がより望ましい。   Carbon nanotubes (CNT) used in combination with particulate conductive material A are fibers produced by carbonizing vapor-grown carbon or pitch (by-products such as petroleum, coal, coal tar, etc.) at a high temperature as a raw material, acrylic fibers The carbon fiber etc. which were manufactured from (Polyacrylonitrile) can be used. As the manufacturing method, other existing manufacturing methods such as a melting method and a chemical vapor deposition method can be used. The average diameter d of the CNTs is preferably 5 <d ≦ 20 nm. The average length of the CNTs is preferably 1 μ or more. In particular, in order to secure an electron conduction path between active materials, the average length of the CNTs is more preferably 2a or more.

本発明のリチウムイオン二次電池正極合剤の直流抵抗比（Ω／Ω）は、１．０以下が好ましく、これを考慮すると、正極合剤中のカーボンナノチューブに対する粒子状の導電材Ａの重量割合は、２０ｗｔ％以上１００％以下であることが好ましく、より好ましくは、２０ｗｔ％以上８０ｗｔ％以下、さらに好ましくは、３０ｗｔ％以上６０ｗｔ％以下が好ましい（後述する図５より）。
カーボンナノチューブは、嵩密度が小さく、アスペクト比が大きい為、正極合剤が高密度であっても、空孔に入り込むことができる為、導電性を上げることができる。アスペクト比としては、例えば１００以上、１０００以上のものを用いることができる
粒子状の導電材Ａの割合が多い場合、正極活物質同士の導電パスの経路が少なくなる為、抵抗が上昇する。ＣＮＴの割合が多い場合、ＣＮＴ同士の凝集が進むため、抵抗が大きくなる虞がある。 The direct current resistance ratio (Ω / Ω) of the lithium ion secondary battery positive electrode mixture of the present invention is preferably 1.0 or less, and in consideration of this, the weight of the particulate conductive material A with respect to carbon nanotubes in the positive electrode mixture The proportion is preferably 20 wt% or more and 100% or less, more preferably 20 wt% or more and 80 wt% or less, and still more preferably 30 wt% or more and 60 wt% or less (from FIG. 5 described later).
Since carbon nanotubes have a small bulk density and a large aspect ratio, they can enter pores even if the positive electrode mixture has a high density, and therefore the conductivity can be increased. As the aspect ratio, for example, 100 or more and 1000 or more can be used. When the ratio of the particulate conductive material A is large, the path of the conductive path between the positive electrode active materials decreases, and the resistance increases. When the proportion of CNTs is high, aggregation of CNTs proceeds, which may increase resistance.

また、正極合剤に対する、導電材（粒子状の導電剤Ａ＋ＣＮＴ）の総比率は、導電性の観点から、２．５〜６ｗｔ％の範囲が好ましい。   The total ratio of the conductive material (particulate conductive agent A + CNT) to the positive electrode mixture is preferably in the range of 2.5 to 6 wt% from the viewpoint of conductivity.

正極集電体には、厚さが１０〜１００μｍのアルミニウム箔、厚さが１０〜１００μｍ、孔径０．１〜１０ｍｍのアルミニウム製穿孔箔、エキスパンドメタル、発泡金属板などが用いられ、材質もアルミニウムの他に、ステンレス鋼、チタンなども適用可能である。本発明では、材質、形状、製造方法などに制限されることなく、任意の集電体を使用することができる。   For the positive electrode current collector, an aluminum foil having a thickness of 10 to 100 μm, a perforated aluminum foil having a thickness of 10 to 100 μm, and a hole diameter of 0.1 to 10 mm, an expanded metal, a foam metal plate, etc. are used. Besides, stainless steel, titanium and the like are also applicable. In the present invention, any current collector can be used without being limited to the material, shape, manufacturing method and the like.

正極１０７の塗布には、ドクターブレード法、ディッピング法、スプレー法などの既知の製法を採ることができ、手段に制限はない。また、スラリを集電体へ付着させた後、有機溶媒を乾燥し、ロールプレスによって正極を加圧成形することにより、正極１０７を作製することができる。また、塗布から乾燥までを複数回おこなうことにより、複数の合剤層を集電体に積層化させることも可能である。   The application of the positive electrode 107 can be carried out using a known production method such as a doctor blade method, a dipping method, a spray method or the like, and the means is not limited. In addition, after the slurry is attached to the current collector, the organic solvent is dried, and the positive electrode is pressure-formed by a roll press, whereby the positive electrode 107 can be manufactured. Moreover, it is also possible to laminate a plurality of mixture layers on the current collector by performing a plurality of times from application to drying.

＜負極＞
負極１０８は、負極合剤層、負極集電体から構成される。負極合剤層は、主に負極活物質とバインダから構成され、必要に応じて導電剤が添加される場合がある。負極の作製方法を説明する。 <Negative electrode>
The negative electrode 108 is composed of a negative electrode mixture layer and a negative electrode current collector. The negative electrode mixture layer mainly includes a negative electrode active material and a binder, and a conductive agent may be added as needed. The method for producing the negative electrode is described.

負極活物質は、グラフェン構造を有する炭素材料と、場合によってはＳｉと酸化Ｓｉ材料もしくはＳｉ合金材料との複合材料から構成されてもよい。グラフェン構造を有する炭素材料は、リチウムイオンを電気化学的に吸蔵・放出可能な天然黒鉛、人造黒鉛、メソフェ−ズ炭素、膨張黒鉛、炭素繊維、気相成長法炭素繊維、ピッチ系炭素質材料、ニードルコークス、石油コークス、ポリアクリロニトリル系炭素繊維、カーボンブラックのなどの炭素質材料、あるいは５員環または６員環の環式炭化水素または環式含酸素有機化合物を熱分解によって合成した非晶質炭素材料、などが利用可能である。 また、ポリアセン、ポリパラフェニレン、ポリアニリン、ポリアセチレンからなる導電性高分子材料も、負極１０８に用いることができる。これらの材料と黒鉛、易黒鉛化炭素、難黒鉛化炭素等のグラフェン構造を有する炭素材料と組み合わせることができる。黒鉛、易黒鉛化炭素、難黒鉛化炭素等の材料の混合材料であっても、本発明を実施する上で障害はない。本発明では負極活物質の炭素材料に特に制限がなく、上述の材料以外でも利用可能である。   The negative electrode active material may be composed of a composite material of a carbon material having a graphene structure, and in some cases, Si and an oxidized Si material or a Si alloy material. Carbon materials having a graphene structure include natural graphite capable of electrochemically absorbing and desorbing lithium ions, artificial graphite, mesophase carbon, expanded graphite, carbon fiber, vapor grown carbon fiber, pitch-based carbonaceous material, Amorphous compounds obtained by thermal decomposition of carbonaceous materials such as needle coke, petroleum coke, polyacrylonitrile carbon fiber, carbon black, etc., or cyclic hydrocarbon or cyclic oxygenated organic compound having a 5- or 6-membered ring Carbon materials can be used. In addition, conductive polymer materials made of polyacene, polyparaphenylene, polyaniline, and polyacetylene can also be used for the negative electrode 108. These materials can be combined with carbon materials having a graphene structure such as graphite, graphitizable carbon, non-graphitizable carbon, and the like. Even a mixture of materials such as graphite, graphitizable carbon, non-graphitizable carbon and the like has no obstacle in practicing the present invention. In the present invention, the carbon material of the negative electrode active material is not particularly limited, and materials other than the above-described materials can be used.

負極活物質の粒径は、負極合剤層の厚さ以下になるように規定される。活物質の粒径は１μｍ以上５μｍ以下である。本発明の電解液量にて効果を表す活物質のＢＥＴ比表面積は３．５ｍ２／ｇ以上であり。好ましくは３．５ｍ２／ｇ以上８ｍ２／ｇ以下である。 The particle size of the negative electrode active material is defined to be equal to or less than the thickness of the negative electrode mixture layer. The particle size of the active material is 1 μm to 5 μm. The BET specific surface area of the active material exhibiting an effect with the amount of the electrolytic solution of the present invention is 3.5 m 2 / g or more. It is preferably at most 3.5 m 2 / g or more 8m 2 / g.

上述で作製した負極活物質と本発明の一実施形態に係るバインダからなる混合物に溶媒を添加し、十分に混練または分散させて、スラリを調製する。溶媒は、有機溶媒、水などであって、本発明のバインダを変質させないものであれば、任意に選択することができる。   A solvent is added to the mixture comprising the negative electrode active material prepared above and the binder according to one embodiment of the present invention, and the mixture is sufficiently kneaded or dispersed to prepare a slurry. The solvent may be arbitrarily selected as long as it is an organic solvent, water or the like and does not deteriorate the binder of the present invention.

負極活物質とバインダの混合比は、重量比率で８０：２０〜９９：１の範囲が好適である。導電性を十分に発揮させ、大電流の充放電を可能にするために、上記重量組成は９９：１に対し負極活物質比率の小さい値になるようにすることが望ましい。逆に、電池のエネルギー密度を高めるために、９０：１０よりも大きな負極活物質比率になるように、配合することが好適である。   The mixing ratio of the negative electrode active material to the binder is preferably 80:20 to 99: 1 by weight. It is desirable that the above-mentioned weight composition has a smaller value of the ratio of the negative electrode active material to 99: 1 in order to sufficiently exhibit the conductivity and to enable the charge and discharge of a large current. On the contrary, in order to increase the energy density of the battery, it is preferable to blend so as to have a negative electrode active material ratio larger than 90:10.

導電剤は必要に応じて負極に添加される。例えば、大電流の充電または放電を行う場合に、少量の導電剤を添加して、負極の抵抗を下げることが望ましい。導電剤には、黒鉛、非晶質炭素、易黒鉛化炭素、カーボンブラック、活性炭、炭素繊維、カーボンナノチューブなどの公知の材料を用いることができる。導電性繊維は、気相成長炭素、またはピッチ（石油、石炭、コールタールなどの副生成物）を原料に高温で炭化して製造した繊維、アクリル繊維（Ｐｏｌｙａｃｒｙｌｏｎｉｔｒｉｌｅ）から製造した炭素繊維などがある。   A conductive agent is added to the negative electrode as needed. For example, when performing high current charging or discharging, it is desirable to add a small amount of a conductive agent to reduce the resistance of the negative electrode. As the conductive agent, known materials such as graphite, amorphous carbon, graphitizable carbon, carbon black, activated carbon, carbon fiber, carbon nanotube and the like can be used. Conductive fibers include vapor grown carbon or fibers produced by carbonizing pitch (by-products such as petroleum, coal, coal tar, etc.) at high temperature, carbon fibers produced from acrylic fibers (Polyacrylonitrile), etc. .

上述のスラリは、負極集電体に塗布し、溶媒を蒸発させて乾燥することによって、負極１０８を製造する。負極集電体には、厚さが１０〜１００μｍの銅箔、厚さが１０〜１００μｍ、孔径０．１〜１０ｍｍの銅製穿孔箔、エキスパンドメタル、発泡金属板などが用いられ、材質も銅の他に、ステンレス鋼、チタンなども適用可能である。本発明では、材質、形状、製造方法などに制限されることなく、任意の集電体を使用することができる。   The above-mentioned slurry is applied to the negative electrode current collector, and the solvent is evaporated and dried to manufacture the negative electrode 108. For the negative electrode current collector, a copper foil having a thickness of 10 to 100 μm, a perforated copper foil having a thickness of 10 to 100 μm and a pore diameter of 0.1 to 10 mm, an expanded metal, a foam metal plate, etc. are used. Besides, stainless steel, titanium and the like are also applicable. In the present invention, any current collector can be used without being limited to the material, shape, manufacturing method and the like.

負極１０８の塗布には、ドクターブレード法、ディッピング法、スプレー法などの既知の製法を採ることができ、手段に制限はない。また、負極スラリを集電体へ付着させた後、溶媒を乾燥し、ロールプレスによって負極を加圧成形することにより、負極１０８を作製することができる。また、塗布から乾燥までを複数回おこなうことにより、複数の負極合剤層を集電体に積層化させることも可能である。   The application of the negative electrode 108 can be carried out using a known method such as a doctor blade method, a dipping method, a spray method or the like, and the means is not limited. In addition, after the negative electrode slurry is attached to the current collector, the solvent is dried, and the negative electrode is press-molded by a roll press, whereby the negative electrode 108 can be manufactured. In addition, it is also possible to laminate a plurality of negative electrode mixture layers on the current collector by performing the process from application to drying a plurality of times.

＜電解液＞
本発明の一実施形態における電解液には、有機溶媒、電解質、添加剤が含まれる。 <Electrolyte solution>
The electrolytic solution in one embodiment of the present invention contains an organic solvent, an electrolyte, and an additive.

＜有機溶媒＞
有機溶媒が混合溶液の形態で使用される場合、１種以上のさらなる有機溶媒としては、当該技術分野で通常使用される環状カーボネート、例えば、エチレンカーボネート（ＥＣ）若しくはプロピレンカーボネート；鎖状（直鎖状若しくは分岐鎖状）カーボネート、例えば、ジメチルカーボネート、エチルメチルカーボネート（ＥＭＣ）若しくはジエチルカーボネート；環状エーテル、例えば、テトラヒドロフラン、１，３−ジオキソラン；鎖状（直鎖状若しくは分岐鎖状）エーテル、例えば、ジメトキシエタン；環状エステル、例えば、γ−ブチロラクトン；及び、鎖状（直鎖状若しくは分岐鎖状）エステル、例えば、メチルアセテート若しくはエチルアセテート等を挙げることができる。１種以上のさらなる有機溶媒は、エチレンカーボネート（ＥＣ）、エチルメチルカーボネート（ＥＭＣ）及びプロピレンカーボネートからなる群より選択されることが好ましい。１種以上のさらなる有機溶媒を用いることにより、有機溶媒に対する電解質の溶解度を向上させることができる。 <Organic solvent>
When the organic solvent is used in the form of a mixed solution, as one or more additional organic solvents, cyclic carbonates commonly used in the art, such as ethylene carbonate (EC) or propylene carbonate; Or branched) carbonates such as dimethyl carbonate, ethyl methyl carbonate (EMC) or diethyl carbonate; cyclic ethers such as tetrahydrofuran, 1,3-dioxolane; chained (linear or branched) ethers such as And dimethoxyethane; cyclic esters such as γ-butyrolactone; and chained (linear or branched) esters such as methyl acetate or ethyl acetate. Preferably, the one or more further organic solvents are selected from the group consisting of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and propylene carbonate. By using one or more further organic solvents, the solubility of the electrolyte in the organic solvent can be improved.

＜電解質＞
本発明の一実施形態におけるリチウムイオン二次電池用電解液において、電解質は、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＣＦ３ＳＯ３、ＬｉＮ（ＳＯ２Ｆ）２、ＬｉＣｌＯ４、ＬｉＣＦ３ＣＯ２、ＬｉＡｓＦ６及びＬｉＳｂＦ６からなる群より選択される１種以上のリチウム塩であることが望ましい。電解質は、ＬｉＰＦ６であることが好ましい。ＬｉＰＦ６は、イオン伝導度が高く、且つ上記の有機溶媒に対する溶解度が高い。それ故、電解質としてＬｉＰＦ６を用いることにより、結果として得られるリチウムイオン二次電池の電池特性（例えば、充放電特性）を向上させることができる。 <Electrolyte>
In the electrolyte for a lithium ion secondary battery in one embodiment of the present invention, the electrolyte is LiPF 6 , LiBF 4 , LiCF 3 SO 3 , LiN (SO 2 F) 2 , LiClO 4 , LiCF 3 CO 2 , LiAsF 6 and it is desirable that one or more lithium salts selected from the group consisting of LiSbF 6. The electrolyte is preferably LiPF 6. LiPF 6 has high ion conductivity and high solubility in the above organic solvents. Therefore, by using LiPF 6 as the electrolyte, battery characteristics (for example, charge and discharge characteristics) of the resulting lithium ion secondary battery can be improved.

本発明の一実施形態におけるリチウムイオン二次電池用電解液において、電解質は、少なくとも０．５ｍｏｌ／Ｌ（ｍｏｌ／ｄｍ−３）の濃度で含有されることが好ましい。濃度は、電解液の総体積に対するモル濃度である。電解質の濃度は、０．５〜２ｍｏｌ／Ｌの範囲であることが好ましく、０．５〜１．５ｍｏｌ／Ｌの範囲であることがより好ましく、０．５〜１ｍｏｌ／Ｌの範囲であることが特に好ましい。濃度で電解質を含有させることにより、結果として得られるリチウムイオン二次電池の電池特性（例えば、充放電特性）を向上させることができる。 In the electrolyte for a lithium ion secondary battery in one embodiment of the present invention, the electrolyte is preferably contained at a concentration of at least 0.5 mol / L (mol / dm −3 ). The concentration is the molar concentration relative to the total volume of the electrolyte. The concentration of the electrolyte is preferably in the range of 0.5 to 2 mol / L, more preferably in the range of 0.5 to 1.5 mol / L, and in the range of 0.5 to 1 mol / L. Is particularly preferred. By containing the electrolyte at a concentration, battery characteristics (for example, charge and discharge characteristics) of the resulting lithium ion secondary battery can be improved.

＜添加剤＞
前期電解質に加えて、添加剤を含有することができる。前記添加剤は、例えば、ビニレンカーボネート、ビニルエチレンカーボネート、フルオロエチレンカーボネートのような環状カーボネートが挙げられる。その中でも負極界面の安定化の観点からビニレンカーボネートが望ましい。 <Additives>
In addition to the electrolyte, additives can be included. Examples of the additive include cyclic carbonates such as vinylene carbonate, vinyl ethylene carbonate and fluoroethylene carbonate. Among these, vinylene carbonate is desirable from the viewpoint of stabilization of the negative electrode interface.

本発明の一実施形態におけるリチウムイオン二次電池用電解液において、添加剤は、少なくとも電解液の総重量に対して、０．１〜５ｗｔ％の濃度で含有されることが好ましい。より好ましく、０．１〜３ｗｔ％の範囲であることが特に好ましい。先に記載した範囲の濃度で添加剤を含有させることにより、電極界面での溶媒の分解を実質的に抑制して、リチウムイオン二次電池の電池特性（例えば、充放電特性）を向上させることができる。   In the electrolyte for a lithium ion secondary battery in one embodiment of the present invention, the additive is preferably contained at a concentration of 0.1 to 5 wt% with respect to at least the total weight of the electrolyte. More preferably, the range of 0.1 to 3 wt% is particularly preferable. By containing the additive in the concentration described above, the decomposition of the solvent at the electrode interface is substantially suppressed to improve the battery characteristics (for example, charge and discharge characteristics) of the lithium ion secondary battery. Can.

（実施例）
以下に実施例を用いて本発明をさらに具体的に示す。以下の実施例では、正極として、活物質にはＬｉＮｉ０．３３Ｃｏ０．３３Ｍｎ０．３３Ｏ２および、導電材Ａにはアセチレンブラック、バインダにはポリビニリデンフルオライド、平均直径が１０ｎｍ、平均長さが１０μｍのカーボンナノチューブ（ＣＮＴ）を用い、表１〜５の構成からなる正極をそれぞれ作製した。上記各正極と、活物質が、平均粒径が４μｍ、比表面積が３．７ｍ２／ｇのグラファイトおよび、バインダがポリビニリデンフルオライドからなる負極、ポリオレフィンからなるセパレータからなる電池を作成した。電解液には１．０ｍｏｌ／ｄｍ−３のＬｉＰＦ６を溶解させたＥＣ、ＥＭＣ、ＤＭＣからなる体積比にて２５：３０：４５の混合溶媒に１ｗｔ％のＶＣを加えた溶液を用いた。 (Example)
Hereinafter, the present invention will be more specifically described using examples. In the following examples, as the positive electrode, LiNi 0.33 Co 0.33 Mn 0.33 O 2 for the active material, acetylene black for the conductive material A, polyvinylidene fluoride for the binder, average diameter 10 nm, The positive electrode which consists of a structure of Tables 1-5 was produced using the carbon nanotube (CNT) whose average length is 10 micrometers, respectively. A battery was prepared comprising each of the above positive electrodes, a negative electrode comprising an active material of graphite having an average particle diameter of 4 μm and a specific surface area of 3.7 m 2 / g, and a binder comprising polyvinylidene fluoride, and a separator comprising polyolefin. As the electrolytic solution, a solution of 1 wt% of VC added to a mixed solvent of 25:30:45 in volume ratio consisting of EC, EMC, and DMC in which 1.0 mol / dm 3 of LiPF 6 was dissolved was used.

この電池構成において、初期エージングの処理を行った。まず、開回路の状態から充電を開始した。電流は２．５Ａとし、４．２Ｖに到達した時点でその電圧を維持し、８時間の定電圧充電を継続した。その後３０分の休止時間を設けて、２．５Ａにて放電を始めた。電池電圧が２．８Ｖに達したときに放電を停止させ、３０分の休止を行った。同じように、充電と放電を２回繰り返して、電池の初期エージングの処理を終了させた。   In this battery configuration, an initial aging process was performed. First, charging was started from the open circuit state. The current was 2.5 A, and when the voltage reached 4.2 V, the voltage was maintained and constant voltage charging was continued for 8 hours. Then, a 30-minute rest time was established, and the discharge was started at 2.5A. When the battery voltage reached 2.8 V, the discharge was stopped and rested for 30 minutes. Similarly, charging and discharging were repeated twice to terminate the process of initial aging of the battery.

その後、電池を３．７Ｖまで充電させた後、電池を−４０℃で３時間放置した後の直流抵抗を測定した。直流抵抗測定は初期エージングの３サイクル目の放電容量に対する電流値を１Ｃ電流値とし、１Ｃ、２Ｃ、５Ｃ、１０Ｃ、２０Ｃ、３０Ｃにおける３．７Ｖからの１０秒後の電圧降下値を抽出し、電流値とその電圧降下値との関係性を示した直線の傾きから直流抵抗値（Ω）を算出した。直流抵抗比（Ω／Ω）は、実施低１との直流抵抗値の比を表わす。   Thereafter, after the battery was charged to 3.7 V, the direct current resistance was measured after the battery was left at -40 ° C for 3 hours. The DC resistance measurement uses the current value for the discharge capacity at the third cycle of initial aging as the 1 C current value, and extracts the voltage drop value after 10 seconds from 3.7 V at 1 C, 2 C, 5 C, 10 C, 20 C, 30 C, The direct current resistance value (Ω) was calculated from the slope of the straight line showing the relationship between the current value and the voltage drop value. The DC resistance ratio (Ω / Ω) represents the ratio of the DC resistance value to the working low 1.

Figure 2019061734
Figure 2019061734

（実施例１）
活物質の平均粒子径が４．７μｍ、導電材Ａの平均粒子径が０．０５μｍ、電極の合剤層の厚みが１４μｍ、導電材Ａの合剤中の重量割合が５．６ｗｔ％、ＣＮＴの合剤中の重量割合が０．１ｗｔ％の正極において、上記の直流抵抗測定を行い、得た抵抗値を基準とし、各条件における抵抗値と比較した。 Example 1
The average particle size of the active material is 4.7 μm, the average particle size of the conductive material A is 0.05 μm, the thickness of the mixture layer of the electrode is 14 μm, the weight ratio of the conductive material A in the mixture is 5.6 wt%, CNT The above-mentioned direct current resistance measurement was performed on a positive electrode having a weight ratio of 0.1 wt% in the mixture, and the obtained resistance value was used as a reference to compare with the resistance value under each condition.

（比較例１）
活物質の平均粒子径が３．３μｍ、導電材Ａの平均粒子径が１０μｍ、電極の合剤層の厚みが１４μｍ、導電材Ａの合剤中の重量割合が２．４ｗｔ％の正極において、上記の直流抵抗測定を行い、実施例１の電池で求めた直流抵抗値に対する抵抗比を表１に示す。 (Comparative example 1)
In a positive electrode, the average particle diameter of the active material is 3.3 μm, the average particle diameter of the conductive material A is 10 μm, the thickness of the mixture layer of the electrode is 14 μm, and the weight ratio in the mixture of the conductive material A is 2.4 wt% The above-mentioned direct current resistance measurement was performed, and the resistance ratio to the direct current resistance value obtained by the battery of Example 1 is shown in Table 1.

（比較例２）
活物質の平均粒子径が５．１μｍ、導電材Ａの平均粒子径が１０μｍ、電極の合剤層の厚みが１４μｍ、導電材Ａの合剤中の重量割合が２．４ｗｔ％の正極において、上記の直流抵抗測定を行い、実施例１の電池で求めた直流抵抗値に対する抵抗比を表１に示す。 (Comparative example 2)
In a positive electrode, the average particle diameter of the active material is 5.1 μm, the average particle diameter of the conductive material A is 10 μm, the thickness of the mixture layer of the electrode is 14 μm, and the weight ratio of the conductive material A in the mixture is 2.4 wt% The above-mentioned direct current resistance measurement was performed, and the resistance ratio to the direct current resistance value obtained by the battery of Example 1 is shown in Table 1.

（比較例３）
活物質の平均粒子径が９．６μｍ、導電材Ａの平均粒子径が１０μｍ、電極の合剤層の厚みが１４μｍ、導電材Ａの合剤中の重量割合が２．４ｗｔ％の正極において、上記の直流抵抗測定を行い、実施例１の電池で求めた直流抵抗値に対する抵抗比を表１に示す。 (Comparative example 3)
In a positive electrode, the average particle diameter of the active material is 9.6 μm, the average particle diameter of the conductive material A is 10 μm, the thickness of the mixture layer of the electrode is 14 μm, and the weight ratio of the conductive material A in the mixture is 2.4 wt% The above-mentioned direct current resistance measurement was performed, and the resistance ratio to the direct current resistance value obtained by the battery of Example 1 is shown in Table 1.

表１の結果から、比較例１〜３の構成において、電極の薄膜化が可能であるが、本発明の構成条件を満たさない場合、セルの抵抗を低減できない事がわかる。   From the results of Table 1, it can be seen that although thinning of the electrode is possible in the configurations of Comparative Examples 1 to 3, the resistance of the cell can not be reduced if the configuration conditions of the present invention are not satisfied.

表２〜５および図２〜５では、正極合剤の抵抗に影響を与える要因についてさらに詳細を調べた結果を示す。   Tables 2 to 5 and FIGS. 2 to 5 show the results of examining in more detail the factors affecting the resistance of the positive electrode mixture.

表２および図２は、正極合剤が薄い場合（１４μｍ）において正極活物質粒径ａが抵抗に与える影響を調べた結果である。   Table 2 and FIG. 2 show the results of examining the influence of the particle diameter a of the positive electrode active material on the resistance when the positive electrode mixture is thin (14 μm).

Figure 2019061734
Figure 2019061734

（実施例２）
活物質の平均粒子径が３．３μｍ、導電材Ａの平均粒子径が０．０５μｍ、電極の合剤層の厚みが１４μｍ、導電材Ａの合剤中の重量割合が５．６ｗｔ％、ＣＮＴの合剤中の重量割合が０．１ｗｔ％の正極において、上記の直流抵抗測定を行い、実施例１の電池で求めた直流抵抗値に対する抵抗比を表２および図２に示す。 (Example 2)
The average particle size of the active material is 3.3 μm, the average particle size of the conductive material A is 0.05 μm, the thickness of the mixture layer of the electrode is 14 μm, the weight ratio of the conductive material A in the mixture is 5.6 wt%, CNT The above-mentioned direct current resistance measurement was performed on a positive electrode having a weight ratio of 0.1 wt% in the mixture, and the resistance ratio to the direct current resistance value obtained by the battery of Example 1 is shown in Table 2 and FIG.

（実施例３）
活物質の平均粒子径が３．７μｍ、導電材Ａの平均粒子径が０．０５μｍ、電極の合剤層の厚みが１４μｍ、導電材Ａの合剤中の重量割合が５．６ｗｔ％、ＣＮＴの合剤中の重量割合が０．１ｗｔ％の正極において、上記の直流抵抗測定を行い、実施例１の電池で求めた直流抵抗値に対する抵抗比を表２および図２に示す。 (Example 3)
The average particle size of the active material is 3.7 μm, the average particle size of the conductive material A is 0.05 μm, the thickness of the mixture layer of the electrode is 14 μm, the weight ratio of the conductive material A in the mixture is 5.6 wt%, CNT The above-mentioned direct current resistance measurement was performed on a positive electrode having a weight ratio of 0.1 wt% in the mixture, and the resistance ratio to the direct current resistance value obtained by the battery of Example 1 is shown in Table 2 and FIG.

（比較例４）
活物質の平均粒子径が５．１μｍ、導電材Ａの平均粒子径が０．０５μｍ、電極の合剤層の厚みが１４μｍ、導電材Ａの合剤中の重量割合が５．６ｗｔ％、ＣＮＴの合剤中の重量割合が０．１ｗｔ％の正極において、上記の直流抵抗測定を行い、実施例１の電池で求めた直流抵抗値に対する抵抗比を表２および図２に示す。 (Comparative example 4)
The average particle size of the active material is 5.1 μm, the average particle size of the conductive material A is 0.05 μm, the thickness of the mixture layer of the electrode is 14 μm, the weight ratio of the conductive material A in the mixture is 5.6 wt%, CNT The above-mentioned direct current resistance measurement was performed on a positive electrode having a weight ratio of 0.1 wt% in the mixture, and the resistance ratio to the direct current resistance value obtained by the battery of Example 1 is shown in Table 2 and FIG.

（比較例５）
活物質の平均粒子径が９．６μｍ、導電材Ａの平均粒子径が０．０５μｍ、電極の合剤層の厚みが１４μｍ、導電材Ａの合剤中の重量割合が５．６ｗｔ％、ＣＮＴの合剤中の重量割合が０．１ｗｔ％の正極において、上記の直流抵抗測定を行い、実施例１の電池で求めた直流抵抗値に対する抵抗比を表２および図２に示す。 (Comparative example 5)
The average particle size of the active material is 9.6 μm, the average particle size of the conductive material A is 0.05 μm, the thickness of the mixture layer of the electrode is 14 μm, the weight ratio of the conductive material A in the mixture is 5.6 wt%, CNT The above-mentioned direct current resistance measurement was performed on a positive electrode having a weight ratio of 0.1 wt% in the mixture, and the resistance ratio to the direct current resistance value obtained by the battery of Example 1 is shown in Table 2 and FIG.

表２および図２の結果から、薄膜電極（１４μｍ）において活物質の平均粒子径ａが５μｍよりも大きい場合、セルの抵抗を低減できなく、活物質粒子径ａに対する正極合剤層の膜厚（Ｌ／ａ）は、３以上が好ましいことが分かる。この一つの理由としては、正極合剤中の正極活物質の充填密が低下する事に起因すると考えられる。   From the results in Table 2 and FIG. 2, when the average particle diameter a of the active material is larger than 5 μm in the thin film electrode (14 μm), the cell resistance can not be reduced and the film thickness of the positive electrode mixture layer relative to the active material particle diameter a It is understood that (L / a) is preferably 3 or more. One reason for this is considered to be that the packing density of the positive electrode active material in the positive electrode mixture decreases.

表３は、図３は活物質粒子径ａに対する正極合剤層の膜厚（Ｌ／ａ）の上限を調べた結果である。   Table 3 shows the result of examining the upper limit of the film thickness (L / a) of the positive electrode mixture layer with respect to the active material particle diameter a.

Figure 2019061734
Figure 2019061734

（実施例４）
活物質の平均粒子径が３．３μｍ、導電材Ａの平均粒子径が０．０５μｍ、電極の合剤層の厚みが１２μｍ、導電材Ａの合剤中の重量割合が２．８ｗｔ％、ＣＮＴの合剤中の重量割合が０．１ｗｔ％の正極において、上記の直流抵抗測定を行い、実施例１の電池で求めた直流抵抗値に対する抵抗比を表３および図３に示す。 (Example 4)
The average particle diameter of the active material is 3.3 μm, the average particle diameter of the conductive material A is 0.05 μm, the thickness of the mixture layer of the electrode is 12 μm, the weight ratio in the mixture of the conductive material A is 2.8 wt%, CNT The above-mentioned direct current resistance measurement was performed on a positive electrode having a weight ratio of 0.1 wt% in the mixture, and the resistance ratio to the direct current resistance value obtained by the battery of Example 1 is shown in Table 3 and FIG.

（実施例５）
活物質の平均粒子径が３．３μｍ、導電材Ａの平均粒子径が０．０５μｍ、電極の合剤層の厚みが１９μｍ、導電材Ａの合剤中の重量割合が２．８ｗｔ％、ＣＮＴの合剤中の重量割合が０．１ｗｔ％の正極において、上記の直流抵抗測定を行い、実施例１の電池で求めた直流抵抗値に対する抵抗比を表３および図３に示す。 (Example 5)
The average particle size of the active material is 3.3 μm, the average particle size of the conductive material A is 0.05 μm, the thickness of the mixture layer of the electrode is 19 μm, the weight ratio of the conductive material A in the mixture is 2.8 wt%, CNT The above-mentioned direct current resistance measurement was performed on a positive electrode having a weight ratio of 0.1 wt% in the mixture, and the resistance ratio to the direct current resistance value obtained by the battery of Example 1 is shown in Table 3 and FIG.

（実施例６）
活物質の平均粒子径が３．３μｍ、導電材Ａの平均粒子径が０．０５μｍ、電極の合剤層の厚みが２５μｍ、導電材Ａの合剤中の重量割合が２．８ｗｔ％、ＣＮＴの合剤中の重量割合が０．１ｗｔ％の正極において、上記の直流抵抗測定を行い、実施例１の電池で求めた直流抵抗値に対する抵抗比を表３および図３に示す。 (Example 6)
The average particle size of the active material is 3.3 μm, the average particle size of the conductive material A is 0.05 μm, the thickness of the mixture layer of the electrode is 25 μm, the weight ratio of the conductive material A in the mixture is 2.8 wt%, CNT The above-mentioned direct current resistance measurement was performed on a positive electrode having a weight ratio of 0.1 wt% in the mixture, and the resistance ratio to the direct current resistance value obtained by the battery of Example 1 is shown in Table 3 and FIG.

（比較例６）
活物質の平均粒子径が３．３μｍ、導電材Ａの平均粒子径が０．０５μｍ、電極の合剤層の厚みが３５μｍ、導電材Ａの合剤中の重量割合が２．８ｗｔ％、ＣＮＴの合剤中の重量割合が０．１ｗｔ％の正極において、上記の直流抵抗測定を行い、実施例１の電池で求めた直流抵抗値に対する抵抗比を表３および図３に示す。 (Comparative example 6)
The average particle size of the active material is 3.3 μm, the average particle size of the conductive material A is 0.05 μm, the thickness of the mixture layer of the electrode is 35 μm, the weight ratio in the mixture of the conductive material A is 2.8 wt%, CNT The above-mentioned direct current resistance measurement was performed on a positive electrode having a weight ratio of 0.1 wt% in the mixture, and the resistance ratio to the direct current resistance value obtained by the battery of Example 1 is shown in Table 3 and FIG.

表４および図４の結果から、活物質粒子径ａに対する、合剤層厚みＬの値であるＬ／ａが１０を超える場合、セルの抵抗は１．０（直流抵抗比（Ω／Ω））を越えることが分かった。これは、厚膜方向への積層粒子数が増えると、厚膜方向への電子伝導パスが確保できない事に起因する。表２および、表３を考慮すると、活物質粒子径ａに対する、合剤層厚みＬの値であるＬ／ａは３≦Ｌ／ａ≦１０の範囲であることが好ましいことが分かる。   From the results of Table 4 and FIG. 4, when L / a which is the value of the mixture layer thickness L with respect to the active material particle diameter a exceeds 10, the cell resistance is 1.0 (DC resistance ratio (Ω / Ω) It turned out that it exceeds. This is because the electron conduction path in the thick film direction can not be secured if the number of laminated particles in the thick film direction increases. When Table 2 and Table 3 are considered, it is understood that L / a which is a value of the mixture layer thickness L with respect to the active material particle diameter a is preferably in the range of 3 ≦ L / a ≦ 10.

表４は、図４は正極活物質の粒径ａと粒子状の導電剤Ａの粒径ｂとの比率（b／a）と抵抗の関係を調べた結果である。   Table 4 shows the results of examining the relationship between the ratio (b / a) of the particle size a of the positive electrode active material and the particle size b of the particulate conductive agent A and the resistance.

Figure 2019061734
Figure 2019061734

（実施例７）
活物質の平均粒子径が３．３μｍ、導電材Ａの平均粒子径が０．０３μｍ、電極の合剤層の厚みが１４μｍ、導電材Ａの合剤中の重量割合が５．６ｗｔ％、ＣＮＴの合剤中の重量割合が０．１ｗｔ％の正極において、上記の直流抵抗測定を行い、実施例１の電池で求めた直流抵抗値に対する抵抗比を表４および図４に示す。 (Example 7)
The average particle size of the active material is 3.3 μm, the average particle size of the conductive material A is 0.03 μm, the thickness of the mixture layer of the electrode is 14 μm, the weight ratio of the conductive material A in the mixture is 5.6 wt%, CNT The above-mentioned direct current resistance measurement was performed on a positive electrode having a weight ratio of 0.1 wt% in the mixture, and the resistance ratio to the direct current resistance value obtained by the battery of Example 1 is shown in Table 4 and FIG.

（比較例７）
活物質の平均粒子径が３．３μｍ、導電材Ａの平均粒子径が０．１５μｍ、電極の合剤層の厚みが１４μｍ、導電材Ａの合剤中の重量割合が５．６ｗｔ％、ＣＮＴの合剤中の重量割合が０．１ｗｔ％の正極において、上記の直流抵抗測定を行い、実施例１の電池で求めた直流抵抗値に対する抵抗比を表４および図４に示す。 (Comparative example 7)
The average particle size of the active material is 3.3 μm, the average particle size of the conductive material A is 0.15 μm, the thickness of the mixture layer of the electrode is 14 μm, the weight ratio of the conductive material A in the mixture is 5.6 wt%, CNT The above-mentioned direct current resistance measurement was performed on a positive electrode having a weight ratio of 0.1 wt% in the mixture, and the resistance ratio to the direct current resistance value obtained by the battery of Example 1 is shown in Table 4 and FIG.

（比較例８）
活物質の平均粒子径が３．３μｍ、導電材Ａの平均粒子径が１０μｍ、電極の合剤層の厚みが１４μｍ、導電材Ａの合剤中の重量割合が５．６ｗｔ％、ＣＮＴの合剤中の重量割合が０．１ｗｔ％の正極において、上記の直流抵抗測定を行い、実施例１の電池で求めた直流抵抗値に対する抵抗比を表４および図４に示す。 (Comparative example 8)
The average particle diameter of the active material is 3.3 μm, the average particle diameter of the conductive material A is 10 μm, the thickness of the mixture layer of the electrode is 14 μm, the weight ratio of the conductive material A in the mixture is 5.6 wt%, the CNT composite The above direct current resistance measurement was performed on a positive electrode having a weight ratio of 0.1 wt% in the preparation, and the resistance ratio to the direct current resistance value obtained by the battery of Example 1 is shown in Table 4 and FIG.

表４および図４の結果から、正極活物質の粒子径ａに対する、粒子状の導電材Ａの粒子径ｂの値で表わされるｂ／ａが、０．０４以上であると、リチウムイオン二次電池の抵抗は１．０（直流抵抗比（Ω／Ω））を越えることが分かった。これは、薄膜電極に対して嵩高い導電材Ａがあると、合剤中の活物質の充填密度が低下し、それに伴い反応抵抗が低下する事に起因する。   From the results of Table 4 and FIG. 4, it is found that the value of b / a represented by the value of the particle diameter b of the particulate conductive material A with respect to the particle diameter a of the positive electrode active material is 0.04 or more The cell resistance was found to exceed 1.0 (DC resistance ratio (Ω / Ω)). This is attributed to the fact that if there is a bulky conductive material A with respect to the thin film electrode, the packing density of the active material in the mixture decreases and the reaction resistance accordingly decreases.

なお、比較例７，８では、合剤層の厚みが１４μｍとなるよう、正極活物質の量を減らしている。正極活物質の量を減らさない場合、粒子状の導電剤Ａの嵩高さにより合剤層の厚みを１４μｍに調節することが難しい。   In Comparative Examples 7 and 8, the amount of the positive electrode active material is reduced so that the thickness of the mixture layer is 14 μm. If the amount of the positive electrode active material is not reduced, it is difficult to adjust the thickness of the mixture layer to 14 μm due to the bulkiness of the particulate conductive agent A.

表５、図５は、正極合剤中のカーボンナノチューブに対する粒子状の導電材Ａの重量割合の影響を調べた結果である。   Table 5 and FIG. 5 show the results of examining the influence of the weight ratio of the particulate conductive material A to the carbon nanotubes in the positive electrode mixture.

Figure 2019061734
Figure 2019061734

（実施例８）
活物質の平均粒子径が３．３μｍ、導電材Ａの平均粒子径が０．０５μｍ、電極の合剤層の厚みが１４μｍ、導電材Ａの合剤中の重量割合が４．２ｗｔ％、ＣＮＴの合剤中の重量割合が０．１ｗｔ％の正極において、上記の直流抵抗測定を行い、実施例１の電池で求めた直流抵抗値に対する抵抗比を表５および図５に示す。 (Example 8)
The average particle size of the active material is 3.3 μm, the average particle size of the conductive material A is 0.05 μm, the thickness of the mixture layer of the electrode is 14 μm, the weight ratio in the mixture of the conductive material A is 4.2 wt%, CNT The above-mentioned direct current resistance measurement was performed on a positive electrode having a weight ratio of 0.1 wt% in the mixture, and the resistance ratio to the direct current resistance value obtained by the battery of Example 1 is shown in Table 5 and FIG.

（実施例９）
活物質の平均粒子径が３．３μｍ、導電材Ａの平均粒子径が０．０５μｍ、電極の合剤層の厚みが１４μｍ、導電材Ａの合剤中の重量割合が２．８ｗｔ％、ＣＮＴの合剤中の重量割合が０．１ｗｔ％の正極において、上記の直流抵抗測定を行い、実施例１の電池で求めた直流抵抗値に対する抵抗比を表５および図５に示す。 (Example 9)
The average particle size of the active material is 3.3 μm, the average particle size of the conductive material A is 0.05 μm, the thickness of the mixture layer of the electrode is 14 μm, the weight ratio of the conductive material A in the mixture is 2.8 wt%, CNT The above-mentioned direct current resistance measurement was performed on a positive electrode having a weight ratio of 0.1 wt% in the mixture, and the resistance ratio to the direct current resistance value obtained by the battery of Example 1 is shown in Table 5 and FIG.

（実施例１０）
活物質の平均粒子径が３．３μｍ、導電材Ａの平均粒子径が０．０５μｍ、電極の合剤層の厚みが１４μｍ、導電材Ａの合剤中の重量割合が５．５ｗｔ％、ＣＮＴの合剤中の重量割合が０．２ｗｔ％の正極において、上記の直流抵抗測定を行い、実施例１の電池で求めた直流抵抗値に対する抵抗比を表５および図５に示す。 (Example 10)
The average particle size of the active material is 3.3 μm, the average particle size of the conductive material A is 0.05 μm, the thickness of the mixture layer of the electrode is 14 μm, the weight ratio of the conductive material A in the mixture is 5.5 wt%, CNT The above-mentioned direct current resistance measurement was performed on a positive electrode having a weight ratio of 0.2 wt% in the mixture, and the resistance ratio to the direct current resistance value obtained by the battery of Example 1 is shown in Table 5 and FIG.

（比較例９）
活物質の平均粒子径が３．３μｍ、導電材Ａの平均粒子径が０．０５μｍ、電極の合剤層の厚みが１４μｍ、ＣＮＴの合剤中の重量割合が０．１ｗｔ％の正極において、上記の直流抵抗測定を行い、実施例１の電池で求めた直流抵抗値に対する抵抗比を表５および図５に示す。 (Comparative example 9)
In a positive electrode in which the average particle size of the active material is 3.3 μm, the average particle size of the conductive material A is 0.05 μm, the thickness of the mixture layer of the electrode is 14 μm, and the weight ratio in the mixture of CNTs is 0.1 wt% The above-mentioned direct current resistance measurement was performed, and the resistance ratio to the direct current resistance value obtained by the battery of Example 1 is shown in Table 5 and FIG.

（比較例１０）
活物質の平均粒子径が３．３μｍ、導電材Ａの平均粒子径が０．０５μｍ、電極の合剤層の厚みが１４μｍ、導電材Ａの合剤中の重量割合が５．６ｗｔ％、ＣＮＴの合剤中の重量割合が０．０５ｗｔ％の正極において、上記の直流抵抗測定を行い、実施例１の電池で求めた直流抵抗値に対する抵抗比を表５および図５に示す。 (Comparative example 10)
The average particle size of the active material is 3.3 μm, the average particle size of the conductive material A is 0.05 μm, the thickness of the mixture layer of the electrode is 14 μm, the weight ratio of the conductive material A in the mixture is 5.6 wt%, CNT The above-mentioned direct current resistance measurement was performed on a positive electrode having a weight ratio of 0.05 wt% in the mixture, and the resistance ratio to the direct current resistance value obtained by the battery of Example 1 is shown in Table 5 and FIG.

（比較例１１）
活物質の平均粒子径が３．３μｍ、導電材Ａの平均粒子径が０．０５μｍ、電極の合剤層の厚みが１４μｍ、導電材Ａの合剤中の重量割合が５．２ｗｔ％、ＣＮＴの合剤中の重量割合が０．５ｗｔ％の正極において、上記の直流抵抗測定を行い、実施例１の電池で求めた直流抵抗値に対する抵抗比を表５および図５に示す。 (Comparative example 11)
The average particle size of the active material is 3.3 μm, the average particle size of the conductive material A is 0.05 μm, the thickness of the mixture layer of the electrode is 14 μm, the weight ratio of the conductive material A in the mixture is 5.2 wt%, CNT The above-mentioned direct current resistance measurement was carried out on a positive electrode having a weight ratio of 0.5 wt% in the mixture, and the resistance ratio to the direct current resistance value obtained by the battery of Example 1 is shown in Table 5 and FIG.

（比較例１２）
活物質の平均粒子径が３．３μｍ、導電材Ａの平均粒子径が０．０５μｍ、電極の合剤層の厚みが１４μｍ、導電材Ａの合剤中の重量割合が５．７ｗｔ％の正極において、上記の直流抵抗測定を行い、実施例１の電池で求めた直流抵抗値に対する抵抗比を表５および図５に示す。 (Comparative example 12)
A positive electrode having an average particle diameter of 3.3 μm of the active material, an average particle diameter of the conductive material A of 0.05 μm, a thickness of the mixture layer of the electrode of 14 μm, and a weight ratio of the conductive material A in the mixture of 5.7 wt% The above-mentioned direct current resistance measurement was carried out, and the resistance ratio to the direct current resistance value obtained by the battery of Example 1 is shown in Table 5 and FIG.

表５および図５の結果から、導電材Ａの合剤中の重量割合に対する、ＣＮＴの合剤中の重量割合２０以下か、もしくは１００以上の場合、抵抗は１．０（直流抵抗比（Ω／Ω））を越えることが分かった。これは、薄膜電極においては、粒子状の導電材Ａ単独でも、ＣＮＴ単独でも、最適な導電ネットワークを形成する事ができず、それぞれを併用で用いることが重要ないことを示している。粒子状の導電材Ａを単独で用いた場合、その嵩高さにより膜厚を薄くすることができず、導電パスを形成することが難しい。   From the results of Table 5 and FIG. 5, when the weight ratio of the CNT mixture to the weight ratio of the conductive material A in the mixture of 20 or less or 100 or more, the resistance is 1.0 (DC resistance ratio (Ω It turned out that it exceeds / (ohm)). This indicates that in the thin film electrode, the conductive material A in the form of particles alone or the CNT alone can not form an optimum conductive network, and it is not important to use each in combination. When the particulate conductive material A is used alone, the film thickness can not be reduced due to its bulkiness, and it is difficult to form a conductive path.

粒子状の導電材ＡとＣＮＴを合剤中に共存させたとしても、ある割合の条件においてのみ、最適なネットワークを形成することを示している。これは、ＣＮＴが少なすぎると、最適な導電パスを形成できず、逆にＣＮＴが多すぎると、凝集による活物質の充填性の低下、および電子導電パスの低下をもたらす事に起因する。この結果から正極合剤中のカーボンナノチューブに対する粒子状の導電材Ａの重量割合は、２０ｗｔ％以上１００％以下であることが好ましいことが分かった。   Even if particulate conductive material A and CNT coexist in the mixture, it has been shown that an optimal network is formed only under a certain ratio of conditions. This is due to the fact that too few CNTs can not form an optimum conductive path, and conversely too many CNTs leads to a reduction in the packing property of the active material due to aggregation and a reduction in the electron conduction path. From these results, it was found that the weight ratio of the particulate conductive material A to the carbon nanotubes in the positive electrode mixture is preferably 20 wt% or more and 100% or less.

以上の結果から、電極の薄膜化においては、活物質の粒子径、粒子状の導電材Ａの粒子径の関係が重要であり、さらにこのような薄膜電極においては、正極活物質粒子と膜厚との関係、および導電材ＡおよびＣＮＴの組成が重要であることがわかった。   From the above results, in thinning the electrode, the relationship between the particle size of the active material and the particle size of the particulate conductive material A is important, and in such a thin film electrode, the positive electrode active material particles and the film thickness And the composition of conductive material A and CNT are important.

なお、本発明は上記した実施例に限定されるものではなく、様々な変形例が含まれる。例えば、上記した実施例は本発明を分かりやすく説明するために詳細に説明したものであり、必ずしも説明した全ての構成を備えるものに限定されるものではない。また、ある実施例の構成の一部を他の実施例の構成に置き換えることが可能であり、また、ある実施例の構成に他の実施例の構成を加えることも可能である。また、各実施例の構成の一部について、他の構成の追加・削除・置換をすることが可能である。特に正極の構成として本発明の実施形態で示される構成であれば、正極活物質の種類、負極活物質の種類、セパレータ、電池構造は限定されるものではない。   The present invention is not limited to the embodiments described above, but includes various modifications. For example, the embodiments described above are described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described. Also, part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. In addition, with respect to a part of the configuration of each embodiment, it is possible to add, delete, and replace other configurations. In particular, the type of the positive electrode active material, the type of the negative electrode active material, the separator, and the battery structure are not limited as long as the configuration of the positive electrode is shown in the embodiment of the present invention.

リチウムイオン二次電池１０１
正極１０７
負極１０８
セパレータ１０９
電池容器１０２
蓋１０３
正極外部端子１０４
負極外部端子１０５
注液口１０６
電解液１１３
正極リード線１１０
負極リード線１１１
絶縁性シール材料１１２ Lithium ion rechargeable battery 101
Positive electrode 107
Negative electrode 108
Separator 109
Battery container 102
Lid 103
Positive electrode external terminal 104
Negative external terminal 105
Filling port 106
Electrolyte 113
Positive electrode lead wire 110
Negative electrode lead wire 111
Insulating sealing material 112

Claims (9)

正極集電体と、前記正極集電体に設けられた正極合剤層を有し、
前記正極合剤層は、正極活物質と、粒子状の導電剤と、カーボンナノチューブを有し、
前記正極活物質の平均粒径ａと、前記粒子状の導電剤の平均粒径ｂの関係ｂ／ａは、ｂ／ａ≦０．０４の範囲であり、
前記ａと、前記正極合剤層の厚さＬの関係Ｌ／ａは、３≦Ｌ／ａ≦１０の範囲であり、
前記正極合剤層における前記カーボンナノチューブの重量割合（ＣＮＴ）と、前記正極合剤層における前記粒子状の導電剤との重量割合（Ａ）の関係Ａ／ＣＮＴは、２０≦Ａ／ＣＮＴ≦１００の範囲であるリチウムイオン二次電池。 A positive electrode current collector, and a positive electrode mixture layer provided on the positive electrode current collector,
The positive electrode mixture layer includes a positive electrode active material, a particulate conductive agent, and a carbon nanotube,
The relationship b / a of the average particle diameter a of the positive electrode active material and the average particle diameter b of the particulate conductive agent is in the range of b / a ≦ 0.04,
The relationship L / a between the a and the thickness L of the positive electrode mixture layer is in the range of 3 ≦ L / a ≦ 10,
The relationship A / CNT between the weight ratio (CNT) of the carbon nanotubes in the positive electrode mixture layer and the weight ratio (A) of the particulate conductive agent in the positive electrode mixture layer is 20 ≦ A / CNT ≦ 100. Lithium ion secondary battery that is in the range of 請求項１において、
前記正極合剤層は、４０μｍ以下であるリチウムイオン二次電池。 In claim 1,
The lithium ion secondary battery in which the positive electrode mixture layer is 40 μm or less. 請求項２において、
前記粒子状の導電剤は、黒鉛、非晶質炭素、易黒鉛化炭素、カーボンブラック、活性炭、アセチレンブラックのいずれか少なくとも一種であるリチウムイオン二次電池。 In claim 2,
The particulate conductive agent is at least one of graphite, amorphous carbon, graphitizable carbon, carbon black, activated carbon, and acetylene black. 前記正極活物質の平均粒径ａと、前記粒子状の導電剤の平均粒径ｂの関係ｂ／ａは、ｂ／ａ≦０．０１５の範囲であるリチウムイオン二次電池。   The lithium ion secondary battery in which the relationship b / a of the average particle diameter a of the positive electrode active material and the average particle diameter b of the particulate conductive agent is in the range of b / a ≦ 0.015. 請求項４において、
前記正極活物質の平均粒径ａは、０＜ａ≦５μｍの範囲であるリチウムイオン二次電池。 In claim 4,
The lithium ion secondary battery in which the average particle diameter a of the positive electrode active material is in the range of 0 <a ≦ 5 μm. 請求項５において、
前記正極合剤層の密度は２．５〜３．５ｇｃｍ−３であるリチウムイオン二次電池。 In claim 5,
The lithium ion secondary battery whose density of the said positive mix layer is 2.5-3.5 gcm < -3 >. 請求項６において、
前記正極合剤層における前記カーボンナノチューブの重量割合（ＣＮＴ）と、前記正極合剤層における前記粒子状の導電剤との重量割合（Ａ）の関係Ａ／ＣＮＴは、２０≦Ａ／ＣＮＴ≦８０の範囲であるリチウムイオン二次電池。 In claim 6,
The relationship A / CNT between the weight ratio (CNT) of the carbon nanotube in the positive electrode mixture layer and the weight ratio (A) of the particulate conductive agent in the positive electrode mixture layer is 20 ≦ A / CNT ≦ 80. Lithium ion secondary battery that is in the range of 請求項１乃至請求項７のいずれかにおいて、前記正極活物質はＬｉＭＯ２（ＭはＮｉ、Ｃｏ、Ｍｎを含む）であるリチウムイオン二次電池。 The lithium ion secondary battery according to any one of claims 1 to 7, wherein the positive electrode active material is LiMO 2 (M includes Ni, Co, and Mn). 請求項８において、
前記カーボンナノチューブの平均直径は、２０ｎｍ以下であり、平均長さが１０μｍ以上であるリチウムイオン二次電池。 In claim 8,
The lithium ion secondary battery, wherein the average diameter of the carbon nanotubes is 20 nm or less, and the average length is 10 μm or more.
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