Resin composition, carbon material dispersion composition, mixture slurry, electrode film, secondary battery, and vehicle

Abstract

To provide: a resin composition and a carbon material dispersion composition which are able to achieve both excellent dispersibility and excellent electrode characteristics; a composite slurry capable of forming an electrode film having high conductivity and high adhesion; and more specifically, a secondary battery having excellent rate characteristics and cycle characteristics, and a vehicle having the secondary battery, which exhibits high safety and improved fuel efficiency.SOLUTION: The resin composition contains a copolymer (X) having an alkylene structural unit and a nitrile group-containing structural unit, and an alkali metal. The content of the alkali metal is greater than or equal to 50 ppm and less than 10,000 ppm. The resin composition has a resistivity from 5,000 Ω cm to 25,000 Ω cm inclusive when the content percentage of non-volatile components in the resin composition is set to 8 mass% by using N-methyl-2 pyrrolidone.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a resin composition and a carbon material dispersion composition. More specifically, it relates to a carbon material dispersion composition containing a resin composition and a carbon material, a composite slurry containing the carbon material dispersion composition and an active material, an electrode film formed by coating them, an electrode having the electrode film, a secondary battery including an electrolyte, and a vehicle including the secondary battery.

Background Art

[0002] With the popularization of electric vehicles, the miniaturization, light weight, and high performance of portable devices, there is a demand for secondary batteries having a high energy density, and further, an increase in the capacity of such secondary batteries. Under such circumstances, non-aqueous electrolyte secondary batteries using non-aqueous electrolytes, particularly lithium-ion secondary batteries, have come to be used in many devices due to their characteristics of high energy density and high voltage.

[0003] As negative electrode materials used in these lithium-ion secondary batteries, carbon materials typified by graphite, which have a low potential close to lithium (Li) and a large charge-discharge capacity per unit mass, are used. However, these electrode materials are used up to a point where the charge-discharge capacity per mass is close to the theoretical value, and the energy density per mass of the battery is approaching its limit. Therefore, in order to increase the utilization rate of the electrode, studies are underway to reduce conductive aids and binders that do not contribute to the discharge capacity.

[0004] The conductive aid plays a role of forming a conductive path inside the electrode, and it is required that it is not easily cut by the expansion and contraction of the electrode film. In order to maintain the conductive path with a small amount of conductive aid, it is effective to use a carbon material having a large specific surface area, particularly carbon nanotubes (CNT), which is a type of nanocarbon. However, since carbon materials having a large specific surface area have strong cohesive forces, there has been a problem that it is difficult to uniformly disperse them in the composite slurry or the electrode film.

[0005] Against such a background, many methods have been proposed for producing a carbon material dispersion composition using various dispersants and manufacturing a composite slurry via the carbon material dispersion composition.

[0006] For example, Patent Documents 1 and 2 propose a carbon material dispersion composition with improved dispersibility by adding a basic compound together with a polymer-based dispersant such as polyvinylpyrrolidone or a hydrogenated nitrile rubber polymer. However, while these dispersants can produce a carbon material dispersion composition in a good dispersion state, in the process of forming an electrode film, the dispersion state of the carbon material may become poor, resulting in deteriorated conductivity.

[0007] Also, Patent Documents 3 and 4 propose that by using a binder composition for an electrode containing a hydrogenated nitrile rubber having a predetermined Mooney viscosity (ML 1+4 , 100 °C), the carbon material can be well dispersed in the composite slurry. Patent Document 5 proposes the use of a dispersant composition containing a hydrogenated nitrile rubber with a weight average molecular weight of 190,000 - 210,000 g / mol. However, these dispersants have low dispersing ability and it is difficult to disperse carbon materials with a large specific surface area at a high concentration.

[0008] Therefore, Patent Document 6 proposes a technique that can well disperse a carbon material in a solvent by using a copolymer having a specific structural unit and molecular weight as a dispersant, and can maintain a good dispersion state also when adjusting the composite slurry and manufacturing the electrode film. However, in order to obtain a specific structure, it is necessary to add a large amount of base, and problems such as a decrease in the molecular weight of the dispersant and a decrease in electrode strength due to the deterioration of the binder resin have arisen.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

[0010] Therefore, the problem to be solved by the present invention is to provide a resin composition capable of achieving both good dispersibility and good electrode characteristics, and a carbon material dispersion composition. Further, it is to provide a composite slurry capable of obtaining an electrode film with high conductivity and adhesion. More specifically, it is to provide a secondary battery having excellent rate characteristics and cycle characteristics, and a vehicle having the secondary battery, which is highly safe and has improved fuel efficiency. [Means for Solving the Problems]

[0011] The inventors of the present invention have intensively studied to solve the above problems. The inventors have found that a copolymer (X) having a specific structure and containing an alkali metal in an amount of 50 ppm or more and less than 10,000 ppm can solve the above problems when the resistivity of the resin composition is in a specific range when the non-volatile content is 8% by mass with N-methyl-2-pyrrolidone.

[0012] That is, the present invention includes the following embodiments. The embodiments of the present invention are not limited to the following. [1] A resin composition comprising a copolymer (X) having an alkylene structural unit and a nitrile group-containing structural unit, and containing an alkali metal, wherein the content of the alkali metal is 50 ppm or more and less than 10,000 ppm, A resin composition, characterized in that when the non-volatile content is adjusted to 8% by mass with N-methyl-2-pyrrolidone, the resistivity is 5,000 Ω·cm or more and 25,000 Ω·cm or less. 〔2〕The resin composition according to 〔1〕, characterized in that the Z-average molecular weight of the copolymer (X) is 20,000 or more and 200,000 or less. 〔3〕The resin composition according to 〔1〕 or 〔2〕, characterized in that the ratio (Mz / Mw) of the Z-average molecular weight (Mz) to the weight-average molecular weight (Mw) of the copolymer (X) is 2.0 or less. 〔4〕A carbon material dispersion composition comprising the resin composition according to any one of 〔1〕 to 〔3〕 and a carbon material. 〔5〕A composite material slurry comprising the carbon material dispersion composition according to 〔4〕 and an active material. 〔6〕An electrode film formed by coating the composite material slurry according to 〔5〕. 〔7〕A secondary battery comprising the electrode having the electrode film according to 〔6〕 and an electrolyte. 〔8〕A vehicle equipped with the secondary battery according to 〔7〕.

Advantages of the Invention

[0013] The resin composition of the present invention is excellent in the dispersibility of a dispersed substance such as a carbon material. By using a carbon material dispersion composition containing this resin composition, an electrode film excellent in conductivity and adhesion can be obtained. Further, a secondary battery excellent in rate characteristics and cycle characteristics can be obtained. As a result, it can be suitably used even in vehicle applications such as hybrid vehicles, plug-in hybrid vehicles, and electric vehicles, where high capacity, high output, and high durability are required for the secondary battery to be mounted.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, the resin composition, carbon material dispersion composition, composite material slurry, electrode film, and secondary battery of the present invention will be described in detail, but are not limited thereto. Note that the numerical values specified in this specification are values obtained by the methods disclosed in the embodiments or examples.

[0015] In addition, in this specification, a numerical range specified using "~" shall include the numerical values described before and after "~" as the range of the lower limit value and the upper limit value.

[0016] In this specification, "N-methyl-2-pyrrolidone" may be denoted as "NMP", "carbon black" as "CB", "carbon nanotube" as "CNT", and "carbon material dispersion composition" as "dispersion composition". In addition, the non-volatile content refers to the solid content excluding the solvent, and is determined by measuring the content of the residue remaining after volatilization or evaporation when the resin composition is heated above the boiling point of the solvent contained therein.

[0017] Note that the resin composition in the embodiments of the present invention means the state before the addition of the carbon material and the electrode active material, and the carbon material dispersion composition means the state before the addition of the electrode active material. In this regard, the resin composition and the carbon material dispersion composition are distinguished from the composite slurry containing the electrode active material. Moreover, this is a concept excluding the state in which the carbon material and the electrode active material are intentionally added to the resin composition. The carbon material and the electrode active material may be 1% by mass or less, 0.5% by mass or less, or 0.1% by mass or less, or may be 0% by mass, based on the non-volatile component amount of the resin composition (100% by mass). Moreover, this is a concept excluding the state in which the electrode active material is intentionally added to the carbon material dispersion composition. The electrode active material may be 1% by mass or less, 0.5% by mass or less, or 0.1% by mass or less, or may be 0% by mass, based on the non-volatile component amount of the carbon material dispersion composition (100% by mass). Unless otherwise noted, the various components appearing in this specification may each be used alone or in combination of two or more. Note that the numerical values specified in this specification are values obtained by the methods disclosed in the embodiments or examples.

[0018] ≪Resin Composition≫ The resin composition of this embodiment contains a copolymer (X) having at least an alkylene structural unit and a nitrile group-containing structural unit and an alkali metal. Further, the content of the alkali metal is 50 ppm or more and less than 10,000 ppm, and when this resin composition is made to have a non-volatile content of 8% by mass with N-methyl-2-pyrrolidone, the resistivity is 5,000 Ω·cm or more and 25,000 Ω·cm or less. Due to such a resin composition, a dispersion composition excellent in the dispersibility of the dispersed material and having good stability can be obtained. Among them, when the dispersed material is a carbon material, a carbon material dispersion composition excellent in dispersibility and oxidation resistance can be obtained, and since it also has excellent conductivity, a secondary battery using this can be made to have excellent rate characteristics and high-temperature cycle characteristics.

[0019] As the dispersed material, in addition to the carbon material described later, any of conventionally known inorganic pigments, organic pigments, etc. can be used, but it can be effectively used particularly for carbon materials.

[0020] Examples of the inorganic pigment include metal powders such as gold, silver, copper, silver-plated copper powder, silver-copper composite powder, silver-copper alloy, amorphous copper, nickel, chromium, palladium, rhodium, ruthenium, indium, silicon, aluminum, tungsten, molybdenum, platinum, etc., inorganic powders coated with these metals, powders of metal oxides such as silver oxide, indium oxide, tin oxide, zinc oxide, ruthenium oxide, etc., inorganic powders coated with these metal oxides, and carbon nanotubes, carbon black, graphite, etc. Examples include powders of metal oxides such as silver oxide, indium oxide, tin oxide, zinc oxide, ruthenium oxide, etc., inorganic powders coated with these metal oxides, and carbon nanotubes, carbon black, graphite, etc.

[0021] Examples of the organic pigment include various pigments used in inks and the like. Such pigments include soluble azo pigments, insoluble azo pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, isoindoline pigments, perylene pigments, perinone pigments, dioxazine pigments, anthraquinone pigments, dianthraquinonyl pigments, anthrapyrimidine pigments, ansanthrone pigments, indanthrone pigments, flavanthrone pigments, pyranthrone pigments, diketopyrrolopyrrole pigments, and the like.

[0022] When the resin composition of the present invention is adjusted to a non-volatile content of 8% by mass with N-methyl-2-pyrrolidone, the resistivity is 5,000 Ω·cm or more and 25,000 Ω·cm or less. By being such a resin composition, it is possible to achieve both good dispersibility and good electrode characteristics. In addition, for the measurement of the resistivity, the non-volatile content of the resin composition can be measured in advance, and N-methyl-2-pyrrolidone can be added so that the non-volatile content is 8% by mass, and then mixed to prepare a sample for measuring the liquid resistance. The resistivity can be measured by the method described in the examples.

[0023] From the viewpoint of achieving both the dispersibility of the material to be dispersed and the electrode resistance, the resistivity is preferably 5,000 Ω·cm or more and 20,000 Ω·cm or less, and more preferably 7,000 Ω·cm or more and 15,000 Ω·cm or less. The resistivity of the resin composition can be adjusted by controlling the molecular weight, molecular weight distribution, ion concentration, etc. of the copolymer by modifying the copolymer with a basic compound such as an alkali metal compound or applying shear stress to the copolymer. In addition, the modification of the copolymer in this specification includes not only the modification of a part of the structural units of the copolymer by hydrolysis or the like, but also the change in the viscoelasticity and molecular weight of the copolymer.

[0024] The initial viscosity of the resin composition of this embodiment is preferably such that the viscosity measured at 100 rpm and 25 °C using a B-type viscometer is 10 mPa·s or more and 2,000 mPa·s or less, more preferably 100 mPa·s or more and 2,000 mPa·s or less. If it is within the above range, the stability of the resin composition can be made more excellent. Furthermore, when the resin composition contains an alkali metal compound, precipitation of the alkali metal compound is suppressed, and the stability is more excellent.

[0025] (Copolymer (X)) Copolymer (X) is a copolymer having an alkylene structural unit and a nitrile group-containing structural unit. This copolymer may have other structural units.

[0026] From the viewpoint of the dispersibility of the dispersed substance, based on 100% by mass of copolymer (X), the total content of the alkylene structural unit and the nitrile group-containing structural unit is preferably 50% by mass or more and 100% by mass or less, more preferably 80% by mass or more. When copolymer (X) is a modified copolymer, from the viewpoint of the dispersibility of the dispersed substance, based on 100% by mass of copolymer (X), the total content of the alkylene structural unit and the nitrile group-containing structural unit is preferably 50% by mass or more and 100% by mass or less. Also, when the nitrile group-containing structural unit is modified by hydrolysis, the total content is preferably 50% by mass or more and 97% by mass or less, more preferably 80% by mass or more and 95% by mass or less. The content of other structural units is preferably 10% by mass or less, more preferably preferably 5% by mass or less, and even more preferably 3% by mass or less. When the nitrile group-containing structural unit is modified and has an amide group-containing structural unit, the content of the structural unit of the amide group-containing structural unit is preferably 5% by mass or less, more preferably 3% by mass or less, based on 100% by mass of copolymer (X). When the content of the structural unit of the amide group-containing structural unit increases, when the copolymer dissolves in the electrolyte, the viscosity of the electrolyte may increase and the ionic conductivity may decrease significantly.

[0027] The modification of the copolymer (X) is preferably carried out by adjusting the addition amount of a basic compound such as an alkali metal compound, so as to control only the properties such as molecular weight or viscoelasticity while maintaining the composition.

[0028] A structural unit is a state in which a monomer is incorporated into a polymer after polymerization. Unless otherwise specified, the content of the structural unit formed by polymerizing the monomer usually coincides with the ratio (charge ratio) of the monomer to all the monomers used for the polymerization of the polymer. That is, the content rate of each monomer based on the total of all monomers is defined as the content rate of each structural unit.

[0029] The copolymer (X) may be a copolymer modified by the addition of a basic compound such as an alkali metal compound. When the nitrile group contained in the nitrile group-containing structural unit of the copolymer is modified by hydrolysis or the like due to the modification, it is preferable that the content rates of the alkylene structural unit and the nitrile group-containing structural unit of the copolymer (X) after the modification are within the above ranges. The content rates of the alkylene structural unit and the nitrile group-containing structural unit can be calculated by IR measurement. For example, they can be calculated by the method described in ISO14558:2016. It can also be measured by the ATR method without using the KBr tablet method. By using the above method, the structural units and their contents can also be specified for the copolymer (X) modified with a basic compound.

[0030] The number average molecular weight (Mn) of the copolymer (X) in this embodiment is preferably 70,000 or less, more preferably 50,000 or less, and even more preferably 30,000 or less. Also, it is preferably 10,000 or more. When the number average molecular weight (Mn) of the copolymer (X) is within the above range, the adsorption of the copolymer to the dispersed material tends to proceed, and the wetting of the dispersed material into the solvent tends to proceed.

[0031] The weight average molecular weight (Mw) of the copolymer (X) of the present embodiment is preferably 20,000 or more and 180,000 or less, more preferably 20,000 or more and 150,000 or less, and even more preferably 20,000 or more and 100,000 or less.

[0032] The Z average molecular weight (Mz) of the copolymer (X) of the present embodiment is preferably 20,000 or more and 250,000 or less, more preferably 20,000 or more and 200,000 or less, even more preferably 25,000 or more and 180,000 or less, and particularly preferably 30,000 or more and 100,000 or less.

[0033] When the weight average molecular weight (Mw) and the Z average molecular weight (Mz) of the copolymer (X) are within the above ranges, when the resin composition contains a dispersed material such as a carbon material, not only is the dispersion likely to proceed, but the viscosity of the resin composition also decreases. Furthermore, thereby, the removal efficiency of metal foreign particles contained in the resin composition can be improved by a filter or a magnet. The number average molecular weight (Mn), the weight average molecular weight (Mw), and the Z average molecular weight (Mz) are values in terms of polystyrene and can be measured by gel permeation chromatography (GPC).

[0034] The Z average molecular weight is a weighted average using the square of the molecular weight as the weight, and is a value that is prone to being affected by high molecular weights. The copolymer (X) has a molecular weight distribution, and the low molecular weight components function to improve the wettability of the dispersed material. In addition, the high molecular weight components function to improve battery characteristics such as the viscosity stability of the dispersed material, the oxidation resistance of the copolymer, and the electrolyte dissolution resistance. By controlling the Z average molecular weight of the copolymer (X) within the above range before adding a dispersed material such as a carbon material to the resin composition, the viscosity of the resin composition can be lowered, and the dispersed material can be easily wetted and the dispersion can proceed easily. In addition, since the viscosity of the carbon material dispersion composition described later becomes low, when using a disperser using media such as a bead mill, the dispersion media move well. Since the kinetic energy of the dispersion media is proportional to the mass and the square of the speed of the dispersion media, by efficiently moving the dispersion media in the carbon material dispersion composition, not only can the dispersion degree be adjusted to the target value, but also the carbon material dispersion composition is homogenized, and a carbon material dispersion composition excellent in stability over time and conductivity can be obtained.

[0035] The Z-average molecular weight (Mz) of the copolymer (X) can be controlled by the synthesis conditions (composition, blending amount, catalyst, reaction temperature, reaction time, etc.) of the copolymer (X), the modification of the copolymer, or applying a shear stress to the copolymer. The shear stress can lower the Z-average molecular weight, for example, by using a roll or a kneader and applying a mechanical shear stress.

[0036] The polydispersity index (Mw / Mn) of the copolymer (X) of the present embodiment is preferably 2.2 or less, more preferably 2.0 or less, and even more preferably 1.8 or less. Also, it is preferably 1.2 or more. When the polydispersity index (Mw / Mn) is within the above range, the ratio of the low molecular weight components contained in the copolymer (X) is appropriate. In particular, when dispersing the carbon material, the wetting of the material to be dispersed progresses quickly, so the dispersion proceeds easily, and a carbon material dispersion composition can be obtained while maintaining the structure of the carbon material, and it is easy to obtain an electrode film and a secondary battery having high conductivity and adhesion.

[0037] The ratio (Mz / Mw) of the weight average molecular weight (Mw) to the Z-average molecular weight (Mz) of the copolymer (X) is preferably 2.2 or less, more preferably 2.0 or less, even more preferably 1.9 or less, and particularly preferably 1.8 or less. Also, it is preferably 1.5 or more, and more preferably 1.6 or more. When the ratio (Mz / Mw) of the weight average molecular weight (Mw) to the Z-average molecular weight (Mz) is within the above range, the ratio of the high molecular weight components contained in the copolymer (X) is appropriate, and a dispersion composition with good dispersion stability of the material to be dispersed can be easily obtained.

[0038] The number average molecular weight (Mn), weight average molecular weight (Mw), and Z average molecular weight (Mz) of the copolymer (X) can be adjusted, for example, by subjecting the copolymer and an amide-based polar solvent to high-pressure dispersion. A resin composition containing an amide-based polar solvent may be subjected to high-pressure dispersion. As the high-pressure dispersion, "Starburst" manufactured by Sugino Machine Limited can be used. Among them, the number average molecular weight (Mn) is preferably prepared by subjecting the copolymer and an amide-based polar solvent to high-pressure dispersion in the presence of an alkali metal.

[0039] [Alkylene structural unit] The alkylene structural unit is a structural unit containing an alkylene structure, preferably a structural unit consisting only of an alkylene structure. The alkylene structure is preferably a linear alkylene structure or a branched alkylene structure. However, this does not include the case where it is a structural unit having a nitrile group.

[0040] The alkylene structural unit preferably includes a structural unit represented by the following general formula (1A). 。

[0041] General formula (1A)

Chemical formula

[0042] In the general formula (1A), n represents an integer of 1 or more. n is preferably an integer of 2 or more, more preferably an integer of 3 or more. n is preferably an integer of 5 or less, more preferably an integer of 4 or less. In particular, n is preferably 3.

[0043] The alkylene structural unit preferably includes a structural unit represented by the following general formula (1B).

[0044] General formula (1B)

Chemical formula

[0045] In the general formula (1B), n represents an integer of 1 or more. It is preferable that n is an integer of 4 or less, more preferably an integer of 3 or less, and still more preferably an integer of 2 or less. In particular, n is preferably 2.

[0046] The method for introducing the alkylene structural unit into the copolymer is not particularly limited, and examples thereof include the following methods (1a) or (1b).

[0047] In the method of (1a), a copolymer is prepared by a polymerization reaction using a monomer composition containing a conjugated diene monomer. The prepared copolymer contains monomer units derived from the conjugated diene monomer. In the present invention, the "monomer unit derived from the conjugated diene monomer" may be referred to as the "conjugated diene monomer unit", and the same may be omitted for monomer units derived from other monomers. Next, at least a part of the conjugated diene monomer units is converted into alkylene structural units by hydrogenating the conjugated diene monomer units. Hereinafter, "hydrogenation" may be referred to as "hydrogenation". The finally obtained copolymer contains units obtained by hydrogenating the conjugated diene monomer units as alkylene structural units.

[0048] Note that the conjugated diene monomer unit contains at least a monomer unit having one carbon-carbon double bond. For example, the 1,3-butadiene monomer unit, which is a conjugated diene monomer unit, contains at least one monomer unit selected from the group consisting of a monomer unit having a cis-1,4 structure, a monomer unit having a trans-1,4 structure, and a monomer unit having a 1,2 structure, and may contain two or more monomer units. Further, the conjugated diene monomer unit may be a monomer unit having no carbon-carbon double bond and further contain a monomer unit containing a branch point. In the present specification, the "branch point" refers to a branch point in a branched polymer. When the conjugated diene monomer unit contains a monomer unit containing a branch point, the above-prepared copolymer and copolymer are branched polymers. When the conjugated diene monomer unit contains a monomer unit containing a branch point, the above-prepared copolymer and copolymer are branched polymers.

[0049] In the method of (1b), a copolymer is prepared by a polymerization reaction using a monomer composition containing an α-olefin monomer. The prepared copolymer contains α-olefin monomer units. The finally obtained copolymer contains α-olefin monomer units as alkylene structural units.

[0050] Among these, the method of (1a) is preferable because the production of the copolymer is easy. The number of carbon atoms of the conjugated diene monomer is 4 or more, preferably 4 or more and 6 or less. Examples of the conjugated diene monomer include conjugated diene compounds such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, and 1,3-pentadiene. Among them, 1,3-butadiene is preferable. The alkylene structural unit preferably contains a structural unit obtained by hydrogenating a conjugated diene monomer unit (hydrogenated conjugated diene monomer unit), and more preferably contains a structural unit obtained by hydrogenating a 1,3-butadiene monomer unit (hydrogenated 1,3-butadiene monomer unit). The conjugated diene monomer can be used alone or in combination of two or more. It more preferably contains a structural unit obtained by hydrogenating a 1,3-butadiene monomer unit (hydrogenated 1,3-butadiene monomer unit). The conjugated diene monomer can be used alone or in combination of two or more.

[0051] The hydrogenation is preferably a method capable of selectively hydrogenating the conjugated diene monomer unit. Examples of the hydrogenation method include known methods such as an oil-phase hydrogenation method or an aqueous-phase hydrogenation method.

[0052] The hydrogenation can be carried out by a usual method. The hydrogenation can be carried out, for example, by treating a copolymer having a conjugated diene monomer unit with hydrogen gas in the presence of a hydrogenation catalyst in a state where it is dissolved in an appropriate solvent. Examples of the hydrogenation catalyst include nickel, palladium, rhodium, platinum, copper, and the like.

[0053] In the method of (1b), the number of carbon atoms of the α-olefin monomer is 2 or more, preferably 3 or more, more preferably 4 or more. The number of carbon atoms of the α-olefin monomer is preferably 6 or less, more preferably 5 or less. Examples of the α-olefin monomer include α-olefin compounds such as ethylene, propylene, 1-butene, and 1-hexene. The α-olefin monomer can be used alone or in combination of two or more.

[0054] The alkylene structural unit preferably contains at least one selected from the group consisting of a structural unit containing a linear alkylene structure and a structural unit containing a branched alkylene structure, more preferably contains at least one selected from the group consisting of a structural unit consisting only of a linear alkylene structure and a structural unit consisting only of a branched alkylene structure, and still more preferably contains at least one selected from the group consisting of the structural unit represented by the above formula (1A) and the structural unit represented by the above formula (1B).

[0055] The content of the alkylene structural unit is preferably 50% by mass or more and 75% by mass or less, more preferably 55% by mass or more and 70% by mass or less, still more preferably 55% by mass or more and 65% by mass or less, based on 100% by mass of the total content of the alkylene structural unit and the nitrile group-containing structural unit. By setting the content of the alkylene structural unit within the above range, the adsorptivity to the dispersoid and the affinity to the dispersion medium can be controlled, and the dispersoid can be stably present in the dispersion medium. In addition, the affinity of the copolymer to the electrolyte can also be controlled, and problems such as the copolymer dissolving in the electrolyte in the battery and increasing the resistance of the electrolyte can be prevented.

[0056] [Nitrile group-containing structural unit] The nitrile group-containing structural unit is a structural unit containing a nitrile group, preferably includes a structural unit containing an alkylene structure substituted by a nitrile group, and more preferably includes a structural unit consisting only of an alkylene structure substituted by a nitrile group. The alkylene structure is preferably a linear or branched alkylene structure. The nitrile group-containing structural unit may further include (or consist only of) a structural unit containing an alkyl structure substituted by a nitrile group. The number of nitrile groups contained in the nitrile group-containing structural unit is preferably one.

[0057] The nitrile group-containing structural unit preferably includes a structural unit represented by the following general formula (2A).

[0058] General formula (2A)

Chemical formula

[0059] In general formula (2A), n represents an integer of 2 or more. n is preferably an integer of 6 or less, more preferably an integer of 4 or less, and even more preferably an integer of 3 or less. In particular, n is preferably 2.

[0060] The nitrile group-containing structural unit may include a structural unit represented by the following general formula (2B).

[0061] General formula (2B)

Chemical formula

[0062] In general formula (2B), R represents a methyl group.

[0063] The method for introducing the nitrile group-containing structural unit into the copolymer is not particularly limited, but a method of preparing a copolymer by a polymerization reaction using a monomer composition containing a nitrile group-containing monomer (the method of (2a)) can be preferably used. The finally obtained copolymer contains the nitrile group-containing structural unit as the nitrile group-containing structural unit. Examples of the nitrile group-containing monomer capable of forming the nitrile group-containing structural unit include monomers containing a polymerizable carbon-carbon double bond and a nitrile group. For example, α,β-ethylenically unsaturated group-containing compounds having a nitrile group can be mentioned, and specifically, acrylonitrile, methacrylonitrile, etc. can be mentioned. In particular, from the viewpoint of enhancing the intermolecular force between the copolymers and / or between the copolymer and the dispersed substance (adsorbed substance), the nitrile group-containing monomer preferably contains acrylonitrile. The nitrile group-containing monomer can be used alone or in combination of two or more.

[0064] The content of the nitrile group-containing structural unit is preferably 25% by mass or more and 50% by mass or less based on 100% by mass of the total content of the alkylene structural unit and the nitrile group-containing structural unit. More preferably, it is 30% by mass or more and 45% by mass or less, and even more preferably, it is 35% by mass or more and 45% by mass or less. By setting the content of the nitrile group-containing structural unit within the above range, the adsorptivity to the dispersed substance and the affinity to the dispersion medium can be controlled, and the dispersed substance can be stably present in the dispersion medium. In addition, the affinity of the resin composition to the electrolyte can also be controlled, and problems such as the resin composition dissolving in the electrolyte in the battery and increasing the resistance of the electrolyte can be prevented.

[0065] [Other structural units] Within a range that does not interfere with the effects of the present invention, structural units other than the alkylene structural unit and the nitrile group-containing structural unit may be provided as necessary. Examples of the other structural units include amide group-containing structural monomers, carboxyl group-containing structural units, and the like.

[0066] (Alkali metal) The resin composition of the present invention contains an alkali metal. The content of the alkali metal in the resin composition is 50 ppm or more and less than 10,000 ppm. Preferably, it is 500 ppm or more and 8,000 ppm or less, and more preferably 2,000 ppm or more and 5,000 ppm or less. When the content of the alkali metal is within the above range, when a dispersed substance such as a carbon material is dispersed, the adsorptivity to the non-dispersed substance and the affinity to the dispersion medium are improved, and the dispersibility is improved. Furthermore, when the amount of the alkali metal in the resin composition is within the above range, it becomes easy to control the molecular weight of the copolymer (X) within an appropriate range by modifying with an alkali metal compound as a basic compound or applying a shear stress to the copolymer, and it has the effect of improving the dispersibility of the dispersed substance.

[0067] The alkali metal is contained in the resin composition by, for example, a monomer used for synthesizing the copolymer before modification or the copolymer (X), an alkali metal compound used for modifying the copolymer, an alkali metal compound used as an additive such as for pH adjustment, or an alkali metal contained in a solvent or the like. That is, the alkali metal contained in the resin composition includes not only the intentionally added alkali metal compound but also the alkali metal derived from the monomer as a raw material, the catalyst, the additive, the solvent, etc.

[0068] Examples of the alkali metal include elements such as lithium, sodium, and potassium. The alkali metal content in the resin composition can be determined by an ICP emission spectroscopic analyzer by the method described in the examples.

[0069] (Solvent) The resin composition of this embodiment preferably contains a solvent. The solvent may be any one that can dissolve the copolymer, but an amide-based polar solvent is preferred. Examples of the amide-based polar solvent include N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone (NEP), N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N-methylcaprolactam, and the like. Among these, it is more preferable to contain at least one selected from the group consisting of N-methyl-2-pyrrolidone and N-ethyl-2-pyrrolidone.

[0070] (Method for producing resin composition) The method for producing the resin composition of this embodiment is not particularly limited, and the resin composition may be produced by any method. For example, using a monomer composition containing a conjugated diene monomer and a nitrile group-containing monomer a copolymer is prepared by a polymerization reaction, and the conjugated diene monomer units of the copolymer are hydrogenated to obtain a resin composition containing the copolymer (X). Further, a copolymer having an alkylene structural unit and a nitrile group-containing structural unit may be modified with a basic compound such as an alkyl metal compound or subjected to a shear stress to obtain a resin composition containing the copolymer (X).

[0071] Furthermore, as a method for making the content of the alkali metal be 50 ppm or more and less than 10,000 ppm and the resistivity of the resin composition be 5,000 Ω·cm or more and 25,000 Ω·cm or less when the non-volatile content is 8% by mass with N-methyl-2-pyrrolidone, in addition to the raw materials, compounding amounts, etc. for producing this copolymer, the following methods can be mentioned. Examples of the method include: <1> a method of applying shear stress to a copolymer containing an alkali metal using a crusher or the like; <2> a method of adding an alkali metal or an alkali metal compound to a copolymer to obtain a modified copolymer and then applying shear stress using the above-mentioned crusher; <3> a method of adding an alkali metal or an alkali metal compound after applying shear stress to a copolymer using a crusher or the like. Among them, the methods <2> or <3> are preferred, and it is particularly preferred to use an alkali metal compound having a maximum particle size of 150 μm or less, especially sodium hydroxide. In the presence of an alkali metal compound having a maximum particle size of 150 μm or less, by applying shear stress to the copolymer, the finely dispersed alkali metal compound absorbs moisture, contacts the copolymer, promotes the hydrolysis reaction of the copolymer, and can control the structure, molecular weight, and molecular weight distribution suitable for dispersing the dispersed substance.

[0072] In <2> or <3>, as the alkali metal compound used for modifying the copolymer, for example, an alkali metal hydroxide or an alkoxide can be used. Preferably, it is an alkali metal hydroxide.

[0073] That is, as a method for producing the resin composition, for example, it preferably includes a step of mixing an alkali metal compound with a copolymer having an alkylene structural unit and a nitrile group-containing structural unit to produce a resin composition containing the copolymer (X) and an alkali metal.

[0074] At this time, the copolymer before modification is preferably a copolymer having an alkylene structural unit and a nitrile group-containing structural unit, to which an alkali metal compound is mixed, and having an alkylene structural unit with a content of 50% by mass or more and 75% by mass or less, and a nitrile group-containing structural unit with a content of 25% by mass or more and 50% by mass or less.

[0075] In order to obtain a resin composition satisfying the above requirements, the copolymer before modification is preferably dissolved in an amide-based polar solvent and used under the conditions of 60°C to 100°C. Further, the alkali metal compound is preferably mixed under the conditions of a temperature of 40°C to 100°C, and more preferably mixed under the conditions of 60°C to 80°C.

[0076] Examples of the alkali metal compound include alkali metal hydroxides or alkali metal alkoxides, etc., and it is preferable to use an alkali metal hydroxide. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide, etc. From the viewpoints of processability and handleability such as particle size control, sodium hydroxide is preferable because it has excellent dispersion stability of the dispersed substance. Sodium hydroxide has hygroscopicity and can exhibit an excellent effect when a part of the structural unit of the copolymer is modified by hydrolysis or the like. Examples of the alkali metal alkoxide include sodium ethoxide, sodium butoxide, etc.

[0077] The alkali metal compound used for modifying the copolymer preferably has a maximum particle size of 150 μm or less, more preferably 100 μm or less, and even more preferably 50 μm or less. Also, 20 μm or more is preferable. When the maximum particle size of the alkali metal compound is within the above range, precipitation of the alkali metal compound in the resin composition is suppressed, and the stability of the resin composition is more excellent. The sedimentation rate of the alkali metal compound in the resin composition can be estimated from Stokes' formula, and the viscosity of the resin composition, the density and particle size of the alkali metal compound are important in controlling the dispersion stability of the dispersed substance. The maximum particle size of the alkali metal compound can be calculated, for example, by filtering through a filter with a known mesh size.

[0078] The particle size of the alkali metal compound is preferably controlled by performing a grinding treatment using a conventionally known grinder in a dry and / or wet manner. A conventionally known grinder can be used for the grinding treatment. By setting the maximum particle size of the alkali metal compound within the above range, not only the composition and structure of the structural units constituting the copolymer (X) but also changes in the molecular weight and the like of the copolymer (X) accompanying the modification can be appropriately controlled. By controlling the molecular weight and molecular weight distribution of the copolymer (X) in this way, a dispersion composition with a lower viscosity can be obtained when the material to be dispersed is dispersed. When the maximum particle size of the alkali metal compound is large, the alkali metal compound precipitates in the resin composition, and not only can the molecular weight of the copolymer not be controlled, but also the stability over time of the carbon material dispersion composition and the composite material slurry described later may decrease.

[0079] A pulverizer is a device that applies forces such as compressive force, impact force, shear force, and frictional force to a sample to make the sample finer. As a device for controlling the particle size, a pulverizer such as a mortar, a pin mill, a hammer mill, a papermaker, an attritor, a jet mill, a cutter mill, a ball mill, a bead mill, a colloid mill, a conical mill, a disk mill, an edge mill, a wonder crusher, a vibration mill, an ultrasonic homogenizer, or a high-shear mixer can be used.

[0080] ≪Carbon material dispersion composition≫ The carbon material dispersion composition of this embodiment contains at least a carbon material and the resin composition of this embodiment. It is also preferably contained in a solvent. By including a solvent in the carbon material dispersion composition, a carbon material dispersion composition with a good dispersion state can be easily obtained.

[0081] (Carbon material) As the carbon material, various carbon blacks such as acetylene black, furnace black, hollow carbon black, channel black, thermal black, and ketjen black can be used. Further, oxidized carbon black, graphitized carbon black, mesophase carbon black; amorphous carbonaceous materials such as soft carbon and hard carbon; carbon fibers such as carbon nanotubes or carbon nanofibers which are fibrous carbon, and vapor-grown carbon fibers can also be used. Among them, it is preferably contains at least one selected from the group consisting of carbon black and carbon fiber, and particularly preferably contains carbon nanotubes.

[0082] The carbon purity of the carbon material is preferably 95% by mass or more, more preferably 97% by mass or more, based on the mass of the carbon material (assuming the mass of the carbon material is 100% by mass).

[0083] Carbon nanotubes have a structure in which planar graphite is wound cylindrically, including single-walled carbon nanotubes and multi-walled carbon nanotubes, and these may be mixed. Among them, it is preferably contains multi-walled carbon nanotubes. Multi-walled carbon nanotubes have a structure in which two or more layers of graphite are wound, and single-walled carbon nanotubes have a structure in which one layer of graphite is wound. The side wall of the carbon nanotube does not have to be a graphite structure. For example, a carbon nanotube having a side wall with an amorphous structure can also be used as the carbon material.

[0084] The average outer diameter of the carbon nanotube is preferably 1 nm or more and 25 nm or less, more preferably 3 nm or more and 20 nm or less, and even more preferably 4 nm or more and 15 nm or less. When the average outer diameter is within the above range, it is easy to form a good conductive network in the electrode, and during charge and discharge, the active material inside the secondary battery is uniformly utilized, so the deterioration of the active material is suppressed and the cycle characteristics of the secondary battery are further improved.

[0085] The BET specific surface area of the carbon nanotubes is preferably 100 m 2 / g or more and 1000 m 2 / g or less, more preferably 200 m 2 / g or more and 700 m 2 / g or less. When the BET specific surface area is within the above range, an efficient conductive network can be formed with a small amount, and the amount of the conductive material in the electrode can be reduced. As a result, the degree of freedom in battery design, such as increasing the amount of the active material and the binder resin, is increased. Furthermore, during the preparation of the composite slurry, the composite of the active material and the carbon nanotubes tends to proceed, so that an electrode film having a homogeneous conductive network in which the surface of the active material is coated with the carbon nanotubes can be easily obtained, suppressing the electrolyte decomposition reaction at the interface between the electrolyte and the active material, and improving the cycle characteristics of the battery. The BET specific surface area can be measured by the BET method described in JIS Z 8830.

[0086] The G / D ratio (peak ratio of G-band and D-band) of the carbon nanotubes is such that when the maximum peak intensity in the range of 1560 cm -1 to 1600 cm -1 is defined as G and the maximum peak intensity in the range of 1310 cm -1 to 1350 cm -1 is defined as D, the G / D ratio is preferably 0.5 to 10, more preferably 0.7 to 4.5. When the G / D ratio of the carbon nanotubes is within the above range, it is considered that the contact resistance between the carbon nanotubes becomes small and good conductivity is easily obtained. It is also presumed that the amount of functional groups on the surface of the multi-walled carbon nanotubes is appropriate, the affinity with the solvent is good, and the dispersibility is better.

[0087] The volume resistivity of the carbon nanotubes is preferably 1.0×10 -2 Ω·cm to 3.0×10 -2 Ω·cm, more preferably 1.0×10 -2 Ω·cm to 2.0×10 -2 Ω·cm. The volume resistivity of the carbon nanotubes can be measured using a powder resistivity measuring apparatus (manufactured by Mitsubishi Chemical Analytech Co., Ltd.: Loresta GP Powder Resistivity Measuring System MCP-PD-51). When the volume resistivity is within the above range, the conductivity of the electrode film tends to be good, and a secondary battery having excellent rate characteristics and cycle characteristics can be easily obtained.

[0088] The carbon nanotubes are preferably those from which metal foreign particles have been removed by using an electromagnet and magnetic force. For example, it is preferable to set an electromagnet in the pulverization process or filling process of the carbon nanotubes and pass the carbon nanotubes through it to remove the metal foreign particles. The higher the carbon purity of the carbon nanotubes, the more preferable it is. Preferably, it is 98.0% by mass or more, more preferably 99.5% by mass or more, still more preferably 99.8% by mass or more, and particularly preferably 99.9% by mass or more in 100% by mass of the carbon nanotubes. That is, the lower the content rate of the metal foreign particles, the more preferable it is. Preferably, it is 2.0% by mass or less, more preferably 0.5% by mass or less, still more preferably 0.2% by mass or less, and particularly preferably 0.1% by mass or less in 100% by mass of the carbon nanotubes. By using carbon nanotubes produced by a production method that does not use a metal catalyst as a nucleus or carbon nanotubes obtained by a purification treatment method such as conventionally known acid treatment, the content rate of the metal foreign particles is made 0.5% by mass or less with respect to 100% by mass of the carbon nanotubes, whereby the content of the metal foreign particles contained in the carbon nanotube dispersion composition can be reduced, and various characteristics of the secondary battery can be improved. The carbon purity of the carbon nanotubes can be determined by an ICP emission spectroscopic analyzer by the method described in the examples.

[0089] The solvent is not particularly limited as long as it is miscible with the resin composition of the present embodiment, but it is preferably capable of dissolving the resin composition, more preferably a high dielectric constant solvent, and preferably includes a solvent composed of any one of high dielectric constant solvents or a mixed solvent composed of two or more of them. Further, one or two or more other solvents may be mixed with the high dielectric constant solvent and used.

[0090] Examples of the high dielectric constant solvent include amide-based (N-methyl-2-pyrrolidone (NMP), N- ethyl-2-pyrrolidone (NEP), N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N-methylcaprolactam, etc.), heterocyclic-based (cyclohexylpyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, γ-butyrolactone, etc.), sulfoxide-based (dimethyl sulfoxide, etc.), sulfone-based (hexamethylphosphoramide, sulfolane, etc.), lower ketone-based (acetone, methyl ethyl ketone, etc.), carbonate-based (diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, fluoroethylene carbonate, propylene carbonate, ethylene carbonate), and others such as tetrahydrofuran, urea, acetonitrile, etc. can be used. As the dispersion medium, it is preferably an amide-based polar solvent, and more preferably includes at least one selected from the group consisting of N-methyl-2-pyrrolidone and N-ethyl-2-pyrrolidone. The relative dielectric constant of the high dielectric constant solvent can be the value described in a solvent handbook or the like, and is preferably 2.5 or more at 20°C. By using a high dielectric constant solvent as the solvent, the interaction between the nitrile group contained in the resin composition of the present embodiment, the carbon material, and the solvent can be enhanced.

[0091] The water content in the solvent is preferably 100 ppm or more and 1500 ppm or less, and more preferably 100 ppm or more and 1000 ppm or less. When it is within the above range, the alkali metal contained in the resin composition of the present embodiment dissolves in the carbon material dispersion composition, and the dispersion stability of the carbon material dispersion composition tends to be good.

[0092] The content ratio of the solvent in this embodiment is preferably 90% by mass to 99% by mass, more preferably 92% by mass to 98% by mass, based on the mass of the carbon material dispersion composition (assuming the mass of the carbon material dispersion composition is 100% by mass). When within the above range, a fluid carbon material dispersion composition is likely to be obtained, and a carbon material dispersion composition with excellent dispersion stability is likely to be obtained. By using a carbon material dispersion composition with excellent dispersion stability, an electrode film with stable conductivity can be obtained, and the quality of the secondary battery is likely to be stable.

[0093] To obtain the carbon material dispersion composition of this embodiment, it is preferable to perform a process of dispersing the carbon material in a solvent. The dispersion device used for performing such a process is not particularly limited.

[0094] As the dispersion device, a disperser commonly used for pigment dispersion or the like can be used. For example, mixers such as a disper, a homomixer, and a planetary mixer, homogenizers (Advanced Digital Sonifer (registered trademark), MODEL 450DA manufactured by BRANSON, "Creamix" manufactured by M. Technique Co., Ltd., "Filmix" manufactured by PRIMI X Co., "Filmix", etc., "Abramix" manufactured by Silverson Co., etc.), paint conditioners (manufactured by Red Devil Co.), colloid mills ("PUC colloid mill" manufactured by PUC Co., Ltd. ,"Colloid Mill MK" manufactured by IKA Co., Ltd.), cone mills ("Cone Mill MKO" manufactured by IKA Co., Ltd., etc.), ball mills, sand mills ("Dynomill" manufactured by Shinmaru Enterprises Co., Ltd., etc.), attritors, pearl mills ("DCP Mill" manufactured by Ehrlich Co., Ltd., etc.), media type dispersers such as coball mills, high-pressure homogenizers ("Genius PY" manufactured by Genius Co., Ltd., "Starburst" manufactured by Sugino Machine Co., Ltd., "Nanomizer" manufactured by Nanomizer Co., Ltd., etc.), media-less dispersers such as "Crea SS-5" manufactured by M. Technique Co., Ltd. and "MICROS" manufactured by Nara Machinery Co., Ltd., and other roll mills, etc. can be mentioned, but it is not limited thereto.

[0095] The content of the carbon material contained in the carbon material dispersion composition is preferably 1% by mass or more and 20% by mass or less, more preferably 2% by mass or more and 15% by mass or less, and even more preferably 3% by mass or more and 10% by mass or less, based on the mass of the carbon material dispersion composition (assuming the mass of the carbon material dispersion composition is 100% by mass).

[0096] The content of the dispersant contained in the carbon material dispersion composition is preferably 5% by mass or more and 100% by mass or less, more preferably 10% by mass or more and 75% by mass or less, and even more preferably 20% by mass or more and 50% by mass or less, based on the mass of the carbon material (assuming the mass of the carbon material is 100% by mass). When the amount of the dispersant is within the above range, the dispersion stability of the carbon material in the carbon material dispersion composition tends to be good. Also, the peel strength of the electrode for the secondary battery becomes good.

[0097] The carbon material dispersion composition preferably has a water content of 100 ppm to 1500 ppm, more preferably 200 ppm to 1000 ppm. When the water content of the carbon material dispersion composition is within the above range, the gelation of the composite slurry described later is suppressed, and it is easy to obtain a composite slurry and an electrode film with stable quality.

[0098] The initial viscosity of the carbon material dispersion composition of the present embodiment, when measured at 25°C and 100 rpm using a B-type viscometer, is preferably 100 mPa·s or more and 2,000 mPa·s or less, more preferably 200 mPa·s or more and 1,000 mPa·s or less. When the initial viscosity of the carbon material dispersion composition is within the above range, it is considered that the dispersion state of the carbon material contained in the carbon material dispersion composition is appropriate and it is easy to form a conductive network.

[0099] The viscosity of the carbon material dispersion composition of the present embodiment after storage for one week under the condition of 60°C, after cooling to 25°C, when measured by a B-type viscometer at 25°C and a rotor rotation speed of 100 rpm, is preferably 500 mPa·s or more and 6,000 mPa·s or less, more preferably 500 mPa·s or more and 3,000 mPa·s or less, and even more preferably 500 mPa·s or more and 2000 mPa·s or less.

[0100] When the carbon material dispersion composition has a viscosity within the above range, it is considered that the composition ratios of the carbon material, resin composition, and solvent and the dispersion process are appropriate, and the dispersion stability is good. Since the adsorption reaction of the resin composition contained in the carbon material dispersion composition to the surface of the carbon material is an endothermic reaction, by evaluating the viscosity of the carbon material dispersion composition after storage under high temperature conditions, in order to obtain a carbon material dispersion composition with excellent dispersion stability, the necessary and sufficient amount of the resin composition can be determined.

[0101] It is preferable to use the carbon material dispersion composition of this embodiment after removing metal foreign matters with a filter or a magnet.

[0102] [Step of removing metal foreign matter particles] The method for removing metal foreign matter particles is not particularly limited, and examples thereof include a filtering step of filtering with a filter and a magnetic separation step such as a magnetic separation treatment using an electromagnet. It is preferable to include a filtering step and a magnetic separation step. By the magnetic separation step, metal foreign matter particles contained in the carbon material can be removed, and by the filtering step, metal foreign matter particles that cannot be removed by a magnet can be recovered. This is because Furthermore, it is more preferable to perform a magnetic separation step after the filtering step. By performing the filtering step at the end before shipping the carbon material dispersion composition, metal foreign matter particles from pipes and the like can also be removed.

[0103] (Magnetic separation step) As a method for removing metal foreign matter particles using magnetic force by the magnetic separation step, various conventionally known methods can be used. For example, during the manufacturing process of the carbon material dispersion composition, a method of setting an electromagnet and passing the carbon material dispersion composition through it to remove metal foreign matter particles is preferable.

[0104] The magnetic flux density of the electromagnet is preferably 5,000 Gauss or more and 20,000 Gauss or less, and more preferably 10,000 Gauss or more and 20,000 Gauss or less. By using an electromagnet within the above range, not only can the metal foreign particles contained in the carbon material be removed, but also the metal foreign particles generated in the manufacturing process can be removed.

[0105] Specifically, for example, CS-150HHH, CS-250HHH, CS-300HHH manufactured by Nippon Magnetics Co., Ltd., DVF-50-6, DVF-50-9, DVF-50-12 manufactured by Nippon Eliz Magnetics Co., Ltd., EMF-100S, EMF-150S, EMF-250S, EMF-300S manufactured by Taiho Magnetic Co., Ltd. etc. can be used.

[0106] The flow rate of the carbon material dispersion composition when it comes into contact with the electromagnet is preferably 1 L / min. or more and 300 L / min. or less, and preferably 30 L / min. or more and 200 L / min. or less.

[0107] The number of times the carbon material dispersion composition passes through the electromagnet is preferably 3 times or more. If the number of passes is small, there is a possibility that metal foreign particles cannot be removed. When passing through the electromagnet in a circulating manner, considering the uniformity in the tank used in the manufacturing process, it is preferable to pass through more times.

[0108] (Filtration step) As the filter for filtering metal foreign particles, it may be a surface filter such as a membrane filter or a depth filter, but a depth filter is more preferable. Since the metal foreign particles are not spherical and many have orientation, by using a depth filter, the metal foreign particles in the carbon material dispersion composition can be efficiently removed.

[0109] Unlike a surface filter (a filter that mainly captures particulate matter in a fluid on the filter surface), a depth filter is a filter that mainly captures particulate matter in a fluid inside the filter medium, and has the characteristics of high particle retention performance and low clogging tendency. By using a depth filter, metal foreign particles in the carbon material dispersion composition can be removed more selectively.

[0110] As the depth filter, for example, a non-woven fabric depth cartridge NT-T series made of 3M(TM)PP can be used.

[0111] The filtration accuracy of the filter is preferably 5 μm or more and 50 μm or less, and more preferably 10 μm or more and 40 μm or less. In order to increase the removal rate of metal foreign particles in the carbon material dispersion composition, when using a filter with a small pore size, the removal efficiency of metal foreign particles may decrease due to clogging of the carbon material. On the other hand, the carbon material dispersion composition filtered by the filter in the above range has a high removal efficiency of metal foreign particles when using the filter, so it is easy to obtain a carbon material dispersion composition with few metal foreign particles.

[0112] ≪Composite Material Slurry≫ The composite material slurry of the present embodiment contains a carbon material dispersion composition and an active material. That is, it preferably contains at least the resin composition of the present invention, a carbon material, and an active material, and further contains a binder resin.

[0113] The binder resin is a resin used to bind between the substances of the carbon material. There is no particular limitation on the binder resin. For example, polymers or copolymers containing units such as fluororesin, ethylene, propylene, vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylic acid ester, methacrylic acid, methacrylic acid ester, acrylonitrile, styrene, vinyl butyral, vinyl acetal, vinyl pyrrolidone, etc.; polyurethane resin, polyester resin, phenol resin, epoxy resin, phenol Xylyl resins, urea resins, melamine resins, alkyd resins, acrylic resins, formaldehyde resins, silicone resins, fluororesins; cellulose resins such as carboxymethyl cellulose ; rubbers such as styrene-butadiene rubber; conductive resins such as polyaniline and polyacetylene, and the like. Among them, from the viewpoint of electrochemical oxidation-reduction resistance, it is preferable to use a fluororesin as the binder resin.

[0114] As the fluororesin of the present embodiment, for example, polyvinylidene fluoride, polyvinyl fluoride, and tetrafluoroethylene are preferable.

[0115] The weight average molecular weight of the fluororesin is preferably 10,000 or more and 2,000,000 or less, more preferably 100,000 or more and 1,000,000 or less, and particularly preferably 200,000 or more and 1,000,000 or less.

[0116] The active material is a material that serves as the basis for the battery reaction. The active material is divided into a positive electrode active material and a negative electrode active material based on the electromotive force. In this specification, the positive electrode active material and the negative electrode active material may be simply referred to as "active material". The active material is a material that serves as the basis for the battery reaction. The active material is divided into a positive electrode active material and a negative electrode active material based on the electromotive force.

[0117] The positive electrode active material is not particularly limited, but lithium ions, metal compounds such as metal oxides and metal sulfides capable of doping or intercalating sodium ions, and conductive polymers can be used. For example, oxides of transition metals such as Fe, Co, Ni, and Mn, composite oxides with lithium or sodium, inorganic compounds such as transition metal sulfides, polyanion compounds, Prussian blues, and the like can be mentioned. Specifically, MnO, V2O5, V6O 13, transition metal oxide powders such as TiO2, lithium-transition metal composite oxide powders such as layered lithium nickelate, lithium cobaltate, lithium manganate, spinel-structured lithium manganate, lithium iron phosphate-based materials which are olivine-structured phosphate compounds, transition metal sulfide powders such as TiS2 and FeS, sodium iron oxide, sodium manganate, sodium chromate, sodium nickelate with a layered structure, sodium iron phosphate-based materials which are olivine-structured phosphate compounds, etc. can be mentioned. Further, conductive polymers such as polyaniline, polyacetylene, polypyrrole, and polythiophene can also be used. Further, the above inorganic compounds and organic compounds may be mixed and used.

[0118] The positive electrode active material is preferably a composite oxide of lithium containing transition metals such as Al, Fe, Co, Ni, and Mn, more preferably a composite oxide of lithium containing any one of Al, Co, Ni, and Mn, and particularly preferably a composite oxide of lithium containing Ni and / or Mn. When these active materials are used, particularly good effects can be obtained.

[0119] The negative electrode active material is not particularly limited as long as it can be doped or intercalated with lithium or sodium ions. For example, metal Li, alloy systems such as its alloys tin alloy, silicon alloy, lead alloy, etc., metal oxide systems such as LiXFe2O3, LiXFe3O4, LiXWO2 (x is a number where 0 < x < 1), lithium titanate, lithium vanadate, lithium silicate, etc., conductive polymer systems such as polyacetylene, poly-p-phenylene, etc., amorphous carbonaceous materials such as soft carbon and hard carbon, artificial graphite such as highly graphitized carbon materials, or carbonaceous powders such as natural graphite, carbon black, mesophase carbon black, resin-fired carbon materials, gas-phase grown carbon fibers, carbon fibers, etc. These negative electrode active materials can be used alone or in combination of two or more.

[0120] The BET specific surface area of the active material is 0.1 m 2 / g or more and 10 m 2Those below 0.2 m / g are preferable, and 0.2 m 2 / g or more and 5 m 2 / g or less are more preferable, and 0.3 m 2 / g or more and 3 m 2 / g or less are even more preferable.

[0121] The average particle diameter of the active material is preferably in the range of 0.05 μm to 100 μm, and more preferably in the range of 0.1 μm to 50 μm. The average particle diameter of the active material as referred to in this specification is the average value of the particle diameters measured by an electron microscope for the active material.

[0122] To obtain the composite material slurry of this embodiment, it is preferable to perform a dispersion treatment after adding the active material to the carbon material dispersion composition. The dispersion device used for performing such treatment is not particularly limited. The composite material slurry can be obtained using the dispersion device described for the carbon material dispersion composition.

[0123] The content of the active material in the composite material slurry is preferably 20% by mass to 85% by mass, and particularly preferably 40% by mass to 85% by mass, based on 100% by mass of the composite material slurry.

[0124] The content of the carbon material in the composite material slurry is preferably 0.05% by mass to 10% by mass, preferably 0.1% by mass to 5% by mass, and preferably 0.1% by mass to 3% by mass, based on 100% by mass of the active material.

[0125] The content of the binder resin in the composite material slurry is preferably 0.5% by mass to 20% by mass, more preferably 1% by mass to 10% by mass, and particularly preferably 1% by mass to 5% by mass, based on 100% by mass of the active material.

[0126] The solid content concentration of the composite material slurry is preferably 30% by mass to 90% by mass, and preferably 40% by mass to 85% by mass, based on 100% by mass of the composite material slurry.

[0127] The water content in the composite slurry is preferably 500 ppm or less, more preferably 300 ppm or less, and particularly preferably 100 ppm or less.

[0128] ≪Electrode≫ The electrode film of this embodiment includes a current collector and an electrode film formed from a composite slurry. The electrode film is a coating film of the composite slurry. For example, by coating and drying the composite slurry on the current collector, it is a coating film in which an electrode composite layer is formed.

[0129] The material and shape of the current collector used for the electrode film of this embodiment are not particularly limited, and those suitable for various secondary batteries can be appropriately selected. For example, as the material of the current collector, metals and alloys such as aluminum , copper, nickel, titanium, or stainless steel can be mentioned. Also, as the shape, generally a foil on a flat plate is used, but those with a roughened surface, perforated foil-like ones, and mesh-shaped current collectors can also be used.

[0130] As a method of coating the composite slurry on the current collector to form the electrode film, there is no particular limitation, and known methods can be used. Specifically, die coating method, dip coating method, roll coating method, doctor coating method, knife coating method, spray coating method, gravure coating method, screen printing method, electrostatic coating method, etc. can be mentioned. As the drying method, air drying, hot air dryer, warm air dryer, infrared heater, far infrared heater, etc. can be used, but it is not particularly limited to these.

[0131] Also, rolling treatment may be performed by a flat plate press, calender roll, etc. after coating. The thickness of the electrode composite layer is generally 1 μm or more and 500 μm or less, preferably 10 μm or more and 300 μm or less.

[0132] ≪Secondary Battery≫ The secondary battery of this embodiment includes an electrode having the electrode film of the present invention and an electrolyte. The carbon material dispersion composition using the resin composition of this embodiment forms a good conductive network in the secondary battery electrode, so it has excellent rate characteristics. During charge and discharge, since the active material is used homogeneously, the deterioration of the active material hardly progresses. Furthermore, overcharge and overdischarge during charge and discharge are suppressed. Therefore, deterioration of battery characteristics due to electrolyte decomposition or metal precipitation hardly occurs, and the cycle characteristics are excellent.

[0133] As the positive electrode, one obtained by coating and drying a composite slurry containing a positive electrode active material on a current collector to form an electrode film can be used.

[0134] As the negative electrode, one obtained by coating and drying a composite slurry containing a negative electrode active material on a current collector to form an electrode film can be used.

[0135] As the electrolyte, various conventionally known ones in which ions can move can be used. For example, those containing lithium salts such as LiBF4, LiClO4, LiPF6, LiAsF6, LiSbF6, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, Li(CF3SO2)3C, LiI, LiBr, LiCl, LiAlCl, LiHF2, LiSCN, or LiBPh4 (where Ph is a phenyl group) can be mentioned, but it is not limited to these, and those containing sodium salts can also be used. The electrolyte is preferably dissolved in a non-aqueous solvent and used as an electrolytic solution.

[0136] The non-aqueous solvent is not particularly limited. For example, carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate; lactones such as γ-butyrolactone, γ-valerolactone, and γ-octanoic lactone; glymes such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,2-methoxyethane, 1,2-ethoxyethane, and 1,2-dibutoxyethane; esters such as methyl formate, methyl acetate, and methyl propionate; sulfoxides such as dimethyl sulfoxide and sulfolane; and nitriles such as acetonitrile, etc. These solvents may be used alone or in combination of two or more.

[0137] The secondary battery of this embodiment preferably includes a separator. Examples of the separator include, but are not particularly limited to, polyethylene non-woven fabric, polypropylene non-woven fabric, polyamide non-woven fabric, and those subjected to hydrophilic treatment. are not particularly limited thereto.

[0138] The structure of the secondary battery of this embodiment is not particularly limited. Generally, it is composed of a positive electrode, a negative electrode, and a separator provided as needed, and can have various shapes according to the purpose of use, such as a paper type, a cylindrical type, a button type, a laminated type, etc.

[0139] The use of the secondary battery of this embodiment is not particularly restricted. Specifically, it can be used as a power source for consumer devices such as mobile phones, notebook computers, digital cameras, etc., as an emergency power source for hospitals, factories, buildings, etc., and for vehicles such as hybrid vehicles, plug-in hybrid vehicles, electric vehicles, assist bicycles, railway vehicles, etc. The secondary battery, for example, recovers the regenerative energy of the vehicle's power.

[0140] Among them, since it is a secondary battery having high charge and discharge performance and excellent cycle characteristics, it can be suitably used for a vehicle, and a vehicle with high safety and expected fuel consumption improvement can be obtained. Further, excellent effects can be exhibited even in the case of vehicle applications where charge and discharge at a large current are desired.

[0141] The mounting position of the secondary battery in the vehicle of this embodiment is not particularly limited. For example, when mounting the secondary battery in an automobile, the secondary battery can be mounted in the engine room of the vehicle, the rear of the vehicle body, or under the seat.

Example

[0142] The present invention will be described more specifically with reference to the following examples. The present invention is not limited to the following examples as long as it does not exceed the gist thereof. Unless otherwise specified, "parts" represents "parts by mass" and "%" represents "% by mass". In addition, the blending amounts in the table are in parts by mass. Note that the blanks in the table indicate that nothing is blended.

[0143] The materials used in the examples and comparative examples are shown below. · Hydrogenated nitrile butadiene rubber (manufactured by Zannan Scitech, liquid hydrogenated nitrile butadiene rubber, number average molecular weight 20,000, weight average molecular weight 35,000, Z average molecular weight 60,000, alkylene structural unit 66% by mass, content of nitrile group-containing structural unit 34% by mass), hereinafter referred to as HNBR1. · Hydrogenated nitrile butadiene rubber (manufactured by Zannan Scitech, ZN35052, Mooney viscosity 20, number average molecular weight 48000, weight average molecular weight 110,000, Z average molecular weight 210,000, alkylene structural unit 66% by mass, content of nitrile group-containing structural unit 34% by mass), hereinafter referred to as HNBR2. · Hydrogenated nitrile butadiene rubber (manufactured by Zannan Scitech, ZN35053, Mooney viscosity 35, number average molecular weight 53000, weight average molecular weight 133,000, Z average molecular weight 270,000, alkylene structural unit 64% by mass, content of nitrile group-containing structural unit 36% by mass), hereinafter referred to as HNBR3. · Hydrogenated nitrile butadiene rubber (manufactured by Zannan Scitech, ZN35056, Mooney viscosity 65, number average molecular weight 75000, weight average molecular weight 183,000, Z average molecular weight 364,000, alkylene structural unit 64% by mass, content of nitrile group-containing structural unit 36% by mass), hereinafter referred to as HNBR4. · Hydrogenated nitrile butadiene rubber (manufactured by ARLANXEO, Therban(R)3406, Mooney viscosity 63, number average molecular weight 78000, weight average molecular weight 209,000, Z average molecular weight 434,000, alkylene structural unit 66% by mass, content of nitrile group-containing structural unit 34% by mass)), hereinafter referred to as HNBR5. · Carbon nanotube (manufactured by JEIO, JENOTUBE6A, average outer diameter 6 nm, BET specific surface area 650 m 2 / g), hereinafter referred to as CNT1. · Carbon nanotube (manufactured by JEIO, JENOTUBE10B, average outer diameter 10 nm, B ET specific surface area 230 m 2 / g), hereinafter referred to as CNT2. · HS-100: Denka black HS-100 (manufactured by Denka, acetylene black, average primary particle diameter 48 nm, BET specific surface area 39 m 2 / g), hereinafter referred to as CB1.

[0144] The methods for measuring the physical properties of the materials used in each example and comparative example are as follows.

[0145] <Specific surface area> The BET specific surface area of carbon nanotubes and carbon black can be measured by the BET method based on nitrogen adsorption measurement in accordance with JIS Z 8830.

[0146] <Average outer diameter> The average outer diameter of the carbon nanotubes can be calculated by observing and imaging the carbon nanotubes with a transmission electron microscope, and then selecting any 300 carbon nanotubes in the obtained observation photograph and measuring their respective outer diameters. Also, the average primary particle diameter of the carbon black can be calculated by first observing and imaging the carbon black with a transmission electron microscope, and then selecting any 100 spherical carbon black primary particles in the observation photograph and measuring their respective outer diameters.

[0147] <Mooney viscosity> The Mooney viscosity of the hydrogenated nitrile butadiene rubber was measured at a temperature of 100 °C using an L-shaped rotor in accordance with Japanese Industrial Standard JIS K6300-1 (Mooney viscosity (ML1+4, 100 °C)).

[0148] <Fabrication of standard negative electrode> To a plastic container with a capacity of 150 ml, 0.5 parts by mass of acetylene black (Denka Black (registered trademark) HS-100, manufactured by Denka), 1 part by mass of MAC500LC (sodium carboxymethyl cellulose salt, Sunrose special type MAC500L, manufactured by Nippon Paper Industries Co., Ltd., non-volatile content 100%), and 98.4 parts by mass of water were added, and then using a rotation-revolution mixer (Sinki's Awatori Rentaro, ARE-310), it was stirred at 2000 rpm for 30 seconds. Further, 92 parts by mass of artificial graphite (manufactured by Nippon Graphite Industry Co., Ltd., CGB-20) and 5 parts by mass of silicon oxide (manufactured by Osaka Titanium Technologies Co., Ltd., SILICON MONOOXIDE SiO 1.3C 5μm, non-volatile content 100%) were added, and using a high-speed stirrer, it was stirred at 3000 rpm for 10 minutes. Subsequently, 3.1 parts by mass of styrene butadiene rubber (SBR, TRD2001, manufactured by JSR Corporation) was added, and using the rotation-revolution mixer, it was stirred at 2000 rpm for 30 seconds to obtain a composite slurry for the negative electrode. Thereafter, the composite slurry for the negative electrode was applied using an applicator so that the basis weight per unit of the electrode was 8 mg / cm 2After coating on a copper foil so as to achieve this, the coating film was dried in an electric oven at 120 °C ± 5 °C for 25 minutes. Further, rolling treatment was performed using a roll press (manufactured by Sanku Metal Co., Ltd., 3t hydraulic roll press), and the density of the composite material layer was 1.6 g / cm 3 A standard negative electrode with this density was produced.

[0149] <Preparation of Alkali Metal Compound Dispersion Liquid> To a plastic container with a volume of 2000 cm 3 950 parts by mass of NMP and 50 parts by mass of NaOH (sodium hydroxide, manufactured by Tosoh Corporation, Tosoh Pearl) were added. A fine emulsifier screen was attached to a high-shear mixer (L5M-A, manufactured by SILVERSON), and dispersion was carried out at a speed of 9000 rpm until the whole became uniform. Then, using a filtration bell, it was passed through a nylon filter with a mesh size of 150 μm to prepare a NaOH dispersion liquid (NaOH concentration: 5% by mass). The maximum particle size of sodium hydroxide was 150 μm or less.

[0150] ≪Physical Property Measurement and Evaluation Methods≫ The physical property measurement and evaluation methods for the resin compositions, carbon material dispersion compositions, electrode films, and secondary batteries used in the following Examples and Comparative Examples are as follows.

[0151] <Measurement of Number Average Molecular Weight, Weight Average Molecular Weight, and Z Average Molecular Weight of Copolymer> (Preparation of Sample for Molecular Weight Measurement) Samples for measuring the number average molecular weight (Mn), weight average molecular weight (Mw), and Z average molecular weight (Mz) of the copolymer were prepared by the following method. The resin composition was dropped into purified water to precipitate the copolymer, which was then filtered with a Buchner funnel to collect the precipitate. The precipitate was directly rinsed with purified water on the Buchner funnel and then dissolved in tetrahydrofuran (THF) to obtain a solution. The obtained solution was dropped into purified water again, and the above filtration and washing steps using purified water were performed. The precipitate was redissolved in THF to obtain a sample for molecular weight measurement.

[0152] (Measurement of Molecular Weight) Using a sample for molecular weight measurement, it was measured by gel permeation chromatography (GPC) equipped with an RI detector. HLC-8320GPC (manufactured by Tosoh Corporation) was used as the apparatus. Three separation columns were connected in series, and the packing materials used were "TSK-GEL SUPER AW-4000", "AW-3000", and "AW-2500" manufactured by Tosoh Corporation in order. The oven temperature was 40 °C, and a solution of 30 mM triethylamine and 10 mM LiBr in N,N-dimethylformamide was used as the eluent. The measurement was carried out at a flow rate of 0.6 mL / min. The measurement sample was adjusted to a concentration of 1% using a solvent consisting of the above eluent, and 20 microliters were injected. The average molecular weight is a polystyrene equivalent value.

[0153] <Content of alkylene structural unit and nitrile group-containing structural unit of copolymer> (Preparation of sample for IR measurement) The resin composition was dropped into purified water to precipitate the copolymer, and the precipitate was collected by filtration with a Buchner funnel. The precipitate was directly rinsed with purified water on the Buchner funnel and then dried at 140 °C for 1 hour using a hot air oven to prepare a sample for IR measurement. (Measurement of IR) Using the sample for IR measurement, it was measured with a Fourier transform infrared spectrometer (NicletiS5, manufactured by Thermo Fisher Scientific), and the content ratios of the alkylene structural unit and the nitrile group-containing structural unit of the copolymer in the resin composition were calculated.

[0154] <Measurement of resistivity of resin composition> (Preparation of sample for resistivity measurement) A 250 cm 3 plastic container was weighed with the resin composition and N-methyl-2-pyrrolidone to prepare 200 parts by mass of a sample for liquid resistance measurement with a non-volatile content of 8% by mass. (Measurement of resistivity) Using a sample for liquid resistance measurement, resistivity was measured with a resistivity meter (IEST Yuaneng Technology (registered trademark), BATTERY SLURRY RESISTIVITY BSR2300), and the resistivity at 25°C was calculated. The value of the resistivity was based on the measurement result of the Middle channel.

[0155] <Measurement of the alkali metal content of the resin composition> After drying the resin composition using a hot air oven, it was acid-digested using a microwave sample pretreatment device (manufactured by Milestone General, ETHOS1), and the alkali metals (lithium, sodium, potassium) contained in the resin composition were calculated. The content of the alkali metals was taken as the sum of the contents of lithium, sodium, and potassium.

[0156] <Initial viscosity of the carbon material dispersion composition> After allowing the carbon material dispersion composition to stand in a constant temperature bath at 25°C for 1 hour or more, the carbon material dispersion composition was immediately measured using a B-type viscometer at a rotor rotation speed of 100 rpm. The evaluation of the initial viscosity was as follows: 100 mPa·s or more and less than 500 mPa·s: ◎ (excellent), 500 mPa·s or more and less than 1000 mPa·s: 〇 (good), 1000 mPa·s or more and 2000 mPa·s or less: △ (acceptable), more than 2000 mPa·s: × (poor).

[0157] <Viscosity over time of the carbon material dispersion composition> After allowing the carbon material dispersion composition to stand in a constant temperature bath at 60°C for 1 week, the carbon material dispersion composition was cooled to 25°C and then immediately measured using a B-type viscometer at a rotor rotation speed of 100 rpm. The evaluation of the viscosity over time was as follows: 500 mPa·s or more and 2000 mPa·s or less: ◎ (excellent), more than 2000 mPa·s and 3000 mPa·s or less: 〇 (good), more than 3000 mPa·s and 6000 mPa·s or less: △ (acceptable), more than 6000 mPa: × (poor).

[0158] <60-degree specular gloss of the carbon material dispersion composition> Based on the gloss value, the surface smoothness of the coating film was evaluated as the degree of dispersion of the material to be dispersed. The carbon material dispersion composition was applied to a PET (polyethylene terephthalate) film using a bar coater No. 7, and then dried in a hot air oven at 120 °C for 5 minutes. From the surface coated with the carbon material dispersion composition, in accordance with JIS Z8741, the 60-degree specular gloss was measured using a gloss meter (manufactured by Nippon Denshoku Industries Co., Ltd., VG7000). The evaluation of the 60-degree specular gloss was as follows: 50 degrees or more and less than 80 degrees: ◎ (excellent), 40 degrees or more and less than 50 degrees, or 80 degrees or more and less than 90 degrees: 〇 (good), 30 degrees or more and less than 40 degrees, or 90 degrees or more: △ (fair), less than 30 degrees: × (poor).

[0159] <Volume resistivity of the electrode film> The composite slurry was applied onto the aluminum foil using an applicator so that the basis weight per unit of the electrode was 20 mg / cm 2 and then the coating film was dried in an electric oven at 120 °C ± 5 °C for 25 minutes. Thereafter, the surface resistivity (Ω / □) of the dried coating film was measured using Loresta GP (MCP-T610, probe: AP2 probe (RMH333)) manufactured by Mitsubishi Chemical Analytech Co., Ltd. After the measurement, the thickness of the electrode composite layer formed on the aluminum foil was multiplied to obtain the volume resistivity (Ω·cm) of the electrode film. The thickness of the electrode composite layer was obtained by subtracting the film thickness of the aluminum foil from the average value measured at three points in the electrode film using a film thickness gauge (manufactured by NIKON Corporation, DIGIMICRO MH-15M) to obtain the volume resistivity (Ω·cm) of the electrode film. The evaluation criteria for the volume resistivity were as follows: less than 8 Ω·cm: ◎ (excellent), 8 Ω·cm or more and less than 12 Ω·cm: 〇 (good), 12 Ω·cm or more and less than 15 Ω·cm: △ (fair), 15 Ω·cm or more: × (poor).

[0160] <Peel strength of the electrode film> The composite slurry was applied onto the aluminum foil using an applicator so that the basis weight per unit of the electrode was 20 mg / cm 2After coating on the aluminum foil so as to achieve the following, the coating film was dried in an electric oven at 120 °C ± 5 °C for 25 minutes. Thereafter, two cuts were made into rectangles of 90 mm × 20 mm with the coating direction as the major axis. For the measurement of the peel strength, a tabletop tensile testing machine (manufactured by Toyo Seiki Seisaku-sho, Ltd., Strograph E3) was used and evaluated by the 180-degree peel test method. Specifically, a double-sided tape (No. 5000NS, manufactured by Nitto Denko Corporation) with a size of 100 mm × 30 mm was attached to a stainless steel plate, and the fabricated battery electrode composite layer was adhered to the other side of the double-sided tape. While pulling upward from below at a constant speed (50 mm / min), it was peeled off, and the average value of the stress at this time was taken as the peel strength. The evaluation criteria for the peel strength were as follows: 1.0 N / cm or more: ◎ (excellent), 0.7 N / cm or more and less than 1.0 N / cm: 〇 (good), 0.5 N / cm or more and less than 0.7 N / cm: △ (fair), less than 0.5 N / cm: × (poor).

[0161] <Evaluation of Rate Characteristics of Lithium-Ion Secondary Batteries> The laminated lithium-ion secondary battery was placed in a constant temperature chamber at 25 °C, and charge and discharge measurements were performed using a charge and discharge device (manufactured by Hokuto Denko Corporation, SM-8). After performing constant current constant voltage charging (cutoff current 1.0 mA (0.02C)) at a charging current of 10 mA (0.2C) and a charging termination voltage of 4.2V, constant current discharge was performed at a discharge current of 10 mA (0.2C) and a discharge termination voltage of 2.5V. After repeating this operation 3 times, constant current constant voltage charging (cutoff current (1.0 mA 0.02C)) was performed at a charging current of 10 mA (0.2C) and a charging termination voltage of 4.2V, and constant current discharge was performed at discharge currents of 0.2C and 3C until the discharge termination voltage of 2.5V was reached, and the discharge capacities were obtained respectively. The rate characteristics can be expressed by the ratio of the 0.2C discharge capacity to the 3C discharge capacity, as shown in the following formula 2. (Formula 2) Rate characteristics = 3C discharge capacity / 0.2C discharge capacity of the third cycle × 100 (%) For the rate characteristic evaluation, those with rate characteristics of 80% or more were rated as ◎ (excellent), those with 70% or more and less than 80% were rated as 〇 (good), those with 60% or more and less than 70% were rated as △ (fair), and those with less than 60% were rated as × (poor).

[0162] <Evaluation of High Temperature Cycle Characteristics of Lithium-Ion Secondary Batteries> A laminated lithium-ion secondary battery was placed in a thermostatic chamber at 45°C, and charge and discharge measurements were performed using a charge and discharge device (manufactured by Hokuto Denko Corporation, SM-8). After performing constant current and constant voltage charging (cutoff current: 1.25 mA (0.025C)) at a charging current of 50 mA (1C) and a charging termination voltage of 4.2V, constant current discharge was performed at a discharge current of 50 mA (1C) and a discharge termination voltage of 2.5V. This operation was repeated 200 times. 1C was defined as the current value for discharging the theoretical capacity of the positive electrode in 1 hour. The cycle characteristics can be represented by the ratio of the 100th 1C discharge capacity to the 3rd 1C discharge capacity at 45°C, as shown by the following formula 3. (Formula 3) High-temperature cycle characteristics = 100th 1C discharge capacity / 3rd 1C discharge capacity × 100 (%) For the evaluation of high-temperature cycle characteristics, when the cycle characteristics were 90% or more, it was rated as ◎ (excellent); when it was 85% or more and less than 90%, it was rated as 〇 (good); when it was 80% or more and less than 85%, it was rated as △ (fair); when it was less than 80%, it was rated as × (poor).

[0163] (Example 1-1) 780 parts by mass of NMP was charged into a reaction vessel equipped with a gas introduction tube, a thermometer, a condenser, and a stirrer, and the vessel was purged with nitrogen gas. Then, the inside of the reaction vessel was heated to 80°C, 200 parts of HNBR1 was added, and the mixture was stirred until the hydrogenated nitrile butadiene rubber was completely dissolved. Then, 20 parts by mass of an NaOH dispersion was added, and the mixture was stirred while adding air. The reaction vessel was heated while maintaining the temperature at 80°C for 12 hours to obtain a copolymer (X), copolymer (A1), and a resin composition (R-1) containing an alkali metal. Based on a total content of 100% by mass of the alkylene structural unit and the nitrile group-containing structural unit in the copolymer (A1), the alkylene structural unit content was 66% by mass, the nitrile group-containing structural unit content was 34% by mass, the number average molecular weight (Mn) was 18,000, the weight average molecular weight (Mw) was 30,000, and the Z average molecular weight (Mz) was 49,000. In addition, other structural units constituting the copolymer (A1) were 3% by mass or less based on 100% by mass of the copolymer (A1). Also, the alkali metal content in the resin composition was 700 ppm.

[0164] (Examples 1-2 to 1-9), (Comparative Examples 1-1 to 1-5, 1-7 to 1-9) Resin compositions (R-2 to R-9) containing copolymer (X) and the like shown in Table 1 and comparative resin compositions (RC-1 to RC-5, RC-7 to RC-9) were obtained in the same manner as in Example 1-1, except that the conditions listed in Table 1 were changed.

[0165] (Example 1-10) The resin composition 9 prepared in Example 1-9 was subjected to a three-pass dispersion treatment using a high-pressure homogenizer (manufactured by Sugino Machine, Starburst Labo). The dispersion treatment was carried out at a nozzle diameter of 0. 17 mm and a pressure of 150 Mpa to obtain a resin composition (R-10) containing copolymer (E2).

[0166] (Example 1-11) The resin composition 9 prepared in Example 1-9 was subjected to a five-pass dispersion treatment using a high-pressure homogenizer (manufactured by Sugino Machine, Starburst Labo). The dispersion treatment was carried out at a nozzle diameter of 0.17 mm and a pressure of 150 Mpa to obtain a resin composition (R-11) containing copolymer (E3).

[0167] (Example 1-12) HNBR1 was subjected to a five-pass dispersion treatment using a high-pressure homogenizer (manufactured by Sugino Machine, Starburst Labo). The dispersion treatment was carried out at a nozzle diameter of 0.17 mm and a pressure of 150 Mpa to obtain a resin composition (R-12) containing copolymer (A4).

[0168] (Comparative Example 1-6) The comparative resin composition 5 prepared in Comparative Example 1-5 was subjected to a five-pass dispersion treatment using a high-pressure homogenizer (manufactured by Sugino Machine, Starburst Labo). The dispersion treatment was carried out at a nozzle diameter of 0.17 mm and a pressure of 150 Mpa to obtain a resin composition (RC-6) containing copolymer (E5).

[0169] Table 2 shows the content rates of the alkylene structural unit and the nitrile group-containing structural unit, based on a total content rate of 100% by mass of the alkylene structural unit and the nitrile group-containing structural unit. In addition, for any of the copolymers, the content of other structural units constituting the copolymer was 3% by mass or less based on 100% by mass of the copolymer).

[0170]

Table 1

[0171] Table 2 shows the evaluation results of the resin compositions prepared in Examples 1-1 to Comparative Examples 1-9.

[0172]

Table 2

[0173] (Example 2-1) 87.75 parts of N-methyl-2-pyrrolidone (NMP) and 8.75 parts of resin composition (R-1) were added to a stainless-steel container and stirred using a disperser. Then, 3.5 parts of carbon nanotubes (manufactured by JEIO, JENOTUBE6A) were weighed and added while stirring with a disperser. A fine emulsifier screen was attached to a high-shear mixer (L5M-A, manufactured by SILVERSON), and batch dispersion was carried out at a speed of 9000 rpm until the whole became uniform and the dispersion particle size became 200 μm or less as measured by a grind gauge. After that, a carbon material preliminary dispersion composition was prepared through a high-magnetic-force magnet filter (manufactured by Aisin, surface magnetic flux density 17000 gauss). Further, thereafter, the carbon material preliminary dispersion composition was fed, and a circulating dispersion treatment with a residence time of 10 minutes (bead filling rate 80%, peripheral speed 13 m / s) was carried out using a bead mill (manufactured by Ashizawa Fine Tech Co., Ltd., Mugunflow (registered trademark)) filled with zirconia beads having a diameter of 1.0 mmφ. The number of circulation times was 50. Subsequently, the liquid to be dispersed was supplied to a high-pressure homogenizer (manufactured by Sugino Machine, Starburst Turbo), and a 15-pass dispersion treatment was carried out. The dispersion treatment was carried out using a single-nozzle chamber at a nozzle diameter of 0.25 mm and a pressure of 100 Mpa. After that, the liquid to be dispersed was supplied to an electromagnet (manufactured by Daibao Magnetic Co., Ltd., EMF-100S, magnetic flux density 16000 gauss, spatial volume 1.7 L, diameter: 10 cm, thickness 1.3 cm, equipped with 31 grid screens), and a 3-pass treatment was carried out. Then, it was passed through two depth filters (manufactured by 3M, PP non-woven fabric depth cartridge NT-T series, filtration accuracy 20 μm) installed in series to obtain Carbon Material Dispersion Composition 1.

[0174] (Examples 2-2 to 2-16), (Comparative Examples 2-1 to 2-9) Carbon Material Dispersion Compositions 2 to 16 and Comparative Carbon Material Dispersion Compositions 1 to 9 were obtained in the same manner as in Example 2-1, except that the dispersion conditions, carbon material, resin composition, addition amount of the resin composition, and NMP listed in Table 3 were changed.

[0175]

Table 3

[0176] Table 4 shows the evaluation results of the carbon material dispersion compositions prepared in Examples 2-1 to 2-16 and Comparative Examples 2-1 to 2-9.

[0177]

Table 4

[0178] (Example 3-1) In a plastic container with a volume of 150 cm 3 , 18.8 parts by mass of an NMP solution in which 8% by mass of PVDF (polyvinylidene fluoride, manufactured by Solvey, Solef#5130) was dissolved and 14.5 parts by mass of NMP were weighed. Then, 11.4 parts by mass of a carbon material dispersion composition (carbon material dispersion composition 1) was added, and using a rotation / revolution mixer (Avatorem, ARE-310), it was stirred at 2000 rpm for 30 seconds. Further, 98.1 parts by mass of a positive electrode active material (manufactured by BASF Toda Battery Materials Co., Ltd., HED (registered trademark) NCM-111 1100) was added, and using a rotation / revolution mixer (Avatorem, ARE-310), it was stirred at 2000 rpm for 2.5 minutes to obtain a composite material slurry (composite material slurry 1).

[0179] Subsequently, the composite material slurry (composite material slurry 1) was applied onto an aluminum foil using an applicator so that the basis weight per unit of the electrode was 20 mg / cm 2 , and then the coating film was dried in an electric oven at 120°C ± 5°C for 25 minutes to obtain an electrode film (electrode film 1). Then, the electrode film (electrode film 1) was subjected to rolling treatment using a roll press (manufactured by Sank Metal, 3t hydraulic roll press) to obtain a positive electrode (positive electrode 1). The basis weight per unit of the composite material layer was 20 mg / cm 2 , and the density of the composite material layer after the rolling treatment was 3.1 g / cc.

[0180] (Examples 3-2 to 3-5, Examples 3-8 to 3-16) (Comparative Examples 3-1 to 3-9) In the same manner as in Example 3-1, except that Carbon Material Dispersion Composition 2 to 16 and Comparative Carbon Material Dispersion Composition 1 to 9 were used instead of Carbon Material Dispersion Composition 1, composite material slurries 2 to 16, Comparative Composite Material Slurries 1 to 9, Electrode Films 2 to 16, Comparative Electrode Films 1 to 9, Positive Electrodes 2 to 16, and Comparative Positive Electrodes 1 to 9 were obtained.

[0181] (Example 3-6) In a plastic container with a volume of 150 cm 3 , 18.8 parts by mass of an NMP solution in which 8% by mass of PVDF (polyvinylidene fluoride, manufactured by Solvey, Solef#5130) was dissolved and 18.9 parts by mass of NMP were weighed. Then, 7.1 parts by mass of a carbon material dispersion composition (carbon material dispersion composition 1) was added, and using a rotation-revolution mixer (Avatore Rentaro, ARE-310), it was stirred at 2000 rpm for 30 seconds. Subsequently, 98.1 parts by mass of a positive electrode active material (manufactured by BASF Toda Battery Materials Co., Ltd., HED (registered trademark) NCM-111 1100) was added, and using a rotation-revolution mixer (Avatore Rentaro, ARE-310), it was stirred at 2000 rpm for 2.5 minutes to obtain a composite material slurry (composite material slurry 6).

[0182] Subsequently, the composite material slurry (composite material slurry 6) was applied onto an aluminum foil using an applicator so that the basis weight per unit of the electrode was 20 mg / cm 2 . After that, the coating film was dried in an electric oven at 120 °C ± 5 °C for 25 minutes to obtain an electrode film (electrode film 6). Then, the electrode film (electrode film 1) was subjected to rolling treatment using a roll press (manufactured by Sanku Metal, 3t hydraulic roll press) to obtain a positive electrode (positive electrode 6). Note that the basis weight per unit of the composite material layer was 20 mg / cm 2 , and the density of the composite material layer after the rolling treatment was 3.1 g / cc.

[0183] (Example 3-7) In a plastic container with a volume of 150 cm 3Into a plastic container, 18.8 parts by mass of an NMP solution in which 8% by mass of PVDF (polyvinylidene fluoride, manufactured by Solvey, Solef#5130) was dissolved and 21.6 parts by mass of NMP were weighed. Then, 5.0 parts by mass of a carbon material dispersion composition (carbon material dispersion composition 1) was added, and using a rotary-revolution mixer (Avatore Rentaro, ARE-310), it was stirred at 2000 rpm for 30 seconds. Subsequently, 97.5 parts by mass of a positive electrode active material (manufactured by BASF Toda Battery Materials Co., Ltd., HED (registered trademark) NCM-111 1100) was added, and using a rotary-revolution mixer (Avatore Rentaro, ARE-310), it was stirred at 2000 rpm for 2.5 minutes to obtain a composite material slurry (composite material slurry 7).

[0184] Subsequently, the composite material slurry (composite material slurry 7) was applied onto an aluminum foil using an applicator so that the basis weight per unit of the electrode was 20 mg / cm 2 Then, the coating film was dried in an electric oven at 120°C ± 5°C for 25 minutes to obtain an electrode film (electrode film 7). Thereafter, the electrode film (electrode film 1) was subjected to rolling treatment using a roll press (manufactured by Sanku Metal, 3t hydraulic roll press) to obtain a positive electrode (positive electrode 6). Note that the basis weight per unit of the composite material layer was 20 mg / cm 2 and the density of the composite material layer after the rolling treatment was 3.1 g / cc.

[0185] Table 5 shows the evaluation results of the electrode films prepared in Examples 3-1 to 3-3-16 and Comparative Examples 3-1 to 3-9.

[0186]

Table 5

[0187] (Example 4-1) The positive electrode (positive electrode 1) and the standard negative electrode were each punched out to 45 mm × 40 mm and 50 mm × 45 mm, and a separator (porous polypropylene film) inserted therebetween was inserted into an aluminum laminate bag and dried in an electric oven at 60°C for 1 hour. Thereafter, in a glove box filled with argon gas, an electrolytic solution (a mixed solvent prepared by mixing ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate at a ratio of 1:1:1 (volume ratio), and further, as an additive, 2 parts by mass of VC (vinylene carbonate) was added to 100 parts by mass of the mixed solvent, and then LiPF6 was dissolved at a concentration of 1 M non-aqueous electrolytic solution) was injected in an amount of 2 mL, and then the aluminum laminate was sealed to fabricate a laminate-type lithium ion secondary battery (secondary battery 1).

[0188] (Examples 4-2 to 4-16, Comparative Examples 4-1 to 4-9) Laminate-type lithium ion secondary batteries (secondary batteries 2) to (comparative secondary battery 9) were fabricated in the same manner as the fabrication of the laminate-type lithium ion secondary battery (secondary battery 1), except that the positive electrode listed in Table 6 was changed.

[0189]

Table 6

[0190] In the above examples, a resin composition containing a copolymer (X) and an alkali metal in an amount of 50 ppm or more and less than 10,000 ppm, and having a resistivity of 5,000 Ω·cm or more and 25,000 Ω·cm or less when the content rate of the copolymer was 8% by mass with respect to N-methyl-2-pyrrolidone was used. In the examples, compared with the comparative examples, a lithium ion secondary battery excellent in the viscosity stability over time of the carbon material dispersion composition and excellent in secondary battery characteristics, particularly high temperature cycle characteristics, was obtained. Therefore, it has become clear that the present invention can provide a lithium ion secondary battery having high capacity, high output, and high durability, which are difficult to achieve with conventional carbon material dispersion compositions. The vehicle having the lithium ion secondary battery of the present invention has high charge and discharge performance and excellent high temperature cycle characteristics, so that a vehicle with high safety and improved fuel efficiency can be obtained.

[0191] As described above, the present invention has been described with reference to the embodiments, but the present invention is not limited thereto. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the invention.

Claims

1. A resin composition comprising a copolymer (X) having an alkylene structural unit and a nitrile group-containing structural unit, and an alkali metal, wherein the content of the alkali metal is 50 ppm or more and less than 10,000 ppm, and the resistivity of the resin composition when the non-volatile content is adjusted to 8% by mass with N-methyl-2-pyrrolidone is 5,000 Ω·cm or more and 25,000 Ω·cm or less.

2. The resin composition according to Claim 1, wherein the Z-average molecular weight of the copolymer (X) is 20,000 or more and 200,000 or less.

3. The resin composition according to Claim 1, wherein the ratio (Mz / Mw) of the Z-average molecular weight (Mz) to the weight-average molecular weight (Mw) of the copolymer (X) is 2.0 or less.

4. A carbon material dispersion composition comprising the resin composition according to any one of Claims 1 to 3 and a carbon material.

5. A composite material slurry comprising the carbon material dispersion composition according to Claim 4 and an active material.

6. An electrode film formed by coating the composite material slurry according to Claim 5.

7. A secondary battery comprising the electrode having the electrode film according to Claim 6 and an electrolyte.

8. A vehicle comprising the secondary battery according to Claim 7.

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