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, a secondary battery including an electrode having the electrode film and 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 a non-aqueous electrolyte, 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 due to the expansion and contraction of the electrode film. In order to maintain a 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 are one type of nanocarbon. However, carbon materials having a large specific surface area have a strong cohesive force, and thus 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 Document 1 and Patent Document 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 hydrogenated nitrile rubber. 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 Document 3 and Patent Document 4 propose that by using a binder composition for an electrode containing 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 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 has been difficult to highly concentrate and disperse carbon materials with a large specific surface area.

[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 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, to provide a composite slurry capable of obtaining an electrode film with high conductivity and adhesion, and more specifically, 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 intensively studied to solve the above problems. The inventors of the present invention have found that by using 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, and the resistivity of the resin composition when the non-volatile content is 8% by mass with N-methyl-2-pyrrolidone is in a specific range, the above problems can be solved.

[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, The resin composition is 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〕, 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 〔1〕 or 〔2〕, 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 〔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. Accordingly, 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 the present invention is not limited thereto. 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, the 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 contained solvent.

[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 where the carbon material and the electrode active material are intentionally added to the resin composition. Based on the non-volatile component amount of the resin composition (100% by mass), 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. Moreover, this is a concept excluding the state where the electrode active material is intentionally added to the carbon material dispersion composition. Based on the non-volatile component amount of the carbon material dispersion composition (100% by mass), 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. Unless otherwise noted, each of the various components appearing in this specification may be used independently 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. Moreover, the content of the alkali metal is 50 ppm or more and less than 10,000 ppm. Further, when this resin composition is made to have a nonvolatile 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 virtue of being such a resin composition, a dispersion composition excellent in the dispersibility of the dispersed material and having good stability can be obtained. Among others, 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 powder coated with these metals, powders of metal oxides such as silver oxide, indium oxide, tin oxide, zinc oxide, ruthenium oxide, etc., inorganic powder 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, etc.

[0022] When the resin composition of the present invention has a nonvolatile 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, good dispersibility and good electrode characteristics can be achieved simultaneously. In addition, for the measurement of resistivity, the nonvolatile content of the resin composition is measured in advance, N-methyl-2-pyrrolidone is added so that the nonvolatile content is 8% by mass, and they are mixed to prepare a sample for measuring 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 a 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 changes 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 an alkali metal compound is contained in the resin composition, precipitation of the alkali metal compound is suppressed, and the stability is more excellent.

[0025] (Copolymer (X)) The 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 the 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, and more preferably 80% by mass or more. When the copolymer (X) is a modified copolymer, from the viewpoint of the dispersibility of the dispersed substance, based on 100% by mass of the 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. Further, 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, and 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 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, and more preferably 3% by mass or less, based on 100% by mass of the 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 significantly decrease.

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

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

[0029] The copolymer (X) may be a copolymer modified by adding 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 ratios of the alkylene structural unit and the nitrile group-containing structural unit possessed by the modified copolymer (X) are within the above ranges. The content ratios 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) of the present 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 easily proceeds, and the wetting of the dispersed material to the solvent easily proceeds.

[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 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 by a filter or a magnet can be improved. The number-average molecular weight (Mn), weight-average molecular weight (Mw), and 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 a weight and is a value that is easily affected by high molecular weights. The copolymer (X) has a molecular weight distribution, and the low molecular weight component functions to improve the wettability of the dispersed material. Also, the high molecular weight component functions 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 becomes easy to wet, making the dispersion likely to proceed. Also, since the viscosity of the carbon material dispersion composition described later is lowered, when using a disperser using media such as a bead mill, the dispersion media moves 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 target degree of dispersion be adjusted, but 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), modification of the copolymer, or applying 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 mechanical shear stress.

[0036] The polydispersity index (Mw / Mn) of the copolymer (X) in this 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 easily proceeds, 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 it is easy to obtain a dispersion composition with good dispersion stability of the material to be dispersed.

[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, and is 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 of a structural unit having a nitrile group.

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

[0041] General formula (1A) [Chemical formula]

[0042] In 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 contains a structural unit represented by the following general formula (1B).

[0044] General formula (1B) [Chemical formula]

[0045] In general formula (1B), n represents an integer of 1 or more. n is preferably 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 units derived from the conjugated diene monomer" may be referred to as "conjugated diene monomer units", and the monomer units derived from other monomers may be similarly omitted. Then, by hydrogenating the conjugated diene monomer units, at least a part of the conjugated diene monomer units is converted into alkylene structural units. Hereinafter, "hydrogenation" may be referred to as "hydrohydrogenation". The finally obtained copolymer contains, as alkylene structural units, units obtained by hydrogenating the conjugated diene monomer units.

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

[0050] Among these, the method of (1a) is preferred because the copolymer can be easily produced. 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 preferred. The alkylene structural unit preferably includes a structural unit obtained by hydrogenating a conjugated diene monomer unit (hydrogenated conjugated diene monomer unit), and more preferably includes 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, etc.

[0053] In the method of (1b), the number of carbon atoms of the α-olefin monomer is 2 or more, preferably 3 or more, and more preferably 4 or more. The number of carbon atoms of the α-olefin monomer is preferably 6 or less, and 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, and 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 dispersed substance and the affinity for the dispersion medium can be controlled, and the dispersed substance can be stably present in the dispersion medium. In addition, the affinity of the copolymer for the electrolytic solution can also be controlled, and problems such as the copolymer dissolving in the electrolytic solution in the battery and increasing the resistance of the electrolytic solution can be prevented.

[0056] [Nitrile group-containing structural unit] The nitrile group-containing structural unit is a structural unit containing a nitrile group, preferably contains a structural unit containing an alkylene structure substituted by a nitrile group, and more preferably contains 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 contain a structural unit containing (or consisting only of) 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 contains 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 ((2a) method) can preferably be 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 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 rate of the nitrile group-containing structural unit is preferably 25% by mass or more and 50% by mass or less, more preferably 30% by mass or more and 45% by mass or less, and still more preferably 35% by mass or more and 45% by mass or less, based on 100% by mass of the total content rate of the alkylene structural unit and the nitrile group-containing structural unit. By setting the content rate 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. Also, the affinity of the resin composition to the electrolyte can be controlled, and problems such as the resin composition dissolving in the electrolyte and increasing the resistance of the electrolyte in the battery can be prevented.

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

[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 it with an alkali metal compound as a basic compound or applying a shear stress to the copolymer, and there is an effect that the dispersibility of the dispersed substance can be improved.

[0067] The alkali metal is contained in the resin composition by an alkali metal contained in a monomer used for synthesizing the copolymer or copolymer (X) before modification, an alkali metal compound used for modifying the copolymer, an alkali metal compound used as an additive for pH adjustment, etc., or a solvent. 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, catalyst, additive, 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 the method described in the examples using an ICP emission spectroscopic analyzer.

[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, etc. 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] (Manufacturing method of resin composition) The manufacturing method of the resin composition of this embodiment is not particularly limited, and the resin composition may be manufactured by any method. For example, a method of preparing a copolymer by a polymerization reaction using a monomer composition containing a conjugated diene monomer and a nitrile group-containing monomer, and hydrogenating the conjugated diene monomer units of the copolymer to obtain a resin composition containing a copolymer (X) can be mentioned. 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 shear stress may be applied thereto to obtain a resin composition containing a 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 making the resistivity of the resin composition be 5,000 Ω·cm or more and 25,000 Ω·cm or less when the nonvolatile 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 applying shear stress using the above-mentioned crusher, <3> a method of applying shear stress to a copolymer using a crusher or the like and then adding an alkali metal or an alkali metal compound, and the like. Among them, the methods <2> or <3> are preferable, and it is preferable to use an alkali metal compound having a maximum particle size of 150 μm or less, particularly 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 material.

[0072] <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 is preferable to include 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 that satisfies the above requirements, the copolymer before modification is preferably dissolved and used in an amide-based polar solvent 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, 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 excellent effects when a part of the structural units 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 to modify 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 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, as well as the density and particle size of the alkali metal compound, are important in controlling the dispersion stability of the dispersed material. 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. Conventionally known grinders 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 dispersed material 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 the stability over time of the carbon material dispersion composition and the composite material slurry described below may decrease.

[0079] A grinder 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, grinders such as mortars, pin mills, hammer mills, pulperizers, attritors, jet mills, cutter mills, ball mills, bead mills, colloid mills, conical mills, disk mills, edge mills, wonder crushers, vibration mills, ultrasonic homogenizers, and high-shear mixers 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. Further, it preferably contains 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. Also, 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 fibers, 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, and include 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 necessarily have to be a graphite structure. For example, carbon nanotubes having side walls with an amorphous structure can also be used as the carbon material.

[0084] The average outer diameter of the carbon nanotubes 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, and 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 conductive material in the electrode can be reduced. Thereby, the degree of freedom in battery design, such as increasing the amount of active material and binder resin, is increased. Furthermore, during the preparation of the composite slurry, the composite of the active material and the carbon nanotubes easily proceeds, so it is easy to obtain an electrode film having a homogeneous conductive network in which the active material surface is coated with carbon nanotubes, 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] When the G / D ratio (peak ratio of G-band and D-band) of the carbon nanotubes is such that, in the Raman spectrum, the maximum peak intensity in the range of 1560 cm -1 ~1600 cm -1 is G, and the maximum peak intensity in the range of 1310 cm -1 ~1350 cm -1 is D, the G / D ratio is preferably 0.5 to 10, and more preferably 0.7 to 4.5. When the G / D ratio of the carbon nanotubes is within the above range, the contact resistance between the carbon nanotubes is considered to be small, and good conductivity is likely to be obtained. In addition, it is 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 becomes 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 device (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 is likely to be good, and a secondary battery having excellent rate characteristics and cycle characteristics is likely to be obtained.

[0088] The carbon nanotubes are preferably those in which metal foreign particles are removed by using an electromagnet and magnetic force. For example, it is preferable to set an electromagnet in the grinding process or filling process of the carbon nanotubes and pass the carbon nanotubes through to remove the metal foreign particles. The higher the carbon purity of the carbon nanotubes, the better. Among 100% by mass of the carbon nanotubes, it is preferably 98.0% by mass or more, more preferably 99.5% by mass or more, further preferably 99.8% by mass or more, and particularly preferably 99.9% by mass or more. That is, the lower the content rate of the metal foreign particles, the better. Among 100% by mass of the carbon nanotubes, it is preferably 2.0% by mass or less, more preferably 0.5% by mass or less, further preferably 0.2% by mass or less, and particularly preferably 0.1% by mass or less. By using carbon nanotubes produced by a production method that does not use a metal catalyst as a core, or carbon nanotubes obtained by a purification method such as a conventionally known acid treatment, the content ratio of metal foreign particles is made 0.5 mass% or less with respect to 100 mass% of the carbon nanotubes, whereby the content of 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 in the manner 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 more other solvents may be mixed with the high dielectric constant solvent and used.

[0090] As the high dielectric constant solvent, 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 contains 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, etc., and is preferably 2.5 or more at 20°C. By using the solvent as a high dielectric constant 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] In this embodiment, the solvent content 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 easily obtained, and a carbon material dispersion composition excellent in dispersion stability is easily obtained. By using a carbon material dispersion composition excellent in dispersion stability, an electrode film having 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 and the like can be used. For example, mixers such as a disper, a homomixer, a planetary mixer, homogenizers (Advanced Digital Sonifer (registered trademark), MODEL 450DA manufactured by BRANSON, "Clear Mix" manufactured by M. Technique Co., Ltd., "Film Mix" manufactured by PRIMIX Co., Ltd., "Abramic Mix" manufactured by Silver Sonics Co., Ltd., etc.), paint conditioners (manufactured by Red Devil), 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 Ehrig Co., Ltd., etc.), media type dispersers such as coball mills, high-pressure homogenizers ("Genius PY" manufactured by GEA Niro Soavi, "Starburst" manufactured by Sugino Machine Ltd., "Nanomizer" manufactured by Nanomizer Co., Ltd., etc.), media-less dispersers such as "Clear SS-5" manufactured by M. Technique Co., Ltd., "MICROS" manufactured by Nara Machinery Co., Ltd., and other roll mills, etc., but are 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 (assuming the mass of the carbon material dispersion composition is 100% by mass), 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.

[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 (assuming the mass of the carbon material is 100% by mass), 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. 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 2000 mPa·s or less, more preferably 200 mPa·s or more and 1000 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 at 25°C and a rotor rotation speed of 100 rpm using a B-type viscometer, is preferably 500 mPa·s or more and 6000 mPa·s or less, more preferably 500 mPa·s or more and 3000 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 ratio 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, it is possible to determine the necessary and sufficient amount of the resin composition in order to obtain a carbon material dispersion composition with excellent dispersion stability.

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

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

[0103] (Magnetic separation step) As a method for removing metal foreign 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, it is preferable to set an electromagnet and pass the carbon material dispersion composition through it to remove metal foreign particles.

[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 Elyz Magnetics Co., Ltd., EMF-100S, EMF-150S, EMF-250S, EMF-300S manufactured by Daiho Magnetic Co., Ltd., etc. can be used.

[0106] The flow rate when the carbon material dispersion composition contacts the electromagnet is preferably 1 L / min or more and 300 L / min or less, and more 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 most metal foreign particles are not spherical but 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 nonwoven 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. When a filter with a small pore diameter is used to increase the removal rate of metal foreign particles in the carbon material dispersion composition, the removal efficiency of metal foreign particles may decrease due to clogging of the carbon material. On the other hand, when the carbon material dispersion composition is filtered with a filter within the above range, since the removal efficiency of metal foreign particles is high when using the filter, a carbon material dispersion composition with few metal foreign particles can be easily obtained.

[0112] ≪Composite Material Slurry≫ The composite material slurry of this 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] A binder resin is a resin used to bind between substances of carbon materials. The binder resin is not particularly limited. For example, polymers or copolymers containing, as constituent units, fluororesins, ethylene, propylene, vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylic esters, methacrylic acid, methacrylic esters, acrylonitrile, styrene, vinyl butyral, vinyl acetal, vinyl pyrrolidone, etc.; polyurethane resins, polyester resins, phenol resins, epoxy resins, phenoxy 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, etc. can be mentioned. 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] An active material is a material that serves as the basis of a 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 sometimes be simply referred to as "active material". An active material is a material that serves as the basis of a 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, and metal compounds such as metal oxides and metal sulfides capable of doping or intercalating lithium ions or 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 blue compounds, etc. can be mentioned. Specifically, transition metal oxide powders such as MnO, V2O5, V6O 13 , TiO2, etc., composite oxide powders of lithium and transition metals such as lithium nickelate, lithium cobaltate, lithium manganate with a layered structure, and lithium manganate with a spinel structure, lithium iron phosphate-based materials which are phosphate compounds with an olivine structure, transition metal sulfide powders such as TiS2 and FeS, sodium iron oxide, sodium manganate, sodium chromate, sodium nickelate with a layered structure, and sodium iron phosphate-based materials which are phosphate compounds with an olivine structure, etc. can be mentioned. Also, conductive polymers such as polyaniline, polyacetylene, polypyrrole, and polythiophene can 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, metallic Li, alloy systems such as its alloys of tin alloy, silicon alloy, and lead alloy, metal oxide systems such as LiXFe2O3, LiXFe3O4, LiXWO2 (x is a number where 0 < x < 1), lithium titanate, lithium vanadate, lithium silicate, conductive polymer systems such as polyacetylene and poly-p-phenylene, 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 and other carbon-based materials. 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 preferably 0.1 m 2 / g or more and 10 m 2 / g or less, more preferably 0.2 m 2 / g or more and 5 m 2 / g or less, and even more preferably 0.3 m 2 / g or more and 3 m 2 / g or less.

[0121] The average particle size 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 size of the active material as used herein refers to the average value of the particle sizes measured by an electron microscope for the active material.

[0122] To obtain the composite material slurry of the present embodiment, it is preferable to add the active material to the carbon material dispersion composition and then perform a dispersion treatment. 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 rate of the active material in the composite material slurry is preferably 20 mass% to 85 mass%, more preferably 40 mass% to 85 mass%, based on 100 mass% of the composite material slurry.

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

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

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

[0127] The water content in the composite material 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 material slurry. The electrode film is a coating film of the composite material slurry. For example, by coating and drying the composite material 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-shaped ones, and mesh-shaped current collectors can also be used.

[0130] As a method of applying a composite slurry onto a current collector to form an electrode film, there are no particular limitations, and known methods can be used. Specifically, examples include a die coating method, a dip coating method, a roll coating method, a doctor coating method, a knife coating method, a spray coating method, a gravure coating method, a screen printing method, or an electrostatic coating method. As the drying method, air drying, hot air drying, infrared heating, far-infrared heating, etc. can be used, but it is not particularly limited thereto.

[0131] Also, a rolling treatment may be performed using a lithographic press, a calendar roll, or the like 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 is less likely to progress. Furthermore, overcharge and over-discharge during charge and discharge are suppressed. Therefore, deterioration of battery characteristics due to electrolyte decomposition or metal precipitation is less likely to occur, and it has excellent cycle characteristics.

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

[0134] As the negative electrode, one obtained by applying and drying a composite slurry containing a negative electrode active material onto a current collector to produce 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) etc. can be mentioned, but it is not limited thereto, 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. can be mentioned. These solvents may be used alone respectively, or two or more kinds may be mixed and used.

[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 obtained by subjecting these to hydrophilic treatment.

[0138] The structure of the secondary battery of this embodiment is not particularly limited, but usually, it is composed of a positive electrode and 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 applications of the secondary battery of this embodiment are not particularly limited. 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 is, for example, one that recovers the regenerative energy of the vehicle's power.

[0140] Among them, since it is a secondary battery having high charge-discharge performance and excellent cycle characteristics, it can be suitably used for vehicles, and a vehicle with high safety and expected fuel consumption improvement can be obtained. Furthermore, excellent effects can also be exhibited 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, the rear of the vehicle body, or under the seat of the vehicle. It can be mounted below.

Examples

[0142] Examples are given below to explain the present invention more specifically. The present invention is not limited to the following examples as long as it does not exceed the gist. Unless otherwise specified, "parts" represents "parts by mass" and "%" represents "% by mass". Also, the compounding amounts in the table are in parts by mass. Note that the blanks in the table indicate that they are not compounded.

[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 48,000, 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 53,000, 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 75,000, 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 78,000, 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, BET 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 physical property measurement methods 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 carbon nanotubes can be calculated by observing and imaging carbon nanotubes with a transmission electron microscope, then selecting any 300 carbon nanotubes in the obtained observation photograph and measuring their respective outer diameters. Also, the average primary particle diameter of carbon black can be calculated by first observing and imaging 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 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] <Preparation 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. After that, using a rotation-revolution mixer (Sinkee Awatori Renkatarou, ARE-310), it was stirred at 2000 rpm for 30 seconds. Further, 92 parts by mass of artificial graphite (manufactured by Nippon Graphite Industries, 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 as active materials, 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 coated on a copper foil using an applicator so that the basis weight per unit of the electrode was 8 mg / cm 2 After coating, 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) to produce a standard negative electrode with a density of the composite layer of 1.6 g / cm 3

[0149] <Preparation of Alkali Metal Compound Dispersion> To a plastic container with a capacity of 2000 cm 3 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 after dispersion was carried out at a speed of 9000 rpm until the whole became uniform, it was passed through a nylon filter with an opening of 150 μm using a filtration bell to prepare a NaOH dispersion (NaOH concentration 5% by mass). The maximum flow rate of sodium hydroxide was 150 μm or less.

[0150] ≪Physical Property Measurement and Evaluation Method≫​ The physical property measurement and evaluation methods of the resin composition, carbon material dispersion composition, electrode film, and secondary battery used in each of 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 molecular weight measurement were prepared by the following method for measuring the number-average molecular weight (Mn), weight-average molecular weight (Mw), and Z-average molecular weight (Mz) of the copolymer. The resin composition was dropped into purified water to precipitate the copolymer, and the precipitate was collected by filtration with a Buchner funnel. After directly sprinkling purified water on the precipitate on the Buchner funnel to wash it, it was dissolved in tetrahydrofuran (THF) to obtain a solution. The obtained solution was dropped into purified water again to perform the above filtration and washing step using purified water, and the precipitate was redissolved in THF to obtain a sample for molecular weight measurement.

[0152] (Measurement of molecular weight) Using the sample for molecular weight measurement, it was measured by gel permeation chromatography (GPC) equipped with an RI detector. As the apparatus, HLC-8320GPC (manufactured by Tosoh Corporation) was used. Three separation columns were connected in series, and as the packing materials, "TSK-GEL SUPER AW-4000", "AW-3000", and "AW-2500" manufactured by Tosoh Corporation were used 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 performed at a flow rate of 0.6 mL / min. The concentration of the measurement sample was adjusted to 1% using a solvent consisting of the above eluent, and 20 microliters were injected. The average molecular weight is a polystyrene conversion value.

[0153] <Contents 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 rinsed by pouring purified water directly onto 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 (manufactured by Thermo Fisher Scientific, Nicolet iS5) to calculate the content of alkylene structural units and nitrile group-containing structural units in the copolymer in the resin composition.

[0154] (Measurement of resistivity of resin composition) (Preparation of sample for resistivity measurement) In a plastic container with a volume of 250 cm 3 of the resin composition and N-methyl-2-pyrrolidone were weighed 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 the sample for liquid resistance measurement, it was measured with a resistivity meter (IEST Yuaneng Technology (registered trademark), BATTERY SLURRY RESISTIVITY BSR2300) to calculate the resistivity at 25 °C. The value of the resistivity was based on the measurement result of the Middle channel.

[0155] (Measurement of alkali metal content in resin composition) After the resin composition was dried using a hot air oven, it was acid-decomposed using a microwave sample pretreatment device (manufactured by Milestone General, ETHOS1) to calculate the alkali metals (lithium, sodium, potassium) contained in the resin composition. The content of alkali metals was the sum of the contents of lithium, sodium, and potassium.

[0156] (Initial viscosity of carbon material dispersion composition) After leaving the carbon material dispersion composition standing in a thermostatic 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 of carbon material dispersion composition over time> After leaving the carbon material dispersion composition standing in a thermostatic 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 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, the 60-degree specular gloss was measured in accordance with JIS Z8741 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: △ (acceptable), less than 30 degrees: × (poor).

[0159] <Volume resistivity of electrode film> The composite slurry was applied using an applicator so that the coating amount per unit area of the electrode was 20 mg / cm 2After coating on the aluminum foil so as to achieve [a certain state], the coating film was dried in an electric oven at 120 °C ± 5 °C for 25 minutes. Then, using Loresta GP (MCP-T610, probe: AP2 probe (RMH333)) manufactured by Mitsubishi Chemical Analytech Co., Ltd., the surface resistivity (Ω / square) of the dried coating film was measured. 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 (DIGIMICRO MH-15M manufactured by NIKON Corporation), and used as the volume resistivity (Ω·cm) of the electrode film. The evaluation criteria for the volume resistivity were set 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] <Peeling Strength of Electrode Film> The composite slurry was coated on the aluminum foil using an applicator so that the basis weight per unit of the electrode was 20 mg / cm 2 After coating on the aluminum foil so as to achieve [a certain state], the coating film was dried in an electric oven at 120 °C ± 5 °C for 25 minutes. Then, it was cut into two rectangles of 90 mm × 20 mm with the coating direction as the major axis. For the measurement of the peeling strength, a tabletop tensile testing machine (Strograph E3 manufactured by Toyo Seiki Seisaku-sho, Ltd.) was used and evaluated by the 180-degree peeling 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 prepared battery electrode composite layer was adhered to the other side of the double-sided tape. While pulling it 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 peeling strength. The evaluation criteria for the peeling strength were set 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] <Rate Performance Evaluation of Lithium-Ion Secondary Battery> A laminated lithium-ion secondary battery was placed in a thermostatic 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 and constant voltage charging (cut-off current: 1.0 mA (0.02C)) at a charging current of 10 mA (0.2C) until the charging cut-off voltage reached 4.2V, constant current discharging was carried out at a discharging current of 10 mA (0.2C) until the discharging cut-off voltage reached 2.5V. After repeating this operation three times, constant current and constant voltage charging (cut-off current: 1.0 mA (0.02C)) was performed at a charging current of 10 mA (0.2C) until the charging cut-off voltage reached 4.2V, and then constant current discharging was carried out at discharging currents of 0.2C and 3C until the discharging cut-off voltage reached 2.5V to obtain the discharge capacities respectively. The rate performance can be represented by the ratio of the 0.2C discharge capacity to the 3C discharge capacity, as shown in Equation 2 below. (Equation 2) Rate performance = 3C discharge capacity / 0.2C discharge capacity after the third cycle × 100 (%) For the rate performance evaluation, those with a rate performance of 80% or more were rated as ◎ (excellent), those with a rate performance of 70% or more but less than 80% were rated as 〇 (good), those with a rate performance of 60% or more but less than 70% were rated as △ (fair), and those with a rate performance of 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 (cut-off current: 1.25 mA (0.025C)) at a charging current of 50 mA (1C) until the charging cut-off voltage reached 4.2V, constant current discharging was carried out at a discharging current of 50 mA (1C) until the discharging cut-off voltage reached 2.5V. This operation was repeated 200 times. 1C was defined as the current value that discharges the theoretical capacity of the positive electrode in one hour. The cycle performance can be represented by the ratio of the 100th 1C discharge capacity to the 3rd 1C discharge capacity at 45°C, as shown in Equation 3 below. (Equation 3) High temperature cycle performance = 100th 1C discharge capacity / 3rd 1C discharge capacity × 100 (%) For the high temperature cycle performance evaluation, those with a cycle performance of 90% or more were rated as ◎ (excellent), those with a cycle performance of 85% or more but less than 90% were rated as 〇 (good), those with a cycle performance of 80% or more but less than 85% were rated as △ (fair), and those with a cycle performance of less than 80% were rated as × (poor).

[0163] (Example 1-1) 780 parts by mass of NMP was charged into a reaction vessel equipped with a gas inlet tube, a thermometer, a condenser, and a stirrer, and replaced with nitrogen gas. Then, the inside of the reaction vessel was heated to 80°C, 200 parts of HNBR1 was added, and stirring was carried out until the hydrogenated nitrile butadiene rubber was completely dissolved. Then, 20 parts by mass of the NaOH dispersion was added, stirring was carried out while adding air, and heating was carried out while maintaining the reaction vessel at 80°C for 12 hours to obtain a copolymer (A1) which is a copolymer (X) 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 was 66% by mass, the content of the nitrile group-containing structural unit 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) and comparative resin compositions (RC-1 to RC-5, RC-7 to RC-9) containing the copolymer (X) and the like shown in Table 1 were obtained in the same manner as in Example 1-1, except that the conditions shown 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 the copolymer (E2).

[0166] (Example 1-11) The resin composition 9 prepared in Examples 1-9 was subjected to a 5-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 a copolymer (E3).

[0167] (Examples 1-12) HNBR1 was subjected to a 5-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 a copolymer (A4).

[0168] (Comparative Examples 1-6) The comparative resin composition 5 prepared in Comparative Examples 1-5 was subjected to a 5-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 a copolymer (E5).

[0169] Table 2 shows the content ratios of the alkylene structural unit and the nitrile group-containing structural unit based on a total content ratio of 100% by mass of the alkylene structural unit and the nitrile group-containing structural unit. In addition, for any copolymer, the other structural units constituting the copolymer were 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 performed at a speed of 9000 rpm until the whole became uniform and the dispersion particle size reached 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 magnetic filter (manufactured by Aisin, surface magnetic flux density of 17000 gauss). Further, the carbon material preliminary dispersion composition was fed, and a circulation-type dispersion treatment with a residence time of 10 minutes (bead filling rate of 80%, peripheral speed of 13 m / s) was performed using a bead mill (manufactured by Asazawa 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 performed. 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 Daiho Magnetic Co., Ltd., EMF-100S, magnetic flux density of 16000 gauss, spatial volume of 1.7 L, grid screen with a diameter of 10 cm and a thickness of 1.3 cm, equipped with 31 sheets), and a 3-pass treatment was performed. Then, it was passed through two depth filters (manufactured by 3M, PP non-woven fabric depth cartridge NT-T series, filtration accuracy of 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 (Avatomaro, 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 (Avatomaro, 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 Sanku 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 Compositions 2 to 16 and Comparative Carbon Material Dispersion Compositions 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 as per Table 5.

[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 (Avatoki Rintaro, 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 K.K., HED (registered trademark) NCM-111 1100) was added, and using a rotation-revolution mixer (Avatoki Rintaro, 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 3To 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 rotation-revolution mixer (Avatoremagoro, ARE-310), it was stirred at 2000 rpm for 30 seconds. After that, 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 rotation-revolution mixer (Avatoremagoro, 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 coated on 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). After that, 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 of the copolymer was 8% by mass with respect to N-methyl-2-pyrrolidone was used. In the examples, a lithium ion secondary battery having excellent viscosity stability over time of the carbon material dispersion composition and excellent secondary battery characteristics, particularly high-temperature cycle characteristics, was obtained as compared with the comparative examples. 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. A 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 by the above. 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, when the 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. The resin composition is characterized by this.

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 an electrode having the electrode film according to claim 6 and an electrolyte.

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

Images