Binder composition for electrochemical element, electrochemical element conductive material dispersion liquid, electrochemical element electrode slurry, electrochemical element electrode, and electrochemical element

Abstract

Provided is an electrode binder composition for an electrochemical element, which has excellent viscosity stability and enables formation of an electrode having excellent peel strength. The electrode binder composition of the present invention comprises: a polymer containing a monomer unit containing a nitrile group, N-methyl-2-pyrrolidone, and a halogenated hydrocarbon, the content of the halogenated hydrocarbon being 2 mass ppm or more and 400 mass ppm or less relative to the content of the polymer.

Description

TECHNICAL FIELD

[0001] The present application relates to a binder composition for an electrochemical element, an electroconductive material dispersion liquid for an electrochemical element, a slurry for an electrode of an electrochemical element, an electrode for an electrochemical element, and an electrochemical element. BACKGROUND

[0002] Electrochemical elements such as lithium ion secondary batteries, lithium ion capacitors, and electric double layer capacitors have characteristics of being small and light, having high energy density, and being capable of repeated charge and discharge, and have been used in a wide range of applications. Therefore, in recent years, improvements in battery components such as electrodes are being studied with the aim of further improving the performance of electrochemical elements.

[0003] Here, an electrode for an electrochemical element generally has a current collector and an electrode composite layer formed on the current collector. Furthermore, the electrode composite layer is formed by applying a slurry such as a binder composition containing an electrode active material, a binder composition containing a binding material, or the like to the current collector, and drying the applied slurry.

[0004] Therefore, in recent years, in order to achieve further improvement in the performance of electrochemical elements, improvements in binder compositions for forming electrode composite layers are being attempted. For example, research is being conducted on techniques that use a polymer containing a nitrile group-containing monomer unit as a binding material included in a binder composition (for example, refer to Patent Documents 1 and 2).

[0005] PRIOR ART DOCUMENTS

[0006] PATENT DOCUMENTS

[0007] Patent Document 1: International Publication No. 2016 / 103730;

[0008] Patent Document 2: International Publication No. 2017 / 010093. SUMMARY

[0009] PROBLEMS TO BE SOLVED BY THE INVENTION

[0010] Here, for a binder composition for an electrochemical element, it is required to maintain viscosity stability and to firmly adhere an electrode composite layer obtained using the binder composition to a current collector (i.e., to make the electrode exhibit excellent peel strength). Furthermore, in the above-described prior art, there is room for further improvement in terms of ensuring the viscosity stability of the binder composition and improving the peel strength of the electrode.

[0011] Therefore, an object of the present application is to provide a binder composition for an electrochemical element that is excellent in viscosity stability and enables the formation of an electrode excellent in peel strength.

[0012] Further, an object of the present application is to provide an electrochemical element electrode and an electrochemical element having the same.

[0013] Further, an object of the present application is to provide an electrochemical element electrode and an electrochemical element having the same.

[0014] Means for solving the problem

[0015] The present inventors have conducted intensive studies in order to solve the above problems. Then, the present inventors have found that a binder composition containing a polymer containing a monomer unit containing a nitrile group (hereinafter sometimes referred to simply as "nitrile-based polymer"), N-methyl-2-pyrrolidone (hereinafter sometimes referred to simply as "NMP"), and a halogenated hydrocarbon, and the amount of the halogenated hydrocarbon with respect to the nitrile-based polymer is within a prescribed range has excellent viscosity stability, and furthermore, an electrode composite layer formed using the binder composition can be firmly and tightly adhered to a current collector, thereby completing the present application.

[0016] That is, the present application is characterized in that an electrochemical element binder composition of the present application contains a polymer containing a monomer unit containing a nitrile group, N-methyl-2-pyrrolidone, and a halogenated hydrocarbon, and the content of the halogenated hydrocarbon with respect to the polymer is 2 mass ppm or more and 400 mass ppm or less. A binder composition containing a nitrile-based polymer, NMP, and a halogenated hydrocarbon, and the content of the halogenated hydrocarbon is within the above range has excellent viscosity stability, and furthermore, an electrode having excellent peel strength can be produced by using the binder composition.

[0017] In the present application, "containing a monomer unit" means "containing a repeating unit derived from the monomer in a polymer obtained using the monomer". In addition, the proportion of each monomer unit and / or structural unit in the polymer can be determined using 1 H-NMR and 13 C-NMR and the like nuclear magnetic resonance (NMR) method.

[0018] Further, in the present application, the "content of the halogenated hydrocarbon" can be determined by a gas chromatography method.

[0019] Here, in the electrochemical element binder composition of the present application, it is preferable that the peak width of the loss tangent tan δ in the viscoelastic properties of the above polymer be 5°C or more and 30°C or less. If the peak width of the loss tangent tan δ in the viscoelastic properties of the nitrile-based polymer is within the above range, the resistance of the electrode can be reduced and the electrochemical element can exhibit excellent cycle characteristics.

[0020] Further, in the present application, the "peak width of the tangent of the loss angle tan δ in the viscoelastic properties" can be measured using the method described in the examples.

[0021] Further, in the binder composition for an electrochemical element of the present application, it is preferable that the proportion of the molecular terminal composed of a linear alkyl group having 6 or more carbon atoms in the total molecular terminals of the above-mentioned polymer be 30% or more. In the plurality of molecular chains constituting the nitrile-based polymer, if 30% or more of the terminals are linear alkyl groups having 6 or more carbon atoms (in other words, if 30% or more of the terminals are linear alkyl groups having at least 6 carbon atoms connected in a row), the flexibility of the electrode can be improved and the resistance can be reduced, and the rate characteristics of the electrochemical element can be improved.

[0022] Further, in the present application, the "proportion of the molecular terminal composed of a linear alkyl group having 6 or more carbon atoms in the total molecular terminals of the polymer" can be measured using the method described in the examples.

[0023] Further, the present application has an object to advantageously solve the above-mentioned problems, and the electrochemical element electrode slurry of the present application is characterized by comprising an electrode active material and any one of the above-mentioned binder compositions for an electrochemical element. If an electrode slurry comprising an electrode active material and any one of the above-mentioned binder compositions for an electrochemical element is used, an electrode having excellent peeling strength can be produced.

[0024] Here, the electrochemical element electrode slurry of the present application is preferably such that the above-mentioned carbon-containing material comprises carbon nanotubes, the surface base amount of the above-mentioned carbon nanotubes is 0.01 mmol / g or more and 0.10 mmol / g or less, and the ratio of the surface acid amount of the above-mentioned carbon nanotubes to the above-mentioned surface base amount is 0.1 or more and 1.0 or less. As the carbon-containing material, if carbon nanotubes (hereinafter sometimes referred to simply as "CNT") having the above-mentioned properties are used, the dispersion stability of the electroconductive material dispersion liquid can be improved, and the resistance of the obtained electrode can be reduced, and the rate characteristics of the electrochemical element can be improved.

[0025] Further, in the present application, the "surface base amount" and the "surface acid amount" of the CNT can be measured using the method described in the examples.

[0026] Further, the present application has an object to advantageously solve the above-mentioned problems, and the electrochemical element electrode slurry of the present application is characterized by comprising an electrode active material and any one of the above-mentioned binder compositions for an electrochemical element. If an electrode slurry comprising an electrode active material and any one of the above-mentioned binder compositions for an electrochemical element is used, an electrode having excellent peeling strength can be produced.

[0027] Furthermore, in order to advantageously solve the above-mentioned problems, the present invention provides an electrode for electrochemical devices characterized by having an electrode composite material layer formed using the aforementioned electrode slurry for electrochemical devices. The electrode having the electrode composite material layer obtained using the aforementioned electrode slurry exhibits excellent peel strength.

[0028] Furthermore, with the aim of advantageously solving the above-mentioned problems, the electrochemical element of the present invention has the aforementioned electrode for electrochemical elements. The electrochemical element having the aforementioned electrode exhibits excellent element characteristics, such as rate capability.

[0029] Invention Effects

[0030] According to the present invention, an adhesive composition for electrochemical elements that exhibits excellent viscosity stability and is capable of forming electrodes with excellent peel strength can be provided.

[0031] Furthermore, according to the present invention, it is possible to provide a conductive material dispersion for electrochemical elements and a slurry for electrochemical element electrodes capable of forming electrodes with excellent peel strength.

[0032] Furthermore, according to the present invention, it is possible to provide an electrode for an electrochemical element with excellent peel strength and an electrochemical element having the electrode for an electrochemical element. Detailed Implementation

[0033] The embodiments of the present invention will now be described in detail.

[0034] Here, the binder composition for electrochemical elements of the present invention can be used in the preparation of slurries for electrochemical element electrodes. Furthermore, the binder composition for electrochemical elements of the present invention can be mixed with a carbon-containing material as a conductive material to prepare a dispersion of the conductive material for electrochemical elements of the present invention containing the binder composition for electrochemical elements and the carbon-containing material, which is then used to prepare slurries for electrochemical element electrodes. Moreover, the slurry for electrochemical element electrodes of the present invention prepared using the dispersion of the conductive material for electrochemical elements can be used in the formation of electrodes for electrochemical elements such as lithium-ion secondary batteries. Furthermore, the electrochemical element of the present invention is characterized by having an electrode for electrochemical elements of the present invention formed using the slurry for electrochemical element electrodes.

[0035] (Binder composition for electrochemical components)

[0036] The adhesive composition of the present invention contains a nitrile polymer and a haloalkane in N-methyl-2-pyrrolidone as a solvent, and optionally also contains other components. Here, in the adhesive composition of the present invention, the content of the haloalkane relative to the content of the nitrile polymer needs to be 2 ppm by mass or more and 400 ppm by mass or less.

[0037] Furthermore, the binder composition of the present invention exhibits excellent viscosity stability because the content of halogenated hydrocarbons is within the above-mentioned range, and if the binder composition is used, electrodes with excellent peel strength can be produced.

[0038] Furthermore, the reason why the adhesive composition of the present invention has excellent viscosity stability and enables the electrode to exhibit excellent peel strength is unclear, but it is speculated as follows.

[0039] The binder composition of the present invention contains halogenated hydrocarbons in an amount of 2 ppm by mass or more relative to the content of the nitrile polymer. In this way, by the effect of the included halogenated hydrocarbons in a predetermined amount or more, the oxide film present on the surface of the current collector made of aluminum or the like is destroyed when the electrode composite layer is formed, resulting in a strong and tight bond between the electrode composite layer and the current collector. On the other hand, according to the inventors' research, it has been clarified that when the amount of halogenated hydrocarbons is excessive, the halogenated hydrocarbons cause the binder composition to become unstable and thicken. In contrast, since the content of halogenated hydrocarbons in the binder composition of the present invention is 400 ppm by mass or less relative to the content of the nitrile polymer, the thickening caused by excessive halogenated hydrocarbons is suppressed, and the viscosity stability of the binder composition can be ensured.

[0040] <Nitrile Polymers>

[0041] As described above, nitrile polymers are polymers containing nitrile-based monomer units. Nitrile polymers function as a binder in electrode composite material layers formed using binder compositions, preventing active electrode materials from detaching from the current collector. Furthermore, nitrile polymers can also function as dispersants in conductive material dispersions prepared using binder compositions, enabling the dispersion of conductive materials such as carbon-containing materials.

[0042] <<Composition>>

[0043] Here, the nitrile polymer preferably contains alkylene structural units in addition to the monomer units containing nitrile groups. Alternatively, the nitrile polymer may also contain repeating units (other repeating units) other than the monomer units containing nitrile groups and the alkylene structural units.

[0044] Furthermore, in this invention, "alkylene structural unit" refers to "a unit consisting only of the general formula -C n H 2n -[where n is an integer greater than 2] represents the repeating unit composed of alkylene structures.

[0045] [Contains nitrile-based monomer units]

[0046] Examples of nitrile-containing monomers capable of forming nitrile-containing monomer units include α,β-ene unsaturated nitrile monomers. Specifically, there are no particular limitations on α,β-ene unsaturated nitrile monomers, as long as they are α,β-ene unsaturated compounds having a nitrile group; examples include acrylonitrile; α-haloacrylonitrile such as α-chloroacrylonitrile and α-bromoacrylonitrile; and α-alkylacrylonitrile such as methacrylonitrile and α-ethylacrylonitrile. Furthermore, a single nitrile-containing monomer can be used, or two or more can be used in any ratio. Among these, acrylonitrile is preferred.

[0047] Taking all repeating units in the nitrile polymer as 100% by mass, the content of nitrile-containing monomer units in the nitrile polymer is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less. If the content of nitrile-containing monomer units is within the above range, the solubility of the nitrile polymer in NMP can be sufficiently ensured, the viscosity stability of the binder composition can be further improved, and the dispersion stability of the conductive material dispersion can be improved. In addition, the peel strength of the electrode obtained using the binder composition can be further improved.

[0048] [alkylene structural unit]

[0049] The alkylene structural unit can be linear or branched. From the viewpoint of reducing electrode resistance and improving the rate performance of the electrochemical element, it is preferred that the alkylene structural unit is linear, i.e., a linear-chain alkylene structural unit. Furthermore, it is preferred that the alkylene structural unit has 4 or more carbon atoms (i.e., n in the above general formula is an integer of 4 or more).

[0050] Furthermore, there are no particular limitations on the method of introducing alkylene structural units into nitrile polymers, and methods such as (1) and (2) below can be cited as examples:

[0051] (1) A method for preparing a polymer from a monomer composition containing a conjugated diene monomer, and hydrogenating the polymer thereby converting the conjugated diene monomer unit into an alkylene structural unit;

[0052] (2) A method for preparing a polymer from a monomer composition containing a 1-olefin monomer.

[0053] Of these, method (1) is preferred because it readily produces nitrile polymers.

[0054] Examples of conjugated diene monomers include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, and 1,3-pentadiene, which are conjugated diene compounds with 4 or more carbon atoms. Among these, conjugated diene compounds with 4 or more carbon atoms are preferred, and 1,3-butadiene is more preferred. Specifically, the alkylene structural unit is preferably a structural unit obtained by hydrogenating a conjugated diene monomer unit (a conjugated diene hydride unit), more preferably a structural unit obtained by hydrogenating a conjugated diene monomer unit with 4 or more carbon atoms (a conjugated diene hydride unit with 4 or more carbon atoms), and even more preferably a structural unit obtained by hydrogenating a 1,3-butadiene monomer unit (a 1,3-butadiene hydride unit).

[0055] In addition, examples of 1-olefin monomers include ethylene, propylene, and 1-butene.

[0056] These conjugated diene monomers and 1-olefin monomers can be used individually or in combination of two or more in any ratio.

[0057] Furthermore, taking all repeating units in the nitrile polymer as 100% by mass, the content of alkylene structural units in the nitrile polymer is preferably 40% by mass or more, more preferably 45% by mass or more, even more preferably 50% by mass or more, preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less. It is speculated that if the content of alkylene structural units in the nitrile polymer is within the above range, the dispersion stability of the conductive material dispersion can be improved due to the increased affinity between carbon-containing materials such as CNTs and the nitrile polymer. In addition, since the nitrile polymer effectively coats carbon-containing materials such as CNTs, the device characteristics (e.g., cycling characteristics) of the electrochemical element can be improved.

[0058] In addition, when the nitrile polymer is a polymer obtained according to the method described in (1) above, the proportion of alkylene structural units and the total proportion of conjugated diene monomer units in the nitrile polymer preferably satisfy the above range.

[0059] —Other repeating units—

[0060] Other repeating units are not particularly limited, but examples include aromatic vinyl monomer units, monomer units containing acid groups, and (meth)acrylate monomer units. Additionally, nitrile polymers may contain one or more other repeating units.

[0061] In addition, in this invention, "(meth)acrylic acid" refers to acrylic acid and / or methacrylic acid.

[0062] Examples of aromatic vinyl monomers capable of forming aromatic vinyl monomer units include styrene, α-methylstyrene, p-tert-butylstyrene, butoxystyrene, vinyltoluene, chlorostyrene, and vinylnaphthalene. Furthermore, an aromatic vinyl monomer can be used alone or in combination of two or more in any ratio. Among these, styrene is preferred.

[0063] Examples of acid-containing monomers capable of forming acid-containing monomer units include monomers containing carboxylic acid groups, monomers containing sulfonic acid groups, and monomers containing phosphate groups. Furthermore, an acid-containing monomer can be used alone or in combination of two or more in any ratio.

[0064] Examples of monomers containing a carboxylic acid group include: monocarboxylic acids and their derivatives, dicarboxylic acids and their anhydrides, and their derivatives.

[0065] Examples of monocarboxylic acids include acrylic acid, methacrylic acid, and crotonic acid.

[0066] Examples of monocarboxylic acid derivatives include: 2-ethylacrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, and α-chloro-β-E-methoxyacrylic acid.

[0067] Examples of dicarboxylic acids include maleic acid, fumaric acid, and itaconic acid.

[0068] Examples of dicarboxylic acid derivatives include: methylmaleic acid, dimethylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid; nonyl maleate, decyl maleate, dodecyl maleate, octadecyl maleate, fluoroalkyl maleate, and other maleic acid monoesters.

[0069] Examples of anhydrides that are dicarboxylic acids include: maleic anhydride, acrylic anhydride, methylmaleic anhydride, and dimethylmaleic anhydride.

[0070] Furthermore, acid anhydrides that generate carboxylic acid groups through hydrolysis can also be used as monomers containing carboxyl groups. Among these, acrylic acid and methacrylic acid are preferred monomers containing carboxyl groups.

[0071] Examples of monomers containing sulfonic acid groups include: vinyl sulfonic acid, methyl vinyl sulfonic acid, (meth)allyl sulfonic acid, styrene sulfonic acid, ethyl (meth)acrylic acid-2-sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, and 3-allyloxy-2-hydroxypropanesulfonic acid.

[0072] In addition, in this invention, "(methyl)allyl" refers to allyl and / or methylallyl.

[0073] Examples of monomers containing phosphate groups include 2-(meth)acryloyloxyethyl phosphate, methyl-2-(meth)acryloyloxyethyl phosphate, and ethyl-(meth)acryloyloxyethyl phosphate.

[0074] In addition, in this invention, "(meth)acryloyl" refers to acryloyl and / or methacryloyl.

[0075] Examples of (meth)acrylate monomers capable of forming (meth)acrylate monomer units include, for example, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, tert-butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, stearyl acrylate, and other alkyl acrylates; and methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, tert-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n-tetradecyl methacrylate, stearyl methacrylate, and other alkyl methacrylates. Furthermore, a single (meth)acrylate monomer can be used alone, or two or more monomers can be used in any ratio.

[0076] In addition, taking all repeating units in the nitrile polymer as 100% by mass, the content of other repeating units in the nitrile polymer is preferably 0% by mass or more and 30% by mass or less, more preferably 0% by mass or more and 20% by mass or less, even more preferably 0% by mass or more and 10% by mass or less, and particularly preferably 0% by mass or more and 5% by mass or less.

[0077] <<Characteristics>>

[0078] Here, there are no particular limitations on the nitrile polymers, but the following properties are preferred.

[0079] [Iodine value]

[0080] First, the iodine value of the nitrile polymer is preferably 60 mg / 100 mg or less, more preferably 30 mg / 100 mg or less, even more preferably 20 mg / 100 mg or less, and particularly preferably 10 mg / 100 mg or less. If the iodine value of the nitrile polymer is 60 mg / 100 mg or less, the characteristics of the electrochemical device (cycle characteristics, rate performance, etc.) can be improved. Furthermore, the lower limit of the iodine value of the nitrile polymer is not particularly limited, and is, for example, 1 mg / 100 mg or more.

[0081] In addition, in this invention, the "iodine value" can be determined using the method described in the examples.

[0082] [Weight-average molecular weight]

[0083] Next, the weight-average molecular weight of the nitrile polymer is preferably 10,000 or more, more preferably 20,000 or more, more preferably 250,000 or less, more preferably 200,000 or less, and even more preferably 150,000 or less. If the weight-average molecular weight of the nitrile polymer is 10,000 or more, it is presumed that the dissolution of the nitrile polymer into the electrolyte is suppressed, thereby improving the cycle characteristics of the electrochemical element. On the other hand, if the weight-average molecular weight of the nitrile polymer is 250,000 or less, the viscosity stability of the binder composition and the dispersion stability of the conductive material dispersion can be further improved.

[0084] Furthermore, in this invention, the "weight-average molecular weight" can be determined using the method described in the examples.

[0085] [The proportion of molecules with straight-chain alkyl groups having 6 or more carbon atoms at the end of the chain]

[0086] Here, in the nitrile polymer, the proportion of molecular ends composed of straight-chain alkyl groups having 6 or more carbon atoms (hereinafter sometimes simply referred to as "molecular end C6 straight-chain ratio") is preferably 30% or more, more preferably 40% or more, further preferably 50% or more, and particularly preferably 65% ​​or more. When the total number of molecular ends in the plurality of molecular chains constituting the nitrile polymer is taken as 100%, if 30% or more of the ends contain straight-chain alkyl groups having 6 or more carbon atoms, it is presumed that the molecular ends become more mobile, increasing the entanglement of the molecular chains and thus improving the flexibility of the electrode. Furthermore, the electrode resistance can be reduced and the rate performance of the electrochemical element improved.

[0087] Here, the straight-chain alkyl group with 6 or more carbon atoms at the molecule's end is not particularly limited, and can be derived from monomers, polymerization initiators, polymerization catalysts, and / or chain transfer agents used in the preparation of nitrile polymers. Therefore, by changing their types and amounts, the ratio of C6 straight chains at the molecule's end can be controlled.

[0088] For example, in the preparation of nitrile polymers, the proportion of straight-chain alkyl compounds with 6 or more carbon atoms (such as 1-decylthiol) in the chain transfer agent used can be increased to improve the C6 straight-chain ratio at the molecular end.

[0089] In addition, when preparing nitrile polymers, compounds other than those with straight-chain alkyl groups having 6 or more carbon atoms (e.g., tert-dodecyl mercaptan with branched alkyl groups) can be used as chain transfer agents. However, when the proportion of such compounds in the chain transfer agent used is increased, the C6 straight-chain ratio at the molecular end usually decreases.

[0090] [Peak width of the loss tangent tanδ in viscoelastic properties]

[0091] Furthermore, the peak width of the loss tangent tanδ in the viscoelastic properties of the nitrile polymer is preferably 5°C or more and 30°C or less, more preferably 5°C or more and 25°C or less, and even more preferably 5°C or more and 18°C ​​or less. If the peak width of the loss tangent tanδ in the viscoelastic properties is within the above range, it is presumed that since the compositional distribution of the nitrile polymer is not uneven, it can swell uniformly in the electrolyte, thereby improving the cycle characteristics of the electrochemical element. In addition, the electrode resistance can be reduced.

[0092] Furthermore, the peak width of the loss tangent tanδ in the viscoelastic properties can be controlled within a preferred range by adding monomers such as nitrile-containing monomers in batches within the reaction system during the preparation of nitrile polymers. Additionally, by managing the preparation of nitrile polymers in a way that reduces the vibration amplitude of temperature changes, it is possible to control the width within a preferred range.

[0093] <<Preparation Methods of Nitrile Polymers>>

[0094] There are no particular limitations on the preparation method of nitrile polymers. Nitrile polymers can be manufactured by polymerizing, for example, a monomer composition containing one or more monomers in an aqueous solvent, followed by arbitrary hydrogenation. Furthermore, the proportion of each monomer in the monomer composition can be determined based on the proportion of desired repeating units (monomer units and / or structural units) in the polymer.

[0095] Furthermore, there are no particular restrictions on the polymerization method; any of the following methods can be used: solution polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, etc. In addition, as the polymerization reaction, any of the following reactions can be used: ionic polymerization, free radical polymerization, living free radical polymerization, various condensation polymerizations, addition polymerization, etc. Moreover, known emulsifiers, polymerization initiators, and chain transfer agents can be used as needed during polymerization. Furthermore, hydrogenation can be carried out using known methods.

[0096] Here, as a chain transfer agent, as described above, from the viewpoint of easily controlling the C6 linear chain ratio at the molecular end of the nitrile polymer within a preferred range, it is preferable to use a compound having a linear alkyl chain with 6 or more carbon atoms, and 1-decylthiol is particularly preferred.

[0097] The amount of chain transfer agent used also depends on the desired ratio of the C6 linear chains at the molecular ends and / or the weight-average molecular weight of the nitrile polymer. For example, if all the monomers used to prepare the nitrile polymer are taken as 100 parts by mass, the amount of chain transfer agent used is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, preferably 2 parts by mass or less, and more preferably 1.5 parts by mass or less.

[0098] Furthermore, the monomers used to prepare nitrile polymers can be added to the reaction system all at once. However, as mentioned above, from the viewpoint of easily controlling the peak width of the loss tangent (tanδ) in the viscoelastic properties of nitrile polymers, it is preferable to add them in at least two batches. Hereinafter, such batch polymerization methods will be described in terms of the first stage of polymerization and the subsequent second stage of polymerization.

[0099] [First-stage aggregation]

[0100] In the first stage of polymerization, all monomers used to prepare the nitrile polymer are used as 100% by mass, preferably 70% to 95% by mass, more preferably 80% to 90% by mass, to initiate the polymerization. Furthermore, if a chain transfer agent is used, it is preferable to add it to the reaction system during the first stage of polymerization.

[0101] Then, after initiating the first stage of polymerization, when the polymerization conversion rate of the added monomer preferably reaches 10% by mass or more and 50% by mass or less, more preferably 20% by mass or more and 40% by mass or less, a second stage of polymerization is carried out by adding monomer to the reaction system.

[0102] [Aggregation after Phase Two]

[0103] When adding monomers to the reaction system, there is no particular limitation on the number of additions, but two additions are preferred. In other words, it is preferable to carry out the second and third stages of polymerization after the first stage of polymerization.

[0104] In polymerizations following the second stage, monomers not added in the first stage of polymerization are added to the reaction system. Furthermore, if a third stage of polymerization is carried out in addition to the second stage, in the second stage of polymerization, all monomers used to prepare the nitrile polymer are used as 100% by mass, preferably with an additional 5% by mass and 10% by mass of monomers.

[0105] Furthermore, the monomers added in the polymerization after the second stage are preferably nitrile-containing monomers.

[0106] Furthermore, if a third stage of polymerization is carried out in addition to the second stage of polymerization, after the start of the second stage of polymerization, when the polymerization conversion rate of the added monomer preferably reaches 40% by mass or more and 80% by mass or less, more preferably 50% by mass or more and 70% by mass or less, the monomer is added to the reaction system to carry out the third stage of polymerization.

[0107] The polymerization can be terminated using known polymerization terminators such as hydroquinone. After polymerization termination, post-processing can be performed as needed, and as described above, the desired nitrile polymer can be prepared by arbitrary hydrogenation.

[0108] [Temperature Control]

[0109] Furthermore, in the polymerization after the first and second stages, from the viewpoint of controlling the peak width of the loss tangent tanδ in the viscoelastic properties of the nitrile polymer within a preferred range, as mentioned above, it is important to control the temperature within the reaction system. From the start of polymerization to the end of polymerization, the magnitude of the temperature change within the reaction system (the difference between the highest and lowest temperatures) is preferably 6°C or less (±3°C), more preferably 4°C or less (±2°C), and even more preferably 2°C or less (±1°C).

[0110] Furthermore, the temperature within the reaction system is preferably above 1°C and below 9°C, more preferably above 2°C and below 8°C, and even more preferably above 4°C and below 6°C.

[0111] <halogenated hydrocarbons>

[0112] As for halogenated hydrocarbons, there are no particular limitations as long as at least one carbon atom of the hydrocarbon is replaced by a halogen atom; examples include chlorinated hydrocarbons, fluorinated hydrocarbons, and bromine hydrocarbons. These can be used alone or in combination of two or more in any ratio. Moreover, from the viewpoint of further improving the viscosity stability of the binder composition and the peel strength of the electrode, chlorinated hydrocarbons are preferred.

[0113] Examples of chlorinated hydrocarbons include chlorinated alkanes and chlorobenzenes.

[0114] Specific examples of chloroalkanes include: 1-chloropropane, 2-chloropropane, 1-chlorobutane, 2-chlorobutane, 2-methyl-2-chloropropane, 2-methyl-1-chloropropane, 1-chloropentane, 2-chloropentane, 3-chloropentane, 2-chloro-2-methylbutane, 1-chloro-2-ethylbutane, 1-chlorohexane, 2-chlorohexane, 3-chlorohexane, 2-chloro-methyl-pentane, 1-chloroheptane, 2-chloroheptane, 3-chloroheptane, 1-chlorooctane, 2-chlorooctane, 3-chlorooctane, 1-chloro-1,1,3,3-tetramethylbutane, 1-chloro-2,2,4,4-tetramethylbutane, 1-chloro-3-methylheptane, 1-chloro-2-ethylhexane, 1-chlorononane, 2-chlorononane, 3-chlorononane, 1-chloro-1, 1,3-Trimethylhexane, 1-chloro-1,1,3,3-tetramethylpentane, 1-chlorodecane, 2-chlorodecane, 3-chlorodecane, 1-chloro-1,1,3,3,5,5-hexamethylhexane, 1-chloro-8-methyl-nonane, 1-chloroundecane, 2-chloroundecane, 3-chloroundecane, 1-chlorododecane, 2-chlorododecane, 3-chlorododecane, 1-chlorotridecane, 2-chlorotridecane, 3-chlorotridecane, 1-chlorotetradecane, 2-chlorotetradecane, 3-chlorotetradecane, 1-chloropentadecane, 2-chloropentadecane, 3-chloropentadecane, 1-chlorohexadecane, 2-chlorohexadecane, 3-chlorohexadecane, 1-chloroheptadecane, 2-chloroheptadecane, 3-chloroheptadecane, 1-chlorooctadecane, 2-chlorooctadecane, 3-chlorooctadecane, etc.

[0115] Specific examples of chlorobenzenes include: monochlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene, 1,3,5-trichlorobenzene, 1,2,3,4-tetrachlorobenzene, 1,2,4,5-tetrachlorobenzene, pentachlorobenzene, hexachlorobenzene, etc.

[0116] Among these, 1-chloropropane and monochlorobenzene are preferred from the viewpoint of further improving the viscosity stability of the binder composition and the peel strength of the electrode. Additionally, chlorinated hydrocarbons can be used alone or in combination of two or more in any ratio.

[0117] In this invention, the binder composition, as described above, requires that the content of the halogenated hydrocarbon relative to the content of the nitrile polymer be 2 ppm by mass or more and 400 ppm by mass or less, preferably 10 ppm by mass or more, more preferably 30 ppm by mass or more, further preferably 100 ppm by mass or more, particularly preferably 200 ppm by mass or more, preferably 350 ppm by mass or less, and more preferably 300 ppm by mass or less. When the content of the halogenated hydrocarbon relative to the content of the nitrile polymer is less than 2 ppm by mass, the peel strength of the electrode is impaired, and the resistance of the electrode increases, resulting in a decrease in the rate performance of the electrochemical element. On the other hand, when the content of the halogenated hydrocarbon relative to the content of the nitrile polymer is greater than 400 ppm by mass, the viscosity stability of the binder is impaired, and the dispersion stability of the conductive material dispersion decreases, resulting in a decrease in the rate performance of the electrochemical element.

[0118] <Other Ingredients>

[0119] The binder composition of the present invention may contain other components besides nitrile polymers, halogenated hydrocarbons, and NMP, without particular limitation. Examples include binder materials other than nitrile polymers (polyvinylidene fluoride, polyacrylate, etc.), reinforcing materials, leveling agents, viscosity modifiers, and electrolyte additives. These are not particularly limited as long as they do not affect the battery reaction, and other known components, such as those described in International Publication No. 2012 / 115096, can be used. Furthermore, the binder composition of the present invention may also contain solvents other than NMP.

[0120] In addition, these other ingredients can be used alone or in combination of two or more in any ratio.

[0121] (Conductive material dispersion)

[0122] The conductive material dispersion of the present invention is a composition comprising a carbon-containing material and the above-described binder composition. Specifically, the conductive material dispersion of the present invention contains a carbon-containing material, the above-described nitrile polymer, the above-described halogenated hydrocarbon, NMP, and optionally other components described above. Furthermore, since the conductive material dispersion of the present invention contains the binder composition of the present invention, an electrode slurry prepared by combining the conductive material dispersion of the present invention with an electrode active material can be used to produce an electrode with excellent peel strength.

[0123] Furthermore, the conductive material dispersion of the present invention is an intermediate product used to prepare the electrode slurry of the present invention described later, and generally does not contain electrode active substances. In addition, the nitrile polymer and halogenated hydrocarbon contained in the conductive material dispersion of the present invention are derived from the binder composition of the present invention, and their preferred proportions are the same as those of the binder composition of the present invention.

[0124] <Carbon-containing materials>

[0125] As a carbon-containing material, there are no particular limitations on its function as a conductive material that ensures electrical contact between the active electrode materials. Examples of carbon-containing materials include: carbon black (e.g., acetylene black, Ketjen black, furnace black, etc.), single-walled or multi-walled carbon nanotubes (multi-walled carbon nanotubes include stacked cup type), carbon nanotubes, vapor-grown carbon fibers, pulverized carbon fibers obtained by sintering and then crushing polymer fibers, single-layer or multi-layer graphene, and carbon nonwoven fabric sheets obtained by sintering nonwoven fabric formed from polymer fibers. Furthermore, these can be used individually or in any combination of two or more. Among these, carbon nanotubes are preferred.

[0126] <<Carbon Nanotubes>>

[0127] Here, CNTs are not specifically limited, but preferably have the following properties.

[0128] [Surface alkalinity]

[0129] The surface alkalinity of CNTs is preferably 0.01 mmol / g or more, more preferably 0.02 mmol / g or more, more preferably 0.10 mmol / g or less, and more preferably 0.08 mmol / g or less. If the surface alkalinity of CNTs is 0.01 mmol / g or more, the residual acid content adhering to the CNT surface is reduced, which can suppress the decrease in dispersion stability of the conductive material dispersion caused by side reactions. On the other hand, if the surface alkalinity of CNTs is 0.10 mmol / g or less, it is presumed that the aggregation of CNTs can be suppressed, thereby reducing the electrode resistance and improving the rate performance of the electrochemical element.

[0130] Furthermore, in this invention, the "surface alkalinity" and "surface acidity" of carbon nanotubes can be measured using the methods described in the examples.

[0131] [Surface acidity / Surface alkaliness]

[0132] Furthermore, the ratio of surface acidity to surface alkaliity (surface acidity / surface alkaliity) of the CNT is preferably 0.1 or more, more preferably 0.2 or more, preferably 1.0 or less, more preferably 0.8 or less, even more preferably 0.6 or less, and particularly preferably 0.5 or less. If the surface acidity / surface alkaliity ratio is 0.1 or more, the adhesion of the electrode composite layer obtained using the conductive material dispersion can be sufficiently ensured, and the peel strength of the electrode can be further improved. On the other hand, if the surface acidity / surface alkaliity ratio is 1.0 or less, the dispersion stability of the conductive material dispersion can be improved. Moreover, if the surface acidity / surface alkaliity ratio is within the above range, the rate performance of the electrochemical element can be improved.

[0133] Furthermore, the preferred BET specific surface area of ​​CNT is 100 m². 2 / g or more, preferably 150m 2 / g or more, further preferably 200m 2 / g or more, preferably 300m 2 / g or less. If the specific surface area of ​​BET is 100m² 2 If the value is above / g, the electrode resistance can be reduced; if it is 300m 2 If the value is below / g, it is presumed that the nitrile polymer can bond well with CNTs, thus ensuring sufficient peel strength of the electrode.

[0134] Furthermore, in this invention, the "BET specific surface area" of CNT can be measured using the method described in the examples.

[0135] [Preparation method of CNTs]

[0136] There is no particular limitation on the preparation method of CNTs. For example, CNTs with surface alkali content and surface acid content / surface alkali content values ​​within the above-mentioned preferred range can be prepared by the following steps: a step of acid treatment of raw material CNTs (acid treatment step), a step of alkali treatment of acid-treated raw material CNTs (alkali treatment step), and a step of cleaning the alkali-treated raw material CNTs (cleaning step).

[0137] —Acid treatment process—

[0138] In the acid treatment process, the raw material CNTs are acid-treated. There are no particular limitations on the raw material CNTs; they can be appropriately selected from known CNTs based on the desired properties of the surface-treated CNTs (wall count, BET specific surface area, etc.).

[0139] Here, as a method of acid treatment, there is no particular limitation as long as the acid can come into contact with the raw material CNTs, but the method of immersing the raw material CNTs in an acid treatment solution (an aqueous solution of acid) is preferred.

[0140] The acids included in the acid treatment solution are not particularly limited, and examples include nitric acid, sulfuric acid, and hydrochloric acid. One of these can be used alone, or two or more can be used in combination. Among these, nitric acid and sulfuric acid are preferred.

[0141] The immersion time of the raw material CNTs in the acid treatment solution (immersion time) is preferably 1 minute or more, more preferably 10 minutes or more, further preferably 30 minutes or more, particularly preferably 50 minutes or more, preferably 120 minutes or less, more preferably 100 minutes or less, and further preferably 80 minutes or less. If the immersion time is 1 minute or more, the surface acid content of the surface-treated CNTs can be increased. If it is 120 minutes or less, the surface acid content of the surface-treated CNTs will not be excessively increased, and the production efficiency of the surface-treated CNTs can be sufficiently ensured.

[0142] Furthermore, the temperature at which the raw material CNTs are immersed in the acid treatment solution (immersion temperature) is preferably 20°C or higher, more preferably 40°C or higher, more preferably 80°C or lower, and even more preferably 70°C or lower. If the immersion temperature is within the above range, the surface acid content of the obtained surface-treated CNTs can be appropriately increased.

[0143] After the above impregnation, the acid-treated CNTs can be recovered from the mixture of the acid-treated CNTs and the acid-treated solution using known methods such as filtration. The recovered acid-treated CNTs can be washed with water if necessary.

[0144] —Alkali treatment process—

[0145] In the alkali treatment process, the acid-treated CNTs obtained after the above-mentioned acid treatment process are subjected to alkali treatment.

[0146] Here, as a method of alkaline treatment, there is no particular limitation as long as the alkali can come into contact with the acid-treated CNTs, but the method of immersing the acid-treated CNTs in an alkaline treatment solution (an aqueous solution of alkali) is preferred.

[0147] The alkali contained in the alkaline treatment solution is not particularly limited, and examples include lithium hydroxide, ammonium chloride, sodium bicarbonate, and sodium hydroxide. One of these can be used alone, or two or more can be used in combination. Among these, lithium hydroxide and ammonium chloride are preferred, and lithium hydroxide is more preferred.

[0148] The immersion time (immersion time) of acid-treated CNTs in the alkaline treatment solution is preferably 10 minutes or more, more preferably 60 minutes or more, further preferably 80 minutes or more, particularly preferably 90 minutes or more, preferably 240 minutes or less, more preferably 200 minutes or less, and further preferably 150 minutes or less. An immersion time of 10 minutes or more increases the surface alkalinity of the surface-treated CNTs, while an immersion time of 240 minutes or less prevents excessive increase in surface alkalinity and ensures sufficient production efficiency for surface-treated CNTs.

[0149] Furthermore, the temperature at which the acid-treated CNTs are immersed in the alkaline treatment solution (immersion temperature) is preferably 10°C or higher, more preferably 20°C or higher, more preferably 40°C or lower, and even more preferably 27°C or lower. If the immersion temperature is within the above range, the surface alkalinity of the obtained surface-treated CNTs can be appropriately increased.

[0150] —Cleaning Process—

[0151] In the cleaning process, the raw material CNTs (acid-alkali treated CNTs) obtained after the above-mentioned acid treatment and alkali treatment processes are cleaned. Through this cleaning, the remaining acid and alkali components (especially alkali components) adhering to the surface of the acid-alkali treated CNTs can be removed, resulting in surface-treated CNTs with specified properties.

[0152] Furthermore, there are no particular limitations on the method for cleaning acid- and alkali-treated CNTs, but washing with water is preferred. For example, acid- and alkali-treated CNTs can be recovered from a mixture of acid- and alkali-treated CNTs and alkali-treated solution using known methods such as filtration, and then the acid- and alkali-treated CNTs can be washed with water. In this case, by measuring the conductivity of the water used to clean the acid- and alkali-treated CNTs (washing water), the extent to which acid and alkali components have been removed can be estimated.

[0153] After the above cleaning process, the water and other substances adhering to the surface can be removed by drying as needed to obtain surface-treated CNTs.

[0154] Furthermore, the surface acidity and alkaliity of surface-treated CNTs can be adjusted by changing the conditions of the aforementioned acid treatment, alkali treatment, and cleaning processes. For example, by changing the types and concentrations of acid and alkali contained in the acid and alkali treatment solutions used in the acid and alkali treatment processes, respectively, the surface acidity and alkaliity of the surface-treated CNTs can be adjusted. Moreover, by extending the immersion time in the acid treatment process, the surface acidity of the surface-treated CNTs can be increased; similarly, by extending the immersion time in the alkali treatment process, the surface alkaliity of the surface-treated CNTs can be increased. Furthermore, in the cleaning process, by changing the degree of cleaning, the surface acidity and alkaliity (especially the surface alkaliity) can be adjusted.

[0155] <Adhesive Composition>

[0156] As an adhesive composition, the adhesive composition of the present invention containing the above-mentioned nitrile polymer, the above-mentioned halogenated hydrocarbon, and NMP, and optionally containing other components mentioned above, is used.

[0157] Here, when mixing the carbon-containing material and the binder composition to obtain a conductive material dispersion, the ratio of the carbon-containing material to the binder composition is not particularly limited. For example, the carbon-containing material and the binder composition can be mixed in a ratio where the obtained conductive material dispersion preferably contains 5 or more but less than 40 parts by mass, and more preferably 10 or more but less than 30 parts by mass of a nitrile polymer, relative to 100 parts by mass of the carbon-containing material.

[0158] <Preparation Method of Conductive Material Dispersion>

[0159] There are no particular limitations on the method for preparing conductive material dispersions. Conductive material dispersions can be prepared by mixing a carbon-containing material and a binder composition using, for example, a known mixing device.

[0160] (Slurry for electrodes of electrochemical components)

[0161] The electrode slurry of the present invention is a composition comprising an electrode active material and the aforementioned conductive material dispersion. Specifically, the electrode slurry of the present invention contains the electrode active material, the aforementioned carbon-containing material, the aforementioned nitrile polymer, the aforementioned halogenated hydrocarbon, NMP, and optionally other aforementioned components. Furthermore, the electrode slurry of the present invention contains the conductive material dispersion of the present invention; therefore, if this electrode slurry is used, an electrode with excellent peel strength can be produced.

[0162] Furthermore, the carbon-containing materials, nitrile polymers, and halogenated hydrocarbons contained in the electrode slurry of the present invention are derived from the binder composition and conductive material dispersion of the present invention, and their preferred proportions are the same as those of the binder composition and conductive material dispersion of the present invention.

[0163] <Electrode Active Materials>

[0164] There are no particular limitations on the electrode active materials (positive electrode active material and negative electrode active material) used in electrode slurries, and known electrode active materials can be used.

[0165] As a positive electrode active material for applications such as lithium-ion secondary batteries, there are no particular limitations, and examples include lithium (Li)-containing metal oxides. Furthermore, as a positive electrode active material, it is preferable to include, in addition to lithium (Li), at least one selected from cobalt (Co), nickel (Ni), manganese (Mn), and iron (Fe). Examples of such positive electrode active materials include: lithium-containing cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), lithium-containing nickel oxide (LiNiO2), Co-Ni-Mn lithium-containing composite oxides, Ni-Mn-Al lithium-containing composite oxides, Ni-Co-Al lithium-containing composite oxides, olivine-type lithium manganese phosphate (LiMnPO4), olivine-type lithium iron phosphate (LiFePO4), and Li... 1+x Mn2-x Spinel compounds with excess lithium represented by O4(0 < X < 2), Li[Ni[[ATEXT]] 0.17 Li[[ATEXT]] 0.2 Co[[ATEXT]] 0.07 Mn[[ATEXT]] 0.56 O2, LiNi[[ATEXT]] 0.5 Mn[[ATEXT]] 1.5 O4, etc. In addition, the positive electrode active material can be used alone or two or more kinds can be used in any ratio. [[ATEXT]]

[0166] In addition, the particle size of the electrode active material is not particularly limited and can be the same as the electrode active material used in the past. [[ATEXT]]

[0167] Furthermore, the amount of the electrode active material in the electrode paste is not particularly limited and can be within the range used in the past. [[ATEXT]]

[0168] <Conductive material dispersion liquid>[[ATEXT]]

[0169] As the conductive material dispersion liquid, the conductive material dispersion liquid of the present invention containing the above carbon-containing material, the above nitrile polymer, the above halogenated hydrocarbon, and NMP, and optionally containing the above other components is used. [[ATEXT]]

[0170] <Method for preparing electrode paste>[[ATEXT]]

[0171] The method for preparing the electrode paste is not particularly limited. The electrode paste can be prepared by mixing the electrode active material and the conductive material dispersion liquid using, for example, a known mixing device. [[ATEXT]]

[0172] (Electrode for electrochemical element)[[ATEXT]]

[0173] The electrode of the present invention has an electrode composite material layer obtained using the above electrode paste of the present invention. More specifically, the electrode of the present invention usually has the above electrode composite material layer on the current collector. Moreover, since the electrode composite material layer of the electrode of the present invention is formed from the above electrode paste of the present invention, the peel strength is excellent. [[ATEXT]]

[0174] <Current collector>[[ATEXT]]

[0175] The current collector is made of a material having conductivity and electrochemical durability. The current collector is not particularly limited, and a known current collector can be used. For example, as the current collector of the positive electrode of a lithium ion secondary battery, a current collector made of aluminum or an aluminum alloy can be used. At this time, aluminum and an aluminum alloy can be used in combination, or different types of aluminum alloys can be used in combination. Aluminum and an aluminum alloy are excellent current collector materials because they have heat resistance and are electrochemically stable. [[ATEXT]]

[0176] <Method for manufacturing electrode>[[ATEXT]]

[0177] The method for manufacturing the electrode of the present invention is not particularly limited. For example, the electrode of the present invention can be manufactured by coating at least one side of the current collector with the electrode slurry described above and drying it to form an electrode composite material layer. More specifically, the manufacturing method includes: a step of coating the electrode slurry onto at least one side of the current collector (coating step); and a step of drying the electrode slurry coated on at least one side of the current collector to form an electrode composite material layer on the current collector (drying step).

[0178] <<Coating Process>>

[0179] There are no particular limitations on the method for applying the electrode paste to the current collector, and any known method can be used. Specifically, the coating method can include doctor blade coating, dip coating, reverse roller coating, direct roller coating, gravure coating, extrusion coating, brush coating, etc. The electrode paste can be applied to only one side of the current collector or to both sides. The thickness of the paste film on the current collector before drying can be appropriately set according to the thickness of the electrode composite layer obtained after drying.

[0180] <<Drying Process>>

[0181] There are no particular limitations on the method for drying the electrode on the current collector with a slurry; known methods can be used, such as drying with warm air, hot air, or low-humidity air; vacuum drying; and drying by irradiation with infrared rays, electron beams, etc. By drying the electrode on the current collector with a slurry in this way, an electrode composite material layer can be formed on the current collector, resulting in an electrode having a current collector and an electrode composite material layer.

[0182] In addition, after the drying process, the electrode composite material layer can be pressurized using methods such as metal molding or rolling. This pressurization process ensures a good seal between the electrode composite material layer and the current collector.

[0183] Furthermore, if the electrode composite layer contains a curable polymer, the polymer can be cured after the electrode composite layer is formed.

[0184] (Electrochemical element)

[0185] The electrochemical element of the present invention has the electrode described above. Furthermore, because it has the electrode of the present invention, the electrochemical element of the present invention exhibits excellent element characteristics such as rate capability. Additionally, the electrochemical element of the present invention is, for example, a non-aqueous secondary battery, preferably a lithium-ion secondary battery.

[0186] Hereinafter, the structure of a lithium-ion secondary battery, which is an example of an electrochemical element of the present invention, will be described. This lithium-ion secondary battery includes a positive electrode, a negative electrode, an electrolyte, and a spacer. Furthermore, at least one of the positive and negative electrodes is an electrode of the present invention. That is, in this lithium-ion secondary battery, the positive electrode may be an electrode of the present invention and the negative electrode may be an electrode other than the electrode of the present invention; the positive electrode may be an electrode other than the electrode of the present invention and the negative electrode may be the electrode of the present invention; or both the positive and negative electrodes may be electrodes of the present invention.

[0187] <Electrodes other than the electrodes of this invention>

[0188] There are no particular limitations on the electrode used, which is not part of this invention, and any known electrode can be used.

[0189] Electrolyte

[0190] As the electrolyte, an organic electrolyte in which the supporting electrolyte is dissolved in an organic solvent is typically used. As the supporting electrolyte, lithium salts can be used, for example. Examples of lithium salts include LiPF6, LiAsF6, LiBF4, LiSbF6, LiAlCl4, LiClO4, CF3SO3Li, C4F9SO3Li, CF3COOLi, (CF3CO)2NLi, (CF3SO2)2NLi, and (C2F5SO2)NLi. Among these, LiPF6, LiClO4, and CF3SO3Li are preferred due to their high degree of dissociation, with LiPF6 being particularly preferred. Furthermore, a single electrolyte can be used, or two or more can be used in any ratio. Generally, there is a tendency for higher dissociation degrees of supporting electrolytes to result in higher lithium-ion conductivity; therefore, the lithium-ion conductivity can be adjusted according to the type of supporting electrolyte.

[0191] As for the organic solvent used in the electrolyte, there are no particular limitations as long as it can dissolve the supporting electrolyte. Preferred solvents include: carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butyl carbonate (BC), and methyl ethyl carbonate (EMC); esters such as γ-butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; and sulfur-containing compounds such as sulfolane and dimethyl sulfoxide. Mixtures of these solvents can also be used. Among these, carbonates are preferred due to their high dielectric constant and wide stable potential range, and mixtures of ethylene carbonate and methyl ethyl carbonate are even more preferred.

[0192] Furthermore, the concentration of the electrolyte in the electrolyte solution can be appropriately adjusted, for example, preferably 0.5 to 15% by mass, more preferably 2 to 13% by mass, and even more preferably 5 to 10% by mass. In addition, known additives, such as ethylene fluorocarbonate and ethyl methanesulfonate, can be added to the electrolyte solution.

[0193] <spacer>

[0194] There are no particular limitations on the spacer used; for example, the spacer described in Japanese Patent Application Publication No. 2012-204303 can be used. Among these, from the viewpoint that the overall film thickness of the spacer can be reduced, thereby increasing the ratio of electrode active materials in the lithium-ion secondary battery and increasing the capacity per unit volume, a microporous membrane formed of a polyolefin-based resin (polyethylene, polypropylene, polybutene, polyvinyl chloride) is preferred.

[0195] <Manufacturing Method of Lithium-ion Secondary Batteries>

[0196] The lithium-ion secondary battery of the present invention can be manufactured by, for example, overlapping the positive and negative electrodes with a spacer between them, winding or folding them according to the battery shape as needed, placing them into a battery container, injecting electrolyte into the battery container, and sealing it. To prevent internal pressure rise and overcharging / discharging, overcurrent protection components such as fuses and PTC elements, porous metal mesh, and conductive plates can be provided as needed. The shape of the secondary battery can be, for example, coin-shaped, button-shaped, sheet-shaped, cylindrical, square, or flat.

[0197] Example

[0198] The present invention will now be specifically described based on embodiments, but the present invention is not limited to these embodiments. Furthermore, unless otherwise specified, in the following description, "%", "ppm", and "parts" refer to quantities based on mass.

[0199] Furthermore, unless otherwise specified, in polymers manufactured by copolymerizing multiple monomers, the proportion of monomer units formed by polymerizing a particular monomer in the polymer is generally consistent with the proportion (feed ratio) of that particular monomer in all monomers used to polymerize the polymer. Additionally, when the polymer is a hydrogenated polymer formed by hydrogenating a polymer containing conjugated diene monomer units, the total proportion of unhydrogenated conjugated diene monomer units and alkylene structural units that are the hydrogenated conjugated diene monomer units in the hydrogenated polymer is consistent with the proportion (feed ratio) of the conjugated diene monomer used in the polymerization of the polymer in all monomers.

[0200] In the examples and comparative examples, the weight-average molecular weight of the nitrile polymer, the ratio of C6 linear chains at the molecular ends, the iodine value, and the peak width of the loss tangent tanδ in the viscoelastic properties, the surface acidity, surface alkaliness, and BET specific surface area of ​​the CNT, the viscosity stability of the binder composition, the dispersion stability of the conductive material dispersion, the peel strength, flexibility, and resistance of the electrode, and the cycle characteristics and rate characteristics of the secondary battery were evaluated by the following methods.

[0201] <weight-average molecular weight>

[0202] The weight-average molecular weight (Mw) of nitrile polymers was determined by gel permeation chromatography (GPC) under the following conditions using a 10 mM LiBr-dimethylformamide (DMF) solution.

[0203] • Separation column: Shodex KD-806M (manufactured by Showa Denko Co., Ltd.)

[0204] • Detector: Differential refractive index detector RID-10A (manufactured by Shimadzu Corporation)

[0205] • Flow rate of eluent: 0.3 mL / min

[0206] Column temperature: 40℃

[0207] • Standard polymer: TSK standard polystyrene (Tosoh Corporation)

[0208] <C6 straight chain ratio at the molecular terminal>

[0209] For nitrile polymers, extraction with methanol was performed according to JIS K6229 to remove free thiols, etc. The polymers were then dried and heated at 150°C for 20 minutes. The generated gases were analyzed by gas chromatography-mass spectrometry (GC-MS). Standards (tert-dodecylthiol and 1-decylthiol) were used, and the proportion of molecular ends composed of straight-chain alkyl groups with 6 or more carbon atoms in all molecular ends of the nitrile polymer was determined using a standard curve method based on retention time, MS spectra, and peak areas. The GC-MS determination conditions are as follows.

[0210] Separation column: HP-5ms (length 30m, inner diameter 0.25mm, membrane thickness 0.25μm)

[0211] The column oven temperature rise: after holding at 40℃ for 3 minutes, increase to 280℃ at a rate of 10℃ / minute.

[0212] Injection temperature: 300℃

[0213] Detector temperature: 280℃

[0214] Ions to be measured: 29–550

[0215] <Iodine value>

[0216] The iodine value of the nitrile-based polymer rubber is determined in accordance with JIS K 6235.

[0217] <Peak width of tanδ>

[0218] The nitrile-based polymer is compression-molded at 170 °C for 5 minutes while being pressed with a metal mold to obtain a test piece with a width of 10 mm, a length of 50 mm, and a thickness of 2.15 mm. Then, for the obtained test piece, using a viscoelasticity measuring device (manufactured by GABO QUALIMETER Testanlagen GmbH, product name "Explexor500N"), the measurement is carried out under the following conditions: measurement frequency: 10 Hz, static strain: 0.5%, dynamic strain: 0.2%, measurement temperature range: -50 to 100 °C, heating rate: 3 °C / minute, distance between chucks: 30 mm, measurement mode: tension mode. Next, a temperature-Tanδ chart of viscoelasticity is made, taking the temperature on the low-temperature side of this chart as the starting-point temperature, the temperature on the high-temperature side as the ending-point temperature, and the absolute value of (ending-point temperature - starting-point temperature) as the peak width of tanδ. In addition, when the tanδ value deviates at the starting point and the ending point, a baseline can be drawn to calculate the peak width.

[0219] <Amount of surface acid>

[0220] Precisely weigh approximately 1 g of the CNT to be measured and immerse it in 100 ml of 0.01 mol dm -3 tetrabutylammonium hydroxide (TBA OH) / 4-methyl-2-pentanone (MIBK) solution, and stir with a stirrer for 1 hour. After that, perform centrifugation and filter the supernatant with a filter. By performing non-aqueous potentiometric titration with 0.01 mol dm -3 perchloric acid (HClO4) / MIBK solution, the residual TBA OH in the obtained 50 mL filtrate is quantitatively analyzed, and the acid amount (mmol / g) per 1 g of CNT is determined based on the obtained value. In addition, an automatic potentiometric titrator (manufactured by Kyoto Electronics Industry Co., Ltd., product name "AT-700") was used in the analysis. Furthermore, a series of operations were carried out under an argon gas flow at room temperature.

[0221] <Amount of surface base>

[0222] Precisely weigh approximately 1 g of the CNT to be measured and immerse it in 100 ml of 0.01 mol dm -3 HClO4 / MIBK solution, and stir with a stirrer for 1 hour. After that, perform centrifugation and filter the supernatant with a filter. By using 0.01 mol dm- 3 The TBA OH / MIBK solution was used for non-aqueous potentiometric titration to quantitatively analyze the residual HClO4 in the obtained 50 mL filtrate, and the base amount (mmol / g) per 1 g of CNT was determined based on the obtained value. In addition, an automatic potentiometric titrator (manufactured by Kyoto Electronics Industry Co., Ltd., product name "AT-700") was used in the analysis. Furthermore, a series of operations were carried out under an argon stream at room temperature.

[0223] <BET specific surface area>

[0224] The BET specific surface area of CNT was measured using Belsorp-mini (manufactured by Micromeritics Co., Ltd., in accordance with ASTM D3037-81).

[0225] <Viscosity stability>

[0226] The viscosity η0 of the obtained binder composition was measured using a B-type viscometer (manufactured by Toki Sangyo Co., Ltd., product name "TVB-10", rotation speed: 60 rpm). Then, the binder composition with the measured viscosity was stirred for 24 hours using a planetary mixer (rotation speed: 60 rpm), and the viscosity η1 of the stirred binder composition was measured using the same B-type viscometer as above (rotation speed: 60 rpm). Then, the viscosity retention rate Δη = η1 / η0 × 100 (%) of the binder composition before and after stirring was calculated, and the viscosity stability of the binder composition was evaluated according to the following criteria. In addition, the temperature during viscosity measurement was 25°C. The closer the value of the viscosity retention rate Δη is to 100%, the more excellent the viscosity stability of the binder composition is.

[0227] A: The viscosity retention rate Δη is 90% or more and 110% or less

[0228] B: The viscosity retention rate Δη is 80% or more and less than 90%

[0229] C: The viscosity retention rate Δη is less than 80% or greater than 110%

[0230] <Dispersion stability>

[0231] The viscosity η2 of the conductive material dispersion was measured using a Type B viscometer (manufactured by Toki Sangyo Co., Ltd., product name "TVB-10", speed: 60 rpm). Next, the conductive material dispersion with the measured viscosity was stirred for 24 hours using a planetary mixer (speed: 60 rpm), and the viscosity η3 of the stirred conductive material dispersion was measured using the same Type B viscometer (speed: 60 rpm). Then, the viscosity retention rate Δη' of the conductive material dispersion before and after stirring was calculated as η3 / η2 × 100 (%), and the dispersion stability of the conductive material dispersion was evaluated using the following criteria. The temperature during viscosity measurement was 25°C. The closer the viscosity retention rate Δη' is to 100%, the better the dispersion stability of the conductive material dispersion.

[0232] A: Viscosity retention rate Δη' is above 90% and below 110%.

[0233] B: Viscosity retention rate Δη' is above 80% and less than 90%.

[0234] C: Viscosity retention rate Δη' is above 70% and less than 80%.

[0235] D: Viscosity retention rate Δη' is less than 70% or greater than 110%.

[0236] <Peel strength>

[0237] A rectangular piece, 100 mm in length and 10 mm in width, was cut from the positive electrode of a lithium-ion secondary battery and used as a test piece. With the positive electrode composite layer facing down, transparent tape (according to JIS Z1522) was applied to the surface of the positive electrode composite layer. One end of the current collector was stretched vertically at a speed of 100 mm / min, and the stress during peeling was measured (the transparent tape was fixed to the test bench). Three measurements were performed, and the average value was calculated as the peel strength. The peel strength was evaluated according to the following criteria: A higher peel strength value indicates a stronger and more secure bond between the positive electrode composite layer and the current collector made of aluminum foil.

[0238] A: Peel strength is above 30 N / m

[0239] B: Peel strength is above 20N / m and below 30N / m

[0240] C: Peel strength less than 20 N / m

[0241] <Flexibility>

[0242] SUS cylindrical rods of different diameters were placed on the positive electrode composite layer of the positive electrode for lithium-ion secondary batteries. The positive electrode was then wound around the cylindrical rods, and the presence of cracks in the positive electrode composite layer was visually evaluated. The smaller the diameter, the better the flexibility of the positive electrode composite layer and the positive electrode.

[0243] A: It won't break with a 2.0mm Φ rod.

[0244] B: A 2.5mm diameter rod will not break.

[0245] C: A 3.0mm Φ rod will not break.

[0246] D: It won't break when using a 3.5mm Φ rod.

[0247] <Resistance (Penetrating Resistance)>

[0248] A lithium-ion secondary battery was stamped into a 12mm diameter circle using the positive electrode. The thickness d (μm) and area S of the stamped test piece were measured. The test piece was clamped in the fixture of a tensile compression testing machine (manufactured by Imada Corporation, product name "SV-301NA"), and pressurized to 20MPa. A two-terminal clamp was connected to the fixture, and the measuring cable was connected to an automatic polarization system (manufactured by Hokuto Electric Co., Ltd., product name "HSV-110"). Using the time-potential meter mode, a constant current I = 10mA was flowed through the fixture for 10 minutes, and the voltage V (V) was measured. According to Ohm's law, the resistance R (Ω) = V / I was calculated, and then the volume resistivity ρ (Ω·cm) = R × S / d was calculated to obtain the volume resistivity ρ in the transmission mode. The volume resistivity ρ calculated in this way was evaluated according to the following evaluation criteria.

[0249] A: Volume resistivity ρ is less than 15 Ω·cm

[0250] B: Volume resistivity ρ is above 15 Ω·cm and below 30 Ω·cm

[0251] C: Volume resistivity ρ is above 30 Ω·cm and less than 45 Ω·cm

[0252] D: Volume resistivity ρ is above 45 Ω·cm

[0253] <Cyclic Characteristics>

[0254] After electrolyte filling, the lithium-ion secondary battery was left to stand at 25°C for 5 hours. Then, it was charged at 0.2C using a constant current method at 25°C until the cell voltage reached 3.65V. Next, it underwent an aging treatment at 60°C for 12 hours. Then, it was discharged at 0.2C using a constant current method at 25°C until the cell voltage reached 3.00V. Finally, it underwent CC-CV charging at 0.2C (upper limit cell voltage 4.20V) and CC discharging at 0.2C using a constant current method until 3.00V. This 0.2C charge-discharge cycle was repeated three times.

[0255] Then, at a temperature of 25°C, 100 charge-discharge cycles were performed with a battery cell voltage of 4.20-3.00V and a charge-discharge rate of 1.0C. The discharge capacity of the first cycle is defined as X1, and the discharge capacity of the 100th cycle is defined as X2. Using discharge capacity X1 and discharge capacity X2, the capacity retention rate, expressed as ΔC = (X2 / X1) × 100 (%), was calculated and evaluated using the following benchmarks. The larger the value of this capacity retention rate ΔC, the better the cycle characteristics of the lithium-ion secondary battery.

[0256] A: Capacity retention rate ΔC is above 93%.

[0257] B: Capacity retention rate ΔC is above 90% and less than 93%.

[0258] C: Capacity retention ΔC is above 87% and less than 90%.

[0259] D: Capacity retention rate ΔC is less than 87%.

[0260] <Magnification Characteristics>

[0261] After electrolyte filling, the lithium-ion secondary batteries were left to stand at 25°C for 5 hours. Then, they were charged at 0.2C using a constant current method at 25°C until the cell voltage reached 3.65V. Following this, they underwent an aging treatment at 60°C for 12 hours. Next, they were discharged at 0.2C using a constant current method at 25°C until the cell voltage reached 3.00V. Then, they were subjected to CC-CV charging at 0.2C (upper limit cell voltage 4.20V) and CC discharging at 0.2C using a constant current method until 3.00V. This 0.2C charge-discharge cycle was repeated three times.

[0262] Next, at 25°C, the battery was charged to 4.2V using a constant current method at 0.1C, and then discharged to 3.0V at 0.1C to determine the 0.1C discharge capacity. Then, it was charged to 4.2V at 0.1C, and then discharged to 3.0V at 1C to determine the 1C discharge capacity. These measurements were performed on 10 lithium-ion secondary batteries. The average values ​​of each measurement were set as the 0.1C discharge capacity *a* and the 1C discharge capacity *b*. The ratio of the capacitance of the 1C discharge capacity *b* to the capacitance of the 0.1C discharge capacity *a* (=b / a×100(%)) was calculated and evaluated according to the following criteria. A higher value for this capacitance ratio indicates better rate performance of the lithium-ion secondary battery.

[0263] A: The capacitance ratio is above 85%.

[0264] B: The capacitance ratio is above 75% and below 85%.

[0265] C: The capacitance ratio is above 60% and less than 75%.

[0266] D: The capacitance ratio is less than 60%.

[0267] (Example 1)

[0268] <Preparation of Nitrile Polymers>

[0269] A soap solution was prepared by adding 200 parts of deionized water and 2.25 parts of potassium fatty acid soap (potassium salt of fatty acids) to the reactor. Then, 21 parts of acrylonitrile and 0.8 parts of 1-decyl mercaptan (chain transfer agent) were added sequentially to the soap solution. After purging the internal gas three times with nitrogen, 64 parts of 1,3-butadiene were added. Next, the reactor was maintained at 5±1°C, and 0.1 parts of cumene hydroperoxide (polymerization initiator) were added, initiating the first stage of polymerization while stirring. Then, when the polymerization conversion relative to the added monomer reached 30%, 8 parts of acrylonitrile were added to initiate the second stage of polymerization. Subsequently, when the polymerization conversion relative to the added monomer reached 60%, 7 parts of acrylonitrile were added to initiate the third stage of polymerization. Finally, when the polymerization conversion relative to the added monomer reached 90%, 0.1 parts of a 10% aqueous solution of hydroquinone (polymerization terminator) was added to terminate the polymerization reaction. After terminating the polymerization reaction, residual monomers were removed using a rotary evaporator at a water temperature of 60°C to obtain the latex of the polymer rubber (solid content concentration of approximately 25% by weight).

[0270] Next, the latex of the obtained polymer rubber was added to an aqueous solution of aluminum sulfate at a concentration of 3% relative to the rubber composition. The mixture was stirred to allow the latex to coagulate. After washing with water and filtering, the latex was vacuum-dried at 60°C for 12 hours to obtain the polymer rubber. Then, the obtained polymer rubber was dissolved in acetone at a concentration of 12%, and placed in an autoclave. 500 ppm of palladium-silica catalyst was added to the nitrile copolymer rubber, and a hydrogenation reaction was carried out at a hydrogen pressure of 3 MPa and a temperature of 50°C. After the hydrogenation reaction was terminated, the mixture was poured into a large amount of water to coagulate, filtered, and dried to obtain the nitrile polymer. The weight-average molecular weight, the percentage of terminal C6 straight chains, the iodine value, and the peak width of tanδ were determined for the obtained nitrile polymer. The results are shown in Table 1.

[0271] <Preparation of binder compositions for positive electrodes>

[0272] A binder composition for the positive electrode was prepared by heating and mixing 8 parts of the nitrile polymer obtained as described above, 0.0016 parts of 1-chloropropane (200 ppm relative to the nitrile polymer), and 92 parts of NMP. The binder stability of the obtained binder composition for the positive electrode was determined. The results are shown in Table 1.

[0273] <Preparation of Surface-Treated CNTs>

[0274] Weigh 1g of multi-walled carbon nanotubes (BET specific surface area: 250m²). 2 The CNT solids were added to a mixed solution of 40 mL concentrated nitric acid and 40 mL 2M sulfuric acid, and stirred at 60°C for 1 hour (acid treatment). Afterwards, the mixture was filtered using filter paper (Toyo Filter Paper Co., Ltd., filter paper No. 2, 125 mm) for solid-liquid separation. The solids on the filter paper were washed with 200 mL of purified water, and the CNT solids were recovered (acid-treated CNTs). Then, the CNT solids were added to 200 mL of a 2.5 mol / L lithium hydroxide aqueous solution, and stirred at 25°C in a water bath for 2 hours (alkali treatment). Afterwards, the mixture was filtered through a 10 μm membrane filter for solid-liquid separation. The CNT solids on the membrane filter were repeatedly washed with purified water (acid-alkali treated CNTs). When the conductivity of the washing water became below 50 μS / m, the CNT solids were separated into solid and liquid components using the same method described above. The obtained CNT solids were dried under reduced pressure at 50°C for 8 hours to prepare surface-treated CNTs. For this CNT surface treatment, the surface acidity, surface alkaliity, and BET specific surface area were measured. Furthermore, the ratio of surface acidity to surface alkaliity was calculated. The results are shown in Table 1.

[0275] <Preparation of Conductive Material Dispersions>

[0276] Five parts of the above-mentioned surface-treated CNTs (as a carbon-containing material), one part of the above-mentioned binder composition (converted to the solids content of hydrogenated nitrile rubber), and 94 parts of NMP were stirred using a disperser (3000 rpm, 10 minutes). Then, the mixture was dispersed for 1 hour using a bead mill with 1 mm diameter zirconia beads at a circumferential speed of 8 m / s, thereby preparing a conductive material dispersion with a solids concentration of 6.0%. The dispersion stability of this conductive material dispersion was evaluated. The results are shown in Table 1.

[0277] <Preparation of Cathode Slurry>

[0278] 100 parts of a layered ternary active material (LiNi) with a layered structure was added as a positive electrode active material to the conductive material dispersion obtained as described above. 0.6 Co 0.2 Mn 0.2 O2 (volume average particle size: 10 μm) and an appropriate amount of NMP as a dispersion medium were stirred in a disperser (3000 rpm, 20 minutes) to prepare a slurry for the positive electrode. Furthermore, the amount of NMP added was adjusted to ensure that the viscosity of the obtained positive electrode slurry was in the range of 3000–4000 mPa·s at 60 rpm.

[0279] <The Making of the Positive Electrode>

[0280] Prepare an aluminum foil with a thickness of 20 μm as the current collector. Use a notched wheel coater to coat the positive electrode slurry obtained as described above until the dried weight per unit area is 20 mg / cm². 2 The coating was applied to one side of aluminum foil, dried at 90℃ for 20 minutes, then dried at 120℃ for 20 minutes, and finally heat-treated at 60℃ for 10 hours to obtain the positive electrode raw material. This positive electrode raw material was then calendered using a roller press to produce a positive electrode composite material layer (density: 3.2 g / cm³). 3 A sheet-shaped positive electrode was formed using aluminum foil and aluminum foil. This sheet-shaped positive electrode was then cut into pieces with a width of 48.0 mm and a length of 47 cm for use as a positive electrode in lithium-ion secondary batteries. The peel strength, flexibility, and resistance of this positive electrode were evaluated. The results are shown in Table 1.

[0281] <Making the Negative Electrode>

[0282] A slurry for the negative electrode was prepared by mixing 90 parts of spherical artificial graphite (volume average particle size: 12 μm) and 10 parts of SiOx (volume average particle size: 10 μm) as the negative electrode active material, 1 part of styrene-butadiene polymer as the negative electrode binder, 1 part of carboxymethyl cellulose as the thickener, and an appropriate amount of water as the dispersion medium using a planetary mixer.

[0283] Next, a copper foil with a thickness of 15 μm is prepared as the current collector. The negative electrode slurry obtained as described above is applied to achieve a coating weight of 10 mg / cm² after drying. 2 The coating was applied to one side of copper foil using a specific method, and then dried at 60°C for 20 minutes, followed by drying at 120°C for 20 minutes. Afterward, it was heat-treated at 150°C for 2 hours to obtain the negative electrode raw material. This negative electrode raw material was then calendered using a roller press to produce a product with a density of 1.6 g / cm³. 3 A sheet-shaped negative electrode is formed by a negative electrode composite material layer and copper foil. Then, the sheet-shaped negative electrode is cut into pieces with a width of 50.0 mm and a length of 52 cm to serve as the negative electrode for lithium-ion secondary batteries.

[0284] <Manufacturing of Lithium-ion Secondary Batteries>

[0285] The positive and negative electrodes, fabricated as described above, are arranged with electrode composite material layers facing each other, separated by a 15 μm thick spacer (a microporous membrane made of polypropylene). A 20 mm diameter core is then wound to obtain a wound body. The wound body is then compressed in one direction at a speed of 10 mm / s until its thickness becomes 4.5 mm. Furthermore, the compressed wound body, when viewed from above, is elliptical in shape, with a major axis to minor axis ratio (major axis / minor axis) of 7.7.

[0286] In addition, prepare an electrolyte (a 1.0 M LiPF6 solution (the solvent is a mixed solution of ethylene carbonate / ethyl methyl carbonate = 3 / 7 (mass ratio) with 5% by mass of fluoroethylene carbonate added, and 2% by volume of ethylene carbonate added as an additive)).

[0287] Next, the compressed winding and 3.2g of electrolyte are placed together in an aluminum laminated shell. Then, a nickel wire is connected to the designated position for the negative electrode of the lithium-ion secondary battery, and an aluminum wire is connected to the designated position for the positive electrode. Finally, the opening of the shell is sealed using heat to obtain the lithium-ion secondary battery. This lithium-ion secondary battery is a pouch-shaped battery with a width of 35mm, a height of 60mm, and a thickness of 5mm, and its nominal capacity is 700mAh.

[0288] The cycle characteristics and rate performance of the obtained lithium-ion secondary batteries were evaluated. The results are shown in Table 1.

[0289] (Example 2)

[0290] In preparing the binder composition for the positive electrode, the amount of 1-chloropropane was changed to 0.0028 parts (350 ppm relative to the amount of the nitrile polymer). Otherwise, the nitrile polymer, the binder composition for the positive electrode, the surface-treated CNT, the conductive material dispersion, the positive electrode slurry, the positive electrode, the negative electrode, and the lithium-ion secondary battery were prepared in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 1.

[0291] (Example 3)

[0292] In preparing the binder composition for the positive electrode, the amount of 1-chloropropane was changed to 0.0008 parts (100 ppm relative to the amount of the nitrile polymer). Otherwise, the nitrile polymer, the binder composition for the positive electrode, the surface-treated CNT, the conductive material dispersion, the slurry for the positive electrode, the positive electrode, the negative electrode, and the lithium-ion secondary battery were prepared in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 1.

[0293] (Example 4)

[0294] In preparing the binder composition for the positive electrode, the amount of 1-chloropropane was changed to 0.00008 parts (10 ppm relative to the amount of the nitrile polymer). Otherwise, the nitrile polymer, the binder composition for the positive electrode, the surface-treated CNT, the conductive material dispersion, the positive electrode slurry, the positive electrode, the negative electrode, and the lithium-ion secondary battery were prepared in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 1.

[0295] (Example 5)

[0296] In preparing the binder composition for the positive electrode, monochlorobenzene was used instead of 1-chloropropane. Otherwise, nitrile polymers, binder compositions for the positive electrode, surface-treated CNTs, conductive material dispersions, positive electrode slurries, positive electrodes, negative electrodes, and lithium-ion secondary batteries were prepared in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 1.

[0297] (Example 6)

[0298] In preparing the nitrile polymer, 0.48 parts of 1-decylthiol and 0.32 parts of tert-dodecylthiol (TDM) were used instead of 0.8 parts of 1-decylthiol as a chain transfer agent. Otherwise, the nitrile polymer, cathode binder composition, surface-treated CNT, conductive material dispersion, cathode slurry, cathode, anode, and lithium-ion secondary battery were prepared in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 1.

[0299] (Example 7)

[0300] In preparing the nitrile polymer, 0.32 parts of 1-decylthiol and 0.48 parts of TDM were used instead of 0.8 parts of 1-decylthiol as a chain transfer agent. Otherwise, the nitrile polymer, cathode binder composition, surface-treated CNT, conductive material dispersion, cathode slurry, cathode, anode, and lithium-ion secondary battery were prepared in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 1.

[0301] (Example 8)

[0302] In preparing the nitrile polymer, 0.8 parts of TDM were used instead of 0.8 parts of 1-decylthiol as a chain transfer agent. Otherwise, the nitrile polymer, the binder composition for the positive electrode, the surface-treated CNT, the conductive material dispersion, the slurry for the positive electrode, the positive electrode, the negative electrode, and the lithium-ion secondary battery were prepared in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 1.

[0303] (Example 9)

[0304] Using the nitrile polymer prepared as described below, except for the preparation of the positive electrode binder composition, surface-treated CNTs, conductive material dispersions, positive electrode slurries, positive electrodes, negative electrodes, and lithium-ion secondary batteries, various evaluations were performed in the same manner as in Example 1. The results are shown in Table 2.

[0305] <Preparation of Nitrile Polymers>

[0306] A soap solution was prepared by adding 200 parts of deionized water and 2.25 parts of potassium fatty acid soap (potassium salt of fatty acids) to the reactor. Then, 21 parts of acrylonitrile and 0.8 parts of 1-decyl mercaptan (chain transfer agent) were added sequentially to the soap solution. After purging the internal gas three times with nitrogen, 64 parts of 1,3-butadiene were added. Next, the reactor was maintained at 5±1°C, and 0.1 parts of cumene hydroperoxide (polymerization initiator) were added while stirring to begin the first stage of polymerization. Then, when the polymerization conversion relative to the added monomer reached 50%, 15 parts of acrylonitrile were added to initiate the second stage of polymerization. Afterward, when the polymerization conversion relative to the added monomer reached 90%, 0.1 parts of a 10% aqueous solution of hydroquinone (polymerization terminator) was added to terminate the polymerization reaction. After termination of the polymerization reaction, residual monomer was removed using a rotary evaporator at 60°C to obtain a latex of polymer rubber (solid content concentration approximately 25% by weight).

[0307] Using the latex of the obtained polymer rubber, except that the same steps as in Example 1 are followed to obtain a nitrile polymer.

[0308] (Example 10)

[0309] Using the nitrile polymer prepared as described below, except for the preparation of the positive electrode binder composition, surface-treated CNTs, conductive material dispersions, positive electrode slurries, positive electrodes, negative electrodes, and lithium-ion secondary batteries, various evaluations were performed in the same manner as in Example 1. The results are shown in Table 2.

[0310] <Preparation of Nitrile Polymers>

[0311] A soap solution was prepared by adding 200 parts of deionized water and 2.25 parts of potassium fatty acid soap (potassium salt of fatty acids) to the reactor. Then, 36 parts of acrylonitrile and 0.8 parts of 1-decyl mercaptan (chain transfer agent) were added sequentially to the soap solution. After purging the internal gas three times with nitrogen, 64 parts of 1,3-butadiene were added. Next, the reactor was maintained at 5±1°C, and 0.1 parts of cumene hydroperoxide (polymerization initiator) were added, and polymerization was initiated while stirring. Then, when the polymerization conversion relative to the added monomer reached 90%, 0.1 parts of a 10% aqueous solution of hydroquinone (polymerization terminator) was added to terminate the polymerization reaction. After terminating the polymerization reaction, residual monomer was removed using a rotary evaporator at 60°C to obtain a latex of polymer rubber (solid content concentration approximately 25% by weight).

[0312] Using the latex of the obtained polymer rubber, except that the same steps as in Example 1 are followed to obtain a nitrile polymer.

[0313] (Example 11)

[0314] In preparing the nitrile polymer, the temperature in the first stage of polymerization was changed to 3±1℃, the temperature in the second stage of polymerization was changed to 5±1℃, and the temperature in the third stage of polymerization was changed to 7±1℃. Otherwise, the nitrile polymer, the binder composition for the positive electrode, the surface-treated CNT, the conductive material dispersion, the slurry for the positive electrode, the positive electrode, the negative electrode, and the lithium-ion secondary battery were prepared in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 2.

[0315] (Example 12)

[0316] In preparing the nitrile polymer, the temperature in the first stage of polymerization was changed to 2±1℃, the temperature in the second stage of polymerization was changed to 5±1℃, and the temperature in the third stage of polymerization was changed to 8±1℃. Otherwise, the nitrile polymer, the binder composition for the positive electrode, the surface-treated CNT, the conductive material dispersion, the slurry for the positive electrode, the positive electrode, the negative electrode, and the lithium-ion secondary battery were prepared in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 2.

[0317] (Example 13)

[0318] In the preparation of surface-treated CNTs, the alkaline treatment time was changed from 2 hours to 4 hours. Otherwise, the same procedures as in Example 1 were followed to prepare nitrile polymers, positive electrode binder compositions, surface-treated CNTs, conductive material dispersions, positive electrode slurries, positive electrodes, negative electrodes, and lithium-ion secondary batteries, and various evaluations were performed. The results are shown in Table 2.

[0319] (Example 14)

[0320] In the preparation of surface-treated CNTs, a 2.5 mol / L ammonium chloride aqueous solution was used instead of a 2.5 mol / L lithium hydroxide aqueous solution for alkali treatment. Otherwise, nitrile polymers, positive electrode binder compositions, surface-treated CNTs, conductive material dispersions, positive electrode slurries, positive electrodes, negative electrodes, and lithium-ion secondary batteries were prepared in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 2.

[0321] (Example 15)

[0322] When preparing surface-treated CNTs, other multi-walled CNTs (specific surface area: 110 m²) were used. 2 Using CNTs (g) as raw material, without alkali treatment, the acid-treated CNTs were washed until the conductivity of the washing water became below 50 μs / m. Otherwise, nitrile polymers, positive electrode binder compositions, surface-treated CNTs, conductive material dispersions, positive electrode slurries, positive electrodes, negative electrodes, and lithium-ion secondary batteries were prepared in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 2.

[0323] (Comparative Example 1)

[0324] In preparing the binder composition for the positive electrode, the amount of 1-chloropropane was changed to 0.004 parts (500 ppm relative to the amount of the nitrile polymer). Otherwise, the nitrile polymer, the binder composition for the positive electrode, the surface-treated CNT, the conductive material dispersion, the positive electrode slurry, the positive electrode, the negative electrode, and the lithium-ion secondary battery were prepared in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 2.

[0325] (Comparative Example 2)

[0326] In preparing the binder composition for the positive electrode, 1-chloropropane was not used. Otherwise, nitrile polymers, binder compositions for the positive electrode, surface-treated CNTs, conductive material dispersions, slurries for the positive electrode, positive electrodes, negative electrodes, and lithium-ion secondary batteries were prepared in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 2.

[0327] [Table 1]

[0328]

[0329] [Table 2]

[0330]

[0331] As shown in Tables 1 and 2, the binder compositions of Examples 1 to 15, which contain nitrile polymers, NMP, and halogenated hydrocarbons with the content of halogenated hydrocarbons being 2 ppm by mass or more and 400 ppm by mass or less relative to the content of nitrile polymers, exhibit excellent viscosity stability, and electrodes with excellent peel strength can be fabricated using these binder compositions.

[0332] Industrial availability

[0333] According to the present invention, an adhesive composition for electrochemical elements that exhibits excellent viscosity stability and is capable of forming electrodes with excellent peel strength can be provided.

[0334] Furthermore, according to the present invention, it is possible to provide a conductive material dispersion for electrochemical elements and a slurry for electrochemical element electrodes capable of forming electrodes with excellent peel strength.

[0335] Furthermore, according to the present invention, it is possible to provide an electrode for an electrochemical element with excellent peel strength and an electrochemical element having the electrode for an electrochemical element.

Claims

1. A binder composition for electrochemical components, comprising a nitrile polymer, N-methyl-2-pyrrolidone, and a halogenated hydrocarbon. The nitrile polymer contains nitrile-based monomer units. The content of the halogenated hydrocarbon is more than 2 ppm by mass and less than 400 ppm by mass relative to the content of the nitrile polymer.

2. The binder composition for electrochemical components according to claim 1, wherein, The peak width of the loss tangent tanδ in the viscoelastic properties of the nitrile polymer is above 5°C and below 30°C.

3. The binder composition for electrochemical elements according to claim 1 or 2, wherein, In the nitrile polymer, the proportion of molecular ends composed of straight-chain alkyl groups with 6 or more carbon atoms is more than 30% of all molecular ends.

4. A conductive material dispersion for electrochemical elements, comprising a carbon-containing material and a binder composition for electrochemical elements according to any one of claims 1 to 3.

5. The conductive material dispersion for electrochemical elements according to claim 4, wherein, The carbon-containing material includes carbon nanotubes. The surface alkalinity of the carbon nanotube is above 0.01 mmol / g and below 0.10 mmol / g, and the ratio of the surface acidity to the surface alkalinity of the carbon nanotube is above 0.1 and below 1.

0.

6. A slurry for an electrochemical element electrode, comprising an electrode active material and a dispersion of a conductive material for an electrochemical element as described in claim 4 or 5.

7. An electrode for an electrochemical element having an electrode composite material layer formed using the slurry for an electrochemical element electrode as described in claim 6.

8. An electrochemical element having the electrode for an electrochemical element as described in claim 7.

Images