Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
  • H01M4/386—Silicon or alloys based on silicon
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/052—Li-accumulators
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/052—Li-accumulators
  • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
  • H01M4/134—Electrodes based on metals, Si or alloys
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
  • H01M4/139—Processes of manufacture
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
  • H01M4/139—Processes of manufacture
  • H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
  • H01M4/621—Binders
  • H01M4/622—Binders being polymers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
  • H01M4/624—Electric conductive fillers
  • H01M4/625—Carbon or graphite
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
  • H01M2004/027—Negative electrodes
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries

Definitions

• the present invention relates to a conductive material paste for non-aqueous electrolyte secondary batteries, a slurry composition for non-aqueous electrolyte secondary battery negative electrodes, a negative electrode for non-aqueous electrolyte secondary batteries, and a non-aqueous electrolyte secondary battery.
• Non-aqueous electrolyte secondary batteries such as lithium-ion secondary batteries are small, lightweight, have high energy density, and can be repeatedly charged and discharged, and are used in a wide range of applications.
• the electrode for the non-aqueous electrolyte secondary battery is, for example, an electrode mixture formed by drying a current collector and a slurry composition for a non-aqueous electrolyte secondary battery electrode on the current collector with layers.
• fibrous conductive carbon such as carbon nanotubes (hereinafter sometimes abbreviated as "CNT") has been used as a conductive material for forming electrode mixture layers.
• CNT carbon nanotubes
• the fibrous conductive carbon and the dispersant are premixed in order to obtain an electrode mixture layer in which the fibrous conductive carbon is well dispersed.
• a conductive material paste for a non-aqueous electrolyte secondary battery electrode, and the obtained conductive material paste and an electrode active material are combined to prepare a slurry composition for a non-aqueous electrolyte secondary battery electrode.
• the present invention can provide a slurry composition for a negative electrode of a non-aqueous electrolyte secondary battery in which paste dispersibility is maintained and slurry viscosity stability is maintained, and the resistance increase rate during a high temperature storage test is
• An object of the present invention is to provide a conductive material paste for a non-aqueous electrolyte secondary battery that can provide a suppressed non-aqueous electrolyte secondary battery.
• the present invention provides a slurry composition for a negative electrode of a non-aqueous electrolyte secondary battery in which slurry viscosity stability is maintained, and at the same time, a non-aqueous electrolyte that suppresses the rate of increase in resistance during a high-temperature storage test.
• An object of the present invention is to provide a slurry composition for a negative electrode of a non-aqueous electrolyte secondary battery capable of providing a secondary battery.
• Another object of the present invention is to provide a negative electrode for a non-aqueous electrolyte secondary battery that can provide a non-aqueous electrolyte secondary battery in which the rate of increase in resistance during a high-temperature storage test is suppressed.
• Another object of the present invention is to provide a non-aqueous electrolyte secondary battery in which the rate of increase in resistance during a high-temperature storage test is suppressed.
• the inventor of the present invention conducted intensive studies with the aim of solving the above problems. Then, the present inventors have found that carbon nanotubes, a dispersant that is a copolymer containing an unsaturated carboxylic acid monomer unit and a (meth)acrylamide group-containing monomer unit, a dispersant that is a thiazoline compound, and a dispersion medium
• a non-aqueous electrolyte secondary battery conductive material paste containing water as a slurry composition for a non-aqueous electrolyte secondary battery negative electrode in which paste dispersibility is maintained and slurry viscosity stability is maintained
• the inventors have found that it is possible to provide a non-aqueous electrolyte secondary battery in which the rate of resistance increase during a high-temperature storage test is suppressed while making it possible to provide the above, and have completed the present invention.
• an object of the present invention is to advantageously solve the above problems, and a conductive material paste for a non-aqueous electrolyte secondary battery of the present invention comprises carbon nanotubes (A), a dispersant (B), Containing a dispersant (C) and water, the dispersant (B) is a copolymer containing at least an unsaturated carboxylic acid monomer unit and a (meth)acrylamide group-containing monomer unit, and the dispersant (C) is characterized by being thiazoline or a derivative thereof.
• the paste dispersibility of the paste can be maintained.
• Slurry composition for non-aqueous electrolyte secondary battery negative electrode maintaining slurry viscosity stability, non-aqueous electrolyte secondary capable of providing non-aqueous electrolyte secondary battery with suppressed resistance increase rate during high temperature storage test It is possible to provide a battery negative electrode and a non-aqueous electrolyte secondary battery in which the rate of increase in resistance during a high-temperature storage test is suppressed.
• the copolymer that is the dispersant (B) preferably further contains aromatic sulfonic acid monomer units.
• the content of the unsaturated carboxylic acid monomer units is 5 parts by mass or more and 80 parts by mass or less when the total monomer units are 100 parts by mass. Preferably.
• the content of the (meth)acrylamide group-containing monomer units is 25 when the content of the unsaturated carboxylic acid monomer units is 100 parts by mass. It is preferably at least 400 parts by mass.
• At least part of the unsaturated carboxylic acid monomer units contained in the copolymer that is the dispersant (B) is preferably in the form of a neutralized salt that is an alkali metal salt or an ammonium salt.
• the thiazoline or its derivative as the dispersing agent (C) is isothiazoline or its derivative.
• the conductive material paste for a non-aqueous electrolyte secondary battery of the present invention further contains carbon black.
• the conductive material paste further includes a particulate polymer, and the particulate polymer contains at least an unsaturated carboxylic acid monomer unit, an aromatic vinyl monomer unit, and a diene monomer unit as constituent units of the polymer. It is preferably characterized by comprising:
• the conductive material paste has a pH of 6 or more and 9 or less.
• the slurry composition for a non-aqueous electrolyte secondary battery negative electrode of the present invention is characterized by containing a conductive material paste for a non-aqueous electrolyte secondary battery and at least a silicon-based active material.
• the negative electrode for a non-aqueous electrolyte secondary battery of the present invention includes a negative electrode mixture layer formed using the slurry composition described above.
• non-aqueous electrolyte secondary battery of the present invention includes the negative electrode described above.
• a slurry composition for a non-aqueous electrolyte secondary battery negative electrode in which paste dispersibility is maintained and slurry viscosity stability is maintained. It is possible to provide a conductive material paste for a non-aqueous electrolyte secondary battery that can provide a suppressed non-aqueous electrolyte secondary battery.
• a slurry composition for a non-aqueous electrolyte secondary battery negative electrode in which slurry viscosity stability is maintained, and a non-aqueous electrolysis in which the rate of increase in resistance during a high-temperature storage test is suppressed.
• a slurry composition for a non-aqueous electrolyte secondary battery negative electrode that can provide a liquid secondary battery.
• a negative electrode for a non-aqueous electrolyte secondary battery that can provide a non-aqueous electrolyte secondary battery in which the rate of increase in resistance during a high-temperature storage test is suppressed.
• the conductive material paste for non-aqueous electrolyte secondary batteries of the present invention is used as a material for producing a slurry composition for non-aqueous electrolyte secondary battery negative electrodes.
• the negative electrode for nonaqueous electrolyte secondary batteries of this invention is equipped with the negative electrode mixture layer formed using the slurry composition for nonaqueous electrolyte secondary battery negative electrodes of this invention.
• the non-aqueous electrolyte secondary battery of the present invention includes the negative electrode for non-aqueous electrolyte secondary batteries of the present invention.
• the conductive material paste for a non-aqueous electrolyte secondary battery of the present invention contains carbon nanotubes (A), a dispersant (B), and a dispersant (C). It is a composition dispersed and/or dissolved in water as a medium.
• the dispersant (B) is a copolymer containing at least unsaturated carboxylic acid monomer units and (meth)acrylamide group-containing monomer units.
• the dispersant (C) is thiazoline or a derivative thereof.
• a slurry composition for a non-aqueous electrolyte secondary battery negative electrode in which slurry viscosity stability is maintained.
• Slurry composition for non-aqueous electrolyte secondary battery negative electrode capable of providing non-aqueous electrolyte secondary battery with suppressed resistance increase rate during test, non-aqueous electrolyte solution with suppressed resistance increase rate during high temperature storage test
• a negative electrode for a non-aqueous electrolyte secondary battery capable of providing a secondary battery, and a non-aqueous electrolyte secondary battery having a suppressed rate of increase in resistance during a high-temperature storage test can be produced.
• the carbon nanotube (A) is not particularly limited as long as it is a carbon nanotube (CNT) that achieves the object of the present invention.
• Carbon nanotubes include single-walled (SW) carbon nanotubes and multi-walled (MW) carbon nanotubes, depending on the type of layer type.
• the carbon nanotube (A) may be a single-walled carbon nanotube, a multi-walled carbon nanotube, or a combination thereof. is preferred.
• the average diameter of the CNTs is preferably 0.5 nm or more, more preferably 1 nm or more, even more preferably 2 nm or more, and preferably 50 nm or less, more preferably 40 nm or less, and even more preferably 20 nm or less. good.
• the average length of the CNTs is preferably 1 ⁇ m or more, more preferably 3 ⁇ m or more, even more preferably 5 ⁇ m or more, and preferably 40 ⁇ m or less, more preferably 30 ⁇ m or less, and even more preferably 20 ⁇ m or less. .
• the average diameter and average length are equal to or greater than the above lower limits, aggregation of CNTs can be sufficiently suppressed, and the dispersibility of CNTs as a conductive material can be sufficiently ensured. Moreover, when the average diameter and average length are equal to or less than the above upper limits, good conductive paths can be formed in the electrode mixture layer, and the output characteristics of the secondary battery can be further improved.
• the "average diameter” and “average length” can be determined by measuring the diameter (outer diameter) and length of 100 randomly selected CNTs using a TEM.
• the aspect ratio (length/diameter) of CNTs is usually greater than 5, preferably 10 or more.
• the "aspect ratio" of CNTs can be obtained by measuring the major axis and minor axis of 100 randomly selected CNTs using a transmission electron microscope.
• CNTs having the properties described above can be prepared by known methods such as an arc discharge method, a laser ablation method, and a super-growth method, without being particularly limited.
• the content ratio of the carbon nanotubes (A) to the total solid content of the conductive material paste may be, for example, 20% by mass or more, preferably 30% by mass or more, and more preferably 40% by mass or more. Also, this content may be, for example, 90% by mass or less, preferably 85% by mass or less, and more preferably 80% by mass or less. If the content of the carbon nanotubes (A) is at least the above lower limit, the electrical contact of the carbon nanotubes (A) in the electrode mixture layer can be better ensured, the internal resistance of the obtained secondary battery can be reduced, Better output characteristics can be exhibited. Also, the capacity of the secondary battery can be more stably preserved.
• the content ratio of the carbon nanotubes (A) is equal to or less than the above upper limit, the content ratio of the dispersant (B) can be increased, and the paste dispersibility of the resulting conductive material paste by the dispersant (B), And the effect of improving the slurry viscosity stability of the resulting slurry composition can be enhanced.
• the dispersant (B) is a water-soluble copolymer containing at least unsaturated carboxylic acid monomer units and (meth)acrylamide group-containing monomer units. Moreover, the copolymer as the dispersant (B) may preferably further contain an aromatic sulfonic acid monomer unit from the viewpoint of further improving the dispersibility of the carbon nanotubes.
• the term "water-soluble polymer” refers to a polymer having an insoluble content of less than 1.0% by mass when 0.5 g of the polymer is dissolved in 100 g of water at a temperature of 25°C.
• a polymer contains a monomer unit means that "the polymer obtained using the monomer contains a repeating unit derived from the monomer”.
• the content of monomer units in the polymer can be measured using nuclear magnetic resonance (NMR) methods such as 1 H-NMR and 13 C-NMR.
• Examples of unsaturated carboxylic acid monomer units constituting the copolymer that is the dispersant (B) include ethylenically unsaturated carboxylic acid monomer units.
• Ethylenically unsaturated carboxylic acid monomers capable of forming ethylenically unsaturated carboxylic acid monomer units generally do not have hydroxyl groups (--OH) other than the hydroxyl group in the carboxyl group.
• ethylenically unsaturated carboxylic acid monomers include ethylenically unsaturated monocarboxylic acids and derivatives thereof, ethylenically unsaturated dicarboxylic acids and acid anhydrides thereof, and derivatives thereof.
• the ethylenically unsaturated carboxylic acid monomers may be used singly or in combination of two or more at any ratio.
• Examples of ethylenically unsaturated monocarboxylic acids include acrylic acid, methacrylic acid, and crotonic acid.
• Examples of ethylenically unsaturated monocarboxylic acid derivatives include 2-ethylacrylic acid, isocrotonic acid, ⁇ -acetoxyacrylic acid, ⁇ -trans-aryloxyacrylic acid, ⁇ -chloro- ⁇ -E-methoxyacrylic acid. acid, ⁇ -diaminoacrylic acid, and the like.
• Examples of ethylenically unsaturated dicarboxylic acids include maleic acid, fumaric acid and itaconic acid.
• Examples of acid anhydrides of ethylenically unsaturated dicarboxylic acids include maleic anhydride, diacrylic anhydride, methyl maleic anhydride, and dimethyl maleic anhydride.
• Examples of ethylenically unsaturated dicarboxylic acid derivatives include methylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, and fluoromaleic acid.
• the ethylenically unsaturated carboxylic acid monomers are preferably ethylenically unsaturated monocarboxylic acids and ethylenically unsaturated dicarboxylic acids, more preferably acrylic acid, methacrylic acid and itaconic acid. Acrylic acid and methacrylic acid are more preferred.
• acrylic acid is more preferable as the ethylenically unsaturated carboxylic acid monomer from the viewpoint of suppressing excessive swelling of the resulting copolymer in the electrolytic solution.
• At least part of the unsaturated carboxylic acid monomer units may be in the form of a neutralized salt in which the carboxyl group portion is an alkali metal salt or an ammonium salt.
• alkali metal salts include lithium salts, sodium salts, potassium salts, rubidium salts, and cesium salts, with lithium salts being preferred.
• the content of the unsaturated carboxylic acid monomer units is preferably 15 parts by mass or more, when the total monomer units are 100 parts by mass. It is more preferably at least 25 parts by mass, preferably at most 80 parts by mass, more preferably at most 70 parts by mass, and at most 60 parts by mass. More preferred. If the content of the unsaturated carboxylic acid monomer unit in the copolymer that is the dispersant (B) is at least the above lower limit, the paste dispersibility of the obtained conductive material paste can be improved.
• the resulting non-aqueous electrolyte secondary battery will increase in resistance during the high-temperature storage test. rate suppression can be improved.
• a (meth)acrylamide monomer that can form a (meth)acrylamide group-containing monomeric unit is acrylamide, methacrylamide, or a combination thereof.
• the content of the (meth)acrylamide group-containing monomer units is preferably 15 parts by mass or more when the total monomer units are 100 parts by mass. , more preferably 20 parts by mass or more, more preferably 25 parts by mass or more, preferably 50 parts by mass or less, more preferably 60 parts by mass or less, and 85 parts by mass or less is more preferred.
• the content of the (meth)acrylamide group-containing monomer unit is 25 parts by mass when the content of the unsaturated carboxylic acid monomer unit is 100 parts by mass.
• the content of the (meth)acrylamide group-containing monomer unit is at least the above lower limit, the cycle characteristics of the obtained non-aqueous electrolyte secondary battery can be improved. On the other hand, if the content of (meth)acrylamide monomer units is equal to or less than the above upper limit, the viscosity stability of the resulting slurry composition can be improved.
• aromatic sulfonic acid monomer capable of forming an aromatic sulfonic acid monomer unit refers to a compound having an aromatic ring, an ethylenically unsaturated bond and a sulfonic acid group.
• aromatic sulfonic acid monomers include styrenesulfonic acid, naphthylvinylsulfonic acid, and divinylbenzenesulfonic acid.
• At least part of the aromatic sulfonic acid monomer units may be in the form of a neutralized salt, which is an alkali metal salt or an ammonium salt.
• alkali metal salts include lithium salts, sodium salts, potassium salts, rubidium salts and cesium salts, with sodium salts and lithium salts being preferred.
• the content of the aromatic sulfonic acid monomer units is preferably 3 parts by mass or more when the total monomer units are 100 parts by mass. It is more preferably 10 parts by mass or more, more preferably 40 parts by mass or less, more preferably 35 parts by mass or less, and 30 parts by mass or less. More preferred. If the content ratio of the aromatic sulfonic acid monomer units in the copolymer as the dispersant (B) is at least the above lower limit, the paste dispersibility of the obtained conductive material paste can be improved.
• the resulting non-aqueous electrolyte secondary battery will not increase in resistance during the high-temperature storage test. Rate control and cycle characteristics can be improved.
• any monomer that can be copolymerized with a monomer having an unsaturated bond between carbon atoms can be used.
• examples thereof include monomers having an unsaturated bond between carbon atoms other than the above-described unsaturated carboxylic acid monomers, (meth)acrylamide group-containing monomers, and aromatic sulfonic acid monomers. .
• Examples of such monomers having an unsaturated bond between carbon atoms include cyano group-containing vinyl monomers, amino group-containing vinyl monomers, pyridyl group-containing vinyl monomers, alkoxyl group-containing vinyl monomers, and the like. is mentioned.
• the above-described monomer having an unsaturated bond between carbon atoms and a copolymerizable monomer may be used alone, or two or more may be used in combination at an arbitrary ratio. .
• the weight-average molecular weight of the copolymer that is the dispersant (B) is preferably 4,000 or more, more preferably 8,000 or more, and even more preferably 10,000 or more. It is preferably 000,000 or less, more preferably 1,000,000 or less, and even more preferably 800,000 or less. If the weight average molecular weight of the dispersant (B) is at least the above lower limit, the dispersibility of the conductive material paste can be improved. On the other hand, if the weight-average molecular weight of the copolymer that is the dispersant (B) is equal to or less than the above upper limit, the solid content concentration of the conductive material paste can be increased. In the present invention, the "weight average molecular weight" of the polymer can be measured using the method described in Examples.
• the method for producing the dispersant (B) is not particularly limited.
• the dispersant (B) is prepared, for example, by polymerizing a monomer composition containing one or more monomers in an aqueous solvent.
• the content ratio of each monomer in the monomer composition can be determined according to the content ratio of desired monomer units in the polymer.
• the polymerization mode is not particularly limited, and any method such as a solution polymerization method, a suspension polymerization method, a bulk polymerization method and an emulsion polymerization method can be used.
• any reaction such as ionic polymerization, radical polymerization, living radical polymerization, various types of condensation polymerization, and addition polymerization can be used.
• known emulsifiers and polymerization initiators can be used as necessary.
• the content ratio of the solid content of the dispersant (B) to the total solid content of the conductive material paste may be, for example, 5% by mass or more, preferably 10% by mass or more, and more preferably 15% by mass or more. Also, the content may be, for example, 70% by mass or less, preferably 50% by mass or less, more preferably 40% by mass or less. If the content of the dispersant (B) is at least the above lower limit, it is possible to improve the paste dispersibility of the obtained conductive material paste and the slurry viscosity stability of the obtained slurry composition.
• the content of the dispersant (B) is equal to or less than the above upper limit, the content of the carbon nanotubes (A) can be increased, and the electrical contact of the carbon nanotubes (A) in the electrode mixture layer can be improved. It is possible to reduce the internal resistance of the obtained secondary battery and enhance the effect of exhibiting better output characteristics.
• Dispersant (C) is a thiazoline or derivative thereof.
• the dispersant (C) is a compound having a thiazoline skeleton.
• thiazoline (including variations of the term and part of the compound name) refers to both thiazolines and isothiazolines in which the nitrogen and sulfur atoms are not adjacent.
• thiazoline or its derivative may be referred to as "thiazoline-based compound”.
• Thiazoline-based compounds include thiazolines substituted with one or more substituents, and thiazoline condensed rings formed by condensation of thiazolines with another ring (which may be further substituted with one or more substituents). .
• substituents include optionally substituted hydrocarbon groups, oxo, halogen atoms (e.g., chlorine atoms, fluorine atoms, bromine atoms, iodine atoms, etc.), hydroxyl groups, cyano groups, amino groups, carboxyl groups, Examples include, but are not limited to, an optionally substituted hydrocarbon-oxy group, an optionally substituted hydrocarbon-thio group, and the like.
• Hydrocarbon groups (“hydrocarbon” of hydrocarbon-oxy group and hydrocarbon-thio group are the same) include, for example, alkyl groups having 1 to 10 carbon atoms (e.g., methyl group, ethyl group, propyl group, etc.) ), an alkenyl group having 2 to 6 carbon atoms (e.g., vinyl group, allyl group, etc.), an alkynyl group having 2 to 6 carbon atoms (e.g., ethynyl group, propynyl group, etc.), a cycloalkyl group having 3 to 10 carbon atoms ( Examples include a cyclopentyl group, a cyclohexyl group, etc.), and an aryl group having 6 to 14 carbon atoms (eg, a phenyl group, etc.), etc., but are not limited thereto.
• Examples of the ring that may be condensed with thiazoline include hydrocarbon rings (aliphatic hydrocarbon rings, aromatic hydrocarbon rings), heterocyclic rings (non-aromatic heterocyclic rings, aromatic heterocyclic rings) and the like.
• Aliphatic hydrocarbon rings include, for example, cycloalkane rings (e.g., cyclopropane ring, cyclobutane ring, cyclopentane ring, cyclohexane ring), cycloolefin rings (e.g., cyclopropene ring, cyclobutene ring, cyclopentene ring, cyclohexene ring). etc., but not limited to these.
• aromatic hydrocarbon ring examples include, but are not limited to, benzene ring, naphthalene ring and the like.
• non-aromatic heterocyclic rings include pyrrolidine ring, tetrahydrofuran ring, tetrahydrothiophene ring, pyrroline ring, pyrrole ring, dihydrofuran ring, dihydrothiophene ring, piperidine ring, piperazine ring, tetrahydropyran ring, morpholine ring, thian ring, Examples include, but are not limited to, thiomorpholine ring, pyran ring, oxazine ring, thiopyran ring, thiazine ring and the like.
• aromatic heterocyclic ring examples include furan ring, oxazole ring, isoxazole ring, thiophene ring, thiazole ring, isothiazole ring, pyridine ring, pyridazine ring, pyrimidine ring, pyrazine ring, triazine ring and the like. Not limited.
• the thiazoline-based compound is an isothiazoline-based compound from the viewpoint of improving the paste dispersibility of the conductive material paste obtained, and the cycle characteristics of the obtained non-aqueous electrolyte secondary battery and resistance increase rate suppression during high temperature storage tests.
• An isothiazoline-based compound has, for example, a structure represented by the following formula (1).
• Y is a hydrogen atom or an optionally substituted hydrocarbon group
• X 1 and X 2 are each independently a hydrogen atom, a halogen atom, or an optionally substituted carbon number 1 to 6 alkyl groups, or X 1 and X 2 jointly form an aromatic ring, and when X 1 and X 2 do not jointly form an aromatic ring, X 1 and X 2 are They may be the same or different.
• the hydrocarbon group for Y includes, for example, an alkyl group having 1 to 10 carbon atoms (methyl group, etc.), an alkenyl group having 2 to 6 carbon atoms (vinyl group, allyl group, etc.), a carbon number of 2 to 6 alkynyl groups (ethynyl group, propynyl group, etc.), cycloalkyl groups having 3 to 10 carbon atoms (cyclopentyl group, cyclohexyl group, etc.), aryl groups having 6 to 14 carbon atoms (phenyl group), and the like.
• Some or all of the hydrogen atoms in the hydrocarbon group represented by Y may be substituted with substituents.
• substituents include, for example, hydroxyl group, halogen atom (eg, chlorine atom, fluorine atom, bromine atom, iodine atom, etc.), cyano group, amino group, carboxyl group, alkoxy group having 1 to 4 carbon atoms (eg, methoxy group, ethoxy group, etc.), an aryloxy group having 6 to 10 carbon atoms (eg, phenoxy group, etc.), an alkylthio group having 1 to 4 carbon atoms (eg, methylthio group, ethylthio group, etc.) and an arylthio group having 6 to 10 carbon atoms ( for example, a phenylthio group, etc.).
• the hydrocarbon group of Y has a plurality of substituents, the substituents may be the same or different.
• Y is preferably a methyl group or a hydrogen atom, more preferably a hydrogen atom.
• the halogen atoms of X 1 and X 2 include, for example, a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.
• examples of the alkyl group having 1 to 6 carbon atoms for X 1 and X 2 include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group and tert-butyl. group, pentyl group, and the like. Some or all of the hydrogen atoms in these alkyl groups may be substituted with substituents.
• examples of such a substituent include those similar to those described above as the substituent for the hydrocarbon group of Y.
• examples of the aromatic ring jointly formed by X 1 and X 2 include a benzene ring.
• a compound of formula (1) in which X 1 and X 2 jointly form an aromatic ring is referred to as an "aromatic ring-isothiazoline compound", and a formula in which X 1 and X 2 do not jointly form an aromatic ring
• the compound of (1) is referred to as a “non-aromatic ring-isothiazoline compound”.
• X 1 and X 2 are each preferably a hydrogen atom or jointly form an aromatic ring, and the carbon nanotube (A) in the conductive material paste From the viewpoint of better dispersing the and further suppressing the deposition of lithium metal on the negative electrode in the case of a lithium ion secondary battery, X 1 and X 2 jointly form an aromatic ring. More preferably, the isothiazoline compound is an aromatic ring-isothiazoline compound.
• Benzisothiazoline compounds As the aromatic ring-isothiazoline compound, a benzoisothiazoline compound having a structure represented by the following formula (2) in which X 1 and X 2 form a benzene ring as an aromatic ring is preferable.
• Y is the same as in Formula (1), and X 3 to X 6 each independently represent a hydrogen atom, a halogen atom, a hydroxyl group, a cyano group, an amino group, a carboxyl group, a carbon It is either an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms, and X 3 to X 6 may be the same or different.
• the halogen atoms of X 3 to X 6 include the same as X 1 and X 2 in formula (1).
• the alkyl group having 1 to 4 carbon atoms includes methyl group, ethyl group, propyl group, butyl group, isobutyl group, sec-butyl group and tert-butyl group.
• examples of the alkoxy group having 1 to 4 carbon atoms include a methoxy group and an ethoxy group.
• Y and X 3 to X 6 are preferably hydrogen atoms.
• Thiazoline compounds include, for example, thiazoline, alkylthiazoline (e.g., methylthiazoline, ethylthiazoline, octylthiazoline), cycloalkylthiazoline (e.g., cyclohexylthiazoline), thiazoline halide (e.g., chlorothiazoline, dichlorothiazoline), alkylhalogen thiazoline (e.g., methylchlorothiazoline, ethylchlorothiazoline, octylchlorothiazoline, methyldichlorothiazoline, ethyldichlorothiazoline, octyldichlorothiazoline), cycloalkylhalogenated thiazoline (e.g., cyclohexylchlorothiazoline, cyclohexyldichlorothiazoline), thiazolinone,
• alkylthiazoline e
• methylthiazolinone ethylthiazolinone, octylthiazolinone
• cycloalkylthiazolinones e.g. cyclohexylthiazolinone
• halogenated thiazolinones e.g.
• cyclohexylchlorobenzothiazoline cyclohexyldichlorobenzothiazoline
• benzothiazolinones alkylbenzothiazolinones (e.g. methylbenzothiazolinone, ethylbenzothiazolinone) non, octylbenzothiazolinone), cycloalkylbenzothiazolinones (e.g., cyclohexylbenzothiazolinone), halogenated benzothiazolinones (e.g., chlorobenzothiazolinone) azolinone, dichlorobenzothiazolinone), alkylhalogenated benzothiazolinones (e.g., methylchlorobenzothiazolinone, ethylchlorobenzothiazolinone, octylchlorobenzothiazolinone, methyldichlorobenzothiazolin
• isothiazolinone compounds represented by formula (1) include, for example, methylchlorothiazolinone (eg, 5-chloro-2-methyl-4-isothiazolin-3-one), methylthiazolinone (eg, , 2-methyl-4-isothiazolin-3-one (MIT)), octylthiazolinone (e.g., 2-n-octyl-4-isothiazolin-3-one), octyldichlorothiazolinone (e.g., 4,5 -dichloro-2-n-octyl-4-isothiazolin-3-one), ethylthiazolinone (e.g., 2-ethyl-4-isothiazolin-3-one), cyclohexyldichlorothiazolinone (e.g., 4,5- dichloro-2-cyclohexyl-4-isothiazolin-3-one), ethylthi
• MIT 2-methyl-4-isothiazolin-3-one
• BIT 1,2-benzisothiazolin-3-one
• the conductive carbon is better dispersed in the conductive material paste.
• 1,2-benzisothiazolin-3-one (BIT) is particularly preferable from the viewpoint of further suppressing deposition of lithium metal on the negative electrode of the secondary battery.
• the content of the solid content of the dispersant (C) relative to the total solid content of the conductive material paste may be, for example, 0.1% by mass or more, preferably 0.2% by mass or more, and more preferably 0.5% by mass or more. . Also, this content may be, for example, 20% by mass or less, preferably 10% by mass or less, more preferably 5% by mass or less.
• the content of the dispersant (C) is at least the above lower limit, the paste dispersibility of the obtained conductive material paste, the slurry viscosity stability of the obtained slurry composition, and the cycle of the obtained non-aqueous electrolyte secondary battery It is possible to improve the characteristics and resistance increase rate suppression during high temperature storage test.
• the content of the dispersant (C) is at least the above lower limit, the content of the carbon nanotubes (A) and the dispersant (B) can be increased. It is possible to increase the effect of lowering and exhibiting better output characteristics.
• Other components that the conductive material paste may contain are not particularly limited, and include a dispersion medium other than water, carbon black as a conductive material other than the carbon nanotube (A), and "non-aqueous electrolyte secondary battery negative electrode slurry composition Ingredients other than the electrode active material described later in the section of "Materials" can be mentioned.
• another component can be used individually by 1 type or in combination of 2 or more types.
• dispersion media other than water examples include organic solvents.
• organic solvents include, but are not limited to, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, and amyl alcohol.
• alcohols such as; acetone, methyl ethyl ketone, ketones such as cyclohexanone; esters such as ethyl acetate, butyl acetate; ethers such as diethyl ether, dioxane, tetrahydrofuran; N,N-dimethylformamide, N-methyl-2-pyrrolidone amide-based organic solvents such as (NMP); aromatic hydrocarbons such as toluene, xylene, chlorobenzene, ortho-dichlorobenzene, and para-dichlorobenzene;
• an organic solvent can be used individually by 1 type or in combination of 2 or more types.
• the conductive material paste of the present invention may further contain carbon black in order to improve conductivity and reduce resistance.
• the carbon black used in the present invention is an aggregate in which several layers of graphitic carbon microcrystals are gathered to form a turbostratic structure, and specifically, acetylene black, ketjen black, furnace black, channel black, and thermal lamp. black and the like.
• carbon blacks acetylene black, furnace black, and ketjen black are particularly preferable in that the conductive adhesive layer can be filled at a high density, the electron transfer resistance can be reduced, and the internal resistance of the electrochemical element can be reduced.
• the carbon black used in the present invention preferably contains a hetero element different from the carbon element that is the main component.
• the hetero element include silicon, nitrogen, and boron. Boron is particularly preferable because it can reduce the electron transfer resistance and the internal resistance of the electrochemical device.
• the heteroelement content in the carbon black used in the present invention is preferably in the range of 0.01 to 20% by weight, more preferably in the range of 0.05 to 10% by weight, and 0.1 to A range of 5% by weight is particularly preferred.
• the content of the hetero element in carbon black is within this range, the electron transfer resistance is reduced, and the internal resistance of the electrochemical device is reduced.
• the specific surface area of the carbon black used in the present invention is 25 m 2 /g or more and 300 m 2 /g or less, preferably 30 m 2 /g or more and 200 m 2 /g or less. It is preferably 40 m 2 /g or more and 150 m 2 /g or less. If the specific surface area is too large, the viscosity becomes high, making it difficult to produce a slurry suitable for high-speed coating. Conversely, if the specific surface area is too small, the electrical conductivity will decrease. Also, the dispersibility of the slurry deteriorates.
• the volume average particle size of the carbon black used in the present invention is preferably 0.01 ⁇ m or more and less than 1.0 ⁇ m, more preferably 0.05 ⁇ m or more and less than 0.8 ⁇ m, and particularly preferably 0.1 ⁇ m or more and less than 0.5 ⁇ m. is.
• the volume-average particle size is the volume-average particle size measured and calculated using a laser diffraction particle size distribution analyzer (eg, SALD-3100; manufactured by Shimadzu Corporation).
• the conductive material paste may further contain a particulate polymer (particulate binder) as a binder.
• the particulate polymer contains at least unsaturated carboxylic acid monomer units, aromatic vinyl monomer units, and diene-based monomer units as polymer constituent units.
• Examples of the unsaturated carboxylic acid monomer units constituting the particulate polymer as the binder include those exemplified as the unsaturated carboxylic acid monomer units constituting the dispersant (B).
• the content of the unsaturated carboxylic acid monomer unit is preferably 2 parts by mass or more, and 4 parts by mass when the total monomer units are 100 parts by mass. It is more preferably 8 parts by mass or more, preferably 20 parts by mass or less, more preferably 25 parts by mass or less, and even more preferably 30 parts by mass or less. .
• the content of the unsaturated carboxylic acid monomer units in the particulate polymer as the binder is at least the above lower limit, the stability of slurry viscosity over time can be improved.
• the content of the unsaturated carboxylic acid monomer unit in the particulate polymer as the binder is equal to or less than the above upper limit, the solid content concentration of the slurry can be increased.
• Aromatic vinyl monomers capable of forming aromatic vinyl monomer units include, for example, styrene, ⁇ -methylstyrene, pt-butylstyrene, butoxystyrene, vinyltoluene, chlorostyrene and vinylnaphthalene. .
• the aromatic vinyl monomers may be used singly or in combination of two or more at any ratio. Among these, styrene is preferred.
• the content of the aromatic vinyl monomer units is preferably 20 parts by mass or more, and preferably 25 parts by mass or more when the total monomer units are 100 parts by mass. is more preferably 30 parts by mass or more, preferably 90 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 70 parts by mass or less. If the content of the aromatic vinyl monomer unit in the particulate polymer as the binder is at least the above lower limit, the stability during preparation of the negative electrode slurry can be enhanced, and the slurry viscosity can be prevented from increasing. .
• the degree of swelling with respect to the electrolytic solution used in the secondary battery can be within a suitable range. .
• diene-based monomers capable of forming diene-based monomer units include aliphatic conjugated diene monomers.
• aliphatic conjugated diene monomers include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadienechloroprene, and cyanobutadiene. be done.
• the conjugated diene-based monomers described above may be used alone, or two or more of them may be used in combination at an arbitrary ratio. Among these, 1,3-butadiene and isoprene are preferred, and 1,3-butadiene is more preferred, in terms of easy availability.
• the content of the diene-based monomer unit is preferably 20 parts by mass or more, more preferably 25 parts by mass or more when the total monomer units are 100 parts by mass. more preferably 30 parts by mass or more, preferably 80 parts by mass or less, more preferably 85 parts by mass or less, and even more preferably 70 parts by mass or less. If the content of the diene-based monomer unit in the particulate polymer as the binder is at least the above lower limit, the binding strength of the electrode can be increased. On the other hand, if the content of diene-based monomer units in the particulate polymer as the binder is not more than the above upper limit, mechanical stability can be maintained during preparation of the negative electrode slurry.
• the diene-based monomer that can form other monomer units constituting the particulate polymer is not particularly limited as long as it is a monomer that can be copolymerized with the diene-based monomer.
• Examples thereof include unsaturated carboxylic acid monomers and monomers having an unsaturated bond between carbon atoms other than aromatic vinyl monomer units.
• Examples of such monomers having an unsaturated bond between carbon atoms include cyano group-containing vinyl monomers, amino group-containing vinyl monomers, pyridyl group-containing vinyl monomers, alkoxyl group-containing vinyl monomers, and the like. is mentioned.
• the monomer copolymerizable with the diene-based monomer described above may be used alone, or two or more thereof may be used in combination at an arbitrary ratio.
• the pH of the conductive material paste is preferably 6 or higher, more preferably 6.5 or higher, preferably 9 or lower, and more preferably 8 or lower. If the pH of the conductive material paste is equal to or higher than the above lower limit, the viscosity stability of the negative electrode slurry can be enhanced. On the other hand, if the pH of the conductive material paste is equal to or less than the above upper limit, the binding strength as the negative electrode can be increased.
• the conductive material paste of the present invention contains the above-described carbon nanotubes (A), dispersant (B), dispersant (C), water, and other components used as necessary in the above-described blending amounts. It can be produced by mixing.
• the above-described mixing is preferably performed through a step of preparing a premix containing the carbon nanotube (A), the dispersant (C), and water, and a step of adding the dispersant (B) to the premix.
• a step of preparing a premix containing the carbon nanotube (A), the dispersant (C), and water and a step of adding the dispersant (B) to the premix.
• the surface of the carbon nanotube (A) It is presumed that the dispersant (C) can be adsorbed first, and the dispersant (B) can be further adsorbed well through the dispersant (C), but the paste dispersibility of the conductive material paste is While making it possible to provide a slurry composition for a non-aqueous electrolyte secondary battery negative electrode in which the viscosity stability of the slurry is maintained, the resistance increase rate during the high-temperature storage test can be suppressed.
• the mixing of various components is not particularly limited, and can be performed using a known mixing device.
• mixing devices include dispersers, homomixers, planetary mixers, kneaders, ball mills, and bead mills.
• the slurry composition for a negative electrode of a non-aqueous electrolyte secondary battery of the present invention (hereinafter sometimes simply referred to as "slurry composition") comprises the above-described conductive material paste and at least a negative electrode active material (eg, silicon-based active material, etc.) ), and may optionally contain a thickener, a binder, carbon black, a negative electrode active material (eg, silicon-based active material, etc.), and other optional components.
• a negative electrode active material eg, silicon-based active material, etc.
• the slurry composition containing the conductive material paste described above maintains slurry viscosity stability, and according to the electrode provided with the electrode mixture layer formed from the slurry composition, the non-aqueous electrolyte secondary battery On the other hand, it is possible to suppress the resistance increase rate during the high temperature storage test.
• Silicon-based active materials include, for example, silicon (Si), alloys containing silicon, SiO, SiO x , composites of Si-containing materials and conductive carbon obtained by coating or combining Si-containing materials with conductive carbon, and the like. is mentioned.
• the particle size of the silicon-based active material is not particularly limited, and may be the same as that of conventionally used electrode active materials. Also, the amount of the silicon-based active material in the slurry composition is not particularly limited, and can be within the conventionally used range. Silicon-based active materials may be used singly or in combination of two or more.
• negative electrode active materials include, but are not particularly limited to, carbon-based negative electrode active materials, metal-based negative electrode active materials, and negative electrode active materials in which these are combined.
• the carbon-based negative electrode active material refers to an active material having carbon as a main skeleton and capable of inserting lithium (also referred to as “doping”).
• Examples of carbon-based negative electrode active materials include carbonaceous materials and graphite quality materials.
• Examples of the carbonaceous material include graphitizable carbon and non-graphitizable carbon having a structure close to an amorphous structure represented by glassy carbon.
• graphitizable carbon includes, for example, carbon materials made from tar pitch obtained from petroleum or coal. Specific examples include coke, mesocarbon microbeads (MCMB), mesophase pitch-based carbon fibers, and pyrolytic vapor growth carbon fibers.
• Non-graphitic carbons include, for example, phenolic resin sintered bodies, polyacrylonitrile-based carbon fibers, pseudoisotropic carbons, furfuryl alcohol resin sintered bodies (PFA), and hard carbons.
• examples of graphite materials include natural graphite and artificial graphite.
• artificial graphite for example, artificial graphite obtained by heat-treating carbon containing graphitizable carbon mainly at 2800 ° C. or higher, graphitized MCMB obtained by heat-treating MCMB at 2000 ° C. or higher, mesophase pitch-based carbon fiber at 2000 ° C.
• Graphitized mesophase pitch-based carbon fibers heat-treated as described above may be used.
• the metal-based negative electrode active material is an active material containing a metal, and usually contains an element capable of intercalating lithium in its structure, and the theoretical electric capacity per unit mass when lithium is intercalated is 500 mAh / g or more.
• the metal-based active material for example, lithium metal, a single metal capable of forming a lithium alloy (eg, Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, P, Pb, Sb, Sn, Sr , Zn, Ti, etc.) and alloys thereof, as well as their oxides, sulfides, nitrides, carbides, phosphides, etc. are used.
• the particle size of other negative electrode active materials is not particularly limited, and may be the same as that of conventionally used electrode active materials. Also, the amount of the negative electrode active material in the slurry composition is not particularly limited, and can be within the conventionally used range. And the negative electrode active material can be used individually by 1 type or in combination of 2 or more types.
• the content ratio of the negative electrode active material to the total solid content of the slurry composition may be, for example, 90% by mass or more, preferably 92% by mass or more, more preferably 95% by mass or more, and may be, for example, 99% by mass or less, preferably 98% by mass. 0.5% by mass or less, more preferably 98% by mass or less. If the content of the negative electrode active material is at least the above lower limit, the capacity of the obtained secondary battery can be increased. Moreover, when the content of the negative electrode active material is equal to or less than the above upper limit, the cycle characteristics of the resulting secondary battery can be improved.
• the content of carbon nanotubes (A) in the negative electrode active material may be, for example, 0.01% by mass or more, preferably 0.05% by mass or more, more preferably 0.1% by mass or more, for example 5% by mass. Below, preferably 2% by mass or less, more preferably 1% by mass or less.
• the content ratio of the silicon-based active material to the total solid content of the slurry composition may be, for example, 3% by mass or more, preferably 5% by mass or more, more preferably 8% by mass or more, and for example, 40% by mass or less, preferably It may be 35% by mass or less, more preferably 30% by mass or less. If the content of the silicon-based active material is at least the above lower limit, the capacity of the obtained secondary battery can be further increased.
• the content of the silicon-based active material is equal to or less than the above upper limit, the cycle characteristics of the obtained secondary battery can be further improved.
• the content ratio of the carbon nanotubes (A) to the silicon-based active material may be, for example, 0.01% by mass or more, preferably 0.05% by mass or more, more preferably 0.1% by mass or more, for example 5% by mass. % or less, preferably 3 mass % or less, more preferably 1 mass % or less.
• thickeners include, but are not limited to, carboxymethylcellulose, methylcellulose, hydroxypropylmethylcellulose, hydroxyethylmethylcellulose, polyvinyl alcohol, polymethacrylic acid, polyacrylic acid, acrylamide/acrylic acid/N-hydroxyethylacrylamide ternary A copolymer is mentioned. These can be used individually by 1 type or in combination of 2 or more types. Moreover, these can be used in either an unneutralized state or a neutralized state. Among these, a terpolymer of acrylamide/acrylic acid/N-hydroxyethylacrylamide is preferred.
• the thickener preferably has a weight average molecular weight of 500,000 or more, more preferably 800,000 or more, and preferably 10,000,000 or less. The following are more preferable. If the weight average molecular weight of the thickener is 500,000 or more, the peel strength of the electrode can be increased, and if it is 10,000,000 or less, the cycle characteristics of the electrochemical device can be further improved.
• the amount of the thickener mentioned above is preferably 0.2 parts by mass or more, preferably 0.4 parts by mass or more, per 100 parts by mass of the negative electrode active material. More preferably, it is 5.0 parts by mass or less, and more preferably 4.0 parts by mass or less. If the amount of the thickening agent per 100 parts by mass of the negative electrode active material is 0.2 parts by mass or more, the cycle characteristics of the electrochemical device can be further improved. The capacity of the element can be improved.
• the binder As the binder, the particulate polymer (particulate binder) described above can be used.
• the amount of the binder described above is preferably 0.1 parts by mass or more and 2.0 parts by mass or less per 100 parts by mass of the electrode active material. If the amount of the binder compounded per 100 parts by mass of the electrode active material is within the range described above, it is possible to further improve the cycle characteristics of the electrochemical device while increasing the peel strength of the electrode.
• Other optional components that can be included in the slurry composition include, for example, reinforcing materials, antioxidants, and electrolytic solution additives that have the function of suppressing decomposition of the electrolytic solution. These arbitrary components can be used individually by 1 type or in combination of 2 or more types.
• the mixing method is not particularly limited, and for example, a known mixing device can be used.
• the negative electrode for a non-aqueous electrolyte secondary battery of the present invention (hereinafter sometimes simply referred to as the "negative electrode of the present invention") is a negative electrode mixture obtained by using the slurry composition of the present invention described above. Have a layer. More specifically, the negative electrode of the present invention usually has a structure in which a negative electrode mixture layer made of the dried slurry composition of the present invention is provided on a current collector.
• the negative electrode mixture layer contains carbon nanotubes (A), a dispersant (B), and a dispersant (C), and if necessary, a thickener, a binder, carbon black, and a negative electrode active material (e.g., silicon-based active material, etc.) and other optional components.
• the preferred abundance ratio of each component in the electrode mixture layer is the same as the preferred abundance ratio of each component in the slurry composition. Since the negative electrode of the present invention includes the negative electrode mixture layer formed using the slurry composition of the present invention, the non-aqueous electrolyte secondary battery can exhibit excellent cycle characteristics.
• the negative electrode current collector is made of a material having electrical conductivity and electrochemical durability.
• a current collector made of iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, platinum, or the like can be used. These materials can be used singly or in combination of two or more.
• a current collector made of copper (copper foil, etc.) is preferable.
• the method for producing the negative electrode of the present invention is not particularly limited.
• the negative electrode of the present invention can be produced by applying the slurry composition of the present invention described above to at least one surface of a current collector and drying it to form an electrode mixture layer.
• the production method includes a step of applying a slurry composition to at least one surface of a current collector (application step), and drying the slurry composition applied to at least one surface of the current collector. and a step of forming an electrode mixture layer on the current collector (drying step).
• the method for applying the slurry composition onto the current collector is not particularly limited, and known methods can be used. Specifically, as the coating method, a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, a brush coating method, or the like can be used. At this time, the slurry composition may be applied to only one side of the current collector, or may be applied to both sides. The thickness of the slurry film on the current collector after application and before drying can be appropriately set according to the thickness of the electrode mixture layer obtained by drying.
• the method for drying the slurry composition on the current collector is not particularly limited, and known methods can be used. drying method. By drying the slurry composition on the current collector in this manner, an electrode mixture layer can be formed on the current collector, and a negative electrode including the current collector and the electrode mixture layer can be obtained.
• the electrode mixture layer may be pressurized using a mold press or a roll press.
• the pressure treatment can improve the peel strength of the negative electrode.
• Non-aqueous electrolyte secondary battery includes the negative electrode of the present invention described above. And, since the non-aqueous electrolyte secondary battery of the present invention includes the negative electrode of the present invention, it is excellent in resistance increase rate suppression property and cycle characteristics during a high-temperature storage test.
• Examples of nonaqueous electrolyte secondary batteries of the present invention include lithium ion secondary batteries and sodium ion secondary batteries.
• This lithium ion secondary battery comprises the negative electrode, positive electrode, electrolytic solution, and separator of the present invention.
• the positive electrode is not particularly limited, and a known positive electrode for non-aqueous electrolyte secondary batteries (eg, lithium ion secondary batteries) can be used.
• a known positive electrode for non-aqueous electrolyte secondary batteries eg, lithium ion secondary batteries
• an organic electrolytic solution in which a supporting electrolyte is dissolved in an organic solvent is usually used.
• a lithium salt for example, is used as the supporting electrolyte.
• lithium salts include LiPF 6 , LiAsF 6 , LiBF 4 , LiSbF 6 , LiAlCl 4 , LiClO 4 , CF 3 SO 3 Li, C 4 F 9 SO 3 Li, CF 3 COOLi, (CF 3 CO) 2 NLi. , (CF 3 SO 2 ) 2 NLi, (C 2 F 5 SO 2 ) NLi and the like.
• LiPF 6 , LiClO 4 and CF 3 SO 3 Li are preferable, and LiPF 6 is particularly preferable, because they are easily dissolved in a solvent and exhibit a high degree of dissociation.
• one electrolyte may be used alone, or two or more electrolytes may be used in combination at an arbitrary ratio.
• lithium ion conductivity tends to increase as a supporting electrolyte with a higher degree of dissociation is used, so the lithium ion conductivity can be adjusted depending on the type of supporting electrolyte.
• the organic solvent used in the electrolytic solution is not particularly limited as long as it can dissolve the supporting electrolyte.
• Examples include dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), carbonates such as butylene carbonate (BC) and methyl ethyl carbonate (EMC); esters such as ⁇ -butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; sulfur-containing compounds such as sulfolane and dimethylsulfoxide and the like are preferably used. A mixture of these solvents may also be used.
• carbonates are preferably used because they have a high dielectric constant and a wide stable potential range, and a mixture of ethylene carbonate and ethyl methyl carbonate is more preferably used.
• concentration of the electrolyte in the electrolytic solution can be adjusted as appropriate, for example, it is preferably 0.5 to 15% by mass, more preferably 2 to 13% by mass, and 5 to 10% by mass. is more preferred.
• known additives such as fluoroethylene carbonate (FEC), vinylene carbonate (VC), ethyl methyl sulfone, etc. may be added to the electrolytic solution.
• the separator is not particularly limited, and for example, those described in JP-A-2012-204303 can be used. Among these, the film thickness of the entire separator can be made thin, and as a result, the ratio of the electrode active material in the lithium ion secondary battery can be increased to increase the capacity per volume. Microporous membranes made of resins of the system (polyethylene, polypropylene, polybutene, polyvinyl chloride) are preferred.
• a non-aqueous electrolyte secondary battery according to the present invention can be produced, for example, by stacking the negative electrode of the present invention and a positive electrode with a separator interposed therebetween, and winding or folding this according to the shape of the battery as necessary to form a battery container. It can be produced by putting it in a battery container, injecting an electrolytic solution into the battery container, and sealing the battery container. In order to prevent an increase in internal pressure of the secondary battery and the occurrence of overcharge/discharge, etc., a fuse, an overcurrent protection element such as a PTC element, an expanded metal, a lead plate, or the like may be provided as necessary.
• the shape of the non-aqueous electrolyte secondary battery may be, for example, coin-shaped, button-shaped, sheet-shaped, cylindrical, rectangular, or flat.
• a water-soluble polymer (corresponding to dispersant (B)) was used as a polymer to be measured, and the weight average molecular weight was measured by gel permeation chromatography (GPC) in the following procedure.
• the polymer to be measured was added to about 5 mL of the eluent so that the solid content concentration was about 0.5 g/L, and slowly dissolved at room temperature. After visually confirming the dissolution of the polymer, the mixture was gently filtered with a filter having a pore size of 0.45 ⁇ m to prepare a sample for measurement. Then, by creating a calibration curve using the standard substance, the weight average molecular weight was calculated as a value converted to the standard substance.
• the measurement conditions are as follows. ⁇ Measurement conditions>> Column: manufactured by Showa Denko, product name Shodex OHpak (SB-G, SB-807HQ, SB-806MHQ) Eluent: 0.1 M Tris buffer (0.1 M potassium chloride added) Flow rate: 0.5 mL/min Sample concentration: 0.05 g/L (solid concentration) Injection volume: 200 ⁇ L Column temperature: 40°C Detector: Differential refractive index detector RI (manufactured by Tosoh Corporation, product name "RI-8020") Reference material: Monodisperse pullulan (manufactured by Showa Denko)
• ⁇ Dispersion stability> The viscosity ⁇ 1 immediately after preparation of the conductive material paste was measured using a Brookfield viscometer at a temperature of 25° C. and a spindle rotation speed of 60 rpm after 60 seconds had passed since the start of spindle rotation. After the measurement of ⁇ 1, the conductive material paste was stored under static conditions at 25° C. for 10 days, and the viscosity ⁇ 2 after storage was measured in the same manner as the viscosity ⁇ 1. The ratio of ⁇ 2 to ⁇ 1 ( ⁇ 2/ ⁇ 1) was defined as the paste viscosity ratio and evaluated according to the following criteria.
• Paste viscosity ratio is less than 1.15
• B Paste viscosity ratio is 1.15 or more and less than 1.6
• C Paste viscosity ratio is 1.6 or more and less than 2.0
• D Paste viscosity ratio is 2.0 or more
• ⁇ Viscosity stability> The viscosity ⁇ 3 immediately after preparation of the slurry composition was measured using a Brookfield viscometer under conditions of a temperature of 25° C. and a spindle rotation speed of 60 rpm, 60 seconds after the start of spindle rotation. After the measurement of ⁇ 3, the slurry composition was stored under static conditions at 25° C. for 3 days, and the viscosity ⁇ 4 after storage was measured in the same manner as the viscosity ⁇ 3. The ratio of ⁇ 4 to ⁇ 3 ( ⁇ 4/ ⁇ 3) was defined as the slurry viscosity ratio and evaluated according to the following criteria.
• a higher capacity retention rate indicates that the lithium-ion secondary battery is more excellent in cycle characteristics.
• ⁇ Resistance change rate during high temperature storage test> The lithium ion secondary battery was allowed to stand in an environment of 25° C. for 24 hours after electrolyte injection. Then, the battery was charged to a cell voltage of 4.35 V and discharged to a cell voltage of 2.75 V by a 0.1 C constant current method, and the initial capacity was measured. After that, after charging to a depth of charge (SOC) of 50%, charging is performed for 30 seconds and discharging is performed for 30 seconds at 1.0 C centering on SOC 50%. IV resistance R1 was calculated by dividing by . Again, the cell voltage was charged to 4.35 V by a constant current method of 0.1 C, and the temperature of the constant temperature bath was set to 60 ° C.
• SOC depth of charge
• Example 1 ⁇ Preparation of water-soluble polymer> 900 parts of ion-exchanged water was put into a 1.5 L glass flask equipped with a stirring blade, heated to 40° C., and the inside of the flask was replaced with nitrogen gas at a flow rate of 100 mL/min. Next, as monomers, 30 parts of acrylic acid as an unsaturated carboxylic acid monomer, 40 parts of acrylamide as a (meth)acrylamide group-containing monomer, sodium styrene sulfonate as an aromatic sulfonic acid monomer 30 parts were mixed and poured into a flask.
• agent (B) An aqueous solution of a water-soluble polymer (weight average molecular weight: 106,000) was obtained as agent (B).
• ⁇ Preparation of conductive material paste > 100 parts of CNT (single wall, length 6.3 ⁇ m, diameter (outer diameter) 1.8 nm) as carbon nanotube (A) and 1,2-benzisothiazolin-3-one as dispersant (C)1. 0 part and an appropriate amount of ion-exchanged water as a dispersion medium (solvent) are stirred with a disper (3000 rpm, 60 minutes), and then a bead mill using zirconia beads with a diameter of 1 mm is used at a peripheral speed of 8 m / s. and mixed for 30 minutes.
• CNT single wall, length 6.3 ⁇ m, diameter (outer diameter) 1.8 nm
• dispersant C
• 0 part and an appropriate amount of ion-exchanged water as a dispersion medium (solvent) are stirred with a disper (3000 rpm, 60 minutes), and then a bead mill using zirconia beads with a diameter of 1
• a particulate binder (particulate polymer) as a binder was prepared as follows. 5 MPa pressure vessel A with a stirrer, 3.15 parts of styrene, 1.66 parts of 1,3-butadiene, 0.2 parts of sodium lauryl sulfate as an emulsifier, 20 parts of ion-exchanged water, and a polymerization initiator. After 0.03 part of potassium sulfate was added and sufficiently stirred, the mixture was heated to 60° C. to initiate polymerization and allowed to react for 6 hours to obtain seed particles.
• ⁇ Preparation of negative electrode slurry composition In a planetary mixer with a disper, 90 parts of artificial graphite (volume average particle diameter: 24.5 ⁇ m, specific surface area: 3.5 m 2 /g) as a carbon-based negative electrode active material, and SiO x as a silicon-based negative electrode active material. 10 parts and 2.0 parts of an aqueous solution of carboxymethyl cellulose sodium salt as a thickener (solid content equivalent) were added, adjusted to a solid content concentration of 58% with deionized water, and mixed at room temperature for 60 minutes. After mixing, the conductive material paste obtained as described above was added to the planetary mixer so that the amount of carbon nanotubes was 0.1 part (solid content equivalent), and mixed.
• the negative electrode slurry composition obtained as described above was coated on a copper foil (current collector) having a thickness of 16 ⁇ m with a comma coater so that the film thickness after drying was 105 ⁇ m and the coating amount was 10 mg/cm 2 . I applied it so that it would be.
• the copper foil coated with the slurry composition for a negative electrode was conveyed at a speed of 0.5 m/min in an oven at a temperature of 100°C for 2 minutes and then in an oven at a temperature of 120°C for 2 minutes.
• the negative electrode slurry composition on the foil was dried to obtain a negative electrode raw fabric.
• This negative electrode original fabric was rolled by a roll press to obtain a negative electrode having a negative electrode mixture layer with a thickness of 80 ⁇ m.
• Table 1 shows the results.
• the aluminum foil coated with the positive electrode slurry composition was transported at a speed of 0.5 m/min through an oven at a temperature of 60°C for 2 minutes and then through an oven at a temperature of 120°C for 2 minutes to obtain aluminum.
• the positive electrode slurry composition on the foil was dried to obtain a positive electrode blank.
• This positive electrode material was rolled by a roll press to obtain a positive electrode having a positive electrode mixture layer with a thickness of 70 ⁇ m.
• a single-layer polypropylene separator (width 65 mm, length 500 mm, thickness 25 ⁇ m; manufactured by dry method; porosity 55%) was prepared. This separator was cut into a square of 5 cm ⁇ 5 cm and used for manufacturing the following lithium ion secondary battery.
• An aluminum packaging material exterior was prepared as the exterior of the battery.
• the positive electrode was cut into a square of 4 cm ⁇ 4 cm, and placed so that the surface on the side of the current collector was in contact with the exterior of the aluminum packaging material.
• the square separator was placed on the surface of the positive electrode mixture layer of the positive electrode.
• the negative electrode was cut into a square of 4.2 cm ⁇ 4.2 cm, and this was placed on a separator so that the surface on the negative electrode mixture layer side faced the separator.
• Example 2 In the preparation of the water-soluble polymer, a water-soluble polymer (Various productions, measurements and evaluations were carried out in the same manner as in Example 1, except that an aqueous solution having a weight average molecular weight of 214,000 was obtained. Table 1 shows the results.
• Example 3 In the preparation of the conductive material paste, the conductive material paste was obtained in the same manner as in Example 1, except that CNT (multilayer, length 3.9 ⁇ m, diameter (outer diameter) 14 nm) was used as the carbon nanotube (A). , various manufacturing, measurement and evaluation. Table 1 shows the results.
• Example 4 In the preparation of the conductive material paste, various productions, measurements and evaluations were carried out in the same manner as in Example 3, except that 50 parts (solid content equivalent) of an aqueous solution of a water-soluble polymer as a dispersant (B) was added. rice field. Table 1 shows the results.
• Example 5 In the preparation of the water-soluble polymer, as monomers, acrylic acid as an unsaturated carboxylic acid monomer: acrylamide as a (meth)acrylamide group-containing monomer: styrene sulfonic acid as an aromatic sulfonic acid monomer Sodium was added in an amount of 60:20:20 parts in Example 5, 72:24:4 parts in Example 6, and 15:55:30 parts in Example 8.
• Example 1 except that an aqueous solution of a water-soluble polymer (weight average molecular weight: 87,000 in Example 5, 87,000 in Example 6, 25,000 in Example 8) was obtained.
• Table 1 shows the results.
• Example 7 In the preparation of the binder, the blending ratio of styrene:butadiene:acrylic acid as monomers was set to 61 parts:37 parts:2 parts, except that a particulate binder (particulate polymer) was obtained as the binder. , in the same manner as in Example 1, various productions, measurements and evaluations were carried out. Table 1 shows the results.
• Example 9 Various production, measurements and evaluations were carried out in the same manner as in Example 1, except that 2-methylthiazoline was used as the dispersant (C) in preparing the conductive material paste. Table 1 shows the results.
• Example 3 (Comparative Example 3) Example 1 except that 21 parts of vinylnaphthalene and 79 parts of allylsulfonic acid were used as monomers in the preparation of the water-soluble polymer to obtain an aqueous solution of the water-soluble polymer (weight average molecular weight: 143,000). Various production, measurement and evaluation were performed in the same manner as in . Table 1 shows the results.
• Example 4 In the preparation of the water-soluble polymer, various productions were carried out in the same manner as in Example 1, except that only acrylic acid was used as the monomer to obtain an aqueous solution of the water-soluble polymer (weight average molecular weight: 250,000). , was measured and evaluated. Table 1 shows the results.
• Example 6 Comparative Example 6 except that 40 parts of acrylic acid and 60 parts of styrenesulfonic acid were used as monomers in the preparation of the water-soluble polymer to obtain an aqueous solution of the water-soluble polymer (weight average molecular weight: 159,000).
• Various production, measurement and evaluation were performed in the same manner as in . Table 1 shows the results.
• Example 8 When preparing the conductive material paste, the aqueous solution of the water-soluble polymer was not added as the dispersant (B), and instead, when preparing the slurry composition for the negative electrode, the aqueous solution of the thickening agent was prepared in Example 1. Various productions, measurements and evaluations were carried out in the same manner as in Example 1, except that an aqueous solution of a water-soluble polymer was added. Table 1 shows the results.
• a slurry composition for a non-aqueous electrolyte secondary battery negative electrode in which paste dispersibility is maintained and slurry viscosity stability is maintained. It is possible to provide a conductive material paste for a non-aqueous electrolyte secondary battery that can provide a suppressed non-aqueous electrolyte secondary battery. Further, according to the present invention, it is possible to provide a slurry composition for a negative electrode of a non-aqueous electrolyte secondary battery in which slurry viscosity stability is maintained, and a non-aqueous electrolysis in which the rate of increase in resistance during a high-temperature storage test is suppressed.
• a slurry composition for a negative electrode of a non-aqueous electrolyte secondary battery that can provide a liquid secondary battery.
• a negative electrode for a non-aqueous electrolyte secondary battery that can provide a non-aqueous electrolyte secondary battery in which the rate of increase in resistance during a high-temperature storage test is suppressed.

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