Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/02—Elements
  • C08K3/04—Carbon
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L101/00—Compositions of unspecified macromolecular compounds
  • C08L101/02—Compositions of unspecified macromolecular compounds characterised by the presence of specified groups, e.g. terminal or pendant functional groups
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L33/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides or nitriles thereof; Compositions of derivatives of such polymers
  • C08L33/18—Homopolymers or copolymers of nitriles
• • 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
  • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
  • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
  • H01M10/0566—Liquid materials
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/13—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
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
• • 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
• • 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 method for producing a slurry composition for a secondary battery positive electrode, a positive electrode for a secondary battery, and a secondary battery.
• Secondary batteries such as lithium ion secondary batteries are small and light, have high energy density, and can be repeatedly charged and discharged, and are used in a wide range of applications. Therefore, in recent years, improvement of battery members such as electrodes has been studied for the purpose of further improving the performance of secondary batteries.
• a positive electrode used in a secondary battery such as a lithium ion secondary battery usually includes a current collector and an electrode mixture layer (positive electrode mixture layer) formed on the current collector.
• the positive electrode mixture layer is prepared by, for example, dispersing and / or dissolving a positive electrode active material and a binder in a dispersion medium to prepare a slurry composition, and applying the slurry composition onto a current collector. And dried.
• Patent Document 1 a positive electrode active material and a particulate binder each having a predetermined average particle diameter are dry-mixed at a predetermined quantitative ratio, and the resulting mixed powder is fixed on a current collector.
• a method of providing a positive electrode mixture layer on a current collector has been proposed. It has been reported that by providing the positive electrode mixture layer by this method, it is possible to increase the active material density in the positive electrode mixture layer and suppress cycle deterioration while increasing the capacity of the secondary battery.
• secondary batteries are required to exhibit battery characteristics such as excellent life characteristics even when exposed to a high potential for a long time.
• a positive electrode having a positive electrode mixture layer provided on a current collector by the above conventional method is exposed to a high potential for a long time, the battery characteristics may be significantly deteriorated due to deterioration of the surface of the positive electrode active material. It was. Therefore, there is a demand for a new technique that improves the high-potential durability of the positive electrode and improves the battery characteristics of the secondary battery.
• an object of this invention is to provide the method of manufacturing the slurry composition for secondary battery positive electrodes which exhibits the high potential durability excellent in the positive electrode.
• Another object of the present invention is to provide a secondary battery positive electrode excellent in high potential durability and a secondary battery including the secondary battery positive electrode and excellent in battery characteristics.
• the present inventor has intensively studied to achieve the above object.
• the inventor then dry-mixes the polymer particles having a predetermined composition and properties with the positive electrode active material and the conductive material, and then mixes the obtained mixture with a dispersion medium to form a slurry composition for a secondary battery positive electrode.
• a dispersion medium to form a slurry composition for a secondary battery positive electrode.
• the manufacturing method of the slurry composition for secondary battery positive electrodes of this invention is the polymer particle for secondary battery positive electrodes, positive electrode active material, And a step of dry mixing the conductive material to obtain a dry mixture, and a step of mixing the dry mixture and a dispersion medium to obtain a slurry composition for a secondary battery positive electrode, wherein the polymer particles for a secondary battery positive electrode are: A copolymer containing both a nitrile group-containing monomer unit and a hydrophilic group-containing monomer unit, a volume average particle diameter D50 of 1 ⁇ m or more, and a volume average particle diameter of the positive electrode active material The ratio of the volume average particle diameter D50 of the polymer particles for secondary battery positive electrode to D50 is 0.1 or more.
• the slurry composition for a secondary battery positive electrode prepared by dry-mixing the polymer particles having the predetermined composition and properties, the positive electrode active material, and the conductive material, and then mixing the dispersion medium is used, A positive electrode excellent in high potential durability can be produced.
• the polymer "contains a monomer unit” means "a monomer-derived structural unit is contained in a polymer obtained using the monomer".
• the “volume average particle diameter D50” is a particle whose cumulative volume calculated from the small diameter side is 50% in the particle diameter distribution measured dry using a laser diffraction / scattering particle diameter distribution measuring apparatus. It can be obtained as a diameter.
• dry mixing means mixing at a solid content concentration of 90% by mass or more during mixing.
• the volume average particle diameter D50 of the polymer particles for the secondary battery positive electrode is 2000 ⁇ m or less
• the volume average particle diameter D50 of the positive electrode active material is The ratio of the volume average particle diameter D50 of the polymer particles for the secondary battery positive electrode is preferably 200 or less. If the ratio of the volume average particle diameter D50 of the polymer particles to the volume average particle diameter D50 of the polymer particles and the volume average particle diameter D50 of the positive electrode active material is less than or equal to the above value, the internal resistance of the secondary battery can be reduced. Because it can.
• the copolymer contains 80% by mass or more and 99.9% by mass or less of the nitrile group-containing monomer unit, and the hydrophilic group-containing single unit. It is preferable to contain 0.1 to 20% by mass of a monomer unit.
• the molecular weight distribution (Mw / Mn) of the said copolymer is 10 or less. This is because the internal resistance of the secondary battery can be reduced by using a copolymer having a molecular weight distribution of 10 or less.
• “molecular weight distribution (Mw / Mn)” refers to the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn).
• “number average molecular weight (Mn)” and “weight average molecular weight (Mw)” can be measured using gel permeation chromatography.
• the glass transition temperature of the copolymer is preferably 60 ° C. or higher and 170 ° C. or lower. If a copolymer having a glass transition temperature of 60 ° C. or higher and 170 ° C. or lower is used, high potential durability can be further improved while increasing the peel strength of the positive electrode, and the internal resistance of the secondary battery can be reduced. It is.
• the “glass transition temperature” can be measured according to JIS K7121.
• the positive electrode for secondary batteries of this invention was provided in the at least one surface of the electrical power collector and the said electrical power collector.
• the positive electrode formed from the slurry composition for secondary battery positive electrode obtained by the method for producing the slurry composition for secondary battery positive electrode described above is excellent in high potential durability.
• the secondary battery of this invention is equipped with a positive electrode, a negative electrode, electrolyte solution, and a separator,
• the said positive electrode is for secondary batteries mentioned above. It is a positive electrode. If the positive electrode for secondary batteries described above is used, a secondary battery having excellent battery characteristics such as life characteristics can be obtained even when exposed to a high potential for a long time.
• the method of manufacturing the slurry composition for secondary battery positive electrodes which exhibits the high-potential durability excellent in the positive electrode can be provided.
• the secondary battery which is equipped with the positive electrode for secondary batteries excellent in high-potential durability, and the said positive electrode for secondary batteries, and is excellent in a battery characteristic can be provided.
• the manufacturing method of the slurry composition for secondary battery positive electrodes of this invention is used for preparation of the slurry composition for secondary battery positive electrodes.
• the positive electrode for secondary batteries of this invention is produced using the slurry composition for secondary battery positive electrodes obtained by the manufacturing method of the slurry composition for secondary battery positive electrodes of this invention, It is characterized by the above-mentioned.
• the secondary battery of this invention is equipped with the positive electrode for secondary batteries of this invention, It is characterized by the above-mentioned.
• the method for producing a slurry composition for a secondary battery positive electrode according to the present invention includes a secondary battery by mixing at least polymer particles for a secondary battery positive electrode, a positive electrode active material, a conductive material, and a dispersion medium in a predetermined procedure.
• This is a method for producing a positive electrode slurry composition.
• the polymer particles for a secondary battery positive electrode used in the method for producing a slurry composition for a secondary battery positive electrode of the present invention include both a nitrile group-containing monomer unit and a hydrophilic group-containing monomer unit.
• a polymer is contained, the volume average particle diameter D50 is 1 ⁇ m or more, and the ratio of the positive electrode active material to the volume average particle diameter D50 (the ratio of the particle diameter of the polymer particles to the positive electrode active material) is 0.1 or more. It is characterized by that.
• the manufacturing method of the slurry composition for secondary battery positive electrodes of this invention is a process which dry-mixes the polymer particle for secondary battery positive electrodes mentioned above, a positive electrode active material, and a electrically conductive material, and obtains a dry-type mixture, The said dry-type mixture And a dispersion medium are mixed to obtain a slurry composition for a secondary battery positive electrode.
• the manufacturing method of the slurry composition for secondary battery positive electrodes of the present invention is used, the above-mentioned predetermined polymer particles for secondary battery positive electrodes are dry-mixed with the positive electrode active material and the conductive material, and then the dry mixture obtained Is mixed with the dispersion medium, a slurry composition for a secondary battery positive electrode that can sufficiently enhance the high potential durability of the positive electrode can be prepared.
• a secondary battery exhibiting battery characteristics such as excellent life characteristics can be obtained even when exposed to a high potential for a long time.
• the high potential durability of the positive electrode is sufficiently increased, and the secondary battery is The reason why the excellent battery characteristics can be exhibited is not clear, but is presumed to be due to the following reasons. That is, by premixing the polymer particles having the above-described composition and properties, the positive electrode active material, and the conductive material, the conductive material is suitably dispersed, so that the conductive path in the positive electrode mixture layer is well formed and premixed.
• the polymer particles are uniformly adsorbed on the surface of the positive electrode active material, whereby the positive electrode obtained can sufficiently protect the surface of the positive electrode active material with the copolymer. This is presumably because deterioration of the surface of the positive electrode active material at a high potential is suppressed.
• the polymer particle for secondary battery positive electrode is a component containing a copolymer that functions as a binder.
• this copolymer prevents components contained in the positive electrode mixture layer from being detached from the positive electrode mixture layer. Hold on.
• the copolymer contained in the polymer particle for secondary battery positive electrodes needs to contain both a nitrile group containing monomer unit and a hydrophilic group containing monomer unit.
• the copolymer may optionally contain a monomer unit other than the nitrile group-containing monomer unit and the hydrophilic group-containing monomer unit as long as the effects of the present invention are not impaired.
• the nitrile group-containing monomer unit is a repeating unit derived from a nitrile group-containing monomer.
• examples of the nitrile group-containing monomer capable of forming a nitrile group-containing monomer unit include ⁇ , ⁇ -ethylenically unsaturated nitrile monomers.
• the ⁇ , ⁇ -ethylenically unsaturated nitrile monomer is not particularly limited as long as it is an ⁇ , ⁇ -ethylenically unsaturated compound having a nitrile group.
• acrylonitrile; ⁇ -chloroacrylonitrile, ⁇ -halogenoacrylonitrile such as ⁇ -bromoacrylonitrile; ⁇ -alkylacrylonitrile such as methacrylonitrile and ⁇ -ethylacrylonitrile; and the like acrylonitrile and methacrylonitrile are preferable as the nitrile group-containing monomer from the viewpoint of increasing the cohesive strength of the copolymer, and acrylonitrile is more preferable. These can be used alone or in combination of two or more.
• the content ratio of the nitrile group-containing monomer unit in the copolymer is preferably 80% by mass or more, more preferably 82% by mass or more, when all repeating units in the copolymer are 100% by mass. 85 mass% or more, more preferably 90 mass% or more, particularly preferably 99.9 mass% or less, more preferably 99 mass% or less, and further preferably 98.5 mass% or less. If the content ratio of the nitrile group-containing monomer unit in the copolymer is within the above range, the cohesive strength of the copolymer and the dispersibility of the resulting slurry composition are improved, and the peel strength of the positive electrode is sufficiently increased. The high potential durability of the copolymer itself can also be improved. Therefore, peeling of the positive electrode mixture layer is prevented, the internal resistance of the secondary battery is reduced, and a secondary battery having excellent battery characteristics such as life characteristics is obtained even when exposed to a high potential for a long time. be able to.
• the hydrophilic group-containing monomer unit is a repeating unit derived from a hydrophilic group-containing monomer.
• examples of the hydrophilic group-containing monomer include a monomer having a carboxylic acid group, a monomer having a sulfonic acid group, a monomer having a phosphoric acid group, and a monomer having a hydroxyl group.
• Examples of the monomer having a carboxylic acid group include monocarboxylic acids and derivatives thereof, dicarboxylic acids and acid anhydrides, and derivatives thereof.
• Examples of monocarboxylic acids include acrylic acid, methacrylic acid, and crotonic acid.
• Examples of monocarboxylic acid derivatives include 2-ethylacrylic acid, isocrotonic acid, ⁇ -acetoxyacrylic acid, ⁇ -trans-aryloxyacrylic acid, ⁇ -chloro- ⁇ -E-methoxyacrylic acid, ⁇ -diaminoacrylic acid, and the like.
• Examples of the dicarboxylic acid include maleic acid, fumaric acid, itaconic acid and the like.
• Dicarboxylic acid derivatives include methylmaleic acid, dimethylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, methylallyl maleate, diphenyl maleate, nonyl maleate, decyl maleate, dodecyl maleate And maleate esters such as octadecyl maleate and fluoroalkyl maleate.
• the acid anhydride of dicarboxylic acid include maleic anhydride, acrylic anhydride, methyl maleic anhydride, and dimethyl maleic anhydride.
• generates a carboxyl group by hydrolysis can also be used.
• monoesters and diesters of ⁇ , ⁇ -ethylenically unsaturated polyvalent carboxylic acids such as monobutyl itaconate and dibutyl itaconate.
• Examples of monomers having a sulfonic acid group include vinyl sulfonic acid, methyl vinyl sulfonic acid, (meth) allyl sulfonic acid, styrene sulfonic acid, (meth) acrylic acid-2-ethyl sulfonate, 2-acrylamido-2-methyl. Examples thereof include propanesulfonic acid and 3-allyloxy-2-hydroxypropanesulfonic acid.
• “(meth) allyl” means allyl and / or methallyl.
• (meth) acryl means acryl and / or methacryl.
• Examples of the monomer having a phosphate group include 2- (meth) acryloyloxyethyl phosphate, methyl-2- (meth) acryloyloxyethyl phosphate, ethyl phosphate- (meth) acryloyloxyethyl, and the like.
• (meth) acryloyl means acryloyl and / or methacryloyl.
• Examples of the monomer having a hydroxyl group include ethylenically unsaturated alcohols such as (meth) allyl alcohol, 3-buten-1-ol and 5-hexen-1-ol; 2-hydroxyethyl acrylate, acrylic acid-2 Ethylenic acid such as hydroxypropyl, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, di-2-hydroxyethyl maleate, di-4-hydroxybutyl maleate, di-2-hydroxypropyl itaconate Alkanol esters of unsaturated carboxylic acids; general formula CH 2 ⁇ CR 1 —COO— (C n H 2n O) m —H (wherein m is an integer from 2 to 9, n is an integer from 2 to 4, R 1 of the esters of a polyalkylene glycol and (meth) acrylic acid represented by hydrogen or a methyl group); 2-hydroxyethyl - Mono (meth) acrylic acid esters of dihydroxy esters of dicarbox
• hydrophilic group-containing monomers can be used alone or in combination of two or more.
• methacrylic acid, acrylic acid, and itaconic acid are more preferable from the viewpoint of increasing the peel strength and high potential durability of the positive electrode. That is, it is more preferable that the copolymer includes a monomer unit derived from at least one selected from the group consisting of methacrylic acid, acrylic acid, and itaconic acid as the hydrophilic group-containing monomer unit.
• the content ratio of the hydrophilic group-containing monomer unit in the copolymer is preferably 0.1% by mass or more when the total repeating unit in the copolymer is 100% by mass. More preferably, it is more preferably at least 2% by mass, more preferably at least 20% by mass, more preferably at most 17% by mass, and at most 15% by mass. More preferred is 10% by mass or less. If the content ratio of the hydrophilic group-containing monomer unit in the copolymer is 0.1% by mass or more, the adhesive strength of the copolymer is improved and the peel strength of the positive electrode is increased, and the positive electrode mixture layer Since the copolymer can coat the positive electrode active material better, the high potential durability of the positive electrode can be improved.
• the positive electrode active material is not excessively covered with the copolymer in the positive electrode mixture layer, An increase in internal resistance can be suppressed.
• the copolymer may contain monomer units other than the nitrile group-containing monomer unit and the hydrophilic group-containing monomer unit.
• examples of such other monomer units include (meth) acrylic acid ester monomer units.
• the (meth) acrylate monomer that can form a (meth) acrylate monomer unit methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t- Acrylic acid such as butyl acrylate, isobutyl acrylate, n-pentyl acrylate, isopentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, stearyl acrylate Alkyl ester; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl Methacrylate,
• the monomer which can form another monomer unit can be used individually or in combination of 2 or more types.
• the content ratio of the other monomer units is not particularly limited, but from the viewpoint of sufficiently obtaining the desired effect of the present invention, when the total repeating units in the copolymer is 100% by mass, 20% by mass. % Or less, more preferably 15% by mass or less, still more preferably 10% by mass or less.
• the copolymer preferably has a weight average molecular weight of 500,000 or more, more preferably 1,000,000 or more, preferably 2,500,000 or less, and 2,000,000. The following is more preferable. If the weight average molecular weight of the copolymer is 500,000 or more, the internal resistance of the secondary battery can be reduced without excessively covering the copolymer with the positive electrode active material due to an increase in the low molecular weight component. it can. Moreover, if the weight average molecular weight of the polymer is 2,500,000 or less, the slurry composition obtained using the polymer particles does not excessively thicken, and a positive electrode mixture layer having a uniform thickness is formed. can do. Therefore, the internal resistance of the secondary battery can be reduced while improving the high potential durability of the positive electrode.
• the copolymer preferably has a molecular weight distribution of 10 or less, more preferably 9 or less, still more preferably 8 or less, and particularly preferably 7 or less.
• the molecular weight distribution of the copolymer is 10 or less, the internal resistance of the secondary battery can be reduced without excessively covering the copolymer with the positive electrode active material due to an increase in the low molecular weight component.
• the copolymer preferably has a glass transition temperature of 60 ° C or higher, more preferably 80 ° C or higher, further preferably 100 ° C or higher, preferably 170 ° C or lower, and 160 ° C or lower. It is more preferable that it is 150 degreeC or less.
• the glass transition temperature of the copolymer is 60 ° C. or higher, blocking of particles during dry mixing is suppressed, and the polymer particles, the positive electrode active material, and the conductive material can be uniformly dispersed. Therefore, the copolymer can better coat the positive electrode active material in the positive electrode mixture layer, and the internal resistance of the secondary battery can be reduced while improving the high potential durability of the positive electrode.
• the glass transition temperature of a copolymer is 170 degrees C or less, the softness
• the polymer particles containing the copolymer are, for example, formed by polymerizing the monomer composition containing the above-described monomer in an aqueous solvent to form a copolymer, and then coagulating and filtering as necessary. It can also be obtained through drying under reduced pressure, etc., or obtained by polymerizing a monomer composition containing the above-described monomer in an arbitrary polymerization solvent to obtain a copolymer, followed by spray drying. You can also.
• the content ratio of each monomer in the monomer composition can be determined according to the content ratio of each monomer unit in the copolymer constituting the polymer particles.
• 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.
• As the polymerization reaction any reaction such as ionic polymerization, radical polymerization, and living radical polymerization can be used.
• a radical employing a suspension polymerization method as a polymerization mode it is preferable to polymerize the monomer composition by polymerization.
• known additives such as a dispersant and a polymerization initiator can be used. Examples of such known additives include those described in Japanese Patent No. 5573966.
• volume average particle diameter D50 of polymer particles The volume average particle diameter D50 of the polymer particles obtained as described above is required to be 1 ⁇ m or more, preferably 10 ⁇ m or more, more preferably 50 ⁇ m or more, and 100 ⁇ m or more. More preferably, it is 200 ⁇ m or more, particularly preferably 2000 ⁇ m or less, more preferably 1800 ⁇ m or less, still more preferably 1000 ⁇ m or less, and particularly preferably 500 ⁇ m or less. If the volume average particle diameter D50 of the polymer particles is less than 1 ⁇ m, the layer of the copolymer covering the positive electrode active material in the positive electrode mixture layer becomes excessively thin, so that the high potential durability of the positive electrode can be ensured.
• the peel strength of the positive electrode also decreases.
• the volume average particle diameter D50 of the polymer particles is 2000 ⁇ m or less, the copolymer layer covering the positive electrode active material in the positive electrode mixture layer is not excessively thick, and the internal resistance of the secondary battery is reduced. Can be reduced.
• the volume average particle diameter D50 of the polymer particles is determined based on the polymer particle preparation conditions (polymerization concentration, polymerization temperature and stirring speed, type and amount of dispersant, polymerization initiator and chain transfer agent, and spray drying spray speed and drying. It can be changed by adjusting the temperature.
• the ratio of the volume average particle diameter D50 of the polymer particles to the volume average particle diameter D50 of the positive electrode active material needs to be 0.1 or more, preferably 1 or more, and more preferably 5 or more. Preferably, it is more preferably 10 or more, particularly preferably 20 or more, preferably 200 or less, more preferably 100 or less, and still more preferably 50 or less.
• the particle size ratio of the polymer particles to the positive electrode active material is less than 0.1, the layer of the copolymer covering the positive electrode active material in the positive electrode mixture layer becomes excessively thin. It cannot be ensured, and the peel strength of the positive electrode also decreases.
• the particle size ratio of the polymer particles to the positive electrode active material is 200 or less, the layer of the copolymer covering the positive electrode active material in the positive electrode mixture layer is not excessively thick, and the inside of the secondary battery Resistance can be reduced.
• the positive electrode active material is a material that transfers electrons at the positive electrode of the secondary battery.
• a positive electrode active material for a lithium ion secondary battery a material that can occlude and release lithium is usually used.
• the positive electrode active material for the lithium ion secondary battery is not particularly limited, and lithium-containing cobalt oxide (LiCoO 2 ), lithium manganate (LiMn 2 O 4 ), lithium-containing nickel oxide (LiNiO 2 ), Co—Ni—Mn lithium-containing composite oxide (Li (Co Mn Ni) O 2 ), Ni—Mn—Al lithium-containing composite oxide, Ni—Co—Al lithium-containing composite oxide Olivine lithium iron phosphate (LiFePO 4 ), olivine lithium manganese phosphate (LiMnPO 4 ), Li 1 + x Mn 2 ⁇ x O 4 (0 ⁇ X ⁇ 2)
• Known positive electrode active materials such as Li [Ni 0.17 Li 0.2 Co 0.07 Mn 0.56 ] O 2 and LiNi 0.5 Mn 1.5 O 4 may be mentioned.
• the positive electrode active material includes lithium-containing cobalt oxide (LiCoO 2 ), lithium-containing nickel oxide (LiNiO 2 ), and Co—Ni—Mn.
• Lithium-containing composite oxide Li [Ni 0.17 Li 0.2 Co 0.07 Mn 0.56 ] O 2 or LiNi 0.5 Mn 1.5 O 4 is preferably used, and lithium-containing cobalt oxide (LiCoO 2 ), Li [Ni 0.17 Li 0.2 Co 0.07 It is more preferable to use Mn 0.56 ] O 2 or LiNi 0.5 Mn 1.5 O 4 .
• Mn 0.56 LiNi 0.5 Mn 1.5 O 4 .
• the volume average particle diameter D50 of the positive electrode active material is not particularly limited as long as the particle diameter ratio of the polymer particles to the positive electrode active material is within a predetermined range, but is preferably 0.1 ⁇ m or more and 100 ⁇ m or less.
• the conductive material is for ensuring electrical contact between the positive electrode active materials.
• carbon black for example, acetylene black, ketjen black (registered trademark), furnace black, etc.
• graphite carbon fiber, carbon flake, and ultra-short carbon fiber (for example, carbon nanotube or vapor grown carbon)
• Conductive carbon materials such as fibers); fibers and foils of various metals can be used.
• carbon black is preferable, and acetylene black is more preferable. These can be used alone or in combination of two or more.
• the dispersion medium added to the dry mixture obtained after dry-mixing the above-described polymer particles, positive electrode active material and conductive material is not particularly limited, and an organic solvent can be used.
• the organic solvent include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, amyl alcohol and the like, Ketones such as acetone, methyl ethyl ketone and cyclohexanone, esters such as ethyl acetate and butyl acetate, ethers such as diethyl ether, dioxane and tetrahydrofuran, N, N-dimethylformamide, N-methyl-2-pyrrolidone (NMP) and the like
• NMP N-dimethyl
• components other than those described above may be used.
• examples of such other components include a polymer powder containing a binder other than the above-described copolymer, a reinforcing material described in International Publication No. 2012/115096, a leveling agent, a viscosity modifier, Known additives such as an electrolytic solution additive may be mentioned.
• These components may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. And the addition time of these other components is not specifically limited, What is necessary is just to add suitably in either process according to the property.
• the property of the binder (polymer) which comprises the polymer powder mentioned above is arbitrary, For example, the polymer whose glass transition temperature is 40 degrees C or less can also be used.
• a slurry composition is prepared using the component mentioned above. Specifically, a step of dry mixing polymer particles for a secondary battery positive electrode, a positive electrode active material, and a conductive material to obtain a dry mixture (dry mixing step), and a dry mixture and a dispersion medium obtained in the dry mixing step A slurry composition is prepared through a step of mixing to obtain a slurry composition for a secondary battery positive electrode (dispersion medium mixing step).
• the mixing method of dry mixing is not particularly limited, but it is preferable to mix using a mixer.
• Mixers used for dry mixing include dry tumblers, super mixers, Henschel mixers, flash mixers, air blenders, flow jet mixers, drum mixers, ribocorn mixers, pug mixers, nauter mixers, ribbon mixers, and Spartan Luzers.
• a redige mixer, a planetary mixer, and a kneader such as a screw type kneader, a defoaming kneader, a paint shaker, a pressure kneader, or a two-roller.
• mixers such as a planetary mixer that can be dispersed by stirring, and planetary mixers and Henschel mixers are particularly preferred.
• the mixing time of dry mixing is not particularly limited as long as each component is uniformly mixed, but for example, preferably 1 minute or more, more preferably 2 minutes or more, further preferably 10 minutes or more, preferably 60 minutes or less, More preferably, it is 30 minutes or less, More preferably, it is 20 minutes or less.
• the ratio of the addition amount of the polymer particles, the positive electrode active material, and the conductive material is not particularly limited during dry mixing.
• the amount of polymer particles added is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 5 parts by mass or less, per 100 parts by mass of the positive electrode active material. It is more preferable that the amount is not more than part by mass. If the amount of polymer particles added per 100 parts by mass of the positive electrode active material is 0.5 parts by mass or more, the copolymer is preferably used as the positive electrode active material in the positive electrode mixture layer formed using the resulting slurry composition. It is possible to sufficiently ensure the high potential durability and peel strength of the positive electrode.
• the internal resistance of the secondary battery will not increase excessively.
• the amount of the conductive material added is preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, and preferably 7 parts by mass or less, per 100 parts by mass of the positive electrode active material. More preferably, it is 5 parts by mass or less. If the addition amount of the conductive material is within the above range, the conductive path is well formed in the positive electrode mixture layer formed using the resulting slurry composition, while reducing the internal resistance of the secondary battery, The high potential durability of the positive electrode can be sufficiently secured.
• the method of adding the dispersion medium to the dry mixture is not particularly limited and may be batch addition or sequential addition, but sequential addition is preferable from the viewpoint of obtaining a slurry composition in which each component is uniformly dispersed. .
• the amount of the dispersion medium added in the dispersion medium mixing step is not particularly limited.
• the solid content concentration of the obtained slurry composition is preferably 50% by mass or more, more preferably 60% by mass or more, and preferably 80% by mass or less. More preferably, the dispersion medium is added in an amount of 75% by mass or less.
• the method of mixing the dry mixture and the dispersion medium is not particularly limited.
• the slurry composition can be prepared by mixing the dry mixture and the dispersion medium.
• the mixing time in the dispersion medium mixing step is not particularly limited as long as the dry mixture and the dispersion medium are uniformly mixed, but is preferably 1 minute or more, more preferably 2 minutes or more, still more preferably 10 minutes or more, preferably Is 120 minutes or less, more preferably 90 minutes or less, still more preferably 60 minutes or less.
• a positive electrode for a secondary battery according to the present invention includes a current collector and a positive electrode mixture layer formed on the current collector, and the positive electrode mixture layer is obtained by the method for producing a slurry composition for a secondary battery positive electrode. It is formed using the slurry composition for secondary battery positive electrodes obtained.
• the positive electrode for secondary battery of the present invention is produced using the slurry composition for secondary battery positive electrode obtained by the method for producing the slurry composition for secondary battery positive electrode of the present invention. Excellent in properties and peel strength.
• the positive electrode for a secondary battery according to the present invention can reduce the internal resistance of the secondary battery, and exhibits excellent life characteristics even when exposed to a high potential for a long time. Can be made.
• the positive electrode for a secondary battery according to the present invention includes, for example, a step of applying the slurry composition described above on the current collector (application step), and a slurry composition applied on the current collector by drying. It is manufactured through a step (drying step) of forming a positive electrode mixture layer on the electric body.
• the positive electrode for secondary batteries of the present invention can be prepared by a method in which the above-mentioned slurry composition is dried and granulated to prepare composite particles, and a positive electrode mixture layer is formed on a current collector using the composite particles. Can be manufactured.
• the method for applying the slurry composition onto the current collector is not particularly limited, and a known method can be used. Specifically, as a 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 positive electrode mixture layer obtained by drying.
• an electrically conductive and electrochemically durable material is used as the current collector to which the slurry composition is applied.
• a current collector for example, a current collector made of iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, platinum, or the like can be used.
• a collector used for a positive electrode an aluminum foil is particularly preferable.
• the said material may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.
• a method for drying the slurry composition on the current collector is not particularly limited, and a known method can be used. A drying method is mentioned. By drying the slurry composition on the current collector in this way, a positive electrode mixture layer is formed on the current collector, and a positive electrode for a secondary battery comprising the current collector and the positive electrode mixture layer can be obtained. it can.
• the positive electrode mixture layer may be subjected to pressure treatment using a die press or a roll press. By the pressure treatment, the adhesion between the positive electrode mixture layer and the current collector can be improved. Furthermore, when the positive electrode mixture layer contains a curable polymer, the polymer is preferably cured after the positive electrode mixture layer is formed.
• the secondary battery of the present invention includes a positive electrode, a negative electrode, an electrolytic solution, and a separator, and uses the positive electrode for a secondary battery of the present invention as the positive electrode. And since the secondary battery of this invention is equipped with the positive electrode for secondary batteries of this invention, the raise of internal resistance is suppressed and it is exposed to high potential (for example, 4.4V or more) for a long time. Even in such a case, the life characteristics are excellent.
• a known negative electrode can be used as the negative electrode.
• the negative electrode for example, a negative electrode made of a thin plate of metallic lithium or a negative electrode formed by forming a negative electrode mixture layer on a current collector can be used.
• a collector what consists of metal materials, such as iron, copper, aluminum, nickel, stainless steel, titanium, a tantalum, gold
• the negative electrode mixture layer a layer containing a negative electrode active material and a binder can be used.
• the binder is not particularly limited, and any known material can be used.
• an organic electrolytic solution in which a supporting electrolyte is dissolved in an organic solvent is usually used.
• a lithium salt is used as the supporting electrolyte for the lithium ion secondary battery.
• the lithium salt 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 it is easily soluble in a solvent and exhibits a high degree of dissociation.
• electrolyte may be used individually by 1 type and may be used combining two or more types by arbitrary ratios. Usually, the lithium ion conductivity tends to increase as the supporting electrolyte having a higher degree of dissociation is used, so that the lithium ion conductivity can be adjusted depending on the type of the supporting electrolyte.
• the organic solvent used in the electrolytic solution is not particularly limited as long as it can dissolve the supporting electrolyte.
• carbonates because they have a high dielectric constant and a wide stable potential region, and it is more preferable to use a mixture of ethylene carbonate and ethyl methyl carbonate.
• 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 preferable.
• known additives such as fluoroethylene carbonate and ethyl methyl sulfone can be added to the electrolytic solution.
• the separator is not particularly limited, and for example, those described in JP 2012-204303 A can be used. Among these, the film thickness of the entire separator can be reduced, thereby increasing the ratio of the electrode active material in the secondary battery and increasing the capacity per volume.
• a microporous film made of a resin such as polyethylene, polypropylene, polybutene, or polyvinyl chloride is preferable.
• the secondary battery of the present invention includes, for example, a positive electrode and a negative electrode that are stacked with a separator interposed between them, wound as necessary according to the shape of the battery, folded into a battery container, and electrolyzed in the battery container. It can be manufactured by injecting and sealing the liquid. In order to prevent an increase in pressure inside the secondary battery, overcharge / discharge, and the like, a fuse, an overcurrent prevention element such as a PTC element, an expanded metal, a lead plate, and the like may be provided as necessary.
• the shape of the secondary battery may be any of, for example, a coin shape, a button shape, a sheet shape, a cylindrical shape, a square shape, and a flat shape.
• the volume average particle diameter D50 of each particle, the molecular weight of the copolymer (weight average molecular weight, number average molecular weight, molecular weight distribution) and glass transition temperature, positive electrode peel strength and high potential durability was measured and evaluated by the following method.
• ⁇ Volume average particle diameter D50> In a particle size distribution measured dry using a laser diffraction / scattering particle size distribution measuring apparatus (manufactured by Nikkiso Co., Ltd., “Microtrac MT3200II”), the particle size was determined as the particle size at which the cumulative volume calculated from the small diameter side was 50%. .
• ⁇ Molecular weight> The weight average molecular weight (Mw) and number average molecular weight (Mn) of the copolymer contained in the polymer particles were measured by gel permeation chromatography (GPC) using a LiBr-DMF solution having a concentration of 10 mM under the following measurement conditions. In addition, the molecular weight distribution (Mw / Mn) was calculated.
• the dried film was used as a sample in accordance with JIS K 7121 under the conditions of a measurement temperature of ⁇ 100 ° C. to 180 ° C. and a heating rate of 5 ° C./min.
• DSC6220SII differential scanning calorimeter, manufactured by Nanotechnology Inc.
• the positive electrodes produced in the examples and comparative examples were cut into rectangles having a width of 1.0 cm and a length of 10 cm to obtain test pieces. Then, a cellophane tape was attached to the surface of the test piece on the positive electrode mixture layer side.
• the cellophane tape defined in JIS Z1522 was used. Then, the stress when the test piece was peeled from the one end side toward the other end side at a speed of 50 mm / min with the cellophane tape fixed to the test stand was measured. The measurement was performed 10 times, the average value of the stress was obtained, and this was taken as the peel strength, and evaluated according to the following criteria. It shows that the adhesiveness of the positive mix layer with respect to a collector is excellent, so that peel strength is large.
• the slurry composition for a secondary battery positive electrode produced in the examples and comparative examples was applied on an aluminum foil (thickness 20 ⁇ m) as a current collector with a comma coater so that the basis weight after drying was 20 mg / cm 2. After drying at 90 ° C. for 20 minutes and at 120 ° C. for 20 minutes, heat treatment was further performed at 60 ° C. for 10 hours under vacuum to obtain a positive electrode provided with a positive electrode mixture layer on the current collector.
• This positive electrode is cut into a circle with a diameter of 12 mm, and a circular polypropylene porous membrane (diameter 18 mm, thickness 25 ⁇ m), metallic lithium (diameter 14 mm), and expanded metal are arranged in this order on the positive electrode mixture layer side of the cut-out positive electrode. It laminated
• the IV resistance was measured as follows.
• Example 1 Preparation of polymer particles for secondary battery positive electrode> A pressure vessel equipped with a stirrer, thermometer, cooling pipe and nitrogen gas introduction pipe was charged with 400 parts of ion-exchanged water, and while rotating the stirrer gently, reduced pressure (-600 mmHg) and normalization with nitrogen gas were performed. It repeated 3 times, It confirmed using the dissolved oxygen meter that the oxygen concentration of the gaseous-phase part of reaction container was 1% or less, and the dissolved oxygen in water was 1 ppm or less.
• partially saponified polyvinyl alcohol manufactured by Nippon Synthetic Chemical Industry Co., Ltd., “GOHSENOL GH-20” (saponification degree: 86.5 mol% to 89.0 mol%)
• a dispersant is gradually added and dispersed well. Then, stirring was continued while raising the temperature to 60 ° C., and kept for 30 minutes to dissolve the partially saponified polyvinyl alcohol.
• the polymer particles obtained were collected on a 200-mesh filter cloth, washed with 100 parts of ion exchange water three times, and then dried under reduced pressure at 70 ° C. for 12 hours for isolation and purification (recovery rate 70%).
• the volume average particle diameter D50 of the polymer particles after isolation and purification, the molecular weight (weight average molecular weight, number average molecular weight, molecular weight distribution) and glass transition temperature of the copolymer constituting the polymer particles were measured. The results are shown in Table 1.
• a ternary active material LiNi 0.5 Co 0.2 Mn 0.3 O 2
• acetylene black Diska black powder: electrochemistry
• a slurry composition for a secondary battery positive electrode was obtained by sequentially adding an appropriate amount of NMP as a dispersion medium to the obtained dry mixture and mixing for 20 minutes (dispersion medium mixing step).
• the solid content concentration of the obtained slurry composition is 70% by mass
• the viscosity at 60 rpm measured by a B-type viscometer according to JIS Z8803: 1991 is 4400 mPa ⁇ s (25 ° C., spindle shape: 4). Met.
• the high potential durability of the positive electrode was evaluated using this slurry composition. The results are shown in Table 1.
• An aluminum foil with a thickness of 20 ⁇ m was prepared as a current collector.
• a 40% aqueous dispersion of a styrene-butadiene copolymer (glass transition temperature: ⁇ 15 ° C.) as a binder is added in an amount corresponding to a solid content of 1.0 part and ion-exchanged water to obtain a final solid.
• the partial concentration was adjusted to 50% and further mixed for 10 minutes. This was defoamed under reduced pressure to obtain a slurry composition for a secondary battery negative electrode having good fluidity.
• the slurry composition for a secondary battery negative electrode was applied on a copper foil having a thickness of 20 ⁇ m as a current collector by a comma coater so that the film thickness after drying was about 150 ⁇ m and dried.
• This drying was performed by conveying the copper foil in an oven at 60 ° C. at a speed of 0.5 m / min for 2 minutes. Thereafter, heat treatment was performed at 120 ° C. for 2 minutes to obtain a negative electrode raw material.
• This negative electrode raw material was rolled with a roll press to produce a negative electrode having a negative electrode mixture layer thickness of 80 ⁇ m.
• ⁇ Preparation of separator> A single-layer polypropylene separator (width 65 mm, length 500 mm, thickness 25 ⁇ m, manufactured by a dry method, porosity 55%) was cut into a 5 cm ⁇ 5 cm square.
• An aluminum packaging exterior was prepared as the battery exterior.
• the positive electrode obtained above was cut into a 4 cm ⁇ 4 cm square and arranged so that the current collector-side surface was in contact with the aluminum packaging exterior.
• the 5 cm ⁇ 5 cm square separator obtained above was disposed on the surface of the positive electrode mixture layer of the positive electrode.
• the negative electrode obtained above was cut into a square of 4.2 cm ⁇ 4.2 cm, and this was placed on the separator so that the surface on the negative electrode mixture layer side faces the separator.
• Example 2 In the same manner as in Example 1, except that the amount of the partially saponified polyvinyl alcohol as the dispersant was changed to 0.1 part and 2.0 parts, respectively, in the preparation of the polymer particles, the polymer particles for the secondary battery positive electrode A slurry composition for a secondary battery positive electrode, a positive electrode for a secondary battery, a negative electrode for a secondary battery, and a secondary battery were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1.
• Example 6 In the preparation of the polymer particles, the polymer particles for the secondary battery positive electrode and the secondary battery positive electrode were used in the same manner as in Example 1 except that the monomers listed in Table 1 were used in the ratios shown in the table. A slurry composition, a positive electrode for a secondary battery, a negative electrode for a secondary battery, and a secondary battery were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1. In Example 6, 2-ethylhexyl acrylate was used as the (meth) acrylic acid ester monomer.
• Example 7 In the same manner as in Example 1, except that the amount of t-dodecyl mercaptan as a chain transfer agent was changed to 0.1 part when preparing the polymer particles, the polymer particles for the secondary battery positive electrode, the secondary battery positive electrode Slurry compositions, positive electrodes for secondary batteries, negative electrodes for secondary batteries, and secondary batteries were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1.
• Example 1 Except for using particles made of polyvinylidene fluoride (volume average particle diameter D50: 300 ⁇ m) as the polymer particles, the same as in Example 1, the polymer particles for the secondary battery positive electrode, the slurry composition for the secondary battery positive electrode, A secondary battery positive electrode, a secondary battery negative electrode and a secondary battery were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1.
• a ternary active material LiNi 0.5 Co 0.2 Mn 0.3 O 2
• acetylene black Diska black powder: electrochemistry
• the slurry mixture for secondary battery positive electrodes was obtained by mixing for 20 minutes, adding the varnish (2.0 parts by solid content) mentioned above and an appropriate amount of NMP as a dispersion medium sequentially to the obtained mixture.
• the solid content concentration of the obtained slurry composition is 70% by mass, and the viscosity at 60 rpm measured by a B-type viscometer according to JIS Z8803: 1991 is 4400 mPa ⁇ s (25 ° C., spindle shape: 4). Met.
• the high potential durability of the positive electrode was evaluated. The results are shown in Table 1.
• Example 1 a secondary battery positive electrode, a secondary battery negative electrode and a secondary battery were produced in the same manner as in Example 1 except that the slurry composition for a secondary battery positive electrode thus obtained was used. Evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.
• Example 3 In the same manner as in Example 1 except that the amount of the partially saponified polyvinyl alcohol as the dispersant was changed to 3.0 parts during the preparation of the polymer particles, the polymer particles for the secondary battery positive electrode and the secondary battery positive electrode were used. A slurry composition, a positive electrode for a secondary battery, a negative electrode for a secondary battery, and a secondary battery were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1.
• Comparative Example 4 Polymer particles for secondary battery positive electrode, slurry for secondary battery positive electrode, in the same manner as in Example 1 except that the monomers listed in Table 1 were used in the ratio shown in the table when preparing the polymer particles.
• a composition, a positive electrode for a secondary battery, a negative electrode for a secondary battery, and a secondary battery were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1.
• 2-ethylhexyl acrylate was used as the (meth) acrylic acid ester monomer.
• AN stands for acrylonitrile
• MAA methacrylic acid
• 2EHA 2-ethylhexyl acrylate
• PVDF polyvinylidene fluoride
• the high potential durability of the positive electrode can be further improved by adjusting the molecular weight distribution of the copolymer contained in the polymer particles, and the internal resistance of the secondary battery can be further increased. It can be seen that it can be reduced.
• the method of manufacturing the slurry composition for secondary battery positive electrodes which exhibits the high-potential durability excellent in the positive electrode can be provided.
• the secondary battery which is equipped with the positive electrode for secondary batteries excellent in high-potential durability, and the said positive electrode for secondary batteries, and is excellent in a battery characteristic can be provided.

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