WO2015133423A1 - Binder composition for secondary cell - Google Patents

Binder composition for secondary cell Download PDF

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Publication number
WO2015133423A1
WO2015133423A1 PCT/JP2015/056046 JP2015056046W WO2015133423A1 WO 2015133423 A1 WO2015133423 A1 WO 2015133423A1 JP 2015056046 W JP2015056046 W JP 2015056046W WO 2015133423 A1 WO2015133423 A1 WO 2015133423A1
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WO
WIPO (PCT)
Prior art keywords
binder composition
expandable particles
heat
secondary battery
sensitive gas
Prior art date
Application number
PCT/JP2015/056046
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French (fr)
Japanese (ja)
Inventor
金田　拓也
智一 佐々木
Original Assignee
日本ゼオン株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 日本ゼオン株式会社 filed Critical 日本ゼオン株式会社
Priority to JP2016506476A priority Critical patent/JP6414201B2/en
Priority to CN201580004094.2A priority patent/CN105900271B/en
Priority to KR1020167017184A priority patent/KR102310732B1/en
Publication of WO2015133423A1 publication Critical patent/WO2015133423A1/en

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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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • 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
    • 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

  • This invention relates to the binder composition for secondary batteries used in order to form the electrode compound-material layer of secondary batteries, such as a lithium ion secondary battery.
  • Lithium ion secondary batteries have a high energy density and are used in the fields of mobile phones and laptop computers. However, with the expansion and development of applications, further improvements in performance are required, such as lowering resistance and increasing capacity. Has been.
  • the separator has an important function of preventing an electrical short circuit between the positive electrode and the negative electrode of the lithium ion secondary battery.
  • a separator used in the lithium ion secondary battery for example, a microporous film made of polyolefin resin is used. in use.
  • the separator normally melts and closes the micropore, thereby preventing lithium ion migration and shutting down the current, thereby shutting down the lithium ion secondary battery. It plays a role in maintaining the safety of secondary batteries.
  • the separator contracts rapidly, and the positive electrode and the negative electrode may be in direct contact with each other, thereby expanding the location where the short circuit occurs.
  • the battery temperature may reach a state where it is abnormally overheated to several hundred degrees Celsius or higher.
  • Patent Document 1 a conductive material whose resistance increases in a temperature range of 90 to 160 ° C. is included in the electrode mixture layer, and electrical insulation can be maintained even at a temperature higher than 160 ° C.
  • a lithium ion secondary battery using a separator made of a material that exhibits ion conductivity even when the temperature rises to 160 ° C. or higher and then is cooled to 100 ° C. or lower has been proposed.
  • Patent Document 1 an electrode mixture layer containing a predetermined conductive material and a separator made of a predetermined material are used in combination, but the separator material is a polyolefin resin or the like that is usually used. However, it is also required to form an electrode mixture layer that can ensure safety corresponding to abnormal heating.
  • the objective of this invention is providing the binder composition for secondary batteries which can obtain the electrode compound-material layer which can improve the safety
  • the present inventors have found that the above object can be achieved by using heat-sensitive gas-expandable particles that expand with gas at a predetermined temperature or higher, and have completed the present invention.
  • V 25 ° C. represents the volume of the heat-sensitive gas-expandable particles at 25 ° C.
  • the binder composition for a secondary battery according to (1) (3)
  • Secondary battery binder composition as described above (4)
  • the thermal gas expandable particles have a core-shell structure, and the core material of the thermal gas expandable particles is a hydrocarbon having a boiling point of 10 to 150 ° C.
  • a binder composition for a secondary battery (6)
  • the thermal gas expandable particle has a core-shell structure, and the shell material of the thermal gas expandable particle is a polymer containing a polymer unit having a nitrile group.
  • the binder composition for secondary batteries as described in 1 above is provided.
  • a binder composition for a secondary battery that can provide an electrode mixture layer that can improve the safety of the secondary battery.
  • the binder composition for a secondary battery according to the present invention is a binder composition for a secondary battery containing heat-sensitive gas-expandable particles and a binder resin, and is formed by the binder composition for a secondary battery.
  • the heat-sensitive gas-expandable particles used in the binder composition for a secondary battery of the present invention are particles that expand due to gas when the temperature exceeds a predetermined temperature.
  • the heat-sensitive gas-expandable particles those having a core-shell structure including a shell material formed of a resin or an elastomer and a core material containing a low boiling point solvent are preferable.
  • the heat-sensitive gas-expandable particles having the core-shell structure are, for example, low-boiling solvents that form the core portion and polymer monomers that form the shell portion with the polymer monomer. And a method of polymerizing in stages by changing the ratio of these monomers over time, a hydrophobic low boiling point solvent and a lipophilic monomer that can become core particles, and a hydrophilic It can be produced by mixing and polymerizing a monomer corresponding to a high shell material.
  • “highly hydrophilic” means that the water solubility at a temperature of 20 ° C. is 1 or more (unit: g / 100 g), preferably 3 or more from the viewpoint that the boundary of the core-shell structure becomes clearer, 4 or more. Are more preferred. There is no particular upper limit, but it is preferably 30 or less.
  • the water solubility at 20 ° C. can be measured by the EPA method (EPA Chemical Fate testing Guideline CG-1500 Water Solubility).
  • the water solubility (unit: g / 100 g) of a typical monomer and solvent at a temperature of 20 ° C. is shown in parentheses as follows.
  • the material of the shell material is not particularly limited as long as it has electrolyte resistance and is flexible enough to prevent cracking when the heat-sensitive gas-expandable particles expand. Polymerization having a nitrile group It is preferable to use a polymer containing units.
  • polymer unit having a nitrile group examples include an ⁇ , ⁇ -ethylenically unsaturated nitrile monomer unit.
  • the “monomer unit” is a structural unit formed by polymerizing monomers.
  • the monomer forming the ⁇ , ⁇ -ethylenically unsaturated nitrile monomer unit is not limited as long as it is an ⁇ , ⁇ -ethylenically unsaturated compound having a nitrile group, and acrylonitrile; ⁇ -chloroacrylonitrile, ⁇ - ⁇ -halogenoacrylonitrile such as bromoacrylonitrile; ⁇ -alkylacrylonitrile such as methacrylonitrile; and the like. Acrylonitrile and methacrylonitrile are preferred. These ⁇ , ⁇ -ethylenically unsaturated nitrile monomers may be used in combination.
  • the polymer containing a polymer unit having a nitrile group may be a copolymer of a monomer that forms a polymer unit having a nitrile group and a copolymerizable monomer.
  • the copolymerizable monomer include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, and fumaric acid; two or more carbons such as ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, and trimethylolpropane triacrylate.
  • Carboxylates having carbon double bonds including styrene, chlorostyrene, vinyl toluene, t-butyl styrene, vinyl benzoic acid, methyl vinyl benzoate, vinyl naphthalene, chloromethyl styrene, hydroxymethyl styrene, ⁇ -methyl styrene, Styrene monomers such as divinylbenzene; Amide monomers such as acrylamide, N-methylolacrylamide, and acrylamide-2-methylpropanesulfonic acid; Olefins such as ethylene and propylene; Diene monomers such as soprene; monomers containing halogen atoms such as vinyl chloride and vinylidene chloride; vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl benzoate; methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether Vinyl ethers such as methyl vinyl ketone, eth
  • the core material as the inclusion of the shell material of the heat-sensitive gas-expandable particles is not particularly limited as long as it vaporizes when the secondary battery becomes high temperature, but is a hydrocarbon having a boiling point of 10 to 150 ° C. Preferably there is.
  • hydrocarbon having a boiling point of 10 to 150 ° C. examples include isopentane, isooctane, n-pentane, n-hexane, isohexane, heptane, petroleum ether and the like.
  • the volume change of the heat-sensitive gas expandable particles can be obtained, for example, as the volume change of the cast film formed of the heat-sensitive gas expandable particles.
  • the particle size of the heat-sensitive gas-expandable particles is preferably 0.1 to 10 ⁇ m, more preferably 0.3 to 3 ⁇ m, and particularly preferably 0.3 to 1 ⁇ m.
  • the particle diameter can be obtained from an average value obtained by observing an electron microscope and calculating (a + b) / 2 with respect to 100 or more particles, where a is the longest side of the particle image and b is the shortest side.
  • the diene polymer is a polymer containing monomer units obtained by polymerizing conjugated dienes such as butadiene and isoprene.
  • the proportion of monomer units obtained by polymerizing conjugated diene in the diene polymer is usually 40% by weight or more, preferably 50% by weight or more, more preferably 60% by weight or more.
  • Examples of the polymer include homopolymers of conjugated dienes such as polybutadiene and polyisoprene; and copolymers of monomers that are copolymerizable with conjugated dienes.
  • Examples of the copolymerizable monomer include ⁇ , ⁇ -unsaturated nitrile compounds such as acrylonitrile and methacrylonitrile; unsaturated carboxylic acids such as acrylic acid and methacrylic acid; styrene, chlorostyrene, vinyltoluene, and t-butyl.
  • Styrene monomers such as styrene, vinyl benzoic acid, methyl vinyl benzoate, vinyl naphthalene, chloromethyl styrene, hydroxymethyl styrene, ⁇ -methyl styrene and divinyl benzene; olefins such as ethylene and propylene; vinyl chloride and vinylidene chloride Halogen atom-containing monomers such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl benzoate, etc .; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether; methyl vinyl ketone, ethyl vinyl Vinyl ketones such as ketone, butyl vinyl ketone, hexyl vinyl ketone, and isopropenyl vinyl ketone; and heterocyclic ring-containing vinyl compounds such as N-vinyl pyrrolidone, vinyl pyridine, and vinyl imidazole.
  • the acrylic polymer is a polymer containing a monomer unit obtained by polymerizing an acrylic ester and / or a methacrylic ester.
  • the proportion of monomer units obtained by polymerizing acrylic acid ester and / or methacrylic acid ester in the acrylic polymer is usually 40% by weight or more, preferably 50% by weight or more, more preferably 60% by weight or more.
  • Examples of the polymer include homopolymers of acrylic acid esters and / or methacrylic acid esters, and copolymers with monomers copolymerizable therewith.
  • Examples of the copolymerizable monomer include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, and fumaric acid; two or more carbons such as ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, and trimethylolpropane triacrylate.
  • unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, and fumaric acid
  • two or more carbons such as ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, and trimethylolpropane triacrylate.
  • Carboxylates having carbon double bonds including styrene, chlorostyrene, vinyl toluene, t-butyl styrene, vinyl benzoic acid, methyl vinyl benzoate, vinyl naphthalene, chloromethyl styrene, hydroxymethyl styrene, ⁇ -methyl styrene, Styrenic monomers such as divinylbenzene; Amide monomers such as acrylamide, N-methylolacrylamide, and acrylamide-2-methylpropanesulfonic acid; ⁇ , ⁇ -insoluble such as acrylonitrile and methacrylonitrile Nitrile compounds; olefins such as ethylene and propylene; diene monomers such as butadiene and isoprene; monomers containing halogen atoms such as vinyl chloride and vinylidene chloride; vinyl acetate, vinyl propionate, vinyl butyrate, vinyl benzoate Vinyl esters such as methyl vinyl
  • the fluorine-based polymer is a polymer containing a monomer unit containing a fluorine atom.
  • Specific examples of the fluoropolymer include polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, ethylene / tetrafluoroethylene copolymer, ethylene / chlorotrifluoroethylene copolymer, A perfluoroethylene propene copolymer may be mentioned.
  • the binder composition for secondary batteries of the present invention comprises the above-mentioned heat-sensitive gas-expandable particles and a binder resin.
  • V (25 ° C. represents the volume of the cast film at 25 ° C.), and is preferably from 15 to 25.
  • the volume change of the cast film formed by the secondary battery binder composition of the present invention is too large, the adhesive strength / cohesive strength of the secondary battery binder composition will be reduced, and the cycle characteristics of the secondary battery obtained will be descend.
  • the volume change of the cast film formed by the binder composition for a secondary battery of the present invention is too small, the distance between the electrode active materials cannot be sufficiently widened, so that the desired safety may not be obtained. is there.
  • the mixing method of the heat-sensitive gas-expandable particles and the binder resin is not particularly limited, and examples thereof include a method using a mixing apparatus such as a stirring type, a shaking type, and a rotary type.
  • the binder composition of this invention can be used for the electrode for secondary batteries.
  • An electrode for a secondary battery is obtained by forming an electrode mixture layer on a current collector, and the electrode mixture layer is made of an electrode active material, the binder composition of the present invention, and a thickener used as necessary. And a conductive material.
  • the content of the binder composition in the electrode mixture layer is 0.1 to 20 parts by weight, preferably 0.2 to 15 parts by weight, and more preferably 0.3 parts by weight with respect to 100 parts by weight of the electrode mixture layer. ⁇ 10 parts by weight.
  • the electrode mixture layer is formed by applying and drying an electrode active material, a binder composition of the present invention, a slurry composition for an electrode containing a thickener and a conductive material, if necessary, on a current collector.
  • the method for applying the electrode slurry composition on the current collector is not particularly limited. Examples thereof include a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, a comma direct coating, a slide die coating, and a brush coating method.
  • the drying method include drying with warm air, hot air, low-humidity air, vacuum drying, and drying by irradiation with (far) infrared rays or electron beams.
  • the drying time is usually 1 to 60 minutes, and the drying temperature is usually 40 to 180 ° C.
  • the electrode mixture layer may be formed by repeating the application and drying of the electrode slurry composition a plurality of times.
  • the slurry composition for an electrode can be obtained by mixing an electrode active material, a binder, a thickener and a conductive material used as necessary, and a solvent such as water.
  • the mixing method is not particularly limited, and examples thereof include a method using a mixing apparatus such as a stirring type, a shaking type, and a rotary type.
  • a method using a dispersion kneader such as a homogenizer, a ball mill, a sand mill, a roll mill, a planetary mixer, and a planetary kneader can be used.
  • the material of the current collector is, for example, metal, carbon, conductive polymer, etc., and metal is preferably used.
  • As the current collector metal aluminum, platinum, nickel, tantalum, titanium, stainless steel, copper, other alloys and the like are usually used. Among these, it is preferable to use copper, aluminum, or an aluminum alloy in terms of conductivity and voltage resistance.
  • the thickness of the current collector is preferably 5 to 100 ⁇ m, more preferably 8 to 70 ⁇ m, and still more preferably 10 to 50 ⁇ m.
  • the electrode active material (positive electrode active material) of the positive electrode for the lithium ion secondary battery includes a metal oxide capable of reversibly doping and dedoping lithium ions. It is done. Examples of the metal oxide include lithium cobaltate, lithium nickelate, lithium manganate, and lithium iron phosphate.
  • the positive electrode active material illustrated above may be used independently according to a use, and may be used in mixture of multiple types.
  • the negative electrode active material (negative electrode active material) as the counter electrode of the positive electrode for a lithium ion secondary battery
  • low crystalline carbon non-graphitizable carbon, non-graphitizable carbon, pyrolytic carbon, etc.
  • Crystalline carbon graphite (natural graphite, artificial graphite)
  • alloy materials such as tin and silicon, oxides such as silicon oxide, tin oxide, and lithium titanate.
  • the negative electrode active material illustrated above may be used independently according to a use suitably, and may be used in mixture of multiple types.
  • the shape of the electrode active material of the electrode for a lithium ion secondary battery is preferably a granulated particle.
  • a higher-density electrode can be formed during electrode molding.
  • the volume average particle diameter of the electrode active material of the electrode for a lithium ion secondary battery is usually 0.1 to 100 ⁇ m, preferably 0.5 to 50 ⁇ m, more preferably 0.8 to 30 ⁇ m for both the positive electrode and the negative electrode.
  • the electrode mixture layer of the present invention may contain a conductive material as necessary.
  • the conductive material is not particularly limited as long as it is a conductive material, but a conductive particulate material is preferable.
  • conductive carbon black such as furnace black, acetylene black, and ketjen black
  • natural graphite such as artificial graphite
  • carbon fibers such as polyacrylonitrile-based carbon fiber, pitch-based carbon fiber, and vapor grown carbon fiber.
  • the average particle diameter when the conductive material is a particulate material is not particularly limited, but is preferably smaller than the average particle diameter of the electrode active material, from the viewpoint of expressing sufficient conductivity with a smaller amount of use,
  • the thickness is preferably 0.001 to 10 ⁇ m, more preferably 0.05 to 5 ⁇ m, and still more preferably 0.1 to 1 ⁇ m.
  • the electrode mixture layer of the present invention may contain a thickener as necessary.
  • thickeners include cellulosic polymers such as carboxymethylcellulose, methylcellulose, hydroxypropylcellulose, and ammonium salts and alkali metal salts thereof; (modified) poly (meth) acrylic acid and ammonium salts and alkali metal salts thereof; ) Polyvinyl alcohols such as polyvinyl alcohol, copolymers of acrylic acid or acrylate and vinyl alcohol, maleic anhydride or copolymers of maleic acid or fumaric acid and vinyl alcohol; polyethylene glycol, polyethylene oxide, polyvinyl pyrrolidone, modified Examples thereof include polyacrylic acid, oxidized starch, phosphoric acid starch, casein, various modified starches, acrylonitrile-butadiene copolymer hydride, and the like. Among these, it is preferable to use carboxymethylcellulose, ammonium salt of carboxymethylcellulose, and alkali metal salt.
  • the content of the thickener in the electrode mixture layer is preferably within a range that does not affect the battery characteristics, and is preferably 0.1 to 5 parts by weight, more preferably 0.2 parts per 100 parts by weight of the electrode mixture layer. -4 parts by weight, more preferably 0.3-3 parts by weight.
  • the usage mode of the electrode for an electrochemical element of the present invention includes a lithium ion secondary battery using such an electrode.
  • a lithium ion secondary battery uses an electrode for an electrochemical device in which an electrode mixture layer containing the binder composition of the present invention is formed as at least one of a positive electrode and a negative electrode, and further includes a separator and an electrolytic solution.
  • a polyolefin resin such as polyethylene or polypropylene
  • a microporous film or nonwoven fabric containing an aromatic polyamide resin a porous resin coat containing an inorganic ceramic powder, or the like
  • a porous resin coat containing an inorganic ceramic powder, or the like can be used.
  • the thickness of the separator is preferably 0.5 to 40 ⁇ m, more preferably from the viewpoint of reducing resistance due to the separator in the lithium ion secondary battery and excellent workability when manufacturing the lithium ion secondary battery.
  • the thickness is 1 to 30 ⁇ m, more preferably 1 to 25 ⁇ m.
  • the electrolytic solution is not particularly limited.
  • a solution obtained by dissolving a lithium salt as a supporting electrolyte in a non-aqueous solvent can be used.
  • 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 other lithium salts.
  • LiPF 6 , LiClO 4 , and CF 3 SO 3 Li that are easily soluble in a solvent and exhibit a high degree of dissociation are preferably used. These can be used alone or in admixture of two or more.
  • the amount of the supporting electrolyte is usually 1 wt% or more, preferably 5 wt% or more, and usually 30 wt% or less, preferably 20 wt% or less with respect to the electrolytic solution. If the amount of the supporting electrolyte is too small or too large, the ionic conductivity is lowered, and the charging characteristics and discharging characteristics of the battery are degraded.
  • the solvent used in the electrolytic solution is not particularly limited as long as it can dissolve the supporting electrolyte.
  • Alkyl carbonates such as carbonate (BC) and methyl ethyl carbonate (MEC); esters such as ⁇ -butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane; tetrahydrofuran; sulfolane and dimethyl sulfoxide Sulfur-containing compounds are used.
  • dimethyl carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate, and methyl ethyl carbonate are preferable because high ion conductivity is easily obtained and the use temperature range is wide. These can be used alone or in admixture of two or more. Moreover, it is also possible to use an electrolyte containing an additive.
  • the additive is preferably a carbonate compound such as vinylene carbonate (VC).
  • electrolytic solutions include gel polymer electrolytes in which a polymer electrolyte such as polyethylene oxide or polyacrylonitrile is impregnated with an electrolytic solution, lithium sulfide, LiI, Li 3 N, Li 2 SP—P 2 S 5 glass ceramic, etc.
  • An inorganic solid electrolyte can be mentioned.
  • a lithium ion secondary battery is obtained by stacking a negative electrode and a positive electrode through a separator, winding this according to the shape of the battery, folding it into a battery container, pouring the electrolyte into the battery container and sealing it. It is done. Further, if necessary, an expanded metal, an overcurrent prevention element such as a fuse or a PTC element, a lead plate and the like can be inserted to prevent an increase in pressure inside the battery and overcharge / discharge.
  • the shape of the battery may be any of a laminated cell type, a coin type, a button type, a sheet type, a cylindrical type, a square type, a flat type, and the like.
  • a binder composition for a secondary battery that can provide an electrode mixture layer that can improve the safety of the secondary battery.
  • the volume change of the binder composition, the high-temperature cycle characteristics of the lithium ion secondary battery, and the safety test were evaluated as follows.
  • V (150 degreeC) volume of the cast film of the binder composition at 150 degreeC
  • V (150 degreeC) volume of the cast film of the binder composition at 150 degreeC
  • the volume change (v (150 ° C.) / V (25 ° C.)) of the cast film of heat-sensitive gas-expandable particles was also calculated in the same manner as the volume change of the binder composition. That is, the dispersion of the heat-sensitive gas-expandable particles is poured into a Teflon (registered trademark) container, formed into a film in an environment of 23 ° C. and 50% RH, and further vacuum dried at 25 ° C. for 24 hours. A film of heat-sensitive gas expandable particles having a thickness of 1 mm was obtained. This film was cut into a size of 10 cm long ⁇ 1 cm wide to obtain a test piece.
  • Teflon registered trademark
  • v (25 ° C.) volume of cast film of heat-sensitive gas-expandable particles at 25 ° C.
  • v (150 ° C.) volume of cast film of heat-sensitive gas-expandable particles at 150 ° C.
  • volume change (v (150 ° C.) / V (25 ° C.)) of the cast film of heat-sensitive gas-expandable particles was determined.
  • volume change of the binder resin was calculated in the same manner as the volume change of the binder composition.
  • volume changes of the cast films of the binder resins a to d used in the examples and comparative examples are all the same. 1.0.
  • the elapsed time was evaluated according to the following criteria, and the results are shown in Table 1. The longer the elapsed time, the higher the safety of the battery. A: 30 minutes or more B: 20 minutes or more and less than 30 minutes C: 10 minutes or more and less than 20 minutes D: Less than 10 minutes
  • Example 1 (Production of heat-sensitive gas expandable particles A) In a reactor equipped with a stirrer, 94.0 parts of acrylonitrile as a monomer, 5.0 parts of methacrylic acid, 1.0 part of ethylene glycol dimethacrylate (Kyoeisha Chemical Co., Ltd.
  • Light Ester EG Light Ester EG
  • isopentane as a swelling agent 20.0 parts
  • 1.0 part of sodium dodecylbenzenesulfonate as an emulsifier 1.0 part of t-butylperoxy-2-ethylhexanoate (“NOBUTYL CO.”
  • NOBUTYL CO t-butylperoxy-2-ethylhexanoate
  • aqueous phase polymerization inhibitor 0.5 part of hydroquinone and 400 parts of ion-exchanged water were added and stirred until coarse droplets could not be visually confirmed.
  • binder composition 1 50 parts of heat-sensitive gas-expandable particles A corresponding to the solid content, 50 parts of binder resin a corresponding to the solid content, and ion-exchanged water were stirred for 1 hour in a 25 ° C. environment. This obtained the water dispersion of the binder composition 1 whose solid content concentration is 30 weight%. The volume change (V (150 ° C.) / V (25 ° C.)) of the cast film formed from this binder composition 1 was 17.0.
  • the above-mentioned slurry composition for negative electrode was applied on a copper foil (current collector) having a thickness of 20 ⁇ m by a comma coater so that the coating amount was 9.8 to 10.2 mg / cm 2 .
  • the copper foil coated with the negative electrode slurry composition is transported in an oven at 80 ° C. for 2 minutes and further in an oven at 120 ° C. for 2 minutes at a speed of 0.3 m / min.
  • the slurry composition of was dried and the negative electrode original fabric was obtained.
  • the obtained negative electrode raw material was pressed with a roll press machine so that the density of the composite layer became 1.45 to 1.55 g / cm 3, and further placed in an environment of 120 ° C. under vacuum conditions for 10 hours.
  • a negative electrode sheet having a negative electrode mixture layer formed thereon was produced.
  • the negative electrode sheet was cut into a predetermined size, processed, and the negative electrode lead was welded to obtain a negative electrode.
  • the obtained positive electrode slurry composition was applied onto a 20 ⁇ m thick aluminum foil with a comma coater and dried. This drying was performed by transporting the aluminum 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 positive electrode raw material.
  • the obtained positive electrode raw material is dried and then pressed with a roll press machine so that the mixed material layer density is 3.40 to 3.50 g / cm 3 , and vacuum conditions are used for the purpose of removing moisture.
  • a positive electrode sheet in which a positive electrode mixture layer was formed on a current collector was produced in an environment of 120 ° C. for 3 hours. The positive electrode sheet was cut into a predetermined size, processed, and the positive electrode lead was welded to obtain a positive electrode.
  • the negative electrode manufactured above and the positive electrode were wound into a jelly roll shape together with a single-layer polypropylene separator (thickness 25 ⁇ m, porosity 55%) manufactured by a dry method to produce an electrode group. .
  • This electrode group was inserted into a pouch-type battery case, and after pouring a nonaqueous electrolytic solution, the opening of the battery case was sealed with a heat sealer to complete a lithium ion secondary battery.
  • the design capacity of the battery was 2000 mAh.
  • the non-aqueous electrolyte a solution obtained by adding 2% by volume of VC (vinylene carbonate) to a LiPF 6 solution having a concentration of 1.0 M was used as the non-aqueous electrolyte.
  • Example 2 (Preparation of binder composition 2)
  • the heat-sensitive gas-expandable particles A were stirred for 5 hours under an environment of 25 ° C., and 5 parts by weight corresponding to the solid content, 95 parts by weight of the binding resin a, and ion-exchanged water. This obtained the water dispersion of the binder composition 2 whose solid content concentration is 30 weight%.
  • the volume change (V (150 ° C.) / V (25 ° C.)) of the cast film formed from this binder composition 2 was 2.6.
  • a negative electrode, a positive electrode, and a lithium ion secondary battery were manufactured in the same manner as in Example 1 except that the binder composition 2 was used.
  • Example 3 (Preparation of binder composition 3)
  • the heat-sensitive gas-expandable particles A were agitated for 1 hour in an environment of 25 ° C. in an amount of 85 parts in terms of solids, the binder resin a 15 in terms of solids, and ion-exchanged water. This obtained the water dispersion of the binder composition 3 whose solid content concentration is 30 weight%.
  • the volume change (V (150 ° C.) / V (25 ° C.)) of the cast film formed from this binder composition 3 was 28.2.
  • a negative electrode, a positive electrode, and a lithium ion secondary battery were manufactured in the same manner as in Example 1 except that the binder composition 3 was used.
  • Example 4 (Production of heat-sensitive gas-expandable particles B) In a reactor equipped with a stirrer, 93.0 parts of methacrylonitrile as a monomer, 5.0 parts of acrylic acid, 2.0 parts of divinylbenzene, 20.0 parts of isopentane as a swelling agent, dodecylbenzenesulfonic acid as an emulsifier 1.0 part of sodium, 1.0 part of t-butylperoxy-2-ethylhexanoate (NOF "Perbutyl O") as a polymerization initiator, 0.5 part of hydroquinone as an aqueous phase polymerization inhibitor And 400 parts of ion-exchanged water were added and stirred until coarse droplets could not be visually confirmed.
  • Example 5 (Production of heat-sensitive gas-expandable particles C) 1. In a reactor equipped with a stirrer, 50.0 parts of acrylonitrile and 44.0 parts of methacrylonitrile, 5.0 parts of methacrylic acid, ethylene glycol dimethacrylate (Kyoeisha Chemical Co., Ltd.
  • Light Ester EG 0 parts, 20.0 parts of isooctane as a swelling agent, 0.3 part of sodium dodecylbenzenesulfonate as an emulsifier, t-butylperoxy-2-ethylhexanoate as a polymerization initiator (“Perbutyl O )), 1.0 part of hydroquinone as an aqueous phase polymerization inhibitor, and 400 parts of ion-exchanged water were added and stirred until no coarse droplets could be visually confirmed.
  • Perbutyl O t-butylperoxy-2-ethylhexanoate
  • binder composition 5 Preparation of binder composition 5 50 parts of heat-sensitive gas-expandable particles C corresponding to solid content, 50 parts of binder resin a corresponding to solid content, and ion-exchanged water were stirred for 1 hour in a 25 ° C. environment. This obtained the water dispersion of the binder composition 5 whose solid content concentration is 30 weight%. The volume change (V (150 ° C.) / V (25 ° C.)) of the cast film formed from this binder composition 5 was 9.5. A negative electrode, a positive electrode, and a lithium ion secondary battery were manufactured in the same manner as in Example 1 except that the binder composition 5 was used.
  • Example 7 (Production of binder resin c) In a 5 MPa pressure vessel equipped with a stirrer, 19.9 parts of acrylonitrile as a monomer, 80.0 parts of acrylic acid, 0.1 part of ethylene glycol dimethacrylate (“Kyoeisha Chemical Co., Ltd.“ Light Ester EG ”), ion exchange as a solvent 150 parts of water and 1.0 part of potassium persulfate as a polymerization initiator were added and stirred sufficiently, and then heated to 55 ° C. to initiate polymerization. When the monomer consumption reached 95.0%, the reaction was stopped by cooling.
  • a 5% aqueous sodium hydroxide solution was added to the aqueous dispersion containing the polymer thus obtained to adjust the pH to 8. Then, the unreacted monomer was removed by heating under reduced pressure. Furthermore, it cooled to 30 degrees C or less after that. Thereby, water-soluble binder resin c was obtained.
  • Example 8 (Preparation of binder composition 8) An aqueous dispersion of heat-sensitive gas-expandable particles A and PVDF (polyvinylidene fluoride, “KF-1100” manufactured by Kureha Chemical Co., Ltd.) as a binder resin d are mixed at a weight to solid content ratio of 1: 1. Further, NMP (N-methyl-2-pyrrolidone) was added. The binder composition 8 which uses NMP as a solvent was prepared by removing water from this by vacuum distillation. The volume change (V (150 ° C.) / V (25 ° C.)) of the cast film formed from this binder composition 8 was 17.0.
  • PVDF polyvinylidene fluoride, “KF-1100” manufactured by Kureha Chemical Co., Ltd.
  • NMP N-methyl-2-pyrrolidone
  • the obtained positive electrode slurry composition was applied onto a 20 ⁇ m thick aluminum foil with a comma coater and dried. This drying was performed by transporting the aluminum 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 positive electrode raw material.
  • the obtained positive electrode raw material is dried and then pressed with a roll press machine so that the mixed material layer density is 3.40 to 3.50 g / cm 3 , and vacuum conditions are used for the purpose of removing moisture.
  • a positive electrode sheet was formed by forming a positive electrode mixture layer on the current collector in an environment of 120 ° C. for 3 hours. The positive electrode sheet was cut into a predetermined size, processed, and the positive electrode lead was welded to obtain a positive electrode.
  • the above-mentioned slurry composition for negative electrode was applied on a copper foil (current collector) having a thickness of 20 ⁇ m by a comma coater so that the coating amount was 9.8 to 10.2 mg / cm 2 .
  • the copper foil coated with the negative electrode slurry composition is transported in an oven at 80 ° C. for 2 minutes and further in an oven at 120 ° C. for 2 minutes at a speed of 0.3 m / min.
  • the slurry composition of was dried and the negative electrode original fabric was obtained.
  • the obtained negative electrode raw material was pressed with a roll press machine so that the density of the composite layer became 1.45 to 1.55 g / cm 3, and further placed in an environment of 120 ° C. under vacuum conditions for 10 hours.
  • a negative electrode sheet having a negative electrode mixture layer formed thereon was prepared. The negative electrode sheet was cut into a predetermined size, processed, and the negative electrode lead was welded to obtain a negative electrode.
  • the negative electrode manufactured above and the positive electrode were wound into a jelly roll shape together with a single-layer polypropylene separator (thickness 25 ⁇ m, porosity 55%) manufactured by a dry method to produce an electrode group. .
  • This electrode group was inserted into a pouch-type battery case, and after pouring a nonaqueous electrolytic solution, the opening of the battery case was sealed with a heat sealer to complete a lithium ion secondary battery.
  • the design capacity of the battery was 2000 mAh.
  • the non-aqueous electrolyte a solution obtained by adding 2% by volume of VC (vinylene carbonate) to a LiPF 6 solution having a concentration of 1.0 M was used as the non-aqueous electrolyte.
  • Example 2 (Production of heat-sensitive gas-expandable particles D) Thermally-sensitive gas-expandable particles were produced under the same conditions as in Example 1 except that the amount of isopentane used in Example 1 (Production of thermal-sensitive gas-expandable particles A) was 1.8 parts. An aqueous dispersion of heat-sensitive gas-expandable particles D having a diameter of 600 nm was obtained. The volume change of the heat-sensitive gas expandable particles D was 2.7.
  • Example 4 (Production of heat-sensitive gas expandable particles E) Thermally-sensitive gas-expandable particles were produced under the same conditions as in Example 1 except that the amount of isopentane used in (Production of thermal-sensitive gas-expandable particles A) in Example 1 was 40.0 parts. An aqueous dispersion of heat-sensitive gas-expandable particles E having a diameter of 600 nm was obtained. The volume change of the heat-sensitive gas expandable particles E was 65.0.
  • binder composition 12 50 parts of heat-sensitive gas-expandable particles E corresponding to the solid content, 50 parts of binder resin a corresponding to the solid content, and ion-exchanged water were stirred for 1 hour in a 25 ° C. environment. Thus, an aqueous dispersion of the binder composition 12 having a solid content concentration of 30% by weight was obtained. The volume change (V (150 ° C.) / V (25 ° C.)) of the cast film formed from this binder composition 12 was 33.0. A negative electrode, a positive electrode, and a lithium ion secondary battery were produced in the same manner as in Example 1 except that the binder composition 12 was used.
  • the obtained positive electrode slurry composition was applied onto a 20 ⁇ m thick aluminum foil with a comma coater and dried. This drying was performed by transporting the aluminum 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 positive electrode raw material.
  • the obtained positive electrode raw material is dried and then pressed with a roll press machine so that the mixed material layer density is 3.40 to 3.50 g / cm 3 , and vacuum conditions are used for the purpose of removing moisture.
  • a positive electrode sheet was formed by forming a positive electrode mixture layer on the current collector in an environment of 120 ° C. for 3 hours. The positive electrode sheet was cut into a predetermined size, processed, and the positive electrode lead was welded to obtain a positive electrode.
  • the obtained slurry composition for negative electrode was applied on a copper foil (current collector) having a thickness of 20 ⁇ m by a comma coater so that the coating amount was 9.8 to 10.2 mg / cm 2 .
  • the copper foil coated with the negative electrode slurry composition is transported in an oven at 80 ° C. for 2 minutes and further in an oven at 120 ° C. for 2 minutes at a speed of 0.3 m / min.
  • the slurry composition of was dried and the negative electrode original fabric was obtained.
  • the obtained negative electrode raw material was pressed with a roll press machine so that the density of the composite layer became 1.45 to 1.55 g / cm 3, and further placed in an environment of 120 ° C. under vacuum conditions for 10 hours.
  • a negative electrode sheet having a negative electrode mixture layer formed thereon was produced.
  • the negative electrode sheet was cut into a predetermined size, processed, and the negative electrode lead was welded to obtain a negative electrode.
  • a lithium ion secondary battery was produced in the same manner as in Example 1 except that the positive electrode and the negative electrode obtained above were used.
  • the lithium ion secondary battery obtained by using the secondary battery binder composition was good in high-temperature cycle characteristics and safety.

Abstract

　A binder composition for a secondary cell, the binder composition including thermosensitive gas-expandable particles and a binding resin, wherein the binder composition for a secondary cell is such that the volume change (V(150°C)/V(25°C)) of a cast film formed by the binder composition for a secondary cell is 2-30 (where "V(150°C)" indicates the volume of the cast film at 150°C, and "V(25°C)" indicates the volume of the cast film at 25°C).

Description

二次電池用バインダー組成物Secondary battery binder composition
　本発明は、リチウムイオン二次電池等の二次電池の電極合材層を形成するために用いられる二次電池用バインダー組成物に関するものである。 This invention relates to the binder composition for secondary batteries used in order to form the electrode compound-material layer of secondary batteries, such as a lithium ion secondary battery.
　小型で軽量、且つエネルギー密度が高く、繰り返し充放電が可能なリチウムイオン二次電池は、環境対応からも今後の需要の拡大が見込まれている。リチウムイオン二次電池は、エネルギー密度が大きく携帯電話やノート型パソコン等の分野で利用されているが、用途の拡大や発展に伴い、低抵抗化、大容量化等より一層の性能向上が要求されている。 Demand for lithium-ion secondary batteries that are small, lightweight, have high energy density, and can be repeatedly charged and discharged is expected to increase in the future from the environmental viewpoint. Lithium ion secondary batteries have a high energy density and are used in the fields of mobile phones and laptop computers. However, with the expansion and development of applications, further improvements in performance are required, such as lowering resistance and increasing capacity. Has been.
　セパレーターは、リチウムイオン二次電池の正極と負極の電気的短絡を防ぐ重要な機能を担っており、通常、リチウムイオン二次電池に用いられるセパレーターとしては、例えばポリオレフィン系樹脂から成る微多孔膜が使用されている。また、セパレーターは通常、電池内部の温度が１３０℃近傍等の高温になった場合、溶融して微多孔を塞ぐことで、リチウムイオンの移動を防ぎ、電流を遮断させるシャットダウン機能により、リチウムイオン二次電池の安全性を保持する役割を担っている。しかしながら、瞬間的な発熱によって電池温度が、樹脂の融点をさらに超えると、セパレーターは急激に収縮して、正極及び負極が直接接触し、短絡する箇所が拡大することがある。この場合、電池温度は数百℃以上にまで異常過熱された状態に至ることがある。 The separator has an important function of preventing an electrical short circuit between the positive electrode and the negative electrode of the lithium ion secondary battery. Usually, as a separator used in the lithium ion secondary battery, for example, a microporous film made of polyolefin resin is used. in use. In addition, when the temperature inside the battery becomes high, such as around 130 ° C., the separator normally melts and closes the micropore, thereby preventing lithium ion migration and shutting down the current, thereby shutting down the lithium ion secondary battery. It plays a role in maintaining the safety of secondary batteries. However, when the battery temperature further exceeds the melting point of the resin due to instantaneous heat generation, the separator contracts rapidly, and the positive electrode and the negative electrode may be in direct contact with each other, thereby expanding the location where the short circuit occurs. In this case, the battery temperature may reach a state where it is abnormally overheated to several hundred degrees Celsius or higher.
　そこで、特許文献１では、電極合材層に９０～１６０℃の温度域で抵抗が大きくなる導電性材料を含ませ、さらに１６０℃より高い温度においても電気絶縁性を保持することができ、一旦温度が１６０℃以上に上昇した後、１００℃以下に冷却してもイオン伝導性を示す材料からなるセパレーターを用いたリチウムイオン二次電池が提案されている。 Therefore, in Patent Document 1, a conductive material whose resistance increases in a temperature range of 90 to 160 ° C. is included in the electrode mixture layer, and electrical insulation can be maintained even at a temperature higher than 160 ° C. A lithium ion secondary battery using a separator made of a material that exhibits ion conductivity even when the temperature rises to 160 ° C. or higher and then is cooled to 100 ° C. or lower has been proposed.
特開２００４－３２７１８３号公報JP 2004-327183 A
　特許文献１においては、所定の導電性材料を含む電極合材層と、所定の材料からなるセパレーターとを組み合わせて用いているが、セパレーターの材料が通常用いられるポリオレフィン系樹脂等の場合であっても、異常加熱に対応した安全性を確保することができる電極合材層を形成することも求められている。
　本発明の目的は、二次電池の安全性を向上させることができる電極合材層を得られる二次電池用バインダー組成物を提供することである。 In Patent Document 1, an electrode mixture layer containing a predetermined conductive material and a separator made of a predetermined material are used in combination, but the separator material is a polyolefin resin or the like that is usually used. However, it is also required to form an electrode mixture layer that can ensure safety corresponding to abnormal heating.
The objective of this invention is providing the binder composition for secondary batteries which can obtain the electrode compound-material layer which can improve the safety | security of a secondary battery.
　本発明者は、鋭意検討の結果、所定の温度以上でガスにより膨張する感熱ガス膨張性粒子を用いることにより、上記目的を達成できることを見出し、本発明を完成するに至った。 As a result of intensive studies, the present inventors have found that the above object can be achieved by using heat-sensitive gas-expandable particles that expand with gas at a predetermined temperature or higher, and have completed the present invention.
　即ち、本発明によれば、
（１）　感熱ガス膨張性粒子と、結着性樹脂とを含む二次電池用バインダー組成物であって、前記二次電池用バインダー組成物により形成されるキャストフィルムの体積変化がＶ(150℃)／Ｖ(25℃)＝２～３０（Ｖ(150℃)は１５０℃における前記キャストフィルムの体積を示し、Ｖ(25℃)は２５℃における前記キャストフィルムの体積を示す。）である二次電池用バインダー組成物、
（２）　前記感熱ガス膨張性粒子の体積変化が、ｖ(150℃)／ｖ(25℃)＝３～６０（ｖ(150℃)は１５０℃での前記感熱ガス膨張性粒子の体積を示し、ｖ(25℃)は２５℃での前記感熱ガス膨張性粒子の体積を示す）である（１）記載の二次電池用バインダー組成物、
（３）　前記感熱ガス膨張性粒子と前記結着性樹脂との比率が、感熱ガス膨張性粒子／結着性樹脂＝９７／３～３／９７（重量比）である（１）または（２）記載の二次電池用バインダー組成物、
（４）　前記感熱ガス膨張性粒子の粒子径が０．１～１０μｍである（１）～（３）の何れかに記載の二次電池用バインダー組成物、
（５）　前記感熱ガス膨張性粒子は、コアシェル構造を有し、前記感熱ガス膨張性粒子のコア材が、沸点１０～１５０℃の炭化水素である（１）～（４）の何れかに記載の二次電池用バインダー組成物、
（６）　前記感熱ガス膨張性粒子は、コアシェル構造を有し、前記感熱ガス膨張性粒子のシェル材が、ニトリル基を有する重合単位を含む重合体である（１）～（５）の何れかに記載の二次電池用バインダー組成物
が提供される。 That is, according to the present invention,
(1) A binder composition for a secondary battery comprising heat-sensitive gas-expandable particles and a binder resin, wherein the volume change of the cast film formed by the secondary battery binder composition is V (150 ° C. ) / V (25 ° C.) = 2-30 (V (150 ° C.) indicates the volume of the cast film at 150 ° C., and V (25 ° C.) indicates the volume of the cast film at 25 ° C.) Secondary battery binder composition,
(2) Volume change of the heat-sensitive gas expandable particles is v (150 ° C.) / V (25 ° C.) = 3 to 60 (v (150 ° C.) indicates the volume of the heat-sensitive gas expandable particles at 150 ° C. V (25 ° C. represents the volume of the heat-sensitive gas-expandable particles at 25 ° C.)), the binder composition for a secondary battery according to (1),
(3) The ratio of the heat-sensitive gas-expandable particles to the binder resin is thermal gas-expandable particles / binding resin = 97/3 to 3/97 (weight ratio) (1) or (2 ) Secondary battery binder composition as described above,
(4) The binder composition for a secondary battery according to any one of (1) to (3), wherein the heat-sensitive gas-expandable particles have a particle size of 0.1 to 10 μm.
(5) The thermal gas expandable particles have a core-shell structure, and the core material of the thermal gas expandable particles is a hydrocarbon having a boiling point of 10 to 150 ° C. A binder composition for a secondary battery,
(6) The thermal gas expandable particle has a core-shell structure, and the shell material of the thermal gas expandable particle is a polymer containing a polymer unit having a nitrile group. The binder composition for secondary batteries as described in 1 above is provided.
　本発明によれば、二次電池の安全性を向上させることができる電極合材層を得られる二次電池用バインダー組成物を提供することができる。 According to the present invention, it is possible to provide a binder composition for a secondary battery that can provide an electrode mixture layer that can improve the safety of the secondary battery.
　以下、本発明の二次電池用バインダー組成物について説明する。本発明の二次電池用バインダー組成物は、感熱ガス膨張性粒子と、結着性樹脂とを含む二次電池用バインダー組成物であって、前記二次電池用バインダー組成物により形成されるキャストフィルムの体積変化がＶ(150℃)／Ｖ(25℃)＝２～３０（Ｖ(150℃)は１５０℃における前記キャストフィルムの体積を示し、Ｖ(25℃)は２５℃における前記キャストフィルムの体積を示す。）である。 Hereinafter, the binder composition for a secondary battery of the present invention will be described. The binder composition for a secondary battery according to the present invention is a binder composition for a secondary battery containing heat-sensitive gas-expandable particles and a binder resin, and is formed by the binder composition for a secondary battery. The volume change of the film is V (150 ° C.) / V (25 ° C.) = 2 to 30 (V (150 ° C.) indicates the volume of the cast film at 150 ° C., V (25 ° C.) is the cast film at 25 ° C. Is shown.).
　（感熱ガス膨張性粒子）
　本発明の二次電池用バインダー組成物に用いる感熱ガス膨張性粒子は、所定の温度以上となるとガスにより膨張する粒子である。感熱ガス膨張性粒子としては、樹脂やエラストマーなどにより形成されたシェル材と、低沸点溶剤を含むコア材とを含むコアシェル構造を有するものが好ましい。 (Heat-sensitive gas expandable particles)
The heat-sensitive gas-expandable particles used in the binder composition for a secondary battery of the present invention are particles that expand due to gas when the temperature exceeds a predetermined temperature. As the heat-sensitive gas-expandable particles, those having a core-shell structure including a shell material formed of a resin or an elastomer and a core material containing a low boiling point solvent are preferable.
　コアシェル構造を製造する方法としては特に限定されないが、コアシェル構造を有する感熱ガス膨張性粒子は、例えば、コア部を形成する低沸点溶剤及び重合体の単量体とシェル部を形成する重合体の単量体とを用い、経時的にそれらの単量体の比率を変えて段階的に重合する手法や、コア粒子になりうる疎水性の低沸点溶剤及び親油性単量体と、親水性の高いシェル材に相当する単量体とを混合させて重合させることにより、製造しうる。 Although the method for producing the core-shell structure is not particularly limited, the heat-sensitive gas-expandable particles having the core-shell structure are, for example, low-boiling solvents that form the core portion and polymer monomers that form the shell portion with the polymer monomer. And a method of polymerizing in stages by changing the ratio of these monomers over time, a hydrophobic low boiling point solvent and a lipophilic monomer that can become core particles, and a hydrophilic It can be produced by mixing and polymerizing a monomer corresponding to a high shell material.
　ここで親水性が高いとは温度２０℃における水溶解度が１以上（単位：ｇ／１００ｇ）を示すものを指し、よりコアシェル構造の境界が鮮明になる点から３以上のものが好ましく、４以上のものがより好ましい。特に上限はないが３０以下であることが好ましい。なお、温度２０℃における水溶解度は、ＥＰＡ法（EPA Chemical Fate testing Guideline CG-1500 Water Solubility）で測定することができる。
　代表的な単量体、溶剤の温度２０℃における水溶解度（単位：ｇ／１００ｇ）を括弧内に示すと以下になる。アクリロニトリル（７）、メチルアクリレート（６）、エチルアクリレート（２）、ブチルアクリレート（２）、スチレン（０．０３）、ブタジエン（０．０７）、イソオクタン（不溶）イソペンタン（不溶）。 Here, “highly hydrophilic” means that the water solubility at a temperature of 20 ° C. is 1 or more (unit: g / 100 g), preferably 3 or more from the viewpoint that the boundary of the core-shell structure becomes clearer, 4 or more. Are more preferred. There is no particular upper limit, but it is preferably 30 or less. The water solubility at 20 ° C. can be measured by the EPA method (EPA Chemical Fate testing Guideline CG-1500 Water Solubility).
The water solubility (unit: g / 100 g) of a typical monomer and solvent at a temperature of 20 ° C. is shown in parentheses as follows. Acrylonitrile (7), methyl acrylate (6), ethyl acrylate (2), butyl acrylate (2), styrene (0.03), butadiene (0.07), isooctane (insoluble) isopentane (insoluble).
　シェル材の材料としては、耐電解液性を有し、感熱ガス膨張性粒子が膨張した際にひび割れが発生しない程度の柔軟性を有するものであれば、特に制限されないが、ニトリル基を有する重合単位を含む重合体を用いることが好ましい。 The material of the shell material is not particularly limited as long as it has electrolyte resistance and is flexible enough to prevent cracking when the heat-sensitive gas-expandable particles expand. Polymerization having a nitrile group It is preferable to use a polymer containing units.
　ニトリル基を有する重合単位としては、α，β－エチレン性不飽和ニトリル単量体単位等が挙げられる。前記の「単量体単位」とは、単量体を重合することにより形成される構造単位である。 Examples of the polymer unit having a nitrile group include an α, β-ethylenically unsaturated nitrile monomer unit. The “monomer unit” is a structural unit formed by polymerizing monomers.
　α，β－エチレン性不飽和ニトリル単量体単位を形成する単量体としては、ニトリル基を有するα，β－エチレン性不飽和化合物であれば限定されず、アクリロニトリル；α－クロロアクリロニトリル、α－ブロモアクリロニトリルなどのα－ハロゲノアクリロニトリル；メタクリロニトリルなどのα－アルキルアクリロニトリル；などが挙げられ、アクリロニトリルおよびメタクリロニトリルが好ましい。α，β－エチレン性不飽和ニトリル単量体として、これらの複数種を併用してもよい。 The monomer forming the α, β-ethylenically unsaturated nitrile monomer unit is not limited as long as it is an α, β-ethylenically unsaturated compound having a nitrile group, and acrylonitrile; α-chloroacrylonitrile, α -Α-halogenoacrylonitrile such as bromoacrylonitrile; α-alkylacrylonitrile such as methacrylonitrile; and the like. Acrylonitrile and methacrylonitrile are preferred. These α, β-ethylenically unsaturated nitrile monomers may be used in combination.
　ニトリル基を有する重合単位を含む重合体は、ニトリル基を有する重合単位を形成する単量体と共重合可能な単量体との共重合体であってもよい。前記共重合可能な単量体としては、アクリル酸、メタクリル酸、イタコン酸、フマル酸などの不飽和カルボン酸類；エチレングリコールジメタクリレート、ジエチレングリコールジメタクリレート、トリメチロールプロパントリアクリレートなどの２つ以上の炭素－炭素二重結合を有するカルボン酸エステル類；スチレン、クロロスチレン、ビニルトルエン、ｔ－ブチルスチレン、ビニル安息香酸、ビニル安息香酸メチル、ビニルナフタレン、クロロメチルスチレン、ヒドロキシメチルスチレン、α－メチルスチレン、ジビニルベンゼン等のスチレン系単量体；アクリルアミド、Ｎ－メチロールアクリルアミド、アクリルアミド－２－メチルプロパンスルホン酸などのアミド系単量体；エチレン、プロピレン等のオレフィン類；ブタジエン、イソプレン等のジエン系単量体；塩化ビニル、塩化ビニリデン等のハロゲン原子含有単量体； 酢酸ビニル、プロピオン酸ビニル、酪酸ビニル、安息香酸ビニル等のビニルエステル類；メチルビニルエーテル、エチルビニルエーテル、ブチルビニルエーテル等のビニルエーテル類；メチルビニルケトン、エチルビニルケトン、ブチルビニルケトン、ヘキシルビニルケトン、イソプロペニルビニルケトン等のビニルケトン類； Ｎ－ビニルピロリドン、ビニルピリジン、ビニルイミダゾール等の複素環含有ビニル化合物が挙げられる。前記共重合可能な単量体として、これらの複数種を併用してもよい。 The polymer containing a polymer unit having a nitrile group may be a copolymer of a monomer that forms a polymer unit having a nitrile group and a copolymerizable monomer. Examples of the copolymerizable monomer include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, and fumaric acid; two or more carbons such as ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, and trimethylolpropane triacrylate. Carboxylates having carbon double bonds; styrene, chlorostyrene, vinyl toluene, t-butyl styrene, vinyl benzoic acid, methyl vinyl benzoate, vinyl naphthalene, chloromethyl styrene, hydroxymethyl styrene, α-methyl styrene, Styrene monomers such as divinylbenzene; Amide monomers such as acrylamide, N-methylolacrylamide, and acrylamide-2-methylpropanesulfonic acid; Olefins such as ethylene and propylene; Diene monomers such as soprene; monomers containing halogen atoms such as vinyl chloride and vinylidene chloride; vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl benzoate; methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether Vinyl ethers such as methyl vinyl ketone, ethyl vinyl ketone, butyl vinyl ketone, hexyl vinyl ketone, isopropenyl vinyl ketone and the like; heterocyclic ring-containing vinyl compounds such as N-vinyl pyrrolidone, vinyl pyridine and vinyl imidazole . A plurality of these may be used in combination as the copolymerizable monomer.
　感熱ガス膨張性粒子のシェル材の内包物としてのコア材としては、二次電池が高温となった際に気化するものであれば特に制限はないが、沸点が１０～１５０℃の炭化水素であることが好ましい。 The core material as the inclusion of the shell material of the heat-sensitive gas-expandable particles is not particularly limited as long as it vaporizes when the secondary battery becomes high temperature, but is a hydrocarbon having a boiling point of 10 to 150 ° C. Preferably there is.
　沸点が１０～１５０℃の炭化水素としては、例えば、イソペンタン、イソオクタン、ｎ－ペンタン、ｎ－ヘキサン、イソヘキサン、へプタン、石油エーテル等が挙げられる。 Examples of the hydrocarbon having a boiling point of 10 to 150 ° C. include isopentane, isooctane, n-pentane, n-hexane, isohexane, heptane, petroleum ether and the like.
　また、感熱ガス膨張性粒子の体積変化は、ｖ(150℃)／ｖ(25℃)＝３～６０（ｖ(150℃)は１５０℃での感熱ガス膨張性粒子の体積を示し、ｖ(25℃)は２５℃での感熱ガス膨張性粒子の体積を示す）であることが好ましい。ここで、感熱ガス膨張性粒子の体積変化は、例えば、感熱ガス膨張性粒子により形成されるキャストフィルムの体積変化として求めることができる。 The volume change of the heat-sensitive gas expandable particles is v (150 ° C.) / V (25 ° C.) = 3 to 60 (v (150 ° C.) indicates the volume of the heat-sensitive gas expandable particles at 150 ° C., and v ( 25 ° C) is preferably the volume of the heat-sensitive gas expandable particles at 25 ° C). Here, the volume change of the heat-sensitive gas expandable particles can be obtained, for example, as the volume change of the cast film formed of the heat-sensitive gas expandable particles.
　また、感熱ガス膨張性粒子の粒子径は０．１～１０μｍであることが好ましく、０．３～３μｍであることがより好ましく、０．３～１μｍであることが特に好ましい。粒子径を上記範囲とすることにより、体積変化の膨張バランスを適度に調整することができる。粒子径は、電子顕微鏡観察を行い、１００個以上の粒子について、その粒子像の最長辺をａ、最短辺をｂとし、（ａ＋ｂ）／２を算出し、その平均値から求めることができる。 The particle size of the heat-sensitive gas-expandable particles is preferably 0.1 to 10 μm, more preferably 0.3 to 3 μm, and particularly preferably 0.3 to 1 μm. By setting the particle diameter within the above range, the expansion balance of the volume change can be adjusted appropriately. The particle diameter can be obtained from an average value obtained by observing an electron microscope and calculating (a + b) / 2 with respect to 100 or more particles, where a is the longest side of the particle image and b is the shortest side.
　（結着性樹脂）
　本発明の二次電池用バインダー組成物に用いる結着性樹脂としては、例えば、ジエン系重合体、アクリル系重合体、フッ素系重合体、シリコーン系重合体などが挙げられる。
　これらのなかでも電極活物質同士の結着力に優れるため、ジエン系重合体、又はアクリル系重合体が好ましい。 (Binding resin)
Examples of the binder resin used in the binder composition for a secondary battery of the present invention include a diene polymer, an acrylic polymer, a fluorine polymer, a silicone polymer, and the like.
Among these, a diene polymer or an acrylic polymer is preferable because of excellent binding force between electrode active materials.
　（ジエン系重合体）
　ジエン系重合体とは、ブタジエン、イソプレンなどの共役ジエンを重合してなる単量体単位を含む重合体である。ジエン系重合体中の共役ジエンを重合してなる単量体単位の割合は通常４０重量％以上、好ましくは５０重量％以上、より好ましくは６０重量％以上である。重合体としては、ポリブタジエンやポリイソプレンなどの共役ジエンの単独重合体；共役ジエンと共重合可能な単量体との共重合体が挙げられる。前記共重合可能な単量体としては、アクリロニトリル、メタクリロニトリルなどのα，β－不飽和ニトリル化合物；アクリル酸、メタクリル酸などの不飽和カルボン酸類；スチレン、クロロスチレン、ビニルトルエン、ｔ－ブチルスチレン、ビニル安息香酸、ビニル安息香酸メチル、ビニルナフタレン、クロロメチルスチレン、ヒドロキシメチルスチレン、α－メチルスチレン、ジビニルベンゼン等のスチレン系単量体；エチレン、プロピレン等のオレフィン類；塩化ビニル、塩化ビニリデン等のハロゲン原子含有単量体； 酢酸ビニル、プロピオン酸ビニル、酪酸ビニル、安息香酸ビニル等のビニルエステル類；メチルビニルエーテル、エチルビニルエーテル、ブチルビニルエーテル等のビニルエーテル類；メチルビニルケトン、エチルビニルケトン、ブチルビニルケトン、ヘキシルビニルケトン、イソプロペニルビニルケトン等のビニルケトン類； Ｎ－ビニルピロリドン、ビニルピリジン、ビニルイミダゾール等の複素環含有ビニル化合物が挙げられる。 (Diene polymer)
The diene polymer is a polymer containing monomer units obtained by polymerizing conjugated dienes such as butadiene and isoprene. The proportion of monomer units obtained by polymerizing conjugated diene in the diene polymer is usually 40% by weight or more, preferably 50% by weight or more, more preferably 60% by weight or more. Examples of the polymer include homopolymers of conjugated dienes such as polybutadiene and polyisoprene; and copolymers of monomers that are copolymerizable with conjugated dienes. Examples of the copolymerizable monomer include α, β-unsaturated nitrile compounds such as acrylonitrile and methacrylonitrile; unsaturated carboxylic acids such as acrylic acid and methacrylic acid; styrene, chlorostyrene, vinyltoluene, and t-butyl. Styrene monomers such as styrene, vinyl benzoic acid, methyl vinyl benzoate, vinyl naphthalene, chloromethyl styrene, hydroxymethyl styrene, α-methyl styrene and divinyl benzene; olefins such as ethylene and propylene; vinyl chloride and vinylidene chloride Halogen atom-containing monomers such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl benzoate, etc .; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether; methyl vinyl ketone, ethyl vinyl Vinyl ketones such as ketone, butyl vinyl ketone, hexyl vinyl ketone, and isopropenyl vinyl ketone; and heterocyclic ring-containing vinyl compounds such as N-vinyl pyrrolidone, vinyl pyridine, and vinyl imidazole.
　（アクリル系重合体）
　アクリル系重合体とは、アクリル酸エステルおよび／またはメタクリル酸エステルを重合してなる単量体単位を含む重合体である。アクリル系重合体中のアクリル酸エステルおよび／またはメタクリル酸エステルを重合してなる単量体単位の割合は、通常４０重量％以上、好ましくは５０重量％以上、より好ましくは６０重量％以上である。重合体としては、アクリル酸エステル及び／又はメタクリル酸エステルの単独重合体、これと共重合可能な単量体との共重合体が挙げられる。前記共重合可能な単量体としては、アクリル酸、メタクリル酸、イタコン酸、フマル酸などの不飽和カルボン酸類；エチレングリコールジメタクリレート、ジエチレングリコールジメタクリレート、トリメチロールプロパントリアクリレートなどの２つ以上の炭素－炭素二重結合を有するカルボン酸エステル類；スチレン、クロロスチレン、ビニルトルエン、ｔ－ブチルスチレン、ビニル安息香酸、ビニル安息香酸メチル、ビニルナフタレン、クロロメチルスチレン、ヒドロキシメチルスチレン、α－メチルスチレン、ジビニルベンゼン等のスチレン系単量体；アクリルアミド、Ｎ－メチロールアクリルアミド、アクリルアミド－２－メチルプロパンスルホン酸などのアミド系単量体；アクリロニトリル、メタクリロニトリルなどのα，β－不飽和ニトリル化合物；エチレン、プロピレン等のオレフィン類；ブタジエン、イソプレン等のジエン系単量体；塩化ビニル、塩化ビニリデン等のハロゲン原子含有単量体； 酢酸ビニル、プロピオン酸ビニル、酪酸ビニル、安息香酸ビニル等のビニルエステル類；メチルビニルエーテル、エチルビニルエーテル、ブチルビニルエーテル等のビニルエーテル類；メチルビニルケトン、エチルビニルケトン、ブチルビニルケトン、ヘキシルビニルケトン、イソプロペニルビニルケトン等のビニルケトン類； Ｎ－ビニルピロリドン、ビニルピリジン、ビニルイミダゾール等の複素環含有ビニル化合物が挙げられる。 (Acrylic polymer)
The acrylic polymer is a polymer containing a monomer unit obtained by polymerizing an acrylic ester and / or a methacrylic ester. The proportion of monomer units obtained by polymerizing acrylic acid ester and / or methacrylic acid ester in the acrylic polymer is usually 40% by weight or more, preferably 50% by weight or more, more preferably 60% by weight or more. . Examples of the polymer include homopolymers of acrylic acid esters and / or methacrylic acid esters, and copolymers with monomers copolymerizable therewith. Examples of the copolymerizable monomer include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, and fumaric acid; two or more carbons such as ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, and trimethylolpropane triacrylate. Carboxylates having carbon double bonds; styrene, chlorostyrene, vinyl toluene, t-butyl styrene, vinyl benzoic acid, methyl vinyl benzoate, vinyl naphthalene, chloromethyl styrene, hydroxymethyl styrene, α-methyl styrene, Styrenic monomers such as divinylbenzene; Amide monomers such as acrylamide, N-methylolacrylamide, and acrylamide-2-methylpropanesulfonic acid; α, β-insoluble such as acrylonitrile and methacrylonitrile Nitrile compounds; olefins such as ethylene and propylene; diene monomers such as butadiene and isoprene; monomers containing halogen atoms such as vinyl chloride and vinylidene chloride; vinyl acetate, vinyl propionate, vinyl butyrate, vinyl benzoate Vinyl esters such as methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether; vinyl ketones such as methyl vinyl ketone, ethyl vinyl ketone, butyl vinyl ketone, hexyl vinyl ketone, isopropenyl vinyl ketone; N-vinyl pyrrolidone, vinyl Heterocycle-containing vinyl compounds such as pyridine and vinylimidazole can be mentioned.
　（フッ素系重合体）
　フッ素系重合体は、フッ素原子を含む単量体単位を含有する重合体である。フッ素系重合体の具体例としては、ポリテトラフルオロエチレン、ポリフッ化ビニリデン、テトラフルオロエチレン・パーフルオロアルキルビニルエーテル共重合体、エチレン・テトラフルオロエチレン共重合体、エチレン・クロロトリフルオロエチレン共重合体、パーフルオロエチレン・プロペン共重合体が挙げられる。 (Fluoropolymer)
The fluorine-based polymer is a polymer containing a monomer unit containing a fluorine atom. Specific examples of the fluoropolymer include polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, ethylene / tetrafluoroethylene copolymer, ethylene / chlorotrifluoroethylene copolymer, A perfluoroethylene propene copolymer may be mentioned.
　（二次電池用バインダー組成物）
　本発明の二次電池用バインダー組成物は、上述の感熱ガス膨張性粒子と結着性樹脂とを含んでなる。感熱ガス膨張性粒子と前記結着性樹脂との混合比率は、感熱ガス膨張性粒子／結着性樹脂＝９７／３～３／９７（重量比）であることが好ましく、４０/６０～６０/４０がより好ましい。 (Binder composition for secondary battery)
The binder composition for secondary batteries of the present invention comprises the above-mentioned heat-sensitive gas-expandable particles and a binder resin. The mixing ratio of the heat-sensitive gas expandable particles and the binding resin is preferably heat-sensitive gas expandable particles / binding resin = 97/3 to 3/97 (weight ratio), and 40/60 to 60 / 40 is more preferable.
　本発明の二次電池用バインダー組成物により形成されるキャストフィルムの体積変化は、Ｖ(150℃)／Ｖ(25℃)＝２～３０（Ｖ(150℃)は１５０℃におけるキャストフィルムの体積を示し、Ｖ(25℃)は２５℃におけるキャストフィルムの体積を示す。）であり、１５～２５が好ましい。 The volume change of the cast film formed by the binder composition for secondary batteries of the present invention is V (150 ° C.) / V (25 ° C.) = 2 to 30 (V (150 ° C.) is the volume of the cast film at 150 ° C. V (25 ° C. represents the volume of the cast film at 25 ° C.), and is preferably from 15 to 25.
　本発明の二次電池用バインダー組成物により形成されるキャストフィルムの体積変化が大きすぎると、二次電池用バインダー組成物の接着力・凝集力が低下し、得られる二次電池のサイクル特性が低下する。また、本発明の二次電池用バインダー組成物により形成されるキャストフィルムの体積変化が小さすぎると、電極活物質間の距離を十分に広げられないため、所望の安全性が得られない虞がある。 If the volume change of the cast film formed by the secondary battery binder composition of the present invention is too large, the adhesive strength / cohesive strength of the secondary battery binder composition will be reduced, and the cycle characteristics of the secondary battery obtained will be descend. In addition, if the volume change of the cast film formed by the binder composition for a secondary battery of the present invention is too small, the distance between the electrode active materials cannot be sufficiently widened, so that the desired safety may not be obtained. is there.
　また、感熱ガス膨張性粒子と結着性樹脂との混合方法は特に限定はされないが、例えば、撹拌式、振とう式、および回転式などの混合装置を使用した方法が挙げられる。 The mixing method of the heat-sensitive gas-expandable particles and the binder resin is not particularly limited, and examples thereof include a method using a mixing apparatus such as a stirring type, a shaking type, and a rotary type.
　（二次電池用電極）
　本発明のバインダー組成物は、二次電池用電極に用いることができる。二次電池用電極は、集電体上に電極合材層を形成することにより得られ、電極合材層は、電極活物質、本発明のバインダー組成物、必要に応じて用いられる増粘剤及び導電材等を含む。また、電極合材層におけるバインダー組成物の含有量は、電極合材層１００重量部に対して、０．１～２０重量部、好ましくは０．２～１５重量部、より好ましくは０．３～１０重量部である。 (Electrode for secondary battery)
The binder composition of this invention can be used for the electrode for secondary batteries. An electrode for a secondary battery is obtained by forming an electrode mixture layer on a current collector, and the electrode mixture layer is made of an electrode active material, the binder composition of the present invention, and a thickener used as necessary. And a conductive material. The content of the binder composition in the electrode mixture layer is 0.1 to 20 parts by weight, preferably 0.2 to 15 parts by weight, and more preferably 0.3 parts by weight with respect to 100 parts by weight of the electrode mixture layer. ~ 10 parts by weight.
　電極合材層は、集電体上に電極活物質、本発明のバインダー組成物、必要に応じて用いられる増粘剤及び導電材を含む電極用スラリー組成物を塗布、乾燥することにより形成される。 The electrode mixture layer is formed by applying and drying an electrode active material, a binder composition of the present invention, a slurry composition for an electrode containing a thickener and a conductive material, if necessary, on a current collector. The
　集電体上に電極用スラリー組成物を塗布する方法は特に限定されない。例えば、ドクターブレード法、ディップ法、リバースロール法、ダイレクトロール法、グラビア法、エクストルージョン法、コンマダイレクトコート、スライドダイコート、およびハケ塗り法などの方法が挙げられる。乾燥方法としては例えば、温風、熱風、低湿風による乾燥、真空乾燥、（遠）赤外線や電子線などの照射による乾燥法が挙げられる。乾燥時間は通常１～６０分であり、乾燥温度は通常４０～１８０℃である。電極用スラリー組成物の塗布、乾燥を複数回繰り返すことにより電極合材層を形成してもよい。 The method for applying the electrode slurry composition on the current collector is not particularly limited. Examples thereof include a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, a comma direct coating, a slide die coating, and a brush coating method. Examples of the drying method include drying with warm air, hot air, low-humidity air, vacuum drying, and drying by irradiation with (far) infrared rays or electron beams. The drying time is usually 1 to 60 minutes, and the drying temperature is usually 40 to 180 ° C. The electrode mixture layer may be formed by repeating the application and drying of the electrode slurry composition a plurality of times.
　ここで、電極用スラリー組成物は、電極活物質、バインダー、必要に応じ用いられる増粘剤及び導電材、さらに水などの溶媒等を混合することにより得ることができる。 Here, the slurry composition for an electrode can be obtained by mixing an electrode active material, a binder, a thickener and a conductive material used as necessary, and a solvent such as water.
　混合方法は特に限定はされないが、例えば、撹拌式、振とう式、および回転式などの混合装置を使用した方法が挙げられる。また、ホモジナイザー、ボールミル、サンドミル、ロールミル、プラネタリーミキサーおよび遊星式混練機などの分散混練装置を使用した方法が挙げられる。 The mixing method is not particularly limited, and examples thereof include a method using a mixing apparatus such as a stirring type, a shaking type, and a rotary type. In addition, a method using a dispersion kneader such as a homogenizer, a ball mill, a sand mill, a roll mill, a planetary mixer, and a planetary kneader can be used.
　（集電体）
　集電体の材料は、例えば、金属、炭素、導電性高分子などであり、好適には金属が用いられる。集電体用金属としては、通常、アルミニウム、白金、ニッケル、タンタル、チタン、ステンレス鋼、銅、その他の合金等が使用される。これらの中で導電性、耐電圧性の面から銅、アルミニウムまたはアルミニウム合金を使用するのが好ましい。
　集電体の厚みは、好ましくは５～１００μｍ、より好ましくは８～７０μｍ、さらに好ましくは１０～５０μｍである。 (Current collector)
The material of the current collector is, for example, metal, carbon, conductive polymer, etc., and metal is preferably used. As the current collector metal, aluminum, platinum, nickel, tantalum, titanium, stainless steel, copper, other alloys and the like are usually used. Among these, it is preferable to use copper, aluminum, or an aluminum alloy in terms of conductivity and voltage resistance.
The thickness of the current collector is preferably 5 to 100 μm, more preferably 8 to 70 μm, and still more preferably 10 to 50 μm.
　（電極活物質）
　二次電池がリチウムイオン二次電池である場合の、リチウムイオン二次電池用正極の電極活物質（正極活物質）としては、リチウムイオンを可逆的にドープ・脱ドープ可能な金属酸化物が挙げられる。かかる金属酸化物としては、例えば、コバルト酸リチウム、ニッケル酸リチウム、マンガン酸リチウム、燐酸鉄リチウム等を挙げることができる。なお、上記にて例示した正極活物質は適宜用途に応じて単独で使用してもよく、複数種混合して使用してもよい。 (Electrode active material)
When the secondary battery is a lithium ion secondary battery, the electrode active material (positive electrode active material) of the positive electrode for the lithium ion secondary battery includes a metal oxide capable of reversibly doping and dedoping lithium ions. It is done. Examples of the metal oxide include lithium cobaltate, lithium nickelate, lithium manganate, and lithium iron phosphate. In addition, the positive electrode active material illustrated above may be used independently according to a use, and may be used in mixture of multiple types.
　なお、リチウムイオン二次電池用正極の対極としての負極の活物質（負極活物質）としては、たとえば、易黒鉛化性炭素、難黒鉛化性炭素、熱分解炭素などの低結晶性炭素（非晶質炭素）、グラファイト（天然黒鉛、人造黒鉛）、錫やケイ素等の合金系材料、ケイ素酸化物、錫酸化物、チタン酸リチウム等の酸化物等が挙げられる。なお、上記にて例示した負極活物質は適宜用途に応じて単独で使用してもよく、複数種混合して使用してもよい。 As the negative electrode active material (negative electrode active material) as the counter electrode of the positive electrode for a lithium ion secondary battery, for example, low crystalline carbon (non-graphitizable carbon, non-graphitizable carbon, pyrolytic carbon, etc.) Crystalline carbon), graphite (natural graphite, artificial graphite), alloy materials such as tin and silicon, oxides such as silicon oxide, tin oxide, and lithium titanate. In addition, the negative electrode active material illustrated above may be used independently according to a use suitably, and may be used in mixture of multiple types.
　リチウムイオン二次電池用電極の電極活物質の形状は、粒状に整粒されたものが好ましい。粒子の形状が粒状であると、電極成形時により高密度な電極が形成できる。 The shape of the electrode active material of the electrode for a lithium ion secondary battery is preferably a granulated particle. When the shape of the particles is granular, a higher-density electrode can be formed during electrode molding.
　リチウムイオン二次電池用電極の電極活物質の体積平均粒子径は、正極、負極ともに通常０．１～１００μｍ、好ましくは０．５～５０μｍ、より好ましくは０．８～３０μｍである。 The volume average particle diameter of the electrode active material of the electrode for a lithium ion secondary battery is usually 0.1 to 100 μm, preferably 0.5 to 50 μm, more preferably 0.8 to 30 μm for both the positive electrode and the negative electrode.
　（導電材）
　本発明の電極合材層は、必要に応じて導電材を含有していてもよい。導電材としては、導電性を有する材料であれば特に限定されないが、導電性を有する粒子状の材料が好ましく、たとえば、ファーネスブラック、アセチレンブラック、及びケッチェンブラック等の導電性カーボンブラック；天然黒鉛、人造黒鉛等の黒鉛；ポリアクリロニトリル系炭素繊維、ピッチ系炭素繊維、気相法炭素繊維等の炭素繊維；が挙げられる。導電材が粒子状の材料である場合の平均粒子径は、特に限定されないが、電極活物質の平均粒子径よりも小さいものが好ましく、より少ない使用量で十分な導電性を発現させる観点から、好ましくは０．００１～１０μｍ、より好ましくは０．０５～５μｍ、さらに好ましくは０．１～１μｍである。 (Conductive material)
The electrode mixture layer of the present invention may contain a conductive material as necessary. The conductive material is not particularly limited as long as it is a conductive material, but a conductive particulate material is preferable. For example, conductive carbon black such as furnace black, acetylene black, and ketjen black; natural graphite; And graphite such as artificial graphite; carbon fibers such as polyacrylonitrile-based carbon fiber, pitch-based carbon fiber, and vapor grown carbon fiber. The average particle diameter when the conductive material is a particulate material is not particularly limited, but is preferably smaller than the average particle diameter of the electrode active material, from the viewpoint of expressing sufficient conductivity with a smaller amount of use, The thickness is preferably 0.001 to 10 μm, more preferably 0.05 to 5 μm, and still more preferably 0.1 to 1 μm.
　（増粘剤）
　本発明の電極合材層は、必要に応じて増粘剤を含んでもよい。増粘剤としては、カルボキシメチルセルロース、メチルセルロース、ヒドロキシプロピルセルロースなどのセルロース系ポリマーおよびこれらのアンモニウム塩並びにアルカリ金属塩；（変性）ポリ（メタ）アクリル酸およびこれらのアンモニウム塩並びにアルカリ金属塩；（変性）ポリビニルアルコール、アクリル酸又はアクリル酸塩とビニルアルコールの共重合体、無水マレイン酸又はマレイン酸もしくはフマル酸とビニルアルコールの共重合体などのポリビニルアルコール類；ポリエチレングリコール、ポリエチレンオキシド、ポリビニルピロリドン、変性ポリアクリル酸、酸化スターチ、リン酸スターチ、カゼイン、各種変性デンプン、アクリロニトリル－ブタジエン共重合体水素化物などが挙げられる。これらのなかでも、カルボキシメチルセルロース及びカルボキシメチルセルロースのアンモニウム塩並びにアルカリ金属塩を用いることが好ましい。なお、本発明において、「（変性）ポリ」は「未変性ポリ」又は「変性ポリ」を意味する。 (Thickener)
The electrode mixture layer of the present invention may contain a thickener as necessary. Examples of thickeners include cellulosic polymers such as carboxymethylcellulose, methylcellulose, hydroxypropylcellulose, and ammonium salts and alkali metal salts thereof; (modified) poly (meth) acrylic acid and ammonium salts and alkali metal salts thereof; ) Polyvinyl alcohols such as polyvinyl alcohol, copolymers of acrylic acid or acrylate and vinyl alcohol, maleic anhydride or copolymers of maleic acid or fumaric acid and vinyl alcohol; polyethylene glycol, polyethylene oxide, polyvinyl pyrrolidone, modified Examples thereof include polyacrylic acid, oxidized starch, phosphoric acid starch, casein, various modified starches, acrylonitrile-butadiene copolymer hydride, and the like. Among these, it is preferable to use carboxymethylcellulose, ammonium salt of carboxymethylcellulose, and alkali metal salt. In the present invention, “(modified) poly” means “unmodified poly” or “modified poly”.
　電極合材層中の増粘剤の含有量は、電池特性に影響のない範囲が好ましく、電極合材層１００重量部に対して好ましくは０．１～５重量部、より好ましくは０．２～４重量部、さらに好ましくは０．３～３重量部である。 The content of the thickener in the electrode mixture layer is preferably within a range that does not affect the battery characteristics, and is preferably 0.1 to 5 parts by weight, more preferably 0.2 parts per 100 parts by weight of the electrode mixture layer. -4 parts by weight, more preferably 0.3-3 parts by weight.
　（二次電池）
　本発明の電気化学素子用電極の使用態様としては、かかる電極を用いたリチウムイオン二次電池などが挙げられる。たとえばリチウムイオン二次電池は、本発明のバインダー組成物を含む電極合材層が形成された電気化学素子用電極を正極および負極の少なくとも一方に用い、さらにセパレーターおよび電解液を備える。 (Secondary battery)
The usage mode of the electrode for an electrochemical element of the present invention includes a lithium ion secondary battery using such an electrode. For example, a lithium ion secondary battery uses an electrode for an electrochemical device in which an electrode mixture layer containing the binder composition of the present invention is formed as at least one of a positive electrode and a negative electrode, and further includes a separator and an electrolytic solution.
　セパレーターとしては、例えば、ポリエチレン、ポリプロピレンなどのポリオレフィン樹脂や、芳香族ポリアミド樹脂を含んでなる微孔膜または不織布；無機セラミック粉末を含む多孔質の樹脂コート；などを用いることができる。 As the separator, for example, a polyolefin resin such as polyethylene or polypropylene, a microporous film or nonwoven fabric containing an aromatic polyamide resin, a porous resin coat containing an inorganic ceramic powder, or the like can be used.
　セパレーターの厚さは、リチウムイオン二次電池内でのセパレーターによる抵抗が小さくなり、またリチウムイオン二次電池を製造する時の作業性に優れる観点から、好ましくは０．５～４０μｍ、より好ましくは１～３０μｍ、さらに好ましくは１～２５μｍである。 The thickness of the separator is preferably 0.5 to 40 μm, more preferably from the viewpoint of reducing resistance due to the separator in the lithium ion secondary battery and excellent workability when manufacturing the lithium ion secondary battery. The thickness is 1 to 30 μm, more preferably 1 to 25 μm.
　（電解液）
　電解液は、特に限定されないが、例えば、非水系の溶媒に支持電解質としてリチウム塩を溶解したものが使用できる。リチウム塩としては、例えば、ＬｉＰＦ6、ＬｉＡｓＦ6、ＬｉＢＦ4、ＬｉＳｂＦ6、ＬｉＡｌＣｌ4、ＬｉＣｌＯ4、ＣＦ3ＳＯ3Ｌｉ、Ｃ4Ｆ9ＳＯ3Ｌｉ、ＣＦ3ＣＯＯＬｉ、（ＣＦ3ＣＯ）2ＮＬｉ、（ＣＦ3ＳＯ2）2ＮＬｉ、（Ｃ2Ｆ5ＳＯ2）ＮＬｉなどのリチウム塩が挙げられる。特に溶媒に溶けやすく高い解離度を示すＬｉＰＦ6、ＬｉＣｌＯ4、ＣＦ3ＳＯ3Ｌｉは好適に用いられる。これらは、単独、または２種以上を混合して用いることができる。支持電解質の量は、電解液に対して、通常１ｗｔ％以上、好ましくは５ｗｔ％以上、また通常は３０ｗｔ％以下、好ましくは２０ｗｔ％以下である。支持電解質の量が少なすぎても多すぎてもイオン導電度は低下し電池の充電特性、放電特性が低下する。 (Electrolyte)
The electrolytic solution is not particularly limited. For example, a solution obtained by dissolving a lithium salt as a supporting electrolyte in a non-aqueous solvent can be used. Examples of 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 other lithium salts. In particular, LiPF 6 , LiClO 4 , and CF 3 SO 3 Li that are easily soluble in a solvent and exhibit a high degree of dissociation are preferably used. These can be used alone or in admixture of two or more. The amount of the supporting electrolyte is usually 1 wt% or more, preferably 5 wt% or more, and usually 30 wt% or less, preferably 20 wt% or less with respect to the electrolytic solution. If the amount of the supporting electrolyte is too small or too large, the ionic conductivity is lowered, and the charging characteristics and discharging characteristics of the battery are degraded.
　電解液に使用する溶媒としては、支持電解質を溶解させるものであれば特に限定されないが、通常、ジメチルカーボネート（ＤＭＣ）、エチレンカーボネート（ＥＣ）、ジエチルカーボネート（ＤＥＣ）、プロピレンカーボネート（ＰＣ）、ブチレンカーボネート（ＢＣ）、およびメチルエチルカーボネート（ＭＥＣ）などのアルキルカーボネート類；γ－ブチロラクトン、ギ酸メチルなどのエステル類、１，２－ジメトキシエタン、およびテトラヒドロフランなどのエーテル類；スルホラン、およびジメチルスルホキシドなどの含硫黄化合物類；が用いられる。特に高いイオン伝導性が得易く、使用温度範囲が広いため、ジメチルカーボネート、エチレンカーボネート、プロピレンカーボネート、ジエチルカーボネート、メチルエチルカーボネートが好ましい。これらは、単独、または２種以上を混合して用いることができる。また、電解液には添加剤を含有させて用いることも可能である。また、添加剤としてはビニレンカーボネート（ＶＣ）などのカーボネート系の化合物が好ましい。 The solvent used in the electrolytic solution is not particularly limited as long as it can dissolve the supporting electrolyte. Usually, dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene. Alkyl carbonates such as carbonate (BC) and methyl ethyl carbonate (MEC); esters such as γ-butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane; tetrahydrofuran; sulfolane and dimethyl sulfoxide Sulfur-containing compounds are used. In particular, dimethyl carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate, and methyl ethyl carbonate are preferable because high ion conductivity is easily obtained and the use temperature range is wide. These can be used alone or in admixture of two or more. Moreover, it is also possible to use an electrolyte containing an additive. The additive is preferably a carbonate compound such as vinylene carbonate (VC).
　上記以外の電解液としては、ポリエチレンオキシド、ポリアクリロニトリルなどのポリマー電解質に電解液を含浸したゲル状ポリマー電解質や、硫化リチウム、ＬｉＩ、Ｌｉ3Ｎ、Ｌｉ2Ｓ－Ｐ2Ｓ5ガラスセラミックなどの無機固体電解質を挙げることができる。 Other electrolytic solutions include gel polymer electrolytes in which a polymer electrolyte such as polyethylene oxide or polyacrylonitrile is impregnated with an electrolytic solution, lithium sulfide, LiI, Li 3 N, Li 2 SP—P 2 S 5 glass ceramic, etc. An inorganic solid electrolyte can be mentioned.
　リチウムイオン二次電池は、負極と正極とをセパレーターを介して重ね合わせ、これを電池形状に応じて巻く、折るなどして電池容器に入れ、電池容器に電解液を注入して封口して得られる。さらに必要に応じてエキスパンドメタルや、ヒューズ、ＰＴＣ素子などの過電流防止素子、リード板などを入れ、電池内部の圧力上昇、過充放電の防止をすることもできる。電池の形状は、ラミネートセル型、コイン型、ボタン型、シート型、円筒型、角形、扁平型などいずれであってもよい。 A lithium ion secondary battery is obtained by stacking a negative electrode and a positive electrode through a separator, winding this according to the shape of the battery, folding it into a battery container, pouring the electrolyte into the battery container and sealing it. It is done. Further, if necessary, an expanded metal, an overcurrent prevention element such as a fuse or a PTC element, a lead plate and the like can be inserted to prevent an increase in pressure inside the battery and overcharge / discharge. The shape of the battery may be any of a laminated cell type, a coin type, a button type, a sheet type, a cylindrical type, a square type, a flat type, and the like.
　本発明によれば、二次電池の安全性を向上させることができる電極合材層を得られる二次電池用バインダー組成物を提供することができる。 According to the present invention, it is possible to provide a binder composition for a secondary battery that can provide an electrode mixture layer that can improve the safety of the secondary battery.
　以下、実施例を示して本発明について具体的に説明するが、本発明は以下の実施例に限定されるものではなく、本発明の要旨及び均等の範囲を逸脱しない範囲において任意に変更して実施できる。なお、以下の説明において量を表す「％」及び「部」は、特に断らない限り、重量基準である。 EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples, and may be arbitrarily changed without departing from the gist and equivalent scope of the present invention. Can be implemented. In the following description, “%” and “parts” representing amounts are based on weight unless otherwise specified.
　実施例及び比較例においてバインダー組成物の体積変化、リチウムイオン二次電池の高温サイクル特性及び安全性試験の評価はそれぞれ以下のように行った。 In the examples and comparative examples, the volume change of the binder composition, the high-temperature cycle characteristics of the lithium ion secondary battery, and the safety test were evaluated as follows.
　〔バインダー組成物の体積変化〕
　バインダー組成物の分散液をテフロン（登録商標）製の容器に流しこみ、２３℃、５０％ＲＨの環境下でフィルム化し、さらに２５℃で２４時間真空乾燥を行うことで、厚さ１ｍｍのバインダー組成物のフィルムを得た。このフィルムを縦１０ｃｍ×横１ｃｍのサイズに切り出し、試験片とした。２５℃の環境下で、試験片を流動パラフィンで満たしたメスシリンダーに浸漬することで、Ｖ(25℃)（２５℃でのバインダー組成物のキャストフィルムの体積）を算出した。さらに、試験片入りのメスシリンダーを１５０℃のオーブンに１０分間静置することで、Ｖ(150℃)（１５０℃でのバインダー組成物のキャストフィルムの体積）を算出した。そして、キャストフィルムの体積変化（Ｖ(150℃)／Ｖ(25℃)）を求めた。 [Volume change of binder composition]
The binder composition dispersion is poured into a Teflon (registered trademark) container, formed into a film in an environment of 23 ° C. and 50% RH, and further vacuum-dried at 25 ° C. for 24 hours, whereby a binder having a thickness of 1 mm is obtained. A film of the composition was obtained. This film was cut into a size of 10 cm long × 1 cm wide to obtain a test piece. V (25 ° C.) (volume of the cast film of the binder composition at 25 ° C.) was calculated by immersing the test piece in a graduated cylinder filled with liquid paraffin in an environment of 25 ° C. Furthermore, V (150 degreeC) (volume of the cast film of the binder composition at 150 degreeC) was computed by leaving the measuring cylinder containing a test piece still in 150 degreeC oven for 10 minutes. And the volume change (V (150 degreeC) / V (25 degreeC)) of the cast film was calculated | required.
　なお、下記実施例及び比較例において、感熱ガス膨張性粒子のキャストフィルムの体積変化（ｖ(150℃)／ｖ(25℃)）についても、バインダー組成物の体積変化と同様にして算出した。即ち、感熱ガス膨張性粒子の分散液をテフロン（登録商標）製の容器に流しこみ、２３℃、５０％ＲＨの環境下でフィルム化し、さらに２５℃で２４時間真空乾燥を行うことで、厚さ１ｍｍの感熱ガス膨張性粒子のフィルムを得た。このフィルムを縦１０ｃｍ×横１ｃｍのサイズに切り出し、試験片とした。２５℃の環境下で、試験片を流動パラフィンで満たしたメスシリンダーに浸漬することで、ｖ(25℃)（２５℃での感熱ガス膨張性粒子のキャストフィルムの体積）を算出した。さらに、試験片入りのメスシリンダーを１５０℃のオーブンに１０分間静置することで、ｖ(150℃)（１５０℃での感熱ガス膨張性粒子のキャストフィルムの体積）を算出した。そして、感熱ガス膨張性粒子のキャストフィルムの体積変化（ｖ(150℃)／ｖ(25℃)）（以下、「感熱ガス膨張性粒子の体積変化」ということがある。）を求めた。 In the following examples and comparative examples, the volume change (v (150 ° C.) / V (25 ° C.)) of the cast film of heat-sensitive gas-expandable particles was also calculated in the same manner as the volume change of the binder composition. That is, the dispersion of the heat-sensitive gas-expandable particles is poured into a Teflon (registered trademark) container, formed into a film in an environment of 23 ° C. and 50% RH, and further vacuum dried at 25 ° C. for 24 hours. A film of heat-sensitive gas expandable particles having a thickness of 1 mm was obtained. This film was cut into a size of 10 cm long × 1 cm wide to obtain a test piece. Under the environment of 25 ° C., the test piece was immersed in a measuring cylinder filled with liquid paraffin to calculate v (25 ° C.) (volume of cast film of heat-sensitive gas-expandable particles at 25 ° C.). Furthermore, v (150 ° C.) (volume of cast film of heat-sensitive gas-expandable particles at 150 ° C.) was calculated by leaving the graduated cylinder containing the test piece in an oven at 150 ° C. for 10 minutes. Then, the volume change (v (150 ° C.) / V (25 ° C.)) of the cast film of heat-sensitive gas-expandable particles (hereinafter sometimes referred to as “volume change of heat-sensitive gas-expandable particles”) was determined.
　また、結着性樹脂の体積変化についても、バインダー組成物の体積変化と同様にして算出したが、実施例及び比較例において用いる結着性樹脂ａ～ｄのキャストフィルムの体積変化は、いずれも１．０であった。 Further, the volume change of the binder resin was calculated in the same manner as the volume change of the binder composition. However, the volume changes of the cast films of the binder resins a to d used in the examples and comparative examples are all the same. 1.0.
　〔高温サイクル特性〕
　実施例及び比較例で製造したパウチ型のリチウムイオン二次電池を、２４時間静置した後に、０．２Ｃの充放電レートにて４．２Ｖまで充電し３．０Ｖまで放電を行う操作を行い、初期容量Ｃ0を測定した。さらに、４５℃環境下で、１．０Ｃの充放電レートで４．３５Ｖに充電し、３．０Ｖまで放電する充放電を繰り返し、１００サイクル後の容量Ｃ1を測定し、ΔＣ＝Ｃ1／Ｃ0×１００（％）で示す容量維持率を求めた。この容量維持率を下記基準により評価し、結果を表１に示した。この容量維持率の値が高いほど、放電容量の低下が少なく、サイクル特性に優れていることを示す。
Ａ：８０％以上
Ｂ：７５％以上８０％未満
Ｃ：７０％以上７５％未満
Ｄ：７０％未満 [High temperature cycle characteristics]
After the pouch-type lithium ion secondary batteries manufactured in Examples and Comparative Examples were left to stand for 24 hours, an operation of charging to 4.2 V at a charge / discharge rate of 0.2 C and discharging to 3.0 V was performed. The initial capacity C 0 was measured. Further, in a 45 ° C. environment, the battery was charged to 4.35 V at a charge / discharge rate of 1.0 C, discharged to 3.0 V repeatedly, the capacity C 1 after 100 cycles was measured, and ΔC = C 1 / The capacity retention rate indicated by C 0 × 100 (%) was determined. This capacity retention rate was evaluated according to the following criteria, and the results are shown in Table 1. The higher the capacity retention ratio, the less the discharge capacity is reduced and the better the cycle characteristics.
A: 80% or more B: 75% or more and less than 80% C: 70% or more and less than 75% D: less than 70%
　〔安全性試験〕
　実施例及び比較例で製造したパウチ型のリチウムイオン二次電池を、２４時間静置した後に、０．２Ｃの充放電レートにて４．２Ｖまで充電し３．０Ｖまで放電を行う操作を行った。その後、２５℃で０．２Ｃの充電レートで４．３５Ｖまで充電した。このパウチ型のリチウムイオン二次電池に電圧測定端子を接続して、加熱試験装置の内部に置いた。その後、５℃／分の速度で、１５０℃まで昇温し、１５０℃で保持した。１５０℃到達から、短絡が発生するまでの経過時間を測定した。この経過時間を下記基準により評価し、結果を表１に示した。経過時間が長いほど、電池の安全性が高いことを示す。
Ａ：３０分以上
Ｂ：２０分以上３０分未満
Ｃ：１０分以上２０分未満
Ｄ：１０分未満 [Safety test]
After the pouch-type lithium ion secondary batteries manufactured in Examples and Comparative Examples were allowed to stand for 24 hours, an operation of charging to 4.2 V at a charge / discharge rate of 0.2 C and discharging to 3.0 V was performed. It was. Then, it charged to 4.35V at the charge rate of 0.2C at 25 degreeC. A voltage measurement terminal was connected to this pouch-type lithium ion secondary battery and placed inside the heating test apparatus. Thereafter, the temperature was raised to 150 ° C. at a rate of 5 ° C./min and held at 150 ° C. The elapsed time from reaching 150 ° C. until the occurrence of a short circuit was measured. The elapsed time was evaluated according to the following criteria, and the results are shown in Table 1. The longer the elapsed time, the higher the safety of the battery.
A: 30 minutes or more B: 20 minutes or more and less than 30 minutes C: 10 minutes or more and less than 20 minutes D: Less than 10 minutes
　［実施例１］
　（感熱ガス膨張性粒子Ａの製造）
　攪拌機を備えた反応器に、単量体としてアクリロニトリル９４．０部、メタクリル酸５．０部、エチレングリコールジメタクリレート（共栄社化学株式会社「ライトエステルＥＧ」）１．０部、膨張剤としてイソペンタンを２０．０部、乳化剤としてドデシルベンゼンスルホン酸ナトリウムを１．０部、重合開始剤としてｔ－ブチルパーオキシ－２－エチルヘキサノエート（日油社製「パーブチルＯ」）を１．０部、水相の重合禁止剤としてハイドロキノン０．５部、及びイオン交換水を４００部入れ、粗い液滴が目視で確認できなくなるまで撹拌した。これを、インライン型乳化分散機（太平洋機工社製「キャビトロン」）を用いて、１５，０００ｒｐｍの回転数で１分間高速剪断攪拌して、重合性単量体組成物の分散液を得た。なお、撹拌温度は５～１０℃で管理した。この重合性単量体組成物の分散液を、攪拌機を備えた５ＭＰａ耐圧容器に仕込み反応温度７０℃で１２時間反応させた。反応時の圧力は０．５ＭＰａで行った。こうして得られた重合体を含んだ水分散体に、５％水酸化ナトリウム水溶液を添加して、ｐＨ８に調整した。これにより、個数平均粒子径６００ｎｍの感熱ガス膨張性粒子Ａの水分散体を得た。この感熱ガス膨張性粒子Ａの体積変化は、３３．０であった。 [Example 1]
(Production of heat-sensitive gas expandable particles A)
In a reactor equipped with a stirrer, 94.0 parts of acrylonitrile as a monomer, 5.0 parts of methacrylic acid, 1.0 part of ethylene glycol dimethacrylate (Kyoeisha Chemical Co., Ltd. “Light Ester EG”), and isopentane as a swelling agent 20.0 parts, 1.0 part of sodium dodecylbenzenesulfonate as an emulsifier, 1.0 part of t-butylperoxy-2-ethylhexanoate (“NOBUTYL CO.” Manufactured by NOF Corporation) as a polymerization initiator, As an aqueous phase polymerization inhibitor, 0.5 part of hydroquinone and 400 parts of ion-exchanged water were added and stirred until coarse droplets could not be visually confirmed. This was subjected to high-speed shearing stirring for 1 minute at a rotational speed of 15,000 rpm using an in-line type emulsifying disperser (“Cabitron” manufactured by Taiheiyo Kiko Co., Ltd.) to obtain a dispersion of a polymerizable monomer composition. The stirring temperature was controlled at 5 to 10 ° C. This dispersion of the polymerizable monomer composition was charged into a 5 MPa pressure vessel equipped with a stirrer and reacted at a reaction temperature of 70 ° C. for 12 hours. The pressure during the reaction was 0.5 MPa. A 5% aqueous sodium hydroxide solution was added to the aqueous dispersion containing the polymer thus obtained to adjust the pH to 8. As a result, an aqueous dispersion of heat-sensitive gas-expandable particles A having a number average particle diameter of 600 nm was obtained. The volume change of the heat-sensitive gas-expandable particles A was 33.0.
　（結着性樹脂ａの製造）
　攪拌機を備えた５ＭＰａ耐圧容器に、芳香族ビニル単量体としてスチレン６２．０部、脂肪族共役ジエン単量体として１，３－ブタジエン３３．０部、エチレン性不飽和カルボン酸単量体としてイタコン酸４．０部、水酸基含有単量体として２－ヒドロキシエチルアクリレート１．０部、分子量調整剤としてｔ－ドデシルメルカプタン０．３部、乳化剤としてドデシルベンゼンスルホン酸ナトリウム１．０部、溶媒としてイオン交換水１５０部、及び重合開始剤として過硫酸カリウム１．０部を入れ、十分に攪拌した後、５５℃に加温して重合を開始した。モノマー消費量が９５．０％になった時点で冷却し、反応を停止した。こうして得られた重合体を含んだ水分散体に、５％水酸化ナトリウム水溶液を添加して、ｐＨ８に調整した。その後、加熱減圧蒸留によって未反応単量体の除去を行った。さらにその後、３０℃以下まで冷却した。これにより、個数平均粒子径１５０ｎｍの結着性樹脂ａを得た。 (Manufacture of binder resin a)
In a 5 MPa pressure vessel equipped with a stirrer, 62.0 parts of styrene as an aromatic vinyl monomer, 33.0 parts of 1,3-butadiene as an aliphatic conjugated diene monomer, and as an ethylenically unsaturated carboxylic acid monomer 4.0 parts of itaconic acid, 1.0 part of 2-hydroxyethyl acrylate as a hydroxyl group-containing monomer, 0.3 part of t-dodecyl mercaptan as a molecular weight regulator, 1.0 part of sodium dodecylbenzenesulfonate as an emulsifier, as a solvent After adding 150 parts of ion-exchanged water and 1.0 part of potassium persulfate as a polymerization initiator and stirring sufficiently, the mixture was heated to 55 ° C. to initiate polymerization. When the monomer consumption reached 95.0%, the reaction was stopped by cooling. A 5% aqueous sodium hydroxide solution was added to the aqueous dispersion containing the polymer thus obtained to adjust the pH to 8. Then, the unreacted monomer was removed by heating under reduced pressure. Furthermore, it cooled to 30 degrees C or less after that. Thereby, a binder resin a having a number average particle diameter of 150 nm was obtained.
　（バインダー組成物１の調製）
　感熱ガス膨張性粒子Ａを固形分相当で５０部、結着性樹脂ａを固形分相当で５０部、およびイオン交換水を２５℃環境下で１時間撹拌した。これにより、固形分濃度が３０重量％のバインダー組成物１の水分散体を得た。このバインダー組成物１により形成されるキャストフィルムの体積変化（Ｖ(150℃)／Ｖ(25℃)）は、１７．０であった。 (Preparation of binder composition 1)
50 parts of heat-sensitive gas-expandable particles A corresponding to the solid content, 50 parts of binder resin a corresponding to the solid content, and ion-exchanged water were stirred for 1 hour in a 25 ° C. environment. This obtained the water dispersion of the binder composition 1 whose solid content concentration is 30 weight%. The volume change (V (150 ° C.) / V (25 ° C.)) of the cast film formed from this binder composition 1 was 17.0.
　（負極用スラリー組成物の調製）
　プラネタリーミキサーに、炭素系活物質である天然黒鉛９７．０部、増粘剤としてカルボキシメチルセルロースナトリウム（ＣＭＣＮａ；日本製紙社製「ＭＡＣ－３５０ＨＣ」）１．０部、バインダーとして、バインダー組成物１の水分散体を固形物相当で２．０部投入し、さらに固形分濃度が５２％となるようにイオン交換水を加えて混合することで、負極用スラリー組成物を得た。 (Preparation of slurry composition for negative electrode)
In a planetary mixer, 97.0 parts of natural graphite as a carbon-based active material, 1.0 part of sodium carboxymethylcellulose (CMCNa; “MAC-350HC” manufactured by Nippon Paper Industries Co., Ltd.) as a thickener, binder composition 1 as a binder The aqueous dispersion was added in an amount of 2.0 parts corresponding to a solid, and ion-exchanged water was added and mixed so that the solid content concentration was 52%, thereby obtaining a slurry composition for a negative electrode.
　（負極の製造）
　上述の負極用スラリー組成物を、コンマコーターで、厚さ２０μｍの銅箔（集電体）の上に塗布量が９．８～１０．２ｍｇ／ｃｍ2となるように塗布した。この負極用スラリー組成物が塗布された銅箔を、０．３ｍ／分の速度で８０℃のオーブン内を２分間、さらに１２０℃のオーブン内を２分間かけて搬送することにより、銅箔上のスラリー組成物を乾燥させ、負極原反を得た。 (Manufacture of negative electrode)
The above-mentioned slurry composition for negative electrode was applied on a copper foil (current collector) having a thickness of 20 μm by a comma coater so that the coating amount was 9.8 to 10.2 mg / cm 2 . The copper foil coated with the negative electrode slurry composition is transported in an oven at 80 ° C. for 2 minutes and further in an oven at 120 ° C. for 2 minutes at a speed of 0.3 m / min. The slurry composition of was dried and the negative electrode original fabric was obtained.
　そして得られた負極原反をロールプレス機にて合材層密度が１．４５～１．５５ｇ／ｃｍ3となるようプレスし、さらに真空条件下１２０℃の環境に１０時間置き、集電体上に負極合材層を形成してなる負極シートを作製した。負極シートを所定のサイズに切断し、加工し、負極リードを溶接して、負極を得た。 Then, the obtained negative electrode raw material was pressed with a roll press machine so that the density of the composite layer became 1.45 to 1.55 g / cm 3, and further placed in an environment of 120 ° C. under vacuum conditions for 10 hours. A negative electrode sheet having a negative electrode mixture layer formed thereon was produced. The negative electrode sheet was cut into a predetermined size, processed, and the negative electrode lead was welded to obtain a negative electrode.
　（正極の製造）
　プラネタリーミキサーに、正極活物質としてＬｉＣｏＯ2９６．０部、導電材としてアセチレンブラック（ＡＢ；電気化学工業（株）製「ＨＳ－１００」）２．０部、バインダーとしてＰＶＤＦ（ポリフッ化ビニリデン、（株）クレハ化学製「ＫＦ－１１００」）２．０部、さらに全固形分濃度が６７％となるようにＮ－メチルピロリドンを加えて混合し、正極用スラリー組成物を調製した。 (Manufacture of positive electrode)
In a planetary mixer, 96.0 parts of LiCoO 2 as a positive electrode active material, 2.0 parts of acetylene black (AB; “HS-100” manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive material, PVDF (polyvinylidene fluoride, A slurry composition for a positive electrode was prepared by adding 2.0 parts of “KF-1100” manufactured by Kureha Chemical Co., Ltd. and further adding and mixing N-methylpyrrolidone so that the total solid concentration was 67%.
　得られた正極用スラリー組成物をコンマコーターで、厚さ２０μｍのアルミ箔の上に塗布し、乾燥した。なお、この乾燥は、アルミ箔を０．５ｍ／分の速度で６０℃のオーブン内を２分間かけて搬送することにより行った。その後、１２０℃にて２分間加熱処理して正極原反を得た。 The obtained positive electrode slurry composition was applied onto a 20 μm thick aluminum foil with a comma coater and dried. This drying was performed by transporting the aluminum 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 positive electrode raw material.
　得られた正極原反を乾燥後、ロールプレス機にてプレス後の合材層密度が３．４０～３．５０ｇ／ｃｍ3になるようにプレスし、さらに水分の除去を目的として、真空条件下１２０℃の環境に３時間置き、集電体上に正極合材層を形成してなる正極シートを作製した。正極シートを所定のサイズに切断し、加工し、正極リードを溶接して正極を得た。 The obtained positive electrode raw material is dried and then pressed with a roll press machine so that the mixed material layer density is 3.40 to 3.50 g / cm 3 , and vacuum conditions are used for the purpose of removing moisture. A positive electrode sheet in which a positive electrode mixture layer was formed on a current collector was produced in an environment of 120 ° C. for 3 hours. The positive electrode sheet was cut into a predetermined size, processed, and the positive electrode lead was welded to obtain a positive electrode.
　（リチウムイオン二次電池の製造）
　上記で製造した負極と、正極とを、乾式法で製造した単層のポリプロピレン製セパレータ（厚さ２５μｍ、気孔率５５％）とともにゼリーロール（Ｊｅｌｌｙ　Ｒｏｌｌ）状に捲回して、電極群を作製した。この電極群をパウチ型の電池ケース内に挿入し、非水電解液を注液した後に、ヒートシーラーで電池ケースの開口を封口することでリチウムイオン二次電池を完成させた。電池の設計容量は２０００ｍＡｈとした。ここで、非水電解液は、濃度１．０ＭのＬｉＰＦ6溶液にＶＣ（ビニレンカーボネート）を２容量％添加したものを用いた。前記ＬｉＰＦ6溶液の溶媒は、エチレンカーボネート（ＥＣ）とエチルメチルカーボネート（ＥＭＣ）との混合溶媒（ＥＣ／ＥＭＣ＝３／７重量比）である。 (Manufacture of lithium ion secondary batteries)
The negative electrode manufactured above and the positive electrode were wound into a jelly roll shape together with a single-layer polypropylene separator (thickness 25 μm, porosity 55%) manufactured by a dry method to produce an electrode group. . This electrode group was inserted into a pouch-type battery case, and after pouring a nonaqueous electrolytic solution, the opening of the battery case was sealed with a heat sealer to complete a lithium ion secondary battery. The design capacity of the battery was 2000 mAh. Here, as the non-aqueous electrolyte, a solution obtained by adding 2% by volume of VC (vinylene carbonate) to a LiPF 6 solution having a concentration of 1.0 M was used. The solvent of the LiPF 6 solution is a mixed solvent (EC / EMC = 3/7 weight ratio) of ethylene carbonate (EC) and ethyl methyl carbonate (EMC).
　［実施例２］
　（バインダー組成物２の調製）
　感熱ガス膨張性粒子Ａを固形分相当で５部、結着性樹脂ａを固形分相当で９５部、およびイオン交換水を２５℃環境下で１時間撹拌した。これにより、固形分濃度が３０重量％のバインダー組成物２の水分散体を得た。このバインダー組成物２により形成されるキャストフィルムの体積変化（Ｖ(150℃)／Ｖ(25℃)）は、２．６であった。
　バインダー組成物２を用いた以外は、実施例１と同様に負極の製造、正極の製造及びリチウムイオン二次電池の製造を行った。 [Example 2]
(Preparation of binder composition 2)
The heat-sensitive gas-expandable particles A were stirred for 5 hours under an environment of 25 ° C., and 5 parts by weight corresponding to the solid content, 95 parts by weight of the binding resin a, and ion-exchanged water. This obtained the water dispersion of the binder composition 2 whose solid content concentration is 30 weight%. The volume change (V (150 ° C.) / V (25 ° C.)) of the cast film formed from this binder composition 2 was 2.6.
A negative electrode, a positive electrode, and a lithium ion secondary battery were manufactured in the same manner as in Example 1 except that the binder composition 2 was used.
　［実施例３］
　（バインダー組成物３の調製）
　感熱ガス膨張性粒子Ａを固形分相当で８５部、結着性樹脂ａを固形分相当で１５部、およびイオン交換水を２５℃環境下で１時間撹拌した。これにより、固形分濃度が３０重量％のバインダー組成物３の水分散体を得た。このバインダー組成物３により形成されるキャストフィルムの体積変化（Ｖ(150℃)／Ｖ(25℃)）は、２８．２であった。
　バインダー組成物３を用いた以外は、実施例１と同様に負極の製造、正極の製造及びリチウムイオン二次電池の製造を行った。 [Example 3]
(Preparation of binder composition 3)
The heat-sensitive gas-expandable particles A were agitated for 1 hour in an environment of 25 ° C. in an amount of 85 parts in terms of solids, the binder resin a 15 in terms of solids, and ion-exchanged water. This obtained the water dispersion of the binder composition 3 whose solid content concentration is 30 weight%. The volume change (V (150 ° C.) / V (25 ° C.)) of the cast film formed from this binder composition 3 was 28.2.
A negative electrode, a positive electrode, and a lithium ion secondary battery were manufactured in the same manner as in Example 1 except that the binder composition 3 was used.
　［実施例４］
　（感熱ガス膨張性粒子Ｂの製造）
　攪拌機を備えた反応器に、単量体としてメタクリロニトリル９３．０部、アクリル酸５．０部、ジビニルベンゼン２．０部、膨張剤としてイソペンタンを２０．０部、乳化剤としてドデシルベンゼンスルホン酸ナトリウムを１．０部、重合開始剤としてｔ－ブチルパーオキシ－２－エチルヘキサノエート（日油社製「パーブチルＯ」）を１．０部、水相の重合禁止剤としてハイドロキノン０．５部、及びイオン交換水を４００部入れ、粗い液滴が目視で確認できなくなるまで撹拌した。これを、インライン型乳化分散機（太平洋機工社製「キャビトロン」）を用いて、１５，０００ｒｐｍの回転数で１分間高速剪断攪拌して、重合性単量体組成物の分散液を得た。なお、撹拌温度は５～１０℃で管理した。この重合性単量体組成物の分散液を、攪拌機を備えた５ＭＰａ耐圧容器に仕込み反応温度７０℃で１２時間反応させた。反応時の圧力は０．５ＭＰａで行った。こうして得られた重合体を含んだ水分散体に、５％水酸化ナトリウム水溶液を添加して、ｐＨ８に調整した。これにより、個数平均粒子径６００ｎｍの感熱ガス膨張性粒子Ｂの水分散体を得た。この感熱ガス膨張性粒子Ｂの体積変化は、２５．０であった。 [Example 4]
(Production of heat-sensitive gas-expandable particles B)
In a reactor equipped with a stirrer, 93.0 parts of methacrylonitrile as a monomer, 5.0 parts of acrylic acid, 2.0 parts of divinylbenzene, 20.0 parts of isopentane as a swelling agent, dodecylbenzenesulfonic acid as an emulsifier 1.0 part of sodium, 1.0 part of t-butylperoxy-2-ethylhexanoate (NOF "Perbutyl O") as a polymerization initiator, 0.5 part of hydroquinone as an aqueous phase polymerization inhibitor And 400 parts of ion-exchanged water were added and stirred until coarse droplets could not be visually confirmed. This was subjected to high-speed shearing stirring for 1 minute at a rotational speed of 15,000 rpm using an in-line type emulsifying disperser (“Cabitron” manufactured by Taiheiyo Kiko Co., Ltd.) to obtain a dispersion of a polymerizable monomer composition. The stirring temperature was controlled at 5 to 10 ° C. This dispersion of the polymerizable monomer composition was charged into a 5 MPa pressure vessel equipped with a stirrer and reacted at a reaction temperature of 70 ° C. for 12 hours. The pressure during the reaction was 0.5 MPa. A 5% aqueous sodium hydroxide solution was added to the aqueous dispersion containing the polymer thus obtained to adjust the pH to 8. As a result, an aqueous dispersion of heat-sensitive gas-expandable particles B having a number average particle diameter of 600 nm was obtained. The volume change of the heat-sensitive gas expandable particles B was 25.0.
　（バインダー組成物４の調製）
　感熱ガス膨張性粒子Ｂを固形分相当で５０部、結着性樹脂ａを固形分相当で５０部、およびイオン交換水を２５℃環境下で１時間撹拌した。これにより、固形分濃度が３０重量％のバインダー組成物４の水分散体を得た。このバインダー組成物４により形成されるキャストフィルムの体積変化（Ｖ(150℃)／Ｖ(25℃)）は、１３．０であった。
　バインダー組成物４を用いた以外は、実施例１と同様に負極の製造、正極の製造及びリチウムイオン二次電池の製造を行った。 (Preparation of binder composition 4)
The heat-sensitive gas-expandable particles B were stirred for 50 hours in a solid content, the binder resin a was 50 parts in a solid content, and ion-exchanged water was stirred at 25 ° C. for 1 hour. This obtained the water dispersion of the binder composition 4 whose solid content concentration is 30 weight%. The volume change (V (150 ° C.) / V (25 ° C.)) of the cast film formed from this binder composition 4 was 13.0.
A negative electrode, a positive electrode, and a lithium ion secondary battery were manufactured in the same manner as in Example 1 except that the binder composition 4 was used.
　［実施例５］
　（感熱ガス膨張性粒子Ｃの製造）
　攪拌機を備えた反応器に、単量体としてアクリロニトリル５０．０部及びメタクリロニトリル４４．０部、メタクリル酸５．０部、エチレングリコールジメタクリレート（共栄社化学株式会社「ライトエステルＥＧ」）１．０部、膨張剤としてイソオクタンを２０．０部、乳化剤としてドデシルベンゼンスルホン酸ナトリウムを０．３部、重合開始剤としてｔ－ブチルパーオキシ－２－エチルヘキサノエート（日油社製「パーブチルＯ」）を１．０部、水相の重合禁止剤としてハイドロキノン０．５部、及びイオン交換水を４００部入れ、粗い液滴が目視で確認できなくなるまで撹拌した。これを、インライン型乳化分散機（太平洋機工社製「キャビトロン」）を用いて、１５，０００ｒｐｍの回転数で１分間高速剪断攪拌して、重合性単量体組成物の分散液を得た。なお、撹拌温度は５～１０℃で管理した。この重合性単量体組成物の分散液を、攪拌機を備えた５ＭＰａ耐圧容器に仕込み反応温度７０℃で１２時間反応させた。反応時の圧力は０．５ＭＰａで行った。こうして得られた重合体を含んだ水分散体に、５％水酸化ナトリウム水溶液を添加して、ｐＨ８に調整した。これにより、個数平均粒子径２０００ｎｍの感熱ガス膨張性粒子Ｃの水分散体を得た。この感熱ガス膨張性粒子Ｃの体積変化は、１８．０であった。 [Example 5]
(Production of heat-sensitive gas-expandable particles C)
1. In a reactor equipped with a stirrer, 50.0 parts of acrylonitrile and 44.0 parts of methacrylonitrile, 5.0 parts of methacrylic acid, ethylene glycol dimethacrylate (Kyoeisha Chemical Co., Ltd. “Light Ester EG”) 0 parts, 20.0 parts of isooctane as a swelling agent, 0.3 part of sodium dodecylbenzenesulfonate as an emulsifier, t-butylperoxy-2-ethylhexanoate as a polymerization initiator (“Perbutyl O )), 1.0 part of hydroquinone as an aqueous phase polymerization inhibitor, and 400 parts of ion-exchanged water were added and stirred until no coarse droplets could be visually confirmed. This was subjected to high-speed shearing stirring for 1 minute at a rotational speed of 15,000 rpm using an in-line type emulsifying disperser (“Cabitron” manufactured by Taiheiyo Kiko Co., Ltd.) to obtain a dispersion of a polymerizable monomer composition. The stirring temperature was controlled at 5 to 10 ° C. This dispersion of the polymerizable monomer composition was charged into a 5 MPa pressure vessel equipped with a stirrer and reacted at a reaction temperature of 70 ° C. for 12 hours. The pressure during the reaction was 0.5 MPa. A 5% aqueous sodium hydroxide solution was added to the aqueous dispersion containing the polymer thus obtained to adjust the pH to 8. As a result, an aqueous dispersion of heat-sensitive gas-expandable particles C having a number average particle diameter of 2000 nm was obtained. The volume change of the heat-sensitive gas expandable particles C was 18.0.
　（バインダー組成物５の調製）
　感熱ガス膨張性粒子Ｃを固形分相当で５０部、結着性樹脂ａを固形分相当で５０部、およびイオン交換水を２５℃環境下で１時間撹拌した。これにより、固形分濃度が３０重量％のバインダー組成物５の水分散体を得た。このバインダー組成物５により形成されるキャストフィルムの体積変化（Ｖ(150℃)／Ｖ(25℃)）は、９．５であった。
　バインダー組成物５を用いた以外は、実施例１と同様に負極の製造、正極の製造及びリチウムイオン二次電池の製造を行った。 (Preparation of binder composition 5)
50 parts of heat-sensitive gas-expandable particles C corresponding to solid content, 50 parts of binder resin a corresponding to solid content, and ion-exchanged water were stirred for 1 hour in a 25 ° C. environment. This obtained the water dispersion of the binder composition 5 whose solid content concentration is 30 weight%. The volume change (V (150 ° C.) / V (25 ° C.)) of the cast film formed from this binder composition 5 was 9.5.
A negative electrode, a positive electrode, and a lithium ion secondary battery were manufactured in the same manner as in Example 1 except that the binder composition 5 was used.
　［実施例６］
　（結着性樹脂ｂの製造）
　攪拌機を備えた５ＭＰａ耐圧容器に、単量体としてブチルアクリレート４５．０部、エチルアクリレート５２．０部、メタクリル酸２．０部、エチレングリコールジメタクリレート（共栄社化学株式会社「ライトエステルＥＧ」）１．０部、乳化剤としてドデシルベンゼンスルホン酸ナトリウム１．０部、溶媒としてイオン交換水１５０部、及び重合開始剤として過硫酸カリウム１．０部を入れ、十分に攪拌した後、５５℃に加温して重合を開始した。モノマー消費量が９５．０％になった時点で冷却し、反応を停止した。こうして得られた重合体を含んだ水分散体に、５％水酸化ナトリウム水溶液を添加して、ｐＨ８に調整した。その後、加熱減圧蒸留によって未反応単量体の除去を行った。さらにその後、３０℃以下まで冷却した。これにより、個数平均粒子径１５０ｎｍの結着性樹脂ｂを得た。 [Example 6]
(Manufacture of binder resin b)
In a 5 MPa pressure vessel equipped with a stirrer, 45.0 parts of butyl acrylate, 52.0 parts of ethyl acrylate, 2.0 parts of methacrylic acid, ethylene glycol dimethacrylate (Kyoeisha Chemical Co., Ltd. “Light Ester EG”) 1 0.0 part, 1.0 part of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of ion-exchanged water as a solvent, and 1.0 part of potassium persulfate as a polymerization initiator were sufficiently stirred and heated to 55 ° C. Then, polymerization was started. When the monomer consumption reached 95.0%, the reaction was stopped by cooling. A 5% aqueous sodium hydroxide solution was added to the aqueous dispersion containing the polymer thus obtained to adjust the pH to 8. Then, the unreacted monomer was removed by heating under reduced pressure. Furthermore, it cooled to 30 degrees C or less after that. Thereby, a binder resin b having a number average particle diameter of 150 nm was obtained.
　（バインダー組成物６の調製）
　感熱ガス膨張性粒子Ａを固形分相当で５０部、結着性樹脂ｂを固形分相当で５０部、およびイオン交換水を２５℃環境下で１時間撹拌した。これにより、固形分濃度が３０重量％のバインダー組成物６の水分散体を得た。このバインダー組成物６により形成されるキャストフィルムの体積変化（Ｖ(150℃)／Ｖ(25℃)）は、１７．０であった。
　バインダー組成物６を用いた以外は、実施例１と同様に負極の製造、正極の製造及びリチウムイオン二次電池の製造を行った。 (Preparation of binder composition 6)
50 parts of heat-sensitive gas-expandable particles A corresponding to solid content, 50 parts of binder resin b corresponding to solid content, and ion-exchanged water were stirred for 1 hour in a 25 ° C. environment. This obtained the aqueous dispersion of the binder composition 6 whose solid content concentration is 30 weight%. The volume change (V (150 ° C.) / V (25 ° C.)) of the cast film formed from this binder composition 6 was 17.0.
A negative electrode, a positive electrode, and a lithium ion secondary battery were manufactured in the same manner as in Example 1 except that the binder composition 6 was used.
　［実施例７］
　（結着性樹脂ｃの製造）
　攪拌機を備えた５ＭＰａ耐圧容器に、単量体としてアクリロニトリル１９．９部、アクリル酸８０．０部、エチレングリコールジメタクリレート（共栄社化学株式会社「ライトエステルＥＧ」）０．１部、溶媒としてイオン交換水１５０部、及び重合開始剤として過硫酸カリウム１．０部を入れ、十分に攪拌した後、５５℃に加温して重合を開始した。モノマー消費量が９５．０％になった時点で冷却し、反応を停止した。こうして得られた重合体を含んだ水分散体に、５％水酸化ナトリウム水溶液を添加して、ｐＨ８に調整した。その後、加熱減圧蒸留によって未反応単量体の除去を行った。さらにその後、３０℃以下まで冷却した。これにより、水溶性の結着性樹脂ｃを得た。 [Example 7]
(Production of binder resin c)
In a 5 MPa pressure vessel equipped with a stirrer, 19.9 parts of acrylonitrile as a monomer, 80.0 parts of acrylic acid, 0.1 part of ethylene glycol dimethacrylate (“Kyoeisha Chemical Co., Ltd.“ Light Ester EG ”), ion exchange as a solvent 150 parts of water and 1.0 part of potassium persulfate as a polymerization initiator were added and stirred sufficiently, and then heated to 55 ° C. to initiate polymerization. When the monomer consumption reached 95.0%, the reaction was stopped by cooling. A 5% aqueous sodium hydroxide solution was added to the aqueous dispersion containing the polymer thus obtained to adjust the pH to 8. Then, the unreacted monomer was removed by heating under reduced pressure. Furthermore, it cooled to 30 degrees C or less after that. Thereby, water-soluble binder resin c was obtained.
　（バインダー組成物７の調製）
　感熱ガス膨張性粒子Ａを固形分相当で５０部、結着性樹脂ｃを固形分相当で５０部、およびイオン交換水を２５℃環境下で１時間撹拌した。これにより、固形分濃度が３０重量％のバインダー組成物７の水分散体を得た。このバインダー組成物７により形成されるキャストフィルムの体積変化（Ｖ(150℃)／Ｖ(25℃)）は、１７．０であった。
　バインダー組成物７を用いた以外は、実施例１と同様に負極の製造、正極の製造及びリチウムイオン二次電池の製造を行った。 (Preparation of binder composition 7)
The heat-sensitive gas-expandable particles A were stirred in an environment of 25 ° C. for 1 hour in an environment of 25 ° C., 50 parts in a solid content, 50 parts in a binder resin c in a solid content. This obtained the water dispersion of the binder composition 7 whose solid content concentration is 30 weight%. The volume change (V (150 ° C.) / V (25 ° C.)) of the cast film formed from this binder composition 7 was 17.0.
A negative electrode, a positive electrode, and a lithium ion secondary battery were manufactured in the same manner as in Example 1 except that the binder composition 7 was used.
　［実施例８］
　（バインダー組成物８の調製）
　感熱ガス膨張性粒子Ａの水分散体および結着性樹脂ｄとしてのＰＶＤＦ（ポリフッ化ビニリデン、（株）クレハ化学製「ＫＦ－１１００」）を重量固形分比で１対１となるよう混合し、さらにＮＭＰ（Ｎ－メチル－２－ピロリドン）を添加した。これを、減圧蒸留により水分を除去することで、ＮＭＰを溶剤とするバインダー組成物８を調製した。このバインダー組成物８により形成されるキャストフィルムの体積変化（Ｖ(150℃)／Ｖ(25℃)）は、１７．０であった。 [Example 8]
(Preparation of binder composition 8)
An aqueous dispersion of heat-sensitive gas-expandable particles A and PVDF (polyvinylidene fluoride, “KF-1100” manufactured by Kureha Chemical Co., Ltd.) as a binder resin d are mixed at a weight to solid content ratio of 1: 1. Further, NMP (N-methyl-2-pyrrolidone) was added. The binder composition 8 which uses NMP as a solvent was prepared by removing water from this by vacuum distillation. The volume change (V (150 ° C.) / V (25 ° C.)) of the cast film formed from this binder composition 8 was 17.0.
　（正極用スラリー組成物の調製）
　プラネタリーミキサーに、正極活物質としてＬｉＣｏＯ2９６．０部、導電材としてアセチレンブラック２．０部（電気化学工業（株）製「ＨＳ－１００」）、バインダーとして、バインダー組成物８を固形物相当で４．０部、さらに全固形分濃度が６７％となるようにＮ－メチルピロリドンを加えて混合し、正極用スラリー組成物を調製した。 (Preparation of slurry composition for positive electrode)
In a planetary mixer, 96.0 parts of LiCoO 2 as a positive electrode active material, 2.0 parts of acetylene black as a conductive material (“HS-100” manufactured by Denki Kagaku Kogyo Co., Ltd.), and a binder composition 8 as a binder A positive electrode slurry composition was prepared by adding and mixing N-methylpyrrolidone so that the equivalent solid content was 4.0 parts and the total solid content was 67%.
　（正極の製造）
　得られた正極用スラリー組成物をコンマコーターで、厚さ２０μｍのアルミ箔の上に塗布し、乾燥した。なお、この乾燥は、アルミ箔を０．５ｍ／分の速度で６０℃のオーブン内を２分間かけて搬送することにより行った。その後、１２０℃にて２分間加熱処理して正極原反を得た。 (Manufacture of positive electrode)
The obtained positive electrode slurry composition was applied onto a 20 μm thick aluminum foil with a comma coater and dried. This drying was performed by transporting the aluminum 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 positive electrode raw material.
　得られた正極原反を乾燥後、ロールプレス機にてプレス後の合材層密度が３．４０～３．５０ｇ／ｃｍ3になるようにプレスし、さらに水分の除去を目的として、真空条件下１２０℃の環境に３時間置き、集電体上に正極合材層を形成してなる正極シートを作成した。正極シートを所定のサイズに切断し、加工し、正極リードを溶接して正極を得た。 The obtained positive electrode raw material is dried and then pressed with a roll press machine so that the mixed material layer density is 3.40 to 3.50 g / cm 3 , and vacuum conditions are used for the purpose of removing moisture. A positive electrode sheet was formed by forming a positive electrode mixture layer on the current collector in an environment of 120 ° C. for 3 hours. The positive electrode sheet was cut into a predetermined size, processed, and the positive electrode lead was welded to obtain a positive electrode.
　（負極の製造）
　プラネタリーミキサーに、炭素系活物質である天然黒鉛９７．０部、増粘剤としてカルボキシメチルセルロースナトリウム（日本製紙社製「ＭＡＣ－３５０ＨＣ」）１．０部、バインダーとして、結着性樹脂ａを固形物相当で１．０部投入し、さらに固形分濃度が５２％となるようにイオン交換水を加えて混合することで、負極用スラリー組成物を得た。 (Manufacture of negative electrode)
In a planetary mixer, 97.0 parts of natural graphite, which is a carbon-based active material, 1.0 part of sodium carboxymethylcellulose (“MAC-350HC” manufactured by Nippon Paper Industries Co., Ltd.) as a thickener, and binder resin a as a binder A negative electrode slurry composition was obtained by adding 1.0 part of solid equivalent, and adding and mixing ion-exchanged water so that the solid concentration was 52%.
　上述の負極用スラリー組成物を、コンマコーターで、厚さ２０μｍの銅箔（集電体）の上に塗布量が９．８～１０．２ｍｇ／ｃｍ2となるように塗布した。この負極用スラリー組成物が塗布された銅箔を、０．３ｍ／分の速度で８０℃のオーブン内を２分間、さらに１２０℃のオーブン内を２分間かけて搬送することにより、銅箔上のスラリー組成物を乾燥させ、負極原反を得た。 The above-mentioned slurry composition for negative electrode was applied on a copper foil (current collector) having a thickness of 20 μm by a comma coater so that the coating amount was 9.8 to 10.2 mg / cm 2 . The copper foil coated with the negative electrode slurry composition is transported in an oven at 80 ° C. for 2 minutes and further in an oven at 120 ° C. for 2 minutes at a speed of 0.3 m / min. The slurry composition of was dried and the negative electrode original fabric was obtained.
　そして得られた負極原反をロールプレス機にて合材層密度が１．４５～１．５５ｇ／ｃｍ3となるようプレスし、さらに真空条件下１２０℃の環境に１０時間置き、集電体上に負極合材層を形成してなる負極シートを作成した。負極シートを所定のサイズに切断し、加工し、負極リードを溶接して、負極を得た。 Then, the obtained negative electrode raw material was pressed with a roll press machine so that the density of the composite layer became 1.45 to 1.55 g / cm 3, and further placed in an environment of 120 ° C. under vacuum conditions for 10 hours. A negative electrode sheet having a negative electrode mixture layer formed thereon was prepared. The negative electrode sheet was cut into a predetermined size, processed, and the negative electrode lead was welded to obtain a negative electrode.
　（リチウムイオン二次電池の製造）
　上記で製造した負極と、正極とを、乾式法で製造した単層のポリプロピレン製セパレータ（厚さ２５μｍ、気孔率５５％）とともにゼリーロール（Ｊｅｌｌｙ　Ｒｏｌｌ）状に捲回して、電極群を作製した。この電極群をパウチ型の電池ケース内に挿入し、非水電解液を注液した後に、ヒートシーラーで電池ケースの開口を封口することでリチウムイオン二次電池を完成させた。電池の設計容量は２０００ｍＡｈとした。ここで、非水電解液は、濃度１．０ＭのＬｉＰＦ6溶液にＶＣ（ビニレンカーボネート）を２容量％添加したものを用いた。前記ＬｉＰＦ6溶液の溶媒は、エチレンカーボネート（ＥＣ）とエチルメチルカーボネート（ＥＭＣ）との混合溶媒（ＥＣ／ＥＭＣ＝３／７重量比）である。 (Manufacture of lithium ion secondary batteries)
The negative electrode manufactured above and the positive electrode were wound into a jelly roll shape together with a single-layer polypropylene separator (thickness 25 μm, porosity 55%) manufactured by a dry method to produce an electrode group. . This electrode group was inserted into a pouch-type battery case, and after pouring a nonaqueous electrolytic solution, the opening of the battery case was sealed with a heat sealer to complete a lithium ion secondary battery. The design capacity of the battery was 2000 mAh. Here, as the non-aqueous electrolyte, a solution obtained by adding 2% by volume of VC (vinylene carbonate) to a LiPF 6 solution having a concentration of 1.0 M was used. The solvent of the LiPF 6 solution is a mixed solvent (EC / EMC = 3/7 weight ratio) of ethylene carbonate (EC) and ethyl methyl carbonate (EMC).
　［比較例１］
　（バインダー組成物９の調製）
　感熱ガス膨張性粒子Ａを固形分相当で２部、結着性樹脂ａを固形分相当で９８部、およびイオン交換水を２５℃環境下で１時間撹拌した。これにより、固形分濃度が３０重量％のバインダー組成物９の水分散体を得た。このバインダー組成物９により形成されるキャストフィルムの体積変化（Ｖ(150℃)／Ｖ(25℃)）は、１．６であった。
　バインダー組成物９を用いた以外は、実施例１と同様に負極の製造、正極の製造及びリチウムイオン二次電池の製造を行った。 [Comparative Example 1]
(Preparation of binder composition 9)
The heat-sensitive gas-expandable particles A were stirred for 2 hours in an environment of 25 ° C. under a 25 ° C. environment. This obtained the water dispersion of the binder composition 9 whose solid content concentration is 30 weight%. The volume change (V (150 ° C.) / V (25 ° C.)) of the cast film formed from this binder composition 9 was 1.6.
A negative electrode, a positive electrode, and a lithium ion secondary battery were manufactured in the same manner as in Example 1 except that the binder composition 9 was used.
　［比較例２］
　（感熱ガス膨張性粒子Ｄの製造）
　実施例１の（感熱ガス膨張性粒子Ａの製造）において用いるイソペンタンの量を１．８部とした以外は、実施例１と同様の条件で感熱ガス膨張性粒子の製造を行い、個数平均粒子径６００ｎｍの感熱ガス膨張性粒子Ｄの水分散体を得た。この感熱ガス膨張性粒子Ｄの体積変化は、２．７であった。 [Comparative Example 2]
(Production of heat-sensitive gas-expandable particles D)
Thermally-sensitive gas-expandable particles were produced under the same conditions as in Example 1 except that the amount of isopentane used in Example 1 (Production of thermal-sensitive gas-expandable particles A) was 1.8 parts. An aqueous dispersion of heat-sensitive gas-expandable particles D having a diameter of 600 nm was obtained. The volume change of the heat-sensitive gas expandable particles D was 2.7.
　（バインダー組成物１０の調製）
　感熱ガス膨張性粒子Ｄを固形分相当で５０部、結着性樹脂ａを固形分相当で５０部、およびイオン交換水を２５℃環境下で１時間撹拌した。これにより、固形分濃度が３０重量％のバインダー組成物１０の水分散体を得た。このバインダー組成物１０により形成されるキャストフィルムの体積変化（Ｖ(150℃)／Ｖ(25℃)）は、１．９であった。
　バインダー組成物１０を用いた以外は、実施例１と同様に負極の製造、正極の製造及びリチウムイオン二次電池の製造を行った。 (Preparation of binder composition 10)
The heat-sensitive gas-expandable particles D were stirred for 50 hours in an environment of 25 ° C. and 50 parts by weight of the solid resin, and the binder resin a was stirred in an environment of 25 ° C. for 1 hour. This obtained the water dispersion of the binder composition 10 whose solid content concentration is 30 weight%. The volume change (V (150 ° C.) / V (25 ° C.)) of the cast film formed from this binder composition 10 was 1.9.
A negative electrode, a positive electrode, and a lithium ion secondary battery were manufactured in the same manner as in Example 1 except that the binder composition 10 was used.
　［比較例３］
　（バインダー組成物１１の調製）
　感熱ガス膨張性粒子Ａを固形分相当で９８部、結着性樹脂ａを固形分相当で２部、およびイオン交換水を２５℃環境下で１時間撹拌した。これにより、固形分濃度が３０重量％のバインダー組成物１１の水分散体を得た。このバインダー組成物１１により形成されるキャストフィルムの体積変化（Ｖ(150℃)／Ｖ(25℃)）は、３２．４であった。
　バインダー組成物１１を用いた以外は、実施例１と同様に負極の製造、正極の製造及びリチウムイオン二次電池の製造を行った。 [Comparative Example 3]
(Preparation of binder composition 11)
The heat-sensitive gas-expandable particles A were agitated for 98 hours in a solid content, the binding resin a was a solid content equivalent of 2 parts, and ion-exchanged water in a 25 ° C. environment for 1 hour. This obtained the water dispersion of the binder composition 11 whose solid content concentration is 30 weight%. The volume change (V (150 ° C.) / V (25 ° C.)) of the cast film formed from this binder composition 11 was 32.4.
A negative electrode, a positive electrode, and a lithium ion secondary battery were produced in the same manner as in Example 1 except that the binder composition 11 was used.
　［比較例４］
　（感熱ガス膨張性粒子Ｅの製造）
　実施例１の（感熱ガス膨張性粒子Ａの製造）において用いるイソペンタンの量を４０．０部とした以外は、実施例１と同様の条件で感熱ガス膨張性粒子の製造を行い、個数平均粒子径６００ｎｍの感熱ガス膨張性粒子Ｅの水分散体を得た。この感熱ガス膨張性粒子Ｅの体積変化は、６５．０であった。 [Comparative Example 4]
(Production of heat-sensitive gas expandable particles E)
Thermally-sensitive gas-expandable particles were produced under the same conditions as in Example 1 except that the amount of isopentane used in (Production of thermal-sensitive gas-expandable particles A) in Example 1 was 40.0 parts. An aqueous dispersion of heat-sensitive gas-expandable particles E having a diameter of 600 nm was obtained. The volume change of the heat-sensitive gas expandable particles E was 65.0.
　（バインダー組成物１２の調製）
　感熱ガス膨張性粒子Ｅを固形分相当で５０部と、結着性樹脂ａを固形分相当で５０部およびイオン交換水を２５℃環境下で１時間撹拌した。これにより、固形分濃度が３０重量％のバインダー組成物１２の水分散体を得た。このバインダー組成物１２により形成されるキャストフィルムの体積変化（Ｖ(150℃)／Ｖ(25℃)）は、３３．０であった。
　バインダー組成物１２を用いた以外は、実施例１と同様に負極の製造、正極の製造及びリチウムイオン二次電池の製造を行った。 (Preparation of binder composition 12)
50 parts of heat-sensitive gas-expandable particles E corresponding to the solid content, 50 parts of binder resin a corresponding to the solid content, and ion-exchanged water were stirred for 1 hour in a 25 ° C. environment. Thus, an aqueous dispersion of the binder composition 12 having a solid content concentration of 30% by weight was obtained. The volume change (V (150 ° C.) / V (25 ° C.)) of the cast film formed from this binder composition 12 was 33.0.
A negative electrode, a positive electrode, and a lithium ion secondary battery were produced in the same manner as in Example 1 except that the binder composition 12 was used.
　［比較例５］
　（正極の製造）
　カーボンブラック６０部、ポリエチレン４０部を混練してペレット状としたものを、ジェットミル方式により粉砕し、平均粒子径１μｍのＰＴＣ導電性材料を得た。 [Comparative Example 5]
(Manufacture of positive electrode)
A pellet obtained by kneading 60 parts of carbon black and 40 parts of polyethylene was pulverized by a jet mill method to obtain a PTC conductive material having an average particle diameter of 1 μm.
　プラネタリーミキサーに、正極活物質としてＬｉＣｏＯ2９６．０部、導電材としＰＴＣ導電性材料２．０部、ＰＶＤＦ（ポリフッ化ビニリデン；クレハ化学（株）製「ＫＦ－１１００」）２．０部、さらに全固形分濃度が６７％となるようにＮ－メチルピロリドンを加えて混合し、正極用スラリー組成物を調製した。 In a planetary mixer, 96.0 parts of LiCoO 2 as a positive electrode active material, 2.0 parts of PTC conductive material as a conductive material, 2.0 parts of PVDF (polyvinylidene fluoride; “KF-1100” manufactured by Kureha Chemical Co., Ltd.) Further, N-methylpyrrolidone was added and mixed so that the total solid content concentration was 67% to prepare a positive electrode slurry composition.
　得られた正極用スラリー組成物をコンマコーターで、厚さ２０μｍのアルミ箔の上に塗布し、乾燥した。なお、この乾燥は、アルミ箔を０．５ｍ／分の速度で６０℃のオーブン内を２分間かけて搬送することにより行った。その後、１２０℃にて２分間加熱処理して正極原反を得た。 The obtained positive electrode slurry composition was applied onto a 20 μm thick aluminum foil with a comma coater and dried. This drying was performed by transporting the aluminum 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 positive electrode raw material.
　得られた正極原反を乾燥後、ロールプレス機にてプレス後の合材層密度が３．４０～３．５０ｇ／ｃｍ3になるようにプレスし、さらに水分の除去を目的として、真空条件下１２０℃の環境に３時間置き、集電体上に正極合材層を形成してなる正極シートを作成した。正極シートを所定のサイズに切断し、加工し、正極リードを溶接して正極を得た。 The obtained positive electrode raw material is dried and then pressed with a roll press machine so that the mixed material layer density is 3.40 to 3.50 g / cm 3 , and vacuum conditions are used for the purpose of removing moisture. A positive electrode sheet was formed by forming a positive electrode mixture layer on the current collector in an environment of 120 ° C. for 3 hours. The positive electrode sheet was cut into a predetermined size, processed, and the positive electrode lead was welded to obtain a positive electrode.
　（負極の製造）
　プラネタリーミキサーに、炭素系活物質である天然黒鉛９７．０部及び増粘剤としてカルボキシメチルセルロース（ＣＭＣＮａ；日本製紙社製「ＭＡＣ－３５０ＨＣ」）１．０部、バインダーとして結着性樹脂ａを固形分相当で１．０部投入し、さらに固形分濃度が５２．０％となるようにイオン交換水を加えて混合することで、負極用スラリー組成物を得た。 (Manufacture of negative electrode)
In a planetary mixer, 97.0 parts of natural graphite as a carbon-based active material, 1.0 part of carboxymethyl cellulose (CMCNa; “MAC-350HC” manufactured by Nippon Paper Industries Co., Ltd.) as a thickener, and binder resin a as a binder 1.0 part by weight corresponding to the solid content was added, and ion-exchanged water was added and mixed so that the solid content concentration was 52.0%, whereby a negative electrode slurry composition was obtained.
　得られた負極用スラリー組成物を、コンマコーターで、厚さ２０μｍの銅箔（集電体）の上に塗布量が９．８～１０．２ｍｇ／ｃｍ2となるように塗布した。この負極用スラリー組成物が塗布された銅箔を、０．３ｍ／分の速度で８０℃のオーブン内を２分間、さらに１２０℃のオーブン内を２分間かけて搬送することにより、銅箔上のスラリー組成物を乾燥させ、負極原反を得た。 The obtained slurry composition for negative electrode was applied on a copper foil (current collector) having a thickness of 20 μm by a comma coater so that the coating amount was 9.8 to 10.2 mg / cm 2 . The copper foil coated with the negative electrode slurry composition is transported in an oven at 80 ° C. for 2 minutes and further in an oven at 120 ° C. for 2 minutes at a speed of 0.3 m / min. The slurry composition of was dried and the negative electrode original fabric was obtained.
　そして得られた負極原反をロールプレス機にて合材層密度が１．４５～１．５５ｇ／ｃｍ3となるようプレスし、さらに真空条件下１２０℃の環境に１０時間置き、集電体上に負極合材層を形成してなる負極シートを作製した。負極シートを所定のサイズに切断し、加工し、負極リードを溶接して、負極を得た。
　上記で得た正極および負極を用いた以外は、実施例１と同様にリチウムイオン二次電池の製造を行った。 Then, the obtained negative electrode raw material was pressed with a roll press machine so that the density of the composite layer became 1.45 to 1.55 g / cm 3, and further placed in an environment of 120 ° C. under vacuum conditions for 10 hours. A negative electrode sheet having a negative electrode mixture layer formed thereon was produced. The negative electrode sheet was cut into a predetermined size, processed, and the negative electrode lead was welded to obtain a negative electrode.
A lithium ion secondary battery was produced in the same manner as in Example 1 except that the positive electrode and the negative electrode obtained above were used.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　表１に示すように感熱ガス膨張性粒子と、結着性樹脂とを含む二次電池用バインダー組成物であって、前記二次電池用バインダー組成物により形成されるキャストフィルムの体積変化がＶ(150℃)／Ｖ(25℃)＝２～３０（Ｖ(150℃)は１５０℃における前記キャストフィルムの体積を示し、Ｖ(25℃)は２５℃における前記キャストフィルムの体積を示す。）である二次電池用バインダー組成物を用いて得られるリチウムイオン二次電池の高温サイクル特性及び安全性は良好であった。 As shown in Table 1, a secondary battery binder composition containing heat-sensitive gas-expandable particles and a binder resin, wherein the volume change of the cast film formed by the secondary battery binder composition is V. (150 ° C.) / V (25 ° C.) = 2-30 (V (150 ° C.) indicates the volume of the cast film at 150 ° C., and V (25 ° C.) indicates the volume of the cast film at 25 ° C.) The lithium ion secondary battery obtained by using the secondary battery binder composition was good in high-temperature cycle characteristics and safety.

Claims (6)

  1. 　感熱ガス膨張性粒子と、結着性樹脂とを含む二次電池用バインダー組成物であって、
    　前記二次電池用バインダー組成物により形成されるキャストフィルムの体積変化が
    Ｖ(150℃)／Ｖ(25℃)＝２～３０
    （Ｖ(150℃)は１５０℃における前記キャストフィルムの体積を示し、Ｖ(25℃)は２５℃における前記キャストフィルムの体積を示す。）
    である二次電池用バインダー組成物。     A binder composition for a secondary battery comprising heat-sensitive gas-expandable particles and a binder resin,
    The volume change of the cast film formed from the secondary battery binder composition is V (150 ° C.) / V (25 ° C.) = 2-30.
    (V (150 ° C.) indicates the volume of the cast film at 150 ° C., and V (25 ° C.) indicates the volume of the cast film at 25 ° C.)
    A binder composition for a secondary battery.
  2. 　前記感熱ガス膨張性粒子の体積変化が、
    　ｖ(150℃)／ｖ(25℃)＝３～６０
    （ｖ(150℃)は１５０℃での前記感熱ガス膨張性粒子の体積を示し、ｖ(25℃)は２５℃での前記感熱ガス膨張性粒子の体積を示す）
    である請求項１記載の二次電池用バインダー組成物。     The volume change of the heat-sensitive gas expandable particles is
    v (150 ° C) / v (25 ° C) = 3-60
    (V (150 ° C.) indicates the volume of the thermosensitive gas-expandable particles at 150 ° C., v (25 ° C.) indicates the volume of the thermosensitive gas-expandable particles at 25 ° C.)
    The binder composition for a secondary battery according to claim 1.
  3. 　前記感熱ガス膨張性粒子と前記結着性樹脂との比率が、感熱ガス膨張性粒子／結着性樹脂＝９７／３～３／９７（重量比）である請求項１または２記載の二次電池用バインダー組成物。 The secondary according to claim 1 or 2, wherein the ratio of the heat-sensitive gas-expandable particles to the binder resin is thermal gas-expandable particles / binding resin = 97/3 to 3/97 (weight ratio). Battery binder composition.
  4. 　前記感熱ガス膨張性粒子の粒子径が０．１～１０μｍである請求項１～３の何れか一項に記載の二次電池用バインダー組成物。 The binder composition for a secondary battery according to any one of claims 1 to 3, wherein the heat-sensitive gas-expandable particles have a particle size of 0.1 to 10 µm.
  5. 　前記感熱ガス膨張性粒子は、コアシェル構造を有し、前記感熱ガス膨張性粒子のコア材が、沸点１０～１５０℃の炭化水素である請求項１～４の何れか一項に記載の二次電池用バインダー組成物。 The secondary according to any one of claims 1 to 4, wherein the heat-sensitive gas expandable particles have a core-shell structure, and the core material of the heat-sensitive gas expandable particles is a hydrocarbon having a boiling point of 10 to 150 ° C. Battery binder composition.
  6. 　前記感熱ガス膨張性粒子は、コアシェル構造を有し、前記感熱ガス膨張性粒子のシェル材が、ニトリル基を有する重合単位を含む重合体である請求項１～５の何れか一項に記載の二次電池用バインダー組成物。 The heat-sensitive gas-expandable particles have a core-shell structure, and the shell material of the heat-sensitive gas-expandable particles is a polymer including a polymer unit having a nitrile group. A binder composition for a secondary battery.
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