WO2018066430A1 - 二次電池用結着剤及び二次電池用電極合剤 - Google Patents
二次電池用結着剤及び二次電池用電極合剤 Download PDFInfo
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- WO2018066430A1 WO2018066430A1 PCT/JP2017/034954 JP2017034954W WO2018066430A1 WO 2018066430 A1 WO2018066430 A1 WO 2018066430A1 JP 2017034954 W JP2017034954 W JP 2017034954W WO 2018066430 A1 WO2018066430 A1 WO 2018066430A1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/621—Binders
- H01M4/622—Binders being polymers
- H01M4/623—Binders being polymers fluorinated polymers
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F214/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen
- C08F214/18—Monomers containing fluorine
- C08F214/22—Vinylidene fluoride
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/04—Processes of manufacture in general
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Definitions
- the present invention relates to a binder for a secondary battery and an electrode mixture for a secondary battery.
- Secondary batteries such as lithium ion secondary batteries have high voltage, high energy density, low self-discharge, low memory effect, ultra-lightweight, etc. Used for small and portable electric and electronic devices such as smartphones, tablet PCs, ultrabooks, etc., and also practical as a wide range of power sources ranging from in-vehicle power sources for automobiles and large power sources for stationary applications It is becoming. Secondary batteries are required to have higher energy density, and further improvements in battery characteristics are required. At the same time, ensuring safety is also a technical issue.
- an electrode manufacturing technique is a major point.
- a negative electrode when a negative electrode is produced using a carbonaceous material such as coke or carbon as a negative electrode active material, the negative electrode is usually obtained by pulverizing the carbonaceous material and dispersing it in a solvent together with a binder. A mixture is prepared, applied to the negative electrode current collector, dried by removing the solvent, and rolled.
- a carbonaceous material that merely occludes and releases lithium ions is also referred to as an active material.
- the positive electrode is usually powdered with, for example, a lithium-containing oxide as a positive electrode active material, dispersed in a solvent together with a conductive agent and a binder to prepare a positive electrode mixture, and applied to the positive electrode current collector. It is produced by removing the solvent by drying and rolling.
- a lithium-containing oxide as a positive electrode active material
- the density of the positive electrode mixture coating of lithium ion secondary batteries used in electric vehicles is currently 3.4 to 3.6 g / cc, but the positive electrode mixture is used to increase the energy density.
- polyvinylidene fluoride is often used as a binder for lithium ion secondary batteries.
- Patent Document 1 a positive electrode mixture prepared by mixing a lithium-containing oxide such as LiCoO 2 as a positive electrode active material and graphite as a conductive agent with polyvinylidene fluoride is dispersed in N-methylpyrrolidone to form a slurry.
- a positive electrode current collector made of aluminum foil
- a negative electrode mixture prepared by mixing a carbonaceous material as a negative electrode active material and polyvinylidene fluoride is dispersed in N-methylpyrrolidone to form a slurry.
- the polyvinylidene fluoride resin has a low adhesive strength with a base material such as a metal, an improvement in the adhesive strength is desired.
- a rolling process is usually performed to improve the density of the positive electrode mixture coating film, but the polyvinylidene fluoride binder is used.
- the used electrode sheet is poor in flexibility, and it is difficult to further increase the density of the positive electrode mixture coating film.
- the electrode sheet using the polyvinylidene fluoride binder is poor in flexibility, at the time of folding the electrode sheet 180 degrees in the production of the square battery, or at the process of rounding the electrode sheet in the cylindrical battery production, There is a tendency that the electrode sheet is broken or the electrode mixture is peeled off from the electrode sheet, and the production yield tends to deteriorate.
- an active material with a high Ni content when a slurry is made with NMP together with polyvinylidene fluoride and a conductive agent, the viscosity increases due to alkaline conditions, causing gelation, and stable application to the current collector. Often difficult.
- the gelation of the slurry refers to a state in which fluidity and uniformity are lost due to an increase in viscosity, and when the gelation is extremely advanced, application to the current collector becomes impossible. Problems arise.
- Patent Document 2 discloses that a coating composition having good adhesion to a substrate such as a metal can be copolymerized with vinylidene fluoride alone containing 80% by weight or more of vinylidene fluoride or vinylidene fluoride and vinylidene fluoride.
- a vinylidene fluoride monomer composed of a mixture with another monomer, and (i) 0.1 to 3 parts by weight of an unsaturated dibasic acid monoester copolymerizable with vinylidene fluoride or ( B)
- a coating composition containing a polar vinylidene fluoride copolymer obtained by copolymerizing 0.1 to 5 parts by weight of vinylene carbonate in an aqueous medium as a binder is described.
- Patent Document 3 discloses a positive electrode in which a positive electrode mixture composed of a positive electrode active material, a conductive agent, and a binder is held by a positive electrode current collector and / or a negative electrode mixture composed of a negative electrode active material and a binder.
- the binder comprises 50-80 mol% of vinylidene fluoride and tetrafluoroethylene 20
- a binder for a non-aqueous electrolyte secondary battery comprising a binary copolymer composed of ⁇ 50 mol% is described.
- Patent Document 4 a negative electrode in which a negative electrode mixture made of a negative electrode active material and a binder is held in a negative electrode current collector, and a positive electrode mixture made of a positive electrode active material, a conductive agent, and a binder are held in the positive electrode current collector.
- a non-aqueous electrolyte secondary battery comprising a positive electrode and a non-aqueous electrolyte, wherein at least part of the binder contained in the negative electrode mixture and the positive electrode mixture is a polyfluoride having a hydrophilic polar group
- a non-aqueous electrolyte secondary battery characterized by being vinylidene is described.
- Patent Document 5 discloses a linear semi-crystalline copolymer [polymer (A)] containing a repeating unit derived from a vinylidene fluoride (VDF) monomer and a specific hydrophilic (meth) acrylic monomer (MA), Copolymer comprising 0.05 to 10 mol% of repeating units derived from said hydrophilic (meth) acrylic monomer (MA) and characterized by a fraction of randomly distributed units (MA) of at least 40% [polymer
- An electrode-forming composition is described that includes (A)], a powdered electrode material, and optionally, a conductivity-imparting additive and / or a viscosity modifier.
- This invention is made
- the present invention has a polymerization unit based on vinylidene fluoride, a polymerization unit based on tetrafluoroethylene, and a polymerization unit based on the monomer (2-2) represented by the following general formula (2-2) It is a binder for secondary batteries characterized by containing a fluoropolymer.
- R 5 , R 6 and R 7 each independently represent a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms.
- R 8 represents a hydrocarbon group having 1 to 8 carbon atoms.
- Y 1 Represents an inorganic cation and / or an organic cation.
- Y 1 is preferably at least one cation selected from the group consisting of H, Li, Na, K, Mg, Ca, Al, and NH 4 .
- the fluorine-containing polymer has a polymerization unit based on vinylidene fluoride of 50 to 95 mol%, a polymerization unit based on tetrafluoroethylene of 4.8 to 49.95 mol%, and the monomer
- the polymerization unit based on (2-2) is preferably 0.05 to 2.0 mol%.
- the fluorine-containing polymer preferably has a weight average molecular weight of 50,000 to 2,000,000.
- the fluoropolymer preferably has a storage elastic modulus at 25 ° C. of 1000 MPa or less, and more preferably 800 MPa or less.
- the present invention is also an electrode mixture for a secondary battery formed by mixing at least the binder for a secondary battery, a powder electrode material for a battery, and water or a non-aqueous solvent.
- the present invention is also an electrode for a secondary battery including the binder for the secondary battery.
- This invention is also a secondary battery provided with the said electrode for secondary batteries.
- the binder of this invention consists of the said structure, it is excellent in both adhesiveness with a collector, and a softness
- the electrode mixture of the present invention has the above-described configuration, it is possible to form an electrode material layer that is excellent in both adhesion to the current collector and flexibility.
- the binder of the present invention is characterized by containing a fluoropolymer.
- the fluoropolymer includes a polymer unit based on vinylidene fluoride, a polymer unit based on tetrafluoroethylene, and a polymer unit based on the monomer (2-2) represented by the general formula (2-2) described later. And having.
- the binder of this invention is excellent in adhesiveness with a collector, and a softness
- the lithium ion secondary battery which is a typical application, is in the form of a cylindrical type, a rectangular type, a laminated type, etc., and the electrode sheet is introduced by being wound and pressed, so that the electrode sheet is broken or powdered electrode There is a problem that the material is easily dropped or peeled off from the current collector.
- the binder of the present invention is excellent in adhesion with the current collector and flexibility, the electrode material is not cracked even if the electrode material is thickly coated and wound, and pressed for high density, There is no falling off of the powder electrode material or peeling from the current collector.
- the nickel content of the active material has been increased for the purpose of increasing the capacity of the lithium ion secondary battery, there is a problem that the electrode mixture gels due to the alkaline condition when the electrode mixture is prepared. .
- the binder of the present invention contains the above-mentioned fluoropolymer, it does not gel even if it is left for a long time after the preparation of the electrode mixture, and the fluidity is maintained. Furthermore, by using the above-mentioned fluoropolymer, the secondary battery obtained using the binder of the present invention has excellent rate characteristics.
- the fluoropolymer has a polymer unit based on the monomer (2-2). Since the monomer (2-2) has a specific functional group, the adhesion between the binder and the current collector can be improved, and surprisingly, the flexibility is also improved. Can be made.
- the monomer (2-2) is a monomer represented by the following general formula (2-2).
- the monomer (2-2) may be used alone or in combination of two or more.
- R 5 , R 6 and R 7 each independently represent a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms.
- R 8 represents a hydrocarbon group having 1 to 8 carbon atoms.
- Y 1 Represents an inorganic cation and / or an organic cation.
- Y 1 is an inorganic cation and / or an organic cation.
- the inorganic cation include cations such as H, Li, Na, K, Mg, Ca, Al, and Fe.
- the organic cation include cations such as NH 4 , NH 3 R x , NH 2 R x 2 , NHR x 3 , and NR x 4 (R x independently represents an alkyl group having 1 to 4 carbon atoms).
- Y 1 is preferably H, Li, Na, K, Mg, Ca, Al, NH 4, more preferably H, Li, Na, K, Mg, Al, NH 4 , H, Li, Al, NH 4. Is more preferable, and H is particularly preferable.
- the specific example of the said inorganic cation and the organic cation has abbreviate
- R 5 , R 6 and R 7 each independently represent a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms.
- the hydrocarbon group is a monovalent hydrocarbon group.
- the hydrocarbon group preferably has 4 or less carbon atoms.
- Examples of the hydrocarbon group include alkyl groups, alkenyl groups, alkynyl groups and the like having the above carbon number, and a methyl group, an ethyl group, and the like are preferable.
- R 5 and R 6 are preferably each independently a hydrogen atom, a methyl group or an ethyl group
- R 7 is preferably a hydrogen atom or a methyl group.
- R 8 represents a hydrocarbon group having 1 to 8 carbon atoms.
- the hydrocarbon group is a divalent hydrocarbon group.
- the hydrocarbon group preferably has 4 or less carbon atoms.
- Examples of the hydrocarbon group include alkylene groups and alkenylene groups having the above carbon number. Among them, a methylene group, an ethylene group, an ethylidene group, a propylidene group, an isopropylidene group, and the like are preferable, and a methylene group is more preferable.
- Examples of the monomer (2-2) include vinyl acetic acid (3-butenoic acid) and its salt, 3-pentenoic acid and its salt, 4-pentenoic acid and its salt, 3-hexenoic acid and its salt, 4-hexenoic acid and its salt and 5-hexenoic acid and its salt are preferred.
- the polymerization unit based on the monomer (2-2) is preferably 0.05 to 2.0 mol% with respect to the total polymerization units.
- the content of the polymerized unit is within the above range, the adhesion of the binder to the current collector can be improved without impairing the characteristics based on vinylidene fluoride and tetofluoroethylene.
- the content of the polymerized unit is more preferably 0.10 mol% or more, further preferably 0.30 mol% or more, still more preferably 0.40 mol% or more, and more preferably 1.5 mol% or less. .
- the fluoropolymer has a polymer unit based on vinylidene fluoride.
- the said binder is excellent in solvent solubility, oxidation resistance, and electrolyte solution erosion resistance.
- the fluoropolymer has a polymer unit based on tetrafluoroethylene.
- the said binder is excellent in a softness
- chemical resistance particularly alkali resistance is improved.
- the polymerized units based on vinylidene fluoride are 50 to 95 mol% and the polymerized units based on tetrafluoroethylene are 4.8 to 49.95 mol% with respect to the total polymerized units. preferable. Thereby, the softness
- the upper limit of the content of polymerized units based on vinylidene fluoride may be 94 mol% or 89 mol%.
- the upper limit of the content of the polymer units based on tetrafluoroethylene may be 49.90 mol%, 49.70 mol%, 49.60 mol%, 49 mol% It may be 39.90 mol%, 39.70 mol%, 39.60 mol%, or 39 mol%.
- the fluoropolymer has a polymer unit based on vinylidene fluoride, a polymer unit based on tetrafluoroethylene, and a polymer unit based on the monomer (2-2), those monomers It may further have polymerized units based on other monomers copolymerizable with the polymer.
- the other monomer vinyl fluoride, trifluoroethylene, chlorotrifluoroethylene, fluoroalkyl vinyl ether, hexafluoropropylene, 2,3,3,3-tetrafluoropropene, propylene and the like can be used. .
- hexafluoropropylene and 2,3,3,3-tetrafluoropropene are particularly preferred from the viewpoints of flexibility and chemical resistance.
- the polymerized units based on the monomers are preferably 0.1 to 50 mol% with respect to the total polymerized units.
- the above-mentioned fluoropolymer preferably has a weight average molecular weight (in terms of polystyrene) of 50,000 to 2,000,000 in that a homogeneous polymer can be obtained at the time of preparing the electrode slurry. More preferably, it is 80000 to 1700000, and still more preferably 100000 to 1500,000. Further, from the viewpoint of improving battery characteristics, it is more preferably 80000 to 1950,000, still more preferably 100000 to 1900000, and still more preferably 200000 to 1900000.
- the weight average molecular weight can be measured at 50 ° C. using N, N-dimethylformamide as a solvent by gel permeation chromatography (GPC).
- the fluorine-containing polymer preferably has a number average molecular weight (in terms of polystyrene) of 16000 to 1300000 in terms of improving battery characteristics. More preferably, it is 20000 to 1200000.
- the number average molecular weight can be measured by gel permeation chromatography (GPC) at 50 ° C. using N, N-dimethylformamide as a solvent.
- the fluoropolymer preferably has an elongation at break of 100% or more.
- the elongation at break is 100% or more, the flexibility of the binder is further improved.
- the elongation at break is more preferably 200% or more, still more preferably 300% or more.
- the elongation at break can be measured by the following method. That is, the binder (fluorinated polymer) is weighed so as to have a concentration of 5% by mass and dissolved in N-methyl-2-pyrrolidone (NMP) to obtain a binder solution. The binder solution is cast on a glass plate and dried at 100 ° C. for 2 hours to obtain a film having a thickness of about 30 ⁇ m. The film is punched into a dumbbell shape and the elongation at break at 25 ° C. is measured by an autograph.
- NMP N-methyl-2-pyrrolidone
- the fluoropolymer preferably has a storage elastic modulus at 25 ° C. of 1000 MPa or less.
- the storage elastic modulus at 25 ° C. is 1000 MPa or less, the flexibility of the binder is further improved.
- the storage elastic modulus is more preferably 800 MPa or less, and further preferably 600 MPa or less.
- the storage elastic modulus is preferably 100 MPa or more, more preferably 200 MPa or more, and further preferably 250 MPa or more.
- the fluoropolymer preferably has a storage elastic modulus at 100 ° C. of 200 MPa or less.
- the storage elastic modulus at 100 ° C. is 200 MPa or less, the flexibility of the binder is further improved.
- the storage elastic modulus is more preferably 160 MPa or less, still more preferably 140 MPa or less, and even more preferably 110 MPa or less.
- the storage elastic modulus is preferably 1 MPa or more, more preferably 5 MPa or more, and still more preferably 10 MPa or more.
- the storage elastic modulus is 30 mm in length, 5 mm in width, and 40 ⁇ m in thickness.
- the dynamic viscoelasticity measurement is performed by the dynamic viscoelasticity device DVA220 manufactured by IT Measurement Control Co., Ltd. Measured at 25 ° C. and 100 ° C. when measured under the following conditions: 160 ° C., temperature rising rate 2 ° C./min, frequency 1 Hz.
- a binder solution fluorinated polymer
- NMP N-methyl-2-pyrrolidone
- the fluoropolymer of the present invention has a low storage elastic modulus as described above, it can be easily densified in the step of rolling the positive electrode mixture coating film, and the density of the positive electrode mixture coating film is 3 .6 g / cc or more can be expected. Moreover, even if the electrode using the fluoropolymer of the present invention is thickly coated and densified, the electrode does not crack.
- Copolymerization of vinylidene fluoride, tetrafluoroethylene, the above monomer (2-2), and other monomers that can be copolymerized with those monomers as required is suspension polymerization, although methods such as emulsion polymerization and solution polymerization can be employed, aqueous suspension polymerization and emulsion polymerization are preferred from the standpoint of ease of post-treatment.
- a polymerization initiator In the above copolymerization, a polymerization initiator, a surfactant, a chain transfer agent, and a solvent can be used, and conventionally known ones can be used.
- a polymerization initiator an oil-soluble radical polymerization initiator or a water-soluble radical polymerization initiator can be used.
- the oil-soluble radical polymerization initiator may be a known oil-soluble peroxide, for example, dialkyl such as diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, disec-butylperoxydicarbonate, etc.
- Peroxycarbonates, peroxyesters such as t-butylperoxyisobutyrate and t-butylperoxypivalate, dialkylperoxides such as dit-butylperoxide, and the like are also used as di ( ⁇ -hydro -Dodecafluoroheptanoyl) peroxide, di ( ⁇ -hydro-tetradecafluoroheptanoyl) peroxide, di ( ⁇ -hydro-hexadecafluorononanoyl) peroxide, di (perfluorobutyryl) peroxide, di (Perfluorovaleryl) peroxa Di (perfluorohexanoyl) peroxide, di (perfluoroheptanoyl) peroxide, di (perfluorooctanoyl) peroxide, di (perfluorononanoyl) peroxide, di ( ⁇ -chloro-hexafluoro) Butyryl) peroxide
- the water-soluble radical polymerization initiator may be a known water-soluble peroxide, for example, ammonium salts such as persulfuric acid, perboric acid, perchloric acid, perphosphoric acid, percarbonate, potassium salts, sodium salts. , T-butyl permaleate, t-butyl hydroperoxide and the like.
- a reducing agent such as sulfites and sulfites may be used in combination with the peroxide, and the amount used may be 0.1 to 20 times that of the peroxide.
- a known surfactant can be used.
- a nonionic surfactant, an anionic surfactant, a cationic surfactant, or the like can be used.
- fluorine-containing anionic surfactants are preferable, and may include an ether bond (that is, an oxygen atom may be inserted between carbon atoms), or a linear or branched fluorine-containing group having 4 to 20 carbon atoms.
- Anionic surfactants are more preferred.
- the addition amount (with respect to polymerization water) is preferably 50 to 5000 ppm.
- Examples of the chain transfer agent include hydrocarbons such as ethane, isopentane, n-hexane, and cyclohexane; aromatics such as toluene and xylene; ketones such as acetone; acetates such as ethyl acetate and butyl acetate; Examples include alcohols such as methanol and ethanol; mercaptans such as methyl mercaptan; halogenated hydrocarbons such as carbon tetrachloride, chloroform, methylene chloride, and methyl chloride.
- the addition amount may vary depending on the size of the chain transfer constant of the compound used, but is usually used in the range of 0.01 to 20% by mass with respect to the polymerization solvent.
- Examples of the solvent include water, a mixed solvent of water and alcohol, and the like.
- a fluorine-based solvent may be used in addition to water.
- the fluorine-based solvent include hydrochlorofluoroalkanes such as CH 3 CClF 2 , CH 3 CCl 2 F, CF 3 CF 2 CCl 2 H, CF 2 ClCF 2 CFHCl; CF 2 ClCFClCF 2 CF 3 , CF 3 CFClCFClCF 3, etc.
- Perfluoroalkanes such as perfluorocyclobutane, CF 3 CF 2 CF 2 CF 3 , CF 3 CF 2 CF 2 CF 3 , CF 3 CF 2 CF 2 CF 2 CF 3 ; CF 2 HCF 2 CF 2 H, CF 3 CFHCF 2 CF 2 CF 3 , CF 3 CF 2 CF 2 CF 2 H, CF 3 CF 2 CFHCF 2 CF 3 , CF 3 CFHCHFHCF 2 CF 3 , CF 2 HCF 2 CF 2 CF 2 CF 2 H, CF 2 HCFH F 2 CF 2 CF 3, CF 3 CF 2 CF 2 CF 2 CF 2 H, CF 3 CH (CF 3) CF 3 CF 2 CF 3, CF 3 CF (CF 3) CFHCF 2 CF 3, CF 3 CF (CF 3 ) CFHCHFHC 3 , CF 3
- the polymerization temperature is not particularly limited, and may be 0 to 100 ° C.
- the polymerization pressure is appropriately determined according to other polymerization conditions such as the type, amount and vapor pressure of the solvent to be used, and the polymerization temperature, but it may usually be 0 to 9.8 MPaG.
- a suspending agent such as methyl cellulose, methoxylated methyl cellulose, propoxylated methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, polyvinyl alcohol, polyethylene oxide, and gelatin is added to 0.005 with respect to water. It can be used by adding in the range of -1.0% by mass, preferably 0.01-0.4% by mass.
- polymerization initiators include diisopropyl peroxydicarbonate, dinormalpropyl peroxydicarbonate, dinormalheptafluoropropyl peroxydicarbonate, isobutyryl peroxide, di (chlorofluoroacyl) peroxide, di (peroxide). Fluoroacyl) peroxide and the like can be used.
- the amount used is the total amount of monomers (vinylidene fluoride and tetrafluoroethylene, the above monomer (2-2), and other monomers copolymerizable with these monomers as necessary.
- the total amount is preferably 0.1 to 5% by mass.
- a chain transfer agent such as ethyl acetate, methyl acetate, acetone, ethanol, n-propanol, acetaldehyde, propyl aldehyde, ethyl propionate or carbon tetrachloride may be added to adjust the degree of polymerization of the resulting polymer.
- the amount used is usually from 0.1 to 5% by mass, preferably from 0.5 to 3% by mass, based on the total amount of monomers.
- the total amount of monomers charged is 1: 1 to 1:10, preferably 1: 2 to 1: 5 in a weight ratio of the total amount of monomer to water, and the polymerization is carried out at a temperature of 10 to 50 ° C. 100 hours.
- the above emulsion polymerization is carried out in the presence of an aqueous medium.
- an aqueous medium water is preferable.
- the water used for the polymerization is preferably ion-exchanged water, and the electrical conductivity is preferably 10 ⁇ S / cm or less and lower. If the ion content is large, the reaction rate may not be stable. Even in the fluorinated solvent, it is preferable to have high purity with few components such as an acid and a compound containing a chlorine group contained in the production process.
- a compound containing an acid content, chlorine, or the like may have chain transfer properties, which is preferable in stabilizing the polymerization rate and molecular weight.
- a high-purity material having few chain transfer components in the other raw materials (monomers such as vinylidene fluoride and tetrafluoroethylene, initiators, chain transfer agents, etc.) used in the polymerization.
- the purory stage of the reaction after water is charged, an air tightness test is performed while stirring the tank, and then the inside of the tank is repeatedly depressurized, slightly pressurized with nitrogen, and depressurized, so that the oxygen concentration in the tank can be 1000 ppm or less. It is preferable to stabilize the reaction rate and adjust the molecular weight after confirming that the oxygen concentration has decreased to a low level and then reducing the pressure again to charge the starting materials such as monomers.
- the polymerization temperature is not particularly limited, and may be 0 to 150 ° C.
- the polymerization pressure is appropriately determined according to other polymerization conditions such as the polymerization temperature, but may be usually 0 to 9.8 MPaG.
- one or more surfactants may be added.
- a known emulsifier may be used.
- the following surfactant groups [A] to [G] may be used.
- Fluorine-containing anionic alkyl surfactants such as NH 2 (surfactant group [B]) Formula: CF 3 O—CF (CF 3 ) CF 2 O—CX a (CF 3 ) —Y a (where X a represents H or F, Y a represents —COOM 1 , —SO 3 M 2 , Represents —SO 2 NM 3 M 4 or —PO 3 M 5 M 6.
- M 1 , M 2 , M 3 , M 4 , M 5 and M 6 are the same or different and are H, NH 4 or monovalent Represents a cation) or formula: CF 3 O—CF 2 CF 2 CF 2 O—CFX a CF 2 —Y a (where X a represents H or F, and Y a is the same as above) or And a fluorine-containing anionic alkyl represented by the formula: CF 3 CF 2 O—CF 2 CF 2 O—CFX a —Y a (wherein X a represents H or F, and Y a is the same as above) Ether surfactants (surfactant group [C]) Fluorine-containing allyl ethers (surfactant group [D]) such as CH 2 ⁇ CFCF 2 —O— (CF (CF 3 ) CF 2 O) —CF (CF 3 ) —COONH 4 Linear 1-octanesulfonic acid, linear 2-oc
- the amount of the surfactant used is preferably 1 to 50000 ppm of the aqueous medium.
- an oil-soluble radical polymerization initiator or a water-soluble radical polymerization initiator can be used, and a water-soluble radical polymerization initiator is preferably used.
- the oil-soluble radical polymerization initiator may be a known oil-soluble peroxide, for example, dialkyl such as diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, disec-butylperoxydicarbonate, etc.
- Peroxycarbonates, peroxyesters such as t-butylperoxyisobutyrate and t-butylperoxypivalate, dialkylperoxides such as dit-butylperoxide, and the like are also used as di ( ⁇ -hydro -Dodecafluoroheptanoyl) peroxide, di ( ⁇ -hydro-tetradecafluoroheptanoyl) peroxide, di ( ⁇ -hydro-hexadecafluorononanoyl) peroxide, di (perfluorobutyryl) peroxide, di (Perfluorovaleryl) peroxa Di (perfluorohexanoyl) peroxide, di (perfluoroheptanoyl) peroxide, di (perfluorooctanoyl) peroxide, di (perfluorononanoyl) peroxide, di ( ⁇ -chloro-hexafluoro) Butyryl) peroxide
- the water-soluble radical polymerization initiator may be a known water-soluble peroxide, for example, ammonium salts such as persulfuric acid, perboric acid, perchloric acid, perphosphoric acid, percarbonate, potassium salts, sodium salts. , T-butyl permalate, t-butyl hydroperoxide and the like.
- a reducing agent such as sulfites and sulfites may be used in combination with the peroxide, and the amount used may be 0.1 to 20 times that of the peroxide.
- a persulfate is more preferable as the polymerization initiator for the emulsion polymerization.
- the amount used is in the range of 0.001 to 20% by mass relative to the aqueous medium.
- a chain transfer agent can be used.
- the chain transfer agent include hydrocarbons such as ethane, isopentane, n-hexane, and cyclohexane; aromatics such as toluene and xylene; ketones such as acetone; acetates such as ethyl acetate and butyl acetate; Examples include alcohols such as methanol and ethanol; mercaptans such as methyl mercaptan; halogenated hydrocarbons such as carbon tetrachloride, chloroform, methylene chloride, and methyl chloride.
- the amount added may vary depending on the chain transfer constant of the compound used, but it is used in the range of 0.001 to 20% by weight based on the aqueous medium.
- the method is not particularly limited and can be performed by a conventionally known method.
- coagulation by adding an acid coagulation by adding an inorganic metal salt, coagulation by adding an organic solvent, freeze coagulation and the like
- a known coagulant may be used as the coagulant used for the acid coagulation, and examples thereof include hydrochloric acid, sulfuric acid, nitric acid and the like.
- a known coagulant may be used, and examples thereof include sodium sulfate, magnesium sulfate, and aluminum sulfate.
- the remaining surfactant, polymerization initiator, chain transfer agent, excess coagulant, etc. may be washed away using water or an organic solvent. Then, a dry powder can be obtained by drying the wet polymer.
- the amount of the monomer to be copolymerized with vinylidene fluoride and tetrafluoroethylene is determined by the adhesion of the resulting copolymer. It is determined in consideration of properties, chemical resistance, molecular weight, polymerization yield and the like.
- the binder of the present invention may further contain other components as long as it contains the above-mentioned fluoropolymer, and one or more of these other components can be used.
- Examples of the other components that can be used in the binder include vinylidene fluoride [VdF] polymer, polymethacrylate, polymethyl methacrylate, polyacrylonitrile, polyimide, polyamide, polyamideimide, polycarbonate, styrene rubber, and butadiene rubber. Can be mentioned. Among these, a VdF polymer is preferable. The content of these other components is preferably 10 to 900% by mass with respect to the fluoropolymer.
- VdF polymer examples include polyvinylidene fluoride [PVdF], VdF / tetrafluoroethylene [TFE] copolymer, VdF / hexafluoropropylene [HFP] copolymer, and VdF / chlorotrifluoroethylene [CTFE] copolymer. VdF / 2,3,3,3-tetrafluoropropene copolymer and the like.
- the VdF polymer preferably has a weight average molecular weight (in terms of polystyrene) of 50,000 to 2,000,000. More preferably, it is 80000 to 1700000, and still more preferably 100000 to 1500,000.
- the weight average molecular weight can be measured at 50 ° C. using N, N-dimethylformamide as a solvent by gel permeation chromatography (GPC).
- the VdF polymer preferably has a number average molecular weight (in terms of polystyrene) of 35,000 to 1400000. More preferably, it is 40,000 to 1300000, and still more preferably 50000 to 1200000.
- the number average molecular weight can be measured by gel permeation chromatography (GPC) at 50 ° C. using N, N-dimethylformamide as a solvent.
- the PVdF may be a homopolymer consisting only of polymerized units based on VdF (VdF units), or from polymerized units based on VdF and polymerized units based on the monomer (x) copolymerizable with VdF. It may be.
- Examples of the monomer (x) include tetrafluoroethylene, vinyl fluoride, trifluoroethylene, chlorotrifluoroethylene, fluoroalkyl vinyl ether, hexafluoropropylene, 2,3,3,3-tetrafluoropropene, and propylene. Etc. Further, unsaturated dibasic acid monoesters such as those described in JP-A-6-172452, such as maleic acid monomethyl ester, citraconic acid monomethyl ester, citraconic acid monoethyl ester, vinylene carbonate, etc.
- the adhesiveness with the collector which consists of metal foils of aluminum or copper by giving the flexibility to the material by slightly lowering the crystallinity of the above-mentioned fluoropolymer other than the compound containing the polar group as described above.
- the improvement can be inferred from previous studies.
- fluoromonomers such as ethylene trifluoride and hexafluoropropylene.
- Z is —CH 2 OH, —COOH, carboxylate, carboxyl ester group or epoxy group
- X and X ′ are the same or different, and both are hydrogen atoms or fluorine atoms
- R f is 1 to 40 carbon atoms.
- a divalent fluorine-containing alkylene group or a divalent fluorine-containing alkylene group containing an ether bond having 1 to 40 carbon atoms) and a fluorine-containing ethylenic monomer having at least one functional group Is possible.
- the polymerization unit based on the monomer (x) is preferably 5 mol% or less, more preferably 4.5 mol% or less, and more preferably less than 4 mol% of the total polymerization units. More preferably, it is still more preferable that it is less than 3 mol%.
- the PVdF preferably has a weight average molecular weight (in terms of polystyrene) of 50,000 to 2,000,000. More preferably, it is 80000 to 1700000, and further preferably 100000 to 1500,000.
- the weight average molecular weight can be measured at 50 ° C. using N, N-dimethylformamide as a solvent by gel permeation chromatography (GPC).
- the PVdF preferably has a number average molecular weight (polystyrene conversion) of 35,000 to 1400000. When it is less than 35,000, the adhesion of the obtained electrode is lowered. When it exceeds 1400000, it will become easy to gelatinize when preparing an electrode mixture.
- the number average molecular weight is preferably 40000 or more, more preferably 50000 or more, still more preferably 60000 or more, preferably 1300000 or less, and more preferably 1200000 or less.
- the number average molecular weight can be measured by gel permeation chromatography (GPC) at 50 ° C. using N, N-dimethylformamide as a solvent.
- the PVdF is conventionally known, for example, by suitably mixing VdF forming a polymerization unit and the monomer (x) and an additive such as a polymerization initiator to perform solution polymerization, suspension polymerization, or emulsion polymerization. It can manufacture by the method of.
- VdF / TFE copolymer is a copolymer comprising polymerized units based on VdF (VdF units) and polymerized units based on TFE (TFE units).
- the VdF / TFE copolymer preferably contains 50 to 95 mol% of VdF units with respect to all polymerized units. When the VdF unit is less than 50 mol%, the change with time of the viscosity of the electrode mixture increases, and when it exceeds 95 mol%, the flexibility of the electrode obtained from the mixture tends to be inferior.
- the VdF / TFE copolymer preferably contains 55 mol% or more, more preferably 60 mol% or more of VdF units based on all polymerized units. Further, the VdF / TFE copolymer preferably contains 92 mol% or less, more preferably 89 mol% or less, of VdF units based on the total polymerization units.
- the composition of the VdF / TFE copolymer can be measured using an NMR analyzer.
- the VdF / TFE copolymer may contain a polymer unit based on a monomer that can be copolymerized with VdF and TFE in addition to the VdF unit and the TFE unit.
- a copolymer of VdF and TFE is sufficient, but a monomer that can be copolymerized with them to such an extent that the excellent electrolytic solution swelling resistance of the copolymer is not impaired.
- the body can be copolymerized to further improve adhesion.
- the content of polymerized units based on monomers that can be copolymerized with VdF and TFE is preferably less than 3.0 mol% based on the total polymerized units of the VdF / TFE copolymer.
- it is 3.0 mol% or more, generally the crystallinity of the copolymer of VdF and TFE is remarkably lowered, and as a result, the electrolytic solution swelling resistance tends to be lowered.
- Examples of monomers that can be copolymerized with VdF and TFE include unsaturated dibasic acid monoesters such as maleic acid monomethyl ester, citraconic acid monomethyl ester, and citraconic acid as described in JP-A-6-172245.
- the adhesiveness with the collector which consists of metal foils of aluminum or copper by giving the flexibility to the material by slightly lowering the crystallinity of the above-mentioned fluoropolymer other than the compound containing the polar group as described above.
- the improvement can be inferred from previous studies.
- fluoromonomers such as ethylene trifluoride and hexafluoropropylene.
- Z is —CH 2 OH, —COOH, carboxylate, carboxyl ester group or epoxy group
- X and X ′ are the same or different, and both are hydrogen atoms or fluorine atoms
- R f is 1 to 40 carbon atoms.
- a divalent fluorine-containing alkylene group or a divalent fluorine-containing alkylene group containing an ether bond having 1 to 40 carbon atoms) and a fluorine-containing ethylenic monomer having at least one functional group Is possible.
- the VdF / TFE copolymer may contain other polymerization units in addition to the VdF unit and the TFE unit, but more preferably comprises only the VdF unit and the TFE unit.
- the VdF / TFE copolymer preferably has a weight average molecular weight (polystyrene conversion) of 50,000 to 2,000,000. More preferably, it is 80000 to 1700000, and still more preferably 100000 to 1500,000.
- the weight average molecular weight can be measured at 50 ° C. using N, N-dimethylformamide as a solvent by gel permeation chromatography (GPC).
- the VdF / TFE copolymer preferably has a number average molecular weight (in terms of polystyrene) of 35000 to 1400000. More preferably, it is 40,000 to 1300000, and still more preferably 50000 to 1200000.
- the number average molecular weight can be measured by gel permeation chromatography (GPC) at 50 ° C. using N, N-dimethylformamide as a solvent.
- VdF / TFE copolymer for example, monomers such as VdF and TFE that form polymerization units and additives such as a polymerization initiator are appropriately mixed, and suspension polymerization or emulsion polymerization is performed.
- a method of performing solution polymerization or the like can be employed, aqueous suspension polymerization and emulsion polymerization are preferable from the viewpoint of ease of post-treatment and the like.
- a polymerization initiator, a surfactant, a chain transfer agent, and a solvent can be used, and conventionally known ones can be used.
- the VdF / HFP copolymer is a copolymer comprising polymerized units based on VdF (VdF units) and polymerized units based on HFP (HFP units).
- the VdF / HFP copolymer preferably contains 80 to 98 mol% of VdF units with respect to all polymerized units. When the VdF unit is less than 80 mol%, the resulting electrode has a large swelling property with respect to the electrolyte, and the battery characteristics are greatly reduced. When the VdF unit is more than 98 mol%, the flexibility of the electrode obtained from the mixture tends to be inferior. is there.
- the VdF / HFP copolymer preferably contains VdF units in an amount of 83 mol% or more, more preferably 85 mol% or more based on the total polymerization units.
- the VdF / HFP copolymer preferably contains 97 mol% or less, more preferably 96 mol% or less of VdF units based on the total polymerization units.
- the composition of the VdF / HFP copolymer can be measured using an NMR analyzer.
- the VdF / HFP copolymer may contain a polymer unit based on a monomer that can be copolymerized with VdF and HFP in addition to the VdF unit and the HFP unit.
- a copolymer of VdF and HFP is sufficient, but a single amount that can be copolymerized with them to such an extent that the excellent electrolytic solution swelling resistance of the copolymer is not impaired.
- the body can be copolymerized to further improve adhesion.
- the content of polymerized units based on monomers that can be copolymerized with VdF and HFP is preferably less than 3.0 mol% based on the total polymerized units of the VdF / HFP copolymer.
- it is 3.0 mol% or more, generally, the crystallinity of the copolymer of VdF and HFP is remarkably lowered, and as a result, the electrolytic solution swelling resistance tends to be lowered.
- Examples of the monomer that can be copolymerized with VdF and HFP include the same monomers and TFE as the monomers that can be copolymerized with VdF and TFE exemplified for the VdF / TFE copolymer.
- the VdF / HFP copolymer preferably has a weight average molecular weight (polystyrene conversion) of 50,000 to 2,000,000. More preferably, it is 80000 to 1700000, and still more preferably 100000 to 1500,000.
- the weight average molecular weight can be measured at 50 ° C. using N, N-dimethylformamide as a solvent by gel permeation chromatography (GPC).
- the VdF / HFP copolymer preferably has a number average molecular weight (polystyrene conversion) of 35000 to 1400000. More preferably, it is 40,000 to 1300000, and still more preferably 50000 to 1200000.
- the number average molecular weight can be measured by gel permeation chromatography (GPC) at 50 ° C. using N, N-dimethylformamide as a solvent.
- Examples of the method for producing the VdF / HFP copolymer include suspension polymerization and emulsion polymerization by appropriately mixing monomers such as VdF and HFP forming polymerization units and additives such as a polymerization initiator. Although a method of performing solution polymerization or the like can be employed, aqueous suspension polymerization and emulsion polymerization are preferable from the viewpoint of ease of post-treatment and the like. In the above polymerization, a polymerization initiator, a surfactant, a chain transfer agent, and a solvent can be used, and conventionally known ones can be used.
- the VdF / CTFE copolymer is a copolymer comprising polymerized units based on VdF (VdF units) and polymerized units based on CTFE (CTFE units).
- the VdF / CTFE copolymer preferably contains 80 to 98 mol% of VdF units based on all polymerized units. Even if the VdF unit is less than 80 mol% or more than 98 mol%, the change with time of the viscosity of the electrode mixture becomes large. Further, the VdF / CTFE copolymer preferably contains 97.5 mol% or less, and more preferably 97 mol% or less of VdF units based on the total polymerization units. The VdF / CTFE copolymer preferably contains 85% by mole or more, more preferably 90% by mole or more of VdF units with respect to all the polymerized units. The composition of the VdF / CTFE copolymer can be measured using an NMR analyzer.
- the VdF / CTFE copolymer may include a polymer unit based on a monomer that can be copolymerized with VdF and CTFE in addition to the VdF unit and the CTFE unit.
- a copolymer of VdF and CTFE is sufficient, but a monomer that can be copolymerized with them to such an extent that the excellent electrolytic solution swelling resistance of the copolymer is not impaired.
- the body can be copolymerized to further improve adhesion.
- the content of polymerized units based on monomers that can be copolymerized with VdF and CTFE is preferably less than 3.0 mol% based on the total polymerized units of the VdF / CTFE copolymer.
- it is 3.0 mol% or more, generally the crystallinity of the copolymer of VdF and CTFE is remarkably lowered, and as a result, the electrolytic solution swelling resistance tends to be lowered.
- Examples of the monomer that can be copolymerized with VdF and CTFE include monomers similar to the monomers that can be copolymerized with VdF and TFE exemplified for the VdF / TFE copolymer, and TFE and HFP. it can.
- the VdF / CTFE copolymer preferably has a weight average molecular weight (in terms of polystyrene) of 50,000 to 2,000,000. More preferably, it is 80000 to 1700000, and still more preferably 100000 to 1500,000.
- the weight average molecular weight can be measured at 50 ° C. using N, N-dimethylformamide as a solvent by gel permeation chromatography (GPC).
- the VdF / CTFE copolymer preferably has a number average molecular weight (polystyrene conversion) of 35,000 to 1400000. More preferably, it is 40,000 to 1300000, and still more preferably 50000 to 1200000.
- the number average molecular weight can be measured by gel permeation chromatography (GPC) at 50 ° C. using N, N-dimethylformamide as a solvent.
- Examples of a method for producing the VdF / CTFE copolymer include suspension polymerization and emulsion polymerization by appropriately mixing monomers such as VdF and CTFE forming polymerization units and additives such as a polymerization initiator. Although a method of performing solution polymerization or the like can be employed, aqueous suspension polymerization and emulsion polymerization are preferable from the viewpoint of ease of post-treatment and the like. In the above polymerization, a polymerization initiator, a surfactant, a chain transfer agent, and a solvent can be used, and conventionally known ones can be used.
- the VdF / 2,3,3,3-tetrafluoropropene copolymer includes polymerized units based on VdF (VdF units) and polymerized units based on 2,3,3,3-tetrafluoropropene (2,3,3 , 3-tetrafluoropropene unit).
- the VdF / 2,3,3,3-tetrafluoropropene copolymer preferably contains 80 to 98 mol% of VdF units with respect to all polymerized units. Even if the VdF unit is less than 80 mol% or more than 98 mol%, the change with time of the viscosity of the electrode mixture becomes large.
- the VdF / 2,3,3,3-tetrafluoropropene copolymer preferably contains 97.5 mol% or less, more preferably 97 mol% or less of VdF units based on the total polymerization units. preferable.
- the VdF / 2,3,3,3-tetrafluoropropene copolymer preferably contains 85 mol% or more, more preferably 90 mol% or more of VdF units based on the total polymerization units.
- the composition of the VdF / 2,3,3,3-tetrafluoropropene copolymer can be measured using an NMR analyzer.
- the VdF / 2,3,3,3-tetrafluoropropene copolymer includes VdF and 2,3,3,3-tetrafluoro in addition to VdF units and 2,3,3,3-tetrafluoropropene units. It may contain a polymerized unit based on a monomer copolymerizable with propene. In order to achieve the effect of the present invention, a copolymer of VdF and 2,3,3,3-tetrafluoropropene is sufficient, but further does not impair the excellent electrolytic solution swelling resistance of the copolymer. Adhesiveness can be further improved by copolymerizing monomers capable of copolymerizing with them to an extent.
- the content of polymerized units based on the monomer capable of copolymerizing with VdF and 2,3,3,3-tetrafluoropropene is the total content of the VdF / 2,3,3,3-tetrafluoropropene copolymer.
- the amount is preferably less than 3.0 mol% based on the polymerized units. When it is 3.0 mol% or more, generally, the crystallinity of the copolymer of VdF and 2,3,3,3-tetrafluoropropene is remarkably lowered, and as a result, the electrolytic solution swelling resistance tends to be lowered. is there.
- Monomers that can be copolymerized with VdF and 2,3,3,3-tetrafluoropropene are the same monomers as those that can be copolymerized with VdF and TFE exemplified for the VdF / TFE copolymer. Mention may be made of monomers, TFE and HFP.
- the VdF / 2,3,3,3-tetrafluoropropene copolymer preferably has a weight average molecular weight (in terms of polystyrene) of 50,000 to 2,000,000. More preferably, it is 80000 to 1700000, and still more preferably 100000 to 1500,000.
- the weight average molecular weight can be measured at 50 ° C. using N, N-dimethylformamide as a solvent by gel permeation chromatography (GPC).
- the VdF / 2,3,3,3-tetrafluoropropene copolymer preferably has a number average molecular weight (in terms of polystyrene) of 35,000 to 1400000. More preferably, it is 40,000 to 1300000, and still more preferably 50000 to 1200000.
- the number average molecular weight can be measured by gel permeation chromatography (GPC) at 50 ° C. using N, N-dimethylformamide as a solvent.
- VdF / 2,3,3,3-tetrafluoropropene copolymer for example, monomers such as VdF and CTFE that form polymerization units, and additives such as a polymerization initiator are appropriately used.
- a method of mixing and performing suspension polymerization, emulsion polymerization, solution polymerization and the like can be employed, but aqueous suspension polymerization and emulsion polymerization are preferred from the viewpoint of ease of post-treatment.
- a polymerization initiator, a surfactant, a chain transfer agent, and a solvent can be used, and conventionally known ones can be used.
- VdF polymers PVdF and VdF / TFE copolymers are preferable, and PVdF is more preferable.
- the mass ratio of the fluoropolymer to the VdF polymer (fluoropolymer) / (VdF polymer) is preferably 90/10 to 10/90, more preferably 80/20 to 13/87. 75/25 to 15/85 is more preferable.
- the binder of the present invention is used for a secondary battery.
- the fluorine-containing polymer is suitable as a binder used for an electrode of a secondary battery because it has good adhesion to a current collector and excellent flexibility.
- the binder of the present invention can also be used as a binder for a separator coating of a secondary battery.
- the binder for a secondary battery includes a binder used for a positive electrode, a negative electrode, and a separator of a secondary battery.
- the secondary battery is preferably a lithium ion secondary battery.
- the binder of this invention can also comprise an electrode mixture with an active material, water, or a nonaqueous solvent.
- the secondary battery to which the binder of the present invention is applied includes a positive electrode in which a positive electrode mixture is held on a positive electrode current collector, a negative electrode in which a negative electrode mixture is held on a negative electrode current collector, and electrolysis It has liquid. Below, the example of the mixture for electrode manufacture of a battery using the binder of this invention is demonstrated.
- non-aqueous electrolyte batteries that use organic or non-aqueous electrolytes as electrolytes, such as lithium ion secondary batteries, improved low heavy load performance due to the low conductivity of non-aqueous electrolytes For this reason, the active material layer is thinned to increase the electrode area.
- a current collector made of a metal foil such as iron, stainless steel, copper, aluminum, nickel, titanium, or a metal net, a fine powdery active material, a conductive agent such as carbon, and a binder. It has been attempted to apply and bond an electrode mixture forming composition to be an electrode. It is necessary to reduce the amount of the binder used as much as possible, and it is required to maintain the active material and the like even with a small amount and to have excellent adhesion to the current collector. In addition, since the binder is usually electrically insulating, an increase in the amount of use increases the internal resistance of the battery. Also in this respect, the binder is required to perform its function with the smallest possible use amount.
- the amount of the binder is very small and is preferably 30% by mass or less based on the total electrode mixture. With such a small amount of binder, the binder cannot completely fill the gaps between the fine particle components of the electrode mixture or between the fine particle components and the current collector. In the case of paints and lining materials containing fillers such as pigments, the binder uses a sufficient amount of binder to completely fill the gaps between the fillers. Almost no problem. However, in the case of a binder for electrodes, the amount used is extremely small as described above, and a material that retains the active material well even in a small amount and has excellent adhesion to the current collector is required.
- the present invention is also an electrode mixture for a secondary battery obtained by mixing at least the binder for a secondary battery of the present invention described above, a powder electrode material for a battery, and water or a non-aqueous solvent.
- the above electrode mixture is a secondary formed by mixing a solution or dispersion obtained by dispersing or dissolving the above-described binder for a secondary battery of the present invention in water or a nonaqueous solvent, and a powder electrode material for the battery.
- a battery electrode mixture is preferable. More preferably, it is an electrode mixture for lithium ion secondary batteries. Since the electrode mixture of the present invention contains the binder described above, an electrode material layer having excellent adhesion to the current collector and flexibility can be formed.
- the electrode mixture may be a positive electrode mixture used for preparing a positive electrode or a negative electrode mixture used for preparing a negative electrode, but is preferably a positive electrode mixture.
- the powder electrode material preferably contains an electrode active material.
- the electrode active material is divided into a positive electrode active material and a negative electrode active material.
- the positive electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions, but a lithium composite oxide is preferable, and a lithium transition metal composite oxide is preferable. More preferred.
- a lithium-containing transition metal phosphate compound is also preferable.
- the positive electrode active material is also preferably a material containing lithium and at least one transition metal, such as a lithium transition metal composite oxide or a lithium-containing transition metal phosphate compound.
- the transition metal of the lithium transition metal composite oxide is preferable as the transition metal of the lithium transition metal composite oxide
- a specific example of the lithium transition metal composite oxide is a lithium-cobalt composite such as LiCoO 2.
- the above-mentioned substitutes include lithium / nickel / manganese composite oxide, lithium / nickel / cobalt / aluminum composite oxide, lithium / nickel / cobalt / manganese composite oxide, lithium / manganese / aluminum composite oxide, and lithium / titanium. Complex oxide etc.
- LiNi 0.5 Mn 0.5 O 2 LiNi 0.85 Co 0.10 Al 0.05 O 2 , LiNi 0.33 Co 0.33 Mn 0 .33 O 2 , LiNi 0.5 Mn 0.3 Co 0.2 O 2 , LiNi 0.6 Mn 0.2 Co 0.2 O 2 , LiNi 0.8 Mn 0.1 Co 0.1 O 2 , LiMn 1.8 Al 0.2 O 4, LiMn 1.5 Ni 0.5 O 4, Li 4 Ti 5 O 12, LiNi 0.82 Co 0.15 l 0.03 O 2 and the like.
- the transition metal of the lithium-containing transition metal phosphate compound V, Ti, Cr, Mn, Fe, Co, Ni, Cu and the like are preferable.
- the lithium-containing transition metal phosphate compound include LiFePO 4 , Li 3 Fe 2 (PO 4 ) 3 , iron phosphates such as LiFeP 2 O 7 , cobalt phosphates such as LiCoPO 4 , and some of the transition metal atoms that are the main components of these lithium transition metal phosphate compounds are Al , Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si and the like substituted with other metals.
- LiCoO 2 , LiNiO 2 , LiMn 2 O 4 , LiNi 0.82 Co 0.15 Al 0.03 O 2 , LiNi 0.33 Mn 0.33 Co 0.33 O 2 , LiNi 0.5 Mn 0.3 Co 0.2 O 2 , LiNi 0.6 Mn 0.2 Co 0.2 O 2 , LiNi 0.8 Mn 0.1 Co 0.1 O 2 and LiFePO 4 are preferred.
- a material in which a substance having a composition different from that of the substance constituting the main cathode active material is attached to the surface of the cathode active material can be used.
- Surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate And sulfates such as aluminum sulfate and carbonates such as lithium carbonate, calcium carbonate and magnesium carbonate.
- These surface adhering substances are, for example, a method of dissolving or suspending in a solvent and impregnating and drying the positive electrode active material, and a method of dissolving or suspending a surface adhering substance precursor in a solvent and impregnating and adding to the positive electrode active material, followed by heating. It can be made to adhere to the positive electrode active material surface by the method of making it react by the method etc., the method of adding to a positive electrode active material precursor, and baking simultaneously.
- the amount of the surface adhering substance is by mass with respect to the positive electrode active material, preferably 0.1 ppm or more, more preferably 1 ppm or more, still more preferably 10 ppm or more, and the upper limit is preferably 20% or less, more preferably 10%. % Or less, more preferably 5% or less.
- the surface adhering substance can suppress the oxidation reaction of the non-aqueous electrolyte solution on the surface of the positive electrode active material, and can improve the battery life. However, when the amount of the adhering quantity is too small, the effect is not sufficiently exhibited. If the amount is too large, the resistance may increase in order to inhibit the entry and exit of lithium ions.
- the shape of the positive electrode active material particles a lump shape, a polyhedron shape, a spherical shape, an elliptical spherical shape, a plate shape, a needle shape, a columnar shape, etc., which are conventionally used, are used. It is preferable that the secondary particles have a spherical shape or an elliptical shape.
- an electrochemical element expands and contracts as the active material in the electrode expands and contracts as it is charged and discharged. Therefore, the active material is easily damaged due to the stress or the conductive path is broken.
- the primary particles are aggregated to form secondary particles, rather than a single particle active material having only primary particles, in order to relieve expansion and contraction stress and prevent deterioration.
- spherical or oval spherical particles are less oriented during molding of the electrode than plate-like equiaxed particles, so that the expansion and contraction of the electrode during charging and discharging is small, and the electrode is produced.
- the mixing with the conductive agent is also preferable because it can be easily mixed uniformly.
- the tap density of the positive electrode active material is usually 1.3 g / cm 3 or more, preferably 1.5 g / cm 3 or more, more preferably 1.6 g / cm 3 or more, and most preferably 1.7 g / cm 3 or more. . If the tap density of the positive electrode active material is lower than the lower limit, the amount of the required dispersion medium increases when the positive electrode active material layer is formed, and the necessary amount of the conductive material and the binder increases. In some cases, the filling rate of the substance is limited, and the battery capacity is limited. By using a metal composite oxide powder having a high tap density, a high-density positive electrode active material layer can be formed. In general, the tap density is preferably as large as possible, but there is no particular upper limit.
- the tap density is 2.5 g / cm 3 or less, preferably 2.4 g / cm 3 or less.
- the tap density of the positive electrode active material is measured by passing a sieve having a mesh size of 300 ⁇ m, dropping the sample onto a 20 cm 3 tapping cell to fill the cell volume, and then measuring a powder density measuring device (for example, tap denser manufactured by Seishin Enterprise Co., Ltd.). ), A tapping with a stroke length of 10 mm is performed 1000 times, and the density obtained from the volume at that time and the weight of the sample is defined as the tap density.
- a powder density measuring device for example, tap denser manufactured by Seishin Enterprise Co., Ltd.
- the median diameter d50 (secondary particle diameter when primary particles are aggregated to form secondary particles) of the positive electrode active material particles is usually 0.1 ⁇ m or more, preferably 0.5 ⁇ m or more, more preferably 1 ⁇ m. Above, most preferably 3 ⁇ m or more, usually 20 ⁇ m or less, preferably 18 ⁇ m or less, more preferably 16 ⁇ m or less, and most preferably 15 ⁇ m or less. If the lower limit is not reached, a high bulk density product may not be obtained, and if the upper limit is exceeded, it takes time for the diffusion of lithium in the particles. When a conductive agent, a binder, or the like is slurried with a solvent and applied as a thin film, problems such as streaking may occur.
- the median diameter d50 in the present invention is measured by a known laser diffraction / scattering particle size distribution measuring apparatus.
- LA-920 manufactured by HORIBA is used as a particle size distribution meter
- a 0.1% by mass sodium hexametaphosphate aqueous solution is used as a dispersion medium for measurement, and a measurement refractive index of 1.24 is set after ultrasonic dispersion for 5 minutes. Measured.
- the average primary particle diameter of the positive electrode active material is usually 0.01 ⁇ m or more, preferably 0.05 ⁇ m or more, more preferably 0.08 ⁇ m or more, Most preferably, it is 0.1 ⁇ m or more, usually 3 ⁇ m or less, preferably 2 ⁇ m or less, more preferably 1 ⁇ m or less, and most preferably 0.6 ⁇ m or less. If the above upper limit is exceeded, it is difficult to form spherical secondary particles, which adversely affects the powder filling property, or the specific surface area is greatly reduced, so that there is a high possibility that battery performance such as output characteristics will deteriorate. is there.
- the primary particle diameter is measured by observation using a scanning electron microscope (SEM). Specifically, in a photograph at a magnification of 10000 times, the longest value of the intercept by the left and right boundary lines of the primary particles with respect to the horizontal straight line is obtained for any 50 primary particles and obtained by taking the average value. It is done.
- the BET specific surface area of the positive electrode active material is 0.2 m 2 / g or more, preferably 0.3 m 2 / g or more, more preferably 0.4 m 2 / g or more, 4.0 m 2 / g or less, preferably 2 .5m 2 / g or less, still more preferably not more than 1.5 m 2 / g. If the BET specific surface area is smaller than this range, the battery performance tends to be lowered, and if the BET specific surface area is larger, the tap density is difficult to increase, and there may be a problem in applicability when forming the positive electrode active material.
- the BET specific surface area is determined by using a surface area meter (for example, a fully automated surface area measuring device manufactured by Okura Riken), preliminarily drying the sample for 30 minutes at 150 ° C. under nitrogen flow, and then measuring the relative pressure of nitrogen relative to atmospheric pressure. It is defined by a value measured by a nitrogen adsorption BET one-point method using a gas flow method using a nitrogen-helium mixed gas that is accurately adjusted to have a value of 0.3.
- a surface area meter for example, a fully automated surface area measuring device manufactured by Okura Riken
- a general method is used as a manufacturing method of the inorganic compound.
- various methods are conceivable for producing a spherical or elliptical spherical active material.
- transition metal raw materials such as transition metal nitrates and sulfates and, if necessary, raw materials of other elements such as water.
- Dissolve or pulverize and disperse in a solvent adjust the pH while stirring, create and recover a spherical precursor, and dry it as necessary.
- LiOH, Li 2 CO 3 , LiNO 3 and other Li A method of obtaining an active material by adding a source and baking at a high temperature, transition metal raw materials such as transition metal nitrates, sulfates, hydroxides and oxides, and if necessary, raw materials of other elements in a solvent such as water Dissolve or pulverize and disperse in the powder and dry mold it with a spray drier to make a spherical or oval spherical precursor.
- a Li source such as LiOH, Li 2 CO 3 , or LiNO 3 and calcinate at a high temperature.
- Transition metal source materials such as transition metal nitrates, sulfates, hydroxides and oxides, Li sources such as LiOH, Li 2 CO 3 and LiNO 3 , and source materials of other elements as necessary, such as water
- Transition metal source materials such as transition metal nitrates, sulfates, hydroxides and oxides, Li sources such as LiOH, Li 2 CO 3 and LiNO 3 , and source materials of other elements as necessary, such as water
- Examples thereof include a method of dissolving or pulverizing and dispersing in a solvent and drying and molding it with a spray dryer or the like to obtain a spherical or elliptical precursor, which is fired at a high temperature to obtain an active material.
- one kind of positive electrode active material powder may be used alone, or two or more kinds having different compositions or different powder physical properties may be used in any combination and ratio.
- the negative electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions.
- the metal composite oxide is not particularly limited as long as it can occlude and release lithium, but preferably contains titanium and / or lithium as a constituent component from the viewpoint of high current density charge / discharge characteristics.
- carbonaceous material As a carbonaceous material, (1) natural graphite, (2) Artificial carbonaceous material and artificial graphite material; carbonaceous material ⁇ for example, natural graphite, coal-based coke, petroleum-based coke, coal-based pitch, petroleum-based pitch, or those obtained by oxidizing these pitches, needle coke, pitch Coke and carbon materials partially graphitized, furnace black, acetylene black, pyrolysis products of organic substances such as pitch-based carbon fibers, carbonizable organic substances (for example, coal tar pitch from soft pitch to hard pitch, or dry distillation liquefaction Heavy oil such as coal, heavy oil of normal pressure, straight oil of vacuum residue, crude oil, cracked petroleum heavy oil such as ethylene tar produced during thermal decomposition of naphtha, acenaphthylene, decacyclene , Aromatic hydrocarbons such as anthracene and phenanthrene, N-ring compounds such as phenazine and acridine, thiophene and bithioph
- Organic polymers such as cellulose, lignin, mannan, polygalacturonic acid, chitosan, natural polymers such as polysaccharides represented by sucrose, thermoplastic resins such as polyphenylene sulfide and polyphenylene oxide, furfuryl alcohol resin, phenol-formaldehyde Thermosetting resins such as resins and imide resins) and their carbides or carbonizable organic substances in low molecular organic solvents such as benzene, toluene, xylene, quinoline, n-hexane, and their charcoal Carbonaceous material things ⁇ heat treated one or more times in the range of 400 to 3200 ° C., (3) a carbonaceous material in which the negative electrode active material layer is composed of at least two types of carbonaceous materials having different crystallinity and / or has an interface in contact with the different crystalline carbonaceous materials, (4) a carbonaceous material in which the negative electrode active material layer is composed of carbonaceous materials having at
- the content of the electrode active material (positive electrode active material or negative electrode active material) is preferably 40% by mass or more in the electrode mixture in order to increase the capacity of the obtained electrode.
- the powder electrode material may further contain a conductive agent.
- a conductive agent examples include carbon blacks such as acetylene black and ketjen black, carbon materials such as graphite, carbon fibers, carbon nanotubes, and carbon nanohorns.
- the ratio of the powder component (active material and conductive agent) to the fluoropolymer in the electrode mixture is usually about 80:20 to 99.5: 0.5 by weight, and the powder component is retained. It is determined in consideration of the adhesion to the current collector and the conductivity of the electrode.
- the fluorine-containing polymer in the electrode mixture layer formed on the current collector, cannot completely fill the voids between the powder components, but the fluorine-containing polymer as a solvent. It is preferable to use a liquid that dissolves or disperses the polymer well, because the fluorine-containing polymer is uniformly dispersed and stitched in the electrode mixture layer after drying, and the powder component is well retained.
- Non-aqueous solvents include, for example, nitrogen-containing organic solvents such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide, and dimethylformamide; ketone solvents such as acetone, methyl ethyl ketone, cyclohexanone, and methyl isobutyl ketone; ethyl acetate And ester solvents such as butyl acetate; ether solvents such as tetrahydrofuran and dioxane; and low-boiling general-purpose organic solvents such as mixed solvents thereof.
- the liquid is preferably N-methyl-2-pyrrolidone and / or N, N-dimethylacetamide from the viewpoint of excellent stability and coating property of the electrode mixture.
- the amount of the liquid in the electrode mixture is determined in consideration of applicability to the current collector, thin film formation after drying, and the like.
- the weight ratio of the binder to the liquid is preferably 0.5: 99.5 to 20:80.
- the fluoropolymer is desirably used with a small particle size of an average particle size of 1000 ⁇ m or less, particularly 50 to 350 ⁇ m, in order to enable rapid dissolution or dispersion in the liquid.
- the electrode mixture may further contain, for example, an acrylic resin such as polymethacrylate and polymethyl methacrylate, polyimide, polyamide, and a polyamideimide resin. .
- an acrylic resin such as polymethacrylate and polymethyl methacrylate
- polyimide such as polyimide
- polyamide such as polyamide
- a polyamideimide resin such as polyamide
- you may add a crosslinking agent and irradiate radiation, such as a gamma ray and an electron beam, and may form a crosslinked structure.
- the crosslinking treatment method is not limited to radiation irradiation, and other crosslinking methods such as an amine group-containing compound or a cyanurate group-containing compound that can be thermally crosslinked may be added for thermal crosslinking.
- the electrode mixture may be added with a dispersant such as a resin-based surfactant, a cationic surfactant, or a nonionic surfactant.
- a dispersant such as a resin-based surfactant, a cationic surfactant, or a nonionic surfactant.
- the blending ratio of the binder of the present invention in the electrode mixture is preferably 0.1 to 20% by mass, more preferably 1 to 10% by mass of the electrode mixture.
- an electrode mixture containing the binder As a method for preparing an electrode mixture containing the binder, a method in which the powder electrode material is dispersed and mixed in a solution or dispersion obtained by dissolving or dispersing the binder in the liquid is generally used. . Then, the obtained electrode mixture is uniformly applied to a current collector such as a metal foil or a metal net, dried, and pressed as necessary to form a thin electrode mixture layer on the current collector to form a thin film electrode And
- the liquid may be added to produce a mixture.
- the powder of the binder and electrode material are heated and melted and extruded with an extruder to produce a thin film mixture, which is then bonded onto a current collector coated with a conductive adhesive or general-purpose organic solvent.
- An electrode sheet can also be produced.
- a binder solution or dispersion may be applied to a preformed electrode material.
- the application method as a binder is not specifically limited.
- the present invention is also an electrode for a secondary battery including the above-described binder for a secondary battery of the present invention. Since the electrode of the present invention contains the binder described above, the electrode material is not cracked even if the electrode material is thickly coated, wound, and pressed for high density, and the powder electrode material can be removed from the current collector. There is no peeling.
- the electrode preferably includes a current collector and an electrode material layer formed on the current collector and made of the powder electrode material and the binder.
- the electrode may be a positive electrode or a negative electrode, but is preferably a positive electrode.
- Examples of the current collector include metal foils such as iron, stainless steel, copper, aluminum, nickel, and titanium, or metal nets.
- metal foils such as iron, stainless steel, copper, aluminum, nickel, and titanium, or metal nets.
- the positive electrode current collector an aluminum foil or the like is preferable, and as the negative electrode current collector, a copper foil or the like is preferable.
- the electrode of the present invention can be produced, for example, by the method described above.
- This invention is also a secondary battery provided with the electrode for secondary batteries of this invention mentioned above.
- the secondary battery of the present invention at least one of the positive electrode and the negative electrode may be the above-described secondary battery electrode of the present invention, and the positive electrode is preferably the above-described secondary battery electrode of the present invention.
- the secondary battery is preferably a lithium ion secondary battery.
- the secondary battery of the present invention preferably further comprises a non-aqueous electrolyte.
- the non-aqueous electrolytic solution is not particularly limited, and examples of the organic solvent include propylene carbonate, ethylene carbonate, butylene carbonate, ⁇ -butyllactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, and dimethyl carbonate.
- Known hydrocarbon solvents such as diethyl carbonate; one or more of fluorine solvents such as fluoroethylene carbonate, fluoroether and fluorinated carbonate can be used.
- any conventionally known electrolyte can be used, and LiClO 4 , LiAsF 6 , LiPF 6 , LiBF 4 , LiCl, LiBr, CH 3 SO 3 Li, CF 3 SO 3 Li, cesium carbonate, and the like can be used.
- LiClO 4 , LiAsF 6 , LiPF 6 , LiBF 4 , LiCl, LiBr, CH 3 SO 3 Li, CF 3 SO 3 Li, cesium carbonate, and the like can be used.
- acrylic resins such as polymethacrylate and polymethylmethacrylate, polyimide, polyamide and polyamide
- An imide resin or the like may be used in combination.
- a separator may be interposed between the positive electrode and the negative electrode.
- a conventionally well-known thing may be used as a separator, and the separator which used the binder of this invention mentioned above for coating may be used.
- binder of the present invention for at least one of a positive electrode, a negative electrode, and a separator of a secondary battery (preferably a lithium ion secondary battery).
- a film for a secondary battery comprising the above-described binder of the present invention is also a preferred embodiment of the present invention.
- the laminated body for secondary batteries which has a base material and the layer which consists of the binder of this invention mentioned above formed on the said base material is also one of the suitable aspects of this invention.
- the substrate include those exemplified as the current collector, and known substrates (porous membranes) used for separators of secondary batteries.
- a mixed gas of tetrafluoroethylene / vinylidene fluoride 10/90 molar ratio was supplied so as to maintain the internal pressure of the tank, and 70 g of mixed gas was added by the end of the reaction. 3-Butenoic acid was continuously added in accordance with the supply of the mixed gas, and 0.54 g was added until the end of the reaction. After the addition of 70 g of mixed gas was completed, the gas in the tank was released and the reaction was terminated. The reaction product was washed with water and dried to obtain 69 g of fluoropolymer A. The composition and physical properties of the obtained fluoropolymer A are shown in Table 1.
- a mixed gas of tetrafluoroethylene / vinylidene fluoride 15/85 molar ratio was supplied so as to maintain the internal pressure of the tank, and 70 g of mixed gas was added by the end of the reaction. 3-Butenoic acid was continuously added in accordance with the supply of the mixed gas, and 0.44 g was added until the end of the reaction. After the addition of 70 g of mixed gas was completed, the gas in the tank was released and the reaction was terminated. The reaction product was washed with water and dried to obtain 69 g of fluoropolymer B. The composition and physical properties of the obtained fluoropolymer B are shown in Table 1.
- a mixed gas of tetrafluoroethylene / vinylidene fluoride 11/89 molar ratio was supplied so as to maintain the internal pressure of the tank, and 70 g of mixed gas was added by the end of the reaction. 4-Pentenoic acid was continuously added in accordance with the supply of the mixed gas, and 0.36 g was added by the end of the reaction. After the addition of 70 g of mixed gas was completed, the gas in the tank was released and the reaction was terminated. The reaction product was washed with water and dried to obtain 68 g of fluoropolymer C. The composition and physical properties of the obtained fluoropolymer C are shown in Table 1.
- a mixed gas of tetrafluoroethylene / vinylidene fluoride 15/85 molar ratio was supplied so as to maintain the internal pressure of the tank, and 70 g of mixed gas was added by the end of the reaction. 4-Pentenoic acid was continuously added in accordance with the supply of the mixed gas, and 0.43 g was added by the end of the reaction. After the addition of 70 g of mixed gas was completed, the gas in the tank was released and the reaction was terminated. The reaction product was washed with water and dried to obtain 69 g of fluoropolymer D. The composition and physical properties of the resulting fluoropolymer D are shown in Table 1.
- a mixed gas of tetrafluoroethylene / vinylidene fluoride 33/67 molar ratio was supplied so as to maintain the internal pressure of the tank, and 420 g of mixed gas was added by the end of the reaction. A total of 0.15 g of ammonium persulfate was added after the start of the reaction until the end of the reaction. After the addition of 420 g of the mixed gas was completed, the gas in the tank was released and the reaction was terminated. The inside of the tank was cooled to obtain an aqueous dispersion having a polymer solid content of 20.2% by mass. 8 g of 28 mass% aluminum sulfate aqueous solution was added to the obtained dispersion, and the slurry was filtered. The recovered slurry was washed with 2 L of pure water and dried to obtain 401 g of fluoropolymer X. The composition and physical properties of the resulting fluoropolymer X are shown in Table 1.
- Polymer composition 1 The ratio of VdF and TFE was measured in a DMF-d 7 solution state of the polymer by 19 F-NMR measurement using an NMR analyzer (manufactured by Agilent Technologies, VNS 400 MHz). The following peak areas (A, B, C, D) were determined by 19 F-NMR measurement, and the ratio of VdF to TFE was calculated.
- the molecular weight of TFE, VdF, 3-butenoic acid or 4-pentenoic acid so as to satisfy the following formula: 3-butenoic acid of the fluorinated polymer
- the ratio Y [mol%] of 4-pentenoic acid was determined.
- VdF ratio X VdF ⁇ (100 ⁇ Y) / 100 [mol%]
- TFE ratio X TFE ⁇ (100 ⁇ Y) / 100 [mol%]
- Ratio of 3-butenoic acid or 4-pentenoic acid Y [mol%]
- VdF ratio ⁇ 1- (molecular weight of maleic acid monomethyl ester) ⁇ ⁇ / [1- ⁇ (molecular weight of maleic acid monomethyl ester) ⁇ (molecular weight of VdF) ⁇ ⁇ ⁇ ] ⁇ 100 [mol%]
- Ratio of maleic acid monomethyl ester (molecular weight of VdF) ⁇ ⁇ / [1- ⁇ (molecular weight of maleic acid monomethyl ester) ⁇ (molecular weight of VdF) ⁇ ⁇ ⁇ ] ⁇ 100 [mol%]
- binder solution preparation of binder solution
- the binder fluorinated polymer
- NMP N-methyl-2-pyrrolidone
- the binder solution obtained above was cast on a glass plate and dried at 100 ° C. for 2 hours to obtain a film having a thickness of about 30 ⁇ m. These films were punched into a dumbbell shape having a shape conforming to ASTM D1708, and the elongation at break at 25 ° C. was measured by an autograph.
- a binder solution obtained by weighing a binder (fluorinated polymer) to a concentration of 8% by mass and dissolving it in N-methyl-2-pyrrolidone (NMP) was cast on a glass plate, and 100 The film was dried at 12 ° C. for 12 hours and further dried under vacuum at 100 ° C. for 12 hours to obtain a film having a thickness of about 40 ⁇ m. These films were cut into a length of 30 mm and a width of 5 mm to obtain samples.
- the positive electrode was produced as follows using the fluoropolymer of an Example and a comparative example, and various physical properties were measured and evaluated. The results are shown in Table 1.
- Table 1 shows the positive electrode active material (NMC (532) (LiNi 0.5 Mn 0.3 Co 0.2 O 2 )), conductive agent acetylene black (AB), and binder (fluorinated polymer). It was weighed so that the mass ratio shown was obtained. After dissolving the fluoropolymer in N-methyl-2-pyrrolidone (NMP) so as to have a concentration of 8% by mass, a predetermined amount of a positive electrode active material and a conductive agent are added to the NMP solution of the binder, Thorough mixing with a stirrer ensured good homogeneity. The solid content concentration in the slurry was 70%.
- the prepared slurry for positive electrode mixture was uniformly applied to an electrode current collector plate made of an aluminum foil having a thickness of 20 ⁇ m, and NMP was completely volatilized to produce a positive electrode.
- the produced electrode was rolled by a roll press machine until the density of the positive electrode mixture coating film reached a predetermined density.
- the density was calculated by measuring area / film thickness / weight.
- Electrode flexibility evaluation positive electrode bending test
- the produced positive electrode was cut into a length of 3 cm and a width of 6 cm, then folded 180 ° and then expanded, and the presence or absence of scratches or cracks on the positive electrode was visually confirmed.
- the evaluation was ⁇ , when the crack was confirmed, ⁇ , and when the positive electrode broke, it was evaluated as ⁇ . This evaluation was carried out for the electrode densities shown in Table 1.
- Electrode adhesion evaluation positive electrode peeling test
- the positive electrode active material NCA LiNi 0.82 Co 0.15 Al 0.03 O 2
- the conductive agent acetylene black (AB) and the binder (fluorinated polymer) are in a mass ratio of active material / AB /
- the polymer was weighed so as to be 93/4/3.
- NMP N-methyl-2-pyrrolidone
- a predetermined amount of a positive electrode active material and a conductive agent are added to the NMP solution of the binder, Thorough mixing with a stirrer ensured good homogeneity.
- the solid content concentration of the composition was 70%.
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Abstract
Description
ビニリデンフルオライドに基づく重合単位の含有量の上限は、94モル%であってもよく、89モル%であってもよい。
テトラフルオロエチレンに基づく重合単位の含有量の上限は、49.90モル%であってもよく、49.70モル%であってもよく、49.60モル%であってもよく、49モル%であってもよく、39.90モル%であってもよく、39.70モル%であってもよく、39.60モル%であってもよく、39モル%であってもよい。
これらの単量体を用いる場合、該単量体に基づく重合単位は、全重合単位に対して0.1~50モル%であることが好ましい。
また、電池特性が向上するという点で、より好ましくは80000~1950000であり、更に好ましくは100000~1900000、更により好ましくは200000~1900000である。
上記重量平均分子量は、ゲルパーミエーションクロマトグラフィ(GPC)により溶媒としてN,N-ジメチルホルムアミドを用い50℃で測定することができる。
上記数平均分子量は、ゲルパーミエーションクロマトグラフィ(GPC)により溶媒としてN,N-ジメチルホルムアミドを用い50℃で測定することができる。
測定サンプルは例えば、結着剤(含フッ素重合体)を濃度が8質量%になるよう秤量し、N-メチル-2-ピロリドン(NMP)に溶解させて得た結着剤溶液を、ガラス板上にキャストし100℃で12時間乾燥し、更に真空下で100℃で12時間乾燥し、得た厚さ40μmに成形したフィルムを、長さ30mm、巾5mmにカットすることで作製することができる。
(界面活性剤群[A])
CF3(CF2)4COONH4、CF3(CF2)3COONH4、CF3(CF2)2COONH4、CF3(CF2)3SO3Na、CF3(CF2)3SO2NH2等の含フッ素アニオン性アルキル界面活性剤類
(界面活性剤群[B])
式:CF3O-CF(CF3)CF2O-CXa(CF3)-Ya(式中、XaはH又はFを表し、Yaは-COOM1、-SO3M2、-SO2NM3M4又は-PO3M5M6を表す。上記M1、M2、M3、M4、M5及びM6は、同一又は異なって、H、NH4又は一価カチオンを表す。)又は、式:CF3O-CF2CF2CF2O-CFXaCF2-Ya(式中、XaはH又はFを表し、Yaは上記と同じ。)又は、式:CF3CF2O-CF2CF2O-CFXa-Ya(式中、XaはH又はFを表し、Yaは上記と同じ。)で表される含フッ素アニオン性アルキルエーテル界面活性剤類
(界面活性剤群[C])
CH2=CFCF2-O-(CF(CF3)CF2O)-CF(CF3)-COONH4等の、含フッ素アリルエーテル類
(界面活性剤群[D])
線状1-オクタンスルホン酸、線状2-オクタンスルホン酸、線状1,2-オクタンジスルホン酸、線状1-デカンスルホン酸、線状2-デカンスルホン酸、線状1,2-デカンジスルホン酸、線状1,2-ドデカンジスルホン酸、線状1-ドデカンスルホン酸、線状2-ドデカンスルホン酸、線状1,2-ドデカンジスルホン酸等のアルカンスルホン酸又はそれらの塩、1-オクチルスルフェート、2-オクチルスルフェート、1,2-オクチルジスルフェート、1-デシルスルフェート、2-デシルスルフェート、1,2-デシルジスルフェート、1-ドデシルスルフェート、2-ドデシルスルフェート、1,2-ドデシルジスルフェート等のアルキルスルフェート又はそれらの塩、ポリビニルホスホン酸又はその塩、ポリアクリル酸又はその塩、ポリビニルスルホン酸又はその塩等の非フッ素化界面活性剤類
(界面活性剤群[E])
ポリエチレングリコールアクリレート、ポリエチレングリコール、ポリエチレングリコールフェノールオキシド、ポリプロピレングリコールアクリレート及びポリプロピレングリコール等の非フッ素エーテル界面活性剤類
(界面活性剤群[F])
非フッ素界面活性剤(例えば、界面活性剤群[D]から選択される少なくとも1種)、及び分子量が400未満である含フッ素界面活性剤からなる群より選択される少なくとも1種の界面活性剤、及び官能性フルオロポリエーテル(フルオロポリオキシアルキレン鎖(例えば、式:-(CF2)j-CFZeO-(式中、ZeはF又は炭素数1~5の(パー)フルオロ(オキシ)アルキル基、jは0~3の整数)を繰り返し単位として1つ以上含む鎖)と官能基(例えば、カルボン酸基、ホスホン酸基、スルホン酸基及びそれらの酸塩型の基からなる群より選択される少なくとも1種)とを含む化合物)の混合物類
(界面活性剤群[G])
不活性化させた非フッ素界面活性剤類(例えば、ドデシル硫酸ナトリウム、直鎖状アルキルポリエーテルスルホン酸ナトリウム、シロキサン界面活性剤等の炭化水素含有界面活性剤を、過酸化水素又は後述する重合開始剤等と反応させたもの)
これらその他の成分の含有量は、含フッ素重合体に対して10~900質量%であることが好ましい。
上記重量平均分子量は、ゲルパーミエーションクロマトグラフィ(GPC)により溶媒としてN,N-ジメチルホルムアミドを用い50℃で測定することができる。
上記数平均分子量は、ゲルパーミエーションクロマトグラフィ(GPC)により溶媒としてN,N-ジメチルホルムアミドを用い50℃で測定することができる。
そのほか式:
上記重量平均分子量は、ゲルパーミエーションクロマトグラフィ(GPC)により溶媒としてN,N-ジメチルホルムアミドを用い50℃で測定することができる。
35000未満であると、得られた電極の密着性が低くなる。1400000を超えると、電極合剤を調製する際にゲル化しやすくなる。
上記数平均分子量は、40000以上が好ましく、50000以上がより好ましく、60000以上が更に好ましく、1300000以下が好ましく、1200000以下がより好ましい。
上記数平均分子量は、ゲルパーミエーションクロマトグラフィ(GPC)により溶媒としてN,N-ジメチルホルムアミドを用い50℃で測定することができる。
上記VdF/TFE共重合体は、VdF単位を全重合単位に対して55モル%以上含むことが好ましく、60モル%以上含むことがより好ましい。また、上記VdF/TFE共重合体は、VdF単位を全重合単位に対して92モル%以下含むことがより好ましく、89モル%以下含むことが更に好ましい。
上記VdF/TFE共重合体の組成は、NMR分析装置を用いて測定することができる。
上記VdF及びTFEと共重合し得る単量体に基づく重合単位の含有量は、上記VdF/TFE共重合体の全重合単位に対して3.0モル%未満が好ましい。3.0モル%以上であると、一般的にVdFとTFEの共重合体の結晶性が著しく低下し、その結果耐電解液膨潤性が低下する傾向がある。
ところで、以上のような極性基等を含む化合物以外でも上記含フッ素重合体の結晶性を少し低下させ材料に柔軟性を与えることによりアルミや銅の金属箔からなる集電体との接着性が向上しうることがこれまでの研究より類推できるようになった。これより、例えばエチレン、プロピレン等の不飽和炭化水素系モノマー(CH2=CHR、Rは水素原子、アルキル基又はCl等のハロゲン)や、フッ素系モノマーである3フッ化塩化エチレン、ヘキサフルオロプロピレン、ヘキサフルオロイソブテン、2,3,3,3-テトラフルオロプロペン、CF2=CF-O-CnF2n+1(nは1以上の整数)、CH2=CF-CnF2n+1(nは1以上の整数)、CH2=CF-(CF2CF2)nH(nは1以上の整数)、更にCF2=CF-O-(CF2CF(CF3)O)m-CnF2n+1(m、nは1以上の整数)も使用可能である。
そのほか式:
これら単量体の中でも、柔軟性と耐薬品性の観点から、ヘキサフルオロプロピレン、2,3,3,3-テトラフルオロプロペンが特に好ましい。
上記重量平均分子量は、ゲルパーミエーションクロマトグラフィ(GPC)により溶媒としてN,N-ジメチルホルムアミドを用い50℃で測定することができる。
上記数平均分子量は、ゲルパーミエーションクロマトグラフィ(GPC)により溶媒としてN,N-ジメチルホルムアミドを用い50℃で測定することができる。
上記重合においては、重合開始剤、界面活性剤、連鎖移動剤、及び、溶媒を使用することができ、それぞれ従来公知のものを使用することができる。
上記VdF/HFP共重合体は、VdF単位を全重合単位に対して83モル%以上含むことがより好ましく、85モル%以上含むことが更に好ましい。また、上記VdF/HFP共重合体は、VdF単位を全重合単位に対して97モル%以下含むことがより好ましく、96モル%以下含むことが更に好ましい。
上記VdF/HFP共重合体の組成は、NMR分析装置を用いて測定することができる。
上記VdF及びHFPと共重合し得る単量体に基づく重合単位の含有量は、上記VdF/HFP共重合体の全重合単位に対して3.0モル%未満が好ましい。3.0モル%以上であると、一般的にVdFとHFPの共重合体の結晶性が著しく低下し、その結果耐電解液膨潤性が低下する傾向がある。
上記重量平均分子量は、ゲルパーミエーションクロマトグラフィ(GPC)により溶媒としてN,N-ジメチルホルムアミドを用い50℃で測定することができる。
上記数平均分子量は、ゲルパーミエーションクロマトグラフィ(GPC)により溶媒としてN,N-ジメチルホルムアミドを用い50℃で測定することができる。
上記重合においては、重合開始剤、界面活性剤、連鎖移動剤、及び、溶媒を使用することができ、それぞれ従来公知のものを使用することができる。
上記VdF/CTFE共重合体は、VdF単位を全重合単位に対して85モル%以上含むことが好ましく、90モル%以上含むことがより好ましい。
上記VdF/CTFE共重合体の組成は、NMR分析装置を用いて測定することができる。
上記VdF及びCTFEと共重合し得る単量体に基づく重合単位の含有量は、上記VdF/CTFE共重合体の全重合単位に対して3.0モル%未満が好ましい。3.0モル%以上であると、一般的にVdFとCTFEの共重合体の結晶性が著しく低下し、その結果耐電解液膨潤性が低下する傾向がある。
上記重量平均分子量は、ゲルパーミエーションクロマトグラフィ(GPC)により溶媒としてN,N-ジメチルホルムアミドを用い50℃で測定することができる。
上記数平均分子量は、ゲルパーミエーションクロマトグラフィ(GPC)により溶媒としてN,N-ジメチルホルムアミドを用い50℃で測定することができる。
上記重合においては、重合開始剤、界面活性剤、連鎖移動剤、及び、溶媒を使用することができ、それぞれ従来公知のものを使用することができる。
上記VdF/2,3,3,3-テトラフルオロプロペン共重合体は、VdF単位を全重合単位に対して85モル%以上含むことが好ましく、90モル%以上含むことがより好ましい。
上記VdF/2,3,3,3-テトラフルオロプロペン共重合体の組成は、NMR分析装置を用いて測定することができる。
上記VdF及び2,3,3,3-テトラフルオロプロペンと共重合し得る単量体に基づく重合単位の含有量は、上記VdF/2,3,3,3-テトラフルオロプロペン共重合体の全重合単位に対して3.0モル%未満が好ましい。3.0モル%以上であると、一般的にVdFと2,3,3,3-テトラフルオロプロペンの共重合体の結晶性が著しく低下し、その結果耐電解液膨潤性が低下する傾向がある。
上記重量平均分子量は、ゲルパーミエーションクロマトグラフィ(GPC)により溶媒としてN,N-ジメチルホルムアミドを用い50℃で測定することができる。
上記数平均分子量は、ゲルパーミエーションクロマトグラフィ(GPC)により溶媒としてN,N-ジメチルホルムアミドを用い50℃で測定することができる。
上記重合においては、重合開始剤、界面活性剤、連鎖移動剤、及び、溶媒を使用することができ、それぞれ従来公知のものを使用することができる。
以下に、本発明の結着剤を用いた、電池の電極製造用合剤の例について説明する。
(1)天然黒鉛、
(2)人造炭素質物質並びに人造黒鉛質物質;炭素質物質{例えば天然黒鉛、石炭系コークス、石油系コークス、石炭系ピッチ、石油系ピッチ、或いはこれらピッチを酸化処理したもの、ニードルコークス、ピッチコークス及びこれらを一部黒鉛化した炭素材、ファーネスブラック、アセチレンブラック、ピッチ系炭素繊維等の有機物の熱分解物、炭化可能な有機物(例えば軟ピッチから硬ピッチまでのコールタールピッチ、或いは乾留液化油等の石炭系重質油、常圧残油、減圧残油の直留系重質油、原油、ナフサ等の熱分解時に副生するエチレンタール等分解系石油重質油、更にアセナフチレン、デカシクレン、アントラセン、フェナントレン等の芳香族炭化水素、フェナジンやアクリジン等のN環化合物、チオフェン、ビチオフェン等のS環化合物、ビフェニル、テルフェニル等のポリフェニレン、ポリ塩化ビニル、ポリビニルアルコール、ポリビニルブチラール、これらのものの不溶化処理品、含窒素性のポリアクリロニトリル、ポリピロール等の有機高分子、含硫黄性のポリチオフェン、ポリスチレン等の有機高分子、セルロース、リグニン、マンナン、ポリガラクトウロン酸、キトサン、サッカロースに代表される多糖類等の天然高分子、ポリフェニレンサルファイド、ポリフェニレンオキシド等の熱可塑性樹脂、フルフリルアルコール樹脂、フェノール-ホルムアルデヒド樹脂、イミド樹脂等の熱硬化性樹脂)及びこれらの炭化物、又は炭化可能な有機物をベンゼン、トルエン、キシレン、キノリン、n-へキサン等の低分子有機溶媒に溶解させた溶液及びこれらの炭化物}を400から3200℃の範囲で一回以上熱処理された炭素質材料、
(3)負極活物質層が少なくとも2種類以上の異なる結晶性を有する炭素質から成り立ちかつ/又はその異なる結晶性の炭素質が接する界面を有している炭素質材料、
(4)負極活物質層が少なくとも2種類以上の異なる配向性を有する炭素質から成り立ちかつ/又はその異なる配向性の炭素質が接する界面を有している炭素質材料、
から選ばれるものが初期不可逆容量、高電流密度充放電特性のバランスが良く好ましい。
なかでも、上記液体としては、電極合剤の安定性、塗工性に優れている点から、N-メチル-2-ピロリドン、及び/又は、N,N-ジメチルアセトアミドであることが好ましい。
攪拌機を備えた内容積2Lのオートクレーブに純水0.6kgとメチルセルロース0.6gを投入し、十分に窒素置換を行った後、1,1,1,3,3-ペンタフルオロブタン0.57kgを仕込み、系内を37℃に保った。テトラフルオロエチレン/ビニリデンフルオライド=5/95モル比の混合ガスを仕込み、槽内圧を1.5MPaにした。3-ブテン酸0.20g、ジ-n-プロピルパーオキシジカーボネートの50質量%メタノール溶液を0.5g添加して重合を開始した。槽内圧を保つようにテトラフルオロエチレン/フッ化ビニリデン=10/90モル比の混合ガスを供給し、反応終了までに70gの混合ガスを追加した。3-ブテン酸を混合ガスの供給に合わせて連続的に追加し、反応終了までに0.54g追加した。混合ガス70g追加完了後、槽内ガスを放出し、反応を終了させた。
反応生成物を水洗、乾燥して、含フッ素重合体Aを69g得た。
得られた含フッ素重合体Aの組成及び物性は表1に示す。
攪拌機を備えた内容積2Lのオートクレーブに純水0.6kgとメチルセルロース0.6gを投入し、十分に窒素置換を行った後、1,1,1,3,3-ペンタフルオロブタン0.57kgを仕込み、系内を37℃に保った。テトラフルオロエチレン/ビニリデンフルオライド=7/93モル比の混合ガスを仕込み、槽内圧を1.5MPaにした。3-ブテン酸0.29g、ジ-n-プロピルパーオキシジカーボネートの50質量%メタノール溶液を0.5g添加して重合を開始した。槽内圧を保つようにテトラフルオロエチレン/フッ化ビニリデン=15/85モル比の混合ガスを供給し、反応終了までに70gの混合ガスを追加した。3-ブテン酸を混合ガスの供給に合わせて連続的に追加し、反応終了までに0.44g追加した。混合ガス70g追加完了後、槽内ガスを放出し、反応を終了させた。
反応生成物を水洗、乾燥して、含フッ素重合体Bを69g得た。
得られた含フッ素重合体Bの組成及び物性は表1に示す。
攪拌機を備えた内容積2Lのオートクレーブに純水0.6kgとメチルセルロース0.6gを投入し、十分に窒素置換を行った後、1,1,1,3,3-ペンタフルオロブタン0.57kgを仕込み、系内を37℃に保った。テトラフルオロエチレン/ビニリデンフルオライド=4/96モル比の混合ガスを仕込み、槽内圧を1.5MPaにした。4-ペンテン酸0.09g、ジ-n-プロピルパーオキシジカーボネートの50質量%メタノール溶液を0.5g添加して重合を開始した。槽内圧を保つようにテトラフルオロエチレン/フッ化ビニリデン=11/89モル比の混合ガスを供給し、反応終了までに70gの混合ガスを追加した。4-ペンテン酸を混合ガスの供給に合わせて連続的に追加し、反応終了までに0.36g追加した。混合ガス70g追加完了後、槽内ガスを放出し、反応を終了させた。
反応生成物を水洗、乾燥して、含フッ素重合体Cを68g得た。
得られた含フッ素重合体Cの組成及び物性は表1に示す。
攪拌機を備えた内容積2Lのオートクレーブに純水0.6kgとメチルセルロース0.6gを投入し、十分に窒素置換を行った後、1,1,1,3,3-ペンタフルオロブタン0.57kgを仕込み、系内を37℃に保った。テトラフルオロエチレン/ビニリデンフルオライド=7/93モル比の混合ガスを仕込み、槽内圧を1.5MPaにした。4-ペンテン酸0.17g、ジ-n-プロピルパーオキシジカーボネートの50質量%メタノール溶液を0.5g添加して重合を開始した。槽内圧を保つようにテトラフルオロエチレン/フッ化ビニリデン=15/85モル比の混合ガスを供給し、反応終了までに70gの混合ガスを追加した。4-ペンテン酸を混合ガスの供給に合わせて連続的に追加し、反応終了までに0.43g追加した。混合ガス70g追加完了後、槽内ガスを放出し、反応を終了させた。
反応生成物を水洗、乾燥して、含フッ素重合体Dを69g得た。
得られた含フッ素重合体Dの組成及び物性は表1に示す。
攪拌機を備えた内容積2Lのオートクレーブに純水0.6kgとメチルセルロース0.6gを投入し、十分に窒素置換を行った後、1,1,1,3,3-ペンタフルオロブタン0.57kgを仕込み、系内を37℃に保った。TFE/VdF=18/82モル比の混合ガスを仕込み、槽内圧を1.5MPaにした。3-ブテン酸0.69g、ジ-n-プロピルパーオキシジカーボネートの50質量%メタノール溶液を1.6g添加して重合を開始した。槽内圧を保つようにTFE/VdF=33/67モル比の混合ガスを供給し、反応終了までに70gの混合ガスを追加した。3-ブテン酸を混合ガスの供給に合わせて連続的に追加し、反応終了までに0.56g追加した。混合ガス70g追加完了後、槽内ガスを放出し、反応を終了させた。
反応生成物を水洗、乾燥して、含フッ素重合体Eを67g得た。
得られた含フッ素重合体Eの組成及び物性は表1に示す。
攪拌機を備えた内容積2Lのオートクレーブに純水0.6kgとメチルセルロース0.6gを投入し、十分に窒素置換を行った後、1,1,1,3,3-ペンタフルオロブタン0.57kgを仕込み、系内を37℃に保った。TFE/VdF=17/83モル比の混合ガスを仕込み、槽内圧を1.5MPaにした。3-ブテン酸0.92g、ジ-n-プロピルパーオキシジカーボネートの50質量%メタノール溶液を1.4g添加して重合を開始した。槽内圧を保つようにTFE/VdF=32/68モル比の混合ガスを供給し、反応終了までに70gの混合ガスを追加した。3-ブテン酸を混合ガスの供給に合わせて連続的に追加し、反応終了までに0.73g追加した。混合ガス70g追加完了後、槽内ガスを放出し、反応を終了させた。
反応生成物を水洗、乾燥して、含フッ素重合体Fを66g得た。
得られた含フッ素重合体Fの組成及び物性は表1に示す。
攪拌機を備えた内容積2Lのオートクレーブに純水0.6kgとメチルセルロース0.6gを投入し、十分に窒素置換を行った後、1,1,1,3,3-ペンタフルオロブタン0.57kgを仕込み、系内を37℃に保った。TFE/VdF=18/82モル比の混合ガスを仕込み、槽内圧を1.5MPaにした。4-ペンテン酸0.56g、ジ-n-プロピルパーオキシジカーボネートの50質量%メタノール溶液を2.2g添加して重合を開始した。槽内圧を保つようにTFE/VdF=33/67モル比の混合ガスを供給し、反応終了までに70gの混合ガスを追加した。4-ペンテン酸を混合ガスの供給に合わせて連続的に追加し、反応終了までに0.65g追加した。混合ガス70g追加完了後、槽内ガスを放出し、反応を終了させた。
反応生成物を水洗、乾燥して、含フッ素重合体Gを66g得た。
得られた含フッ素重合体Gの組成及び物性は表1に示す。
攪拌機を備えた内容積2Lのオートクレーブに純水0.6kgとメチルセルロース0.6gを投入し、十分に窒素置換を行った後、1,1,1,3,3-ペンタフルオロブタン0.57kgを仕込み、系内を37℃に保った。TFE/VdF=17/83モル比の混合ガスを仕込み、槽内圧を1.5MPaにした。4-ペンテン酸0.74g、ジ-n-プロピルパーオキシジカーボネートの50質量%メタノール溶液を1.0g添加して重合を開始した。槽内圧を保つようにTFE/VdF=32/68モル比の混合ガスを供給し、反応終了までに70gの混合ガスを追加した。4-ペンテン酸を混合ガスの供給に合わせて連続的に追加し、反応終了までに0.84g追加した。混合ガス70g追加完了後、槽内ガスを放出し、反応を終了させた。
反応生成物を水洗、乾燥して、含フッ素重合体Hを66g得た。
得られた含フッ素重合体Hの組成及び物性は表1に示す。
攪拌機を備えた内容積3Lのオートクレーブに、乳化剤F(CF2)5COONH4が1.0質量%になるよう調製した純水1480gを投入し、十分に窒素置換を行った後、系内を70℃に保った。その後、テトラフルオロエチレン/ビニリデンフルオライド=35/65モル比の混合ガスを仕込み、槽内圧を0.8MPaにした。その後、イソプロピルアルコール0.5g、過硫酸アンモニウム0.15gを添加し重合を開始した。槽内圧を保つようにテトラフルオロエチレン/ビニリデンフルオライド=33/67モル比の混合ガスを供給し、反応終了までに420gの混合ガスを追加した。反応開始後、反応終了までに過硫酸アンモニウムを合計0.15g追加した。混合ガス420g追加完了後、槽内ガスを放出し、反応を終了させた。
槽内を冷却して、ポリマーの固形分が20.2質量%の水性ディスパージョンを得た。得られたディスパージョンに28質量%硫酸アルミニウム水溶液を8g投入し、スラリーをろ別した。回収したスラリーを2Lの純水で水洗、乾燥して、含フッ素重合体Xを401g得た。
得られた含フッ素重合体Xの組成及び物性は表1に示す。
特開2001-19896号公報の実施例を参考に、含フッ素重合体Yを合成した。
得られた含フッ素重合体Yの組成及び物性は表1に示す。
電池結着剤用のホモPVdFを用いた。組成及び物性は表1に示す。
表1に示す含フッ素重合体を用いて、各種物性を以下の方法により測定・評価した。結果を表1に示す。
VdFとTFEの比率については、NMR分析装置(アジレント・テクノロジー株式会社製、VNS400MHz)を用いて、19F-NMR測定でポリマーのDMF-d7溶液状態にて測定した。
19F-NMR測定にて、下記のピークの面積(A、B、C、D)を求め、VdFとTFEの比率を計算した。
A:-86ppm~-98ppmのピークの面積
B:-105ppm~-118ppmのピークの面積
C:-119ppm~-122ppmのピークの面積
D:-122ppm~-126ppmのピークの面積
VdFの割合:XVdF=(4A+2B)/(4A+3B+2C+2D)×100[mol%]
TFEの割合:XTFE=(B+2C+2D)/(4A+3B+2C+2D)×100[mol%]
3-ブテン酸又は4-ペンテン酸の含有量については、カルボキシ基の酸-塩基滴定によって測定した。従った手順を以下に詳述する。
約0.5gの含フッ素重合体を70~80℃の温度で15gのアセトンに溶解させた。5mlの水を次に、ポリマーが凝固しないよう加えた。約-270mVでの中性転移で、酸性度の完全な中和まで0.1Nの濃度を有する水性NaOHでの滴定を次に実施した。測定結果から、含フッ素重合体1g中に含まれる3-ブテン酸又は4-ペンテン酸の含有物質量α[mol/g]を求めた。α、上記方法で求めた含フッ素重合体のVdF/TFE組成、TFE、VdF、3-ブテン酸又は4-ペンテン酸の分子量に基づき、下記式を満たすように含フッ素重合体の3-ブテン酸又は4-ペンテン酸の比率Y[mol%]を求めた。
α=Y/[{TFEの分子量}×{XTFE×(100-Y)/100}+{VdFの分子量}×{XVdF×(100-Y)/100}+{3-ブテン酸又は4-ペンテン酸の分子量}×Y]
得られたXVdF、XTFE、Yの値から、最終組成比を以下の通り計算した。
VdFの割合:XVdF×(100-Y)/100[mol%]
TFEの割合:XTFE×(100-Y)/100[mol%]
3-ブテン酸又は4-ペンテン酸の割合:Y[mol%]
含フッ素重合体YのVdFとマレイン酸モノメチルエステルの比率については、特開2001-19896号公報に記載の方法でカルボニル基含有量β[mol/g]を計算し、以下の式に当てはめ、ポリマー組成を決定した。
VdFの割合:{1-(マレイン酸モノメチルエステルの分子量)×β}/[1-{(マレイン酸モノメチルエステルの分子量)-(VdFの分子量)}×β]×100[mol%]
マレイン酸モノメチルエステルの割合:(VdFの分子量)×β/[1-{(マレイン酸モノメチルエステルの分子量)-(VdFの分子量)}×β]×100[mol%]
ゲルパーミエーションクロマトグラフィ(GPC)により測定した。東ソー株式会社製のAS-8010、CO-8020、カラム(GMHHR-Hを3本直列に接続)、及び、株式会社島津製作所製RID-10Aを用い、溶媒としてジメチルホルムアミド(DMF)を流速1.0ml/分で流して測定したデータ(リファレンス:ポリスチレン)より算出した。
含フッ素重合体の5質量%N-メチル-2-ピロリドン(NMP)溶液を調製し、東機産業株式会社製B型粘度計TV-10Mを用いて25℃で粘度を測定した。
結着剤(含フッ素重合体)を濃度が5質量%になるように秤量し、N-メチル-2-ピロリドン(NMP)に溶解させて結着剤溶液を得た。
上記で得た結着剤溶液を、ガラス板上にキャストし100℃で2時間乾燥し、厚さ約30μmのフィルムを得た。
これらのフィルムを、ASTM D1708に準拠した形状のダンベル型に打ち抜き、オートグラフにて25℃における破断点伸度を測定した。
結着剤(含フッ素重合体)を濃度が8質量%になるよう秤量し、N-メチル-2-ピロリドン(NMP)に溶解させて得た結着剤溶液を、ガラス板上にキャストし100℃で12時間乾燥し、更に真空下で100℃で12時間乾燥し、厚さ約40μmのフィルムを得た。これらのフィルムを長さ30mm、巾5mmにカットし、サンプルとした。アイティー計測制御社製動的粘弾性装置DVA220で長さ30mm、巾5mm、厚み40μmのサンプルについて、引張モード、つかみ巾20mm、測定温度-30℃から160℃、昇温速度2℃/min、周波数1Hzの条件で、25℃及び100℃における貯蔵弾性率を測定した。
正極活物質(NMC(532)(LiNi0.5Mn0.3Co0.2O2))、導電剤アセチレンブラック(AB)、及び、結着剤(含フッ素重合体)を、表1に示す質量比になるように秤量した。含フッ素重合体を濃度が8質量%になるようにN-メチル-2-ピロリドン(NMP)に溶解させたのち、この結着剤のNMP溶液に所定量の正極活物質と導電剤を加え、撹拌機で十分に混合して、良好な均質性を確実にした。
スラリー中の固形分濃度は70%とした。
調製した上記正極合剤用スラリーを厚さ20μmのアルミ箔からなる電極集電板に均一に塗布し、NMPを完全に揮発させ、正極を作製した。
作製した電極を、ロールプレス機により、正極合剤塗膜の密度が所定密度になるまで圧延した。密度は、面積/膜厚/重量を測定して算出した。
作製した正極を縦3cm、横6cmに切り取った後、180°折り畳んだ後拡げて、正極の傷や割れの有無を目視で確認した。傷や割れが確認されない場合は○、ひび割れが確認された場合は△、正極が破断した場合は×と評価した。
この評価は、表1に示す電極密度について実施した。
縦1.2cm、横8.0cmに切り取った正極の電極側を両面テープで可動式治具に固定し、集電体を100mm/分の速度で90度に引っ張った時の応力(N/mm)をオートグラフにて測定した。
Ni含有量の高い正極活物質NCA(LiNi0.82Co0.15Al0.03O2)を用いて以下のようにスラリーを作製し、正極合剤スラリーの耐ゲル化特性の評価を実施した。結果を表2に示す。
正極活物質NCA(LiNi0.82Co0.15Al0.03O2)、導電剤アセチレンブラック(AB)、及び、結着剤(含フッ素重合体)を、質量比が活物質/AB/ポリマー=93/4/3になるように秤量した。含フッ素重合体を濃度が8質量%になるようにN-メチル-2-ピロリドン(NMP)に溶解させたのち、この結着剤のNMP溶液に所定量の正極活物質と導電剤を加え、撹拌機で十分に混合して、良好な均質性を確実にした。組成物の固形分濃度は70%とした。
上記で作製したNCAを用いた正極合剤用スラリーを、B型粘度計を用いてスラリー作製直後と作製から24時間後の粘度を測定した。
24時間後スラリー粘度×100/作製直後スラリー粘度
上記算出により、300(%)以上の場合は×(ゲル化)、300(%)未満の場合は○と評価した。
Claims (9)
- 前記Y1が、H、Li、Na、K、Mg、Ca、Al及びNH4からなる群より選択される少なくとも1種のカチオンである請求項1記載の二次電池用結着剤。
- 前記含フッ素重合体は、全重合単位に対して、ビニリデンフルオライドに基づく重合単位が50~95モル%、テトラフルオロエチレンに基づく重合単位が4.8~49.95モル%、前記単量体(2-2)に基づく重合単位が0.05~2.0モル%である請求項1又は2記載の二次電池用結着剤。
- 前記含フッ素重合体は、重量平均分子量が50000~2000000である請求項1、2又は3記載の二次電池用結着剤。
- 前記含フッ素重合体は、25℃における貯蔵弾性率が1000MPa以下である請求項1、2、3又は4記載の二次電池用結着剤。
- 前記含フッ素重合体は、25℃における貯蔵弾性率が800MPa以下である請求項1、2、3、4又は5記載の二次電池用結着剤。
- 請求項1、2、3、4、5又は6記載の二次電池用結着剤と電池用粉末電極材料と水又は非水溶剤とを少なくとも混合してなる二次電池用電極合剤。
- 請求項1、2、3、4、5又は6記載の二次電池用結着剤を含む二次電池用電極。
- 請求項8記載の二次電池用電極を備える二次電池。
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US10847800B2 (en) | 2020-11-24 |
CN109075342A (zh) | 2018-12-21 |
KR20180116451A (ko) | 2018-10-24 |
JP6269890B1 (ja) | 2018-01-31 |
US20190296359A1 (en) | 2019-09-26 |
CN109075342B (zh) | 2020-03-24 |
EP3447831A4 (en) | 2020-01-01 |
EP3447831A1 (en) | 2019-02-27 |
JP2018195552A (ja) | 2018-12-06 |
KR101947979B1 (ko) | 2019-02-13 |
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