Classifications

• • 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
  • C08F214/20—Vinyl fluoride
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L27/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Compositions of derivatives of such polymers
  • C08L27/02—Compositions of homopolymers or 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; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L27/12—Compositions of homopolymers or 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; Compositions of derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
  • C08L27/14—Homopolymers or copolymers of vinyl fluoride
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L27/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Compositions of derivatives of such polymers
  • C08L27/02—Compositions of homopolymers or 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; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L27/12—Compositions of homopolymers or 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; Compositions of derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
  • C08L27/16—Homopolymers or copolymers or vinylidene fluoride
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D127/00—Coating compositions based on homopolymers or 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; Coating compositions based on derivatives of such polymers
  • C09D127/02—Coating compositions based on homopolymers or 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; Coating compositions based on derivatives of such polymers not modified by chemical after-treatment
  • C09D127/12—Coating compositions based on homopolymers or 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; Coating compositions based on derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
  • C09D127/16—Homopolymers or copolymers of vinylidene fluoride
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
  • H01M4/621—Binders
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
  • H01M4/621—Binders
  • H01M4/622—Binders being polymers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
  • H01M4/621—Binders
  • H01M4/622—Binders being polymers
  • H01M4/623—Binders being polymers fluorinated polymers
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2205/00—Polymer mixtures characterised by other features
  • C08L2205/02—Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group
• • 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 invention relates to improved fluoropolymer binders for binding electrode materials in the fabrication of battery electrodes.
• PVDF polyvinylidene fluoride
• the lithium-ion secondary battery is used widely as a battery meeting these requirements.
• the anode uses an aluminum foil as the current collector.
• Powder lithium composite oxide such as LiCoO 2 , LiNiO 2 or LiMn 2 O 4 is mixed with a conductive material (such as carbon), a binder and a solvent to form a paste, which is coated and dried on the surface of the current collector.
• the cathode is prepared by coating a paste obtained by mixing carbon, a binder and a solvent onto a copper foil.
• electrodes are layered in the order of the cathode, a separator (polymer porous film), the anode and a separator and then coiled and housed in a cylindrical or rectangular can.
• a binder is a material that is important for bonding the active mass (electrode materials) essential to the battery to the current collector of the electrodes.
• the adhesive and chemical properties of the binder have a great impact on the performance of the battery.
• PVDF polyvinylidene fluoride
• N- solvent
• Polyvinylidene fluoride is soluble in NMP and allows for the preparation of a paste having a proper viscosity. Furthermore, polyvinylidene fluoride shows good chemical resistance and demonstrates bonding capability even in a carbonate-based organic solvent used in the electrolytic solution of a battery.
• polyvinylidene fluoride does not completely meet all of the binder properties required for batteries.
• the active mass tends to delaminate or break away from the current collector when coiling the electrodes in the battery fabrication process. Such delamination of the active mass will result in an increase in the internal resistance of the battery, causing a decline in the performance of the battery. For this reason, there is an urgent need to develop a binder that will reduce the delamination of the active mass.
• As a means for improving the adhesion strength of a binder a method in which various functional groups are introduced into the resin used in a binder is reported. For example, it is described in the Japanese Patent No. 3467499 that the adhesion strength of polyvinylidene fluoride was improved from the level of the conventional polyvinylidene fluoride by using a copolymer of vinylidene fluoride and a monomer having an epoxy group.
• the invention provides a binder for a battery electrode comprising a vinyl fluoride-based copolymer.
• the vinyl fluoride-based copolymer preferably comprises about 25 to about 85 mol% vinyl fluoride and about 75 to about 15 mol% of at least one other fluorine-containing monomer.
• the binder comprises a mixture of at least two types of vinyl fluoride-based polymers.
• the binder comprises a vinyl fluoride-based copolymer and at least one other fluorine-based polymer.
• the present invention provides a new fluoropolymer resin binder that has a higher bonding capability than the conventional binders, reduces the delamination of the active mass in the battery fabrication process and shows improved adhesion strength and electrochemical stability
• the present invention relates to vinyl fluoride-based copolymer binders having improved properties required of electrode binders, such as adhesion strength and flexibility.
• the vinyl fluoride-based copolymers and their preparation used in forming the binders of the present invention are fully disclosed in U.S. Patents 6,403,303 B1 ; 6,271 ,303 B1 and 6,242,547 (Uschold).
• the vinyl fluoride-based copolymer of the present invention preferably contains about 25 to about 85 mol% of the vinyl fluoride component.
• the vinyl fluoride-based copolymer >ut 85 mol% vinyl fluoride and about 75 to about 15 mol% of at least one fluorine-containing monomer selected from the group consisting of vinylidene fluoride, tetrafluoroethylene, trifluoroethylene, chlorotrifluoroethylene, fluorinated vinyl ethers, fluorinated alkyl acrylates/methacrylates, perfluoroolefins having 3-10 carbon atoms, perfluoro Ci-Cs alkyl ethylenes and fluorinated dioxoles.
• binder of the present invention binder comprises a mixture of at least two types of vinyl fluoride-based copolymers.
• the vinyl fluoride-based copolymer comprises at least one copolymer selected from vinyl fluoride- tetrafluoroethylene copolymer, vinyl fluoride-tetrafluoroethylene- hexafluoropropylene copolymer, vinyl fluoride-tetrafluoroethylene- perfluorobutylethylene copolymer.
• the binder is preferably a mixture of a vinyl fluoride-based copolymer and at least one other fluorine- based polymer.
• the fluorine-based polymer is at least one polymer selected from a homopolymer or a copolymer prepared from monomers of vinylidene fluoride, tetrafluoroethylene, trifluoroethylene, chlorotrifluoroethylene, fluorinated vinyl ethers, fluorinated alkyl acrylates/methacrylates, perfluoroolefins having 3-10 carbon atoms, perfluoro Ci-Cs alkyl ethylenes and fluorinated dioxoles.
• a preferable method for using the vinyl fluoride-based copolymer binder is to prepare a dispersion by dispersing the vinyl fluoride-based copolymer in organic solvents or water.
• Another embodiment for preparing the vinyl fluoride-based copolymer binder is to prepare a solution of the vinyl based polymer in organic solvents.
• Preferred organic solvents are selected from N-methyl-2-pyrrolidone, ⁇ -butyrolactone, N 1 N- dimethylformamide, N,N-dimethylacetoamide, dimethylsulfoxide, ketones, nitriles or esters or mixtures thereof.
• the vinyl fluoride-based copolymer employed in accordance with the present invention can be used in a similar procedure to the conventional process for using a binder in forming battery electrodes.
• the vinyl fluoride-based copolymer binder is dissolved or vent or water which is then mixed with the active mass and a conductive material to obtain a paste.
• the paste is coated onto a metal foil, preferably aluminum or copper foil, used as the current collector, The paste is dried, preferably with heat, so that the active mass is bonded to the current collector.
• the vinyl fluoride-based copolymer of the present invention is not soluble in polar organic solvents such as propylene carbonate, ethylene carbonate and ethylmethyl carbonate and their mixtures and therefore can be used advantageously as a stable binder in batteries.
• the battery active mass that can be bonded with a binder in the present invention is not particularly limited.
• lithium composite oxides such as UCOO 2 , LiNiO 2 or LiMn 2 O 4 can be cited as examples of the battery active mass for the anode
• carbonacious materials such as graphite and ketjen black can be cited as examples of the battery active mass for the cathode.
• aluminum and copper foils can be cited as examples of the current collector of the electrodes.
• the binder of the present invention may be used for both the anode and cathode.
• the binder of the present invention shows higher adhesion strength than the conventional binders of polyvinylidene fluoride. Consequently, a smaller amount of vinyl fluoride-based copolymer binder can be used to achieve equivalent adhesion strength as conventional polyvinylidene fluoride binder. As a result, the use of the binder of the present invention allows the amount of the active mass to be increased when using a smaller amount of the binder, thus allowing for an increase in the battery capacity.
• the melting point is measured by use of a differential scanning calorimeter (Pyris 1 available from PerkinElmer) at a temperature increase rate of 10°C/min, and the peak is taken as the melting point.
• the adhesion strength of the aluminum foil used for the binder is measured by use of TENSILON (UTM-1T available from Toyo Baldwin) at the crosshead speed of 50 mm/min and the load cell of 5 kg. Cyclic voltammetrv:
• Cyclic voltammetry is measured under an atmosphere of nitrogen by using an aluminum foil on which a paste obtained by mixing the vinyl fluoride-based copolymer mixed with organic solvent and carbon (ketjen black), is coated and dried as the test electrode, Pt wire as the counter electrode, Ag/Ag + (for an organic solvent, 0.7 V/SHE) as the reference electrode and 1 mol/liter of LiPF 6 (ethylene carbonate + ethylmethyl carbonate mixed solvent: 1 :1 by weight) as the electrolytic solution.
• the scanning range is 0.00 to 5.00 V (125 cycles), and the scanning rate is 0.10 V/s.
• the current values at 3.50 V in each cycle is compared, and the electrochemical stability of the electrodes is compared in terms of the extent of a decrease in current.
• Raw materials :
• the vinyl fluoride-based copolymer powder (0.2 ⁇ m in average particle size) that has composition and melting point shown in Tables 1 and 2 is used in the Examples.
• Adhesion strength evaluation tests After preparing an organosol of resin by mixing 5 wt% of the vinyl fluoride-based copolymer shown in Table 1 or PVDF powder with an organic solvent, 5 wt% of ketjen black are mixed to form a paste.
• the paste is coated on the frosted side of an aluminum foil 15 ⁇ m in thickness (5 cm x 10 cm), the coated side of the aluminum foil is sandwiched with 3 same size, and the coated paste is spread manually by means of a film applicator. The thickness of the sample is 120 ⁇ m.
• the coated sheet is dried in a vacuum dryer (LCV-232 available from Tabai Espec) at 190 degree C for 3 hours. After that, a test specimen, 1 cm x 5 cm, is cut out and used for the adhesion strength test.
• Adhesion strength is determined by peeling strength test in the 180- degree direction. Results are shown in Table 1. The adhesion strength of the test specimen is compared with a test specimen prepared under the same conditions using PVDF used as the conventional binder. The comparison indicates that the vinyl fluoride-based copolymer shows considerably higher adhesion strength than PVDF.
• NMP N-methyl-2-pyrrolidone
• MA Methyl acetate
• DMA N,N-dimethylacetoamine
• VF Vinyl fluoride
• TFE Tetrafluoroethylene
• VDF polyvinylidene fluoride
• NMP N-methyl-2-pyrrolidone
• MA Methyl acetate
• DMA Methyl acetate
• the paste used in the adhesion strength test is coated on the end of one side of an aluminum foil 15 ⁇ m in thickness (0.5 cm x 5 cm) and dried under the conditions of 190 degree C and 3 hours. This sample is used as the test electrode, and the stability of the electrode is determined by cyclic voltammetry. Results are shown in Table 3.
• electrodes that suppress the delamination of the active mass in a battery such as a lithium-ion secondary battery and have better electrochemical stability can be prepared by using the vinyl fluoride-based copolymer as the binder.

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• 2006
  • 2006-09-07 US US11/517,109 patent/US20070060708A1/en not_active Abandoned
  • 2006-09-12 WO PCT/US2006/035411 patent/WO2007033130A1/en not_active Ceased
  • 2006-09-12 EP EP06790211A patent/EP1924616A1/en not_active Withdrawn
  • 2006-09-12 CN CNA2006800333376A patent/CN101263167A/zh active Pending
  • 2006-09-12 KR KR1020087008652A patent/KR20080058374A/ko not_active Ceased
  • 2006-09-12 TW TW095133689A patent/TW200745296A/zh unknown
  • 2006-09-12 JP JP2008531235A patent/JP5128481B2/ja not_active Expired - Fee Related

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