WO2023007933A1 - Mélange d'électrode négative, électrode négative et batterie secondaire - Google Patents

Mélange d'électrode négative, électrode négative et batterie secondaire Download PDF

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WO2023007933A1
WO2023007933A1 PCT/JP2022/021521 JP2022021521W WO2023007933A1 WO 2023007933 A1 WO2023007933 A1 WO 2023007933A1 JP 2022021521 W JP2022021521 W JP 2022021521W WO 2023007933 A1 WO2023007933 A1 WO 2023007933A1
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negative electrode
electrode mixture
random copolymer
group
units
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PCT/JP2022/021521
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Japanese (ja)
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佑磨 市瀬
穣輝 山崎
俊晴 下岡
和哉 浅野
千紘 細田
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ダイキン工業株式会社
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/32—Carbon-based
    • H01G11/38—Carbon pastes or blends; Binders or additives therein
    • 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
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • 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 disclosure relates to a negative electrode mixture, a negative electrode, and a secondary battery.
  • Patent Document 1 discloses a silicon graphite negative electrode containing a negative electrode active material, an aqueous binder composition and a carbon-based conductive material, wherein the aqueous binder composition comprises 50 to 100% by weight of one or more thermoplastic fluoropolymers. wherein said fluoropolymer is in the form of a latex and contains monomers having at least one functional group selected from carboxyl, epoxy, carbonyl and hydroxyl and 0-50% by weight of a water-soluble thickener A silicon graphite anode is described.
  • Patent Document 2 discloses an electrode mixture slurry containing an electrode binder composition and an electrode active material (J), wherein the organosol composition comprises polytetrafluoroethylene particles (A), a polymer (B) and a non and a fluorinated organic solvent (C), wherein the polymer (B) is soluble in the non-fluorinated organic solvent (C).
  • Patent Document 3 discloses a current collector, an electrode active material layer containing an electrode active material formed on at least one surface of the current collector, and an inorganic filler and a binder formed on the surface of the electrode active material layer. and the binder is a fluorine-containing copolymer having structural units based on tetrafluoroethylene and structural units based on propylene. .
  • Non-Patent Document 1 describes a highly elastic block copolymer binder for silicon negative electrodes of lithium ion batteries.
  • An object of the present invention is to provide a negative electrode mixture that can obtain a low-cost battery.
  • a negative electrode mixture containing a binder and a negative electrode active material wherein the binder contains a random copolymer containing vinylidene fluoride units and tetrafluoroethylene units, and the negative electrode active material is , a negative electrode mixture containing a negative electrode active material containing a metal is provided.
  • the random copolymer preferably has a structure exhibiting an NMR spectrum that satisfies the following relational expression. 0.42 ⁇ (a*1/2)/[(a*1/2)+b] a: the area of all peaks appearing in the chemical shift range of -108 to -111 ppm in the NMR spectrum of the random copolymer obtained by 19 F-NMR analysis b: the random copolymer obtained by 19 F-NMR analysis
  • the content of vinylidene fluoride units in the random copolymer is is preferably 60.0 to 95.0 mol %.
  • the content of tetrafluoroethylene units in the random copolymer is preferably 5.0 to 40.0 mol % with respect to all monomer units.
  • the random copolymer substantially contains only vinylidene fluoride units and tetrafluoroethylene units.
  • the metal in the negative electrode active material containing the metal is a metal that can be electrochemically alloyed with an alkali metal.
  • the negative electrode active material containing the metal is at least selected from the group consisting of Si, Zn, Sn, W, oxides of these metals, and alloys containing these metals.
  • One type is preferred.
  • the negative electrode mixture of the present disclosure preferably does not contain polytetrafluoroethylene.
  • the negative electrode mixture of the present disclosure preferably further contains a vinylidene fluoride homopolymer.
  • the negative electrode mixture of the present disclosure preferably further contains a solvent.
  • a negative electrode including a negative electrode mixture layer formed from the above negative electrode mixture is provided.
  • a secondary battery including the above negative electrode is provided.
  • the negative electrode current collector with a peel strength sufficiently high for practical use, and it is possible to form a negative electrode mixture layer having excellent flexibility, a high cycle capacity retention rate, and an increase in resistance. It is possible to provide a negative electrode mixture capable of obtaining a battery with a low rate.
  • the negative electrode mixture of the present disclosure contains a binder and a negative electrode active material.
  • the negative electrode mixture of the present disclosure contains a random copolymer containing vinylidene fluoride (VdF) units and tetrafluoroethylene (TFE) units as a binder. Since the negative electrode mixture of the present disclosure contains a random copolymer in which VdF units, TFE units, and arbitrary monomer units are randomly arranged as a binder, the negative electrode mixture has sufficiently high peel strength for practical use. It is possible to form a negative electrode mixture layer that adheres to an electric body and is extremely flexible. Therefore, even when a negative electrode mixture layer containing a high proportion of the negative electrode active material is formed and the negative electrode including such a negative electrode mixture layer is wound, the negative electrode mixture layer is less likely to crack.
  • VdF vinylidene fluoride
  • TFE tetrafluoroethylene
  • a random copolymer has a structure in which each monomer unit constituting the copolymer is randomly arranged.
  • a random copolymer it is possible to form a negative electrode mixture layer that is more excellent in flexibility, and it is possible to obtain a battery with a higher cycle capacity retention rate and a lower resistance increase rate. Random copolymers having structures that exhibit satisfactory NMR spectra are preferred.
  • One or more peaks appearing in the chemical shift range of -108 to -111 ppm in the NMR spectrum are peaks derived from adjacent VdF units and TFE units in the molecule of the random copolymer.
  • One or more peaks appearing in the chemical shift range of -119 to -126 ppm in the NMR spectrum are peaks derived from TFE units adjacent to VdF units in the molecules of the random copolymer, and in the molecules of the random copolymer. Either or both of the peaks originating from two adjacent TFE units. Both peaks may overlap and be detected as one peak.
  • a random copolymer that satisfies the above relational expression has a structure that contains a relatively large proportion of sequences in which VdF units and TFE units are adjacent in the copolymer molecule.
  • a PTFE-PVdF block copolymer containing a segment composed of continuous VdF units and a segment composed of continuous TFE units contains many sequences of continuous TFE units, and VdF units and TFE units does not satisfy the above relation because it contains few adjacent sequences.
  • a random copolymer can form a negative electrode mixture layer with even more excellent flexibility, and a battery with a higher cycle capacity retention rate and a lower resistance increase rate can be obtained.
  • /2)/[(a ⁇ 1/2)+b] is more preferably greater than 0.44, still more preferably greater than 0.46.
  • the upper limit of the calculated value may be the theoretical upper limit that the structure of the random copolymer can take, but it is preferably 0.52 or less.
  • the random copolymer contains VdF units and TFE units.
  • the content of VdF units in the random copolymer is preferably 50.0 to 99.0 mol%, more preferably 57.0 mol% or more, and still more preferably, based on the total monomer units. is 60.0 mol % or more, particularly preferably 63.0 mol % or more, more preferably 97.0 mol % or less, still more preferably 95.0 mol % or less.
  • the content of TFE units in the random copolymer is preferably 1.0 mol% or more, more preferably 3.0 mol% or more, and still more preferably 5.0 mol%, based on the total monomer units.
  • mol% or more particularly preferably 10.0 mol% or more, most preferably 15.0 mol% or more, preferably 50.0 mol% or less, more preferably 43.0 mol% or less , more preferably 40.0 mol % or less, and particularly preferably 37.0 mol % or less.
  • composition of random copolymers can be measured, for example, by 19 F-NMR measurement.
  • the random copolymer may further contain fluorinated monomer units (excluding VdF units and TFE units).
  • fluorinated monomers examples include vinyl fluoride, trifluoroethylene, chlorotrifluoroethylene (CTFE), fluoroalkyl vinyl ether, hexafluoropropylene (HFP), (perfluoroalkyl ) ethylene, 2,3,3,3-tetrafluoropropene and trans-1,3,3,3-tetrafluoropropene.
  • CTFE chlorotrifluoroethylene
  • HFP hexafluoropropylene
  • perfluoroalkyl ethylene, 2,3,3,3-tetrafluoropropene and trans-1,3,3,3-tetrafluoropropene.
  • Fluoroalkyl vinyl ether is preferably a fluoroalkyl vinyl ether having a fluoroalkyl group having 1 to 5 carbon atoms, and is selected from the group consisting of perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether) and perfluoro(propyl vinyl ether). At least one selected is more preferred.
  • Fluorinated monomer units may or may not have a polar group.
  • the random copolymer may further contain non-fluorinated monomer units.
  • the non-fluorinated monomer include non-fluorinated monomers having no polar group such as ethylene and propylene, and non-fluorinated monomers having a polar group (hereinafter sometimes referred to as polar group-containing monomers ) and the like.
  • the polar group that the random copolymer may have is selected from the group consisting of a carbonyl group-containing group, an epoxy group, a hydroxyl group, a sulfonic acid group, a sulfuric acid group, a phosphoric acid group, an amino group, an amide group and an alkoxy group. At least one is preferred, at least one selected from the group consisting of a carbonyl group-containing group, an epoxy group and a hydroxy group is more preferred, and a carbonyl group-containing group is even more preferred.
  • the hydroxy group does not include a hydroxy group that forms part of the carbonyl group-containing group.
  • the amino group is a monovalent functional group obtained by removing hydrogen from ammonia, primary or secondary amine.
  • a group represented by the general formula: --COOR R represents a hydrogen atom, an alkyl group or a hydroxyalkyl group
  • a carboxylic acid anhydride group is preferable.
  • the number of carbon atoms in the alkyl group and hydroxyalkyl group is preferably 1-16, more preferably 1-6, still more preferably 1-3.
  • groups represented by the general formula: -COOR include -COOCH 2 CH 2 OH, -COOCH 2 CH(CH 3 )OH, -COOCH(CH 3 )CH 2 OH, -COOH, and -COOCH 3 , —COOC 2 H 5 and the like.
  • -COOR is -COOH or contains -COOH
  • -COOH may be a carboxylate such as a metal carboxylate or an ammonium carboxylate.
  • the carbonyl group-containing group has the general formula: -X-COOR
  • X is an atomic group whose main chain is composed of 2 to 15 atoms and has a molecular weight of 350 or less.
  • R is a hydrogen atom, an alkyl group or represents a hydroxyalkyl group).
  • the number of carbon atoms in the alkyl group and hydroxyalkyl group is preferably 1-16, more preferably 1-6, still more preferably 1-3.
  • amide group a group represented by the general formula: -CO-NRR' (R and R' independently represent a hydrogen atom or a substituted or unsubstituted alkyl group), or a group represented by the general formula:- A bond represented by CO--NR''-- (R'' represents a hydrogen atom, a substituted or unsubstituted alkyl group or a substituted or unsubstituted phenyl group) is preferred.
  • polar group-containing monomer examples include hydroxyalkyl (meth)acrylates such as hydroxyethyl acrylate and 2-hydroxypropyl acrylate; alkylidene malonate esters such as dimethyl methylidenemalonate; vinyl carboxymethyl ether, vinyl carboxyethyl ether, and the like.
  • carboxyalkyl (meth)acrylates such as 2-carboxyethyl acrylate and 2-carboxyethyl methacrylate; acryloyloxyethyl succinate, acryloyloxypropyl succinate, methacryloyloxyethyl succinate, acryloyloxyethyl phthalate, (meth)acryloyloxyalkyldicarboxylic acid esters such as methacryloyloxyethyl phthalic acid; monoesters of unsaturated dibasic acids such as maleic acid monomethyl ester, maleic acid monoethyl ester, citraconic acid monomethyl ester, citraconic acid monoethyl ester; Formula (2): (wherein R 1 to R 3 independently represent a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms; R 4 represents a single bond or a hydrocarbon group having 1 to 8 carbon atoms; Y 1 represents an inorganic cation and/or an organic
  • polar group-containing monomer unit that can be contained in the random copolymer units based on the monomer (2) represented by the general formula (2) are preferable.
  • Y 1 represents an inorganic cation and/or an organic cation.
  • inorganic cations include cations such as H, Li, Na, K, Mg, Ca, Al, and Fe.
  • organic cations include cations such as NH 4 , NH 3 R 5 , NH 2 R 5 2 , NHR 5 3 and NR 5 4 (R 5 independently represents an alkyl group having 1 to 4 carbon atoms). mentioned.
  • Y1 is preferably H, Li, Na, K, Mg, Ca, Al, NH4 , more preferably H, Li, Na, K, Mg, Al, NH4 , H, Li, Al, NH4 is more preferred, and H is particularly preferred.
  • specific examples of inorganic cations and organic cations are described with the symbols and valence numbers omitted.
  • R 1 to R 3 independently represent a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms.
  • the hydrocarbon group is a monovalent hydrocarbon group.
  • the number of carbon atoms in the hydrocarbon group is preferably 4 or less.
  • Examples of the hydrocarbon group include an alkyl group, an alkenyl group, an alkynyl group, and the like having the number of carbon atoms described above, and a methyl group or an ethyl group is preferable.
  • R 1 and R 2 are independently preferably a hydrogen atom, a methyl group or an ethyl group, and R 3 is preferably a hydrogen atom or a methyl group.
  • R 4 represents a single bond or a hydrocarbon group having 1 to 8 carbon atoms.
  • the hydrocarbon group is a divalent hydrocarbon group.
  • the number of carbon atoms in the hydrocarbon group is preferably 4 or less.
  • Examples of the hydrocarbon group include an alkylene group and an alkenylene group having the above carbon number, and among them, at least one selected from the group consisting of a methylene group, an ethylene group, an ethylidene group, a propylidene group and an isopropylidene group.
  • a methylene group is preferred, and a methylene group is more preferred.
  • Examples of the monomer (2) include (meth)acrylic acid and its salts, vinylacetic acid (3-butenoic acid) and its salts, 3-pentenoic acid and its salts, 4-pentenoic acid and its salts, 3-hexenoic acid and salts thereof, 4-heptenoic acid and salts thereof, and 5-hexenoic acid and at least one selected from the group consisting of salts thereof, 3-butenoic acid and salts thereof, and 4-pentenoic acid and its At least one selected from the group consisting of salts is more preferred.
  • the content of the polar group-containing monomer units in the random copolymer is preferably 0.05 to 2.0 mol%, more preferably 0.10 mol% or more, relative to the total monomer units. is more preferably 0.25 mol % or more, particularly preferably 0.40 mol % or more, and more preferably 1.5 mol % or less.
  • the polar group is an acid group such as carboxylic acid
  • the content of the polar group-containing monomer unit in the random copolymer can be measured by acid-base titration of the acid group.
  • random copolymers containing substantially only VdF units and TFE units are preferred as random copolymers.
  • a random copolymer containing substantially only VdF units and TFE units means that the fluorinated monomer units (excluding VdF units and TFE units) and the non-fluorinated It means that the content of the monomer units is less than 0.05 mol % with respect to the total monomer units.
  • the weight average molecular weight (polystyrene equivalent) of the random copolymer is preferably 50,000 to 3,000,000, more preferably 80,000 or more, still more preferably 100,000 or more, particularly preferably 200,000 or more, and more preferably 2,400,000. or less, more preferably 2,200,000 or less, and particularly preferably 2,000,000 or less.
  • the weight average molecular weight can be measured by gel permeation chromatography (GPC) using dimethylformamide as a solvent.
  • Number average molecular weight (polystyrene equivalent) of the random copolymer is preferably 20,000 to 1,500,000, more preferably 40,000 or more, still more preferably 70,000 or more, particularly preferably 140,000 or more, more preferably 1,400,000. or less, more preferably 1,200,000 or less, and particularly preferably 1,100,000 or less.
  • the number average molecular weight can be measured by gel permeation chromatography (GPC) using dimethylformamide as a solvent.
  • the melting point of the random copolymer is preferably 100 to 170°C, more preferably 110 to 165°C, still more preferably 120 to 163°C.
  • the above melting point was measured using a differential scanning calorimetry (DSC) device, and the temperature was raised from 30°C to 220°C at a rate of 10°C/min, then lowered at 10°C/min to 30°C, and again at 10°C/min. It is obtained as the temperature corresponding to the maximum value in the heat of fusion curve when the temperature is raised to 220°C at a high speed.
  • DSC differential scanning calorimetry
  • the random copolymer preferably has a storage modulus of 1100 MPa or less at 30°C and a storage modulus of 500 MPa or less at 60°C.
  • the storage modulus of the random copolymer at 30°C is more preferably 800 MPa or less, still more preferably 600 MPa or less.
  • the storage modulus of the random copolymer at 60°C is more preferably 350 MPa or less.
  • the storage modulus of the random copolymer at 30°C is preferably 100 MPa or higher, more preferably 150 MPa or higher, and still more preferably 200 MPa or higher.
  • the storage modulus of the random copolymer at 60°C is preferably 50 MPa or higher, more preferably 80 MPa or higher, and still more preferably 130 MPa or higher.
  • the storage elastic modulus was obtained by measuring the dynamic viscoelasticity of a sample with a length of 30 mm, a width of 5 mm, and a thickness of 50 to 100 ⁇ m using a dynamic viscoelasticity device DVA220 manufactured by IT Keisoku Co., Ltd. in tensile mode, grip width 20 mm, measurement temperature -30. C. to 160.degree. C., a heating rate of 2.degree. C./min, and a frequency of 1 Hz.
  • a random copolymer solution obtained by dissolving a random copolymer in N-methyl-2-pyrrolidone (NMP) to a concentration of 10 to 20% by mass is cast on a glass plate. It is dried at 100° C. for 12 hours, and further dried at 100° C. for 12 hours under vacuum.
  • NMP N-methyl-2-pyrrolidone
  • Random copolymers can be produced by known methods such as emulsion polymerization, suspension polymerization, and solution polymerization.
  • the random copolymer is preferably produced by a suspension polymerization method from the viewpoint of easily adjusting the ratio of sequences in which the VdF unit and the TFE unit in the random copolymer are adjacent to each other.
  • the negative electrode mixture of the present disclosure preferably does not contain polytetrafluoroethylene.
  • the negative electrode mixture of the present disclosure preferably further contains a VdF homopolymer as a binder.
  • a VdF homopolymer is a polymer consisting only of VdF units.
  • the weight average molecular weight (polystyrene equivalent) of the VdF homopolymer is preferably 50000 to 3000000, more preferably 80000 or more, still more preferably 100000 or more, particularly preferably 200000 or more, more preferably 2400000 or less, more preferably 2,200,000 or less, and particularly preferably 2,000,000 or less.
  • the weight average molecular weight can be measured by gel permeation chromatography (GPC) using dimethylformamide as a solvent.
  • the number average molecular weight (polystyrene equivalent) of the VdF homopolymer is preferably 20000 to 1500000, more preferably 40000 or more, still more preferably 70000 or more, particularly preferably 140000 or more, more preferably 1400000 or less, more preferably 1,200,000 or less, and particularly preferably 1,100,000 or less.
  • the number average molecular weight can be measured by gel permeation chromatography (GPC) using dimethylformamide as a solvent.
  • the melting point of the VdF homopolymer is preferably 100-240°C.
  • the above melting point can be obtained as the temperature at the maximum value in the heat of fusion curve when the temperature is raised at a rate of 10° C./min using a differential scanning calorimetry (DSC) apparatus.
  • DSC differential scanning calorimetry
  • a VdF homopolymer can be produced by a conventionally known method such as solution polymerization or suspension polymerization by appropriately mixing additives such as VdF and a polymerization initiator.
  • the storage modulus of the VdF homopolymer at 30°C is preferably 2000 MPa or less, more preferably 1800 MPa or less.
  • the storage modulus of the VdF homopolymer at 60° C. is preferably 1500 MPa or less, more preferably 1300 MPa or less.
  • the storage modulus of the VdF homopolymer at 30°C is preferably 1000 MPa or more, more preferably 1100 MPa or more.
  • the storage modulus of the VdF homopolymer at 60°C is preferably 600 MPa or more, more preferably 700 MPa or more.
  • the storage modulus of the VdF homopolymer can be measured by the same method as the storage modulus of the random copolymer.
  • the mass ratio of the VdF homopolymer and the random copolymer is preferably 99/ 1 to 1/99, more preferably 97/3 to 10/90, still more preferably 95/5 to 40/60, and most preferably 90/10 to 50/50.
  • the content of the random copolymer in the binder is preferably 1% by mass or more, more preferably 3% by mass or more, still more preferably 5% by mass or more, and particularly preferably It is 10% by mass or more, most preferably 15% by mass or more, and may be 100% by mass or less.
  • the content of the binder in the negative electrode mixture is preferably 0.1 to 20 parts by mass, more preferably 0.3 to 15 parts by mass, and still more preferably 0 parts by mass with respect to 100 parts by mass of the negative electrode active material. .5 to 10 parts by mass.
  • the negative electrode mixture of the present disclosure contains a negative electrode active material containing a metal as a negative electrode active material.
  • Metals include simple metals, metals in metal compounds, and the like.
  • the metal contained in the negative electrode active material is usually a metal that can be electrochemically alloyed with alkali metals such as Li and Na.
  • the negative electrode active material simple metals that can be electrochemically alloyed with Li such as Si, Zn, Sn, W, Al, Sb, Ge, Bi, In; Si, Zn, Sn, W, Al, Sb, alloys containing Ge, Bi, In; lithium alloys such as lithium aluminum alloys and lithium tin alloys; metal oxides such as tin oxide and silicon oxide; lithium titanate; One or more of these can be used as the negative electrode active material.
  • the negative electrode active material is preferably at least one selected from the group consisting of Si, Zn, Sn, W, oxides of these metals, and alloys containing these metals.
  • a negative electrode active material containing Si, Zn, Sn, or W expands in volume due to an alloying reaction with an alkali metal such as Li or Na when the secondary battery is charged, and when the secondary battery is discharged, Alkali metals such as Li and Na are desorbed and shrink. Therefore, when a negative electrode active material containing Si, Zn, Sn, or W is used, the volume of the negative electrode mixture layer is repeatedly changed by charging and discharging of the secondary battery, so the binder cannot follow the volume change of the negative electrode active material.
  • the negative electrode mixture of the present disclosure contains, as a binder, a random copolymer in which VdF units, TFE units and optional monomer units are randomly arranged.
  • a battery with a high cycle capacity retention rate and a low resistance increase rate can be obtained.
  • a carbonaceous material such as graphite powder may be further used as a negative electrode active material together with the negative electrode active material containing metal.
  • Carbonaceous materials include natural graphite, artificial carbonaceous substances, artificial graphite substances, carbonaceous substances ⁇ for example, natural graphite, coal-based coke, petroleum-based coke, coal-based pitch, petroleum-based pitch, or oxidized pitches of these carbon materials, needle coke, pitch coke and partially graphitized carbon materials, furnace black, acetylene black, pyrolyzates of organic substances such as pitch-based carbon fibers, carbonizable organic substances (for example, soft pitch to hard pitch Coal-based heavy oil such as coal tar pitch or dry-distilled liquefied oil, atmospheric residual oil, straight-run heavy oil such as vacuum residual oil, cracked petroleum heavy oil such as ethylene tar, which is a by-product of the thermal cracking of crude oil, naphtha, etc.
  • aromatic hydrocarbons such as acenaphthylene, decacyclene, anthracene, and phenanthrene
  • N-ring compounds such as phenazine and acridine
  • S-ring compounds such as thiophene and bithiophene
  • polyphenylenes such as biphenyl and terphenyl
  • polyvinyl butyral insolubilized products thereof, nitrogen-containing polyacrylonitrile
  • organic polymers such as polypyrrole, sulfur-containing polythiophene, organic polymers such as polystyrene, cellulose, lignin, mannan, polygalacturonic acid, chitosan
  • natural polymers such as polysaccharides represented by sucrose, thermoplastic resins such as polyphenylene sulfide and polyphenylene oxide, thermosetting resins such as furfuryl alcohol resin, phenol-formaldehyde resin, and imide resin) and carbonized products thereof, or A carbonaceous material obtained
  • the mass ratio of the metal-containing negative electrode active material and the carbonaceous material is preferably 1/99 to 99/1, and more It is preferably 5/95 to 95/5, more preferably 10/10 to 90/10.
  • the content of the negative electrode active material in the negative electrode mixture is preferably 80.0 to 99.9% by mass, more preferably 90.0 to 99.0% by mass, based on the mass of the negative electrode mixture. , more preferably 95.0 to 98.0% by mass.
  • the negative electrode mixture of the present disclosure preferably contains a solvent.
  • the solvent include water and organic solvents.
  • organic solvents include 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, Ester solvents such as butyl acetate; Ether solvents such as tetrahydrofuran and dioxane; ⁇ -Methoxy-N,N-dimethylpropionamide, ⁇ -n-butoxy-N,N-dimethylpropionamide, ⁇ -n-hexyloxy- ⁇ -alkoxypropionamides such as N,N-dimethylpropionamide; and low-boiling general-purpose organic solvents such as mixed solvents thereof.
  • nitrogen-containing organic solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide and dimethylformamide
  • organic solvent a solvent represented by general formula (1) can also be used.
  • Solvents represented by general formula (1) include 3-methoxy-N,N-dimethylpropanamide, N-ethyl-2-pyrrolidone (NEP), N-butyl-2-pyrrolidone (NBP), acryloylmorpholine , N-cyclohexyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, 3-butoxy-N,N-dimethylpropanamide, N,N,N',N'-tetraethylurea, N,N-dimethylacetoaceta At least one selected from the group consisting of amide, N-octyl-2-pyrrolidone and N,N-diethylacetamide is preferred.
  • N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone and ⁇ -alkoxypropion are used because of their excellent coating properties.
  • At least one selected from the group consisting of amides is preferred, and at least one selected from the group consisting of N-methyl-2-pyrrolidone and N,N-dimethylacetamide is more preferred.
  • the negative electrode mixture of the present disclosure may further contain other components such as conductive aids, leveling agents, and reinforcing materials.
  • the negative electrode mixture of the present disclosure can be suitably used as a material for forming a secondary battery. Even when using a negative electrode active material that greatly expands in volume during charging and contracts significantly during discharging, the use of the negative electrode mixture of the present disclosure enables adhesion to the negative electrode current collector with sufficiently high peel strength for practical use. In addition, it is possible to form a negative electrode mixture layer that is excellent in flexibility and can follow volume changes during charging and discharging, and it is possible to obtain a battery with a high cycle capacity retention rate and a low resistance increase rate. Therefore, the negative electrode mixture of the present disclosure is suitable as a negative electrode mixture used for the negative electrode of secondary batteries.
  • a secondary battery to which the negative electrode mixture of the present disclosure is applied includes a positive electrode in which the positive electrode mixture is held in a positive electrode current collector, a negative electrode in which the negative electrode mixture is held in the negative electrode current collector, and an electrolyte. I have.
  • the negative electrode mixture of the present disclosure may be a negative electrode mixture for secondary batteries, and may be a negative electrode mixture for lithium ion secondary batteries.
  • a negative electrode of the present disclosure includes a current collector and a negative electrode mixture layer.
  • the negative electrode mixture layer is formed using the negative electrode mixture of the present disclosure, and may be provided on one side or both sides of the current collector.
  • Examples of current collectors included in the negative electrode of the present disclosure include metal foils or metal nets of iron, stainless steel, copper, aluminum, nickel, titanium, etc. Among them, copper foil is preferable.
  • the negative electrode of the present disclosure can be suitably manufactured by a manufacturing method in which the negative electrode mixture of the present disclosure is applied to a current collector. After applying the negative electrode mixture, the coating film may be dried, optionally subjected to heat treatment, and the obtained dry coating film may be pressed.
  • a secondary battery including the above negative electrode includes a positive electrode, a negative electrode, and a non-aqueous electrolyte, and the negative electrode is preferably the negative electrode described above.
  • the secondary battery of the present disclosure includes the negative electrode formed using the negative electrode mixture of the present disclosure, the cycle capacity retention rate is high and the resistance increase rate is low.
  • the non-aqueous electrolyte is not particularly limited, but propylene carbonate, ethylene carbonate, butylene carbonate, ⁇ -butyl lactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, etc. 1 or 2 or more of known solvents can be used. Any known electrolyte can be used, such as 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.
  • the negative electrode of the present disclosure can be suitably used as a negative electrode for wound secondary batteries.
  • the secondary battery of the present disclosure may be a wound secondary battery.
  • the negative electrode of the present disclosure is useful not only for lithium ion secondary batteries using the liquid electrolyte described above, but also for polymer electrolyte lithium secondary batteries as non-aqueous electrolyte secondary batteries. It is also useful for electric double layer capacitors.
  • A Area of peak from -86 ppm to -98 ppm
  • B Area of peak from -105 ppm to -118 ppm
  • C Area of peak from -119 ppm to -122 ppm
  • D Area of peak from -122 ppm to -126 ppm
  • VdF ratio (4A + 2B ) / (4A + 3B + 2C + 2D) ⁇ 100 [mol%]
  • Proportion of TFE (B + 2C + 2D) / (4A + 3B + 2C + 2D) ⁇ 100 [mol%]
  • Random exponent (a x 1/2)/[(a x 1/2) + b] a: the area of all peaks appearing in the chemical shift range of -108 to -111 ppm in the NMR spectrum of the random copolymer obtained by 19 F-NMR analysis b: the random copolymer obtained by 19 F-NMR analysis The area of all peaks appearing in the chemical shift range of -119 to -126 ppm in the NMR spectrum of
  • the obtained fluorine-containing copolymer (A1) had the following composition and physical properties.
  • VdF/TFE 93/7 (mol%) Number average molecular weight: 290000 Weight average molecular weight: 800000 Random index: 0.49
  • the obtained fluorine-containing copolymer (A2) had the following composition and physical properties.
  • VdF/TFE 80/20 (mol%) Number average molecular weight: 370000 Weight average molecular weight: 960000 Random index: 0.48
  • the obtained fluorine-containing copolymer (A3) had the following composition and physical properties.
  • VdF/TFE 62/38 (mol%) Number average molecular weight: 380000 Weight average molecular weight: 920000 Random index: 0.45
  • PVdF vinylidene fluoride homopolymer
  • Examples 1-11, Comparative Examples 1-3 Preparation of binder solution
  • the fluorine-containing copolymer, PVdF, and N-methyl-2-pyrrolidone (NMP) were added according to the composition shown in Table 1 so that the concentration of the binder (fluorine-containing copolymer and PVdF) in the NMP solution was 8% by mass. to prepare a composition containing a binder (binder solution).
  • the obtained negative electrode mixture was applied to one side or both sides of a negative electrode current collector made of copper foil, and dried. This was cut into a predetermined electrode size and rolled using a roll press to prepare a negative electrode having a negative electrode mixture layer formed on one or both sides of the negative electrode current collector, which was evaluated by the following methods. Table 1 shows the evaluation results.
  • Bending strength (3-point bending test) was measured by a method according to ASTM D790.
  • a negative electrode having negative electrode mixture layers on both sides was cut into a size of 15 mm ⁇ 20 mm to prepare a test piece.
  • the test piece is placed between the first point and the second point, which are 10 mm apart, and the middle (third point) of the test piece is moved with a probe in the thickness direction of the test piece.
  • a constant speed push and bending property test was performed. The force applied while moving at the thickness direction moving speed of 5 mm/min at the third point was measured.
  • the maximum bending force (or maximum bending strength) is the maximum force applied to the specimen according to the moving distance of the probe.
  • the magnitude of the maximum test force is an index of the flexibility of the negative electrode, and the more flexible the negative electrode, the smaller the maximum test force.
  • test piece of 1.2 cm ⁇ 7.0 cm was produced by cutting out a negative electrode having a negative electrode mixture layer on one side. After fixing the negative electrode mixture layer side of the test piece to a movable jig with double-sided tape, the tape was applied to the surface of the negative electrode current collector, and the stress (N /m) was measured with an autograph. 1N was used for the autograph load cell.
  • Ethylene carbonate, a high dielectric constant solvent, and ethyl methyl carbonate, a low viscosity solvent were mixed in a volume ratio of 30:70, and LiPF 6 was added to a concentration of 1.0 mol/liter. , and 2% by mass of vinylene carbonate was added thereto to obtain a non-aqueous electrolyte.
  • a negative electrode having a negative electrode mixture layer on one side prepared in Examples and Comparative Examples was cut into a size of ⁇ 13 mm as the size of the negative electrode mixture layer.
  • the negative electrode and the Li metal punched to ⁇ 15 mm are opposed to the negative electrode and the Li metal via a microporous polyethylene film (separator) having a thickness of 20 ⁇ m, and the non-aqueous electrolyte obtained above is injected.
  • a Li metal-negative electrode half cell was prepared by sufficiently permeating the separator and the like with the aqueous electrolyte.
  • Cycle capacity retention (%) (discharge capacity after 100 cycles) / (initial discharge capacity) x 100

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Abstract

L'invention concerne un mélange d'électrode négative contenant un liant et un matériau actif d'électrode négative, le liant contenant un copolymère aléatoire comprenant une unité de fluorure de vinylidène et une unité de tétrafluoroéthylène ; et le matériau actif d'électrode négative contient un matériau actif d'électrode négative contenant du métal.
PCT/JP2022/021521 2021-07-30 2022-05-26 Mélange d'électrode négative, électrode négative et batterie secondaire WO2023007933A1 (fr)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010092977A1 (fr) * 2009-02-12 2010-08-19 ダイキン工業株式会社 Suspension pour mélange d'électrode de batterie secondaire au lithium, électrode et batterie secondaire au lithium qui utilisent ladite suspension
WO2017199572A1 (fr) * 2016-05-17 2017-11-23 ソニー株式会社 Batterie rechargeable, bloc-batterie, véhicule électrique, système de stockage d'énergie électrique, outil électrique et dispositif électronique
JP2021102731A (ja) * 2019-12-25 2021-07-15 ダイキン工業株式会社 フルオロポリマーの製造方法

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010092977A1 (fr) * 2009-02-12 2010-08-19 ダイキン工業株式会社 Suspension pour mélange d'électrode de batterie secondaire au lithium, électrode et batterie secondaire au lithium qui utilisent ladite suspension
WO2017199572A1 (fr) * 2016-05-17 2017-11-23 ソニー株式会社 Batterie rechargeable, bloc-batterie, véhicule électrique, système de stockage d'énergie électrique, outil électrique et dispositif électronique
JP2021102731A (ja) * 2019-12-25 2021-07-15 ダイキン工業株式会社 フルオロポリマーの製造方法

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