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
  • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile 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 polymer for non-aqueous secondary batteries, a binder composition for non-aqueous secondary batteries, and a non-aqueous secondary battery electrode.
• Non-aqueous secondary batteries can be made smaller and lighter, so they are widely used as power sources for notebook computers, mobile phones, power tools, electronic and communication equipment, etc. In recent years, non-aqueous secondary batteries have also been used as power sources for electric vehicles and hybrid vehicles.
• a typical example of non-aqueous secondary batteries is a lithium ion secondary battery.
• a non-aqueous secondary battery includes a positive electrode using a metal oxide as an active material, a negative electrode using a carbon material such as graphite as an active material, and an electrolyte.
• the positive electrode and negative electrode each include a current collector and an electrode active material layer formed on the current collector.
• the electrode active material layer usually contains a binder that binds the active materials together and the active material and the current collector to fix the electrode active material layer on the current collector.
• binders used in non-aqueous secondary batteries those described in Patent Document 1 and Patent Document 2 are known.
• Patent Document 1 100 parts by mass of an aqueous dispersion of at least one polymer selected from the group consisting of styrene-butadiene copolymer latex and acrylic emulsion, and 1 to 20 parts by mass of a compound having a cloud point of 70° C. or less.
• a binder composition for a secondary battery electrode containing the above is described.
• Patent Document 2 describes a material for medical devices containing a polymer of ⁇ -(allyloxymethyl)acrylate.
• Patent Document 3 describes an electronic component containing a cured product obtained by curing a curable resin composition containing an ⁇ -(allyloxymethyl)acrylate compound.
• non-aqueous secondary batteries are strongly required to have higher output, higher capacity, and longer life. Therefore, in the binder used for non-aqueous secondary batteries, it is possible to form an electrode in which the electrode active material layer is even more difficult to separate from the current collector, and the cycle characteristics of the non-aqueous secondary battery using this can be improved. something is requested.
• the present invention has been made in view of the above circumstances, and can be used as a binder material for obtaining a non-aqueous secondary battery that can form an electrode in which the electrode active material layer is difficult to separate from the current collector and has excellent cycle characteristics.
• An object of the present invention is to provide a binder polymer for non-aqueous secondary batteries, a binder composition for non-aqueous secondary batteries containing the same, a binder for non-aqueous secondary batteries, and a slurry for non-aqueous secondary battery electrodes.
• the present invention provides a non-aqueous secondary battery comprising the binder polymer for a non-aqueous secondary battery of the present invention, in which the electrode active material layer is less likely to peel off from the current collector, and a non-aqueous secondary battery having excellent cycle characteristics can be obtained.
• An object of the present invention is to provide a battery electrode and a non-aqueous secondary battery including the same.
• a first aspect of the present invention provides the following binder polymer for non-aqueous secondary batteries.
• a first structural unit derived from the monomer (a1) a second structural unit derived from the monomer (a2); a third structural unit; and a fourth structural unit derived from the internal cross-linking agent (a4)
• the monomer (a1) is a nonionic compound having only one ethylenically unsaturated bond
• the monomer (a2) is a compound having only one ethylenically unsaturated bond and an anionic functional group
• the internal cross-linking agent (a4) is a compound having a plurality of independent ethylenically unsaturated bonds
• a binder polymer for a non-aqueous secondary battery wherein the third structural unit is a structural unit represented by the following general formula (1).
• Z is a hydrogen atom, an organic group having 1 to 30 carbon atoms, a metal atom, or an ammonium group.
• the binder polymer for non-aqueous secondary batteries of the first aspect of the present invention preferably has the following features [2] to [6]. Combinations of two or more of the following features are also preferred.
• [2] The binder polymer for non-aqueous secondary batteries according to [1], wherein Z in the formula (1) is a linear or branched chain saturated hydrocarbon group.
• [3] According to [1] or [2], wherein Z in the formula (1) is at least one selected from the group consisting of a methyl group, an n-propyl group, and an n-hexyl group. Binder polymer for non-aqueous secondary batteries.
• binder polymer for non-aqueous secondary batteries according to any one of [1] to [3], wherein the anionic functional group is a compound having at least one of a carboxy group and a sulfo group.
• a second aspect of the present invention provides the following binder composition for non-aqueous secondary batteries.
• a binder composition for non-aqueous secondary batteries comprising the binder polymer for non-aqueous secondary batteries according to any one of [1] to [6] and an aqueous medium.
• a third aspect of the present invention provides the following binder for non-aqueous secondary batteries.
• a binder for non-aqueous secondary batteries comprising the binder polymer for non-aqueous secondary batteries according to any one of [1] to [6].
• a fourth aspect of the present invention provides the following non-aqueous secondary battery electrode slurry.
• the binder polymer for non-aqueous secondary batteries according to any one of [1] to [6], an electrode active material, and an aqueous medium
• the slurry for a non-aqueous secondary battery electrode wherein the aqueous medium is one selected from the group consisting of water, a hydrophilic solvent, and a mixture containing water and a hydrophilic solvent.
• a fifth aspect of the present invention provides the following non-aqueous secondary battery electrode.
• a nonaqueous secondary battery electrode comprising the binder polymer for a nonaqueous secondary battery according to any one of [1] to [6].
• a sixth aspect of the present invention provides the following non-aqueous secondary battery.
• a non-aqueous secondary battery comprising the non-aqueous secondary battery electrode according to [10].
• a seventh aspect of the present invention provides the following method for producing a binder polymer for non-aqueous secondary batteries.
• a binder weight for a non-aqueous secondary battery characterized by copolymerizing a monomer (a1), a monomer (a2), a monomer (a3), and an internal cross-linking agent (a4).
• the monomer (a1) is a nonionic compound having an ethylenically unsaturated bond and not having multiple independent ethylenically unsaturated bonds
• the monomer (a2) is a compound having an ethylenically unsaturated bond and an anionic functional group and not having multiple independent ethylenically unsaturated bonds
• the monomer (a3) is a compound represented by the following general formula (2),
• Z is a hydrogen atom, an organic group having 1 to 30 carbon atoms, a metal atom, or an ammonium group.
• a binder polymer for a non-aqueous secondary battery that can be used as a binder material that can form an electrode in which an electrode active material layer is difficult to separate from a current collector and that provides a non-aqueous secondary battery with excellent cycle characteristics.
• a binder composition for a non-aqueous secondary battery that can form an electrode in which the electrode active material layer is difficult to peel off from the current collector and that provides a non-aqueous secondary battery with excellent cycle characteristics.
• a binder for a secondary battery and a slurry for a non-aqueous secondary battery electrode can be provided.
• the electrode active material layer is less likely to peel off from the current collector, and a non-aqueous secondary battery electrode that provides a non-aqueous secondary battery having excellent cycle characteristics, and a non-aqueous secondary battery electrode having excellent cycle characteristics comprising the same Can provide secondary batteries.
• the binder polymer for non-aqueous secondary batteries of the present invention the binder composition for non-aqueous secondary batteries, the binder for non-aqueous secondary batteries, the slurry for non-aqueous secondary battery electrodes, the non-aqueous secondary battery electrodes and non-aqueous
• the aqueous secondary battery A preferred example of the aqueous secondary battery will be described in detail.
• this invention is not limited only to embodiment shown below.
• the number, type, position, amount, ratio, material, configuration, etc. can be added, omitted, replaced, or changed without departing from the scope of the present invention.
• (Meth)acryl is a generic term for acryl and methacryl.
• (Meth)acrylate is a generic term for acrylate and methacrylate.
• ethylenically unsaturated bond refers to a radically polymerizable ethylenically unsaturated bond unless otherwise specified.
• the structural unit derived from the compound having an ethylenically unsaturated bond includes the chemical structure of the portion other than the ethylenically unsaturated bond in the compound, and the It may mean a structural unit having the same chemical structure as the portion other than the portion corresponding to the ethylenically unsaturated bond of the structural unit in the polymer.
• the ethylenically unsaturated bonds of the compounds may be converted to single bonds in forming the polymer.
• the structural unit derived from methyl methacrylate is represented by -CH 2 -C(CH 3 )(COOCH 3 )-.
• Structural units may be structural units derived from the same ionic compound, whether or not part of the functional groups are ion-exchanged.
• a structural unit represented by —CH 2 —C(CH 3 )(COONa)— may also be considered as a structural unit derived from methacrylic acid.
• one or more ethylenically unsaturated bonds may remain inside the structural unit as the structural unit of the polymer of the compound.
• a plurality of independent ethylenically unsaturated bonds means a plurality of ethylenically unsaturated bonds that do not form a conjugated diene with each other.
• the structural unit derived from divinylbenzene has a structure that does not have an ethylenically unsaturated bond (the portions corresponding to the two ethylenically unsaturated bonds of divinylbenzene are both polymer chains It may be a form incorporated in), or a structure having one ethylenically unsaturated bond (a form in which only the portion corresponding to one ethylenically unsaturated bond is incorporated into the polymer chain).
• the combined structural unit be a structural unit derived from a compound having an ethylenically unsaturated bond in the polymer.
• the structural units of the polymer are not vinyl acetate-derived structural units, but vinyl alcohol-derived structural units, based on the chemical structure of the polymer. .
• the "class" attached to the compound name means a group of compounds containing the compound structure, including the compound having a substituent.
• ⁇ -allyloxymethyl acrylates refer to a group of compounds containing an ⁇ -allyloxymethyl acrylate structure.
• the binder polymer for non-aqueous secondary batteries of the present embodiment is a polymer used as a binder for non-aqueous secondary batteries, and may be hereinafter referred to as "binder polymer".
• the binder polymer (P) of the present embodiment comprises a first structural unit derived from the monomer (a1) shown below, a second structural unit derived from the monomer (a2) shown below, and and a fourth structural unit derived from the internal cross-linking agent (a4) shown below.
• the binder polymer (P) of the present embodiment is a monomer (a1), a monomer (a2), a monomer (a3), or an internal cross-linking agent (a4). It may contain structural units derived from body (a5).
• the first structural unit in the binder polymer (P) of the present embodiment is derived from the monomer (a1).
• the monomer (a1) is a nonionic (neither anionic functional group nor cationic functional group) compound having only one ethylenically unsaturated bond.
• the monomer (a1) may be only one type of compound, or may contain two or more types of compounds.
• the monomer (a1) is preferably at least one of a (meth)acrylic acid ester and an ethylenically unsaturated bond-containing aromatic compound, more preferably both.
• the (meth)acrylic acid ester more preferably contains a (meth)acrylic acid alkyl ester.
• the monomer (a1) preferably has neither a hydroxy group nor a cyano group, and more preferably does not have a polar functional group.
• the (meth)acrylic acid alkyl ester and the aromatic compound in the monomer (a1) is preferably 80% by mass or more, more preferably 90% by mass or more, and most preferably 100% by mass.
• the (meth)acrylic acid alkyl ester contained in the (meth)acrylic acid ester used in the monomer (a1) includes, for example, methyl (meth)acrylate, ethyl (meth)acrylate, (meth)acrylic acid n -propyl, isopropyl (meth)acrylate, n-butyl (meth)acrylate, tert-butyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isobornyl (meth)acrylate , lauryl (meth)acrylate, stearyl (meth)acrylate, and the like.
• Examples of the aromatic compound having an ethylenically unsaturated bond used for the monomer (a1) include styrene, t-butylstyrene, ⁇ -methylstyrene, p-methylstyrene, 1,1-diphenylethylene and the like. be done.
• the monomer (a1) contains an aromatic vinyl compound, it more preferably contains at least one of styrene and ⁇ -methylstyrene, because the binder polymer (P) has excellent dispersibility in an aqueous medium. , and more preferably styrene.
• Examples of the monomer (a1) other than at least one of the (meth)acrylic acid ester and the aromatic compound having an ethylenically unsaturated bond include an aliphatic hydrocarbon compound having an ethylenically unsaturated bond, ethylene and alicyclic hydrocarbon compounds having a polyunsaturated bond.
• composition of the monomer (a1) in order to adjust the glass transition point of the binder polymer (P), or to adjust the polymerization rate according to the molecular design, within the range specified in the present invention, It is preferable to adjust the preferred compound and its amount as appropriate.
• the second structural unit in the binder polymer (P) of the present embodiment is derived from the monomer (a2).
• Monomer (a2) is a compound having only one ethylenically unsaturated bond and an anionic functional group.
• the monomer (a2) may be only one type of compound, or may contain two or more types of compounds.
• Examples of the anionic functional group possessed by the monomer (a2) include a carboxy group, a sulfo group, and a phosphate group.
• the monomer (a2) contains a compound having at least one of a carboxy group and a sulfo group to form a binder polymer (P) capable of forming an electrode in which the electrode active material layer is difficult to peel off from the current collector. It is more preferable to include both a compound having a carboxy group and a compound having a sulfo group.
• the monomer (a2) may contain a compound having multiple anionic functional groups of the same kind in one molecule. That is, the binder polymer (P) may contain a plurality of the same type of anionic functional groups in one structural unit.
• the monomer (a2) may contain compounds having two or more different anionic functional groups in one molecule. That is, the binder polymer (P) may contain two or more different anionic functional groups in one structural unit.
• the monomer (a2) may contain two or more compounds having different anionic functional groups. That is, the binder polymer (P) may contain two or more types of structural units containing different anionic functional groups.
• the monomer (a2) examples include unsaturated monocarboxylic acids such as methacrylic acid, acrylic acid and crotonic acid; and unsaturated dicarboxylic acids such as itaconic acid and fumaric acid.
• the monomer (a2) is a binder polymer (P) capable of forming an electrode in which the electrode active material layer is not easily peeled off from the current collector. It is preferred to include one.
• At least part of the structural units derived from the monomer (a2) may form a salt with a basic substance.
• the salt-forming monomer (a2) include sodium (meth)acrylate, sodium p-styrenesulfonate (also referred to as sodium p-styrenesulfonate), and the like.
• the monomer (a2) preferably contains at least one of a sulfonic acid having an ethylenically unsaturated bond and a salt thereof, more preferably a sulfonate having an ethylenically unsaturated bond.
• the sulfonic acid preferably contains an aromatic vinyl compound having a sulfo group, and more preferably contains p-styrenesulfonic acid.
• the sulfonate preferably contains a salt of an aromatic vinyl compound having a sulfo group, and more preferably contains a p-styrenesulfonate. It is more preferable to contain sodium p-styrenesulfonate, because it provides good properties.
• the third structural unit in the binder polymer (P) of this embodiment is a structural unit represented by the following general formula (1). Only one kind of the third structural unit may be contained, or two or more kinds thereof may be contained.
• Z is a hydrogen atom, an organic group having 1 to 30 carbon atoms, a metal atom, or an ammonium group.
• the binder polymer (P) Since the binder polymer (P) has the third structural unit represented by the general formula (1), it is possible to form an electrode in which the electrode active material layer is difficult to peel off from the current collector, and the non-aqueous two-layer polymer is excellent in cycle characteristics. The following battery is obtained. Although the action and function by which such an effect is obtained is not necessarily clear, the inventors presume that it is due to the following. That is, in the non-aqueous secondary battery electrode containing the binder polymer (P) of the present embodiment, it is presumed that the electrode active materials and the electrode active material and the current collector adhere to each other due to the following. .
• the binder polymer (P) contains the ring structure (tetrahydrofuran ring) of the third structural unit represented by the general formula (1) in the main chain, the binder polymer (P) adheres to the electrode active material. Good properties.
• the electrode active material layer of the non-aqueous secondary battery electrode containing the binder polymer (P) is firmly adhered to the current collector. Therefore, it is presumed that a non-aqueous secondary battery comprising this non-aqueous secondary battery electrode will have excellent cycle characteristics.
• Such an effect of the binder polymer (P) of the present embodiment is more effective particularly when the binder polymer (P) is applied to the material of the negative electrode active material layer provided in the negative electrode. can get.
• the third structural unit is derived from the monomer (a3).
• the monomer (a3) is not particularly limited as long as it is a compound represented by the general formula (1) and capable of forming a polymer having a third structural unit.
• the compound corresponding to the monomer (a3) is any one selected from the monomer (a1), the monomer (a2), the monomer (a4), and the monomer (a5) If it corresponds to one or more compounds, it is assumed to be a compound corresponding to the monomer (a3).
• the monomer (a3) it is preferable to use ⁇ -allyloxymethyl acrylates represented by the following general formula (2).
• the compound represented by the general formula (2), which is the monomer (a3), is cyclized to form the third structural unit represented by the general formula (1) of the binder polymer (P). It is preferable because it can be formed more easily.
• Z in formulas (1) and (2) is a hydrogen atom, an organic group having 1 to 30 carbon atoms, a metal atom, or an ammonium group. That is, Z in general formula (2) is the same as Z in general formula (1).
• the monomer (a3) only one type of compound may be used, or two or more types of compounds having different Z in formula (2), for example, may be used.
• ⁇ -allyloxymethyl acrylates in which Z in formula (2) is an organic group having 1 to 30 carbon atoms the organic group is a monovalent to hexavalent organic group having 1 to 30 carbon atoms.
• ⁇ -Allyloxymethyl acrylates which are monovalent to hexavalent organic groups having 1 to 30 carbon atoms, are obtained by combining ⁇ -allyloxymethyl acrylic acid and monovalent to hexavalent alcohols having an organic group having 1 to 30 carbon atoms. or a transesterification reaction between an ester of ⁇ -allyloxymethyl acrylic acid and a monohydric to hexahydric alcohol having an organic group of 1 to 30 carbon atoms.
• the third structural unit represented by general formula (1) obtained by cyclic polymerization thereof is Z in formula (1) may be bonded to 1 to 5 other structural units via an organic group having 1 to 30 carbon atoms.
• the third structural unit represented by general formula (1) includes 1 to 5 separate third structural units represented by general formula (1) and It may be bonded by covalent Z.
• the main chain containing the tetrahydrofuran ring of the binder polymer (P) is —CO—O—Z′(—O—CO—) n1 (where Z′ is Z in formula (1) is a linking group consisting of an organic group having 1 to 30 carbon atoms, n1 is an integer of 1 to 5, and is the number of different third structural units sharing Z in formula (1) It has a crosslinked structure represented by
• ⁇ -allyloxymethyl acrylates in which Z in formula (2) is a metal atom or an ammonium group can be produced by a neutralization reaction between ⁇ -allyloxymethyl acrylic acid and a metal hydroxide or an ammonium compound. . ⁇ -allyloxymethyl acrylates in which Z in formula (2) is a metal atom or an ammonium group is ⁇ -allyloxymethyl acrylic acid having a structure corresponding to the target ⁇ -allyloxymethyl acrylates You may manufacture by the hydrolysis reaction of ester.
• Z in formulas (1) and (2) is an organic group having 1 to 30 carbon atoms, it is preferably a hydrocarbon group having 1 to 30 carbon atoms, and 1 to 6 having 1 to 30 carbon atoms. It is more preferably a valent hydrocarbon group.
• the hydrocarbon group having 1 to 30 carbon atoms may be a hydrocarbon group having any of a linear, branched or cyclic structure, and may have a substituent. Examples of the substituent which the hydrocarbon group having 1 to 30 carbon atoms may have include an alkoxy group, a hydroxy group, a cyano group, an amino group, an amido group and the like.
• Z is a hydrocarbon group having 1 to 30 carbon atoms, the hydrocarbon group may be good.
• organic group having 1 to 30 carbon atoms corresponding to Z in formula (1) and formula (2) include methyl group, ethyl group, n-propyl group, i-propyl group and n-butyl group. , s-butyl group, t-butyl group, n-hexyl group, 2-ethylhexyl group linear or branched chain saturated hydrocarbon group; hydrogen atoms of chain saturated hydrocarbon groups such as methoxyethyl group, methoxyethoxyethyl group, methoxyethoxyethoxyethyl group, 3-methoxybutyl group, ethoxyethyl group, ethoxyethoxyethyl group, phenoxyethyl group and phenoxyethoxyethyl group; an alkoxy-substituted chain saturated hydrocarbon group partially substituted with an alkoxy group; A hydroxy-substituted chain saturated hydrocarbon group in which part of the hydrogen
• Z in the formulas (1) and (2) provides better polymerization stability when producing the binder polymer (P), and is the binder polymer (P) of the present embodiment described above.
• a straight chain or branched chain saturated hydrocarbon group is preferred because the effect is more pronounced.
• a linear or branched chain saturated hydrocarbon group having 1 to 6 carbon atoms is preferable because the effect of forming it can be sufficiently obtained, and it consists of a methyl group, an n-propyl group, and an n-hexyl group. It is more preferably one selected from the group.
• Examples of ⁇ -allyloxymethyl acrylates in which Z in formula (2) is a hydrogen atom or a monovalent hydrocarbon group optionally having a substituent include ⁇ -allyloxymethyl acrylic acid, methyl ⁇ -allyloxymethyl acrylate (compound in which Z in general formula (2) is a methyl group), ethyl ⁇ -allyloxymethyl acrylate, n-propyl ⁇ -allyloxymethyl acrylate (in general formula (2) Z is an n-propyl group), i-propyl ⁇ -allyloxymethyl acrylate, n-butyl ⁇ -allyloxymethyl acrylate, s-butyl ⁇ -allyloxymethyl acrylate, ⁇ -allyloxymethyl acrylic t-butyl acid, n-hexyl ⁇ -allyloxymethyl acrylate (compound in which Z in the general formula (2) is an n-hexyl group), 2-ethylhexyl ⁇ -allyloxymethyl acrylate;
• Z in formula (2) is It is preferably a monovalent hydrocarbon group which may have a substituent, specifically, methyl ⁇ -allyloxymethyl acrylate, n-propyl ⁇ -allyloxymethyl acrylate, and ⁇ -allyl At least one of n-hexyl oxymethyl acrylate is preferable, and ⁇ -methyl oxymethyl acrylate in which Z in formula (2) is a methyl group is more preferable.
• the fourth structural unit in the binder polymer (P) of the present embodiment is derived from the internal cross-linking agent (a4).
• the internal cross-linking agent (a4) is a compound having multiple independent ethylenically unsaturated bonds.
• the internal cross-linking agent (a3) is a compound capable of forming a crosslinked structure in radical polymerization of monomers including the monomer (a1), the monomer (a2) and the monomer (a3). is.
• the internal cross-linking agent (a4) only one compound may be used, or two or more different compounds may be used.
• Examples of the internal cross-linking agent (a4) include divinylbenzene, ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 2-hydroxy-3-acryloyloxypropyl methacrylate, and the like. and compounds having three or more ethylenically unsaturated bonds such as trimethylolpropane tri(meth)acrylate.
• the internal cross-linking agent (a4) should contain at least one of divinylbenzene and trimethylolpropane tri(meth)acrylate since good polymerization stability is obtained when the binder polymer (P) is produced. is preferred.
• Other monomers (a5) are neither monomers (a1), monomers (a2), monomers (a3) nor internal cross-linking agents (a4).
• Other monomers (a5) include compounds having an ethylenically unsaturated bond and a polar functional group, surfactants having an ethylenically unsaturated bond (hereinafter sometimes referred to as "polymerizable surfactants"). , a compound having an ethylenically unsaturated bond and functioning as a silane coupling agent, etc., but not limited to these.
• the polar functional group in the compound having an ethylenically unsaturated bond and a polar functional group preferably contains at least one of a hydroxy group and a cyano group, more preferably a hydroxy group.
• Examples of the compound having an ethylenically unsaturated bond and a polar functional group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, (meth)acrylonitrile and the like. It preferably contains 2-hydroxyethyl acid.
• polymerizable surfactant which is an example of the other monomer (a5)
• a compound having an ethylenically unsaturated bond and functioning as a surfactant can be used.
• polymerizable surfactants include compounds represented by the following chemical formulas (3) to (6).
• R 1 is an alkyl group.
• p is an integer from 10 to 40;
• R 1 is preferably an alkyl group having 10 to 40 carbon atoms, more preferably a linear unsubstituted alkyl group having 10 to 40 carbon atoms.
• R2 is an alkyl group.
• q is an integer of 10-12.
• R 2 is preferably an alkyl group having 10 to 40 carbon atoms, more preferably a linear unsubstituted alkyl group having 10 to 40 carbon atoms.
• Examples of the compound represented by formula (4) include polyoxyethylene alkyl ether sulfate (Aqualon KH-10, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.).
• R3 is an alkyl group.
• M1 is NH4 or Na.
• R 3 is preferably an alkyl group having 10 to 40 carbon atoms, more preferably a linear unsubstituted alkyl group having 10 to 40 carbon atoms.
• R4 is an alkyl group.
• M2 is NH4 or Na.
• R 4 is preferably an alkyl group having 10 to 40 carbon atoms, more preferably a linear unsubstituted alkyl group having 10 to 40 carbon atoms.
• Compounds having an ethylenically unsaturated bond and functioning as a silane coupling agent which are examples of the other monomer (a5), include, for example, vinyltrimethoxysilane, ⁇ -methacryloxypropyltrimethoxysilane, vinyltriethoxysilane, ⁇ -methacryloxypropyltriethoxysilane, and the like.
• the binder polymer (P) of the present embodiment preferably contains a total of 80% by mass or more of the first structural unit and the second structural unit, more preferably 85% by mass or more, and 87% by mass or more. is more preferred.
• the binder polymer (P) may contain the first structural unit and the second structural unit in a total amount of 90% by mass or more, or 95% by mass or more.
• the content of the second structural unit derived from the monomer (a2) is 1 per 100 parts by mass of the first structural unit derived from the monomer (a1). 0 parts by mass or more, more preferably 1.5 parts by mass or more, and even more preferably 3.0 parts by mass or more. This is because better polymerization stability can be obtained when the binder polymer (P) is produced, and an electrode in which the electrode active material layer is more difficult to peel off from the current collector can be formed.
• the content of the second structural unit derived from the monomer (a2) per 100 parts by mass of the first structural unit derived from the monomer (a1) is 30. It is preferably no more than 15 parts by mass, more preferably no more than 7.5 parts by mass. This is because better polymerization stability can be obtained when the binder polymer (P) is produced.
• the content of the third structural unit derived from the monomer (a3) with respect to 100 parts by mass of the first structural unit derived from the monomer (a1) is 0. It is preferably at least 0.050 parts by mass, more preferably at least 0.100 parts by mass, and even more preferably at least 0.150 parts by mass. This is because the binder polymer (P) can be used as a binder material for forming an electrode in which the electrode active material layer is less likely to peel off from the current collector and for obtaining a non-aqueous secondary battery with more excellent cycle characteristics.
• the content of the third structural unit derived from the monomer (a3) is 30 per 100 parts by mass of the first structural unit derived from the monomer (a1). It is preferably no more than 25 parts by mass, more preferably no more than 20 parts by mass. This is because the binder polymer (P) having a sufficiently high molecular weight can be easily obtained, and the gel fraction of the binder composition for a non-aqueous secondary battery containing the polymer (P) can be sufficiently high.
• the content of the fourth structural unit derived from the internal cross-linking agent (a4) with respect to 100 parts by mass of the first structural unit derived from the monomer (a1) is 0. It is preferably at least 0.050 parts by mass, more preferably at least 0.075 parts by mass, and even more preferably at least 0.50 parts by mass. This is because deterioration of the binder polymer (P) is suppressed, and the binder polymer (P) can be used as a binder material for obtaining a non-aqueous secondary battery with more excellent cycle characteristics.
• the content of the fourth structural unit derived from the internal cross-linking agent (a4) per 100 parts by mass of the first structural unit derived from the monomer (a1) is 20. It is preferably no more than 7.5 parts by mass, and even more preferably no more than 2.5 parts by mass. This is because gelation of the binder polymer (P) can be suppressed.
• the binder polymer (P) of the present embodiment contains a fifth structural unit derived from another monomer (a5), and the other monomer (a5) is a polymerizable surfactant
• the monomer The content of the fifth structural unit derived from the other monomer (a5) with respect to 100 parts by mass of the first structural unit derived from the body (a1) is preferably 0.05 parts by mass or more, and 0.05 part by mass or more. 075 parts by mass or more is more preferable. This is because good polymerization stability can be obtained when the binder polymer (P) is produced.
• the first structural unit derived from the other monomer (a5) for 100 parts by mass of the first structural unit derived from the monomer (a1)
• the content of 5 structural units is preferably 30 parts by mass or less, more preferably 15 parts by mass or less. This is because the particle size, viscosity, etc. of the binder polymer (P) can be appropriately adjusted.
• Glass transition point Tg of binder polymer (P) The glass transition point Tg of the binder polymer (P) of the present embodiment is measured using a differential scanning calorimetry (DSC) device (EXSTAR DSC/SS7020 manufactured by Hitachi High-Tech Science) at a heating rate of 10° C./ It is the peak top temperature of the DDSC chart obtained as the temperature differential of the DSC measured by DSC measurement in a nitrogen gas atmosphere.
• DSC differential scanning calorimetry
• the glass transition point Tg of the binder polymer (P) is preferably ⁇ 30° C. or higher, more preferably ⁇ 10° C. or higher, and even more preferably 0° C. or higher. This is because a non-aqueous secondary battery having an electrode containing a binder for a non-aqueous secondary battery containing the binder polymer (P) has excellent cycle characteristics.
• the glass transition point Tg of the binder polymer (P) is preferably 100° C. or lower, more preferably 50° C. or lower, and even more preferably 40° C. or lower.
• the binder polymer (P) contains a monomer (a1), a monomer (a2), a monomer (a3), an internal cross-linking agent (a4), and optionally other monomers (a5 ) can be obtained by copolymerizing monomers containing
• the monomers (components (a1) to (a5)) used for synthesizing the binder polymer (P) are sometimes collectively referred to as the monomer (a).
• Examples of methods for copolymerizing the monomer (a) include an emulsion polymerization method in which the monomer (a) is emulsion-polymerized in an aqueous medium (b).
• a binder polymer (P) is produced by an emulsion polymerization method, in addition to the monomer (a) and the aqueous medium (b), a non-polymerizable surfactant (c) and a basic substance (d ), a radical polymerization initiator (e), a chain transfer agent (f) and the like can be used.
• the aqueous medium (b) is one selected from the group consisting of water, hydrophilic solvents, and mixtures containing water and hydrophilic solvents.
• Hydrophilic solvents include methanol, ethanol, isopropyl alcohol, N-methylpyrrolidone, and the like.
• the aqueous medium (b) is preferably water from the viewpoint of polymerization stability.
• a mixture of water and a hydrophilic solvent may be used as long as the polymerization stability is not impaired.
• a non-polymerizable surfactant (c) is added to a solution containing the aqueous medium (b) and the monomer (a). may be emulsion polymerized.
• a non-polymerizable surfactant (c) is a surfactant (c) that does not have a polymerizable unsaturated bond in its chemical structure.
• Surfactant (c) improves the dispersion stability of the solution during emulsion polymerization and/or the dispersion (emulsion) obtained after polymerization.
• the surfactant (c) it is preferable to use an anionic surfactant or a nonionic surfactant.
• anionic surfactants include alkylbenzene sulfonates, alkyl sulfates, polyoxyethylene alkyl ether sulfates, and fatty acid salts.
• Nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene polycyclic phenyl ethers, polyoxyalkylene alkyl ethers, sorbitan fatty acid esters, and polyoxyethylene sorbitan fatty acid esters.
• the above surfactant (c) may be used alone or in combination of two or more.
• Base substance (d) When the binder polymer (P) is produced by an emulsion polymerization method, a basic substance (d ) may be added. By adding the basic substance (d), the acidic component contained in the monomer (a) is neutralized. As a result, the pH of the solution during emulsion polymerization and/or the dispersion after emulsion polymerization is in an appropriate range, and the stability of the solution during emulsion polymerization and/or the dispersion after emulsion polymerization is improved.
• the dispersion after emulsion polymerization has a pH of 1 at 23° C. when an electrode is produced using a slurry containing a non-aqueous secondary battery binder containing the binder polymer (P) and an electrode active material. It is preferably 0.5 to 10, more preferably 5.0 to 9.0, even more preferably 6.0 to 9.0. This is because sedimentation of the electrode active material in the slurry containing the non-aqueous secondary battery binder and the electrode active material can be suppressed.
• Examples of the basic substance (d) added to the solution for emulsion polymerization and/or the dispersion after emulsion polymerization include ammonia, triethylamine, sodium hydroxide, and lithium hydroxide. These basic substances (d) may be used singly or in combination of two or more.
• radical polymerization initiator (e) used in producing the binder polymer (P) by emulsion polymerization is not particularly limited, and known initiators can be used.
• examples of the radical polymerization initiator (e) include persulfates such as ammonium persulfate and potassium persulfate; hydrogen peroxide; azo compounds; tert-butyl hydroperoxide, tert-butyl peroxybenzoate, cumene hydroperoxide and the like. of organic peroxides. Persulfates and organic peroxides are preferably used as the radical polymerization initiator (e).
• a reducing agent such as sodium bisulfite, Rongalite, ascorbic acid is used together with the radical polymerization initiator (e) to obtain a redox polymer. may be polymerized.
• the amount of the radical polymerization initiator (e) added is 0.001 parts by mass or more with respect to 100 parts by mass of the monomer (a). Preferably, it is more preferably 0.005 parts by mass or more. This is because the conversion rate of the monomer (a) to the binder polymer (P) can be increased when the binder polymer (P) is produced by the emulsion polymerization method.
• the amount of the radical polymerization initiator (e) added is preferably 10 parts by mass or less, more preferably 5 parts by mass or less per 100 parts by mass of the monomer (a). This is because the molecular weight of the binder polymer (P) can be increased, and the swelling ratio of the non-aqueous secondary battery electrode containing the binder polymer (P) of the present embodiment to the electrolytic solution can be decreased.
• Chain transfer agent (f) The chain transfer agent (f) used in producing the binder polymer (P) by emulsion polymerization is used to adjust the molecular weight of the binder polymer (P) obtained by emulsion polymerization.
• Chain transfer agents (f) include n-dodecyl mercaptan, tert-dodecyl mercaptan, n-butyl mercaptan, 2-ethylhexylthioglycolate, 2-mercaptoethanol, ⁇ -mercaptopropionic acid, methyl alcohol, n-propyl alcohol, isopropyl alcohol, t-butyl alcohol, benzyl alcohol and the like.
• Examples of the emulsion polymerization method used for producing the binder polymer (P) include a method of performing emulsion polymerization while continuously supplying each component used in the emulsion polymerization into a reaction vessel.
• the emulsion polymerization temperature is not particularly limited, but is, for example, 30 to 90°C, preferably 50 to 85°C, more preferably 55 to 80°C.
• Emulsion polymerization is preferably carried out while stirring.
• the monomer (a) and the radical polymerization initiator (e) are added during the emulsion polymerization so that the concentrations of the monomer (a) and the radical polymerization initiator (e) in the solution during the emulsion polymerization are uniform. is preferably continuously supplied to the solution of
• Binder for non-aqueous secondary battery contains the binder polymer (P) of the present embodiment.
• the electrode binder for non-aqueous secondary batteries may contain other components together with the binder polymer (P).
• the electrode binder for nonaqueous secondary batteries may contain, for example, a polymer other than the binder polymer (P), a surfactant, and the like.
• the binder for non-aqueous secondary batteries consists of a component that remains without volatilizing even when a process involving heating is performed in the manufacturing method for non-aqueous secondary batteries described later. Specifically, 1 g of the binder composition for non-aqueous secondary batteries containing the binder polymer (P) is weighed and placed on an aluminum dish having a diameter of 5 cm. After drying at 1 atmosphere (1013 hPa) and a temperature of 105° C. for 1 hour while circulating the air in the dryer, it is the component that remains.
• the content of the binder polymer (P) contained in the binder for nonaqueous secondary batteries is preferably 80% by mass or more, more preferably 90% by mass or more, and 95% by mass or more. is more preferable, and more preferably 98% by mass or more. This is because the effect of containing the polymer (P) for binder is remarkable.
• Binder composition for non-aqueous secondary battery contains the binder polymer (P) of the present embodiment and an aqueous medium (B).
• the binder composition for a non-aqueous secondary battery of the present embodiment is preferably one in which the binder polymer (P) is dispersed in the aqueous medium (B).
• the binder composition for non-aqueous secondary batteries may contain other components together with the binder polymer (P) and the aqueous medium (B).
• the binder composition for non-aqueous secondary batteries may contain, for example, the above components used in the synthesis of the binder polymer (P).
• the binder composition for non-aqueous secondary batteries of the present embodiment may be a dispersion liquid obtained by producing a binder polymer (P) by an emulsion polymerization method. Further, the binder composition for a non-aqueous secondary battery of the present embodiment is a dispersion obtained by dispersing the binder polymer (P) obtained by a method other than the emulsion polymerization method in the aqueous medium (B). It may be liquid. In this case, a known method can be used as a method for dispersing the binder polymer (P) in the aqueous medium (B).
• the aqueous medium (B) in the binder composition for non-aqueous secondary batteries of the present embodiment is water, a hydrophilic solvent, or a mixture thereof.
• the hydrophilic solvent include the same hydrophilic solvents as those exemplified as the aqueous medium (b) used for synthesizing the binder polymer (P).
• the aqueous medium (B) may be the same as or different from the aqueous medium (b) used for synthesizing the binder polymer (P).
• the aqueous medium (B) contains the binder polymer (P) may be the aqueous medium (b) used in the synthesis of Further, the aqueous medium (B) may be obtained by adding a new aqueous medium to the aqueous medium (b) used for synthesizing the binder polymer (P). Further, the aqueous medium (B) is obtained by adding a part or all of the aqueous medium (b) contained in the dispersion liquid obtained by producing the binder polymer (P) by an emulsion polymerization method to a new aqueous solvent. It may be replaced.
• the new aqueous medium used in this case may have the same composition as the aqueous medium (b) used for synthesizing the binder polymer (P), or may have a different composition.
• Non-volatile content concentration of binder composition for non-aqueous secondary battery The non-volatile content concentration of the binder composition for non-aqueous secondary batteries of the present embodiment is preferably 20% by mass or more, more preferably 25% by mass or more, and even more preferably 30% by mass or more. . This is for increasing the amount of the active ingredient contained in the binder composition for non-aqueous secondary batteries.
• the non-volatile content concentration of the binder composition for non-aqueous secondary batteries can be adjusted by the content of the aqueous medium (B) contained in the binder composition for non-aqueous secondary batteries.
• the non-volatile content of the binder composition for non-aqueous secondary batteries is preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less. This is because an increase in the viscosity of the binder composition for non-aqueous secondary batteries is suppressed, making it easier to prepare the slurry for non-aqueous secondary battery electrodes.
• the binder composition for a non-aqueous secondary battery of the present embodiment preferably has a gel fraction of 80% or more, more preferably 85% or more, and more preferably 90% or more, as measured by a method described later. is more preferred. It is because it becomes the binder composition for non-aqueous secondary batteries which can form the non-aqueous secondary battery electrode which is excellent in solvent resistance.
• the non-aqueous secondary battery electrode slurry contains the binder polymer (P) of the present embodiment, an electrode active material, and an aqueous medium.
• the binder polymer (P) and the electrode active material contained in the non-aqueous secondary battery electrode slurry are preferably dispersed in an aqueous medium.
• the non-aqueous secondary battery electrode slurry was used to synthesize a binder polymer (P), an electrode active material, an aqueous medium, a thickener, a conductive aid, and a binder polymer (P). It may contain the above components and the like.
• the content of the binder polymer (P) contained in the non-aqueous secondary battery electrode slurry is preferably 0.50 parts by mass or more, and 1.0 parts by mass with respect to 100 parts by mass of the electrode active material. It is more preferable to be above. This is for sufficiently exhibiting the effect of including the binder polymer (P).
• the content of the binder polymer (P) contained in the non-aqueous secondary battery electrode slurry is preferably 5.0 parts by mass or less, and 4.0 parts by mass with respect to 100 parts by mass of the electrode active material. It is more preferably 3.0 parts by mass or less, more preferably 3.0 parts by mass or less. This is because the content of the electrode active material contained in the non-aqueous secondary battery electrode slurry can be increased.
• the electrode active material contained in the non-aqueous secondary battery electrode slurry is a material capable of intercalating/deintercalating ions such as lithium ions that serve as charge carriers.
• the ions serving as charge carriers are preferably alkali metal ions, more preferably lithium ions, sodium ions and potassium ions, and even more preferably lithium ions.
• the electrode active material is the negative electrode active material.
• the negative electrode active material preferably contains at least one of a carbon material, a material containing silicon, and a material containing titanium.
• the carbon material used as the negative electrode active material include coke such as petroleum coke, pitch coke, and coal coke, carbonized organic polymers, and graphite such as artificial graphite and natural graphite.
• the material containing silicon used as the negative electrode active material include simple silicon and silicon compounds such as silicon oxide.
• Materials containing titanium used as the negative electrode active material include, for example, lithium titanate. These materials used as the negative electrode active material may be used alone, or may be used as a mixture or composite.
• the negative electrode active material preferably contains at least one of a carbon material and a material containing silicon, and more preferably contains a carbon material. This is because the binding property between the negative electrode active material and between the negative electrode active material and the current collector by the binder polymer (P) contained in the non-aqueous secondary battery electrode slurry is greatly improved. be.
• the electrode active material is a positive electrode active material.
• the positive electrode active material a material whose standard electrode potential is nobler than that of the negative electrode active material is used.
• the positive electrode active material contains nickel such as Ni—Co—Mn-based lithium composite oxide, Ni—Mn—Al-based lithium composite oxide, and Ni—Co—Al-based lithium composite oxide.
• chalcogen compounds such as lithium composite oxides, lithium cobaltate ( LiCoO2 ), spinel-type lithium manganese oxide ( LiMn2O4 ), olivine- type lithium iron phosphate, TiS2 , MnO2 , MoO3 , V2O5 , and the like. mentioned.
• LiCoO2 lithium cobaltate
• LiMn2O4 spinel-type lithium manganese oxide
• olivine- type lithium iron phosphate TiS2 , MnO2 , MoO3 , V2O5 , and the like. mentioned.
• One of these substances used as the positive electrode active material may be used alone, or two or more of them may be used in combination.
• the aqueous medium contained in the non-aqueous secondary battery electrode slurry of the present embodiment is one selected from the group consisting of water, a hydrophilic solvent, and a mixture containing water and a hydrophilic solvent.
• the hydrophilic solvent include the same hydrophilic solvents as those exemplified as the aqueous medium (b) used for synthesizing the binder polymer (P).
• the aqueous medium contained in the non-aqueous secondary battery electrode slurry may be the same as or different from the aqueous medium (b) used to synthesize the binder polymer (P).
• thickeners examples include celluloses such as carboxymethylcellulose (CMC), hydroxyethylcellulose, and hydroxypropylcellulose, ammonium salts of celluloses, alkali metal salts of celluloses, Polyvinyl alcohol, polyvinylpyrrolidone and the like can be mentioned.
• the thickener preferably contains at least one of carboxymethylcellulose, an ammonium salt of carboxymethylcellulose, and an alkali metal salt of carboxymethylcellulose. This is because the electrode active material in the slurry for the non-aqueous secondary battery electrode can be easily dispersed.
• the content of the thickener contained in the non-aqueous secondary battery electrode slurry is preferably 0.50 parts by mass or more, and preferably 0.80 parts by mass or more with respect to 100 parts by mass of the electrode active material. more preferred. This is because the adhesion between the electrode active material contained in the non-aqueous secondary battery electrode produced using the non-aqueous secondary battery electrode slurry and between the electrode active material and the current collector is improved.
• the content of the thickener contained in the non-aqueous secondary battery electrode slurry is preferably 3.0 parts by mass or less, and preferably 2.0 parts by mass or less with respect to 100 parts by mass of the electrode active material. More preferably, it is 1.5 parts by mass or less. This is because the coating properties of the slurry for non-aqueous secondary battery electrodes are improved.
• Carbon black, carbon fiber, etc. are mentioned as a conductive support agent which may be contained in the slurry for non-aqueous secondary battery electrodes of this embodiment.
• Examples of carbon black include furnace black, acetylene black, Denka Black (registered trademark) (manufactured by Denka Co., Ltd.), Ketjen Black (registered trademark) (manufactured by Ketjen Black International Co., Ltd.), and the like.
• Examples of carbon fibers include carbon nanotubes and carbon nanofibers. A preferred example of the carbon nanotube is VGCF (registered trademark, manufactured by Showa Denko KK), which is a vapor-grown carbon fiber.
• Method for producing slurry for non-aqueous secondary battery electrode for example, the binder polymer (P) of the present embodiment, the electrode active material, the aqueous medium, and if necessary A thickener, an optional conductive aid, and optional other components are mixed together.
• the mixing order of each component which is the raw material of the slurry for a non-aqueous secondary battery electrode, is not particularly limited and can be determined as appropriate.
• a method for mixing each component a method using a mixing device such as a stirring type, a rotating type, or a shaking type can be used.
• the electrode of the present embodiment contains the binder polymer (P) of the present embodiment.
• the electrode of this embodiment includes a current collector and an electrode active material layer formed on the current collector.
• the shape of the electrode of the present embodiment is not particularly limited and may be, for example, a laminate, a wound body, or the like.
• the formation range of the electrode active material layer on the current collector is not particularly limited, and the electrode active material layer may be formed on the entire surface of the current collector, or may be formed only on a part of the surface of the current collector.
• An electrode active material layer may be formed.
• the electrode active material layer may be formed on both sides of the current collector, or may be formed on only one side.
• the current collector is preferably a metal sheet with a thickness of 0.001 mm or more and 0.5 mm or less. Metals forming the metal sheet include iron, copper, aluminum, nickel, stainless steel, and the like. When the electrode of the present embodiment is the negative electrode of a lithium ion secondary battery, the current collector is preferably copper foil.
• the electrode active material layer contains the binder polymer (P) of the present embodiment and an electrode active material.
• the electrode active material layer may contain a conductive aid, a thickening agent, and the like.
• the electrode active material, conductive aid, and thickener may be the same as those exemplified as the components of the non-aqueous secondary battery electrode slurry.
• the electrode of this embodiment can be manufactured, for example, by the method described below. First, the slurry for non-aqueous secondary battery electrodes of the present embodiment is applied onto a current collector. Subsequently, the non-aqueous secondary battery electrode slurry is dried. As a result, an electrode active material layer containing the binder polymer (P) is formed on the current collector to form an electrode sheet. Thereafter, the electrode sheet is cut into suitable sizes as required. By performing the above steps, the electrode of the present embodiment is obtained.
• the method of applying the non-aqueous secondary battery electrode slurry on the current collector is not particularly limited, but for example, the reverse roll method, the direct roll method, the doctor blade method, the knife method, the extrusion method, the curtain method, and the gravure method. method, bar method, dip method, squeeze method and the like.
• these coating methods it is possible to use any method selected from a doctor blade method, a knife method, or an extrusion method in consideration of various physical properties such as viscosity and drying properties of the slurry for non-aqueous secondary battery electrodes. preferable. This is because an electrode active material layer with a smooth surface and a small variation in thickness can be obtained.
• the non-aqueous secondary battery electrode slurry When the non-aqueous secondary battery electrode slurry is applied to both surfaces of the current collector, it may be applied to each surface one by one, or may be applied to both surfaces at the same time. Moreover, the non-aqueous secondary battery electrode slurry may be applied continuously or intermittently on the current collector. The application amount of the non-aqueous secondary battery electrode slurry can be appropriately determined according to the design capacity of the battery, the composition of the non-aqueous secondary battery electrode slurry, and the like.
• the method for drying the non-aqueous secondary battery electrode slurry applied on the current collector is not particularly limited, but for example, a method selected from hot air, reduced pressure or vacuum environment, (far) infrared rays, and low temperature air may be used alone or They can be used in combination.
• the drying temperature and drying time for drying the slurry for non-aqueous secondary battery electrodes can be appropriately adjusted depending on the concentration of non-volatile matter in the slurry for non-aqueous secondary battery electrodes, the amount applied to the current collector, and the like.
• the drying temperature is preferably 40° C. or higher and 350° C. or lower, and more preferably 60° C. or higher and 100° C. or lower from the viewpoint of productivity.
• the drying time is preferably 1 minute or more and 30 minutes or less.
• An electrode sheet in which an electrode active material layer is formed on a current collector may be cut into a size and shape suitable for an electrode.
• a method for cutting the electrode sheet is not particularly limited, and for example, a slit, a laser, a wire cut, a cutter, a Thomson, or the like can be used.
• the electrode sheet before or after cutting the electrode sheet, the electrode sheet may be pressed if necessary.
• the electrode active material can be more firmly bound to the current collector, and the thickness of the electrode can be reduced, so that the size of the non-aqueous secondary battery can be reduced.
• a general method can be used as a method of pressing the electrode sheet.
• the pressing method it is particularly preferable to use a die pressing method or a roll pressing method.
• the press pressure is not particularly limited, but is preferably 0.5 t/cm 2 or more and 5 t/cm 2 or less.
• the press load is not particularly limited, but is preferably 0.5 t/cm or more and 8 t/cm or less. This is because it is possible to suppress a decrease in the capacity of the electrode active material to insert and desorb charge carriers such as lithium ions while obtaining the above-described effects of pressing.
• the peel strength of the electrode active material layer against the current collector measured by the method described later is preferably 10.0 mN / mm or more, and is 12.5 mN / mm or more. It is more preferably 15.0 mN/mm or more. This is because the non-aqueous secondary battery using the non-aqueous secondary battery electrode has better cycle characteristics and durability.
• Non-aqueous secondary battery a lithium ion secondary battery will be described as a preferred example of the non-aqueous secondary battery according to this embodiment.
• the structure of the non-aqueous secondary battery of the present invention is not limited to the examples shown below.
• the lithium-ion secondary battery of this embodiment includes a positive electrode, a negative electrode, an electrolytic solution, and known parts such as a separator provided as necessary, which are housed in an exterior body.
• the shape of the lithium ion secondary battery may be any shape such as coin type, button type, sheet type, cylindrical type, square type, flat type, and the like.
• the positive electrode and the negative electrode are provided with the electrode active material layer of the present embodiment containing the binder polymer (P) of the present embodiment.
• the negative electrode out of the positive electrode and the negative electrode has an electrode active material layer containing the binder polymer (P).
• the binder of the present embodiment As the electrode containing no polymer (P) for binder, an electrode containing a known binder such as polyvinylidene fluoride is used in place of the polymer (P) for binder of the present embodiment.
• electrolytic solution a non-aqueous liquid having ionic conductivity is used.
• the electrolytic solution include a solution in which an electrolyte is dissolved in an organic solvent, an ionic liquid, and the like, and the former is preferred. This is because a lithium ion secondary battery with low manufacturing cost and low internal resistance can be obtained.
• an alkali metal salt can be used, which can be appropriately selected according to the type of electrode active material and the like.
• electrolytes include LiClO 4 , LiBF 6 , LiPF 6 , LiCF 3 SO 3 , LiCF 3 CO 2 , LiAsF 6 , LiSbF 6 , LiB 10 Cl 10 , LiAlCl 4 , LiCl, LiBr, LiB(C 2 H 5 ). 4 , CF 3 SO 3 Li, CH 3 SO 3 Li, LiCF 3 SO 3 , LiC 4 F 9 SO 3 , Li(CF 3 SO 2 ) 2 N, lithium aliphatic carboxylate, and the like.
• Other alkali metal salts can also be used as the electrolyte.
• the organic solvent that dissolves the electrolyte is not particularly limited, but examples include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), dimethyl carbonate (DMC), fluoroethylene carbonate (FEC), carbonic ester compounds such as vinylene carbonate (VC), nitrile compounds such as acetonitrile, and carboxylic acid esters such as ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, and propyl propionate.
• EC ethylene carbonate
• PC propylene carbonate
• DEC diethyl carbonate
• EMC ethylmethyl carbonate
• DMC dimethyl carbonate
• FEC fluoroethylene carbonate
• carbonic ester compounds such as vinylene carbonate (VC)
• nitrile compounds such as acetonitrile
• carboxylic acid esters such as ethyl
• Exterior body for example, one made of an aluminum laminate material composed of an aluminum foil and a resin film can be appropriately used, but the exterior body is not limited to this.
• the resulting water-based emulsion was cooled to room temperature, and 160 parts by mass of water and 25% by mass of ammonia water were added.
• the particulate binder polymers of Examples 1 to 10 and Comparative Examples 1 to 3 are dispersed in the aqueous medium (b), Examples 1 to 10 and Comparative Examples Binder compositions for non-aqueous secondary batteries of Examples 1 to 3 were produced.
• the amount of ammonia as the basic substance (d) shown in Tables 1 to 3 is the amount (parts by mass) of ammonia contained in the aqueous ammonia.
• the amount of water as the aqueous medium (b) shown in Tables 1 to 3 is the total amount (parts by mass) of water contained in the binder composition for non-aqueous secondary batteries.
• the polymerizable surfactant (a5) shown in Tables 1 to 3 is a polyoxyethylene alkyl ether sulfate (Aqualon KH-10, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.).
• the polymerization initiator (e2) is tert-butyl peroxybenzoate (Kayabutyl B manufactured by Kayaku Akzo Co., Ltd.).
• the polymerization initiator (e3) is tert-butyl hydroperoxide (Kayabutyl H-70, manufactured by Kayaku Akzo Co., Ltd.).
• the binder composition for non-aqueous secondary batteries was coated on a release PET (polyethylene terephthalate) film and dried at 50° C. for 5 hours to obtain a 2 mm-thick film made of the binder polymer.
• a square test piece having a length of 2 mm and a width of 2 mm was cut from the obtained film. Seal the test piece in an aluminum pan, using a differential scanning calorimeter (EXSTAR DSC / SS7020 manufactured by Hitachi High-Tech Science Co., Ltd.), in a nitrogen gas atmosphere, at a temperature increase rate of 10 ° C./min, the differential scanning calorie of the test piece ( DSC) measurements were made.
• EXSTAR DSC / SS7020 manufactured by Hitachi High-Tech Science Co., Ltd.
• the temperature range for DSC measurement was -40°C to 200°C. Then, the peak top temperature of the DDSC chart obtained as the temperature differential of the DSC was measured, and this temperature was defined as the glass transition point Tg (°C) of the binder polymer.
• Non-volatile concentration 1 g of the binder composition for non-aqueous secondary batteries was weighed, placed on an aluminum dish with a diameter of 5 cm, and placed in a dryer. While circulating the air in the dryer, it was dried at 1 atmospheric pressure (1013 hPa) and a temperature of 105° C. for 1 hour, and the mass of the remaining components was measured. The mass ratio (% by mass) of the components remaining after drying with respect to the mass (1 g) of the binder composition for non-aqueous secondary batteries before drying was calculated and used as the non-volatile concentration.
• the binder composition for non-aqueous secondary batteries was applied onto a release PET film and dried at 160° C. for 1 hour to obtain a spot film having a diameter of 5 mm made of the binder polymer. 0.1000 to 0.2000 g of the obtained spot film was weighed (A2) and put into a 300-mesh metal mesh basket whose mass (A1) was measured in advance.
• the wire mesh basket containing the spot film was placed in a glass bottle containing 20 g of THF (tetrahydrofuran), and the spot film in the wire mesh basket was immersed in THF and allowed to stand at 20°C for 24 hours.
• the wire mesh basket containing the spot film was taken out from the glass bottle, and the THF adhering to the wire mesh basket was wiped off with a Kimwipe.
• the wire mesh jaw containing the spot film was then placed in a dryer and dried at 160° C. for 10 minutes. Subsequently, the wire mesh basket containing the spot film was taken out from the dryer, cooled at 23° C. for 20 minutes, and the mass (A3) was measured.
• (A1) in the formula is the mass (g) of the 300-mesh wire mesh cage.
• (A2) is the mass (g) of the spot film put into the wire mesh basket.
• (A3) is the weight of the wire mesh basket containing the spot film after being immersed in THF and dried (total weight (g) of the spot film and the wire mesh basket).
• Gel fraction (%) 100 - ⁇ A2 - (A3 - A1) / A2 ⁇ x 100
• non-aqueous secondary battery Using the binder compositions for nonaqueous secondary batteries of Examples 1 to 10 and Comparative Examples 1 to 3, respectively, a negative electrode was prepared by the method shown below, and using the negative electrode, Examples 1 to 3 were used. Lithium ion secondary batteries, which are non-aqueous secondary batteries of Example 10 and Comparative Examples 1 to 3, were produced.
• LiNi 0.6 Mn 0.2 Co 0.2 O 2 94 parts by mass as a positive electrode active material, 3 parts by mass of acetylene black as a conductive aid, and 3 parts by mass of polyvinylidene fluoride as a binder are mixed, A mixture was obtained. 50 parts by mass of N-methylpyrrolidone was added to the resulting mixture and further mixed to obtain a positive electrode slurry.
• An aluminum foil having a thickness of 15 ⁇ m was prepared as a positive electrode current collector.
• the positive electrode slurry was applied to both surfaces of the positive electrode current collector by a direct roll method.
• the amount of the positive electrode slurry applied to the positive electrode current collector was adjusted so that the thickness of the positive electrode current collector after the roll press treatment described later was 125 ⁇ m per side.
• the positive electrode slurry applied on the positive electrode current collector is dried at 120° C. for 5 minutes, and pressed by a roll press method using a roll press (manufactured by Thank Metal Co., Ltd., press load 5 t/cm, roll width 7 cm).
• a positive electrode sheet having positive electrode active material layers on both sides of the positive electrode current collector was obtained.
• the resulting positive electrode sheet was cut into a rectangle of 50 mm long and 40 mm wide, and a conductive tab was attached to make a positive electrode.
• a copper foil having a thickness of 10 ⁇ m was prepared as a negative electrode current collector.
• the negative electrode slurry was applied to both surfaces of the negative electrode current collector by a direct roll method.
• the amount of the negative electrode slurry applied to the negative electrode current collector was adjusted so that the thickness of the negative electrode current collector after the roll press treatment described later was 170 ⁇ m per side.
• the negative electrode slurry applied on the negative electrode current collector is dried at 90° C. for 10 minutes, and pressed by a roll press method using a roll press (manufactured by Thank Metal Co., Ltd., press load 8 t/cm, roll width 7 cm).
• a negative electrode sheet having negative electrode active material layers on both sides of the negative electrode current collector was obtained.
• the obtained negative electrode sheet was cut into a rectangle of 52 mm long and 42 mm wide, and a conductive tab was attached to the negative electrode sheet.
• Test pieces each having a width of 25 mm and a length of 70 mm were cut out from the negative electrode sheets produced to obtain the negative electrodes of Examples 1 to 10 and Comparative Examples 1 to 3.
• the obtained test pieces were subjected to the following method using a peel tester (Tensilon (registered trademark), manufactured by A&D Co., Ltd.) in an atmosphere at a temperature of 23 ° C. and a relative humidity of 50% by mass. , the peel strength of the negative electrode active material layer was measured. The results are shown in Tables 1-3.
• a double-sided tape (NITTOTAPE (registered trademark) No5, manufactured by Nitto Denko Corporation) was placed on the entire surface of the negative electrode active material layer of the test piece. Then, the negative electrode active material layer of the test piece and a metal plate having a width of 50 mm and a length of 200 mm are attached via double-sided tape so that the center of the test piece in the width direction and the center of the metal plate in the width direction are aligned, Let stand for 10 minutes.
• NITTOTAPE registered trademark
• No5 manufactured by Nitto Denko Corporation
• the negative electrode current collector (copper foil) was peeled off from the negative electrode active material layer of the test piece by 20 mm from one longitudinal end of the test piece and folded back 180°. Then, the portion peeled off from the test piece of the negative electrode current collector was gripped with the upper chuck of the peel tester. In addition, of the lengthwise ends of the metal plate, the end on the side where the negative electrode current collector was peeled off was gripped with the lower chuck of the peel tester. In this state, the upper chuck was pulled at a speed of 100 ⁇ 10 mm/min in the direction of widening the gap between the upper chuck and the lower chuck by a peel tester, thereby peeling the negative electrode current collector from the negative electrode active material layer.
• the average value (mN) of the peeling force when the length of the negative electrode current collector peeled from the negative electrode active material layer is within the range of 10 to 45 mm is calculated and divided by the width (25 mm) of the test piece. was taken as the peel strength (mN/mm) of the negative electrode active material layer.
• a separator made of a polyolefin-based porous film (made of polyethylene, thickness 25 ⁇ m) is interposed between the positive electrode and the negative electrode, and the positive electrode active material layer and the negative electrode active material layer are laminated so as to face each other, and an aluminum laminate material is formed. It was housed in an exterior body (battery pack) consisting of After that, an electrolytic solution was poured into the exterior body, vacuum impregnation was performed, and packing was performed with a vacuum heat sealer to obtain a lithium ion secondary battery.
• an exterior body battery pack
• EC ethylene carbonate
• EMC ethylmethyl carbonate
• DEC diethyl carbonate
• the lithium ion secondary batteries of Examples 1 to 10 all have higher capacity retention rates than the lithium ion secondary batteries of Comparative Examples 1 to 3. I was able to confirm that. Moreover, in the lithium ion secondary batteries of Examples 1 to 10, the peel strength of the negative electrode active material layer was sufficiently high. This is because the binder polymer contained in the negative electrode of the lithium ion secondary battery of Examples 1 to 10 is the monomer (a1) shown in Table 1 or Table 2, the monomer (a2), and the monomer It is presumed that it is a copolymer obtained by emulsion polymerization of the polymer (a3) and the internal cross-linking agent (a4). In addition, as shown in Tables 1 to 3, the lithium ion secondary batteries of Examples 1 to 10 and Comparative Examples 1 to 3 are practically sufficiently low in terms of internal resistance. It could be confirmed.
• the present invention it is possible to form an electrode in which the electrode active material layer is less likely to peel off from the current collector, and to provide a binder with which a non-aqueous secondary battery with excellent cycle characteristics can be obtained.

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• 2022
  • 2022-11-01 JP JP2023570702A patent/JPWO2023127300A1/ja active Pending
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