Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/13—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
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/052—Li-accumulators
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/052—Li-accumulators
  • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
  • H01M4/621—Binders
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
  • H01M4/621—Binders
  • H01M4/622—Binders being polymers
  • H01M4/623—Binders being polymers fluorinated polymers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
  • H01M2004/028—Positive electrodes
• • 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 positive electrode binder, a positive electrode mixture, a positive electrode, and a non-aqueous electrolyte secondary battery.
• Patent Document 1 describes the use of a polymer of vinylidene fluoride and 2-carboxyethyl acrylate as a binder.
• the amount of the insulating component contained in the mixture layer that is, the amount of the component derived from the binder, and increase the amount of the active material.
• An object of the present invention is to provide a positive electrode binder exhibiting high adhesiveness to an active material and a current collector even in a small amount, a positive electrode mixture containing the same, a positive electrode, and a non-aqueous electrolyte secondary battery.
• the present invention is a positive electrode binder for a nonaqueous electrolyte secondary battery, which contains a vinylidene fluoride polymer and an epoxy compound having two or more epoxy groups, and the epoxy equivalent of the epoxy compound is 500 g/eq. and the total amount of the vinylidene fluoride polymer is 600 g/eq or more and 3000 g/eq or less with respect to the total number of moles of the epoxy groups in the positive electrode binder.
• the present invention provides a positive electrode mixture containing the positive electrode binder and the positive electrode active material.
• the present invention provides a positive electrode having a current collector and a positive electrode mixture layer disposed on the current collector, wherein the positive electrode mixture layer contains a cured product of the positive electrode mixture.
• the present invention provides a nonaqueous electrolyte secondary battery having the above positive electrode.
• a positive electrode binder that exhibits high adhesiveness to an active material or current collector even in a small amount, a positive electrode mixture containing the same, and a positive electrode or non-aqueous electrolyte containing a cured product of the positive electrode binder.
• a secondary battery is obtained.
• the binder for positive electrode of the present invention is a binder used for forming the positive electrode of a non-aqueous electrolyte secondary battery. Since the positive electrode binder exhibits extremely high adhesiveness to the positive electrode active material and current collector, it is suitably used for forming the positive electrode mixture layer. However, the use of the positive electrode binder of the present invention is not limited to this.
• the positive electrode binder of the present invention contains a vinylidene fluoride polymer and an epoxy compound having two or more epoxy groups.
• the epoxy equivalent of the epoxy compound is 500 g/eq or less. That is, the proportion of epoxy groups in the epoxy compound is relatively high.
• the total amount of the vinylidene fluoride polymer is 600 g/eq or more and 3000 g/eq or less with respect to the total number of moles of epoxy groups in the positive electrode binder. That is, the amount of vinylidene fluoride polymer per mole of epoxy groups is relatively small.
• a vinylidene fluoride polymer is a polymer whose main component is a structural unit derived from vinylidene fluoride.
• the positive electrode binder may contain only one kind of vinylidene fluoride polymer, or may contain two or more kinds thereof.
• the vinylidene fluoride polymer may be a homopolymer of vinylidene fluoride, or may be a copolymer of vinylidene fluoride and another compound.
• the proportion of structural units derived from vinylidene is preferably 50% by mass or more and 100% by mass or less, more preferably 80% by mass or more and 100% by mass or less, and even more preferably 90% by mass or more and 100% by mass or less.
• the amount of structural units derived from vinylidene fluoride in the vinylidene fluoride polymer is 50% by mass or more, the properties derived from vinylidene fluoride are easily obtained, and the vinylidene fluoride polymer, the positive electrode active material, and the current collector Adhesiveness with etc. is improved.
• the amount of structural units derived from vinylidene fluoride in the vinylidene fluoride polymer can be identified by 19 F-NMR analysis or the like.
• the type of the other compound is not particularly limited, and examples thereof include the following general formulas (1) to (3) compounds represented, unsaturated basic acids, unsaturated basic acid monoesters, halogenated alkylvinyl compounds, and the like.
• R 1 , R 2 , and R 3 in general formula (1) above each independently represent a hydrogen atom, a fluorine atom, a chlorine atom, or an alkyl group having 1 to 5 carbon atoms.
• steric hindrance during polymerization with vinylidene fluoride is preferably small, and R 1 and R 2 are preferably hydrogen or an alkyl group having 1 to 3 carbon atoms, more preferably hydrogen or a methyl group.
• both R 1 and R 2 are hydrogen or only one of R 1 and R 2 is a methyl group.
• X 1 in the general formula (1) represents an atomic group having a main chain of 1 to 19 atoms and a molecular weight of 472 or less.
• the molecular weight of the atomic group is preferably 14 or more and 172 or less.
• the number of atoms in the main chain of X1 is preferably 1 or more and 14 or less, more preferably 1 or more and 9 or less.
• the number of atoms in the main chain of X1 means the number of atoms in the longest chain among the chains connecting the acryloyl group and the carboxyl group.
• the main chain of X 1 may be a hydrocarbon chain, and may contain a nitrogen atom, a sulfur atom, an oxygen atom, or the like.
• Examples of the compound represented by the general formula (1) include 2-carboxyethyl (meth)acrylate; (meth)acryloyloxyethyl succinic acid; (meth)acryloyloxypropylsuccinic acid; (meth)acryloyl (meth)acrylamide compounds such as N-carboxyethyl(meth)acrylamide; thio(meth)acrylate compounds such as carboxyethylthio(meth)acrylate;
• (meth)acrylate means methacrylate, acrylate, or a mixture thereof
• (meth)acryl means methacrylic, acrylic, or a mixture thereof
• (meth)acryloyl means methacryloyl. , acryloyl, or mixtures thereof.
• R 4 , R 5 and R 6 in the general formula (2) each independently represent a hydrogen atom, a fluorine atom, a chlorine atom, or an alkyl group having 1 to 5 carbon atoms.
• steric hindrance during polymerization with vinylidene fluoride is preferably small, and R 4 and R 5 are preferably hydrogen or an alkyl group having 1 to 3 carbon atoms, more preferably hydrogen or a methyl group.
• both R 4 and R 5 are hydrogen or only one of R 4 and R 5 is a methyl group.
• X 2 in the general formula (2) represents an atomic group having a main chain of 1 to 19 atoms and a molecular weight of 484 or less.
• the molecular weight of the atomic group is preferably 14 or more and 184 or less.
• the number of atoms in the main chain of X2 is preferably 1 or more and 14 or less, more preferably 1 or more and 9 or less.
• the number of atoms in the X2 main chain refers to the number of atoms in the longest chain among the chains connecting the oxygen bonded to the carbon-carbon double bond and the carboxyl group.
• the main chain of X2 may be a hydrocarbon chain, and may contain a nitrogen atom, a sulfur atom, an oxygen atom, or the like.
• Examples of the compound represented by the general formula (2) include vinyl carboxyalkyl ethers such as vinyl carboxymethyl ether and vinyl carboxyethyl ether.
• R 7 , R 8 , and R 9 in general formula (3) above each independently represent a hydrogen atom, a fluorine atom, a chlorine atom, or an alkyl group having 1 to 5 carbon atoms.
• steric hindrance during polymerization with vinylidene fluoride is preferably small, and R 7 and R 8 are preferably hydrogen or an alkyl group having 1 to 3 carbon atoms, more preferably hydrogen or a methyl group.
• both R 7 and R 8 are hydrogen or only one of R 7 and R 8 is a methyl group.
• X 3 in the general formula (3) represents a hydrogen atom or a hydrocarbon group having 1 to 5 carbon atoms and containing at least one hydroxy group.
• hydrocarbon groups containing a hydroxy group include a hydroxyethyl group and a hydroxypropyl group.
• Examples of the compound represented by the general formula (3) include acrylic acid, methacrylic acid, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethylmethyl acrylate, 2-hydroxypropyl methacrylate and the like. .
• the unsaturated basic acid may be an unsaturated carboxylic acid or a derivative thereof, and examples thereof include linear or branched unsaturated Included are compounds bound by saturated alkylene groups. More specific examples of unsaturated basic acids include crotonic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid and the like.
• the unsaturated basic acid ester is an ester compound derived from the unsaturated basic acid, and specific examples thereof include monomethyl maleate, monoethyl maleate, dimethyl maleate, monomethyl citraconic acid, Citraconic acid monoethyl ester and the like are included.
• the halogenated alkyl vinyl compound is a compound having one vinyl group and one or more halogenated alkyl groups, or a compound having one vinyl group and a halogen atom bonded to the vinyl group (excluding vinylidene fluoride ).
• Specific examples thereof include vinyl fluoride, trifluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene, fluoroalkyl vinyl ether, perfluoromethyl vinyl ether and the like.
• the vinylidene fluoride polymer may contain only one type of structure derived from other compounds, or may contain two or more types. Among these, it is particularly preferable that the vinylidene fluoride polymer contains one or more structural units derived from the compound represented by any one of the general formulas (1) to (3). When the vinylidene fluoride polymer contains these structural units, the carboxyl group and hydroxyl group of the vinylidene fluoride polymer react with the epoxy group of the epoxy compound, and the adhesion strength of the positive electrode binder to the positive electrode active material, current collector, etc. tend to be stronger. Among the above, it is particularly preferable to contain a structural unit derived from a carboxyl group.
• the proportion of structural units derived from other compounds (in particular, the proportion of structural units derived from compounds represented by any of the general formulas (1) to (3) above) in the vinylidene fluoride polymer is 0.5. 1% by mass or more and 50% by mass or less is preferable, 0.1% by mass or more and 20% by mass or less is more preferable, and 0.1% by mass or more and 10% by mass or less is even more preferable. That is, when the vinylidene fluoride polymer contains structural units derived from other compounds, the vinylidene fluoride polymer preferably contains 50% by mass or more and 99.9% by mass or less of structural units derived from vinylidene fluoride.
• the amount of structural units derived from other compounds in the vinylidene fluoride polymer is within the above range, the adhesion between the vinylidene fluoride polymer and the positive electrode active material, current collector, and the like is improved.
• the amount of structural units derived from other compounds can be identified, for example, by analyzing the vinylidene fluoride copolymer by 19 F-NMR or by FT-IR.
• the positive electrode binder may contain a plurality of types of vinylidene fluoride polymers.
• a vinylidene fluoride polymer that is difficult to swell with an electrolytic solution, etc. (such as a copolymer containing a structural unit).
• the amount of the vinylidene fluoride polymer that easily swells with the electrolytic solution is preferably small. % is preferred.
• Examples of vinylidene fluoride polymers that are likely to swell with an electrolytic solution or the like include vinylidene fluoride polymers that mainly contain a structural unit derived from an alkyl vinyl halide compound and a structural unit derived from vinylidene fluoride.
• the weight average molecular weight of the vinylidene fluoride polymer is preferably 100,000 to 10,000,000, more preferably 200,000 to 5,000,000, and even more preferably 300,000 to 2,000,000.
• the weight-average molecular weight of the vinylidene fluoride polymer is within the above range, the physical properties of the vinylidene fluoride polymer tend to fall within the desired range, and the vinylidene fluoride polymer easily binds to the active material, current collector, and conductive aid.
• the said weight average molecular weight is a polystyrene conversion value measured by a gel permeation chromatography (GPC).
• the total amount of the vinylidene fluoride polymer in the positive electrode binder is preferably 80% by mass or more and 99.9% by mass or less with respect to the solid content of the positive electrode binder (the total amount excluding the component that volatilizes during curing). 90% by mass or more and 99% by mass or less is more preferable.
• the amount of the vinylidene fluoride polymer is within this range, the positive electrode binder tends to exhibit the physical properties derived from the vinylidene fluoride polymer.
• Epoxy compound is a compound having two or more epoxy groups in one molecule and having an epoxy equivalent of 500 g/eq or less.
• the "epoxy equivalent” as used herein is theoretically a value obtained by dividing the molecular weight of an epoxy compound by the number of epoxy groups contained in the epoxy compound. In this specification, the value calculated by the measurement method standardized in JIS K7236:2001 is also referred to as "epoxy equivalent".
• the epoxy equivalent of the epoxy compound is 500 g/eq or less, the epoxy compound tends to interact with the active material, the current collector, and the like when the positive electrode mixture layer is formed using the positive electrode binder.
• the epoxy equivalent is more preferably 300 g/eq or less, and even more preferably 200 g/eq or less. Typically the lower limit is 43 g/eq.
• the epoxy equivalent can be calculated theoretically by specifying the structure of the epoxy compound. It can also be calculated by the measurement method standardized in JIS K7236:2001.
• the structure of the epoxy compound is not particularly limited, and may be, for example, an aliphatic epoxy compound, an aromatic epoxy compound, or an alicyclic epoxy compound.
• aliphatic epoxy compounds examples include neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and the like.
• Trifunctional aliphatic epoxy compounds such as glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, triglycidyl isocyanurate and derivatives thereof, pentaerythritol triglycidyl ether; pentaerythritol tetraglycidyl ether, Tetrafunctional aliphatic epoxy compounds such as diglycerol tetraglycidyl ether, ditrimethylolpropane tetraglycidyl ether, sorbitol tetraglycidyl ether; Functional aliphatic epoxy compounds; hexafunctional aliphatic epoxy compounds such as sorbitol hexaglycidyl ether and dipentaerythritol hexaglycidyl ether; trimethylolpropane polyglycidyl ether, pentaerythritol polyglycidyl ether, digly
• aromatic epoxy compounds examples include diglycidyl terephthalate, diglycidyl-o-phthalate, diglycidyl resorcinol ether, bisphenol A type diglycidyl compounds such as 2,2-bis(4-glycidyloxyphenyl)propane, bisphenol F bifunctional aromatic epoxy compounds such as diglycidyl compound and biphenyl diglycidyl compound; polyfunctional aromatic epoxy compounds such as phenol novolac type epoxy compound and cresol novolac type epoxy compound; and the like.
• alicyclic epoxy compounds include bifunctional alicyclic epoxy compounds such as hydrogenated bisphenol A diglycidyl compounds, hydrogenated bisphenol F diglycidyl compounds, and hydrogenated biphenyl diglycidyl compounds. is included.
• the epoxy compound may be a glycidylamine compound such as 4,4'-methylenebis(N,N-diglycidylaniline) or N,N-diglycidyl-4-glycidyloxyaniline.
• an epoxy compound that does not contain amine is preferable from the viewpoint of suppressing thickening of the positive electrode binder.
• the epoxy compound may be a solid compound, but it is preferable that it is a liquid compound because it is easily mixed uniformly with the vinylidene fluoride polymer.
• the viscosity of the liquid epoxy compound measured at 25° C. with an E-type viscometer is preferably 100 Pa ⁇ s or less, more preferably 50 Pa ⁇ s or less.
• the molecular weight of the epoxy compound is preferably 2000 or less, more preferably 1000 or less. Moreover, the molecular weight of the epoxy compound is 80 or more. When the molecular weight of the epoxy compound is within this range, it becomes easier to mix uniformly with the vinylidene fluoride polymer. Furthermore, when the molecular weight of the epoxy compound becomes small, the epoxy equivalent tends to become small.
• the amount of the epoxy compound in the positive electrode binder is preferably 0.1% by mass or more and 20% by mass or less, preferably 1% by mass or more and 10% by mass, based on the solid content of the positive electrode binder (the total amount excluding the component that volatilizes during curing). % by mass or less is more preferable.
• the total amount of the vinylidene fluoride polymer relative to the total number of epoxy groups contained in the positive electrode binder can be 600 g/eq or more and 3000 g/eq.
• the binder for positive electrodes may further contain a polar solvent.
• the vinylidene fluoride polymer and the epoxy compound can be dissolved or dispersed, and the positive electrode binder can be made liquid.
• polar solvents include amide compounds such as dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone; methanol, ethanol, isopropyl alcohol, 2-ethyl-1-hexanol, 1-nonanol, lauryl alcohol, tripropylene alcohols such as glycol; amine compounds such as o-toluidine, m-toluidine and p-toluidine; 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide; lactones such as ⁇ -butyrolactone and ⁇ -butyrolactone; Sulfoxide/sulfone compounds such as dimethylsulfoxide and sulfolane are included.
• the positive electrode binder may contain only one type of polar solvent, or may contain two or more types.
• the amount of the polar solvent is preferably 500 parts by mass or more and 50000 parts by mass or less, more preferably 1000 parts by mass or more and 10000 parts by mass or less with respect to 100 parts by mass as the total amount of the vinylidene fluoride polymer and the epoxy compound.
• the amount of the polar solvent is within this range, it is possible to uniformly disperse or dissolve the vinylidene fluoride polymer or the epoxy compound in the polar solvent.
• the positive electrode binder may contain components other than the vinylidene fluoride polymer, the epoxy compound, and the polar solvent as long as the objects and effects of the present invention are not impaired.
• other resins such as acrylic resins, fillers such as inorganic fillers, and various additives may be further included.
• the positive electrode binder may contain a vinylidene fluoride polymer and an epoxy compound, and may be a solid composition, a liquid composition, or a slurry composition. may be
• the amount of the vinylidene fluoride polymer with respect to the total number of epoxy groups in the positive electrode binder is 600 g/eq or more and 3000 g/eq or less, preferably 700 g/eq or more and 2500 g/eq or less, and 800 g/eq or more and 2000 g/eq. The following are more preferred.
• the amount of the vinylidene fluoride polymer relative to the total number of epoxy groups is within the above range, the positive electrode active material and current collector can be strongly adhered even when the amount of the positive electrode binder is small.
• the value can be determined by analyzing the composition and determining the amount of the vinylidene fluoride polymer, the amount of the epoxy compound, and the structure of the epoxy compound. It can also be specified by specifying the amount of the vinylidene fluoride polymer, the amount of the epoxy compound, and the epoxy equivalent of the epoxy compound calculated by the measurement method standardized in JIS K7236:2001.
• the preparation method of the positive electrode binder is not particularly limited, and is appropriately selected according to its composition.
• the positive electrode binder contains a powdery vinylidene fluoride polymer and a liquid epoxy compound
• the liquid epoxy compound is mixed with the powdery vinylidene fluoride polymer to obtain the epoxy compound.
• a method of adsorbing to a vinylidene fluoride polymer may also be used.
• the positive electrode binder further contains a polar solvent, the vinylidene fluoride polymer, the epoxy compound, and the polar solvent are mixed to disperse the vinylidene fluoride polymer and the epoxy compound in the polar solvent. or dissolved.
• Positive Electrode Mixture The positive electrode binder described above and the positive electrode active material can be mixed to form a positive electrode mixture. At this time, a conductive aid, a solvent, other additives, and the like may be further added.
• the amount of the positive electrode binder in the positive electrode mixture is not particularly limited, as described above, even a small amount of the positive electrode binder exhibits sufficient adhesion to the positive electrode active material and the like. Therefore, the ratio of the solid content derived from the positive electrode binder to the total amount of the positive electrode binder-derived solid content (the total amount excluding the components that volatilize during curing), the positive electrode active material, and the conductive aid is 0.2% by mass or more.
• the content is preferably 20 mass % or less, more preferably 0.4 mass % or more and 10 mass % or less, and even more preferably 0.6 mass % or more and 4 mass % or less.
• a conventionally known positive electrode active material can be used as the positive electrode active material.
• positive electrode active materials include lithium-based positive electrode active materials containing lithium. Specific examples thereof include general formula LiMY 2 such as LiCoO 2 and LiNi x Co 1-x O 2 (0 ⁇ x ⁇ 1) (where M is Co, a transition metal such as Ni, Fe, Mn, Cr, V, etc.). and Y represents a chalcogen element such as O or S); a complex metal oxide having a spinel structure such as LiMn 2 O 4 ; olivine-type lithium compounds such as LiFePO4 ; Moreover, the surface of the positive electrode active material may be coated with various substances.
• the positive electrode active material may be a commercially available product.
• the amount of the positive electrode active material in the positive electrode mixture is appropriately selected according to the type of the positive electrode active material and the physical properties of the desired positive electrode mixture layer, and is not particularly limited, but usually the solid content derived from the positive electrode binder ( It is preferably 50% by mass or more and 99.9% by mass or less with respect to the total amount of the total amount excluding the component that volatilizes during curing), the positive electrode active material, and the conductive aid.
• the amount of the positive electrode active material is within this range, for example, sufficient charge/discharge capacity can be obtained, and battery performance tends to be good.
• the positive electrode binder described above exhibits sufficient adhesion to the positive electrode active material and the like even in a small amount
• the amount of active material may be 90% by mass or more.
• the conductive aid is not particularly limited as long as it is a compound that can further increase the conductivity between the positive electrode active materials or between the positive electrode active material and the current collector.
• conductive aids include acetylene black, ketjen black, carbon black, graphite powder, carbon nanofibers, carbon nanotubes, carbon fibers, and the like.
• the amount of conductive aid contained in the positive electrode mixture is appropriately selected according to its type. From the viewpoint of improving both the conductivity and the dispersibility of the conductive aid, the total amount of the solid content derived from the positive electrode binder, the positive electrode active material, and the conductive aid is 0.1% by mass and 15% by mass or less. , more preferably 0.1% by mass or more and 7% by mass or less, and even more preferably 0.1% by mass or more and 5% by mass or less.
• the positive electrode mixture may contain a solvent or the like different from the polar solvent contained in the positive electrode binder.
• the solvent can be selected from among the polar solvents that the positive electrode binder can contain.
• the total amount of the solvent in the positive electrode mixture (including the amount of the polar solvent in the binder) is not particularly limited, but is usually preferably 20 parts by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the positive electrode active material.
• the positive electrode mixture may further contain dispersants, adhesion aids, thickeners, and the like, and known compounds can be used for these. These amounts are not particularly limited as long as they do not impair the object and effect of the present invention, but are preferably 15% by mass or less with respect to the total amount of the solid content derived from the positive electrode binder and the positive electrode active material.
• the positive electrode mixture includes nitrogen compounds such as phosphorus compounds, sulfur compounds, organic acids, amine compounds, and ammonium compounds; organic esters, various silane-based, titanium-based and aluminum-based coupling agents; vinylidene fluoride copolymers described above.
• Resins such as vinylidene fluoride polymers other than polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), and polyacrylonitrile (PAN); These are not particularly limited as long as they do not impair the object and effect of the present invention, but are preferably 15% by mass or less with respect to the total amount of the solid content derived from the positive electrode binder and the positive electrode active material.
• the positive electrode mixture may be prepared by mixing all the components at once, or may be prepared by first mixing some components and then mixing the remaining components. Alternatively, the preparation of the positive electrode mixture and the preparation of the positive electrode binder may be performed at the same time. For example, the vinylidene fluoride polymer described above, an epoxy compound, a positive electrode active material, a polar solvent, etc. are mixed, and a positive electrode containing a positive electrode binder (vinylidene fluoride polymer and epoxy compound) and a positive electrode active material A mixture may be obtained.
• the viscosity of the positive electrode mixture can prevent dripping, uneven coating, and delay in drying after coating when the positive electrode mixture is applied to obtain the positive electrode mixture layer.
• the viscosity of the positive electrode mixture is measured with an E-type viscometer or the like.
• a positive electrode of a non-aqueous electrolyte secondary battery includes, for example, a current collector and a positive electrode mixture layer disposed on the current collector. At this time, the positive electrode mixture described above can be used to form the positive electrode mixture layer.
• a current collector is a terminal for taking out electricity.
• the material of the current collector is not particularly limited, and metal foils or meshes of aluminum, copper, iron, stainless steel, steel, nickel, titanium, or the like can be used. Alternatively, the surface of another medium may be provided with the above metal foil or metal net.
• the positive electrode mixture layer is a layer obtained by applying the positive electrode mixture described above onto a current collector and curing the layer.
• the positive electrode material mixture layer may be formed only on one surface of the current collector, or may be arranged on both surfaces.
• the components in the positive electrode mixture layer are appropriately selected according to the type of non-aqueous electrolyte secondary battery.
• the positive electrode mixture layer usually contains the above-described cured positive electrode binder and positive electrode active material, and may also contain various additives such as a conductive aid, a dispersant, an adhesion aid, and a thickener. You can stay. These can be the same as those described for the positive electrode mixture.
• the thickness of the positive electrode mixture layer is not particularly limited, but in one example, it is preferably 1 ⁇ m or more and 1000 ⁇ m or less.
• the weight per unit area of the positive electrode mixture layer formed on one side of the current collector is not particularly limited, and may be any weight per unit area. /m 2 or less is preferable, and 100 g/m 2 or more and 500 g/m 2 or less is more preferable.
• the positive electrode mixture layer can be formed by performing a step of applying the above positive electrode mixture onto a current collector and a step of curing it.
• the method of applying the positive electrode mixture is not particularly limited, and a doctor blade method, a reverse roll method, a comma bar method, a gravure method, an air knife method, a die coating method, a dip coating method, and the like can be applied.
• the positive electrode mixture After applying the positive electrode mixture, it is heated at an arbitrary temperature to dry the polar solvent and thermally cure the epoxy compound.
• the curing temperature is preferably 60° C. or higher and 500° C. or lower, more preferably 80° C. or higher and 200° C. or lower. Heating may be performed multiple times at different temperatures.
• the solvent in the positive electrode mixture may be dried under atmospheric pressure, increased pressure, or reduced pressure. A heat treatment may be further performed after drying.
• a press treatment may be performed.
• the electrode density can be improved.
• the press pressure is preferably 1 kPa or more and 10 GPa or less.
• Non-aqueous electrolyte secondary batteries The positive electrode binders and positive electrode mixtures described above can be used for the positive electrodes of various non-aqueous electrolyte secondary batteries, etc. May be used for forming.
• Vinylidene fluoride polymers A and B were prepared by the following method.
• Examples 1-9 and Comparative Examples 1-4 An epoxy compound, a vinylidene fluoride polymer A, a positive electrode active material (NCM523), and a conductive agent (Super-P) having composition ratios shown in Table 2 were dispersed in N-methylpyrrolidone to prepare a positive electrode mixture. bottom.
• the obtained positive electrode was cut into a piece having a length of 50 mm and a width of 20 mm, and the peel strength of the mixture layer was evaluated by the following method. Results are shown in Tables 2 and 3.
• a 90° peel strength test (measurement of strength required for peeling) is performed according to JISK6854-1. did The test speed was 10 mm/min. It can be said that the higher the value, the higher the adhesive strength.
• the measured peel strength was measured using the same type of vinylidene fluoride polymer and the same amount of the conductive aid with respect to the amount of the positive electrode active material. It was evaluated by comparing with the peel strength of any of Examples 1-3. The larger the difference or ratio from the reference example, the better the result.
• the binder contains an epoxy compound and a vinylidene fluoride polymer, and the epoxy equivalent of the epoxy compound is 500 g/eq or less.
• the peel strength (strength required for peeling) increased by 1.4 times or more ( Examples 1-13).
• the peel strength does not change, or The peel strength was greatly reduced. It is believed that the mechanical strength was lowered due to the excessive amount of the epoxy compound having a relatively low molecular weight.
• a positive electrode binder that exhibits high adhesiveness to an active material or current collector even in a small amount, a positive electrode mixture containing the same, and a positive electrode or non-aqueous electrolyte containing a cured product of the positive electrode binder.
• a secondary battery is obtained. Therefore, it is very useful for manufacturing non-aqueous electrolyte secondary batteries and the like.

Landscapes

• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Battery Electrode And Active Subsutance (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

Family

ID=86159822

Family Applications (1)

Country Status (4)

Citations (6)

Family Cites Families (1)

• 2022
  • 2022-09-29 CN CN202280065292.XA patent/CN118043986A/zh active Pending
  • 2022-09-29 JP JP2023556230A patent/JP7633424B2/ja active Active
  • 2022-09-29 WO PCT/JP2022/036379 patent/WO2023074245A1/ja not_active Ceased
  • 2022-09-29 EP EP22886577.0A patent/EP4425593A4/en active Pending

Patent Citations (6)

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events