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
  • 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

• This disclosure relates to a binder for a lithium ion battery positive electrode, a slurry for forming a lithium ion battery positive electrode composite layer, a lithium ion battery positive electrode, and a lithium ion battery.
• lithium-ion batteries have come to be widely used as power sources for electrical devices and the like. Furthermore, their use has recently expanded to include use as a power source for electric vehicles, and there is a demand for improved characteristics such as higher capacity, higher output, and improved cycle life, as well as a high level of safety.
• the electrodes of lithium-ion batteries have a structure in which a porous body consisting mainly of powdered active material, conductive additives, and binders is layered and bonded onto a current collector. Therefore, it is known that the performance of the electrode is greatly affected not only by the properties of the active material, but also by the type of binder.
• PVDF polyvinylidene fluoride
• aqueous binders that can be dispersed and dissolved in water without using organic solvents
• the use of polyvinyl alcohol and methyl cellulose see, for example, Patent Document 1
• the use of xanthan gum see, for example, Patent Document 2
• the use of starch-type polysaccharides such as amylose and aminopectin see, for example, Patent Documents 3 and 4
• the use of alginic acid or alginic acid derivatives see, for example, Patent Documents 5 to 9
• Binders obtained using aqueous emulsions are preferable because they do not require decontamination equipment during electrode sheet production and also improve the working environment.
• lithium composite oxides such as LiMn2O4 , LiNi0.5Mn1.5O4 , LiNi0.5Mn0.3Co0.2O2 , LiNi0.33Mn0.33Co0.33O2 , and LiNi0.8Mn0.1Co0.1O2 are often used as positive electrode active materials .
• manganese and nickel in these lithium composite oxides dissolve and ionize during charging and discharging , and precipitate and accumulate on the negative electrode, resulting in deterioration of cycle characteristics and rate characteristics.
• the present disclosure aims to provide a binder for a lithium ion battery positive electrode that is highly flexible (flexible), unlikely to crack during winding, has excellent workability during electrode fabrication, and can suppress the precipitation and deposition of manganese from the positive electrode active material to the negative electrode active material, thereby enabling the fabrication of a battery that can extend the cycle life; a slurry for forming a positive electrode composite layer for a lithium ion battery, which is used to form a positive electrode composite layer comprising the binder; and a positive electrode for a lithium ion battery and a lithium ion battery comprising the binder.
• the present disclosure aims to provide a binder for a lithium ion battery positive electrode that is highly flexible, unlikely to crack during electrode fabrication, and enables the fabrication of a battery with an extended cycle life, as well as a slurry for forming a positive electrode composite layer for a lithium ion battery, a positive electrode for a lithium ion battery, and a lithium ion battery using the binder.
• a binder for the positive electrode of a lithium ion battery that binds a positive electrode active material, a conductive additive, and a current collector in a lithium ion battery, the binder including a chelate group-containing polymer compound and a flexible polymer.
• a binder for a lithium-ion battery positive electrode according to any one of [1] to [3] above, in which the flexible polymer is a dried product of an aqueous emulsion (obtained by drying an aqueous emulsion).
• a slurry for forming a positive electrode composite layer for a lithium ion battery comprising a positive electrode active material, a conductive assistant, a chelate group-containing polymer compound, a flexible polymer, and water, and the positive electrode composite layer is provided with the binder for a lithium ion battery positive electrode described in any one of [1] to [4] above.
• a positive electrode for a lithium ion battery comprising the binder for a positive electrode for a lithium ion battery described in any one of [1] to [4] above.
• the inventors speculate as follows as to why the lithium-ion battery positive electrode binder, which is one aspect of the present disclosure, achieves the above-mentioned objective.
• the chelate group captures manganese ions and nickel ions eluted from the positive electrode active material near the positive electrode. This has the effect of suppressing manganese precipitation and deposition on the negative electrode active material. As a result, excellent charge/discharge characteristics and a long cycle life can be achieved.
• a flexible polymer more preferably a dried product of an aqueous polymer emulsion
• the adhesion of the positive electrode mixture layer to the current collector is improved, and even if the positive electrode mixture layer is applied thickly, peeling of the positive electrode mixture layer is suppressed.
• the occurrence of cracks during winding can also be suppressed. Since the occurrence of cracks during winding can be suppressed in this way, by using the binder for the positive electrode of one embodiment of the present disclosure, it is possible to efficiently manufacture the positive electrode by applying the winding process during the manufacture of the positive electrode, and it is possible to improve the workability during the manufacture of the positive electrode.
• a binder for a lithium-ion battery positive electrode that is highly flexible (bendable), unlikely to crack when wound, has excellent workability when fabricating an electrode, and can suppress the precipitation and deposition of manganese from the positive electrode active material to the negative electrode active material, thereby enabling the fabrication of a battery that can extend the cycle life; a slurry for forming a positive electrode composite layer for a lithium-ion battery, which is used to form a positive electrode composite layer comprising the binder; and a positive electrode for a lithium-ion battery and a lithium-ion battery that comprise the binder.
• a binder for lithium-ion battery positive electrodes and a slurry for forming a positive electrode composite layer for lithium-ion batteries which are easy to work with when producing positive electrodes, are flexible and less susceptible to cracking, and enable the production of electrodes with extended cycle life. Furthermore, by using the same, it is possible to provide a lithium-ion battery positive electrode and a lithium-ion battery with extended cycle life.
• the binder for the positive electrode of a lithium-ion battery which is one aspect of the present disclosure, contains a polymer compound containing a chelate group.
• a chelating group refers to a ligand having multiple coordination sites, and is a functional group capable of forming a chelate with a polyvalent metal ion.
• an aminocarboxylic acid-based chelating group, an aminophosphonic acid-based chelating group, or a polyamine-based chelating group is preferably used.
• aminocarboxylic acid-based chelating functional groups include iminodiacetic acid group, nitrilotriacetic acid group, N,N-bis(2-hydroxyethyl)glycine group, hydroxyethyliminodiacetic acid group, ethylenediaminetriacetic acid group, ethylenediaminetetraacetic acid group, 1,2-bis(2-aminophenoxy)ethanetetraacetic acid group, 1,2-diaminocyclohexanetetraacetic acid group, diethylenetriaminepentaacetic acid group, (2-hydroxyethyl)ethylenediaminetriacetic acid group, bis(2-aminoethyl)ethyleneglycoltetraacetic acid group, and triethylenetriaminehexaacetic acid group.
• aminocarboxylic acid-based chelating functional group at least one selected from the groups exemplified here can be preferably used.
• aminophosphonic acid chelating groups include aminomethylphosphonic acid groups and nitrilotris(methylphosphonic acid) groups. At least one selected from the groups exemplified here can be suitably used as such aminophosphonic acid chelating groups.
• polyamine chelating groups include polyethyleneimine groups, polyamidoamine dendrimer groups, and tetrakis(2-pyridylmethyl)ethylenediamine groups. At least one selected from the groups exemplified here can be suitably used as such polyamine chelating groups.
• the acidic functional groups are in the form of monovalent salts such as alkali metal salts or ammonium salts rather than in the proton form, since this makes it easier to exchange ions with heavy metal ions.
• such a chelating group is preferably at least one of an amino carboxylic acid chelating group, an amino phosphonic acid chelating group, and an alkali metal salt thereof.
• a chelating group is preferably at least one selected from the group consisting of an iminodiacetic acid group, an ethylenediaminetetraacetic acid group, a nitrilotris (methylphosphonic acid) group, a nitrilotriacetic acid group, an ethylenediaminetriacetic acid group, an aminomethylphosphonic acid group, and a group consisting of an alkali metal salt thereof, more preferably at least one selected from the group consisting of an iminodiacetic acid group, an ethylenediaminetetraacetic acid group, a nitrilotris (methylphosphonic acid) group, and a group consisting of an alkali metal salt thereof, and particularly preferably at least one selected from
• the amount of chelate groups contained in the chelate group-containing polymer compound is 0.2 mmol/g or more and 6 mmol/g or less, preferably 0.5 mmol/g or more and 5 mmol/g or less.
• the content of such chelate groups is not particularly limited, and the content can be determined appropriately depending on the type of chelate group.
• the chelate group contains a nitrogen element such as an aminocarboxylic acid chelate group or an aminophosphonic acid chelate group
• the part of the polymer compound (the part of the polymer to which the chelate group is introduced) has a structure that does not contain a nitrogen element
• a method of determining the content ratio of nitrogen atoms by performing elemental analysis on the chelate group-containing polymer compound and converting the molar amount of the chelate group from the content may be adopted.
• the method of elemental analysis referred to here is not particularly limited, but for example, a method can be used in which a MICRO CORDER JM10 manufactured by J Science Corporation is used as a measuring device, a sample is completely combusted in an oxygen atmosphere, and the generated CO2 , H2O , and N2 are measured with a thermal conductivity detector to determine the amount of each element.
• the polymer compound into which the chelate group is introduced the compound constituting the part of the polymer compound excluding the chelate group in the chelate group-containing polymer compound.
• the polymer compound into which the chelate group is introduced include vinyl polymers, polyamides, polyesters, polyurethanes, polysaccharides, and cellulose.
• the polymer compound is preferably water-soluble at the time the chelate group is introduced, and is therefore preferably hydrophilic.
• polysaccharides are more preferred, and at least one of acidic polysaccharides and basic polysaccharides is even more preferred, and at least one selected from the group consisting of alginic acid, sulfated alginic acid, and salts thereof is particularly preferred, with alginic acid being the most preferred.
• the molecular weight of the chelate group-containing polymer compound is preferably 10,000 to 1,000,000, more preferably 50,000 to 1,000,000, in terms of weight average molecular weight.
• a weight average molecular weight in this range is preferable because it ensures sufficient mechanical strength and allows the viscosity during electrode coating to be adjusted to a range that does not affect workability.
• the "weight average molecular weight" of the chelate group-containing polymer compound can be measured using a Tosoh HLC-8320GPC measuring device, a TSKgel GMPXL column, a pH 8.0, 0.1 mol/L phosphate buffer solution as the eluent, and polyethylene glycol as the standard sample at a flow rate of 1 mL/min.
• a "chelate group-containing polymer compound” refers to a polymer compound in which a chelate group is bonded to the polymer compound via a covalent bond and/or an ionic bond.
• a "chelate group-containing polymer compound” refers to a polymer compound in which a chelate group is bonded to the polymer compound via at least one type of bond selected from the group consisting of a covalent bond and an ionic bond.
• PS represents an acidic polysaccharide or a basic polysaccharide.
• X represents a group represented by -O- or -N(R)-, R represents a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms.
• A represents an organic group having 3 to 30 carbon atoms, and CL represents an organic group containing a chelating group and having 1 to 30 carbon atoms.
• PS in the general formula (1) represents an acidic polysaccharide or a basic polysaccharide.
• the acidic polysaccharide refers to a polysaccharide containing a functional group exhibiting acidity, such as a carboxyl group or a sulfate group.
• the acidic polysaccharide examples include at least one selected from the group consisting of carboxymethylcellulose, gellan gum, alginic acid, sulfated alginic acid, carrageenan, xanthan gum, chondroitin sulfate, heparin, hyaluronic acid, pectinic acid, gum arabic, agar, and tragacanth gum, and salts thereof.
• the acidic polysaccharide may be mixed with a neutral polysaccharide or another water-soluble polymer within a range that does not significantly reduce the amount of chelating group introduced.
• Alginic acid is composed of mannuronic acid and guluronic acid.
• the ratio of mannuronic acid and guluronic acid, which are components of alginic acid, is arbitrary.
• the alginic acid in this embodiment may be either alginic acid with a high mannuronic acid ratio that produces a soft gel, or alginic acid with a high guluronic acid ratio that produces a rigid gel.
• basic polysaccharides refer to polysaccharides that contain functional groups that exhibit basicity, such as amino groups.
• An example of a basic polysaccharide is chitosan.
• sulfated polysaccharides in which sulfate groups have been introduced into the polysaccharides are also suitable for use as PS in the general formula (1).
• the sulfate group both in its basic salt and neutral salt form, is a strongly acidic cation exchange group capable of ion exchange. Therefore, the "sulfate group" referred to here may be in the form of a basic salt or a neutral salt.
• the sulfate group is introduced at the site of a hydroxyl group contained in the polysaccharide structure, and is introduced by substituting hydrogen of the hydroxyl group with -SO 3 H.
• the amount of sulfate group introduced into the polysaccharide is preferably 0.5 to 5.0 mmol/g. It is preferable that the amount of sulfate group introduced is within the above range, since oxidation resistance is improved while maintaining the amount of chelating group introduced.
• X represents a group represented by -O- or -N(R)-
• R represents a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms.
• the hydrocarbon group having 1 to 6 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an isobutyl group, an n-pentyl group, a sec-pentyl group, a tert-pentyl group, an isopentyl group, a neopentyl group, a 3-pentyl group, a cyclopentyl group, an n-hexyl group, an isohexyl group, a sec-hexyl group, a tert-hexyl group, a neohexyl group,
• a in the general formula (1) is an organic group having 3 to 30 carbon atoms, and is preferably a divalent hydrocarbon group such as a propylene group, a butylene group, or a phenylene group, or a group in which a hydroxyl group or the like has been introduced into such a hydrocarbon group.
• organic groups that can be used as A in the formula (1) include 2-hydroxypropylene, 2,2-bis[4-(hydroxypropyloxy)phenyl]propane, 1,2-bis(2-hydroxypropyloxy)ethyl, and 1,3-bis(2-hydroxypropyloxy)benzene.
• organic group used in this disclosure refers to a divalent hydrocarbon group as described above, as well as a group containing heteroatoms such as oxygen, nitrogen, phosphorus, and sulfur as constituent atoms in addition to carbon and hydrogen (in addition to carbon and hydrogen).
• CL in general formula (1) may contain a chelating group, may have 1 to 30 carbon atoms, and may contain heteroatoms such as oxygen, nitrogen, phosphorus, and sulfur in addition to carbon and hydrogen.
• CL may be the above-mentioned chelating group alone, but may also be a chelating group to which a hydrocarbon group such as a methyl group, an ethyl group, or a phenyl group, an ester group such as an acetate ester, an ether group such as an ethyl ether, an amide group such as a benzoic acid amide, or a sulfonate ester group such as a toluenesulfonate ester is bonded.
• a hydrocarbon group such as a methyl group, an ethyl group, or a phenyl group
• an ester group such as an acetate ester
• an ether group such as an ethyl ether
• an amide group such as
• a polymer compound having a structure represented by the following general formula (2) in which the chelating group is introduced into the graft chain is also preferably used in the binder which is one embodiment of the present disclosure.
• PS and X have the same meanings as PS and X in the general formula (1)
• B represents a vinyl monomer residue having 4 to 30 carbon atoms and containing a chelating group
• D represents a vinyl monomer residue having 4 to 30 carbon atoms and not containing a chelating group
• l and m each independently represent an integer of 10 to 500.
• the chelate group is introduced into the graft polymer chain and is bonded to the acidic polysaccharide or basic polysaccharide via a covalent bond.
• the chelate group may be the same as the chelate group of the chelate group-containing polymer compound of the above general formula (1).
• Examples of the vinyl monomer residue having a chelate group represented by B in the general formula (2) include a reaction product of an epoxy group and an amino group in a vinyl monomer residue having an epoxy group, such as glycidyl methacrylate, and an amino group in a compound having a chelate group.
• Examples of the vinyl monomer residue having 4 to 30 carbon atoms and not containing a chelate group represented by D in the general formula (2) include a vinyl monomer residue in which the epoxy group remains as it is in a vinyl monomer residue having an epoxy group, such as glycidyl methacrylate, and a vinyl monomer residue that has been hydrolyzed and ring-opened, as well as a vinyl monomer residue that does not have an epoxy group.
• the fact that the chelating group is bound to the polymer compound via a covalent bond can be confirmed, for example, by measuring the weight increase before and after the introduction of the chelating group.
• an example of such a structure is one in which a polymer compound having an anionic functional group and a chelating group-containing compound having a cationic functional group (e.g., a compound having an amino group and a chelating group) are bonded by an ionic bond.
• anionic functional groups include carboxyl groups, sulfonic acid groups, phosphoric acid groups, and phenolic hydroxyl groups.
• polymer compounds having an anionic functional group include poly(acrylic acid), poly(methacrylic acid), poly(itaconic acid), poly(maleic acid), ethylene-maleic acid copolymer, isobutene-maleic acid copolymer, methyl vinyl ether-maleic acid copolymer, styrene-maleic acid copolymer, poly(fumaric acid), poly(vinyl sulfonic acid), poly(styrene sulfonic acid), poly(2-sulfoethyl methacrylate), poly(2-sulfoethyl acrylate), poly(3-sulfopropyl methacrylate), poly(3-sulfopropyl ...
• Suitable binders include vinyl polymers consisting of poly(4-sulfobutyl methacrylate), poly(4-sulfobutyl acrylate), poly(2-acrylamido-2-methylpropanesulfonic acid), poly(2-methacrylamido-2-methylpropanesulfonic acid) and copolymers thereof; and acidic polysaccharides such as carboxymethylcellulose, gellan gum, alginic acid, sulfated alginic acid, carrageenan, xanthan gum, chondroitin sulfate, heparin, hyaluronic acid, pectinic acid, gum arabic, agar, and tragacanth gum.
• acidic polysaccharides such as carboxymethylcellulose, gellan gum, alginic acid, sulfated alginic acid, carrageenan, xanthan gum, chondroitin sulfate, heparin, hyaluronic acid, pec
• polymers may be copolymerized with other monomers as long as the oxidation resistance and reduction resistance are acceptable.
• acidic polysaccharides with high oxidation resistance are preferably used as the binder for the positive electrode, and alginic acid and sulfated alginic acid are more preferably used.
• poly(acrylic acid), poly(styrenesulfonic acid), and copolymers thereof, alginic acid, and sulfated alginic acid, which have excellent reduction resistance are preferably used as the binder for the negative electrode.
• examples of chelating group-containing compounds having cationic functional groups include chelating group-containing compounds containing ammonium groups, phosphonium groups, sulfonium groups, etc.
• Specific compounds include iminodiacetic acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid, N,N-bis(2-hydroxyethyl)glycine, 1,2-diaminocyclohexanetetraacetic acid, diethylenetriaminepentaacetic acid, N-(2-hydroxyethyl)ethylenediaminetriacetic acid, bis(2-aminoethyl)ethyleneglycoltetraacetic acid, bis(2-aminophenyl)ethyleneglycoltetraacetic acid, N-(2-hydroxyethyl)iminodiacetic acid, tetrakis(2-pyridylmethyl)ethylenediamine, triethylenetetraminehexaacetic acid, aminomethylphosphonic acid, aminoethylphosphoric acid
• the acetate group and phosphonic acid group in the above compounds are preferably in the form of a monovalent salt such as an alkali metal salt or ammonium salt rather than in the proton form, since they are more easily ion-exchanged with heavy metal ions.
• the chelating group-containing polymer compound is a compound obtained by reacting hydrogen ion type alginic acid with disodium iminodiacetic acid salt
• the hydrogen ion type alginic acid of the raw material has an absorption derived from the stretching vibration of the carbonyl of the carboxylic acid at 1740 cm -1
• the absorption at 1740 cm -1 disappears, and a new absorption derived from the stretching vibration of the carbonyl of the carboxylate at 1600 cm -1 derived from the disodium iminodiacetic acid salt can be confirmed, so that by measuring such a change in the absorption wavelength
• the method for producing such a chelate group-containing polymer compound is not particularly limited, but may be, for example, a method in which a polymer compound having an anionic functional group (preferably at least one of a carboxyl group, a sulfonic acid group, and a sulfate group) is contacted with an acid to convert the anionic functional group into a hydrogen ion form, and then contacted with a chelate group-containing compound having a cationic functional group (for example, a compound having an amino group and a chelate group) to introduce the chelate group into the anionic polymer to obtain a chelate group-containing polymer compound.
• a polymer compound having an anionic functional group preferably at least one of a carboxyl group, a sulfonic acid group, and a sulfate group
• a chelate group-containing compound having a cationic functional group for example, a compound having an amino group and a chelate group
• Another method for producing a chelate group-containing polymer compound may be, for example, a method in which an acidic polysaccharide and/or a basic polysaccharide is reacted with epihalohydrin and/or a polyfunctional epoxy compound having 2 to 6 epoxy groups, and then reacted with a chelate group-containing compound having a cationic functional group (for example, a compound having an amino group and a chelate group) to introduce the chelate group into the acidic polysaccharide or basic polysaccharide via a covalent bond to obtain a chelate group-containing polymer compound.
• a cationic functional group for example, a compound having an amino group and a chelate group
• epihalohydrins examples include epichlorohydrin, epibromohydrin, epiiodohydrin, and mixtures thereof.
• polyfunctional epoxy compounds having 2 to 6 epoxy groups include bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, resorcinol diglycidyl ether, ethylene glycol diglycidyl ether, glycerin triglycidyl ether, and 1,3-bis(oxiran-2-ylmethoxy)-2,2-bis[(oxiran-2-ylmethoxy)methyl]propane.
• One aspect of the present disclosure is a binder for a lithium-ion battery positive electrode that includes a flexible polymer.
• the flexible polymer in such a binder is preferably a polymer (dried product of an aqueous emulsion) obtained by using a polymer dispersed as an emulsion in an aqueous medium (aqueous polymer emulsion).
• the flexible polymer is preferably a dried product of an aqueous emulsion (obtained by drying an aqueous emulsion).
• the flexible polymer may also be obtained by utilizing a solution in which a polymer is dissolved in water.
• the flexible polymer is not particularly limited, but since one of the purposes of adding it is to impart flexibility to the positive electrode, it is preferable that the polymer be highly flexible.
• flexible polymers include fluororesins such as polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, perfluoromethylvinyl ether-tetrafluoroethylene copolymer, polytetrafluoroethylene, and fluororubber, and hydrocarbon elastomers such as styrene-butadiene copolymer and ethylene-propylene copolymer, with preferred examples being polymers containing an aromatic vinyl monomer and an aliphatic conjugated diene monomer, such as polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, and styrene-butadiene copolymer.
• fluororesins such as polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, perfluoromethylvinyl ether-tetrafluor
• a flexible polymer is a metal salt of polyacrylic acid.
• the flexible polymer is preferably at least one of a metal salt of polyacrylic acid, polyvinylidene fluoride and its copolymer, and a polymer containing an aromatic vinyl monomer and an aliphatic conjugated diene monomer, more preferably at least one of polyvinylidene fluoride and its copolymer, and a polymer containing an aromatic vinyl monomer and an aliphatic conjugated diene monomer, and even more preferably at least one of polyvinylidene fluoride and its copolymer, and a copolymer containing at least a styrene monomer and a butadiene monomer.
• the molecular weight of the flexible polymer is 50,000 to 2,000,000, preferably 100,000 to 1,000,000, in terms of weight average molecular weight. A weight average molecular weight in this range is preferable because it ensures flexibility and sufficient mechanical strength.
• the "weight average molecular weight" of the flexible polymer can be determined by using GPC as the measuring device, selecting a solvent that dissolves the polymer as the eluent, and using polyethylene glycol as the standard sample.
• the "water-based" in water-based polymer emulsion refers to a medium whose main component is water, and components other than water may include organic compounds such as alcohol, ether, ester, amine, and amide, as long as they are soluble in water.
• the emulsion in water-based polymer emulsion refers to a dispersion medium in which fine particles are dispersed, with the size of the fine particles being on the order of several tens to several hundreds of nanometers. The dispersion state of the polymer in the emulsion may be confirmed by the presence or absence of settling from a stationary state.
• the proportion (content) of the flexible polymer component in the emulsion is preferably 20% by mass to 60% by mass (more preferably 30% by mass to 50% by mass).
• aqueous polymer emulsion aqueous polymer emulsion
• the proportion (content) of the flexible polymer component in the emulsion is preferably 20% by mass to 60% by mass (more preferably 30% by mass to 50% by mass).
• any known method can be used as appropriate.
• a commercially available product may be used as such an aqueous polymer emulsion.
• the binder for the positive electrode of a lithium ion battery is composed of a chelate group-containing polymer compound and a flexible polymer (preferably a dried aqueous polymer emulsion), and the weight ratio of the chelate group-containing polymer compound:flexible polymer (preferably a dried aqueous polymer emulsion (mass of solids in emulsion)) is preferably 50-90:10-50 (more preferably 60-80:20-40).
• the content (mixture amount) of the binder which is one aspect of the present disclosure, is preferably 1 to 20 mass % relative to the total amount of the active material, binder, and conductive additive, and more preferably 3 to 10 mass %.
• a mixture (composition) of a chelate group-containing polymer compound and a flexible polymer can be prepared by adding a flexible polymer in the form of an aqueous polymer emulsion to the chelate group-containing polymer compound and mixing them.
• a mixture (composition) it is possible to efficiently prepare a slurry, a positive electrode, and a lithium-ion battery, which will be described later.
• the binder according to one aspect of the present disclosure is highly flexible, and therefore can follow the volumetric changes of the electrodes during charging and discharging, preventing cracking of the electrodes due to volumetric changes, the peeling and falling off of the active material that accompanies such changes, and the destruction of the conductive channel. Furthermore, the binder according to one aspect of the present disclosure has excellent performance as a binder for lithium-ion battery electrodes, such as excellent ion conductivity due to excellent affinity with the electrolyte, and excellent oxidation resistance and reduction resistance that ensure the stability of the electrodes.
• a chelating group is introduced into the binder, which is one aspect of the present disclosure.
• This chelating group captures manganese ions and the like that are eluted from the positive electrode active material near the positive electrode and/or negative electrode, suppressing precipitation and deposition on the negative electrode active material, thereby achieving excellent charge/discharge characteristics and a long cycle life.
• the binder for the positive electrode of a lithium ion battery may contain a chelate group-containing polymer compound and a flexible polymer, and may further contain other components in addition to these components.
• the binder for the positive electrode of a lithium ion battery which is one aspect of the present disclosure, may contain other components in addition to the chelate group-containing polymer compound and the flexible polymer.
• Such other components are not particularly limited, and known components (known binding agents, etc.) that can be used in binders in the field of lithium ion batteries may be used as appropriate. Suitable examples of such other components include silane coupling agents and inorganic components (e.g., colloidal silica, heavy phosphate, alumina sol).
• transition metal oxides such as CuO , Cu2O , MnO2 , MoO3 , V2O5 , CrO3 , Fe2O3 , Ni2O3 , and CoO3
• lithium composite oxides such as LiXCoO2, LiXNiO2, LiX
• examples of the positive electrode active material include at least one of the transition metal oxides and the lithium composite oxides.
• the transition metal oxide is preferably at least one selected from the group consisting of CuO, Cu2O, MnO2, MoO3, V2O5 , CrO3 , Fe2O3 , Ni2O3 , and CoO3
• the positive electrode active material is more preferably a composite oxide of lithium and at least one transition metal selected from transition metals such as Co, Ni, and Mn.
• transition metals such as Co, Ni, and Mn.
• lithium composite oxides may be doped with a small amount of elements such as fluorine, boron, Al, Cr, Zr, Mo, and Fe, or may be a positive electrode active material in which the particle surface of the lithium composite oxide is surface-treated with carbon, MgO, Al 2 O 3 , SiO 2, or the like.
• the lithium composite oxide may be the above-mentioned lithium composite oxide doped with at least one element selected from the group consisting of fluorine, boron, Al, Cr, Zr, Mo, and Fe, or may be a surface-treated product in which the particle surfaces of the above-mentioned lithium composite oxide are surface-treated with at least one element selected from the group consisting of carbon, MgO , Al2O3 , and SiO2 .
• the negative electrode active material is not particularly limited as long as it is capable of inserting and extracting lithium ions.
• the negative electrode active material include natural graphite, artificial graphite, graphite, mesocarbon microbeads (MCMB), tin and/or tin alloys, tin oxide, silicon and/or silicon alloys, and silicon oxide.
• the negative electrode active material is an alloy
• the negative electrode active material may contain a material that alloys with lithium.
• the material that alloys with lithium include one or more selected from the group consisting of germanium, tin, lead, zinc, magnesium, sodium, aluminum, gallium, and indium, as well as alloys thereof.
• the average particle size there are no particular limitations on the average particle size, but it is preferable that it be 5 ⁇ m or more and 20 ⁇ m or less.
• conductive assistants include conductive carbon such as Ketjen black and acetylene black, carbon materials such as natural graphite, artificial graphite, carbon whiskers, carbon nanotubes (CNT), and carbon fiber powder, metal powders and metal fibers such as Cu, Fe, Ag, Ni, Pd, Au, Pt, In, and W, and conductive metal oxides such as indium oxide and tin oxide.
• At least one selected from the group consisting of the conductive carbon, the carbon material, the metal powder, the metal fiber, and the conductive metal oxide can be suitably used as the conductive assistant, and among them, at least one selected from the group consisting of the conductive carbon and the carbon material is more preferable, since it is possible to impart higher conductivity with a small amount of use, and at least one selected from the group consisting of Ketjen black, carbon nanotubes, and acetylene black is even more preferable.
• conductive additives are more effective in forming conductive paths, it is preferable to use conductive carbon in combination with carbon nanotubes (CNTs).
• the amount of these conductive additives to be added is preferably 1 to 30% by mass relative to the active material.
• the lithium ion battery positive electrode composite layer forming slurry is a slurry for forming a lithium ion battery positive electrode composite layer comprising the binder, and contains a positive electrode active material, a conductive assistant, a chelate group-containing polymer compound, a flexible polymer, and water.
• the slurry may contain a viscosity regulator such as carboxymethyl cellulose, or a pH regulator such as an acid or alkali, as necessary.
• the solid content concentration of the slurry is not particularly limited, but is preferably 20 to 80 mass % in consideration of the viscosity of the slurry, the dispersibility of the solid content, the load on the drying process, and the like.
• Examples of the method for producing the slurry include a method in which the chelate group-containing polymer compound, the flexible polymer, the active material, and the conductive assistant are mixed in water, dispersed and/or dissolved, and a method in which the chelate group-containing polymer compound and the flexible polymer are first dissolved and/or dispersed in water, and then the active material and the conductive assistant are added to an aqueous solution or dispersion of the chelate group-containing polymer compound and the flexible polymer, and mixed to produce a slurry, and a method in which the active material and the conductive assistant are first mixed, and then mixed with an aqueous solution or dispersion of the binder components.
• a mortar, a roll mill, a ball mill, a screw mill, a vibration mill, a homogenizer, a planetary mixer, etc. can be used.
• a mortar, a roll mill, a ball mill, a screw mill, a vibration mill, a homogenizer, a planetary mixer, etc. it is preferable to use an aqueous emulsion of a flexible polymer when introducing the flexible polymer into the slurry. In this way, by preparing a slurry using an aqueous emulsion of a flexible polymer, it tends to be possible to produce an electrode with higher flexibility.
• the lithium ion battery positive electrode according to one embodiment of the present disclosure includes the binder.
• the lithium ion battery positive electrode is composed of an electrode mixture layer (positive electrode mixture layer) obtained by applying the slurry onto a current collector and drying it, and a current collector.
• the thickness of the electrode mixture layer (positive electrode mixture layer) made of the active material, binder, and conductive additive is preferably 10 to 200 ⁇ m, and in order to form an electrode mixture layer of this thickness on the current collector, it is preferable to set the basis weight of the electrode mixture layer (positive electrode mixture layer) to 4 to 25 mg/ cm2 .
• the current collector may be any conductor whose surface in contact with the electrode mixture layer (positive electrode mixture layer) exhibits electrical conductivity, and examples of such conductors include metals such as copper, gold, aluminum, titanium, nickel, stainless steel, or alloys thereof, conductive metal oxides such as indium oxide or tin oxide, and conductive materials such as conductive carbon.
• metals such as copper, gold, aluminum, titanium, nickel, stainless steel, or alloys thereof, conductive metal oxides such as indium oxide or tin oxide, and conductive materials such as conductive carbon.
• shape of the current collector and shapes such as foil, film, sheet, net, expanded metal, punched metal, and foam can be used.
• the thickness of the current collector and it is preferable that it be around 1 to 100 ⁇ m.
• the manufacturing method of the positive electrode for lithium-ion batteries there are no particular restrictions on the manufacturing method of the positive electrode for lithium-ion batteries, and it can be manufactured by applying the above-mentioned slurry to a current collector and drying it.
• the method of applying the slurry and methods such as slit coating, die coating, roll coating, dip coating, blade coating, knife coating, and wire bar coating can be used.
• the drying method and conditions There are no particular restrictions on the drying method and conditions, and a normal hot air circulation type dryer, reduced pressure dryer, infrared dryer, or microwave heating dryer can be used. If heating is performed during drying, there is no restriction on the heating temperature, and it can be heated and dried at, for example, 50 to 150°C.
• the porous structure can be made uniform by applying pressure to the electrode during or after drying.
• the slurry is applied onto a current collector and dried to produce a positive electrode composite layer, so that the flexible polymer in the binder in the positive electrode for a lithium ion battery is made of a dried aqueous emulsion.
• a lithium ion battery (lithium ion secondary battery; LIB) according to one embodiment of the present disclosure has the above-mentioned positive electrode for lithium ion batteries.
• a high-performance lithium ion battery that achieves excellent charge/discharge characteristics and a long cycle life can be provided.
• a lithium ion battery is generally composed of a positive electrode, a negative electrode, a separator, a non-aqueous electrolyte, and the like.
• the positive electrode is a structure in which the above-mentioned positive electrode active material is bound to a positive electrode current collector by a binder together with the above-mentioned conductive assistant, and a positive electrode mixture layer made of a positive electrode active material, a binder, and a conductive assistant is formed on the current collector.
• the negative electrode also has a structure similar to that of the positive electrode, and the above-mentioned negative electrode active material and the above-mentioned conductive assistant are bound to a negative electrode current collector by a binder.
• a porous film such as polyolefin is generally used as the separator, and is sandwiched between the positive electrode and the negative electrode to perform a shutdown function when the battery goes into thermal runaway.
• the non-aqueous electrolyte is a solution of an electrolyte salt such as LiPF4 in an organic solvent such as a cyclic carbonate.
• the inside of the battery is filled with a non-aqueous electrolyte, and lithium ions move from the positive electrode to the negative electrode during charging, and move from the negative electrode to the positive electrode during discharging.
• the non-aqueous electrolyte is not particularly limited, and a known material can be used.
• the non-aqueous electrolyte is a solution of an electrolyte salt dissolved in an organic solvent.
• the electrolyte salt include CF3SO3Li , ( CF3SO2 ) 2NLi , ( CF3SO2 ) 2CLi , LiBF4 , LiB (C6H8 ) 4 , LiPF4 , LiClO4 , LiAsF6 , LiCl , and LiBr.
• organic solvents that dissolve the electrolyte salt include ethylene carbonate, vinylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, ⁇ -butyrolactone, tetrahydrofuran, 1,4-dioxane, anisole, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propionitrile, butyronitrile, valeronitrile, benzonitrile, dimethylformamide, dimethylsulfoxide, trimethyl phosphate, and triethyl phosphate.
• concentration of the electrolyte salt in the nonaqueous electrolyte solution can be selected from the range of preferably 0.1 to 5 mol/L, more preferably 0.5 to 3 mol/L.
• separator there are no particular restrictions on the separator, and any known separator can be used.
• separators include a polyethylene microporous membrane, a polypropylene microporous membrane, a laminated membrane of a polyethylene microporous membrane and a polypropylene microporous membrane, and nonwoven fabrics made of polyester fibers, aramid fibers, glass fibers, etc.
• the dispersion gradually became transparent, and after the dropwise addition was completed, it became a transparent viscous aqueous solution.
• This aqueous solution was stirred at room temperature for 1 hour, and then dropped into 4 L of acetone to generate a precipitate.
• the obtained precipitate was collected by filtration, washed with acetone, and then isolated by drying under reduced pressure.
• the isolated yield was 1.9 g, the nitrogen content determined by elemental analysis was 3.7% by mass, and the chelating group content calculated from the nitrogen content was 2.6 mmol/g, which was easily soluble in water.
• the FT-IR spectrum was compared before and after the reaction.
• a method of elemental analysis for determining the nitrogen content of the obtained chelate group-containing polymer compound (chelate polymer) a method was adopted in which a MICRO CORDER JM10 manufactured by J Science Co., Ltd. was used to completely combust a sample under an oxygen atmosphere, and the generated CO 2 , H 2 O, and N 2 were measured with a thermal conductivity detector.
• the FT-IR spectrum of the chelate group-containing polymer compound was measured by the ATR method using a Fourier transform infrared spectrophotometer (FT-IR) (SPECTRUM ONE manufactured by PerkinElmer) as a measuring device.
• FT-IR Fourier transform infrared spectrophotometer
• the measurement of the chelate group-containing polymer compound by aqueous GPC was performed using a Tosoh HLC-8320GPC as a measuring device, a TSKgel GMPXL as a column, a column temperature set to 40°C, and a pH 8.0, 0.1 mol/L phosphate buffer aqueous solution as an eluent, at a flow rate of 1 mL/min.
• Polyethylene glycol was used as a standard sample, and the conditions for converting the molecular weight into polyethylene glycol equivalent were adopted, thereby determining the weight average molecular weight of the chelating group-containing polymer compound.
• the properties of the obtained chelate group-containing polymer compound were confirmed in the same manner as in Reference Example 1, and the chelate group content calculated from the nitrogen content was 3.8 mmol/g, and the weight average molecular weight measured using aqueous GPC was 370,000.
• the properties of the obtained chelate group-containing polymer compound were confirmed in the same manner as in Reference Example 1, and the chelate group content calculated from the nitrogen content was 1.2 mmol/g, and the weight average molecular weight measured using aqueous GPC was 900,000.
• reaction intermediate 0.30 g of the reaction intermediate was weighed and dissolved in 100 ml of pure water to obtain an aqueous solution.
• 8.4 g (43 mmol) of iminodiacetic acid disodium monohydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added to the aqueous solution, dissolved, and reacted at 80° C. for 2 hours.
• the aqueous solution after the reaction was purified using an ultrafiltration membrane (manufactured by Nippon Pall, molecular weight cutoff 1000) to remove excess iminodiacetic acid from the aqueous solution.
• the purified aqueous solution was dropped into acetone to precipitate the polymer, and the precipitate was collected by filtration and dried under reduced pressure to isolate the reaction product (chelate group-containing polymer compound: chelate polymer).
• the isolated yield of the obtained chelate group-containing polymer compound was 0.33 g, and it was soluble in water. Furthermore, the properties of the obtained chelate group-containing polymer compound were confirmed in the same manner as in Reference Example 1.
• the weight average molecular weight measured using aqueous GPC was 420,000, and the iminodiacetic acid group content calculated from the nitrogen content was 1.8 mmol/g.
• Teflon (registered trademark) container 1.0 g was taken from the mixture, placed in a Teflon (registered trademark) container, dried under reduced pressure at 120° C. for 4 hours, and then sealed.
• the obtained filtrate was decomposed with acid, and the manganese ion was quantified by ICP-MS.
• the manganese ion concentration was found to be less than 1 ppm by mass, confirming that the manganese ion eluted from the LMO by heating was captured by the chelating polymer.
• Reference Example 7 0.05 g of the chelate polymer obtained in Reference Example 1, 0.05 g of a styrene-butadiene copolymer emulsion having a concentration of 48% by mass (aqueous emulsion, solvent: water, weight average molecular weight of styrene-butadiene copolymer (SBR) in the emulsion: 120,000, hereinafter, such an emulsion is referred to as "SBR emulsion") as a solid content, and 1.9 g of LMO were added to 20 ml of pure water to prepare a slurry.
• SBR weight average molecular weight of styrene-butadiene copolymer
• the obtained slurry was concentrated with an evaporator and then dried under reduced pressure at 80°C to remove water, and the manganese ion concentration was measured in the same manner as in Reference Example 6, except that a mixture of the chelate polymer, SBR, and LMO was obtained.
• the manganese ion concentration was less than 1 ppm by mass, and it was confirmed that even when used in combination with the SBR emulsion, manganese ions eluted from the LMO by heating were captured by the chelate polymer.
• the manganese ion concentration was less than 1 ppm by mass, and it was confirmed that even when used in combination with the PVDF emulsion, manganese ions eluted from the LMO by heating were captured by the chelating polymer.
• the LMO, SBR emulsion, and PVDF emulsion used in the reference examples and working examples described below are similar to the LMO used in Reference Example 6, the SBR emulsion used in Reference Example 7, and the PVDF emulsion used in Reference Example 8, respectively.
• Example 1 A slurry for a positive electrode was prepared from the following materials, and a positive electrode was fabricated.
• Positive electrode active material LMO 94 parts by mass
• Conductive assistant Acetylene black (AB) (Li-400 manufactured by Denka Co., Ltd.) 2.5 parts by weight
• Binder chelate group-containing alginic acid (Reference Example 1) 3 parts by weight SBR 0.5 parts by weight LMO 94 parts by weight, 3 parts by weight of the chelate group-containing alginic acid produced in Reference Example 1, and 2.5 parts by weight of AB were added, and stirred with a planetary mixer while adding water.
• Example 2 A positive electrode was produced in the same manner as in Example 1, except that the emulsion was changed from the SBR emulsion to the PVDF emulsion. In this manner, a positive electrode was produced in the same manner as in Example 1, except that the PVDF emulsion was used instead of the SBR emulsion.
• the basis weight was 16.4 mg/ cm2 .
• Example 3 A positive electrode was produced in the same manner as in Example 2, except that the electrode was thickly coated to give a basis weight of 28.2 mg/ cm2 . That is, a positive electrode was produced in the same manner as in Example 2, except that the slurry was thickly coated so that the basis weight of the electrode mixture layer was 28.2 mg/ cm2 .
• Example 4 A positive electrode was prepared in the same manner as in Example 1 except that the amount of SBR solid content was changed to 1 part by mass and the amount of AB was changed to 2 parts by mass. That is, a positive electrode was prepared in the same manner as in Example 1 except that the amount of SBR emulsion used in terms of SBR solid content was changed to 1 part by mass and the amount of AB used was changed to 2 parts by mass. The basis weight was 19.7 mg/ cm2 .
• Example 5 A positive electrode was prepared in the same manner as in Example 4, except that the emulsion was changed from the SBR emulsion to the PVDF emulsion. In this manner, a positive electrode was prepared in the same manner as in Example 1, except that the PVDF emulsion was used instead of the SBR emulsion. The basis weight was 19.2 mg/ cm2 .
• Example 6 A positive electrode slurry having the following composition was prepared from the following materials to fabricate a positive electrode.
• Positive electrode active material LMO 95 parts by mass Conductive assistant: Acetylene black (AB) (Li-400 manufactured by Denka Co., Ltd.) 1 part by mass Carbon nanotube (CNT) 1 part by mass
• Binder chelate group-containing alginic acid (Reference Example 1) 2 parts by mass SBR 1 part by mass First, 95 parts by mass of LMO, 2 parts by mass of the chelate group-containing alginic acid produced in Reference Example 1, 1 part by mass of AB, and 1 part by mass of CNT were added to a planetary mixer, and then these were stirred with a planetary mixer while adding water.
• Example 7 A positive electrode was produced in the same manner as in Example 4, except that the type of emulsion was changed from SBR emulsion to PVDF emulsion.
• the basis weight of the positive electrode mixture layer was 20.7 mg/ cm2 .
• a positive electrode was prepared in the same manner as in Example 1 using 94 parts by mass of LMO, 3 parts by mass of AB, and 3 parts by mass of chelate-containing alginic acid (Reference Example 1). That is, a positive electrode was prepared in the same manner as in Example 1 except that the amount of LMO, AB, and chelate-containing alginic acid (Reference Example 1) used was changed to 94 parts by mass of LMO, 3 parts by mass of AB, and 3 parts by mass of chelate-containing alginic acid (Reference Example 1) without using an SBR emulsion.
• the basis weight of the positive electrode mixture layer was 16.8 mg/ cm2 .
• the positive electrodes prepared in each example were cut to a width of 15 mm and a length of 8 cm, and were attached so that the positive electrode composite layer surface of the positive electrode was adhered to the adhesive surface of the adherend tape. At that time, the electrode was not attached to the range of 1 cm in length from the end of the adherend tape, and the positive electrode was attached to the adherend tape while leaving the range floating. Then, a PET film was attached to the part 1 cm in length from the end where the positive electrode was not attached, and this was used as a pulling allowance. In this way, a test specimen was prepared in which the positive electrode composite layer part was firmly adhered to the adherend tape.
• the obtained test specimen was fixed to a tensile testing machine (Tensilon RTG-1210, manufactured by A&D Co., Ltd.) and the tensile portion of the test specimen was pulled at a peel speed of 100 mm/min to perform a 180° peel.
• the tensile strength was measured at the points where the specimen had been pulled 10 mm, 20 mm, 30 mm, and 40 mm from the start of peeling, and the average value was calculated as the peel strength.
• the results are shown in Table 1. It should be noted that if the peel strength measured in this way is 5 mN/mm or more, it can be said that the specimen has excellent adhesion.
• the penetration resistance the more excellent the input/output characteristics of the positive electrode can be evaluated. From this perspective, when the penetration resistance is 10 ⁇ or less, it can be evaluated as having a higher level of input/output characteristics that can be particularly suitably used for the positive electrodes of lithium batteries, and further, when the penetration resistance is 3 ⁇ or less, it can be evaluated as exhibiting even more excellent characteristics in terms of input/output characteristics.
• Table 1 show that the electrodes (positive electrodes) manufactured in Examples 1 to 7 have an electrode composite layer with excellent flexibility (bending property) and adhesiveness, and are less likely to crack when wound.
• these results show that the electrodes can be manufactured efficiently by adopting a winding process during manufacturing, and that the slurry used during the manufacture of the positive electrode can also improve the workability during electrode manufacture.
• Example 8 Instead of using 2 parts by mass of the chelate group-containing alginic acid produced in Reference Example 1, 2.5 parts by mass of the chelate group-containing alginic acid obtained in Reference Example 2 was used, and the amount of AB used was changed from 1 part by mass to 0.5 parts by mass.
• a positive electrode was produced in the same manner as in Example 6.
• the basis weight of the positive electrode mixture layer was 26.6 mg/ cm2 .
• the thickness of the positive electrode mixture layer was 110 ⁇ m, the peel strength was 13 mN/mm, and the electrode penetration resistance was 16 ⁇ . Furthermore, there was no crack in the appearance of the electrode when visually confirmed, and no crack occurred in the winding test.
• Example 9 A positive electrode was prepared in the same manner as in Example 8, except that the type of emulsion was changed from SBR emulsion to PVDF emulsion.
• the basis weight of the positive electrode mixture layer was 25.3 mg/ cm2 .
• the thickness of the positive electrode mixture layer was 114 ⁇ m, the peel strength was 7 mN/mm, and the electrode penetration resistance was 9 ⁇ . Furthermore, there were no cracks in the appearance of the electrode when visually confirmed, and no cracks occurred in the winding test.
• a positive electrode slurry having the following composition was prepared from the following materials to fabricate a positive electrode.
• Positive electrode active material LMO 95 parts by mass
• Conductive assistant Acetylene black (AB) (Li-400 manufactured by Denka Co., Ltd.) 0.5 parts by mass Carbon nanotubes (CNT) 1 part by mass
• Binder chelate group-containing alginic acid (Reference Example 3) 2.5 parts by mass SBR 1 part by mass First, 95 parts by mass of LMO, 2.5 parts by mass of the chelate group-containing alginic acid produced in Reference Example 3, 0.5 parts by mass of AB, and 1 part by mass of CNT were added to a planetary mixer, and then these were stirred with a planetary mixer while adding water.
• the weight per unit area of the positive electrode mixture layer was 28.9 mg / cm 2.
• the thickness of the positive electrode mixture layer was 110 ⁇ m, the peel strength was 17 mN / mm, and the electrode penetration resistance was 19.5 ⁇ .
• Example 11 A positive electrode was produced in the same manner as in Example 10, except that the amount of the chelate group-containing alginic acid produced in Reference Example 3 was changed to 2 parts by mass, the amount of the SBR converted to solid content was changed to 0.5 parts by mass, and the amount of the CNT was changed to 2 parts by mass.
• the weight per unit area of the positive electrode mixture layer was 32.3 mg/ cm2 .
• the thickness of the positive electrode mixture layer was 135 ⁇ m, the peel strength was 6 mN/mm, and the electrode penetration resistance was 2.5 ⁇ . In addition, there were no cracks in the appearance of the electrode when visually confirmed, and no cracks occurred in the winding test.
• Example 12 A positive electrode was produced in the same manner as in Example 10, except that the amount of chelate group-containing alginic acid produced in Reference Example 3 was changed to 1.5 parts by mass, the amount of AB was changed to 1 part by mass, and the amount of CNT was changed to 1.5 parts by mass.
• the weight per unit area of the positive electrode mixture layer was 27.7 mg/ cm2 .
• the thickness of the positive electrode mixture layer was 128 ⁇ m, the peel strength was 12 mN/mm, and the electrode penetration resistance was 3.5 ⁇ . Furthermore, there were no cracks in the appearance of the electrode when visually confirmed, and no cracks occurred in the winding test.
• Example 13 A positive electrode was produced in the same manner as in Example 10, except that the amount of chelate group-containing alginic acid produced in Reference Example 3 was changed to 1 part by mass, the amount of AB was changed to 1.5 parts by mass, and the amount of CNT was changed to 1.5 parts by mass.
• the weight per unit area of the positive electrode mixture layer was 28.3 mg/ cm2 .
• the thickness of the positive electrode mixture layer was 114 ⁇ m, the peel strength was 7 mN/mm, and the electrode penetration resistance was 1.5 ⁇ . Furthermore, there were no cracks in the appearance of the electrode when visually confirmed, and no cracks occurred in the winding test.
• Example 14 A positive electrode was prepared in the same manner as in Example 10, except that the type of emulsion was changed from SBR emulsion to PVDF emulsion.
• the basis weight of the positive electrode mixture layer was 27.7 mg/ cm2 .
• the thickness of the positive electrode mixture layer was 120 ⁇ m, the peel strength was 10 mN/mm, and the electrode penetration resistance was 35 ⁇ . Furthermore, there were no cracks in the appearance of the electrode when visually confirmed, and no cracks occurred in the winding test.
• Example 15 A positive electrode was produced in the same manner as in Example 14, except that the amount of PVDF used in terms of solid content was changed to 0.5 parts by mass and the amount of CNT used was changed to 1.5 parts by mass.
• the basis weight of the positive electrode mixture layer was 30.8 mg/cm 2.
• the thickness of the positive electrode mixture layer was 137 ⁇ m, the peel strength was 6 mN/mm, and the electrode penetration resistance was 5.5 ⁇ . Furthermore, there were no cracks in the appearance of the electrode when visually confirmed, and no cracks occurred in the winding test.
• Example 16 A positive electrode was produced in the same manner as in Example 10, except that the chelate group-containing alginic acid produced in Reference Example 4 was used instead of the chelate group-containing alginic acid produced in Reference Example 3.
• the basis weight of the positive electrode mixture layer was 29.0 mg/ cm2 .
• the thickness of the positive electrode mixture layer was 110 ⁇ m, the peel strength was 15 mN/mm, and the electrode penetration resistance was 11.1 ⁇ . Furthermore, there was no crack in the appearance of the electrode when visually confirmed, and no crack occurred in the winding test.
• Example 17 A positive electrode was prepared in the same manner as in Example 16, except that the type of emulsion was changed from SBR emulsion to PVDF emulsion.
• the basis weight of the positive electrode mixture layer was 26.2 mg/ cm2 .
• the thickness of the positive electrode mixture layer was 114 ⁇ m, the peel strength was 9 mN/mm, and the electrode penetration resistance was 7.8 ⁇ . Furthermore, there were no cracks in the appearance of the electrode when visually confirmed, and no cracks occurred in the winding test.
• Example 18 A positive electrode was produced in the same manner as in Example 10, except that the chelate group-containing alginic acid produced in Reference Example 5 was used instead of the chelate group-containing alginic acid produced in Reference Example 3.
• the basis weight of the positive electrode mixture layer was 28.8 mg/cm2.
• the thickness of the positive electrode mixture layer was 122 ⁇ m, the peel strength was 16 mN/mm, and the electrode penetration resistance was 17 ⁇ . Furthermore, there was no crack in the appearance of the electrode when visually confirmed, and no crack occurred in the winding test.
• Example 19 A positive electrode was produced in the same manner as in Example 18, except that the type of emulsion was changed from SBR emulsion to PVDF emulsion.
• the basis weight of the positive electrode mixture layer was 28.4 mg/ cm2 .
• the thickness of the positive electrode mixture layer was 108 ⁇ m, the peel strength was 12 mN/mm, and the electrode penetration resistance was 8.6 ⁇ . Furthermore, there were no cracks in the appearance of the electrode when visually confirmed, and no cracks occurred in the winding test.
• Example 2 A positive electrode was produced in the same manner as in Example 18, except that the amount of chelate group-containing alginic acid produced in Reference Example 5 was changed to 3 parts by mass, SBR emulsion was not used, and the amount of AB was changed to 1 part by mass.
• the positive electrode composite layer had a basis weight of 29.2 mg/ cm2 .
• the positive electrode composite layer had a thickness of 130 ⁇ m, a peel strength of 2 mN/mm, and an electrode penetration resistance of 7 ⁇ . Furthermore, no cracks were found in the electrode appearance by visual inspection, but cracks occurred in a 4 mm diameter winding test.
• Example 20 A positive electrode was prepared in the same manner as in Example 10, except that the sodium polyacrylate aqueous solution prepared in Reference Example 21 (a sodium polyacrylate aqueous solution having a concentration of 13 mass% of sodium polyacrylate having a weight average molecular weight of 510,000) was used instead of the SBR emulsion.
• the weight per unit area of the positive electrode mixture layer was 24.7 mg/cm 2.
• the thickness of the positive electrode mixture layer was 83 ⁇ m, the peel strength was 9 mN/mm, and the electrode penetration resistance was 4.4 ⁇ . In addition, there was no crack in the appearance of the electrode when visually confirmed, and no crack occurred in the winding test.
• Example 21 A positive electrode was produced in the same manner as in Example 20, except that the amount of the chelate group-containing alginic acid produced in Reference Example 3 was changed to 1.5 parts by mass.
• the basis weight of the positive electrode mixture layer was 23.0 mg/ cm2 .
• the thickness of the positive electrode mixture layer was 81 ⁇ m, the peel strength was 9 mN/mm, and the electrode penetration resistance was 1.3 ⁇ .
• a binder for a lithium ion battery positive electrode and a slurry for forming a lithium ion battery positive electrode composite layer which are excellent in workability during electrode fabrication and enable the fabrication of a battery with an extended cycle life. Furthermore, by using the binder and a slurry for forming a lithium ion battery positive electrode composite layer, it is possible to provide a lithium ion battery positive electrode and a lithium ion battery with excellent charge/discharge characteristics and an extended cycle life.

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