Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
  • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
  • C08F220/04—Acids; Metal salts or ammonium salts thereof
  • C08F220/06—Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F8/00—Chemical modification by after-treatment
  • C08F8/44—Preparation of metal salts or ammonium salts
• • 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
  • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
  • H01M4/134—Electrodes based on metals, Si or alloys
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries

Definitions

• the present specification relates to a binder for a secondary battery electrode and use thereof.
• This application is a related application of Japanese Patent Application No. 2018-102905, which is a Japanese patent application filed on May 30, 2018, and claims priority based on this Japanese application. It is incorporated herein by reference.
• the electrodes used in these secondary batteries are produced by applying and drying a composition for forming an electrode mixture layer containing an active material and a binder on a current collector.
• a composition for forming an electrode mixture layer containing an active material and a binder on a current collector For example, in a lithium ion secondary battery, an aqueous binder containing styrene butadiene rubber (SBR) latex and carboxymethyl cellulose (CMC) is used as a binder used in the negative electrode mixture layer composition.
• SBR styrene butadiene rubber
• CMC carboxymethyl cellulose
• a binder excellent in dispersibility and binding property a binder containing an acrylic acid polymer aqueous solution or an aqueous dispersion is known.
• NMP N-methyl-2-pyrrolidone
• PVDF polyvinylidene fluoride
• Patent Document 1 As a binder having good binding properties and an effect of improving durability, a binder using the acrylic acid polymer has been proposed.
• Patent Document 1 by using a polymer obtained by cross-linking polyacrylic acid with a specific cross-linking agent as a binder, the electrode structure is not destroyed even when an active material containing silicon is used. It is described that it can be provided.
• Patent Document 2 describes a lithium battery binder comprising a monomer unit derived from acrylic acid as a constituent component and made of a polymer crosslinked with a specific crosslinking agent, and has a high capacity even when charging and discharging are repeated. It is described that the maintenance rate is shown.
• Patent Document 3 discloses a binder for a lithium ion secondary battery positive electrode obtained by polymerizing a monomer composition containing an ethylenically unsaturated carboxylic acid compound and a copolymerizable compound having a specific solubility in water. A composition is disclosed, which describes that battery life characteristics can be improved.
• any of the binders disclosed in Patent Documents 1 to 3 can impart good binding properties, but as the performance of the secondary battery improves, an electrode mixture layer with higher binding properties is required. It is like that.
• the present disclosure has been made in view of such circumstances, and when a polymer having a carboxyl group such as an acrylic acid polymer is used as a binder, a secondary battery electrode having a higher binding property than conventional ones.
• a composition for a secondary battery electrode mixture layer from which a mixture layer can be obtained is provided. Moreover, this indication provides the secondary battery electrode obtained using the said composition.
• the present inventors have obtained a crosslink obtained by polymerizing a monomer composition containing an ethylenically unsaturated carboxylic acid monomer and a specific crosslinkable monomer.
• the present inventors have found that when a binder containing a polymer which is a polymer and has excellent dispersion stability is used, the binding property of the obtained electrode mixture layer can be made higher. According to the present disclosure, the following means are provided based on such findings.
• a binder for a secondary battery electrode containing a crosslinked polymer is obtained by polymerizing a monomer composition containing a non-crosslinkable monomer and a crosslinkable monomer,
• the non-crosslinkable monomer contains 50% by mass or more and 100% by mass or less of an ethylenically unsaturated carboxylic acid monomer with respect to the total amount of the non-crosslinkable monomer
• the crosslinkable monomer includes a monomer having at least one polymerizable unsaturated group other than an allyl group
• the crosslinked polymer is neutralized to a neutralization degree of 80 to 100 mol%, and then has a particle diameter measured in an aqueous medium of 0.1 ⁇ m or more and 10 ⁇ m or less in terms of volume-based median diameter.
• Binder [2] The amount of the crosslinkable monomer used is 0.1 to 10 parts by mass with respect to 100 parts by mass of the total amount of the non-crosslinkable monomer. Binder for water electrolyte secondary battery electrodes. [3] The crosslinkable monomer has one or more polymerizable unsaturated groups selected from the group consisting of a (meth) acryloyl group, a (meth) acryloyloxy group, a (meth) acrylamide group, and a styryl group. The binder for secondary battery electrodes as described in [1] or [2].
• the binder for a secondary battery electrode according to any one of [1] to [3], wherein the crosslinked polymer is a salt in which 50 mol% or more of the carboxyl groups of the crosslinked polymer are neutralized.
• a method for producing a crosslinked polymer or a salt thereof used for a binder for a secondary battery electrode A polymerization step of polymerizing a monomer composition containing a non-crosslinkable monomer and a crosslinkable monomer by precipitation polymerization;
• the non-crosslinkable monomer contains 50% by mass or more and 100% by mass or less of an ethylenically unsaturated carboxylic acid monomer with respect to the total amount of the non-crosslinkable monomer,
• the crosslinkable monomer includes a monomer having at least one polymerizable unsaturated group other than an allyl group, A method in which the crosslinked polymer is neutralized to a degree of neutralization of 80 to 100 mol%, and the particle diameter measured in an aqueous
• a composition for a secondary battery electrode mixture layer comprising the binder according to any one of [1] to [4], an active material, and water.
• a secondary battery electrode comprising a mixture layer formed on the current collector surface from the composition for a secondary battery electrode mixture layer according to [6] or [7].
• the secondary battery electrode binder of the present disclosure exhibits excellent binding properties to electrode active materials and the like. Moreover, the said binder can exhibit favorable adhesiveness with a collector. For this reason, the electrode mixture layer containing the binder and the electrode provided with the binder have excellent binding properties and can maintain the integrity thereof.
• the secondary battery electrode binder of the present disclosure contains a crosslinked polymer, and can be made into a composition for an electrode mixture layer by mixing with an active material and water.
• the composition described above may be in a slurry state that can be applied to the current collector, or may be prepared in a wet powder state so that it can be applied to pressing on the surface of the current collector.
• the secondary battery electrode of the present disclosure is obtained by forming a mixture layer formed from the above composition on the surface of a current collector such as a copper foil or an aluminum foil.
• (meth) acryl means acryl and / or methacryl
• (meth) acrylate means acrylate and / or methacrylate
• the “(meth) acryloyl group” means an acryloyl group and / or a methacryloyl group.
• the binder of the present disclosure includes a crosslinked polymer.
• the crosslinked polymer contains an ethylenically unsaturated carboxylic acid monomer in a constituent monomer unit, and is a crosslinked polymer having a carboxyl group.
• the crosslinked polymer of the present disclosure (hereinafter also referred to as “the present polymer”) can be obtained by polymerizing a monomer composition containing a non-crosslinkable monomer and a crosslinkable monomer.
• the non-crosslinkable monomer is a compound having only one ethylenically unsaturated functional group in the molecule, and examples thereof include an ethylenically unsaturated carboxylic acid monomer and other ethylenically unsaturated monomers.
• ⁇ Ethylenically unsaturated carboxylic acid monomer> By polymerizing a monomer composition containing an ethylenically unsaturated carboxylic acid monomer (hereinafter also referred to as “component (a)”), a carboxyl group is introduced into the polymer. As a result, adhesion to the current collector is improved, and since the lithium ion desolvation effect and ion conductivity are excellent, an electrode having low resistance and excellent high rate characteristics can be obtained. Moreover, since water swelling property is provided, dispersion stability of the active material etc. in a mixture layer composition can be improved.
• component (a) ethylenically unsaturated carboxylic acid monomer
• Examples of ethylenically unsaturated carboxylic acid monomers include (meth) acrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid; (meth) acrylamide alkyl such as (meth) acrylamide hexanoic acid and (meth) acrylamide dodecanoic acid Carboxylic acid; ethylenically unsaturated monomer having a carboxyl group such as succinic acid monohydroxyethyl (meth) acrylate, ⁇ -carboxy-caprolactone mono (meth) acrylate, ⁇ -carboxyethyl (meth) acrylate or the like (partial thereof) ) Alkali neutralized products are exemplified, and one of these may be used alone, or two or more may be used in combination.
• a compound having an acryloyl group as a polymerizable functional group is preferable in that a polymer having a long primary chain length is obtained due to a high polymerization rate, and a binder has a good binding force, and particularly preferably acrylic acid. is there.
• acrylic acid is used as the ethylenically unsaturated carboxylic acid monomer, a polymer having a high carboxyl group content can be obtained.
• the content of the component (a) in the present polymer is not particularly limited, but can be, for example, 10% by mass to 100% by mass with respect to the total amount of non-crosslinkable monomers.
• the lower limit is, for example, 20% by mass or more, for example, 30% by mass or more, and for example, 40% by mass or more.
• the lower limit is 50% by mass or more, it is preferable because the dispersion stability of the composition for electrode mixture layer becomes good and higher binding force is obtained, and may be 60% by mass or more, and 70% by mass or more. It may be 80% by mass or more.
• the upper limit is, for example, 99.9% by mass or less, for example, 99.5% by mass or less, for example, 99% by mass or less, for example, 98% by mass or less, and for example, 95% by mass. Or less, for example 90% by mass or less, and for example 80% by mass or less.
• it can be set as the range which combined these lower limits and upper limits suitably, but is 10 mass% or more and 100 mass% or less, for example, is 50 mass% or more and 100 mass% or less, for example, 50 mass% or more and 99.9 mass% or less, for example, 50 mass% or more and 98 mass% or less, for example, 70 mass% or more, 95 mass% or less, etc. can be used.
• the non-crosslinkable monomer constituting the present polymer includes other ethylenically unsaturated monomers copolymerizable with these (hereinafter also referred to as “component (b)”).
• component (b) examples include an ethylenically unsaturated monomer compound having an anionic group other than a carboxyl group such as a sulfonic acid group and a phosphoric acid group, or a nonionic ethylenically unsaturated monomer. Can be mentioned.
• An anionic group other than a carboxyl group such as a sulfonic acid group and a phosphoric acid group, or a nonionic structural unit can be introduced into the polymer by polymerizing a monomer composition containing the component (b). It can.
• a nonionic ethylenically unsaturated monomer is preferable from the viewpoint of obtaining an electrode having good bending resistance, and (meth) acrylamide is excellent in binder binding properties. And derivatives thereof, and nitrile group-containing ethylenically unsaturated monomers are preferred.
• a structural unit derived from a hydrophobic ethylenically unsaturated monomer having a solubility in water of 1 g / 100 ml or less is introduced as the component (b), it can exert a strong interaction with the electrode material, Good binding property to the active material can be exhibited. This is preferable because an electrode mixture layer that is firm and has good integrity can be obtained.
• an alicyclic structure-containing ethylenically unsaturated monomer is preferred.
• the ratio of a component can be 0 mass% or more and 90 mass% or less with respect to the total amount of a non-crosslinkable monomer.
• the proportion of the component (b) may be 1% by mass or more and 60% by mass or less, 2% by mass or more and 50% by mass or less, or 5% by mass or more and 40% by mass or less. 10 mass% or more and 30 mass% or less may be sufficient.
• the affinity to the electrolytic solution is improved, so that an effect of improving lithium ion conductivity can be expected.
• Examples of (meth) acrylamide derivatives include N-alkyl (meth) acrylamide compounds such as isopropyl (meth) acrylamide and t-butyl (meth) acrylamide; Nn-butoxymethyl (meth) acrylamide, N-isobutoxymethyl N-alkoxyalkyl (meth) acrylamide compounds such as (meth) acrylamide; and N, N-dialkyl (meth) acrylamide compounds such as dimethyl (meth) acrylamide and diethyl (meth) acrylamide are listed. You may use individually and may be used in combination of 2 or more type.
• nitrile group-containing ethylenically unsaturated monomer examples include (meth) acrylonitrile; (meth) acrylic acid cyanoalkyl ester compounds such as (meth) acrylic acid cyanomethyl and (meth) acrylic acid cyanoethyl; 4-cyanostyrene Cyano group-containing unsaturated aromatic compounds such as 4-cyano- ⁇ -methylstyrene; vinylidene cyanide and the like, and one of these may be used alone, or two or more may be used in combination. May be used.
• acrylonitrile is preferred because of its high nitrile group content.
• Examples of the alicyclic structure-containing ethylenically unsaturated monomer include cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, methyl cyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, (meth ) (Meth) acrylic acid cycloalkyl ester optionally having an aliphatic substituent such as cyclodecyl acrylate and cyclododecyl (meth) acrylate; isobornyl (meth) acrylate, adamantyl (meth) acrylate, (meth ) Dicyclopentenyl acrylate, dicyclopentenyloxyethyl (meth) acrylate, dicyclopentanyl (meth) acrylate, and cyclohexanedimethanol mono (meth) acrylate and cyclodecane dimethanol mono (me
• (meth) acrylic acid esters may be used as other nonionic ethylenically unsaturated monomers.
• (meth) acrylic acid esters include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate.
• (Meth) acrylic acid alkyl ester compounds Aromatic (meth) acrylate compounds such as phenyl (meth) acrylate, phenylmethyl (meth) acrylate, phenylethyl (meth) acrylate, phenoxyethyl (meth) acrylate; (Meth) acrylic acid alkoxyalkyl ester compounds such as (meth) acrylic acid 2-methoxyethyl and (meth) acrylic acid ethoxyethyl; (Meth) acrylic acid hydroxyalkyl, (meth) acrylic acid hydroxypropyl and (meth) acrylic acid hydroxyalkyl ester compounds such as hydroxybutyl, etc. are used, and one of these is used alone. You may use it in combination of 2 or more types.
• An aromatic (meth) acrylic acid ester compound can be preferably used from the viewpoints of adhesion with the active material and cycle characteristics.
• compounds having an ether bond such as (meth) acrylic acid alkoxyalkyl esters such as 2-methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate are preferred. More preferred is 2-methoxyethyl (meth) acrylate.
• nonionic ethylenically unsaturated monomers a compound having an acryloyl group is preferable in that a polymer having a long primary chain length is obtained due to a high polymerization rate, and a binder has a good binding force.
• a compound having a glass transition temperature (Tg) of a homopolymer of 0 ° C. or less is preferable in that the obtained electrode has good bending resistance.
• the present polymer may be in the form of a salt in which some or all of the carboxyl groups contained in the polymer are neutralized.
• a salt in which some or all of the carboxyl groups contained in the polymer are neutralized.
• Alkali metal salts such as lithium, sodium, and potassium
• Alkaline earth metal salts such as calcium salt and barium salt
• Other metal salts such as magnesium salt and aluminum salt
• Ammonium salt and organic Examples include amine salts.
• alkali metal salts and magnesium salts are preferred, and alkali metal salts are more preferred because they are less likely to adversely affect battery characteristics.
• the crosslinkable monomer in the present disclosure includes a polyfunctional polymerizable monomer having two or more polymerizable unsaturated groups, and a monomer having a self-crosslinkable functional group such as a hydrolyzable silyl group. And a monomer having at least one polymerizable unsaturated group other than an allyl group.
• the polyfunctional polymerizable monomer is a compound having two or more radically polymerizable unsaturated groups in the molecule and at least one polymerizable unsaturated group other than an allyl group.
• Examples of the polymerizable unsaturated group other than the allyl group include groups represented by the following general formula (1) and general formula (2).
• R 1 represents a hydrogen atom, a methyl group, a nitrile group or a halogen atom.
• A represents an oxygen atom, a divalent organic group or a single bond.
• CH 2 C (R 2 ) -B- (2)
• R 2 represents a hydrogen atom, a methyl group, a nitrile group or a halogen atom.
• B represents an arylene group which may have a substituent.
• R 1 in the general formula (1) is a hydrogen atom or a methyl group
• the general formula (1) represents a (meth) acryloyl group
• A is an oxygen atom (meta ) Represents an acryloyloxy group.
• a as the divalent organic group include NH, NR (R represents an alkyl group), and an alkylene group.
• R 1 in the general formula (1) is a hydrogen atom or a methyl group and A is NH is referred to as a “(meth) acrylamide group”.
• Other specific groups of the general formula (1) include ⁇ -cyanoacryloyl group, ⁇ -halogen acryloyl group and the like.
• polyfunctional polymerizable monomer having the group represented by the general formula (1) examples include ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, and 1,6-hexanediol.
• Di (meth) acrylates of polyhydric alcohols such as di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, 2-hydroxy-3-acryloyloxypropyl methacrylate; trimethylolpropane tri (Meth) acrylate, trimethylolpropane ethylene oxide modified tri (meth) acrylate, glycerin tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, Tri (meth) acrylates of trihydric or higher polyhydric alcohols such as pentaerythritol penta and
• Specific examples of the general formula (2) include a styryl group.
• Specific examples of the polyfunctional polymerizable monomer having these groups include divinylbenzene and divinylnaphthalene.
• the monomer having a crosslinkable functional group capable of self-crosslinking include hydrolyzable silyl group-containing vinyl monomers, N-methylol (meth) acrylamide, N-methoxyalkyl (meth) acrylate, and the like. Is mentioned. These compounds can be used alone or in combination of two or more.
• the hydrolyzable silyl group-containing vinyl monomer is not particularly limited as long as it is a monomer having a polymerizable unsaturated group other than an allyl group and a hydrolyzable silyl group.
• vinyl silanes such as vinyltrimethoxysilane, vinyltriethoxysilane, vinylmethyldimethoxysilane, and vinyldimethylmethoxysilane
• silyl such as trimethoxysilylpropyl acrylate, triethoxysilylpropyl acrylate, and methyldimethoxysilylpropyl acrylate Group-containing acrylic acid esters
• silyl group-containing methacrylates such as trimethoxysilylpropyl methacrylate, triethoxysilylpropyl methacrylate, methyldimethoxysilylpropyl methacrylate, dimethylmethoxysilylpropyl methacrylate
• trimethoxysilylpropyl vinyl ether etc
• the amount of the crosslinkable monomer used is not particularly limited, but is preferably 0.1 parts by mass or more with respect to 100 parts by mass of the total amount of non-crosslinkable monomers, More preferably, it is 0.5 mass part or more.
• the amount of the crosslinkable monomer used may be, for example, 1.0 part by mass or more, may be 2.0 parts by mass or more, and may be, for example, 3.0 parts by mass or more.
• the upper limit of the amount used is not particularly limited, but may be, for example, 20 parts by mass or less, may be, for example, 15 parts by mass or less, and may be, for example, 10 parts by mass or less. . Further, for example, it may be 5 parts by mass or less.
• the crosslinkable monomer may be 3 parts by mass or less.
• these upper limit and lower limit can be combined, for example, 0.1 to 20 parts by mass, for example, 0.1 to 10 parts by mass, Moreover, it is 0.5 mass part or more and 10 mass parts or less, for example.
• the use amount of the crosslinkable monomer is 0.1 parts by mass or more, the binding property and the stability of the mixture layer slurry are preferable. If it is 20 parts by mass or less, the stability of the polymer tends to increase.
• the amount of the crosslinkable monomer used is preferably 0.02 to 2.5 mol%, and preferably 0.03 to 1.5 mol% with respect to the total amount of the non-crosslinkable monomer. More preferably.
• This polymer can lower the crosslinking density on the particle surface as compared with a crosslinked polymer crosslinked only by a crosslinking monomer having no polymerizable unsaturated group other than an allyl group.
• the degree of swelling of the surface portion of the polymer in water is relatively high, and a bonding area with the active material and the current collector is ensured. Therefore, the binder containing the polymer exhibits good binding properties. It is conceivable that.
• the above mechanism is an estimation and does not limit the scope of the present disclosure.
• the polymer is well dispersed as water-swelling particles having an appropriate particle size without the polymer being present as a large particle size lump (secondary aggregate).
• the binder containing the said crosslinked polymer can exhibit favorable binding performance, it is preferable.
• the crosslinked polymer or a salt thereof has a particle size (water-swelled particle size) when dispersed in water having a neutralization degree of 80 to 100 mol% based on the carboxyl group of the crosslinked polymer.
• the reference median diameter is preferably in the range of 0.1 ⁇ m or more and 10.0 ⁇ m or less.
• a more preferable range of the particle diameter is 0.1 ⁇ m or more and 8.0 ⁇ m or less, a further preferable range is 0.1 ⁇ m or more and 7.0 ⁇ m or less, and a more preferable range is 0.2 ⁇ m or more and 5.0 ⁇ m or less. There is an even more preferable range of 0.5 ⁇ m or more and 3.0 ⁇ m or less.
• a preferable range is 0.1 micrometer or more and 2.0 micrometers or less. If the particle size is in the range of 0.1 ⁇ m or more and 10.0 ⁇ m or less, the mixture layer composition is uniformly present in a suitable size, so that the mixture layer composition has high stability and excellent binding. It becomes possible to demonstrate wearability. If the particle diameter exceeds 10.0 ⁇ m or less, the binding property may be insufficient as described above. Moreover, there exists a possibility that coating property may become inadequate at the point which cannot obtain a smooth coating surface. On the other hand, when the particle diameter is less than 0.1 ⁇ m, there is a concern from the viewpoint of stable productivity. In addition, the said water swelling particle diameter can be measured by the method as described in an Example of this specification.
• the particle diameter is measured when neutralized with an alkali metal hydroxide to a neutralization degree of 80 to 100 mol% and dispersed in water. do it.
• a crosslinked polymer or a salt thereof often exists as aggregated particles in which primary particles are associated and aggregated in a powder or solution (dispersion) state.
• the crosslinked polymer or salt thereof has extremely excellent dispersibility, and is neutralized to a neutralization degree of 80 to 100 mol% to give water.
• the aggregated particles are released, and even if it is a primary particle dispersion or secondary aggregate, a stable dispersion state is formed in which the particle diameter is in the range of 0.1 to 10.0 ⁇ m. Is.
• the particle size distribution which is a value obtained by dividing the volume-based median diameter of the water-swelling particle diameter by the number-based median diameter, is preferably 10 or less, more preferably 5.0 or less, from the viewpoints of binding properties and coatability. Yes, more preferably 3.0 or less, still more preferably 2.0 or less, and even more preferably 1.5 or less.
• the lower limit of the particle size distribution is usually 1.0.
• the particle diameter (dry particle diameter) of the crosslinked polymer or salt thereof when dried is preferably in the range of 0.03 ⁇ m or more and 3 ⁇ m or less in terms of volume-based median diameter.
• a more preferable range of the particle diameter is 0.1 ⁇ m or more and 1 ⁇ m or less, and a further preferable range is 0.3 ⁇ m or more and 0.8 ⁇ m or less.
• the present polymer or a salt thereof is neutralized with an acid group such as a carboxyl group derived from an ethylenically unsaturated carboxylic acid monomer so that the degree of neutralization is 20 mol% or more. It is preferably used as a salt embodiment.
• the degree of neutralization is more preferably 50 mol%, still more preferably 60 mol% or more, still more preferably 70 mol% or more, still more preferably 80 mol% or more, and particularly preferably 85 mol%. More than mol%.
• the upper limit of the degree of neutralization is 100 mol%, which may be 98 mol% or 95 mol%.
• the range of the degree of neutralization can be appropriately combined with the above lower limit value and upper limit value, for example, may be 50 mol% or more and 100 mol% or less, or 70 mol% or more and 100 mol% or less. 80 mol% or more and 100 mol% or less.
• the degree of neutralization is 20 mol% or more, water swellability is good and a dispersion stabilizing effect is easily obtained.
• the said neutralization degree can be computed by calculation from the preparation value of the monomer which has acid groups, such as a carboxyl group, and the neutralizing agent used for neutralization.
• the degree of neutralization is measured by IR measurement of the crosslinked polymer or salt thereof, and the powder after drying treatment at 80 ° C. for 3 hours under reduced pressure, and the peak derived from the C ⁇ O group of the carboxylic acid and the C ⁇ of the carboxylate. This can be confirmed from the intensity ratio of the peak derived from the O group.
• ⁇ Method for producing the present polymer or a salt thereof> known polymerization methods such as solution polymerization, precipitation polymerization, suspension polymerization, emulsion polymerization and the like can be used, but precipitation polymerization and suspension polymerization (reverse phase suspension polymerization) are considered in terms of productivity. ) Is preferred.
• a heterogeneous polymerization method such as precipitation polymerization, suspension polymerization, and emulsion polymerization is preferable in that better performance can be obtained with respect to binding properties and the like, and precipitation polymerization is more preferable.
• Precipitation polymerization is a method for producing a polymer by carrying out a polymerization reaction in a solvent that dissolves an unsaturated monomer as a raw material but does not substantially dissolve the produced polymer.
• the polymer particles become larger due to aggregation and growth, and a dispersion of polymer particles in which primary particles of several tens to several hundreds of nm are secondarily aggregated to several ⁇ m to several tens of ⁇ m is obtained.
• a dispersion stabilizer can also be used to control the particle size of the polymer.
• the secondary aggregation can be suppressed by selecting a dispersion stabilizer, a polymerization solvent, and the like. In general, precipitation polymerization in which secondary aggregation is suppressed is also called dispersion polymerization.
• a solvent selected from water and various organic solvents can be used as the polymerization solvent in consideration of the type of monomer used.
• a solvent having a small chain transfer constant In order to obtain a polymer having a longer primary chain length, it is preferable to use a solvent having a small chain transfer constant.
• Specific polymerization solvents include water-soluble solvents such as methanol, t-butyl alcohol, acetone, methyl ethyl ketone, acetonitrile and tetrahydrofuran, as well as benzene, ethyl acetate, dichloroethane, n-hexane, cyclohexane and n-heptane. These can be used alone or in combination of two or more. Or you may use as a mixed solvent of these and water.
• the water-soluble solvent refers to a solvent having a solubility in water at 20 ° C. of more than 10 g / 100 ml.
• Methyl ethyl ketone and acetonitrile are preferred from the standpoints that a polymer having a small chain transfer constant and a high degree of polymerization (primary chain length) can be obtained, and that the operation can be easily performed during the process neutralization described later. .
• a highly polar solvent preferably includes water and methanol.
• the amount of the highly polar solvent used is preferably 0.05 to 20.0% by mass based on the total mass of the medium, more preferably 0.1 to 10.0% by mass, and even more preferably 0.1 to 5%. 0.0 mass%, more preferably 0.1 to 1.0 mass%. If the ratio of the highly polar solvent is 0.05% by mass or more, the effect on the neutralization reaction is recognized, and if it is 20.0% by mass or less, no adverse effect on the polymerization reaction is observed.
• the production of the present polymer or a salt thereof preferably includes a polymerization step of polymerizing a monomer component containing a non-crosslinkable monomer and a crosslinkable monomer.
• a non-crosslinkable monomer it is preferable that 50 to 100 mass% of ethylenically unsaturated carboxylic acid monomers are included with respect to the total amount of the non-crosslinkable monomer.
• the ethylenically unsaturated carboxylic acid monomer the compounds listed as the component (a) in the description of the constituent monomer of the crosslinked polymer in the present specification can be used.
• the non-crosslinkable monomer may contain 0% by mass or more and 50% by mass or less of other ethylenically unsaturated monomers in addition to the ethylenically unsaturated carboxylic acid monomer.
• the compounds mentioned as the component (b) in the description of the constituent monomers of the crosslinked polymer in this specification can be used.
• structural units derived from the component (a) and the component (b) are introduced at a ratio corresponding to the amount of use.
• the crosslinkable monomer a monomer having at least one polymerizable unsaturated group other than an allyl group, which is exemplified as the crosslinkable monomer in the present polymer, can be used.
• the monomer concentration at the time of polymerization is preferably higher from the viewpoint of obtaining a polymer having a longer primary chain length.
• the monomer concentration at the start of polymerization is generally in the range of about 2 to 40% by mass, preferably in the range of 5 to 40% by mass.
• the “monomer concentration” refers to the monomer concentration in the reaction solution at the time of starting the polymerization.
• the present polymer may be produced by performing a polymerization reaction in the presence of a base compound. By carrying out the polymerization reaction in the presence of the base compound, the polymerization reaction can be carried out stably even under high monomer concentration conditions.
• the monomer concentration may be 13.0% by mass or more, preferably 15.0% by mass or more, more preferably 17.0% by mass or more, and further preferably 19.0% by mass or more. And more preferably 20.0% by mass or more.
• the monomer concentration is still preferably 22.0% by mass or more, and more preferably 25.0% by mass or more. Generally, the higher the monomer concentration during polymerization, the higher the molecular weight, and when this polymer is a crosslinked polymer, a polymer having a long primary chain length can be produced.
• the upper limit of the monomer concentration varies depending on the type of monomer and solvent used, the polymerization method and various polymerization conditions, etc., but if the heat of polymerization reaction can be removed, precipitation polymerization is as described above. About 40%, about 50% for suspension polymerization, and about 70% for emulsion polymerization.
• the basic compound is a so-called alkaline compound, and any of an inorganic basic compound and an organic basic compound may be used.
• the polymerization reaction can be carried out stably even under high monomer concentration conditions, for example, exceeding 13.0% by mass.
• a polymer obtained by polymerization at such a high monomer concentration has a high molecular weight (because of a long primary chain length) and is excellent in binding properties.
• the inorganic base compound include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide and potassium hydroxide, and alkaline earth metal hydroxides such as calcium hydroxide and magnesium hydroxide.
• 1 type (s) or 2 or more types can be used.
• the organic base compound include ammonia and organic amine compounds such as monoethylamine, diethylamine and triethylamine, and tri-n-octylamine, and one or more of them can be used.
• an organic amine compound is preferable from the viewpoints of polymerization stability and binding properties of a binder containing the obtained polymer or a salt thereof.
• the amount of the base compound used is preferably in the range of 0.001 mol% to 4.0 mol% with respect to the ethylenically unsaturated carboxylic acid monomer. If the usage-amount of a basic compound is this range, a polymerization reaction can be performed smoothly.
• the amount used may be 0.05 mol% or more and 4.0 mol% or less, 0.1 mol% or more and 4.0 mol% or less, or 0.1 mol% or more and 3.0 mol% or less. % Or less, or 0.1 mol% or more and 2.0 mol% or less.
• the usage-amount of a base compound represents the molar concentration of the base compound used with respect to the ethylenically unsaturated carboxylic acid monomer, and does not mean the degree of neutralization. That is, the valence of the base compound used is not taken into consideration.
• the polymerization initiator may be a known polymerization initiator such as an azo compound, an organic peroxide, or an inorganic peroxide, but is not particularly limited.
• the use conditions can be adjusted by a known method such as thermal initiation, redox initiation using a reducing agent in combination, UV initiation, or the like so as to obtain an appropriate radical generation amount.
• thermal initiation redox initiation using a reducing agent in combination
• UV initiation or the like so as to obtain an appropriate radical generation amount.
• Examples of the azo compound include 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (N-butyl-2-methylpropionamide), 2- (tert-butylazo) -2. -Cyanopropane, 2,2'-azobis (2,4,4-trimethylpentane), 2,2'-azobis (2-methylpropane), etc., and one or more of these are used be able to.
• organic peroxide examples include 2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane (manufactured by NOF Corporation, trade name “Pertetra A”), 1,1-di (t- Hexylperoxy) cyclohexane (same as “Perhexa HC”), 1,1-di (t-butylperoxy) cyclohexane (same as “PerhexaC”), n-butyl-4,4-di (t-butylperoxy) Valerate ("Perhexa V"), 2,2-di (t-butylperoxy) butane ("Perhexa 22"), t-butyl hydroperoxide ("Perbutyl H”), cumene hydroperoxide (Japan) Made by Oil Co., Ltd., trade name “Park Mill H”), 1,1,3,3-tetramethylbutyl hydroperoxide (“Perocta H”), t-
• inorganic peroxide examples include potassium persulfate, sodium persulfate, and ammonium persulfate.
• potassium persulfate sodium persulfate
• sodium persulfate sodium persulfate
• ammonium persulfate sodium sulfite, sodium thiosulfate, sodium formaldehyde sulfoxylate, ascorbic acid, sulfurous acid gas (SO 2 ), ferrous sulfate and the like can be used as a reducing agent.
• the preferred use amount of the polymerization initiator is, for example, 0.001 to 2 parts by mass, for example 0.005 to 1 part by mass when the total amount of the monomer components to be used is 100 parts by mass, For example, it is 0.01 to 0.1 parts by mass.
• the amount of the polymerization initiator used is 0.001 part by mass or more, the polymerization reaction can be stably performed, and when it is 2 parts by mass or less, a polymer having a long primary chain length is easily obtained.
• the polymerization temperature is preferably 0 to 100 ° C., more preferably 20 to 80 ° C., although it depends on conditions such as the type and concentration of the monomer used.
• the polymerization temperature may be constant or may change during the polymerization reaction.
• the polymerization time is preferably 1 minute to 20 hours, and more preferably 1 hour to 10 hours.
• the polymer dispersion obtained through the polymerization step can be obtained in a powder state by subjecting the polymer dispersion to a reduced pressure and / or heat treatment in the drying step and distilling off the solvent.
• a solid-liquid separation step such as centrifugation and filtration, water
• methanol or the same solvent as the polymerization solvent.
• step neutralization an alkali compound is added to the polymer dispersion obtained in the polymerization step to neutralize the polymer (hereinafter also referred to as “step neutralization”), and then the solvent is removed in the drying step. Good.
• step neutralization an alkali compound is added when preparing the electrode mixture layer slurry to neutralize the polymer (hereinafter, May also be referred to as “sum”.
• sum the process neutralization is preferable because the secondary aggregate tends to be easily broken.
• the composition for a secondary battery electrode mixture layer of the present invention includes a binder containing the present polymer or a salt thereof, an active material, and water.
• the usage-amount of this polymer or its salt in the electrode mixture layer composition of this invention is 0.1 to 20 mass% with respect to the whole quantity of an active material, for example.
• the amount used is, for example, 0.2% by mass or more and 10% by mass or less, for example, 0.3% by mass or more and 8% by mass or less, and for example, 0.4% by mass or more and 5% by mass or less. .
• the amount of the present polymer and its salt used is less than 0.1% by mass, sufficient binding properties may not be obtained.
• the dispersion stability of the active material or the like becomes insufficient, and the uniformity of the formed mixture layer may be lowered.
• the electrode mixture layer composition may have a high viscosity and the coating property to the current collector may be lowered. As a result, bumps and irregularities are generated in the obtained mixture layer, which may adversely affect the electrode characteristics.
• the amount of the present polymer and its salt used is within the above range, a composition having excellent dispersion stability can be obtained, and a mixture layer with extremely high adhesion to the current collector can be obtained. As a result, the durability of the battery is improved. Furthermore, the present bridge polymer and its salt show sufficiently high binding properties even in a small amount (for example, 5% by mass or less) with respect to the active material, and have a carboxy anion, so that the interface resistance is small and the high rate property is excellent. An electrode is obtained.
• a lithium salt of a transition metal oxide can be used as the positive electrode active material.
• a layered rock salt type and a spinel type lithium-containing metal oxide can be used.
• Specific compounds of the positive electrode active material of layered rock-salt, lithium cobaltate, lithium nickelate, and, NCM ⁇ Li (Ni x, Co y, Mn z), x + y + z 1 ⁇ called ternary and NCA ⁇ Li (Ni 1-ab Co a Al b ) ⁇ and the like.
• the spinel positive electrode active material include lithium manganate.
• phosphates In addition to oxides, phosphates, silicates, sulfur and the like are used, and examples of the phosphate include olivine type lithium iron phosphate.
• the positive electrode active material one of the above may be used alone, or two or more may be used in combination as a mixture or a composite.
• the positive electrode active material containing a layered rock salt type lithium-containing metal oxide when dispersed in water, the dispersion exhibits alkalinity by exchanging lithium ions on the active material surface with hydrogen ions in water. For this reason, there exists a possibility that the aluminum foil (Al) etc. which are general collector materials for positive electrodes may be corroded. In such a case, it is preferable to neutralize the alkali content eluted from the active material by using the unneutralized or partially neutralized polymer as a binder. In addition, the amount of unneutralized or partially neutralized polymer used should be such that the amount of carboxyl groups that are not neutralized in the polymer is equal to or greater than the amount of alkali eluted from the active material. Is preferred.
• any positive electrode active material has low electrical conductivity, it is common to add a conductive auxiliary agent.
• the conductive assistant include carbon-based materials such as carbon black, carbon nanotube, carbon fiber, graphite fine powder, and carbon fiber. Among these, carbon black, carbon nanotube, and carbon fiber are easy to obtain excellent conductivity. Are preferred. Moreover, as carbon black, ketjen black and acetylene black are preferable.
• the conductive assistant one of the above may be used alone, or two or more may be used in combination. From the viewpoint of achieving both conductivity and energy density, the use amount of the conductive auxiliary agent can be, for example, 0.2 to 20% by mass with respect to the total amount of the active material, and for example, 0.2 to 10%. It can be made into the mass%.
• the positive electrode active material may be a surface coated with a conductive carbon-based material.
• examples of the negative electrode active material include carbon materials, lithium metals, lithium alloys, metal oxides, and the like, and one or more of them can be used in combination.
• active materials composed of carbon-based materials such as natural graphite, artificial graphite, hard carbon, and soft carbon (hereinafter, also referred to as “carbon-based active material”) are preferable, graphite such as natural graphite and artificial graphite, and Hard carbon is more preferable.
• carbon-based active material such as natural graphite, artificial graphite, hard carbon, and soft carbon
• graphite such as natural graphite and artificial graphite
• Hard carbon is more preferable.
• spheroidized graphite is preferably used from the viewpoint of battery performance, and the preferred particle size range is, for example, 1 to 20 ⁇ m, and for example, 5 to 15 ⁇ m.
• a metal or metal oxide that can occlude lithium such as silicon or tin can be used as the negative electrode active material.
• silicon has a higher capacity than graphite, and an active material composed of silicon-based materials such as silicon, silicon alloys and silicon oxides such as silicon monoxide (SiO) (hereinafter referred to as “silicon-based active material”).
• silicon-based active material has a high capacity, but has a large volume change due to charge / discharge. For this reason, it is preferable to use together with the carbon-based active material. In this case, if the compounding amount of the silicon-based active material is large, the electrode material may be collapsed and the cycle characteristics (durability) may be greatly reduced. From such a point of view, when a silicon-based active material is used in combination, the amount used is, for example, 60% by mass or less, for example, 30% by mass or less with respect to the carbon-based active material.
• the binder containing the present polymer has a structural unit (component (a)) derived from the ethylenically unsaturated carboxylic acid monomer.
• component (a) has a high affinity for the silicon-based active material and exhibits good binding properties.
• the binder of the present disclosure exhibits an excellent binding property even when a high-capacity type active material containing a silicon-based active material is used, and thus is effective for improving the durability of the obtained electrode. It is considered a thing.
• the carbon-based active material itself has good electrical conductivity, it is not always necessary to add a conductive additive.
• a conductive additive is added for the purpose of further reducing the resistance, the amount used is, for example, 10% by mass or less, for example, 5% by weight or less with respect to the total amount of the active material from the viewpoint of energy density. It is.
• the amount of the active material used is, for example, in the range of 10 to 75% by mass, for example, 30 to 65% by mass with respect to the total amount of the composition. Range.
• the amount of the active material used is 10% by mass or more, the migration of the binder and the like is suppressed, and the medium drying cost is advantageous.
• it is 75 mass% or less, the fluidity
• the amount of the active material used is, for example, in the range of 60 to 97% by mass relative to the total amount of the composition, and for example, 70 to 90 It is the range of mass%. Further, from the viewpoint of energy density, it is preferable that the non-volatile components other than the active material such as the binder and the conductive assistant are as small as possible within a range in which necessary binding properties and conductivity are ensured.
• the composition for the secondary battery electrode mixture layer uses water as a medium.
• water-soluble organic solvents such as lower alcohols such as methanol and ethanol, carbonates such as ethylene carbonate, ketones such as acetone, tetrahydrofuran, N-methylpyrrolidone, etc. It is good also as a mixed solvent.
• the ratio of water in the mixed medium is, for example, 50% by mass or more, and for example, 70% by mass or more.
• the content of the medium containing water in the entire composition is determined from the viewpoints of slurry coating properties, energy costs required for drying, and productivity. From, for example, it can be in the range of 25-90% by mass, and can be, for example, 35-70% by mass.
• the content of the medium can be set in the range of 3 to 40% by mass, for example, from the viewpoint of the uniformity of the mixture layer after pressing. It can be in the range of ⁇ 30% by mass.
• the binder of the present disclosure may be composed only of the present polymer or a salt thereof, but other binders such as styrene / butadiene latex (SBR), acrylic latex, and polyvinylidene fluoride latex are also available. You may use an ingredient together.
• SBR styrene / butadiene latex
• acrylic latex acrylic latex
• polyvinylidene fluoride latex polyvinylidene fluoride latex
• the amount used can be, for example, 0.1 to 5% by mass or less, for example, 0.1 to 2% by mass or less based on the active material. For example, it can be 0.1 to 1% by mass or less.
• the amount of other binder components used exceeds 5% by mass, the resistance increases and the high rate characteristics may be insufficient.
• styrene / butadiene latex is preferable in terms of excellent balance between binding properties and bending resistance.
• the styrene / butadiene latex is a copolymer having a structural unit derived from an aromatic vinyl monomer such as styrene and a structural unit derived from an aliphatic conjugated diene monomer such as 1,3-butadiene.
• An aqueous dispersion is shown.
• the aromatic vinyl monomer include ⁇ -methylstyrene, vinyltoluene, divinylbenzene and the like in addition to styrene, and one or more of these can be used.
• the structural unit derived from the aromatic vinyl monomer in the copolymer can be, for example, in the range of 20 to 60% by mass mainly from the viewpoint of binding properties, and for example, 30 to 50%. It can be made into the range of the mass%.
• Examples of the aliphatic conjugated diene monomer include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, and 2-chloro-1,3-butadiene. Butadiene and the like can be mentioned, and one or more of these can be used.
• the structural unit derived from the aliphatic conjugated diene monomer in the copolymer is, for example, 30 to 70% by mass in that the binder binding property and the flexibility of the resulting electrode are good. For example, it can be in the range of 40 to 60% by mass.
• the styrene / butadiene latex is a monomer containing a nitrile group such as (meth) acrylonitrile, )
• a carboxyl group-containing monomer such as acrylic acid, itaconic acid and maleic acid may be used as a copolymerization monomer.
• the structural unit derived from the other monomer in the copolymer can be, for example, in the range of 0 to 30% by mass, and can be in the range of 0 to 20% by mass, for example.
• the composition for a secondary battery electrode mixture layer of the present disclosure contains the above active material, water, and binder as essential components, and can be obtained by mixing each component using a known means.
• the mixing method of each component is not particularly limited, and a known method can be adopted.
• a method of mixing with a dispersion medium such as water and kneading the mixture is preferable.
• the composition for an electrode mixture layer is obtained in a slurry state, it is preferable to finish the slurry without any poor dispersion or aggregation.
• a mixing means known mixers such as a planetary mixer, a thin film swirl mixer, and a self-revolving mixer can be used, but a thin film swirl mixer is used because a good dispersion state can be obtained in a short time. It is preferable to carry out. Moreover, when using a thin film swirling mixer, it is preferable to perform preliminary dispersion with a stirrer such as a disper in advance.
• the viscosity of the slurry can be, for example, in the range of 500 to 100,000 mPa ⁇ s as B-type viscosity at 60 rpm, and for example, in the range of 1,000 to 50,000 mPa ⁇ s. it can.
• the electrode mixture layer composition when obtained in a wet powder state, it is preferably kneaded to a uniform state without unevenness in density using a Henschel mixer, blender, planetary mixer, biaxial kneader, or the like.
• the electrode for a secondary battery of the present disclosure includes a mixture layer formed from the above composition for an electrode mixture layer on the surface of a current collector such as copper or aluminum.
• the mixture layer is formed by drying and removing a medium such as water after applying the composition for an electrode mixture layer of the present disclosure to the surface of the current collector.
• the method for applying the mixture layer composition is not particularly limited, and a known method such as a doctor blade method, a dip method, a roll coat method, a comma coat method, a curtain coat method, a gravure coat method, and an extrusion method is adopted. be able to.
• the said drying can be performed by well-known methods, such as hot air spraying, pressure reduction, (far) infrared rays, and microwave irradiation.
• the mixture layer obtained after drying is subjected to a compression treatment by a die press, a roll press or the like.
• a compression treatment by a die press, a roll press or the like.
• the strength of the mixture layer and the adhesiveness to the current collector can be improved.
• the thickness of the mixture layer can be adjusted to, for example, about 30 to 80% before compression, and the thickness of the mixture layer after compression is generally about 4 to 200 ⁇ m.
• a secondary battery can be produced by providing the electrode for a secondary battery of the present disclosure with a separator and an electrolytic solution.
• the electrolytic solution may be liquid or gelled.
• the separator is disposed between the positive electrode and the negative electrode of the battery, and plays a role of ensuring ionic conductivity by preventing a short circuit due to contact between both electrodes and holding an electrolytic solution.
• the separator is preferably a film-like insulating microporous film having good ion permeability and mechanical strength.
• polyolefins such as polyethylene and polypropylene, polytetrafluoroethylene, and the like can be used.
• the electrolytic solution a known one that is generally used according to the type of the active material can be used.
• specific solvents cyclic carbonates having high dielectric constant and high electrolyte dissolving ability such as propylene carbonate and ethylene carbonate, and low viscosity chains such as ethyl methyl carbonate, dimethyl carbonate and diethyl carbonate are used. And the like, and these can be used alone or as a mixed solvent.
• the electrolytic solution is used by dissolving lithium salts such as LiPF 6 , LiSbF 6 , LiBF 4 , LiClO 4 , and LiAlO 4 in these solvents.
• an aqueous potassium hydroxide solution can be used as the electrolytic solution.
• a secondary battery is obtained by making a positive electrode plate and a negative electrode plate partitioned by a separator into a spiral or laminated structure and storing them in a case or the like.
• the secondary battery electrode binder disclosed in the present specification exhibits excellent binding properties with the electrode material and excellent adhesion with the current collector in the mixture layer. Secondary batteries equipped with electrodes obtained using the above binders are able to ensure good integrity and are expected to show good durability (cycle characteristics) even after repeated charge and discharge. Suitable for batteries and the like. Moreover, according to the indication of this specification, the manufacturing method of the binder for secondary battery electrodes, the manufacturing method of the electrode for secondary batteries, and the electrode for secondary batteries are also provided.
• the reactor was sufficiently purged with nitrogen and then heated to raise the internal temperature to 55 ° C. After confirming that the internal temperature was stable at 55 ° C., 2,2′-azobis (2,4-dimethylvaleronitrile) (trade name “V-65”, manufactured by Wako Pure Chemical Industries, Ltd.) 0 as a polymerization initiator When .040 parts was added, white turbidity was observed in the reaction solution, and this point was taken as the polymerization initiation point. The monomer concentration was calculated to be 15.0%. The polymerization reaction was continued while adjusting the external temperature (water bath temperature) to maintain the internal temperature at 55 ° C., and the internal temperature was raised to 65 ° C. after 6 hours had elapsed from the polymerization start point.
• the external temperature water bath temperature
• the internal temperature was maintained at 65 ° C., and cooling of the reaction liquid was started when 12 hours had elapsed from the polymerization start point. After the internal temperature dropped to 25 ° C., lithium hydroxide monohydrate (hereinafter referred to as “LiOH”). 52.5 parts) of “H 2 O”. After the addition, stirring was continued at room temperature for 12 hours to obtain a slurry-like polymerization reaction liquid in which particles of the crosslinked polymer salt R-1 (Li salt, neutralization degree 90 mol%) were dispersed in the medium. Moreover, it was confirmed by liquid chromatography analysis that the obtained polymer had a composition as prepared.
• LiOH lithium hydroxide monohydrate
• the resulting polymerization reaction liquid was centrifuged to precipitate polymer particles, and then the supernatant was removed. Then, after the sediment was redispersed in acetonitrile having the same weight as the polymerization reaction solution, the washing operation of sedimenting the polymer particles by centrifugation and removing the supernatant was repeated twice.
• the precipitate was collected, dried under reduced pressure at 80 ° C. for 3 hours, and volatile components were removed to obtain a carboxyl group-containing polymer salt R-1 powder. Since the crosslinked polymer salt R-1 has a hygroscopic property, it was hermetically stored in a container having a water vapor barrier property.
• IR measurement was performed on the powder of the carboxyl group-containing polymer salt R-1, and the degree of neutralization was determined from the intensity ratio of the C ⁇ O group-derived peak of the carboxylic acid and the C ⁇ O-derived peak of the carboxylic acid Li. It was 90 mol% equal to the calculated value from the preparation.
• a hydrogel swollen in water was prepared.
• the particle size distribution of the hydrogel was measured with a laser diffraction / scattering particle size distribution meter (Microtrac MT-3300EXII, manufactured by Microtrac Bell) using ion-exchanged water as a dispersion medium.
• a laser diffraction / scattering particle size distribution meter Microtrac MT-3300EXII, manufactured by Microtrac Bell
• an amount of the hydrogel capable of obtaining an appropriate scattered light intensity was added, and the particle size distribution shape measured after a few minutes was stabilized.
• volume-based particle size distribution measurement was performed and the median diameter (D50) was determined as the average particle diameter, which was 1.7 ⁇ m.
• volume-based median diameter / number-based median diameter is less than 1.5
• volume-based median diameter / number-based median diameter is 1.5 or more and less than 3.0
• Volume-based median diameter / number-based median diameter is 3 0.0 or more and less than 10
• AA Acrylic acid DMAA: Dimethylacrylamide
• HEA Hydroxyethyl acrylate
• TMPTMA Trimethylolpropane trimethacrylate (Kyoeisha Chemical Co., Ltd., trade name “Light Ester TMP”)
• EDGMA Ethylene glycol dimethacrylate (Fuji Film Wako Pure Chemical Industries, reagent "ethylene dimethacrylate”)
• HAPMA 2-hydroxy-3-acryloyloxypropyl methacrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name “Light Ester G-201P”)
• DPEPA Dipentaerythritol penta and hexaacrylate (trade name “Aronix M-403” manufactured by Toagosei Co., Ltd.)
• PETA Pentaerythritol tetraacrylate (manufactured by Shin-Nakamura Chemical Co.,
• graphite which is an active material for a negative electrode, or silicon particles and graphite
• the composition for a mixture layer using a crosslinked polymer salt as a binder its stability and the formed mixture layer / current collector
• the peel strength between the bodies was measured.
• Natural graphite manufactured by Nippon Graphite Co., Ltd., trade name “CGB-10” was used as graphite, and (Sigma-Aldrich, Si nanopowder, particle size ⁇ 100 nm) was used as silicon particles.
• Example 1 After weighing 3.2 parts of powdered crosslinked polymer Li salt R-1 into 100 parts of natural graphite and mixing well in advance, 160 parts of ion exchange water was added and predispersed with a disper, and then a thin film swirl type This dispersion was carried out for 15 seconds under the condition of a peripheral speed of 20 m / sec using a mixer (manufactured by Primics, FM-56-30) to obtain a slurry-like composition for a negative electrode mixture layer. The slurry concentration (solid content) was calculated to be 39.2%.
• the mixture layer composition is applied onto a 20 ⁇ m thick copper foil (manufactured by Nippon Foil Co., Ltd.) and dried in an air dryer at 100 ° C. for 15 minutes. A layer was formed. Thereafter, the mixture layer was rolled to have a thickness of 70 ⁇ 5 ⁇ m and a packing density of 1.70 ⁇ 0.20 g / cm 3 to prepare a negative electrode.
• the mixture layer surface of the sample was attached to a double-sided tape fixed on a horizontal surface to prepare a sample for a peel test. After the test sample was dried at 60 ° C. under reduced pressure overnight, 90 ° peeling at a tensile speed of 50 mm / min was performed, and the peel strength between the mixture layer and the copper foil was measured. The peel strength was as good as 16.0 N / m.
• Example 2 to 24 and Comparative Examples 1 and 2 A mixture layer composition was prepared by the same operation as in Example 1 except that the carboxyl group-containing polymer salt used as the active material and the binder was used as shown in Tables 3 to 5.
• Example 3 and Example 4 natural graphite and silicon particles were stirred for 1 hour at 400 rpm using a planetary ball mill (manufactured by FRITSCH, P-5), and the resulting mixture was powdered cross-linked polymer.
• a mixture layer composition was prepared by performing the same operation as in Example 1. The 90 ° peel strength of each mixture layer composition was evaluated, and the results are shown in Tables 3 to 5.
• an electrode mixture layer composition containing a binder for a secondary battery electrode belonging to the present disclosure and an electrode produced using the electrode mixture layer composition had a high value, and exhibited excellent binding properties.
• Comparative Example 1 using a polymer salt not using a crosslinkable monomer and Comparative Example 2 using a crosslinkable polymer salt using a crosslinkable monomer having no polymerizable unsaturated group other than an allyl group The peel strength was a low value compared to the examples.
• the secondary battery electrode binder of the present disclosure exhibits excellent binding properties in the mixture layer, the secondary battery including the electrode obtained using the binder has good durability (cycle characteristics). ) And is expected to be applied to in-vehicle secondary batteries. It is also useful for the use of active materials containing silicon, and is expected to contribute to higher battery capacity.
• the binder for a secondary battery electrode of the present disclosure can be suitably used particularly for a nonaqueous electrolyte secondary battery electrode, and is particularly useful for a nonaqueous electrolyte lithium ion secondary battery having a high energy density.

Landscapes

• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Electrochemistry (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Health & Medical Sciences (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
• Battery Electrode And Active Subsutance (AREA)
• Electric Double-Layer Capacitors Or The Like (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (1)

Family

ID=68698847

Family Applications (1)

Country Status (2)

Cited By (6)

Citations (1)

• 2019
  • 2019-05-28 JP JP2020522208A patent/JP7226442B2/ja active Active
  • 2019-05-28 WO PCT/JP2019/021079 patent/WO2019230714A1/ja not_active Ceased

Patent Citations (1)

Also Published As

Similar Documents

Legal Events