JP2019057488A - Slurry for thermal crosslinking type lithium ion battery, manufacturing method thereof, electrode for lithium ion battery, separator for lithium ion battery, separator/electrode laminate for lithium ion battery, and lithium ion battery - Google Patents

Abstract

To provide a slurry for a thermal crosslinking type lithium ion battery, a manufacturing method thereof, an electrode for a lithium ion battery, a separator for a lithium ion battery, a separator/electrode laminate for a lithium ion battery, and a lithium ion battery.SOLUTION: A slurry for a thermal crosslinking type lithium ion battery is provided according to a disclosure hereof, which comprises: a water-soluble poly(meth)acrylamide(A) including no less than 50 mol% of constituting units originating from an N-unsubstituted or one-substituted (meth)acrylamide group-bearing compound (a) to 100 mol% of constituents; a water-soluble crosslinking agent (A1) including one or more selected from a group consisting of formaldehyde, glyoxal, hexamethylenetetramine, an urea formaldehyde resin and a methylol melamine resin; and water.SELECTED DRAWING: None

Description

  The present disclosure relates to a slurry for a thermal crosslinking lithium ion battery and a method for producing the same, an electrode for a lithium ion battery, a separator for a lithium ion battery, a separator / electrode laminate for a lithium ion battery, and a lithium ion battery.

  Lithium ion batteries are small and light, have high energy density, and can be repeatedly charged and discharged, and are used in a wide range of applications. Therefore, in recent years, improvement of battery members such as electrodes and separators has been studied for the purpose of further improving the performance of lithium ion batteries.

  Both the positive electrode and the negative electrode of a lithium ion battery are obtained by dispersing an electrode active material and a binder resin in a solvent to form a slurry on both sides of a current collector (for example, a metal foil), and removing the solvent by drying. After the layer is formed, it is manufactured by compression molding with a roll press or the like.

  In recent years, in the electrode for lithium ion batteries, various electrode active materials have been proposed as electrode active materials from the viewpoint of increasing the battery capacity. However, some electrode active materials easily expand and contract with charge / discharge. For this reason, the lithium ion battery electrode undergoes a volume change from the beginning of repeated charge and discharge (springback property), and there is a problem in that the electrical characteristics such as the cycle characteristics of the lithium ion battery using the same tend to be reduced. Yes.

  Therefore, in this field, studies have been made to solve the above problems with a binder resin. For example, an emulsion cross-linking system (Patent Document 1) and N-methylolacrylamide (Patent Document 2) have been proposed.

  In recent years, as a separator for a lithium ion battery, a heat-resistant separator in which a coating layer (heat-resistant layer) containing ceramic fine particles and a binder is formed on the surface of a polyolefin microporous film has been proposed. It is known that the coating layer has an effect of suppressing the shrinkage of the separator even when exposed to a high temperature. However, the obtained heat-resistant separator has a problem that it cannot maintain the adhesion between the coating layer and the polyolefin microporous membrane due to deformation such as bending in the production line or in the battery cell, and is easily dropped. It was.

  Therefore, in this field, studies have been made to solve the above problems with a binder resin. For example, a separator (Patent Document 3) characterized in that polyacrylic acid includes a polyacrylate salt crosslinked with a metal cation is also proposed. Has been. Further, a porous membrane composition for a lithium ion secondary battery (Patent Document 4) containing a water-soluble thickener containing a carboxyl group, a carbodiimide compound crosslinking agent, and a particulate polymer has been proposed.

International Publication No. 2016/159198 Japanese Patent Laying-Open No. 2015-185530 Japanese Patent Laid-Open No. 2006-012478 Japanese Patent No. 6187464

  Regarding an electrode of a lithium ion battery, Patent Document 1 proposes a crosslinked product of an emulsion, and the degree of crosslinking can be increased, but the effect of springback resistance is insufficient.

  The N-methylol acrylamide described in Patent Document 2 has a problem of gelation because the resin itself has crosslinkability. For this reason, the amount of introduction cannot be increased and the degree of crosslinking cannot be increased, so that the effect of springback resistance is insufficient.

  About the separator of a lithium ion battery, since the polyacrylic acid salt by which polyacrylic acid of patent document 3 was bridge | crosslinked with the metal cation has a remarkably low bridge | crosslinking effect, there exists a subject that the adhesive improvement effect is low.

  Further, Patent Document 4 proposes a separator porous layer using a composition containing a specific water-soluble thickener and a carbodiimide compound in addition to a binder, but the reactivity between the binder and the carbodiimide compound is high. Therefore, the stability of the slurry is poor and tends to gel. For this reason, fine particles aggregate and settle over time, resulting in uneven thickness during coating, making it difficult to form a uniform porous film.

  Therefore, the problem to be solved by the present invention is an electrode capable of imparting excellent springback resistance and electrical characteristics to a lithium ion battery, as well as excellent heat shrinkage resistance, dust resistance, substrate adhesion, and rate characteristics. Then, what can manufacture the separator which can provide an output characteristic to a lithium ion battery is provided. In the present disclosure, the anti-powder resistance means the binding property between the ceramic fine particles, and the base material adhesion is a layer obtained by applying and drying the base material and the slurry according to the present invention on the base material ( Means adhesion to the coating layer).

  As a result of intensive studies to solve the above problems, the present inventor has obtained a slurry for a heat-crosslinking type lithium ion battery containing poly (meth) acrylamide produced using a specific monomer, a water-soluble crosslinking agent and water. By using it, it discovered that the said subject could be solved and came to complete this invention.

The present disclosure provides the following items.
(Item 1)
Water-soluble poly (meth) acrylamide (A) containing 50 mol% or more of a structural unit derived from N-unsubstituted or monosubstituted (meth) acrylamide group-containing compound (a) with respect to 100 mol% of the structural unit,
A water-soluble crosslinking agent (A1) comprising one or more selected from the group consisting of formaldehyde, glyoxal, hexamethylenetetramine, urea formaldehyde resin, and methylolmelamine resin,
And a slurry for a thermally cross-linked lithium ion battery, which contains water.
(Item 2)
The water-soluble cross-linking agent (A1) is 0 with respect to 100% by mass of the structural unit derived from the N-unsubstituted or mono-substituted (meth) acrylamide group-containing compound (a) in the water-soluble poly (meth) acrylamide (A). The slurry for thermal bridge type lithium ion batteries as described in the above item, containing 0.001 to 3.0% by mass.
(Item 3)
The slurry for heat-crosslinking type lithium ion batteries as described in the above item, comprising an electrode active material (B).
(Item 4)
The slurry for a thermally crosslinked lithium ion battery according to the above item, wherein the electrode active material (B) contains 10 mass% or more of silicon or silicon oxide.
(Item 5)
The slurry for heat-crosslinking type lithium ion batteries as described in the above item, comprising ceramic fine particles (C).
(Item 6)
The method for producing a slurry for a thermal crosslinking lithium ion battery according to any one of the above items, comprising a step of adding the water-soluble crosslinking agent (A1) to an aqueous solution containing the water-soluble poly (meth) acrylamide (A). .
(Item 7)
The electrode for lithium ion batteries obtained by apply | coating the slurry for thermal crosslinking type lithium ion batteries of any one of the said item to a collector, and carrying out a thermal crosslinking reaction.
(Item 8)
A lithium ion battery comprising the lithium ion battery electrode according to the above item.
(Item 9)
The separator for lithium ion batteries obtained by apply | coating the slurry for thermal crosslinking type lithium ion batteries as described in the said item to a porous polyolefin resin base material or a plastic nonwoven fabric, and carrying out thermal crosslinking.
(Item 10)
The slurry for the thermal crosslinking type lithium ion battery described in the above item,
A separator / electrode laminate for a lithium ion battery, which is obtained by applying to the active material side of an electrode material and thermally crosslinking.
(Item 11)
A lithium ion battery comprising the lithium ion battery separator as described above and / or the lithium ion battery separator / electrode laminate as described above.

  In the present disclosure, one or more of the features described above may be provided in further combinations in addition to the express combinations.

  By using the binder aqueous solution for lithium ion batteries and the slurry for lithium ion batteries of the present invention, a lithium ion battery with improved battery capacity and improved springback resistance can be provided.

  Provided is a lithium ion battery separator that has improved heat shrinkage resistance, dust resistance, substrate adhesion, rate characteristics, and output characteristics by using the lithium ion battery binder aqueous solution and lithium ion battery slurry of the present invention. it can.

  Throughout the present disclosure, ranges of numerical values such as each physical property value and content can be set as appropriate (for example, selected from the upper limit and lower limit values described in the following items). Specifically, for the numerical value α, the upper limit of the numerical value α is exemplified as A1, A2, A3, etc., and the lower limit of the numerical value α is exemplified as B1, B2, B3, etc., the range of the numerical value α is A1 or less, A2 or less, A3 or less, B1 or more, B2 or more, B3 or more, A1-B1, A1-B2, A1-B3, A2-B1, A2-B2, A2-B3, A3-B1, A3-B2, A3-B3 Etc. are exemplified.

[1. Thermally-crosslinked lithium ion battery slurry: Lithium ion battery slurry, also called slurry]
The present disclosure relates to a water-soluble poly (meth) acrylamide (A) containing 50 mol% or more of a structural unit derived from an N-unsubstituted or monosubstituted (meth) acrylamide group-containing compound (a) with respect to 100 mol% of the structural unit,
A water-soluble crosslinking agent (A1) comprising one or more selected from the group consisting of formaldehyde, glyoxal, hexamethylenetetramine, urea formaldehyde resin, and methylolmelamine resin,
In addition, a slurry for a thermal crosslinking type lithium ion battery containing water is provided.

  In the present disclosure, “slurry” means a suspension of liquid and solid particles.

  In the present disclosure, “water-soluble” means that an insoluble content is less than 0.5 mass% (less than 2.5 mg) when 0.5 g of the compound is dissolved in 100 g of water at 25 ° C. To do.

  In the present disclosure, “(meth) acryl” means “at least one selected from the group consisting of acryl and methacryl”. Similarly, “(meth) acrylate” means “at least one selected from the group consisting of acrylate and methacrylate”. “(Meth) acryloyl” means “at least one selected from the group consisting of acryloyl and methacryloyl”.

  In one embodiment, the water-soluble poly (meth) acrylamide (A) is obtained by polymerizing a monomer group containing an N-unsubstituted or monosubstituted (meth) acrylamide group-containing compound (a). In the present disclosure, “poly (meth) acrylamide” means a (co) polymer ((co) polymer) obtained by polymerizing a monomer group containing a (meth) acrylamide group-containing compound.

  In the present disclosure, the “N-unsubstituted (meth) acrylamide group-containing compound” means a compound in which two hydrogen atoms on the nitrogen of the (meth) acrylamide group are not substituted with groups other than hydrogen. “N-monosubstituted (meth) acrylamide group-containing compound” means a compound in which one hydrogen on nitrogen of a (meth) acrylamide group is substituted with a group other than hydrogen. The N-unsubstituted or monosubstituted (meth) acrylamide group-containing compound (a) may be used alone or in combination of two or more.

The N-unsubstituted or monosubstituted (meth) acrylamide group-containing compound (a) has the following structural formula
[Wherein, R ^A1 is hydrogen or a methyl group, one of R ^A2 and R ^A3 is hydrogen, and the other is hydrogen, a substituted or unsubstituted alkyl group, an acetyl group, or a sulfonic acid group, R ^A4 and R ^A5 are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a carboxyl group, a hydroxy group, an amino group <-NR ^Aa R ^Ab (R ^Aa and R ^Ab are each independently hydrogen or substituted Or an unsubstituted alkyl group)>, an acetyl group, a sulfonic acid group, and the like. ]
The compound etc. which are represented by are illustrated.

  Examples of the alkyl group include a linear alkyl group, a branched alkyl group, and a cycloalkyl group.

The linear alkyl group is represented by a general formula of —C _n H _{2n + 1} (n is an integer of 1 or more). Straight chain alkyl groups include methyl, ethyl, propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decamethyl, etc. Is exemplified.

  A branched alkyl group is a group in which at least one hydrogen of a linear alkyl group is substituted with an alkyl group. Examples of the branched alkyl group include a diethylpentyl group, a trimethylbutyl group, a trimethylpentyl group, and a trimethylhexyl group.

  Examples of the cycloalkyl group include a monocyclic cycloalkyl group, a bridged ring cycloalkyl group, and a condensed ring cycloalkyl group.

  In the present disclosure, a single ring means a cyclic structure having no bridge structure inside formed by a covalent bond of carbon. Further, the condensed ring means a cyclic structure in which two or more monocycles share two atoms (that is, only one side of each ring is shared (condensed) with each other). A bridged ring means a cyclic structure in which two or more monocycles share three or more atoms.

  Examples of the monocyclic cycloalkyl group include a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclodecyl group, and a 3,5,5-trimethylcyclohexyl group.

  Examples of the bridged ring cycloalkyl group include a tricyclodecyl group, an adamantyl group, and a norbornyl group.

  Examples of the fused ring cycloalkyl group include a bicyclodecyl group.

  Examples of the N-unsubstituted (meth) acrylamide group-containing compound include (meth) acrylamide, maleic acid amide, and salts thereof.

  N-monosubstituted (meth) acrylamide group-containing compounds are N-isopropyl (meth) acrylamide, N-methylol (meth) acrylamide, diacetone (meth) acrylamide, (meth) acrylamide t-butylsulfonic acid, hydroxyethyl (meth) Acrylamide, Nn-butoxymethyl (meth) acrylamide, N-isobutoxymethyl (meth) acrylamide, N-methoxymethyl (meth) acrylamide, Nt-butyl (meth) acrylamide, N, N-methylenebis (meth) Examples include acrylamide, Nt-butyl (meth) acrylamide sulfonic acid, and salts thereof.

  The above salts are dimethylaminopropyl (meth) acrylamide methyl chloride quaternary salt, dimethylaminoethyl (meth) acrylate benzyl chloride quaternary salt, 3-((meth) acrylamide) propyltrimethylammonium chloride quaternary salt, 3-(( Examples include meth) acrylamide) propyltrimethylammonium methylsulfate quaternary salt and the like.

  In one embodiment, the upper limit of the ratio of the structural unit derived from the N-unsubstituted or monosubstituted (meth) acrylamide group-containing compound (a) contained in the water-soluble poly (meth) acrylamide (A) is 99.95. 99.8, 99.7, 99.2, 95, 90, 85, 80, 75, 70, 65 mol%, etc., and the lower limit is 99.8, 99.7, 99.2, 95, 90 85, 80, 75, 70, 65, 60, 55, 50 mol%, and the like. In one embodiment, the proportion of the structural units is preferably 50 mol% or more, more preferably 55.0 to 99.8 mol%, and 60.0 to 99.7 mol%. Is particularly preferred.

  The upper limit of the ratio of the structural unit derived from the N-unsubstituted or monosubstituted (meth) acrylamide group-containing compound (a) contained in 100% by mass of the water-soluble poly (meth) acrylamide (A) is 100, 90, 80. 70, 60, 50, 45% by mass, etc., and the lower limit is exemplified by 90, 80, 70, 60, 50, 45, 40% by mass, etc. In one embodiment, 40-100 mass% is preferable, it is more preferable that it is 45-100 mass%, and it is especially preferable that it is 50-100 mass%.

  Dispersibility of electrode active materials, fillers, ceramic fine particles, etc. is good when the structural unit derived from N-unsubstituted or monosubstituted (meth) acrylamide group-containing compound (a) is contained in component (A) in a specific amount. Thus, since a uniform layer (electrode active material layer, ceramic fine particle layer, etc.) can be produced, structural defects are eliminated and good charge / discharge characteristics are exhibited. Furthermore, since the structural unit derived from the (meth) acrylamide group-containing compound is contained in the component (A) in a specific amount, the polymer has good oxidation resistance and reduction resistance, so that deterioration at high voltage is suppressed. Good charge / discharge durability characteristics.

(Monomer that is not component (a): Also referred to as component (b))
A monomer that is not the component (a) (component (b)) can be used in the monomer group as long as the desired effect of the present invention is not impaired. As the component (b), various known compounds may be used alone, or two or more kinds may be used in combination.

  Component (b) is an N, N-disubstituted (meth) acrylamide group-containing compound, an acid group-containing monomer such as an unsaturated carboxylic acid, an unsaturated sulfonic acid, or an unsaturated phosphoric acid, an unsaturated carboxylic acid ester, α , Β-unsaturated nitrile, conjugated diene, aromatic vinyl compound and the like.

The N, N-disubstituted (meth) acrylamide group-containing compound has the following structural formula
(Wherein R ^B1 is hydrogen or a methyl group, and R ^B2 and R ^B3 are each independently a substituted or unsubstituted alkyl group, an acetyl group, or a sulfonic acid group, or R ^B2 and R ^B3 Together form a ring structure, and R ^B4 and R ^B5 each independently represent hydrogen, a substituted or unsubstituted alkyl group, a carboxyl group, a hydroxy group, an amino group (—NR ^Ba R ^Bb ( R ^Ba and R ^Bb are each independently hydrogen or a substituted or unsubstituted alkyl group)), an acetyl group, or a sulfonic acid group, and the substituted alkyl group has a hydroxy group, an amino group, an acetyl group, a sulfone group. Examples include acid groups, etc. In addition, examples of the group in which R ^B2 and R ^B3 together form a ring structure include morpholyl groups.
The compound etc. which are represented by are illustrated.

  The above N, N-disubstituted (meth) acrylamide group-containing compounds are N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, ( Examples include (meth) acryloylmorpholine and salts thereof. Examples of the salt include those described above.

  Although the content of the N, N-disubstituted (meth) acrylamide group-containing compound in 100 mol% of the structural unit is not particularly limited, in one embodiment, the affinity of the N, N-disubstituted (meth) acrylamide group-containing compound Is less than 50 mol% (for example, less than 40, 30, 20, 15, 10, 9, 5, 1 mol%) of 100 mol% of the structural unit.

  The upper limit of the content of the N, N-disubstituted (meth) acrylamide group-containing compound in the structural unit of 100% by mass is 49, 45, 40, 35, 30, 25, 20, 15, 10, 5, 2% by mass, etc. The lower limit is exemplified by 45, 40, 35, 30, 25, 20, 15, 10, 5, 2, 1% by mass and the like. In one embodiment, the content of the N, N-disubstituted (meth) acrylamide group-containing compound in 100% by mass of the structural unit is preferably 1 to 49% by mass.

  Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, and salts thereof.

  The content of the unsaturated carboxylic acid in 100 mol% of the structural unit is not particularly limited, but considering the reaction between the component (b) other than the unsaturated carboxylic acid and the unsaturated carboxylic acid, the content of the unsaturated carboxylic acid is 40 with respect to 100 mol% of the structural unit. Less than mol% (for example, 30, 20, 19, 15, 10, 5, less than 1 mol%, 0 mol%) is preferable.

  The upper limit of the unsaturated carboxylic acid content relative to 100% by mass of the structural unit is exemplified by 60, 50, 40, 30, 20, 10, 5, 1% by mass, and the lower limit is 50, 40, 30, 20, Examples thereof are 10, 5, 1, 0% by mass and the like. In one embodiment, 0.0-60 mass% is preferable as content of unsaturated carboxylic acid with respect to 100 mass% of structural units.

  Unsaturated sulfonic acids include α, β-ethylenically unsaturated sulfonic acids such as vinyl sulfonic acid, styrene sulfonic acid, and (meth) allyl sulfonic acid; (meth) acrylamide t-butyl sulfonic acid, 2- (meth) acrylamide- Examples include 2-methylpropanesulfonic acid, 2- (meth) acrylamide-2-hydroxypropanesulfonic acid, 3-sulfopropane (meth) acrylic acid ester, bis- (3-sulfopropyl) itaconic acid ester, and salts thereof. Is done.

  The content of unsaturated sulfonic acid in 100 mol% of the structural unit is not particularly limited. However, in consideration of the reaction between the component (b) other than the unsaturated sulfonic acid and the unsaturated sulfonic acid, the unsaturated unit with respect to 100 mol% of the structural unit is unsaturated. Examples of the upper limit of the sulfonic acid content include 40, 30, 20, 19, 15, 10, 5, 1, 0.5, 0.1, 0.05, 0.02 mol%, and the lower limit. 30, 20, 19, 15, 10, 5, 1, 0.5, 0.1, 0.05, 0.02, 0.01, 0 mol% and the like are exemplified.

  The upper limit of the content of unsaturated sulfonic acid with respect to 100% by mass of the structural unit is 70, 60, 50, 40, 30, 20, 10, 5, 1, 0.05, 0.02, 0.01% by mass or the like. The lower limit is exemplified by 60, 50, 40, 30, 20, 10, 5, 1, 0.05, 0.02, 0.01, 0% by mass or the like. In one embodiment, as for content of unsaturated sulfonic acid to 100 mass% of structural units, 0-70 mass% is preferred.

  Unsaturated phosphoric acid monomers are vinyl phosphonic acid, vinyl phosphate, bis ((meth) acryloxyethyl) phosphate, diphenyl-2- (meth) acryloyloxyethyl phosphate, dibutyl-2- (meth) acryloyloxy Examples include ethyl phosphate, dioctyl-2- (meth) acryloyloxyethyl phosphate, monomethyl-2- (meth) acryloyloxyethyl phosphate, 3- (meth) acryloxy-2-hydroxypropane phosphate, and salts thereof. The

  The content of an acid group-containing monomer such as unsaturated phosphoric acid in 100 mol% of the structural unit is not particularly limited, but considering the reaction between the component (b) other than unsaturated phosphoric acid and unsaturated phosphoric acid, Less than 40 mol% (for example, less than 30, 20, 19, 15, 10, 5, 1 mol%, 0 mol%) is preferable with respect to 100 mol% of the structural unit.

  The upper limit of the unsaturated phosphoric acid monomer with respect to 100% by mass of the structural unit is exemplified by 60, 50, 40, 30, 20, 10, 5, 1% by mass, and the lower limit is 50, 40, 30, 20, Examples thereof are 10, 5, 1, 0% by mass and the like. In one embodiment, 0-60 mass% is preferable as content of the unsaturated phosphoric acid monomer with respect to 100 mass% of structural units.

  In one embodiment, the total content of acid group-containing monomers such as unsaturated carboxylic acid, unsaturated sulfonic acid, and unsaturated phosphoric acid in 100 mol% of the structural unit is 40 mol% with respect to 100 mol% of the structural unit. Less than (for example, 30, 20, 19, 15, 10, 5, 1 mol%, less than 0 mol%) is preferable.

  The upper limit of the total content of acid group-containing monomers such as unsaturated carboxylic acid, unsaturated sulfonic acid, and unsaturated phosphoric acid with respect to 100% by mass of the structural unit is 70, 60, 50, 40, 30, 20, 10, 5, 1% by mass and the like are exemplified, and the lower limit is exemplified by 60, 50, 40, 30, 20, 10, 5, 1, 0% by mass and the like. In one embodiment, the total content of acid group-containing monomers such as unsaturated carboxylic acid, unsaturated sulfonic acid, and unsaturated phosphoric acid with respect to 100% by mass of the structural unit is preferably 0 to 70% by mass.

  The unsaturated carboxylic acid ester is preferably a (meth) acrylic acid ester. Examples of (meth) acrylic acid esters include linear (meth) acrylic acid esters, branched (meth) acrylic acid esters, alicyclic (meth) acrylic acid esters, and substituted (meth) acrylic acid esters.

  Linear (meth) acrylic acid esters are methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, and n-amyl (meth) acrylate. Hexyl (meth) acrylate, n-octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, and the like.

  Examples of the branched (meth) acrylic acid ester include i-propyl (meth) acrylate, i-butyl (meth) acrylate, i-amyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and the like.

  Examples of alicyclic (meth) acrylic acid esters include cyclohexyl (meth) acrylic acid.

  Substituted (meth) acrylic esters are glycidyl (meth) acrylate, hydroxymethyl (meth) acrylate, hydroxyethyl (meth) acrylate, ethylene glycol (meth) acrylate, ethylene glycol di (meth) acrylate, di Propylene glycol (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, allyl (meth) acrylate, di (meth) acrylic acid Ethylene and the like are exemplified.

  The content of the unsaturated carboxylic acid ester in 100 mol% of the structural unit is not particularly limited, but by using the unsaturated carboxylic acid ester, flexibility can be imparted to the electrode, particularly for wound type and cylindrical type batteries. It is useful when used, and is useful from the viewpoint that curling of the separator due to a decrease in the glass transition temperature of the component (A) can be suppressed when the separator is produced. On the other hand, considering the water solubility of the component (A), the content of the unsaturated carboxylic acid ester in 100 mol% of the structural unit is less than 40 mol% (for example, 30, 20, 19, 15, 10 and 100 mol% of the structural unit). 5, less than 1 mol%, 0 mol%) is preferred.

  The content of the unsaturated carboxylic acid ester with respect to 100% by mass of the structural unit is 90% by mass or less (for example, less than 80, 70, 60, 50, 40, 30, 20, 19, 15, 10, 5, 1% by mass). , 0% by mass).

  The α, β-unsaturated nitrile can be suitably used for the purpose of giving flexibility to the electrode and the separator. Examples of the α, β-unsaturated nitrile include (meth) acrylonitrile, α-chloro (meth) acrylonitrile, α-ethyl (meth) acrylonitrile, vinylidene cyanide and the like. Of these, (meth) acrylonitrile is preferable, and acrylonitrile is particularly preferable.

  The content of α, β-unsaturated nitrile in 100 mol% of the structural unit is not particularly limited, but is less than 40 mol% (for example, 30, 20, 19, 15, 10, 5, 1 mol% relative to 100 mol% of the structural unit). Less than 0 mol%). By being less than 40 mol% with respect to 100 mol% of the structural unit, the slurry layer (coating layer) becomes uniform while maintaining the solubility of the component (A) in water, and the flexibility is easily exhibited. .

  The upper limit of the content of α, β-unsaturated nitrile with respect to 100% by mass of the structural unit is exemplified by 60, 50, 40, 30, 20, 10, 5, 1% by mass, etc. The lower limit is 50, 40, 30 20, 10, 5, 1, 0% by mass, and the like. In one embodiment, the content of α, β-unsaturated nitrile with respect to 100% by mass of the structural unit is preferably 0 to 60% by mass.

  Conjugated dienes are 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, substituted linear conjugated pentadienes, substituted and Examples include side chain conjugated hexadiene.

  The content of the conjugated diene in 100 mol% of the structural unit is not particularly limited, but is preferably less than 10 mol% and more preferably 0 mol% in 100 mol% of the structural unit from the viewpoint of the cycle characteristics of the lithium ion battery.

  The upper limit of the conjugated diene content with respect to 100% by mass of the structural unit is exemplified by 30, 20, 10, 5, 1% by mass, and the lower limit is exemplified by 20, 10, 5, 1, 0% by mass, etc. . In one embodiment, as for content of the conjugated diene with respect to 100 mass% of structural units, 0-30 mass% is preferable.

  Examples of the aromatic vinyl compound include styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, chlorostyrene, divinylbenzene, and the like.

  The content of the aromatic vinyl compound in 100 mol% of the structural unit is not particularly limited, but from the viewpoint of the cycle characteristics of the lithium ion battery, it is preferably less than 10 mol% and more preferably 0 mol% of the 100 mol% of the structural unit. .

  The upper limit of the content of the aromatic vinyl compound relative to 100% by mass of the structural unit is exemplified by 30, 20, 10, 5, 1% by mass, and the lower limit is exemplified by 20, 10, 5, 1, 0% by mass, etc. Is done. In one embodiment, as for content of an aromatic vinyl compound with respect to 100 mass% of structural units, 0-30 mass% is preferable.

  (C) Other than the above-mentioned unsaturated carboxylic acid, unsaturated sulfonic acid, unsaturated phosphoric acid and the like acid group-containing monomer, unsaturated carboxylic acid ester, α, β-unsaturated nitrile, conjugated diene, aromatic vinyl compound The proportion of the component in the monomer group is less than 10 mol%, less than 5 mol%, less than 2 mol%, less than 1 mol%, less than 0.1 mol%, less than 0.01 mol% with respect to 100 mol% of the structural unit. Less than mol%, 0 mol%, etc. are exemplified, and with respect to 100 mass% of the structural unit, less than 10 mass%, less than 5 mass%, less than 1 mass%, less than 0.5 mass%, less than 0.1 mass%, Examples are less than 0.01% by mass and 0% by mass.

  The upper limit of the content of the component (A) with respect to 100% by mass of the slurry is 99.9, 95, 90, 80, 70, 60, 50, 40, 30, 20, 10, 5, 1, 0.5, 0.00. The lower limit is 95, 90, 80, 70, 60, 50, 40, 30, 20, 10, 5, 1, 0.5, 0.2, 0.1 mass%, etc. Illustrated. In one embodiment, 0.1-99.9 mass% of (A) component is included with respect to 100 mass% of slurry.

<Production method of component (A)>
The component (A) can be synthesized by various known polymerization methods, preferably radical polymerization methods. Specifically, it is preferable to perform a polymerization reaction at a reaction temperature of 50 to 100 ° C. while adding a radical polymerization initiator and, if necessary, a chain transfer agent to the monomer mixture containing the above components and stirring. The reaction time is not particularly limited and is preferably 1 to 10 hours.

  Various known radical polymerization initiators are used without particular limitation. The radical polymerization initiator is a persulfate such as potassium persulfate or ammonium persulfate; a redox polymerization initiator in which the persulfate is combined with a reducing agent such as sodium hydrogen sulfite; 2,2′-azobis-2-amidino An azo initiator such as propane dihydrochloride is exemplified. Although the usage-amount of a radical polymerization initiator is not restrict | limited in particular, 0.05-5.00 mass% is preferable with respect to 100 mass% of monomer groups which give (A) component, and 0.1-3.0 mass% is More preferred.

  General purpose such as ammonia, organic amine, potassium hydroxide, sodium hydroxide, lithium hydroxide, etc. for the purpose of improving the production stability before the radical polymerization reaction and / or when the obtained component (A) is water-solubilized. The pH of the reaction solution may be adjusted with a neutralizing agent. In that case, the pH is preferably 2 to 11. For the same purpose, it is also possible to use EDTA which is a metal ion sealing agent or a salt thereof.

  When the component (A) has an acid group, the neutralization rate can be appropriately adjusted depending on the application. Here, the neutralization rate of 100% indicates neutralization with the same number of moles of alkali as the acid component contained in the component (A). Moreover, the neutralization rate of 50% indicates that the acid component contained in the component (A) was neutralized with half the number of moles of alkali. Although the neutralization rate is not particularly limited, the neutralization rate is preferably 70 to 120% and more preferably 80 to 120% after the formation of the coating layer and the like. By setting the degree of neutralization after manufacturing the coating layer within the above range, most of the acid is in a neutralized state and is preferably combined with Li ions or the like in the battery so that the capacity is not reduced. Examples of the neutralized salt include Li salt, Na salt, K salt, ammonium salt, Mg salt, Ca salt, Zn salt, Al salt and the like.

<Physical properties of component (A)>
The weight average molecular weight (Mw) of the component (A) is not particularly limited, but the upper limit of the weight average molecular weight (Mw) is 6 million, 5.5 million, 5 million, 4.5 million, 4 million, 3.5 million, 3 million, 2.5 million. 2 million, 1.5 million, 1 million, 950,000, 900,000, 850,000, 800,000, 750,000, 700,000, 650,000, 600,000, 550,000, 500,000, 450,000, 400,000, etc. The lower limit is 5.5 million, 5 million, 4.5 million, 4 million, 3.5 million, 3 million, 22.9 million, 2.5 million, 2 million, 1.5 million, 1 million, 950,000, 900,000, 850,000, 800,000, 750,000 , 700,000, 650,000, 600,000, 550,000, 500,000, 450,000, 400,000, 350,000, 300,000, etc. In one embodiment, from the viewpoint of dispersion stability of the lithium ion battery slurry, the weight average molecular weight (Mw) of the component (A) is preferably 300,000 to 6,000,000, and more preferably 350,000 to 6,000,000.

  The upper limit of the number average molecular weight (Mn) of the component (A) is 6 million, 5.5 million, 5 million, 4.5 million, 4 million, 3.5 million, 3 million, 2.5 million, 2 million, 1.5 million, 1 million, 950,000 900,000, 800,000, 750,000, 700,000, 650,000, 600,000, 550,000, 500,000, 450,000, 400,000, 300,000, 200,000, 100,000, 50,000, etc. The lower limit is 5.5 million, 5 million, 4.5 million, 4 million, 3.5 million, 3 million, 22.9 million, 2.5 million, 2 million, 1.5 million, 1 million, 950,000, 900,000, 850,000, 800,000, 750,000 , 700,000, 650,000, 600,000, 550,000, 500,000, 450,000, 400,000, 350,000, 300,000, 200,000, 100,000, 50,000, 10,000, etc. In one embodiment, the number average molecular weight (Mn) of the component (A) is preferably 10,000 or more.

  A weight average molecular weight and a number average molecular weight can be calculated | required as a polyacrylic acid conversion value measured in a suitable solvent, for example by gel permeation chromatography (GPC).

  The B type viscosity of the component (A) is not particularly limited, but the upper limit is 100,000, 90,000, 70,000, 60,000, 40,000, 30,000, 20,000, 10,000, 9000, 8000, 7000, 6000, 5000, 4000, 3000, 2000 mPa · s, etc. are exemplified, and the lower limit is 90,000, 80,000, 60,000, 50,000, 40,000, 30,000, 20,000, 10,000, Examples include 9000, 8000, 7000, 6000, 5000, 4000, 3000, 2000, 1000 mPa · s. In one embodiment, the range of the B type viscosity of the component (A) is preferably 1000 to 100,000 mPa · s. The B type viscosity is measured with a B type viscometer such as a product name “B type viscometer model BM” manufactured by Toki Sangyo Co., Ltd.

  The gel fraction of the component (A) is not particularly limited, but the upper limit of the gel fraction of the component (A) is 99.9%, 95%, 90%, 85%, 80%, 75%, 70%, 65 % And 60% are exemplified, and the lower limit is exemplified by 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50% and the like. In one embodiment, the gel fraction of the component (A) is preferably 50% or more, and more preferably 55% or more.

The gel fraction means the following formula gel fraction (%) = {insoluble residue in solution (g) / mass of solid in solution (g)} × 100
Is a value calculated by.

<Water-soluble crosslinking agent (A1): Also referred to as component (A1))
The water-soluble crosslinking agent (A1) of the present invention comprises an amide group (—C (N) derived from an N-unsubstituted or monosubstituted (meth) acrylamide group-containing compound (a) present in the water-soluble poly (meth) acrylamide (A). = O) Those having a functional group excellent in thermal crosslinking reaction with NHR-) and having the potential to exist stably without crosslinking at room temperature are preferable. That is, the water-soluble crosslinking agent (A1) is stably present in the slurry state without crosslinking with the water-soluble poly (meth) acrylamide (A), and when the slurry layer (coating layer) is dried after the slurry is applied. Alternatively, it serves to thermally crosslink water-soluble poly (meth) acrylamide (A) in a hot press. Note that the above is only one theory, and that the present invention is not intended to be bound by the above theory.

  In one embodiment, the water-soluble crosslinking agent (A1) is used by selecting at least one from the group consisting of formaldehyde, glyoxal, hexamethylenetetramine, urea formaldehyde resin, and methylolmelamine resin.

  The content of the water-soluble crosslinking agent (A1) with respect to the water-soluble poly (meth) acrylamide (A) is not particularly limited. The upper limit of the content of the water-soluble crosslinking agent (A1) is 3, 2.9, 2, 1, 0.5, 0.1, 0 with respect to 100% by mass of the water-soluble poly (meth) acrylamide (A). .01, 0.005 mass%, etc. are exemplified, and the lower limit is 2.9, 2.5, 2, 1, 0.5, 0.1, 0.01, 0.005, 0.001 mass%, etc. Is exemplified. In one embodiment, 0.001 to 3% by mass is preferable from the viewpoint of springback resistance and electrode manufacturability, and / or from the viewpoint of substrate adhesion of ceramic fine particles and manufacturability of the separator, and a water-soluble crosslinking agent. From the viewpoint of the addition effect of (A1) and prevention of formation of aggregated particles of electrode active material particles and / or ceramic fine particles, 0.01 to 2.9% by mass is more preferable.

  Examples of the water include ultra pure water, pure water, distilled water, ion exchange water, and tap water.

<Electrode active material (B): Also referred to as component (B)>
In one embodiment, the said slurry for lithium ion batteries contains an electrode active material (B). Examples of the electrode active material include a negative electrode active material and a positive electrode active material.

  The negative electrode active material is not particularly limited as long as it can reversibly occlude and release lithium, and an appropriate material can be appropriately selected depending on the type of the target lithium ion battery. You may use the above together. Examples of the negative electrode active material include carbon materials, silicon materials, oxides containing lithium atoms, lead compounds, tin compounds, arsenic compounds, antimony compounds, and materials that form an alloy with lithium, such as aluminum compounds.

  The carbon material is graphite (also called graphite, natural graphite, artificial graphite, etc.) which is highly crystalline carbon, low crystalline carbon (soft carbon, hard carbon), carbon black (Ketjen black, acetylene black) , Channel black, lamp black, oil furnace black, thermal black, etc.), fullerene, carbon nanotube, carbon nanofiber, carbon nanohorn, carbon fibril, mesocarbon microbead (MCMB), pitch-based carbon fiber, and the like.

In addition to silicon, silicon oxide, and silicon alloy, the silicon material includes SiC, SiO _x C _y (0 <x ≦ 3, 0 <y ≦ 5), Si ₃ N ₄ , Si ₂ N ₂ O, and SiO _x (0 <X ≦ 2) described in silicon oxide composites (for example, materials described in JP-A No. 2004-185810 and JP-A No. 2005-259697), JP-A No. 2004-185810 Examples include silicon materials. Moreover, you may use the silicon material described in the patent 5390336 and the patent 59033761.

The silicon oxide is preferably a silicon oxide represented by a composition formula SiO _x (0 <x <2, preferably 0.1 ≦ x ≦ 1).

  The silicon alloy is preferably an alloy of silicon and at least one transition metal selected from the group consisting of titanium, zirconium, nickel, copper, iron and molybdenum. These transition metal silicon alloys are preferable because they have high electron conductivity and high strength. The silicon alloy is more preferably a silicon-nickel alloy or a silicon-titanium alloy, and particularly preferably a silicon-titanium alloy. 10 mol% or more is preferable with respect to 100 mol% of metal elements in the said alloy, and, as for the content rate of the silicon in a silicon alloy, 20-70 mol% is more preferable. Note that the silicon material may be single crystal, polycrystalline, or amorphous.

Moreover, when using a silicon material as an electrode active material, you may use together electrode active materials other than a silicon material. Such an electrode active material includes the above carbon material; a conductive polymer such as polyacene; A _X B _Y O _Z (A is an alkali metal or transition metal, B is a transition such as cobalt, nickel, aluminum, tin, manganese, etc. At least one selected from metals, O represents an oxygen atom, and X, Y, and Z are 0.05 <X <1.10, 0.85 <Y <4.00, and 1.5 <Z <5. The number is a number in the range of 00.) and other metal oxides. In the case where a silicon material is used as the electrode active material, it is preferable to use a carbon material in combination because the volume change associated with insertion and extraction of lithium is small.

The oxide containing a lithium atom includes ternary nickel cobalt lithium manganate, lithium-manganese composite oxide (LiMn ₂ O ₄ etc.), lithium-nickel composite oxide (LiNiO ₂ etc.), lithium-cobalt composite oxide. (LiCoO ₂ etc.), lithium-iron composite oxide (LiFeO ₂ etc.), lithium-nickel-manganese composite oxide (LiNi _0.5 Mn _0.5 O ₂ etc.), lithium-nickel-cobalt composite oxide (LiNi _0.8 Co _0.2 O ₂ etc.), lithium-transition metal phosphate compounds (LiFePO ₄ etc.), and lithium-transition metal sulfate compounds (Li _x Fe ₂ (SO ₄ ) ₃ ), lithium-titanium composite oxides Lithium-transition metal composite oxides such as (lithium titanate: Li ₄ Ti ₅ O ₁₂ ), and other conventionally known An electrode active material etc. are illustrated.

  From the viewpoint that the effect of the present invention is remarkably exhibited, the carbon material and / or the material alloyed with lithium is preferably 50% by mass or more, more preferably 80% by mass or more, and still more preferably 90% in the electrode active material. It is contained by mass% or more, particularly preferably 100 mass%.

The positive electrode active material is roughly classified into an active material containing an inorganic compound and an active material containing an organic compound. Examples of the inorganic compound contained in the positive electrode active material include transition metal oxides, composite oxides of lithium and transition metals, and transition metal sulfides. Examples of the transition metal include Fe, Co, Ni, Mn, and Al. Inorganic compounds used for the positive electrode active material include LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiFePO ₄ , LiNi _1/2 Mn _3/2 O ₄ , LiCo _1/3 Ni _1/3 Mn _{1 /} Lithium-containing composite metal oxides such as ₃ O ₂ , Li [Li _0.1 Al _0.1 Mn _1.9 ] O ₄ , LiFeVO ₄ ; Transition metal sulfides such as TiS ₂ , TiS ₃ , and amorphous MoS ₂ Examples include transition metal oxides such as Cu ₂ V ₂ O ₃ , amorphous V ₂ O—P ₂ O ₅ , MoO ₃ , V ₂ O ₅ , V ₆ O _{13, and the} like. These compounds may be partially element-substituted. Examples of the organic compound contained in the positive electrode active material include conductive polymers such as polyacetylene and poly-p-phenylene. An iron-based oxide having poor electrical conductivity may be used as an electrode active material covered with a carbon material by allowing a carbon source material to be present during reduction firing. These compounds may be partially element-substituted. Among these, LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiFePO ₄ , LiNi _1/2 Mn _3/2 O ₄ , LiCo _1/3 Ni _{1 / 3} Mn _1/3 O ₂ and Li [Li _0.1 Al _0.1 Mn _1.9 ] O ₄ are preferred.

  The shape of the electrode active material is not particularly limited, and may be any shape such as a fine particle shape or a thin film shape, but the fine particle shape is preferable. The average particle diameter of the electrode active material is not particularly limited, but the upper limit is 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, 4, 3, 2.9, 2, 1, 0. .5, 0.1 μm, etc., are exemplified, and the lower limit is 45, 40, 35, 30, 25, 20, 15, 10, 5, 4, 3, 2.9, 2, 1, 0.5,. An example is 1 μm. In one embodiment, from the viewpoint of forming a uniform and thin coating film, more specifically, if the thickness is 0.1 μm or more, the handleability is good, and if it is 50 μm or less, the electrode can be easily applied. The average particle diameter of the electrode active material is preferably 0.1 to 50 μm, more preferably 0.1 to 45 μm, further preferably 1 to 10 μm, and particularly preferably 5 μm.

  In the present disclosure, the “particle diameter” means the maximum distance among the distances between any two points on the particle outline (the same applies hereinafter). In the present disclosure, the “average particle diameter” means particles observed in several to several tens of fields using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM) unless otherwise specified. The value calculated as the average value of the particle diameters of these particles shall be adopted (the same applies hereinafter).

  The upper limit of the content of the component (A) with respect to 100% by mass of the electrode active material (B) in the slurry is 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1.5% by mass, etc. are exemplified, and the lower limit is 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1.5, 1% by mass, etc. Illustrated. In one embodiment, as for content of (A) component with respect to 100 mass% of electrode active materials (B), 1-15 mass% is preferable.

  In one embodiment, the content of silicon or silicon oxide in the electrode active material is 20% by mass or more (for example, 30% by mass or more, 40% with respect to 100% by mass of the electrode active material from the viewpoint of increasing the battery capacity of the lithium ion battery. % By mass or more, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, and 100% by mass) are preferable.

  In one embodiment, a conductive aid can be included in the slurry. Conductive aids include fibrous carbon such as vapor grown carbon fiber (VGCF), carbon nanotube (CNT), carbon nanofiber (CNF), carbon black such as graphite particles, acetylene black, ketjen black, furnace black, average Examples thereof include fine powders made of Cu, Ni, Al, Si or alloys thereof having a particle size of 10 μm or less. Although content of a conductive support agent is not specifically limited, 0-10 mass% is preferable with respect to an electrode active material component, and 0.5-6 mass% is more preferable.

<Ceramic fine particles (C): Also referred to as component (C)>
In one embodiment, the lithium ion battery slurry includes ceramic fine particles (C). The ceramic fine particles are components coated on the active material side of the porous polyolefin resin base material, plastic nonwoven fabric, and electrode material, and the gaps between the ceramic fine particles can form pores. Since the ceramic fine particles have non-conductivity, they can be made insulative, and therefore, a short circuit in a lithium ion battery can be prevented. Moreover, since the ceramic fine particles usually have high rigidity, the mechanical strength of the lithium ion battery separator can be increased. Therefore, even when a stress that tends to shrink the porous polyolefin resin base material or plastic nonwoven fabric is generated by heat, the lithium ion battery separator can withstand the stress. As a result, it is possible to prevent occurrence of a short circuit due to shrinkage of the porous polyolefin resin base material and the plastic nonwoven fabric.

  By using ceramic fine particles, it is excellent in dispersion stability in water, hardly settles in the slurry for lithium ion batteries, and can maintain a uniform slurry state for a long time. Further, when ceramic fine particles are used, the heat resistance can be increased. The ceramic fine particles may be used alone or in combination of two or more.

The material of the ceramic fine particles is preferably an electrochemically stable material. From such a viewpoint, examples of the ceramic fine particles include oxide particles, nitride particles, covalently bonded crystal particles, hardly soluble ionic crystal particles, and clay fine particles.
The oxide particles include aluminum oxide (alumina), aluminum oxide hydrate (boehmite (AlOOH), gibbsite (Al (OH) ₃ ), bakelite, iron oxide, silicon oxide, magnesium oxide (magnesia), magnesium hydroxide, Examples include calcium oxide, titanium oxide (titania), BaTiO ₃ , ZrO, and alumina-silica composite oxide.
Examples of the nitride particles include aluminum nitride, silicon nitride, and boron nitride.
Examples of the covalently bonded crystal particles include silicon and diamond.
Examples of the hardly soluble ionic crystal particles include barium sulfate, calcium fluoride, and barium fluoride.
Examples of the fine clay particles include fine clay particles such as silica, talc, and montmorillonite.
Among these, boehmite, alumina, magnesium oxide, and barium sulfate are preferable from the viewpoint of low water absorption and excellent heat resistance, and boehmite is more preferable.

  The upper limit of the average particle size of the ceramic fine particles is exemplified by 30, 25, 20, 15, 10, 5, 1, 0.5, 0.1, 0.05 μm, etc. The lower limit is 25, 20, 15, 10 5, 1, 0.5, 0.1, 0.05, 0.01 μm and the like. In one embodiment, the average particle size of the ceramic fine particles is preferably 0.01 to 30 μm.

  The upper limit of the content of the ceramic fine particles (C) with respect to 100% by mass of the slurry is 99.9, 95, 90, 80, 70, 60, 50, 40, 30, 20, 10, 5, 1, 0.5, 0.2% by mass is exemplified, and the lower limit is 95, 90, 80, 70, 60, 50, 40, 30, 20, 10, 5, 1, 0.5, 0.2, 0.1% by mass. Etc. are exemplified. In one Embodiment, 0.1-99.9 mass% of ceramic fine particles (C) are included with respect to 100 mass% of slurry.

  The upper limit of the content of the component (A) with respect to 100% by mass of the ceramic fine particles (C) in the slurry is 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1.5% by mass, and the lower limit is 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1.5, 1% by mass, etc. Is done. In one embodiment, 1-15 mass% is preferable, as for content of (A) component with respect to 100 mass% of ceramic fine particles (C), 1.5-14 mass% is more preferable, and 2-12 mass% is further preferable. By setting it as such content, the lithium ion battery separator which was excellent in adhesiveness, and was excellent in the charge / discharge characteristic with small resistance can be manufactured.

<Slurry viscosity adjusting solvent>
The slurry viscosity adjusting solvent is not particularly limited, but may include a non-aqueous medium having a standard boiling point of 80 to 350 ° C. A slurry viscosity adjusting solvent may be used independently and may use 2 or more types together. The slurry viscosity adjusting solvent is an amide solvent such as N-methylpyrrolidone, dimethylformamide, N, N-dimethylacetamide; a hydrocarbon solvent such as toluene, xylene, n-dodecane, tetralin; methanol, ethanol, 2-propanol, isopropyl alcohol. Alcohol solvents such as 2-ethyl-1-hexanol, 1-nonanol and lauryl alcohol; ketone solvents such as acetone, methyl ethyl ketone, cyclohexanone, phorone, acetophenone and isophorone; ether solvents such as dioxane and tetrahydrofuran (THF); benzyl acetate, Ester solvents such as isopentyl butyrate, methyl lactate, ethyl lactate, butyl lactate; amine solvents such as o-toluidine, m-toluidine, p-toluidine; γ-butyrolactone, δ-butyrolactone, etc. Examples include lactones; sulfoxide / sulfone solvents such as dimethyl sulfoxide and sulfolane; water and the like. Among these, N-methylpyrrolidone is preferable from the viewpoint of coating workability. Although content of the said non-aqueous medium is not specifically limited, 0-10 mass% is preferable with respect to 100 mass% of said slurries.

<Additives>
As the above-mentioned slurry for the thermal crosslinking type lithium ion battery, those which do not correspond to any of (A) component, (A1) component, (B) component, (C) component, water, conductive auxiliary agent and slurry viscosity adjusting solvent are added. It can be included as an agent.

  Examples of the additive include a dispersant, a leveling agent, an antioxidant, a thickener, a dispersion (emulsion), and a crosslinking agent.

  Examples of the content of the additive include 0 to 5% by mass, less than 1% by mass, less than 0.1% by mass, less than 0.01% by mass, and 0% by mass with respect to 100% by mass of the component (A). .

  Examples of the content of the additive include 0 to 5% by mass, less than 1% by mass, less than 0.1% by mass, less than 0.01% by mass, and 0% by mass with respect to 100% by mass of the component (A1). .

  The content of the additive is 0 to 5% by mass, less than 1% by mass, less than 0.1% by mass, less than 0.01% by mass, and 0% by mass with respect to 100% by mass of component (B) or component (C). Etc. are exemplified.

  As for content of an additive, 0-5 mass%, less than 1 mass%, less than 0.1 mass%, less than 0.01 mass%, 0 mass%, etc. are illustrated with respect to 100 mass% of said slurry aqueous solution.

  Examples of the dispersant include an anionic compound, a cationic compound, a nonionic compound, and a polymer compound.

  Examples of the leveling agent include surfactants such as alkyl surfactants, silicon surfactants, fluorine surfactants, and metal surfactants. By using the surfactant, it is possible to prevent the repelling that occurs during coating and to improve the smoothness of the slurry layer (coating layer).

  Examples of the antioxidant include a phenol compound, a hydroquinone compound, an organic phosphorus compound, a sulfur compound, a phenylenediamine compound, and a polymer type phenol compound. The polymer type phenol compound is a polymer having a phenol structure in the molecule. 200-1000 are preferable and, as for the weight average molecular weight of a polymer type phenol compound, 600-700 are more preferable.

  Thickeners include cellulosic polymers such as carboxymethylcellulose, methylcellulose, hydroxypropylcellulose, and ammonium salts and alkali metal salts thereof; (modified) poly (meth) acrylic acid and ammonium salts and alkali metal salts thereof; (modified) Polyvinyl alcohols such as polyvinyl alcohol, copolymers of acrylic acid or acrylates and vinyl alcohol, maleic anhydride or copolymers of maleic acid or fumaric acid and vinyl alcohol; polyethylene glycol, polyethylene oxide, polyvinyl pyrrolidone, modified poly Examples include acrylic acid, oxidized starch, phosphoric acid starch, casein, various modified starches, acrylonitrile-butadiene copolymer hydride, and the like.

  Dispersion (emulsion) is styrene-butadiene copolymer latex, polystyrene polymer latex, polybutadiene polymer latex, acrylonitrile-butadiene copolymer latex, polyurethane polymer latex, polymethyl methacrylate polymer latex. , Methyl methacrylate-butadiene copolymer latex, polyacrylate polymer latex, vinyl chloride polymer latex, vinyl acetate polymer emulsion, vinyl acetate-ethylene copolymer emulsion, polyethylene emulsion, carboxy-modified styrene butadiene copolymer Polymer resin emulsion, acrylic resin emulsion, polyethylene, polypropylene, polyethylene terephthalate, polyamide (PA), polyimide (PI), poly Midimide (PAI), aromatic polyamide, alginic acid and its salt, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl Examples include vinyl ether copolymer (PFA) and ethylene-tetrafluoroethylene copolymer (ETFE).

  Crosslinking agents include formaldehyde, glyoxal, hexamethylenetetramine, urea formaldehyde resin, methylol melamine resin, carbodiimide compound, polyfunctional epoxy compound, oxazoline compound, polyfunctional hydrazide compound, isocyanate compound, melamine compound, urea compound, and mixtures thereof. Illustrated.

  The lithium ion battery slurry may contain a binder other than the component (A), but the content of the component (A) in all binders is 90% by mass or more (for example, 91, 95, 98, 99 mass% or more and 100 mass%) is preferable.

  In addition, binders other than the component (A) may be used alone or in combination of two or more, fluorine-based resins (polyvinylidene fluoride, polytetrafluoroethylene, etc.), polyolefins (polyethylene, polypropylene, etc.) ), Polymers having an unsaturated bond (styrene-butadiene rubber, isoprene rubber, butadiene rubber, etc.), acrylic polymers (acrylic acid copolymers, methacrylic acid copolymers), carboxymethylcellulose salts, polyvinyl alcohol copolymer Examples thereof include polyvinyl pyrrolidone and the like.

  The slurry for a thermal crosslinking type lithium ion battery includes a slurry for a thermal crosslinking type lithium ion battery electrode, a slurry for a thermal crosslinking type lithium ion battery negative electrode, a slurry for a thermal crosslinking type lithium ion battery positive electrode, and a slurry for a thermal crosslinking type lithium ion battery separator. Can be used as

[3. Method for producing slurry for lithium ion battery]
This indication provides the manufacturing method of the slurry for the above-mentioned lithium ion battery including the process of adding the water-soluble crosslinking agent (A1) to the aqueous solution containing water-soluble poly (meth) acrylamide (A). In addition, what was mentioned above etc. are illustrated for (A) component etc. which are described in this item.

In one embodiment, the step of obtaining a slurry solution includes the step of adding and mixing the water-soluble poly (meth) acrylamide (A), the water-soluble crosslinking agent (A1), water, and the electrode active material or ceramic fine particles. Including. The method of adding the water-soluble cross-linking agent (A1) is: • Mixing after the production of the water-soluble poly (meth) acrylamide (A) aqueous solution • Dispersing the electrode active material or ceramic fine particles in the water-soluble poly (meth) acrylamide (A) aqueous solution And then mix (also called post-addition)
The post-addition is more preferable from the viewpoint of stability.

  Examples of the slurry mixing means include a ball mill, a sand mill, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, a planetary mixer, and a Hobart mixer.

[4. Lithium ion battery electrode]
The present disclosure relates to a lithium ion battery having a dried product of the lithium ion battery slurry obtained by applying the thermal crosslinkable lithium ion battery slurry on a current collector and causing a thermal cross-linking reaction on the current collector surface. An electrode is provided.

  Various known collectors can be used without particular limitation. The material of the current collector is not particularly limited, and examples thereof include metal materials such as copper, iron, aluminum, nickel, stainless steel, and nickel-plated steel, and carbon materials such as carbon cloth and carbon paper. The form of the current collector is not particularly limited, and in the case of a metal material, a metal foil, a metal cylinder, a metal coil, a metal plate, and the like are exemplified. In the case of a carbon material, a carbon plate, a carbon thin film, a carbon cylinder, and the like are exemplified. Especially, when using an electrode active material for a negative electrode, since copper foil is currently used for industrialized products as a collector, it is preferable.

  The application means is not particularly limited, and examples thereof include conventionally known coating apparatuses such as a comma coater, a gravure coater, a micro gravure coater, a die coater, and a bar coater.

  The drying means is not particularly limited, and the temperature is preferably 60 to 200 ° C, more preferably 100 to 195 ° C. The atmosphere may be dry air or an inert atmosphere.

  Although the thickness of an electrode (cured coating film) is not specifically limited, 5-300 micrometers is preferable and 10-250 micrometers is more preferable. By setting it as the above range, a sufficient Li occlusion / release function for a high-density current value can be easily obtained.

  The lithium ion battery electrode can be used as a positive electrode for a lithium ion battery and a negative electrode for a lithium ion battery.

[5. Lithium-ion battery separator]
The present disclosure provides a porous product obtained by applying the slurry for a heat-crosslinking lithium ion battery to a porous polyolefin resin substrate or a plastic nonwoven fabric and drying the slurry. The separator for lithium ion batteries which has on the surface of the polyolefin resin base material of this, or a plastic nonwoven fabric is provided.

  The lithium ion battery slurry may be applied to only one surface of the base material, or may be applied to both surfaces.

(Porous polyolefin resin substrate)
In one embodiment, the base material is preferably a porous membrane having a fine pore size, which has no electron conductivity, ion conductivity, and high resistance to organic solvents. As such a porous membrane, there is a porous polyolefin resin substrate. The porous polyolefin resin substrate is a microporous membrane containing a resin such as polyolefin and a mixture or copolymer thereof as a main component. The porous polyolefin resin base material is excellent in the coating property of the coating liquid when the polymer layer is obtained through the coating process, the separator film thickness is made thinner, and the active material ratio in the lithium ion battery is increased. From the viewpoint of increasing the capacity per volume. In addition, “including as a main component” means including more than 50% by mass, preferably 75% by mass or more, more preferably 85% by mass or more, further preferably 90% by mass or more, and still more preferably. Is 95% by mass or more, particularly preferably 98% by mass or more, and may be 100% by mass.

  In one embodiment, the content of the polyolefin resin in the porous polyolefin resin base material is not particularly limited, but from the viewpoint of shutdown performance when used as a separator for a lithium ion battery, the porous polyolefin resin base material The content of the polyolefin resin in is preferably 50% by mass or more and 100% by mass or less, more preferably 60% by mass or more and 100% by mass or less, and more preferably 70% by mass or more and 100% by mass or less of all components constituting the substrate. More preferably.

  The polyolefin resin is not particularly limited, but may be a polyolefin resin used for extrusion, injection, inflation, blow molding and the like, and may be used alone or in combination of two or more. Examples of the polyolefin resin include homopolymers such as ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, and 1-octene, copolymers, multistage polymers, and the like. The polymerization catalyst used in the production of these polyolefin resins is not particularly limited, and examples thereof include Ziegler-Natta catalysts, Phillips catalysts, metallocene catalysts, and the like.

  The polyolefin resin used as the material for the porous polyolefin resin base material has a low melting point and a high strength, and therefore a resin mainly composed of high-density polyethylene is preferred. Furthermore, from the viewpoint of improving the heat resistance of the polyolefin porous substrate, it is more preferable to use a porous polyolefin resin substrate containing polypropylene and a polyolefin resin other than polypropylene.

  Here, the three-dimensional structure of polypropylene is not limited, and any of isotactic polypropylene, syndiotactic polypropylene, and atactic polypropylene may be used.

  The proportion of polypropylene relative to the total amount of polyolefin contained in the polyolefin resin composition is not particularly limited, but is preferably 1 to 35% by mass, more preferably 3 to 20% by mass, from the viewpoint of achieving both heat resistance and a good shutdown function. 4-10 mass% is still more preferable.

  In this case, the polyolefin resin other than polypropylene is not limited. For example, a homopolymer or copolymer of olefin hydrocarbon such as ethylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene and the like. Is exemplified. Specifically, examples of the polyolefin resin other than polypropylene include polyethylene, polybutene, and ethylene-propylene random copolymer.

From the viewpoint of shutdown characteristics in which the pores of the polyolefin porous substrate are blocked by heat melting, polyolefin resins other than polypropylene include low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene, ultra high molecular weight polyethylene, etc. It is preferable to use polyethylene. Among these, polyethylene having a density measured according to JIS K 7112 of 0.93 g / cm ³ or more is more preferable from the viewpoint of strength.

  The porous polyolefin resin substrate may contain a filler and a fiber compound for the purpose of controlling strength, hardness, and heat shrinkage. In addition, the surface of a porous polyolefin resin substrate with a low-molecular compound or polymer compound in advance for the purpose of improving the adhesion with the adhesive layer or reducing the surface tension with the electrolytic solution to improve the liquid impregnation property. May be subjected to a coating treatment, an electromagnetic ray treatment such as ultraviolet rays, or a plasma treatment such as corona discharge / plasma gas. In particular, it contains polar groups such as a carboxylic acid group, a hydroxyl group, and a sulfonic acid group from the viewpoint of high impregnation of the electrolytic solution and easy adhesion to the coating layer obtained by applying the slurry to a substrate and drying. Those coated with a polymer compound are preferred.

  The thickness of the porous polyolefin resin substrate is not particularly limited, but is preferably 2 μm or more, more preferably 5 μm or more, preferably 100 μm or less, more preferably 60 μm or less, and even more preferably 50 μm or less. It is preferable to adjust the thickness to 2 μm or more from the viewpoint of improving the mechanical strength. On the other hand, it is preferable to adjust the film thickness to 100 μm or less because the occupied volume of the separator in the battery is reduced, which tends to be advantageous in terms of increasing the capacity of the battery.

(Plastic non-woven fabric)
In one embodiment, the average fiber diameter of the plastic nonwoven fabric used for the lithium ion battery separator is preferably 1 to 15 μm and more preferably 1 to 10 μm from the viewpoint of adhesion to the nonwoven fabric and separator thickness.

  In one embodiment, the average pore diameter of the plastic nonwoven fabric is preferably 1 to 20 μm, more preferably 3 to 20 μm, and even more preferably 5 to 20 μm. If the average pore diameter is less than 1 μm, the internal resistance increases and the output characteristics deteriorate. On the other hand, if the average pore diameter is 20 μm or more, an internal short circuit may occur when lithium dendrite is generated.

  In the present disclosure, the pore diameter means a gap between synthetic fibers forming a plastic nonwoven fabric. The average fiber diameter means an average value of the fiber diameters of 20 fibers randomly selected from the scanning electron micrographs. Similarly, the average pore diameter means an average value of the pore diameters of 20 fibers randomly selected from the scanning electron micrographs.

  The nonwoven fabric is preferably composed only of synthetic fibers having an average fiber diameter of 1 to 10 μm and an average pore diameter of 1 to 20 μm, but is necessary when the need for thinning the separator is not so high. Depending on the case, a synthetic fiber having an average fiber diameter and a pore diameter different from those described above may be used in combination. Moreover, you may use together fibers other than a synthetic fiber suitably from the same viewpoint. When using these fibers together (synthetic resin fibers whose average fiber diameter and average pore diameter are outside the range specified in the present application or fibers other than synthetic fibers), the content is 30 from the viewpoint of securing the strength of the nonwoven fabric and the like. % By mass or less is preferable, 20% by mass or less is more preferable, and 10% by mass or less is further preferable.

  The synthetic resin used as the material of the synthetic resin fiber is a polyolefin resin, a polyester resin, a polyvinyl acetate resin, an ethylene-vinyl acetate copolymer resin. , Polyamide resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyvinyl ether resin, polyvinyl ketone Resin, polyether resin, polyvinyl alcohol (polyvi yl alcohol resin, diene resin, polyurethane resin, phenol resin, melamine resin, furan resin, urea resin, aniline resin Resin, Unsaturated Polyester Resin, Alkyd Resin, Fluorocarbon Resin, Silicone Resin, Polyamide Imide Resin, Polyphenylene Sulfide Resin Polyimide resin, polycarbonate resin, polyazo Polymethine resin, Polyesteramide resin, Polyetheretherketone resin, Poly-p-phenylenebenzobisoxazole resin, Polybenzimidazole (polyzene) resin Examples thereof include an ethylene-vinyl alcohol copolymer resin. Of these, polyester resins, acrylonitrile resins, and polyolefin resins are preferable for improving the adhesion to the ceramic fine particles. Moreover, when a polyester resin, an acrylic resin, or a polyamide resin is used, the heat resistance of the separator can be improved.

  Polyester resins include polyethylene terephthalate (PET) series, polybutylene terephthalate (PBT) series, polytrimethylene terephthalate (PPT) series, polyethylene methyl phthalate (PPT) series, polyethylene methyl phthalate (PPT) series, polyethylene methyl phthalate (PPT) series, polyethylene methyl phthalate (PPT) series, polyethylene methyl phthalate (PPT) series, polyethylene methacrylate (PPT), Examples include resins such as butylene naphthalate-based, polyethylene isonaphthalate-based, and fully aromatic polyester-based resins. . Also, derivatives of these resins can be used. Among these resins, a polyethylene terephthalate-based resin is preferable for improving heat resistance, electrolytic solution resistance, and adhesion with ceramic fine particles.

  Acrylonitrile resin is made of 100% acrylonitrile polymer, acrylic acid, methacrylic acid, acrylic acid ester, (meth) acrylic acid derivative such as methacrylic acid ester, copolymer of vinyl acetate, etc. Is exemplified.

  Examples of the polyolefin resin include polypropylene, polyethylene, polymethylpentene, ethylene-vinyl alcohol copolymer, olefin copolymer and the like. From the viewpoint of heat resistance, the polyolefin resin is preferably polypropylene, polymethylpentene, ethylene-vinyl alcohol copolymer, olefin copolymer or the like.

  Polyamide-based resins include aliphatic polyamides such as nylon, poly-p-phenylene terephthalamide, poly-p-phenylene terephthalamide-3,4-diphenyl ether terephthalamide, wholly aromatic polyamides such as poly-m-phenylene isophthalamide, Examples thereof include semi-aromatic polyamide having a fatty chain in a part of the main chain in the aromatic polyamide. The wholly aromatic polyamide may be para-type or meta-type.

  The synthetic resin fiber may be a fiber (single fiber) made of a single resin, or may be a fiber (composite fiber) made of two or more kinds of resins. Examples of the composite fiber include a core-sheath type, an eccentric type, a side-by-side type, a sea-island type, an orange type, and a multiple bimetal type.

  Examples of fibers other than synthetic resin fibers that can be used in combination with synthetic resin fibers include solvent-spun cellulose and regenerated cellulose short fibers and fibrillated products, natural cellulose fibers, pulped products and fibrillated products of natural cellulose fibers, and inorganic fibers. The

  The thickness of the plastic nonwoven fabric is preferably 5 to 25 μm and more preferably 5 to 15 μm from the viewpoint of reducing the thickness and obtaining a separator having a low internal resistance.

  The method of coating the lithium ion battery slurry on the substrate is not particularly limited, but various coating methods such as blade, rod, reverse roll, lip, die, curtain, air knife, flexo, screen, offset, gravure, Examples include various printing methods such as inkjet, transfer methods such as roll transfer and film transfer, and methods such as scraping off the coating liquid on the non-coating surface after a pulling method such as dipping.

  In the lithium ion battery slurry layer (coating layer), the lithium ion battery slurry containing the component (A) and the component (C) may be crosslinked to form the lithium ion battery slurry layer. . The cross-linking reaction can proceed when the lithium ion battery slurry is dried. Specific examples of the drying method include drying with warm air, hot air, low-humidity air, and the like; vacuum drying; drying by irradiation with infrared rays, far infrared rays, electron beams, and the like.

  The lower limit of the temperature during drying is preferably 40 ° C. or higher, more preferably 45 ° C. or higher, and particularly preferably 50 ° C. or higher, from the viewpoint of efficiently removing the solvent and low molecular weight compound from the porous membrane composition. The upper limit is preferably 90 ° C. or less, more preferably 80 ° C. or less, from the viewpoint of suppressing deformation of the base material due to heat.

  The lower limit of the drying time is preferably 5 seconds or more, more preferably 10 seconds or more, particularly preferably 15 seconds or more, and the upper limit is preferably 3 minutes or less, more preferably 2 minutes or less. By setting the drying time to be equal to or more than the lower limit of the above range, the solvent can be sufficiently removed from the porous membrane composition, so that the output characteristics of the battery can be improved. Moreover, manufacturing efficiency can be improved by setting it as an upper limit or less.

  The manufacturing method of the said lithium ion battery separator may include arbitrary processes other than the above-mentioned. The manufacturing method of the said lithium ion battery separator can include the pressurization process of the layer (coating layer) of the slurry for lithium ion batteries by presses, such as a metal mold press and a roll press. By performing the pressure treatment, the binding property between the base material and the layer of the lithium ion battery slurry can be improved. However, from the viewpoint of keeping the porosity of the lithium ion battery slurry within a preferable range, it is preferable to appropriately control the pressure and the pressurization time so as not to become excessively large. Moreover, the said manufacturing method of the separator for lithium ion batteries may include the process of drying in a vacuum drying, a dry room, etc. for residual moisture removal.

[6. Lithium-ion battery separator / electrode laminate]
The present disclosure provides a separator / electrode laminate for a lithium ion battery, which is a dried product of the slurry for a thermal bridge type lithium ion battery, obtained by applying the slurry for the thermal bridge type lithium ion battery to an electrode and drying the slurry. provide.

  Various known electrodes can be used as the electrode used when producing the separator / electrode laminate for a lithium ion battery, and the electrode provided by the present disclosure may be used or provided by the present disclosure. It may not be an electrode.

A method for producing a separator / electrode laminate for a lithium ion battery includes a step of applying, drying, and pressing an electrode material-containing slurry such as the lithium ion battery slurry to a current collector,
Examples include a method including a step of applying and drying the slurry for a lithium ion battery on the dried material of the electrode material-containing slurry (that is, not on the current collector side but on the electrode active material side). Examples of the application method, the drying method, and the conditions described above are exemplified.

[7. Lithium ion battery]
The present disclosure provides a lithium ion battery including the lithium ion battery electrode. Moreover, this indication provides the lithium ion battery containing the said separator for lithium ion batteries, and / or the said separator / electrode laminated body for lithium ion batteries. The battery includes an electrolytic solution and a packaging material, and these are not particularly limited.

(Electrolyte)
Examples of the electrolytic solution include a non-aqueous electrolytic solution in which a supporting electrolyte is dissolved in a non-aqueous solvent. The non-aqueous electrolyte may contain a film forming agent.

  As the non-aqueous solvent, various known solvents can be used without particular limitation, and they may be used alone or in combination of two or more. Non-aqueous solvents include linear carbonate solvents such as diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate; cyclic carbonate solvents such as ethylene carbonate, propylene carbonate, and butylene carbonate; linear ether solvents such as 1,2-dimethoxyethane; tetrahydrofuran, Cyclic ether solvents such as 2-methyltetrahydrofuran, sulfolane, 1,3-dioxolane; chain ester solvents such as methyl formate, methyl acetate, and methyl propionate; cyclic ester solvents such as γ-butyrolactone and γ-valerolactone; acetonitrile, etc. Is exemplified. Among these, the combination of the mixed solvent containing a cyclic carbonate and a chain carbonate is preferable.

Lithium salt is used for the supporting electrolyte. Various known lithium salts can be used without particular limitation, and may be used alone or in combination of two or more. The supporting electrolyte is LiPF ₆ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAlCl ₄ , LiClO ₄ , CF ₃ SO ₃ Li, C ₄ F ₉ SO ₃ Li, CF ₃ COOLi, (CF ₃ CO) ₂ NLi, (CF 3 ₃ SO ₂ ) ₂ NLi, (C ₂ F ₅ SO ₂ ) NLi and the like are exemplified. Among these, LiPF ₆ , LiClO ₄ , and CF ₃ SO ₃ Li that are easily soluble in a solvent and exhibit a high degree of dissociation are preferable. Since the lithium ion conductivity increases as the supporting electrolyte having a higher degree of dissociation is used, the lithium ion conductivity can be adjusted depending on the type of the supporting electrolyte.

  Various known film forming agents can be used without particular limitation, and may be used alone or in combination of two or more. Film-forming agents are carbonate compounds such as vinylene carbonate, vinylethylene carbonate, vinylethyl carbonate, methylphenyl carbonate, fluoroethylene carbonate, difluoroethylene carbonate; alkene sulfides such as ethylene sulfide and propylene sulfide; 1,3-propane sultone, 1 And sultone compounds such as 1,4-butane sultone; acid anhydrides such as maleic anhydride and succinic anhydride. The content of the film forming agent in the electrolyte solution is not particularly limited, but is preferably 10% by mass or less, 8% by mass or less, 5% by mass or less, and 2% by mass or less. By controlling the content to 10% by mass or less, it is easy to obtain the advantages of the film forming agent, such as suppression of initial irreversible capacity, improvement of low temperature characteristics and rate characteristics, and the like.

  The form of the lithium ion battery is not particularly limited. Examples of the form of the lithium ion battery include a cylinder type in which the sheet electrode and the separator are spiral, a cylinder type having an inside-out structure in which the pellet electrode and the separator are combined, a coin type in which the pellet electrode and the separator are stacked, and the like. In addition, by storing batteries of these forms in an optional outer case, the battery can be used in an arbitrary shape such as a coin shape, a cylindrical shape, or a square shape.

  The method for producing the lithium ion battery is not particularly limited, and may be assembled by an appropriate procedure according to the structure of the battery. Examples of the method for producing a lithium ion battery include the method described in JP2013-089437A. A battery can be manufactured by placing a negative electrode on an outer case, providing an electrolyte and a separator thereon, and further placing a positive electrode so as to face the negative electrode, and fixing with a gasket and a sealing plate.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. The present invention is not limited to the following examples. In the following, “parts” and “%” indicate parts by mass and mass%, respectively, unless otherwise specified.

1. (A) Production of component 1
In a reactor equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction tube, 1095 g of ion-exchanged water, 400 g (2.81 mol) of 50% acrylamide aqueous solution, 0.22 g (0.0014 mol) of sodium methallylsulfonate After removing oxygen in the reaction system through nitrogen gas, the temperature was raised to 50 ° C. 2,2′-Azobis-2-amidinopropane dihydrochloride (product name “NC-32”, manufactured by Nichiho Chemical Co., Ltd.) 2.0 g and ion-exchanged water 50 g were added thereto, and the temperature was raised to 80 ° C. 3 A time reaction was performed to obtain an aqueous solution containing polyacrylamide.

Production Example 2
In a reactor equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction tube, 1428 g of ion-exchanged water, 400 g (2.81 mol) of a 50% aqueous acrylamide solution, and 63.5 g (0.70 mol) of an 80% aqueous acrylic acid solution. , 0.56 g (0.0035 mol) of sodium methallyl sulfonate was added. After removing oxygen in the reaction system through nitrogen gas, the temperature was raised to 50 ° C. Thereto, 2.5 g of 2,2′-azobis-2-amidinopropane dihydrochloride (product name “NC-32”, manufactured by Niho Chemical Co., Ltd.) and 50 g of ion-exchanged water were added, and the temperature was raised to 80 ° C. 3 Reaction was performed for 0 hour to obtain an aqueous solution containing a polyacrylamide-acrylic acid copolymer.

Production Examples 3 to 11
An aqueous solution containing water-soluble poly (meth) acrylamide was prepared in the same manner as in Production Example 2 except that the monomer composition and the amount of initiator were changed to those shown in Table 1 in Production Example 2.

Comparative production example 1
In a reactor equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, 2.5 g of sodium dodecylbenzenesulfonate as an emulsifier, 944 g of ion-exchanged water, and 1.9 g of potassium persulfate as a polymerization initiator are placed. Polymerization was carried out by dropping 14 g of 50% acrylamide aqueous solution, 21 g of acrylamide t-butylsulfonic acid, 576 g of butyl acrylate, and 30 g of N-methylolacrylamide at 50 ° C. over 1 hour. After polymerization at the same temperature for 2 hours, the mixture was cooled to 25 ° C. to obtain an aqueous dispersion containing particulate polyacrylamide-acrylic acid ester.

・ AM: Acrylamide (“50% acrylamide” manufactured by Mitsubishi Chemical Corporation)
ATBS: Acrylamide t-butyl sulfonic acid (“ATBS” manufactured by Toagosei Co., Ltd.)
NMAM: N-methylolacrylamide (manufactured by Tokyo Chemical Industry Co., Ltd.)
DMAA: N, N-dimethylacrylamide (manufactured by Tokyo Chemical Industry Co., Ltd.)
AA: Acrylic acid (“80% acrylic acid” manufactured by Osaka Organic Chemical Industry Co., Ltd.)
・ AN: Acrylonitrile (“Acrylonitrile” manufactured by Mitsubishi Chemical Corporation)
・ HEMA: 2-hydroxyethyl methacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.)
-BA: butyl acrylate (Wako Pure Chemical Industries, Ltd.)
-SMAS: sodium methallyl sulfonate

The physical properties of the component (A) described in the table were measured as follows.

B-type viscosity The viscosity of each aqueous binder solution was measured using a B-type viscometer (product name “B-type viscometer model BM” manufactured by Toki Sangyo Co., Ltd.) at 25 ° C. under the following conditions.
In the case of a viscosity of 100,000 to 20,000 mPa · s: No. When using 4 rotors, rotating at 6 rpm, viscosity less than 20,000 mPa · s: Three rotors are used and the rotation speed is 6 rpm.

Weight average molecular weight The weight average molecular weight was calculated | required as a polyacrylic acid conversion value measured under 0.2M phosphate buffer / acetonitrile solution (90/10, PH8.0) by the gel permeation chromatography (GPC). The GPC apparatus used was HLC-8220 (manufactured by Tosoh Corporation), and the column used was SB-806M-HQ (manufactured by SHODEX).

Formulation Example 1
To 100 parts by mass of the water-soluble poly (meth) acrylamide (A) obtained in Production Example 1, 1 part by mass of a 37% aqueous formaldehyde solution (hereinafter also referred to as formalin) was added in terms of solid content, and the concentration was reduced to 0. The mixture was mixed for 5 hours to obtain a uniform water-soluble battery binder. The gel fraction of the obtained water-soluble battery binder was measured by the following procedure.

<Gel fraction>
A water-soluble battery binder in which a water-soluble cross-linking agent (A1) was blended with water-soluble poly (meth) acrylamide (A) was dried at 120 ° C. for 4 hours in a circulating drier to obtain a solid resin. The mass of the solid resin was accurately measured, immersed in water for 3 hours, and then filtered under reduced pressure with Kiriyama funnel filter paper (Kiriyama Seisakusho No. 50B). Thereafter, the filtrate was dried at 120 ° C. for 3 hours, and then the mass of the insoluble residue was accurately measured, and the gel fraction of the resin after thermal crosslinking of the water-soluble battery binder was calculated from the following formula.
Gel fraction (%) = {insoluble residue (g) / mass of solid resin (g)} × 100

Formulation Examples 2-12, Comparative Formulation Examples 1-3
The gel fraction of the resin obtained in the same manner as in Formulation Example 1 was measured except that the type and amount of the water-soluble crosslinking agent (A1) in Formulation Example 1 were changed to those shown in Table 2 and numerical values.

-Formalin: 37% formaldehyde aqueous solution-Glyoxal: 40% glyoxal solution (manufactured by Wako Pure Chemical Industries, Ltd.)
・ Hexamethylenetetramine (Wako Pure Chemical Industries, Ltd.)
・ Methylol melamine resin ・ Urea formaldehyde resin

Example 1-1: Electrode Evaluation (1) Production of Slurry for Lithium Ion Battery Electrode Using a commercially available revolution mixer (product name “Awatori Nertaro”, manufactured by Shinky Corporation), a container dedicated to the mixer 7 parts by mass of a binder aqueous solution containing the poly (meth) acrylamide (A) obtained in Formulation Example 1 and the water-soluble crosslinking agent (A1) in terms of solid content, and 50 parts by mass of silicon particles having a D50 of 5 μm, Natural graphite (product name “Z-5F” manufactured by Ito Graphite Industries Co., Ltd.) was mixed with 50 parts by mass. Ion exchange water was added thereto so that the solid concentration was 40%, and the container was set in the mixer. Next, after kneading at 2000 rpm for 10 minutes, defoaming was performed for 1 minute to obtain an electrode slurry.

(2) Production of Lithium Ion Battery Electrode The above lithium ion battery slurry was uniformly applied to the surface of a current collector made of copper foil by a doctor blade method so that the film thickness after drying was 25 μm. After drying at 30 ° C. for 30 minutes, an electrode was obtained by heat treatment at 150 ° C./vacuum for 120 minutes. Then, the electrode was obtained by pressing with a roll press so that the density of a film | membrane (electrode active material layer) might be 1.5 g / cm < ³ >.

(3) Manufacture of lithium half-cell In a glove box purged with argon, the above-mentioned electrode is punched and molded to a diameter of 16 mm and placed on a bipolar coin cell (trade name “HS Flat Cell” manufactured by Hosen Co., Ltd.). I put it. Next, a separator (CS TECH CO., LTD, trade name “Selion P2010”) made of a polypropylene porous membrane punched to a diameter of 24 mm is placed, and further, 500 μL of electrolyte is injected so that air does not enter. A lithium metal half cell was assembled by placing a commercially available metal lithium foil stamped to 16 mm and sealing the outer body of the bipolar coin cell with a screw. The electrolytic solution used here is a solution obtained by dissolving LiPF ₆ at a concentration of 1 mol / L in a solvent of ethylene carbonate / ethyl methyl carbonate = 1/1 (mass ratio).

Examples 1-2 to 1-12, Comparative Examples 1-1 to 1-3
A lithium half cell was obtained in the same manner except that the composition was changed as shown in the following table.

  The slurry dispersibility, springback rate, and discharge capacity retention rate in the table were measured by the following methods.

<Slurry dispersibility evaluation>
The dispersibility immediately after slurry preparation was visually evaluated according to the following criteria.
A: The whole is a homogeneous paste, there is no liquid separation, and no aggregates are observed.
○: The whole is a substantially homogeneous paste, and a slight liquid separation is observed, but no agglomerates are observed.
(Triangle | delta): A small amount of aggregates and a little more liquid separation are recognized by the container bottom part.
X: Many clay-like aggregates are observed at the bottom of the container, and a large amount of liquid separation is also observed.

<Electrical property evaluation: Springback rate and discharge capacity maintenance rate>
(1) Charging / discharging measurement The lithium half cell produced above is put in a thermostat at 25 ° C., charging is started at a constant current (0.1 C), and charging is completed when the voltage reaches 0.01 V (cut-off). ). Next, discharging was started at a constant current (0.1 C), and charging / discharging was repeated 30 times to complete the discharge (cutoff) when the voltage reached 1.0 V.

(2) Springback rate of electrode accompanying repeated charge / discharge After 30 cycles of charge / discharge cycle test at room temperature (25 ° C.), the lithium half cell was disassembled and the thickness of the electrode was measured. The springback rate of the electrode was determined by the following formula.
Springback rate = {(electrode thickness after 30 cycles−current collector thickness) / (electrode thickness before charging / discharging−current collector thickness)} × 100-100 (%)

(3) Discharge capacity maintenance rate The discharge capacity maintenance rate was calculated | required from the following formula | equation.
Discharge capacity maintenance ratio = {(discharge capacity at 30th cycle) / (discharge capacity at 1st cycle)} × 100 (%)

  In the above measurement conditions, “1C” indicates a current value at which discharge is completed in one hour after constant current discharge of a cell having a certain electric capacity. For example, “0.1 C” is a current value at which discharge is completed over 10 hours, and “10 C” is a current value at which discharge is completed over 0.1 hours.

  As is clear from the table, in the electrode slurry prepared using the binder aqueous solution of Examples 1-1 to 1-12 and in the lithium half cell evaluation prepared from this electrode slurry, both of the springback rate and the discharge capacity maintenance rate Evaluation was good.

  The obtained separators were measured for heat shrinkage resistance, dust resistance, adhesion, rate resistance and output characteristics by the following methods.

<Heat-resistant shrinkage>
The separators and separator / electrode laminates obtained in the examples and comparative examples were cut into squares having a width of 12 cm and a length of 12 cm, and a square having a side of 10 cm was drawn inside the square to obtain a test piece. The test piece was heated in a constant temperature bath at 150 ° C. for 1 hour. After the heat treatment, the area of the square drawn inside was measured, the change in the area before and after the heat treatment was determined as the heat shrinkage, and the heat resistance was evaluated according to the following criteria. The smaller the heat shrinkage rate, the better the heat shrinkage of the separator.
○: Area shrinkage rate is less than 1% Δ: Area shrinkage rate is 1% or more and less than 3% ×: Area shrinkage rate is 3% or more

<Powder resistance>
The separators and separator / electrode laminates obtained in Examples and Comparative Examples were cut into 10 cm × 10 cm squares, weighed exactly (X0), fixed one piece on cardboard, and then fixed with cotton cloth on the ceramic layer side. A covered weight of 5 cm and 900 g was placed, and these were rubbed together at a rotation speed of 50 rpm for 10 minutes. Thereafter, the mass (X1) is again measured accurately, and the following formula: Powder fallability = {(X0−X1) / X0} × 100
According to the above, the powder resistance (mass%) was calculated to evaluate the powder resistance of the separator according to the following criteria.
A: Powder fall-off property is less than 2% by mass B: Powder fall-off property is 2% by mass or more and less than 5% by mass C: Powder fall-off property is 5% by mass or more

<Separator adhesion (peel strength)>
A test piece having a width of 2 cm and a length of 10 cm is cut out from the separator and the separator / electrode laminate obtained in Examples and Comparative Examples, and fixed with the coating surface facing upward. Next, an adhesive tape having a width of 15 mm (“Cello Tape (registered trademark)” manufactured by Nichiban Co., Ltd.)) (specified in JIS Z1522) was applied to the surface of the ceramic layer of the test piece while pressing, and then the condition was maintained at 25 ° C. Using a tensile tester ("Tensilon RTM-100" manufactured by A & D Co., Ltd.), the stress when the adhesive tape was peeled off from one end of the test piece in the direction of 180 ° at a speed of 30 mm / min. Was measured. The measurement was performed 5 times, converted to a value per 15 mm width, and the average value was calculated as the peel strength. The higher the peel strength, the higher the adhesion strength between the base material and the ceramic layer or the binding property between the ceramic layers, indicating that the ceramic layer or the ceramic layers are less likely to peel from the separator base material.

<Rate tolerance, output characteristics>
(1) Manufacture of Laminate Type Lithium Ion Battery A laminate type lithium ion battery was manufactured as follows in measuring rate resistance and output characteristics.
(1-1) Manufacture of negative electrode Using a commercially available rotating and revolving mixer (product name “Awatori Nertaro”, manufactured by Shinky Corporation), styrene butadiene rubber (SBR) / carboxymethyl cellulose ( CMC) (mass ratio 1/1) 2 parts of an aqueous solution in terms of solid content and 98 parts of natural graphite (product name “Z-5F” manufactured by Ito Graphite Industries Co., Ltd.) were mixed. Thereto, ion exchange water was added so as to have a solid concentration of 40%, and the container was set in the mixer. Next, after kneading at 2000 rpm for 10 minutes, defoaming was performed for 1 minute to obtain a slurry for a lithium ion battery. A slurry for a lithium ion battery was placed on a current collector made of copper foil, and applied to a film using a doctor blade. The current collector applied with the lithium ion battery slurry was dried at 80 ° C. for 20 minutes to volatilize and remove the water, and then tightly bonded by a roll press. At this time, the density of the electrode active material layer was set to 1.0 g / cm ² . The joined product was heated with a vacuum dryer at 120 ° C. for 2 hours, cut into a predetermined shape (26 mm × 31 mm rectangular shape), and a negative electrode having an electrode active material layer thickness of 15 μm was obtained.

(1-2) Production of Positive Electrode 88 parts by mass of LiNi _0.5 Co _0.2 Mn _0.3 O ₂ as a positive electrode active material, acetylene black as a conductive additive, and polyvinylidene fluoride (PVDF) as a binder, respectively 6 parts by mass and 6 parts by mass were mixed, and the mixture was dispersed in an appropriate amount of N-methyl-2-pyrrolidone (NMP) to produce a lithium ion battery positive electrode slurry. Next, an aluminum foil was prepared as a positive electrode current collector, and a slurry for a lithium ion battery positive electrode was placed on the aluminum foil and applied to form a film using a doctor blade. The aluminum foil after the application of the lithium ion battery positive electrode slurry was dried at 80 ° C. for 20 minutes to volatilize and remove NMP, and then tightly bonded by a roll press. At this time, the density of the positive electrode active material layer was set to 3.2 g / cm ² . The joined product was heated at 120 ° C. for 6 hours with a vacuum dryer, cut into a predetermined shape (rectangular shape of 25 mm × 30 mm), and a positive electrode having a positive electrode active material layer thickness of about 45 μm was obtained.

(1-3) Production of Laminate Type Lithium Ion Battery A laminate type lithium ion secondary battery was produced using the negative electrode and the positive electrode or the positive electrode obtained in Examples. Specifically, the separators obtained in Examples and Comparative Examples were sandwiched between a positive electrode and a negative electrode with a rectangular sheet (27 × 32 mm, thickness 25 μm) to form an electrode plate group. The electrode plate group was covered with a set of two laminated films, and the three sides were sealed, and then an electrolyte solution was injected into the bag-like laminated film. As an electrolytic solution, a solution obtained by dissolving LiPF ₆ at a concentration of 1 mol / L in a solvent of ethylene carbonate / ethyl methyl carbonate = 1/1 (mass ratio) was used. Thereafter, the remaining one side was sealed to obtain a laminate type lithium ion secondary battery in which the four sides were hermetically sealed and the electrode plate group and the electrolyte were sealed. Note that the positive electrode and the negative electrode each have a tab that can be electrically connected to the outside, and a part of the tab extends to the outside of the laminated lithium ion secondary battery. When the laminate type lithium ion battery manufactured in the above process was energized, no operational problem occurred.

(2) Measurement of rate tolerance and output characteristics Using the lithium ion secondary battery produced above, the battery was charged at a voltage of 2.5 to 4.2 V at 0.1 C at 25 ° C., and the voltage became 4.2 V. Then, charging was continued at a constant voltage (4.2 V), and the time when the current value reached 0.01 C was regarded as charging completion (cut-off). Next, charging / discharging at 0.1 C to 2.5 V was repeated 5 times, and after the sixth cycle, only discharging was changed to 1 C, and charging / discharging was repeated 50 cycles. A value obtained by calculating a percentage of the 1C discharge capacity at the 6th cycle in the charge capacity at the 6th cycle was defined as an initial rate maintenance rate. The higher this value, the better the rate tolerance. Further, a value obtained by calculating a percentage of the 1C discharge capacity at the 50th cycle with respect to the 1C discharge capacity at the 5th cycle was defined as a capacity maintenance rate. The larger this value, the better the output characteristics.

Example 2-1
(1) Manufacture of slurry for separator 5 parts by mass of the aqueous solution obtained in Formulation Example 1 and 113 parts by mass of water were mixed with stirring, and 100 parts by mass of boehmite (average particle size 0.8 μm) was added. The mixture was dispersed and stirred with a homogenizer (IK25 T25 digital ULTRA-TURRAX) at 15000 rpm for 60 minutes. Further, ion exchange water was added to adjust the viscosity to produce a slurry.

(2) Manufacture of separator: lamination of separator slurry layer (coating layer) A single-layer polyethylene separator substrate (PE substrate) manufactured by a wet method having a width of 250 mm, a length of 200 mm, and a thickness of 6 μm was prepared. . The slurry liquid obtained above was coated on one surface of the separator using a gravure coater so that the thickness after drying was 3.0 μm, and dried to obtain a lithium ion battery separator.

Examples 2-2 to 2-20, Comparative Examples 2-1 to 2-4
A separator for a lithium ion battery was obtained in the same manner as in Example 2-1, except that the changes were made as shown in the following table.

Example 2-21
In Example 2-5, the slurry liquid was coated not on the separator but on the positive electrode side, coated and dried using a gap coater so that the thickness after drying was 3.0 μm, and a positive electrode for a lithium ion battery was obtained. Obtained.

Example 2-22
In Example 2-5 in the previous period, the slurry was coated on a polyethylene terephthalate nonwoven fabric substrate (PET substrate) having a width of 200 mm, a length of 200 mm, a thickness of 9 μm, and a basis weight of 11 g / m ^2. A lithium ion battery separator was obtained by the above operation.

Claims (11)

Water-soluble poly (meth) acrylamide (A) containing 50 mol% or more of a structural unit derived from N-unsubstituted or monosubstituted (meth) acrylamide group-containing compound (a) with respect to 100 mol% of the structural unit,
A water-soluble crosslinking agent (A1) comprising one or more selected from the group consisting of formaldehyde, glyoxal, hexamethylenetetramine, urea formaldehyde resin, and methylolmelamine resin,
And a slurry for a thermally cross-linked lithium ion battery, which contains water. The water-soluble cross-linking agent (A1) is 0 with respect to 100% by mass of the structural unit derived from the N-unsubstituted or mono-substituted (meth) acrylamide group-containing compound (a) in the water-soluble poly (meth) acrylamide (A). The slurry for a heat-crosslinking type lithium ion battery according to claim 1, comprising 0.001 to 3.0% by mass. The slurry for thermal bridge type lithium ion batteries according to claim 1 or 2 containing an electrode active material (B). The slurry for thermal bridge type lithium ion batteries according to claim 3 in which said electrode active material (B) contains 10 mass% or more of silicon or silicon oxide. The slurry for thermal bridge type lithium ion batteries according to claim 1 or 2, comprising ceramic fine particles (C). The slurry for thermally crosslinked lithium ion batteries according to any one of claims 1 to 5, comprising a step of adding the water-soluble crosslinking agent (A1) to an aqueous solution containing the water-soluble poly (meth) acrylamide (A). Manufacturing method. The electrode for lithium ion batteries obtained by apply | coating the slurry for thermal bridge type lithium ion batteries of any one of Claims 1-4 to a collector, and carrying out a thermal crosslinking reaction. A lithium ion battery comprising the electrode for a lithium ion battery according to claim 7. The separator for lithium ion batteries obtained by apply | coating the slurry for thermal crosslinking type lithium ion batteries of Claim 1, 2, or 5 to a porous polyolefin resin base material or a plastic nonwoven fabric, and carrying out thermal crosslinking. The slurry for a heat-crosslinking type lithium ion battery according to claim 1, 2, or 5.
A separator / electrode laminate for a lithium ion battery, which is obtained by applying to the active material side of an electrode material and thermally crosslinking. A lithium ion battery comprising the lithium ion battery separator according to claim 9 and / or the lithium ion battery separator / electrode laminate according to claim 10.